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Sample records for zero gravity

  1. Zero gravity liquid mixer

    NASA Technical Reports Server (NTRS)

    Booth, F. W.; Bruce, R. A. (Inventor)

    1973-01-01

    An apparatus for mixing liquids under conditions of zero gravity is disclosed. The apparatus is comprised of a closed reservoir for the liquids, with a means for maintaining a positive pressure on the liquids in the reservoir. A valved liquid supply line is connected to the reservoir for supplying the reservoir with the liquids to be mixed in the reservoir. The portion of the reservoir containing the liquids to be mixed is in communication with a pump which alternately causes a portion of the liquids to flow out of the pump and into the reservoir to mix the liquids. The fluids in the reservoir are in communication through a conduit with the pump which alternately causes a portion of the fluids to flow out of the pump and into the sphere. The conduit connecting the pump and sphere may contain a nozzle or other jet-forming structure such as a venturi for further mixing the fluids.

  2. Zero-gravity movement studies

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  3. Modeling of zero gravity venting

    NASA Technical Reports Server (NTRS)

    Merte, H., Jr.

    1984-01-01

    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.

  4. Tribology experiment in zero gravity

    NASA Technical Reports Server (NTRS)

    Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.

    1984-01-01

    A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates studies of the motion of liquid lubricants over solid surfaces as controlled by interfacial and capillary forces. Observations were made of phenomena associated with the liquid on one solid surface and also with the liquid between a pair of closely spaced surfaces. Typical photographic records obtained on Spacelab 1 are described.

  5. Tribology Experiment in Zero Gravity

    NASA Technical Reports Server (NTRS)

    Pan, C. H. T.; Gause, R. L.; Whitaker, A. F.; Finckenor, M. M.

    2015-01-01

    A tribology experiment in zero gravity was performed during the orbital flight of Spacelab 1 to study the motion of liquid lubricants over solid surfaces. The absence of a significant gravitational force facilitates observation of such motions as controlled by interfacial and capillary forces. Two experimental configurations were used. One deals with the liquid on one solid surface, and the other with the liquid between a pair of closed spaced surfaces. Time sequence photographs of fluid motion on a solid surface yielded spreading rate data of several fluid-surface combinations. In general, a slow spreading process as governed by the tertiary junction can be distinguished from a more rapid process which is driven by surface tension controlled internal fluid pressure. Photographs were also taken through the transparent bushings of several experimental journal bearings. Morphology of incomplete fluid films and its fluctuation with time suggest the presence or absence of unsteady phenomena of the bearing-rotor system in various arrangements.

  6. Zero-gravity venting of three refrigerants

    NASA Technical Reports Server (NTRS)

    Labus, T. L.; Aydelott, J. C.; Amling, G. E.

    1974-01-01

    An experimental investigation of venting cylindrical containers partially filled with initially saturated liquids under zero-gravity conditions was conducted in the NASA Lewis Research Center 5-second zero-gravity facility. The effect of interfacial mass transfer on the ullage pressure response during venting was analytically determined, based on a conduction analysis applied to an infinitely planer (flat) liquid-vapor interface. This pressure response was compared with both the experimental results and an adiabatic decompression computation.

  7. Artificial gravity - A countermeasure for zero gravity

    NASA Technical Reports Server (NTRS)

    Nicogossian, A. E.; Mccormack, P. D.

    1987-01-01

    Current knowledge on artificial gravity is presented with emphasis placed on the unique characteristics of such an environment and their effects on crew performance and vehicle habitability. A parametric optimization of the vehicle size and operation is performed. The following set of 'optimum' parameter values is obtained: a cost of 15.8 billion dollars, a radius of 80 feet, a rotation rate of 4.8 rpm, and a g-value of 0.62. Consideration is also given to the problems of adaptation, retention of adaptation, and simultaneous adaptation to both nonrotating and rotating environments.

  8. Zero-gravity quantity gaging system

    NASA Technical Reports Server (NTRS)

    1989-01-01

    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.

  9. Zero gravity tissue-culture laboratory

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  10. Containing Hair During Cutting In Zero Gravity

    NASA Technical Reports Server (NTRS)

    Haines, Richard F.

    1992-01-01

    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.

  11. Zero Gravity Research Facility User's Guide

    NASA Technical Reports Server (NTRS)

    Thompson, Dennis M.

    1999-01-01

    The Zero Gravity Research Facility (ZGF) is operated by the Space Experiments Division of the NASA John H. Glenn Research Center (GRC) for investigators sponsored by the Microgravity Science and Applications Division of NASA Headquarters. This unique facility has been utilized by scientists and engineers for reduced gravity experimentation since 1966. The ZGF has provided fundamental scientific information, has been used as an important test facility in the space flight hardware design, development, and test process, and has also been a valuable source of data in the flight experiment definition process. The purpose of this document is to provide information and guidance to prospective researchers regarding the design, buildup, and testing of microgravity experiments.

  12. Zero-gravity open-type urine receptacle

    NASA Technical Reports Server (NTRS)

    Girala, A. S.

    1972-01-01

    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 to urinate. This device may be used in a gravity environment, varying from zero gravity to earth gravity, such as may be experienced in a space station or space base.

  13. Damping performance of bean bag dampers in zero gravity environments

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Chen, Tianning; Wang, Xiaopeng

    2016-06-01

    Bean bag dampers (BBDs), developed from impact damping technology, have been widely applied in engineering field to attenuate the vibration of a structural system. The damping effect of a BBD on vibration control in ground gravity environments is good, but its performance in zero gravity environments is not clear, and there are few studies on it. Therefore, the damping effect of BBDs in zero gravity environments was investigated based on the discrete element method (DEM) in this paper. Firstly, a three-dimensional DEM model of a BBD was established, and the damping effects of the single degree of freedom (SDOF) systems with BBDs and non-obstructive particle dampers (NOPDs) in zero gravity environments were compared. Moreover, the influences of the diameter of the inner ball, the tightness of BBD, the vibration frequency of SDOF system and the gap between BBD and cavity on the vibration reduction effect of BBD in zero gravity environments were also studied, and the results were compared with the system with BBD in ground gravity environments. There are optimum ranges of the diameter of the inner ball, tightness and gap for BBD, and the effects of these parameters on the damping performances of BBD in gravity and zero gravity environments are similar in evolving trends, and the values are without big differences in the optimum ranges. Thereby the parameter selection in BBD design in zero gravity environments is similar to that in gravity environments. However, the diameter of BBD should be a slightly larger than the size of the cavity when the structures with BBD work in zero gravity environments. The BBD is supposed to be picked tightly when the vibration frequency is high, and the BBD has better to be picked more tightly in zero gravity environments. These results can be used as a guide in the design of BBDs in zero gravity environments.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

  15. Experiments with the Skylab fire detectors in zero gravity

    NASA Technical Reports Server (NTRS)

    Linford, R. M. F.

    1972-01-01

    The Skylab fire detector was evaluated in a zero gravity environment. To conduct the test, small samples of spacecraft materials were ignited in a 5 psi oxygen-rich atmosphere inside a combustion chamber. The chamber free-floated in the cabin of a C-135 aircraft, as the aircraft executed a Keplerian parabola. Up to 10 seconds of zero-gravity combustion were achieved. The Skylab fire-detector tubes viewed the flames from a simulated distance of 3m, and color movies were taken to record the nature of the fire. The experiments established the unique form of zero-gravity fires for a wide range of materials. From the tube-output data, the alarm threshold and detector time constant were verified for the Skylab Fire Detection System.

  16. Combustion of solid carbon rods in zero and normal gravity

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

  17. The International Heat Pipe Experiment. [ten experiments in zero gravity

    NASA Technical Reports Server (NTRS)

    Mcintosh, R.; Ollendorf, S.; Harwell, W.

    1975-01-01

    On October 4, 1974 the International Heat Pipe Experiment was launched aboard a Black Brant Sounding Rocket from White Sands, New Mexico. The flight provided six minutes of near zero gravity during which a total of ten separate heat pipe experiments were performed. The fifteen heat pipes which were tested represent some of the latest American and European technology. This flight provided the first reported zero gravity data on cryogenic and flat plate vapor chamber heat pipes. Additionally, valuable design and engineering data was obtained on several other heat pipe configurations. This paper will discuss the payload and four of the individual experiments.

  18. Passive zero-gravity leg restraint

    NASA Technical Reports Server (NTRS)

    Miller, Christopher R. (Inventor)

    1989-01-01

    A passive zero or microgravity leg restraint is described which includes a central support post with a top and a bottom. Extending from the central support post are a calf pad tab, to which calf pad is attached, and a foot pad tab, to which foot tab is attached. Also extending from central support post are knee pads. When the restraint is in use the user's legs are forced between pads by a user imposed scissors action of the legs. The user's body is then supported in a zero or microgravity neutral body posture by the leg restraint. The calf pad has semi-ridig elastic padding material covering structural stiffener. The foot pad has padding material and a structural stiffener. Knee pads have s structural tube stiffener at their core.

  19. Glass fining experiments in zero gravity

    NASA Technical Reports Server (NTRS)

    Smith, H. D.

    1977-01-01

    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.

  20. Solution growth of crystals in zero gravity

    NASA Technical Reports Server (NTRS)

    Lai, R. B.

    1982-01-01

    A series of experiments will be performed in which triglycine sulfate (TGS) crystals will be grown by a low-temperature solution growth technique in the microgravity environment of the orbital Spacelab. Triglycine sulfate (TGS) crystals will be grown in the Fluid Experiment System (FES) facility on Spacelab 3 by slowly extracting heat at a controlled rate through a seed crystal of TGS suspended on an insulated sting in a saturated solution of TGS. The FES rack assembly designed for SL-3 is shown in Figure I-1, and a detailed view of the test cell layout is presented in Figure I-2. Variations in the liquid density, solution concentration and temperature around the growing crystal will be studied using a variety of techniques, such as schlieren, shadowgraph, and interferometric measurements. Growth in Earth gravity will also be studied by the same optical techniques, and in both cases the resulting crystalline features will be compared and correlated with the growth conditions.

  1. The response of single human cells to zero-gravity

    NASA Technical Reports Server (NTRS)

    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

    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.

  2. Acceleration display system for aircraft zero-gravity research

    NASA Technical Reports Server (NTRS)

    Millis, Marc G.

    1987-01-01

    The features, design, calibration, and testing of Lewis Research Center's acceleration display system for aircraft zero-gravity research are described. Specific circuit schematics and system specifications are included as well as representative data traces from flown trajectories. Other observations learned from developing and using this system are mentioned where appropriate. The system, now a permanent part of the Lewis Learjet zero-gravity program, provides legible, concise, and necessary guidance information enabling pilots to routinely fly accurate zero-gravity trajectories. Regular use of this system resulted in improvements of the Learjet zero-gravity flight techniques, including a technique to minimize later accelerations. Lewis Gates Learjet trajectory data show that accelerations can be reliably sustained within 0.01 g for 5 consecutive seconds, within 0.02 g for 7 consecutive seconds, and within 0.04 g for up to 20 second. Lewis followed the past practices of acceleration measurement, yet focussed on the acceleration displays. Refinements based on flight experience included evolving the ranges, resolutions, and frequency responses to fit the pilot and the Learjet responses.

  3. Zero-Gravity Fuel-Cell Product-Water Accumulator

    NASA Technical Reports Server (NTRS)

    Barrera, Thomas P.

    1989-01-01

    Assortment of documents describes simple, passive system that removes water formed from reaction of hydrogen and oxygen in proton-exchange-membrane fuel cell. Designed for use in zero gravity, system does not require any machinery or external source of power. Works by capillary action and differential pressure.

  4. Transient Heat Transfer in Zero Gravity Environment

    NASA Technical Reports Server (NTRS)

    Giarratano, P. G.; Arp, V. D.; Kumakawa, A.

    1985-01-01

    The objective is to provide computer codes and/or correlations for application in the design of transient heat transfer systems. The mathematical models in the computer codes are being tested by experimental data obtained in the laboratory using optical techniques. The elimination of natural convection (buoyancy) in the experimental data obtained in zero-g (KC-135) facilitates the study of thermal expansion effects which is of interest in the development and testing of the mathematical models of the transient heat transfer. Initial flight in the KC 135 (June 1983) suggested some modifications to the experimental apparatus and the data acquisition technique (high speed video will replace high speed movies for recording optical records generated during the experiments). A series of KC-135 flights with this experiment on board are scheduled for summer/fall 1984. The acquisition of the aforementioned data using interferometry and beam deflection optical techniques is anticipated. The measurements provide time dependent temperature fields above a horizontal heater surface submerged in a static fluid (Freon 13). The heater surface is electrically heated for a time interval approximately 0.100 sec. during which the data are optically recorded.

  5. 4He crystals in superfluid under zero gravity.

    PubMed

    Takahashi, Takuya; Nomura, Ryuji; Okuda, Yuichi

    2012-03-01

    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

  6. Experiments on thermoacoustic convection heat transfer in gravity and zero-gravity environments

    NASA Technical Reports Server (NTRS)

    Parang, Masood; Salah-Eddine, Adel

    1987-01-01

    The results of an experimental study of thermoacoustic convection (TAC) heat transfer in gravity and zero-gravity environments are presented. The experimental apparatus consisted of a cylinder containing air as the compressible fluid. The enclosed air was heated electrically at the top surface which consisted of a thin high-resistance steel foil connected to a power source. Thermocouples were used to measure the transient temperature of the air on the axis of the cylinder and the heated surface in the both zero-gravity and gravity environments. The zero-gravity tests were performed in the Zero-Gravity Drop Tower Facility of NASA-Lewis Research Center. The experimental results were corrected for the error due to radiation absorption by the thermocouples. A conduction-only numerical heat transfer model was developed to compute the transient air temperature in the cylindrical geometry. The results were compared to the experimental data to determine the significance of the thermoacoustic convection heat transfer mechanism. It is observed that the rate of heat transfer to the air measured during the experiments is consistently higher than that obtained by the conduction-only solution indicating a significant presence of the TAC heat transfer. Further experiments are planned to measure directly (1) the radiative heat transfer contribution to the rise in the air temperature, and (2) the air pressure oscillations within the cylinder that are responsible for the convective heat transfer mode.

  7. Experimental Investigation of Laminar Gas Jet Diffusion Flames in Zero Gravity

    NASA Technical Reports Server (NTRS)

    Cochran, Thomas H.

    1972-01-01

    An experimental program was conducted to study the burning of laminar gas jet diffusion flames in a zero-gravity environment. The tests were conducted in a 2.2-Second-Zero-Gravity Facility and were a part of a continuing effort investigating the effects of gravity on basic combustion processes. The photographic results indicate that steady state gas jet diffusion flames existed in zero gravity but they were geometrically quite different than their normal-gravity counterparts. Methane-air flames were found to be approximately 50 percent longer and wider in zero gravity than in normal gravity.

  8. The response of single human cells to zero gravity

    NASA Technical Reports Server (NTRS)

    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

    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.

  9. Development of a compact dilution refrigerator for zero gravity operation

    NASA Technical Reports Server (NTRS)

    Roach, Pat R.; Helvensteijn, Ben

    1990-01-01

    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.

  10. Development of a compact dilution refrigerator for zero gravity operation

    NASA Astrophysics Data System (ADS)

    Roach, Pat R.; Helvensteijn, Ben

    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.

  11. Development of coatings to control electroosmosis in zero gravity electrophoresis

    NASA Technical Reports Server (NTRS)

    Krupnick, A. C.

    1974-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  13. Cool flames at terrestrial, partial, and near-zero gravity

    SciTech Connect

    Foster, Michael; Pearlman, Howard

    2006-10-15

    Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra<600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; and reduced gravity, {approx}10{sup -2}g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350? deg C (593-623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive-diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results. (author)

  14. Ocular Blood Flow Measured Noninvasively in Zero Gravity

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  15. Zero-Gravity Vortex Vent and PVT Gaging System

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  16. Sediment-transport experiments in zero-gravity

    NASA Technical Reports Server (NTRS)

    Iversen, James D.; Greeley, Ronald

    1987-01-01

    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.

  17. Zero Gravity Cryogenic Vent System Concepts for Upper Stages

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  18. Zero Gravity Cryogenic Vent System Concepts for Upper Stages

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  19. Development of coatings to control electroosmosis in zero gravity electrophoresis

    NASA Technical Reports Server (NTRS)

    Krupnick, A. C.

    1974-01-01

    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 phenomena. Of necessity, factors, such as adhesion, biocompatibility, protein adsorption, and insolubility were considered in this investigation because of the long buffer-coating exposure times required by present space operations. Based upon tests employing microcapillary electrophoresis, it has been found that gamma amino propyl trihydroxysilane produced a coating which provides the lowest potential (minus 3.86 mv) at the surface of shear between the stationary and mobile layers. This coating has been soaked in both borate and saline buffers, up to three months, in a pH range of 6.5 to 10 without deleterious effects or a change in its ability to control electrokinetic effects.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  1. Modeling of zero gravity venting: Studies of two-phase heat transfer under reduced gravity

    NASA Technical Reports Server (NTRS)

    Merte, H., Jr.

    1986-01-01

    The objective is to predict the pressure response of a saturated liquid-vapor system when undergoing a venting or depressurization process in zero gravity at low vent rates. An experimental investigation of the venting of cylindrical containers partially filled with initially saturated liquids was previously conducted under zero-gravity conditions and compared with an analytical model which incorporated the effect of interfacial mass transfer on the ullage pressure response during venting. A new model is presented to improve the estimation of the interfacial mass transfer. Duhammel's superposition integral is incorporated to approximate the transient temperature response of the interface, treating the liquid as a semi-infinite solid with conduction heat transfer. Account is also taken of the condensation taking place within the bulk of a saturated vapor as isentropic expansion takes place. Computational results are presented for the venting of R-11 from a given vessel and initial state for five different venting rates over a period of three seconds, and compared to prior NASA experiments. An improvement in the prediction of the final pressure takes place, but is still considerably below the measurements.

  2. Adiabatic demagnetization refrigerator for use in zero gravity

    NASA Technical Reports Server (NTRS)

    Dingus, Michael L.

    1988-01-01

    In this effort, a new design concept for an adiabatic demagnetization refrigerator (ADR) that is capable of operation in zero gravity has been developed. The design uses a vortex precooler to lower the initial temperature of magnetic salt from the initial space superfluid helium dewar of 1.8 K to 1.1 K. This reduces the required maximum magnetic field from 4 Tesla to 2 Tesla. The laboratory prototype vortex precooler reached a minimum temperature of 0.78 K, and had a cooling power of 1 mW at 1.1 K. A study was conducted to determine the dependence of vortex cooler performance on system element configuration. A superfluid filled capillary heat switch was used in the design. The laboratory prototype ADR reached a minimum temperature of 0.107 K, and maintained temperatures below 0.125 K for 90 minutes. Demagnetization was carried out from a maximum field of 2 T. A soft iron shield was developed that reduced the radial central field to 1 gauss at 0.25 meters.

  3. A helium-3/helium-4 dilution cryocooler for operation in zero gravity

    NASA Technical Reports Server (NTRS)

    Hendricks, John B.

    1988-01-01

    This research effort covered the development of He-3/He-4 dilution cryocooler cycles for use in zero gravity. The dilution cryocooler is currently the method of choice for producing temperatures below 0.3 Kelvin in the laboratory. However, the current dilution cryocooler depends on gravity for their operation, so some modification is required for zero gravity operation. In this effort, we have demonstrated, by analysis, that the zero gravity dilution cryocooler is feasible. We have developed a cycle that uses He-3 circulation, and an alternate cycle that uses superfluid He-4 circulation. The key elements of both cycles were demonstrated experimentally. The development of a true 'zero-gravity' dilution cryocooler is now possible, and should be undertaken in a follow-on effort.

