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1

Test Frame Simulates Zero Gravity  

NASA Technical Reports Server (NTRS)

Counterweighted frame simulates zero gravity in tests of solar-array wing. Net effect close simulation of zero-gravity environment in which wing must function. Frame also facilitates testing and replacement of solar-cell elements and panels.

Chung, D.; Lindberg, D.

1984-01-01

2

Zero-gravity movement studies  

NASA Technical Reports Server (NTRS)

The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms.

Badler, N. I.; Fishwick, P.; Taft, N.; Agrawala, M.

1985-01-01

3

Trying out zero gravity  

Microsoft Academic Search

Discusses the NASA Reduced Gravity Student Opportunities Program. The funding of the program together with the projects involved are discussed. The principles behind microgravity experiments carried out on an aircraft are also considered

E. Sopensky

1998-01-01

4

Zero-gravity cloud physics.  

NASA Technical Reports Server (NTRS)

The first results of an ongoing preliminary-concept and detailed-feasibility study of a zero-gravity earth-orbital cloud physics research facility are reviewed. Current planning and thinking are being shaped by two major conclusions of this study: (1) there is a strong requirement for and it is feasible to achieve important and significant research in a zero-gravity cloud physics facility; and (2) some very important experiments can be accomplished with 'off-the-shelf' type hardware by astronauts who have no cloud-physics background; the most complicated experiments may require sophisticated observation and motion subsystems and the astronaut may need graduate level cloud physics training; there is a large number of experiments whose complexity varies between these two extremes.

Hollinden, A. B.; Eaton, L. R.; Vaughan, W. W.

1972-01-01

5

Zero-gravity aerosol behavior  

NASA Technical Reports Server (NTRS)

The feasibility and scientific benefits of a zero gravity aerosol study in an orbiting laboratory were examined. A macroscopic model was devised to deal with the simultaneous effects of diffusion and coagulation of particles in the confined aerosol. An analytical solution was found by treating the particle coagulation and diffusion constants as ensemble parameters and employing a transformation of variables. The solution was used to carry out simulated zero gravity aerosol decay experiments in a compact cylindrical chamber. The results demonstrate that the limitations of physical space and time imposed by the orbital situation are not prohibitive in terms of observing the history of an aerosol confined under zero gravity conditions. While the absence of convective effects would be a definite benefit for the experiment, the mathematical complexity of the problem is not greatly reduced when the gravitational term drops out of the equation. Since the model does not deal directly with the evolution of the particle size distribution, it may be desirable to develop more detailed models before undertaking an orbital experiment.

Edwards, H. W.

1981-01-01

6

Modeling of zero gravity venting  

NASA Technical Reports Server (NTRS)

The venting of cylindrical containers partially filled with initially saturated liquids was conducted under zero gravity conditions and compared with an analytical model which determined the effect of interfacial mass transfer on the ullage pressure response during venting. A model is proposed to improve the estimation of the interfacial mass transfer. Duhammel's superposition integral is incorporated in this analysis to approximate the transient temperature response of the interface, treating the liquid as a semiinfinite solid with conduction heat transfer. This approach to estimating interfacial mass transfer gives improved response when compared to previous models. The model still predicts a pressure decrease greater than those in the experiments reported.

Merte, H., Jr.

1984-01-01

7

Zero-gravity quantity gaging system  

NASA Technical Reports Server (NTRS)

The Zero-Gravity Quantity Gaging System program is a technology development effort funded by NASA-LeRC and contracted by NASA-JSC to develop and evaluate zero-gravity quantity gaging system concepts suitable for application to large, on-orbit cryogenic oxygen and hydrogen tankage. The contract effective date was 28 May 1985. During performance of the program, 18 potential quantity gaging approaches were investigated for their merit and suitability for gaging two-phase cryogenic oxygen and hydrogen in zero-gravity conditions. These approaches were subjected to a comprehensive trade study and selection process, which found that the RF modal quantity gaging approach was the most suitable for both liquid oxygen and liquid hydrogen applications. This selection was made with NASA-JSC concurrence.

1989-01-01

8

Early cardiovascular adaptation to simulated zero gravity  

NASA Technical Reports Server (NTRS)

A study was conducted on five normal male volunteers (23-29 yr), under controlled conditions, to evaluate early adaptive responses to zero gravity. Specific objectives are (1) to characterize the hemodynamic, renal and hormonal responses to a central fluid shift, and (2) to compare data obtained during and after head-down tilt with corresponding data from actual space flight to validate tilt as a physiological model for simulation of zero gravity. Zero gravity is simulated by a 24-hr period of head-down tilt at 5 deg. The results suggest that hemodynamic adaptation occurs rapidly and is essentially accomplished by 6 hr, and that adaptation includes diuresis and reduction in blood volume. The validity of head-down tilt at 5 deg as an experimental model is established by comparing the results obtained with data from Apollo and Skylab astronauts on body fluid distributions and postflight responses to orthostatic and exercise stress.

Nixon, J. V.; Murray, R. G.; Bryant, C.; Johnson, R. L., Jr.; Mitchell, J. H.; Holland, O. B.; Gomez-Sanchez, C.; Vergne-Marini, P.; Blomqvist, C. G.

1979-01-01

9

Zero Temperature Black Holes in Semiclassical Gravity  

NASA Astrophysics Data System (ADS)

Static spherically symmetric zero temperature black holes are very interesting and important at the classical, semiclassical, and quantum levels. Classically the only static black hole solution to Einstein's equations with zero surface gravity (and hence zero temperature) is the extreme Reissner-Nordström (ERN) black hole, which possesses a charge equal in magnitude to its mass. At the quantum level, the statistical mechanical entropy of zero temperature (extreme) black holes has been calculated in string theory1 and shown to be identical to the usual Bekenstein-Hawking thermodynamic entropy. The usual semiclassical temperature and entropy calculations for ERN black holes have all been made in the test field approximation where the effects of quantized fields on the spacetime geometry are ignored. However, it is well known that quantum effects alter the spacetime geometry near the event horizon of a black hole. In particular they can change its surface gravity and hence its temperature2,3,4...

Anderson, Paul R.; Hiscock, William A.; Taylor, Brett E.

2002-12-01

10

Zero gravity testing of flexible solar arrays  

NASA Technical Reports Server (NTRS)

Zero gravity testing in the KC-135 aircraft of flat fold flexible solar array test specimens sufficiently demonstrated the adequacy of the panel design. The aircraft flight crew provided invaluable assistance and significantly contributed to the design and development of the flexible solar array, and ultimately to the potential success of the solar electric propulsion solar array shuttle flight experiment program.

Chung, D. T.; Young, L. E.

1981-01-01

11

Zero gravity tissue-culture laboratory  

NASA Technical Reports Server (NTRS)

Hardware was developed for performing experiments to detect the effects that zero gravity may have on living human cells. The hardware is composed of a timelapse camera that photographs the activity of cell specimens and an experiment module in which a variety of living-cell experiments can be performed using interchangeable modules. The experiment is scheduled for the first manned Skylab mission.

Cook, J. E.; Montgomery, P. O., Jr.; Paul, J. S.

1972-01-01

12

Containing Hair During Cutting In Zero Gravity  

NASA Technical Reports Server (NTRS)

Proposed device collects loose hair during barbering and shaving in zero gravity to prevent hair clippings from contaminating cabin of spacecraft. Folds for storage, opens into clear, bubblelike plastic dome surrounding user's head, tray fits around user's throat, and fanlike ring surrounds back of neck. Device fits snugly but comfortably around neck, preventing hair from escaping to outside. Flow of air into hose connected to suction pump removes hair from bubble as cut. Filter at end of hose collects hair.

Haines, Richard F.

1992-01-01

13

Airborne space simulator with zero gravity effects  

US Patent & Trademark Office Database

Systems, devices, apparatus and methods of using a simulator cabin module with an interior space which replicates a space ship, where the simulator module is mounted in a real aircraft, as a real airborne simulator. The aircraft lifts off to provide airborne maneuvers such as parabolic flight paths to cause G force and zero gravity effects to passengers in the cabin module. The cabin module includes rows of seats where passengers experience realistic sounds, lights, different temperatures, and physical effects (vibrations) of space ship liftoffs and space travel by having realistic simulation effects distributed over the seated passengers. Passengers can be seated in special reclinable seats with 5 point harnesses and pilot helmets with operable wireless communications and uniforms to add to the realistic simulation effects. Simulator modules can also be mounted in other moving vehicles, such as but not limited to submersibles, ships, and the like.

2012-08-14

14

Marangoni bubble motion in zero gravity. [Lewis zero gravity drop tower  

NASA Technical Reports Server (NTRS)

It was shown experimentally that the Marangoni phenomenon is a primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low gravity environment. A mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented. Parameter perturbation theory is used to solve this boundary value problem; the expansion parameter is the Marangoni number. The zeroth, first, and second order approximations for the velocity, temperature and pressure distributions in the liquid and in the bubble, and the deformation and terminal velocity of the bubble are determined. Experimental zero gravity data for a nitrogen bubble in ethylene glycol, ethanol, and silicone oil subjected to a linear temperature gradient were obtained using the NASA Lewis zero gravity drop tower. Comparison of the zeroth order analytical results for the bubble terminal velocity showed good agreement with the experimental measurements. The first and second order solutions for the bubble deformation and bubble terminal velocity are valid for liquids having Prandtl numbers on the order of one, but there is a lack of appropriate data to test the theory fully.

Thompson, R. L.; Dewitt, K. J.

1979-01-01

15

Marangoni Bubble Motion in Zero Gravity.  

National Technical Information Service (NTIS)

It was shown experimentally that the Marangoni phenomenon is a primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low gravity environment. A mathematical model consisting of the Navier-Stokes and thermal energy equations, to...

R. L. Thompson K. J. Dewitt

1979-01-01

16

Combustion of solid carbon rods in zero and normal gravity  

NASA Technical Reports Server (NTRS)

In order to investigate the mechanism of carbon combustion, spectroscopic carbon rods were resistance ignited and burned in an oxygen environment in normal and zero gravity. Direct mass spectrometric sampling was used in the normal gravity tests to obtain concentration profiles of CO2, CO, and O2 as a function of distance from the carbon surface. The experimental concentrations were compared to those predicted by a stagnant film model. Zero gravity droptower tests were conducted in order to assess the effect of convection on the normal gravity combustion process. The ratio of flame diameter to rod diameter as a function of time for oxygen pressures of 5, 10, 15, and 20 psia was obtained for three different diameter rods. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter.

Spuckler, C. M.; Kohl, F. J.; Miller, R. A.; Stearns, C. A.; Dewitt, K. J.

1979-01-01

17

Glass fining experiments in zero gravity  

NASA Technical Reports Server (NTRS)

Ground based experiments were conducted to demonstrate that thermal migration actually operated in glass melts. Thermal migration consistent with the theory was found in one experiment on a borax melt, i.e., there was an approximately linear relation between the bubble diameter and bubble velocity for a given temperature and temperature gradient. It also appeared that nearby bubbles were attracted to one another, which could greatly aid fining. Interpretation of these results was not possible because of complications arising from gravity, i.e., floating of the bubbles, circulation currents due to buoyancy-driven natural connection, and flow of the melt out from the cell.

Smith, H. D.

1977-01-01

18

Zero-Gravity Open-Type Urine Receptacle.  

National Technical Information Service (NTIS)

The development of the zero-gravity open-type urine receptacle used in the Apollo command module is described. This type receptacle eliminates the need for a cuff-type urine collector or for the penis to circumferentially contact the receptacle in order t...

A. S. Girala

1972-01-01

19

The response of single human cells to zero-gravity  

NASA Technical Reports Server (NTRS)

Microscopic and histochemical evaluations of human embrionic lung cells after exposure to zero-gravity are reported. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of fixed cells revealed no effects on the cultures. Minor unexplained differences have been found in biochemical constituents of the samples.

Montgomery, P. O., Jr.; Cook, J. E.; Reynolds, R. C.; Paul, J. S.; Hayflick, L.; Stock, D.; Shulz, W. W.; Kimzey, S. L.; Thirolf, R. G.; Rogers, T.

1977-01-01

20

Zero Gravity Cryogenic Vent System Concepts for Upper Stages  

Microsoft Academic Search

The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid\\/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical

Alain Ravex; Robin Flachbart; Barney Holt

1999-01-01

21

Baroreceptor activity potentially facilitates cortical inhibition in zero gravity.  

PubMed

Baroreceptor stimulation induces cortical inhibition. With blood not drawn by gravity from the upper to lower body, adopting a less upright posture leads to increases in thoracic blood volume and baroreceptor stimulation. Consistent with these effects are observations of cortical activity being inhibited when reclining or tilted head-down. As with less upright postures, in zero gravity there is a redistribution of blood towards the upper body that stimulates baroreceptors. Effects associated with this stimulation could be expected to facilitate an inhibition of cortical activity during zero gravity, as recently reported to occur during parabolic flight (Schneider et al., 2008. What happens to the brain in weightlessness? A first approach by EEG tomography. NeuroImage 42, 1316-1323). PMID:19457387

Lipnicki, Darren M

2009-05-15

22

4He crystals in superfluid under zero gravity.  

PubMed

The response of 4He crystals to the rapid reduction of gravity down to practically zero in a superfluid was investigated visually, utilizing the parabolic flight of a jet plane. At a high temperature of 1.6 K, the shape of 4He crystals in the bcc phase did not change with a reduction of gravity during a parabolic period of 20 s, due to the low crystallization rate. At lower temperatures, such as 0.63 K, where the crystallization rate is sufficiently high, the shape of 4He crystals in the hcp phase changed significantly, relaxing to a quasiequilibrium shape under zero gravity, where the c facet became enlarged and the a facet emerged on the surface. The crystal did not detach from the sample cell wall at any time because the adhesive force manifested as partial wetting to the wall was sufficiently strong. Some crystals removed from the wall by an acoustic wave pulse were found to float and drift in the superfluid for approximately 4.2 s under zero gravity, although most of them were quickly reattached to the wall. PMID:22587030

Takahashi, Takuya; Nomura, Ryuji; Okuda, Yuichi

2012-03-01

23

The response of single human cells to zero gravity  

NASA Technical Reports Server (NTRS)

Twenty separate cultures of Wistar-38 human embryonic lung cells were exposed to a zero-gravity environment on Skylab for periods of time ranging from one to 59 days. Duplicate cultures were run concurrently as ground controls. Ten cultures were fixed on board the satellite during the first 12 days of flight. Growth curves, DNA microspectrophotometry, phase microscopy, and ultrastructural studies of the fixed cells revealed no effects of a zero-gravity environment on the ten cultures. Two cultures were photographed with phase time lapse cinematography during the first 27 days of flight. No differences were found in mitotic index, cell cycle, and migration between the flight and control cells. Eight cultures were returned to earth in an incubated state. Karyotyping and chromosome banding tests show no differences between the flight and control cells.

Montgomery, P. O., Jr.; Cook, J. E.; Reynolds, R. C.; Paul, J. S.; Hayflick, L.; Schulz, W. W.; Stock, D.; Kinzey, S.; Rogers, T.; Campbell, D.

1975-01-01

24

Development of a compact dilution refrigerator for zero gravity operation  

NASA Technical Reports Server (NTRS)

A compact dilution refrigerator design based on internal charcoal adsorption is being tested for operation in zero gravity. This refrigerator is self-contained with no external pumps or gas handling system and provides reliable operation since it has no moving parts. All operations are performed with heaters and are completely computer controlled. The refrigerator is capable of providing many hours of operation at very low temperature before the charcoal pumps must be recycled.

Roach, Pat R.; Helvensteijn, Ben

1990-01-01

25

Fluid management system for a zero gravity cryogenic storage system  

NASA Technical Reports Server (NTRS)

The fluid management system comprises a mixing/recirculation system including an external recirculation pump for receiving fluid from a zero gravity storage system and returning an output flow of the fluid to the storage system. An internal axial spray injection system is provided for receiving a portion of the output flow from the recirculation pump. The spray injection system thermally de-stratifies liquid and gaseous cryogenic fluid stored in the storage system.

Lak, Tibor I. (Inventor)

1995-01-01

26

Investigation of crystal growth from solutions. [in zero gravity environments  

NASA Technical Reports Server (NTRS)

The quality was investigated of a crystal of Rochelle salt grown from a solution placed in the zero-gravity environment of Skylab 4. The crystal has the following unique features: (1) the typical cavity is a long tube extending along the c-axis, the average length being 4mm, compared to 0.1mm that is the average size for earth-grown crystals; and (2) the crystal consists of several single crystals, the axes of which are parallel to each other. A preliminary measurement was made on the ferroelectric hysteresis curve of this Rochelle salt crystal.

Miyagawa, I.

1974-01-01

27

Dichotomous behavior of capillary surfaces in zero gravity  

NASA Technical Reports Server (NTRS)

A mathematical procedure is described for determining the behavior of the free surface of a fluid in static equilibrium and partly filling a cylindrical container with cross-section of general form in zero gravity. Either of two qualitatively distinct situations must prevail, depending on geometry and contact angle. Several illustrative examples are discussed, and the procedure is applied in detail to a container with a rectangular section on which the corners have been rounded, thereby determining the effect of rounding on the 'critical' contact angle that separates the two types of behavior. This last example is intended in part as a guide for application to general geometries.

Concus, Paul; Finn, Robert

1990-01-01

28

Development of coatings to control electroosmosis in zero gravity electrophoresis  

NASA Technical Reports Server (NTRS)

A major problem confronting the operation of free fluid electrophoresis in zero gravity is the control of electrokinetic phenomena and, in particular, electroosmosis. Due to the severity of counter flow as a result of electroosmosis, the electrical potential developed at the surface of shear must be maintained at near, or as close, to zero millivolts as possible. Based upon this investigation, it has been found that the amount of bound water or the degree of hydroxylation plays a major role in the control of this phenomenon. Based upon tests employing microcapillary electrophoresis, it has been found that gamma amino propyl trihydroxysilane produced a coating which provides the lowest potential (about 3.86 mV) at the surface of shear between the stationary and mobile layers.

Krupnick, A. C.

1974-01-01

29

Zero-gravity cloud physics laboratory: Experiment program definition and preliminary laboratory concept studies  

NASA Technical Reports Server (NTRS)

The experiment program definition and preliminary laboratory concept studies on the zero G cloud physics laboratory are reported. This program involves the definition and development of an atmospheric cloud physics laboratory and the selection and delineations of a set of candidate experiments that must utilize the unique environment of zero gravity or near zero gravity.

Eaton, L. R.; Greco, E. V.

1973-01-01

30

Ocular Blood Flow Measured Noninvasively in Zero Gravity  

NASA Technical Reports Server (NTRS)

In spaceflight or a reduced-gravity environment, bodily fluids shift to the upper extremities of the body. The pressure inside the eye, or intraocular pressure, changes significantly. A significant number of astronauts report changes in visual acuity during orbital flight. To date this remains of unknown etiology. Could choroidal engorgement be the primary mechanism and a change in the curvature or shape of the cornea or lens be the secondary mechanism for this change in visual acuity? Perfused blood flow in the dense meshwork of capillaries of the choroidal tissue (see the preceding illustration) provides necessary nutrients to the outer layers of the retina (photoreceptors) to keep it healthy and maintain good vision. Unlike the vascular system, the choroid has no baroreceptors to autoregulate fluid shifts, so it can remain engorged, pushing the macula forward and causing a hyperopic (farsighted) shift of the eye. Experiments by researchers at the NASA Glenn Research Center could help answer this question and facilitate planning for long-duration missions. We are investigating the effects of zero gravity on the choroidal blood flow of volunteer subjects. This pilot project plans to determine if choroidal blood flow is autoregulated in a reduced-gravity environment.

Ansari, Rafat R.; Manuel, Francis K.; Geiser, Martial; Moret, Fabrice; Messer, Russell K.; King, James F.; Suh, Kwang I.

2003-01-01

31

Zero-Gravity Vortex Vent and PVT Gaging System  

NASA Technical Reports Server (NTRS)

Space Station and satellite reservicing will require the ability to vent gas on orbit from liquid supply or storage tanks and to gage liquid quantity under microgravity conditions. In zero gravity, (zero-g) the vortex vent is capable of venting gas from a tank of liquid containing gas randomly distributed as bubbles. The concept uses a spinning impeller to create centrifugal force inside a vortex tube within a tank. This creates a gas pocket and forces the liquid through a venturi and back into the tank. Gas is then vented from the gas pocket through a liquid detector and then out through an exhaust port. If the liquid detector senses liquid in the vent line, the fluid is directed to the low-pressure port on the venturi and is returned to the tank. The advantages of this system is that it has no rotating seals and is compatible with most corrosive and cryogenic fluids. A prototype was designed and built at the NASA Johnson Space Center and flown on the KC-135 zero-g aircraft. During these test flights, where microgravity conditions are obtained for up to 30 sec, the prototype demonstrated that less than 0.10 percent of the volume of fluid vented was liquid when the tank was half full of liquid. The pressure volume temperature (PVT) gaging system is used in conjunction with the vortex vent to calculate the amount of liquid remaining in a tank under microgravity conditions. The PVT gaging system is used in conjunction with the vortex vent to gage liquid quantity in zero or low gravity. The system consists of a gas compressor, accumulator, and temperature and pressure instrumentation. To measure the liquid in a tank a small amount of gas is vented from the tank to the compressor and compressed into the accumulator. Pressure and temperature in the tank and accumulator are measured before and after the gas transfer occurs. Knowing the total volume of the tank, the volume of the accumulator, the volume of the intermediate lines, and initial and final pressures and temperatures, the mass of the gas leaving the tank is equated to the mass of the gas entering the accumulator. The volume of liquid remaining in the tank is calculated using the ideal gas law.

Downey, M. G.; Trevathan, J. T.

1989-01-01

32

Sediment-transport experiments in zero-gravity  

NASA Technical Reports Server (NTRS)

One of the important parameters in the analysis of sediment entrainment and transport is gravitational attraction. The availability of a laboratory in earth orbit would afford an opportunity to conduct experiments in zero and variable gravity environments. Elimination of gravitational attraction as a factor in such experiments would enable other critical parameters (such as particle cohesion and aerodynamic forces) to be evaluated much more accurately. A Carousel Wind Tunnel (CWT) is proposed for use in conducting experiments concerning sediment particle entrainment and transport in a space station. In order to test the concept of this wind tunnel design a one third scale model CWT was constructed and calibrated. Experiments were conducted in the prototype to determine the feasibility of studying various aeolian processes and the results were compared with various numerical analysis. Several types of experiments appear to be feasible utilizing the proposed apparatus.

Iversen, James D.; Greeley, Ronald

1987-01-01

33

Mass estimation and discrimination during brief periods of zero gravity  

NASA Technical Reports Server (NTRS)

Under zero gravity, the gravitational cues to mass are removed, but the inertial cues remain. A sensation of heaviness is generated if objects are shaken, and hence given a changing acceleration. A magnitude estimation experiment was conducted during the 0-G phase of parabolic flight and on the ground, and the results suggested that objects felt lighter under 0 G than under 1 G. Mass discrimination was also measured in flight, and yielded Weber fractions of .18 under 0 G, .16 under 1.8 G, and .09 under 1 G. Poor performance under microgravity and macrogravity was probably due mainly to lack of time for adaptation to changed G levels. It is predicted that discrimination should improve during the course of prolonged spaceflight, and that there should be an aftereffect of poor discrimination on return to earth.

Ross, H. E.; Reschke, M. F.

1982-01-01

34

Experiments on the properties of superfluid helium in zero gravity  

NASA Technical Reports Server (NTRS)

The paper describes a research program designed to study the behavior of superfluid liquid helium in low and zero gravity in order to determine the properties which are critically important to its use as a stored cryogen for cooling scientific instruments aboard spacecraft for periods up to several months. The experiment program consists of a series of flights of an experiment package on a free-fall trajectory both on an aircraft and on a rocket. The objectives are to study thickness of thin films of helium as a function of acceleration, heat transfer in thin films, heat transfer across copper-liquid helium interfaces, fluid dynamics of bulk helium in high and low accelerations and under various conditions of rotations, alternate methods of separation of liquid and vapor phases and of efficient venting of the vapor, and undesirable thermomechanical oscillations in the vent pipes. Preliminary results from aircraft tests are discussed.

Mason, P.; Collins, D.; Petrac, D.; Yang, L.; Edeskuty, F.; Williamson, K.

1976-01-01

35

Zero Gravity Cryogenic Vent System Concepts for Upper Stages  

NASA Technical Reports Server (NTRS)

The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray bar system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy is required. a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point. the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating, boil-off losses.

Flachbart, Robin H.; Holt, James B.; Hastings, Leon J.

1999-01-01

36

Zero Gravity Cryogenic Vent System Concepts for Upper Stages  

NASA Technical Reports Server (NTRS)

The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space, and would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray-bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray-bar system consists of a recirculation pump, a parallel flow concentric tube heat exchanger, and a spray-bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses.

Flachbart, Robin H.; Holt, James B.; Hastings, Leon J.

2001-01-01

37

Comprehensive solution to the cosmological constant, zero-point energy, and quantum gravity problems  

Microsoft Academic Search

We present a solution to the cosmological constant, the zero-point energy, and the quantum gravity problems within a single\\u000a comprehensive framework. We show that in quantum theories of gravity in which the zero-point energy density of the gravitational\\u000a field is well-defined, the cosmological constant and zero-point energy problems solve each other by mutual cancellation between\\u000a the cosmological constant and the

Philip D. Mannheim

2011-01-01

38

Precise Determination of the Zero-Gravity Surface Figure of a Mirror without Gravity-Sag Modeling  

NASA Technical Reports Server (NTRS)

The zero-gravity surface figure of optics used in spaceborne astronomical instruments must be known to high accuracy, but earthbound metrology is typically corrupted by gravity sag. Generally, inference of the zero-gravity surface figure from a measurement made under normal gravity requires finite-element analysis (FEA), and for accurate results the mount forces must be well characterized. We describe how to infer the zero-gravity surface figure very precisely using the alternative classical technique of averaging pairs of measurements made with the direction of gravity reversed. We show that mount forces as well as gravity must be reversed between the two measurements and discuss how the St. Venant principle determines when a reversed mount force may be considered to be applied at the same place in the two orientations. Our approach requires no finite-element modeling and no detailed knowledge of mount forces other than the fact that they reverse and are applied at the same point in each orientation. If mount schemes are suitably chosen, zero-gravity optical surfaces may be inferred much more simply and more accurately than with FEA.

Bloemhof, Eric E.; Lam, Jonathan C.; Feria, V. Alfonso; Chang, Zensheu

2007-01-01

39

Zero-gravity liquid-vapor interfaces in circular cylinders  

NASA Astrophysics Data System (ADS)

The zero-gravity problems of a liquid volume sealing a circular tube of gas and a gaseous volume in a circular tube of liquid both involve one phase obstructing another. The two problems differ only in contact angle. From pulmonary research there is a history of axisymmetric analyses for liquid droplets in circular tubes of gas. These analyses consider only axisymmetric solutions-an annulus and an axisymmetric plug. Only recently have nonsymmetric solutions for nonzero contact angle wetting liquids (0°-90° contact angle) been realized by the authors with the use of the Surface Evolver code. Similar to the problem of droplets in a gas filled tube, a bubble in a liquid-filled tube is of interest to the commercial satellite industry and in vascular physiology. Further analysis by the authors now fills in the other half of contact angle range, i.e., either a nonwetting liquid in a tube of gas (contact angles of 90°-180°), or equivalently, a gaseous bubble in a liquid that wets the tube wall. Conditions for the existence and stability of solutions of three topologies are examined.

Collicott, Steven H.; Lindsley, William G.; Frazer, David G.

2006-08-01

40

Steady state detached solidification of water at zero gravity  

NASA Astrophysics Data System (ADS)

Steady-state detached solidification of water was calculated using the Moving Meniscus Model. Similar to the experimental observation of many materials in microgravity, detached solidification of water is predicted to occur in a sealed ampoule at zero gravity under proper conditions. For steady detachment, the freezing rate must exceed a critical value, Henry's constant of the dissolved gas must be below a critical value, the temperature of the top of the water must be below a critical value, the contact angle of water on the ampoule wall must exceed a critical value, and the diffusion coefficient must exceed a critical value. Each critical value depends on the physical properties and the other operating conditions. Thus different results are obtained for InSb and water. The critical gas pressure above the melt for water is much smaller than for InSb, the critical freezing rate is larger for water, and the critical contact angle of the melt on the ampoule wall is larger for water. For the gases examined here, the solubilities of Ar, N 2 and Ne in water are sufficient for detachment to occur, while the solubility of He is not.

Wang, Yazhen; Regel, Liya L.; Wilcox, William R.

2001-06-01

41

Thermocapillary simulation of single bubble dynamics in zero gravity  

NASA Astrophysics Data System (ADS)

The lack of significant buoyancy effects in zero gravity conditions poses an issue with fluid transfer in a stagnant liquid. In this paper bubble movement in a stagnant liquid is analysed and presented numerically using a computational fluid dynamics (CFD) approach. The governing continuum conservation equations for two phase flow are solved using the commercial software package Ansys-Fluent v.13 and the Volume of Fluid (VOF) method is used to track the liquid/gas interface in 2D and 3D domains. The simulation results are in reasonable agreement with the earlier experimental observations, the VOF algorithm is found to be a valuable tool for studying the phenomena of gas-liquid interaction. The flow is driven via Marangoni influence induced by the temperature difference which in turn drives the bubble from the cold to the hot region. A range of thermal Reynolds (ReT) and Marangoni numbers (MaT) are selected for the numerical simulations, specifically ReT=13-658 and MaT=214-10,721 respectively. The results indicate that the inherent velocity of bubbles decreases with an increase of the Marangoni number, a result that is line with the results of previous space experiments (Kang et al., 2008) [1]. An expression for predicting the scaled velocity of bubble has been derived based on the data obtained in the present numerical study. Some three-dimensional simulations are also performed to compare and examine the results with two-dimensional simulations.

Alhendal, Yousuf; Turan, Ali; Hollingsworth, Peter

2013-07-01

42

Zero Gravity Cryogenic Vent System Concepts for Upper Stages  

NASA Astrophysics Data System (ADS)

The capability to vent in zero gravity without resettling is a technology need that involves practically all uses of sub-critical cryogenics in space. Venting without resettling would extend cryogenic orbital transfer vehicle capabilities. However, the lack of definition regarding liquid/ullage orientation coupled with the somewhat random nature of the thermal stratification and resulting pressure rise rates, lead to significant technical challenges. Typically a zero gravity vent concept, termed a thermodynamic vent system (TVS), consists of a tank mixer to destratify the propellant, combined with a Joule-Thomson (J-T) valve to extract thermal energy from the propellant. Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (MHTB) was used to test both spray bar and axial jet TVS concepts. The axial jet system consists of a recirculation pump heat exchanger unit. The spray bar system consists of a recirculation pump, a parallel flow concentric tube, heat exchanger, and a spray bar positioned close to the longitudinal axis of the tank. The operation of both concepts is similar. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it into the tank liquid, ullage, and exposed tank surfaces. When energy extraction is required, a small portion of the recirculated liquid is passed sequentially through the J-T expansion valve, the heat exchanger, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. The pump operates alone, cycling on and off, to destratify the tank liquid and ullage until the liquid vapor pressure reaches the lower set point. At that point, the J-T valve begins to cycle on and off with the pump. Thus, for short duration missions, only the mixer may operate, thus minimizing or even eliminating boil-off losses. TVS performance testing demonstrated that the spray bar was effective in providing tank pressure control within a 6.89 kPa (1psi) band for fill levels of 90%, 50%, and 25%. Complete destratification of the liquid and ullage was achieved at these fill levels. The axial jet was effective in providing tank pressure control within the same pressure control band at the 90% fill level. However, at the 50% level, the system reached a point at which it was unable to extract enough energy to keep up with the heat leak into the tank. Due to a hardware problem, the recirculation pump operated well below the axial jet design flow rate. Therefore, it is likely that the performance of the axial jet would have improved had the pump operated at the proper flow rate. A CFD model is being used to determine if the desired axial jet performance would be achieved if a higher pump flow rate were available. Testing conducted thus far has demonstrated that both TVS concepts can be effective in destratifying a propellant tank, rejecting stored heat energy, and thus, controlling tank pressure.

Ravex, Alain; Flachbart, Robin; Holt, Barney

43

An experimental and analytical investigation of thermoacoustic convection heat transfer in gravity and zero-gravity environments  

NASA Technical Reports Server (NTRS)

An experimental and analytical study of Thermoacoustic Convection heat transfer in gravity and zero-gravity environments is presented. The experimental apparatus consisted of a cylinder containing air as a fluid. The side wall of the cylinder was insulated while the bottom wall was allowed to remain at the ambient temperature. The enclosed air was rapidly heated by the top surface which consisted of a thin stainless steel foil connected to a battery pack as the power source. Thermocouples were used to measure the transient temperature of the air on the axis of the cylinder. The ouput of the thermocouples was displayed on digital thermometers and the temperature displays were recorded on film using a high-speed movie camera. Temperature measurements were obtained in the zero-gravity environment by dropping the apparatus in the 2-Seconds Zero-Gravity Drop Tower Facilities of NASA Lewis Research Center. In addition, experiments were also performed in the gravity environment and the results are compared in detail with those obtained under zero-gravity conditions.

Parang, Masood

1986-01-01

44

Assessment of geophysical flows for zero-gravity simulation  

NASA Technical Reports Server (NTRS)

The results of research relating to the feasibility of using a low gravity environment to model geophysical flows are presented. Atmospheric and solid earth flows are considered. Possible experiments and their required apparatus are suggested.

Winn, C. B.; Cox, A.; Srivatsangam, R.

1976-01-01

45

Thermo-hydro-dynamic characteristics of a zero-gravity, spherical model of the troposphere  

NASA Technical Reports Server (NTRS)

A model that exploits the radial inertia forces of a rotating fluid contained in a spherical annulus is described. The model would be flown in a satellite and experiments would be performed in very low or zero gravity. In such a model it would not be necessary to artificially simulate a radial gravity field. Thus small amounts of electrical energy would be sufficient to perform experiments. Since the only forces involved are thermo-hydro-dynamic ones, electromagnetic equations need not be considered.

Srivatsangam, S.

1976-01-01

46

On Calculating the Zero-Gravity Surface Figure of a Mirror  

NASA Technical Reports Server (NTRS)

An analysis of the classical method of calculating the zero-gravity surface figure of a mirror from surface-figure measurements in the presence of gravity has led to improved understanding of conditions under which the calculations are valid. In this method, one measures the surface figure in two or more gravity- reversed configurations, then calculates the zero-gravity surface figure as the average of the surface figures determined from these measurements. It is now understood that gravity reversal is not, by itself, sufficient to ensure validity of the calculations: It is also necessary to reverse mounting forces, for which purpose one must ensure that mountingfixture/ mirror contacts are located either at the same places or else sufficiently close to the same places in both gravity-reversed configurations. It is usually not practical to locate the contacts at the same places, raising the question of how close is sufficiently close. The criterion for sufficient closeness is embodied in the St. Venant principle, which, in the present context, translates to a requirement that the distance between corresponding gravity-reversed mounting positions be small in comparison to their distances to the optical surface of the mirror. The necessity of reversing mount forces is apparent in the behavior of the equations familiar from finite element analysis (FEA) that govern deformation of the mirror.

Bloemhof, Eric E.

2010-01-01

47

Study on processing immiscible materials in zero gravity  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to evaluate mixing immiscible metal combinations under several process conditions. Under one-gravity, these included thermal processing, thermal plus electromagnetic mixing, and thermal plus acoustic mixing. The same process methods were applied during free fall on the MSFC drop tower facility. The design is included of drop tower apparatus to provide the electromagnetic and acoustic mixing equipment, and a thermal model was prepared to design the specimen and cooling procedure. Materials systems studied were Ca-La, Cd-Ga and Al-Bi; evaluation of the processed samples included the morphology and electronic property measurements. The morphology was developed using optical and scanning electron microscopy and microprobe analyses. Electronic property characterization of the superconducting transition temperatures were made using an impedance change-tuned coil method.

Reger, J. L.; Mendelson, R. A.

1975-01-01

48

Vacuum/Zero Net-Gravity Application for On-Orbit TPS Tile Repair  

NASA Technical Reports Server (NTRS)

The Orbiter Columbia catastrophically failed during reentry February 1, 2003. All space Shuttle flights were suspended, including logistics support for the International Space Station. NASA LaRC s Structures and Materials Competency is performing characterizations of candidate materials for on-orbit repair of orbiter Thermal Protection System (TPS) tiles to support Return-to-Flight activities led by JSC. At least ten materials properties or attributes (adhesion to damage site, thermal protection, char/ash strength, thermal expansion, blistering, flaming, mixing ease, application in vacuum and zero gravity, cure time, shelf or storage life, and short-term outgassing and foaming) of candidate materials are of interest for on-orbit repair. This paper reports application in vacuum and zero net-gravity (for viscous flow repair materials). A description of the test apparatus and preliminary results of several candidate materials are presented. The filling of damage cavities is different for some candidate repair materials in combined vacuum and zero net-gravity than in either vacuum or zero net- gravity alone.

Harvey, Gale A.; Humes, Donald H.; Siochi, Emilie J.

2004-01-01

49

Silverton Conference on Applications of the Zero Gravity Space Shuttle Environment to Problems in Fluid Dynamics.  

National Technical Information Service (NTIS)

The possible utilization of the zero gravity resource for studies in a variety of fluid dynamics and fluid-dynamic related problems was investigated. A group of experiments are discussed and described in detail; these include experiments in the areas of g...

M. Eisner

1974-01-01

50

Vacuum/Zero Net-Gravity Application for On-Orbit TPS Tile Repair  

NASA Technical Reports Server (NTRS)

The Orbiter Columbia catastrophically failed during reentry February 1, 2003. All Space Shuttle flights were suspended, including logistics support for the International Space Station. NASA Langley Research Center s (LaRC) Structures and Materials Competency is performing characterizations of candidate materials for on-orbit repair of orbiter Thermal Protection System (TPS) tiles to support Return-to-Flight activities led by Johnson Space Center (JSC). At least ten materials properties or attributes (adhesion to damage site, thermal protection, char/ash strength, thermal expansion, blistering, flaming, mixing ease, application in vacuum and zero gravity, cure time, shelf or storage life, and short-term outgassing and foaming) of candidate materials are of interest for on-orbit repair. This paper reports application in vacuum and zero net-gravity (for viscous flow repair materials). A description of the test apparatus and preliminary results of several candidate materials are presented. The filling of damage cavities is different for some candidate repair materials in combined vacuum and zero net-gravity than in either vacuum or zero net-gravity alone.

Harvey, Gale A.; Humes, Donald H.; Siochi, Emilie J.

2004-01-01

51

Laboratory outreach: student assessment of flow cytometer fluidics in zero gravity.  

PubMed

Due to the the clinical utility of the flow cytometer, the National Aeronautics and Space Administration (NASA) is interested in the design of a space flight-compatible cytometer for use on long-duration space missions. Because fluid behavior is altered dramatically during space flight, it was deemed necessary to validate the principles of hydrodynamic focusing and laminar flow (cytometer fluidics) in a true microgravity environment. An experiment to validate these properties was conducted by 12 students from Sweetwater High School (Sweetwater, TX) participating in the NASA Reduced Gravity Student Flight Opportunity, Class of 2000. This program allows high school students to gain scientific experience by conducting an experiment on the NASA KC-135 zero gravity laboratory aircraft. The KC-135 creates actual zero-gravity conditions in 30-second intervals by flying a highly inclined parabolic flight path. The experiment was designed by their mentor in the program, the Johnson Space Center's flow cytometrist Brian Crucian, PhD, MT(ASCP). The students performed the experiment, with the mentor, onboard the NASA zero-gravity research aircraft in April 2000. PMID:12442765

Crucian, B; Norman, J; Brentz, J; Pietrzyk, R; Sams, C

2000-10-01

52

Some physiological effects of alternation between zero gravity and one gravity  

NASA Technical Reports Server (NTRS)

The anatomy and physiology of the healthy vestibular system and the history of its study, maintenance of muskuloskeletal fitness under low-gravity conditions, tests of motion sickness, and data and techniques on testing subjects in a slow rotation room, are covered. Components of the inner ear labyrinth and their behavior in relation to equilibrium, gravity and inertial forces, motion sickness, and dizziness are discussed. Preventive medicine, the biologically effective force environment, weightlessness per se, activity in a weightless spacecraft, exercizing required to maintain musculoskeletal function, and ataxia problems are dealt with.

Graybiel, A.

1977-01-01

53

Liquid jet impingement normal to a disk in zero gravity. Ph.D. Thesis Toledo Univ.  

NASA Technical Reports Server (NTRS)

The free surface shapes of circular liquid jets impinging normal to sharp-edged disks in zero gravity are determined. Zero gravity drop tower experiments yielded three distinct flow patterns that were classified in terms of the relative effects of surface tension and inertial forces. An order of magnitude analysis was conducted that indicated regions where viscous forces were not significant in the computation of free surface shapes. The free surface analysis was simplified by transforming the governing potential flow equations and boundary conditions into the inverse plane, where the stream function and velocity potential became the coordinates. The resulting nonlinear equations were solved by standard finite difference methods, and comparisons were made with the experimental data for the inertia dominated regime.

Labus, T. L.

1977-01-01

54

Liquid jet impingement normal to a disk in zero gravity. Ph.D. Thesis - Toledo Univ.  

NASA Technical Reports Server (NTRS)

An experimental and analytical investigation was conducted to determine the free surface shapes of circular liquid jets impinging normal to sharp-edged disks under both normal and zero gravity conditions. An order of magnitude analysis was conducted indicating regions where viscous forces were not significant when computing free surface shapes. The demarcation between the viscous and inviscid region was found to depend upon the flow Reynolds number and the ratio between the jet and disk radius.

Labus, T. L.

1976-01-01

55

The Marshall Space Flight Center KC-135 zero gravity test program for FY 1982  

NASA Technical Reports Server (NTRS)

During FY-82, researchers and experimenters from Marshall Space Flight Center (MSFC) conducted 11 separate investigations during 26.3 hr of testing aboard the KC-135 zero-gravity aircraft, based at Ellington Air force Base, Texas. Although this represented fewer hours than initially projected, all experiment and test objectives were met or exceeded. This Technical Memorandum compiles all results achieved by MSFC users during FY-82, a year considered to be highly productive.

Shurney, R. E. (editor)

1983-01-01

56

Preliminary concept, specifications, and requirements for a zero-gravity combustion facility for spacelab  

NASA Technical Reports Server (NTRS)

The preliminary concept, specifications, and requirements of a reusable zero gravity combustion facility (0-GCF) for use by experimenters aboard the spacelab payload of the space transportation system (STS) orbiter are described. The facility will be amenable to any mission of the STS orbiter in which a spacelab habitable segment and pallet segment are integral and for which orbital mission plans specify induced accelerations of 0.0001 g or less for sufficiently long periods so as not to impact experiment performance.

Dewitt, R. L.

1978-01-01

57

The study of single crystals for space processing and the effect of zero gravity  

NASA Technical Reports Server (NTRS)

A study was undertaken to analyze different growth techniques affected by a space environment. Literature on crystal growth from melt, vapor phase and float zone was reviewed and the physical phenomena important for crystal growth in zero-gravity environment was analyzed. Recommendations for potential areas of crystal growth feasible for space missions are presented and a bibliography of articles in the area of crystal growth in general is listed.

Lal, R. B.

1975-01-01

58

STS-45 crewmembers during zero gravity activities onboard KC-135 NASA 930  

NASA Technical Reports Server (NTRS)

STS-45 Atlantis, Orbiter Vehicle (OV) 104, crewmembers and backup payload specialist participate in zero gravity activities onboard KC-135 NASA 930. The crewmembers, wearing flight suits and floating, pose around an inflated globe. Clockwise from bottom left are Payload Specialist Byron K. Lichtenberg, Mission Specialist (MS) and Payload Commander (PLC) Kathryn D. Sullivan (with eye glasses), Commander Charles F. Bolden, MS C. Michael Foale, Payload Specialist Dirk D. Frimout, backup Payload Specialist Charles R. Chappell, and Pilot Brian Duffy.

