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  • Aircraft Propulsion and Power
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  • 2020-2024
  • 2000-2004  (62)
  • 1970-1974  (578)
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  • 1905-1909
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  • 1
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    Kelvin's age of the Earth paradox revisited (2000)
    In:  J. Geophys. Res., Houston, Akademie-Verlag, vol. 105, no. B6, pp. 13,155-13,158, pp. L08310, (ISSN: 1340-4202)
    Details
    Publication Date: 2000
    Keywords: Geothermics ; Geomagnetics ; evolution ; 1739 ; History ; of ; geophysics ; JGR ; Solar/planetary ; relationships ; 1799 ; 5418 ; Planetology: ; solid ; surface ; planets ; Heat ; flow ; 9699 ; Information ; related ; to ; geologic ; time ; General ; or ; miscellaneous
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Test Medium Effects on Ignition, Combustion and Flameholding Processes in Scramjet Combustors (2000)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: The total temperatures (enthalpies) required to ground-test air-breathing (aero-propulsion) engines at high Mach number flight conditions can be achieved in a number of ways. Among these are: 1. Heat exchangers, including pre-heated ceramic beds. 2. direct electrical heating, e.g., arc discharge and resistance heaters. 3. Compression heating. 4. Shock heating, and 5. In-stream combustion, with oxygen replenishment to match air content. Each method has distinct advantages, disadvantages and limitations. All have a common characteristic of being designed for intermittent flow, due to the extreme energy required for continuous operation at simulated Mach numbers above about 3. All also distort the composition of atmospheric air to some degree, due to the high temperatures that occur in the plenum section prior to expansion of the flow to simulated flight conditions. In the case of in-stream combustion, the resulting test medium is commonly referred to as "vitiated air", being composed of oxygen, nitrogen and some fraction of combustion products.
    Keywords: Aircraft Propulsion and Power
    Type: JANNAF 25th Airbreathing Propulsion Subcommittee, 37th Combustion Subcommittee and 1st Modeling and Simultation Subcommittee Joint Meeting; Volume 1; 243-271; CPIA-Publ-703-Vol-1
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    NASA TECHNICAL REPORTS
  • 3
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    General Aviation Propulsion Program and Beyond (2000)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The purpose of this presentation is to show flight demonstrations, complete preflight ground tests, and the assembling of the first QRT 4 engine.
    Keywords: Aircraft Propulsion and Power
    Type: 1999 NASA Seal/Secondary Air System Workshop; Volume 1; 61-78; NASA/CP-2000-210472/VOL1
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  • 4
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    Acoustics and Thrust of Separate Flow Exhaust Nozzles With Mixing Devices Investigated for High Bypass Ratio Engines (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: Typical installed separate-flow exhaust nozzle system. The jet noise from modern turbofan engines is a major contributor to the overall noise from commercial aircraft. Many of these engines use separate nozzles for exhausting core and fan streams. As a part of NASA s Advanced Subsonic Technology (AST) program, the NASA Glenn Research Center at Lewis Field led an experimental investigation using model-scale nozzles in Glenn s Aero-Acoustic Propulsion Laboratory. The goal of the investigation was to develop technology for reducing the jet noise by 3 EPNdB. Teams of engineers from Glenn, the NASA Langley Research Center, Pratt & Whitney, United Technologies Research Corporation, the Boeing Company, GE Aircraft Engines, Allison Engine Company, and Aero Systems Engineering contributed to the planning and implementation of the test.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 5
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    Propulsion Aeroelastic Analysis Developed for Flutter and Forced Response (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The NASA Glenn Research Center at Lewis Field develops new technologies to increase the fuel efficiency of aircraft engines, improve the safety of engine operation, reduce emissions, and reduce engine noise. With the development of new designs for fans, compressors, and turbines to achieve these goals, the basic aeroelastic requirements are that there should be no flutter (self-excited vibrations) or high resonant blade stresses (due to forced response) in the operating regime. Therefore, an accurate prediction and analysis capability is required to verify the aeroelastic soundness of the designs. Such a three-dimensional viscous propulsion aeroelastic analysis capability has been developed at Glenn with support from the Advanced Subsonic Technology (AST) program. This newly developed aeroelastic analysis capability is based on TURBO, a threedimensional unsteady aerodynamic Reynolds-averaged Navier-Stokes turbomachinery code developed previously under a grant from Glenn. TURBO can model the viscous flow effects that play an important role in certain aeroelastic problems such as flutter with flow separation, flutter at high loading conditions near the stall line (stall flutter), flutter in the presence of shock and boundary-layer interaction, and forced response due to wakes and shock impingement. In aeroelastic analysis, the structural dynamics representation of the blades is based on normal modes. A finite-element analysis code is used to calculate these in-vacuum vibration modes and the associated natural frequencies. In an aeroelastic analysis using the TURBO code, flutter and forced response are modeled as being uncoupled. To calculate if a blade row will flutter, one prescribes the motion of the blade to be a harmonic vibration in a specified in-vacuum normal mode. An aeroelastic analysis preprocessor is used to generate the displacement field required for the analysis. The work done by aerodynamic forces on the vibrating blade during a cycle of vibration is calculated. If this work is positive, the blade is dynamically unstable, since it will extract energy from the flow, leading to an increase in the blade s oscillation amplitude. The forced-response excitations on a blade row are calculated by modeling the flow through two adjacent blade rows using the TURBO code. The blades are assumed to be rigid. As an option, a single blade row can be modeled with the upstream blade row influence represented by a time-varying disturbance (gust) at the inlet boundary. The unsteady forces on a blade row from such analyses are used in a structural analysis along with the blade structural dynamics characteristics and aerodynamic damping associated with blade vibration to calculate the resulting dynamic stresses on the blade.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 6
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    Accuracy of Numerical Simulations of Tip Clearance Flow in Transonic Compressor Rotors Improved Dramatically (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The tip clearance flows of transonic compressor rotors have a significant impact on rotor and stage performance. Although numerical simulations of these flows are quite sophisticated, they are seldom verified through rigorous comparisons of numerical and measured data because, in high-speed machines, measurements acquired in sufficient detail to be useful are rare. Researchers at the NASA Glenn Research Center at Lewis Field compared measured tip clearance flow details (e.g., trajectory and radial extent) of the NASA Rotor 35 with results obtained from a numerical simulation. Previous investigations had focused on capturing the detailed development of the jetlike flow leaking through the clearance gap between the rotating blade tip and the stationary compressor shroud. However, we discovered that the simulation accuracy depends primarily on capturing the detailed development of a wall-bounded shear layer formed by the relative motion between the leakage jet and the shroud.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 7
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    Turbine Blade and Endwall Heat Transfer Measured in NASA Glenn's Transonic Turbine Blade Cascade (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: Higher operating temperatures increase the efficiency of aircraft gas turbine engines, but can also degrade internal components. High-pressure turbine blades just downstream of the combustor are particularly susceptible to overheating. Computational fluid dynamics (CFD) computer programs can predict the flow around the blades so that potential hot spots can be identified and appropriate cooling schemes can be designed. Various blade and cooling schemes can be examined computationally before any hardware is built, thus saving time and effort. Often though, the accuracy of these programs has been found to be inadequate for predicting heat transfer. Code and model developers need highly detailed aerodynamic and heat transfer data to validate and improve their analyses. The Transonic Turbine Blade Cascade was built at the NASA Glenn Research Center at Lewis Field to help satisfy the need for this type of data.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 8
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    Numerical Propulsion System Simulation: An Overview (2000)
    In:  CASI
    Details
    Publication Date: 2017-10-04
    Description: The cost of implementing new technology in aerospace propulsion systems is becoming prohibitively expensive and time consuming. One of the main contributors to the high cost and lengthy time is the need to perform many large-scale hardware tests and the inability to integrate all appropriate subsystems early in the design process. The NASA Glenn Research Center is developing the technologies required to enable simulations of full aerospace propulsion systems in sufficient detail to resolve critical design issues early in the design process before hardware is built. This concept, called the Numerical Propulsion System Simulation (NPSS), is focused on the integration of multiple disciplines such as aerodynamics, structures and heat transfer with computing and communication technologies to capture complex physical processes in a timely and cost-effective manner. The vision for NPSS, as illustrated, is to be a "numerical test cell" that enables full engine simulation overnight on cost-effective computing platforms. There are several key elements within NPSS that are required to achieve this capability: 1) clear data interfaces through the development and/or use of data exchange standards, 2) modular and flexible program construction through the use of object-oriented programming, 3) integrated multiple fidelity analysis (zooming) techniques that capture the appropriate physics at the appropriate fidelity for the engine systems, 4) multidisciplinary coupling techniques and finally 5) high performance parallel and distributed computing. The current state of development in these five area focuses on air breathing gas turbine engines and is reported in this paper. However, many of the technologies are generic and can be readily applied to rocket based systems and combined cycles currently being considered for low-cost access-to-space applications. Recent accomplishments include: (1) the development of an industry-standard engine cycle analysis program and plug 'n play architecture, called NPSS Version 1, (2) A full engine simulation that combines a 3D low-pressure subsystem with a 0D high pressure core simulation. This demonstrates the ability to integrate analyses at different levels of detail and to aerodynamically couple components, the fan/booster and low-pressure turbine, through a 3D computational fluid dynamics simulation. (3) Simulation of all of the turbomachinery in a modern turbofan engine on parallel computing platform for rapid and cost-effective execution. This capability can also be used to generate full compressor map, requiring both design and off-design simulation. (4) Three levels of coupling characterize the multidisciplinary analysis under NPSS: loosely coupled, process coupled and tightly coupled. The loosely coupled and process coupled approaches require a common geometry definition to link CAD to analysis tools. The tightly coupled approach is currently validating the use of arbitrary Lagrangian/Eulerian formulation for rotating turbomachinery. The validation includes both centrifugal and axial compression systems. The results of the validation will be reported in the paper. (5) The demonstration of significant computing cost/performance reduction for turbine engine applications using PC clusters. The NPSS Project is supported under the NASA High Performance Computing and Communications Program.
    Keywords: Aircraft Propulsion and Power
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  • 9
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    Probabilistic Multi-Scale, Multi-Level, Multi-Disciplinary Analysis and Optimization of Engine Structures (2000)
    In:  CASI
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    Publication Date: 2017-10-04
    Description: Aircraft engines are assemblies of dynamically interacting components. Engine updates to keep present aircraft flying safely and engines for new aircraft are progressively required to operate in more demanding technological and environmental requirements. Designs to effectively meet those requirements are necessarily collections of multi-scale, multi-level, multi-disciplinary analysis and optimization methods and probabilistic methods are necessary to quantify respective uncertainties. These types of methods are the only ones that can formally evaluate advanced composite designs which satisfy those progressively demanding requirements while assuring minimum cost, maximum reliability and maximum durability. Recent research activities at NASA Glenn Research Center have focused on developing multi-scale, multi-level, multidisciplinary analysis and optimization methods. Multi-scale refers to formal methods which describe complex material behavior metal or composite; multi-level refers to integration of participating disciplines to describe a structural response at the scale of interest; multidisciplinary refers to open-ended for various existing and yet to be developed discipline constructs required to formally predict/describe a structural response in engine operating environments. For example, these include but are not limited to: multi-factor models for material behavior, multi-scale composite mechanics, general purpose structural analysis, progressive structural fracture for evaluating durability and integrity, noise and acoustic fatigue, emission requirements, hot fluid mechanics, heat-transfer and probabilistic simulations. Many of these, as well as others, are encompassed in an integrated computer code identified as Engine Structures Technology Benefits Estimator (EST/BEST) or Multi-faceted/Engine Structures Optimization (MP/ESTOP). The discipline modules integrated in MP/ESTOP include: engine cycle (thermodynamics), engine weights, internal fluid mechanics, cost, mission and coupled structural/thermal, various composite property simulators and probabilistic methods to evaluate uncertainty effects (scatter ranges) in all the design parameters. The objective of the proposed paper is to briefly describe a multi-faceted design analysis and optimization capability for coupled multi-discipline engine structures optimization. Results are presented for engine and aircraft type metrics to illustrate the versatility of that capability. Results are also presented for reliability, noise and fatigue to illustrate its inclusiveness. For example, replacing metal rotors with composites reduces the engine weight by 20 percent, 15 percent noise reduction, and an order of magnitude improvement in reliability. Composite designs exist to increase fatigue life by at least two orders of magnitude compared to state-of-the-art metals.
    Keywords: Aircraft Propulsion and Power
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  • 10
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    Noise-Reduction Benefits Analyzed for Over-the-Wing-Mounted Advanced Turbofan Engines (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: As we look to the future, increasingly stringent civilian aviation noise regulations will require the design and manufacture of extremely quiet commercial aircraft. Also, the large fan diameters of modern engines with increasingly higher bypass ratios pose significant packaging and aircraft installation challenges. One design approach that addresses both of these challenges is to mount the engines above the wing. In addition to allowing the performance trend towards large diameters and high bypass ratio cycles to continue, this approach allows the wing to shield much of the engine noise from people on the ground. The Propulsion Systems Analysis Office at the NASA Glenn Research Center at Lewis Field conducted independent analytical research to estimate the noise reduction potential of mounting advanced turbofan engines above the wing. Certification noise predictions were made for a notional long-haul commercial quadjet transport. A large quad was chosen because, even under current regulations, such aircraft sometimes experience difficulty in complying with certification noise requirements with a substantial margin. Also, because of its long wing chords, a large airplane would receive the greatest advantage of any noise-shielding benefit.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 11
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    Surge Flow in a Centrifugal Compressor Measured by Digital Particle Image Velocimetry (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A planar optical velocity measurement technique known as Particle Image Velocimetry (PIV) is being used to study transient events in compressors. In PIV, a pulsed laser light sheet is used to record the positions of particles entrained in a fluid at two instances in time across a planar region of the flow. Determining the recorded particle displacement between exposures yields an instantaneous velocity vector map across the illuminated plane. Detailed flow mappings obtained using PIV in high-speed rotating turbomachinery components are used to improve the accuracy of computational fluid dynamics (CFD) simulations, which in turn, are used to guide advances in state-of-the-art aircraft engine hardware designs.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 1999; NASA/TM-2000-209639
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  • 12
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    Advanced Methods for Aircraft Engine Thrust and Noise Benefits: Nozzle-Inlet Flow Analysis (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: In this project, we continue to develop the previous joint research between the Fluid Mechanics and Acoustics Laboratory (FM&AL) at Hampton University (HU) and the Jet Noise Team (JNT) at the NASA Langley Research Center (NASA LaRC). The FM&AL was established at Hampton University in June of 1996 and has conducted research under two NASA grants: NAG-1-1835 (1996-99), and NAG-1-1936 (1997-00). In addition, the FM&AL has jointly conducted research with the Central AeroHydrodynamics Institute (TsAGI, Moscow) in Russia under a Civilian Research and Development Foundation (CRDF) grant #RE2-136 (1996-99). The goals of the FM&AL programs are twofold: (1) to improve the working efficiency of the FM&AUs team in generating new innovative ideas and in conducting research in the field of fluid dynamics and acoustics, basically for improvement of supersonic and subsonic aircraft engines, and (2) to attract promising minority students to this research and training and, in cooperation with other HU departments, to teach them basic knowledge in Aerodynamics, Gas Dynamics, and Theoretical and Experimental Methods in Aeroacoustics and Computational Fluid Dynamics (CFD). The research at the HU FM&AL supports reduction schemes associated with the emission of engine pollutants for commercial aircraft and concepts for reduction of observables for military aircraft. These research endeavors relate to the goals of the NASA Strategic Enterprise in Aeronautics concerning the development of environmentally acceptable aircraft. It is in this precise area, where the US aircraft industry, academia, and Government are in great need of trained professionals and which is a high priority goal of the Minority University Research and Education (MUREP) Program, that the HU FM&AL can make its most important contribution. The main achievements for the reporting period in the development of concepts for noise reduction and improvement in efficiency for jet exhaust nozzles and inlets for aircraft engines are as follows: (1) Publications- The AIAA Paper #99-1924 has been presented at the 5th AIAA/CEAS Aeroacoustics Conference, May 10-12, 1999, Seattle, WA; the AIAA Paper #00-3315 has been accepted for the 36th AIAA/ASME/ SAE/ASEE Joint Propulsion Conference, 17-19 July, 2000, Huntsville, AL; and another paper has been accepted for the International Environmental Congress, 14-16 June, 2000, St.-Petersburg, Russia. (2) Two patents were granted on July 20, 1999, and January 12, 2000. (3) Three reports/presentations at the NASA LaRC and GRC (06/22199, 09/26/ 99, and 06/25/00). (4) Grants and Proposals: Four proposals were submitted to the NASA and CRDF; a NASA Faculty Award was granted on January, 2000. A CRDF Young Investigator Program Award was granted for a 3 months visit of the Russian scientist to the HU FM&AL (03/99-05/99). (5) Theory and Numerical Simulations- Analytical theory, numerical simulation, comparison of theoretical with experimental results, and modification of theoretical approaches, models, grids etc. have been conducted for several complicated 2D and 3D nozzle and inlet designs using NASA codes based on full Euler and Navier-Stokes solvers: CFL3D, CRAFT, GODUNOV, and others. New approach for environmental monitoring via infrasound. (6) Experimental Tests: Experimental acoustic tests at the TsAGI, Moscow, with nozzles having Screwdriver or Axisymmetric Plug and Permeable Shells. A small scale working model of the NASA Low Speed Wind Tunnel (LSWT) has been installed in the Experimental Hall of the HU FM&AL (June, 1999). Preliminary preparations for experimental tests were made. (7) Students Research Activity: Involvement of the two graduate students as research assistants in the current research project.
