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  • Fluid Mechanics and Thermodynamics  (3)
  • Proton  (2)
  • Spacecraft Propulsion and Power  (2)
  • 1995-1999  (7)
  • 1
    Electronic Resource
    Electronic Resource
    The track structures of ionizing particles and their application to radiation biophysics (1999)
    Springer
    Radiation and environmental biophysics 38 (1999), S. 249-259 
    Details
    ISSN: 1432-2099
    Keywords: Key words Alpha-particle ; Deuteron ; Proton ; Biophysical modelling ; Radiosensitivity ; Bacillus subtilis ; Haploid yeast ; Human diploid fibroblasts ; DNA repair systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract  Using knowledge of the track structure generated by ionizing particles together with details of the organisms being irradiated, the application of a new analytical method to two biophysical models to explain the inactivation of cells by radiation has been developed. It is shown that both models are equally successful in predicting experimental results and that good agreement is found with the data for single-strand phage, Bacillus subtilis spores, various strains of Escherichia coli, haploid and diploid yeast, and human diploid fibroblasts. The only significant discrepancy arose with T1-phage, for which a tentative explanation is offered. The differences in inherent radiosensitivity between organisms, after allowance is made for differences in target size, are attributed to differences in enzymatic repair systems and in the packing of the DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004110050165
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The track structures of ionizing particles and their application to radiation biophysics (1999)
    Springer
    Radiation and environmental biophysics 38 (1999), S. 175-184 
    Details
    ISSN: 1432-2099
    Keywords: Key words Alpha particle ; Deuteron ; Proton ; Biophysical modeling ; Radiation quality influence ; Bacillus subtilis ; DNA density ; Monte Carlo calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract  A new approach to the interpretation of the effects of radiation on cells is described, in which sample particle tracks are constructed using a Monte Carlo computer program and the exposure of cellular targets to these tracks is simulated using a second program known as BIOPHYS. Data on the shapes and DNA contents of the cell nuclei are obtained from the literature. It is assumed that the sensitive material is DNA, and that the target is divided into cubes of approximately 2 nm (the diameter of the DNA helix) per side; the numbers of these cubes containing different numbers of ionizations are derived. Two different methods of analysing the output of BIOPHYS are described. In the first, it is assumed that lethality is caused by the occurrence of a number of ionizations equal to or greater than a certain threshold in one cube; in the second method, it is assumed that only two ionizations are required, in different parts of the cube, but that only some fraction of the cube is sensitive. These models have been applied to the interpretation of the variation of radiosensitivity with a linear energy transfer (LET) of spores of Bacillus subtilis exposed wet and dry, and good fits to the published experimental data were obtained using both models. Fits to experimental data for a range of other cell lines will be presented in a second paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004110050153
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    Paper (German National Licenses)
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  • 3
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    PTA1 Helium Pressurization System Model (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A transient model of the Propulsion Test Article 1 (PTA1) Helium Pressurization System was developed using the Generalized Fluid System Simulation Program (GFSSP). The model included feed lines from the facility interface to the engine purge interface and Liquid Oxygen (LOX) and Rocket Propellant 1 (RP-1) tanks, the propellant tanks themselves including ullage space and propellant feed lines to their respective pump interfaces. GFSSPs capability was extended to model a control valve to maintain ullage pressure within a specified limit and pressurization processes such as heat transfer between ullage gas, propellant and the tank wall. The purpose of the model is to predict the flow system characteristics in the entire pressurization system during 80 seconds of pre-pressurization operation, 420 seconds of pressurization stand-by operation and 150 seconds of engine operation. Subsequent to the work presented here, the PTA1 model has been updated to include the LOX and RP-1 pumps, while the pressurization option itself has been modified to include the effects of mass transfer. This updated model will be compared with PTA1 test data as it becomes available.