1991-01-01

59

Zero-Gravity Atmospheric Cloud Physics Experiment Laboratory engineering concepts/design tradeoffs. Volume 1: Study results  

NASA Technical Reports Server (NTRS)

The work is summarized which was accomplished from January 1974 to October 1974 for the Zero-Gravity Atmospheric Cloud Physics Laboratory. The definition and development of an atmospheric cloud physics laboratory and the selection and delineation of candidate experiments that require the unique environment of zero gravity or near zero gravity are reported. The experiment program and the laboratory concept for a Spacelab payload to perform cloud microphysics research are defined. This multimission laboratory is planned to be available to the entire scientific community to utilize in furthering the basic understanding of cloud microphysical processes and phenomenon, thereby contributing to improved weather prediction and ultimately to provide beneficial weather control and modification.

Greco, R. V.; Eaton, L. R.; Wilkinson, H. C.

1974-01-01

60

EVA Assembly of Large Space Structure Neutral Buoyancy, Zero-Gravity Simulation  

NASA Technical Reports Server (NTRS)

EVA Assembly of Large Space Structure Neutral Buoyancy, Zero-Gravity Simulation: NASA-LaRC Nestable Columns and Joints. The film depicts an extravehicular activity (EVA) that involved the assembly of six 'space-weight' columns into a regular tetrahedral cell by a team of two 'space'-suited test subjects. This cell represents the fundamental 'element' of a tetrahedral truss structure. The tests were conducted under simulated zero-gravity conditions, achieved by neutral buoyancy in water. The cell was assembled on an 'outrigger' assembly aid off the side of a mockup of the Shuttle Orbiter cargo bay. Both manual and simulated remote manipulator system (RMS) modes were evaluated. The simulated RMS was used only to transfer stowed hardware from the cargo bay to the work sites. Articulation limits of the pressure suit and zero gravity could be accommodated by work stations with foot restraints. The results of this study have confirmed that astronaut EVA assembly of large, erectable space structur is well within man's capabilities. [Entire movie available on DVD from CASI as Doc ID 20070031008. Contact help@sti.nasa.gov

1979-01-01

61

Digital holographic microscopy for the cytomorphological imaging of cells under zero gravity  

NASA Astrophysics Data System (ADS)

Digital holographic microscopy (DHM) has been gaining interest from cell biology community because of its label free nature and quantitative phase signal output. Besides, fast shutter time, image reconstruction by numerical propagation of the wave fields, and numerical compensation of the aberrations are other intrinsic advantages of this technique that can be explored for harsh imaging conditions. In the frame of this work, a transmission type DHM is developed with a decoupled epifluorescence microscopy mode for cytomorphological monitoring under zero gravity and hyper gravity. With the implemented automatic post processing routines, real time observation of the cell morphology is proven to be feasible under the influence of mechanical disturbances of zero gravity platforms. Post processing of holograms is composed from dynamic numerical compensation of holograms, robust autofocusing and phase image registration. Experiments on live myoblast cells are carried out on two different platforms; random positioning machine (RPM), a ground base microgravity simulation platform, and parabolic flight campaign (PFC), a fixed wing plane flight providing short durations of alternating gravity conditions. Results show clear perinuclear phase increase. During seconds scale microgravity exposure, measurable scale morphological modifications are observed with the accumulated effect of repetitive exposures and short breaks.

Toy, M. Fatih; Richard, Stephane; Kühn, Jonas; Franco-Obregón, Alfredo; Egli, Marcel; Depeursinge, Christian

2012-02-01

62

Zero-Gravity Atmospheric Cloud Physics Experiment Laboratory Engineering Concepts/Design Tradeoffs. Volume 1: Study Results.  

National Technical Information Service (NTIS)

The work is summarized which was accomplished from January 1974 to October 1974 for the Zero-Gravity Atmospheric Cloud Physics Laboratory. The definition and development of an atmospheric cloud physics laboratory and the selection and delineation of candi...

R. V. Greco L. R. Eaton H. C. Wilkinson

1974-01-01

63

Aerosol deposition along the respiratory tract at zero gravity: a theoretical study  

SciTech Connect

Significant fractions of airborne particles composing inhaled aerosols can deposit along the respiratory tract during breathing. Depending on the environmental condition, some particles that enter the body via the respiratory route can pose health hazards. On earth, three general rate mechanisms are active in this deposition process: (1) inertial impaction; (2) diffusion; and (3) gravity-dependent sedimentation. Space craft, stations, and bases represent unique settings where potentially pathogenic aerosols may be encountered under the unique condition of zero or reduced gravity. The present study was undertaken in order to predict how particle deposition in the human respiratory tract at zero gravity may differ from that on earth. We employed the aerosol deposition model of the Task Group on Lung Dynamics to assess the regional deposition of particles ranging from 0.01 to 10 ..mu..m diameter at two particulate densities, 1 and 4, during simulated tidal breathing and breathing during moderate - heavy exercise. Our results suggest the gas exchange regions of the lungs of space travelers and residents are afforded some protection, relative to their earth-bound counterparts, against the deposition of particles due to the absence of gravity; and approximately 2 to 10 fold reduction in the efficiency of collection of particles > 0.5 ..mu..m in diameter occurred in the pulmonary region during resting conditions and exercise. Deposition along the tracheobronchial tree, however, is not markedly altered in the absence of gravity, indicating airway sites contributing to this structure remain susceptible to insults by inhaled aerosols. 18 references, 2 figures, 2 tables.

Lehnert, B.E.; Smith, D.M.; Holland, L.M.; Tillery, M.I.; Thomas, R.G.

1984-01-01

64

Behavior of the lean methane-air flame at zero-gravity  

NASA Technical Reports Server (NTRS)

A special rig was designed and constructed to be compatible with the NASA Lewis Research Center Airborne Research Laboratory to allow the study of the effect of gravity on the behavior of lean limit in a standard 50.4 mm (2 in.) internal diameter tube when the mixtures are ignited at the open end and propagate towards the closed end of the tube. The lean limit at zero gravity was found to be 5.10% methane and the flame was found to extenguish in a manner previously observed for downward propagating flames at one g. It was observed that g-jitter could be maintained at less than + or 0.04 g on most zero g trajectories. All of propagating lean limit flames were found to be sporadically cellularly unstable at zero g. There was no observable correlation between the occurrence of g-jitter and the lean limit, average propagation speed of the flame through the tube or the occurrence of cellular instability.

Noe, K. A.; Strehlow, R. A.

1985-01-01

65

The translaminar pressure gradient in sustained zero gravity, idiopathic intracranial hypertension, and glaucoma.  

PubMed

Papilledema has long been associated with elevated intracranial pressure. Classically, tumors, idiopathic intracranial hypertension, and obstructive hydrocephalus have led to an increase in intracranial pressure causing optic nerve head edema and observable optic nerve swelling. Recent reports describe astronauts returning from prolonged space flight on the International Space Station with papilledema (Mader et al., 2011) [1]. Papilledema has not been observed in shorter duration space flight. Other recent work has shown that the difference in intraocular pressure (IOP) and cerebrospinal fluid pressure (CSFp) may be very important in the pathogenesis of diseases of the optic nerve, especially glaucoma (Berdahl and Allingham, 2009; Berdahl, Allingham, et al., 2008; Berdahl et al., 2008; Ren et al., 2009; Ren et al., 2011) [2-6]. The difference in IOP and CSFp across the lamina cribrosa is known as the translaminar pressure difference (TLPD). We hypothesize that in zero gravity, CSF no longer pools in the caudal spinal column as it does in the upright position on earth. Instead, CSF diffuses throughout the subarachnoid space resulting in a moderate but persistently elevated cranial CSF pressure, including the region just posterior to the lamina cribrosa known as the optic nerve subarachnoid space (ONSAS). This small but chronically elevated CSFp could lead to papilledema when CSFp is greater than the IOP. If the TLPD is the cause of optic nerve head edema in astronauts subjected to prolonged zero gravity, raising IOP and/or orbital pressure may treat this condition and protect astronauts in future space travels from the effect of zero gravity on the optic nerve head. Additionally, the same TLPD concept may offer a deeper understanding of the pathogenesis and treatment options of idiopathic intracranial hypertension (IIH), glaucoma and other diseases of the optic nerve head. PMID:22981592

Berdahl, John P; Yu, Dao Yi; Morgan, William H

2012-12-01

66

STS-45 crewmembers during zero gravity activities onboard KC-135 NASA 930  

NASA Technical Reports Server (NTRS)

STS-45 Atlantis, Orbiter Vehicle (OV) 104, crewmembers and backup payload specialist participate in zero gravity activities onboard KC-135 NASA 930. The crewmembers, wearing flight suits, float and tumble around an inflated globe during the few seconds of microgravity created by parabolic flight. With his hand on the fuselage ceiling is Payload Specialist Dirk D. Frimout. Clockwise from his position are Mission Specialist (MS) C. Michael Foale, Pilot Brian Duffy, backup Payload Specialist Charles R. Chappell, MS and Payload Commander (PLC) Kathryn D. Sullivan (with eye glasses), Commander Charles F. Bolden, and Payload Specialist Byron K. Lichtenberg.

1991-01-01

67

STS-45 crewmembers during zero gravity activities onboard KC-135 NASA 930  

NASA Technical Reports Server (NTRS)

STS-45 Atlantis, Orbiter Vehicle (OV) 104, crewmembers and backup payload specialist participate in zero gravity activities onboard KC-135 NASA 930. The crewmembers, wearing flight suits, float and tumble around an inflated globe during the few seconds of microgravity created by parabolic flight. Clockwise from the globe are backup Payload Specialist Charles R. Chappell, Commander Charles F. Bolden, Payload Specialist Byron K. Lichtenberg, Mission Specialist (MS) and Payload Commander (PLC) Kathryn D. Sullivan (with eye glasses), MS C. Michael Foale, Payload Specialist Dirk D. Frimout (face partially blocked by globe), and Pilot Brian Duffy.

1991-01-01

68

Early cardiovascular adaptation to zero gravity simulated by head-down tilt  

NASA Technical Reports Server (NTRS)

The early cardiovascular adaptation to zero gravity, simulated by head-down tilt at 5 deg, was studied in a series of 10 normal young men. The validity of the model was confirmed by comparing the results with data from Apollo and Skylab flights. Tilt produced a significant central fluid shift with a transient increase in central venous pressure, later followed by an increase in left ventricular size without changes in cardiac output, arterial pressure, or contractile state. The hemodynamic changes were transient with a nearly complete return to the control state within 6 h. The adaptation included a diuresis and a decrease in blood volume, associated with ADH, renin, and aldosterone inhibition.

Blomqvist, C. G.; Nixon, J. V.; Johnson, R. L., Jr.; Mitchell, J. H.

1979-01-01

69

Zero-Gravity Locomotion Simulators: New Ground-Based Analogs for Microgravity Exercise Simulation  

NASA Technical Reports Server (NTRS)

Maintaining health and fitness in crewmembers during space missions is essential for preserving performance for mission-critical tasks. NASA's Exercise Countermeasures Project (ECP) provides space exploration exercise hardware and monitoring requirements that lead to devices that are reliable, meet medical, vehicle, and habitat constraints, and use minimal vehicle and crew resources. ECP will also develop and validate efficient exercise prescriptions that minimize daily time needed for completion of exercise yet maximize performance for mission activities. In meeting these mission goals, NASA Glenn Research Center (Cleveland, OH, USA), in collaboration with the Cleveland Clinic (Cleveland, Ohio, USA), has developed a suite of zero-gravity locomotion simulators and associated technologies to address the need for ground-based test analog capability for simulating in-flight (microgravity) and surface (partial-gravity) exercise to advance the health and safety of astronaut crews and the next generation of space explorers. Various research areas can be explored. These include improving crew comfort during exercise, and understanding joint kinematics and muscle activation pattern differences relative to external loading mechanisms. In addition, exercise protocol and hardware optimization can be investigated, along with characterizing system dynamic response and the physiological demand associated with advanced exercise device concepts and performance of critical mission tasks for Exploration class missions. Three zero-gravity locomotion simulators are currently in use and the research focus for each will be presented. All of the devices are based on a supine subject suspension system, which simulates a reduced gravity environment by completely or partially offloading the weight of the exercising test subject s body. A platform for mounting treadmill is positioned perpendicularly to the test subject. The Cleveland Clinic Zero-g Locomotion Simulator (ZLS) utilizes a pneumatic subject load device to apply a near constant gravity-replacement load to the test subject during exercise, and is currently used in conjunction with the General Clinical Research Center for evaluating exercise protocols using a bedrest analog. The enhanced ZLS (eZLS) at NASA Glenn Research Center features an offloaded treadmill that floats on a thin film of air and interfaces to a force reaction frame via variably-compliant isolators, or vibration isolation system. The isolators can be configured to simulate compliant interfaces to the vehicle, which affects mechanical loading to crewmembers during exercise, and has been used to validate system dynamic models for new countermeasures equipment designs, such as the second International Space Station treadmill slated for use in 2010. In the eZLS, the test subject and exercise device can be pitched at the appropriate angle for partial gravity simulations, such as lunar gravity (1/6th earth gravity). On both the eZLS and the NASA-Johnson Space Center standalone ZLS installed at the University of Texas Medical Branch in Galveston, Texas, USA, the subject's body weight relative to the treadmill is controlled via a linear motor subject load device (LM-SLD). The LM-SLD employs a force-feedback closed-loop control system to provide a relatively constant force to the test subject during locomotion, and is set and verified for subject safety prior to each session. Locomotion data were collected during parabolic flight and on the eZLS. The purpose was to determine the similarities and differences between locomotion in actual and simulated microgravity. Subjects attained greater amounts of hip flexion during walking and running during parabolic flight. During running, subjects had greater hip range of motion. Trunk motion was significantly less on the eZLS than during parabolic flight. Peak impact forces, loading rate, and impulse were greater on the eZLS than during parabolic while walking with a low external load (EL) and rning with a high EL. Activation timing differences existed between locations in all muscles excep

Perusek, Gail P.; DeWitt, John K.; Cavanagh, Peter R.; Grodsinsky, Carlos M.; Gilkey, Kelly M.

2007-01-01

70

Centaur zero gravity coast and engine restart demonstration on the Titan/Centaur (TC-2) extended mission  

NASA Technical Reports Server (NTRS)

The Centaur propellant management and thermal control techniques required for zero gravity coasting were successfully demonstrated during an extended mission following spacecraft separation on the TC-2 flight. As part of the demonstration, two successful engine starts were accomplished. The first engine start followed a one-hour zero gravity coast, and the second engine start followed a three-hour zero gravity coast. All of the Centaur systems performed satisfactorily, the design parameters for zero gravity coasting were verified, and no significant problems were encountered. The flight results showed that the propellant location and behavior, propellant heating, and tank pressure rise rates observed during the zero-gravity coasts were less severe than expected. Consequently, the majority of the propellants remained at the tank bottom, the propellant collection times were very short, and more than 7 hours of coast could have been achieved before a tank venting was required. The tank pressurization prior to the engine starts provided boost pump Net Positive Suction Head values well in excess of the values required. The LO2 tank pressurization was accomplished by a new bubbler method that greatly reduced the helium usage.

Lacovic, R. F.

1975-01-01

71

Assessment of zero gravity effects on space worker health and safety  

SciTech Connect

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the reference Solar Power Satellite (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers - either immediate or delayed - due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiently in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five-year career period. The proposed 90-day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five-year career. (JGB)

Not Available

1980-11-01

72

Assessment of zero gravity effects on space worker health and safety  

NASA Technical Reports Server (NTRS)

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

1980-01-01

73

Design, fabrication and acceptance testing of a zero gravity whole body shower  

NASA Technical Reports Server (NTRS)

Recent research and development programs have established the ability of the zero gravity whole body shower to maintain a comfortable environment in which the crewman can safely cleanse and dry the body. The purpose of this program was to further advance the technology of whole body bathing and to demonstrate technological readiness including in-flight maintenance by component replacement for flight applications. Three task efforts of this program are discussed. Conceptual designs and system tradeoffs were accomplished in task 1. Task 2 involved the formulation of preliminary and final designs for the shower, while task 3 included the fabrication and test of the shower assembly. Particular attention is paid to the evaluation and correction of test anomalies during the final phase of the program.

Schumacher, E. A.; Lenda, J. A.

1974-01-01

74

STS-42 closeup view shows SE 81-09 Convection in Zero Gravity experiment  

NASA Technical Reports Server (NTRS)

STS-42 closeup view shows Student Experiment 81-09 (SE 81-09), Convection in Zero Gravity experiment, with radial pattern caused by convection induced by heating an oil and aluminum powder mixture in the weightlessness of space. While the STS-42 crewmembers activated the Shuttle Student Involvement Program (SSIP) experiment on Discovery's, Orbiter Vehicle (OV) 103's, middeck, Scott Thomas, the student who designed the experiment, was able to observe the procedures via downlinked television (TV) in JSC's Mission Control Center (MCC). Thomas, now a physics doctoral student at the University of Texas, came up with the experiment while he participated in the SSIP as a student at Richland High School in Johnstown, Pennsylvia.

1992-01-01

75

Pressure drop in fully developed, turbulent, liquid-vapor annular flows in zero gravity  

NASA Technical Reports Server (NTRS)

The prediction of frictional pressure drop in fully developed, turbulent, annular liquid-vapor flows in zero gravity using simulation experiments conducted on earth is described. The scheme extends the authors' earlier work on dispersed flows. The simulation experiments used two immiscible liquids of identical density, namely, water and n-butyl benzoate. Because of the lack of rigorous analytical models for turbulent, annular flows, the proposed scheme resorts to existing semiempirical correlations. Results based on two different correlations are presented and compared. Others may be used. It was shown that, for both dispersed and annular flow regimes, the predicted frictional pressure gradients in 0-g are lower than those in 1-g under otherwise identical conditions. The physical basis for this finding is given.

Sridhar, K. R.; Chao, B. T.; Soo, S. L.

1992-01-01

76

Myosin heavy chain expression in rodent skeletal muscle: effects of exposure to zero gravity  

NASA Technical Reports Server (NTRS)

This study ascertained the effects of 9 days of zero gravity on the relative (percentage of total) and calculated absolute (mg/muscle) content of isomyosin expressed in both antigravity and locomotor skeletal muscle of ground control (CON) and flight-exposed (FL) rats. Results showed that although there were no differences in body weight between FL and CON animals, a significant reduction in muscle mass occurred in the vastus intermedius (VI) (P < 0.05) but not in the vastus lateralis (VL) or the tibialis anterior. Both total muscle protein and myofibril protein content were not different between the muscle regions examined in the FL and CON groups. In the VI, there were trends for reductions in the relative content of type I and IIa myosin heavy chains (MHCs) that were offset by increases in the relative content of both type IIb and possibly type IIx MHC protein (P > 0.05). mRNA levels were consistent with this pattern (P < 0.05). The same pattern held true for the red region of the VL as examined at both the protein and mRNA level (P < 0.05). When the atrophy process was examined, there were net reductions in the absolute content of both type I and IIa MHCs that were offset by calculated increases in type IIb MHC in both VI and red VL. Collectively, these findings suggest that there are both absolute and relative changes occurring in MHC expression in the "red" regions of antigravity skeletal muscle during exposure to zero gravity that could affect muscle function.

Haddad, F.; Herrick, R. E.; Adams, G. R.; Baldwin, K. M.

1993-01-01

77

Transient boiling heat transfer in saturated liquid nitrogen and F113 at standard and zero gravity  

NASA Technical Reports Server (NTRS)

Transient and steady state nucleate boiling in saturated LN2 and F113 at standard and near zero gravity conditions were investigated for the horizontal up, vertical and horizontal down orientations of the heating surface. Two distinct regimes of heat transfer mechanisms were observed during the interval from the step increase of power input to the onset of nucleate boiling: the conduction and convection dominated regimes. The time duration in each regime was considerably shorter with LN2 than with F113, and decreased as heat flux increased, as gravity was reduced, and as the orientation was changed from horizontal up to horizontal down. In transient boiling, boiling initiates at a single point following the step increase in power, and then spreads over the surface. The delay time for the inception of boiling at the first site, and the velocity of spread of boiling varies depending upon the heat flux, orientation, body force, surface roughness and liquid properties, and are a consequence of changes in boundary layer temperature levels associated with changes in natural convection. Following the step increase in power input, surface temperature overshoot and undershoot occur before the steady state boiling temperature level is established.

Oker, E.; Merte, H., Jr.

1973-01-01

78

A study of orientation in a zero gravity environment by means of virtual reality simulation  

NASA Astrophysics Data System (ADS)

This study intends to clarify how people acquire visual information and recognize their orientation in a zero gravity environment. An experiment was conducted using virtual reality. In Study 1, each subject was given tasks in which a subject moves through virtual reality from the central room into one of six rooms such as operation room and habitation room. Textures composed by alphabetical letters were stuck on the six surrounding surfaces of the central cubic room. Visual information of the cubic room and the degree-of-freedom of motion were varied, and the subjects' performance was measured. To some extent, the experiment produced a subjective sense of weightlessness. Moreover, we identified different strategies of spatial cognition and behavior under conditions of virtual weightlessness. In Study 2, subjects' orientational skills were tested with pointing and orienting tasks. Subjects followed virtual routes that were constructed of three or four rectangular modules that were connected by the cubical modules. Each subject moved from one end to the other end, and pointed to the start point and reproduced the experienced route using a scale model. The shapes of the routes were changed systematically. Analyses of the results indicate that the ability of special cognition changes with such variables as the number of corners of routes, the geometric number of fields and the number of fields with consideration to the body posture. .

Aoki, Hirofumi; Yamaguchi, Takao; Ohno, Ryuzo

2001-02-01

79

Spray Bar Zero-Gravity Vent System for On-Orbit Liquid Hydrogen Storage  

NASA Technical Reports Server (NTRS)

During zero-gravity orbital cryogenic propulsion operations, a thermodynamic vent system (TVS) concept is expected to maintain tank pressure control without propellant resettling. In this case, a longitudinal spray bar mixer system, coupled with a Joule-Thompson (J-T) valve and heat exchanger, was evaluated in a series of TVS tests using the 18 cu m multipurpose hydrogen test bed. Tests performed at fill levels of 90, 50, and 25 percent, coupled with heat tank leaks of about 20 and 50 W, successfully demonstrated tank pressure control within a 7-kPa band. Based on limited testing, the presence of helium constrained the energy exchange between the gaseous and liquid hydrogen (LH2) during the mixing cycles. A transient analytical model, formulated to characterize TVS performance, was used to correlate the test data. During self-pressurization cycles following tank lockup, the model predicted faster pressure rise rates than were measured; however, once the system entered the cyclic self-pressurization/mixing/venting operational mode, the modeled and measured data were quite similar. During a special test at the 25-percent fill level, the J-T valve was allowed to remain open and successfully reduced the bulk LH2 saturation pressure from 133 to 70 kPa in 188 min.

Hastings, L. J.; Flachbart, R. H.; Martin, J. J.; Hedayat, A.; Fazah, M.; Lak, T.; Nguyen, H.; Bailey, J. W.

2003-01-01

80

Stress, temperature, heart rate, and hibernating factors in hamsters. [pathophysiological conditions resulting from exposure to zero gravity  

NASA Technical Reports Server (NTRS)

Pathophysiological conditions resulting from prolonged exposure to zero gravity, cabin constraint, altered ambient environment, whether it be noise, vibrations, high temperatures, or combinations of such factors, are studied in laboratory animals and applied to manned space flight. Results and plans for further study are presented. Specific topics covered include: thermoregulation and its role in reflecting stress and adaptation to the gravity free environment and cabin confinement with its altered circadian forcings; renal function and its measurement in electrolyte distribution and blood flow dynamics; gastronintestinal function and an assessment of altered absorptive capacity in the intestinal mucosa; and catecholamine metabolism in terms of distribution and turnover rates in specific tissues.

Musacchia, X. J.

1974-01-01

81

Binding of alpha-fetoprotein by immobilized monoclonal antibodies during episodes of zero-gravity obtained by parabolic flight.  

PubMed

Alpha-fetoprotein (AFP), a single chain polypeptide which is synthesized by the liver and yolk sac of the human fetus, provided a model ligand for assessing the effects of microgravity on ligand binding to surface-immobilized model receptor molecules. Monoclonal antibodies, used as receptors for AFP, were immobilized by covalent attachment to latex microparticles. Zero gravity environment was obtained by parabolic flight aboard NASA 930, a modified KC-135 aircraft. During the onset of an episode of zero gravity, ligand and receptor were mixed. Timed incubation (20 s) was terminated by centrifugation, the supernatant removed, and microparticles were assessed for bound AFP by immunochemical methods. The extent of binding was not influenced by microgravity, when compared with 1-G controls, which suggests that aberrant cellular activities observed in microgravity are not the simple expression of altered macromolecular interactions. PMID:1698053

Spooner, B S; Guikema, J A; Barnes, G

1990-08-01

82

Marangoni instability in a liquid layer confined between two concentric spherical surfaces under zero-gravity conditions  

Microsoft Academic Search

A liquid layer containing a single solute is bounded on the outside by a rigid spherical surface and on the inside by a concentric gas\\/liquid interface. The solute evaporates from the liquid to the gas phase and, if the surface tension depends on the solute concentration, surface-tension driven convective flows may arise (Marangoni instability). Assuming zero-gravity conditions and using a

H. C. J. Hoefsloot; H. W. Hoogstraten; L. P. B. M. Janssen

1990-01-01

83

Effects of zero gravity on myofibril content and isomyosin distribution in rodent skeletal muscle.  

PubMed

The purpose of this experiment was to investigate the effects of 12.5 days of zero gravity (0 g) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n = 5 each group) designated as flight group (FG), vivarium control (VC), and synchronous control (SC). Body weight of the FG was significantly lower than that of the two control groups (P less than 0.05). Compared with the two control groups, VI weight was lower by 23% (P less than 0.10), whereas no such pattern was apparent for the VL muscle. Myofibril yields (mg protein/g muscle) in the VI were 35% lower in the FG than in controls (P less than 0.05), whereas no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0 g. Analysis of myosin isoforms indicated that slow myosin (Sm) was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following spaceflight. Myofibril ATPase activity of the VI was increased in the FG compared with controls, which is consistent with the observation of preferential Sm degradation. These data suggest that muscles containing a high percentage of slow-twitch fibers undergo greater degrees of myofibril protein degradation than muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0 g exposure, and the primary target appears to be the Sm molecule. PMID:2136840

Baldwin, K M; Herrick, R E; Ilyina-Kakueva, E; Oganov, V S

1990-01-01

84

Substrate oxidation capacity in rodent skeletal muscle: effects of exposure to zero gravity  

NASA Technical Reports Server (NTRS)

A study was conducted, as part of the integrated National Aeronautics and Space Administration Space Life Sciences 1 mission flown in June of 1991, to ascertain the effects of 9 days of exposure to zero gravity on the capacity of rodent skeletal muscle fiber types to oxidize either [14C]pyruvate or [14C]palmitate under state 3 metabolic conditions, i.e., nonlimiting amounts of substrate and cofactors. In addition, activity levels of marker enzymes of the tricarboxylic acid cycle, malate shuttle, and beta-oxidation were measured. Results showed that significant differences in muscle weight occurred in both the predominantly slow vastus intermedius and predominantly fast vastus lateralis of flight vs. control groups (P < 0.05). Total protein content of the muscle samples was similar between groups. Both pyruvate oxidation capacity and the marker oxidative enzymes were not altered in the flight relative to control animals. However, the capacity to oxidize long-chain fatty acids was significantly reduced by 37% in both the high- and low-oxidative regions of the vastus muscle (P < 0.05). Although these findings of a selective reduction in fatty acid oxidation capacity in response to spaceflight are surprising, they are consistent with previous findings showing 1) an increased capacity to take up glucose and upregulate glucose transporter proteins and 2) a marked accumulation of triglycerides in the skeletal muscles of rats subjected to states of unloading. Thus, skeletal muscle of animals exposed to non-weight-bearing environments undergo subcellular transformations that may preferentially bias energy utilization to carbohydrates.

Baldwin, K. M.; Herrick, R. E.; McCue, S. A.

1993-01-01

85

Effects of zero gravity on myofibril content and isomyosin distribution in rodent skeletal muscle  

NASA Technical Reports Server (NTRS)

The purpose of this experiment was to investigate the effects of 12.5 days of zero gravity (0 g) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n = 5 each group) designated as flight group (FG), vivarium control (VC), and synchronous control (SC). Body weight of the FG was significantly lower than that of the two control groups (P less than 0.05). Compared with the two control groups, VI weight was lower by 23% (P less than 0.10), whereas no such pattern was apparent for the VL muscle. Myofibril yields (mg protein/g muscle) in the VI were 35% lower in the FG than in controls (P less than 0.05), whereas no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0 g. Analysis of myosin isoforms indicated that slow myosin (Sm) was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following spaceflight. Myofibril ATPase activity of the VI was increased in the FG compared with controls, which is consistent with the observation of preferential Sm degradation. These data suggest that muscles containing a high percentage of slow-twitch fibers undergo greater degrees of myofibril protein degradation than muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0 g exposure, and the primary target appears to be the Sm molecule.

Baldwin, K. M.; Herrick, R. E.; Ilyina-Kakueva, E.; Oganov, V. S.

1990-01-01

86

N-Decane-Air Droplet Combustion Experiments in the NASA-Lewis 5 Second Zero-Gravity Facility  

NASA Technical Reports Server (NTRS)

The burning of single fuel (n-decane) droplets in a microgravity environment (below 0.00001 of the earth's gravity, achieved in the NASA-Lewis 5-Second Zero-Gravity Facility) was studied, as part of the development of the Droplet Combustion Experiment for eventual operation aboard either the Shuttle middeck or Spacelab. Special attention is given to the combustion equipment used and its operations and performance. Temporal analysis of the local burning rates in these tests showed increasing rates of change in the local burning as droplet combustion progressed. Result point to the need of studying large droplets, with long droplet combustion lifetimes as well as low gas/droplet motion to understand reasons for this unsteadiness.

Haggard, John B.; Brace, Michael H.; Dryer, Frederick L.; Choi, Mun Y.; Williams, Forman A.

1990-01-01

87

A Human Factors Evaluation of a Methodology for Pressurized Crew Module Acceptability for Zero-Gravity Ingress of Spacecraft  

NASA Technical Reports Server (NTRS)

This project aimed to develop a methodology for evaluating performance and acceptability characteristics of the pressurized crew module volume suitability for zero-gravity (g) ingress of a spacecraft and to evaluate the operational acceptability of the NASA crew return vehicle (CRV) for zero-g ingress of astronaut crew, volume for crew tasks, and general crew module and seat layout. No standard or methodology has been established for evaluating volume acceptability in human spaceflight vehicles. Volume affects astronauts'ability to ingress and egress the vehicle, and to maneuver in and perform critical operational tasks inside the vehicle. Much research has been conducted on aircraft ingress, egress, and rescue in order to establish military and civil aircraft standards. However, due to the extremely limited number of human-rated spacecraft, this topic has been un-addressed. The NASA CRV was used for this study. The prototype vehicle can return a 7-member crew from the International Space Station in an emergency. The vehicle's internal arrangement must be designed to facilitate rapid zero-g ingress, zero-g maneuverability, ease of one-g egress and rescue, and ease of operational tasks in multiple acceleration environments. A full-scale crew module mockup was built and outfitted with representative adjustable seats, crew equipment, and a volumetrically equivalent hatch. Human factors testing was conducted in three acceleration environments using ground-based facilities and the KC-135 aircraft. Performance and acceptability measurements were collected. Data analysis was conducted using analysis of variance and nonparametric techniques.

Sanchez, Merri J.

2000-01-01

88

Combustion of solid carbon rods in zero and normal gravity. Ph.D. Thesis - Toledo Univ., Ohio  

NASA Technical Reports Server (NTRS)

In order to investigate the mechanism of carbon combustion and to assess the importance of gravitational induced convection on the process, zero and normal gravity experiments were conducted in which spectroscopic carbon rods were resistance ignitied and burned in dry oxygen environments. In the zero-gravity drop tower tests, a blue flame surrounded the rod, showing that a gas phase reaction in which carbon monoxide was oxidized to carbon dioxide was taking place. The ratio of flame diameter to rod diameter was obtained as a function of time. It was found that this ratio was inversely proportional to both the oxygen pressure and the rod diameter. In the normal gravity tests, direct mass spectrometric sampling was used to measure gas phase concentrations. The gas sampling probe was positioned near the circumference of a horizontally mounted 0.615 cm diameter carbon rod, either at the top or at angles of 45 deg to 90 deg from the top, and yielded concentration profiles of CO2, CO, and O2 as a function of distance from the surface. The mechanism controlling the combustion process was found to change from chemical process control at the 90 deg and 45 deg probe positions to mass transfer control at the 0 deg probe position at the top of the rod. Under the experimental conditions used, carbon combustion was characterized by two surface reactions, 2C + O2 yields 2CO and CO2 + C yields 2CO, and a gas phase reaction, 2CO + O2 yields 2CO2.

Spuckler, C. M.

1981-01-01

89

Aerosol deposition along the respiratory tract at zero gravity: a theoretical study  

Microsoft Academic Search

Significant fractions of airborne particles composing inhaled aerosols can deposit along the respiratory tract during breathing. Depending on the environmental condition, some particles that enter the body via the respiratory route can pose health hazards. On earth, three general rate mechanisms are active in this deposition process: (1) inertial impaction; (2) diffusion; and (3) gravity-dependent sedimentation. Space craft, stations, and

B. E. Lehnert; D. M. Smith; L. M. Holland; M. I. Tillery; R. G. Thomas

1984-01-01

90

The Awful Truth About Zero-Gravity: Space Acceleration Measurement System; Orbital Acceleration Research Experiment  

NASA Technical Reports Server (NTRS)

Earth's gravity holds the Shuttle in orbit, as it does satellites and the Moon. The apparent weightlessness experienced by astronauts and experiments on the Shuttle is a balancing act, the result of free-fall, or continuously falling around Earth. An easy way to visualize what is happening is with a thought experiment that Sir Isaac Newton did in 1686. Newton envisioned a mountain extending above Earth's atmosphere so that friction with the air would be eliminated. He imagined a cannon atop the mountain and aimed parallel to the ground. Firing the cannon propels the cannonball forward. At the same time, Earth's gravity pulls the cannonball down to the surface and eventual impact. Newton visualized using enough powder to just balance gravity so the cannonball would circle the Earth. Like the cannonball, objects orbiting Earth are in continuous free-fall, and it appears that gravity has been eliminated. Yet, that appearance is deceiving. Activities aboard the Shuttle generate a range of accelerations that have effects similar to those of gravity. The crew works and exercises. The main data relay antenna quivers 17 times per second to prevent 'stiction,' where parts stick then release with a jerk. Cooling pumps, air fans, and other systems add vibration. And traces of Earth's atmosphere, even 200 miles up, drag on the Shuttle. While imperceptible to us, these vibrations can have a profound impact on the commercial research and scientific experiments aboard the Shuttle. Measuring these forces is necessary so that researchers and scientists can see what may have affected their experiments when analyzing data. On STS-107 this service is provided by the Space Acceleration Measurement System for Free Flyers (SAMS-FF) and the Orbital Acceleration Research Experiment (OARE). Precision data from these two instruments will help scientists analyze data from their experiments and eliminate outside influences from the phenomena they are studying during the mission.

2002-01-01

91

A preliminary analysis of the data from experiment 77-13 and final report on glass fining experiments in zero gravity  

NASA Technical Reports Server (NTRS)

Thermal fining, thermal migration of bubbles under reduced gravity conditions, and data to verify current theoretical models of bubble location and temperatures as a function of time are discussed. A sample, sodium borate glass, was tested during 5 to 6 minutes of zero gravity during rocket flight. The test cell contained a heater strip; thermocouples were in the sample. At present quantitative data are insufficient to confirm results of theoretical calculations.

Wilcox, W. R.; Subramanian, R. S.; Meyyappan, M.; Smith, H. D.; Mattox, D. M.; Partlow, D. P.

1981-01-01

92

NSTA-NASA Shuttle Student Involvement Project. Experiment Results: Insect Flight Observation at Zero Gravity  

NASA Technical Reports Server (NTRS)

The flight responses of common houseflies, velvetbean caterpillar moths, and worker honeybees were observed and filmed for a period of about 25 minutes in a zero-g environment during the third flight of the Space Shuttle Vehicle (flight number STS-3; March 22-30, 1982). Twelve fly puparia, 24 adult moths, 24 moth pupae, and 14 adult bees were loaded into an insect flight box, which was then stowed aboard the Shuttle Orbiter, the night before the STS-3 launch at NASA's Kennedy Space Center (KSC). The main purpose of the experiment was to observe and compare the flight responses of the three species of insects, which have somewhat different flight control mechanisms, under zero-g conditions.

Nelson, T. E.; Peterson, J. R.

1982-01-01

93

Solidification under zero gravity: A Long Duration Exposure Facility (LDEF) experiment for an early space shuttle mission. [project planning  

NASA Technical Reports Server (NTRS)

Project planning for two series of simple experiments on the effect of zero gravity on the melting and freezing of metals and nonmetals is described. The experiments will be performed in the Long Duration Exposure Facility, and their purpose will be to study: (1) the general morphology of metals and nonmetals during solidification, (2) the location of ullage space (liquid-vapor interfaces), and (3) the magnitude of surface tension driven convection during solidification of metals and nonmetals. The preliminary design of the experiments is presented. Details of the investigative approach, experimental procedure, experimental hardware, data reduction and analysis, and anticipated results are given. In addition a work plan and cost analysis are provided.

Bailey, J. A.

1976-01-01

94

Steady state growth and segregation under zero gravity: InSb  

NASA Technical Reports Server (NTRS)

It was established that ideal diffusion controlled steady state conditions, never accomplished on earth, were achieved during the growth of Te-doped InSb crystals in Skylab. Surface tension effects were found to establish non-wetting conditions under which free surface solidification took place in confined geometry. It was further found that, under forced contact conditions, surface tension effects led to the formation of surface ridges (not previously observed on earth) which isolated the growth system from its container. In addition, it was possible for the first time to identify unambiguously: the origin of segregation discontinuities associated with facet growth, the mode of nucleation and propagation or rotational twin boundaries, and the specific effect of mechanical-shock perturbations on segregation. The results obtained prove the advantageous conditions provided by outer space. Thus, fundamental data on solidification thought to be unattainable because of gravity induced interference on earth are now within reach.

Witt, A. F.; Lichtensteiger, M.; Lavine, M. C.; Herman, C. J.

1974-01-01

95

Liquid-Vapor Flow Regime Transitions for Use in Design of Heat Transfer Loops in Spacecraft - An Investigation of Two-Phase Flow in Zero Gravity Conditions.  

National Technical Information Service (NTIS)

The behavior of viscous (or low velocity) two-phase vapor-liquid flow under zero gravity was simulated in the laboratory by using two immiscible fluids of equal density flowing together in a one inch diameter glass tube. The fluids used wer Polypropylene ...

T. W. Lovell

1985-01-01

96

Zero-gravity cloud physics laboratory: Candidate experiments definition and preliminary concept studies  

NASA Technical Reports Server (NTRS)

The candidate definition studies on the zero-g cloud physics laboratory are covered. This laboratory will be an independent self-contained shuttle sortie payload. Several critical technology areas have been identified and studied to assure proper consideration in terms of engineering requirements for the final design. Areas include chambers, gas and particle generators, environmental controls, motion controls, change controls, observational techniques, and composition controls. This unique laboratory will allow studies to be performed without mechanical, aerodynamics, electrical, or other type techniques to support the object under study. This report also covers the candidate experiment definitions, chambers and experiment classes, laboratory concepts and plans, special supporting studies, early flight opportunities and payload planning data for overall shuttle payload requirements assessments.

Eaton, L. R.; Greco, R. V.; Hollinden, A. B.

1973-01-01

97

Mechanistic studies on reduced exercise performance and cardiac deconditioning with simulated zero gravity  

NASA Technical Reports Server (NTRS)

The primary purpose of this research is to study the physiological mechanisms associated with the exercise performance of rats subjected to conditions of simulated weightlessness. A secondary purpose is to study related physiological changes associated with other systems. To facilitate these goals, a rodent suspension model was developed (Overton-Tipton) and a VO2 max testing procedure was perfected. Three methodological developments occurred during this past year deserving of mention. The first was the refinement of the tail suspension model so that (1) the heat dissipation functions of the caudal artery can be better utilized, and (2) the blood flow distribution to the tail would have less external constriction. The second was the development on a one-leg weight bearing model for use in simulated weightlessness studies concerned with change in muscle mass, muscle enzyme activity, and hind limb blood flow. The chemical body composition of 30 rats was determined and used to develop a prediction equation for percent fat using underwater weighing procedures to measure carcass specific gravity and to calculate body density, body fat, and fat free mass.

Tipton, Charles M.

1991-01-01

98

Liquid-vapor flow regime transitions for use in design of heat transfer loops in spacecraft: An investigation of two-phase flow in zero gravity conditions  

NASA Astrophysics Data System (ADS)

The behavior of viscous (or low velocity) two-phase vapor-liquid flow under zero gravity was simulated in the laboratory by using two immiscible fluids of equal density flowing together in a one inch diameter glass tube. The fluids used were Polypropylene Glycol (PPG) which simulated the liquid phase and water which simulated the vapor phase. Various tests were conducted varying flow rates and entrance conditions. Four existing flow regime models were analyzed, modeled on a computer, and extrapolated to predict zero-gravity conditions. The flow regimes were the Horizontal Dukler-Taitel, Vertical Dukler-Taitel, Vertical Weisman and Horizontal Weisman. None of these models when extrapolated to zero-g conditions agreed well with the lab data, and some of the observed flow regimes were not predicted at all.

Lovell, T. W.

1985-05-01

99

New portable time-resolved photometer for monitoring the calcium dynamics of osteoblasts under mechanical and zero-gravity stimulation  

NASA Astrophysics Data System (ADS)

We introduce a compact and portable photometric system for measurements of the calcium dynamics in cells. The photometer is designed for applications in centrifuges or in zero-gravity environment and thus extremely compact and reliable. It operates with the calcium-sensitive dye Indo-1. The excitation wavelength of 345nm is generated by frequency doubling of a laser diode. Two compact photomultiplier tubes detect the fluorescent emission. The electronics provides the sensitivity of photon counting combined with simultaneous measurement of the temperature, of air pressure, and of gravitational force. Internal data storage during the experiment is possible. A newly developed cell chamber stabilizes the cell temperature to 37.0 percent C +/- 0.1 degree C and includes a perfusion system to supply the cells with medium. The system has a modular set-up providing the possibility to change light source and detectors for investigation of other ions than calcium. Quantitative measurements of the intracellular calcium concentration are based on a comprehensive calibration of our system. First experiments show that the calcium dynamics of osteosarcoma cells stimulated by parathyroid hormone is observable.

Struckmeier, Jens; Tenbosch, Jochen; Klopp, Erk; Born, Matthias; Hofmann, Martin R.; Jones, David W.

2000-04-01

100

Test Data Analysis of a Spray Bar Zero-Gravity Liquid Hydrogen Vent System for Upper Stages  

NASA Technical Reports Server (NTRS)

To support development of a zero-gravity pressure control capability for liquid hydrogen (LH2), a series of thermodynamic venting system (TVS) tests was conducted in 1996 and 1998 using the Marshall Space Flight Center (MSFC) multipurpose hydrogen test bed (MHTB). These tests were performed with ambient heat leaks =20 and 50 W for tank fill levels of 90%, 50%, and 25%. TVS performance testing revealed that the spray bar was highly effective in providing tank pressure control within a 7-kPa band (131-138 Wa), and complete destratification of the liquid and the ullage was achieved with all test conditions. Seven of the MHTB tests were correlated with the TVS performance analytical model. The tests were selected to encompass the range of tank fill levels, ambient heat leaks, operational modes, and ullage pressurants. The TVS model predicted ullage pressure and temperature and bulk liquid saturation pressure and temperature obtained from the TVS model were compared with the test data. During extended self-pressurization periods, following tank lockup, the model predicted faster pressure rise rates than were measured. However, once the system entered the cyclic mixing/venting operational mode, the modeled and measured data were quite similar.

Hedayat, A.; Bailey, J. W.; Hastings, L. J.; Flachbart, R. H.

2003-01-01

101

Experiment K-6-10. Effects of zero gravity on myofibril protein content and isomyosin distribution in rodent skeletal muscle  

NASA Technical Reports Server (NTRS)

The purpose of this experiment was to investigate the effects of 12 days of zero gravity (0G) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n=5 each group) designated as flight-group (FG), vivarium-control (VC), and synchronous-control (SC). Body weight of the FG was significantly lower than the two control groups (p less than 0.05). Compared to the two control groups, VI weight was lower by 23 percent (p less than 0.10); whereas no such reduction was observed for the VL muscle. Myofibril yields (mg protein/g of muscle) in the VI were 35 percent lower in the FG compared to the controls (p less than 0.05); whereas, no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0G. Analysis of myosin isoforms indicated that slow-myosin was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following space flight. Myofibril ATPase activity of the VI was increased in the FG compared to controls, which is consistent with the observation of preferential slow-myosin degradation. These data suggest that muscles containing a high percent of slow-twitch fibers undergo greater degrees of myofibril protein degradation than do muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0G exposure, and the primary target appears to be the slow-myosin molecule.