    Keywords: Aircraft Propulsion and Power
    Type: HBCUs/OMUs Research Conference Agenda and Abstracts; 21; NASA/TM-2000-210042
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  • 13
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    Power Requirement for Nonequilibrium MHD-Bypass Scramjet (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: It has been suggested previously that the performance of scramjet propulsion system may be improved by the use of magnetohydrodynamic (MHD) energy bypass: an MHD generator could be made to decelerate the flow entering the combustor, thereby improving combustion efficiency, and the electrical power generated could be made to accelerate the flow exiting from the combustor prior to expanding through the nozzle. In one of such proposed schemes, the MHD generator is proposed to be operated at a low temperature and ionization is to be achieved under nonequilibrium by the application of an external power. In the present work, the required power of such an external source is calculated assuming a 100%-efficient nonequilibrium ionization scheme. The power required is that needed to prevent the degree of ionization from reaching equilibrium with the low gas temperature. The flow is seeded with potassium or cesium. Specific impulse is calculated with and without turbulent friction. The results show that, for typical intended flight conditions, the specific impulse obtained is substantially higher than that of a typical scramjet, but the required external-power is several times that of the power generated in the MHD generator.
    Keywords: Aircraft Propulsion and Power
    Type: 39th AIAA Aerospace Sciences Meeting; Jan 01, 2001; Reno, NV; United States
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  • 14
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    Load Capacity Estimation of Foil Air Journal Bearings for Oil-Free Turbomachinery Applications (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper introduces a simple "Rule of Thumb" (ROT) method to estimate the load capacity of foil air journal bearings, which are self-acting compliant-surface hydrodynamic bearings being considered for Oil-Free turbo-machinery applications such as gas turbine engines. The ROT is based on first principles and data available in the literature and it relates bearing load capacity to the bearing size and speed through an empirically based load capacity coefficient, D. It is shown that load capacity is a linear function of bearing surface velocity and bearing projected area. Furthermore, it was found that the load capacity coefficient, D, is related to the design features of the bearing compliant members and operating conditions (speed and ambient temperature). Early bearing designs with basic or "first generation" compliant support elements have relatively low load capacity. More advanced bearings, in which the compliance of the support structure is tailored, have load capacities up to five times those of simpler designs. The ROT enables simplified load capacity estimation for foil air journal bearings and can guide development of new Oil-Free turbomachinery systems.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209782 , E-12067 , ARL-TR-2334 , NAS 1.15:209782 , International Joint Tribology; Oct 01, 2000 - Oct 04, 2000; Seattle, WA; United States
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  • 15
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    Ensemble Diffraction Measurements of Spray Combustion in a Novel Vitiated Coflow Turbulent Jet Flame Burner (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental investigation is presented of a novel vitiated coflow spray flame burner. The vitiated coflow emulates the recirculation region of most combustors, such as gas turbines or furnaces; additionally, since the vitiated gases are coflowing, the burner allows exploration of the chemistry of recirculation without the corresponding fluid mechanics of recirculation. As such, this burner allows for chemical kinetic model development without obscurations caused by fluid mechanics. The burner consists of a central fuel jet (droplet or gaseous) surrounded by the oxygen rich combustion products of a lean premixed flame that is stabilized on a perforated, brass plate. The design presented allows for the reacting coflow to span a large range of temperatures and oxygen concentrations. Several experiments measuring the relationships between mixture stoichiometry and flame temperature are used to map out the operating ranges of the coflow burner. These include temperatures as low 300 C to stoichiometric and oxygen concentrations from 18 percent to zero. This is achieved by stabilizing hydrogen-air premixed flames on a perforated plate. Furthermore, all of the CO2 generated is from the jet combustion. Thus, a probe sample of NO(sub X) and CO2 yields uniquely an emission index, as is commonly done in gas turbine engine exhaust research. The ability to adjust the oxygen content of the coflow allows us to steadily increase the coflow temperature surrounding the jet. At some temperature, the jet ignites far downstream from the injector tube. Further increases in the coflow temperature results in autoignition occurring closer to the nozzle. Examples are given of methane jetting into a coflow that is lean, stoichiometric, and even rich. Furthermore, an air jet with a rich coflow produced a normal looking flame that is actually 'inverted' (air on the inside, surrounded by fuel). In the special case of spray injection, we demonstrate the efficacy of this novel burner with a methanol spray in a vitiated coflow. As a proof of concept, an ensemble light diffraction (ELD) optical instrument was used to conduct preliminary measurements of droplet size distribution and liquid volume fraction.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-210466 , E-12462 , NAS 1.26:210466 , Mar 13, 2000 - Mar 14, 2000; Golden, CO; United States
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  • 16
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    Internal Designs Application for Inlet and Nozzle Aeroperformance Improvement (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The following research results are based on development of an approach previously proposed by the authors for optimum nozzle design to obtain maximum thrust. The design was denoted a Telescope nozzle. A Telescope nozzle contains one or several internal designs of certain location, which are inserted at certain locations into a divergent conical or planar main nozzle near its exit. Such a design provides additional thrust augmentation over 20% by comparison with the optimum single nozzle of equivalent lateral area. What is more, recent experimental acoustic tests have discovered an essential noise reduction due to Telescope nozzles application. In this paper, some additional theoretical results are presented for Telescope nozzles and a similar approach is applied for aeroperformance improvement of a supersonic inlet. In addition, a classic gas dynamics problem of a similar supersonic flow into a plate has been analyzed. In some particular cases, new exact analytical solutions are obtained for a flow into a wedge with an oblique shock wave. Numerical simulations were conducted for supersonic flow into a divergent portion of a 2D or axisymmetric nozzle with several plane or conuical designs as well as into a 2D or axisymmetric supersonic inlet with a forebody. The 1st order Kryko-Godunov marching numerical scheme for inviscid supersonic flows was used. Several cases were tested using the NASA CFL3d code based on full Navier-Stokes equations. Numerical simulation results have confirmed essential benefits of Telescope design applications in propulsion systems.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 00-3315 , 36th Joint Propulsion Conference; Jul 17, 2000 - Jul 19, 2000; Huntsville, AL; United States
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  • 17
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    A Probabilistic Approach to Aeropropulsion System Assessment (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A probabilistic approach is described for aeropropulsion system assessment. To demonstrate this approach, the technical performance of a wave rotor-enhanced gas turbine engine (i.e. engine net thrust, specific fuel consumption, and engine weight) is assessed. The assessment accounts for the uncertainties in component efficiencies/flows and mechanical design variables, using probability distributions. The results are presented in the form of cumulative distribution functions (CDFS) and sensitivity analyses, and are compared with those from the traditional deterministic approach. The comparison shows that the probabilistic approach provides a more realistic and systematic way to assess an aeropropulsion system.
    Keywords: Aircraft Propulsion and Power
    Type: Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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  • 18
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    The Numerical Propulsion System Simulation: An Overview (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Advances in computational technology and in physics-based modeling are making large-scale, detailed simulations of complex systems possible within the design environment. For example, the integration of computing, communications, and aerodynamics has reduced the time required to analyze major propulsion system components from days and weeks to minutes and hours. This breakthrough has enabled the detailed simulation of major propulsion system components to become a routine part of designing systems, providing the designer with critical information about the components early in the design process. This paper describes the development of the numerical propulsion system simulation (NPSS), a modular and extensible framework for the integration of multicomponent and multidisciplinary analysis tools using geographically distributed resources such as computing platforms, data bases, and people. The analysis is currently focused on large-scale modeling of complete aircraft engines. This will provide the product developer with a "virtual wind tunnel" that will reduce the number of hardware builds and tests required during the development of advanced aerospace propulsion systems.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209915 , E-12152 , NAS 1.15:209915 , Computational Aerosciences; Feb 15, 2000 - Feb 17, 2000; Moffett Field, CA; United States
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  • 19
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    Noise Reduction Potential of Large, Over-the-Wing Mounted, Advanced Turbofan Engines (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As we look to the future, increasingly stringent civilian aviation noise regulations will require the design and manufacture of extremely quiet commercial aircraft. Indeed, the noise goal for NASA's Aeronautics Enterprise calls for technologies that will help to provide a 20 EPNdB reduction relative to today's levels by the year 2022. Further, the large fan diameters of modem, increasingly higher bypass ratio engines pose a significant packaging and aircraft installation challenge. One design approach that addresses both of these challenges is to mount the engines above the wing. In addition to allowing the performance trend towards large, ultra high bypass ratio cycles to continue, this over-the-wing design is believed to offer noise shielding benefits to observers on the ground. This paper describes the analytical certification noise predictions of a notional, long haul, commercial quadjet transport with advanced, high bypass engines mounted above the wing.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210025 , NAS 1.15:210025 , E-12222 , 14th International Symposium on Air Breathing Engines; Sep 05, 1999 - Sep 10, 1999; Florence; Italy
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    Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modem first stage gas turbine rotor blade with a blade tip profile of a GE-E(sup 3) aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1 x 10(exp 6). A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. 'Me heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1 % case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.
    Keywords: Aircraft Propulsion and Power
    Type: ASME Paper-2000-FT-0195 , ASME Turbo 2000; May 08, 2000 - May 11, 2000; Munich; Germany
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    Three-Dimensional Effects in Modeling of Dual-Mode Scramjets (2000)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: A numerical investigation of an experimental dual-mode scramjet configuration is performed. Both experimental and numerical results indicate significant upstream interaction for this case. Several computational cases are examined: these include the use of jet-to-jet symmetry and entire half-duct modeling. Grid convergence, turbulence modeling, and wall temperature effects are studied in terms of wall pressure predictions and flow-field characteristics. Wall pressure comparisons between CFD and experiment show fair agreement for the jet-to-jet case. However, further computations of the entire half-duct show the development of a large sidewall separation zone extending much further upstream than the separation zone at the duct centerline. This sidewall separation is the dominant feature in the CFD-generated flowfield but is not evident in the experimental data, resulting in a unfavorable comparison between CFD and experimental data. Current work aimed at resolving this issue and at further understanding asymmetric flow-structures in dual-mode flow-fields is discussed.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2000-3704
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  • 22
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    Lean direct wall fuel injection method and devices (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A fuel combustion chamber, and a method of and a nozzle for mixing liquid fuel and air in the fuel combustion chamber in lean direct injection combustion for advanced gas turbine engines, including aircraft engines. Liquid fuel in a form of jet is injected directly into a cylindrical combustion chamber from the combustion chamber wall surface in a direction opposite to the direction of the swirling air at an angle of from about 50.degree. to about 60.degree. with respect to a tangential line of the cylindrical combustion chamber and at a fuel-lean condition, with a liquid droplet momentum to air momentum ratio in the range of from about 0.05 to about 0.12. Advanced gas turbines benefit from lean direct wall injection combustion. The lean direct wall injection technique of the present invention provides fast, uniform, well-stirred mixing of fuel and air. In addition, in order to further improve combustion, the fuel can be injected at a venturi located in the combustion chamber at a point adjacent the air swirler.
    Keywords: Aircraft Propulsion and Power
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  • 23
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    Fatigue Failure of Development Space Shuttle Main Engine Turbine Blades (2000)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: This presentation focuses on the use of single crystal material, uniaxial LCF specimen data, and on development blade failure analysis.
