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  • ENERGY PRODUCTION AND CONVERSION  (10)
  • Life Sciences (General)  (5)
  • Alpha and Beta cells  (1)
Collection
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Light and electron microscopy of the hepatopancreas of the isopod Acellus intermedius (1975)
    Springer
    Cell & tissue research 163 (1975), S. 403-410 
    Details
    ISSN: 1432-0878
    Keywords: Hepatopancreas ; Isopod ; Alpha and Beta cells ; Light and electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hepatopancreas from Acellus intermedius, a small freshwater isopod, was examined by light and electron microscopy. Of particular interest are the two cell types present in the hepatopancreas. Their ultrastructural features indicate that the major role of the large alpha cells is to absorb material from the lumen as well as secrete materials into the lumen while the major role of the small beta cells is to store the absorbed materials as well as break down stored materials before transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219474
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    Paper (German National Licenses)
    Fulltext
  • 2
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    NASA Lewis Research Center combustion MHD experiment (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: The MHD power generation experiments were conducted in a high field strength cryomagnet which was adapted from an existing facility. In its original construction, it consisted of 12 high purity aluminum coils pool cooled in a bath of liquid neon. In this configuration, a peak field of 15 tesla was produced. For the present experiments, the center four coils were removed and a 23 cm diameter transverse warm bore tube was inserted to allow the placement of the MHD experiment between the remaining eight coils. In this configuration, a peak field of 6 tesla should be obtainable. The time duration of the experiment is limited by the neon supply which allows on the order of 1 minute of total operating time followed by an 18-hour reliquefaction period. As a result, the experiments are run in a pulsed mode. The run duration for the data presented here was 5 sec. The magnetic field profile along the MHD duct is shown. Since the working fluid is in essence superheated steam, it is easily water quenched at the exit of the diffuser and the components are designed vacuum tight so that the exhaust pipe and demister an be pumped down to simulate the vacuum of outer space.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: R and D Associates Proc. of the AFOSR Spec. Conf. on Prime-Power for High Energy Space Systems, Vol. 1; 10 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Quantitative analysis of defects in silicon. Silicon sheet growth development for the large are silicon sheet task of the low-cost solar array project (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: One hundred and seventy four silicon sheet samples were analyzed for twin boundary density, dislocation pit density, and grain boundary length. Procedures were developed for the quantitative analysis of the twin boundary and dislocation pit densities using a QTM-720 Quantitative Image Analyzing system. The QTM-720 system was upgraded with the addition of a PDP 11/03 mini-computer with dual floppy disc drive, a digital equipment writer high speed printer, and a field-image feature interface module. Three versions of a computer program that controls the data acquisition and analysis on the QTM-720 were written. Procedures for the chemical polishing and etching were also developed.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-163140 , MRI-276 , DOE/JPL-954977-79/9
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Analysis of defect structure in silicon. Silicon sheet growth development for the large area silicon sheet task of the Low-Cost Solar array Project (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: One hundred ninety-three silicon sheet samples, approximately 880 square centimeters, were analyzed for twin boundary density, dislocation pit density, and grain boundary length. One hundred fifteen of these samples were manufactured by a heat exchanger method, thirty-eight by edge defined film fed growth, twenty-three by the silicon on ceramics process, and ten by the dendritic web process. Seven solar cells were also step-etched to determine the internal defect distribution on these samples. Procedures were developed or the quantitative characterization of structural defects such as dislocation pits, precipitates, twin & grain boundaries using a QTM 720 quantitative image analyzing system interfaced with a PDP 11/03 mini computer. Characterization of the grain boundary length per unit area for polycrystalline samples was done by using the intercept method on an Olympus HBM Microscope.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-169058 , DOE/JPL-955676-1 , JPL-9950-677 , NAS 1.26:169058 , MRI-289
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Velocity and temperature distributions of coal-slag layers on magnetohydrodynamic generators walls (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Approximate analytical expressions are derived for the velocity and temperature distributions in steady state coal slag deposits flowing over MHD generator walls. Effects of slag condensation and Joule heating are included in the analysis. The transport conditions and the slag temperature at the slag-gas interface are taken to be known parameters in the formulation. They are assumed to have been predetermined either experimentally or from the slag properties and the gas dynamic calculations of the free stream flow. The analysis assumes a power law velocity profile for the slag and accounts for the coupling between the energy and momentum conservation equations. Comparisons are made with the more exact numerical solutions to verify the accuracy of the results.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-TN-D-8396 , E-8929
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Variability in surface ECG morphology: signal or noise? (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Using data collected from canine models of acute myocardial ischemia, we investigated two issues of major relevance to electrocardiographic signal averaging: ECG epoch alignment, and the spectral characteristics of the beat-to-beat variability in ECG morphology. With initial digitization rates of 1 kHz, an iterative a posteriori matched filtering alignment scheme, and linear interpolation, we demonstrated that there is sufficient information in the body surface ECG to merit alignment to a precision of 0.1 msecs. Applying this technique to align QRS complexes and atrial pacing artifacts independently, we demonstrated that the conduction delay from atrial stimulus to ventricular activation may be so variable as to preclude using atrial pacing as an alignment mechanism, and that this variability in conduction time be modulated at the frequency of respiration and at a much lower frequency (0.02-0.03Hz). Using a multidimensional spectral technique, we investigated the beat-to-beat variability in ECG morphology, demonstrating that the frequency spectrum of ECG morphological variation reveals a readily discernable modulation at the frequency of respiration. In addition, this technique detects a subtle beat-to-beat alternation in surface ECG morphology which accompanies transient coronary artery occlusion. We conclude that physiologically important information may be stored in the variability in the surface electrocardiogram, and that this information is lost by conventional averaging techniques.
