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At least 775 records · Page 43Linked to original sources

PubMed1990

A new type of blood component collector: plasma separation using gravity without any electrical devices.

A new type of blood component collector (BCC) was developed to divide 450 ml of whole blood into plasma and a red cell concentrate using gravity without electrical devices. This BCC system is composed of one whole blood collection bag, two product collection bags and a plasma separator, which consists of a bundle of hydrophilized polyethylene hollow fibers (0.2 micron pore size). Without rinsing the plasma separator, the whole blood (458.1 +/- 13.5 ml, n = 22) was run through the separator using gravity without a pump. An average of 175.9 ml of plasma was collected within 11 min without hemolysis. In this completely cell-free plasma, the recovery of total protein, albumin, globulin, IgG and IgA was nearly 100%. Prothrombin time and activated partial thromboplastin time were in a normal range and the activity of coagulation factors did not change after the separation. In the red cell concentrate, the recovery of red cells, white cells and platelets was 94.7, 98.4 and 82.7%, respectively. Osmotic fragility of red cells, platelet morphology and functions did not change. These observations suggest that this new type of BCC is useful as a simple, fast and safe component collector.

Blood Platelets↗

PubMed2005

Improvement of ethanol production in very high gravity fermentation by horse gram (Dolichos biflorus) flour supplementation.

AIMS: To determine the effect of osmotic stress on yeast and to investigate the protective role of horse gram flour during very high gravity (VHG) ethanol fermentation. METHODS AND RESULTS: Saccharomyces cerevisiae was inoculated into high sugar (30-40%, w/v) containing medium with and without supplementation of horse gram flour. The fermentation experiments were carried out in batch mode. The effect of 4 or 6% of horse gram flour to the medium on the metabolic behaviour and viability of yeast was studied. Significant increase in ethanol yield up to 50% and dramatic decrease in glycerol production up to 100% was observed in the presence of horse gram flour. The fermentation rate was increased from 3 to 5 days with increased viable cell count. The physical and chemical factors of horse gram flour may aid in reducing the osmotic stress of high gravity fermentation of ethanol as well as enhancing ethanol yield. CONCLUSIONS: It was found that horse gram flour not only reduced fermentation time but also enhanced ethanol production by better utilization of sugar. SIGNIFICANCE AND IMPACT OF THE STUDY: Production of high ethanol concentration by using VHG sugar fermentation eliminates the expensive steps in the conventional process and saves time.

Dolichos↗

PubMed1983

Comparative thermoresistance of two biological indicators for monitoring steam autoclaves. I. Comparison performed in a gravity BIER/Steam Vessel.

The thermoresistance of two biological indicators (BIs) for steam sterilization control (Swedish spore tablets and Attest No. 1242 BI) was compared at 121 degrees C and at 134 degrees C, saturated steam, in a special test autoclave (a gravity BIER/Steam Vessel). In this autoclave, three lots of Attest No. 1242 BI (ABI) demonstrated longer survival exposure times than did the three lots of the Scandinavian BI (SBI) tested while the survival-kill range was approx. the same. Also, the ABI had higher D121 degrees C- and D134 degrees C- values based on fraction-negative tests. The D121 degrees C-value of approx, 1.5 min as suggested by the European Pharmacopoeia, was met by both BIs. The larger spore population and the package configuration of the ABI units contribute to the higher thermoresistance of the ABI in the gravity BIER/Steam Vessel.

Geobacillus stearothermophilus↗

PubMed1988

Organizational principles of velocity storage in three dimensions. The effect of gravity on cross-coupling of optokinetic after-nystagmus.

