scholarly journals A First-Order Design Requirement to Prevent Edema in Mechanical Counter-Pressure Space Suit Garments

2019 ◽  
Author(s):  
Christopher E. Carr ◽  
Loretta Treviño
Keyword(s):  
Hydrostatic Pressure ◽  
Space Suit ◽  
Volume Flux ◽  
Design Requirement ◽  
First Order ◽  
Counter Pressure ◽  
Space Suits ◽  
Glove Finger ◽  
Enhanced Mobility ◽  
Mechanical Counter

ABSTRACTIntroductionMechanical counter-pressure (MCP) space suits may provide enhanced mobility relative to gas-pressure space suits. One challenge to realizing operational MCP suits is the potential for edema caused by spatial variations in the applied body-surface pressure (dP). We determined a first-order requirement for these variations.MethodsDarcy’s law relates volume flux, of fluid from capillaries to the interstitial space, to transmural hydraulic and osmotic pressure differences. Albumin and fibrinogen levels determine, to first order, the capillary oncotic pressure (COP). We estimated dP, neglecting hydrostatic pressure differences, by equating the volume flux under MCP and under normal with the volume flux under abnormal variations in COP; then we compared these estimates to results from MCP garment studies.ResultsNormal COP varies from 20-32 mm Hg; with constant hydraulic conductivity, dP≈12 mm Hg. In nephrotic syndrome, COP may drop to 11 mm Hg, yielding dP≈15 mm Hg relative to mid-normal COP. Previous studies found dPmax =151 mm Hg (MCP glove; finger and hand dorsum relative to palm), dPmax=51 mm Hg (MCP arm; finger, hand dorsum, and wrist relative to arm), and dP=52, 90 and 239 mm Hg (three MCP lower leg garments).ConclusionsMCP garments with dPmax≤12 mm Hg are unlikely to produce edema or restrict capillary blood flow; however, garments with dPmax>12 mm Hg will not necessarily produce edema. For example, the hydrostatic pressure gradient at the feet in 1g can range from 70-90 mm Hg. Current garment prototypes do not meet our conservative design requirement.

scholarly journals Materials and Textile Architecture Analyses for Mechanical Counter-Pressure Space Suits using Active Materials

2012 ◽  
Author(s):  
Bradley Holschuh ◽  
Edward Obropta ◽  
Leah Buechley ◽  
Dava Newman
Keyword(s):  
Active Materials ◽  
Counter Pressure ◽  
Space Suits ◽  
Mechanical Counter

scholarly journals Development of Underwater Motion Capture System for Space Suit Mobility Assessment

2017 ◽  
Vol 61 (1) ◽  
pp. 945-949 ◽  
Author(s):  
Yaritza Bernal ◽  
K. Han Kim ◽  
Elizabeth Benson ◽  
Sarah Jarvis ◽  
Lauren Harvill ◽  
...  
Keyword(s):  
Motion Capture ◽  
Whole Body ◽  
Microgravity Environment ◽  
Motion Capture System ◽  
Space Suit ◽  
Neutral Buoyancy ◽  
Dry Land ◽  
Mobility Assessment ◽  
Space Suits ◽  
Land Condition

The objective of this study was to develop and deploy a novel motion capture system that utilizes off-the-shelf, dive-rated hardware to measure 3-D whole body reach envelopes of space suits in an underwater analog, which simulates a microgravity environment. The accuracy of the developed system was compared to a gold standard motion capture system in a dry-land condition before deployment. This study is ultimately aimed at providing a methodology for quantitative metrics to evaluate and compare the mobility performances of a newly developed prototype space suit versus an existing space suit at the Neutral Buoyancy Laboratory (NBL) at NASA’s Johnson Space Center.

scholarly journals Rapid compressions in a captive bubble apparatus are isothermal

2003 ◽  
Vol 95 (5) ◽  
pp. 1896-1900
Author(s):  
Wenfei Yan ◽  
Stephen B. Hall
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Phase ◽  
Pulmonary Surfactant ◽  
First Order ◽  
First Order Kinetics ◽  
Gas Phase Molecules ◽  
Actual Change ◽  
Phase Temperature ◽  
Two Phases ◽  
Interfacial Films

Captive bubbles are commonly used to determine how interfacial films of pulmonary surfactant respond to changes in surface area, achieved by varying hydrostatic pressure. Although assumed to be isothermal, the gas phase temperature (Tg) would increase by >100°C during compression from 1 to 3 atm if the process were adiabatic. To determine the actual change in temperature, we monitored pressure (P) and volume (V) during compressions lasting <1 s for bubbles with and without interfacial films and used P · V to evaluate Tg. P · V fell during and after the rapid compressions, consistent with reductions in n, the moles of gas phase molecules, because of increasing solubility in the subphase at higher P. As expected for a process with first-order kinetics, during 1 h after the rapid compression P · V decreased along a simple exponential curve. The temporal variation of n moles of gas was determined from P · V >10 min after the compression when the two phases should be isothermal. Back extrapolation of n then allowed calculation of Tg from P · V immediately after the compression. Our results indicate that for bubbles with or without interfacial films compressed to >3 atm within 1 s, the change in Tg is <2°C.