Baldwin, K.; Herrick, R.; Oganov, V.

1990-01-01

102

Quantitative determination of zero-gravity effects on electronic materials processing germanium crystal growth with simultaneous interface demarcation experiment MA-060, section 5  

NASA Technical Reports Server (NTRS)

The crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero g conditions were investigated. The germanium (doped with gallium) system was selected because it was extensively studied on Earth and because it lends itself to a very detailed macroscopic and microscopic characterization. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. On the basis of the results obtained to date, there is no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.

Gatos, H. C.; Witt, A. F.; Lichtensteiger, M.; Herman, C. J.

1982-01-01

103

Analysis of gravity-induced particle motion and fluid perfusion flow in the NASA-designed rotating zero-head-space tissue culture vessel  

NASA Technical Reports Server (NTRS)

The gravity induced motions, through the culture media, is calculated of living tissue segments cultured in the NASA rotating zero head space culture vessels. This is then compared with the media perfusion speed which is independent of gravity. The results may be interpreted as a change in the physical environment which will occur by operating the NASA tissue culture systems in actual microgravity (versus unit gravity). The equations governing particle motions which induce flows at the surface of tissues contain g terms. This allows calculation of the fluid flow speed, with respect to a cultured particle, as a function of the external gravitational field strength. The analysis is approached from a flow field perspective. Flow is proportional to the shear exerted on a structure which maintains position within the field. The equations are solved for the deviation of a particle from its original position in a circular streamline as a function of time. The radial deviation is important for defining the operating limits and dimensions of the vessel because of the finite radius at which particles necessarily intercept the wall. This analysis uses a rotating reference frame concept.

Wolf, David A.; Schwarz, Ray P.

1991-01-01

104

Solidification under zero gravity: A Long Duration Exposure Facility (LDEF) experiment for an early space shuttle mission  

NASA Technical Reports Server (NTRS)

The preliminary design of two series of simple experiments the objectives of which are to determine the effect of an absence of gravity on (1) the general morphology of the structure, (2) location of ullage space, and (3) magnitude of surface tension driven convection, during the solidification of several metallic and nonmetallic systems is described. Details of the investigative approach, experimental procedure, experimental hardware, data reduction and analysis, and anticipated results are given.

Bailey, J. A.; Whitfield, J. K.

1976-01-01

105

N-Decane Droplet Combustion in the NASA-Lewis 5 Second Zero-Gravity Facility - Results in Test Gas Environments Other than Air  

NASA Technical Reports Server (NTRS)

The burning rate of single droplets of n-decane in a microgravity environment of the NASA-Lewis 5 Second Zero-Gravity Facility was investigated as a function of time, together with the flame diameter/droplet diameter ratio, for a wide range of test environments other than normal air conditions, using an engineering model of the flight experiment. Oxygen mole fractions were varied from 18 to 50 percent, the total test chamber pressure was varied from 0.5 to 2 atmospheres, and the initial droplet diameter was varied from 0.98 to 2.41 mm. Measurements showed that the average burning rates for n-decane droplets exhibited the same qualitative trends as are found in two current models. Temporal analysis of the local burning rates showed variable rates of change in local burning as the droplet combustion progressed. The causes and implications of these findings are discussed.

Haggard, John B.; Borowski, Brian A.; Dryer, Frederick L.; Choi, Mun Y.; Williams, Forman A.

1991-01-01

106

A large motion zero-gravity suspension system for experimental simulation of orbital construction and deployment. M.S. Thesis  

NASA Technical Reports Server (NTRS)

The design and implementation of a vertical degree of freedom suspension system is described which provides a constant force off-load condition to counter gravity over large displacements. By accommodating motions up to one meter for structures weighing up to 100 pounds, the system is useful for experiments which simulate orbital construction events such as docking, multiple component assembly, or structural deployment. A unique aspect of this device is the combination of a large stroke passive off-load device augmented by electromotive torque actuated force feedback. The active force feedback has the effect of reducing break-away friction by a factor of twenty over the passive system alone. The thesis describes the development of the suspension hardware and the control algorithm. Experiments were performed to verify the suspensions system's effectiveness in providing a gravity off-load and simulating the motion of a structure in orbit. Additionally, a three dimensional system concept is presented as an extension of the one dimensional suspension system which was implemented.

Straube, Timothy Milton

1993-01-01

107

An example of branching in a variational problem. [shape of liquid suspended from wire in zero gravity  

NASA Technical Reports Server (NTRS)

In an experiment in space it was found that when a cubical frame was slowly withdrawn from a soap solution, the wire frame retained practically a full cube of liquid. Removed from the frame (by shaking), the faces of the cube became progressively more concave, until adjacent faces became tangential. In the present paper a mathematical model describing the shape a liquid takes due to its surface tension while suspended on a wire frame in zero-g is solved by use of Lagrange multipliers. It is shown how the configuration of soap films so bounded is dependent upon the volume of liquid trapped in the films. A special case of the solution is a soap film naturally formed on a cubical wire frame.

Darbro, W.

1978-01-01

108

Zero-gravity Mean Free Surface Curvature of a Confined Liquid in a Radially-Vaned Container  

NASA Technical Reports Server (NTRS)

A variety of increasingly intricate container geometries are under consideration for the passive manipulation of liquids aboard spacecraft where the impact of gravity may be neglected. In this study we examine the mean curvature of a liquid volume confined within a radial array of disconnected vanes of infinite extent. This particular geometry possesses a number of desirable characteristics relevant to waste water treatment aboard spacecraft for life support. It is observed that under certain conditions the slender shape of the free surface approaches an asymptote, which can be predicted analytically using new hybrid boundary conditions proposed herein. This contribution represents possibly the final extension of what has been referred to as the method of de Lazzer et al. (1996). The method enables the integration of the Young-Laplace equation over a domain with its boundaries, including the wetted portion of the solid boundaries, symmetry planes, and circular arcs representing free surfaces at the center plane of the liquid body. Asymptotic solutions at several limits are obtained and the analysis is confirmed with numerical computations.

Chen, Yongkang; Callahan, Michael; Weislogel, Mark

2013-01-01

109

Analysis of changes in leg volume parameters, and orthostatic tolerance in response to lower body negative pressure during 59 days exposure to zero gravity Skylab 3  

NASA Technical Reports Server (NTRS)

The cardiovascular responses of the Apollo crewmen associated with postflight evaluations indicate varying decrements of orthostatic tolerance. The postflight changes indicate a slightly diminished ability to the cardiovascular system to function effectively against gravity following exposure to weightlessness. The objective of the Skylab LBNP experiments (M092) was to provide information about the magnitude and time course of the cardiovascular changes associated with prolonged periods of exposure to weightlessness. This report details the equipment, signal processing and analysis of the leg volume data obtained from the M092 experiment of the Skylab 3 Mission.

Barnett, R. D.; Gowen, R. J.; Carroll, D. R.

1975-01-01

110

Analysis of changes in leg volume parameters, and orthostatic tolerance in response to lower body negative pressure during 28-days exposure to zero gravity Skylab 2  

NASA Technical Reports Server (NTRS)

The design of the leg volume measuring system employed for the M092 portion of the Skylab missions required the development of a system sensitive to large and small volume changes at the calf of the leg. These changes in volume were produced in response to the orthostatic stress of a Lower Body Negative Pressure Device (LBNPD) or by venous occlusion. The cardiovascular responses of the Apollo crewman associated with the postflight evaluations indicate varying decrements of orthostatic tolerance. The postflight changes indicate a slightly diminished ability of the cardiovascular system to function effectively against gravity following exposure to weightlessness. The objective of the Skylab LBNP experiments (M092) was to provide information about the magnitude and time course of the cardiovascular changes associated with prolonged periods of exposure to weightlessness. The equipment, signal processing, and analysis of the leg volume data obtained from the M092 experiment of the Skylab 2 Mission are described.

Barnett, R. D.; Gowen, R. J.; Carroll, D. R.

1975-01-01

111

Local Gravity Anomalies Produced by Dislocation Sources  

Microsoft Academic Search

Gravity anomalies due to other dislocation sources in three dimensions are as follows: For strike-slip faulting the ratio of the gravity change to uplift depends upon position; however, the gravity change contours are roughly similar to those corresponding to a zero free air gravity anomaly. Nor is the ratio constantfor dip-slip faulting except for the two special cases of dip

J. C. Savage

1984-01-01

112

GENERAL RELATIVITY AND THE ZERO POINT ENERGY  

Microsoft Academic Search

An exploration is made of the stochastic electrodynamic (SED) interpretation of mass and gravity. On this approach, gravity has been shown to originate in the attractive secondary electromagnetic fields emitted by charged point particles jostled by the impacting waves of the Zero Point Energy (ZPE). This exploration finds that the four major predictions of General Relativity can be readily reproduced

Barry Setterfield

2001-01-01

113

GAS-611 firefly in zero gravity  

NASA Technical Reports Server (NTRS)

The Get Away Special 611 (GAS-611) project will carry a small, self-contained biological experiment into a microgravity environment for a period of 120 hours. The payload will be a colony of Lampyridae (fireflies). The ability of this beetle to produce light with an efficiency of 98 pct will be evaluated in the micro-G environment. The chemical process that occurs could be assisted by the earth's gravitational pull and the very complex tracheae system found within this species of beetle. The effects of microgravity on mating and beetle larvae will also be studied.

Williams, Tony

1988-01-01

114

On Gravity and Mass  

Microsoft Academic Search

Motivated mainly by the fact that no charged elementary particles having zero mass have been observed up to now, we investigate the question whether the mass of the elementary particles is connected with their electric charge and whether gravity can be derived from QED. The graviton is considered as a two-photon bound state. A relation between mass and charge of

Athanasios Markou

2009-01-01

115

Solidifying Cast Iron in Low Gravity  

NASA Technical Reports Server (NTRS)

Report describes study of solidification of cast iron in low and normal gravity. Because flotation, sedimentation, and convection suppressed, alloys that solidify at nearly zero gravity have unusual and potentially useful characteristics. Study conducted in airplane that repeatedly flew along parabolic trajectories. Appears iron/carbon alloys made at low gravity have greater carbon content (as high as 5 to 10 percent) than those made of Earth gravity because carbon particles do not float to top of melt.

Hendrix, J. C.; Curreri, P. A.; Stefanescu, D. M.

1986-01-01

116

"Patient Zero":  

PubMed Central

Summary This article contextualizes the production and reception of And the Band Played On, Randy Shilts’s popular history of the initial recognition of the American AIDS epidemic. Published over twenty-five years ago, the book and its most notorious character, “Patient Zero,” are in particular need of a critical historical treatment. The article presents a more balanced consideration—a “patient’s view”—of Gaétan Dugas’s experience of the early years of AIDS. I oppose the assertion that Dugas, the so-called Patient Zero, ignored incontrovertible information about the condition and was intent on spreading his infection. Instead I argue that scientific ideas in 1982 and 1983 about AIDS and the transmissibility of a causative agent were later portrayed to be more self-evident than they were at the time. The article also traces how Shilts’s highly selective—and highly readable—characterization of Dugas rapidly became embedded in discussions about the need to criminalize the reckless transmission of HIV.

McKay, Richard A.

2014-01-01

117

Brane worlds in critical gravity  

NASA Astrophysics Data System (ADS)

Recently, Lü and Pope proposed critical gravities in [Phys. Rev. Lett. 106, 181302 (2011)]. In this paper we construct analytic brane solutions in critical gravity with matter. The Gibbons-Hawking surface term and junction condition are investigated, and the thin and thick brane solutions are obtained. All these branes are embedded in five-dimensional anti-de Sitter spacetimes. Our solutions are stable against scalar perturbations, and the zero modes of scalar perturbations cannot be localized on the branes.

Chen, Feng-Wei; Liu, Yu-Xiao; Zhong, Yuan; Wang, Yong-Qiang; Wu, Shao-Feng

2013-11-01

118

Gravity Waves  

article title:  Gravity Waves Ripple over Marine Stratocumulus Clouds   ... Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar ...

2013-04-19

119

Passive and Active Stabilization of Liquid Bridges in Low Gravity  

Microsoft Academic Search

The cylindrical liquid bridge of arbitrary size surrounded by air or vacuum is a fluid configuration that is essentially unique to the zero-gravity environment. An associated technology, which is enhanced in zero gravity, is the float-zone process of crystal growth, which involves a molten liquid bridge between a feed rod and the growing cylindrical crystal. There are several advantages to

David B. Thiessen; Wei Wei; Philip L. Marston

2002-01-01

120

Zero: A "None" Number?  

ERIC Educational Resources Information Center

This article discusses the challenges students face in making sense of zero as a number. A range of different student responses to a computation problem involving zero reveal students' different understandings of zero.

Anthony, Glenda J.; Walshaw, Margaret A.

2004-01-01

121

Venus gravity  

NASA Technical Reports Server (NTRS)

The anomalous gravity field of Venus shows high correlation with surface features revealed by radar. We extract gravity models from the Doppler tracking data from the Pioneer Venus Orbiter (PVO) by means of a two-step process. In the first step, we solve the nonlinear spacecraft state estimation problem using a Kalman filter-smoother. The Kalman filter was evaluated through simulations. This evaluation and some unusual features of the filter are discussed. In the second step, we perform a geophysical inversion using a linear Bayesian estimator. To allow an unbiased comparison between gravity and topography, we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps. The maps presented cover 2/3 of the surface of Venus and display the strong topography-gravity correlation previously reported. The topography-gravity scatter plots show two distinct trends.

Reasenberg, Robert D.

1993-01-01

122

Gravity Fountains  

NSDL National Science Digital Library

This activity (located on page 3 of the PDF) is a full inquiry investigation into the forces of gravity and air pressure. Groups of learners will construct a simple gravity fountain by making a hole near the bottom of a 2-liter bottle, filling it with water, then as the bottle empties, collecting measurements of the water levels and length of the stream, to make a graph for analysis. Relates to linked video, DragonflyTV GPS: Gravity Fountain.

Twin Cities Public Television, Inc.

2007-01-01

123

Quantum gravity  

NASA Astrophysics Data System (ADS)

Quantum Gravity is the name given to any theory that describes gravity in the regimes where quantum effects cannot be disregarded. At present, there is no such a theory which is universally accepted and confirmed by experience. Therefore the term "Quantum Gravity" indicates more an open problem than a specific theory. Several research lines, at different levels of development, offer tentative solutions to the problem. These tentative quantum-gravity theories are variously viewed as competing research directions, or as contributions to the common goal of finding the physically correct theory. The quest for the good quantum theory of gravity bears on a number of fundamental issues and it is sometimes presented as the most important open problem in fundamental physics: the "Holy Grail" of contemporary theoretical physics.

Rovelli, Carlo

2008-05-01

124

Regge Gravity from Spinfoams  

NASA Astrophysics Data System (ADS)

We consider spinfoam quantum gravity in the flipped limit, which is the double scaling limit ? ? 0, j ? ? with ?j = const., where ? is the Immirzi parameter, j is the spin and ?j gives the physical area in Planck units. In this regime the amplitude for a 2-complex becomes effectively an integral over Regge-like metrics and seems to enforce Einstein equations in the semiclassical regime. The Immirzi parameter must be considered as dynamical in the sense that it runs to zero when the fine structure of the foam is averaged. In addition to quantum corrections which vanish for ? ? 0, we find new corrections due to the discreteness of geometric spectra.

Magliaro, Elena; Perini, Claudio

2013-02-01

125

Multiple zeros of polynomials  

NASA Technical Reports Server (NTRS)

For polynomials of higher degree, iterative numerical methods must be used. Four iterative methods are presented for approximating the zeros of a polynomial using a digital computer. Newton's method and Muller's method are two well known iterative methods which are presented. They extract the zeros of a polynomial by generating a sequence of approximations converging to each zero. However, both of these methods are very unstable when used on a polynomial which has multiple zeros. That is, either they fail to converge to some or all of the zeros, or they converge to very bad approximations of the polynomial's zeros. This material introduces two new methods, the greatest common divisor (G.C.D.) method and the repeated greatest common divisor (repeated G.C.D.) method, which are superior methods for numerically approximating the zeros of a polynomial having multiple zeros. These methods were programmed in FORTRAN 4 and comparisons in time and accuracy are given.

Wood, C. A.

1974-01-01

126

Droplet burning at zero G  

NASA Technical Reports Server (NTRS)

Questions of the importance and feasibility of performing experiments on droplet burning at zero gravity in Spacelab were studied. Information on the physics and chemistry of droplet combustion, with attention directed specifically to the chemical kinetics, heat and mass transfer, and fluid mechanics of the phenomena involved, are presented. The work was divided into three phases, the justification, the feasibility, and the conceptual development of a preliminary design. Results from the experiments performed revealed a few new facts concerning droplet burning, notably burning rates in excess of theoretical prediction and a phenomenon of flash extinction, both likely traceable to accumulation of carbon produced by gas-phase pyrolysis in the fuel-rich zone enclosed by the reaction surface. These experiments also showed that they were primarily due to timing difficulties.

Williams, F. A.

1978-01-01

127

The Zero Saga  

NSDL National Science Digital Library

We have heard of calling someone "a total zero" as an insult, but what does "zero" really mean? This thoughtful and informative Website from Dr. Hossein Arsham, Wright Distinguished Research Professor of Statistics and Management Science at the University of Baltimore, discusses the history and philosophy of zero. Items presented include arguments for and against dividing by zero, the ideas of zero as a void and as a number, zero in limits, square roots, and divergent series and floating points. The text is peppered with links to related mathematics, computer science, and history of mathematics sites. The Zero Saga is a good read for mathematicians, college and graduate level students in mathematics, or anyone interested in logic.

Arsham, Hossein.

128

Improved Airborne Gravity Results Using New Relative Gravity Sensor Technology  

NASA Astrophysics Data System (ADS)

Airborne gravity data has contributed greatly to our knowledge of subsurface geophysics particularly in rugged and otherwise inaccessible areas such as Antarctica. Reliable high quality GPS data has renewed interest in improving the accuracy of airborne gravity systems and recent improvements in the electronic control of the sensor have increased the accuracy and ability of the classic Lacoste and Romberg zero length spring gravity meters to operate in turbulent air conditions. Lacoste and Romberg type gravity meters provide increased sensitivity over other relative gravity meters by utilizing a mass attached to a horizontal beam which is balanced by a ';zero length spring'. This type of dynamic gravity sensor is capable of measuring gravity changes on the order of 0.05 milliGals in laboratory conditions but more commonly 0.7 to 1 milliGal in survey use. The sensor may have errors induced by the electronics used to read the beam position as well as noise induced by unwanted accelerations, commonly turbulence, which moves the beam away from its ideal balance position otherwise known as the reading line. The sensor relies on a measuring screw controlled by a computer which attempts to bring the beam back to the reading line position. The beam is also heavily damped so that it does not react to most unwanted high frequency accelerations. However this heavily damped system is slow to react, particularly in turns where there are very high Eotvos effects. New sensor technology utilizes magnetic damping of the beam coupled with an active feedback system which acts to effectively keep the beam locked at the reading line position. The feedback system operates over the entire range of the system so there is now no requirement for a measuring screw. The feedback system operates at very high speed so that even large turbulent events have minimal impact on data quality and very little, if any, survey line data is lost because of large beam displacement errors. Airborne testing along with results from ground based van testing and laboratory results have shown that the new sensor provides more consistent gravity data, as measured by repeated line surveys, as well as preserving the inherent sensitivity of the Lacoste and Romberg zero length spring design. The sensor also provides reliability during survey operation as there is no mechanical counter screw. Results will be presented which show the advantages of the new sensor system over the current technology in both data quality and survey productivity. Applications include high resolution geoid mapping, crustal structure investigations and resource mapping of minerals, oil and gas.

Brady, N.

2013-12-01

129

Orbital Gravity Gradiometry Beyond GOCE: Instrument Concept  

Microsoft Academic Search

With the recent maturation of 4-K space cryocooler technology, a multi-year gravity mapping mission based on an advanced superconducting gravity gradiometer (SGG) can now be planned. The original SGG fully developed in the 1990's had mechanically suspended test masses, which limited the intrinsic sensitivity to 1 mE\\/&surd;Hz. In zero-g, mechanically free test masses can be magnetically levitated around a common

M. V. Moody; H. Paik; K. Y. Venkateswara; P. J. Shirron; M. J. Dipirro; E. R. Canavan; S. Han; P. Ditmar; R. Klees; C. Jekeli; C. Shum

2010-01-01

130

On the partition function of non-perturbative gravity  

NASA Astrophysics Data System (ADS)

The partition function of the zero-dimensional anharminic oscillator is found explicitly. As an application of this result the partition function of two-dimensional quantum gravity is expressed as a determinant of the functions of the parabolic cylinder.

Ivanov, B. V.

1991-01-01

131

Zero Energy Use School.  

ERIC Educational Resources Information Center

The economic and physical realities of an energy shortage have caused many educators to consider alternative sources of energy when constructing their schools. This book contains studies and designs by fifth-year architecture students concerning the proposed construction of a zero energy-use elementary school in Albany, Oregon. "Zero energy use"…

Nelson, Brian, Ed.; And Others

132

Zero-G Condensing Heat Exchanger with Integral Disinfection  

NASA Technical Reports Server (NTRS)

The system that operates in a zero gravity environment and has an integral ozone generating capability is disclosed. The system contributes to the control of metabolic water vapors in the air, and also provided disinfection of any resulting condensate within the system, as well as disinfection of the air stream that flows throughout the disclosed system.

Burke, Kenneth A. (Inventor)

2012-01-01

133

Net Zero Water Update.  

National Technical Information Service (NTIS)

The Army is committed to a holistic approach using proven solutions, technical expertise, partnerships, and leveraged resources to achieve the goal of net zero installations. Seventeen Army pilot installations were identified on 19 April 11. The Army will...

K. Kingery

2011-01-01

134

Emergent gravity from a mass deformation in warped spacetime  

Microsoft Academic Search

We consider a deformation of five-dimensional warped gravity with bulk and boundary mass terms to quadratic order in the action. We show that massless zero modes occur for special choices of the masses. The tensor zero mode is a smooth deformation of the Randall-Sundrum graviton wave function and can be localized anywhere in the bulk. There is also a vector

Tony Gherghetta; Marco Peloso; Erich Poppitz

2005-01-01

135

Expanding Gravity  

NASA Astrophysics Data System (ADS)

Newton's gravitational constant Gn and Laws of Gravity are based upon observations in our solar system. Mysteries appear when they are used far outside our solar system Apparently, Newton's gravitational constant can not be applied at large distances. Dark matter was needed to explain the observed flat rotational velocity curves of spiral galaxies (Rubin), and of groups of remote galaxies (Zwicky). Our expansion of Newton's gravitational constant Gn as a power series in distance r, is sufficient to explain these observations without using dark matter. This is different from the MOND theory of Milgrom involving acceleration. Also, our Expanded Gravitational Constant (EGC) can show the correct use of the red shift. In addition to the Doppler contribution, there are three other contributions and these depend only upon gravity. Thus, velocity observations only based on the red shift can not be used to support the concept of the expanding universe, the accelerating expansion, or dark energy. Our expanded gravity constant can predict and explain Olbers' paradox (dark sky), and the temperature of the CMB (cosmic microwave background). Thus, CMB may not support the big bang and inflation.

Aisenberg, Sol

2005-04-01

136

Teacher in Space Christa McAuliffe on the KC-135 for zero-G training  

NASA Technical Reports Server (NTRS)

Teacher in Space Christa McAuliffe on the KC-135 for zero-G training. McAuliffe, 51-L citizen observer/payload specialist, gets a preview of microgravity during a special flight aboard NASA's KC-135 'zero gravity' aircraft.

1986-01-01

137

Neural-Thyroid Interaction on Skeletal Isomyosin in Zero Gravity  

NASA Technical Reports Server (NTRS)

The primary goal of the project was to develop a ground based model to first study the role of the nerve and of thyroid hormone (T3) in the regulation of body growth and skeletal muscle growth and differentiation in rodents. A primary objective was to test the hypothesis that normal weight bearing activity is essential for the development of antigravity, slow twitch skeletal muscle and the corresponding slow myosin heavy chain (MHC) gene; whereas, T3 was obligatory for general body and muscle growth and the establishment of fast MHC phenotype in typically fast locomoter muscles. These ground based experiments would provide both the efficacy and background for a spaceflight experiment (referred to as the Neurolab Mission) jointly sponsored by the NIH and NASA.

Baldwin, Kenneth M.

2000-01-01

138

Design, development, and operation of a zero gravity shower  

NASA Technical Reports Server (NTRS)

The high mission penalty associated with water and electrical power usage constrained the shower configuration concept for the Skylab project to a procedure in which water is sprayed on the body to wet down and soaping is accomplished without water flow. The soap is then finally rinsed off. Initial concept confirmation tests are discussed along with details of the flight shower configuration, the shower water bottle, the shower stall assembly, the liquid-gas separator, the collection box and bag assembly, the hydrophobic filter assembly, and the soap dispenser. Aspects of microbial evaluation of flight qualification hardware are also considered.

Middleton, R. L.; Krupnick, A. C.; Reily, J. C.; Schrick, B. J.

1974-01-01

139

Fluid mass sensor for a zero gravity environment  

NASA Technical Reports Server (NTRS)

A sensor for measuring the mass of fluids, is described which includes a housing having an inlet and outlet for receiving and dumping the fluid, a rotary impeller within the housing for imparting centrifugal motion to the fluid and a pressure sensitive transducer attached to the housing to sense the rotating fluid pressure. The fluid may be drawn into the housing by entrainment within a gas stream. The resulting mixture is then separated into two phases: gas and liquid. The gas is removed from the housing and the pressure of the liquid, under centrifugal motion, is sensed and correlated with the mass of the fluid.

Fogal, G. L. (inventor)

1976-01-01

140

Venipuncture and intravenous infusion access during zero-gravity flight  

NASA Technical Reports Server (NTRS)

The purpose of this experiment is to establish the difficulty associated with securing an intravenous (IV) catheter in place in microgravity flight and the techniques applicable in training the Crew Medical Officer (CMO) for Space Station Freedom, as well as aiding in the selection of appropriate hardware and supplies for the Health Maintenance Facility (HMF). The objectives are the following: (1) to determine the difficulties associated with venipuncture in a microgravity environment; (2) to evaluate the various methods of securing an IV catheter and attached tubing for infusion with regard to the unique environment; (3) to evaluate the various materials available for securing an intravenous catheter in place; and (4) to evaluate the fluid therapy administration system when functioning in a complete system. The inflight test procedures and other aspects of the KC-135 parabolic flight test to simulate microgravity are presented.

Krupa, Debra T.; Gosbee, John; Billica, Roger; Bechtle, Perry; Creager, Gerald J.; Boyce, Joey B.

1991-01-01

141

Intravenous fluid flow meter concept for zero gravity environment  

NASA Technical Reports Server (NTRS)

Measuring chamber, included in infusion-set tubing, and peristaltic flow meter concept can be incorporated into flow meter that measures fluid flow rates between 100 and 600 cu cm per hour and at the same time maintains sterilization.

Miller, C. G.

1972-01-01

142

A Zero-Gravity Cup for Drinking Beverages in Microgravity  

NASA Technical Reports Server (NTRS)

To date, the method for astronauts to drink liquids in microgravity or weightless environments is to suck the liquid from a bag or pouch through a straw. A new beverage cup works in microgravity and allows astronauts to drink liquids from a cup in a manner consistent with that on Earth. The cup is capable of holding beverages with an angled channel running along the wall from the bottom to the lip. In microgravity, a beverage is placed into the cup using the galley dispenser. The angled channel acts as an open passage that contains only two sides where capillary forces move the liquid along the channel until it reaches the top lip where the forces reach an equilibrium and the flow stops. When one sips the liquid at the lip of the channel, the capillary force equilibrium is upset and more liquid flows to the lip from the reservoir at the bottom to re-establish the equilibrium. This sipping process can continue until the total liquid contents of the cup is consumed, leaving only a few residual drops about the same quantity as in a ceramic cup when it is drunk dry on Earth.

Pettit, Donald R.; Weislogel, Mark; Concus, Paul; Finn, Robert

2011-01-01

143

Dental equipment test during zero-gravity flight  

NASA Technical Reports Server (NTRS)

The overall objectives of this program were to establish performance criteria and develop prototype equipment for use in the Health Maintenance Facility (HMF) in meeting the needs of dental emergencies during space missions. The primary efforts during this flight test were to test patient-operator relationships, patent (manikin) restraint and positioning, task lighting systems, use and operation of dental rotary instruments, suction and particle containment system, dental hand instrument delivery and control procedures, and the use of dental treatment materials. The initial efforts during the flight focused on verification of the efficiency of the particle containment system. An absorptive barrier was also tested in lieu of the suction collector. To test the instrument delivery system, teeth in the manikin were prepared with the dental drill to receive restorations, some with temporary filling materials and another with definitive filling material (composite resin). The best particle containment came from the combination use of the laminar-air/suction collector in concert with immediate area suction from a surgical high-volume suction tip. Lighting in the treatment area was provided by a flexible fiberoptic probe. This system is quite effective for small areas, but for general tasks ambient illumination is required. The instrument containment system (elastic cord network) was extremely effective and easy to use. The most serious problem with instrument delivey and actual treatment was lack of time during the microgravity sequences. The restorative materials handled and finished well.

Young, John; Gosbee, John; Billica, Roger

1991-01-01

144

Gravity Launch  

NSDL National Science Digital Library

In this online game, learners attempt to send a rocket ship to various targets. Learners can adjust the angle and thrust of the rocket before it is launched. The game simulates the pull of gravity on the rocket from the Earth and Moon. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Smart Attack game after they've completed several activities.

Science, American A.

2009-01-01

145

Gravity Base Station Descriptions.  

National Technical Information Service (NTIS)

Descriptions of gravity base stations occupied by the Woods Hole Oceanographic Institution during the years 1962 through September 1973 are presented. The measurements were made with LaCoste and Romberg Geodtic Gravity Meter No. G-18. The gravity values, ...

C. Bowin L. Gove

1974-01-01

146

Combustion of velcro in low gravity  

NASA Technical Reports Server (NTRS)

An experimental program was conducted to investigate the low gravity burning characteristics on nylon and Nomex Velcro fastening tapes in an atmosphere of 30-percent oxygen, 70-percent nitrogen at a 70-kPa pressure. The tests were conducted using the NASA Lewis Research Center Zero Gravity Facility. The test results, as documented by high-speed cameras, indicate that both nylon and Nomex burn in low gravity for the full 5.18 sec test time but that Nomex burns less vigorously than nylon. Nylon melts as it burns, whereas Nomex forms a solid char. Nylon also sputters burning droplets as it burns. Thus, from these limited tests, it appears that Nomex Velcro is less hazardous than nylon Velcro for spacecraft applications. The results also show that residual gas velocities, and by analogy spacecraft air circulation, can enhance the low-gravity combustion.

Olson, Sandra L.; Sotos, Raymond G.

1987-01-01

147

Gravity Virgins  

NASA Astrophysics Data System (ADS)

As an exercise in imagining a first encounter with gravity, let's begin with the barest gravitational circumstance. On a planet-sized spherical mass we find rigid poles extending to astronomical distances. At regular intervals along each pole there are Instrument Stations containing a clock, an accelerometer and light senders and receivers. Now imagine a civilization (the RC's) that has evolved in a huge self-sustaining Rotating Cylinder far removed from the sphere or any other astronomical body. The RC's are totally ignorant of gravity but understand well light propagation and the effect of motion on clocks, lengths, etc. Motion is sacred to the RC's because they know they'd die if their cylinder stopped rotating. Their clocks are synchronized so as to reflect the anisotropy of light sent in opposite directions along the cylinder's wall. When they set out to explore the Universe, they come upon the top of one of our tall poles. The RC's inspect the instruments, take data and leave their rocket off except when, in the nick of time, they turn it back on to navigate a soft landing. In their attempt to make sense of their experience, will they prefer a hypothesis resembling General Relativity or a hypothesis more like the one found at GravitationLab.com?

Benish, Richard

2008-05-01

148

Zero Tolerance versus Privacy.  

ERIC Educational Resources Information Center

In a case involving questionable canine search-and-seizure practices, a circuit court upheld a school board's decision to terminate a teacher's contract. While touting zero tolerance, the board fired an honored teacher 3 years from retirement who may not have known about the marijuana cigarette in her car. (MLH)

Dowling-Sendor, Benjamin

2000-01-01

149

Earnings Management Around Zero  

Microsoft Academic Search

Literature earnings management aims to determine what causes\\/motivates managers to disclose earnings close to zero and to use this as an instrument to influence users' decisions. However, limited research has been carried out on this subject in the public sector. Therefore, the main purpose of this paper is to evaluate whether local politicians (in Portuguese municipalities), aiming to demonstrate their

Augusta Ferreira; João Carvalho; Fátima Pinho

2012-01-01

150

The Riemann Zeros and  

Microsoft Academic Search

Comparison between formulae for the counting functions of the heights tn of the Riemann zeros and of semiclassical quantum eigenvalues En suggests that the tn are eigenvalues of an (unknown) hermitean operator H, obtained by quantizing a classical dynamical system with hamiltonian Hcl. Many features of Hcl are provided by the analogy; for example, the \\\\Riemann dynamics\\

151

Positive, Zero, or Negative?  

NSDL National Science Digital Library

This lesson involves students using positive and negative numbers to represent quantities in real-world contexts, explaining the meaning of zero in each situation. Students will understand the positive and negative numbers are used together to describe quantities having opposite values.

Brown, Kathleen

2012-09-16

152

Conformal and Einstein gravity from twistor actions  

NASA Astrophysics Data System (ADS)

We use the embedding of Einstein gravity with cosmological constant into conformal gravity as a basis for using the twistor action for conformal gravity to obtain maximal-helicity-violating (MHV) scattering amplitudes not just for conformal gravity, but also for Einstein gravity on backgrounds with non-zero cosmological constant. The new formulae for the gravitational MHV amplitude with cosmological constant arise by summing Feynman diagrams using the matrix-tree theorem. We show that this formula is well-defined (i.e., is independent of certain gauge choices) and that it non-trivially reproduces Hodges’ formula for the MHV amplitude in the flat-space limit. We give a preliminary discussion of an MHV formalism for more general amplitudes obtained from the conformal gravity twistor action in an axial gauge. We also see that the embedding of Einstein data into the conformal gravity action can be performed off-shell in twistor space to give a proposal for an Einsten twistor action that automatically gives the same MHV amplitude. These ideas extend naturally to {N}=4 supersymmetry.

Adamo, Tim; Mason, Lionel

2014-02-01

153

Graviresponses of osteocytes under altered gravity  

NASA Astrophysics Data System (ADS)

Single cell was capable of sensing and responding to alterations of gravity. Osteocytes, as the most abundant cells of the bone tissue playing an important role in the bone mechanotransduction, are very sensitive to mechanical stimuli. However, the effect of altered gravity on osteocytes so far is less known according to the public papers. Further study on this issue will help to verify and develop the theory of how cells perceive and respond to gravity. It also brings new ideas to the study of space bone loss. In our study, Osteocyte-like MLO-Y4 cells were exposed to 30 parabolic flights three times on ZERO-G airbus A300 to investigate the comprehensive effect on osteocytes stimulated by hyper- and hypo-gravity forces. It showed that the cell morphology, as well as cell area and height, was not changed significantly by hyper-gravity and hypo-gravity. However, the cytoskeleton was reorganized. In flight cells, F-actin polymerization was enhanced at the cell periphery and microtubule organizing center disappeared, but no apoptotic feathers were detected. The results of western blot showed that connexin 43 (Cx43) expression was down-regulated, indicating an decrease of gap-junction. In conclusion, hyper- and hypo-gravity stimulation altered the cytoskeleton architecture and suppressed gap-junction of osteocyte-like MLO-Y4 cells.

Di, S. M.; Qian, A. R.; Qu, L. N.; Zhang, W.; Wang, Z.; Ding, C.; Li, Y. H.; Ren, H. G.; Shang, P.

2011-09-01

154

One-dimensional polymer Fermi gas at zero temperature  

NASA Astrophysics Data System (ADS)

In this work we study a completely degenerated fermion gas at zero temperature employing a semi-classical approximation obtained from polymer quantum mechanics. Polymer quantum systems are quantum mechanical models quantized in a similar way as in loop quantum gravity. These models allow the study in a simplified way of the discreteness of space present in loop quantum gravity. We obtain the thermodynamic quantities modified by the polymer scale and we note that the corresponding Fermi energy is exactly the same as if one directly polymerizes the momentum pF.

Chacón-Acosta, Guillermo; Hernández, Héctor H.

2013-07-01

155

Approaches to Quantum Gravity  

NASA Astrophysics Data System (ADS)

Preface; Part I. Fundamental Ideas and General Formalisms: 1. Unfinished revolution C. Rovelli; 2. The fundamental nature of space and time G. 't Hooft; 3. Does locality fail at intermediate length scales R. Sorkin; 4. Prolegomena to any future quantum gravity J. Stachel; 5. Spacetime symmetries in histories canonical gravity N. Savvidou; 6. Categorical geometry and the mathematical foundations of quantum gravity L. Crane; 7. Emergent relativity O. Dreyer; 8. Asymptotic safety R. Percacci; 9. New directions in background independent quantum gravity F. Markopoulou; Questions and answers; Part II: 10. Gauge/gravity duality G. Horowitz and J. Polchinski; 11. String theory, holography and quantum gravity T. Banks; 12. String field theory W. Taylor; Questions and answers; Part III: 13. Loop Quantum Gravity T. Thiemann; 14. Covariant loop quantum gravity? E. LIvine; 15. The spin foam representation of loop quantum gravity A. Perez; 16. 3-dimensional spin foam quantum gravity L. Freidel; 17. The group field theory approach to quantum gravity D. Oriti; Questions and answers; Part IV. Discrete Quantum Gravity: 18. Quantum gravity: the art of building spacetime J. Ambjørn, J. Jurkiewicz and R. Loll; 19. Quantum Regge calculations R. Williams; 20. Consistent discretizations as a road to quantum gravity R. Gambini and J. Pullin; 21. The causal set approach to quantum gravity J. Henson; Questions and answers; Part V. Effective Models and Quantum Gravity Phenomenology: 22. Quantum gravity phenomenology G. Amelino-Camelia; 23. Quantum gravity and precision tests C. Burgess; 24. Algebraic approach to quantum gravity II: non-commutative spacetime F. Girelli; 25. Doubly special relativity J. Kowalski-Glikman; 26. From quantum reference frames to deformed special relativity F. Girelli; 27. Lorentz invariance violation and its role in quantum gravity phenomenology J. Collins, A. Perez and D. Sudarsky; 28. Generic predictions of quantum theories of gravity L. Smolin; Questions and answers; Index.

Oriti, Daniele

2009-03-01

156

Noninteractive Zero-Knowledge  

Microsoft Academic Search

We investigate the possibility of disposing of interaction between Prover and Verifier in a zeroknowledgeproof if they share beforehand a short random string.Without any assumption, we prove that non-interactive zero-knowledge proofs exist for some numbertheoretic languages for which no efficient algorithm is known.If deciding quadratic residuosity (modulo composite integers whose factorization is not known) iscomputationally hard, we show that the

Manuel Blum; Alfredo De Santis; Silvio Micali; Giuseppe Persiano

1991-01-01

157

Zero Energy Windows  

SciTech Connect

Windows in the U.S. consume 30 percent of building heating and cooling energy, representing an annual impact of 4.1 quadrillion BTU (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort. An additional 1 quad of lighting energy could be saved if buildings employed effective daylighting strategies. The ENERGY STAR{reg_sign} program has made standard windows significantly more efficient. However, even if all windows in the stock were replaced with today's efficient products, window energy consumption would still be approximately 2 quads. However, windows can be ''net energy gainers'' or ''zero-energy'' products. Highly insulating products in heating applications can admit more useful solar gain than the conductive energy lost through them. Dynamic glazings can modulate solar gains to minimize cooling energy needs and, in commercial buildings, allow daylighting to offset lighting requirements. The needed solutions vary with building type and climate. Developing this next generation of zero-energy windows will provide products for both existing buildings undergoing window replacements and products which are expected to be contributors to zero-energy buildings. This paper defines the requirements for zero-energy windows. The technical potentials in terms of national energy savings and the research and development (R&D) status of the following technologies are presented: (1) Highly insulating systems with U-factors of 0.1 Btu/hr-ft{sup 2}-F; (2) Dynamic windows: glazings that modulate transmittance (i.e., change from clear to tinted and/or reflective) in response to climate conditions; and (3) Integrated facades for commercial buildings to control/ redirect daylight. Market transformation policies to promote these technologies as they emerge into the marketplace are then described.

Arasteh, Dariush; Selkowitz, Steve; Apte, Josh; LaFrance, Marc

2006-05-17

158

Gravity data of Nevada  

USGS Publications Warehouse

Gravity data for the entire state of Nevada and adjacent parts of California, Utah, and Arizona are available on this CD-ROM. About 80,000 gravity stations were compiled primarily from the National Geophysical Data Center and the U.S. Geological Survey. Gravity data was reduced to the Geodetic Reference System of 1967 and adjusted to the Gravity Standardization Net 1971 gravity datum. Data were processed to complete Bouguer and isostatic gravity anomalies by applying standard gravity corrections including terrain and isostatic corrections. Selected principal fact references and a list of sources for data from the National Geophysical Data Center are included.

Ponce, David A.

1997-01-01

159

Effect of a zero g environment on flammability limits as determined using a standard flammability tube apparatus  

NASA Technical Reports Server (NTRS)

Flammability limits in a zero gravity environment were defined. Key aspects of a possible spacelab experiment were investigated analytically, experimentally on the bench, and in drop tower facilities. A conceptual design for a spacelab experiment was developed.

Strehlow, R. A.; Reuss, D. L.

1980-01-01

160

Boosting Majorana Zero Modes  

NASA Astrophysics Data System (ADS)

One-dimensional topological superconductors are known to host Majorana zero modes at domain walls terminating the topological phase. Their non-Abelian nature allows for processing quantum information by braiding operations that are insensitive to local perturbations, making Majorana zero modes a promising platform for topological quantum computation. Motivated by the ultimate goal of executing quantum-information processing on a finite time scale, we study domain walls moving at a constant velocity. We exploit an effective Lorentz invariance of the Hamiltonian to obtain an exact solution of the associated quasiparticle spectrum and wave functions for arbitrary velocities. Essential features of the solution have a natural interpretation in terms of the familiar relativistic effects of Lorentz contraction and time dilation. We find that the Majorana zero modes remain stable as long as the domain wall moves at subluminal velocities with respect to the effective speed of light of the system. However, the Majorana bound state dissolves into a continuous quasiparticle spectrum after the domain wall propagates at luminal or even superluminal velocities. This relativistic catastrophe implies that there is an upper limit for possible braiding frequencies even in a perfectly clean system with an arbitrarily large topological gap. We also exploit our exact solution to consider domain walls moving past static impurities present in the system.

Karzig, Torsten; Refael, Gil; von Oppen, Felix

2013-10-01

161

Propulsion Investigation for Zero and Near-Zero Emissions Aircraft.  

National Technical Information Service (NTIS)

As world emissions are further scrutinized to identify areas for improvement, aviation s contribution to the problem can no longer be ignored. Previous studies for zero or near-zero emissions aircraft suggest aircraft and propulsion system sizes that woul...

A. F. Kascak C. A. Gallo C. A. Snyder C. J. Marek D. J. Eichenberg G. Brown G. L. Stefko J. E. Freeh J. J. Berton J. L. Dolce K. A. Geiselhat K. P. Kundu M. G. Millis M. V. Dravid P. L. Murthy R. M. Sullivan R. T. Tornabene S. M. Jones T. D. Smith T. M. Roach

2009-01-01

162

Small amplitude forced fluid dynamics from gravity at T=0  

NASA Astrophysics Data System (ADS)

The usual derivative expansion of gravity duals of charged fluid dynamics is known to break down in the zero temperature limit. In this case, fluid-gravity duality is not understood precisely. We explore this problem for a zero temperature charged fluid driven by a low frequency, small amplitude and spatially homogeneous external force. In the gravity dual, this corresponds to a time dependent boundary value of the dilaton. We calculate the bulk solution for the dilaton and the leading back reaction to the metric and the gauge fields using the modified low frequency expansion of Faulkner et al. ( arXiv:0907.2694 [hep-th]). The resulting solutions are regular everywhere, establishing fluid-gravity duality to this order.