  4. Vortex motion phase separator for zero gravity liquid transfer

    NASA Technical Reports Server (NTRS)

    Howard, Frank S. (Inventor); Fraser, Wilson M., Jr. (Inventor)

    1989-01-01

    A vortex motion phase separator is disclosed for transferring a liquid in a zero gravity environment while at the same time separating the liquid from vapors found within either the sender or the receiving tanks. The separator comprises a rigid sender tank having a circular cross-section and rigid receiver tank having a circular cross-section. A plurality of ducts connects the sender tank and the receiver tank. Disposed within the ducts connecting the receiver tank and the sender tank is a pump and a plurality of valves. The pump is powered by an electric motor and is adapted to draw either the liquid or a mixture of the liquid and the vapor from the sender tank. Initially, the mixture drawn from the sender tank is directed through a portion of the ductwork and back into the sender tank at a tangent to the inside surface of the sender tank, thereby creating a swirling vortex of the mixture within the sender tank. As the pumping action increases, the speed of the swirling action within the sender tank increases creating an increase in the centrifugal force operating on the mixture. The effect of the centrifugal force is to cause the heavier liquid to migrate to the inside surface of the sender tank and to separate from the vapor. When this separation reaches a predetermined degree, control means is activated to direct the liquid conveyed by the pump directly into the receiver tank. At the same time, the vapor within the receiver tank is directed from the receiver tank back into the sender tank. This flow continues until substantially all of the liquid is transferred from the sender tank to the receiver tank.

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

    NASA Technical Reports Server (NTRS)

    Parang, Masood

    1986-01-01

    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.

  6. Forced and natural convection in laminar-jet diffusion flames. [normal-gravity, inverted-gravity and zero-gravity flames

    NASA Technical Reports Server (NTRS)

    Haggard, J. B., Jr.

    1981-01-01

    An experimental investigation was conducted on methane, laminar-jet, diffusion flames with coaxial, forced-air flow to examine flame shapes in zero-gravity and in situations where buoyancy aids (normal-gravity flames) or hinders (inverted-gravity flames) the flow velocities. Fuel nozzles ranged in size from 0.051 to 0.305 cm inside radius, while the coaxial, convergent, air nozzle had a 1.4 cm inside radius at the fuel exit plane. Fuel flows ranged from 1.55 to 10.3 cu cm/sec and air flows from 0 to 597 cu cm/sec. A computer program developed under a previous government contract was used to calculate the characteristic dimensions of normal and zero-gravity flames only. The results include a comparison between the experimental data and the computed axial flame lengths for normal gravity and zero gravity which showed good agreement. Inverted-gravity flame width was correlated with the ratio of fuel nozzle radius to average fuel velocity. Flame extinguishment upon entry into weightlessness was studied, and it was found that relatively low forced-air velocities (approximately 10 cm/sec) are sufficient to sustain methane flame combustion in zero gravity. Flame color is also discussed.

  7. The solidification under zero gravity conditions of binary alloys exhibiting solid state immiscibility

    NASA Technical Reports Server (NTRS)

    Johnson, A. A.; Anantatmula, R. P.; Horylev, R. J.; Gupta, S. P.; Vatne, R. S.

    1975-01-01

    The solidification behavior of gold-silicon alloys containing up to 25 at. % silicon was studied, and a mathematical model of gravity segregation during solidification was developed. A background of knowledge is provided which can be used in the design of zero gravity solidification experiments to be carried out in the 300-ft drop tower, in Aerobee rockets and in future space missions. Such experiments are needed to develop the basic scientific knowledge required for the design of economically viable space manufacturing processes. Some preliminary zero gravity experiments were carried out on a gold-25 at. % silicon alloy using the drop tower facility.

  8. Assessment of geophysical flows for zero-gravity simulation

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  9. Feasibility study of a zero-gravity (orbital) atmospheric cloud physics experiments laboratory

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    A feasibility and concepts study for a zero-gravity (orbital) atmospheric cloud physics experiment laboratory is discussed. The primary objective was to define a set of cloud physics experiments which will benefit from the near zero-gravity environment of an orbiting spacecraft, identify merits of this environment relative to those of groundbased laboratory facilities, and identify conceptual approaches for the accomplishment of the experiments in an orbiting spacecraft. Solicitation, classification and review of cloud physics experiments for which the advantages of a near zero-gravity environment are evident are described. Identification of experiments for potential early flight opportunities is provided. Several significant accomplishments achieved during the course of this study are presented.

  10. Future utilization of space: Silverton Conference on material science and phase transformations in zero-gravity, summary of proceeding

    NASA Technical Reports Server (NTRS)

    Eisner, M. (Editor)

    1975-01-01

    The importance of zero gravity environment in the development and production of new and improved materials is considered along with the gravitational effects on phase changes or critical behavior in a variety of materials. Specific experiments discussed include: fine scale phase separation in zero gravity; glass formation in zero gravity; effects of gravitational perturbations on determination of critical exponents; and light scattering from long wave fluctuations in liquids in zero gravity. It is concluded that the space shuttle/spacelab system is applicable to various fields of interest.

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

    NASA Technical Reports Server (NTRS)

    Srivatsangam, S.

    1976-01-01

    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.

  12. Development of a large support surface for an air-bearing type zero-gravity simulator

    NASA Technical Reports Server (NTRS)

    Glover, K. E.

    1976-01-01

    The methods used in producing a large, flat surface to serve as the supporting surface for an air-bearing type zero-gravity simulator using low clearance, thrust-pad type air bearings are described. Major problems encountered in the use of self-leveled epoxy coatings in this surface are discussed and techniques are recommended which proved effective in overcoming these problems. Performance requirements of the zero-gravity simulator vehicle which were pertinent to the specification of the air-bearing support surface are also discussed.

  13. The International Heat Pipe Experiment. [Black Brant sounding rocket payload zero gravity experiment

    NASA Technical Reports Server (NTRS)

    Mcintosh, R.; Ollendorf, S.; Sherman, A.; Harwell, W.

    1976-01-01

    On October 4, 1974, the International Heat Pipe Experiment was launched aboard a Black Brant sounding rocket from White Sands, New Mexico. The flight provided six min of near zero gravity during which a total of ten separate heat pipe experiments was performed. The fifteen heat pipes tested represent some of the latest American and European technology. This flight provided the first reported zero gravity data on cryogenic and flat plate vapor chamber heat pipes. Additionally, valuable design and engineering data were obtained on several other heat pipe configurations. The payload and several of its experiments are discussed.

  14. Extracting Zero-Gravity Surface Figure of a Mirror

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    The technical innovation involves refinement of the classic optical technique of averaging surface measurements made in different orientations with respect to gravity, so the effects of gravity cancel in the averaged image. Particularly for large, thin mirrors subject to substantial deformation, the further requirement is that mount forces must also cancel when averaged over measurement orientations. The zerogravity surface figure of a mirror in a hexapod mount is obtained by analyzing the summation of mount forces in the frame of the optic as surface metrology is averaged over multiple clockings. This is illustrated with measurements taken from the Space Interferometry Mission (SIM) PT-Ml mirror for both twofold and threefold clocking. The positive results of these measurements and analyses indicate that, from this perspective, a lighter mirror could be used; that is, one might place less reliance on the damping effects of the elliptic partial differential equations that describe the propagation of forces through glass. The advantage over prior art is relaxing the need for an otherwise substantial thickness of glass that might be needed to ensure accurate metrology in the absence of a detailed understanding and analysis of the mount forces. The general insights developed here are new, and provide the basic design principles on which mirror mount geometry may be chosen.

  15. An Experimental Study of Boiling in Reduced and Zero Gravity Fields

    NASA Technical Reports Server (NTRS)

    Usiskin, C. M.; Siegel, R.

    1961-01-01

    A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.

  16. On Calculating the Zero-Gravity Surface Figure of a Mirror

    NASA Technical Reports Server (NTRS)

    Bloemhof, Eric E.

    2010-01-01

    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.

  17. Study on processing immiscible materials in zero gravity

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Eisner, M. (Editor)

    1974-01-01

    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 geophysical fluid models, fluid dynamics, mass transfer processes, electrokinetic separation of large particles, and biophysical and physiological areas.

  19. Statistical support for the ATL program. [microbial growth in zero gravity

    NASA Technical Reports Server (NTRS)

    Hinkelmann, K.; Myers, R. H.

    1976-01-01

    Statistical experimental designs are presented for various numbers of organisms and agar solutions pertinent to the experiment, ""colony growth in zero gravity''. Missions lasting 7 and 30 days are considered. For the designs listed, the statistical analysis of the observations obtained on the space shuttle are outlined.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  2. Investigation of crystal growth in zero gravity environment and investigation of metallic whiskers

    NASA Technical Reports Server (NTRS)

    Davis, J. H.; Lal, R. B.; Walter, H. U.; Castle, J. G., Jr.

    1972-01-01

    Theoretical and experimental work reported relates to the effects of near-zero gravity on growths of crystals and metallic whiskers during Skylab and Apollo flight experiments. Studies on growth and characterization of candidate materials for flight experiments cover indium-bismuth compounds, bismuth single crystals, gallium arsenide films and single crystals, and cadmium whiskers.

  3. Fixed contact line helical interfaces in zero gravity

    NASA Astrophysics Data System (ADS)

    Lowry, Brian J.; Thiessen, David B.

    2007-02-01

    Fluid interfaces supported in microgravity by a helical structure are shown to have a more robust stability than more common structures such as liquid bridges. In particular, helical interfaces can take the form of infinite right circular cylinders over a broad range of configurations. In the case of a single fixed contact line support, the infinite cylinder is stable for all cases in which the pitch to diameter ratio is less than π /√3 (more tightly coiled interfaces). When there are two or more equally spaced fixed contact line supports, the infinite cylinder is stable for all configurations. Furthermore, in the two support case (the double helix), stability persists for all volumes from the cylinder to zero volume, when the pitch to diameter ratio is greater than 2.082 (more loosely coiled interfaces). The equivalent to the axisymmetric Young-Laplace equation is derived for helical interfaces. Interfacial stability is determined from equilibrium branch structure following the application of Maddocks' method by Lowry and Steen [Proc. R. Soc. London, Ser. A 449, 411 (1995)]. Perturbations to finite wavelength disturbances are considered for the case of a single helical support. Overall stability envelopes are presented for single and multiple support cases. Limited experimental results verify the infinite length stability limit for the single helical support case.

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

    PubMed

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

    2000-10-01

    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

  5. Criticality in the slowed-down boiling crisis at zero gravity.

    PubMed

    Charignon, T; Lloveras, P; Chatain, D; Truskinovsky, L; Vives, E; Beysens, D; Nikolayev, V S

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough. PMID:26066249

  6. Criticality in the slowed-down boiling crisis at zero gravity

    NASA Astrophysics Data System (ADS)

    Charignon, T.; Lloveras, P.; Chatain, D.; Truskinovsky, L.; Vives, E.; Beysens, D.; Nikolayev, V. S.

    2015-05-01

    Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.

  7. Some physiological effects of alternation between zero gravity and one gravity

    NASA Technical Reports Server (NTRS)

    Graybiel, A.

    1977-01-01

    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.

  8. Separation of biogenic materials by electrophoresis under zero gravity (L-3)

    NASA Technical Reports Server (NTRS)

    Kuroda, Masao

    1993-01-01

    Electrophoresis separates electrically charged materials by imposing a voltage between electrodes. Though free-flow electrophoresis is used without carriers such as colloids to separate and purify biogenic materials including biogenic cells and proteins in blood, its resolving power and separation efficiency is very low on Earth due to sedimentation, flotation, and thermal convection caused by the specific gravity differences between separated materials and buffer solutions. The objective of this experiment is to make a comparative study of various electrophoresis conditions on the ground and in zero-gravity in order to ultimately develop a method for separating various important 'vial' components which are difficult to separate on the ground.

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

    NASA Technical Reports Server (NTRS)

    Labus, T. L.

    1977-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Lal, R. B.

    1975-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Labus, T. L.

    1976-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Shurney, R. E. (Editor)

    1983-01-01

    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.

  14. Keyhole and weld shapes for plasma arc welding under normal and zero gravity

    NASA Technical Reports Server (NTRS)

    Keanini, R. G.; Rubinsky, B.

    1990-01-01

    A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

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

    NASA Technical Reports Server (NTRS)

    1979-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  17. Equilibrium shape of 4He crystal under zero gravity below 200 mK

    PubMed Central

    Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

    2015-01-01

    Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. 4He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of 4He. We report the relaxation processes of macroscopic 4He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened 4He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff’s origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained. PMID:26601315

  18. Equilibrium shape of (4)He crystal under zero gravity below 200 mK.

    PubMed

    Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

    2015-10-01

    Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. (4)He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of (4)He. We report the relaxation processes of macroscopic (4)He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened (4)He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff's origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained. PMID:26601315

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

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

    PubMed

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

    2012-12-01

    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

  1. Subject Load-Harness Interaction During Zero-Gravity Treadmill Exercise

    NASA Technical Reports Server (NTRS)

    McCrory, Jean L.; Baron, Heidi A.; Derr, Janice A.; Davis, Brian L.; Cavanagh, Peter R.

    1996-01-01

    When astronauts exercise on orbit, a subject load device (SLD) must be used to return the subject back to the supporting surface. The load in the SLD needs to be transferred the body by a harness which typically distributes this load between the pelvis and We shoulders. Through the use of a zero-gravity simulator, this research compared subject comfort and ground reaction forces during treadmill running at three levels of subject load (60%,80%, and 100% of body weight) in two harness designs ("shoulder only" and "waist "and shoulder ").

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    1991-01-01

    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.

  4. Vibrational convection of ternary mixtures in rectangular cavities in zero gravity conditions

    NASA Astrophysics Data System (ADS)

    Lyubimova, T. P.; Zubova, N. A.; Shevtsova, V. M.

    2016-02-01

    The present paper is devoted to the investigation of the onset and nonlinear regimes of the vibrational convection of ternary mixtures in rectangular cavities with rigid boundaries in zero gravity conditions. We consider translational linearly polarized vibrations of finite amplitude and frequency. The axis of vibrations is perpendicular to the temperature gradient. The problem is solved by finite difference method in the framework of 2D unsteady approach. Numerical data on the time evolution of instantaneous and average fields and characteristics of convective flows and concentration fields are obtained for different vibration intensities and aspect ratios.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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 except for the rectus femoris. The tibialis anterior and gluteus maximus were active for longer durations on the eZLS than in parabolic flight during walking. Ground reaction forces were greater with the LM-SLD than with bungees during eZLS locomotion. While the eZLS serves as a ground-based analog, researchers should be aware that subtle, but measurable, differences in kinematics and leg musculature activities exist between the environments. Aside from space applications, zero-gravity locomotion simulators may help medical researchers in the future with development of rehabilitative or therapeutic protocols for injured or ill patients. Zero-gravity locomotion simulators may be used as a ground-based test bed to support future missions for space exploration, and eventually may be used to simulate planetary locomotion in partial gravity environments, including the Moon and Mars. Figure: Zero-gravity Locomotion Simulator at the Cleveland Clinic, Cleveland, Ohio, USA

  6. A Biomechanical Comparison of 1-G and Fully-Loaded Simulated Zero-Gravity Locomotion

    NASA Technical Reports Server (NTRS)

    McCrory, Jean L.

    1997-01-01

    Exercise will almost certainly play an integral part in minimizing the bone mineral loss and muscular atrophy that occur during spaceflight. It has been hypothesized that an effective exercise regimen can be developed to elicit loads on the lower extremities and require muscle actions which resemble those encountered on Earth. The Penn State Zero-Gravity Simulator (PSZS) is a device which suspends subjects horizontally from multiple latex cords, with each cord negating the weight of a limb segment. A treadmill mounted on the wall under the PSZS enables subjects to run in simulated 0G. Subjects wear a harness to which a number of springs, which provide a gravity replacement load, are connected. The opposite end of each spring is connected to the side of the treadmill. During exercise, astronauts currently wear a similar harness in which the spring tethering load pulls at both the waist and shoulders. Ground reaction forces, muscular activations, and joint angles of the left leg during overground, treadmill, and fully-loaded zero-gravity simulated (ZLS) locomotion were assessed in order to gain insight into the effectiveness of the exercise regimen used by NASA to prevent the muscular atrophy and bone demineralization which occur in weightlessness. There were three hypotheses to this research. It was hypothesized that there will be no differences in peak ground reaction forces and peak loading rates between overground gait and gait in the full body weight loaded conditions in the ZLS. A second hypothesis was that that there will be no differences in hip, knee, and ankle joint positions between walking or running overground, on a standard treadmill, and in full bodyweight loaded conditions in the ZLS. The third hypothesis was that the muscular activations, as a percentage of maximal voluntary contraction, will be similar between walking or running overground, on a standard treadmill, and in full body-weight loaded conditions in the ZLS.

  7. Assessment of zero gravity effects on space worker health and safety

    SciTech Connect

    Not Available

    1980-11-01

    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)

  8. Assessment of zero gravity effects on space worker health and safety

    NASA Technical Reports Server (NTRS)

    1980-01-01

    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.

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

    PubMed

    Gao, Zhan; Desai, Jaydev P

    2010-04-01

    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 tension testing. A maximum stretching band is observed in the incremental strain field when a region of tissue passes from compression and enters a state of tension. A new method for estimating the zero-strain state is proposed: the zero strain position is close to, but ahead of the position of the maximum stretching band, or in other words, the tangent of a nominal stress-stretch curve reaches minimum at lambda greater or similar 1. The approach, to identify zero strain by using maximum incremental strain, can be implemented in other types of image-based soft tissue analysis. The experimental results of 10 samples from seven porcine livers are presented and material parameters for the Ogden model fit are obtained. The finite element simulation based on the fitted model confirms the effect of gravity on the deformation of very soft tissue and validates our approach. PMID:20015676

  10. Testing of a Spray-Bar Zero Gravity Cryogenic Vent System for Upper Stages

    NASA Technical Reports Server (NTRS)

    Lak, Tibor; Flachbart, Robin; Nguyen, Han; Martin, James

    1999-01-01

    The capability to vent in zero gravity without resettling is a fundamental technology need that involves practically all uses of subcritical 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 then-nal energy from the propellant. In a cooperative effort, Marshall Space Flight Center's (MSFC's) Multipurpose Hydrogen Test Bed (N4HTB) was used to test a unique "spray bar" TVS system developed by Boeing. A schematic of this system is included in Figure 1. The 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. In the mixing mode, the recirculation pump withdraws liquid from the tank and sprays it radially 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 spray bar heat exchanger element, and is vented overboard. The vented vapor cools the circulated bulk fluid, thereby removing thermal energy and reducing tank pressure. Figure 2 is a plot of ullage pressure (P4) and liquid vapor pressure (PSAI) versus time. 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. The primary advantage of the spray bar configuration is that pressure reduction is achieved independent of liquid and vapor location, thereby enhancing the applicability of normal gravity test data to zero gravity conditions. The in-tank components are minimized with the proposed TVS design. Because the recirculation pump is external to the tank, no electrical power penetration of the tank is required for pump or valve operation. This is especially desirable for L02 tanks since the presence of an electrical ignition source in oxygen represents a critical failure mode. Also, since the critical components (pump, motor, valve, orifice) are external to the tank, system checkout and ground servicing/replacement are easier. For zero-g operation, component replacement external to the tank may be a significant benefit. In addition to satisfying the zero g TVS design objectives, the TVS concept tested offers additional benefits to the integrated subcritical cryogenic storage and launch system.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  13. Human physiological problems in zero gravity - An attempt at understanding through systems analysis

    NASA Technical Reports Server (NTRS)

    White, R. J.; Croston, R. C.