1. Optokinetic nystagmus was elicited in alert monkeys by movement of the visual surround in their horizontal or yaw plane, and optokinetic after-nystagmus was recorded in darkness. The animals were upright or were statically tilted at various angles from the upright. While upright, the OKAN was horizontal, and there were no vertical or roll components. When animals were tilted to either side or forward or back, vertical or roll components appeared both in the primary and secondary OKAN. Such components were also observed during nystagmus and after-nystagmus induced by electrical stimulation of the nucleus of the optic tract. The characteristics of the cross-coupled components indicated that they were mediated through the velocity storage mechanism in the vestibulo-ocular reflex. 2. A principle was inferred that explained the appearance of cross-coupled vertical or roll components in the primary and secondary OKAN: With the animal in a tilted position, a vector of eye velocity during OKN along the body-vertical axis was converted during primary OKAN toward a spatial-vertical axis with the same sense by a right hand rule. Thus, slow phase velocity along a vector toward the top of the animal's head during horizontal OKN rotated so that it tended to be directed spatially upward during primary OKAN. The reverse was true for OKN with a velocity vector directed toward the animal's feet. It rotated during primary OKAN so that it tended to be aligned with the direction of gravity. The vector of velocity during secondary OKAN was opposite to the direction of the vector during primary OKAN and was approximately aligned with spatial vertical. 3. OKN and OKAN were elicited about the animal's pitch and roll axes while they were upright and statically tilted at various angles away from the spatial vertical. There was a graded increase in the strength of vertical and roll OKN and OKAN and in the falling time constant of OKAN as the animals were tilted so that the axis of pitch or roll eye movements was moved toward alignment with the spatial vertical. Thus, velocity storage during pure vertical and roll nystagmus was similar to that during yaw OKN and OKAN in tilted positions: it was maximal along the pitch and roll axes when these axes were aligned with gravity. 4. The data indicate that the gravitational field is of fundamental importance in imposing a spatial reference onto the velocity storage integrator.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2002

The influence of gravity on composition uniformity and microstructure in immiscible Al-In alloys.

The results obtained from flight experiments on hypermonotectic Al-In alloys carried out during the Life and Microgravity Spacelab mission are presented and compared to those predicted from models that have been developed for solute redistribution in eutectic alloy systems. Experimental results from microgravity experiments are also compared with results obtained from unit gravity directional solidification experiments. Unit gravity directional solidification of hypermonotectic alloys results in macrosegregation due to convective instability inherent in these alloy systems. Identical samples directionally solidified under microgravity conditions reveal a much more uniform composition profile. Results indicate steady-state coupled growth is possible in hypermonotectic alloys through microgravity processing.

Journal Article↗

PubMed2002

Experimental investigation of the liquid interface reorientation upon step reduction in gravity.

Experiments have been carried out to investigate the settling behavior of a free liquid/gas interface in a partly filled right circular cylinder upon step reduction in gravity. Microgravity conditions were obtained within milliseconds after the release of a drop capsule in the drop tower facility in Bremen. In the experiments the cylinder radius was varied from 10 mm to 20mm with static contact angles of 2 degrees to 60 degrees. In addition to a series of silicone fluids, two different test liquids with a refractive index matched with the value of the cylinder material were used for experiments. The use of a digital high-speed recording system with a recording frequency of up to 500 fps allowed both an observation of the entire free liquid interface and a detail view on the moving contact line. Digital image processing techniques were applied to detect the contour of the free surface. For the initial condition the system is dominated by hydrostatic forces. In this case the equilibrium of the free liquid surface is characterized by a high Bond number yielding a flat surface and a small liquid ascent at the cylinder wall depending on the static contact angle. After transition to reduced gravity with a very low Bond number, capillary forces govern the flow and a capillary driven reorientation of the liquid to the new equilibrium position is established in a damped oscillation. The particular interest of this study is the investigation of the initial behavior of the free surface reorientation. It was found that the initial rise velocity of the contact point is determined by the Morton number and the static contact angle. Experimental results are presented that show an increasing rise velocity for decreasing Morton numbers. Further results characterize the initial behavior of the free surface at the center point as a function of characteristic time scales.

Journal Article↗

PubMed2002

Annular flow film characteristics in variable gravity.

Annular flow is a frequently occurring flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space systems. Annular two-phase flow occurs in the mining and transportation of oil and natural gas, petrochemical processes, and boilers and condensers in heating and refrigeration systems. The flow regime is also anticipated during the refueling of space vehicles, and thermal management systems for space use. Annular flow is mainly inertia driven with little effect of buoyancy. However, the study of this flow regime is still desirable in a microgravity environment. The influence of gravity can create an unstable, chaotic film. The absence of gravity, therefore, allows for a more stable and axisymmetric film. Such conditions allow for the film characteristics to be easily studied at low gas flow rates. Previous studies conducted by the Microgravity Research Group dealt with varying the gas or liquid mass fluxes at a reduced gravitational acceleration.(1,2) The study described here continues this work by examining the effect of changing the gravitational acceleration (hypergravity) on the film characteristics. In particular, the film thickness and the associated pressure drops are examined. The film thickness was measured using a pair of two-wire conductance probes. Experimental data was collected over a range of annular flow set points by changing the liquid and gas mass flow rates, the liquid-to-gas density ratio and the gravitational acceleration. The liquid-to-gas density ratio was varied by collecting data with helium-water and air-water at the same flow rates. The gravitational effect was examined by collecting data during the microgravity and pull-up (hypergravity) portions of the parabolic flights.