Oh, Jae-Hyuk

2011-12-01

163

Zero adhesion system  

NASA Astrophysics Data System (ADS)

This patent discloses a zero adhesion system whereby a protective missile launch pad is held against an Environmental Protection Material (EPM) coated missile skin surface having an intermediary cloth sheet inbetween. The pad comprises a steel sheet having perforated cleats defined therein, which sheet is affixed to the underside of the pad and releasably bears against the intermediary cloth sheet. This arrangement operates such that the protective missile launch pad is freely released from the missile at launch without adhession to the EPM coated missile skin.

Steinmetz, Joseph N., Jr.

1986-07-01

164

Why not zero waste  

SciTech Connect

Clairol`s plant in Camarillo, California, handles about 20 percent of its national production volume, employing 79 people. In 1985, when the local disposal facility was abruptly closed to liquids, the Camarillo plant was producing an average of 1,000 gallons per day of waste rinsewater that required disposal off-site. In January 1986, Clairol`s Camarillo plant adopted a `zero-waste program` aimed at eliminating off-site disposal by 1991. All employees were encouraged to participate in the program, and each process was studied for its contribution to the waste stream.

Woodman, J.H.

1989-12-01

165

Running gauge coupling in asymptotically safe quantum gravity  

Microsoft Academic Search

We investigate the non-perturbative renormalization group behavior of the gauge coupling constant using a truncated form of\\u000a the functional flow equation for the effective average action of the Yang-Mills-gravity system. We find a non-zero quantum\\u000a gravity correction to the standard Yang-Mills beta function which has the same sign as the gauge boson contribution. Our results\\u000a fit into the picture according

Jan-Eric Daum; Ulrich Harst; Martin Reuter

2010-01-01

166

NOVA: Absolute Zero  

NSDL National Science Digital Library

On a hot day, some might wish they could get the temperature down a bit. They might not wish it to be as cold as, say absolute zero, but there are many scientists who are interested in doing just that. For those who are curious, absolute zero clocks in at around minus 460 degrees Fahrenheit. This engaging website is meant to serve as a complementary resource to the two-part series that recently aired on NOVA on this engaging topic. Visitors can start by watching a short preview of the program, and then continuing on to look over some of the special interactive features on the site. All told, there are ten different features, including "A Sense of Scale", "How Low Can You Go?", and "Milestones in Cold Research". The "Milestones in Cold Research" is a great place to start, as it's an interactive timeline that chronicles the "netherworld of extraordinarily low temperatures" as investigated by everyone from Galileo to current researchers. Of course, there are also more playful features here, such as "The Ice Trade", which asks users to dispatch ships loaded with natural ice to Florida, Brazil, and India.

167

Neutrino oscillations under gravity: mass independent oscillation  

Microsoft Academic Search

I discuss the possibility of neutrino oscillation in presence of gravity. In this respect I consider the propagation of neutrinos in the early phase of universe and around black holes. It is seen that whether the rest masses of a neutrino and corresponding anti-neutrino are considered to be same or not due to space-time curvature effect non-zero oscillation probability between

Banibrata Mukhopadhyay

2003-01-01

168

Feeling Gravity's Pull: Gravity Modeling. The Gravity Field of Mars  

NASA Technical Reports Server (NTRS)

Most people take the constant presence of gravitys pull for granted. However, the Earth's gravitational strength actually varies from location to location. This variation occurs because mass, which influences an object's gravitational pull, is not evenly distributed within the planet. Changes in topography, such as glacial movement, an earthquake, or a rise in the ocean level, can subtly affect the gravity field. An accurate measurement of the Earth's gravity field helps us understand the distribution of mass beneath the surface. This insight can assist us in locating petroleum, mineral deposits, ground water, and other valuable substances. Gravity mapping can also help notice or verify changes in sea surface height and other ocean characteristics. Such changes may indicate climate change from polar ice melting and other phenomena. In addition, gravity mapping can indicate how land moves under the surface after earthquakes and other plate tectonic processes. Finally, changes in the Earth's gravity field might indicate a shift in water distribution that could affect agriculture, water supplies for population centers, and long-term weather prediction. Scientists can map out the Earth's gravity field by watching satellite orbits. When a satellite shifts in vertical position, it might be passing over an area where gravity changes in strength. Gravity is only one factor that may shape a satellite's orbital path. To derive a gravity measurement from satellite movement, scientists must remove other factors that might affect a satellite's position: 1. Drag from atmospheric friction. 2. Pressure from solar radiation as it heads toward Earth and. as it is reflected off the surface of the Earth 3. Gravitational pull from the Sun, the Moon, and other planets in the Solar System. 4. The effect of tides. 5. Relativistic effects. Scientists must also correct for the satellite tracking process. For example, the tracking signal must be corrected for refraction through the atmosphere of the Earth. Supercomputers can calculate the effect of gravity for specific locations in space following a mathematical process known as spherical harmonics, which quantifies the gravity field of a planetary body. The process is based on Laplace's fundamental differential equation of gravity. The accuracy of a spherical harmonic solution is rated by its degree and order. Minute variations in gravity are measured against the geoid, a surface of constant gravity acceleration at mean sea level. The geoid reference gravity model strength includes the central body gravitational attraction (9.8 m/sq s) and a geopotential variation in latitude partially caused by the rotation of the Earth. The rotational effect modifies the shape of the geoid to be more like an ellipsoid, rather than a perfect, circle. Variations of gravity strength from the ellipsoidal reference model are measured in units called milli-Galileos (mGals). One mGal equals 10(exp -5) m/sq s. Research projects have also measured the gravity fields of other planetary bodies, as noted in the user profile that follows. From this information, we may make inferences about our own planet's internal structure and evolution. Moreover, mapping the gravity fields of other planets can help scientists plot the most fuel-efficient course for spacecraft expeditions to those planets.

Lemoine, Frank; Smith, David; Rowlands, David; Zuber, Maria; Neumann, G.; Chinn, Douglas; Pavlis, D.

2000-01-01

169

Zero-dimensional magnetite  

NASA Astrophysics Data System (ADS)

Low-dimensional magnetic systems are of interest due to several new effects and modifications that occur at sizes below the average domain grain boundary within the bulk material. Molecule-like magnetite (Fe3O4) nanoparticles, with sizes ranging from one to two nm were synthesized and characterized in order to investigate new properties arising from quantum size effects. These small systems will provide opportunities to investigate magnetism of zero-dimension systems. A zero-dimensional object is usually called a quantum dot or artificial atom because its electronic states are few and sharply separated in energy, resembling those within an atom. Since the surface to volume ratio is the highest for zero-dimensional systems, most of the changes to magnetic behavior will be observed in ultra-fine magnetic particles. Chemically functional magnetic nanoparticles, comprised of a Fe 3O4 magnetite core encased in a thin aliphatic carboxylate, have been prepared by sequential high temperature decomposition of organometallic compounds in a coordinating solvent. In this work, aliphatic carboxylic acid chain length, reaction temperature and duration were varied to produce small core diameters. In order to correlate size effects with changes in particle formation, it is important to have a through understanding of the structural components. This includes studies of the core size, surface effects, decomposition, electronic properties and magnetic behavior. Quantum size effects were observed in the (Fe3O4)X(carboxylate)Y monolayer protected clusters (MPCs) when the average core diameter was ?2.0 nm, evidenced by a blue shifted absorbance band maxima, suggesting the onset of quantum confinement. These (Fe3O4)X(carboxylate) Y MPCs also posses a complex interplay between surface and finite size effects, which govern the magnetic properties of these zero-dimensional systems. These MPCs are all superparamagnetic above their blocking temperatures with total magnetic anisotropy values greater than the bulk value due to an increase in surface and magnetocrystalline anisotropy. A non-linear decrease in saturation magnetization (MS) (muB per cluster) as a function of the reciprocal of core radius have been attributed to surface effects such as a magnetically inactive layer or an increase in spin disorder as core diameter decreases. The reduced core dimensions of these MPCs make them ideal candidates for further investigation of quantum magnetic systems. Chapter 1 provides a brief introduction to magnetic properties on the quantum scale and methods to examine those properties. Chapter 2 is an introduction to nanostructured magnetic systems including metals and oxides. Specific instrumentation and methodologies needed to provide insight about nanoparticles are discussed. Chapter 3 is an investigation of zero-dimensional magnetite monolayer protected clusters. The aim of this research is the preparation, isolation, and characterization of sub-colloidal (diameter ?2.0 nm) magnetite (Fe3O4) nanocrystals. The synthetic procedures within are the first reports of 1.0--2.0 nm (Fe 3O4)x(carboxylate)y materials, approaching the scale of single-molecule magnets. Appendix A includes some of the common units and formulas used in magnetism while Appendix B summarizes the Langevin model of paramagnetism and how it relates to quantum effects, and Appendix C presents a table of values pertaining to photon energies in various units.

Arredondo, Melissa Gayle

170

Resonance mass spectra of gravity and fermion on Bloch branes  

NASA Astrophysics Data System (ADS)

In this paper, by presenting the potentials of Kaluza-Klein (KK) modes in the corresponding Schrödinger equations, we investigate the localization and resonances of gravity and fermion on the symmetric and asymmetric Bloch branes. We find that the localization properties of zero modes for gravity and fermion in the symmetric brane case are the same, whereas, for the asymmetric brane case, the fermion zero mode is localized on one of the sub-branes, while the gravity zero mode is localized on another sub-brane. The spectra of the gravity and the left- or right-handed fermion are composed of a bound zero mode and a series of gapless continuous massive KK modes. Among the continuous massive KK modes, we obtain some discrete gravity and fermion resonant (quasilocalized) KK states on the brane, which have a finite probability of escaping into the bulk. The KK states with lower resonant masses have a longer lifetime on the brane. And the number of the resonant KK states increases linearly with the width of the brane and the scalar-fermion coupling constant, but it decreases with the asymmetric factor ?. The structure of the resonance spectrum is investigated in detail.

Xie, Qun-Ying; Yang, Jie; Zhao, Li

2013-11-01

171

Lunar Bouguer gravity anomalies - Imbrian age craters  

NASA Technical Reports Server (NTRS)

The Bouguer gravity of mass anomalies associated with four Imbrian age craters, analyzed in the present paper, are found to differ considerably from the values of the mass anomalies associated with some young lunar craters. Of the Imbrian age craters, only Piccolomini exhibits a negative gravity anomaly (i.e., a low density region) which is characteristic of the young craters studied. The Bouguer gravity anomalies are zero for each of the remaining Imbrian age craters. Since, Piccolomini is younger, or at least less modified, than the other Imbrian age craters, it is suggested that the processes responsible for the post-impact modification of the Imbrian age craters may also be responsible for removing the negative mass anomalies initially associated with these features.

Dvorak, J.; Phillips, R. J.

1978-01-01

172

Entropic force, noncommutative gravity, and ungravity  

NASA Astrophysics Data System (ADS)

After recalling the basic concepts of gravity as an emergent phenomenon, we analyze the recent derivation of Newton’s law in terms of entropic force proposed by Verlinde. By reviewing some points of the procedure, we extend it to the case of a generic quantum gravity entropic correction to get compelling deviations to the Newton’s law. More specifically, we study: (1) noncommutative geometry deviations and (2) ungraviton corrections. As a special result in the noncommutative case, we find that the noncommutative character of the manifold would be equivalent to the temperature of a thermodynamic system. Therefore, in analogy to the zero temperature configuration, the description of spacetime in terms of a differential manifold could be obtained only asymptotically. Finally, we extend the Verlinde’s derivation to a general case, which includes all possible effects, noncommutativity, ungravity, asymptotically safe gravity, electrostatic energy, and extra dimensions, showing that the procedure is solid versus such modifications.

Nicolini, Piero

2010-08-01

173

Multiphase Flow: The Gravity of the Situation  

NASA Technical Reports Server (NTRS)

A brief survey is presented of flow patterns in two-phase, gas-liquid flows at normal and microgravity, the differences between them being explored. It seems that the flow patterns in zero gravity are in general much simpler than those in normal gravity with only three main regimes (namely bubbly, slug and annular flows) being observed. Each of these three regimes is then reviewed, with particular reference to identification of areas of study where investigation of flows at microgravity might not only be interesting in themselves, but also throw light on mechanisms at normal earth gravity. In bubbly flow, the main area of interest seems to be that of bubble coalescence. In slug flow, the extension of simple displacement experiments to the zero gravity case would appear to be a useful option, supplemented by computational fluid dynamics (CFD) studies. For annular flow, the most interesting area appears to be the study of the mechanisms of disturbance waves; it should be possible to extend the region of investigation of the onset and behavior of these waves to much low gas velocities where measurements are clearly much easier.

Hewitt, Geoffrey F.

1996-01-01

174

Zero Emission Coal  

NASA Astrophysics Data System (ADS)

Unless the economic development of the majority of the world's population is prohibited, thereby forcing thereby forcing them to remain in poverty, world energy consumption and therefore carbon dioxide greenhouse gas emission rates could easily increase by an order of magnitude during this century. Given that we have already increased global atmospheric concentrations by 30% compared to their pre-industrial age level, without massive intervention, we will completely overwhelm Nature's ability to cope. In order to stabilize atmospheric CO2 levels, while allowing desired world economic development, the future allowable US per capita CO2 emissions are only 3 % of today's value. This is effectively zero, and thus what is required is the development of technologies that aim for emission of zero CO2 as well as other pollutants. If we continue to rely on our lowest cost, readily available, and dominant energy source, this will involve both a separation of the energy from the fossil fuel carbon followed by a permanent disposal of the CO2. To set the scale, today's yearly global emissions are approaching 25 cubic kilometers of CO2 at liquid densities, and these could grow by an order of magnitude by the end of the century. We describe a zero emission coal technology that would be able to deal with both the scope of the problem and the emission goal. The energy production process is a chemical conversion of coal to electricity or hydrogen, which involves no combustion and thus no smoke stack. The process provides a pure stream of CO2 for disposal while simultaneously achieving fuel to electricity conversion efficiencies that are two times better than today's value. This high efficiency by itself extends cuts pollutant production by a factor of two while also extending the lifetime of our fossil fuel reserves by a factor of two to many hundreds of years. By concentrating on coal, we also lay the groundwork for energy security and complete independence for the US, given the huge coal reserves of the US, and the ability to create liquid and gaseous fuels from coal through the production of hydrogen. To dispose of the carbon dioxide permanently, we are investigating its permanent disposal in the form of solid, thermodynamically stable, mineral carbonates. This is the form in which Nature has chosen to store the vast quantities of CO2 that once dominated the world's atmosphere in its early history. The total amount of carbonates formed is many orders of magnitude greater than all the carbon found in the world's fossil fuels.

Ziock, H.; Guthrie, G. D.; Lackner, K. S.; Harrison, D. P.; Johnson, A. A.

2002-05-01

175

Zero Temperature Hope Calculations  

SciTech Connect

The primary purpose of the HOPE code is to calculate opacities over a wide temperature and density range. It can also produce equation of state (EOS) data. Since the experimental data at the high temperature region are scarce, comparisons of predictions with the ample zero temperature data provide a valuable physics check of the code. In this report we show a selected few examples across the periodic table. Below we give a brief general information about the physics of the HOPE code. The HOPE code is an ''average atom'' (AA) Dirac-Slater self-consistent code. The AA label in the case of finite temperature means that the one-electron levels are populated according to the Fermi statistics, at zero temperature it means that the ''aufbau'' principle works, i.e. no a priory electronic configuration is set, although it can be done. As such, it is a one-particle model (any Hartree-Fock model is a one particle model). The code is an ''ion-sphere'' model, meaning that the atom under investigation is neutral within the ion-sphere radius. Furthermore, the boundary conditions for the bound states are also set at the ion-sphere radius, which distinguishes the code from the INFERNO, OPAL and STA codes. Once the self-consistent AA state is obtained, the code proceeds to generate many-electron configurations and proceeds to calculate photoabsorption in the ''detailed configuration accounting'' (DCA) scheme. However, this last feature is meaningless at zero temperature. There is one important feature in the HOPE code which should be noted; any self-consistent model is self-consistent in the space of the occupied orbitals. The unoccupied orbitals, where electrons are lifted via photoexcitation, are unphysical. The rigorous way to deal with that problem is to carry out complete self-consistent calculations both in the initial and final states connecting photoexcitations, an enormous computational task. The Amaldi correction is an attempt to address this problem by distorting the outer part of the self-consistent potential in such a way that in the final state after photoexcitation or photoionization the newly occupied orbital sees the hole left in the initial state. This is very important to account for the large number of Rydberg states in the case of low densities. In the next Section we show calculated photoabsorptions compared with experimental data in figures with some rudimentary explanations.

Rozsnyai, B F

2002-07-26

176

Theory of Edge Capillary-Gravity Waves  

NASA Astrophysics Data System (ADS)

We consider a body of fluid in equilibrium in a gravitational field and having a free surface and a plane-sloping beach with a straight coastline. If, under the action of some external disturbances, the surface is moved its equilibrium position, motion will occur in the fluid. This motion will be propagated along the coast in the form of waves, which are driven under the action of gravity and surface tension forces. We call these waves edge capillary-gravity waves, if their amplitude decays exponentially with distance from the coast. The fluid is considered inviscid, irrotational and incompressible. Under these conditions the velocity potencial satisfies the Laplace's equation everywhere in the fluid. The boundary conditions are such that the normal velocity at the bottom is zero and on the free surface in the presence of surface tension the linearized kinematic and dynamic boundary conditions are satisfied. The main difficulty for solution of this problem is that the variables are not separated. We present explicit solutions for all modes of the edge capillary-gravity waves and the dispersion equation. Capillary forces affect markedly the edge gravity waves profiles over the high frequency range. The peaks and lows have become larger as compared to pure edge gravity waves, dependence on the radial coordinate becomes more complicated, and a number of zeros of a mode might not coincide with the number of the mode. When ignoring capillary forces, our results are in complete agreement with the classic results of Ursell (1952) for the edge gravity waves on a sloping beach.

Muzylev, S. V.; Bulgakov, S. N.

2004-12-01

177

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

Tethered gravity laboratories study is presented. The following subject areas are covered: variable gravity laboratory; attitude tether stabilizer; configuration analysis (AIT); dynamic analysis (SAO); and work planned for the next reporting period.

Lucchetti, F.

1989-01-01

178

On Gravity Reductions.  

National Technical Information Service (NTIS)

Bouguer's and isostatic methods for the evaluation of gravity anomalies on the earth's physical surface are discussed. Errors involved in the reduction of gravity down to sea level are compared for condensation, isostatic, and Rudzki's anomalies. The conn...

E. Groten

1964-01-01

179

Survival of scalar zero modes in warped extra dimensions  

SciTech Connect

Models with an extra dimension generally contain background scalar fields in a nontrivial configuration, whose stability must be ensured. With gravity present, the extra dimension is warped by the scalars, and the spin-0 degrees of freedom in the metric mix with the scalar perturbations. Where possible, we formally solve the coupled Schroedinger equations for the zero modes of these spin-0 perturbations. When specializing to the case of two scalars with a potential generated by a superpotential, we are able to fully solve the system. We show how these zero modes can be used to construct a solution matrix, whose eigenvalues tell whether a normalizable zero mode exists, and how many negative mass modes exist. These facts are crucial in determining stability of the corresponding background configuration. We provide examples of the general analysis for domain-wall models of an infinite extra dimension and domain-wall soft-wall models. For five-dimensional models with two scalars constructed using a superpotential, we show that a normalizable zero mode survives, even in the presence of warped gravity. Such models, which are widely used in the literature, are therefore phenomenologically unacceptable.

George, Damien P. [Nikhef Theory Group, Science Park 105, 1098 XG Amsterdam (Netherlands)

2011-05-15

180

Analytical Study of Gravity Effects on Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

A mathematical model is presented for the description of axisymmetric laminar-jet diffusion flames. The analysis includes the effects of inertia, viscosity, diffusion, gravity and combustion. These mechanisms are coupled in a boundary layer type formulation and solutions are obtained by an explicit finite difference technique. A dimensional analysis shows that the maximum flame width radius, velocity and thermodynamic state characterize the flame structure. Comparisons with experimental data showed excellent agreement for normal gravity flames and fair agreement for steady state low Reynolds number zero gravity flames. Kinetics effects and radiation are shown to be the primary mechanisms responsible for this discrepancy. Additional factors are discussed including elipticity and transient effects.

Edelman, R. B.; Fortune, O.; Weilerstein, G.

1972-01-01

181

The Gravitational Deflection of Light in f( R)-Gravity  

NASA Astrophysics Data System (ADS)

Gravitation deflects light, which has been confirmed by a large number of observation data. f( R)-gravity is modification of Einstein's gravity. According to the field equations obtained by the action of the f( R) form, a similar Schwarzschild metric is obtained. According to the condition that four-dimension momenta of the photon return to zero and conservation of covariant momenta, we obtain an equation of photon motion in a specific form of f( R)-gravity. We solve the equation to get gravitational deflection angle of light that grazes surface of sun and the calculation result is consistent with the experimental observation data.

Huang, Long; He, Feng; Huang, Hai; Yao, Min

2014-06-01

182

The mass, gravity field, and ephemeris of Mercury  

NASA Technical Reports Server (NTRS)

In the present gravity analysis of Mariner 10/Deep Space Network radio Doppler and range data for Mercury encounters in March 1974 and March 1975, a combined least-squares fit to the Doppler data has determined two second-degree gravity harmonics that are referred to a 2439-km equatorial radius. It is noted that the 1-sigma error limits on the gravity results encompass the possibility that harmonics other than J2 and C22 significantly differ from zero. The Deep Space Network radio range data obtained with Mariner 10 are primarily applicable to such improvements of Mercury's ephemeris as the more precise determination of perihelion precession.

Anderson, John D.; Esposito, Pasquale B.; Lau, Eunice L.; Trager, Gayle B.; Colombo, Giuseppe

1987-01-01

183

Running gauge coupling in asymptotically safe quantum gravity  

NASA Astrophysics Data System (ADS)

We investigate the non-perturbative renormalization group behavior of the gauge coupling constant using a truncated form of the functional flow equation for the effective average action of the Yang-Mills-gravity system. We find a non-zero quantum gravity correction to the standard Yang-Mills beta function which has the same sign as the gauge boson contribution. Our results fit into the picture according to which Quantum Einstein Gravity (QEG) is asymptotically safe, with a vanishing gauge coupling constant at the non-trivial fixed point.

Daum, J.-E.; Harst, U.; Reuter, M.

2010-01-01

184

Equilibrium fluid interfaces in the absence of gravity  

NASA Technical Reports Server (NTRS)

Mathematical properties of capillary surfaces under zero gravity conditions are examined in the framework of the Laplace-Young theory, considering the equilibrium interface between a liquid and a gas or between two immiscible liquids for a cylindrical container of general cross section. The predicted liquid surface behavior is compared with the results obtained in a drop-tower experiment in the Zero-G Facility at the NASA Lewis Research Center.

Concus, P.

1986-01-01

185

Gravity is Geometry.  

ERIC Educational Resources Information Center

Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)

MacKeown, P. K.

1984-01-01

186

Challenging Entropic Gravity  

NASA Astrophysics Data System (ADS)

A recent proposal by Erik Verlinde claims that gravity should be viewed not as a fundamental force, but an emergent thermodynamic phenomenon due to some yet undetermined microscopic theory. We present a challenge to this reformulation of gravity. Our claim is that a detailed derivation using Verlinde's proposed theory fails to correctly give Newton's laws or Einstein gravity.

Roveto, Jonathan

2011-11-01

187

Feeling Gravity's Pull: Gravity Modeling. The Gravity Field of Mars.  

National Technical Information Service (NTIS)

Most people take the constant presence of gravitys pull for granted. However, the Earth's gravitational strength actually varies from location to location. This variation occurs because mass, which influences an object's gravitational pull, is not evenly ...

F. Lemoine D. Smith D. Rowlands M. Zuber G. Neumann D. Chinn D. Pavlis

2000-01-01

188

Aerosol bolus dispersion in acinar airways--influence of gravity and airway asymmetry  

PubMed Central

The aerosol bolus technique can be used to estimate the degree of convective mixing in the lung; however, contributions of different lung compartments to measured dispersion cannot be differentiated unambiguously. To estimate dispersion in the distal lung, we studied the effect of gravity and airway asymmetry on the dispersion of 1 ?m-diameter particle boluses in three-dimensional computational models of the lung periphery, ranging from a single alveolar sac to four-generation (g4) structures of bifurcating airways that deformed homogeneously during breathing. Boluses were introduced at the beginning of a 2-s inhalation, immediately followed by a 3-s exhalation. Dispersion was estimated by the half-width of the exhaled bolus. Dispersion was significantly affected by the spatial orientation of the models in normal gravity and was less in zero gravity than in normal gravity. Dispersion was strongly correlated with model volume in both normal and zero gravity. Predicted pulmonary dispersion based on a symmetric g4 acinar model was 391 ml and 238 ml under normal and zero gravity, respectively. These results accounted for a significant amount of dispersion measured experimentally. In zero gravity, predicted dispersion in a highly asymmetric model accounted for ?20% of that obtained in a symmetric model with comparable volume and number of alveolated branches, whereas normal gravity dispersions were comparable in both models. These results suggest that gravitational sedimentation and not geometrical asymmetry is the dominant factor in aerosol dispersion in the lung periphery.

Ma, Baoshun

2012-01-01

189

Zero emission coal  

SciTech Connect

We discuss a novel, emission-free process for producing hydrogen or electricity from coal. Even though we focus on coal, the basic design is compatible with any carbonaceous fuel. The process uses cyclical carbonation of calcium oxide to promote the production of hydrogen from carbon and water. The carbonation of the calcium oxide removes carbon dioxide from the reaction products and provides the additional energy necessary to complete hydrogen production without additional combustion of carbon. The calcination of the resulting calcium carbonate is accomplished using the high temperature waste heat from solid oxide fuel cells (SOFC), which generate electricity from hydrogen fuel. Converting waste heat back to useful chemical energy allows the process to achieve very high conversion efficiency from fuel energy to electrical energy. As the process is essentially closed-loop, the process is able to achieve zero emissions if the concentrated exhaust stream of CO{sub 2} is sequestered. Carbon dioxide disposal is accomplished by the production of magnesium carbonate from ultramafic rock. The end products of the sequestration process are stable naturally occurring minerals. Sufficient rich ultramafic deposits exist to easily handle all the world's coal.

Ziock, H.; Lackner, K.

2000-08-01

190

Zero Power Reactor Simulation  

ScienceCinema

Ever wanted to see a nuclear reactor core in action? Here's a detailed simulation of the Zero Power Reactor experiment, run by Argonne's unique "UNIC" code. Here, we use VisIt to visualize a numerical model of the ZPR-6 Assembly 6a experiment simulated using the Argonne UNIC code. 0:00-0:06: The fuel and other plates are dropped into an example drawer, and the drawer is inserted into the matrix tube. 0:06-0:21: The two matrix halves are brought together to make a critical (self-sustaining) assembly. 0:21-0:35: The fission power is revealed to be centralized in the thin, enriched Uranium plates. 0:35-0:53: Returning to our example drawer, we show the detailed local plate powers and their relation to the drawer composition. 0:53-1:11: Our model shows that each plate can have widely-varying local changes in the space and energy neutron densities. Read more at http://www.anl.gov/Media_Center/News/2010/news100121.html

191

UVIS Photometric Zero Points  

NASA Astrophysics Data System (ADS)

This proposal obtains the photometric zero points in 53 of the 62 UVIS/WFC3 filters: the 18 broad-band filters, 8 medium-band filters, 16 narrow-band filters, and 11 of the 20 quad filters {those being used in cycle 17}. The observations will be primary obtained by observing the hot DA white dwarf standards GD153 and G191-B2B. A redder secondary standard, P330E, will be observed in a subset of the filters to provide color corrections. Repeat observations in 16 of the most widely used cycle 17 filters will be obtained once per month for the first three months, and then once every second month for the duration of cycle 17, alternating and depending on target availability. These observations will enable monitoring of the stability of the photometric system. Photometric transformation equations will be calculated by comparing the photometry of stars in two globular clusters, 47 Tuc and NGC 2419, to previous measurements with other telescopes/instruments.;

Kalirai, Jasonjot

2008-07-01

192

Absolute Zero: Science Educator's Guide  

NSDL National Science Digital Library

This guide provides recommendations for curricular modules on low temperature physics. Designed for teachers and informal educators of middle school students. this guide complements the Absolute Zero Community Education Outreach Guide. Suggestions on leading discussions, increasing student participation, and the use of inquiry are included. This material is related to a two-part public broadcasting special, Absolute Zero, produced by Meridian Productions and Windfall Films. Absolute Zero is underwritten by the National Science Foundation and the Alfred P. Sloan Foundation and is based largely on Tom Shachtmanâs acclaimed book, Absolute Zero and the Conquest of Cold.

2008-09-18

193

LOW COMPLEXITY ZERO-PADDING ZERO-JAMMING DMT SYSTEMS  

Microsoft Academic Search

Discrete multitone (DMT) systems have been widely adopted in broadband communications. When the transmission chan- nel is frequency selective, there will be interblock interfer- ence (IBI). IBI can be avoided by zero-padding (ZP) (1). Another solution is to allow IBI during transmission, and at the receiver the samples that contain IBI are removed by zero-jamming (ZJ) (2). The ZP DMT

Yuan-Hwui Chung; See-May Phoong

2006-01-01

194

Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind.  

National Technical Information Service (NTIS)

The role of gravity wave forcing in the zonal mean circulation of the stratosphere is discussed. Starting from some very simple assumptions about the momentum flux spectrum of nonstationary (non-zero phase speed) waves at forcing levels in the troposphere...

M. J. Alexander K. H. Rosenlof

1996-01-01

195

Extinction Coefficient at Zero Concentration  

Microsoft Academic Search

THE use of extinction coefficients to characterize substances depends on the validity of Lambert-Beer's law. The following shows that a constant-extinction coefficient at zero concentration-which is the tangent to the extinction-concentration curve at zero concentration, may be calculated even if Lambert-Beer's law is not followed.

J. Fog

1962-01-01

196

Zero knowledge proofs of identity  

Microsoft Academic Search

In this paper we extend the notion of zero knowledge proofs of membership (which reveal one bit of information) to zero knowledge proofs of knowledge (which reveal no information whatsoever). After formally defining this notion, we show its relevance to identification schemes, in which parties prove their identity by demonstrating their knowledge rather than by proving the validity of assertions.

U. Fiege; Amos Fiat; Adi Shamir

1987-01-01

197

Precision zero-home locator  

DOEpatents

A zero-home locator includes a fixed phototransistor switch and a moveable actuator including two symmetrical, opposed wedges, each wedge defining a point at which switching occurs. The zero-home location is the average of the positions of the points defined by the wedges.

Stone, W.J.

1983-10-31

198

Riding the Gravity Wave  

NSDL National Science Digital Library

Students write a biographical sketch of an artist or athlete who lives on the edge, riding the gravity wave, to better understand how these artists and athletes work with gravity and manage risk. Note: The literacy activities for the Mechanics unit are based on physical themes that have broad application to our experience in the world â concepts of rhythm, balance, spin, gravity, levity, inertia, momentum, friction, stress and tension.

Integrated Teaching And Learning Program

199

Gravity and Muscles  

NSDL National Science Digital Library

In this activity about center of gravity (page 23 of PDF), learners investigate how the body adjusts to the force of gravity to remain balanced. In part 1, learners use different amounts of weight and meter sticks to explore balance and stability. In part 2, learners will conduct two experiments to explore their own centers of gravity. This guide includes background information, extensions, and data sheets.

Chang, Kimberly; Moreno, Nancy P.; Tharp, Barbara Z.; Institute, National S.

2000-01-01

200

Eliminating clutter by coordinate zeroing  

NASA Astrophysics Data System (ADS)

Shallow water doppler sonar is limited by clutter that masks the presence of slow targets. Clutter arises from scattering from irregularities in the bottom or from fish schools. If the source and receiver are fixed in a bi-static sonar configuration, then the bottom scatterers (and sometimes the fish) have only a zero doppler component. Clutter arises from the doppler leakage resulting from sonar signals that are inherently short in time and therefore cannot resolve bottom reverberation in frequency. Here long continuous pulse compressions signals are considered (m-sequences). Ambiguity diagrams are compared with simple CW pulse and PCM pulses. The unique correlation properties of M-sequences lead to a signal sampling method that resolves sonar returns in complete ortho-normal (CON) data sets. Zero doppler returns are identified as either direct arrivals or reverberation returns and then their particular coordinate can be set zero (coordinate zeroing) without affecting other data points. In this way, the zero-doppler bottom reverberation and all doppler leakage is eliminated. As an example, the return from a slow doppler target is imbedded in a very large number of reverberation returns that have higher signal level. As the zero doppler contributions are removed by coordinate zeroing the target becomes detectable.

Deferrari, Harry; Rodgers, Andrew

2005-04-01

201

Apollo-Soyuz pamphlet no. 8: Zero-g technology. [experimental designispace processing and aerospace engineering  

NASA Technical Reports Server (NTRS)

The behavior of liquids in zero gravity environments is discussed with emphasis on foams, wetting, and wicks. A multipurpose electric furnace (MA-010) for the high temperature processing of metals and salts in zero-g is described. Experiments discussed include: monolectic and synthetic alloys (MA-041); multiple material melting point (MA-150); zero-g processing of metals (MA-070); surface tension induced convection (MA-041); halide eutectic growth; interface markings in crystals (MA-060); crystal growth from the vapor phase (MA-085); and photography of crystal growth (MA-028).

Page, L. W.; From, T. P.

1977-01-01

202

Feeling Gravity's Pull: Gravity Modeling. The Gravity Field of Mars  

Microsoft Academic Search

Most people take the constant presence of gravitys pull for granted. However, the Earth's gravitational strength actually varies from location to location. This variation occurs because mass, which influences an object's gravitational pull, is not evenly distributed within the planet. Changes in topography, such as glacial movement, an earthquake, or a rise in the ocean level, can subtly affect the

Frank Lemoine; David Smith; David Rowlands; Maria Zuber; G. Neumann; Douglas Chinn; D. Pavlis

2000-01-01

203

Shear waves in inhomogeneous, compressible fluids in a gravity field.  

PubMed

While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere. PMID:24606251

Godin, Oleg A

2014-03-01

204

Surface tension and bubble shapes in a partially filled rotating cylinder under low gravity  

NASA Technical Reports Server (NTRS)

A computer algorithm is developed to simulate the profile of a free liquid surface for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry. The equilibrium shape of the free surface is governed by a balance of capillary, centrifugal, and gravity forces. The results can be used to determine the profile of a bubble at various rotating speeds under the gravity environments from low gravity, microgravity to zero-gravity. The present paper discusses the further extension of the study of the determination of bubble shape in a higher rotating speed container developed by Hung and Leslie.

Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.

1988-01-01

205

Disappearing cosmological constant in f( R) gravity  

NASA Astrophysics Data System (ADS)

For higher-derivative f( R) gravity, where R is the Ricci scalar, a class of models is proposed, which produce viable cosmology different from the ACDM at recent times and satisfy cosmological, Solar System, and laboratory tests. These models have both flat and de Sitter spacetimes as particular solutions in the absence of matter. Thus, a cosmological constant is zero in a flat spacetime, but appears effectively in a curved one for sufficiently large R. A “smoking gun” for these models would be a small discrepancy in the values of the slope of the primordial perturbation power spectrum determined from galaxy surveys and CMB fluctuations. On the other hand, a new problem for dark energy models based on f( R) gravity is pointed out, which is connected with the possible overproduction of new massive scalar particles (scalarons) arising in this theory in the very early Universe.

Starobinsky, A. A.

2007-10-01

206

Unified theory of nonlinear electrodynamics and gravity  

SciTech Connect

We describe a class of unified theories of electromagnetism and gravity. The Lagrangian is of the BF type, with a potential for the B field, the gauge group is U(2) (complexified). Given a choice of the potential function the theory is a deformation of (complex) general relativity and electromagnetism, and describes just two propagating polarizations of the graviton and two of the photon. When gravity is switched off the theory becomes the usual nonlinear electrodynamics with a general structure function. The Einstein-Maxwell theory can be recovered by sending some of the parameters of the defining potential to zero, but for any generic choice of the potential the theory is indistinguishable from Einstein-Maxwell at low energies. A real theory is obtained by imposing suitable reality conditions. We also study the spherically-symmetric solution and show how the usual Reissner-Nordstrom solution is recovered.

Torres-Gomez, Alexander; Krasnov, Kirill; Scarinci, Carlos [School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD (United Kingdom)

2011-01-15

207

Grasping objects autonomously in simulated KC-135 zero-g  

NASA Technical Reports Server (NTRS)

The KC-135 aircraft was chosen for simulated zero gravity testing of the Extravehicular Activity Helper/retriever (EVAHR). A software simulation of the EVAHR hardware, KC-135 flight dynamics, collision detection and grasp inpact dynamics has been developed to integrate and test the EVAHR software prior to flight testing on the KC-135. The EVAHR software will perform target pose estimation, tracking, and motion estimation for rigid, freely rotating, polyhedral objects. Manipulator grasp planning and trajectory control software has also been developed to grasp targets while avoiding collisions.

Norsworthy, Robert S.

1994-01-01

208

Gravity Driven Universe  

NASA Astrophysics Data System (ADS)

Flowing global gravitation initially produced space without time or mass. Space-time and mass are properties of flowing global gravitation. From its fabric, primal mass spins spontaneously giving rise to local gravitational space-time curvatures. Global gravity is the unifying background field. Gravity began flowing from its singularity with a big whoosh. It curves with angular rotational precession, creating a spatial geometry similar to the windings of a ball of string. Three-dimensional global gravity swirls locally into massive densities. Concurrently with these densities, local gravity curvatures of space-time arise. The expanse between celestial objects is not completely empty, void space as generally believed; it is antecedent gravity, a prerequisite associated field necessary for originating the first quantum particles. Gravity is dark energy; gravity's spin, as the second fundamental force, is electromagnetic dark matter. Electromagnetic masses attract then gravity compresses hot, dense and small---then bang, the first hydrogen star of which there are many. There may have been many big bangs, but no Big Bang that ultimately created the universe.

Masters, Roy

2010-03-01

209

Canonical gravity with fermions  

Microsoft Academic Search

Canonical gravity in real Ashtekar-Barbero variables is generalized to allow for fermionic matter. The resulting torsion changes several expressions in Holst's original vacuum analysis, which are summarized here. This in turn requires adaptations to the known loop quantization of gravity coupled to fermions, which is discussed on the basis of the classical analysis. As a result, parity invariance is not

Martin Bojowald; Rupam Das

2008-01-01

210

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

The use is studied of tether systems to improve the lowest possible steady gravity level on the Space Station. Particular emphasis is placed by the microgravity community on the achievement of high quality microgravity conditions. The tether capability is explored for active control of the center of gravity and the analysis of possible tethered configurations.

Lucchetti, F.

1989-01-01

211

Gravity assisted mass transit  

Microsoft Academic Search

In fixed guideway transit with established station stops, the propulsion energy can be reduced by grading the guideway downward on leaving the station (using gravity to assist in the acceleration) and grading upward on arrival at the next station (again using gravity, but this time to assist in the braking). A computerized conceptual cost model has been developed incorporating parameters

A. Z. Kovacs; G. B. Shaw; R. F. Weiss; J. K. Jr Nelson

1975-01-01

212

Anti-gravity device  

NASA Technical Reports Server (NTRS)

An educational toy useful in demonstrating fundamental concepts regarding the laws of gravity is described. The device comprises a sphere 10 of radius r resting on top of sphere 12 of radius R. The center of gravity of sphere 10 is displaced from its geometrical center by distance D. The dimensions are so related that D((R+r)/r) is greater than r. With the center of gravity of sphere 10 lying on a vertical line, the device is in equilibrium. When sphere 10 is rolled on the surface of sphere 12 it will return to its equilibrium position upon release. This creates an illusion that sphere 10 is defying the laws of gravity. In reality, due to the above noted relationship of D, R, and r, the center of gravity of sphere 10 rises from its equilibrium position as it rolls a short distance up or down the surface of sphere 12.

Palsingh, S. (inventor)

1975-01-01

213

Particle cloud combustion in reduced gravity  

NASA Technical Reports Server (NTRS)

The prinicipal objectives of this microgravity experiment program are to obtain flame propagation rate and flame extinction limit data for several important premixed, quiescent particle cloud combustion systems under near zero-gravity conditions. The data resulting from these experiments are needed for utilization with currently available and tractable flame propagation and extinction theory. These data are also expected to provide standards for the evaluation of fire hazards in particle suspensions in both Earth-based and space-based applications. Both terrestrial and space-based fire safety criteria require the identification of the critical concentrations of particulate fuels and inerts at the flame extinction conditions.

Berlad, A. L.

1988-01-01

214

Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind  

NASA Technical Reports Server (NTRS)

The role of gravity wave forcing in the zonal mean circulation of the stratosphere is discussed. Starting from some very simple assumptions about the momentum flux spectrum of nonstationary (non-zero phase speed) waves at forcing levels in the troposphere, a linear model is used to calculate wave propagation through climatological zonal mean winds at solstice seasons. As the wave amplitudes exceed their stable limits, a saturation criterion is imposed to account for nonlinear wave breakdown effects, and the resulting vertical gradient in the wave momentum flux is then used to estimate the mean flow forcing per unit mass. Evidence from global, assimilated data sets are used to constrain these forcing estimates. The results suggest the gravity-wave-driven force is accelerative (has the same sign as the mean wind) throughout most of the stratosphere above 20 km. The sense of the gravity wave forcing in the stratosphere is thus opposite to that in the mesosphere, where gravity wave drag is widely believed to play a principal role in decelerating the mesospheric jets. The forcing estimates are further compared to existing gravity wave parameterizations for the same climatological zonal mean conditions. Substantial disagreement is evident in the stratosphere, and we discuss the reasons for the disagreement. The results suggest limits on typical gravity wave amplitudes near source levels in the troposphere at solstice seasons. The gravity wave forcing in the stratosphere appears to have a substantial effect on lower stratospheric temperatures during southern hemisphere summer and thus may be relevant to climate.

Alexander, M. J.; Rosenlof, K. H.

1996-01-01

215

Riemann zeta zeros and zero-point energy  

NASA Astrophysics Data System (ADS)

We postulate the existence of a self-adjoint operator associated to a system with countably infinite number of degrees of freedom whose spectrum is the sequence of the nontrivial zeros of the Riemann zeta function. We assume that it describes a massive scalar field coupled to a background field in a $(d+1)$-dimensional flat space-time. The scalar field is confined to the interval $[0,a]$ in one dimension and is not restricted in the other dimensions. The renormalized zero-point energy of this system is presented using techniques of dimensional and analytic regularization. In even dimensional space-time, the series that defines the regularized vacuum energy is finite. For the odd-dimensional case, to obtain a finite vacuum energy per unit area we are forced to introduce mass counterterms. A Riemann mass appears, which is the correction to the mass of the field generated by the nontrivial zeros of the Riemann zeta function.

Dueñas, J. G.; Svaiter, N. F.