    1974-01-01

    When the experimental situation is that of man exposed to a gravitationless environment for varying periods of time, the possible importance and value of a related modeling effort is readily apparent. One of the main objectives of the Skylab Program, with its missions of 28, 59, and 85 day duration concerned biomedical investigations of various types, and large amounts of relevant experimental data have been gathered and are in the process of being sorted and interpreted. In order to be of eventual usefulness in forming and testing consistent physiological hypotheses concerning the effect of zero gravity on man, a modeling effort was established in 1972 through the General Electric Company, Space Division, Houston, Texas. An account is given of some of the developments completed or in progress as part of this modeling effort. A long-term cardiovascular model and a large model of the systemic circulation are discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  15. Strength capabilities and load requirements while performing torquing tasks in zero gravity

    NASA Technical Reports Server (NTRS)

    Poliner, Jeffrey; Wilmington, Robert P.; Klute, Glenn K.

    1993-01-01

    A generic examination of the loads produced by individuals performing maximal efforts with a torquing tool in zero gravity, to determine operator strength when performing torquing tasks; quantify the loads placed on foot restraints while performing these tasks; and examine effects of orientation and direction of tool rotation on strength effectiveness was conducted. The experiment was conducted aboard NASA's KC-135 reduced-gravity aircraft, using two force plates attached to a test stand, one with a foot restraint. Subjects used a wrench to apply maximum torques to various fittings, in different positions, in clockwise and counterclockwise directions. It was seen that these subjects could produce approximately 400 to 750 N of force, depending on the orientation of the tool and the direction of effort. The most force could be produced when pushing the tool upwards. A force effectiveness ratio (FER) defined as an indication of how much of the subjects' total effort actually went into performing the desired task. Values of FER ranged from 0.55 to 0.90, with the greatest FER occurring with UP and DOWN efforts, and the lowest with AWAY and LEFT efforts. Designers can use these results to set specifications for craft structures; tools can be developed based on the known strength of the tool users; and tasks can be developed to not exceed the crewmembers' capabilities.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  17. A zero-gravity instrument to study low velocity collisions of fragile particles at low temperatures.

    PubMed

    Salter, D M; Heisselmann, D; Chaparro, G; van der Wolk, G; Reissaus, P; Borst, A G; Dawson, R W; de Kuyper, E; Drinkwater, G; Gebauer, K; Hutcheon, M; Linnartz, H; Molster, F J; Stoll, B; van der Tuijn, P C; Fraser, H J; Blum, J

    2009-07-01

    We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for a total of 2.4 h in reduced-gravity conditions and successfully recording over 300 separate collisions of loosely packed dust aggregates and ice samples. The imparted particle velocities achieved range from 0.03 to 0.28 m s(-1) and a high-speed, high-resolution camera captures the events at 107 frames/s from two viewing angles separated by either 48.8 degrees or 60.0 degrees. The particles can be stored inside the experiment vacuum chamber at temperatures of 80-300 K for several uninterrupted hours using a built-in thermal accumulation system. The copper structure allows cooling down to cryogenic temperatures before commencement of the experiments. Throughout the parabolic flight campaigns, add-ons and modifications have been made, illustrating the instrument flexibility in the study of small particle collisions. PMID:19655969

  18. Digital holographic microscopy long-term and real-time monitoring of cell division and changes under simulated zero gravity.

    PubMed

    Pan, Feng; Liu, Shuo; Wang, Zhe; Shang, Peng; Xiao, Wen

    2012-05-01

    The long-term and real-time monitoring the cell division and changes of osteoblasts under simulated zero gravity condition were succeed by combing a digital holographic microscopy (DHM) with a superconducting magnet (SM). The SM could generate different magnetic force fields in a cylindrical cavity, where the gravitational force of biological samples could be canceled at a special gravity position by a high magnetic force. Therefore the specimens were levitated and in a simulated zero gravity environment. The DHM was modified to fit with SM by using single mode optical fibers and a vertically-configured jig designed to hold specimens and integrate optical device in the magnet's bore. The results presented the first-phase images of living cells undergoing dynamic divisions and changes under simulated zero gravity environment for a period of 10 hours. The experiments demonstrated that the SM-compatible DHM setup could provide a highly efficient and versatile method for research on the effects of microgravity on biological samples. PMID:22565769

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  20. One Possible Mechanism to Sustain Combustion inside a Closed Region under Zero Gravity

    NASA Astrophysics Data System (ADS)

    Glushko, G. S.; Kryukov, I. A.

    2001-03-01

    An experimental study carried out aboard the Mirstation showed that a stearin candle can burn for a long time even inside a closed volume without a forced circulation. Such experiments imply that there is some mechanism for a permanent transport of the oxidizer to the flame zone. It can be assumed that a jet of combustion products outflowing along a normal direction with respect to the flame surface produces a vortex motion in the environmental space, which delivers oxygen to the flame zone. To verify the feasibility of combustion to be sustained by such a mechanism, a mathematical statement of the problem of combustion inside a closed region under zero gravity without a forced circulation was formulated. A simplified model was put forward to simulate the combustion of solid and liquid substances, which allowed the effects of chemical reactions to be reduced to boundary conditions. The computations showed that the proposed mechanism of oxygen transport to the flame zone really can sustain an almost stationary regime of combustion.

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

    NASA Technical Reports Server (NTRS)

    Musacchia, X. J.

    1974-01-01

    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.

  2. EVA Assembly of Large Space Structure Neutral Buoyancy, Zero-Gravity Simulation: NASA-LaRC Nestable Columns and Joints

    NASA Technical Reports Server (NTRS)

    1979-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Spooner, Brian S.; Guikema, James A.; Barnes, Grady

    1990-01-01

    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. Buring 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 microparticies 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.

  4. A Study of Blood Flow and of Aggregation of Blood Cells Under Conditions of Zero Gravity: Its Relevance to the Occlusive Diseases and Cancer

    NASA Technical Reports Server (NTRS)

    Dintenfass, L.

    1985-01-01

    The objectives of this program are: (1) to determine whether the size of red cell aggregates, kinetics and morphology of these aggregates are influenced by near-zero gravity; (2) whether viscosity, especially at low shear rate, is afflicted by near-zero gravity (the latter preventing sedimentation of red cells); (3) whether the actual shape of red cells changes; and (4) whether blood samples obtained from different donors (normal and patients suffering from different disorders) react in the same manner to near-zero gravity.

  5. Experimental and analytical study of two-phase flow in zero gravity. Final report, September 1985-October 1987

    SciTech Connect

    Abdollahian, D.; Grief, R.; Carey, V.P.; Li-Ping, W.

    1988-03-01

    More-effective and -efficient thermal-transport techniques will be needed for heat rejection from equipment on satellites. Circulating two-phase fluid loops were suggested and laboratory tested for possible application in the above areas. In comparison to a single-phase loop, the two-phase system operates at considerably smaller flow rates and maintains a tighter temperature control with higher heat-transfer coefficients. However, the two-phase fluid-flow regimes, pressure gradients, and heat-transfer coefficients must be evaluated for application in the weightless environment of an orbiting satellite. This projecting studies two-phase flow behavior under zero-gravity conditions. The overall objectives of this study were to generate a data base for two-phase pressure drop and the void-quality relationship under simulated zero gravity conditions and to develop analytical models to predict these parameters for bubbly and annular flow. The simulation of zero-gravity two-phase flow was achieved by using two immiscible liquids with equal densities to eliminate the buoyancy component. Although this approach does not eliminate the gravity effects, it provides a representation for void distribution in the absence of gravity. The modeling effort is limited to developing relations for the two-phase friction multiplier and void-quality relation under bubbly and annular-flow conditions. The bubbly flow model is based on the assumption of local homogeneous conditions between the phases but allows for void distribution in the radial direction. Separated-flow conservation equations are used, and single-phase turbulent flow eddy diffusivity relations are employed.

  6. Processing yttrium-barium-copper oxide superconductor zero gravity using a double float zone surface

    SciTech Connect

    Pettit, D.R.; Peterson, D.E.; Kubat-Martin, K.A.; Petrovic, J.J.; Sheinberg, H.; Coulter, Y.; Day, D.E.

    1997-04-01

    The effects of processing YBa{sub 2}Cu{sub 3}O{sub x} (Y123) superconductor in the near-zero gravity (0g) environment provided by the NASA KC-135 airplane flying on parabolic trajectories were studied. A new sheet float zone furnace, designed for this study, enabled fast temperature ramps. Up to an 18-gram sample was processed with each parabola. Samples of Y123 were processed as bulk sheets, composites containing Ag and Pd, and films deposited on single crystal Si and MgO substrates. The 0g-processed samples were multi-phase yet retained a localized Y123 stoichiometry where a single ground-based (1g) oxygen anneal at temperatures of 800 C recovered nearly 100-volume percent superconducting Y123. The 1g processed control samples remained multi-phase after the same ground-based anneal with less than 45 volume percent as superconducting Y123. The superconducting transition temperature was 91 K for both 0g and 1g processed samples. A 29 wt.% Ag/Y123 composite had a transition temperature of 93 K. Melt texturing of bulk Y123 in 0g produced aligned grains about a factor of three larger than in analogous 1g samples. Transport critical current densities were at or below 18 A/cm{sup 2}, due to the formation of cracks caused by the rapid heating rates required by the short time at 0g. Y123 deposited on single crystal Si and MgO in 0g was 30 vol.% y123 without an anneal. A weak superconducting transition at 80 K on MgO showed that substrate interactions occurred.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  8. Hydrocephalus: the zero ICP ventricle shunt (ZIPS) to control gravity shunt flow. A clinical study in 56 patients.

    PubMed

    Foltz, E L; Blanks, J; Meyer, R

    1994-01-01

    Significant morbidity from ventricle shunt overdrainage at 6-7 years after initial shunt placement for hydrocephalus is increasingly recognized as due to excessive gravity-flow of shunted CSF when upright. Shunts are designed primarily to control high ICP. Shunts should also mimic normal upright ICP. Normal upright ICP is -65 mm of water (vertex reference), indicating that a level of zero ICP exists at 65 mm below the brain vertex, with negative ICP above and positive ICP below that level. This normal zero ICP level must be maintained by CSF shunts to mimic normal upright ICP. This will prevent and correct CSF shunt overdrainage. The zero ICP shunt (ZIPS) by design controls this zero level with a zero pressure device (ZPD; siphon control device) installed at the normal vertical level of zero ICP (cm/mm) below the vertex (65 mm). The shunt thus prevents excessive gravity-induced CSF shunt flow. Successful use of ZIPS in 56 patients is reported (low ICP group: n = 42; high ICP group: n = 14). Follow-up is up to 4.5 years. Results show that: (1) adjustability of ZPD level can achieve the desired clinical results; (2) the level of ZPD installed correlates within 4 mm of upright ICP attained; (3) the optimal level of ZPD installation to produce normal upright ICP is 65 mm below the vertex; (4) CT ventricle size, both slit ventricles and large ventricles, may or may not normalize when normal upright ICP is attained in this group of complex, previously shunted patients. PMID:8194062

  9. In-shoe force measurements from locomotion in simulated zero gravity during parabolic flight.

    PubMed

    McCrory, JL; Schwass, JP; Connell, RB; Cavanagh, PR

    1997-04-01

    INTRODUCTION:: No effective countermeasure for space-induced bone loss has yet been identified. It has been hypothesized that an effective exercise regimen would elicit loads on the lower extremity which resemble those encountered on Earth. Although a treadmill has been used on shuttle flights, the loads to which the lower extremity was exposed have not yet been quantified. It is believed that these loads are much less than the loads experienced in 1G. The purpose of this study was to determine the magnitude of lower extremity loading during tethered treadmill exercise in a 0G environment. METHODS:: Data were collected on five subjects (avg. ht. 177.3+/-10.1 cm, avg. mass 78.3+/-18.0 kg) onboard the KC-135, a NASA airplane used to simulate periods of zero gravity through parabolic flight. Subjects ambulated at 4 speeds: a walk (1.56m/sec), fast walk (2.0m/sec) slow jog (2.75m/sec), and jog (3.35m/sec) on the NASA treadmill operated in either a passive or motorized mode. Each subject wore a harness connected to the Subject Load Device (SLD) to tether them to the treadmill. The tension in the SLD was subjectively adjusted for comfort by each subject. Force data were collected at 60 Hz using Pedar insoles. The number of parabolas per subject was variable due to motion sickness and hardware problems. RESULTS:: Analysis of the insole data showed that the average SLD load was only 35.2% BW, although the values ranged from 20.1% to 56.6%. Maximum ground reaction force values increased with increasing speed and were not affected by treadmill mode. The impulse was higher during walking with the treadmill in the passive mode than in the active mode, but this difference diminished with increasing speed. Subjects tended to run on their forefeet, as shown from the extremely small heel impulse values. At higher speeds, heel contact was absent, while forefoot impulse became more pronounced. DISCUSSION:: All force values were lower than those reported from 1G studies, where typical peak ground reaction forces are 1.2xBW and 2.5xBW for walking and running, respectively. At every speed, the ratio of the rearfoot to forefoot impulse was much lower than reported from 1G studies, and this ratio decreased with increasing speed. CONCLUSIONS:: If the exposure to forces similar to those in 1G is a requirement for countermeasures against space-induced osteoporosis, the loads in the SLD must be greatly increased and should be directly measured before exercise. PMID:11415704

  10. Rat head direction cell responses in zero-gravity parabolic flight.

    PubMed

    Taube, Jeffrey S; Stackman, Robert W; Calton, Jeffrey L; Oman, Charles M

    2004-11-01

    Astronauts working in zero-gravity (0-G) often experience visual reorientation illusions (VRIs). For example, when floating upside down, they commonly misperceive the spacecraft floor as a ceiling and have a reversed sense of direction. Previous studies have identified a population of neurons in the rat's brain that discharge as a function of the rat's head direction (HD) in a gravitationally horizontal plane and is dependent on an intact vestibular system. Our goal was to characterize HD cell discharge under conditions of acute weightlessness. Seven HD cells in the anterior dorsal thalamus were monitored from rats aboard an aircraft in 0-G parabolic flight. Unrestrained rats locomoted in a clear plexiglas rectangular chamber that had wire mesh covering the floor, ceiling, and one wall. The chamber and surrounding visual environment were relatively up-down symmetrical. Each HD cell was recorded across forty 20-s episodes of 0-G. All HD cells maintained a significant direction-specific discharge when the rat was on the chamber floor during the 0-G and also during the hypergravity pull-out periods. Three of five cells also showed direction-specific responses on the wall in 1-G. In contrast, direction-specific discharge was usually not maintained when the rat locomoted on the vertical wall or ceiling in 0-G. The loss of direction-specific firing was accompanied by an overall increase in background firing. However, while the rat was on the ceiling, some cells showed occasional bursts of firing when the rat's head was oriented in directions that were flipped relative to the long axis of symmetry of the chamber compared with the cell's preferred firing direction on the floor. This finding is consistent with what might be expected if the rat had experienced a VRI. These responses indicate that rats maintain a normal allocentric frame of reference in 0-G and 1-G when on the floor, but may lose their sense of directional heading when placed on a wall or ceiling during acute exposures to 0-G. PMID:15212426

  11. Heart Rate and Blood Pressure Variability under Moon, Mars and Zero Gravity Conditions During Parabolic Flights

    NASA Astrophysics Data System (ADS)

    Aerts, Wouter; Joosen, Pieter; Widjaja, Devy; Varon, Carolina; Vandeput, Steven; Van Huffel, Sabine; Aubert, Andre E.

    2013-02-01

    Gravity changes during partial-G parabolic flights (0g -0.16g - 0.38g) lead to changes in modulation of the autonomic nervous system (ANS), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were assessed via classical time and frequency domain measures. Mean systolic and diastolic blood pressure show both increasing trends towards higher gravity levels. The parasympathetic and sympathetic modulation show both an increasing trend with decreasing gravity, although the modulation is sympathetic predominant during reduced gravity. For the mean heart rate, a non-monotonic relation was found, which can be explained by the increased influence of stress on the heart rate. This study shows that there is a relation between changes in gravity and modulations in the ANS. With this in mind, countermeasures can be developed to reduce postflight orthostatic intolerance.

  12. Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly†

    PubMed Central

    Hill, Richard J. A.; Larkin, Oliver J.; Dijkstra, Camelia E.; Manzano, Ana I.; de Juan, Emilio; Davey, Michael R.; Anthony, Paul; Eaves, Laurence; Medina, F. Javier; Marco, Roberto; Herranz, Raul

    2012-01-01

    Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396

  13. Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly.

    PubMed

    Hill, Richard J A; Larkin, Oliver J; Dijkstra, Camelia E; Manzano, Ana I; de Juan, Emilio; Davey, Michael R; Anthony, Paul; Eaves, Laurence; Medina, F Javier; Marco, Roberto; Herranz, Raul

    2012-07-01

    Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity. PMID:22219396

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  15. Preliminary drop-tower experiments on liquid-interface geometry in partially filled containers at zero gravity

    NASA Technical Reports Server (NTRS)

    Smedley, G.

    1990-01-01

    Plexiglass containers with rounded trapezoidal cross sections were designed and built to test the validity of Concus and Finn's existence theorem (1974, 1983) for a bounded free liquid surface at zero gravity. Experiments were carried out at the NASA Lewis two-second drop tower. Dyed ethanol-water solutions and three immiscible liquid pairs, with one liquid dyed, were tested. High-speed movies were used to record the liquid motion. Liquid rose to the top of the smaller end of the containers when the contact angle was small enough, in agreement with the theory. Liquid interface motion demonstrated a strong dependence on physical properties, including surface roughness and contamination.

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

    NASA Technical Reports Server (NTRS)

    Sanchez, Merri J.

    2000-01-01

    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.

  17. Simulation of the effects of microtubules in the cortical rotation of amphibian embryos in normal and zero gravity.

    PubMed

    Nouri, Comron; Tuszynski, Jack A; Wiebe, Mark W; Gordon, Richard

    2012-09-01

    This paper reports the results of computer modeling of microtubules that end up in the cortical region of a one-cell amphibian embryo, prior to the first cell division. Microtubules are modeled as initially randomly oriented semi-flexible rods, represented by several lines of point-masses interacting with one another like masses on springs with longitudinal and transverse stiffness. They are also considered to be space-filling rods floating in a viscous fluid (cytoplasm) experiencing drag forces and buoyancy from the fluid under a variable gravity field to test gravitational effects. Their randomly distributed interactions with the surrounding spherical container (the cell membrane) have a statistical nonzero average that creates a torque causing a rotational displacement between the cytoplasm and the rigid cortex. The simulation has been done for zero and normal gravity and it validates the observation that cortical rotation occurs in microgravity as well as on Earth. The speed of rotation depends on gravity, but is still substantial in microgravity. PMID:22677068

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

    NASA Technical Reports Server (NTRS)

    Spuckler, C. M.

    1981-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    2002-01-01

    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.

  20. The Dirac point electron in zero-gravity Kerr–Newman spacetime

    SciTech Connect

    Kiessling, M. K.-H.; Tahvildar-Zadeh, A. S.

    2015-04-15

    Dirac’s wave equation for a point electron in the topologically nontrivial maximal analytically extended electromagnetic Kerr–Newman spacetime is studied in a limit G → 0, where G is Newton’s constant of universal gravitation. The following results are obtained: the formal Dirac Hamiltonian on the static spacelike slices is essentially self-adjoint and the spectrum of the self-adjoint extension is symmetric about zero, featuring a continuum with a gap about zero that, under two smallness conditions, contains a point spectrum. The symmetry result extends to the Dirac operator on a generalization of the zero-G Kerr–Newman spacetime with different electric-monopole/magnetic-dipole-moment ratios.

