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  • 1
    Electronic Resource
    Electronic Resource
    Curves of osmotic fragility calculated from the isotonic areas and volumes of individual human erythrocytesThis investigation was supported by a grant from the Life Insurance Medical Research Fund. (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 74 (1969), S. 203-211 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Theoretical osmotic fragility curves were calculated and drawn by computer using the van't Hoff equation and the isotonic areas and volumes of 1000 individual erythrocytes. We studied the influence on the calculated curves of theoretically altering the fraction of the volume which was osmotically active from 50 to 70%, and of altering the permissible stretch before hemolysis from zero to 10%. With the two assumptions-that the membrane does not stretch before hemolysis, and that the osmotically active fraction of the cell volume is 0.58-it was possible to duplicate the general shape of the standard fragility curve; the exact NaCl concentration, however, at which there was 50% hemolysis was approximately 0.1 gm/100 ml higher than found in vitro. The calculated osmotic fragility curves can be made quantitatively similar to in vitro ones if the following statements are true: the osmotically active volume is 58%, the permissible stretch of the membrane without lysis is 6%, the cell membrane resists a slight osmotic pressure gradient of approximately 0.1 atmospheres, and hemolysis is an all or nothing phenomenon. This set of values for the relevant factors is sufficient but not unique in causing the superposition of the calculated and experimental curves. The frequency distribution of the cells according to the hemolytic salt concentrations (the sodium chloride concentration at which an individual cell just hemolyzes) was skewed positively and was leptokurtic for each of the seven normal subjects studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040740212
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sedimentation of single human red blood cells. Differences between normal and glutaraldehyde fixed cellsResearch supported by The Medical Research Council of Canada and The Alberta Heart Foundation. (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 80 (1972), S. 367-372 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The sedimentation behaviour of single human red blood cells fixed with glutaraldehyde at pH 7.4 and 6.4 was studied and compared to resiflts previously reported for normal fresh cells. The cells fixed at pH 7.4 were observed to have normal shapes while those fixed at pH 6.4 were more spherical and less disc-like. Fixation of glutaraldehyde removed “membrane flicker,” resulting in increased stability as indicated by a decrease in the number of orientation changes per minute from 2.93 ± 0.16 (SEM) to 1.74 ± 0.10 (SEM). An orientation change was defined as a change of 45° in any direction. Fixation also increased the edge-to-flat time preference ratio from 2.5 to 4.7, and increased the sedimentation velocities in all three orientations, despite a measured 2.5% decrease in mean cell density.Fixation of cells at pH 6.4 showed that the decrease in stability and preference for the on-edge orientation was associated with an increase in the sphericity of the cell.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040800307
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  • 3
    Electronic Resource
    Electronic Resource
    The rate of sedimentation of individual human red blood cellsThis investigation was supported by a grant from the Medical Research Council of Canada. (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 78 (1971), S. 319-331 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The sedimentation of individual cells was investigated in the context of the Stokes' equation for sedimenting spheres. Blood obtained from a finger prick was diluted 104 times by volume in Tris buffered Ringer solution (pH 7.4, 310 milliosmolar). A small sample of the suspension was put in a plastic, flat bottomed depression slide which was then closed with a coverslip. Thirty-six runs were done in which a cell was kept in focus on an inverted microscope. The 250 μm descent was monitored on a two channel chart recorder. The orientation, determined by the observer as edge, oblique, or flat, and the verticle displacement, indicated by a ten turn potentiometer connected to the fine focussing knob, were recorded simultaneously. The cells studied indicated that cells are more frequently in the edge-on orientation, that larger cells sediment faster than smaller cells despite the lower density for larger cells, and that cells wobble considerably. The biconcave cells made approximately three orientation changes per minute where one change in orientation was considered to be a rotation of 45° in any direction. Brownian motion is thought to be responsible for the wobble, or random rotations of the sedimenting cell. The edge-to-flat velocity ratio was 1.38 ± 0.30 S.D. which is significantly less than 1.5, the theoretical and experimental value for thin discs. There was a moderate dependence of sedimentation velocity on the square of the diameter (R = +0.5) in accordance with Stokes' Law. The variance in this relation can be accounted for by the known variation of cellular density within a normal population of red cells, and by the inherent errors of measurement.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040780302
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  • 4