    Keywords: Spacecraft Propulsion and Power
    Type: Thermal and Fluids Analysis; 13-17 Sept. 1999; Huntsville, AL; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Ongoing Analysis of Rocket Based Combined Cycle Engines by the Applied Fluid Dynamics Analysis Group at Marshall Space Flight Center (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: This paper presents the status of analyses on three Rocket Based Combined Cycle configurations underway in the Applied Fluid Dynamics Analysis Group (TD64). TD64 is performing computational fluid dynamics analysis on a Penn State RBCC test rig, the proposed Draco axisymmetric RBCC engine and the Trailblazer engine. The intent of the analysis on the Penn State test rig is to benchmark the Finite Difference Navier Stokes code for ejector mode fluid dynamics. The Draco engine analysis is a trade study to determine the ejector mode performance as a function of three engine design variables. The Trailblazer analysis is to evaluate the nozzle performance in scramjet mode. Results to date of each analysis are presented.
    Keywords: Spacecraft Propulsion and Power
    Type: Thermal and Fluids Analysis; Sep 13, 1999 - Sep 17, 1999; Huntsville, AL; United States
    Format: text
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  • 5
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    Rheology of Foam Near the Order-Disorder Phase Transition (1999)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Foams are extremely important in a variety of industrial applications. Foams are widely used in fire-fighting applications, and are especially effective in fighting flammable liquid fires. In fact the Fire Suppression System aboard the Space Shuttle utilizes cylinders of Halon foam, which, when fired, force a rapidly expanding foam into the convoluted spaces behind instrument panels. Foams are critical in the process of enhanced oil recovery, due to their surface-active and highly viscous nature. They are also used as drilling fluids in underpressurized geologic formations. They are used as transport agents, and as trapping agents. They are also used as separation agents, where ore refinement is accomplished by froth flotation of the typically lighter and hydrophobic contaminants. The goal of the proposed investigation is the determination of the mechanical and rheological properties of foams, utilizing the microgravity environment to explore foam rheology for foams which cannot exist, or only exist for a short time, in 1g.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Proceedings of the Fourth Microgravity Fluid Physics and Transport Phenomena Conference; 353-358; NASA/CP-1999-208526/SUPPL1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    FDNS CFD Code Benchmark for RBCC Ejector Mode Operation (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi-dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for both Diffusion and Afterburning (DAB) and Simultaneous Mixing and Combustion (SMC) test conditions. Results from both the 2D and the 3D models are presented.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Propulsion; Nov 18, 1999 - Nov 19, 1999; University Park, PA; United States
    Format: application/pdf
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  • 7
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    Sonoluminescence in Space: The Critical Role of Buoyancy in Stability and Emission Mechanisms (1999)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Sonoluminescence is the term used to describe the emission of light from a violently collapsing bubble. Sonoluminescence ("light from sound") is the result of extremely nonlinear pulsations of gas/vapor bubbles in liquids when subject to sufficiently high amplitude acoustic pressures. In a single collapse, a bubble's volume can be compressed more than a thousand-fold in the span of less than a microsecond. Even the simplest consideration of the thermodynamics yields pressures on the order of 10,000 ATM. and temperatures of at least 10,000 K. On the face of things, it is not surprising that light should be emitted from such an extreme process. Since 1990 (the year that Gaitan discovered light from a single bubble) there has been a tremendous amount of experimental and theoretical research in stable, single-bubble sonoluminescence. Yet there remain four fundamental mysteries associated with this phenomenon: 1) the light emission mechanism itself; 2) the mechanism for anomalous mass flux stability; 3) the disappearance of the bubble at some critical acoustic pressure; and 4) the appearance of quasiperiodic and chaotic oscillations in the flash timing. Gravity, in the context of the buoyant force, is implicated in all four of these unexplained phenomena. We are developing microgravity experiments probing the effect of gravity on single bubble sonoluminescence. By determining the stability boundaries experimentally in microgravity, and measuring not only light emission but mechanical bubble response, we will be able to directly test the unambiguous predictions of existing theories. By exploiting the microgravity environment we will gain new knowledge impossible to obtain in earth-based labs which will enable explanations for the above mysteries. We will also be in a position to make new discoveries about bubbles which emit light.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: Proceedings of the Fourth Microgravity Fluid Physics and Transport Phenomena Conference; 347-352; NASA/CP-1999-208526/SUPPL1
    Format: application/pdf
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