    Keywords: Aircraft Propulsion and Power
    Type: Fracture Control Methodology; Oct 31, 2000 - Nov 02, 2000; Huntsville, AL; United States
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    Internal Designs Application for Inlet and Nozzle Aeroperformance Improvement (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The following research results are based on development of an approach previously proposed by the authors for optimum nozzle design to obtain maximum thrust. The design was denoted a Telescope nozzle. A Telescope nozzle contains one or several internal designs of certain location, which are inserted at certain locations into a divergent conical or planar main nozzle near its exit. Such a design provides additional thrust augmentation over 20% by comparison with the optimum single nozzle of equivalent lateral area. What is more, recent experimental acoustic tests have discovered an essential noise reduction due to Telescope nozzles application. In this paper, some additional theoretical results are presented for Telescope nozzles and a similar approach is applied for aeroperformance improvement of a supersonic inlet. In addition, a classic gas dynamics problem of a similar supersonic flow into a plate has been analyzed. In some particular cases, new exact analytical solutions are obtained for a flow into a wedge with an oblique shock wave. Numerical simulations were conducted for supersonic flow into a divergent portion of a 2D or axisymmetric nozzle with several plane or conical designs as well as into a 2D or axisymmetric supersonic inlet with a forebody. The 1st order Kryko-Godunov march- ing numerical scheme for inviscid supersonic flows was used. Several cases were tested using the NASA CFL3d code based on full Navier-Stokes equations. Numerical simulation results have confirmed essential benefits of Telescope design applications in propulsion systems.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2000-3315 , 36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference; Jul 17, 2000 - Jul 19, 2000; Huntsville, AL; United States
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    Augmentation of Stagnation Region Heat Transfer Due to Turbulence From a DLN Can Combustor (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Heat transfer measurements have been made in the stagnation region of a flat plate with a circular leading edge. Electrically heated aluminum strips placed symmetrically about the leading edge stagnation region were used to measure spanwise averaged heat transfer coefficients. The maximum Reynolds number obtained, based on leading edge diameter, was about 100,000. The model was immersed in the flow field downstream of an approximately half scale model of a can-type combustor from a low NO(x), ground based power-generating turbine. The tests were conducted with room temperature air; no fuel was added. Room air flowed into the combustor through six vane type fuel/air swirlers. The combustor can contained no dilution holes. The fuel/air swirlers all swirled the incoming airflow in a counter clockwise direction (facing downstream). A 5-hole probe flow field survey in the plane of the model stagnation point showed the flow was one big vortex with flow angles up to 36' at the outer edges of the rectangular test section. Hot wire measurements showed test section flow had very high levels of turbulence, around 28.5 percent, and had a relatively large axial-length scale-to-leading edge diameter ratio of 0.5. X-wire measurements showed the turbulence to be nearly isotropic. Stagnation heat transfer augmentation over laminar levels was around 77 percent and was about 14 percent higher than predicted by a previously developed correlation for isotropic grid generated turbulence.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210241 , E-12360 , NAS 1.15:210241 , ASME Paper 2000-GT-0215 , International Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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    Marquardt's Mach 4.5 Supercharged Ejector Ramjet (SERJ) High-Performance Aircraft Engine Project: Unfulfilled Aspirations Ca.1970 (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Supercharged Ejector Ramjet (SERJ) engine developments of the 1960s, as pursued by The Marquardt Corporation and its associated industry team members, are described. In just three years, engineering work on this combined-cycle powerplant type evolved, from its initial NASA-sponsored reusable space transportation system study status, into a U.S. Air Force/Navy-supported exploratory development program as a candidate 4.5 high-performance military aircraft engine. Bridging a productive transition from the spaceflight to the aviation arena, this case history supports the expectation that fully-integrated airbreathing/rocket propulsion systems hold high promise toward meeting the demanding propulsion requirements of tomorrow's aircraft-like Spaceliner class transportation systems. Lessons to be learned from this "SERJ Story" are offered for consideration by today's advanced space transportation and combined-cycle propulsion researchers and forward-planning communities.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2000-3109 , Joint Propulsion; Jul 16, 2000 - Jul 19, 2000; Huntsville, AL; United States
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    Longitudinal-Mode Combustion Instabilities: Modeling and Experiments (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Combustion instabilities can lead to increased development time and cost for aeroengine gas turbines. This problem has been evident in the development of very-low emissions stationary gas turbines, and will likely be encountered in the newer, more aggressive aeroengine designs. In order to minimize development time and cost, it is imperative that potential combustion dynamics issues be resolved using analyses and smaller-scale experimentation. This paper discusses a methodology through which a problem in a full-scale engine was replicated in a single-nozzle laboratory combustor. Specifically, this approach is valid for longitudinal and "bulk" mode combustion instabilities. An explanation and partial validation of the acoustic analyses that were used to achieve this replication are also included. This approach yields a testbed for the diagnosis of combustion dynamics problems and for their solution through passive and active control techniques.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210067 , E-12316 , NAS 1.15:210067 , Active Control Technology for Enhanced Performance Operational Capabilities of Military Aircraft, Land Vehicles and Sea Vehicles; May 08, 2000 - May 11, 2000; Braunschweig; Germany
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    Implementation of a Compressor Face Boundary Condition Based on Small Disturbances (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A compressor-face boundary condition that models the unsteady interactions of acoustic and convective velocity disturbances with a compressor has been implemented into a three-dimensional computational fluid dynamics code. Locally one-dimensional characteristics along with a small-disturbance model are used to compute the acoustic response as a function of the local stagger angle and the strength and direction of the disturbance. Simulations of the inviscid flow in a straight duct, a duct coupled to a compressor, and a supersonic inlet demonstrate the behavior of the boundary condition in relation to existing boundary conditions. Comparisons with experimental data show a large improvement in accuracy over existing boundary conditions in the ability to predict the reflected disturbance from the interaction of an acoustic disturbance with a compressor.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209945 , E-12193 , NAS 1.15:209945 , ASME-2000-GT-0005 , International Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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    Engine System Loads Development for the Fastrac 60K Flight Engine (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Early implementation of structural dynamics finite element analyses for calculation of design loads is considered common design practice for high volume manufacturing industries such as automotive and aeronautical industries. However, with the rarity of rocket engine development programs starts, these tools are relatively new to the design of rocket engines. In the new Fastrac engine program, the focus has been to reduce the cost to weight ratio; current structural dynamics analysis practices were tailored in order to meet both production and structural design goals. Perturbation of rocket engine design parameters resulted in a number of Fastrac load cycles necessary to characterize the impact due to mass and stiffness changes. Evolution of loads and load extraction methodologies, parametric considerations and a discussion of load path sensitivities are discussed.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 00-XXXX , 41st Structures, Structural Dynamic and Materials Conference; Apr 04, 2000 - Apr 06, 2000; Atlanta, GA; United States
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    Performance and Durability of High Temperature Foil Air Bearings for Oil-Free Turbomachinery (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The performance and durability of advanced, high temperature foil air bearings are evaluated under a wide range (10-50 kPa) of loads at temperatures from 25 to 650 C. The bearings are made from uncoated nickel based superalloy foils. The foil surface experiences sliding contact with the shaft during initial start/stop operation. To reduce friction and wear, the solid lubricant coating, PS304, is applied to the shaft by plasma spraying. PS304 is a NiCr based Cr2O3 coating with silver and barium fluoride/calcium fluoride solid lubricant additions. The results show that the bearings provide lives well in excess of 30,000 cycles under all of the conditions tested. Several bearings exhibited lives in excess of 100,000 cycles. Wear is a linear function of the bearing load. The excellent performance measured in this study suggests that these bearings and the PS304 coating are well suited for advanced high temperature, oil-free turbomachinery applications.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209187/REV1 , NAS 1.15:209187/REV1 , ARL-TR-2202 , E-11697-1/REV1 , May 07, 2000 - May 11, 2000; Nashville, TN; United States
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    Performance Optimization of a Rotor Alone Nacelle for Acoustic Fan Testing (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper describes the techniques, equipment, and results from the optimization of a two-axis traverse actuation system used to maintain concentricity between a sting-mounted fan and a wall-mounted nacelle in the 9 x 15 (9 Foot by 15 Foot Test Section) Low Speed Wind Tunnel (LSWT) at the NASA Glenn Research Center (GRC). The Rotor Alone Nacelle (RAN) system, developed at GRC by the Engineering Design and Analysis Division (EDAD) and the Acoustics Branch, used nacelle-mounted lasers and an automated control system to maintain concentricity as thermal and thrust operating loads displace the fan relative to the nacelle. This effort was critical to ensuring rig/facility safety and experimental consistency of the acoustic data from a statorless, externally supported nacelle configuration. Although the tip clearances were originally predicted to be about 0.020 in. at maximum rotor (fan) operating speed, proximity probe measurements showed that the nominal clearance was less than 0.004 in. As a result, the system was optimized through control-loop modifications, active laser cooling, data filtering and averaging, and the development of strict operational procedures. The resultant concentricity error of RAN was reduced to +/- 0.0031 in. in the Y-direction (horizontal) and +0.0035 in./-0.001 3 in. in the Z-direction (vertical), as determined by error analysis and experimental results. Based on the success of this project, the RAN system will be transitioned to other wind tunnel research programs at NASA GRC.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210599 , NAS 1.15:210599 , E-12557 , AIAA Paper 2001-0164 , Aerospace Sciences; Jan 08, 2001 - Jan 11, 2001; Reno, NV; United States
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    Optical Measurement and Visualization in High-Pressure, High-Temperature, Aviation Gas Turbine Combustors (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Planar laser-induced fluorescence (PLIF), planar Mie scattering (PMie), and linear (1-D) spontaneous Raman scattering are applied to flame tube and sector combustors that burn Jet-A fuel at a range of inlet temperatures and pressures that simulate conditions expected in future high-performance civilian gas turbine engines. Chemiluminescence arising from C2 in the flame was also imaged. Flame spectral emissions measurements were obtained using a scanning spectrometer. Several different advanced concept fuel injectors were examined. First-ever PLIF and chemiluminescence data are presented from the 60-atm Gas turbine combustor facility.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210377 , E-12431 , NAS 1.15:210377 , EOS/SPIE Symposium on Applied Photonics; May 22, 2000 - May 25, 2000; Glasgow, Scotland; United Kingdom
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    Active Combustion Control for Aircraft Gas Turbine Engines (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Lean-burning combustors are susceptible to combustion instabilities. Additionally, due to non-uniformities in the fuel-air mixing and in the combustion process, there typically exist hot areas in the combustor exit plane. These hot areas limit the operating temperature at the turbine inlet and thus constrain performance and efficiency. Finally, it is necessary to optimize the fuel-air ratio and flame temperature throughout the combustor to minimize the production of pollutants. In recent years, there has been considerable activity addressing Active Combustion Control. NASA Glenn Research Center's Active Combustion Control Technology effort aims to demonstrate active control in a realistic environment relevant to aircraft engines. Analysis and experiments are tied to aircraft gas turbine combustors. Considerable progress has been shown in demonstrating technologies for Combustion Instability Control, Pattern Factor Control, and Emissions Minimizing Control. Future plans are to advance the maturity of active combustion control technology to eventual demonstration in an engine environment.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210346 , NAS 1.15:210346 , E-12393 , AIAA Paper 2000-3500 , 36th Joint Propulsion Conference and Exhibition; Jul 17, 2000 - Jul 19, 2000; Huntsville, AL; United States
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    Tribological Limitations in Gas Turbine Engines: A Workshop to Identify the Challenges and Set Future Directions (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The following report represents a compendium of selected speaker presentation materials and observations made by Prof O. Pinkus at the NASA/ASME/Industry sponsored workshop entitled "Tribological Limitations in Gas Turbine Engines" held on September 15-17, 1999 in Albany, New York. The impetus for the workshop came from the ASME's Research Committee on Tribology whose goal is to explore new tribological research topics which may become future research opportunities. Since this subject is of current interest to other industrial and government entities the conference received cosponsorship as noted above. The conference was well attended by government, industrial and academic participants. Topics discussed included current tribological issues in gas turbines as well as the potential impact (drawbacks and advantages) of future tribological technologies especially foil air bearings and magnetic beatings. It is hoped that this workshop report may serve as a starting point for continued discussions and activities in oil-free turbomachinery systems.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210059 , E-12261 , NAS 1.15:210059 , Tribological Limitations in Gas Turbine Engines; Sep 15, 1999 - Sep 17, 1999; Albany, NY; United States
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    The NPARC Alliance Verification and Validation Archive (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NPARC Alliance (National Project for Applications oriented Research in CFD) maintains a publicly-available, web-based verification and validation archive as part of the development and support of the WIND CFD code. The verification and validation methods used for the cases attempt to follow the policies and guidelines of the ASME and AIAA. The emphasis is on air-breathing propulsion flow fields with Mach numbers ranging from low-subsonic to hypersonic.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209946 , NAS 1.15:209946 , E-12196 , ASME-2000-FED-11233 , 2000 Fluids Engineering Summer Conference; Jun 11, 2000 - Jun 15, 2000; Boston, MA; United States
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    Performance of an Active Noise Control System for Fan Tones Using Vane Actuators (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An Active Noise Control (ANC) system for ducted fan noise was built that uses actuators located in stator vanes. The custom designed actuators A,ere piezoelectric benders manufactured using THUNDER technology. The ANC system was tested in the NASA Active Noise Control Fan rig. A total of 168 actuators in 28 stator vanes were used (six per vane). Simultaneous inlet and exhaust acoustic power level reductions were demonstrated for a fan modal structure that contained two radial modes in each direction. Total circumferential mode power levels were reduced by up to 9 dB in the inlet and 3 dB in the exhaust. The corresponding total 2BPF tone level reductions were by 6 dB in the inlet and 2 dB in the exhaust. Farfield sound pressure level reductions of up to 17 dB were achieved at the peak mode lobe angle. The performance of the system was limited by the constraints of the power amplifiers and the presence of control spillover. Simpler control/actuator systems using carefully selected subsets of the full system and random simulated failures of up to 7% of the actuators were investigated. (The actuators were robust and none failed during the test). Useful reductions still occurred under these conditions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210229 , NAS 1.15:210229 , E-12348 , AIAA Paper 2000-1906 , 6th Aeroacoustics Conference and Exhibit; Jun 12, 2000 - Jun 14, 2000; Lahaina, HI; United States
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    Experimental and Numerical Investigation of Losses in Low-Pressure Turbine Blade Rows (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental data and numerical simulations of low-pressure turbines have shown that unsteady blade row interactions and separation can have a significant impact on the turbine efficiency. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that the performance of low-pressure turbine blades is a strong function of the Reynolds number. In the current investigation, experiments and simulations have been performed to study the behavior of a low-pressure turbine blade at several Reynolds numbers. Both the predicted and experimental results indicate increased cascade losses as the Reynolds number is reduced to the values associated with aircraft cruise conditions. In addition, both sets of data show that tripping the boundary layer helps reduce the losses at lower Reynolds numbers. Overall, the predicted aerodynamic and performance results exhibit fair agreement with experimental data.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209910 , AIAA Paper 2000-0737 , NAS 1.15:209910 , E-12137 , 38th Aerospace Science Meeting; Jan 10, 2000 - Jan 13, 2000; Reno, NV; United States
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    Hyper-X Engine Testing in the NASA Langley 8-Foot High Temperature Tunnel (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Airframe-integrated scramjet engine tests have been completed at Mach 7 in the NASA Langley 8-Foot High Temperature Tunnel under the Hyper-X program. These tests provided critical engine data as well as design and database verification for the Mach 7 flight tests of the Hyper-X research vehicle (X-43), which will provide the first-ever airframe-integrated scramjet flight data. The first model tested was the Hyper-X Engine Model (HXEM), and the second was the Hyper-X Flight Engine (HXFE). The HXEM, a partial-width, full-height engine that is mounted on an airframe structure to simulate the forebody features of the X-43, was tested to provide data linking flowpath development databases to the complete airframe-integrated three-dimensional flight configuration, and to isolate effects of ground testing conditions and techniques. The HXFE, an exact geometric representation of the X-43 scramjet engine mounted on an airframe structure that duplicates the entire three-dimensional propulsion flowpath from the vehicle leading edge to the vehicle base, was tested to verify the complete design as it will be flight tested. This paper presents an overview of these two tests, their importance to the Hyper-X program, and the significance of their contribution to scramjet database development.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2000-3605 , Joint Propulsion Conference; Jul 17, 2000 - Jul 19, 2000; Huntsville, AL; United States
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    Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. While numerical simulations of these flows are quite sophisticated. they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip clearance flow details (e.g. trajectory and radial extent) with corresponding data obtained from a numerical simulation. Recommendations for achieving accurate numerical simulation of tip clearance flows are presented based on this comparison. Laser Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor was simulated using a Navier-Stokes turbomachinery solver that incorporates an advanced k-epsilon turbulence model derived for flows that are not in local equilibrium. Comparison between measured and simulated results indicates that simulation accuracy is primarily dependent upon the ability of the numerical code to resolve important details of a wall-bounded shear layer formed by the relative motion between the over-tip leakage flow and the shroud wall. A simple method is presented for determining the strength of this shear layer.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210347 , E-12395 , NAS 1.15:210347 , International Gas Turbine Institute Exposition; Jul 07, 1999 - Jul 10, 1999; Indianapolis, IN; United States