  1. 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)

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

    1981-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Bailey, J. A.

    1976-01-01

    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.

  4. Steady state growth and segregation under zero gravity: InSb

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  5. Manual control in space research on perceptual-motor functions under zero gravity conditions (L-10)

    NASA Technical Reports Server (NTRS)

    Tada, Akira

    1993-01-01

    Are human abilities to control vehicles and other machines the same in space as those on Earth? The L-10 Manual Control Experiment of the First Materials Processing Tests (FMPT) started from this question. Suppose a pilot has the task to align the head of a space vehicle toward a target. His actions are to look at the target, to determine the vehicle movement, and to operate the manipulator. If the activity of the nervous system were the same as on Earth, the movements, of the eye and hand would become excessive because the muscles do not have to oppose gravity. The timing and amount of movement must be arranged for appropriate actions. The sensation of motion would also be affected by the loss of gravity because the mechanism of the otolith, the major acceleration sensor, depends on gravity. The possible instability of the sensation of direction may cause mistakes in the direction of control of manipulator movement. Thus, the experimental data can be used for designing man-machine systems in space, as well as for investigation of physiological mechanisms. In this experiment, the direction of vehicle heading is expressed by a light spot on an array of light emitting diodes and the manipulator is of a finger stick type. As the light spot moves up and down, the Japanese Payload Specialist, and the subject, must move the manipulator forward and backward to keep the movement of the light spot within the neighborhood of the central point of the display. The position of the light spot is computed in such a manner that when the stick is kept at the neutral position, a motion whose acceleration is proportional to the angle of deflection is added to the movement of the light spot. The Operator Describing Function, which is an expression of human control characteristics, can be calculated from 2 minutes of raw data of the light spot position and stick deflection. The 2 minutes of operation is called a run, and 8 runs with resting periods composes a session. The on-orbit experiment will be conducted on the second, fourth, and seventh days. One session of experiment of each of these days is conducted following the L-4 experiment, which uses the same apparatus. The Payload Specialist, aided by a Mission Specialist, will take our apparatus from a rack container, set up the apparatus, attach electrodes for measurements of eye movement and muscle activity, conduct the L-4 Visual Stability Experiment, conduct one session of the manual control experiment, and then dissemble and stow the apparatus. In addition to the flight experiment, pre-flight and post-flight experiments will be conducted. The data of three sessions on orbit will reflect adaption of physiological systems to microgravity. The data of post-flight experiments, on the other hand, will reflect re-adaptation of physiological systems to the gravity condition on the ground. Control data collected with and without psychological tension will be scheduled just prior to and long before launch.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  7. A zero-gravity demonstration of the collision and coalescence of water droplets

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Vaughan, O. H.; Smith, R. E.

    1974-01-01

    The mechanics of the collision and coalescence of liquid droplets is one of the main research areas in the fields of nuclear physics, astrophysics, meteorology and fluid mechanics. The crew members on the Skylab 3 and 4 missions were requested to perform demonstrations of the collision and coalescence of water droplets under the low gravity environment at orbital altitude. In Skylab 4 two water droplets with equal volumes, 30 cu cm each, were used. A dark colored droplet (contaminated with grape drink) moving with a velocity of 3.14 cm/sec collided with a stationary pink colored droplet (contaminated with strawberry drink) and coalescence occurred. Theoretical models are proposed to study the various stages of the collision-coalescence processes. Special considerations are concentrated in the investigation of the bounce-coalescence and coalescence-instability processes. The surface tension of the coalesced droplets was calculated to be 52 dynes/cm in perfect agreement with laboratory measurements made after the flight using a reproduction of the liquids.

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

    NASA Technical Reports Server (NTRS)

    Tipton, Charles M.

    1991-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  10. Automatic robotic arm operations and sampling in near zero gravity environment - functional tests results from Phobos-Grunt mission

    NASA Astrophysics Data System (ADS)

    Kozlova, Tatiana; Karol Seweryn, D..; Grygorczuk, Jerzy; Kozlov, Oleg

    The sample return missions have made a very significant progress to understanding of geology, the extra-terrestrial materials, processes occurring on surface and subsurface level, as well as of interactions between such materials and mechanisms operating there. The various sample return missions in the past (e.g. Apollo missions, Luna missions, Hayabusa mission) have provided scientists with samples of extra-terrestrial materials allowing to discover answers to critical scientific questions concerning the origin and evolution of the Solar System. Several new missions are currently planned: sample return missions, e.g Russian Luna-28, ESA Phootprint and MarcoPolo-R as well as both robotic and manned exploration missions to the Moon and Mars. One of the key challenges in such missions is the reliable sampling process which can be achieved by using many different techniques, e.g. static excavating technique (scoop), core drilling, sampling using dynamic mechanisms (penetrators), brushes and pneumatic systems. The effectiveness of any sampling strategy depends on many factors, including the required sample size, the mechanical and chemical soil properties (cohesive, hard or porous regolith, stones), the environment conditions (gravity, temperature, pressure, radiation). Many sampling mechanism have been studied, designed and built in the past, two techniques to collect regolith samples were chosen for the Phobos-Grunt mission. The proposed system consisted of a robotic arm with a 1,2m reach beyond the lander (IKI RAN); a tubular sampling device designed for collecting both regolith and small rock fragments (IKI RAN); the CHOMIK device (CBK PAN) - the low velocity penetrator with a single-sample container for collecting samples from the rocky surface. The functional tests were essential step in robotic arm, sampling device and CHOMIK device development process in the frame of Phobos-Grunt mission. Three major results were achieved: (i) operation scenario for autonomous sampling; (ii) technical characteristics of both devices, i.e. progress cycles of CHOMIK device in different materials and torque in the manipulator joints during sampling operations; (iii) confirmation of applicability of both devices to perform such type of tasks. The phases in operational scenario were prepared to meet mission and system requirements mainly connected with: (i) environment (near zero gravity, vacuum, dust), (ii) safety and (iii) to avoid common operation of both devices at the same time.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  12. Effects of transient propellant dynamics on deployment of large liquid stages in zero-gravity with application to shuttle/centaur

    NASA Astrophysics Data System (ADS)

    Martin, R. E.

    A common requirement of the Space Station era will be deployment and docking of orbit transfer vehicles with large quantities of liquid propellants. The maneuver will typically start at zero gravity with short, transient accelerations applied to provide accurate vehicle positioning for clearance during deployment or engagement during docking. Since the propellant tanks are not always full and the initial zero- g position of liquid and ullage may not be known, transient fluid forces can have a major influence on vehicle motion. Until recently, this fluid dynamics problem could not be analyzed adequately. This paper describes the application of a recently developed computational fluid dynamics (CFD) program, HYDR-3D, to the analysis of separation of the Centaur G-Prime vehicle from the Space Shuttle Orbiter. The typical application presented illustrates a particularly difficult design task—deployment of a large, liquid-filled, densely packaged vehicle from a manned vehicle. Since it represents a potential catastrophic hazard, a vast number of conditions and parameters must be analyzed to ensure tolerance of at least two credible failures. Validation of the HYDR-3D program against zero- and low-gravity experimental data is also presented. Using the fluid dynamics program, this approach can be used confidently to analyze and determine design requirements for a variety of orbit transfer vehicle/space station deployment and docking problems.

  13. 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)

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

    1982-01-01

    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.

  14. Execution of "ARC" experiment on space shuttle "Discovery" STS 51-C: some results on aggregation of red blood cells under zero gravity.

    PubMed

    Dintenfass, L

    1986-01-01

    A project on "Aggregation of Red Cells" has been accepted by NASA in 1977. An automated slit-capillary photo-viscometer has been designed during 1979-1984, and its last version met NASA's space hazards requirements. The 'heart' of instrument is a set of two highly polished glass plates, spaced by a gap of 12.5 micrometers. An original drum-like infusion pump allows utilization of up to eight blood samples. During a sequential process, blood flows through the slit, and then stops to allow formation of aggregates. Micro- and macro-photography is carried out, and 500 photographs are obtained. Blood from normal donors and patients with history of ischaemic heart disease, colon cancer, juvenile-onset diabetes, hyperlipidaemia, etc., is anticoagulated and adjusted to haematocrit of 0.30 using native plasma. Samples are divided, and infused into the 'flight' and 'ground' instruments. Prior to experiment temp. is 5 degrees C; temp. during experiment is 25 degrees C. Experiments took place on 24-25 January 1985, on the middeck of space shuttle 'Discovery'. Subsequent results showed that red blood cells do not change shape under zero gravity; that aggregation of red cells does take place; that aggregates in pathologic blood show morphology of normal rouleaux under zero gravity, while identical blood shows clumps of red cells on the ground. The latter observation suggests that zero gravity might affect cell-to-cell interaction, and perhaps microstructure of the cell membrane. These aspects must remain however tentative till a confirmation by subsequent experiments can be obtained. PMID:3779059

  15. Out-reach in-space technology experiments program: Control of flexible robot manipulators in zero gravity, experiment definition phase

    NASA Technical Reports Server (NTRS)

    Phillips, Warren F.

    1989-01-01

    The results obtained show that it is possible to control light-weight robots with flexible links in a manner that produces good response time and does not induce unacceptable link vibrations. However, deflections induced by gravity cause large static position errors with such a control system. For this reason, it is not possible to use this control system for controlling motion in the direction of gravity. The control system does, on the other hand, have potential for use in space. However, in-space experiments will be needed to verify its applicability to robots moving in three dimensions.

  16. 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)

    Wolf, David A.; Schwarz, Ray P.

    1991-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Straube, Timothy Milton

    1993-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Darbro, W.

    1978-01-01

    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.

  20. Zero-gravity mean free surface curvature of a confined liquid in a radially-vaned container

    NASA Astrophysics Data System (ADS)

    Chen, Yongkang; Callahan, Michael; Weislogel, Mark

    2013-11-01

    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 bounded by 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. This research is supported in part by NASA Johnson Space Center.

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

    NASA Technical Reports Server (NTRS)

    Chen, Yongkang; Callahan, Michael; Weislogel, Mark

    2013-01-01

    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.

  2. Zero initial partial derivatives of satellite orbits with respect to force parameters nullify the mathematical basis of the numerical integration method for the determination of standard gravity models from space geodetic measurements

    NASA Astrophysics Data System (ADS)

    Xu, Peiliang

    2015-04-01

    Satellite orbits have been routinely used to produce models of the Earth's gravity field. The numerical integration method is most widely used by almost all major institutions to determine standard gravity models from space geodetic measurements. As a basic component of the method, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this talk, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, setting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies. To conclude, the numerical integration method, as is widely used today by major institutions to produce standard satellite gravity models, is simply incorrect mathematically. As a direct consequence, further work is required to confirm whether the numerical integration method can still be used as a mathematical foundation to produce standard satellite gravity models. More details can be found in Xu (2009, Sci China Ser D-Earth Sci, 52, 562-566).

  3. 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)

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

    1975-01-01

    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.

  4. Project Fog Drops 5. Task 1: A numerical model of advection fog. Task 2: Recommendations for simplified individual zero-gravity cloud physics experiments

    NASA Technical Reports Server (NTRS)

    Rogers, C. W.; Eadie, W. J.; Katz, U.; Kocmond, W. C.

    1975-01-01

    A two-dimensional numerical model was used to investigate the formation of marine advection fog. The model predicts the evolution of potential temperature, horizontal wind, water vapor content, and liquid water content in a vertical cross section of the atmosphere as determined by vertical turbulent transfer and horizontal advection, as well as radiative cooling and drop sedimentation. The model is designed to simulate the formation, development, or dissipation of advection fog in response to transfer of heat and moisture between the atmosphere and the surface as driven by advection over horizontal discontinuities in the surface temperature. Results from numerical simulations of advection fog formation are discussed with reference to observations of marine fog. A survey of candidate fog or cloud microphysics experiments which might be performed in the low gravity environment of a shuttle-type spacecraft in presented. Recommendations are given for relatively simple experiments which are relevent to fog modification problems.

  5. 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)

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

    1975-01-01

    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.

  6. Ground Zero.

    ERIC Educational Resources Information Center

    Vail, Kathleen

    1995-01-01

    In school systems with a zero-tolerance policy, principals must recommend that students who carry weapons on campus be expelled. Some critics say zero-tolerance policies do not allow enough room for exceptions. Describes the Gun-Free Schools Act. (MLF)

  7. GAS-611 firefly in zero gravity

    NASA Technical Reports Server (NTRS)

    Williams, Tony

    1988-01-01

    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.

  8. APOLLO 8: It's Christmas in zero gravity...

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Astronauts and ground control consider how Santa is going to gain access to the command module... From the film documentary 'APOLLO 8:'Debrief': part of a documentary series made in the early 70's on the APOLLO missions, and narrated by Burgess Meredith. (Actual date created is not known at this time) First manned Saturn V flight with Frank Borman, James A. Lovell, Jr.,and william A. Anders. First manned lunar orbit mission; provided a close-up look at the moon during 10 lunar orbits. Mission Duration 147hrs 0m 42s

  9. Zero Quotatives.

    ERIC Educational Resources Information Center

    Mathis, Terrie; Yule, George

    1994-01-01

    Finds that zero quotatives (where direct speech is reported with neither a reporting verb nor an attributed speaker) are found when a speaker is clearly constructing attitude; where the omission of a quotative may serve some dramatic effect; and at sights where conversational partners are displaying strongly convergent behavior. (SR)

  10. Electricity from Gravity

    NASA Astrophysics Data System (ADS)

    Masters, Roy

    2007-03-01

    Einstein's cosmological constant as gravity, will unify quantum mechanics to general relativity and link gravity to electromagnetism. Then, an electromagnetic vacuum engine driven by the force that spins, moves, and sustains mass at the subatomic level, will do free, what generators cannot. Flowing outward-bound sinusoidally from its source, this gravity force assumes a three-dimensional spherical universe. Lines of force intersect, spinning into gyroscopic particles and passes as time-present, with a compression gravity of space-time curvature continuum unifying all mass. The spaces between approaching masses suffer a decrease of right-angled vacuum energy, increasing external pressures, pushing them together. Ubiquitous gravity now interacts electromagnetically with mass. Gravity's ``heat energy'' operates below absolute zero and squeezes mass into thermonuclear ignition of stars. Creation needs a gravity field for the propagation of light that will make sense of its wave/particle behavior. Creation from a white hole recycles down through a black one, into new beginnings of galaxies. ``Vacuum energy'' will light cities and factories; faster than light spacecraft will raise silently from the ground utilizing the very gravity it defies, propelling us to the stars.

  11. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  12. Brane worlds in critical gravity

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  13. Gravity Waves

    Atmospheric Science Data Center

    2013-04-19

    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 ... that occur when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air ...

  14. Zero: A "None" Number?

    ERIC Educational Resources Information Center

    Anthony, Glenda J.; Walshaw, Margaret A.

    2004-01-01

    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.

  15. Venus gravity

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.

    1993-01-01

    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.

  16. The Trouble with Zero

    ERIC Educational Resources Information Center

    Lewis, Robert

    2015-01-01

    The history of the number zero is an interesting one. In early times, zero was not used as a number at all, but instead was used as a place holder to indicate the position of hundreds and tens. This article briefly discusses the history of zero and challenges the thinking where divisions using zero are used.

  17. Cosmological perturbations in unimodular gravity

    SciTech Connect

    Gao, Caixia; Brandenberger, Robert H.; Cai, Yifu; Chen, Pisin E-mail: rhb@hep.physics.mcgill.ca E-mail: chen@slac.stanford.edu

    2014-09-01

    We study cosmological perturbation theory within the framework of unimodular gravity. We show that the Lagrangian constraint on the determinant of the metric required by unimodular gravity leads to an extra constraint on the gauge freedom of the metric perturbations. Although the main equation of motion for the gravitational potential remains the same, the shift variable, which is gauge artifact in General Relativity, cannot be set to zero in unimodular gravity. This non-vanishing shift variable affects the propagation of photons throughout the cosmological evolution and therefore modifies the Sachs-Wolfe relation between the relativistic gravitational potential and the microwave temperature anisotropies. However, for adiabatic fluctuations the difference between the result in General Relativity and unimodular gravity is suppressed on large angular scales. Thus, no strong constraints on the theory can be derived.

  18. Mars mission gravity profile simulation

    NASA Technical Reports Server (NTRS)

    Kuznetz, Lawrence H.

    1990-01-01

    A flight experiment designed to determine the need for artificial gravity for Mars mission architectures at earlier stages of the design process is proposed. The Soviet Mir space station, the NASA Space Shuttle, and the resources of NASA Ames Research Center would be used to duplicate in the terrestrial environment the complete Mars-mission gravity profile in order to assess the need for artificial gravity. All mission phases of 1 G would be on earth; all mission phases of zero or micro G would be in space aboard Mir; and all launch, ascent, orbit, deorbit, approach, departure, and descent G loads would be provided by actual spacecraft in operations that could be designed to simulate the actual G loads, while the Mars stay time would be simulated on earth or in a variable-gravity research facility in space. Methods of simulating activities on the Martian surface are outlined along with data monitoring, countermeasures, and launch site and vehicle selection criteria.

  19. Generalized Vaidya spacetime for cubic gravity

    NASA Astrophysics Data System (ADS)

    Ruan, Shan-Ming

    2016-03-01

    We present a kind of generalized Vaidya solution of a new cubic gravity in five dimensions whose field equations in spherically symmetric spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its spherically symmetric apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally, we present the first law and second law hold in this gravity. Although all the results are analogous to those in Lovelock gravity, we in fact introduce the contribution of a new cubic term in five dimensions where the cubic Lovelock term is just zero.

  20. Gravity investigations

    SciTech Connect

    Healey, D.L.

    1983-12-31

    A large density contrast exists between the Paleozoic rocks (including the rocks of Climax stock) and less dense, Tertiary volcanic rocks and alluvium. This density contrast ranges widely, and herein for interpretive purposes, is assumed to average 0.85 Mg/m{sup 3} (megagrams per cubic meter). The large density contrast makes the gravity method a useful tool with which to study the interface between these rock types. However, little or no density contrast is discernible between the sedimentary Paleozoic rocks that surround the Climax stock and the intrusive rocks of the stock itself. Therefore the gravity method can not be used to define the configuration of the stock. Gravity highs coincide with outcrops of the dense Paleozoic rocks, and gravity lows overlie less-dense Tertiary volcanic rocks and Quaternary alluvium. The positions of three major faults (Boundary, Yucca, and Butte faults) are defined by steep gravity gradients. West of the Climax stock, the Tippinip fault has juxtaposed Paleozoic rocks of similar density, and consequently, has no expression in the gravity data in that area. The gravity station spacing, across Oak Spring Butte, is not sufficient to adequately define any gravity expression of the Tippinip fault. 18 refs., 5 figs.

  1. Keeping the Zero in Zero Discharge.

    ERIC Educational Resources Information Center

    Muldoon, Paul; Jackson, John

    1994-01-01

    This article focuses on Great Lakes pollution as it describes the evolution of the zero discharge concept, outlines the major areas of debate, and explores facets of a developing strategy to ensure the ultimate success of the zero discharge approach. (46 references) (LZ)

  2. Gravity brake

    DOEpatents

    Lujan, Richard E.

    2001-01-01

    A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

  3. Beyond Zero Based Budgeting.

    ERIC Educational Resources Information Center

    Ogden, Daniel M., Jr.

    1978-01-01

    Suggests that the most practical budgeting system for most managers is a formalized combination of incremental and zero-based analysis because little can be learned about most programs from an annual zero-based budget. (Author/IRT)

  4. Multiple zeros of polynomials

    NASA Technical Reports Server (NTRS)

    Wood, C. A.

    1974-01-01

    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.