2014-04-01

216

Applications of standard gravity and conformal gravity  

Microsoft Academic Search

In this Thesis, we explore a number of interesting problems in the study of gravitation. First, we explore the open question of the validity of alternative theories of gravitation through applying the Conformal Gravity theory to galactic rotation curve data. The Curves generated are fits that require no Dark Matter of external fitting parameters, and are of a universal nature

James G. O'Brien

2010-01-01

217

Gravity-induced cellular and molecular processes in plants studied under altered gravity conditions  

NASA Astrophysics Data System (ADS)

With the ability to sense gravity plants possess a powerful tool to adapt to a great variety of environmental conditions and to respond to environmental changes in a most beneficial way. Gravity is the only constant factor that provides organisms with reliable information for their orientation since billions of years. Any deviation of the genetically determined set-point angle of the plants organs from the vector of gravity is sensed by specialized cells, the statocytes of roots and shoots in higher plants. Dense particles, so-called statoliths, sediment in the direction of gravity and activate membrane-bound gravireceptors. A physiological signalling-cascade is initiated that eventually results in the gravitropic curvature response, namely, the readjust-ment of the growth direction. Experiments under microgravity conditions have significantly contributed to our understanding of plant gravity-sensing and gravitropic reorientation. For a gravity-sensing lower plant cell type, the rhizoid of the green alga Chara, and for statocytes of higher plant roots, it was shown that the interactions between statoliths and the actomyosin system consisting of the actin cytoskeleton and motor proteins (myosins) are the basis for highly efficient gravity-sensing processes. In Chara rhizoids, the actomyosin represents a guid-ing system that directs sedimenting statoliths to a specific graviperception site. Parabolic flight experiments aboard the airbus A300 Zero-G have provided evidence that lower and higher plant cells use principally the same statolith-mediated gravireceptor-activation mechanism. Graviper-ception is not dependent on mechanical pressure mediated through the weight of the sedimented statoliths, but on direct interactions between the statoliths's surface and yet unknown gravire-ceptor molecules. In contrast to Chara rhizoids, in the gravity-sensing cells of higher plants, the actin cytoskeleton is not essentially involved in the early phases of gravity sensing. Dis-rupting the actomyosin system did not impair the sedimentation of statoliths and did not prevent the activation of gravireceptors. However, experiments in microgravity and inhibitor experiments have demonstrated that the actomyosin system optimizes the statolith-receptor interactions by keeping the sedimented statoliths in motion causing a consistent activation of different gravireceptor molecules. Thereby, a triggered gravitropic signal is created which is the basis for a highly sensitive control and readjustment mechanism. In addition, the results of recent parabolic flight studies on the effects of altered gravity conditions on the gene expres-sion pattern of Arabidopsis seedlings support these findings and provide new insight into the molecular basis of the plants response to different acceleration conditions. The work was financially supported by DLR on behalf of Bundesministerium für Wirtschaft und Technologie (50WB0815).

Vagt, Nicole; Braun, Markus

218

Satellite gravity gradiometry: Secular gravity field change over polar regions  

Microsoft Academic Search

The ESA Gravity and steady state Ocean and Circulation Explorer, GOCE, mission will utilise the principle of satellite gravity gradiometry to measure the long to medium wavelengths in the static gravity field. Previous studies have demonstrated the low sensitivity of GOCE to ocean tides and to temporal gravity field variations at the seasonal scale. In this study we investigate the

Philip Moore; Matt A. King

2010-01-01

219

Net zero building energy conservation  

NASA Astrophysics Data System (ADS)

This research deals with energy studies performed as part of a net-zero energy study for buildings. Measured data of actual energy utilization by a building for a continuous period of 33 months was collected and studied. The peak design day on which the building consumes maximum energy was found. The averages of the energy consumption for the peak month were determined. The DOE EnergyPlus software was used to simulate the energy requirements for the building and also obtain peak energy requirements for the peak month. Alternative energy sources such as ground source heat pump, solar photovoltaic (PV) panels and day-lighting modifications were applied to redesign the energy consumption for the building towards meeting net-zero energy requirements. The present energy use by the building, DOE Energy software simulations for the building as well as the net-zero model for the building were studied. The extents of the contributions of the individual energy harvesting measures were studied. For meeting Net Zero Energy requirement, it was found that the total energy load for the building can be distributed between alternative energy methods as 5.4% to daylighting modifications, 58% to geothermal and 36.6% to solar photovoltaic panels for electricity supply and thermal energy. Thus the directions to proceed towards achieving complete net-zero energy status were identified.

Kadam, Rohit

220

Quantum Aspects of Gravity  

NASA Astrophysics Data System (ADS)

We study here some models of quantum gravity. In Euclidean quantum gravity, some of the possible consequences of including topology changes in the path integral are studied in the semiclassical approximation. The effects of wormhole interactions on the semiclassical sum are considered. The effects of wormholes in the Yang-Mills-Einstein system on the phase structure of these theories is discussed. Also, we perform the computation of some partition and correlation functions in conformal gauge, in a two dimensional model of quantum gravity, i.e., the sub-critical Polyakov string.

Gupta, Arun Kumar

221

Zero-G Workstation Design  

NASA Technical Reports Server (NTRS)

Zero-g workstations were designed throughout manned spaceflight, based on different criteria and requirements for different programs. The history of design of these workstations is presented along with a thorough evaluation of selected Skylab workstations (the best zero-g experience available on the subject). The results were applied to on-going and future programs, with special emphasis on the correlation of neutral body posture in zero-g to workstation design. Where selected samples of shuttle orbiter workstations are shown as currently designed and compared to experience gained during prior programs in terms of man machine interface design, the evaluations were done in a generic sense to show the methods of applying evaluative techniques.

Gundersen, R. T.; Bond, R. L.

1976-01-01

222

Effects of background gravity stimuli on gravity-controlled behavior  

NASA Technical Reports Server (NTRS)

Physiological and developmental effects of altered gravity were researched. The stimulus properties of gravity have been found to possess reinforcing and aversive properties. Experimental approaches taken, used animals placed into fields of artificial gravity, in the form of parabolic or spiral centrifuges. Gravity preferences were noted and it was concluded that the psychophysics of gravity and background factors which support these behaviors should be further explored.

Mccoy, D. F.

1976-01-01

223

ZERI: Zero Emissions Research Initiative  

NSDL National Science Digital Library

Sponsored by the Zero Emissions Research Foundation based in Geneva, Switzerland, ZERI seeks to support industry's transformation to zero emission operations. ZERI advocates either full use of inputs in an industry's own final product or conversion of the inputs for use by other industries or processes. At the site, the user can get information about the fourth Annual World ZERI Congress, read research articles and reports, or learn about ZERI's Worldwide Projects. The site also provides access to other ZERI sites in Brazil, Mexico, Namibia, Japan, and Germany.

224

Containment of a silicone fluid free surface in reduced gravity  

NASA Technical Reports Server (NTRS)

In support of the surface tension driven convection experiment planned for flight aboard the Space Shuttle, tests were conducted under reduced gravity in the 2.2-sec drop tower and the 5.0-sec Zero-G facility at the Lewis Research Center. The dynamics of controlling the test fluid, a 10-centistoke viscosity silicone fluid, in a low-gravity environment were investigated using different container designs and barrier coatings. Three container edge designs were tested without a barrier coating: a square edge, a sharp edge with a 45-deg slope, and a saw-tooth edge. All three edge designs were successful in containing the fluid below the edge.

Pline, A.; Jacobson, T.

1988-01-01

225

Gravity in quantum mechanics  

NASA Astrophysics Data System (ADS)

Gravity and quantum mechanics tend to stay out of each other's way, but this might change as we devise new experiments to test the applicability of quantum theory to macroscopic systems and larger length scales.

Amelino-Camelia, Giovanni

2014-04-01

226

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

The following subject areas are covered: (1) thermal control issues; (2) attitude control sybsystem; (3) configuration constraints; (4) payload; (5) acceleration requirements on Variable Gravity Laboratory (VGL); and (6) VGL configuration highlights.

Lucchetti, F.

1989-01-01

227

Rotating gravity gradiometer study  

NASA Technical Reports Server (NTRS)

The application of a Rotating Gravity Gradiometer (RGG) system on board a Lunar Polar Orbiter (LPO) for the measurement of the Lunar gravity field was investigated. A data collection simulation study shows that a gradiometer will give significantly better gravity data than a doppler tracking system for the altitudes under consideration for the LOP, that the present demonstrated sensitivity of the RGG is adequate for measurement of the Lunar gravity gradient field, and that a single RGG instrument will provide almost as much data for geophysical interpretation as an orthogonal three axis RGG system. An engineering study of the RGG sensor/LPO spacecraft interface characteristics shows that the RGG systems under consideration are compatible with the present models of the LPO spacecraft.

Forward, R. L.

1976-01-01

228

Reduced Gravity Simulator.  

National Technical Information Service (NTIS)

The project describes the feasibility of using artificial gravity simulators, such as have been used in research training in the National Space Program, to stimulate functional independence in patients with neuromuscular disabilities. It was hypothesized ...

C. Vallbona M. Partridge J. Canzoneri G. Midgley E. Pevny

1970-01-01

229

The Discovery of Gravity  

NSDL National Science Digital Library

These lecture notes cover the contributions that Tycho, Galileo, Kepler, and Newton made towards understanding the concept of gravity. The site includes some biographical information about each man as well as relevant illustrations.

O'Connell, Robert W.

2011-03-08

230

Zero-sum Square Matrices  

Microsoft Academic Search

Let A be a matrix over the integers, and let p be a positive integer. A submatrix B of A is zero-summodp if the sum of each row of B and the sum of each column of B is a multiple of p. Let M(p, k) denote the least integer m for which every square matrix of order at least

Paul Balister; Yair Caro; Cecil C. Rousseau; Raphael Yuster

2002-01-01

231

Stepping Back from Zero Tolerance  

ERIC Educational Resources Information Center

Schools' use of zero tolerance policies has been increasing since the 1980s as part of a societal movement to crack down on drug abuse and violence among youth. But far from making schools safer, this harsh, inflexible approach to discipline has been eroding the culture of schools and creating devastating consequences for children, writes…

Browne-Dianis, Judith

2011-01-01

232

Reviewing the Zero Point Energy  

Microsoft Academic Search

A review of recent developments in the study of the Zero Point Energy (ZPE) is made. The origin and behavior of the electromagnetic fields making up the vacuum ZPE is elucidated. From this it is deduced that the ZPE should increase with time even in a static universe such as Narliker and Arp propose. The small oscillations that a static

Barry Setterfield

233

Partial gravity habitat study  

NASA Technical Reports Server (NTRS)

The purpose of this study is to investigate comprehensive design requirements associated with designing habitats for humans in a partial gravity environment, then to apply them to a lunar base design. Other potential sites for application include planetary surfaces such as Mars, variable-gravity research facilities, and a rotating spacecraft. Design requirements for partial gravity environments include locomotion changes in less than normal earth gravity; facility design issues, such as interior configuration, module diameter, and geometry; and volumetric requirements based on the previous as well as psychological issues involved in prolonged isolation. For application to a lunar base, it is necessary to study the exterior architecture and configuration to insure optimum circulation patterns while providing dual egress; radiation protection issues are addressed to provide a safe and healthy environment for the crew; and finally, the overall site is studied to locate all associated facilities in context with the habitat. Mission planning is not the purpose of this study; therefore, a Lockheed scenario is used as an outline for the lunar base application, which is then modified to meet the project needs. The goal of this report is to formulate facts on human reactions to partial gravity environments, derive design requirements based on these facts, and apply the requirements to a partial gravity situation which, for this study, was a lunar base.

Capps, Stephen; Lorandos, Jason; Akhidime, Eval; Bunch, Michael; Lund, Denise; Moore, Nathan; Murakawa, Kiosuke

1989-01-01

234

Gravity Before Einstein and Schwinger Before Gravity  

NASA Astrophysics Data System (ADS)

Julian Schwinger was a child prodigy, and Albert Einstein distinctly not; Schwinger had something like 73 graduate students, and Einstein very few. But both thought gravity was important. They were not, of course, the first, nor is the disagreement on how one should think about gravity that is being highlighted here the first such dispute. The talk will explore, first, several of the earlier dichotomies: was gravity capable of action at a distance (Newton), or was a transmitting ether required (many others). Did it act on everything or only on solids (an odd idea of the Herschels that fed into their ideas of solar structure and sunspots)? Did gravitational information require time for its transmission? Is the exponent of r precisely 2, or 2 plus a smidgeon (a suggestion by Simon Newcomb among others)? And so forth. Second, I will try to say something about Scwinger's lesser known early work and how it might have prefigured his "source theory," beginning with "On the Interaction of Several Electrons (the unpublished, 1934 "zeroth paper," whose title somewhat reminds one of "On the Dynamics of an Asteroid," through his days at Berkeley with Oppenheimer, Gerjuoy, and others, to his application of ideas from nuclear physics to radar and of radar engineering techniques to problems in nuclear physics. And folks who think good jobs are difficult to come by now might want to contemplate the couple of years Schwinger spent teaching elementary physics at Purdue before moving on to the MIT Rad Lab for war work.

Trimble, Virginia L.

2012-05-01

235

Gravity and Orbits  

NSDL National Science Digital Library

The Gravity and Orbits SciPack explores concepts related to Earth's universal gravitation and how gravity affects the universe around us. The focus is on Standards and Benchmarks related to universal gravitation including variables that influence the amount of gravitational force and how gravity governs the motion of the solar system.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:� Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. � Access to one-on-one support via e-mail to content "Wizards".� Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Gravity and Orbits: Universal Gravitation� Identify gravity as an attractive force associated with all objects, including less intuitive examples (such as soda cans and pencils).� Recognize some examples of phenomena that are the result of Earth's gravity and objects and structures in the universe in general.� Reject the idea that Earth's gravity is an effect of air pushing down toward the surface.� Recognize that gravitational force does not require air (or any other substance) as a medium to act.� Describe gravitational force as a mutual attraction, rather than as one object pulling on another.Gravity and Orbits: Gravitational Force� Identify variables that affect the strength of the gravitational force acting between any two objects.� Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.� Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.� Provide a quantitative description of the relationship between distance and gravitational force. � Provide a qualitative description of the inverse square relationship.� Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored. Gravity and Orbits: Orbits� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2007-03-21

236

Acquirement of pure gravity orbit using precise formation flying technology  

NASA Astrophysics Data System (ADS)

Pure gravity orbit is an orbit removed non-gravity disturbances, which can give a more precise relation between gravity and orbit, and can be used to navigation satellite, earth gravity felid measurement, gravity wave detection and other fundamental physical test mission. In this paper, the author propose a system concept of a new pure gravity orbit acquirement method named inner formation flying system, which treats the PM and the outer satellite as a pair of formation flying satellites. The inner formation flying system consists of an outer satellite and an inner satellite. The outer satellite is a small satellite with a cavity in the center. The inner satellite is a PM flying in the housing of the outer satellite's cavity. So the inner satellite is shielded from non-gravitational forces of atmosphere drag and radiation pressure and flies along a purely gravitational path. From the view of formation flying, the outer satellite can be treated as a formation satellite with zero or small distance to the inner reference satellite. So the analysis of mechanic and dynamics of inner formation is made at first. Then a control architecture including feed forward and feedback strategies is presented and the controller is designed. The simulation is carried out in a high precision formation flying simulation environment at last to validate the inner formation flying methods.

Zhaokui, Wang; Yulin, Zhang

2013-01-01

237

Scalar-tensor gravity theory for dynamical light velocity  

Microsoft Academic Search

A gravity theory is developed with the metric g???=g??+B??????. In the present universe the additional contribution from the scalar field in the metric g??? can generate an acceleration in the expansion of the universe, without negative pressure and with a zero cosmological constant. In this theory, gravitational waves will propagate at a different speed from non-gravitational waves. It is suggested

M. A. Clayton; J. W. Moffat

2000-01-01

238

Dimension of Space-Time in Third Quantized Gravity  

NASA Astrophysics Data System (ADS)

Quantum creation of universes is considered within the framework of linear D-dimensional third quantized gravity with non-abelian gauge fields. It is shown that the number density of universes is infinitely peaked up on a sequence of compactified universes Sn+1×Id, where dimensionality of compact internal space Id takes values d=0, 1, …, D-3 and effective n+1-dimensional cosmological constant tends to zero, Sn+1?Mn+1.

Kozimirov, N. G.; Tkachev, I. I.

239

Venus Gravity Handbook  

NASA Technical Reports Server (NTRS)

This report documents the Venus gravity methods and results to date (model MGNP90LSAAP). It is called a handbook in that it contains many useful plots (such as geometry and orbit behavior) that are useful in evaluating the tracking data. We discuss the models that are used in processing the Doppler data and the estimation method for determining the gravity field. With Pioneer Venus Orbiter and Magellan tracking data, the Venus gravity field was determined complete to degree and order 90 with the use of the JPL Cray T3D Supercomputer. The gravity field shows unprecedented high correlation with topography and resolution of features to the 2OOkm resolution. In the procedure for solving the gravity field, other information is gained as well, and, for example, we discuss results for the Venus ephemeris, Love number, pole orientation of Venus, and atmospheric densities. Of significance is the Love number solution which indicates a liquid core for Venus. The ephemeris of Venus is determined to an accuracy of 0.02 mm/s (tens of meters in position), and the rotation period to 243.0194 +/- 0.0002 days.

Konopliv, Alexander S.; Sjogren, William L.

1996-01-01

240

Disposable remote zero headspace extractor  

DOEpatents

The remote zero headspace extractor uses a sampling container inside a stainless steel vessel to perform toxicity characteristics leaching procedure to analyze volatile organic compounds. The system uses an in line filter for ease of replacement. This eliminates cleaning and disassembly of the extractor. All connections are made with quick connect fittings which can be easily replaced. After use, the bag can be removed and disposed of, and a new sampling container is inserted for the next extraction.

Hand, Julie J. (Idaho Falls, ID); Roberts, Mark P. (Arco, ID)

2006-03-21

241

Image reconstruction from zero crossings  

Microsoft Academic Search

This study is concerned with the information in zero crossings (ZC) of images. Logan's conditions, specifying when a one-dimensional signal may be recovered (within a multiplicative constant) from its ZC, are extended for various cases of two-dimensional signals. An algorithm is implemented in reconstruction of context-free band-pass images. It is also successfully applied in reconstruction of contextual images by first

D. Rotem; Y. Zeevi

1986-01-01

242

Zero-Copy Objects System  

NASA Technical Reports Server (NTRS)

Zero-Copy Objects System software enables application data to be encapsulated in layers of communication protocol without being copied. Indirect referencing enables application source data, either in memory or in a file, to be encapsulated in place within an unlimited number of protocol headers and/or trailers. Zero-copy objects (ZCOs) are abstract data access representations designed to minimize I/O (input/output) in the encapsulation of application source data within one or more layers of communication protocol structure. They are constructed within the heap space of a Simple Data Recorder (SDR) data store to which all participating layers of the stack must have access. Each ZCO contains general information enabling access to the core source data object (an item of application data), together with (a) a linked list of zero or more specific extents that reference portions of this source data object, and (b) linked lists of protocol header and trailer capsules. The concatenation of the headers (in ascending stack sequence), the source data object extents, and the trailers (in descending stack sequence) constitute the transmitted data object constructed from the ZCO. This scheme enables a source data object to be encapsulated in a succession of protocol layers without ever having to be copied from a buffer at one layer of the protocol stack to an encapsulating buffer at a lower layer of the stack. For large source data objects, the savings in copy time and reduction in memory consumption may be considerable.

Burleigh, Scott C.

2011-01-01

243

The Zero Exemplar Distance Problem  

NASA Astrophysics Data System (ADS)

Given two genomes with duplicate genes, Zero Exemplar Distance is the problem of deciding whether the two genomes can be reduced to the same genome without duplicate genes by deleting all but one copy of each gene in each genome. Blin, Fertin, Sikora, and Vialette recently proved that Zero Exemplar Distance for monochromosomal genomes is NP-hard even if each gene appears at most two times in each genome, thereby settling an important open question on genome rearrangement in the exemplar model. In this paper, we give a very simple alternative proof of this result. We also study the problem Zero Exemplar Distance for multichromosomal genomes without gene order: from one direction, we show that this problem is NP-hard even if each gene appears at most two times in each genome; from the other direction, we show that this problem admits a polynomial-time algorithm if only one of the two genomes has duplicate genes, and is fixed-parameter tractable if the parameter is the maximum number of chromosomes in each genome.

Jiang, Minghui

244

Approaches to Validation of Models for Low Gravity Fluid Behavior  

NASA Technical Reports Server (NTRS)

This paper details the author experiences with the validation of computer models to predict low gravity fluid behavior. It reviews the literature of low gravity fluid behavior as a starting point for developing a baseline set of test cases. It examines authors attempts to validate their models against these cases and the issues they encountered. The main issues seem to be that: Most of the data is described by empirical correlation rather than fundamental relation; Detailed measurements of the flow field have not been made; Free surface shapes are observed but through thick plastic cylinders, and therefore subject to a great deal of optical distortion; and Heat transfer process time constants are on the order of minutes to days but the zero-gravity time available has been only seconds.

Chato, David J.; Marchetta, Jeffery; Hochstein, John I.; Kassemi, Mohammad

2005-01-01

245

Variational principle and one-point functions in three-dimensional flat space Einstein gravity  

NASA Astrophysics Data System (ADS)

We provide a well-defined variational principle for three-dimensional flat space Einstein gravity by adding one-half of the Gibbons-Hawking-York boundary term to the bulk action. We check the zero-point function, recovering consistency with thermodynamics of flat space cosmologies. We then apply our result to calculate the one-point functions in flat space Einstein gravity for the vacuum and all flat space cosmologies. The results are compatible with the ones for the zero-mode charges obtained by canonical analysis.

Detournay, Stephane; Grumiller, Daniel; Schöller, Friedrich; Simón, Joan

2014-04-01

246

Terrestrial gravity data analysis for interim gravity model improvement  

NASA Technical Reports Server (NTRS)

This is the first status report for the Interim Gravity Model research effort that was started on June 30, 1986. The basic theme of this study is to develop appropriate models and adjustment procedures for estimating potential coefficients from terrestrial gravity data. The plan is to use the latest gravity data sets to produce coefficient estimates as well as to provide normal equations to NASA for use in the TOPEX/POSEIDON gravity field modeling program.

1987-01-01

247

Role of Gravity Waves in Determining Cirrus Cloud Properties  

NASA Technical Reports Server (NTRS)

Cirrus clouds are important in the Earth's radiation budget. They typically exhibit variable physical properties within a given cloud system and from system to system. Ambient vertical motion is a key factor in determining the cloud properties in most cases. The obvious exception is convectively generated cirrus (anvils), but even in this case, the subsequent cloud evolution is strongly influenced by the ambient vertical motion field. It is well know that gravity waves are ubiquitous in the atmosphere and occur over a wide range of scales and amplitudes. Moreover, researchers have found that inclusion of statistical account of gravity wave effects can markedly improve the realism of simulations of persisting large-scale cirrus cloud features. Here, we use a 1 -dimensional (z) cirrus cloud model, to systematically examine the effects of gravity waves on cirrus cloud properties. The model includes a detailed representation of cloud microphysical processes (bin microphysics and aerosols) and is run at relatively fine vertical resolution so as to adequately resolve nucleation events, and over an extended time span so as to incorporate the passage of multiple gravity waves. The prescribed gravity waves "propagate" at 15 m s (sup -1), with wavelengths from 5 to 100 km, amplitudes range up to 1 m s (sup -1)'. Despite the fact that the net gravity wave vertical motion forcing is zero, it will be shown that the bulk cloud properties, e.g., vertically-integrated ice water path, can differ quite significantly from simulations without gravity waves and that the effects do depend on the wave characteristics. We conclude that account of gravity wave effects is important if large-scale models are to generate realistic cirrus cloud property climatology (statistics).

OCStarr, David; Singleton, Tamara; Lin, Ruei-Fong

2008-01-01

248

Singularity perturbed zero dynamics of nonlinear systems  

NASA Technical Reports Server (NTRS)

Stability properties of zero dynamics are among the crucial input-output properties of both linear and nonlinear systems. Unstable, or 'nonminimum phase', zero dynamics are a major obstacle to input-output linearization and high-gain designs. An analysis of the effects of regular perturbations in system equations on zero dynamics shows that whenever a perturbation decreases the system's relative degree, it manifests itself as a singular perturbation of zero dynamics. Conditions are given under which the zero dynamics evolve in two timescales characteristic of a standard singular perturbation form that allows a separate analysis of slow and fast parts of the zero dynamics.

Isidori, A.; Sastry, S. S.; Kokotovic, P. V.; Byrnes, C. I.

1992-01-01

249

Results from the Middeck 0-gravity Dynamics Experiment  

NASA Astrophysics Data System (ADS)

The experimental results of the Middick Zero-gravity Dynamics Experiment (MODE) are presented. MODE investigated the dynamics of two key spacecraft components; contained fluids and jointed truss structures. The change in the lateral slosh behavior of contained fluids and the changes in the modal parameters of space structural test articles from one- to zero-gravity were studied. The experimental apparatus used to determine the dynamic characteristics is described. For the MODE fluid experiments, the forced response characteristics of silicone oil and distilled water in cylinder tanks with either a flat or spherical bottom are reported and discussed. A comparison of the measured earth and space results identifies and highlights the effects of gravity on the linear and nonlinear slosh behavior of these fluids. For the MODE structural experiments, an analytic and experimental study is presented. Deployable, erectable, and rotary modules were assembled to form three one- and two-dimensional structures in which variations in bracing wire and rotary joint preload could be introduced. Analysis is compared with ground experimental measurements made on a spring/wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, and ambient gravity level.

van Schoor, M. C.; Crawley, E. F.; Miller, D. W.

250

Results from the Middeck 0-gravity Dynamics Experiment  

NASA Technical Reports Server (NTRS)

The experimental results of the Middick Zero-gravity Dynamics Experiment (MODE) are presented. MODE investigated the dynamics of two key spacecraft components; contained fluids and jointed truss structures. The change in the lateral slosh behavior of contained fluids and the changes in the modal parameters of space structural test articles from one- to zero-gravity were studied. The experimental apparatus used to determine the dynamic characteristics is described. For the MODE fluid experiments, the forced response characteristics of silicone oil and distilled water in cylinder tanks with either a flat or spherical bottom are reported and discussed. A comparison of the measured earth and space results identifies and highlights the effects of gravity on the linear and nonlinear slosh behavior of these fluids. For the MODE structural experiments, an analytic and experimental study is presented. Deployable, erectable, and rotary modules were assembled to form three one- and two-dimensional structures in which variations in bracing wire and rotary joint preload could be introduced. Analysis is compared with ground experimental measurements made on a spring/wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, and ambient gravity level.

Van Schoor, M. C.; Crawley, E. F.; Miller, D. W.

1993-01-01

251

Orbital Gravity Gradiometry Beyond GOCE: Instrument Concept  

NASA Astrophysics Data System (ADS)

With the recent maturation of 4-K space cryocooler technology, a multi-year gravity mapping mission based on an advanced superconducting gravity gradiometer (SGG) can now be planned. The original SGG fully developed in the 1990’s had mechanically suspended test masses, which limited the intrinsic sensitivity to 1 mE/?Hz. In zero-g, mechanically free test masses can be magnetically levitated around a common central tube, which improves the sensitivity and axis alignment by two orders of magnitude beyond the earlier device. Using multiple pairs of such magnetically levitated test masses with a baseline of 20 cm, one can construct a three-axis or tensor gradiometer of 0.01 mE/?Hz sensitivity over a frequency band of 0.5 mHz to 0.1 Hz. With the instrument's acceleration rejection capability of one part in 10^9, drag-free and attitude control requirements for the spacecraft will be within the capability of current technology. Such a mission represents a factor of 300 improvement in gradient sensitivity over GOCE with a wider bandwidth. Time-varying gravity signals will be resolved with harmonic degrees up to ~100, extending the resolution of GRACE by a factor of 2. The multiple-axis measurement of the gradiometer will give a better east-west resolution of gravity over satellite-to-satellite tracking. In this paper, we will discuss the design and expected performance of the SGG. We will also report the test results of the new magnetic levitation scheme by a current on a single tube.

Moody, M. V.; Paik, H.; Venkateswara, K. Y.; Shirron, P. J.; Dipirro, M. J.; Canavan, E. R.; Han, S.; Ditmar, P.; Klees, R.; Jekeli, C.; Shum, C.

2010-12-01

252

Brane-World Gravity  

NASA Astrophysics Data System (ADS)

The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+d-dimensional spacetime (the "bulk"), with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (˜TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity “leaks” into the bulk, behaving in a truly higher-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting and potentially testable implications for high-energy astrophysics, black holes, and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review analyzes the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models. We also cover the simplest brane-world models in which 4-dimensional gravity on the brane is modified at low energies - the 5-dimensional Dvali-Gabadadze-Porrati models. Then we discuss co-dimension two branes in 6-dimensional models.

Maartens, Roy; Koyama, Kazuya

2010-09-01

253

Brans-Dicke gravity theory from topological gravity  

NASA Astrophysics Data System (ADS)

We consider a model that suggests a mechanism by which the four dimensional Brans-Dicke gravity theory may emerge from the topological gravity action. To achieve this goal, both the Lie algebra and the symmetric invariant tensor that define the topological gravity Lagrangian are constructed by means of the Lie algebra S-expansion procedure with an appropriate abelian semigroup S.

Inostroza, C.; Salazar, A.; Salgado, P.

2014-06-01

254

The Direction of Gravity  

NASA Astrophysics Data System (ADS)

Given a uniformly dense sphere with a hole through its center, gravity is supposed to cause an object dropped into the hole to oscillate between the extremities. This is a prediction of both Newton's and Einstein's theories of gravity. Though every physicist knows what is supposed to happen, nobody has ever seen it happen. Failure to back up the predicted oscillation with empirical evidence is not due to insurmountable technical obstacles; a laboratory experiment to test it is quite feasible. According to the ideals of science, we should not be satis ed with analogies or extrapolations suggesting that the prediction is correct. We should, if possible, get the answer directly from Nature.

Benish, R.

2011-06-01

255

Maglev Facility for Simulating Variable Gravity  

NASA Technical Reports Server (NTRS)

An improved magnetic levitation apparatus ("Maglev Facility") has been built for use in experiments in which there are requirements to impose variable gravity (including zero gravity) in order to assess the effects of gravity or the absence thereof on physical and physiological processes. The apparatus is expected to be especially useful for experiments on the effects of gravity on convection, boiling, and heat transfer in fluids and for experiments on mice to gain understanding of bone loss induced in human astronauts by prolonged exposure to reduced gravity in space flight. The maglev principle employed by the apparatus is well established. Diamagnetic cryogenic fluids such as liquid helium have been magnetically levitated for studying their phase transitions and critical behaviors. Biological entities consist mostly of diamagnetic molecules (e.g., water molecules) and thus can be levitated by use of sufficiently strong magnetic fields having sufficiently strong vertical gradients. The heart of the present maglev apparatus is a vertically oriented superconducting solenoid electromagnet (see figure) that generates a static magnetic field of about 16 T with a vertical gradient sufficient for levitation of water in normal Earth gravity. The electromagnet is enclosed in a Dewar flask having a volume of 100 L that contains liquid helium to maintain superconductivity. The Dewar flask features a 66-mm-diameter warm bore, lying within the bore of the magnet, wherein experiments can be performed at room temperature. The warm bore is accessible from its top and bottom ends. The superconducting electromagnet is run in the persistent mode, in which the supercurrent and the magnetic field can be maintained for weeks with little decay, making this apparatus extremely cost and energy efficient to operate. In addition to water, this apparatus can levitate several common fluids: liquid hydrogen, liquid oxygen, methane, ammonia, sodium, and lithium, all of which are useful, variously, as rocket fuels or as working fluids for heat transfer devices. A drop of water 45 mm in diameter and a small laboratory mouse have been levitated in this apparatus.

Liu, Yuanming; Strayer, Donald M.; Israelsson, Ulf E.

2010-01-01

256

Properties of the random zero sphygmomanometer.  

PubMed

The random zero sphygmomanometer is widely used in studies involving blood pressure measurement because it is believed to eliminate digit preference and reduce measurement error. We performed blood pressure measurements sequentially using random zero and standard sphygmomanometers in random order in 1,356 participants in the Cardiovascular Health Study. Despite adherence to the manufacturer's instructions, we observed a substantially nonuniform distribution of zero levels generated by the random zero sphygmomanometer and a disturbing correlation between the zero level and blood pressures taken with the standard sphygmomanometer. With the random zero device, the pooled estimated slopes for the regression of standard systolic and diastolic pressures on the zero level were -0.71 and -0.17, respectively (both p < 0.0001). The only plausible explanation for this relation between the random zero device and the standard device is that by some unknown mechanism the subject's blood pressure is influencing the zero level. Systolic and diastolic blood pressures measured with the random zero device were, respectively, 1.65 and 1.84 mm Hg lower (both p < 0.0001) than standard blood pressures. Digit preference was detectable in the uncorrected blood pressure and zero level measured with the random zero device but was eliminated after calculation of the corrected blood pressure. For most epidemiological studies, the random zero sphygmomanometer offers no significant advantage over the standard sphygmomanometer. It may still be useful in those epidemiological studies and clinical trials where blinding is important. PMID:8491498

Kronmal, R A; Rutan, G H; Manolio, T A; Borhani, N O

1993-05-01

257

Our World: Gravity in Space  

NASA Video Gallery

What is gravity? Find out about the balance between gravity and inertia that keeps the International Space Station in orbit. Learn why astronauts "float" in space and how the space shuttle has to s...

258

External Resource: Gravity Assist Simulator  

NSDL National Science Digital Library

A Messenger Education site to explore gravity assist maneuvers, interaction with gravity, and the idea of a collision, to understand the effects of that interaction. Students explore the simulated encounters of spacecraft and planets to answer the questio

1900-01-01

259

Propulsion Investigation for Zero and Near-Zero Emissions Aircraft  

NASA Technical Reports Server (NTRS)

As world emissions are further scrutinized to identify areas for improvement, aviation s contribution to the problem can no longer be ignored. Previous studies for zero or near-zero emissions aircraft suggest aircraft and propulsion system sizes that would perform propulsion system and subsystems layout and propellant tankage analyses to verify the weight-scaling relationships. These efforts could be used to identify and guide subsequent work on systems and subsystems to achieve viable aircraft system emissions goals. Previous work quickly focused these efforts on propulsion systems for 70- and 100-passenger aircraft. Propulsion systems modeled included hydrogen-fueled gas turbines and fuel cells; some preliminary estimates combined these two systems. Hydrogen gas-turbine engines, with advanced combustor technology, could realize significant reductions in nitrogen emissions. Hydrogen fuel cell propulsion systems were further laid out, and more detailed analysis identified systems needed and weight goals for a viable overall system weight. Results show significant, necessary reductions in overall weight, predominantly on the fuel cell stack, and power management and distribution subsystems to achieve reasonable overall aircraft sizes and weights. Preliminary conceptual analyses for a combination of gas-turbine and fuel cell systems were also performed, and further studies were recommended. Using gas-turbine engines combined with fuel cell systems can reduce the fuel cell propulsion system weight, but at higher fuel usage than using the fuel cell only.

Snyder, Christopher A.; Berton, Jeffrey J.; Brown, Gerald v.; Dolce, James L.; Dravid, Marayan V.; Eichenberg, Dennis J.; Freeh, Joshua E.; Gallo, Christopher A.; Jones, Scott M.; Kundu, Krishna P.; Marek, Cecil J.; Millis, Marc G.; Murthy, Pappu L.; Roach, Timothy M.; Smith, Timothy D.; Stefko, George L.; Sullivan, Roy M.; Tornabene, Robert T.; Geiselhat, Karl A.; Kascak, Albert F.

2009-01-01

260

Gravity-driven bubbly flows  

Microsoft Academic Search

? Abstract Gravity-driven bubbly flows are a specific class of flows, where all action is provided by gravity. An industrial example,is formed,by the so-called bubble column: a vertical cylinder filled with liquid through,which,bubbles,flow that are introduced at the bottom of the cylinder. On the bubble scale, gravity gives rise to buoyancy of individual bubbles. On larger scales, gravity acts on

Robert F. Mudde

2005-01-01

261

Bilateral, Zero-Impedance Static Semiconductor Switch  

NASA Technical Reports Server (NTRS)

Static semiconductor switching circuit eliminates the undesirable features of electromechanical relays and conventional semiconductor switching circuits. There is a net zero voltage drop at the terminals and thus a zero impedance for bilateral currents there.

Doughman, C. L.

1968-01-01

262

Brief Survey of Zero-Knowledge Proofs.  

National Technical Information Service (NTIS)

The zero knowledge proofs in the literature are reviewed. The notion of zero knowledge is important in cryptography and is also related to complexity theory. The (interactive) proof systems addressed are: for languages; for decision problems; of knowledge...

H. Shin

1992-01-01

263

Thermodynamics and Gravity.  

National Technical Information Service (NTIS)

A calculation of the effects of a gravitational field on the state equations of real materials is presented. The effects arise from the broken symmetry of the spacetime coordinates of the region in which the gravity field is located. The form of the laws ...

R. A. Weiss

1992-01-01

264

Singularities and Quantum Gravity  

Microsoft Academic Search

Although there is general agreement that a removal of classical gravitational singularities is not only a crucial conceptual test of any approach to quantum gravity but also a prerequisite for any fundamental theory, the precise criteria for non-singular behavior are often unclear or controversial. Often, only special types of singularities such as the curvature singularities found in isotropic cosmological models

Martin Bojowald

2007-01-01

265

Acoustic Gravity Wave Study.  

National Technical Information Service (NTIS)

The report describes the efforts of the first four months of a one-year contract to study the propagation of acoustic gravity waves in the lower atmosphere and ionosphere, considering in particular the static firing of rocket engines and the occurrence of...

D. G. Detert C. A. Moo A. L. Oster W. E. Woolhiser

1967-01-01

266

Spaceborne Gravity Gradiometers  

NASA Technical Reports Server (NTRS)

The current status of gravity gradiometers and technology that could be available in the 1990's for the GRAVSAT-B mission are assessed. Problems associated with sensors, testing, spacecraft, and data processing are explored as well as critical steps, schedule, and cost factors in the development plan.

Wells, W. C. (editor)

1984-01-01

267

What is Gravity  

NSDL National Science Digital Library

This resource provides an explanation of gravity, the weakest of the four universal forces. Newton's Law of Universal Gravitation is presented, and certain gravitational phenomena are explained, such as why astronauts float in space. A table that compares gravitational forces on Earth with that on the Moon, the Sun, and other planets is included.

268

Statistical origin of gravity  

NASA Astrophysics Data System (ADS)

Starting from the definition of entropy used in statistical mechanics we show that it is proportional to the gravity action. For a stationary black hole this entropy is expressed as S=E/2T, where T is the Hawking temperature and E is shown to be the Komar energy. This relation is also compatible with the generalized Smarr formula for mass.

Banerjee, Rabin; Majhi, Bibhas Ranjan

2010-06-01

269

A Trick of Gravity  

ERIC Educational Resources Information Center

It's both surprising and rewarding when an old, standard problem reveals a subtlety that expands its pedagogic value. I realized recently that the role of gravity in the range equation for a projectile is not so simple as first appears. This realization may be completely obvious to others but was quite new to me.

Newburgh, Ronald

2010-01-01

270

SO(3) massive gravity  

NASA Astrophysics Data System (ADS)

In this Letter, we propose a massive gravity theory with 5 degrees of freedom. The mass term is constructed by 3 Stückelberg scalar fields, which respects SO(3) symmetry in the fields' configuration. By the analysis on the linear cosmological perturbations, we found that such 5 d.o.f. are free from ghost instability, gradient instability, and tachyonic instability.

Lin, Chunshan

2013-11-01

271

Revamped braneworld gravity  

SciTech Connect

Gravity in five-dimensional braneworld backgrounds often exhibits problematic features, including kinetic ghosts, strong coupling, and the van Dam-Veltman-Zakharov (vDVZ) discontinuity. These problems are an obstacle to producing and analyzing braneworld models with interesting and potentially observable modifications of 4d gravity. We examine these problems in a general AdS{sub 5}/AdS{sub 4} setup with two branes and localized curvature from arbitrary brane kinetic terms. We use the interval approach and an explicit straight gauge-fixing. We compute the complete quadratic gauge-fixed effective 4d action, as well as the leading cubic order corrections. We compute the exact Green's function for gravity as seen on the brane. In the full parameter space, we exhibit the regions which avoid kinetic ghosts and tachyons. We give a general formula for the strong coupling scale, i.e., the energy scale at which the linearized treatment of gravity breaks down, for relevant regions of the parameter space. We show how the vDVZ discontinuity can be naturally but nontrivially avoided by ultralight graviton modes. We present a direct comparison of warping versus localized curvature in terms of their effects on graviton mode couplings. We exhibit the first example of Dvali-Gabadadze-Porrati (DGP)-like crossover behavior in a general warped setup.

Bao Ruoyu; Park, Minjoon [Enrico Fermi Institute and Department of Physics, University of Chicago, 5640 South Ellis Ave., Chicago, Illinois 60637 (United States); Carena, Marcela; Santiago, Jose [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510 (United States); Lykken, Joseph [Enrico Fermi Institute and Department of Physics, University of Chicago, 5640 South Ellis Ave., Chicago, Illinois 60637 (United States); Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510 (United States)

2006-03-15

272

Statistical origin of gravity  

SciTech Connect

Starting from the definition of entropy used in statistical mechanics we show that it is proportional to the gravity action. For a stationary black hole this entropy is expressed as S=E/2T, where T is the Hawking temperature and E is shown to be the Komar energy. This relation is also compatible with the generalized Smarr formula for mass.

Banerjee, Rabin; Majhi, Bibhas Ranjan [S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata-700098 (India)

2010-06-15

273

The Flavor of Gravity  

SciTech Connect

I show how the observed particle spectrum in its various flavors and generations can be accommodated within a scheme involving five complex anticommuting Lorentz scalar coordinates {zeta}, carrying 'property'. A general relativistic extension of the scheme shows that gravity lies in the x - x sector, gauge fields in the x - {zeta} sector and Higgs field in the {zeta} - {zeta} sector.

Delbourgo, R. [University of Tasmania, Private Bag 37, GPO Hobart, 7001 (Australia)

2007-06-19

274

Gravity and crustal structure  

NASA Technical Reports Server (NTRS)

Lunar gravitational properties were analyzed along with the development of flat moon and curved moon computer models. Gravity anomalies and mascons were given particular attention. Geophysical and geological considerations were included, and comparisons were made between the gravitional fields of the Earth, Mars, and the Moon.

Bowin, C. O.

1976-01-01

275

A New Exponential Gravity  

NASA Astrophysics Data System (ADS)

We propose a new exponential f(R) gravity model with f(R) = (R - ?c) e ?(c/R)n and n > 3, ? >= 1, c > 0 to explain late-time acceleration of the universe. At the high curvature region, the model behaves like the ? CDM model. In the asymptotic future, it reaches a stable de-Sitter spacetime. It is a cosmologically viable model and can evade the local gravity constraints easily. This model shares many features with other f(R) dark energy models like Hu-Sawicki model and Exponential gravity model. In it the dark energy equation of state is of an oscillating form and can cross phantom divide line ?de = -1. In particular, in the parameter range 3 < n <= 4, ? ~ 1, the model is most distinguishable from other models. For instance, when n = 4, ? = 1, the dark energy equation of state will cross -1 in the earlier future and has a stronger oscillating form than the other models, the dark energy density in asymptotical future is smaller than the one in the high curvature region. This new model can evade the local gravity tests easily when n > 3 and ? > 1.

Xu, Qiang; Chen, Bin

2014-01-01

276

Test of emergent gravity  

NASA Astrophysics Data System (ADS)

In this paper we examine a small but detailed test of the emergent gravity picture with explicit solutions in gravity and gauge theory. We first derive symplectic U(1) gauge fields starting from the Eguchi-Hanson metric in four-dimensional Euclidean gravity. The result precisely reproduces the U(1) gauge fields of the Nekrasov-Schwarz instanton previously derived from the top-down approach. In order to clarify the role of noncommutative spacetime, we take the Braden-Nekrasov U(1) instanton defined in ordinary commutative spacetime and derive a corresponding gravitational metric. We show that the Kähler manifold determined by the Braden-Nekrasov instanton exhibits a spacetime singularity while the Nekrasov-Schwarz instanton gives rise to a regular geometry—the Eguchi-Hanson space. This result implies that the noncommutativity of spacetime plays an important role for the resolution of spacetime singularities in general relativity. We also discuss how the topological invariants associated with noncommutative U(1) instantons are related to those of emergent four-dimensional Riemannian manifolds according to the emergent gravity picture.

Lee, Sunggeun; Roychowdhury, Raju; Yang, Hyun Seok

2013-10-01

277

A study of two-phase flow in a reduced gravity environment  

NASA Technical Reports Server (NTRS)

A test loop was designed and fabricated for observing and measuring pressure drops of two-phase flow in reduced gravity. The portable flow test loop was then tested aboard the NASA-JSC KC135 reduced gravity aircraft. The test loop employed the Sundstrand Two-Phase Thermal Management System (TPTMS) concept which was specially fitted with a clear two-phase return line and condenser cover for flow observation. A two-phase (liquid/vapor) mixture was produced by pumping nearly saturated liquid through an evaporator and adding heat via electric heaters. The quality of the two-phase flow was varied by changing the evaporator heat load. The test loop was operated on the ground before and after the KC135 flight tests to create a one-gravity data base. The ground testing included all the test points run during the reduced gravity testing. Two days of reduced gravity tests aboard the KC135 were performed. During the flight tests, reduced-gravity, one-gravity, and nearly two-gravity accelerations were experienced. Data was taken during the entire flight which provided flow regime and pressure drop data for the three operating conditions. The test results show that two-phase pressure drops and flow regimes can be accurately predicted in zero-gravity.

