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  • Life Sciences (General)  (3)
  • Communications and Radar  (1)
  • PACS. 47.54.+r Pattern selection; pattern formation – 61.30.-v Liquid crystals – 47.20.Ky Nonlinearity (including bifurcation theory)  (1)
  • cables  (1)
  • nonlinear dynamics  (1)
  • 2000-2004  (7)
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  • 1
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    Shuttle Imaging Radar Application in Geology (2000)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Keywords: Communications and Radar
    Type: International Geological Congress; Rio de Janeiro; Brazil
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Effects of Hypergravity Exposure on Plasma Oxytocin (OT) Concentrations in Pregnant and Lactating Rat Dams (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: From pregnancy to weaning there is a progressive elevation of plasma oxytocin (OT) levels associated with nursing activity, irrespective of litter size. In the present study, we analyzed the effects of continuous 1.5G, 1.75G and 2.0G hypergravity exposure on OT plasma concentration in prepartum (Gestation Day 20) (G20) and lactating (Postnatal day) (P10) rat dams. For this study, litter size was controlled with a yoking procedure established in our lab where individual control litters were yoked-matched to individual hypergravity litters. We reviewed all data at hypergravity irrespective of gravitational level and compared the values with the controls in both G20 (HG, n=15;SC, n=9) and P10 (HG, n=21;SC, n=16). Results showed that over time, we did observe the expected OT increase in both groups. In G20 dams, measurement of OT concentrations showed no significance. However, at P10, measurements of OT concentrations suggest a reduction of about 20% compared to established controls in our laboratory, 0.9+/-0.09 ng/ml for the controls and 0.7+/-0.06 ng/ml for centrifuged animals (p〈0.02). These data suggest that exposure to centrifugation may reduce OT levels during lactation. When these plasma samples were obtained, the dams were removed from the litters, and values were not adjusted for the size of the litters. The reduction in OT with centrifugation may reflect a decrease in nursing activity or a decreased responsiveness of the mammary hypothalamic axis. In addition, we have analyzed data on plasma prolactin concentrations and mammary gland development, which may give additional insight to the results of our OT measurements.
    Keywords: Life Sciences (General)
    Type: International Society for Gravitational Physiology Meeting; Jun 02, 2002 - Jun 09, 2002; Stockholm; Sweden
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Body Weight Gain During a Discrete Nursing Episode in Suckling Rats Reared at 1.5-g or 1.5-g Exceeds that of 1.0-g Controls and is Independent of Material Hypergravity Exposure (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: We recently reported that body weights of suckling rats reared during 1.5-g centrifugation are approximately 10% lower than those of 1.0-g controls. This finding raises the possibility that hypergravity exposed pups ingest less milk than controls due to either impairments in their ability to acquire milk from the nipple, or to decreased availability or palatability of their mother's milk. In the present study, we analyzed body weight gain in suckling rats reared during a discrete nursing episode following rearing at either 1.75-g, 1.5-g or 1.0-g. On Gestational day (G) 10 of the rats' 22-day pregnancy, time-bred SD rat dams were 1:1 matched based on body weight and assigned to either Hypergravity (HG) or Stationary Yoked Control (SYC) conditions and to either 1.75-g or 1.5-g conditions. Beginning on G11, HG dams and litters were exposed to 26 days of continuous centrifugation with brief daily stops for veterinary inspection and animal maintenance. On the day following birth (Postnatal day), litters were pooled within each condition then randomly re-assigned in equivalent proportions to HG and SYC dams. On P15, HG litters were removed from their mother's and placed in an incubator (33 C). Following a 4hr deprivation period, four neonates were tested from each litter, with two pups placed with either their own dam or the SYC dam; two pups from the yoked mother were paired with the HG pups. Pups were individually weighed, permitted to suckle for 75 min, then re-weighed. At the start of the test, the body weights of HG pups were significantly less than those of SYC pups (p less than 0.05). Relative to SYC pups, BG pups showed significantly greater proportional body weight gain (p less than 0.05), possibly due to augmented post-centrifugation feeding. Pup weight gain was independent of maternal hypergravity exposure. Neither impairments in milk acquisition nor milk availability or palatibility of hypergravity-exposed dams cannot account for reduced body mass of hypergravity-reared offspring.