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    Qualification and Issues with Space Flight Laser Systems and Components (2006)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The art of flight quality solid-state laser development is still relatively young, and much is still unknown regarding the best procedures, components, and packaging required for achieving the maximum possible lifetime and reliability when deployed in the harsh space environment. One of the most important issues is the limited and unstable supply of quality, high power diode arrays with significant technological heritage and market lifetime. Since Spectra Diode Labs Inc. ended their involvement in the pulsed array business in the late 199O's, there has been a flurry of activity from other manufacturers, but little effort focused on flight quality production. This forces NASA, inevitably, to examine the use of commercial parts to enable space flight laser designs. System-level issues such as power cycling, operational derating, duty cycle, and contamination risks to other laser components are some of the more significant unknown, if unquantifiable, parameters that directly effect transmitter reliability. Designs and processes can be formulated for the system and the components (including thorough modeling) to mitigate risk based on the known failures modes as well as lessons learned that GSFC has collected over the past ten years of space flight operation of lasers. In addition, knowledge of the potential failure modes related to the system and the components themselves can allow the qualification testing to be done in an efficient yet, effective manner. Careful test plan development coupled with physics of failure knowledge will enable cost effect qualification of commercial technology. Presented here will be lessons learned from space flight experience, brief synopsis of known potential failure modes, mitigation techniques, and options for testing from the system level to the component level.
    Keywords: Lasers and Masers
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Qualification and Issues with Space Flight Laser Systems and Components (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The art of flight quality solid-state laser development is still relatively young, and much is still unknown regarding the best procedures, components, and packaging required for achieving the maximum possible lifetime and reliability when deployed in the harsh space environment. One of the most important issues is the limited and unstable supply of quality, high power diode arrays with significant technological heritage and market lifetime. Since Spectra Diode Labs Inc. ended their involvement in the pulsed array business in the late 1990's, there has been a flurry of activity from other manufacturers, but little effort focused on flight quality production. This forces NASA, inevitably, to examine the use of commercial parts to enable space flight laser designs. System-level issues such as power cycling, operational derating, duty cycle, and contamination risks to other laser components are some of the more significant unknown, if unquantifiable, parameters that directly effect transmitter reliability. Designs and processes can be formulated for the system and the components (including thorough modeling) to mitigate risk based on the known failures modes as well as lessons learned that GSFC has collected over the past ten years of space flight operation of lasers. In addition, knowledge of the potential failure modes related to the system and the components themselves can allow the qualification testing to be done in an efficient yet, effective manner. Careful test plan development coupled with physics of failure knowledge will enable cost effect qualification of commercial technology. Presented here will be lessons learned from space flight experience, brief synopsis of known potential failure modes, mitigation techniques, and options for testing from the system level to the component level.
    Keywords: Lasers and Masers
    Type: The International Society for Optical Engineering (SPIE); Jan 21, 2006 - Jan 26, 2006; San Jose, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Contamination and Radiation Effects on Nonlinear Crystals for Space Laser Systems (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Space Lasers are vital tools for NASA s space missions and military applications. Although, lasers are highly reliable on the ground, several past space laser missions proved to be short-lived and unreliable. In this communication, we are shedding more light on the contamination and radiation issues, which are the most common causes for optical damages and laser failures in space. At first, we will present results based on the study of liquids and subsequently correlate these results to the particulates of the laser system environment. We present a model explaining how the laser beam traps contaminants against the optical surfaces and cause optical damages and the role of gravity in the process. We also report the results of the second harmonic generation efficiency for nonlinear optical crystals irradiated with high-energy beams of protons. In addition, we are proposing to employ the technique of adsorption to minimize the presence of adsorbing molecules present in the laser compartment.
    Keywords: Lasers and Masers
    Type: Optics and Photonics 2005; Jul 31, 2005 - Aug 04, 2005; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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