Denaturation and Renaturation of Bovine Liver Glutamic Dehydrogenase after Dissociation in Various Denaturants

1980 ◽  
Vol 35 (3-4) ◽  
pp. 222-228 ◽  
Author(s):  
Klaus Müller ◽  
Rainer Jaenicke
Keyword(s):  
Hydrostatic Pressure ◽  
Sodium Dodecylsulfate ◽  
Side Reaction ◽  
Bovine Liver ◽  
Enzyme Concentration ◽  
Native Enzyme ◽  
Spectroscopic Techniques ◽  
First Order ◽  
Residual Structure ◽  
Glutamic Dehydrogenase

Abstract Oligomeric glutamic dehydrogenase from bovine liver is dissociated to inactive monomers (Mr = 56 000) under a wide variety of conditions: 3 ≥ pH ≥ 12, 6 ᴍ guanidine · HCl, 6 ᴍ urea, 0.2% sodium dodecylsulfate. High hydrostatic pressure (< 1 kbar) only affects the association equilibrium of the native hexamer to higher polymers. The respective reaction volume (ΔV=28 ± 5 ml · mol-1 at 298 K, 1 bar) is linearly dependent on temperature and pressure. At p > 1.5 kbar dissociation of the hexamer occurs; this reaction is accompanied by irreversible deactivation. Depending on the denaturant applied for the monomerization, the final conformational stale of the polypeptide chain differs widely regarding its residual structure. As taken from laser light scattering measurements the rate of dissociation at pH 1.8 follows first order kinetics with a rate constant k1 = 0.42 ± 0.06 s-1. In the range of the oligomer ⇌ monomer transition, dissociation is accompanied by irreversible aggregation leading to inactive high molecular weight material. At low concentration (c < 5 µg/ml) this side reaction can be slowed down, so that the reconstitution of the enzyme can be monitored using spectroscopic techniques. Concentration dependent stopped-flow experiments prove the regain of fluorescence to be a rapid first order process; the respective half-times at pH 7.4 are τ1/2 = 2.0 ± 0.5 ms and 0.7 ± 0.2 ms for the “renaturation” from 6 ᴍ guanidine · HCl, pH 6, and pH ~ 2, respectively. The product of reconstitution shows the fluorescence and circular dichroism pattern characteristic for the native enzyme. However, no reactivation can be achieved under any of the following conditions: optimum protection against chemical modification; variation of enzyme concentration, temperature, and hydrostatic pressure; addition of specific ligands such as coenzymes, substrates, ADP, membrane constituents (cardiolipin, electron transfer particles ETPH). Obviously, the “renaturation” (D → N) of glutamic dehydrogenase is governed by a side reaction according to N → D ⇌ R → A which causes aggregation of intermediates R instead of reconstitution of the native enzyme.

Mechanism of Stress-Enhanced Solid-Phase Epitaxy

1991 ◽  
Vol 237 ◽  
Author(s):  
T. K. Chaki
Keyword(s):  
Hydrostatic Pressure ◽  
Point Defects ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Amorphous Layer ◽  
Crystalline Phases ◽  
Self Diffusion ◽  
Bending Stresses ◽  
Enhanced Mobility ◽  
The Difference

ABSTRACTEnhancement of solid-phase epitaxial growth (SPEG) due to hydrostatic pressures and bending stresses is explained by stress-enhanced mobility of point defects in the amorphous solid. The crystallization is by the adjustment of atomic positions in the vicinity of the crystallization/amorphous (c-a) interface due to self-diffusion in the amorphous phase, assisted by a free energy decrease equal to the difference in free energies between the amorphous and crystalline phases. Due to a mismatch in the bulk moduli between the amorphous and crystalline phases, the application of a hydrostatic pressure can develop tensile stresses in the amorphous layer near the c-a interface. Non-hydrostatic stresses in the amorphous layer enhance the mobility of point defects in the amorphous layer and, therefore, an enhancement of the SPEG rate. In the cases of both hydrostatic pressure and bending, the enhancement occurs in the tensile side, indicating that vacancy-like mechanism is predominant in SPEG.

Bio-Suit Development: Viable Options for Mechanical Counter Pressure

2004 ◽  
Author(s):  
Kristen Bethke ◽  
Christopher E. Carr ◽  
Bradley M. Pitts ◽  
Dava J. Newman
Keyword(s):  
Counter Pressure ◽  
Mechanical Counter

A mathematical model for washing a tow of fibres: Part 1

1994 ◽  
Vol 5 (4) ◽  
pp. 525-535 ◽  
Author(s):  
E. L. Terrill ◽  
J. G. Byatt-Smith
Keyword(s):  
Mathematical Model ◽  
Numerical Solutions ◽  
Fluid Pressure ◽  
Critical Value ◽  
Existence Proof ◽  
Volume Flux ◽  
First Order ◽  
Flow Through ◽  
Viscous Boundary ◽  
Gap Width

A mathematical model is presented for the washing of a band, or tow, of fibres which is pulled past a submerged obstacle. A lubrication flow between the obstacle and the tow is coupled to a flow through the tow, which is modelled as a porous medium. Coupled first-order ordinary differential equations for the fluid pressure and volume flux are solved numerically and the results are analysed. The washing of the tow induced by the reversal of the viscous boundary layers lying above and below the tow is discussed briefly. In Part 2, the model is extending to allow for fibre bending. The numerical solution of the resulting differential equation shows that at a critical value of the tow porosity, the tow touches the obstacle. An existence proof for a family of touching solutions is obtained. Using the existence of these solutions, a method for constructing a solution with a rubbing region, where the gap width is zero, is outlined. The numerical solutions for these solutions are also given.

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