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    A Probabilistic Approach to Aeropropulsion System Assessment (2000)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A probabilistic approach is described for aeropropulsion system assessment. To demonstrate this approach, the technical performance of a wave rotor-enhanced gas turbine engine (i.e. engine net thrust, specific fuel consumption, and engine weight) is assessed. The assessment accounts for the uncertainties in component efficiencies/flows and mechanical design variables, using probability distributions. The results are presented in the form of cumulative distribution functions (CDFs) and sensitivity analyses, and are compared with those from the traditional deterministic approach. The comparison shows that the probabilistic approach provides a more realistic and systematic way to assess an aeropropulsion system.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210334 , E-12036-1 , NAS 1.15:210334 , International Gas Turbine and Aeroengine Technical Congress; May 08, 2000 - May 11, 2000; Munich; Germany
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    Numerical Propulsion System Simulation (NPSS) 1999 Industry Review (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The technologies necessary to enable detailed numerical simulations of complete propulsion systems are being developed at the NASA Glenn Research Center in cooperation with industry, academia, and other government agencies. Large scale, detailed simulations will be of great value to the nation because they eliminate some of the costly testing required to develop and certify advanced propulsion systems. In addition, time and cost savings will be achieved by enabling design details to be evaluated early in the development process before a commitment is made to a specific design. This concept is called the Numerical Propulsion System Simulation (NPSS). NPSS consists of three main elements: (1) engineering models that enable multidisciplinary analysis of large subsystems and systems at various levels of detail, (2) a simulation environment that maximizes designer productivity, and (3) a cost-effective, high-performance computing platform. A fundamental requirement of the concept is that the simulations must be capable of overnight execution on easily accessible computing platforms. This will greatly facilitate the use of large-scale simulations in a design environment. This paper describes the current status of the NPSS with specific emphasis on the progress made over the past year on air breathing propulsion applications. In addition, the paper contains a summary of the feedback received from industry partners in the development effort and the actions taken over the past year to respond to that feedback. The NPSS development was supported in FY99 by the High Performance Computing and Communications Program.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209795 , E-12085 , NAS 1.15:209795 , Oct 06, 1999 - Oct 07, 1999; Cleveland, OH; United States
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    Developing Conceptual Hypersonic Airbreathing Engines Using Design of Experiments Methods (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Designing a hypersonic vehicle is a complicated process due to the multi-disciplinary synergy that is required. The greatest challenge involves propulsion-airframe integration. In the past, a two-dimensional flowpath was generated based on the engine performance required for a proposed mission. A three-dimensional CAD geometry was produced from the two-dimensional flowpath for aerodynamic analysis, structural design, and packaging. The aerodynamics, engine performance, and mass properties arc inputs to the vehicle performance tool to determine if the mission goals were met. If the mission goals were not met, then a flowpath and vehicle redesign would begin. This design process might have to be performed several times to produce a "closed" vehicle. This paper will describe an attempt to design a hypersonic cruise vehicle propulsion flowpath using a Design of' Experiments method to reduce the resources necessary to produce a conceptual design with fewer iterations of the design cycle. These methods also allow for more flexible mission analysis and incorporation of additional design constraints at any point. A design system was developed using an object-based software package that would quickly generate each flowpath in the study given the values of the geometric independent variables. These flowpath geometries were put into a hypersonic propulsion code and the engine performance was generated. The propulsion results were loaded into statistical software to produce regression equations that were combined with an aerodynamic database to optimize the flowpath at the vehicle performance level. For this example, the design process was executed twice. The first pass was a cursory look at the independent variables selected to determine which variables are the most important and to test all of the inputs to the optimization process. The second cycle is a more in-depth study with more cases and higher order equations representing the design space.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2000-2694 , Aerodynamic Measurement Technology and Ground Testing; Jun 19, 2000 - Jun 22, 2000; Denver, CO; United States
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    Numerical Zooming Between a NPSS Engine System Simulation and a One-Dimensional High Compressor Analysis Code (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Within NASA's High Performance Computing and Communication (HPCC) program, NASA Glenn Research Center is developing an environment for the analysis/design of aircraft engines called the Numerical Propulsion System Simulation (NPSS). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structures, and heat transfer along with the concept of numerical zooming between zero-dimensional to one-, two-, and three-dimensional component engine codes. In addition, the NPSS is refining the computing and communication technologies necessary to capture complex physical processes in a timely and cost-effective manner. The vision for NPSS is to create a "numerical test cell" enabling full engine simulations overnight on cost-effective computing platforms. Of the different technology areas that contribute to the development of the NPSS Environment, the subject of this paper is a discussion on numerical zooming between a NPSS engine simulation and higher fidelity representations of the engine components (fan, compressor, burner, turbines, etc.). What follows is a description of successfully zooming one-dimensional (row-by-row) high-pressure compressor analysis results back to a zero-dimensional NPSS engine simulation and a discussion of the results illustrated using an advanced data visualization tool. This type of high fidelity system-level analysis, made possible by the zooming capability of the NPSS, will greatly improve the capability of the engine system simulation and increase the level of virtual test conducted prior to committing the design to hardware.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209913 , E-12144 , NAS 1.15:209913 , Computational Aerosciences; Feb 15, 2000 - Feb 17, 2000; Moffett Field, CA; United States
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    An Overview of the NASA Aviation Safety Program Propulsion Health Monitoring Element (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NASA Aviation Safety Program (AvSP) has been initiated with aggressive goals to reduce the civil aviation accident rate, To meet these goals, several technology investment areas have been identified including a sub-element in propulsion health monitoring (PHM). Specific AvSP PHM objectives are to develop and validate propulsion system health monitoring technologies designed to prevent engine malfunctions from occurring in flight, and to mitigate detrimental effects in the event an in-flight malfunction does occur. A review of available propulsion system safety information was conducted to help prioritize PHM areas to focus on under the AvSP. It is noted that when a propulsion malfunction is involved in an aviation accident or incident, it is often a contributing factor rather than the sole cause for the event. Challenging aspects of the development and implementation of PHM technology such as cost, weight, robustness, and reliability are discussed. Specific technology plans are overviewed including vibration diagnostics, model-based controls and diagnostics, advanced instrumentation, and general aviation propulsion system health monitoring technology. Propulsion system health monitoring, in addition to engine design, inspection, maintenance, and pilot training and awareness, is intrinsic to enhancing aviation propulsion system safety.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210348 , E-12396 , NAS 1.15:210348 , ARL-TR-2272 , AIAA Paper 2000-3624 , Joint Propulsion; Jul 16, 2000 - Jul 19, 2000; Huntsville, AL; United States
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    Mixing of an Airblast-atomized Fuel Spray Injected into a Crossflow of Air (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The injection of a spray of fuel droplets into a crossflow of air provides a means of rapidly mixing liquid fuel and air for combustion applications. Injecting the liquid as a spray reduces the mixing length needed to accommodate liquid breakup, while the transverse injection of the spray into the air stream takes advantage of the dynamic mixing induced by the jet-crossflow interaction. The structure of the spray, formed from a model plain-jet airblast atomizer, is investigated in order to determine and understand the factors leading to its dispersion. To attain this goal, the problem is divided into the following tasks which involve: (1) developing planar imaging techniques that visualize fuel and air distributions in the spray, (2) characterizing the airblast spray without a crossflow, and (3) characterizing the airblast spray upon injection into a crossflow. Geometric and operating conditions are varied in order to affect the atomization, penetration, and dispersion of the spray into the crossflow. The airblast spray is first characterized, using imaging techniques, as it issues into a quiescent environment. The spray breakup modes are classified in a liquid Reynolds number versus airblast Weber number regime chart. This work focuses on sprays formed by the "prompt" atomization mode, which induces a well-atomized and well-dispersed spray, and which also produces a two-lobed liquid distribution corresponding to the atomizing air passageways in the injector. The characterization of the spray jet injected into the crossflow reveals the different processes that control its dispersion. Correlations that describe the inner and outer boundaries of the spray jet are developed, using the definition of a two-phase momentum-flux ratio. Cross-sections of the liquid spray depict elliptically-shaped distributions, with the exception of the finely-atomized sprays which show kidney-shaped distributions reminiscent of those obtained in gaseous jet in crossflow systems. A droplet trajectory analysis overpredicts the liquid mass penetration, and indicates a need for a more rigorous model to account for the three-dimensional mixing field induced by the jet-crossflow interaction. Nonetheless, the general procedures and criteria that are outlined can be used to efficiently assess and compare the quality of sprays formed under different conditions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-210467 , E-12463 , NAS 1.26:210467 , UCI-ARTR-00-05
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    Multi-Disciplinary Design Optimization Using WAVE (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The current preliminary design tools lack the product performance, quality and cost prediction fidelity required to design Six Sigma products. They are also frequently incompatible with the tools used in detailed design, leading to a great deal of rework and lost or discarded data in the transition from preliminary to detailed design. Thus, enhanced preliminary design tools are needed in order to produce adequate financial returns to the business. To achieve this goal, GEAE has focused on building the preliminary design system around the same geometric 3D solid model that will be used in detailed design. With this approach, the preliminary designer will no longer convert a flowpath sketch into an engine cross section but rather, automatically create 3D solid geometry for structural integrity, life, weight, cost, complexity, producibility, and maintainability assessments. Likewise, both the preliminary design and the detailed design can benefit from the use of the same preliminary part sizing routines. The design analysis tools will also be integrated with the 3D solid model to eliminate manual transfer of data between programs. GEAE has aggressively pursued the computerized control of engineering knowledge for many years. Through its study and validation of 3D CAD programs and processes, GEAE concluded that total system control was not feasible at that time. Prior CAD tools focused exclusively on detail part geometry and Knowledge Based Engineering systems concentrated on rules input and data output. A system was needed to bridge the gap between the two to capture the total system. With the introduction of WAVE Engineering from UGS, the possibilities of an engineering system control device began to formulate. GEAE decided to investigate the new WAVE functionality to accomplish this task. NASA joined GEAE in funding this validation project through Task Order No. 1. With the validation project complete, the second phase under Task Order No. 2 was established to develop an associative control structure (framework) in the UG WAVE environment enabling multi-disciplinary design of turbine propulsion systems. The capabilities of WAVE were evaluated to assess its use as a rapid optimization and productivity tool. This project also identified future WAVE product enhancements that will make the tool still more beneficial for product development.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-210218 , E-12337 , NAS 1.26:210218
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    Numerical Simulation of Dual-Mode Scramjet Combustors (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Results of a numerical investigation of a three-dimensional dual-mode scramjet isolator-combustor flow-field are presented. Specifically, the effect of wall cooling on upstream interaction and flow-structure is examined for a case assuming jet-to-jet symmetry within the combustor. Comparisons are made with available experimental wall pressures. The full half-duct for the isolator-combustor is then modeled in order to study the influence of side-walls. Large scale three-dimensionality is observed in the flow with massive separation forward on the side-walls of the duct. A brief review of convergence-acceleration techniques useful in dual-mode simulations is presented, followed by recommendations regarding the development of a reliable and unambiguous experimental data base for guiding CFD code assessments in this area.
    Keywords: Aircraft Propulsion and Power
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    Full 3D Analysis of the GE90 Turbofan Primary Flowpath (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The multistage simulations of the GE90 turbofan primary flowpath components have been performed. The multistage CFD code, APNASA, has been used to analyze the fan, fan OGV and booster, the 10-stage high-pressure compressor and the entire turbine system of the GE90 turbofan engine. The code has two levels of parallel, and for the 18 blade row full turbine simulation has 87.3 percent parallel efficiency with 121 processors on an SGI ORIGIN. Grid generation is accomplished with the multistage Average Passage Grid Generator, APG. Results for each component are shown which compare favorably with test data.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-209951 , E-12205 , NAS 1.26:209951
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    Effect of Film-Hole Shape on Turbine Blade Film Cooling Performance (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The detailed heat transfer coefficient and film cooling effectiveness distributions as well as tile detailed coolant jet temperature profiles on the suction side of a gas turbine blade A,ere measured using a transient liquid crystal image method and a traversing cold wire and a traversing thermocouple probe, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. The hole geometries studied include standard cylindrical holes and holes with diffuser shaped exit portion (i.e. fanshaped holes and laidback fanshaped holes). Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 or 0.1. Coolant blowing ratio was varied from 0.4 to 1.2. Results show that both expanded holes have significantly improved thermal protection over the surface downstream of the ejection location, particularly at high blowing ratios. However, the expanded hole injections induce earlier boundary layer transition to turbulence and enhance heat transfer coefficients at the latter part of the blade suction surface. In general, the unsteady wake tends to reduce film cooling effectiveness.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-209932 , E-12176 , NAS 1.26:209932
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    Unsteady High Turbulence Effects on Turbine Blade Film Cooling Heat Transfer Performance Using a Transient Liquid Crystal Technique (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Unsteady wake effect, with and without trailing edge ejection, on detailed heat transfer coefficient and film cooling effectiveness distributions is presented for a downstream film-cooled gas turbine blade. Tests were performed on a five-blade linear cascade at an exit Reynolds number of 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.4 to 1.2; air and CO2 were used as coolants to simulate different density ratios. Surface heat transfer and film effectiveness distributions were obtained using a transient liquid crystal technique; coolant temperature profiles were determined with a cold wire technique. Results show that Nusselt numbers for a film cooled blade are much higher compared to a blade without film injection. Unsteady wake slightly enhances Nusselt numbers but significantly reduces film effectiveness versus no wake cases. Nusselt numbers increase only slic,htly but film cooling, effectiveness increases significantly with increasing, blowing ratio. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher 0 effectiveness at lower blowing ratios (M = 0.8). Trailing edge ejection generally has more effect on film effectiveness than on the heat transfer, typically reducing film effectiveness and enhancing heat transfer. Similar data is also presented for a film cooled cylindrical leading edge model.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-209929 , E-12173 , NAS 1.26:209929
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    Unsteady Analysis of Inlet-Compressor Acoustic Interactions Using Coupled 3-D and 1-D CFD Codes (2000)
    In:  CASI
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    Publication Date: 2019-07-10
    Description: It is well known that the dynamic response of a mixed compression supersonic inlet is very sensitive to the boundary condition imposed at the subsonic exit (engine face) of the inlet. In previous work, a 3-D computational fluid dynamics (CFD) inlet code (NPARC) was coupled at the engine face to a 3-D turbomachinery code (ADPAC) simulating an isolated rotor and the coupled simulation used to study the unsteady response of the inlet. The main problem with this approach is that the high fidelity turbomachinery simulation becomes prohibitively expensive as more stages are included in the simulation. In this paper, an alternative approach is explored, wherein the inlet code is coupled to a lesser fidelity 1-D transient compressor code (DYNTECC) which simulates the whole compressor. The specific application chosen for this evaluation is the collapsing bump experiment performed at the University of Cincinnati, wherein reflections of a large-amplitude acoustic pulse from a compressor were measured. The metrics for comparison are the pulse strength (time integral of the pulse amplitude) and wave form (shape). When the compressor is modeled by stage characteristics the computed strength is about ten percent greater than that for the experiment, but the wave shapes are in poor agreement. An alternate approach that uses a fixed rise in duct total pressure and temperature (so-called 'lossy' duct) to simulate a compressor gives good pulse shapes but the strength is about 30 percent low.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-210247 , E-12367 , NAS 1.15:210247
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    Undulated Nozzle for Enhanced Exit Area Mixing (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A nozzle having an undulating surface for enhancing the mixing of a primary flow with a secondary flow or ambient air, without requiring an ejector. The nozzle includes a nozzle structure and design for introducing counter-rotating vorticity into the primary flow either through (i) internal surface corrugations where an axisymmetric line through each corrugation is coincident with an axisymmetric line through the center of the flow passageway or (ii) through one or more sets of alternating convexities and cavities in the internal surface of the nozzle where an axisymmetric line through each convexity and cavity is coincident with an axisymmetric line through the center of the flow passageway, and where the convexities contract from the entrance end towards the exit end. Exit area mixing is also enhanced by one or more chevrons attached to the exit edge of the nozzle. The nozzle is ideally suited for application as a jet engine nozzle. When used as a jet engine nozzle, noise suppression with simultaneous thrust augmentation/minimal thrust loss is achieved.