  5. Droplet burning at zero G

    NASA Technical Reports Server (NTRS)

    Williams, F. A.

    1978-01-01

    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.

  6. Improved Airborne Gravity Results Using New Relative Gravity Sensor Technology

    NASA Astrophysics Data System (ADS)

    Brady, N.

    2013-12-01

    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.

  7. The tetradic approach and BF-gravity

    NASA Astrophysics Data System (ADS)

    Shishanin, A. O.

    Here we discuss a limit of the gravitational constant G goes to zero for the Einstein gravity. It is convenient to use for this a tetradic approach (using tetrads and spin-connection) and the Palatini formalism. Also some external field B is entered, which is 2-form. In this limit an equation for the spin-connection is obtained. Such an equation was obtained earlier in the MacDowell-Mansouri-Stelle-West gravity.

  8. Role of gravity in preparative electrophoresis

    NASA Technical Reports Server (NTRS)

    Bier, M.; Hinckley, J. O. N.; Smolka, A. J. K.; Binder, M. J.; Coxon, M.; Nee, T. W.; Scully, M. O.; Shih, H. S. T.; Snyder, R. S.

    1974-01-01

    Electrophoresis has contributed significantly to the methodology of biological sciences, and shows the potential for large scale fractionation of a wide range of medically important substances, including living cells. Gravity plays an important role in the electrophoretic process, and hence the importance of the NASA effort to develop a zero-gravity separation facility as part of its shuttle program. The current state of art in electrophoresis is reviewed with particular emphasis on the role of gravity and the possible use of istachophoresis. This technique utilizes a discontinuous buffer system, and appears to be the only high resolution electrophoretic technique currently available for separation of living cells.

  9. Simulating Gravity

    ERIC Educational Resources Information Center

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity

  10. Gravity settling

    DOEpatents

    Davis, Hyman R.; Long, R. H.; Simone, A. A.

    1979-01-01

    Solids are separated from a liquid in a gravity settler provided with inclined solid intercepting surfaces to intercept the solid settling path to coalesce the solids and increase the settling rate. The intercepting surfaces are inverted V-shaped plates, each formed from first and second downwardly inclined upwardly curved intersecting conical sections having their apices at the vessel wall.

  11. Simulating Gravity

    ERIC Educational Resources Information Center

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  12. Cosmologically designed modified gravity theories

    NASA Astrophysics Data System (ADS)

    Hwang, Jai-chan; Noh, Hyerim; Park, Chan-Gyung

    2013-02-01

    Versions of parameterized pseudo-Newtonian gravity theories specially designed for cosmology have been introduced in recent cosmology literature. The modifications often consider the zero-pressure fluid in the context of versions of modified Poisson-like equation with two different gravitational potentials or an effective gravitational constant. We consider such modifications available in the context of relativistic gravity theories where the action is a general algebraic function of the scalar curvature, the scalar field, and the kinetic term of the field. We show that in general it is not possible to isolate the fluid component even in Einstein’s gravity. Only in the small-scale (far inside the horizon) limit, to the linear order, and assuming the quasistatic approximation, we can realize some special forms of the attempted modifications with limited validity. Theoretically motivated relativistic generalized gravity theories we are considering have much richer cosmological aspects than simply captured by some pseudo-Newtonian modifications. We show that even Einstein’s gravity with a minimally coupled scalar field as a dynamical dark energy demands similar modification in Poisson’s equation and the baryon density perturbation equation.

  13. Zero-Based Budgeting.

    ERIC Educational Resources Information Center

    Wichowski, Chester

    1979-01-01

    The zero-based budgeting approach is designed to achieve the greatest benefit with the fewest undesirable consequences. Seven basic steps make up the zero-based decision-making process: (1) identifying program goals, (2) classifying goals, (3) identifying resources, (4) reviewing consequences, (5) developing decision packages, (6) implementing a…

  14. The Zero Program

    ERIC Educational Resources Information Center

    Roland, Erling; Midthassel, Unni Vere

    2012-01-01

    Zero is a schoolwide antibullying program developed by the Centre for Behavioural Research at the University of Stavanger, Norway. It is based on three main principles: a zero vision of bullying, collective commitment among all employees at the school using the program, and continuing work. Based on these principles, the program aims to reduce…

  15. Tolerating Zero Tolerance?

    ERIC Educational Resources Information Center

    Moore, Brian N.

    2010-01-01

    The concept of zero tolerance dates back to the mid-1990s when New Jersey was creating laws to address nuisance crimes in communities. The main goal of these neighborhood crime policies was to have zero tolerance for petty crime such as graffiti or littering so as to keep more serious crimes from occurring. Next came the war on drugs. In federal…

  16. Zero Energy Use School.

    ERIC Educational Resources Information Center

    Nelson, Brian, Ed.; And Others

    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"…

  17. Zero-mode waveguides

    DOEpatents

    Levene, Michael J.; Korlach, Jonas; Turner, Stephen W.; Craighead, Harold G.; Webb, Watt W.

    2007-02-20

    The present invention is directed to a method and an apparatus for analysis of an analyte. The method involves providing a zero-mode waveguide which includes a cladding surrounding a core where the cladding is configured to preclude propagation of electromagnetic energy of a frequency less than a cutoff frequency longitudinally through the core of the zero-mode waveguide. The analyte is positioned in the core of the zero-mode waveguide and is then subjected, in the core of the zero-mode waveguide, to activating electromagnetic radiation of a frequency less than the cut-off frequency under conditions effective to permit analysis of the analyte in an effective observation volume which is more compact than if the analysis were carried out in the absence of the zero-mode waveguide.

  18. Quantum gravity

    SciTech Connect

    Markov, M.A.; West, P.C.

    1984-01-01

    This book discusses the state of the art of quantum gravity, quantum effects in cosmology, quantum black-hole physics, recent developments in supergravity, and quantum gauge theories. Topics considered include the problems of general relativity, pregeometry, complete cosmological theories, quantum fluctuations in cosmology and galaxy formation, a new inflationary universe scenario, grand unified phase transitions and the early Universe, the generalized second law of thermodynamics, vacuum polarization near black holes, the relativity of vacuum, black hole evaporations and their cosmological consequences, currents in supersymmetric theories, the Kaluza-Klein theories, gauge algebra and quantization, and twistor theory. This volume constitutes the proceedings of the Second Seminar on Quantum Gravity held in Moscow in 1981.

  19. Cohomological gravity

    NASA Astrophysics Data System (ADS)

    Birmingham, Danny; Rakowski, Mark

    1993-07-01

    We construct a theory of cohomological gravity in arbitrary dimensions based upon a local vector supersyrnmetry algebra. The observables in this theory are polynomial, but generally non-local operators, and have a natural interpretation in terms of a universal bundle for gravity. As such, their correlation functions correspond to cohomology classes on moduli spaces of Riemannian connections. In this uniformization approach different moduli spaces are obtained by introducing curvature singularities on codimension two submanifolds via a puncture operator. This puncture operator is constructed from a naturally occurring differential form of co-degree two in the theory, and we are led to speculate on connections between this continuum quantum field theory, and the discrete Regge calculus.

  20. Measurement of the biological center of gravity using an X-ray

    NASA Astrophysics Data System (ADS)

    Kawasaki, Tomomi; Hasegawa, Katsuya

    It is very important knowledge the center of gravity when observing the behavior of the animals in the low-gravity space. The center of gravity can be measured by using the center of gravity meter. However, the center of gravity meter that measures the use in zero-gravity space. Therefore, we have developed a method for determination of the center of gravity using an X-ray. Absorption of X-rays is related to the mass of the transmission path, so we determined the mass distribution by the X-ray image. It was possible to calculate the center of gravity by analyzing the image. It is not only static data but also to get the dynamic data using the movie. We can analyze the center of gravity changes in the animals in the low-gravity. It may be useful for the analysis of animal behavior to gravity changes.

  1. Zeroing in on Supersymmetric Radiation Amplitude Zeros

    SciTech Connect

    Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC

    2012-02-15

    Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.

  2. Zero-G Condensing Heat Exchanger with Integral Disinfection

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth A. (Inventor)

    2012-01-01

    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.

  3. Gravity and positional homeostasis of the cell

    NASA Astrophysics Data System (ADS)

    Nace, George W.

    Normally bilateralization takes place in the presence of the Earth's gravity which produces torque, shear, tension and compression acting upon the naked aggregates of cytoplasm in the zygote which is only stabilized by a weak cytoskeleton. In an initial examination of the effects of these quantities on development, an expression is derived to describe the tendency of torque to rotate the egg and reorganize its constituents. This expression yields the net torque resulting from buoyancy and gravity acting upon a dumbbell shaped cell with heavy and light masses at either end and ``floating'' in a medium. Using crude values for the variables, torques of 2.5 × 10-13 to 8.5 × 10-1 dyne-cm are found to act upon cells ranging from 6.4 μm to 31 mm (chicken egg). By way of comparison six microtubules can exert a torque of 5 × 10-9 dyne-cm. (1) Gravity imparts torque to cells; (2) torque is reduced to zero as gravity approaches zero; and (3) torque is sensitive to cell size and particulate distribution. Cells must expend energy to maintain positional homeostasis against gravity. Although not previously recognized, Skylab 3 results support this hypothesis: tissue cultures used 58% more glucose on Earth than in space. The implications for developmental biology, physiology, genetics, and evolution are considered. At the cellular and tissue level the concept of ``gravity receptors'' may be unnecessary.

  4. Cosmological perturbations in mimetic Horndeski gravity

    NASA Astrophysics Data System (ADS)

    Arroja, Frederico; Bartolo, Nicola; Karmakar, Purnendu; Matarrese, Sabino

    2016-04-01

    We study linear scalar perturbations around a flat FLRW background in mimetic Horndeski gravity. In the absence of matter, we show that the Newtonian potential satisfies a second-order differential equation with no spatial derivatives. This implies that the sound speed for scalar perturbations is exactly zero on this background. We also show that in mimetic G3 theories the sound speed is equally zero. We obtain the equation of motion for the comoving curvature perturbation (first order differential equation) and solve it to find that the comoving curvature perturbation is constant on all scales in mimetic Horndeski gravity. We find solutions for the Newtonian potential evolution equation in two simple models. Finally we show that the sound speed is zero on all backgrounds and therefore the system does not have any wave-like scalar degrees of freedom.

  5. Starting From Ground Zero

    ERIC Educational Resources Information Center

    Fischer, William B.; Stauffer, Robert A.

    1978-01-01

    Erie County Community College (New York) has developed a zero-based program budgeting system to meet current fiscal problems and diminished resources. The system allocates resources on the basis of program effectiveness and market potential. (LH)

  6. Behavioral responses to partial-gravity conditions in rats.

    PubMed

    Zeredo, Jorge L; Toda, Kazuo; Matsuura, Masaaki; Kumei, Yasuhiro

    2012-11-01

    The effects of microgravity or hypergravity on living organisms have been studied extensively; however, thus far no studies have addressed the effects of "partial-gravity", that is, the low-gravity levels between the unit gravity (1G) on Earth and zero gravity (0 G) in space. The purpose of the present study was to examine behavioral responses in rats under partial-gravity conditions. Rat behavior was monitored by video cameras during parabolic flights. The flight trajectory was customized in order to generate graded levels of partial gravity. Gravity-dependent behavior patterns were observed in rats. In the conditions of 0.4 G through 0.2G, rats showed startle and crouching. Hindlimb stretching emerged at 0.15 G and was more frequently observed toward 0.01 G. Different thresholds may exist for emotional and balance/posture-related behaviors. PMID:23036524

  7. Fluid mass sensor for a zero gravity environment

    NASA Technical Reports Server (NTRS)

    Fogal, G. L. (Inventor)

    1976-01-01

    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.

  8. A Zero-Gravity Cup for Drinking Beverages in Microgravity

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  9. Dental equipment test during zero-gravity flight

    NASA Technical Reports Server (NTRS)

    Young, John; Gosbee, John; Billica, Roger

    1991-01-01

    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.

  10. Venipuncture and intravenous infusion access during zero-gravity flight

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  11. Separation Of Liquid And Gas In Zero Gravity

    NASA Technical Reports Server (NTRS)

    Howard, Frank S.; Fraser, Wilson S.

    1991-01-01

    Pair of reports describe scheme for separating liquid from gas so liquid could be pumped. Designed to operate in absence of gravitation. Jet of liquid, gas, or liquid/gas mixture fed circumferentially into cylindrical tank filled with liquid/gas mixture. Jet starts liquid swirling. Swirling motion centrifugally separates liquid from gas. Liquid then pumped from tank at point approximately diametrically opposite point of injection of jet. Vortex phase separator replaces such devices as bladders and screens. Requires no components inside tank. Pumps for gas and liquid outside tank and easily accessible for maintenance and repairs.

  12. Neural-Thyroid Interaction on Skeletal Isomyosin in Zero Gravity

    NASA Technical Reports Server (NTRS)

    Baldwin, Kenneth M.

    2000-01-01

    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.

  13. Zero-gravity atmospheric Cloud Physics Experiment Laboratory; Programmatics report

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The programmatics effort included comprehensive analyses in four major areas: (1) work breakdown structure, (2) schedules, (3) costs, and (4) supporting research and technology. These analyses are discussed in detail in the following sections which identify and define the laboratory project development schedule, cost estimates, funding distributions and supporting research and technology requirements. All programmatics analyses are correlated among themselves and with the technical analyses by means of the work breakdown structure which serves as a common framework for program definition. In addition, the programmatic analyses reflect the results of analyses and plans for reliability, safety, test, and maintenance and refurbishment.

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

    NASA Technical Reports Server (NTRS)

    1986-01-01

    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.

  15. Ultraviolet behavior of transverse gravity

    NASA Astrophysics Data System (ADS)

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J. J.

    2008-10-01

    The structure of the divergences for transverse theories of gravity is studied to one-loop order. These theories are invariant only under those diffeomorphisms that enjoy unit Jacobian determinant (TDiff), so that the determinant of the metric transforms as a true scalar instead of a density. Generically, the models include an additional scalar degree of freedom contained in the metric besides the usual spin two component. When the cosmological constant is fine tuned to zero, there are only two theories which are on shell finite, namely the one in which the symmetry is enhanced to the full group of diffeomorphisms, i.e. Einstein's gravity, and another one denoted by WTDiff which enjoys local Weyl invariance. Both of them are free from the additional scalar.

  16. Quasilocalization of gravity on a brane by resonant modes.

    PubMed

    Csáki, C; Erlich, J; Hollowood, T J

    2000-06-26

    We examine the behavior of gravity in brane theories with extra dimensions in a nonfactorizable background geometry. We find that for metrics which are asymptotically flat far from the brane there is a resonant graviton mode at zero energy. The presence of this resonance ensures quasilocalization of gravity, whereby at intermediate scales the gravitational laws on the brane are approximately four dimensional. However, for scales larger than the lifetime of the graviton resonance the five-dimensional laws of gravity will be reproduced due to the decay of the four-dimensional graviton. We also give a simple classification of effective gravity theories for general background geometries. PMID:10991092

  17. The spinning artificial gravity environment: A design project

    NASA Technical Reports Server (NTRS)

    Pignataro, Robert; Crymes, Jeff; Marzec, Tom; Seibert, Joe; Walker, Gary

    1987-01-01

    The SAGE, or Spinning Artificial Gravity Environment, design was carried out to develop an artificial gravity space station which could be used as a platform for the performance of medical research to determine the benefits of various, fractional gravity levels for astronauts normally subject to zero gravity. Desirable both for its medical research mission and a mission for the study of closed loop life-support and other factors in prolonged space flight, SAGE was designed as a low Earth orbiting, solar powered, manned space station.

  18. Artificial gravity.

    PubMed

    Scott, William B

    2005-04-25

    NASA's Artificial Gravity program consists of a team of researchers from Wyle Laboratories, NASA Johnson Space Center, and the University of Texas Medical Branch (UTMB). The short-radius centrifuge (SRC), built by Wyle Laboratories, will be integrated with UTMB's conducted bedrest studies, which mimic the detrimental effects of weightlessness (or microgravity). Bedrest subjects will be spun on the SRC at various accelerations and for various time periods, while being monitored medically. Parameters such as bone loss, muscle atrophy, balance control, and oxygen consumption will then be compared in order to research ways of mitigating the impact on astronauts' physiology. Other potential benefits from these studies extend to population groups on Earth, such as bedridden patients. PMID:15852559

  19. Graviresponses of osteocytes under altered gravity

    NASA Astrophysics Data System (ADS)

    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

    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.

  20. Zero-leak valve

    NASA Technical Reports Server (NTRS)

    Macglashan, W. F., Jr.

    1980-01-01

    Zero-leakage valve has fluid-sealing diaphragm support and flat sievelike sealing surface. Diaphragm-support valve is easy to fabricate and requires minimum maintenance. Potential applications include isolation valve for waste systems and remote air-actuated valve. Device is also useful in controlling flow of liquid fluorine and corrosive fluids at high pressures.

  1. Zero-Base Budgeting.

    ERIC Educational Resources Information Center

    Yagielski, John

    In outline form, this document presents basic information on the school district, the reasons the district considered zero-base budgeting (ZBB), the formation and membership of the advisory School Cost Analysis Team, the district's investigation of the ZBB concept, an overview of the ways the district used the ZBB process, the identification of…

  2. Zero-Base Budgeting.

    ERIC Educational Resources Information Center

    Harvey, L. James

    The concept of Zero-Base Budgeting (ZBB) is discussed in terms of its application, advantages, disadvantages, and implementation in an effective planning, management, and evaluation (PME) system. A ZBB system requires administrators to: review all programs and expenditures annually, set clear cut goals, and analyze all possible alternatives for…

  3. Those Elusive Imaginary Zeros.

    ERIC Educational Resources Information Center

    Travers, Robert; Kim, David

    1982-01-01

    A method for finding the complex roots of a graph is detailed. A conjecture is made regarding the nature of zero points of fourth-degree polynomial functions, but it is not proven in general. Mathematical induction is viewed as a promising tool to prove the conjecture that turned out unproductive. (MP)

  4. Zero Tolerance versus Privacy.

    ERIC Educational Resources Information Center

    Dowling-Sendor, Benjamin

    2000-01-01

    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)

  5. Zero Base Budgeting.

    ERIC Educational Resources Information Center

    Sarndal, Anne G.