Hill, D.; Downing, Robert S.

1987-01-01

278

Zero Tolerance: Advantages and Disadvantages. Research Brief  

ERIC Educational Resources Information Center

What are the positives and negatives of zero tolerance? What should be considered when examining a school's program? Although there are no definitive definitions of zero tolerance, two commonly used ones are as follows: "Zero tolerance means that a school will automatically and severely punish a student for a variety of infractions" (American Bar…

Walker, Karen

2009-01-01

279

Zero Tolerance in Tennessee Schools: An Update.  

ERIC Educational Resources Information Center

As required by Tennessee law, this report examines the state's zero-tolerance disciplinary data collected by the Tennessee Department of Education for school years 1999-00, 2000-01, and 2001-02. The first section displays statewide zero-tolerance statistics. The second section focuses on the zero-tolerance statistics of Tennessee's five major…

Potts, Kim; Njie, Bintou; Detch, Ethel R.; Walton, Jason

280

Role of Zero in Grading. Research Brief  

ERIC Educational Resources Information Center

What is the role of "zero" in grading? According to several authors, giving students a zero lets them too easily off the hook, seldom serves as a motivator for them to do better and is not an accurate reflection of what has been learned. While students do need to be responsible and accountable for their work, assigning a zero skews the grade and…

Walker, Karen

2006-01-01

281

Fisher's Zeros and Perturbative Series in Gluodynamics  

Microsoft Academic Search

We study the zeros of the partition function in the complex beta plane (Fisher's zeros) in SU(2) and SU(3) gluodynamics. We discuss their effects on the asymptotic behavior of the perturbative series for the average plaquette. We present new methods to infer the existence of these zeros in region of the complex beta plane where MC reweighting is not reliable.

A. Denbleyker; D. Du; Y. Meurice; A. Velytsky

2007-01-01

282

Zero point energy of renormalized Wilson loops  

Microsoft Academic Search

The quark-antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to

Yoshimasa Hidaka; Robert D. Pisarski

2009-01-01

283

Dark energy and gravity  

NASA Astrophysics Data System (ADS)

I review the problem of dark energy focussing on cosmological constant as the candidate and discuss what it tells us regarding the nature of gravity. Section 1 briefly overviews the currently popular “concordance cosmology” and summarizes the evidence for dark energy. It also provides the observational and theoretical arguments in favour of the cosmological constant as a candidate and emphasizes why no other approach really solves the conceptual problems usually attributed to cosmological constant. Section 2 describes some of the approaches to understand the nature of the cosmological constant and attempts to extract certain key ingredients which must be present in any viable solution. In the conventional approach, the equations of motion for matter fields are invariant under the shift of the matter Lagrangian by a constant while gravity breaks this symmetry. I argue that until the gravity is made to respect this symmetry, one cannot obtain a satisfactory solution to the cosmological constant problem. Hence cosmological constant problem essentially has to do with our understanding of the nature of gravity. Section 3 discusses such an alternative perspective on gravity in which the gravitational interaction—described in terms of a metric on a smooth spacetime—is an emergent, long wavelength phenomenon, and can be described in terms of an effective theory using an action associated with normalized vectors in the spacetime. This action is explicitly invariant under the shift of the matter energy momentum tensor T ab ? T ab + ? gab and any bulk cosmological constant can be gauged away. Extremizing this action leads to an equation determining the background geometry which gives Einstein’s theory at the lowest order with Lanczos-Lovelock type corrections. In this approach, the observed value of the cosmological constant has to arise from the energy fluctuations of degrees of freedom located in the boundary of a spacetime region.

Padmanabhan, T.

2008-02-01

284

Gravity waves in severe weather  

NASA Technical Reports Server (NTRS)

With a view to determining the role of severe weather in producing gravity waves, two tests were made. In the first, the wind speed measured at two nearby radiosonde stations, Peoria and Salem, was correlated with the stratosphere gravity-wave intensity at Urbana. Although the gravity-wave intensity fluctuated greatly from day to day, these is little if any correlation with the stratospheric wind speed. This suggests that orographic forcing is not a factor in generating gravity waves in Urbana. On the other hand, a clear correlation is found between cloud to heights exceeding 20,000 ft and an increased gravity-wave amplitude in the stratosphere.

Bowhill, S. A.; Gnanalingam, S.

1986-01-01

285

Plants and gravity. Special issue  

NASA Technical Reports Server (NTRS)

This issue of the Journal of Plant Growth Regulation explores the effects of gravity on plant growth and development from several perspectives. Most of the review papers consider plants and gravity from the viewpoint of ground-based laboratory research, and several papers consider gravitropism, the directed growth in response to gravity, in some detail. However, another approach to study the effects of gravity on plant is to effectively remove the force due to gravity. A very dramatic way to accomplish this goal is through the free-fall conditions achieved by spacecraft in low Earth orbit, so some of the authors have reviewed recent advances in spaceflight research with plant systems.

Kiss, J. Z. (Principal Investigator)

2002-01-01

286

[Low Fidelity Simulation of a Zero-Y Robot  

NASA Technical Reports Server (NTRS)

The item to be cleared is a low-fidelity software simulation model of a hypothetical freeflying robot designed for use in zero gravity environments. This simulation model works with the HCC simulation system that was developed by Xerox PARC and NASA Ames Research Center. HCC has been previously cleared for distribution. When used with the HCC software, the model computes the location and orientation of the simulated robot over time. Failures (such as a broken motor) can be injected into the simulation to produce simulated behavior corresponding to the failure. Release of this simulation will allow researchers to test their software diagnosis systems by attempting to diagnose the simulated failure from the simulated behavior. This model does not contain any encryption software nor can it perform any control tasks that might be export controlled.

Sweet, Adam

2001-01-01

287

Dirac cone and double zero materials  

SciTech Connect

Materials with zero permittivity and zero permeability (double zero) possess very interesting wave manipulation characteristics. Systems with Dirac cones in the band structure also possess amazing wave transport properties. These two classes of material are actually related to each other. We show that dielectric photonic crystals can be designed and fabricated which exhibit Dirac cones at k = 0 at a finite frequency. A subset of such materials behave as if they have zero permittivity and zero permeability at the Dirac point, as well as exhibiting properties intrinsic to a Dirac cone.

Chan, C. T.; Huang Xueqin; Hang Zhihong; Zheng Huihuo [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Lai Yun [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Department of Physics, Soochow University, 1 Shizi Street, Suzhou 215006 (China)

2011-10-03

288

Zero point energy of renormalized Wilson loops  

SciTech Connect

The quark-antiquark potential, and its associated zero point energy, can be extracted from lattice measurements of the Wilson loop. We discuss a unique prescription to renormalize the Wilson loop, for which the perturbative contribution to the zero point energy vanishes identically. A zero point energy can arise nonperturbatively, which we illustrate by considering effective string models. The nonperturbative contribution to the zero point energy vanishes in the Nambu model, but is nonzero when terms for extrinsic curvature are included. At one loop order, the nonperturbative contribution to the zero point energy is negative, regardless of the sign of the extrinsic curvature term.

Hidaka, Yoshimasa [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Pisarski, Robert D. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2009-10-01

289

Quantum gravity partition functions in three dimensions  

NASA Astrophysics Data System (ADS)

We consider pure three-dimensional quantum gravity with a negative cosmological constant. The sum of known contributions to the partition function from classical geometries can be computed exactly, including quantum corrections. However, the result is not physically sensible, and if the model does exist, there are some additional contributions. One possibility is that the theory may have long strings and a continuous spectrum. Another possibility is that complex geometries need to be included, possibly leading to a holomorphically factorized partition function. We analyze the subleading corrections to the Bekenstein-Hawking entropy and show that these can be correctly reproduced in such a holomorphically factorized theory. We also consider the Hawking-Page phase transition between a thermal gas and a black hole and show that it is a phase transition of Lee-Yang type, associated with a condensation of zeros in the complex temperature plane. Finally, we analyze pure three-dimensional supergravity, with similar results.

Maloney, Alexander; Witten, Edward

2010-02-01

290

Black hole remnant from gravity's rainbow  

NASA Astrophysics Data System (ADS)

In this work, we investigate black hole (BH) physics in the context of the gravity rainbow. We investigate this through rainbow functions that have been proposed by Amelino-Camelia [Living Rev. Relativity 16, 5 (2013)] and Amelino-Camelia et al. in [Int. J. Mod. Phys. A 12, 607 (1997)]. This modification will give corrections to both the temperature and the entropy of BHs, and hence it changes the picture of Hawking radiation greatly when the size of the BH approaches the Planck scale. It prevents the BH from total evaporation, predicting the existence of a BH remnant, which may resolve the catastrophic behavior of Hawking radiation as the BH mass approaches zero.

Farag Ali, Ahmed

2014-05-01

291

Magnetic bearings with zero bias  

NASA Technical Reports Server (NTRS)

A magnetic bearing operating without a bias field has supported a shaft rotating at speeds up to 12,000 rpm with the usual four power supplies and with only two. A magnetic bearing is commonly operated with a bias current equal to half of the maximum current allowable in its coils. This linearizes the relation between net force and control current and improves the force slewing rate and hence the band width. The steady bias current dissipates power, even when no force is required from the bearing. The power wasted is equal to two-thirds of the power at maximum force output. Examined here is the zero bias idea. The advantages and disadvantages are noted.

Brown, Gerald V.; Grodsinsky, Carlos M.

1991-01-01

292

Gravity wave initiated convection  

NASA Technical Reports Server (NTRS)

The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.

Hung, R. J.

1990-01-01

293

Antimatter gravity experiment  

SciTech Connect

An experiment is being developed to measure the acceleration of the antiproton in the gravitational field of the earth. Antiprotons of a few MeV from the LEAR facility at CERN will be slowed, captured, cooled to a temperature of about 10 K, and subsequently launched a few at a time into a drift tube where the effect of gravity on their motion will be determined by a time-of-flight method. Development of the experiment is proceeding at Los Alamos using normal matter. The fabrication of a drift tube that will produce a region of space in which gravity is the dominant force on moving ions is of major difficulty. This involves a study of methods of minimizing the electric fields produced by spatially varying work functions on conducting surfaces. Progress in a number of areas is described, with stress on the drift-tube development.

Brown, R.E.; Camp, J.B.; Darling, T.W.

1990-01-01

294

Plant gravity sensing  

NASA Technical Reports Server (NTRS)

This review of plant gravity sensing examines sensing in organ gravitropism, sensing in single-cell gravitropism, and nongravitropic sensing. Topics related to sensing in organ gravitropism are (1) identification of the gravitropic susceptors, including intracellular asymmetry in equilibrium position and after reorientation, susceptor signal-to-noise ratio, signal integration over threshold stimulation periods, intracellular asymmetry and gravitropic competence, and starch deficiency and gravitropic competence; (2) possible root statocytes and receptors, including identification of presumptive statocytes, cytology, and possible receptors and models of sensing; and (3) negatively gravitropic organs, including identification and distribution of presumptive statocytes and cytology and possible receptors. Topics related to nongravitropic sensing include gravitaxis, reaction wood, gravimorphogenesis, other gravity-influenced organ movements, and cytoplasmic streaming.

Sack, F. D.

1991-01-01

295

A gravity assist primer  

NASA Technical Reports Server (NTRS)

An account is given of the method by which the 'energy gain' accruing to a spacecraft as a result of its 'gravity-assist', parabolic-trajectory flyby of a massive body, such as a planet. The procedure begins with the solution of the two-body portion of the problem, and the results thus obtained are used to calculate changes with respect to the other massive body in the overall scenario, namely the sun. Attention is given to the 'vector diagram' often used to display the gravity-assist effect. The present procedure is noted to be reasonably accurate for flybys in which the plane of the spacecraft's trajectory is approximately the same as that of the planet's orbit around the sun, or the ecliptic plane; this reduces the problem to one in two dimensions.

Cesarone, R. J.

1989-01-01

296

Gravity Behaves Like That?  

NASA Astrophysics Data System (ADS)

Many concepts of chaotic action in astrodynamics can be appreciated through simulations with home computers and software. Many astrodynamical cases are illustrated. Although chaos theory is now applied to spaceflight trajectories, this presentation employs only inert bodies with no onboard impulse, e.g., from rockets or outgassing. Other nongravitational effects are also ignored, such as atmosphere drag, solar pressure, and radiation. The ability to simulate gravity behavior, even if not completely rigorous, on small mass-market computers allows a fuller understanding of the new approach to astrodynamics by home astronomers, scientists outside orbital mechanics, and students in middle and high school. The simulations can also help a lay audience visualize gravity behavior during press conferences, briefings, and public lectures. No review, evaluation, critique of the programs shown in this presentation is intended. The results from these simulations are not valid for - and must not be used for - making earth-colliding predictions.

Pazmino, John

2007-02-01

297

Tides and gravity labs  

NSDL National Science Digital Library

How does gravity cause tides in the oceans? This section, part of an interactive laboratory series for grades 8-12, introduces students to four activities on tides and gravity that cover critical orbital speed between Earth and the moon, gravitational forces between two bodies, tidal effects from the sun and moon, and the change in tidal levels over time. The activities include hands-on animations of concepts whose variables can be manipulated by students. Questions posed to students include answer boxes that are printable upon conclusion of the activities. The final activity involves collecting tidal data over 24-hour and 29-day periods. Student data are stored in printable tables. Views of moon phases for each time period are provided, as is a downloadable worksheet. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2002-01-01

298

Hamiltonian spinfoam gravity  

NASA Astrophysics Data System (ADS)

This paper presents a Hamiltonian formulation of spinfoam gravity, which leads to a straightforward canonical quantization. To begin with, we derive a continuum action adapted to a simplicial decomposition of space-time. The equations of motion admit a Hamiltonian formulation, allowing us to perform the constraint analysis. We do not find any secondary constraints, but only get restrictions on the Lagrange multipliers enforcing the reality conditions. This comes as a surprise—in the continuum theory, the reality conditions are preserved in time, only if the torsionless condition (a secondary constraint) holds true. Studying an additional conservation law for each spinfoam vertex, we discuss the issue of torsion and argue that spinfoam gravity may still miss an additional constraint. Finally, we canonically quantize and recover the EPRL (Engle-Pereira-Rovelli-Livine) face amplitudes. Communicated by P R L V Moniz

Wieland, Wolfgang M.

2014-01-01

299

Zero-order bows in radially inhomogeneous spheres: direct and inverse problems.  

PubMed

Zero-order ray paths are examined in radially inhomogeneous spheres with differentiable refractive index profiles. It is demonstrated that zero-order and sometimes twin zero-order bows can exist when the gradient of refractive index is sufficiently negative. Abel inversion is used to "recover" the refractive index profiles; it is therefore possible in principle to specify the nature and type of bows and determine the refractive index profile that induces them. This may be of interest in the field of rainbow refractometry and optical fiber studies. This ray-theoretic analysis has direct similarities with the phenomenon of "orbiting" and other phenomena in scattering theory and also in seismological, surface gravity wave, and gravitational "lensing" studies. For completeness these topics are briefly discussed in the appendixes; they may also be of pedagogic interest. PMID:22016245

Adam, John A

2011-10-01

300

Cambridge Cosmology: Quantum Gravity  

NSDL National Science Digital Library

This section of Cambridge Cosmology explains the concepts of quantum gravity and quantum cosmology, and how they are useful in understanding space and the space-time continuum. This includes the M-theory, formerly known as the string theory, and the Holographic Principle, in order to explain phenomena such as black holes and the first one-hundredth of a second of the Big Bang.

Hertog, Thomas; Herdeiro, Carlos; Chamblin, H.; Ashbourn, J.; Reall, Harvey

301

Gravity in noncommutative geometry  

Microsoft Academic Search

We study general relativity in the framework of non-commutative differential geom- etry. In particular, we introduce a gravity action for a space-time which is the product of a four dimensional manifold by a two-point space. In the simplest situation, where the Riemannian metric is taken to be the same on the two copies of the manifold, one obtains a model

A. H. Chamseddine; G. Felder; J. Fröhlich

1993-01-01

302

Free-Air Gravity  

NSDL National Science Digital Library

Students take a series of gravity measurements to estimate the height of the walkway near the top of the atrium in Howe-Russell. Students turn in a copy of the data sheet plus 1) an explanation of how they converted dial measurements to mgals; 2) plot of instrument drift/Earth tides correction; 3) estimate of elevation of the walkway using a Free-Air Correction; and 4) a brief (paragraph or two) discussion of potential errors in the survey.

303

Gravity, Time, and Lagrangians  

ERIC Educational Resources Information Center

Feynman mentioned to us that he understood a topic in physics if he could explain it to a college freshman, a high school student, or a dinner guest. Here we will discuss two topics that took us a while to get to that level. One is the relationship between gravity and time. The other is the minus sign that appears in the Lagrangian. (Why would one…

Huggins, Elisha

2010-01-01

304

Gravity and Falling  

NSDL National Science Digital Library

This fun and simple hands-on astronomy activity lets learners experiment with a bucket, stretchy fabric, marbles, and weights to discover some basics about gravity. Learners will explore how mass curves space, how an object with more mass will curve more space, why things fall to Earth, and why all objects, regardless of their mass, will fall at the same rate into the same massive object. The pdf contains step-by-step instructions, photos, presentation tips, and links to background information.

Pacific, Astronomical S.

2008-01-01

305

Dark energy and gravity  

Microsoft Academic Search

I review the problem of dark energy focussing on cosmological constant as the candidate and discuss what it tells us regarding\\u000a the nature of gravity. Section 1 briefly overviews the currently popular “concordance cosmology” and summarizes the evidence\\u000a for dark energy. It also provides the observational and theoretical arguments in favour of the cosmological constant as a\\u000a candidate and emphasizes

T. Padmanabhan

2008-01-01

306

Mars Gravity Anomoly Map  

NASA Technical Reports Server (NTRS)

This is a vertical gravity map of Mars color-coded in mgals based on radio tracking. Note correlations and lack of correlations with the Mars Orbiter Laser Altimeter (MOLA) global topography.

This map was created using MGS data under the direction of Bill Sjogren, a member of the MGS Radio Science Team. The Radio Science Team is led by G. Leonard Tyler of Stanford University in Palo Alto, CA.

2001-01-01

307

Granular Superconductors and Gravity  

NASA Technical Reports Server (NTRS)

As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with a relatively high percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 104 was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field and exposed without levitation to low-field strength AC magnetic fields. Changes in observed gravity signals were measured to be less than 2 parts in 108 of the normal gravitational acceleration. Given the high sensitivity of the test, future work will examine variants on the basic magnetic behavior of granular superconductors, with particular focus on quantifying their proposed importance to gravity.

Noever, David; Koczor, Ron

1999-01-01

308

Full gravity gradient tensors from vertical gravity by cosine transform  

NASA Astrophysics Data System (ADS)

We present a method to calculate the full gravity gradient tensors from pre-existing vertical gravity data using the cosine transform technique and discuss the calculated tensor accuracy when the gravity anomalies are contaminated by noise. Gravity gradient tensors computation on 2D infinite horizontal cylinder and 3D "Y" type dyke models show that the results computed with the DCT technique are more accurate than the FFT technique regardless if the gravity anomalies are contaminated by noise or not. The DCT precision has increased 2 to 3 times from the standard deviation. In application, the gravity gradient tensors of the Hulin basin calculated by DCT and FFT show that the two results are consistent with each other. However, the DCT results are smoother than results computed with FFT. This shows that the proposed method is less affected by noise and can better reflect the fault distribution.

Jiang, Fu-Yu; Huang, Yan; Yan, Ke

2012-06-01

309

Gravity field information from Gravity Probe-B  

NASA Technical Reports Server (NTRS)

The Gravity Probe-B Mission will carry the Stanford Gyroscope relativity experiment into orbit in the mid 1990's, as well as a Global Positioning System (GPS) receiver whose tracking data will be used to study the earth gravity field. Estimates of the likely quality of a gravity field model to be derived from the GPS data are presented, and the significance of this experiment to geodesy and geophysics are discussed.

Smith, D. E.; Lerch, F. J.; Colombo, O. L.; Everitt, C. W. F.

1989-01-01

310

Perturbations of nested branes with induced gravity  

NASA Astrophysics Data System (ADS)

We study the behaviour of weak gravitational fields in models where a 4D brane is embedded inside a 5D brane equipped with induced gravity, which in turn is embedded in a 6D spacetime. We consider a specific regularization of the branes internal structures where the 5D brane can be considered thin with respect to the 4D one. We find exact solutions corresponding to pure tension source configurations on the thick 4D brane, and study perturbations at first order around these background solutions. To perform the perturbative analysis, we adopt a bulk-based approach and we express the equations in terms of gauge invariant and master variables using a 4D scalar-vector-tensor decomposition. We then propose an ansatz on the behaviour of the perturbation fields when the thickness of the 4D brane goes to zero, which corresponds to configurations where gravity remains finite everywhere in the thin limit of the 4D brane. We study the equations of motion using this ansatz, and show that they give rise to a consistent set of differential equations in the thin limit, from which the details of the internal structure of the 4D brane disappear. We conclude that the thin limit of the ``ribbon'' 4D brane inside the (already thin) 5D brane is well defined (at least when considering first order perturbations around pure tension configurations), and that the gravitational field on the 4D brane remains finite in the thin limit. We comment on the crucial role of the induced gravity term on the 5D brane.

Sbisà, Fulvio; Koyama, Kazuya

2014-06-01

311

Gravity-dependent estimates of object mass underlie the generation of motor commands for horizontal limb movements.  

PubMed

Moving requires handling gravitational and inertial constraints pulling on our body and on the objects that we manipulate. Although previous work emphasized that the brain uses internal models of each type of mechanical load, little is known about their interaction during motor planning and execution. In this report, we examine visually guided reaching movements in the horizontal plane performed by naive participants exposed to changes in gravity during parabolic flight. This approach allowed us to isolate the effect of gravity because the environmental dynamics along the horizontal axis remained unchanged. We show that gravity has a direct effect on movement kinematics, with faster movements observed after transitions from normal gravity to hypergravity (1.8g), followed by significant movement slowing after the transition from hypergravity to zero gravity. We recorded finger forces applied on an object held in precision grip and found that the coupling between grip force and inertial loads displayed a similar effect, with an increase in grip force modulation gain under hypergravity followed by a reduction of modulation gain after entering the zero-gravity environment. We present a computational model to illustrate that these effects are compatible with the hypothesis that participants partially attribute changes in weight to changes in mass and scale incorrectly their motor commands with changes in gravity. These results highlight a rather direct internal mapping between the force generated during stationary holding against gravity and the estimation of inertial loads that limb and hand motor commands must overcome. PMID:24790173

Crevecoeur, F; McIntyre, J; Thonnard, J-L; Lefèvre, P

2014-07-15

312

The New Gravity System: Changes in International Gravity Base Values and Anomaly Values.  

National Technical Information Service (NTIS)

The effect of adopting the Geodetic Reference System 1967 (GRS 67) theoretical gravity formula and the International Gravity Standardization Net 1971 (IGSN 71) on gravity anomaly values is assessed. The gravity standard represented in the IGSN 71 values i...

G. P. Woollard V. M. Godley

1980-01-01

313

Geometric scalar theory of gravity  

NASA Astrophysics Data System (ADS)

We present a geometric scalar theory of gravity. Our proposal will be described using the ``background field method" introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor — which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models — does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ``geometric" pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.

Novello, M.; Bittencourt, E.; Moschella, U.; Goulart, E.; Salim, J. M.; Toniato, J. D.

2013-06-01

314

Zero-crossings of a wavelet transform  

Microsoft Academic Search

The completeness, stability, and application to pattern recognition of a multiscale representation based on zero-crossings is discussed. An alternative projection algorithm is described that reconstructs a signal from a zero-crossing representation, which is stabilized by keeping the value of the wavelet transform integral between each pair of consecutive zero-crossings. The reconstruction algorithm has a fast convergence and each iteration requires

Stéphane Mallat

1991-01-01

315

Zero sound in dipolar Fermi gases  

SciTech Connect

We study the propagation of sound in a homogeneous dipolar gas at zero temperature, which is known as zero sound. We find that undamped zero sound propagation is possible only in a range of solid angles around the direction of polarization of the dipoles. Above a critical dipole moment, we find an unstable mode, by which the gas collapses locally perpendicular to the dipoles' direction.

Ronen, Shai [JILA and Department of Physics, University of Colorado, Boulder, Colorado 80301 (United States); Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Bohn, John L. [JILA and Department of Physics, University of Colorado, Boulder, Colorado 80301 (United States)

2010-03-15

316

Frequently asked questions about gravity gradiometry  

Microsoft Academic Search

We will provide some answers to the following frequently asked questions regarding gravity gradiometry: Given that gravity, gravity gradients, and geoid measurements are all derived from the identical gravity potential what is the benefit of one kind of measurement over the others? Why do we need gradient measurements when we could, theoretically, get the same results from gravity or geoid

M. Talwani

2003-01-01

317

Gravity: Simple Experiments for Young Scientists.  

ERIC Educational Resources Information Center

This book contains 12 simple experiments through which students can learn about gravity and its implications. Some of the topics included are weight, weightlessness, artificial gravity, the pull of gravity on different shapes, center of gravity, the universal law of gravity, and balancing. Experiments include: finding the balancing point; weighing…

White, Larry

318

Module theoretic zero structures for system matrices  

NASA Technical Reports Server (NTRS)

The coordinate-free module-theoretic treatment of transmission zeros for MIMO transfer functions developed by Wyman and Sain (1981) is generalized to include noncontrollable and nonobservable linear dynamical systems. Rational, finitely-generated-modular, and torsion-divisible interpretations of the Rosenbrock system matrix are presented; Gamma-zero and Omega-zero modules are defined and shown to contain the output-decoupling and input-decoupling zero modules, respectively, as submodules; and the cases of left and right invertible transfer functions are considered.

Wyman, Bostwick F.; Sain, Michael K.

1987-01-01

319

[Biology of size and gravity].  

PubMed

Gravity is a force that acts on mass. Biological effects of gravity and their magnitude depend on scale of mass and difference in density. One significant contribution of space biology is confirmation of direct action of gravity even at the cellular level. Since cell is the elementary unit of life, existence of primary effects of gravity on cells leads to establish the firm basis of gravitational biology. However, gravity is not limited to produce its biological effects on molecules and their reaction networks that compose living cells. Biological system has hierarchical structure with layers of organism, group, and ecological system, which emerge from the system one layer down. Influence of gravity is higher at larger mass. In addition to this, actions of gravity in each layer are caused by process and mechanism that is subjected and different in each layer of the hierarchy. Because of this feature, summing up gravitational action on cells does not explain gravity for biological system at upper layers. Gravity at ecological system or organismal level can not reduced to cellular mechanism. Size of cells and organisms is one of fundamental characters of them and a determinant in their design of form and function. Size closely relates to other physical quantities, such as mass, volume, and surface area. Gravity produces weight of mass. Organisms are required to equip components to support weight and to resist against force that arise at movement of body or a part of it. Volume and surface area associate with mass and heat transport process at body. Gravity dominates those processes by inducing natural convection around organisms. This review covers various elements and process, with which gravity make influence on living systems, chosen on the basis of biology of size. Cells and biochemical networks are under the control of organism to integrate a consolidated form. How cells adjust metabolic rate to meet to the size of the composed organism, whether is gravity responsible for this feature, are subject we discuss in this article. Three major topics in gravitational and space biology are; how living systems have been adapted to terrestrial gravity and evolved, how living systems respond to exotic gravitational environment, and whether living systems could respond and adapt to microgravity. Biology of size can contribute to find a way to answer these question, and answer why gravity is important in biology, at explaining why gravity has been a dominant factor through the evolutional history on the earth. PMID:15173628

Yamashita, Masamichi; Baba, Shoji A

2004-03-01

320

A Challenge to Entropic Gravity  

NASA Astrophysics Data System (ADS)

In a recent publication, Erik Verlinde attempts to show that gravity should be viewed not as a fundamental force, but rather as an emergent thermodynamic phenomenon arising from an unspecified microscopic theory via equipartition and holography. We present a challenge to his reformulation of gravity. A detailed examination of Verlinde's derivation leads to a number of questions that severely weaken the claim that such a theory correctly reproduces Newton's laws or Einstein gravity. In particular, we find that neither Newtonian gravity nor the Einstein equations are uniquely determined using Verlinde's postulates.

Roveto, Jonathan; Munoz, Gerardo

2012-03-01

321

An underlying theory for gravity  

NASA Astrophysics Data System (ADS)

A new direction to understand gravity has recently been explored by considering classical gravity to be a derived interaction from an underlying theory. This underlying theory would involve new degrees of freedom at a deeper level, and it would be structurally different from classical gravitation. It may conceivably be a quantum theory or a non-quantum theory. The relation between this underlying theory and Einstein's gravity is similar to the connection between statistical mechanics and thermodynamics. We discuss the apparent lack of evidence of any quantum nature of spacetime and the meaning of quantum gravity in this context.

Ha, Y. K.

2014-03-01

322

Born-Infeld Gravity Revisited  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the behavior of linearized gravitational excitation in the Born-Infeld gravity in AdS3 space. We obtain the linearized equation of motion and show that this higher-order gravity propagate two gravitons, massless and massive, on the AdS3 background. In contrast to the R2 models, such as TMG or NMG, Born-Infeld gravity does not have a critical point for any regular choice of parameters. So the logarithmic solution is not a solution of this model, due to this one cannot find a logarithmic conformal field theory as a dual model for Born-Infeld gravity.

Setare, M. R.; Sahraee, M.

2013-12-01

323

Gravity field of the Western Weddell Sea: Comparison of airborne gravity and Geosat derived gravity  

NASA Technical Reports Server (NTRS)

Marine gravity surveying in polar regions was typically difficult and costly, requiring expensive long range research vessels and ice-breakers. Satellite altimetry can recover the gravity field in these regions where it is feasible to survey with a surface vessel. Unfortunately, the data collected by the first global altimetry mission, Seasat, was collected only during the austral winter, producing a very poor quality gravitational filed for the southern oceans, particularly in the circum-Antarctic regions. The advent of high quality airborne gravity (Brozena, 1984; Brozena and Peters, 1988; Bell, 1988) and the availability of satellite altimetry data during the austral summer (Sandwell and McAdoo, 1988) has allowed the recovery of a free air gravity field for most of the Weddell Sea. The derivation of the gravity field from both aircraft and satellite measurements are briefly reviewed, before presenting along track comparisons and shaded relief maps of the Weddell Sea gravity field based on these two data sets.

Bell, R. E.; Brozena, J. M.; Haxby, W. F.; Labrecque, J. L.

1989-01-01

324

Dynamics of Superfluid Helium in Low-Gravity  

NASA Technical Reports Server (NTRS)

This report summarizes the work performed under a contract entitled 'Dynamics of Superfluid Helium in Low Gravity'. This project performed verification tests, over a wide range of accelerations of two Computational Fluid Dynamics (CFD) codes of which one incorporates the two-fluid model of superfluid helium (SFHe). Helium was first liquefied in 1908 and not until the 1930s were the properties of helium below 2.2 K observed sufficiently to realize that it did not obey the ordinary physical laws of physics as applied to ordinary liquids. The term superfluidity became associated with these unique observations. The low temperature of SFHe and it's temperature unifonrmity have made it a significant cryogenic coolant for use in space applications in astronomical observations with infrared sensors and in low temperature physics. Superfluid helium has been used in instruments such as the Shuttle Infrared Astronomy Telescope (IRT), the Infrared Astronomy Satellite (IRAS), the Cosmic Background Observatory (COBE), and the Infrared Satellite Observatory (ISO). It is also used in the Space Infrared Telescope (SIRTF), Relativity Mission Satellite formally called Gravity Probe-B (GP-B), and the Test of the Equivalence Principle (STEP) presently under development. For GP-B and STEP, the use of SFHE is used to cool Superconducting Quantum Interference Detectors (SQUIDS) among other parts of the instruments. The Superfluid Helium On-Orbit Transfer (SHOOT) experiment flown in the Shuttle studied the behavior of SFHE. This experiment attempted to get low-gravity slosh data, however, the main emphasis was to study the low-gravity transfer of SFHE from tank to tank. These instruments carried tanks of SFHE of a few hundred liters to 2500 liters. The capability of modeling the behavior of SFHE is important to spacecraft control engineers who must design systems that can overcome disturbances created by the movement of the fluid. In addition instruments such as GP-B and STEP are very sensitive to quasi-steady changes in the mass distribution of the liquid. The CFD codes were used to model the fluid's dynamic motion. Tests in one-g were performed with the main emphasis on being able to compute the actual damping of the fluid. A series of flights on the NASA Lewis reduced gravity DC-9 aircraft were performed with the Jet Propulsion Laboratory (JPL) Low Temperature Flight Facility and a superfluid Test Cell. The data at approximately 0.04g, lg and 2g were used to determine if correct fundamental frequencies can be predicted based on the acceleration field. Tests in zero gravity were performed to evaluate zero gravity motion.

Frank, David J.

1997-01-01

325

Fast gravity, gravity partials, normalized gravity, gravity gradient torque and magnetic field: Derivation, code and data  

NASA Technical Reports Server (NTRS)

Derivation of first and second partials of the gravitational potential is given in both normalized and unnormalized form. Two different recursion formulas are considered. Derivation of a general gravity gradient torque algorithm which uses the second partial of the gravitational potential is given. Derivation of the geomagnetic field vector is given in a form that closely mimics the gravitational algorithm. Ada code for all algorithms that precomputes all possible data is given. Test cases comparing the new algorithms with previous data are given, as well as speed comparisons showing the relative efficiencies of the new algorithms.

Gottlieb, Robert G.

1993-01-01

326

Gravity and Granular Materials  

NASA Technical Reports Server (NTRS)

We describe experiments that probe a number of different types of granular flow where either gravity is effectively eliminated or it is modulated in time. These experiments include the shaking of granular materials both vertically and horizontally, and the shearing of a 2D granular material. For the shaken system, we identify interesting dynamical phenomena and relate them to standard simple friction models. An interesting application of this set of experiments is to the mixing of dissimilar materials. For the sheared system we identify a new kind of dynamical phase transition.

Behringer, R. P.; Hovell, Daniel; Kondic, Lou; Tennakoon, Sarath; Veje, Christian

1999-01-01

327

Massive gravity acausality redux  

NASA Astrophysics Data System (ADS)

Massive gravity (mGR) is a 5(=2s+1) degree of freedom, finite range extension of GR. However, amongst other problems, it is plagued by superluminal propagation, first uncovered via a second order shock analysis. First order mGR shock structures have also been studied, but the existence of superluminal propagation in that context was left open. We present here a concordance of these methods, by an explicit (first order) characteristic matrix computation, which confirms mGR's superluminal propagation as well as acausality.

Deser, S.; Izumi, K.; Ong, Y. C.; Waldron, A.

2013-10-01

328

Hypersonic Interplanetary Flight: Aero Gravity Assist  

NASA Technical Reports Server (NTRS)

The use of aero-gravity assist during hypersonic interplanetary flights is highlighted. Specifically, the use of large versus small planet for gravity asssist maneuvers, aero-gravity assist trajectories, launch opportunities and planetary waverider performance are addressed.

Bowers, Al; Banks, Dan; Randolph, Jim

2006-01-01

329

Simulation of gaseous diffusion in partially saturated porous media under variable gravity with lattice Boltzmann methods  

NASA Technical Reports Server (NTRS)

Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.

Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.; Steinberg, S. L. (Principal Investigator)

2005-01-01

330

Classical evolution and quantum generation in generalized gravity theories including string corrections and tachyons: Unified analyses  

SciTech Connect

We present cosmological perturbation theory based on generalized gravity theories including string theory correction terms and a tachyonic complication. The classical evolution as well as the quantum generation processes in these varieties of gravity theories are presented in unified forms. These apply both to the scalar- and tensor-type perturbations. Analyses are made based on the curvature variable in two different gauge conditions often used in the literature in Einstein's gravity; these are the curvature variables in the comoving (or uniform-field) gauge and the zero-shear gauge. Applications to generalized slow-roll inflation and its consequent power spectra are derived in unified forms which include a wide range of inflationary scenarios based on Einstein's gravity and others.

Hwang, Jai-chan [Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Taegu (Korea, Republic of); Noh, Hyerim [Korea Astronomy and Space Science Institute, Daejon (Korea, Republic of)

2005-03-15

331

Simulation of gaseous diffusion in partially saturated porous media under variable gravity with lattice Boltzmann methods.  

PubMed

Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity. PMID:16173154

Chau, Jessica Furrer; Or, Dani; Sukop, Michael C

2005-08-01

332

Determining Absolute Zero Using a Tuning Fork  

ERIC Educational Resources Information Center

The Celsius and Kelvin temperature scales, we tell our students, are related. We explain that a change in temperature of 1 degree C corresponds to a change of 1 Kelvin and that atoms and molecules have zero kinetic energy at zero Kelvin, -273 degrees C. In this paper, we will show how students can derive the relationship between the Celsius and…

Goldader, Jeffrey D.

2008-01-01

333

ON THE GRENANDER ESTIMATOR AT ZERO  

PubMed Central

We establish limit theory for the Grenander estimator of a monotone density near zero. In particular we consider the situation when the true density f0 is unbounded at zero, with different rates of growth to infinity. In the course of our study we develop new switching relations using tools from convex analysis. The theory is applied to a problem involving mixtures.

Balabdaoui, Fadoua; Jankowski, Hanna; Pavlides, Marios; Seregin, Arseni; Wellner, Jon

2011-01-01

334

Zero Tolerance Policies. ERIC Digest Number 146.  

ERIC Educational Resources Information Center

State legislatures and school boards are adopting a growing number of zero-tolerance polices toward weapons, guns, and violence. Zero-tolerance polices are rules intended to address specific school-safety issues. They have arisen in part as a response to the threat of the withdrawal of federal funds under the 1994 Gun-Free Schools Act, and…

McAndrews, Tobin

335

Student Dress Codes Using Zero Tolerance?  

ERIC Educational Resources Information Center

In this article, the author focuses on the issue involving zero tolerance in the Texas district whether the dress code policy is reasonable. In a small Texas school district, over 700 students were suspended in a single month for violating a zero-tolerance dress code policy. This suspension, which attracted national attention and threats of…

Essex, Nathan L.

2004-01-01

336

Zero voltage switching approach for flyback converter  

Microsoft Academic Search

A zero voltage switched flyback power converter which realizes soft switching for every semiconductor is proposed. The sinusoidal resonant current flows through the secondary side rectifier diode and zero current switching of the diode is realized. Diode recovery is not generated. The proposed converter can operate with constant frequency pulse width modulation. High frequency switching and low noise are achieved

K. Yoshida; T. Ishii; N. Nagagata

1992-01-01

337

Zero-Knowledge Proofs of Identity  

Microsoft Academic Search

In this paper we extend the notion of interactive proofs of assertions to interactive proofs of knowledge. This leads to the definition of unrestricted input zero-knowledge proofs of knowledge in which the prover demonstrates possession of knowledge without revealing any computational information whatsoever (not even the one bit revealed in zero-knowledge proofs of assertions). We show the relevance of these

Uriel Feige; Amos Fiat; Adi Shamir

1988-01-01

338

New Zero Voltage Transition PWM Converters  

Microsoft Academic Search

In this paper a new auxiliary circuit is introduced for buck, buck-boost, forward and flyback converters. This auxiliary circuit provides zero voltage switching condition for the main switch and diode while providing zero current switching condition for the auxiliary switch and diodes. The proposed ZVT PWM buck converter is analyzed and various converter operating modes are presented. A very simple

E. Adib; H. Farzaneh-fard

2006-01-01

339

Zero-point energy in spheroidal geometries  

Microsoft Academic Search

We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.

A. R. Kitson; A. I. Signal

2006-01-01

340

CIX. The zero point energy and ? crystals  

Microsoft Academic Search

The calculations of Montroll of the moments of the frequency spectrum of a number of crystal lattices enable an accurate estimate to be made of the zero point energy of these lattices. It has been customary to use the value 9\\/8k?, based on the Debye approximation, to estimate the zero point energy, and it is shown that this formula is

C. Domb; L. Salter

1952-01-01

341

Gravitational Zero Point Energy induces Physical Observables  

Microsoft Academic Search

We consider the contribution of Zero Point Energy on the induced Cosmological Constant and on the induced Electric\\/Magnetic charge in absence of matter fields. The method is applicable to every spherically symmetric background. Extensions to a generic $f(R) $ theory are also allowed. Only the graviton appears to be fundamental to the determination of Zero Point Energy.

Remo Garattini; Viale Marconi

2010-01-01

342

Topics in Quantum Gravity  

NASA Astrophysics Data System (ADS)

We study some aspects of conformal field theory, wormhole physics and two-dimensional random surfaces. In spite of being rather different, these topics serve as examples of the issues that are involved, both at high and low energy scales, in formulating a quantum theory of gravity. In conformal field theory we show that fusion and braiding properties can be used to determine the operator product coefficients of the non-diagonal Wess-Zumino-Witten models. In wormhole physics we show how Coleman's proposed probability distribution would result in wormholes determining the value of theta_{rm QCD}. We attempt such a calculation and find the most probable value of theta_ {rm QCD} to be pi . This hints at a potential conflict with nature. In random surfaces we explore the behaviour of conformal field theories coupled to gravity and calculate some partition functions and correlation functions. Our results throw some light on the transition that is believed to occur when the central charge of the matter theory gets larger than one.

Trivedi, Sandip P.

343

Gravity and Strings  

NASA Astrophysics Data System (ADS)

Preface; Part I. Introduction to Gravity and Supergravity: 1. Differential geometry; 2. Noether's theorems; 3. A perturbative introduction to general relativity; 4. Action principles for gravity; 5. N = 1, 2, d = 4 supergravities; 6. Conserved charges in general relativity; Part II. Gravitating Point-Particles: 7. The Schwarzschild black hole; 8. The Reissner-Nordström black hole; 9. The Taub-NUT solution; 10. Gravitational pp-waves; 11. The Kaluza-Klein black hole; 12. Dilaton and dilaton/axion black holes; 13. Unbroken supersymmetry; Part III. Gravitating Extended Objects of String Theory: 14. String theory; 15. The string effective action and T duality; 16. From eleven to four dimensions; 17. The type-IIB superstring and type-II T duality; 18. Extended objects; 19. The extended objects of string theory; 20. String black holes in four and five dimensions; Appendix A. Lie groups, symmetric spaces and Yang-Mills fields; Appendix B. Gamma matrices and spinors; Appendix C. n-Spheres; Appendix D. Palatini's identity; Appendix E. Conformal rescalings; Appendix F. Connections and curvature components; Appendix G. The harmonic operator on R3 x S1; References; Index.

Ortín, Tomás.

2004-03-01

344

Gravity and Strings  

NASA Astrophysics Data System (ADS)

Preface; Part I. Introduction to Gravity and Supergravity: 1. Differential geometry; 2. Noether's theorems; 3. A perturbative introduction to general relativity; 4. Action principles for gravity; 5. N = 1, 2, d = 4 supergravities; 6. Conserved charges in general relativity; Part II. Gravitating Point-Particles: 7. The Schwarzschild black hole; 8. The Reissner-Nordström black hole; 9. The Taub-NUT solution; 10. Gravitational pp-waves; 11. The Kaluza-Klein black hole; 12. Dilaton and dilaton/axion black holes; 13. Unbroken supersymmetry; Part III. Gravitating Extended Objects of String Theory: 14. String theory; 15. The string effective action and T duality; 16. From eleven to four dimensions; 17. The type-IIB superstring and type-II T duality; 18. Extended objects; 19. The extended objects of string theory; 20. String black holes in four and five dimensions; Appendix A. Lie groups, symmetric spaces and Yang-Mills fields; Appendix B. Gamma matrices and spinors; Appendix C. n-Spheres; Appendix D. Palatini's identity; Appendix E. Conformal rescalings; Appendix F. Connections and curvature components; Appendix G. The harmonic operator on R3 x S1; References; Index.

Ortín, Tomás.

2007-03-01

345

Modifications of gravity.  

