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  • Life Sciences (General)  (162)
  • Geophysics  (102)
  • Aerospace Medicine  (64)
  • 2010-2014
  • 2000-2004  (113)
  • 1995-1999  (215)
  • 1955-1959
  • 1950-1954
  • 2004  (113)
  • 1998  (215)
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  • 2010-2014
  • 2000-2004  (113)
  • 1995-1999  (215)
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  • 1950-1954
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  • 1
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    Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere (1998)
    In:  Other Sources
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    Publication Date: 2019-08-17
    Description: The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HO, required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production Of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about I part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more 03 than expected.
    Keywords: Geophysics
    Type: Science; 279; 49-53
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  • 2
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    Observation of Isolated Structures of the Low Latitude Boundary Layer with the INTERBALL/Tail Probe (1998)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We analyze the structure of magnetospheric transients observed at the dusk-side low-latitude magnetopause with the Interball Tail Probe. Ion and magnetic field measurements are used to investigate one particular transient in more detail. This transient has distinct non-symmetric structure with the plasma characteristics and the flow properties of the leading part of the transient being quite different from those in the trailing part of the transient. The region separating these two parts corresponds to the change of the sign in the B(n) component. These observations support an earlier conclusion that some plasma irregularities within the Low Latitude Boundary Layer (LLBL), formed as a result of sporadic reconnection, disconnect from the magnetopause, propagate and dissipate in the magnetosphere, and form what we call Disconnected Magnetosheath Transfer Events (DMTEs).
    Keywords: Geophysics
    Type: Paper-1998GL900167 , Geophysical Research Letters (ISSN 0094-8276); 25; 23; 4305-4308
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  • 3
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    Drug marker absorption in relation to pellet size, gastric motility and viscous meals in humans (1998)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: PURPOSE: The objective of this study was to evaluate drug marker absorption in relation to the gastric emptying (GE) of 0.7 mm and 3.6 mm enteric coated pellets as a function of viscosity and the underlying gastric motility. METHODS: Twelve subjects were evaluated in a 3-way crossover study. 0.7 mm caffeine and 3.6 mm acetaminophen enteric coated pellets were concurrently administered with a viscous caloric meal at the levels of 4000, 6000 and 8000 cP. Gastric motility was simultaneously measured with antral manometry and compared to time events in the plasma profiles of the drug markers. RESULTS: Caffeine, from the 0.7 mm pellets, was observed significantly earlier in the plasma than acetaminophen, from the 3.6 mm pellets, at all levels of viscosity. Motility related size differentiated GE was consistently observed at all viscosity levels, however, less variability was observed with the 4000 cP meal. Specifically, the onset of absorption from the of 3.6 mm pellets correlated with the onset of Phase II fasted state contractions (r = 0.929, p 〈 0.01). CONCLUSIONS: The timeframe of drug marker absorption and the onset of motility events were not altered within the range of viscosities evaluated. Rather, the differences in drug marker profiles from the non-digestible solids were most likely the result of the interaction between viscosity and motility influencing antral flow dynamics. The administration of the two sizes of pellets and a viscous caloric meal with subsequent monitoring of drug marker profiles is useful as a reference to assess the influence of motility patterns on the absorption profile of orally administered agents.
    Keywords: Life Sciences (General)
    Type: Pharmaceutical research (ISSN 0724-8741); 15; 2; 233-8
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  • 4
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    Spaceflight alters microtubules and increases apoptosis in human lymphocytes (Jurkat) (1998)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Alteration in cytoskeletal organization appears to underlie mechanisms of gravity sensitivity in space-flown cells. Human T lymphoblastoid cells (Jurkat) were flown on the Space Shuttle to test the hypothesis that growth responsiveness is associated with microtubule anomalies and mediated by apoptosis. Cell growth was stimulated in microgravity by increasing serum concentration. After 4 and 48 h, cells filtered from medium were fixed with formalin. Post-flight, confocal microscopy revealed diffuse, shortened microtubules extending from poorly defined microtubule organizing centers (MTOCs). In comparable ground controls, discrete microtubule filaments radiated from organized MTOCs and branched toward the cell membrane. At 4 h, 30% of flown, compared to 17% of ground, cells showed DNA condensation characteristic of apoptosis. Time-dependent increase of the apoptosis-associated Fas/ APO-1 protein in static flown, but not the in-flight 1 g centrifuged or ground controls, confirmed microgravity-associated apoptosis. By 48 h, ground cultures had increased by 40%. Flown populations did not increase, though some cells were cycling and actively metabolizing glucose. We conclude that cytoskeletal alteration, growth retardation, and metabolic changes in space-flown lymphocytes are concomitant with increased apoptosis and time-dependent elevation of Fas/APO-1 protein. We suggest that reduced growth response in lymphocytes during spaceflight is linked to apoptosis.