    1979-01-01

    Traditional budgeting starts with the previous year's budget, but zero base budgeting demands that each activity be justified from "scratch," and establishes a number of increments for each unit, in order of priority. Given the set of increments and the money available, management can determine what activities to finance. (Author)

  6. Parrot "Understands" Zero

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    The walnut sized brain of the African grey parrot may actually be capable of comprehending abstract mathematical concepts. The bird seems to understand a numerical concept akin to zero--an abstract notion that humans don't typically understand until they are three or four years old. Alex, the 28-year-old parrot who lives in a Brandeis University

  7. Parrot "Understands" Zero

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    The walnut sized brain of the African grey parrot may actually be capable of comprehending abstract mathematical concepts. The bird seems to understand a numerical concept akin to zero--an abstract notion that humans don't typically understand until they are three or four years old. Alex, the 28-year-old parrot who lives in a Brandeis University…

  8. Zero Tolerance Expulsions.

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    1999-01-01

    Most courts have flexibly interpreted the constitutional requirement of procedural and substantive due process in favor of zero-tolerance expulsion decisions. While being sensitive to community intolerance for threats to school safety (student possession of guns or drugs), school leaders should modulate development and enforcement of expulsion…

  9. Technology at Ground Zero.

    ERIC Educational Resources Information Center

    Techniques: Connecting Education and Careers, 2002

    2002-01-01

    Describes the robots used to aid in rescue and recovery at Ground Zero after the September 11, 2001 attack on the World Trade Center. The robots were developed as a result of national Science Foundation Quick Response Research Awards. Describes several awards that were made following the attack. (JOW)

  10. How Much Gravity Is Needed to Establish the Perceptual Upright?

    PubMed Central

    Harris, Laurence R.; Herpers, Rainer; Hofhammer, Thomas; Jenkin, Michael

    2014-01-01

    Might the gravity levels found on other planets and on the moon be sufficient to provide an adequate perception of upright for astronauts? Can the amount of gravity required be predicted from the physiological threshold for linear acceleration? The perception of upright is determined not only by gravity but also visual information when available and assumptions about the orientation of the body. Here, we used a human centrifuge to simulate gravity levels from zero to earth gravity along the long-axis of the body and measured observers' perception of upright using the Oriented Character Recognition Test (OCHART) with and without visual cues arranged to indicate a direction of gravity that differed from the body's long axis. This procedure allowed us to assess the relative contribution of the added gravity in determining the perceptual upright. Control experiments off the centrifuge allowed us to measure the relative contributions of normal gravity, vision, and body orientation for each participant. We found that the influence of 1 g in determining the perceptual upright did not depend on whether the acceleration was created by lying on the centrifuge or by normal gravity. The 50% threshold for centrifuge-simulated gravity's ability to influence the perceptual upright was at around 0.15 g, close to the level of moon gravity but much higher than the threshold for detecting linear acceleration along the long axis of the body. This observation may partially explain the instability of moonwalkers but is good news for future missions to Mars. PMID:25184481

  11. How much gravity is needed to establish the perceptual upright?

    PubMed

    Harris, Laurence R; Herpers, Rainer; Hofhammer, Thomas; Jenkin, Michael

    2014-01-01

    Might the gravity levels found on other planets and on the moon be sufficient to provide an adequate perception of upright for astronauts? Can the amount of gravity required be predicted from the physiological threshold for linear acceleration? The perception of upright is determined not only by gravity but also visual information when available and assumptions about the orientation of the body. Here, we used a human centrifuge to simulate gravity levels from zero to earth gravity along the long-axis of the body and measured observers' perception of upright using the Oriented Character Recognition Test (OCHART) with and without visual cues arranged to indicate a direction of gravity that differed from the body's long axis. This procedure allowed us to assess the relative contribution of the added gravity in determining the perceptual upright. Control experiments off the centrifuge allowed us to measure the relative contributions of normal gravity, vision, and body orientation for each participant. We found that the influence of 1 g in determining the perceptual upright did not depend on whether the acceleration was created by lying on the centrifuge or by normal gravity. The 50% threshold for centrifuge-simulated gravity's ability to influence the perceptual upright was at around 0.15 g, close to the level of moon gravity but much higher than the threshold for detecting linear acceleration along the long axis of the body. This observation may partially explain the instability of moonwalkers but is good news for future missions to Mars. PMID:25184481

  12. Gravity and Mirror Gravity in Plebanski Formulation

    NASA Astrophysics Data System (ADS)

    Bennett, D. L.; Laperashvili, L. V.; Nielsen, H. B.; Tureanu, A.

    2013-05-01

    We present several theories of four-dimensional gravity in the Plebanski formulation, in which the tetrads and the connections are the independent dynamical variables. We consider the relation between different versions of gravitational theories: Einsteinian, "topological," "mirror" gravities and gravity with torsion. We assume that our world, in which we live, is described by the self-dual left-handed gravity, and propose that if the Mirror World exists in Nature, then the "mirror gravity" is the right-handed antiself-dual gravity. In this connection, we give a brief review of gravi-weak unification models. In accordance with cosmological measurements, we consider the Universe with broken mirror parity. We also discuss the problems of cosmological constant and communication between visible and mirror worlds. Investigating a special version of the Riemann-Cartan space-time, which has torsion as an additional geometric property, we have shown that in the Plebanski formulation the ordinary and dual "topological" sectors of gravity, as well as the gravity with torsion, are equivalent. Equations of motion are obtained. In this context, we have also discussed a "pure connection gravity" — a diffeomorphism-invariant gauge theory of gravity. Loop Quantum Gravity is also briefly reviewed.

  13. Gravity data of Nevada

    USGS Publications Warehouse

    Ponce, David A.

    1997-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  15. Zero Energy Windows

    SciTech Connect

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

    2006-05-17

    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.

  16. Gravity currents

    NASA Astrophysics Data System (ADS)

    Moodie, T. B.

    2002-07-01

    We review various aspects of buoyancy-driven flows arising from the sudden release of a fixed volume of heavy fluid into a larger body of less dense ambient fluid. The driving density contrasts for these flows may be due to temperature or salinity differences in the case of compositionally driven flows or to the presence of suspended material for their particle-driven counterpart. These so-called gravity currents play an important role in a vast array of geophysical and engineering applications and have been the subject of extensive theoretical, numerical, and experimental investigations over the past few decades. We shall first explore some of what we feel are the pertinent issues related to these flows in the context of their compositionally driven manifestation. In particular, we examine the efficacy of hydraulic theory in this context and explore its limits. We also discuss the notion of hyperbolicity as it relates to the governing hydraulic equations and the role of the stability Froude number in this concept. For the particle-driven flows we demonstrate the role played by the particles in the production of nonhydraulic effects. The roles of settling velocity and volume fraction of suspended particles in the generation of velocity shear will also be explored. The notion that particles give rise to nonhydraulic effects in the form of velocity shear has not been included in any published studies to date that we are aware of. We shall also present a means of accounting for initial turbulent energy of mixing in the release volume. This energy is that which would be injected into the system in the classic lock release experiment involving a well-mixed fixed-volume suspension maintained behind the lock gate prior to release. Results will be related to experimental data where possible.

  17. Type Zero Copper Proteins

    PubMed Central

    Lancaster, Kyle M.; DeBeer George, Serena; Yokoyama, Keiko; Richards, John H.; Gray, Harry B.

    2009-01-01

    Copper proteins play key roles in biological processes such as electron transfer and dioxygen activation; the active site of each of these proteins is classified as either type 1, 2, or 3, depending on its optical and electron paramagnetic resonance properties. We have built a new type of site that we call “type zero copper” by incorporating leucine, isoleucine, or phenylalanine in place of methionine at position 121 in C112D Pseudomonas aeruginosa azurin. X-ray crystallographic analysis shows that these sites adopt distorted tetrahedral geometries, with an unusually short Cu-O(G45 carbonyl) bond (2.35–2.55 Å). Relatively weak absorption near 800 nm and narrow parallel hyperfine splittings in EPR spectra are the spectroscopic signatures of type zero copper. Copper K-edge x-ray absorption spectra suggest elevated Cu(II) 4p character in the d-electron ground state. Cyclic voltammetric experiments demonstrate that the electron transfer reactivities of type zero azurins are enhanced relative to that of the corresponding type 2 (C112D) protein. PMID:20305734

  18. Low Gravity venting of Refrigerant 11

    NASA Technical Reports Server (NTRS)

    Labus, T. L.; Aydelott, J. C.; Lacovic, R. F.

    1972-01-01

    An experimental investigation was conducted in a five-second zero gravity facility to examine the effects of venting initially saturated Refrigerant 11 from a cylindrical container (15-cm diameter) under reduced gravitational conditions. The system Bond numbers studied were 0 (weightlessness), 9 and 63; the liquid exhibited a nearly zero-degree contact angle on the container surface. During the venting process, both liquid-vapor interface and liquid bulk vaporization occurred. The temperature of the liquid in the immediate vicinity of the liquid-vapor interface was found to decrease during venting, while the liquid bulk temperature remained constant. Qualitative observations of the effects of system acceleration, vent rate, and vapor volume presented. Quantitative information concerning the ullage pressure decay during low gravity venting is also included.

  19. First order gravity on the light front

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Speziale, Simone

    2015-03-01

    We study the canonical structure of the real first order formulation of general relativity on a null foliation. We use a tetrad decomposition which allows us to elegantly encode the nature of the foliation in the norm of a vector in the fiber bundle. The resulting constraint structure shows some peculiarities. In particular, the dynamical Einstein equations propagating the physical degrees of freedom appear in this formalism as second class tertiary constraints, which puts them on the same footing as the Hamiltonian constraint of Ashtekar's connection formulation. We also provide a framework to address the issue of zero modes in gravity, in particular, to study the nonperturbative fate of the zero modes of the linearized theory. Our results give a new angle on the dynamics of general relativity and can be used to quantize null hypersurfaces in the formalism of loop quantum gravity or spin foams.

  20. Chiral gravity, log gravity, and extremal CFT

    SciTech Connect

    Maloney, Alexander; Song Wei; Strominger, Andrew

    2010-03-15

    We show that the linearization of all exact solutions of classical chiral gravity around the AdS{sub 3} vacuum have positive energy. Nonchiral and negative-energy solutions of the linearized equations are infrared divergent at second order, and so are removed from the spectrum. In other words, chirality is confined and the equations of motion have linearization instabilities. We prove that the only stationary, axially symmetric solutions of chiral gravity are BTZ black holes, which have positive energy. It is further shown that classical log gravity--the theory with logarithmically relaxed boundary conditions--has finite asymptotic symmetry generators but is not chiral and hence may be dual at the quantum level to a logarithmic conformal field theories (CFT). Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We formally evaluate the Euclidean sum over geometries of chiral gravity and show that it gives precisely the holomorphic extremal CFT partition function. The modular invariance and integrality of the expansion coefficients of this partition function are consistent with the existence of an exact quantum theory of chiral gravity. We argue that the problem of quantizing chiral gravity is the holographic dual of the problem of constructing an extremal CFT, while quantizing log gravity is dual to the problem of constructing a logarithmic extremal CFT.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  2. Minimum length, extra dimensions, modified gravity and black hole remnants

    SciTech Connect

    Maziashvili, Michael

    2013-03-01

    We construct a Hilbert space representation of minimum-length deformed uncertainty relation in presence of extra dimensions. Following this construction, we study corrections to the gravitational potential (back reaction on gravity) with the use of correspondingly modified propagator in presence of two (spatial) extra dimensions. Interestingly enough, for r→0 the gravitational force approaches zero and the horizon for modified Schwarzschild-Tangherlini space-time disappears when the mass approaches quantum-gravity energy scale. This result points out to the existence of zero-temperature black hole remnants in ADD brane-world model.

  3. Inertial waste separation system for zero G WMS

    NASA Technical Reports Server (NTRS)

    1971-01-01

    The design, operation, and flight test are presented for an inertial waste separation system. Training personnel to use this system under simulated conditions is also discussed. Conclusions indicate that before the system is usable in zero gravity environments, a mirror for the user's guidance should be installed, the bounce cycle and bag changing system should be redesigned, and flange clips should be added to improve the user's balance.

  4. Observational bounds on modified gravity models

    SciTech Connect

    De Felice, Antonio; Mukherjee, Pia; Wang Yun

    2008-01-15

    Modified gravity provides a possible explanation for the currently observed cosmic acceleration. In this paper, we study general classes of modified gravity models. The Einstein-Hilbert action is modified by using general functions of the Ricci and the Gauss-Bonnet scalars, both in the metric and in the Palatini formalisms. We do not use an explicit form for the functions, but a general form with a valid Taylor expansion up to second order about redshift zero in the Riemann-scalars. The coefficients of this expansion are then reconstructed via the cosmic expansion history measured using current cosmological observations. These are the quantities of interest for theoretical considerations relating to ghosts and instabilities. We find that current data provide interesting constraints on the coefficients. The next-generation dark energy surveys should shrink the allowed parameter space for modified gravity models quite dramatically.

  5. Gravity-induced stresses in finite slopes

    USGS Publications Warehouse

    Savage, W.Z.

    1994-01-01

    An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

  6. Entropic force, noncommutative gravity, and ungravity

    SciTech Connect

    Nicolini, Piero

    2010-08-15

    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.

  7. Zero Tolerance Policies. Research Brief

    ERIC Educational Resources Information Center

    Muir, Mike

    2004-01-01

    Much of this brief comes from the ERIC Digest on Zero Tolerance Policies (ERIC #: ED451579). 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. Despite the controversies that it has…

  8. Theory of Edge Capillary-Gravity Waves

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    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.

  9. Urine specific gravity test

    MedlinePLUS

    Urine specific gravity is a laboratory test that shows the concentration of all chemical particles in the urine. ... changes to will tell the provider the specific gravity of your urine. The dipstick test gives only ...

  10. Low Gravity Improves Welds

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Kaukler, William F.; Plaster, Teresa C.

    1993-01-01

    Hardnesses and tensile strengths greater. Welds made under right conditions in low gravity appear superior to those made under high gravity. Conclusion drawn from results of welding experiments conducted during low- and high-gravity-simulating maneuvers of KC-135 airplane. Results have implications not only for welding in outer space but also for repeated rapid welding on Earth or in airplanes under simulated low gravity to obtain unusually strong joints.

  11. Terrestrial Gravity Fluctuations

    NASA Astrophysics Data System (ADS)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^-23 Hz^-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.

  12. Physics of Artificial Gravity

    NASA Technical Reports Server (NTRS)

    Bukley, Angie; Paloski, William; Clement, Gilles

    2006-01-01

    This chapter discusses potential technologies for achieving artificial gravity in a space vehicle. We begin with a series of definitions and a general description of the rotational dynamics behind the forces ultimately exerted on the human body during centrifugation, such as gravity level, gravity gradient, and Coriolis force. Human factors considerations and comfort limits associated with a rotating environment are then discussed. Finally, engineering options for designing space vehicles with artificial gravity are presented.

  13. Zero-dimensional magnetite

    NASA Astrophysics Data System (ADS)

    Arredondo, Melissa Gayle

    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.

  14. The mass, gravity field, and ephemeris of Mercury

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  15. Analytical Study of Gravity Effects on Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  16. Gravity is Geometry.

    ERIC Educational Resources Information Center

    MacKeown, P. K.

    1984-01-01

    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)

  17. Challenging Entropic Gravity

    NASA Astrophysics Data System (ADS)

    Roveto, Jonathan

    2011-11-01

    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.

  18. Gravity concentration technology

    SciTech Connect

    Burt, R.O.

    1984-01-01

    This book is devoted to gravity concentration technology for over a half a century. It provides coverage of the entire subject and contains information on both new and classical methods of gravity concentration. Contents: I. Laboratory Techniques and Theoretical Aspects. 1. An Introduction to Gravity Concentration. 2. Development of the Gravity Concentration Flowsheet. 3. Mineralogical Aspects of Gravity Concentration. 4. Heavy Liquid Separation for Specific Gravity Fractionation. 5. Theory of Heavy Medium Separation. 6. Theory of Gravity Concentration. II. Unit Processes. 7. The Unit Processes of Gravity Concentration. 8. Feed Preparation. 9. Heavy Medium Separation. 10. Jigging. 11. Sluice Boxes and Palongs. 12. Pinched Sluice Concentration. 13. Spiral Concentration. 14. The Shaking Table. 15. The Recovery of Fines. 16. Dry Gravity Concentration. 17. Miscellaneous Methods of Concentration. III. Plant Practice. 18. Gravity Concentration in Operation. 19. Coal Preparation in Great Britain. 20. Canadian Coal Preparation: A Growing Resource. 21. Processing of Iron Ore. 22. Industrial Minerals: Processing by Gravity Concentration. 23. Mineral Sands. 24. Gravity Concentration of Gold. 25. Technical Aspects of the Concentration of the Metal Oxides. 26. Cornish Tin Processing. 27. Alluvial Tin Processing in South East Asia. 28. The Treatment of Tungsten Ore. 29. Tantalum Processing. 30. Miscellaneous Minerals. Appendices: Symbols Used in Plant Flowsheets. Author Index. Subject Index.

  19. A manned Mars artificial gravity vehicle

    NASA Technical Reports Server (NTRS)

    Schultz, David N.; Rupp, Charles C.; Hajos, Gregory A.; Butler, John M., Jr.

    1988-01-01

    Data are presented on an artificial-gravity vehicle that is being designed for a manned Mars mission, using a 'split-mission' concept, in which an unmanned cargo vehicle is sent earlier and stored in a Mars orbit for a rendezvous with a manned vehicle about 1.5 years later. Special attention is given to the vehicle trajectory and configuration, the tether design, and the vehicle weight and launch requirements. It is shown that an artificial-G vehicle for a manned Mars missions is feasible technically and programmatically. Using an artificial-G vehicle instead of a zero-G vehicle for the piloted portion of a split mission provides physiological and human-factor-related benefits, does not eliminate requirements for zero-G countermeasures research (since zero-G is an abort mode), and could possibly reduce some life science activities. Diagrams are included.

  20. Survival of scalar zero modes in warped extra dimensions

    SciTech Connect

    George, Damien P.

    2011-05-15

    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.

  1. Zero Emission Coal

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    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.

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

    PubMed

    Ma, Baoshun; Darquenne, Chantal

    2012-08-01

    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 μm-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. PMID:22678957

  3. ZERO SUPPRESSION FOR RECORDERS

    DOEpatents

    Fort, W.G.S.

    1958-12-30

    A zero-suppression circuit for self-balancing recorder instruments is presented. The essential elements of the circuit include a converter-amplifier having two inputs, one for a reference voltage and the other for the signal voltage under analysis, and a servomotor with two control windings, one coupled to the a-c output of the converter-amplifier and the other receiving a reference input. Each input circuit to the converter-amplifier has a variable potentiometer and the sliders of the potentiometer are ganged together for movement by the servoinotor. The particular noveity of the circuit resides in the selection of resistance values for the potentiometer and a resistor in series with the potentiometer of the signal circuit to ensure the full value of signal voltage variation is impressed on a recorder mechanism driven by servomotor.

  4. Gravity wave transmission diagram

    NASA Astrophysics Data System (ADS)

    Tomikawa, Y.

    2015-12-01

    A new method of obtaining power spectral distribution of gravity waves as a function of ground-based horizontal phase speed and propagation direction from airglow observations has recently been proposed. To explain gravity wave power spectrum anisotropy, a new gravity wave transmission diagram was developed in this study. Gravity wave transmissivity depends on the existence of critical and turning levels for waves that are determined by background horizontal wind distributions. Gravity wave transmission diagrams for different horizontal wavelengths in simple background horizontal winds with constant vertical shear indicate that the effects of the turning level reflection are significant and strongly dependent on the horizontal wavelength.

  5. (abstract) Venus Gravity Field

    NASA Technical Reports Server (NTRS)

    Konopliv, A. S.; Sjogren, W. L.

    1995-01-01

    A global gravity field model of Venus to degree and order 75 (5772 spherical harmonic coefficients) has been estimated from Doppler radio tracking of the orbiting spacecraft Pioneer Venus Orbiter (1979-1992) and Magellan (1990-1994). After the successful aerobraking of Magellan, a near circular polar orbit was attained and relatively uniform gravity field resolution (approximately 200 km) was obtained with formal uncertainties of a few milligals. Detailed gravity for several highland features are displayed as gravity contours overlaying colored topography. The positive correlation of typography with gravity is very high being unlike that of the Earth, Moon, and Mars. The amplitudes are Earth-like, but have significantly different gravity-topography ratios for different features. Global gravity, geoid, and isostatic anomaly maps as well as the admittance function are displayed.

  6. NUT-charged black holes in Gauss-Bonnet gravity

    SciTech Connect

    Dehghani, M.H.; Mann, R.B.