    Keywords: Life Sciences (General)
    Type: Computers in cardiology (ISSN 0276-6574); 14; 257-60
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Quantitative Analysis of Defects in Silicon. Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low-cost Solar Array Project (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The various steps involved in the chemical polishing and etching of silicon samples are described. Data on twins, dislocation pits, and grain boundaries from thirty-one (31) silicon sample are also discussed. A brief review of the changes made to upgrade the image analysis system is included.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-158738 , QPR-4 , MRI-269 , DOE/JPL-954977-78/1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Quantitative Analysis of Defects in Silicon (1979)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: The evaluation and prediction of the conversion efficiency for a variety of silicon samples with differences in structural defects, such as grain boundaries, twin boundaries, precipitate particles, dislocations, etc. are discussed. Quantitative characterization of these structural defects, which were revealed by etching the surface of silicon samples, is performed by using an image analyzer. Due to different crystal growth and fabrication techniques the various types of silicon contain a variety of trace impurity elements and structural defects. The two most important criteria in evaluating the various silicon types for solar cell applications are cost and conversion efficiency.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-162173 , MRI-273 , QPR-5 , DOE/JPL-954977-79/6
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    On the precision of automated activation time estimation (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We examined how the assignment of local activation times in epicardial and endocardial electrograms is affected by sampling rate, ambient signal-to-noise ratio, and sinx/x waveform interpolation. Algorithms used for the estimation of fiducial point locations included dV/dtmax, and a matched filter detection algorithm. Test signals included epicardial and endocardial electrograms overlying both normal and infarcted regions of dog myocardium. Signal-to-noise levels were adjusted by combining known data sets with white noise "colored" to match the spectral characteristics of experimentally recorded noise. For typical signal-to-noise ratios and sampling rates, the template-matching algorithm provided the greatest precision in reproducibly estimating fiducial point location, and sinx/x interpolation allowed for an additional significant improvement. With few restrictions, combining these two techniques may allow for use of digitization rates below the Nyquist rate without significant loss of precision.
    Keywords: Life Sciences (General)
    Type: Computers in cardiology (ISSN 0276-6574); 14; 101-4
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Subtle alternating electrocardiographic morphology as an indicator of decreased cardiac electrical stability (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Observations from finite-element computer models, together with analytic developments based on percolation theory have suggested that subtle fluctuations of ECG morphology might serve as an indicator diminished cardiac electrical stability. With fixed-rate atrial pacing in canines, we have previously observed a pattern of alternation in T wave energy which correlated with cardiac electrical stability. We report here on a series of 20 canine experiments in which cardiac electrical stability (measured via Ventricular Fibrillation Threshold determination) was compared to a non-degenerate, multidimensional measurement of the degree of alternating activity present in the ECG complex morphology. The decrease in cardiac electrical stability brought on by both coronary artery occlusion and systemic hypothermia was consistently accompanied by subtle alternation in ECG morphology, with the absolute degree of alternating activity being significantly (negatively) correlated with cardiac electrical stability.
    Keywords: Life Sciences (General)
    Type: Computers in cardiology (ISSN 0276-6574); 12; 109-12
    Format: text
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    NASA TECHNICAL REPORTS
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