    Keywords: Aircraft Propulsion and Power
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    Effect of Jet Injection Angle and Number of Jets on Mixing and Emissions From a Reacting Crossflow at Atmospheric Pressure (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The mixing of air jets into hot, fuel-rich products of a gas turbine primary zone is an important step in staged combustion. Often referred to as "quick quench," the mixing occurs with chemical conversion and substantial heat release. An experiment has been designed to simulate and study this process, and the effect of varying the entry angle (0 deg, 22.5 deg and 45 deg from normal) and number of the air jets (7, 9, and 11) into the main flow, while holding the jet-to-crossflow mass-low ratio, MR, and momentum-flux ratio, J, constant (MR = 2.5;J = 25). The geometry is a crossflow confined in a cylindrical duct with side-wall injection of jets issuing from orifices equally spaced around the perimeter. A specially designed reactor, operating on propane, presents a uniform mixture to a module containing air jet injection tubes that can be changed to vary orifice geometry. Species concentrations of O2, CO, CO2, NO(x) and HC were obtained one duct diameter upstream (in the rich zone), and primarily one duct radius downstream. From this information, penetration of the jet, the spatial extent of chemical reaction, mixing, and the optimum jet injection angle and number of jets can be deduced.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-209949 , E-12202 , NAS 1.26:209949
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    On Flowfield Periodicity in the NASA Transonic Flutter Cascade (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, sidewall interference was minimized and excellent periodicity was obtained.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2000-209933/PT1 , NAS 1.15:209933/PT1 , E-12177/PT1
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    Fuel Plume Image Mixing Analysis Formulation With Proper Treatment of Non-Constant Velocity Flowfields (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A previously developed technique allows an estimate of integral mixing to be obtained from an image of laser scattered light from particle seeded fuel in the hypervelocity flow through a scramjet combustor. This previous mixing analysis formulation contains an assumption of a constant velocity flowfield across the plane of the fuel plume image. For high-speed scramjet combustors, the velocity flowfield is quite uniform and an assumption of constant velocity works well. Applying this same mixing analysis technique to fuel plume images obtained from a mid-speed scramjet combustor makes it desirable to remove the constant velocity assumption. This is due to the non-uniform velocity flowfields present in mid-speed scramjet combustors. A new formulation of the mixing analysis methodology is developed and presented so that the technique can be applied to a mid-speed scramjet combustor without the need to assume a constant velocity flowfield.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-209868 , NAS 1.26:209868
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    Mixing and NOx Emission Calculations of Confined Reacting Jet Flows in Cylindrical and Annular Ducts (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Rapid mixing of cold lateral jets with hot cross-stream flows in confined configurations is of practical interest in gas turbine combustors as it strongly affects combustor exit temperature quality, and gaseous emissions in for example rich-lean combustion. It is therefore important to further improve our fundamental understanding of the important processes of dilution jet mixing especially when the injected jet mass flow rate exceeds that of the cross-stream. The results reported in this report describe some of the main flow characteristics which develop in the mixing process in a cylindrical duct. A three-dimensional computational fluid dynamics (CFD) code has been used to predict the mixing flow field characteristics and NOx emission in a quench section of a rich-burn/quick-mix/lean-burn (RQL) combustor. Sixty configurations have been analyzed in both circular and annular geometries in a fully reacting environment simulating the operating condition of an actual RQL gas turbine combustion liner. The evaluation matrix was constructed by varying the number of orifices per row and orifice shape. Other parameters such as J (momentum-flux ratio), MR (mass flowrate ratio), DR (density ratio), and mixer sector orifice ACd (effective orifice area) were maintained constant throughout the entire study. The results indicate that the mixing flow field can be correlated with the NOx production if they are referenced with the stoichiometric equivalence ratio value and not the equilibrium value. The mixing flowfields in both circular and annular mixers are different. The penetration of equal jets in both annular and circular geometries is vastly different which significantly affects the performance of the mixing section. In the computational results with the circular mixer, most of the NOx formation occurred behind the orifice starting at the orifice wake region. General trends have been observed in the NOx production as the number of orifices is changed and this appears to be common for all hole configurations and mixer types (circular or annular). The performance of any orifice shape (in producing minimum NOx) appears to be acceptable if the number of orifices can be freely varied in order to attain the optimum jet penetration.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-210672 , E-12579 , NAS 1.26:210672
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    Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Hypersonic Airbreathing Engines (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The prospects for realizing a magnetohydrodynamic (MHD) bypass hypersonic airbreathing engine are examined from the standpoint of fundamental thermodynamic feasibility. The MHD-bypass engine, first proposed as part of the Russian AJAX vehicle concept, is based on the idea of redistributing energy between various stages of the propulsion system flow train. The system uses an MHD generator to extract a portion of the aerodynamic heating energy from the inlet and an MHD accelerator to reintroduce this power as kinetic energy in the exhaust stream. In this way, the combustor entrance Mach number can be limited to a specified value even as the flight Mach number increases. Thus, the fuel and air can be efficiently mixed and burned within a practical combustor length, and the flight Mach number operating envelope can be extended. In this paper, we quantitatively assess the performance potential and scientific feasibility of MHD-bypass engines using a simplified thermodynamic analysis. This cycle analysis, based on a thermally and calorically perfect gas, incorporates a coupled MHD generator-accelerator system and accounts for aerodynamic losses and thermodynamic process efficiencies in the various engin components. It is found that the flight Mach number range can be significantly extended; however, overall performance is hampered by non-isentropic losses in the MHD devices.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TP-2000-210387 , M-986 , NAS 1.60:210387
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    Advanced Propulsion System Studies in High Speed Research (2000)
    In:  CASI
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    Publication Date: 2019-07-10
    Description: Propulsion for acceptable supersonic passenger transport aircraft is primarily impacted by the very high jet noise characteristics of otherwise attractive engines. The mixed flow turbofan, when equipped with a special ejector nozzle seems to be the best candidate engine for this task of combining low jet noise with acceptable flight performance. Design, performance, and operation aspects of mixed flow turbofans are discussed. If the special silencing nozzle is too large, too heavy, or not as effective as expected, alternative concepts in mixed flow engines should be examined. Presented herein is a brief summary of efforts performed under cooperative agreement NCC3-193. Three alternative engine concepts, conceived during this study effort, are herein presented and their limitations and potentials are described. These three concepts intentionally avoid the use of special silencing nozzles and achieve low jet noise by airflow augmentation of the engine cycle.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2000-210035 , E-12233 , NAS 1.26:210035
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    The Archaeology of Geological Catastrophes (2000)
    London : The Geological Society
    Details
    Keywords: Geoarchäologie ; Naturkatastrophe ; Archaeological geology ; Archaeology ; Archaeology and natural disasters ; Archäologie ; Archéologie et catastrophes naturelles ; Catastrophes (Geology) ; Catastrophes naturelles ; Earthquakes ; Effect of environment on ; Geschichte ; History ; Human beings ; Methodology ; Tremblements de terre ; Volcanoes ; Volcans
    Description / Table of Contents: Preface / Iain Stewart / Geological Society, London, Special Publications, 171, vii-ix, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.01 --- Creation and destruction of travertine monumental stone by earthquake faulting at Hierapolis, Turkey / P. L. Hancock, R. M. L. Chalmers, E. Altunel, Z. Çakir and A. Becher-Hancock / Geological Society, London, Special Publications, 171, 1-14, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.02 --- Uses of volcanic products in antiquity / D. R. Griffiths / Geological Society, London, Special Publications, 171, 15-23, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.03 --- The advent of archaeoseismology in the Mediterranean / R. E. Jones and S. C. Stiros / Geological Society, London, Special Publications, 171, 25-32, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.04 --- A critical reappraisal of the classical texts and archaeological evidence for earthquakes in the Atalanti region, central mainland Greece / Victoria Buck and Iain Stewart / Geological Society, London, Special Publications, 171, 33-44, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.05 --- Aims and methods in territorial archaeology: possible clues to a strong fourth-century AD earthquake in the Straits of Messina (southern Italy) / Emanuela Guidoboni, Anna Muggia and Gianluca Valensise / Geological Society, London, Special Publications, 171, 45-70, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.06 --- Santorini (Greece) before the Minoan eruption: a reconstruction of the ring-island, natural resources and clay deposits from the Akrotiri excavation / Walter L. Friedrich, Marit-Solveig Seidenkrantz and Ole Bjørslev Nielsen / Geological Society, London, Special Publications, 171, 71-80, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.07 --- The eruption of the Santorini volcano and its effects on Minoan Crete / Jan Driessen and Colin F. MacDonald / Geological Society, London, Special Publications, 171, 81-93, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.08 --- Late Minoan IB marine ware, the marine environment of the Aegean, and the Bronze Age eruption of the Thera volcano / Peter Bicknell / Geological Society, London, Special Publications, 171, 95-103, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.09 --- Ground-penetrating radar mapping of Minoan volcanic deposits and the Late Bronze Age palaeotopography, Thera, Greece / James K. Russell and Mark V. Stasiuk / Geological Society, London, Special Publications, 171, 105-121, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.10 --- Precursory phenomena and destructive events related to the Late Bronze Age Minoan (Thera, Greece) and AD 79 (Vesuvius, Italy) Plinian eruptions; inferences from the stratigraphy in the archaeological areas / Raffaello Cioni, Lucia Gurioli, Alessandro Sbrana and Georges Vougioukalakis / Geological Society, London, Special Publications, 171, 123-141, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.11 --- A geographical information system for the archaeological area of Pompeii / M. T. Pareschi, G. Stefani, A. Varone, L. Cavarra, F. Giannini and A. Meriggi / Geological Society, London, Special Publications, 171, 143-158, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.12 --- Apulian Bronze Age pottery as a long-distance indicator of the Avellino Pumice eruption (Vesuvius, Italy) / Raffaello Cioni, Sara Levi and Roberto Sulpizio / Geological Society, London, Special Publications, 171, 159-177, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.13 --- Human response to Etna volcano during the classical period / D. K. Chester, A. M. Duncan, J. E. Guest, P. A. Johnston and J. J. L. Smolenaars / Geological Society, London, Special Publications, 171, 179-188, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.14 --- The Johnston-Lavis collection: a unique record of Italian volcanism / W. L. Kirk, R. Siddall and S. Stead / Geological Society, London, Special Publications, 171, 189-194, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.15 --- The archaeology of a Plinian eruption of the Popocatépetl volcano / Patricia Plunket and Gabriela Uruñuela / Geological Society, London, Special Publications, 171, 195-203, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.16 --- Timing of the prehistoric eruption of Xitle Volcano and the abandonment of Cuicuilco Pyramid, Southern Basin of Mexico / Silvia Gonzalez, Alejandro Pastrana, Claus Siebe and Geoff Duller / Geological Society, London, Special Publications, 171, 205-224, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.17 --- Volcanic disasters and cultural discontinuities in Holocene time, in West New Britain, Papua New Guinea / Robin Torrence, Christina Pavlides, Peter Jackson and John Webb / Geological Society, London, Special Publications, 171, 225-244, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.18 --- Tephrochronology of the Brooks River Archaeological District, Katmai National Park and Preserve, Alaska: what can and cannot be done with tephra deposits / James R. Riehle, Don. E. Dumond, Charles E. Meyer and Jeanne M. Schaaf / Geological Society, London, Special Publications, 171, 245-266, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.19 --- Endemic stress, farming communities and the influence of Icelandic volcanic eruptions in the Scottish Highlands / R. A. Dodgshon, D. D. Gilbertson and J. P. Grattan / Geological Society, London, Special Publications, 171, 267-280, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.20 --- Comparison and cross-checking of historical, archaeological and geological evidence for the location and type of historical and sub-historical eruptions of multiple-vent oceanic island volcanoes / S. J. Day, J. C. Carracedo, H. Guillou, F. J. Pais Pais, E. Rodriguez Badiola, J. F. B. D. Fonseca and S. I. N. Heleno / Geological Society, London, Special Publications, 171, 281-306, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.21 --- ‘A fire spitting volcano in our dear Germany’: documentary evidence for a low-intensity volcanic eruption of the Gleichberg in 1783? / J. P. Grattan, D. D. Gilbertson and A. Dill / Geological Society, London, Special Publications, 171, 307-315, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.22 --- Volcanic soils: their nature and significance for archaeology / Peter James, David Chester and Angus Duncan / Geological Society, London, Special Publications, 171, 317-338, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.23 --- The use of volcaniclastic material in Roman hydraulic concretes: a brief review / Ruth Siddall / Geological Society, London, Special Publications, 171, 339-344, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.24 --- Olmec stone sculpture: selection criteria for basalt / Patrick Hunt / Geological Society, London, Special Publications, 171, 345-353, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.25 --- Seismic and volcanic hazards affecting the vulnerability of the Sana’a area of Yemen / Richard Hughes and Adrian Collings / Geological Society, London, Special Publications, 171, 355-372, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.26 --- Archaeological, geomorphological and geological evidence for a major earthquake at Sagalassos (SW Turkey) around the middle of the seventh century AD / Marc Waelkens, Manuel Sintubin, Philippe Muchez and Etienne Paulissen / Geological Society, London, Special Publications, 171, 373-383, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.27 --- Fault pattern of Nisyros Island volcano (Aegean Sea, Greece): structural, coastal and archaeological evidence / Stathis C. Stiros / Geological Society, London, Special Publications, 171, 385-397, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.28 --- The geological origins of the oracle at Delphi, Greece / J. Z. De Boer and J. R. Hale / Geological Society, London, Special Publications, 171, 399-412, 1 January 2000, https://doi.org/10.1144/GSL.SP.2000.171.01.29
    Pages: Online-Ressource (IX, 412 Seiten) , Illustrationen, Diagramme, Karten
    ISBN: 1862390622
    URL: http://sp.lyellcollection.org/content/171/1
    Language: English
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    Bleaching of corals on the Great Barrier Reef: differential susceptibilities among taxa (2000)
    Springer
    Coral reefs 19 (2000), S. 155-163 
    Details
    ISSN: 1432-0975
    Keywords: Key Words Acclimatization ; Coral reef ; Disturbance ; History ; Mortality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Large-scale coral bleaching episodes are potentially major disturbances to coral reef systems, yet a definitive picture of variation in assemblage response and species susceptibilities is still being compiled. Here, we provide a detailed analysis of the bleaching response of 4160 coral colonies, representing 45 genera and 15 families, from two depths at four sites on reefs fringing inshore islands on the Great Barrier Reef. Six weeks after the onset of large-scale bleaching in 1998, between 11 and 83% of colonies along replicate transects were affected by bleaching, and mortality was 1 to 16%. There were significant differences in bleaching response between sites, depths and taxa. Cyphastrea, Turbinaria and Galaxea were relatively unaffected by bleaching, while most acroporids and pocilloporids were highly susceptible. The hydrocorals (Millepora spp.) were the most susceptible taxa, with 85% mortality. Spatial variation in assemblage response was linked to the taxonomic composition of reef sites and their bleaching history. We suggest, therefore, that much of the spatial variation in bleaching response was due to assemblage composition and thermal acclimation.