    2005-12-15

    We investigate the existence of Taub-NUT (Newman-Unti-Tamburino) and Taub-bolt solutions in Gauss-Bonnet gravity and obtain the general form of these solutions in d dimensions. We find that for all nonextremal NUT solutions of Einstein gravity having no curvature singularity at r=N, there exist NUT solutions in Gauss-Bonnet gravity that contain these solutions in the limit that the Gauss-Bonnet parameter {alpha} goes to zero. Furthermore there are no NUT solutions in Gauss-Bonnet gravity that yield nonextremal NUT solutions to Einstein gravity having a curvature singularity at r=N in the limit {alpha}{yields}0. Indeed, we have nonextreme NUT solutions in 2+2k dimensions with nontrivial fibration only when the 2k-dimensional base space is chosen to be CP{sup 2k}. We also find that the Gauss-Bonnet gravity has extremal NUT solutions whenever the base space is a product of 2-torii with at most a two-dimensional factor space of positive curvature. Indeed, when the base space has at most one positively curved two-dimensional space as one of its factor spaces, then Gauss-Bonnet gravity admits extreme NUT solutions, even though there a curvature singularity exists at r=N. We also find that one can have bolt solutions in Gauss-Bonnet gravity with any base space with factor spaces of zero or positive constant curvature. The only case for which one does not have bolt solutions is in the absence of a cosmological term with zero curvature base space.

  7. Applications of the gauge/gravity duality

    NASA Astrophysics Data System (ADS)

    Nellore, Abhinav

    The gauge/gravity duality maps quantities computed in classical gravity theories to observables in certain gauge theories in the limits of strong coupling and large number of colors. Though no gauge theories with established gravity duals are known to occur in nature, simple models informed by the gauge/gravity duality could still provide intuition about physical phenomena. This dissertation focuses on two such models. The first model consists of five-dimensional gravity coupled to a single real scalar. Black hole solutions to this model describe a four-dimensional field theory at finite temperature. In Chapter 2, a family of black holes is constructed that closely mimics the equation of state of quantum chromodynamics. The second model consists of a U(1) gauge field minimally coupled to a complex scalar psi in four-dimensional gravity. Black hole solutions to this model describe a three-dimensional field theory at finite temperature and finite chemical potential. Above some critical temperature Tc, psi = psi* = 0. Below Tc, however, |psi| is nonzero along the thermodynamically stable branch of solutions, and the U(1) symmetry is spontaneously broken. Since superconductivity is typically understood as a broken gauge symmetry, the model may capture some features of high-temperature superconductors. Chapter 3 probes the model in the zero-temperature limit, where the black hole disappears. The solutions represent flows between infrared and ultraviolet field theories. In some solutions, the speed of light is lower in an infrared conformal theory than in the ultraviolet theory. Other solutions have an infrared Lifshitz symmetry, which features an anisotropy between the space and time coordinates. Chapter 1 is essentially a user's guide to the gauge/gravity duality. It provides enough information for non-experts to understand the remainder of the dissertation.

  8. 'Disturbance zeros' in multivariable systems

    NASA Technical Reports Server (NTRS)

    Patel, R. V.; Fallside, F.; Sinswat, V.

    1977-01-01

    Zeros of the transfer matrix relating the outputs to the disturbances ('disturbance zeros') of a linear time-invariant system are defined. It is shown that these zeros are invariant under output feedback to control inputs but not under state feedback to control inputs, and the effect of state feedback on disturbance zeros is studied. The results are used to develop an algorithm for assigning disturbance zeros and system poles by means of state feedback. As an application of the algorithm, it is shown that the disturbance zeros can be positioned such that the effect of a class of disturbances at the outputs is eliminated in the steady state. An example is given to illustrate the main results of the paper.

  9. A Demonstration of Einstein's Equivalence of Gravity and Acceleration

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2008-01-01

    In 1907, Einstein described a "Gedankenexperiment" in which he showed that free fall in a gravitational field is indistinguishable from a body at rest in an elevator accelerated upwards in zero gravity. This paper describes an apparatus, which is simple to make and simple to operate, that acts as an observable footnote to Einstein's example. It

  10. BF Models in Dual Formulations of Linearized Gravity

    SciTech Connect

    Bizdadea, Constantin; Cioroianu, Eugen M.; Danehkar, Ashbiz; Iordache, Marius; Saliu, Solange O.; Sararu, Silviu C.

    2009-05-22

    The case of couplings in D = 5 between a simple, maximal BF model and the dual formulation of linearized gravity is considered. All the possible interactions are exhausted by means of computing the 'free' local BRST cohomology in ghost number zero.

  11. A Demonstration of Einstein's Equivalence of Gravity and Acceleration

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2008-01-01

    In 1907, Einstein described a "Gedankenexperiment" in which he showed that free fall in a gravitational field is indistinguishable from a body at rest in an elevator accelerated upwards in zero gravity. This paper describes an apparatus, which is simple to make and simple to operate, that acts as an observable footnote to Einstein's example. It…

  12. Density-metric unimodular gravity: Vacuum maximal symmetry

    SciTech Connect

    Abbassi, A.H.; Abbassi, A.M.

    2011-05-15

    We have investigated the vacuum maximally symmetric solutions of recently proposed density-metric unimodular gravity theory. The results are widely different from inflationary scenario. The exponential dependence on time in deSitter space is substituted by a power law. Open space-times with non-zero cosmological constant are excluded.

  13. Zero emission coal

    SciTech Connect

    Ziock, H.; Lackner, K.

    2000-08-01

    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.

  14. Anisotropic stress and stability in modified gravity models

    SciTech Connect

    Saltas, Ippocratis D.; Kunz, Martin

    2011-03-15

    The existence of anisotropic stress of a purely geometrical origin seems to be a characteristic of higher order gravity models, and has been suggested as a probe to test these models observationally, for example, in weak lensing experiments. In this paper, we seek to find a class of higher order gravity models of f(R,G) type that would give us a zero anisotropic stress and study the consequences for the viability of the actual model. For the special case of a de Sitter background, we identify a subclass of models with the desired property. We also find a direct link between anisotropic stress and the stability of the model as well as the presence of extra degrees of freedom, which seems to be a general feature of higher order gravity models. Particularly, setting the anisotropic stress equal to zero for a de Sitter background leads to a singularity that makes it impossible to reach the de Sitter evolution.

  15. Canonical gravity with fermions

    SciTech Connect

    Bojowald, Martin; Das, Rupam

    2008-09-15

    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 manifestly realized in loop quantum gravity.

  16. Precision zero-home locator

    DOEpatents

    Stone, W.J.

    1983-10-31

    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.

  17. Precision zero-home locator

    DOEpatents

    Stone, William J.

    1986-01-01

    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.

  18. From gravity and the organism to gravity and the cell.

    PubMed

    Brown, A H

    1991-07-01

    This workshop on Gravity and the Cell was modeled on a 1968 conference on Gravity and the Organism. Each conference tried to identify the most salient scientific questions about how gravity is important to living systems. In the roughly two decades between the conferences there have been impressive advances in experimental methods, but the major scientific questions that have driven their applications to problems of gravitational biology, i.e., our broad research goals, remain much the same. In the case of plant research, improvements and extensions of biochemical techniques for investigating the ways organisms use environmental (g-force) information in salubrious ways has kept pace with progress in plant biochemistry. We now know much more about the roles of organic and inorganic substances that plants employ for information transfer and growth regulation and about the avenues and mechanisms for transport of those key substances within organisms. We have seen the acceptance of a "local control" concept that regulation of g-responses depends critically on plasmodesmata and gap junctions which allow plants and animals to throttle the transport of growth regulators across tissue boundaries often, especially in the case of plants, far removed from the morphological regions of concentration of statocytes that were once thought to be the exclusive bioaccelerometers used by plants. NASA's sponsorship of ground-based research in gravitational biology has served as important underpinning for orbital flight programs in space biology. The currently most noteworthy research area of ignorance is the mechanism by which the physical event of g-force susception becomes the biological process of g-force perception. Only rarely has it been possible to perform a definitive test of a theory of mechanism of gravity perception. Therefore, experimental research efforts in gravitational physiology still are essentially dependent on exploratory studies for which stimulus/response experiments require experimental manipulation of test subjects' g-force environment. Many research efforts have focused narrowly on contrasting the responses of test subjects to only two gravitational environments, 1 g versus real or simulated zero g. Much less effort has been devoted to studies at other g levels. For experiments in gravitational physiology three rotating machines have made, and no doubt will continue to make, important contributions: the centrifuge, the clinostat, and, most of all, the orbiting space vehicle. Some research trends, viewpoints, and shifts of emphasis are discussed. PMID:11537184

  19. Three-dimensional Gravity, Holography and Black Holes

    NASA Astrophysics Data System (ADS)

    Lashkari, Nima

    Gauge/gravity dualities and the matrix model provide us with exploratory frameworks for the study of quantum gravity (QG) in the presence of a cosmological constant that is negative or zero, respectively. Currently, in all the known examples instring theory, the gravity theory contains complicated matter fields and interactions. However, the idea of describing theories of quantum gravity in terms of dual non-gravitational theories, i.e. holography, has proven to go well beyond these examples. Motivated by holography, in the course of this thesis we explore simple models of quantum gravity with the goal of obtaining insight into non-perturbative QG, in particular the physics of black holes. We consider three-dimensional gravity with a negative cosmological constant. Weuse Ricci flow techniques to study flows between the potential vacua of topologically massive gravity and show that for large values of the Chern-Simons coupling anti-de Sitter space is the ground state. Moreover, we study spontaneous symmetry-breaking in vacua of theories of gravity coupled to scalars and gauge fields and find examples of discrete symmetry-breaking phases with exotic thermodynamic properties. We study three-dimensional gravity with a positive cosmological constant as a theory of quantum cosmology. We compute the full non-perturbative Euclidean partition function of de Sitter gravity by evaluating the gravity path integral on physically relevant Euclidean continuations of the static patch. The partition function diverges in a non-regularizable way and we interpret this as a hint that the theory does not exist at a quantum level. As we show however, the inclusion of the simplest form of interaction, the Chern-Simons term, removes the undesirable divergences.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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).

  1. A research of 3D gravity inversion based on the recovery of sparse underdetermined linear equations

    NASA Astrophysics Data System (ADS)

    Zhaohai, M.

    2014-12-01

    Because of the properties of gravity data, it is made difficult to solve the problem of multiple solutions. There are two main types of 3D gravity inversion methods:One of two methods is based on the improvement of the instability of the sensitive matrix, solving the problem of multiple solutions and instability in 3D gravity inversion. Another is to join weight function into the 3D gravity inversion iteration. Through constant iteration, it can renewal density values and weight function to achieve the purpose to solve the multiple solutions and instability of the 3D gravity data inversion. Thanks to the sparse nature of the solutions of 3D gravity data inversions, we can transform it into a sparse equation. Then, through solving the sparse equations, we can get perfect 3D gravity inversion results. The main principle is based on zero norm of sparse matrix solution of the equation. Zero norm is mainly to solve the nonzero solution of the sparse matrix. However, the method of this article adopted is same as the principle of zero norm. But the method is the opposite of zero norm to obtain zero value solution. Through the form of a Gaussian fitting solution of the zero norm, we can find the solution by using regularization principle. Moreover, this method has been proved that it had a certain resistance to random noise in the mathematics, and it was more suitable than zero norm for the solution of the geophysical data. 3D gravity which is adopted in this article can well identify abnormal body density distribution characteristics, and it can also recognize the space position of abnormal distribution very well. We can take advantage of the density of the upper and lower limit penalty function to make each rectangular residual density within a reasonable range. Finally, this 3D gravity inversion is applied to a variety of combination model test, such as a single straight three-dimensional model, the adjacent straight three-dimensional model and Y three-dimensional model. They are classical model. We find that the inversion results are basically consistent with the results of forward models. Finally we apply the 3D gravity inversion method to the actual gravity data in Texas of the USA state. And we get the 3D gravity inversion which is almost the same with previous results.

  2. Nonlinear Gravity and Capillary-Gravity Waves

    NASA Astrophysics Data System (ADS)

    Dias, Frdric; Kharif, Christian

    1999-01-01

    This review deals primarily with the bifurcation, stability, and evolution of gravity and capillary-gravity waves. Recent results on the bifurcation of various types of capillary-gravity waves, including two-dimensional solitary waves at the minimum of the dispersion curve, are reviewed. A survey of various mechanisms (including the most recent ones) to explain the frequency downshift phenomenon is provided. Recent significant results are given on "horseshoe" patterns, which are three-dimensional structures observable on the sea surface under the action of wind or in wave tank experiments. The so-called short-crested waves are then discussed. Finally, the importance of surface tension effects on steep waves is studied.

  3. Zero/zero rotorcraft certification issues. Volume 1: Executive summary

    NASA Technical Reports Server (NTRS)

    Adams, Richard J.

    1988-01-01

    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 the 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 exptremely low visibility operations be economically feasible. This is Volume 1 of three. It provides an overview of the Certification Issues Forum held in Phoenix, Arizona in August of 1987. It presents a consensus of 48 experts from government, manufacturer, and research communities on 50 specific Certification Issues. The topics of Operational Requirements, Procedures, Airworthiness, and Engineering Capabilities are discussed.

  4. Low-gravity facilities for Space Station planetology experiments

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A.

    1987-01-01

    For experimentation, space offers an environment which is unobtainable on earth. One characteristic is a gravity force less than 1 g, where g is the mean earth gravity acceleration of 9.8 m/sq s. The production of uniform gravity levels above zero g in space is discussed in relationship to experimental needs. For planetology experiments, providing gravity in space will make it possible to more nearly simulate conditions on natural bodies. The g-level is but one parameter involved in the design of a specific experiment. Other requirements may be: g-level range; g-level tolerance value; Coriolis tolerance value; volume requirement g-level duration; power and materials for the experiment; and automated or man-tended operations. These requirements, and certainly others, will dictate the type of facility which should be considered. The use of the Space Station of the Tethered Satellite System configurations is discussed.

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

    PubMed

    Godin, Oleg A

    2014-03-01

    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

  6. Unified theory of nonlinear electrodynamics and gravity

    SciTech Connect

    Torres-Gomez, Alexander; Krasnov, Kirill; Scarinci, Carlos

    2011-01-15

    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.

  7. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    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.

  8. Gravitomagnetism in massive gravity

    NASA Astrophysics Data System (ADS)

    Tasseten, Kezban; Tekin, Bayram

    2016-02-01

    Massive gravity in the weak field limit is described by the Fierz-Pauli theory with 5 degrees of freedom in four dimensions. In this theory, we calculate the gravitomagnetic effects (potential energy) between two pointlike, spinning sources that also orbit around each other in the limit where the spins and the velocities are small. Spin-spin, spin-orbit and orbit-orbit interactions in massive gravity theory have rather remarkable, discrete differences from their counterparts in general relativity. Our computation is applicable for large distances, for example, for interaction between galaxies or galaxy clusters where massive gravity is expected to play a role. We also extend the computations to quadratic gravity theories in four dimensions and find the lowest order gravitomagnetic effects and show that at small separations quadratic gravity behaves differently than general relativity.

  9. Anti-gravity device

    NASA Technical Reports Server (NTRS)

    Palsingh, S. (Inventor)

    1975-01-01

    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.

  10. Warped brane worlds in critical gravity

    NASA Astrophysics Data System (ADS)

    Zhong, Yi; Chen, Feng-Wei; Xie, Qun-Ying; Liu, Yu-Xiao

    2014-12-01

    We investigate the brane models in arbitrary dimensional critical gravity presented in Lu and Pope (Phys Rev Lett 106:181302, 2011). For the models of the thin branes with codimension one, the Gibbons-Hawking surface term and the junction conditions are derived, with which the analytical solutions for the flat, AdS, and dS branes are obtained at the critical point of the critical gravity. It is found that all these branes are embedded in an AdS spacetime, but, in general, the effective cosmological constant of the AdS spacetime is not equal to the naked one in the critical gravity, which can be positive, zero, and negative. Another interesting result is that the brane tension can also be positive, zero, or negative, depending on the symmetry of the thin brane and the values of the parameters of the theory, which is very different from the case in general relativity. It is shown that the mass hierarchy problem can be solved in the braneworld model in the higher-derivative critical gravity. We also study the thick brane model and find analytical and numerical solutions of the flat, AdS, and dS branes. It is found that some branes will have inner structure when some parameters of the theory are larger than their critical values, which may result in resonant KK modes for some bulk matter fields. The flat branes with positive energy density and AdS branes with negative energy density are embedded in an -dimensional AdS spacetime, while the dS branes with positive energy density are embedded in an -dimensional Minkowski one.

  11. Quantum gravity influences the black hole physics

    NASA Astrophysics Data System (ADS)

    Li, Xiang

    2002-06-01

    The new state equations of thermal radiation is obtained by using the generalized uncertainty relation, in the context of quantum gravity. It is noticeable that the pressure of radiation becomes divergent when the system approaches a non-zero minimal length, which implies the prohibition against the singularity in the formation of black hole. Using the time-energy uncertainty, the corrections to the Schwarzchild black hole thermodynamics are investigated. A negative and logarithmic correction to the Bekenstein-Hawking entropy is obtained. The mass loss rate of the black hole in the Planck realm is also discussed.

  12. Holographic renormalization of new massive gravity

    SciTech Connect

    Alishahiha, Mohsen; Naseh, Ali

    2010-11-15

    We study holographic renormalization for three-dimensional new massive gravity. By studying the general falloff conditions for the metric allowed by the model at infinity, we show that at the critical point where the central charges of the dual conformal field theory (CFT) are zero, it contains a leading logarithmic behavior. In the context of AdS/CFT correspondence it can be identified as a source for an irrelevant operator in the dual CFT. The presence of the logarithmic falloff may be interpreted as the fact that the dual CFT would be a logarithmic conformal field theory.

  13. Anomaly cancellation for super- W -gravity

    NASA Astrophysics Data System (ADS)

    Mansfield, P.; Spence, B.

    1991-08-01

    We generalise the description of minimal superconformal models coupled to supergravity, due to Distler, Hlousek and Kawaii, to super- W -gravity. When the chiral algebra is the generalisation of the W-algebra associated to any contragredient Lie superalgebra the total central charge vanishes as a result of Lie superalgebra identities. When the algebra has only fermionic simple roots there is N = 1 superconformal invariance and for this case we describe the Lax operators and construct gravitationally dressed primary superfields of weight zero. We also prove the anomaly cancellation associated with the generalised non-abelian Toda theories. Address from 1 October 1991: Physics Department, Imperial College, London SW7 2BZ, UK.

  14. Particle cloud combustion in reduced gravity

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.

    1988-01-01

    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.

  15. Dynamical structure of pure Lovelock gravity

    NASA Astrophysics Data System (ADS)

    Dadhich, Naresh; Durka, Remigiusz; Merino, Nelson; Miskovic, Olivera

    2016-03-01

    We study the dynamical structure of pure Lovelock gravity in spacetime dimensions higher than four using the Hamiltonian formalism. The action consists of a cosmological constant and a single higher-order polynomial in the Riemann tensor. Similarly to the Einstein-Hilbert action, it possesses a unique constant curvature vacuum and charged black hole solutions. We analyze physical degrees of freedom and local symmetries in this theory. In contrast to the Einstein-Hilbert case, the number of degrees of freedom depends on the background and can vary from zero to the maximal value carried by the Lovelock theory.

  16. Grasping objects autonomously in simulated KC-135 zero-g

    NASA Technical Reports Server (NTRS)

    Norsworthy, Robert S.

    1994-01-01

    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.

  17. Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Vagt, Nicole; Braun, Markus

    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).

  19. Thermodynamics and gravity

    SciTech Connect

    Weiss, R.A.