PubMed

General relativity (GR) is a phenomenologically successful theory that rests on firm foundations, but has not been tested on cosmological scales. The deep mystery of dark energy (and possibly even the requirement of cold dark matter (CDM)) has increased the need for testing modifications to GR, as the inference of such otherwise undetected fluids depends crucially on the theory of gravity. Here, I discuss a general scheme for constructing consistent and covariant modifications to the Einstein equations. This framework is such that there is a clear connection between the modification and the underlying field content that produces it. I argue that this is mandatory for distinguishing modifications of gravity from conventional fluids. I give a non-trivial example, a simple metric-based modification of the fluctuation equations for which the background is exact ?CDM, but differs from it in the perturbations. I show how this can be generalized and solved in terms of two arbitrary functions. Finally, I discuss future prospects and directions of research. PMID:22084286

Skordis, Constantinos

2011-12-28

346

Logarithmic AdS waves and Zwei-Dreibein gravity  

NASA Astrophysics Data System (ADS)

We show that the parameter space of Zwei-Dreibein Gravity (ZDG) in AdS3 exhibits critical points, where massive graviton modes coincide with pure gauge modes and new `logarithmic' modes appear, similar to what happens in New Massive Gravity. The existence of critical points is shown both at the linearized level, as well as by finding AdS wave solutions of the full non-linear theory, that behave as logarithmic modes towards the AdS boundary. In order to find these solutions explicitly, we give a reformulation of ZDG in terms of a single Dreibein, that involves an infinite number of derivatives. At the critical points, ZDG can be conjectured to be dual to a logarithmic conformal field theory with zero central charges, characterized by new anomalies whose conjectured values are calculated.

Bergshoeff, Eric A.; Goya, Andrés F.; Merbis, Wout; Rosseel, Jan

2014-04-01

347

Utilization of Low Gravity Environment for Measuring Liquid Viscosity  

NASA Technical Reports Server (NTRS)

The method of drop coalescence is used for determining the viscosity of highly viscous undercooled liquids. Low gravity environment is necessary in order to allow for examining large volumes affording much higher accuracy for the viscosity calculations than possible for smaller volumes available under 1 - g conditions. The drop coalescence method is preferred over the drop oscillation technique since the latter method can only be applied for liquids with vanishingly small viscosities. The technique developed relies on both the highly accurate solution of the Navier-Stokes equations as well as on data from experiments conducted in near zero gravity environment. Results are presented for method validation experiments recently performed on board the NASA/KC-135 aircraft. While the numerical solution was produced using the Boundary Element Method. In these tests the viscosity of a highly viscous liquid, glycerine at room temperature, was determined using the liquid coalescence method. The results from these experiments will be discussed.

Antar, Basil N.; Ethridge, Edwin

1998-01-01

348

The International Space University's variable gravity research facility design  

NASA Technical Reports Server (NTRS)

A manned mission to Mars will require long travel times between Earth and Mars. However, exposure to long-duration zero gravity is known to be harmful to the human body. Some of the harmful effects are loss of heart and lung capacity, inability to stand upright, muscular weakness and loss of bone calcium. A variable gravity research facility (VGRF) that would be placed in low Earth orbit (LEO) was designed by students of the International Space University 1989 Summer Session held in Strasbourg, France, to provide a testbed for conducting experiments in the life and physical sciences in preparation for a mission to Mars. This design exercise was unique because it addressed all aspects concerning a large space project. The VGRF design was described which was developed by international participants specializing in the following areas: the politics of international cooperation, engineering, architecture, in-space physiology, material and life science experimentation, data communications, business, and management.

Bailey, Sheila G.; Chiaramonte, Francis P.; Davidian, Kenneth J.

1991-01-01

349

ZeroCal: Automatic MAC Protocol Calibration  

NASA Astrophysics Data System (ADS)

Sensor network MAC protocols are typically configured for an intended deployment scenario once and for all at compile time. This approach, however, leads to suboptimal performance if the network conditions deviate from the expectations. We present ZeroCal, a distributed algorithm that allows nodes to dynamically adapt to variations in traffic volume. Using ZeroCal, each node autonomously configures its MAC protocol at runtime, thereby trying to reduce the maximum energy consumption among all nodes. While the algorithm is readily usable for any asynchronous low-power listening or low-power probing protocol, we validate and demonstrate the effectiveness of ZeroCal on X-MAC. Extensive testbed experiments and simulations indicate that ZeroCal quickly adapts to traffic variations. We further show that ZeroCal extends network lifetime by 50% compared to an optimal configuration with identical and static MAC parameters at all nodes.

Meier, Andreas; Woehrle, Matthias; Zimmerling, Marco; Thiele, Lothar

350

Extensions of 2D gravity  

SciTech Connect

After reviewing some aspects of gravity in two dimensions, I show that non-trivial embeddings of sl(2) in a semi-simple (super) Lie algebra give rise to a very large class of extensions of 2D gravity. The induced action is constructed as a gauged WZW model and an exact expression for the effective action is given.

Sevrin, A.

1993-06-01

351

Quantum gravity and cosmological observations  

Microsoft Academic Search

Quantum gravity places entirely new challenges on the formulation of a consistent theory as well as on an extraction of potentially observable effects. Quantum corrections due to the gravitational field are commonly expected to be tiny because of the smallness of the Planck length. However, a consistent formulation now shows that key features of quantum gravity imply magnification effects on

Martin Bojowald

2007-01-01

352

Quantum Corrections to Entropic Gravity  

NASA Astrophysics Data System (ADS)

The entropic gravity scenario recently proposed by Erik Verlinde reproduced Newton's law of purely classical gravity yet the key assumptions of this approach all have quantum mechanical origins. As is typical for emergent phenomena in physics, the underlying, more fundamental physics often reveals itself as corrections to the leading classical behavior. So one naturally wonders: where is ? hiding in entropic gravity? To address this question, we first revisit the idea of holographic screen as well as entropy and its variation law in order to obtain a self-consistent approach to the problem. Next we argue that since the concept of minimal length has been invoked in the Bekenstein entropic derivation, the generalized uncertainty principle (GUP), which is a direct consequence of the minimal length, should be taken into consideration in the entropic interpretation of gravity. Indeed based on GUP it has been demonstrated that the black hole Bekenstein entropy area law must be modified not only in the strong but also in the weak gravity regime where in the weak gravity limit the GUP modified entropy exhibits a logarithmic correction. When applying it to the entropic interpretation, we demonstrate that the resulting gravity force law does include sub-leading order correction terms that depend on ?. Such deviation from the classical Newton's law may serve as a probe to the validity of entropic gravity.

Chen, Pisin; Wang, Chiao-Hsuan

2013-01-01

353

Earth- A Matter of Gravity  

NSDL National Science Digital Library

In this problem set, learners will analyze a map of Earth's gravity field derived from satellite data to answer questions on gravity averages and anomalies in certain regions. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

354

Gravity...It's So Attractive!  

ERIC Educational Resources Information Center

Describes six simple experiments that can enable students to better understand gravity and the role it plays in the universe. Includes discussions of Newton's experiments, weight and mass, center of gravity, center of mass, and the velocity of falling objects. (JJK)

Lewis, Carol

1992-01-01

355

Quantum Corrections to Entropic Gravity  

NASA Astrophysics Data System (ADS)

The entropic gravity scenario recently proposed by Erik Verlinde reproduced Newton's law of purely classical gravity yet the key assumptions of this approach all have quantum mechanical origins. As is typical for emergent phenomena in physics, the underlying, more fundamental physics often reveals itself as corrections to the leading classical behavior. So one naturally wonders: where is ? hiding in entropic gravity? To address this question, we first revisit the idea of holographic screen as well as entropy and its variation law in order to obtain a self-consistent approach to the problem. Next we argue that as the concept of minimal length has been invoked in the Bekenstein entropic derivation, the generalized uncertainty principle (GUP), which is a direct consequence of the minimal length, should be taken into consideration in the entropic interpretation of gravity. Indeed based on GUP it has been demonstrated that the black hole Bekenstein entropy area law must be modified not only in the strong but also in the weak gravity regime where in the weak gravity limit the GUP modified entropy exhibits a logarithmic correction. When applying it to the entropic interpretation, we demonstrate that the resulting gravity force law does include sub-leading order correction terms that depend on ?. Such deviation from the classical Newton's law may serve as a probe to the validity of entropic gravity.

Chen, Pisin; Wang, Chiao-Hsuan

2013-12-01

356

Reduced Gravity Zblan Optical Fiber  

NASA Technical Reports Server (NTRS)

Two optical fiber pullers have been designed for pulling ZBLAN optical fiber in reduced gravity. One fiber puller was designed, built and flown on board NASA's KC135 reduced gravity aircraft. A second fiber puller has been designed for use on board the International Space Station.

Tucker, Dennis S.; Workman, Gary L.; Smith, Guy A.

2000-01-01

357

An Operational Amplifier with Multipath Miller Zero Cancellation for RHP Zero Removal  

Microsoft Academic Search

The paper presents a Multipath Miller Zero Cancellation (MMZC) technique to remove the Right Half Plane Zero (RHPZ) in Miller compensated operational amplifiers. For comparison four different CMOS amplifiers have been integrated: a reference circuit without RHPZ removal, two circuits with traditional resistor and cascode removal techniques and finally the circuit with Multipath Miller Zero Cancellation Measurements confirm that MMZC

Ruud G. H. Eschauzier; Johan H. Huijsing

1993-01-01

358

Foam formation in low gravity  

NASA Technical Reports Server (NTRS)

An apparatus that produced the first polyurethane foam in low gravity has been described. The chemicals were mixed together in an apparatus designed for operation in low gravity. Mixing was by means of stirring the chemicals with an electric motor and propeller in a mixing chamber. The apparatus was flown on Consort 1, the first low-gravity materials payload launched by a commercial rocket launch team. The sounding rocket flight produced over 7 min of low gravity during which a polyurethane spheroidal foam of approximately 2300 cu cm was formed. Photographs of the formation of the foam during the flight show the development of the spheroidal form. This begins as a small sphere and grows to approximately a 17-cm-diam spheroid. The apparatus will be flown again on subsequent low-gravity flights.

Wessling, Francis C.; Mcmanus, Samuel P.; Matthews, John; Patel, Darayas

1990-01-01

359

Quench cooling under reduced gravity.  

PubMed

We report quench cooling experiments performed with liquid O(2) under different levels of gravity, simulated with magnetic gravity compensation. A copper disk is quenched from 300 to 90 K. It is found that the cooling time in microgravity is very long in comparison with any other gravity level. This phenomenon is explained by the insulating effect of the gas surrounding the disk. A weak gas pressurization (which results in subcooling of the liquid with respect to the saturation temperature) is shown to drastically improve the heat exchange, thus reducing the cooling time (about 20 times). The effect of subcooling on the heat transfer is analyzed at different gravity levels. It is shown that this type of experiment cannot be used for the analysis of the critical heat flux of the boiling crisis. The film boiling heat transfer and the minimum heat flux of boiling are analyzed as functions of gravity and subcooling. PMID:23944546

Chatain, D; Mariette, C; Nikolayev, V S; Beysens, D

2013-07-01

360

Absolute gravity measurements in Indonesia  

NASA Astrophysics Data System (ADS)

For the purposes of the calibration of the superconducting gravimeter in Bandung and the establishment of the absolute gravity points, we have carried out absolute gravity measurements for the first time in Indonesia in November, 2002. We have been conducting a superconducting gravimeter (SG TT-70 #08) observation in Bandung since December 1997, under the cooperation between Kyoto University and the Volcanological Survey of Indonesia. It is one of the GGP observation points and the unique SG point near the equator. Hence the SG data are expected not only for the studies of solid earth dynamics but also for the studies of the fluid envelope (ocean, atmosphere, land water) in equatorial regions. However, the SG is a relative gravimeter and it inevitably requires calibration by means of an absolute gravimeter to ensure the scale factor and to determine instrumental drifts. Moreover, there was no absolute gravity point in Indonesia so far, therefore the realization of absolute gravity measurements in Indonesia had been strongly desired. We have carried out absolute gravity measurements in Bandung during Nov. 10 -19 by means of a FG5 (#210), and we obtained more than 29,000 effective drops. The gravity value newly determined at the gravity base point in Bandung is 977976701.9 uGal (1.e-8 m/s**2) and the scale factor for the SG is 52.281 uGal/V, although both values are still tentative and might be slightly revised in the future. We have also established another absolute gravity point in Yogyakarta near Merapi volcano. The absolute gravity measurements in Yogyakarta have been carried out during Nov. 22-26 and a tentative gravity value obtained is 978203091.9 uGal.

Fukuda, Y.; Higashi, T.; Takemoto, S.; Abe, M.; Sjafra, D.; Dendi, K.; Andan, A.; Doi, K.; Imanishi, Y.; Arguino, G.

2003-04-01

361

Gravity Waves and their Effects on the Mean State and Variability of Mars' Atmosphere  

NASA Astrophysics Data System (ADS)

Data from the Mars Global Surveyor (MGS) spacecraft has revealed the presence of gravity waves in Mars' lower atmosphere and thermosphere. From perturbations in radio occultation temperature profiles of the lower atmosphere, global distributions of gravity wave potential energy density were calculated. The potential energy density distributions served as the basis to compute gravity wave source momentum flux used in a Mars dynamical model, marking the first time that a numerical study of Mars' gravity waves was observationally constrained. The gravity wave source spectrum is believed to include a stationary component from topographic forcing and a non-stationary component from atmospheric tides with large zonal wavenumbers. The model used was a Mars-specific version of the Hybrid Lindzen-Matsuno gravity wave parameterization that was created and integrated into the time-dependent, two-dimensional QNLM model for Mars. Due to the non-stationary waves in the gravity wave spectrum, the effect on predicted zonal wind and temperature fields was profound, particularly in the upper atmosphere above 100 km altitude where Mars' atmosphere is poorly observed. At solstice, the middle atmosphere zonal jets were closed near 80 km, and upper atmosphere zonal winds were significantly diminished from 120--140 m s-1 to near zero. Meridional circulation increased to over 50 m s-1 at altitudes where gravity wave breaking occurred, and adiabatic heating above the winter pole was enhanced. The model results were particularly sensitive to the prescribed phase speed distribution, and multiple phase speed spectra were evaluated to assess sensitivity. The effects of the non-stationary tidal components in the gravity wave spectrum indicate that Mars' GCMs may be underestimating their contribution to middle and upper atmosphere forcing, but open questions remain with respect to the phase speed distribution of non-stationary components and the relative contribution to momentum flux of stationary and non-stationary waves. Direct measurements of wind speed are needed to better constrain the gravity wave spectrum and validate predicted results.

Creasey, John E.

362

Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory  

SciTech Connect

Because of the equivalence principle, a global measurement is necessary to distinguish gravity from acceleration of the reference frame. A gravity gradiometer is therefore an essential instrument needed for precision tests of gravity laws and for applications in gravity survey and inertial navigation. Superconductivity and SQUID (superconducting quantum interference device) technology can be used to obtain a gravity gradiometer with very high sensitivity and stability. A superconducting gravity gradiometer has been developed for a null test of the gravitational inverse-square law and space-borne geodesy. Here we present a complete theoretical model of this instrument. Starting from dynamical equations for the device, we derive transfer functions, a common mode rejection characteristic, and an error model of the superconducting instrument. Since a gradiometer must detect a very weak differential gravity signal in the midst of large platform accelerations and other environmental disturbances, the scale factor and common mode rejection stability of the instrument are extremely important in addition to its immunity to temperature and electromagnetic fluctuations. We show how flux quantization, the Meissner effect, and properties of liquid helium can be utilized to meet these challenges.

Chan, H.A.; Paik, H.J.

1987-06-15

363

Discrete Quantum Gravity in the Regge Calculus Formalism  

SciTech Connect

We discuss an approach to the discrete quantum gravity in the Regge calculus formalism that was developed in a number of our papers. The Regge calculus is general relativity for a subclass of general Riemannian manifolds called piecewise flat manifolds. The Regge calculus deals with a discrete set of variables, triangulation lengths, and contains continuous general relativity as a special limiting case where the lengths tend to zero. In our approach, the quantum length expectations are nonzero and of the order of the Plank scale, 10{sup -33} cm, implying a discrete spacetime structure on these scales.

Khatsymovsky, V.M. [Budker Institute of Nuclear Physics, Siberian Division, Russian Academy of Sciences, pr. Akademika Lavrent'eva 11, Novosibirsk, 630090 (Russian Federation)

2005-09-01

364

Naked singularities are not singular in distorted gravity  

NASA Astrophysics Data System (ADS)

We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheele-DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity.

Garattini, Remo; Majumder, Barun

2014-07-01

365

Progress in the Determination of the Earth's Gravity Field  

NASA Technical Reports Server (NTRS)

Topics addressed include: global gravity model development; methods for approximation of the gravity field; gravity field measuring techniques; global gravity field applications and requirements in geophysics and oceanography; and future gravity missions.

Rapp, Richard H. (editor)

1989-01-01

366

Multiparticle Interactions of Zero-Range Potentials  

SciTech Connect

For two particles it is often convenient to replace local or non-local potentials by zero-range interactions. Since they are zero-range, these interactions can often be replaced by boundary conditions at a point where the separation between two particles vanishes. In either case, zero-range potentials are useful when the details of the interaction at small distances are not critical for the dynamics. The description of Bose condensates is an example where zero-range interactions are basic to theories of the condensed aggregates. These theories employ the model interactions to obtain a mean field description of large numbers of particles. On a more fundamental level, zero-range interactions are employed to model the interactions of three particles, where they have been used to study the properties of loosely bound Efimov states. Owning to their success in these areas they have been generalized to allow for multichannel interactions, interactions for states with non-zero angular momentum and energy dependent zero-range potentials. Properties of these generalized potentials and their applications will be illustrated for the interaction of three particles at vanishingly small kinetic energy.

Macek, J. H. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)

2009-01-01

367

Multiparticle Interactions of Zero-Range Potentials  

NASA Astrophysics Data System (ADS)

For two particles it is often convenient to replace local or non-local potentials by zero-range interactions. Since they are zero-range, these interactions can often be replaced by boundary conditions at a point where the separation between two particles vanishes. In either case, zero-range potentials are useful when the details of the interaction at small distances are not critical for the dynamics. The description of Bose condensates is an example where zero-range interactions are basic to theories of the condensed aggregates. These theories employ the model interactions to obtain a mean field description of large numbers of particles. On a more fundamental level, zero-range interactions are employed to model the interactions of three particles, where they have been used to study the properties of loosely bound Efimov states. Owning to their success in these areas they have been generalized to allow for multichannel interactions, interactions for states with non-zero angular momentum and energy dependent zero-range potentials. Properties of these generalized potentials and their applications will be illustrated for the interaction of three particles at vanishingly small kinetic energy.

Macek, J. H.

2009-05-01

368

AdS Chern-Simons gravity induces conformal gravity  

NASA Astrophysics Data System (ADS)

The leitmotif of this paper is the question of whether four- and higher even-dimensional conformal gravities do have a Chern-Simons pedigree. We show that Weyl gravity can be obtained as the dimensional reduction of a five-dimensional Chern-Simons action for a suitable (gauge-fixed, tractorlike) five-dimensional anti-de Sitter connection. The gauge-fixing and dimensional reduction program readily admits a generalization to higher dimensions for the case of certain conformal gravities obtained by contractions of the Weyl tensor.

Aros, Rodrigo; Díaz, Danilo E.

2014-04-01

369

Phantom Crossing DGP Gravity  

NASA Astrophysics Data System (ADS)

We propose a phantom crossing Dvali-Gabadadze-Porrati (DGP) model. In our model, the effective equation of state of the DGP gravity crosses the phantom divide line. We demonstrate crossing of the phantom divide does not occur within the framework of the original DGP model or the DGP model developed by Dvali and Turner. By extending their model, we construct a model that realizes crossing of the phantom divide. DGP models can account for late-time acceleration of the universe without dark energy. Phantom Crossing DGP model is more compatible with recent observational data from Type Ia Supernovae (SNIa), Cosmic Microwave Background (CMB) anisotropies, and Baryon Acoustic Oscillations (BAO) than the original DGP model or the DGP model developed by Dvali and Turner.

Hirano, Koichi; Komiya, Zen

2010-08-01

370

Gravity waves from thunderstorms  

NASA Technical Reports Server (NTRS)

Gravity waves generated by severe thunderstorms in the eastern Ohio-Pennsylvania area were recorded by an array of microbarovariographs at Palisades, New York and by standard microbarographs across northeastern United States. The waves were associated with the cold mesohigh from the outflow of the thunderstorms. Along their path the waves apparently triggered new thunderstorms. The waves were observed to propagate with the velocity of the wind just below the tropopause. The long-distance propagation of the waves is explained by the presence of a dust associated with the critical level (steering level), in agreement with the derivations given by Lindzen and Tung (1976). The dust was directional and waves were absent to the west of the generating area. In the generating area wave-CISK might have been operating. Sharp vertical temperature gradients associated with the passage of the waves were observed by temperature sensors on a tower.

Balachandran, N. K.

1980-01-01

371

Rotating gravity gradiometer study  

NASA Technical Reports Server (NTRS)

Two rotating gravity gradiometer (RGG) sensors, along with all the external electronics needed to operate them, and the fixtures and special test equipment needed to fill and align the bearings, were assembled in a laboratory, and inspected. The thermal noise threshold of the RGG can be lowered by replacing a damping resistor in the first stage electronics by an active artificial resistor that generates less random voltage noise per unit bandwidth than the Johnson noise from the resistor it replaces. The artificial resistor circuit consists of an operational amplifier, three resistors, and a small DC to DC floating power supply. These are small enough to be retrofitted to the present circuit boards inside the RGG rotor in place of the 3 Megohm resistor. Using the artificial resistor, the thermal noise of the RGG-2 sensor can be lowered from 0.3 Eotvos to 0.15 Eotvos for a 10 sec integration time.

Forward, R. L.

1982-01-01

372

Phantom Crossing DGP Gravity  

SciTech Connect

We propose a phantom crossing Dvali-Gabadadze-Porrati (DGP) model. In our model, the effective equation of state of the DGP gravity crosses the phantom divide line. We demonstrate crossing of the phantom divide does not occur within the framework of the original DGP model or the DGP model developed by Dvali and Turner. By extending their model, we construct a model that realizes crossing of the phantom divide. DGP models can account for late-time acceleration of the universe without dark energy. Phantom Crossing DGP model is more compatible with recent observational data from Type Ia Supernovae (SNIa), Cosmic Microwave Background (CMB) anisotropies, and Baryon Acoustic Oscillations (BAO) than the original DGP model or the DGP model developed by Dvali and Turner.

Hirano, Koichi [Department of Physics, Ichinoseki National College of Technology, Ichinoseki 021-8511 (Japan); Komiya, Zen [Department of Physics, Tokyo University of Science, Tokyo 162-8601 (Japan)

2010-08-12

373

Halos of Modified Gravity  

NASA Astrophysics Data System (ADS)

We describe how a certain simple modification of general relativity, in which the local cosmological constant is allowed to depend on the space-time curvature, predicts the existence of halos of modified gravity surrounding spherically symmetric objects. We show that the gravitational mass of an object weighed together with its halo can be much larger than its gravitational mass as seen from inside the halo. This effect could provide an alternative explanation of the dark-matter phenomenon in galaxies. In this case, the local cosmological constant in the solar system must be some six orders of magnitude larger than its cosmic value obtained in the supernova type Ia experiments. This is well within the current experimental bounds, but may be directly observable in future high-precision experiments.

Krasnov, Kirill; Shtanov, Yuri

374

Operads and quantum gravity  

NASA Astrophysics Data System (ADS)

In this article we try to explain and extend a statement due to Maxim Kontsevich back in 1999 that the Holography Principle in physics should be related to the (higher dimensional) Deligne Conjecture in mathematics. This seems to suggest that the little d-discs operad (or equivalently the notion of a d-algebra) gives a new way to understand the mathematical aspects of quantum gravity using holography. The strategy is as follows: we would like to learn something about quantum gravity in ( d + 1) dimensions: we use holography to reduce our original problem to a CFT in d-dimensions. The deep origin of this dimensional reduction lies on the fact that it is the area and not the volume which appears in the formula giving the entropy of black holes as described long ago by Hawking. Then we use d-algebras (i.e. the little d-discs operad) to study our d-dim CFT. The possible relation between d-dim CFT and d-algebras comes from the lesson we have learnt from strings (namely the 2-dim CFT case): the space of physical states in closed string field theory (i.e. the BRST cohomology) has a natural Gerstenhaber algebra structure and this by Cohen's theorem is related to the little 2-discs operad. The proposal then is that the relation might hold in higher than 2 dimensions. This approach is algebraic although it would have been much more satisfactory if we could generalise Segal's geometric approach to CFT in higher than 2 dimensions. Hopefully the article is mathematically self-contained.

Zois, Ioannis P.

2005-06-01

375

Evaluation of AAFE Apparatus to Measure Residual and Transient Convection in Zero-Gravity.  

National Technical Information Service (NTIS)

An evaluation apparatus which photographs convective and diffusive flows in crystal growth experiments is presented. Results in the following catagories are reported: (1) Human factors; (2) Electrical and mechanical; (3) Optical performance; and (4) Therm...

R. C. Ruff B. R. Facemire W. K. Witherow

1978-01-01

376

Proposal for the design of a zero gravity tool storage device  

NASA Technical Reports Server (NTRS)

Astronauts frequently use a variety of hand tools during space missions, especially on repair missions. A toolbox is needed to allow storage and retrieval of tools with minimal difficulties. The toolbox must contain tools during launch, landing, and on-orbit operations. The toolbox will be used in the Shuttle Bay and therefore must withstand the hazardous space environment. The three main functions of the toolbox in space are: to protect the tools from the space environment and from damaging one another, to allow for quick, one-handed access to the tools; and to minimize the heat transfer between the astronaut's hand and the tools. This proposal explores the primary design issues associated with the design of the toolbox. Included are the customer and design specifications, global and refined function structures, possible solution principles, concept variants, and finally design recommendations.

Stuckwisch, Sue; Carrion, Carlos A.; Phillips, Lee; Laughlin, Julia; Francois, Jason

1994-01-01

377

Response of Differently Axially Excited Viscous Liquid Bridges in Zero-Gravity.  

National Technical Information Service (NTIS)

A cylindrical liquid column of incompressible and viscous liquid is subjected to different axial excitation: one-sided, counter-directional and double-sided unequal excitations. The response of the free liquid surface relating to the velocity and pressure...

H. F. Bauer

1989-01-01

378

Development of a laboratory prototype water quality monitoring system suitable for use in zero gravity  

NASA Technical Reports Server (NTRS)

The development of a laboratory prototype water quality monitoring system for use in the evaluation of candidate water recovery systems and for study of techniques for measuring potability parameters is reported. Sensing techniques for monitoring of the most desirable parameters are reviewed in terms of their sensitivities and complexities, and their recommendations for sensing techniques are presented. Rationale for selection of those parameters to be monitored (pH, specific conductivity, Cr(+6), I2, total carbon, and bacteria) in a next generation water monitor is presented along with an estimate of flight system specifications. A master water monitor development schedule is included.

Misselhorn, J. E.; Witz, S.; Hartung, W. H.

1973-01-01

379

Equilibrium Fluid Interface Behavior Under Low- and Zero-Gravity Conditions. 2  

NASA Technical Reports Server (NTRS)

The mathematical basis for the forthcoming Angular Liquid Bridge investigation on board Mir is described. Our mathematical work is based on the classical Young-Laplace-Gauss formulation for an equilibrium free surface of liquid partly filling a container or otherwise in contact with solid support surfaces. The anticipated liquid behavior used in the apparatus design is also illustrated.

Concus, Paul; Finn, Robert

1996-01-01

380

Cooperative control of two arms in the transport of an inertial load in zero gravity  

NASA Technical Reports Server (NTRS)

In designing a robot control system for dual arm configurations, the control engineer is faced with two challenges: to derive the equations of motion for a given situation, and to meet certain desired control requirements (for instance, minimum energy). The former may involve closed kinematic chains, such as the case when the two arms are grasping a common object. The latter usually involves nonlinear optimization. These issues are considered in the context of transporting an inertial load using two planar three-link arms. A generalized 'reduction transformation' is applied to the dynamics to remove the singularity in the system equations. A suboptimal minimum energy method is presented to reduce a difficult 12-state, six-control nonlinear optimization to two independent, nonconflicting suboptimizations. A simulation example is provided to illustrate the degree of energy reduction possible using the optimal arm torque distribution that was developed.

Carignan, Craig R.; Akin, David L.

1988-01-01

381

Radiation and zero-gravity effects on human leukocytes and Neurospora crassa  

NASA Technical Reports Server (NTRS)

The two parts of this experiment have resulted in proof that neither orbital space flight nor any of the stresses connected with it produced significant, unpredicted genetic damage, at least insofar as chromosomal-aberration production is a valid measure of this general type of effect. Furthermore, the Gemini 11 results lead to the conclusion that no synergistic effect exists between radiation and factors that are associated with space flight. No significant difference was found between dose-effect curves for survival or mutation induction of the inflight and ground-based samples irradiated on filters. Thus, like the blood experiment, this part of the experiment failed to result in data that were appropriate for confirmation of the apparent synergism that was observed in the Gemini 3 blood experiment. Also, the Nuerospora crassa experiment provided conclusive data that there is no difference in the genetic effects of irradiation during space flight and the genetic effects obtained in ground-based experiments. Both the Gemini 11 blood experiment and the Neurospora crassa experiment thus have failed to result in data confirmatory of the apparent synergism observed on the Gemini 3 mission.

Bender, M. A.; Deserres, F. J.; Gooch, P. C.; Miller, I. R.; Smith, D. B.; Kondo, S.

1971-01-01

382

Zero-gravity growth of NaCl-LiF eutectic. Experiment MA-131  

NASA Technical Reports Server (NTRS)

Continuous and discontinuous lithium fluoride fibers embedded in a sodium chloride matrix were produced in space and on earth, respectively. The production of continuous fibers in an eutectic mixture was attributed to the absence of convection current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and earth-grown ingots were made with a light microscope and a spectrometer. It was found that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of lithium fluoride fibers along the growth direction.

Yue, A. S.; Yeh, C. W.; Yue, B. K.

1977-01-01

383

Mobile work station concept for assembly of large space structures (zero gravity simulation tests)  

NASA Astrophysics Data System (ADS)

The concept presented is intended to enhance astronaut assembly of truss structure that is either too large or complex to fold for efficient Shuttle delivery to orbit. The potential of augmented astronaut assembly is illustrated by applying the result of the tests to a barebones assembly of a truss structure. If this structure were assembled from the same nestable struts that were used in the Mobile Work Station assembly tests, the spacecraft would be 55 meters in diameter and consist of about 500 struts. The struts could be packaged in less than 1/2% of the Shuttle cargo bay volume and would take up approximately 3% of the mass lift capability. They could be assembled in approximately four hours. This assembly concept for erectable structures is not only feasible, but could be used to significant economic advantage by permitting the superior packaging feature of erectable structures to be exploited and thereby reduce expensive Shuttle delivery flights.

Heard, W. L., Jr.; Bush, H. G.; Wallsom, R. E.; Jensen, J. K.

1982-03-01

384

Equilibrium fluid interface behavior under low- and zero-gravity conditions. II  

Microsoft Academic Search

We describe here recent mathematical results that form the basis of our forthcoming space experiment, developed jointly with Mark Weislogel of NASA Lewis Research Center, which is scheduled for the Glovebox on the Mir 23 \\/ NASA 4 Mission in December 1996. The mathematical basis for the Angular Liquid Bridge is described. The anticipated liquid behavior used in the apparatus

P. Concus; R. Finn

1996-01-01

385

Equilibrium fluid interface behavior under low- and zero-gravity conditions. II.  

National Technical Information Service (NTIS)

We describe here recent mathematical results that form the basis of our forthcoming space experiment, developed jointly with Mark Weislogel of NASA Lewis Research Center, which is scheduled for the Glovebox on the Mir 23 / NASA 4 Mission in December 1996....

P. Concus R. Finn

1996-01-01

386

Equilibrium fluid interface behavior under low- and zero-gravity conditions. II  

SciTech Connect

We describe here recent mathematical results that form the basis of our forthcoming space experiment, developed jointly with Mark Weislogel of NASA Lewis Research Center, which is scheduled for the Glovebox on the Mir 23 / NASA 4 Mission in December 1996. The mathematical basis for the Angular Liquid Bridge is described. The anticipated liquid behavior used in the apparatus is illustrated.

Concus, P. [Lawrence Berkeley Lab., CA (United States)] [California Univ., Berkeley, CA (United States). Dept. of Mathematics; Finn, R. [Stanford Univ., CA (United States). Dept. of Mathematics

1996-05-01

387

Evaluation of AAFE apparatus to measure residual and transient convection in zero-gravity  

NASA Technical Reports Server (NTRS)

An evaluation apparatus which photographs convective and diffusive flows in crystal growth experiments is presented. Results in the following catagories are reported: (1) Human factors; (2) Electrical and mechanical; (3) Optical performance; and (4) Thermal performance.

Ruff, R. C.; Facemire, B. R.; Witherow, W. K.

1978-01-01

388

Outlet baffles: Effect on liquid residuals from zero-gravity draining of hemispherically ended cylinders  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted to study the relative effectiveness of various outlet baffles in reducing liquid residuals resulting from the draining of hemispherically ended cylindrical tanks in a weightless environment. Three different baffles were employed. The relative effectiveness of each baffle was determined by comparing the results obtained, in the form of liquid residuals, with results for an unbaffled tank. Data indicate that all the baffles tested reduced residuals. Reductions betweem 10 and 60 percent were obtained, depending on baffle geometry and outlfow Weber number.

Symons, E. P.

1972-01-01

389

Application and use of spinal immobilization devices in zero-gravity flight  

NASA Technical Reports Server (NTRS)

A KC-135 parabolic flight was performed for the purpose of evaluation of spinal immobilization techniques in microgravity. The flight followed the standard 40 parabola profile with four NASA/KRUG experimenters involved. One performed as coordinator/recorder, one as test subject, and two as the Crew Medical Officers (CMO). The flight was to evaluate the application of spinal immobilization devices and techniques in microgravity as are performed during initial stabilization or patient transport scenarios. The sequence of detail for examination of the following objectives included: attempted cervical spine immobilization with all free floating, the patient restrained to the floor, various hand positioning techniques; c-collar placement; Kendrick Extrication Device (KED) application with various restraints for patient and CMO; patient immobilization and transport using the KED; patient transported on KED and spine board. Observations for each task are included. Major conclusions and issues are also included.

Krupa, Debra T.; Gosbee, John; Billica, Roger; Boyce, Joey B.

1991-01-01

390

Separation of lymphocytes by electrophoresis under terrestrial conditions and at zero gravity, phase 3  

NASA Technical Reports Server (NTRS)

Electrophoretic mobilities (EPM) of peripheral lymphocytes were studied from normal subjects, chronic hemodialysis patients and kidney transplant recipients. A technique to separate B lymphocytes and null cells from non-T lymphocyte preparation was developed. The experiments were designed to determine which subpopulation of the non-T lymphocytes is primarily affected and shows a decreased EPM in chronic hemodialysis patients and kidney transplant recipients.

Rubin, A. L.; Stenzel, K. H.; Cheigh, J. S.; Seaman, G. V. F.; Novogrodsky, A.

1977-01-01

391

Convective Motions in Near-Critical Fluids under Real Zero-Gravity Conditions  

Microsoft Academic Search

The results of processing and interpreting the data of joint Russian–French experiments for studying the heat and mass transfer in near-critical fluids are presented. The experiments were carried out with the ALICE-1 instrument during an orbital flight of the Mirstation from September 30 to October 2, 1995 [1]. For such fluids with a point-like source of heat, when they are

A. V. Zyuzgin; A. I. Ivanov; V. I. Polezhaev; G. F. Putin; E. B. Soboleva

2001-01-01

392

Instability of ocular torsion in zero gravity - Possible implications for space motion sickness  

NASA Technical Reports Server (NTRS)

It is proposed that study of the eye torsion reflex and its behavior under novel gravitational states may possibly provide the basis for a long-sought test to predict space motion sickness (SMS). Measures of eye torsion such as ocular counterrolling and spontaneous eye torsion, were examined during hypo- and hypergravity in parabolic flight on the NASA KC-135 aircraft. Ten subjects, including two astronauts, one who had experienced SMS and one who had not, were ranked according to scores of torsional inability at 0 G and divided into two equal groups of high and low susceptibility to SMS. At 1.8 G the groups were significantly different in both the instability measure and the measure of torsional ability. No differences were detected in eye torsion in either 0 G or 1.8 G and none of the tests were significantly different in 1 G. Results suggest that tests of eye torsion on the KC-135 might differentiate those who would experience SMS from those who would not, although it is noted that this is not yet proven.

Diamond, Shirley G.; Markham, Charles H.; Money, Ken E.

1990-01-01

393

Mobile work station concept for assembly of large space structures (zero gravity simulation tests)  

NASA Technical Reports Server (NTRS)

The concept presented is intended to enhance astronaut assembly of truss structure that is either too large or complex to fold for efficient Shuttle delivery to orbit. The potential of augmented astronaut assembly is illustrated by applying the result of the tests to a barebones assembly of a truss structure. If this structure were assembled from the same nestable struts that were used in the Mobile Work Station assembly tests, the spacecraft would be 55 meters in diameter and consist of about 500 struts. The struts could be packaged in less than 1/2% of the Shuttle cargo bay volume and would take up approximately 3% of the mass lift capability. They could be assembled in approximately four hours. This assembly concept for erectable structures is not only feasible, but could be used to significant economic advantage by permitting the superior packaging feature of erectable structures to be exploited and thereby reduce expensive Shuttle delivery flights.

Heard, W. L., Jr.; Bush, H. G.; Wallsom, R. E.; Jensen, J. K.

1982-01-01

394

Proposal for the design of a zero gravity tool storage device  

NASA Astrophysics Data System (ADS)

Astronauts frequently use a variety of hand tools during space missions, especially on repair missions. A toolbox is needed to allow storage and retrieval of tools with minimal difficulties. The toolbox must contain tools during launch, landing, and on-orbit operations. The toolbox will be used in the Shuttle Bay and therefore must withstand the hazardous space environment. The three main functions of the toolbox in space are: to protect the tools from the space environment and from damaging one another, to allow for quick, one-handed access to the tools; and to minimize the heat transfer between the astronaut's hand and the tools. This proposal explores the primary design issues associated with the design of the toolbox. Included are the customer and design specifications, global and refined function structures, possible solution principles, concept variants, and finally design recommendations.

Stuckwisch, Sue; Carrion, Carlos A.; Phillips, Lee; Laughlin, Julia; Francois, Jason

1994-04-01

395

Morphogenetic responses of cultured totipotent cells of carrot /Daucus carota var. carota/ at zero gravity  

NASA Technical Reports Server (NTRS)

An experiment designed to test whether embryos capable of developing from isolated somatic carrot cells could do so under conditions of weightlessness in space was performed aboard the unmanned Soviet biosatellite Kosmos 782 under the auspices of the joint United States-Soviet Biological Satellite Mission. Space flight and weightlessness seem to have had no adverse effects on the induction of embryoids or on the development of their organs. A portion of the crop of carrot plantlets originated in space and grown to maturity were not morphologically different from controls.

Krikorian, A. D.; Steward, F. C.

1978-01-01

396

Morphogenetic Responses of Cultured Totipotent Cells of Carrot (Daucus carota var. carota) at Zero Gravity.  

PubMed

An experiment designed to test whether embryos capable of developing from isolated somatic carrot cells could do so under conditions of weightlessness in space was performed aboard the unmanned Soviet biosatellite Kosmos 782 under the auspices of the joint United States-Soviet Biological Satellite Mission. Space flight and weightlessness seem to have had no adverse effects on the induction of embryoids or on the development of their organs. A portion of the crop of carrot plantlets originated in space and grown to maturity were not morphologically different from controls. PMID:17847331

Krikorian, A D; Steward, F C

1978-04-01

397

Preliminary design for a Zero Gravity Test Facility (ZGTF). Volume 1: Technical  

NASA Technical Reports Server (NTRS)

The functional requirements and best conceptual design of a test facility that simulates weightless operating conditions for a high gain antenna systems (HGAS), that will broadcast to the Tracking Data Relay Satellites were defined. The typical HGAS defined is mounted on a low Earth orbiting satellite, and consists of an antenna with a double gimbal pointing system mounted on a 13 foot long mast. Typically, the gimbals are driven by pulse modulated dc motors or stepper motors. These drivers produce torques on the mast, with jitter that excites the satellite and may cause disturbances to sensitive experiments. The dynamic properties of the antenna support structure (mast), including flexible mode characteristics were defined. The torque profile induced on the spacecraft by motion of the high gain antenna was estimated. Gain and phase margins of the servo control loop of the gimbal drive electronics was also verified.

Germain, A.

1981-01-01

398

Separation of lymphocytes by electrophoresis under terrestrial conditions and at zero gravity  

NASA Technical Reports Server (NTRS)

Electrophoretic mobility (EPM) of human peripheral lymphocytes were examined with the following objectives: To determine differences in EPM of lymphocytes under immuno-stimulated and immuno-suppressed states. To define the conditions necessary for the separation of lymphocyte sub-populations in normal and pathological conditions; To investigate immunological active, charged chemical groups on lymphocyte surfaces; and to investigate pathophysiological mechanisms of immune responsiveness, as reflected by alterations in EPM. To evaluate the potential of lymphocyte electrophoresis as: (1) a means of monitoring the immune status of kidney transplant recipients, (2) in predicting the outcome of kidney transplants, and (3) as a method for separation of lymphocyte sub-populations, the EPM was studied for unfractionated human peripheral lymphocytes and of populations enriched with T and "B" cells from normal adults, hemodialysis patients and kidney transplant recipients.

Rubin, A. L.

1977-01-01

399

KC-135 zero-gravity two phase flow pressure drop: Experiments and modeling  

NASA Astrophysics Data System (ADS)

Two-phase flow, thermal management systems are currently being considered as an alternative to conventional, single phase systems for future space missions because of their potential to reduce overall system mass, size, and pumping power requirements. Knowledge of flow regime transitions, heat transfer characteristics, and pressure drop correlations is necessary to design and develop two-phase systems. This work is concerned with microgravity, two-phase flow pressure drop experiments. The data are those of a recent experiment (Hill and Best 1990) funded by the U.S. Air Force and conducted by Foster-Miller in conjunction with Texas A&M University. A boiling and condensing experiment was built in which R-12 was used as the working fluid. A Foster-Miller two phase pump was used to circulate a freon mixture and allow separate measurements of the vapor and liquid flow streams. The experimental package was flown five times aboard the NASA KC-135 aircraft which simulates 0-``g'' conditions by its parabolic flight trajectory. Test conditions included stratified and annual flow regimes in 1-``g'' which became bubbly, slug or annular flow regimes in 0-``g''. A portion of the current work outlines a methodology to analyze data for two-phase, 0-g experimental studies. A technique for correcting the raw pressure drop data collected from the test package is given. The Corrected pressure drop measurements are compared with predictive model. The corrected pressure drop measurements show no statistically significant difference between the 1-``g'' and 0-``g'' tests for mass flow rates between 0.00653 and 0.0544 kg/s in an 8 mm ID tube. An annular flow model gave the best overall predictions of pressure drop. The homogeneous, and Beattle and Whalley (1982) models showed good agreement with the pressure drops measured for the slug and bubbly/slug flow conditions. The two-phase multiplier deduced from the data appeared to follow the Martinelli-Nelson trend but at lower values than for water.

Lambert, Anne; Reinarts, Thomas R.; Best, Frederick R.; Hill, Wayne S.

1991-01-01

400

Zero-gravity growth of NaF-NaCl eutectics in the NASA Skylab program  

NASA Technical Reports Server (NTRS)

Continuous and discontinuous NaF fibers, embedded in a NaCl matrix, were produced in space and on earth. The production of continuous fibers in a eutectic mixture is attributed to the absence of convection current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and earth-grown ingots were made with a light microscope and a spectrometer. It is shown that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of NaF fibers along the ingot axis. A new concept is advanced to explain the phenomenon of transmittance versus far infrared wavelength of the directionally solidified NaCl-NaF eutectic in terms of the two-dimensional Bragg Scattering and the polarization effect of Rayleigh scattering. This concept can be applied to other eutectic systems as long as the index of refraction of the matrix over a range of wavelengths is known. Experimental data are in agreement with the theoretical prediction.

Yue, A. S.; Allen, F. G.; Yu, J. G.