    Keywords: Life Sciences (General)
    Type: The FASEB journal : official publication of the Federation of American Societies for Experimental Biology (ISSN 0892-6638); Volume 12; 11; 1007-18
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  • 5
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    Effects of heavy ions on visual function and electrophysiology of rodents: the ALTEA-MICE project (2004)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: ALTEA-MICE will supplement the ALTEA project on astronauts and provide information on the functional visual impairment possibly induced by heavy ions during prolonged operations in microgravity. Goals of ALTEA-MICE are: (1) to investigate the effects of heavy ions on the visual system of normal and mutant mice with retinal defects; (2) to define reliable experimental conditions for space research; and (3) to develop animal models to study the physiological consequences of space travels on humans. Remotely controlled mouse setup, applied electrophysiological recording methods, remote particle monitoring, and experimental procedures were developed and tested. The project has proved feasible under laboratory-controlled conditions comparable in important aspects to those of astronauts' exposure to particle in space. Experiments are performed at the Brookhaven National Laboratories [BNL] (Upton, NY, USA) and the Gesellschaft fur Schwerionenforschung mbH [GSI]/Biophysik (Darmstadt, FRG) to identify possible electrophysiological changes and/or activation of protective mechanisms in response to pulsed radiation. Offline data analyses are in progress and observations are still anecdotal. Electrophysiological changes after pulsed radiation are within the limits of spontaneous variability under anesthesia, with only indirect evidence of possible retinal/cortical responses. Immunostaining showed changes (e.g. increased expression of FGF2 protein in the outer nuclear layer) suggesting a retinal stress reaction to high-energy particles of potential relevance in space. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.
    Keywords: Life Sciences (General)
    Type: Advances in space research : the official journal of the Committee on Space Research (COSPAR); Volume 33; 8; 1347-51
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  • 6
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    [Clinical and physiological evaluation of bone changes among astronauts after long-term space flights] (1998)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results of the joint Russian/US studies of the effect of microgravity on bone tissues in 18 cosmonauts on return from 4.5- to 14.5-month long missions are presented. Dual-energy x-ray gamma-absorbtiometry (QDR-1000 W, Hologic, USA) was used to measure bone mineral density (BMD, g/cm2) and mineral content (BMC, g) in the whole body, the scalp including cervical vertebra, arms, ribs, sternal and lumbar regions of the spinal column, pelvis and legs. A clearly defined dependence of topography of changes upon the position of a skeletal segment in the gravity vector was established. The greatest BMD losses have been observed in the skeleton of the lower body, i.e. in pelvic bones (-11.99 +/- 1.22%), lumbar vertebra (-5.63 +/- 0.817%), and in proximal femur, particularly in the femoral neck (-8.17 +/- 1.24%). Bones of the upper skeleton were either unchanged (insignificant) or showed a positive trend. Overall changes in bone mass of the whole skeleton of male cosmonauts during the period of about 6 months on mission made up -1.41 +/- 0.406% and suggest the mean balance of calcium over flight equal to -227 +/- 62.8 mg/day. Reasoning is given to qualify these states of cosmonauts' bone tissues as local osteopenia. On the literature and results of authors' clinical evidence, discussed is availability of the densitometric data for predicting risk of trauma. A biological nature of the changes under observation is hypothesized.
    Keywords: Aerospace Medicine
    Type: Aviakosmicheskaia i ekologicheskaia meditsina = Aerospace and environmental medicine (ISSN 0233-528X); Volume 32; 1; 21-5
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  • 7
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    Magnetospheric Response to the Arrival of the Shock Wave in Front of the Magnetic Cloud Event of January 10,1997 (1998)
    In:  Other Sources
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    Publication Date: 2019-07-17
    Description: We are studying the magnetic cloud event of January 6-11, 1997. Specifically, we have investigated the response of the magnetosphere to the shock wave in front of the magnetic cloud on January 10, 1997 using data from WIND, GEOTAIL and POLAR spacecraft as well as ground magnetometer data. The WIND spacecraft, which was located at about 100 Re upstream from the Earth, observed the arrival of the shock wave front at 005OUT. Geotail was located at the equatorial magnetopause (approx. 8.7 Re), while POLAR was located in the northern dawn sector at 8.4 Re, 6.1 MLT and 61.1 MLAT. A magnetic signature was nearly simultaneously observed at about 0104 UT at the POLAR and Geotail spacecraft. Particle density increases were observed on WIND and Geotail, but not on POLAR. The UV aurora shows an asymmetrical dawn-dusk intensification and presubstorm activity. The significance of these findings will be discussed.