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    The discovery, scope, and puzzle of desiccation tolerance in plants (2000)
    Springer
    Plant ecology 151 (2000), S. 5-17 
    Details
    ISSN: 1573-5052
    Keywords: Angiosperm ; Biogeography ; Bryophyte ; Desiccation tolerance ; Growth form ; Habitat ; History
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The modern scientific study of desiccation tolerance began in 1702 when Anthony von Leeuwenhoek discovered that rotifers could survive without water for months. By 1860, the controversy over whether organisms could dry up without dying had reached such a pitch that a special French commission was convened to adjudicate the dispute. In 2000, we know that a few groups of animals and a wide variety of plants can tolerate desiccation in the active, adult stages of their life cycles. Among plants, this includes many lichens and bryophytes, a few ferns, and a very few flowering plants, but no gymnosperms nor trees. Some desiccation-tolerant species can survive without water for over ten years, recover from desiccation to unmeasurably low water potentials, and, when plants are desiccated, endure temperature extremes from −272 to 100 °C. Desiccation-tolerant plants occur on all continents but mainly in xeric habitats or microhabitats where the cover of desiccation-sensitive species is low. Two main puzzles arise from these patterns: What are the mechanisms by which plants tolerate desiccation? and Why are desiccation-tolerant plants not more ecologically widespread? Recent molecular and biochemical studies suggest that there are multiple mechanisms of tolerance, many of which involve protection from oxidants and from the loss of configuration of macromolecules during dehydration. Hypotheses to explain the restricted ecological range of desiccation-tolerance plants include inability to maintain a cumulative positive carbon balance during repeated cycles of wetting and drying and inherent trade offs between desiccation tolerance and growth rate.
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    Indicator Dilution Methods for Measuring Blood Flow, Volume, and Other Properties of Biological Systems: A Brief History and Memoir (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 836-848 
    Details
    ISSN: 1573-9686
    Keywords: Indicator-dilution ; Tracer-dilution ; Blood flow ; Blood volume ; Distribution volume ; History ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract In 1824 Hering introduced an indicator-dilution method for measuring blood velocity. Not until 1897 was the method extended by Stewart to measure blood (volume) flow. For more than two decades, beginning in 1928, Hamilton and colleagues measured blood flow, including cardiac output. They proposed that the first-passsage indicator concentration-time curve could be recovered from observed curves that included recirculation by semilogarithmic extrapolation of the early downslope. Others followed with attempts to fit the complete first-passage curve by various forms, such as by the sum of three exponential terms (three well-stirred compartments in series). Stephenson (1948) thought of looking at indicator-dilution curves as convolutions of indicator input with a probability density function of traversal times through the system. Meier and I reached a similar conclusion, and extended it. The fundamental notion is that there exists a probability density function of transit times, h(t), through the system. We proved that mean transit time t=V/F, where V is volume in which the indicator is distributed. Thus, V, F, and t might all be calculated, or t alone might suffice if one wanted only to know relative blood flow. I extended the analysis to include residue detection of indicator remaining in the system, so that V, F, and t could be calculated by external monitoring. Chinard demonstrated the value of simultaneous multiple indicator-dilution curves with various volumes of distribution. Goresky extended the technique to study cell uptake and metabolism. He also found a transform of indicator-dilution output curves (equivalent to multiplying the ordinate by t and dividing the time by t) which made congruent the family of unalike curves obtained by simultaneous injection of indicators with different volumes of distribution. Bassingthwaighte showed the same congruency with the transform of outputs of a single indicator introduced into a system with experimentally varied blood flows. We showed the same congruency for the pulmonary circulation, adding a correction for delays. Success of these transforms suggests that the architecture of the vascular network is a major determinant of the shape of density functions of transit times through the system, and that there is in this architecture, a high degree of self-similarity, implying that the fractal power function is a component in shaping the observed density of transit times. I proposed that the distribution of capillary critical opening pressures, which describes recruitment of vascular paths, may be important in shaping indicator-dilution curves, and that h(t) may be derived from flow-pressure and volume-pressure curves under some circumstances. © 2000 Biomedical Engineering Society.PAC00: 8719Uv, 0630Bp
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    URL: http://dx.doi.org/10.1114/1.1308496
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    Potassium pyroantimonate and osmium-zinc iodide reactivity in the tubular epithelium of the opisthonephric kidney of the sea lamprey, Petromyzon marinus L (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 119-133 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Pyroantimonate precipitate indicates that the epithelium of the proximal tubule is the only segment of the tubular nephron of the fresh water lamprey where large accumlations of cations are distributed. Unusually large amounts of reaction product are located within the lateral intercellular spaces and within vesicles closely associated with the plasma membrane at the lateral and basal surfaces. This technique suggests the continuity of these vesicles with the plasma membrane and alludes to the possibility of an endomembranous system of vesicles and the intercellular spaces as vehicles for ion transport. Lateral intercellular spaces of proximal tubules of lower vertebrates may play a different role in kidney function that their counterparts in higher vertebrates.Osmium-zinc iodide has a specificity for certain cells within the proximal, intermediate, and distal segments, but no structural differences are noted when these cells are compared to unstained cells. Smooth endoplasmic reticulum remains unstained in the distal segment but the stain has a strong affinity for elements of the Golgi apparatus, lysosomes, and the nuclear envelope of all cell types. This technique does not suggest a structural or functional similarity between cells of the distal segment and the chloride cells of the gills of teleosts.
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    The forebrain and midbrain of some squamates and their bearing on the origin of snakes (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 135-151 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Anatomical analysis of the forebrain and midbrain of Anelytropsis, Dibamus and feyliniids reveals structural similarities with those of skinks and snakes. Skinks and feyliniids are probably derived from a common ancestral stock. This is suggested by mutual reduction of several telencephalic nuclei, by similar trends in the development of the dorsal thalamus, and by similarities in the lamination of their optic tecta. Anelytropsis, Dibamus, feyliniids and snakes show interdigitation of the periventricular gray zones of the optic tectum and enlargement of lamina 7 of the posterior colliculus. Of these three taxa, Dibamus is most similar to burrowing snakes and many of its brain characters are intermediate between skinks and burrowing snakes. These similarities may suggest common ancestry between Dibamus and snakes rather than parallelism.
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    URL: http://dx.doi.org/10.1002/jmor.1051400202
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    Stereotaxic map of the muscle fibers in the indirect flight muscles of Drosophila melanogaster (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 153-158 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: It is possible to monitor the electrical activity of the motor neurons of Drosophila by recording the electrical activity of the muscle fibers. We have found that it is possible to specify the location of the subcuticular terminations and to describe the orientation within the thorax for the individual muscle fibers, because of the large size of the fibers and because the surface anatomy of Drosophila is known in detail. A map has been made to indicate the location of the muscle fibers with respect to superficial landmarks. The importance of the stereotaxic map for physiological studies is discussed.
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    Functional anatomy of pulmonary ventilation in the garter snake, Thamnophis elegansPortions of this paper were presented at the June, 1972 meeting of the Amer. Soc. of Ichthyologists and Herpetologists. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 171-184 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The functional anatomy of pulmonary ventilation in Thamnophis elegans was studied by electromyography. Flow of air into and out of the lungs follows a triphasic pattern and occurs while the glottis is held open by a dilator muscle. Non-ventilatory rest periods characterized by a closed glottis and lack of ventilatory movements occur between breaths. Exhalation is caused by contraction of a pair of dorsolateral sheets of muscle that extends from the ventral surface of the vertebral column to the medial surfaces of the ribs and a pair of ventro-lateral sheets that extends from the medial surfaces of the ribs to the mid-ventral skin. Inspiration is powered by contraction of a series of rib levators and retractors. The last phase of the ventilatory cycle is a passive expiration that may be caused by elastic recoil of the walls of the filled lungs and relaxation of muscles used during inspiration. The site of respiratory pumping is shifted craniad after large prey items have been completely ingested. The significance of this shift and its anatomical basis are considered.
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    Some structural and cytochemical observations on the axial filament complex of lung-fluke spermatozoa (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 185-195 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: As seen in transverse section, doublet elements of the axial unit of spermatozoa of Haematolocchus medioplexus, a frog lung-fluke, possess walls made up of protofibrillar subunits 50-60 Å in diameter. The partition between A and B members of a doublet element often show extra protofibrils which may partially occlude the “lumen” of the A tubule. Each A tubule possesses outer and inner lateral arms which repeat at longitudinal intervals of about 215 Å and which appear to be structurally dissimilar; the outer arm is expanded at its free end and the inner arm often connects to the B tubule of the adjacent doublet element. Regularly-spaced radial links connect the central sheath of an inner core complex to the A tubules of the peripheral doublet elements. Tests for magnesium-activated ATPase activity provide evidence that the enzyme is associated with the surfaces of doublet elements and the surface of the central sheath. Finally, study of an axial unit which developed in an abnormal manner suggests that normal differentiation of an axial unit may depend on the elaboration of a core complex and radial links.
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    Ultrastructure of the spermatozoon of the earthworm as revealed by negative staining (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 197-213 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This is the first demonstration of an apparent acrosome reaction by the use of negative staining (phosphotungstic acid) and electron microscopy. It is also the first report of such a reaction in spermatozoa of an oligochaete annelid (Lumbricus terrestris). The morphology of the negatively stained unreacted acrosomal complexes is entirely comparable to that seen in sectioned material. After reaction, a short straight filament is extruded and the compartmentalization seen in unreacted spermatozoa is no longer visible. In the flagellar axoneme there are short cross-bridges linking the two central singlet microtubules at 150-170 Å intervals. Two fibrous elements are also present, forming, with the singlets, a tetragon. All four of these structures apparently change their elastic properties after incubation in distilled water for two hours, so that instead of following the doublet microtubules in gentle coils, the central complex components fall as a unit in jagged configurations.
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    The role of cell death during morphogenesis of the mammalian eye (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 159-170 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Serial sections of embryonic rat eyes were stained with hematoxylin and eosin, quantified (by counting pycnotic and viable nuclei), reproduced by camera lucida on wax plates, and moulded into reconstructions in order to study the normal progression of cellular death during morphogenesis. At least nine distinct necrotic loci (A through I) can be distinguished. Immediately following contact between the retina and surface ectoderm (day 11) degenerating cells were observed in (A) the ventral extent of the optic vesicle, beginning in the mid-retinal primordium and continuing ventrally in the optic stalk, (B) in the rostral optic stalk base, and (C) in the surface ectoderm encircling the early lens placode. No degeneration was observed in the dorsal half of the presumptive retina, in the entire pigment epithelium, or in the lens placode proper. During day 11.5 the lens placode thickens and forms a degenerating locus (D) in its ventral portion opposite the underlying pycnotic zone in the retina (A). During day 12 the ventral pycnotic zone (A) divides into two subunits (A1 and A2). Invagination of the lens displaces its marginal and ventral components (C and D) so that they come to occupy the lens pore area and presumptive corneal epithelium. Simultaneous invagination of the retinal rudiment juxtaposes the pigment epithelium which concurrently forms a necrotic area (E) adjacent ventrally to that in the retina (A1). Degeneration appears in the caudal optic stalk (I). The density of viable cells decreases adjacent to pycnotic areas in the retina and pigment epithelium and increases within these death centers. During day 13 the optic fissure forms within the subunits of the ventral pycnotic zone (A1 and A2). Degenerations are seen in the dorsal optic stalk (F) and in the walls of the optic fissure (G and H). Throughout these stages necrosis appears only in those portions of the eye rudiment where invagination is either retarded or completely absent.In part, these observations suggest that cell death serves (1) to retard or inhibit invagination within death centers, (2) to integrate the series of invaginations which mould the dorsal optic cup and optic fissure, (3) to assist formation of the pigment epithelium monolayer, and (4) to orient the lens vesicle within the eye cup. The spatio-temporal relationship between necrotic loci suggests that pycnotic cells in the retina may influence their production in the lens and pigment epithelium. Preliminary observations on the mouse, pig, and human substantiate those on the rat.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051400301
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    Ultrastructural features of cardiac muscle cells in a tarantula spider (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 215-241 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ultrastructural features of cardiac muscle cells and their innervation were examined in the tarantula spider Eurypelma marxi Simon. The cells are transversely striated and have an A band length of about three microns. H zones are indistinct and M lines are absent. Thick and thin myofilament diameters are approximately 200 and 70 Å respectively. Eight to 12 thin filaments usually surround each thick one. Accumulations of thick and thin myofilaments occur perpendicular to the bulk of the myofilaments in some cells. The Z line is discontinuous and thick filaments may pass through the spaces in the Z line. Extensive systems of sarcoplasmic reticulum and transverse tubules are present; these form numerous dyadic junctions in both A and I band regions. Sarcolemmal invaginations form Z line tubules; lateral extensions of the plasma membrane portion of these invaginations form dyads. Nerve branches of the cardiac ganglion make multiple neuromuscular synapses with at least some of the cardiac muscle cells. Both large granular and small agranular vesicles are present in the presynaptic terminals. Intercalated discs similar to those present in other arthropod hearts occur between the ends of adjacent cardiac muscle cells.