1976-01-01

401

Estimating zero-strain states of very soft tissue under gravity loading using digital image correlation  

Microsoft Academic Search

This paper presents several experimental techniques and concepts in the process of measuring mechanical properties of very soft tissue in an ex vivo tensile test. Gravitational body force on very soft tissue causes pre-compression and results in a non-uniform initial deformation. The global digital image correlation technique is used to measure the full-field deformation behavior of liver tissue in uniaxial

Zhan Gao; Jaydev P. Desai

2010-01-01

402

Zero-gravity growth of a sodium chloride-lithium fluoride eutectic mixture  

NASA Technical Reports Server (NTRS)

Continuous and discontinuous lithium fluoride fibers embedded in a sodium chloride matrix were produced in space and on Earth, respectively. The production of continuous fibers in a eutectic mixture was attributed to the absence of convective current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and Earth-grown ingots were made with a light microscope and a spectrometer. It was found that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of lithium fluoride fibers along the growth direction.

Yue, A. S.; Yeh, C. W.; Yue, B. K.

1982-01-01

403

Space stations: Living in zero gravity, developmental task for psychologists and space environmental experts  

NASA Technical Reports Server (NTRS)

The recent advances in the psychological aspects of space station design are discussed, including the impact of the increase in awareness of both the public in general as well as space environmental experts of the importance of psychological factors when designing space stations and training astronauts.

Ludwig, E.

1984-01-01

404

Zero Gravity and Cardiovascular Homeostasis. The Relationship Between Endogenous Hyperprolactinemia and Plasma Aldosterone.  

National Technical Information Service (NTIS)

Prolactin, thyrotropin and aldosterone were measured by radioimmunoassay and plasma renin activity by the radioimmunoassay of angiotensin I in normal women before and after the intravenous injection of 200 micrograms of thyrotropin releasing hormone. Prol...

A. C. Weihl E. Haber F. Maloof I. A. Kourides R. N. Re

1978-01-01

405

Design, fabrication and acceptance testing of a zero gravity whole body shower, volume 1  

NASA Technical Reports Server (NTRS)

The effort to design whole body shower for the space station prototype is reported. Clothes and dish washer/dryer concepts were formulated with consideration given to integrating such a system with the overall shower design. Water recycling methods to effect vehicle weight savings were investigated and it was concluded that reusing wash and/or rinse water resulted in weight savings which were not sufficient to outweigh the added degree of hardware complexity. The formulation of preliminary and final designs for the shower are described. A detailed comparison of the air drag vs. vacuum pickup method was prepared that indicated the air drag concept results in more severe space station weight penalties; therefore, the preliminary system design was based on utilizing the vacuum pickup method. Tests were performed to determine the optimum methods of storing, heating and sterilizing the cleansing agent utilized in the shower; it was concluded that individual packages of pre-sterilized cleansing agent should be used. Integration features with the space station prototype system were defined and incorporated into the shower design as necessary.

1973-01-01

406

Options for transpiration water removal in a crop growth system under zero gravity conditions  

NASA Technical Reports Server (NTRS)

The operation of a microgravity crop-growth system is a critical feature of NASA's Closed Ecological Life Support System (CELSS) development program. Transpiration-evolved water must be removed from the air that is recirculated in such a system, perhaps supplying potable water in the process. The present consideration of candidate systems for CELSS water removal gives attention to energy considerations and to a mechanical, inertial-operation water-separation system that was chosen due to the depth of current understanding of its operation.

Blackwell, C. C.; Kliss, M.; Yendler, B.; Borchers, B.; Yendler, Boris S.; Nguyen, Thoi K.; Waleh, Ahmad

1991-01-01

407

Model selection for modified gravity.  

PubMed

In this article, we review model selection predictions for modified gravity scenarios as an explanation for the observed acceleration of the expansion history of the Universe. We present analytical procedures for calculating expected Bayesian evidence values in two cases: (i) that modified gravity is a simple parametrized extension of general relativity (GR; two nested models), such that a Bayes' factor can be calculated, and (ii) that we have a class of non-nested models where a rank-ordering of evidence values is required. We show that, in the case of a minimal modified gravity parametrization, we can expect large area photometric and spectroscopic surveys, using three-dimensional cosmic shear and baryonic acoustic oscillations, to 'decisively' distinguish modified gravity models over GR (or vice versa), with odds of ?1:100. It is apparent that the potential discovery space for modified gravity models is large, even in a simple extension to gravity models, where Newton's constant G is allowed to vary as a function of time and length scale. On the time and length scales where dark energy dominates, it is only through large-scale cosmological experiments that we can hope to understand the nature of gravity. PMID:22084296

Kitching, T D; Simpson, F; Heavens, A F; Taylor, A N

2011-12-28

408

Simplified model of statistically stationary spacecraft rotation and associated induced gravity environments  

NASA Technical Reports Server (NTRS)

A stochastic model of spacecraft motion was developed based on the assumption that the net torque vector due to crew activity and rocket thruster firings is a statistically stationary Gaussian vector process. The process had zero ensemble mean value, and the components of the torque vector were mutually stochastically independent. The linearized rigid-body equations of motion were used to derive the autospectral density functions of the components of the spacecraft rotation vector. The cross-spectral density functions of the components of the rotation vector vanish for all frequencies so that the components of rotation were mutually stochastically independent. The autospectral and cross-spectral density functions of the induced gravity environment imparted to scientific apparatus rigidly attached to the spacecraft were calculated from the rotation rate spectral density functions via linearized inertial frame to body-fixed principal axis frame transformation formulae. The induced gravity process was a Gaussian one with zero mean value. Transformation formulae were used to rotate the principal axis body-fixed frame to which the rotation rate and induced gravity vector were referred to a body-fixed frame in which the components of the induced gravity vector were stochastically independent. Rice's theory of exceedances was used to calculate expected exceedance rates of the components of the rotation and induced gravity vector processes.

Fichtl, G. H.; Holland, R. L.

1978-01-01

409

Stochastic Gravity: Theory and Applications  

NASA Astrophysics Data System (ADS)

Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has, in addition, sources due to the noise kernel. The noise kernel is the vacuum expectation value of the (operator-valued) stress-energy bitensor, which describes the fluctuations of quantum-matter fields in curved spacetimes. A new improved criterion for the validity of semiclassical gravity may also be formulated from the viewpoint of this theory. In the first part of this review we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. The axiomatic approach is useful to see the structure of the theory from the framework of semiclassical gravity, showing the link from the mean value of the stress-energy tensor to the correlation functions. The functional approach uses the Feynman-Vernon influence functional and the Schwinger-Keldysh closed-time-path effective action methods. In the second part, we describe three applications of stochastic gravity. First, we consider metric perturbations in a Minkowski spacetime, compute the two-point correlation functions of these perturbations and prove that Minkowski spacetime is a stable solution of semiclassical gravity. Second, we discuss structure formation from the stochastic-gravity viewpoint, which can go beyond the standard treatment by incorporating the full quantum effect of the inflaton fluctuations. Third, using the Einstein-Langevin equation, we discuss the backreaction of Hawking radiation and the behavior of metric fluctuations for both the quasi-equilibrium condition of a black-hole in a box and the fully nonequilibrium condition of an evaporating black hole spacetime. Finally, we briefly discuss the theoretical structure of stochastic gravity in relation to quantum gravity and point out directions for further developments and applications.

Hu, Bei Lok; Verdaguer, Enric

2008-05-01

410

Ocean gravity and geoid determination  

NASA Technical Reports Server (NTRS)

Gravity anomalies have been recovered in the North Atlantic and the Indian Ocean regions. Comparisons of 63 2 deg x 2 deg mean free air gravity anomalies recovered in the North Atlantic area and 24 5 deg x 5 deg mean free air gravity anomalies in the Indian Ocean area with surface gravimetric measurements have shown agreement to + or - 8 mGal for both solutions. Geoids derived from the altimeter solutions are consistent with altimetric sea surface height data to within the precision of the data, about + or - 2 m.

Kahn, W. D.; Siry, J. W.; Brown, R. D.; Wells, W. T.

1979-01-01

411

Ocean gravity and geoid determination  

NASA Technical Reports Server (NTRS)

Gravity anomalies have been recovered in the North Atlantic and the Indian Ocean regions. Comparisons of 63 2 deg x 2 deg mean free air gravity anomalies recovered in the North Atlantic area and 24 5 deg x 5 deg mean free air gravity anomalies in the Indian Ocean area with surface gravimetric measurements have shown agreement to + or - 8 mgals for both solutions. Geoids derived from the altimeter solutions are consistent with altimetric sea surface height data to within the precision of the data, about + or - 2 meters.

Kahn, W. D.; Siry, J. W.; Brown, R. D.; Wells, W. T.

1977-01-01

412

Zero Temperature Quark Matter Equation of State.  

National Technical Information Service (NTIS)

An equation of state is computed for a plasma of one flavor quarks interacting through some phenomenological potential, in the Hartree approximation, at zero temperature. Assuming that the confining potential is scalar and color-independent, it is shown t...

F. Grassi

1987-01-01

413

Military Family Projects at Zero to Three  

MedlinePLUS

... now available for purchase from the Zero To Three Bookstore. CLICK HERE TO LEARN MORE! Learn More ... Learning Course) - For early child education professionals, these 3 twenty-minute interactive e-learning modules offer insights ...

414

Zero Trust Intrusion Containment for Telemedicine.  

National Technical Information Service (NTIS)

Intrusion Management Systems (IMS) serve to protect complex computer systems from unauthorized intrusions. Our objective is the design and analysis of 'zero-trust' Intrusion Tolerant Systems. These are systems built under the extreme assumption that all i...

A. K. Sood Y. Huang R. Simon E. White K. Cleary

2002-01-01

415

The Effect of Gravity on the Combustion of Bulk Metals  

NASA Technical Reports Server (NTRS)

In recent years, metal combustion studies at the University of Colorado have focused on the effects of gravity (g) on the ignition and burning behavior of bulk metals. The impetus behind this effort is the understanding of the ignition conditions and flammability properties of structural metals found in oxygen (O2) systems for space applications. Since spacecraft are subjected to higher-than-1g loads during launch and reentry and to a zero-gravity environment while in orbit, the study of ignition and combustion of bulk metals at different gravitational accelerations is of great practical concern. From the scientific standpoint, studies conducted under low gravity conditions provide simplified boundary conditions, since buoyancy is removed, and make possible the identification of fundamental ignition and combustion mechanisms. This investigation is intended to provide experimental verification of the influence of natural convection on the burning behavior of metals. In addition, the study offers the first findings of the influence of gravity on ignition of bulk metals and on the combustion mechanism and structure of metal-oxygen, vapor-phase diffusion flames in a buoyancy-free environment. Titanium (Ti) and magnesium (Mg) metals were chosen because of their importance as elements of structural materials and their simple chemical composition-pure metals instead of multicomponent alloys to simplify chemical and spectroscopic analyses. In addition, these elements present the two different combustion modes observed in metals: heterogeneous or surface burning (for Ti) and homogeneous or gas-phase reaction (for Mg). Finally, Mg, Ti, and their oxides exhibit a wide range of thermophysical and chemical properties. Metal surface temperature profiles, critical and ignition temperatures, propagation rates, burning times, and spectroscopic measurements are obtained under normal and reduced gravity. Visual evidence of all phenomena is provided by high-speed photography.

Branch, Melvyn C.; Abbud-Madrid, Angel; Daily, John W.

1997-01-01

416

Local gravity anomalies produced by dislocation sources  

Microsoft Academic Search

Rundle (1979) and Walsh and Rice (1979) have shown that the change in the vertical component of gravity is proportional to uplift for a spherical source of dilation and for slip on an infinitely long dip-slip fault. In the first case, no free air gravity anomaly is produced and in the second case no Bouguer gravity anomaly. Gravity anomalies due

J. C. Savage

1984-01-01

417

Complete spherical Bouguer gravity anomalies over Australia  

Microsoft Academic Search

Complete (or refined) spherical Bouguer gravity anomalies have been computed for all 1 095 065 land gravity observations in the June 2007 release of the Australian national gravity database. The spherical Bouguer shell contribution was computed using the supplied ground elevations of the gravity observations. The spherical terrain corrections, residual to each Bouguer shell, were computed on a 9 arc-second

M. Kuhn; W. E. Featherstone; J. F. Kirby

2009-01-01

418

Bouguer gravity anomalies in West Virginia  

Microsoft Academic Search

Four regional gravity features in West Virginia primarily reflect major basement structures, intra-basement ultramafics and Alleghenian structural grain. The central West Virginia gravity high corresponds with the southern and central West Virginia basement arches. The adjacent western West Virginia gravity low correlates with Rome trough basement structure. Calculated gravity profiles, magnetics, deep well and seismic data support the relationship of

B. R. Kulander; S. L. Dean

1985-01-01

419

The Earth's Gravity and Its Geological Significance.  

ERIC Educational Resources Information Center

Discussed is the earth's gravity and its geological significance. Variations of gravity around the earth can be produced by a great variety of possible distributions of density within the earth. Topics discussed include isostasy, local structures, geological exploration, change of gravity in time, and gravity on the moon and planets. (DS)

Cook, A. H.

1980-01-01

420

Gravity over coronae and chasmata on Venus  

Microsoft Academic Search

The global spherical harmonic model of Venus' gravity field MGNP60FSAAP, with horizontal resolution of about 600 km, shows that most coronae have little or no signature in the gravity field. Nevertheless, some coronae and some segments of chasmata are associated with distinct positive gravity anomalies. No corona has been found to have a negative gravity anomaly. The spatial coincidence of

Gerald Schubert; William B. Moore; David T. Sandwell

1994-01-01

421

Universal fluctuations of zeros of chaotic wavefunctions  

Microsoft Academic Search

Wavefunctions of one and two-dimensional quantum systems can be parametrized by a finite number of zeros lying in phase space. We study correlations of these zeros for fully chaotic systems in terms of a statistical model based on random polynomials. Excellent agreement is found for the two-point correlation function and nearest-neighbour spacing distribution of this model and the results obtained

P. Leboeuf; P. Shukla

1996-01-01

422

ZeroCopy: Techniques, Benets and Pitfalls  

Microsoft Academic Search

We discuss various approaches intended to improve the data processing performance in OS kernels\\/drivers commonly described as ZeroCopy techniques. The main principle of ZeroCopy is to avoid completely or at least minimize unnecessary data copy operations by the CPU while processing I\\/O data in kernel drivers such as networking stacks and disk storage drivers. Modern CPU and memory architectures provide

Eduard Br

423

Zero-Knowledge and Code Obfuscation  

Microsoft Academic Search

In this paper, we investigate the gap between auxiliary-input zero-knowledge (AIZK) and blackbox-simulation zero-knowledge (BSZK). It is an interestingopen problem whether or not there exists a proto- col which achieves AIZK, but not BSZK. We show that the existence of such a protocol is closely related to the existence of secure code obfus- cators. A code obfuscator is used to

Satoshi Hada

2000-01-01

424

Artificial Gravity Research Project  

NASA Technical Reports Server (NTRS)

Protecting the health, safety, and performance of exploration-class mission crews against the physiological deconditioning resulting from long-term weightlessness during transit and long-term hypogravity during surface operations will require effective, multi-system countermeasures. Artificial gravity (AG), which would replace terrestrial gravity with inertial forces generated by rotating the transit vehicle or by a human centrifuge device within the transit vehicle or surface habitat, has long been considered a potential solution. However, despite its attractiveness as an efficient, multi-system countermeasure and its potential for improving the environment and simplifying operational activities (e.g., WCS, galley, etc.), much still needs to be learned regarding the human response to rotating environments before AG can be successfully implemented. This paper will describe our approach for developing and implementing a rigorous AG Research Project to address the key biomedical research questions that must be answered before developing effective AG countermeasure implementation strategies for exploration-class missions. The AG Research Project will be performed at JSC, ARC, extramural academic and government research venues, and international partner facilities maintained by DLR and IMBP. The Project includes three major ground-based human research subprojects that will lead to flight testing of intermittent short-radius AG in ISS crewmembers after 201 0, continuous long-radius AG in CEV crews transiting to and from the Moon, and intermittent short-radius AG plus exercise in lunar habitats. These human ground-based subprojects include: 1) a directed, managed international short-radius project to investigate the multi-system effectiveness of intermittent AG in human subjects deconditioned by bed rest, 2) a directed, managed long-radius project to investigate the capacity of humans to live and work for extended periods in rotating environments, and 3) a focused, investigator-initiated project to investigate system-specific adaptation to and from rotating environments. The AG Research Project also includes two major animal research subprojects: 1) a directed, managed ground-based subproject using rodents and, possibly, sub-human primates, to address mechanistic issues that cannot be studied in humans, to rapidly develop higher sample numbers than can be achieved in the human subprojects, and to establish feasible parameter operating bands to reduce the breadth of the human subprojects, and 2) a flight subproject using rodents to estimate the physiological effects of long term exposure to hypogravity and to investigate the effects of contamination by terrestrial gravity in estimating AG effectiveness. The animal flight subproject would be performed aboard ISS using the CAM module in approximately the 2008-201 1 timeframe. The paper will first present an overview of the key biomedical research questions to be answered. It will then describe the overall approaches to be utilized in developing and implementing the AG Research Project, including definition of the intended scientific research, management and development approaches, identification of roles and responsibilities, risk management, and definition of project deliverables. The primary focus of the paper will be on the first of the three ground-based human research subprojects, since it is the only one currently in development and is scheduled to start active subject investigations in April of 2005.

Kamman, Michelle R.; Paloski, William H.

2005-01-01

425

Defying gravity using Jenga™ blocks  

NASA Astrophysics Data System (ADS)

This paper describes how Jenga™ blocks can be used to demonstrate the physics of an overhanging tower that appears to defy gravity. We also propose ideas for how this demonstration can be adapted for the A-level physics curriculum.

Tan, Yin-Soo; Yap, Kueh-Chin

2007-11-01

426

ISS Update: Reduced Gravity Education  

NASA Video Gallery

NASA Public Affairs Officer Dan Huot interviews Veronica Seyl, Acting Manager for Reduced Gravity Education. NASA works with students and educators to design experiments for flight testing aboard t...

427

Prototype Moving Base Gravity Gradiometer.  

National Technical Information Service (NTIS)

The report covers the technical studies accomplished during the first six months to design and develop a prototype moving base gravity gradiometer. The scope of work is limited to establishing the instrument and system design parameters during the time pe...

A. J. Robinson C. B. Ames P. M. LaHue R. L. Forward R. W. Peterson

1972-01-01

428

Underground Structures and Gravity Gradiometry.  

National Technical Information Service (NTIS)

This report evaluates the use of gravity gradiometry as a tool to characterize underground facilities. The gradient of the Earth's gravitational field can be used to make inferences about the Earth's mass density field. Mass deficits, such as those produc...

M. W. Maier

2002-01-01

429

Critical Gravity in Four Dimensions  

SciTech Connect

We study four-dimensional gravity theories that are rendered renormalizable by the inclusion of curvature-squared terms to the usual Einstein action with a cosmological constant. By choosing the parameters appropriately, the massive scalar mode can be eliminated and the massive spin-2 mode can become massless. This ''critical'' theory may be viewed as a four-dimensional analogue of chiral topologically massive gravity, or of critical 'new massive gravity' with a cosmological constant, in three dimensions. We find that the on-shell energy for the remaining massless gravitons vanishes. There are also logarithmic spin-2 modes, which have positive energy. The mass and entropy of standard Schwarzschild-type black holes vanish. The critical theory might provide a consistent toy model for quantum gravity in four dimensions.

Lue, H. [China Economics and Management Academy, Central University of Finance and Economics, Beijing 100081 (China); Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen 518060 (China); Pope, C. N. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)

2011-05-06

430

Gravity in a Mine Shaft.  

ERIC Educational Resources Information Center

Discusses the effects of gravity, local density compared to the density of the earth, the mine shaft, centrifugal force, and air buoyancy on the weight of an object at the top and at the bottom of a mine shaft. (JRH)

Hall, Peter M.; Hall, David J.

1995-01-01

431

Unifying Einstein and Palatini gravities  

SciTech Connect

We consider a novel class of f(R) gravity theories where the connection is related to the conformally scaled metric g{sub {mu}{nu}=}C(R)g{sub {mu}{nu}} with a scaling that depends on the scalar curvature R only. We call them C theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C theories include completely new physically distinct gravity theories even when f(R)=R. With nonlinear f(R), C theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C theories are modified. The stability of perturbations about flat space is determined by a simple condition on the Lagrangian.

Amendola, Luca; Enqvist, Kari; Koivisto, Tomi [Institut fuer Theoretische Physik, University of Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Physics Department, University of Helsinki, and Helsinki Institute of Physics, FIN-00014 University of Helsinki (Finland); Institute for Theoretical Physics and Spinoza Institute, Leuvenlaan 4, 3584 CE Utrecht (Netherlands)

2011-02-15

432

Quantum gravity and charge renormalization  

SciTech Connect

We study the question of the gauge dependence of the quantum gravity contribution to the running gauge coupling constant for electromagnetism. The calculations are performed using dimensional regularization in a manifestly gauge-invariant and gauge-condition-independent formulation of the effective action. It is shown that there is no quantum gravity contribution to the running charge, and hence there is no alteration to asymptotic freedom at high energies as predicted by Robinson and Wilczek.

Toms, David J. [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

2007-08-15

433

Minimal massive 3D gravity  

NASA Astrophysics Data System (ADS)

We present an alternative to topologically massive gravity (TMG) with the same ‘minimal’ bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new ‘minimal massive gravity’ has both a positive energy graviton and positive central charges for the asymptotic AdS-boundary conformal algebra.

Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.

2014-07-01

434

Zero/zero rotorcraft certification issues. Volume 2: Plenary session presentations  

NASA Technical Reports Server (NTRS)

This report analyzes the Zero/Zero Rotorcraft Certification Issues from the perspectives of manufacturers, operators, researchers and the FAA. The basic premise behind this analysis is that zero/zero, or at least extremely low visibility, rotorcraft operations are feasible today from both a technological and an operational standpoint. The questions and issues that need to be resolved are: What certification requirements do we need to ensure safety. Can we develop procedures which capitalize on the performance and maneuvering capabilities unique to rotorcraft. Will extremely low visibility operations be economically feasible. This is Volume 2 of three. It presents the operator perspectives (system needs), applicable technology and zero/zero concepts developed in the first 12 months of research of this project.

Adams, Richard J.

1988-01-01

435

A study of IGBT turn-off behavior and switching losses for zero-voltage and zero-current switching  

Microsoft Academic Search

The switching losses of insulated gate bipolar transistors (IGBTs) with zero voltage and zero current switching are compared with the switching losses of IGBTs with hard switching. The turn-off behavior of the IGBT is studied in detail for both zero voltage and zero current switching. The effect of a reverse current during turn-off is also investigated for zero current switching

Keming Chen; Thomas A. Stuart

1992-01-01

436

The challenge of designing biomedical equipment during human research for long duration low-gravity NASA missions  

Microsoft Academic Search

NASA has been studying human adaptation to low-gravity (zero-g) environments for several years, beginning with the first manned space flight in 1961. As both flight and scientific opportunities have steadily increased, NASA has advanced in the development of sophisticated human experiments. Difficulties encountered include the ability to preserve samples for extended duration flights and the development of flight certifiable biomedical

Catherine D. Kramer; Elizabeth M. Kalla

1997-01-01

437

Satellite Gravity Drilling the Earth  

NASA Technical Reports Server (NTRS)

Analysis of satellite-measured gravity and topography can provide crust-to-core mass variation models for new insi@t on the geologic evolution of the Earth. The internal structure of the Earth is mostly constrained by seismic observations and geochemical considerations. We suggest that these constraints may be augmented by gravity drilling that interprets satellite altitude free-air gravity observations for boundary undulations of the internal density layers related to mass flow. The approach involves separating the free-air anomalies into terrain-correlated and -decorrelated components based on the correlation spectrum between the anomalies and the gravity effects of the terrain. The terrain-decorrelated gravity anomalies are largely devoid of the long wavelength interfering effects of the terrain gravity and thus provide enhanced constraints for modeling mass variations of the mantle and core. For the Earth, subcrustal interpretations of the terrain-decorrelated anomalies are constrained by radially stratified densities inferred from seismic observations. These anomalies, with frequencies that clearly decrease as the density contrasts deepen, facilitate mapping mass flow patterns related to the thermodynamic state and evolution of the Earth's interior.

vonFrese, R. R. B.; Potts, L. V.; Leftwich, T. E.; Kim, H. R.; Han, S.-H.; Taylor, P. T.; Ashgharzadeh, M. F.

2005-01-01

438

Satellite borne gravity gradiometer study  

NASA Technical Reports Server (NTRS)

Gravity gradiometry is recognized to be a very difficult instrumentation problem because extremely small differential acceleration levels have to be measured, 0.1 EU corresponds to an acceleration of 10 to the minus 11th power g at two points 1 meter apart. A feasibility model of a gravity gradiometer is being developed for airborne applications using four modified versions of the proven Model VII accelerometers mounted on a slowly rotating fixture. Gravity gradients are being measured to 1.07 EU in a vertical rotation axis orientation. Equally significant are the outstanding operational characteristics such as fast reaction time, low temperature coefficients and high degree of bias stability over long periods of time. The rotating accelerometer gravity gradiometer approach and its present status is discussed and it is the foundation for the orbital gravity gradiometer analyzed. The performance levels achieved in a 1 g environment of the earth and under relatively high seismic disturbances, lend the orbital gravity gradiometer a high confidence level of success.

Metzger, E.; Jircitano, A.; Affleck, C.

1976-01-01

439

Gravity's Smoking Gun?  

NASA Astrophysics Data System (ADS)

We present a new constraint on the biased galaxy formation picture. Gravitational instability theory predicts that the two-point mass density correlation function, ?(r), has an inflection point at the separation r=r0, corresponding to the boundary between the linear and nonlinear regime of clustering, ?~=1. We show how this feature can be used to constrain the biasing parameter b2??g(r)/?(r) on scales r~=r0, where ?g is the galaxy-galaxy correlation function, which is allowed to differ from ?. We apply our method to real data: the ?g(r), estimated from the Automatic Plate Measuring (APM) galaxy survey. Our results suggest that the APM galaxies trace the mass at separations r>~5 h-1 Mpc, where h is the Hubble constant in units of 100 km s-1 Mpc-1. The present results agree with earlier studies, based on comparing higher order correlations in the APM with weakly nonlinear perturbation theory. Both approaches constrain the b factor to be within 20% of unity. If the existence of the feature that we identified in the APM ?g(r)-the inflection point near ?g=1-is confirmed by more accurate surveys, we may have discovered gravity's smoking gun: the long-awaited ``shoulder'' in ?, predicted by Gott and Rees 25 years ago.

Gaztañaga, Enrique; Juszkiewicz, Roman

2001-09-01

440

Threshold Gravity Determination and Artificial Gravity Studies Using Magnetic Levitation  

NASA Technical Reports Server (NTRS)

What is the threshold gravity (minimum gravity level) required for the nominal functioning of the human system? What dosage is required (magnitude and duration)? Do human cell lines behave differently in microgravity in response to an external stimulus? The critical need for a variable gravity simulator is emphasized by recent experiments on human epithelial cells and lymphocytes on the Space Shuttle clearly showing that cell growth and function are markedly different from those observed terrestrially. Those differences are also dramatic between cells grown in space and those in Rotating Wall Vessels (RWV), or NASA bioreactor often used to simulate microgravity, indicating that although morphological growth patterns (three dimensional growth) can be successfully simulated using RWVs, cell function performance is not reproduced - a critical difference. If cell function is dramatically affected by gravity off-loading, then cell response to stimuli such as radiation, stress, etc. can be very different from terrestrial cell lines. Yet, we have no good gravity simulator for use in study of these phenomena. This represents a profound shortcoming for countermeasures research. We postulate that we can use magnetic levitation of cells and tissue, through the use of strong magnetic fields and field gradients, as a terrestrial microgravity model to study human cells. Specific objectives of the research are: 1. To develop a tried, tested and benchmarked terrestrial microgravity model for cell culture studies; 2. Gravity threshold determination; 3. Dosage (magnitude and duration) of g-level required for nominal functioning of cells; 4. Comparisons of magnetic levitation model to other models such as RWV, hind limb suspension, etc. and 5. Cellular response to reduced gravity levels of Moon and Mars.

Ramachandran, N.; Leslie, F.

2005-01-01

441

Evaluation of Gravity Data within the Department of Defense Gravity Library.  

National Technical Information Service (NTIS)

The Department of Defense Gravity Library (DODGL) maintains an automated file of worldwide surface gravity observations. The gravity information in the database has been acquired from numerous sources including many scientific and government organizations...

K. L. Hille

1987-01-01

442

Transmission resonances and zeros in multiband models  

NASA Astrophysics Data System (ADS)

We report on an efficient numerical technique for directly locating transmission resonances and zeros in semiconductor heterostructures using tight-binding multiband models. The quantum transmitting boundary method is employed to generate the inverse of the retarded Green's function GR(E) in the tight-binding representation. The poles of GR(E) are located by solving a nonlinear non-Hermitian eigenvalue problem. The eigenvalues are calculated using a shift and invert nonsymmetric Lanczos algorithm followed by Newton refinement. We demonstrate that resonance line shapes are accurately characterized by the location of the poles and zeros of GR(E) in the complex energy plane. The real part of the pole energy corresponds to the resonance peak and the imaginary part corresponds to the resonance width. A Fano resonance is characterized by a zero-pole pair in the complex energy plane. In the case of an isolated Fano resonance, the zero always occurs on the real energy axis. However, we demonstrate that for overlapping Fano resonances the zeros can move off of the real axis in complex conjugate pairs. This behavior is examined using a simple analytic model for multichannel scattering.

Bowen, R. Chris; Frensley, William R.; Klimeck, Gerhard; Lake, Roger K.

1995-07-01

443

Entropy and temperature of black holes in a gravity's rainbow  

SciTech Connect

The linear relation between the entropy and area of a black hole can be derived from the Heisenberg principle, the energy-momentum dispersion relation of special relativity, and general considerations about black holes. There exist results in quantum gravity and related contexts suggesting the modification of the usual dispersion relation and uncertainty principle. One of these contexts is the gravity's rainbow formalism. We analyze the consequences of such a modification for black hole thermodynamics from the perspective of two distinct rainbow realizations built from doubly special relativity. One is the proposal of Magueijo and Smolin and the other is based on a canonical implementation of doubly special relativity put forward recently by the authors. In these scenarios, we obtain modified expressions for the entropy and temperature of black holes. We show that, for a family of doubly special relativity theories satisfying certain properties, the temperature can vanish in the limit of zero black hole mass. For the Magueijo and Smolin proposal, this is only possible for some restricted class of models with bounded energy and unbounded momentum. With the proposal of a canonical implementation, on the other hand, the temperature may vanish for more general theories; in particular, the momentum may also be bounded, with bounded or unbounded energy. This opens new possibilities for the outcome of black hole evaporation in the framework of a gravity's rainbow.

Galan, Pablo; Mena Marugan, Guillermo A. [Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain)

2006-08-15

444

Slowly rotating relativistic stars in scalar-tensor gravity  

NASA Astrophysics Data System (ADS)

We consider the slowly rotating relativistic stars with a uniform angular velocity in scalar-tensor gravity, and examine the rotational effect around such compact objects. For this purpose, we derive a second order differential equation describing the frame dragging in scalar-tensor gravity and solve it numerically. As a result, we find that the total angular momentum is proportional to the angular velocity even in scalar-tensor gravity. We also show that one can observe the spontaneous scalarization in rotational effects as well as the other stellar properties, if the cosmological value of the scalar field is zero. On the other hand, if the cosmological value of the scalar field is nonzero, the deviation from general relativity can be seen in a wide range of coupling constants. Additionally, we find that, independently of the cosmological value of the scalar field, the deviation from general relativity becomes larger with more massive stellar models. Thus, via precise observations of astronomical phenomena associated with rotating relativistic stars, one may probe not only the gravitational theory in the strong-field regime, but also the existence of a scalar field.

Sotani, Hajime

2012-12-01

445

Perfect magnetic compensation of gravity along a vertical axis  

NASA Astrophysics Data System (ADS)

Magnetic compensation of gravity allows for ground-based experiments to be carried out under weightless conditions at reasonable cost and without the time limitation of systems such as zero-g airplanes or drop towers. Most of the time classical superconducting solenoids are operated to perform such experiments, which lead to a poor quality of the gravity compensation due to the non-ideal shape of the current and field distribution. In order to improve the quality of simulated microgravity, scientists need to build novel ground-based systems fully dedicated to magnetic levitation. The magnetic design of these levitation apparatuses would be based on theoretical studies of magnetic forces and associated field distributions. The work presented in this paper demonstrates the possibility of producing a magnetic force on paramagnetic and diamagnetic materials that is constant, thus providing a uniform gravity compensation, along a segment in a 3D geometry. These results come from both the decomposition in spherical harmonics of the magnetic field and specific conditions applied on the magnetic force. The magnetic field configuration leads to conical-shape isohomogeneity of the resulting acceleration. As an additional remark to previous works, the impossibility to get a magnetic force varying as 1/r2 is briefly described.

Lorin, Clément; Mailfert, Alain; Jeandey, Christian; Masson, Philippe J.

2013-04-01

446

Inferring the depth of the zonal jets on Jupiter and Saturn from odd gravity harmonics  

NASA Astrophysics Data System (ADS)

ABSTRACTThe low-order even <span class="hlt">gravity</span> harmonics J2, J4, and J6 are well constrained for Jupiter and Saturn from spacecraft encounters over the past few decades. These <span class="hlt">gravity</span> harmonics are dominated by the oblate shape and radial density distribution of these gaseous planets. In the lack of any north-south asymmetry, odd <span class="hlt">gravity</span> harmonics will be <span class="hlt">zero</span>. However, the winds on these planets are not hemispherically symmetric, and therefore can contribute to the odd <span class="hlt">gravity</span> harmonics through dynamical variations to the density field. Here it is shown that even relatively shallow winds (reaching ~ 40 bars) can cause considerable odd <span class="hlt">gravity</span> harmonics that can be detectable by NASA's Juno and Cassini missions to Jupiter and Saturn. Moreover, these measurements will have better sensitivity to the odd harmonics than to the high-order even harmonics, which have been previously proposed as a proxy for deep winds. Determining the odd <span class="hlt">gravity</span> harmonics will therefore help constrain the depth of the jets on these planets, and may provide valuable information about the planet's core and structure.</p> <div class="credits"> <p class="dwt_author">Kaspi, Yohai</p> <p class="dwt_publisher"></p> <p class="publishDate">2013-02-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">447</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.ntis.gov/search/product.aspx?ABBR=PB212999"> <span id="translatedtitle">Principal Facts for <span class="hlt">Gravity</span> Stations in Sulphur Springs Valley, Arizona.</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.ntis.gov/search/index.aspx">National Technical Information Service (NTIS)</a></p> <p class="result-summary">Observed <span class="hlt">gravity</span> values, station locations, terrain corrections, and Bouguer <span class="hlt">gravity</span> data are provided in tabular form for approximately 410 <span class="hlt">gravity</span> observations in Sulphur Springs Valley, Arizona. (Author)</p> <div class="credits"> <p class="dwt_author">D. L. Peterson</p> <p class="dwt_publisher"></p> <p class="publishDate">1972-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">448</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/6974702"> <span id="translatedtitle">Environmental applications of <span class="hlt">gravity</span> surveying</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">The Allis Park Sanitary Landfill Company developed a new landfill near Onway, Michigan in an area which has glacial alluvium and glacial till overlying limestone. There are several solution karst features in the region and some critics had maintained that a new karst collapse could rupture the liner system and allow escape of leachate into the groundwater. The <span class="hlt">gravity</span> survey was conducted to determine the extent of any karst development at the site. The first portion of the survey was two profiles over some karst features located about five miles southeast of the proposed landfill. These showed negative <span class="hlt">gravity</span> anomalies. The survey of the proposed landfill site resulted in a 50 microGal contour map of the area and also showed a negative anomaly. This could be due to either elevation variations on the till to limestone bedrock surface or to karst development within the limestone. Because there was no evidence of historic development of new karst features in the region, the <span class="hlt">gravity</span> anomaly was not further investigated. In another <span class="hlt">gravity</span> survey, a large retail department store had been remodeled and extended over an area previously occupied by an auto service center. The removal of a waste oil storage tank (UST) had not been documented and the environmental consultant (KEMRON, Inc.) proposed that a <span class="hlt">gravity</span> survey be used to find the tank location. This proposal was based on calculations of the <span class="hlt">gravity</span> effects of a UST. The survey resulted in a four-microGal contour map which showed a couple of anomalies which could be due to a tank or a backfilled tank excavation. During the survey, a store employee identified the previous location of the tank and explained that she had personally witnessed its removal. Based on the employee's eye-witness account of the tank removal and the coincidence of her indicated tank location with one of the <span class="hlt">gravity</span> anomalies the authors recommended the site be granted clean closure.</p> <div class="credits"> <p class="dwt_author">Barrows, L.J. (Illinois State Univ., Normal, IL (United States)); Nesbit, L.C. (KEMRON Environmental Services, Novi, MI (United States)); Khan, W.A. (Environmental Science Engineering, Phoenix, AZ (United States))</p> <p class="dwt_publisher"></p> <p class="publishDate">1994-04-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">449</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.osti.gov/scitech/biblio/69559"> <span id="translatedtitle"><span class="hlt">Gravity</span> and global symmetries</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p class="result-summary">There exists a widely held notion that gravitational effects can strongly violate global symmetries. If this is correct, it may lead to many important consequences. We argue, in particular, that nonperturbative gravitational effects in the axion theory lead to a strong violation of {ital CP} invariance unless they are suppressed by an extremely small factor {ital g}{approx_lt}10{sup {minus}82}. One could hope that this problem disappears if one represents the global symmetry of a pseudoscalar axion field as a gauge symmetry of the Ogievetsky-Polubarinov-Kalb-Ramond antisymmetric tensor field. We show, however, that this gauge symmetry does not protect the axion mass from quantum corrections. The amplitude of gravitational effects violating global symmetries could be strongly suppressed by {ital e}{sup {minus}{ital S}}, where {ital S} is the action of a wormhole which may absorb the global charge. Unfortunately, in a wide variety of theories based on the Einstein theory of <span class="hlt">gravity</span> the action appears to be fairly small, {ital S}{similar_to}10. However, we find that the existence of wormholes and the value of their action are extremely sensitive to the structure of space on the nearly Planckian scale. We consider several examples (Kaluza-Klein theory, conformal anomaly, {ital R}{sup 2} terms) which show that modifications of the Einstein theory on the length scale {ital l}{approx_lt}10{ital M}{sub {ital P}}{sup {minus}1} may strongly suppress violation of global symmetries. We find also that in string theory there exists an additional suppression of topology change by the factor {ital e}{sup {minus}8{pi}2}/{ital g}{sup 2}. This effect is strong enough to save the axion theory for the natural values of the stringy gauge coupling constant.</p> <div class="credits"> <p class="dwt_author">Kallosh, R.; Linde, A.; Linde, D.; Susskind, L. [Department of Physics, Stanford University, Stanford, California 94305-4060 (United States)] [Department of Physics, Stanford University, Stanford, California 94305-4060 (United States); [California Institute of Technology, Pasadena, California 91125 (United States)</p> <p class="dwt_publisher"></p> <p class="publishDate">1995-07-15</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">450</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19900004632&hterms=large+hominid&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlarge%2Bhominid"> <span id="translatedtitle"><span class="hlt">Gravity</span> receptors and responses</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">The overall process of <span class="hlt">gravity</span> sensing and response processes in plants may be divided conveniently into at least four components or stages: Stimulus susception (a physical event, characteristically the input to the G receptor system of environmental information about the G force magnitude, its vector direction, or both); information perception (an influence of susception on some biological structure or process that can be described as the transformation of environmental information into a biologicallly meaningful change); information transport (the export, if required, of an influence (often chemical) to cells and organs other than those at the sensor location); and biological response (almost always (in plants) a growth change of some kind). Some analysts of the process identify, between information perception and information transport, an additional stage, transduction, which would emphasize the importance of a transformation from one form of information to another, for example from mechanical statolith displacement to an electric, chemical, or other alteration that was its indirect result. These four (or five) stages are temporally sequential. Even if all that occurs at each stage can not be confidently identified, it seems evident that during transduction and transport, matters dealt with are found relatively late in the information flow rather than at the perception stage. As more and more is learned about the roles played by plant hormones which condition the G responses, the mechanism(s) of perception which should be are not necessarily better understood. However, if by asking the right questions and being lucky with experiments perhaps the discovery of how some process (such as sedimentation of protoplasmic organelles) dictates what happens down stream in the information flow sequence may be made.</p> <div class="credits"> <p class="dwt_author">Brown, Allan H.</p> <p class="dwt_publisher"></p> <p class="publishDate">1989-01-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">451</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20140004804&hterms=gravity&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2522gravity%2522"> <span id="translatedtitle">2014 Artificial <span class="hlt">Gravity</span> Workshop</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p class="result-summary">Because artificial <span class="hlt">gravity</span> (AG) has the unique feature - in contrast to the traditional countermeasures - of protecting all physiological systems in all individuals against the effects of weightlessness, and because it has become of concern that astronauts might experience increased intracranial pressures in space, it should be considered to use AG for human health protection during future deep space missions. The following AG scenarios should be evaluated: 1) Intermittent intra-vehicular, 2) intermittent part-of-vehicle, or 3) continuous whole-vehicle centrifugation. A technical feasibility study has indicated that continuous whole-vehicle centrifugation is possible during a transit to Mars but that the physiological requirements are needed before the final configuration can be determined. Results of previous ground studies have shown some protective effects on muscle, bone, central nervous system, heart and circulation of intermittent short-radius centrifugation, but more research is needed to better understand the relationship between physiological responses and G-levels between 0 and 1 for definition of 1) minimum requirements for AG engineering, and 2) protective effects of Martian and Lunar surface G-levels. AG rodent research on ISS can be a starting point for this, which is possible from 2015 with the NASA and JAXA rodent habitats. Several ground based short-radius human centrifuges are available worldwide today for intermittent AG research, whereas only a few long-radius centrifuges exist for long-duration exposures (US and Russia). An international AG research program encountering animal investigations on ISS and short- and long-radius centrifugations in humans on the ground should be initiated by NASA as soon as possible for definition of the life science AG technical requirements for future human deep space missions.</p> <div class="credits"> <p class="dwt_author">Cromwell, Ronita</p> <p class="dwt_publisher"></p> <p class="publishDate">2014-01-01</p> </div> </div> </div> </div> <div class="floatContainer result " lang="en"> <div class="resultNumber element">452</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://adsabs.harvard.edu/abs/2012PhLB..715..260M"> <span id="translatedtitle">Dual massive <span class="hlt">gravity</span></span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p class="result-summary">The linearized massive <span class="hlt">gravity</span> in three dimensions, over any maximally symmetric background, is known to be presented in a self-dual form as a first order equation which encodes not only the massive Klein-Gordon type field equation but also the supplementary transverse-traceless conditions. We generalize this construction to higher dimensions. The appropriate dual description in d dimensions, additionally to a (non-symmetric) tensor field h, involves an extra rank-(d-1) field equivalently represented by the torsion rank-3 tensor. The symmetry condition for h arises on-shell as a consequence of the field equations. The action principle of the dual theory is formulated. The focus has been made on four dimensions. Solving one of the fields in terms of the other and putting back in the action one obtains two other equivalent formulations of the theory in which the action is quadratic in derivatives. In one of these representations the theory is formulated entirely in terms of a rank-2 non-symmetric tensor h. This quadratic theory is not identical to the Fierz-Pauli theory and contains the coupling between the symmetric and antisymmetric parts of h. Nevertheless, the only singularity in the propagator is the same as in the Fierz-Pauli theory so that only the massive spin-2 particle is propagating. In the other representation, the theory is formulated in terms of the torsion rank-3 tensor only. We analyze the conditions which follow from the field equations and show that they restrict to 5 degrees of freedom thus producing an alternative description to the massive spin-2 particle. A generalization to higher dimensions is suggested.</p> <div class="credits"> <p class="dwt_author">Morand, Kevin; Solodukhin, Sergey N.</p> <p class="dwt_publisher"></p> <p class="publishDate">2012-08-01</p> </div> </div> </div> </div> <div class="floatContainer result odd" lang="en"> <div class="resultNumber element">453</div> <div class="resultBody element"> <p class="result-title"><a target="resultTitleLink" href="http://science.gov/scigov/link.html?type=RESULT&redirectUrl=http://www.compadre.org/Repository/document/ServeFile.cfm?ID=8053&DocID=718"> <span id="translatedtitle">Absolute <span class="hlt">Zero</span>: Community Education Outreach Guide</span></a>  </p> <div class="result-meta"> <p class="source"><a target="_blank" id="logoLink" href="http://nsdl.org/nsdl_dds/services/ddsws1-1/service_explorer.jsp">NSDL Natio