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  • Polymer and Materials Science  (3)
  • Man/System Technology and Life Support
  • Solanaceae
  • 1
    Electronic Resource
    Electronic Resource
    Tropane alkaloids from Schizanthus hookeri
    Amsterdam : Elsevier
    Phytochemistry 19 (1980), S. 2007-2008 
    Details
    ISSN: 0031-9422
    Keywords: 3α-senecioyloxytropan-6β-ol ; 6β-angeloyloxytropan-3α-ol. ; Schizanthus hookeri ; Solanaceae ; hygrolines ; tropine
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0031-9422(80)83023-8
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Tropane alkaloids from Schizanthus grahamii
    Amsterdam : Elsevier
    Phytochemistry 26 (1987), S. 819-822 
    Details
    ISSN: 0031-9422
    Keywords: 3α-senecioyloxytropane. ; Schizanthus grahamii ; Solanaceae ; mesaconic, itaconic diesters ; tropane alkaloids
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0031-9422(00)84794-9
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of elasticities of components of a cardiac bioprosthesis leaflet (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 30 (1996), S. 47-52 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanoelastic behavior of calf pericardium employed in cardiac bioprostheses was compared with that of three types of thread (Nylon, Prolene, and silk) used to suture this biological tissue. The elastic limit (EL) of each material was determined by means of tensile tests and the mathematical functions that govern the stress/strain curves within the EL have been described. The first derivative of these functions for each point to the curves allowed the immediate calculation of the elastic modulus (EM), which was considered the best parameter for comparing the elasticities of the materials being assessed. It was observed that the deformation of the pericardium produced by the working stress of a pericardial leaflet was approximately 1000 times greater than that produced in the surgical threads. When the elasticities were compared on the basis of the EM, that of pericardium was 749.06, 626.95, and 1253.17 times greater than that of the Nylon, Prolene, and silk suture threads, respectively. These results demonstrate that the interaction between these materials (pericardium and the threads) could be generating detrimental forces that can diminish the durability of the leaflets of the bioprostheses constructed of calf pericardium. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Description of the mathematical law that defines the relaxation of bovine pericardium subjected to stress (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 755-760 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A material subjected to traction stress increases in length; if we maintain the elongation constant, the stress varies over a period of time. This phenomenon has been referred to as relaxation. The purpose of this study was to define a mathematical law that relates the variation in stress to time when elongation remains constant in bovine pericardium. The mathematical function obtained after assaying 34 samples to the point of relaxation, subjected to initial stresses ranging from 0.17-10.07 MPa, responds to the following equation: y = -0.0252 + 0.953 α - (0.0165 + 0.015 α)lnt, where γ is the stress withstood at an instant in time, t, after initial stress α. A normogram, validated by assays of up to 6,340 min duration (4.40 days), is presented for graphic calculation, permitting the computation of the loss of stress due to relaxation of this biomaterial, with initial stresses ranging from 1-10 MPa. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280613
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Selection and interaction of biomaterials used in the construction of cardiac bioprostheses (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 568-574 
    Details
    ISSN: 0021-9304
    Keywords: biomaterial ; bioprostheses ; suture ; pericardium ; heart valves ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanical behavior of calf pericardium employed in the manufacture of cardiac bioprostheses was assessed according to the region from which it was selected. For this purpose, selected samples of the tissue were sewn with different types of commercially available sutures and subjected to tensile testing, the results of which were compared with the findings in selected, but not sutured, tissue used as a control. The results confirm a loss of resistance - that is, a reduction of the capacity of sutured samples of the biomaterial to withstand breakage stress compared with control samples. Taking into account the marked resistance to breakage of the suture thread, this phenomenon can only be explained as a consequence of the deleterious mechanical interaction between the suture and chemically treated pericardium. This interaction is illustrated by the shearing force which is responsible for the loss of resistance in the tested samples. These trials demonstrate that the results can be improved and the deleterious interaction diminished, although not eliminated, when the pericardium is selected from a given region. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 568-574, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
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    Unknown
    Coherent Laser Instrument Would Measure Range and Velocity (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A proposed instrument would project a narrow laser beam that would be frequency-modulated with a pseudorandom noise (PN) code for simultaneous measurement of range and velocity along the beam. The instrument performs these functions in a low mass, power, and volume package using a novel combination of established techniques. Originally intended as a low resource- footprint guidance sensor for descent and landing of small spacecraft onto Mars or small bodies (e.g., asteroids), the basic instrument concept also lends itself well to a similar application guiding aircraft (especially, small unmanned aircraft), and to such other applications as ranging of topographical features and measuring velocities of airborne light-scattering particles as wind indicators. Several key features of the instrument s design contribute to its favorable performance and resource-consumption characteristics. A laser beam is intrinsically much narrower (for the same exit aperture telescope or antenna) than a radar beam, eliminating the need to correct for the effect of sloping terrain over the beam width, as is the case with radar. Furthermore, the use of continuous-wave (CW), erbium-doped fiber lasers with excellent spectral purity (narrow line width) permits greater velocity resolution, while reducing the laser s power requirement compared to a more typical pulsed solid-state laser. The use of CW also takes proper advantage of the increased sensitivity of coherent detection, necessary in the first place for direct measurement of velocity using the Doppler effect. However, measuring range with a CW beam requires modulation to "tag" portions of it for time-of-flight determination; typically, the modulation consists of a PN code. A novel element of the instrument s design is the use of frequency modulation (FM) to accomplish both the PN-modulation and the Doppler-bias frequency shift necessary for signed velocity measurements. This permits the use of a single low-power waveguide electrooptic phase modulator, while simultaneously mitigating the effects of speckle as a noise source in the coherent detection.
    Keywords: Man/System Technology and Life Support
    Type: NPO-40403 , NASA Tech Briefs, February 2005; 9-10
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Propulsive Reaction Control System Model (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This software models a propulsive reaction control system (RCS) for guidance, navigation, and control simulation purposes. The model includes the drive electronics, the electromechanical valve dynamics, the combustion dynamics, and thrust. This innovation follows the Mars Science Laboratory entry reaction control system design, and has been created to meet the Mars Science Laboratory (MSL) entry, descent, and landing simulation needs. It has been built to be plug-and-play on multiple MSL testbeds [analysis, Monte Carlo, flight software development, hardware-in-the-loop, and ATLO (assembly, test and launch operations) testbeds]. This RCS model is a C language program. It contains two main functions: the RCS electronics model function that models the RCS FPGA (field-programmable-gate-array) processing and commanding of the RCS valve, and the RCS dynamic model function that models the valve and combustion dynamics. In addition, this software provides support functions to initialize the model states, set parameters, access model telemetry, and access calculated thruster forces.
    Keywords: Man/System Technology and Life Support
    Type: NPO-46978 , NASA Tech Briefs, November 2011; 13
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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