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    URL: http://dx.doi.org/10.1002/jmor.1051400208
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    The cat step cycle: Hind limb joint angles and muscle lengths during unrestrained locomotion (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 1-41 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response.With due regard for the swing (F and E1) and stance (E2 and E3) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5-2.5 Kg), intermediate (2.6-3.5 Kg) and large (3.6-4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimus in situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69).The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking ( 〈 2 mph) to high speed galloping ( 〉 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the E3 phase, little reduction in the E2 and E1 phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E3 with little change in the E2 phase. In contrast F and E1 phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E1 and E2, all three joints being in phase in F and E3. The digits are essentially out of phase with the other joints except in the stance phase of the gallop.Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: (a) a greater usage of muscles at lengths between Ls and maximum in situ length; (b) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E2 (yield) phase of step; and, (c) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contrast to these changes in active muscle status, the change from walking to galloping has little effect on the extent and rate of passive muscle displacements, particularly the F phase stretch of extensors.For the soleus muscle, calculations were made of the relation between changes in overall muscle length during natural movements and the length of the average muscle fiber and the tendon of insertion. These measurements revealed that the increases in fiber length when passive and decreases in length during active shortening are less than would be anticipated from the extensive liteature on extirpated fibers. In contrast, the increase in fiber length when active is greater than would be expected from the admittedly sparse literature on this subject.The results of this study are discussed largely in relation to two points of neurophysiological interest: the physiological range of muscle stretch as it pertains to the responsiveness of muscle spindles and tendon organs; and those mechanical aspects of lengthening contractions that give insight into the neural control of stepping. For exciting both spindles and tendon organs passive muscle stretch and shortening contractions are shown to be relatively ineffective and lengthening and isometric contractions particularly effective movements. It is suggested that, just as recent literature has emphasized the co-activation of efferent alpha and gamma motoneurons as a muscle becomes active, so too is there a synchronous activation of afferents, particularly the Ia and group II endings of muscle spindles and Ib endings of tendon organs. Finally the thesis is advanced that, while it has been convenient to separate E2 from E3 in the description of the stance phase of the step cycle, extensor muscles are actually undergoing a single mechanical event: an active stretch-shorten cycle for knee and ankle extensors and an active isometric-shorten cycle for hip extensors. This hypothesis has significant implications for the neural control program that regulates the stepping sequence in that it emphasizes the extent to which appropriate changes must be preprogrammed in the mechanical properties of muscles for the smooth execution of stepping.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051410201
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    Regional cytology and cytochemistry of the crayfish kidney tubuleSupported in part by USPHS training grant 2-46-38-78-1-03 PHS GM 738-10. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 133-145 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytological and cytochemical methods were used to identify and characterzie six distinct regions of the crayfish kidney: coelomosac, labyrinth I and II, and nephridial canal I, II, and III. Cells of the coelomosac possess cytoplasm which is strongly PAS-positive, but poor in RNA and protein. Their nuclei possess unusual projections which extend to the basal plasmalemma. Labyrinth I contains columnar cells rich in glycogen. Labyrinth II is characterized by a distended lumen and by shorter cells with high cytoplasmic RNA, many possessing a large intracellular vacuole. A PAS-positive brush border is unique to the two portions of the labyrinth. Cells in the nephridial canal show strong reactions for RNA and Mg++-dependent ATPase. In nephridial canal I and II, cells are flattened to cuboidal with the lumen being more distended in nephridial canal I than anywhere else in the tubule. In nephridial canal III, the cells are large and columnar, and the cytoplasmic RNA concentration is greatest apically. Nuclei in all regions of the tubule epithelium, except coelomosac, are large and react strongly for protein. Coelomosac nuclei and those in blood cells are condensed and contain little protein. The cytoplasm of blood cells displays a significant amount of RNA, and traces of polysaccharide material.These observations demonstrate the presence of highly specialized morphological and histochemical alterations along the length of the kidney tubule and indicate sequential modification of urine in the lumen. Evident morphological and cytochemical likenesses between analogous regions of the mammlian nephron and the crayfish kidney tubule suggest that basic physiological similarities may also exist.
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    The relationship of acetylcholinesterase activity to optic fiber projections in the tiger salamander Ambystoma tigrinum (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 147-156 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the tiger salamnder the distribution of optic fibers, as revealed by the Fink-Heimer method, is compared with the localization of acetylcholinesterase, as revealed by histochemical methods. AChE activity coincides with optic nerve axons in the optic fiber layer of the retina, in the optic nerve, in the optic tracts and in every optic projection. Reginons of optic fiber terminals show heavier activity than optic fibers of passage. Comparison with other vertebrates is also made.
    Additional Material: 11 Ill.
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    The marginal zone and marginal sinus in the spleen of the gerbil. A light and electron microscopy studyThis investigation was supported, in part, by a General Research Support grant FR-05409-07 from the College of Medicine, The Ohio State University, Columbus, Ohio. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 205-215 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spleen of the adult gerbil (M. unguiculatus) is characterized by the absence of venous sinuses and ellipsoid sheaths. The follicle (white pulp) is separated from the surrounding red pulp by a distinct marginal zone. The cell types in the marginal zone are common to both the follicle and red pulp. Separating the marginal zone from the follicle is a vascular channel of capillary dimension, the marginal sinus. A number of terminal segments of the arterial vessels within the follicle were observed to form a direct connection with the marginal sinus. Ultrastructurally, discontinuities were evident within the walls of the marginal sinus that would permit passage of both cellular and plasma components from the marginal sinus to either marginal zone or the follicle.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051400101
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    Musculature and innervation of the neck of the desert locust, Schistocerca gregaria (Forskål)Supported by grants to Dr. G. A. Horridge and the author from the Medical Research Council (G965/64/B) and the Science Research Council (B/SR/3504). (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 439-464 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The innervation of each of the muscles involved in mediating head movement in the desert locust Schistocerca gregaria is described in detail. The number of motor neurones to each muscle and the neutral pathway and ganglion of origin of each are deduced from both histological and electrophysiological evidence. Only two of the muscles are, on histological evidence, innervated by as few as four different neurones, while several receive more than ten, and one at least 13. Individual muscles are shown physiologically to receive, in a few cases, as many as six different motor neurones. At least six muscles are innervated by motor neurones originating in more than one ganglion. One group of four muscles consisting in total of less than 100 muscle fibres receives more than 20 different motor neurones from three different ganglia through three or four different nerve roots. In these muscles, many single muscle fibres receive innervation from at least two different ganglia. It is concluded that the segmental nature of an insect muscle can not be deduced solely from a knowledge of the ganglion of origin of the motor innervation to that muscle. The innervation patterns that exist today must reflect past evolutionary development, but changes in the peripheral distribution of motor neurones, or migration of motor neurone cell bodies from one ganglion to another, or the development of additional motor neurones, or several of these factors together, must have formed a part of that development.
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    Comparative morphology, functions, and homologies of the coxal glands in oribatid mites (Arachnida: Acari)This study was partially supported by NSF grant GB-7982. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 407-429 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 1. Forty-eight species of oribatids in 37 families representing most of the superfamilies were collected from various environments (littoral, salt marsh, litter, sod, and freshwater) and sectioned.2. The coxal gland is composed of a sacculus and a labyrinth in all stages of all oribatid species. Muscles, originating on the body wall, insert at several points on the thin-walled sacculus which opens into the labyrinth. The labyrinth has an internal, chitinous supporting skeleton. The type A labyrinth has 3-180° bends, producing four parallel regions, and occurs in all inferior oribatids. The type B labyrinth has 1-180° bend, producing two parallel regions, and occurs in all superior oribatids. The coxal gland duct and the lateral gland duct join, penetrate the body wall, and empty into the posterior end of the podocephalic canal. All oribatids have lateral accessory glands, but only inferior oribatids have rostral and medial glands. Three ductless coxendral bodies are always present.3. The labyrinth length in oribatids is correlated with body size and the environment of the species. Oribatids from sod, leaflitter, or moss show a simple correlation of labyrinth length (X) to total body length (Y) where Y = 4.64X. Freshwater species have a labyrinth length greater than that of comparably sized terrestrial species and salt water (littoral) species have a labyrinth length less than that of comparably sized terrestrial species. There is a greater reduction in labyrinth length in species restricted to salt marshes than in species not restricted to salt marshes.4. The probable function of oribatid coxal glands is osmoregulation. Hemolymph filtration would occur across the sacculus by positive hemolymph pressure and contraction of the sacculus muscles. Resorption of ions would occur in the labyrinth, which is noncollapsible due to the internal skeleton. The hypothesis is that in freshwater species the rate of filtration is high and resorption of ions would have to be very efficient, therefore they have an elongated labyrinth; but in salt water species water loss must be minimized and preservation of ions would be a disadvantage, therefore they have a shortened labyrinth. Excre ion may also be a function of the coxal glands. The lateral gland may possibly function as an endocrine gland involved with production of a molting hormone. The rostral glands in inferior oribatids may have a salivary function.5. The coxal glands of Peripatus, some millipedes, apterygote insects, decapod crustaceans, and all arachnid orders are homologous. The Tetrastigmata, Notostigmata, Cryptostigmata, and soft ticks have typical arachnid coxal glands. The coxal glands of higher Prostigmata may be modified into salivary, silk, or venom glands. The coxal glands in Mesostigmata, Astigmata, and hard ticks are lacking or highly modified.
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    The blood system of the flabelligerid polychaete Flabelliderma commensalis (Moore)This investigation was supported by Biomedical Sciences Support grant FR-07012-02 from the General Research Support Branch, Division of Research Resources, Bureau of Health Professions Education and Manpower Training, National Institutes of Health. Contribution 7 from the Santa Catalina Marine Biological Laboratory.Portion of a dissertation submitted to the faculty of the University of Southern California in partial fulfillment of the requirements for the Ph.D. degree. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 465-490 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The blood system of the flabelligerid polychaete, Flabelliderma commensalis has been explored by dissection, light and electron microscopy and absorption spectrophotometry. The main longitudinal vessels are the dorsal, ventral, perineural, sub-oesophageal, supra-oesophageal and heart. Each segment has a segmental vessel which communicates with the dorsal vessel in thoracic setigers and the gut sinus in abdominal setigers. Branches of the segmental vessels in setigers 2-9 supply the gonads. A blood sinus envelopes most of the gut. Circulation is maintained by the pumping of the heart which immediately supplies blood to the supra-oesophageal ganglion, the branchiae and the palps. These are paralleled by a system of collecting vessels. The sinus of the supra-oesophageal ganglion receives a number of different axonal endings, some of which may be neurosecretory. The retroperitoneal vessels in their most developed form are composed of an intima, longitudinal and circular muscles and a peritoneum. The heart vessel contains a cardiac body whose cells appear to contain vacuoles of blood pigment. The blood pigment exhibits the absorption characteristics of a chlorocruorin with maxima at 438, 558 and 606 nm.
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    Microtubules and muscle attachment in the integument of the balanidae (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 1-13 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Attachment of muscle of the integument was studied in two species of Balanidae, Balanus balanoides and B. improvisus with electron microscopy. Specilalized epithelial cells (tendon cells) intervene between the muscle and overlying cuticle. An extensive desmosome-like junction exists between these two tissues. The tendon cell contains huge amounts of microtubules aligned parallel to the long axis of the inserting muscle. Tension exerted by contracting muscles is conveyed to the chitinous exoskeleton via the specially organized tendon cells and the extensive myo-tendinal cell junctions.
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    Fine structure of light- and dark-adapted eyes of desert ants, Cataglyphis bicolor (Formicidae, Hymenoptera) (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 15-29 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Among ants, Cataglyphis bicolor shows the best performance in optical orientation. Its eye is of the apposition type with a fused rhabdom. Morphological studies on the general struture of the eye as well as the effect of light have been carried out with transmission and scanning electron microscopy.An ommatidium is composed of a dioptric apparatus, consisting of a cornea, corneal process and a crystalline cone, the sensory retinula, which is made up of eight retinula cells in the distal half and of an additional ninth one in the proximal half. The ommatidia are separated from each other by two primary pigment cells, which surround the crystalline cone and an average of 12 secondary pigment cells, which reach from cornea to the basement membrane.The eye of Cataglyphis bicolor possesses a light intensity dependent adaptation mechanism, which causes a radial and distal movement of the pigment granules within the retinula cells and a dilatation of cisternae of the ER along the rhabdom.Until now, no overall order in arrangement of retinula cells or direction of microvilli has been found from ommatidium to ommatidium. Such an order, however, must exist, either on the retina or the lamina level, since we have proven the ant's capacity for polarized light analysis.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051390101
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    Structure and function of rectal pads in Blattella and Blaberus with respect to the mechanism of water uptake (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 105-118 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The morphology of the rectal pads of two cockroaches, Blattella germanica and Blaberus giganteus is described and contrasted with that of Periplaneta americana, studied previously. The columnar absorptive cells of the three species are similar in structure. However, Blattella and Blaberus rectal pads have a second type of cell, termed the secondary cell, that is not present in Periplaneta. The secondary cells are embedded in the pad epithelium and have crypts of cavities opening into the subepithelial sinus. In addition, a multilayered sheath is present between the pad cells and the sinus. The sheath acts as a barrier, perhaps of low permeability, between the subepithelial sinus and the pads. It is interrupted only at the borders of the secondary cells. A mechanism for fluid absorption is presented and the possible role of secondary cells is discussed. It is proposed that the secondary cells reabsorb solute from the sinus and that this solute can then be recycled through the pad cells. Structures resembling neurosecretory terminals within the cavities of the secondary cells may be involved in regulation of recycling. The arrangement of the rectal pads in these insects has structural and perhaps functional similarities with other transporting systems, particularly the cryptonephric system.
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    Some morphological and ultrastructural changes in the ependyma of the amputation stump during early regeneration of the tail in the lizard, Anolis carolinensisSupported by grants from the American Cancer Society, the National Institutes of Health and the Multiple Sclerosis Society. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 257-269 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light and electron microscope studies indicate that the old ependyma just proximal to the plane of amputation in early lizard tail regenerates shows a sequence of morphological changes which suggests that it as well as the new ependyma growing into the regenerate may play an active role in the initiation and maintenance of early tail regeneration.The old ependyma close to the plane of amputation undergoes hypertrophy and/or hyperplasia causing a partial closure of the central canal and pseudostratification. Its nuclei shift from an original apical position to a basal one. The ependymal processes become more prominent and extend to the pia, a condition not found more rostrally. There is also a significant increase in the amount of Golgi substance and a moderate increase in the rough endoplasmic reticulum. These observations lead to the thought that these cellular changes may be an expression of enhanced secretion and other activities in the old and new ependyma just proximal or distal to the plane of amputation.
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    Cytophysiological basis of disruptive pigmentary patterns in the leopard frog Rana pipiens. I chromatophore densities and cytophysiologyContribution Number 50 from the Amphibian Facility of the University of Michigan. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 271-284 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Statistical analyses of chromatophore densities and morphological states in wild type, burnsi, and kandiyohi: adult Rana pipiens integument yielded the conclusion that disruptive pigmentary pattern is permanently defined by regional chromatophore densities. Spatial chromatophore patterning is enhanced and rendered more visible by the morphological and physiological differences among chromatophores within the various pattern regions. Specifically, (1) chromatophores were differentialy distributed among pattern regions, (2) greater complexity of gross disruptive patterning had greater underlying melanophores densities, (3) there were significant density differences among non-sib individual animals, among fertilization, and among shipment batches, but not among full-sibs, and (4)kandiyohi individuals had more while burnsi individuals had fewer total melanophores than wild type. A stellate morphology was significantly correlated with high melanophore density, although the relationship of melanophore density to melanophore morphology differed among pattern regions and among genotypes. The functional interrelationships of density and morphology, and their role in disruptive patterning and coloration, are discussed.
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    Ultrastructural analysis of the functional copulatory organ of the male rotifer, Asplanchna brightwelli (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 285-305 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The male rotifer copulatory organ is composed of a urethral canal extending from the tip of the copulatory organ internally to a layer of microvilli. The microvilli project from two different cell types, referred to as the internal and peripheral microvillar cells according to their location. At this microvillar junction a second canal, the vas deferens, continues posteriorly and enters the sperm duct region of the testis. The channel of the vas deferens is formed from the inner wall of three separate cells; the cap, intermediate and basal cells. Peripheral to these cells and parallel to them for their entire length, cross sections of seven prostate gland cells can be observed. Anteriorly, these gland cells are connected to the basal end of the microvillar layer via a short neck region, through which glandular secretion occurs only during copulation. The mechanism of secretion appears to be a form of exocytosis whereby the secretory granule membrane fuses with the cell plasmalemma so that rupturing at the point of fusion will release the granule content into the neck region.The prostate gland cells contain an abundance of autophagic vacuoles while most of the other cells of the copulatory organ contain primary lysosomes and cytolosomes. These organelles may be associated with the aging process in rotifers, or, as in the case of the prostate gland-autophagic vacuoles, with a fast organelle turnover during secretion.