Journal Article↗

PubMed1989

Normal brain tissue response to photodynamic therapy: histology, vascular permeability and specific gravity.

The response of photodynamic therapy on normal brain was investigated in 140 Fisher rats. The rats were injected i.p. with Photofrin II (12.5 mg/kg) and 48 h later the dural area over the frontal cortex was photoactivated with red light (630 +/- 1 nm) from an argon dye laser. Treatment was performed with optical energy densities of 140 and 70 J/cm2. Histopathology, vascular permeability and specific gravity measurements were conducted on different populations of rats at 4 h, 24 h, 72 h and 1 week after photodynamic therapy (PDT). Histopathology revealed similar gross and microscopic pathology associated with light energies of 70 and 140 J/cm2 after all time points. A large cerebral infarct approximately the size of the brain surface area treated, evolved 24 h following treatment. Evans blue extravasation indicated a small area of vascular permeability evident as early as 4 h following PDT treatment at both energy levels, with increasing permeability evident at later time points. Specific gravity measurements taken on a representative area of the lesion indicated a significant (P less than 0.01) amount of edema present at 24 h post treatment with a gradual reduction approaching control values over the time period of 1 week. The data indicate a significant amount of damage to normal brain from low PDT treatment doses.

Animals↗

PubMed2003

Large trench-parallel gravity variations predict seismogenic behavior in subduction zones.

We demonstrate that great earthquakes occur predominantly in regions with a strongly negative trench-parallel gravity anomaly (TPGA), whereas regions with strongly positive TPGA are relatively aseismic. These observations suggest that, over time scales up to at least 1 million years, spatial variations of seismogenic behavior within a given subduction zone are stationary and linked to the geological structure of the fore-arc. The correlations we observe are consistent with a model in which spatial variations in frictional properties on the plate interface control trench-parellel variations in fore-arc topography, gravity, and seismogenic behavior.

Journal Article↗

PubMed2006

Measurements of time-variable gravity show mass loss in Antarctica.

Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment satellites, we determined mass variations of the Antarctic ice sheet during 2002-2005. We found that the mass of the ice sheet decreased significantly, at a rate of 152 +/- 80 cubic kilometers of ice per year, which is equivalent to 0.4 +/- 0.2 millimeters of global sea-level rise per year. Most of this mass loss came from the West Antarctic Ice Sheet.

Journal Article↗

PubMed2006

Satellite gravity measurements confirm accelerated melting of Greenland ice sheet.

Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is -239 +/- 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of -224 +/- 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.

Journal Article↗

PubMed2007

Atom interferometer measurement of the newtonian constant of gravity.

We measured the Newtonian constant of gravity, G, using a gravity gradiometer based on atom interferometry. The gradiometer measures the differential acceleration of two samples of laser-cooled Cs atoms. The change in gravitational field along one dimension is measured when a well-characterized Pb mass is displaced. Here, we report a value of G = 6.693 x 10(-11) cubic meters per kilogram second squared, with a standard error of the mean of +/-0.027 x 10(-11) and a systematic error of +/-0.021 x 10(-11) cubic meters per kilogram second squared. The possibility that unknown systematic errors still exist in traditional measurements makes it important to measure G with independent methods.

Journal Article↗

PubMed1998

A free-fall determination of the newtonian constant of gravity

Recent determinations of the Newtonian constant of gravity have produced values that differ by nearly 40 times their individual error estimates (more than 0.5%). In an attempt to help resolve this situation, an experiment that uses the gravity field of a one-half metric ton source mass to perturb the trajectory of a free-falling mass and laser interferometry to track the falling object was performed. This experiment does not suspend the test mass from a support system. It is therefore free of many systematic errors associated with supports. The measured value was G = (6.6873 +/- 0. 0094) x 10(-11) m3 kg-1 sec-2.

Journal Article↗

PubMed1999

The gravity field of Mars: results from Mars Global Surveyor.