    Keywords: Geophysics
    Type: Scientific Assembly: Advances in Auroral Plasma Physics; Jul 12, 1998 - Jul 19, 1998; Nagoya; Japan
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  • 8
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    Bioavailability and Pharmacodynamics of Promethazine in Human Subjects (2004)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: The acute effects of exposure to microgravity include the development of space motion sickness, which usually requires therapeutic intervention. The current drug of choice, promethazine (PMZ), is available to astronauts in three different dosage forms during space flight; its side effects include nausea, dizziness, sedation and impaired psychomotor performance. This ground-based study is designed to validate flight-suitable methods for pharmacodynamic evaluation of PMZ and to estimate bioavailability and pharmacodynamics of PMZ. Experimental design consists of intramuscular administration of three doses of PMZ (12.5,25 and 50 mg) and placebo in a randomized double blind fashion to human subjects and collecting blood, urine and saliva samples for 72 h. Subjects also complete cognitive performance test batteries, WinSCAT (Windows based Space Cognitive Assessment Test) and ARES (ANAM Readiness Evaluation System). Preliminary results indicate a significant relationship (p=9.88e-05) between circulating PMZ levels and cognitive performance parameters. Time to accurately complete memory tasks increases significantly with concentrations; higher concentrations also increase response time and decrease accuracy of substitution and matching tasks. AUC and half-life estimates for PMZ ranged between 0.12 and 1.7 mg.h/L and 15 and 50 h, respectively. These preliminary results indicate that PMZ may exhibit dose-dependent pharmacokinetics in humans; also, WinSCAT and ARES are sensitive for pharmacodynamic assessment of PMZ, and may be applicable for assessing the pharmacodynamics of other neurocognitive drugs.
    Keywords: Aerospace Medicine
    Type: 8th World Congress on Clinical Pharmacologv and Therapeutics Incorporating the Annual Scientific Meeting of ASCEPT; Brisbane; Australia
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  • 9
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    Determination of Particle Sources for a Geotail Distribution Function Observed on May 23, 1995 (1998)
    In:  Other Sources
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    Publication Date: 2019-08-17
    Description: On May 23, 1995, the Comprehensive Plasma Instrumentation (CPI) onboard the Geotail spacecraft observed a complex and structured ion distribution function near the magnetotail midplane at x approximately -10 R(sub E). On the same day, the Wind spacecraft observed a very high density (approximately 40/cubic cm) solar wind and an interplanetary magnetic field (IMF) that was predominantly northward but had several southward turnings. We have inferred the sources of the ions in this distribution function by following approximately 90,000 ion trajectories backward in time using time-dependent electric and magnetic fields obtained from a global MHD (magnetohydrodynamic) simulation. Wind data were used as input for the MHD model. We found that three sources contributed to this distribution: the ionosphere, the plasma mantle which had near-Earth and distant tail components, and the low latitude boundary layer (LLBL). Moreover, distinct structures in the low energy part of the distribution function were found to be associated with individual sources. Structures near 0 deg pitch angle were made up of either ionospheric or plasma mantle ions, while structures near 90 deg pitch angle were dominated by ions from the LLBL source. Particles that underwent nonadiabatic acceleration were numerous in the higher energy part of the ion distribution function, whereas ionospheric and LLBL ions were mostly adiabatic. A large proportion of the near-Earth mantle ions underwent adiabatic acceleration, while most of the distant mantle ions experienced nonadiabatic acceleration.
    Keywords: Geophysics
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  • 10
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    Interactions between CO2 chemoreflexes and arterial baroreflexes (1998)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We studied interactions between CO2 chemoreflexes and arterial baroreflexes in 10 supine healthy young men and women. We measured vagal carotid baroreceptor-cardiac reflexes and steady-state fast Fourier transform R-R interval and photoplethysmographic arterial pressure power spectra at three arterial pressure levels (nitroprusside, saline, and phenylephrine infusions) and three end-tidal CO2 levels (3, 4, and 5%, fixed-frequency, large-tidal-volume breathing, CO2 plus O2). Our study supports three principal conclusions. First, although low levels of CO2 chemoreceptor stimulation reduce R-R intervals and R-R interval variability, statistical modeling suggests that this effect is indirect rather than direct and is mediated by reductions of arterial pressure. Second, reductions of R-R intervals during hypocapnia reflect simple shifting of vagally mediated carotid baroreflex responses on the R-R interval axis rather than changes of baroreflex gain, range, or operational point. Third, the influence of CO2 chemoreceptor stimulation on arterial pressure (and, derivatively, on R-R intervals and R-R interval variability) depends critically on baseline arterial pressure levels: chemoreceptor effects are smaller when pressure is low and larger when arterial pressure is high.
    Keywords: Life Sciences (General)
    Type: The American journal of physiology (ISSN 0002-9513); 274; 6 Pt 2; H2177-87
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