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    Morphology of the reproductive system of the armadillo. The spermatogonia (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 307-319 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatogonia of the nine-banded armadillo, Dasypus novemcinctus mexicanus, were studied morphologically using light and electron microscopy and examined histochemically using light microscopy. Immature flat type spermatogonia have ovoid or irregular nuclei with loosely condensed chromatin. Free ribosomes are abundant while profiles of rough endoplasmic reticulum are scarce. Smooth endoplasmic reticulum is a prominent feature occasionally taking an unusual cylindrical form. Mature spermatogonia exhibit rounder nuclei with greater degrees of chromatin clumping. Smooth endoplasmic reticulum is no longer prominent whereas profiles of rough endoplasmic reticulum are quite common. Occasional lysosomal configurations are found in mature spermatogonia.The majority of spermatogonial cells exhibit weak to moderate reactivity when stained with the periodic acid-Schiff (PAS) reaction. Certain cells in each tubular cross section stain vividly with this reaction and the PAS positivity is removable with salivary amylase. Because of nuclear characteristics, position of the cell immediately upon the basal lamina, intensity of the PAS reaction and the relative paucity of the vividly staining cells, it is suggested that they are members of the immature spermatogonial cell line, perhaps acting as stem cells. None of the several other histochemical procedures employed was capable of selectively demonstrating these cells.
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    URL: http://dx.doi.org/10.1002/jmor.1051400305
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    Morphological and histochemical features of the duodenal glands in six marsupial species (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 321-341 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The duodenal glands of four marsupial species, the kangaroo, native cat, marsupial mouse, and bandicoot, form a narrow lobular collar immediately distal to the gastrointestinal junction. In two species, the koala and wombat, the duodenal glands are diffuse and scattered along the intestinal tract distal to the gastrointestinal junction for considerable distances. The glands of all species examined empty independently into the intestinal lumen. Histochemical studies indicate that the latter two species, the koala and wombat, elaborate an acid mucin whereas the former species produce a neutral mucosubstance. Ultrastructural examination shows that generally the duodenal glands are comprised of large pyramidal cells that show a definite polarity, with basally-placed nuclei and apically-situated secretory granules. Species differences, with regard both to the morphology and nature of the secretory granules and to the proportions of cell organelles, exist. The diversity of diet between species is discussed.
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    Differentiation of the myoepithelial cells of the rat submandibular gland in vivo and in vitro: An ultrastructural study (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 343-354 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytodifferentiation of the myoepithelial cells (MEC) of the rat submandibular gland (SMG) was observed by studying the prenatal and postnatal development of the gland in vivo and in vitro by light and electron microscopy. The anlage of the SMG first appeared on the fourteenth day of gestation and, from its earliest inception, was surrounded by an intact basal lamina. Presumptive myoepithelial cells were first seen at 18 days of gestation coinciding with the onset of secretion in the rudiment. These cells were flattened, peripherally located and subjacent to the epithelial basal lamina. Initial deposition of cytofilaments in the MEC's was observed during the first three days following birth and fully matured cells were seen as early as one week after birth. Presumptive and immature MEC's were observed undergoing mitosis, but once cytofilament deposition had begun in the cells they did not divide. Myoepithelium developed in relation to embryonic secretory structures and were only observed surounding acini and intercalated ducts in the adult gland. New myoepithelial cells were formed as long as new acinar-intercalated duct units were formed. Myoepithelial cells did not produce secretory type granules at any time during their development or in their mature state.Development of the MEC's in vitro paralleled that in vivo and supported the above observations.
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    Ultrastructure of the larval compound setae of the polychaete Nereis vexillosa grubePart of this work has appeared in abstract form elsewhere (Gustus and Cloney, '71). (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 355-366 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Larval compound (jointed) setae of the polychaete Nereis vexillosa Grube were examined by scanning and transmission electron microscopy and by polarization microscopy. Long-bladed spinigers and short-bladed falcigers are described. The proximal shaft of each of these types of setae flares distally into a serrated collar and encloses the proximal end of a toothed blade. The collar projects on one side as a boss. The blade and the cortex of the shaft have longitudinal channels. A large excentric cavity in the shaft (the medullary channel) contains a loose meshwork of trabeculae. In the distal part of the shaft these trabeculae are aggregated into diaphragms. The seta is invested with an electron dense layer of enamel. Juvenile setae contain both chitin and protein. With respect to the long axis of the seta, the blade and the cortex of the shaft are positively birefringent and the medullary diaphragms are negatively birefringent. KOH extraction renders the setae negative to a test for protein and reverses the sign of birefringence of the cortical material of the shaft.
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    Ultrastructure of erythrocytes and leucocytes of Priapulus caudatus (de Lamarck) (Priapulida) (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 367-379 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The marine priapulid Priapulus caudatus has a voluminous body cavity filled with a blood-like fluid containing erythrocytes and leucocytes (amoebocytes). The hematocrit of animals weighing 0.5-14 gm was 2-10%. The erythrocytes contain a hemerythrin blood pigment. The structure of the coelomocytes was studied by light and electron microscopy. The erythrocytes are nucleated and contain marginal bands, vacuoles and occasionally crystals. The cytoplasm has few organelles. The leucocytes are amoeboid motile cells, the cytoplasm of which contains numerous organelles. The most conspicuous of these are oval particles, probably representing developmental stages of lysosomes. Most of these organelles contain tubules stretching from one pole to another. In the hind part of the animal, certain tissues, primarily the posterior warts contain large numbers of coelomocytes. The histological picture is complicated, showing some resemblance to the lymphoepithelial tissues of vertebrates.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051400401
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    Tooth replacement in the bowfin (Amia calva  -  Holostei) (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 140 (1973), S. 381-395 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The dissected tooth bearing bones of 20 specimens of Amia calva (Pisces:Holostei) ranging from the third to tenth season have been examined radiographically and in alizarin red S stained and cleared specimens. Although forms of alternate (1:1) tooth series replacement (sensu Edmund, '60) were frequently observed, even in the youngest, immature specimens, many examples of irregular replacement were recorded. In several bones, the maxillae in particular, series with every third (2:1) or fourth (3:1) tooth replacing were seen and possible patterns of 2:2, were recorded. It is concluded that these data are not consistent with the Zahnreihen concept but support a morphogenic field concept of tooth development.
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    Masthead (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973) 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051390401
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    Developmental and adult morphology of the vertebral column in the plethodontid salamander Eurycea bislineata, with comments on vertebral evolution in the amphibia (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 251-299 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The first description of vertebral development in a plethodontid salamander is presented. Eurycea bislineata has larvae that hatch at a rather early stage of development. Somites and the notochord appear early. Somitic differentiation is slight, and no distinct sclerotome can be found. As a result, there is no clear primary segmentation of the skeletogenous tissue. No evidence of a sclerocoele can be found. The amount of sclerotomal cells surrounding the notochord is very low, relative to other tetrapods. Yet discrete perichordal rings of cells do form, in nearly midsegmental positions, and these give rise to the intervertebral cartilages. Osteogenesis of the centra is initiated prior to hatching and is coincidental with ossification of the neural arch. There is no sign of a neurocentral suture. The centrum forms as a thin shell of bone directly from sclerotomal cells. The notochord is a prominent feature of the vertebral column throughout life, retaining its integrity until late in life when some disintegration occurs locally. The notochord is filled with cartilage midvertebrally in late larval stages, and some additional cartilage forms later in life. The intervertebral cartilage enlarges greatly in late larval life. An opisthocoelous joint forms in this cartilage, apparently as a result of differential changes in the cells of the perichordal ring rather than by an invasion of cells from an external source. The intervertebral cartilage is a dominant structural and highly important functional feature of the adult vertebra. In metamorphosed individuals it may become extensively mineralized, and it consists of many different structural kinds of cartilage.The cranio-vertebral joint seems to form in a single segment, contrary to the condition reported by some early investigators. It is complex, and consists of articulations between the odontoid process of the atlas and the occipital arch, as well as between the occipital condyles and atlantal cotyles. The notochord plays a dominant role in the early development of the odontoid, but then changes radically and is absent in the adult process.The anterior trunk region seems to be much more conservative than posterior parts of the column. The patterns of nerve routes and nature of development of the ribs and rib bearers differs greatly from conditions elsewhere in the column. The rib patterns are similar to presumed ancestral conditions. Rib development on the sacral and caudosacral vertebrae is in some ways more similar to that of the anterior vertebrae than of the central trunk vertebrae.Quantitative aspects of variation in the vertebrae of adult salamanders are presented. There is more regional variation and less site variation than would be expected from literature reports.Evolutionary aspects of the origin of the cranio-vertebral joint, transverse process and ribs, patterns of segmentation, and centrum development are considered in the light of the new information on Eurycea. There is no evidence that more than one vertebra is involved developmentally or evolutionarily in the cranio-vertebral joint. The most generalized condition of rib bearers in living salamanders is one in which the dorsal and ventral bearers are in cartilaginous continuity during development. There are many variations on this theme in living species. It is inappropriate to speak of a resegmentation of the sclerotome in Eurycca, even though the adult vertebra is a transsegmental structure, because there is no primary segmentation of the scanty sclerotome. The important feature found in vertebral development in all tetrapods is the perichordal tube and its subsequent differentiation. Questinos concerning precise homologies of the salamander vertebral centrum with those of other vertebrates cannot be answered by data from development sequences with currently used criteria of homology. On the other hand, it appears that all centra, regardless of subdivision, are homologous in all tetrapods.
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    Scanning electron microscopy of scales from different body regions of three lizard species (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 377-388 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Oberhautchen of scales from the dorsal, parietal, and ventral regions of Sceloporus occidentalis (Iguanidae), Gerrhonotus multicarinatus (Anguinidae), and Anniella pulchra (Anniellidae) were examined with a scanning electron microscope. At low magnification, all scales of S. occidentalis exhibit well-defined outlines of cells belonging to the Oberhautchen layer and the previously overlying clear layer. The dorsal and parietal cells of this species exhibit a minutely dentate Oberhautchen that forms tooth-like spinules 0.2 to 0.5 μ long and arranged in irregular rows. Minute pits 0.1 to 0.3 μ in diameter characterize the Oberhautchen of a ventral scale.Cell outlines are not evident on the scales of G. multicarinatus. The Oberhautchen of dorsal and parietal scales of this species is prominently laminated. Laminae are less prominent on scales of the lateral fold, and no intrinsic surface structure is evident on a ventral scale. In contrast, the fossorial anguinomorph Anniella pulchra exhibits Oberhautchen surfaces with practically no intrinsic microornamentation. However, what appear to be outlines of Oberhautchen cells are visible on the dorsal and ventral scales.These observations suggest that modifications of Oberhautchen microornamentation may have evolved to reduce friction with the substrate or other scales. The lack of pronounced microornamentation of the Oberhautchen on some body scales may indicate that a complex interdigitation between clear layer and Oberhautchen cells is not essential to the sloughing process.
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    Variations in the mode of stolon growth among different genera of colonial hydroids, and their evolutionary implicationsSupported by National Science Foundation grant GB-6245 and National Institutes of Health grant GM 11555. (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 363-375 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Stolonic growth has been compared among several genera of calyptoblastic (Campanularia flexuosa, C. calceolifera, Gonothyraea and Sertularia) and gymnoblastic (Pennaria, Bougainvillia, Eudendrium and Cordylophora) hydroids with respect to such features as the (1) complexity and uniformity of the tip movements, (2) constancy of growth cycle duration, (3) variability in growth among cycles, (4) growth rate, and (5) variability of retractions among cycles.The “growth cycle,” previously described in C. flexuosa, is the basis for elongation in all species observed. Its pattern is indistinguishable between the Campanularia species; however, at the generic level the tip movements show peculiarities which delineate each genus from all others. In addition, the movements in all calyptoblasts are uniform from cycle to cycle and comparatively simple, whereas those of the gymnoblasts are complicated by the variable appearance of one or more secondary forward thrusts between crests.A dichotomy is seen between the calyptoblasts and most gymnoblasts in other respects as well. Cycle time is very predictable and cycle-to-cycle variability in growth is relatively narrow in all calyptoblasts. However, in most gymnoblasts both features are much more loosely regulated: only Pennaria shows some degree of control to its timing mechanism, and only in Bougainvillia and Eudendrium does the uniformity of growth per cycle reach the calyptoblast level.On the premise that calyptoblasts are evolutionarily the more advanced group, simplicity and regularity of growth movements are concluded to be the evolved, and complexity and variability the primitive, conditions. On this basis the evolutionary relations among the four gymnoblasts, as deduced from their stolonic growth behavior alone, are consistent in many but not all respects with those interpreted from morphological considerations.
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    The circulatory system of Amphioxus (Branchiostoma floridae) I. Morphology of the major vessels of the pharyngeal area (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 389-406 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to clarify the morphology of the circulatory system of amphioxus the blood vessels were investigated using modern techniques of light and electron microscopy.The pattern of circulation in amphioxus is forward ventrally and backwards dorsally. In addition, circulating corpuscles, usually associated with the blood of higher chordates, are absent.The circulatory system of amphioxus consists of well defined contractile vessels and vascular spaces or sinuses within a connective tissue matrix. The contractile vessels have a discontinuous endothelial lining resting on a basal lamina and are enclosed by a simple layer of contractile myoepithelial cells. Discontinuous endothelial linings occur throughout the vascular tree, including major and minor afferent and efferent vessels and blood sinuses. This is in contrast to higher animals where the endothelium forms a more or less continuous lining along the inner surface of the boundary layer.It is suggested that the endothelial cells of amphioxus, like the endothelial cells in capillaries of higher chordates, most likely play a role in the physiology of the circulatory system by removing residues of filtration from the basal lamina, thereby facilitating an exchange of materials to and from the surrounding tissues.
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    Development of polarity and bilateral asymmetry in the palleal bud of Botryllus schlosseri (Pallas) (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 139 (1973), S. 1-25 
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    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the polarity and bilateral asymmetry of the future adult zooid has been traced to their earliest morphological expression in the palleal bud of Botryllus. The account is based upon continued observation of living buds. The polarized antero-posterior and dorso-ventral axes are first expressed by the skewing of a symmetrical, hemispherical bud towards the anterior end of the parental bud. Identification of these axes is reinforced by the development of a loop-like blood circulation, the primary circulation, in the horizontal plane during the enlargement of the skewed hemisphere to form a stalked vesicle. Bilateral asymmetry is first expressed by the asymmetrical expansion of the vesicle stage. The right posterior corner of the vesicle expands further posteriorly and becomes more acute than the left posterior corner. This larger expansion persists throughout the development of the right atrial cavity, which finally expands across the mid-line to partially surround the gut. The bilateral asymmetry, expressed in the expanded vesicle, is reinforced by the development in sequence of a rounded gut rudiment and a pericardial rudiment in positions that would be expected from the asymmetry of the expanded vesicle. The first appearance of the gut rudiment occurs earlier than had been recognized previously. Conflicting accounts of the time and mode of formation of the pericardial rudiment have been clarified. The results of this study are discussed in the context of determination of bud territory, polarity and bilateral asymmetry.
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    URL: http://dx.doi.org/10.1002/jmor.1051390102
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