    Keywords: Life Sciences (General)
    Type: Annual Experimental Biology Meeting; Mar 29, 2001 - Apr 04, 2001; Orlando, FL; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Life Sciences Research in the Centrifuge Accommodation Module of the International Space Station (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The Centrifuge Accommodation Module (CAM) will be the home of the fundamental biology research facilities on the International Space Station (ISS). These facilities are being built by the Biological Research Project (BRP), whose goal is to oversee development of a wide variety of habitats and host systems to support life sciences research on the ISS. The habitats and host systems are designed to provide life support for a variety of specimens including cells, bacteria, yeast, plants, fish, rodents, eggs (e.g., quail), and insects. Each habitat contains specimen chambers that allow for easy manipulation of specimens and alteration of sample numbers. All habitats are capable of sustaining life support for 90 days and have automated as well as full telescience capabilities for sending habitat parameters data to investigator homesite laboratories. The habitats provide all basic life support capabilities including temperature control, humidity monitoring and control, waste management, food, media and water delivery as well as adjustable lighting. All habitats will have either an internal centrifuge or are fitted to the 2.5-meter diameter centrifuge allowing for variable centrifugation up to 2 g. Specimen chambers are removable so that the specimens can be handled in the life sciences glovebox. Laboratory support equipment is provided for handling the specimens. This includes a compound and dissecting microscope with advanced video imaging, mass measuring devices, refrigerated centrifuge for processing biological samples, pH meter, fixation and complete cryogenic storage capabilities. The research capabilities provided by the fundamental biology facilities will allow for flexibility and efficiency for long term research on the International Space Station.
    Keywords: Life Sciences (General)
    Type: 7th European Symposium on Space Environmental Control Systems; Jul 10, 2000 - Jul 13, 2000; Toulouse; France|30th International Conference on Environmental Systems; Jul 10, 2000 - Jul 13, 2000; Toulouse; France
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
    Electronic Resource
    Electronic Resource
    Electric Nusselt number characterization of electroconvection in nematic liquid crystals (2002)
    Springer
    The European physical journal 26 (2002), S. 515-520 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 47.54.+r Pattern selection; pattern formation – 61.30.-v Liquid crystals – 47.20.Ky Nonlinearity (including bifurcation theory)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We develop a characterization method of electroconvection structures in a planar nematic liquid crystal layer by a study of the electric current transport. Because the applied potential difference has a sinusoidal time dependence, we define two electric Nusselt numbers corresponding to the in-phase and out-of-phase components of the current. These Nusselt numbers are predicted theoretically using a weakly nonlinear analysis of the standard model. Our measurements of the electric current confirm that both numbers vary linearly with the distance from onset until the occurence of secondary transitions. A systematic comparison between our theoretical and experimental results, using no adjusted parameters, demonstrates moderate agreement, but discrepancies remain. Electric transport measurements during electroconvection represent a quantitative test of the standard model completely independent from optical probes. Thus, the technique described here can be a useful complement to traditional structural measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020121
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  • 6
    Electronic Resource
    Electronic Resource
    Large Motions of a Moored Floating Breakwater Modeled as an Impact Oscillator (2000)
    Springer
    Nonlinear dynamics 23 (2000), S. 319-334 
    Details
    ISSN: 1573-269X
    Keywords: bouncing ball ; breakwater ; cables ; impact oscillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Two-dimensional motions of a floating breakwater moored to thesea floor by two cables are considered. The breakwater is modeled bothas a point mass and as a rigid body. The mooring lines are assumed tohave no effect on the breakwater when they are slack, and to provide aninstantaneous impulsive force when they become taut, analogous to animpact oscillator or a ball bouncing on a rigid surface. The axialcomponent of the velocity is reduced at this instantaneous tautcondition. Fluid inertia and damping are not included, and the waveforces are assumed to be harmonic. A critical force is defined, and theeffects of the forcing frequency, the coefficient of restitution, andthe shape and size of the body on the critical force are examined.Trajectories of the motion are plotted and the impact velocities arecomputed and analyzed. Knowledge of the number and magnitude of theseimpacts is useful in assessing fatigue of the mooring lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008302432739
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  • 7
    Electronic Resource
    Electronic Resource
    Snap Loads in Mooring Lines During Large Three-Dimensional Motions of a Cylinder (2000)
    Springer
    Nonlinear dynamics 23 (2000), S. 271-284 
    Details
    ISSN: 1573-269X
    Keywords: breakwater ; cylinder ; mooring lines ; nonlinear dynamics ; snap loads ; three-dimensional motions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The nonlinear dynamic response of a moored, rigid, horizontalcylinder is considered. Use of the structure as a breakwater or a waveenergy device is envisaged. Inertial and nonlinear damping effects ofthe external fluid are not included, i.e., a ‘dry’ analysis is carriedout. The four mooring lines are modeled as massless springs which onlyresist tension. The six coupled equations of motion of the cylinder arederived and solved numerically. Linear free vibrations are treatedfirst, followed by the nonlinear three-dimensional response to harmonicforces simulating the action of waves. Normal, longitudinal, and obliqueforces are considered, and time histories of the displacements andmooring line tensions are computed. Snap loads tend to occur in thelines when they are alternately slack and taut. The effects of theforcing direction, amplitude, and frequency are investigated. Chaoticmotions are observed in some cases, and the structure collapses forsufficiently large forcing amplitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008368427878
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    Paper (German National Licenses)
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