Observations of the gravity field of Mars reveal a planet that has responded differently in its northern and southern hemispheres to major impacts and volcanic processes. The rough, elevated southern hemisphere has a relatively featureless gravitational signature indicating a state of near-isostatic compensation, whereas the smooth, low northern plains display a wider range of gravitational anomalies that indicates a thinner but stronger surface layer than in the south. The northern hemisphere shows evidence for buried impact basins, although none large enough to explain the hemispheric elevation difference. The gravitational potential signature of Tharsis is approximately axisymmetric and contains the Tharsis Montes but not the Olympus Mons or Alba Patera volcanoes. The gravity signature of Valles Marineris extends into Chryse and provides an estimate of material removed by early fluvial activity.

Atmosphere↗

PubMed1984

Cell sensitivity to gravity.

Cultures of human lymphocytes exposed in microgravity to the mitogen concanavalin A showed less than 3 percent of the activation of ground controls. This result supports the hypothesis, based on simulations at low g and experiments at high g, that microgravity depresses whereas high gravity enhances cell proliferation rates. The effects of gravity are particularly strong in cells undergoing differentiation.

Cell Differentiation↗

PubMed1994

Fuel alcohol production: optimization of temperature for efficient very-high-gravity fermentation.

The time required to end ferment wheat mash decreased as the temperature was increased from 17 to 33 degrees C, but it increased as the concentration of dissolved solids was raised from 14.0 to 36.5 g/100 ml. Ethanol yield was not appreciably affected. Over the range of fermentation temperatures tested, the addition of urea accelerated the rate of fermentation, decreased the time required to complete fermentation at all dissolved-solid concentrations, and stimulated the production of slightly more ethanol than was produced by the corresponding unsupplemented control mashes. The optimum temperature for maximum ethanol production in urea-supplemented very-high-gravity wheat mash was 27 degrees C. These data are important for the industrial assessment of very-high-gravity fermentation technology.

Journal Article↗

PubMed1987

Cardiac muscle ultrastructure and cyclic AMP reactions to altered gravity conditions.

Morphological and biochemical analyses of heart muscle of rats subjected to microgravity on Spacelab 3 (SL-3) flight and rats born and reared under increased gravity (1.7 G) conditions were compared with 1-G controls. Electronmicroscopic studies showed an increase in the number of lipid droplets and in areas of glycogen storage. Distribution changes of microtubules and cytoskeletal elements from both SL-3 and 1.7-G groups were observed. The high Km cyclic AMP phosphodiesterase activity was lower (P less than 0.05) in SL-3 heart muscle, and low Km activity was lower in 1.7-G males but was unaltered in females. Cyclic AMP-dependent protein kinase (cA-PK) activity was decreased in subcellular fractions of heart muscle of SL-3 animals. Recompartmentalization of cA-PK activity occurred in particulate tissue fraction of 1.7-G animals (70.3% of total for 1.7 G vs. 35.9% for controls). Phosphorylation of endogenous low-mobility proteins increased in SL-3 heart-soluble fractions. Photoaffinity labeling (18 h, 4 degrees C) decreased in type II cA-PK regulatory (R) subunits in both SL-3 and in 1.7-G male heart tissue particulate fractions. The 1.7-G female heart R subunit distribution did not differ from controls. These findings indicate that in heart muscle altered gravity conditions influenced physiological reactions similar to catecholamine-induced receptor-mediated hormonal responses.

Adenylyl Cyclases↗

PubMed1982

Effects of gravity and branching on longitudinal gas mixing in glass tube models.

We investigated the effects of gravity and branching on gas mixing in glass tube models. The mixed gas (5% He and 5% SF6) was made to flow through a straight tube and tubes with bifurcated branches, and the effective axial diffusion coefficient (Deff) was measured. The direction of the branches was varied from upward to downward by 90% turns, and the flow distribution to each branch was separately controlled. In the case of a straight horiontal tube, the flow velocity dependency of the Deff of He and SF6 was observed as we expected from Aris' equation. In the case of glass tubes with branches, the Deff of SF6 was greater in the downward-directed branches than it was in the upward-directed branches when gas mixing occurred at the front of the gas mixture; however, when gas mixing occurred at the tail, the opposite effects were observed. These characteristics were more marked at slower flow rates and when the flow to each branch was different. Our findings suggest that gravity has an effect on gas mixing in glass tube airway models, especially at a low flow rate and uneven flow distribution.

Gravitation↗