    1992-03-01

    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 of thermodynamics for matter located in a gravity field is investigated by applying the broken spacetime symmetry forms of the first and second laws of thermodynamics. In a gravity field the laws of thermodynamics are dependent on the internal phase angles theta r(r) of the radial coordinates of a gravitating mass, and this dependence can also be expressed in terms of the gravitational constant Gr(r) whose value depends on radial distance. In this way the effects of a gravity field on the state equations of real gases, solids and quantum liquids is determined. The Debye theory of solids is generalized to include the case of a solid located in a gravity field. This paper suggests thermodynamic measurements that can be used to determine Gr(r) for a planetary gravity field. Because the internal phase angles of the radial coordinates are related to the photon redshift in a gravity field it is suggested that the photon redshift may be used to determine the variation of Gr(r) with radial distance.

  20. Gribov ambiguity in asymptotically AdS three-dimensional gravity

    SciTech Connect

    Anabalon, Andres; Canfora, Fabrizio; Giacomini, Alex; Oliva, Julio

    2011-03-15

    In this paper the zero modes of the de Donder gauge Faddeev-Popov operator for three-dimensional gravity with negative cosmological constant are analyzed. It is found that the AdS{sub 3} vacuum produces (infinitely many) normalizable smooth zero modes of the Faddeev-Popov operator. On the other hand, it is found that the Banados-Teitelboim-Zanelli black hole (including the zero mass black hole) does not generate zero modes. This differs from the usual Gribov problem in QCD where, close to the maximally symmetric vacuum, the Faddeev-Popov determinant is positive definite while 'far enough' from the vacuum it can vanish. This suggests that the zero mass Banados-Teitelboim-Zanelli black hole could be a suitable ground state of three-dimensional gravity with negative cosmological constant. Because of the kinematic origin of this result, it also applies for other covariant gravity theories in three dimensions with AdS{sub 3} as maximally symmetric solution, such as new massive gravity and topologically massive gravity. The relevance of these results for supersymmetry breaking is pointed out.

  1. [Aiming for zero blindness].

    PubMed

    Nakazawa, Toru

    2015-03-01

    Glaucoma is the leading cause of acquired blindness in Japan. One reason that it often leads to blindness is that it can continue to worsen even after effective medical reduction of intraocular pressure (IOP), the only evidence-based treatment. The limitations of current treatments make it critical to identify IOP-independent factors that can cause glaucoma and develop new drugs to target these factors. This is a challenging task, as the pathology of glaucoma is thought to be very complex, with different combinations of factors underlying its development and progression in different patients. Additionally, there is a deficiency in methods to efficiently perform clinical evaluations and reliably probe the state of the disease over relatively short periods. In addition, newly developed drugs need to be evaluated with clinical trials, for which human and financial resources are limited, before they can be widely used for treatment. Taking all these issues into consideration, it is evident that there are two urgent issues to consider: the development of methods to classify glaucoma in detail based on its pathology, and the improvement of clinical evaluation methods. In this review, we discuss some of our efforts to develop new neuroprotective agents for glaucoma, with a focus on the following three areas: 1. Clinical research and development of methods to classify glaucoma in detail based on IOP-independent factors, and the exploration of possibilities for the improvement of clinical evaluation of glaucoma. 2. Pathology-based research and development of new drugs for glaucoma, focusing on comprehensive gene expression analysis and the development of molecule-targeting drugs, using murine optic nerve crush as a disease model. 3. Development of next generation in vivo imaging modalities and the establishment of infrastructure enabling "big-data" analysis. First, we discuss our clinical research and the development of methods to classify glaucoma in detail based on IOP-independent factors, as well as our investigation of ways to improve the clinical evaluation of the disease. Our research was prompted by the multifactorial nature of glaucoma. There is a high degree of variability in the pattern and speed of the progression of visual field defects in individual patients, presenting a major obstacle for successful clinical trials. To overcome this, we classified the eyes of glaucoma patients into 4 types, corresponding to the 4 patterns of glaucomatous optic nerve head morphology described: by Nicolela et al. and then tested the validity of this method by assessing the uniformity of clinical features in each group. We found that in normal tension glaucoma (NTG) eyes, each disc morphology group had a characteristic location in which the loss of circumpapillary retinal nerve fiber layer thickness (cpRNFLT; measured with optical coherence tomography: OCT) was most likely to occur. Furthermore, the incidence of reductions in visual acuity differed between the groups, as did the speed of visual field loss, the distribution of defective visual field test points, and the location of test points that were most susceptible to progressive damage, measured by Humphrey static perimetry. These results indicate that Nicolela's method of classifying eyes with glaucoma was able to overcome the difficulties caused by the diverse nature of the disease, at least to a certain extent. Building on these findings, we then set out to identify sectors of the visual field that correspond to the distribution of retinal nerve fibers, with the aim of detecting glaucoma progression with improved sensitivity. We first mapped the statistical correlation between visual field test points and cpRNFLT in each temporal clock-hour sector (from 6 to 12 o'clock), using OCT data from NTG patients. The resulting series of maps allowed us to identify areas containing visual field test points that were prone to be affected together as a group. We also used a similar method to identify visual field sectors within a 10 x 10 grid displayed by an OCT map of the macula. By analyzing both the visual field and the macular map sectors, we anticipate that a more accurate and sensitive detection of glaucoma progression can become possible. We also used laser speckle flowgraphy (LSFG) to assess optic nerve blood flow. We found that compared to healthy eyes, eyes with early-stage NTG had decreased blood flow, and the peak of the blood flow wave form of each heartbeat was delayed. Finally, we used a method combining swept source OCT (SS-OCT) and newly developed analysis software to reconstruct the entire lamina cribrosa, a structure situated deep in the optic nerve head. This morphological analysis returned preliminary data suggesting that alterations in the morphology of the lamina cribrosa are already present in the early stages of glaucoma. This result indicates that axonal injury, mediated by morphological abnormalities of the lamina cribrosa, is involved in the pathogenesis of glaucoma. The next topic discussed is the pathology-based drug research and development, focusing on the use of comprehensive gene expression analysis and the development of molecule-targeting drugs in a murine model of optic nerve injury. Learning from clinical data on glaucoma and the lamina cribrosa, we carried out basic research to first determine what factors regulate axonal injury, and then develop drugs targeting these factors. Specifically, we performed a comprehensive gene expression analysis, using a next generation sequencer, and pathway analysis of retinal samples obtained from a murine model of axonal injury. This analysis revealed a characteristic upregulation of genes (such as Chop) that belongs to the endoplasmic reticulum stress pathway. An immunohistological analysis revealed that these changes in gene expression took place in the retinal ganglion cells, suggesting that endoplasmic reticulum stress molecules may be suitable therapeutic targets. Among these molecules, we chose CHOP as our primary target for drug development. Currently, we are in the process of screening a library of 1274 drugs, all of which are already used in human subjects, for CHOP inhibitors. The last topic of our discussion is future possibilities for glaucoma management. First, we discuss the development of next generation in vivo imaging modalities that allow detailed description of pathomechanisms of this multifactorial disease, glaucoma. The purpose of this research was to improve the efficacy of glaucoma diagnosis and to visualize its pathology at a cellular/molecular level and develop molecule-specific therapies. Currently available visual field tests are subjective, since they rely on a determination of the threshold of light perception, and are affected by poor reproducibility. The current dependence on visual field tests to ascertain the progression of glaucoma is thus a serious limitation on an important task of ophthalmologists. We, therefore, turned our focus to the establishment of an in vivo imaging method to detect dying retinal ganglion cells, which would highlight the pathologic state of glaucoma with high sensitivity. To this end, we used confocal scanning ophthalmoscopy to assess the usefulness of SYTOX Orange as a cell death probe. Our results showed that this probe could reveal dying retinal ganglion cells clearly, quickly and with high sensitivity. We, therefore, believe that the clinical application of probes that can sensitively detect dying retinal ganglion cells is a highly promising approach. This also applies to the use of molecular tools that can provide information on the molecular pathology of glaucoma. Finally, we would like to introduce our national collaborative work on the analysis of "big-data". The project aims to collect as wide a range of data as possible at an unprecedented scale. The data to be registered ranges from basic glaucoma data, such as IOP and visual field test results, to data from the most sophisticated comprehensive expression analyses or imaging data. This is an important area of research, since it promises to enable the exploration of targets for drug discovery and the identification of new biomarkers to efficiently detect glaucoma progression by applying new analysis strategies to the complex mass data. The project not only depends on the collaborative efforts of various types of clinical settings including private practices, medical centers and university hospitals, but also contributions of the pharmaceutical and the medical device industries. Thus, uniting a wide range of Japanese interests and resources is the key for success. In summary, in order to aim for ZERO BLINDNESS, a drastic improvement in the quality of our patient care, drug development research for unmet medical demands, and a strategic collaboration of various professionals in the ophthalmic industry are essential. With the deep appreciation we fell towards the selfless support extended during the earthquake disaster, we wish to translate our "gratitude" into "power" from Tohoku. In doing so, we as academicians are determined to keep on contributing to the society by making progress in the medicine. PMID:25854109

  2. Effects of background gravity stimuli on gravity-controlled behavior

    NASA Technical Reports Server (NTRS)

    Mccoy, D. F.

    1976-01-01

    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.

  3. Containment of a silicone fluid free surface in reduced gravity

    NASA Technical Reports Server (NTRS)

    Pline, A.; Jacobson, T.

    1988-01-01

    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.

  4. On the Newtonian limit of emergent NC gravity and long-distance corrections

    NASA Astrophysics Data System (ADS)

    Steinacker, Harold

    2009-12-01

    We show how Newtonian gravity emerges on 4-dimensional non-commutative spacetime branes in Yang-Mills matrix models. Large matter clusters such as galaxies are embedded in large-scale harmonic deformations of the space-time brane, which screen gravity for long distances. On shorter scales, the local matter distribution reproduces Newtonian gravity via local deformations of the brane and its metric. The harmonic ``gravity bag'' acts as a halo with effective positive energy density. This leads in particular to a significant enhancement of the orbital velocities around galaxies at large distances compared with the Newtonian case, before dropping to zero as the geometry merges with a Milne-like cosmology. Besides these ``harmonic'' solutions, there is another class of solutions which is more similar to Einstein gravity. Thus the IKKT model provides an accessible candidate for a quantum theory of gravity.

  5. Net zero building energy conservation

    NASA Astrophysics Data System (ADS)

    Kadam, Rohit

    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.

  6. The zero exemplar distance problem.

    PubMed

    Jiang, Minghui

    2011-09-01

    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 article, we give a very simple alternative proof of this result. We also study the problem Zero Exemplar Distance for multichromosomal genomes without gene order, and prove the analogous result that it is also NP-hard even if each gene appears at most two times in each genome. For the positive direction, we show that both variants of Zero Exemplar Distance admit polynomial-time algorithms if each gene appears exactly once in one genome and at least once in the other genome. In addition, we present a polynomial-time algorithm for the related problem Exemplar Longest Common Subsequence in the special case that each mandatory symbol appears exactly once in one input sequence and at least once in the other input sequence. This answers an open question of Bonizzoni et al. We also show that Zero Exemplar Distance for multichromosomal genomes without gene order is fixed-parameter tractable in the general case if the parameter is the maximum number of chromosomes in each genome. PMID:21899417

  7. Introduction to Massive Gravity

    NASA Astrophysics Data System (ADS)

    de Rham, Claudia

    We review recent progress on massive gravity. We first show how extra dimensions prove to be a useful tool in building theories of modified gravity, including Galileon theories and their DBI extensions. DGP arises from an infinite size extra dimension, and we show how massive gravity arises from `deconstructing' the extra dimension in the vielbein formalism. We then explain how the ghost issue is resolved in that special theory of massive gravity. The viability of such models relies on the Vainshtein mechanism which is best described in terms of Galileons. While its implementation is successful in most of these models it also comes hand in hand with superluminalities and strong coupling which are reviewed and their real consequences are discussed.

  8. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    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.

  9. Superconducting tensor gravity gradiometer

    NASA Technical Reports Server (NTRS)

    Paik, H. J.

    1981-01-01

    The employment of superconductivity and other material properties at cryogenic temperatures to fabricate sensitive, low-drift, gravity gradiometer is described. The device yields a reduction of noise of four orders of magnitude over room temperature gradiometers, and direct summation and subtraction of signals from accelerometers in varying orientations are possible with superconducting circuitry. Additional circuits permit determination of the linear and angular acceleration vectors independent of the measurement of the gravity gradient tensor. A dewar flask capable of maintaining helium in a liquid state for a year's duration is under development by NASA, and a superconducting tensor gravity gradiometer for the NASA Geodynamics Program is intended for a LEO polar trajectory to measure the harmonic expansion coefficients of the earth's gravity field up to order 300.

  10. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1989-01-01

    Variable Gravity Laboratory studies are discussed. The following subject areas are covered: (1) conceptual design and engineering analysis; (2) control strategies (fast crawling maneuvers, main perturbations and their effect upon the acceleration level); and (3) technology requirements.

  11. Quantum massive conformal gravity

    NASA Astrophysics Data System (ADS)

    Faria, F. F.

    2016-04-01

    We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.

  12. Marine gravity image available

    NASA Astrophysics Data System (ADS)

    The image below shows the gravity field from 30-72°S computed from Geosat geodetic mission (GM) and exact repeat mission (ERM) data. A color shaded-relief image of these gravity anomalies is available from NOAA in poster form (report MGG-8, [Marks et al., 1993] and also as a digital gridded data set on CD-ROM. To order, contact the National Geophysical Data Center, E/GC3, 325 Broadway, Boulder, CO 80303.

  13. What Is Gravity?

    ERIC Educational Resources Information Center

    Nelson, George

    2004-01-01

    Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of

  14. What Is Gravity?

    ERIC Educational Resources Information Center

    Nelson, George

    2004-01-01

    Gravity is the name given to the phenomenon that any two masses, like you and the Earth, attract each other. One pulls on the Earth and the Earth pulls on one the same amount. And one does not have to be touching. Gravity acts over vast distances, like the 150 million kilometers (93 million miles) between the Earth and the Sun or the billions of…

  15. Partial gravity habitat study

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  16. Gravity Before Einstein and Schwinger Before Gravity

    NASA Astrophysics Data System (ADS)

    Trimble, Virginia L.

    2012-05-01

    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.

  17. Zero-G Workstation Design

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  18. Modeling Candle Flame Behavior In Variable Gravity

    NASA Technical Reports Server (NTRS)

    Alsairafi, A.; Tien, J. S.; Lee, S. T.; Dietrich, D. L.; Ross, H. D.

    2003-01-01

    The burning of a candle, as typical non-propagating diffusion flame, has been used by a number of researchers to study the effects of electric fields on flame, spontaneous flame oscillation and flickering phenomena, and flame extinction. In normal gravity, the heat released from combustion creates buoyant convection that draws oxygen into the flame. The strength of the buoyant flow depends on the gravitational level and it is expected that the flame shape, size and candle burning rate will vary with gravity. Experimentally, there exist studies of candle burning in enhanced gravity (i.e. higher than normal earth gravity, g(sub e)), and in microgravity in drop towers and space-based facilities. There are, however, no reported experimental data on candle burning in partial gravity (g < g(sub e)). In a previous numerical model of the candle flame, buoyant forces were neglected. The treatment of momentum equation was simplified using a potential flow approximation. Although the predicted flame characteristics agreed well with the experimental results, the model cannot be extended to cases with buoyant flows. In addition, because of the use of potential flow, no-slip boundary condition is not satisfied on the wick surface. So there is some uncertainty on the accuracy of the predicted flow field. In the present modeling effort, the full Navier-Stokes momentum equations with body force term is included. This enables us to study the effect of gravity on candle flames (with zero gravity as the limiting case). In addition, we consider radiation effects in more detail by solving the radiation transfer equation. In the previous study, flame radiation is treated as a simple loss term in the energy equation. Emphasis of the present model is on the gas-phase processes. Therefore, the detailed heat and mass transfer phenomena inside the porous wick are not treated. Instead, it is assumed that a thin layer of liquid fuel coated the entire wick surface during the burning process. This is the limiting case that the mass transfer process in the wick is much faster than the evaporation process at the wick surface.

  19. q-Quantum gravity

    NASA Astrophysics Data System (ADS)

    Major, Seth Andrew

    The two most important developments in twentieth century physics remain unreconciled. Not only are general relativity and quantum theory not understood as coming from one theory, but the core principles of the two theories clash. Given the lack of experimental work, the fledgling field of quantum gravity is rich and varied. This dissertation explores one approach to this theory known as non-perturbative canonical quantization. The focus is on a deformation of quantum geometry based on the new variables-q-quantum gravity. A brief survey of the field is presented in Chapter 2. Beginning with Einstein-Hilbert action, a self-dual action suitable for canonical quantization is derived. Included is a discussion of the recent 'Immirzi ambiguity.' The review of non-perturbative quantum gravity continues in Chapter 3 with a discussion on the origins of one of the key structures in nonperturbative quantum gravity, spin networks. These were introduced as a combinatorial basis for spacetime. The connection between the classical theory of gravity and spin networks is discussed in Chapter 4. In both the loop and connection representations, spin networks are introduced as a space of states. The chapter concludes with a detailed look at the regularization of the area operator. Once the review is completed, an analysis of gravity in a bounded region is presented in Chapter 5. By requiring a well-defined variational principle, local boundary conditions are identified, surface observables derived, and their algebra computed. The heart of this work, a new formulation of quantum gravity, is presented in the last four chapters. q- quantum gravity is a deformation of the observable algebra of quantum gravity in which the loop algebra is extended to framed loops. This allows an alternative nonperturbative quantization which is suitable for describing a phase of quantum gravity characterized by states which are normalizable in the measure of Chern- Simons theory. The deformation parameter is related to the cosmological constant. The dissertation concludes with some speculation on the physical content of the deformation in Chapter 9.

  20. Physiological tremor under pseudo-fraction gravity.

    PubMed

    Miao, T; Sakamoto, K

    1995-01-01

    The effect of pseudo-fraction gravity on physiological tremor of the human finger (finger tremor) has been examined experimentally by immersing an index finger into water at different immersion levels. The pseudo-fraction gravity, gamma G, was established by water buoyancy at immersion level omega, G being gravitation acceleration and gamma between zero and unit. The nature of variations of finger tremor under the influence of gamma G is estimated based on FFT spectral analysis. It is illustrated that with a decrease in gamma, or equivalently an increase in omega, two dominant peaks remaining approximately constant in frequencies around 10Hz and 20Hz are found, while peak amplitude is decreased rapidly for higher peak and slowly for lower one. Theoretically the effect of pseudo-fraction gravity is analyzed in terms of a specific model for finger tremor. The experimental results presented in this paper are predicted rather well by two resonant modes which occurred in our model system. It is possible to conclude that the model, which is characterized by a pair of antagonistic muscles and two reflex pathways, provides an adequate quantitative description of finger tremor. PMID:7621132

  1. Gravity localization on hybrid branes

    NASA Astrophysics Data System (ADS)

    Veras, D. F. S.; Cruz, W. T.; Maluf, R. V.; Almeida, C. A. S.

    2016-03-01

    This work deals with gravity localization on codimension-1 brane worlds engendered by compacton-like kinks, the so-called hybrid branes. In such scenarios, the thin brane behavior is manifested when the extra dimension is outside the compact domain, where the energy density is non-trivial, instead of asymptotically as in the usual thick brane models. The zero mode is trapped in the brane, as required. The massive modes, although not localized in the brane, have important phenomenological implications such as corrections to the Newton's law. We study such corrections in the usual thick domain wall and in the hybrid brane scenarios. By means of suitable numerical methods, we attain the mass spectrum for the graviton and the corresponding wavefunctions. The spectra possess the usual linearly increasing behavior from the Kaluza-Klein theories. Further, we show that the 4D gravitational force is slightly increased at short distances. The first eigenstate contributes highly for the correction to the Newton's law. The subsequent normalized solutions have diminishing contributions. Moreover, we find out that the phenomenology of the hybrid brane is not different from the usual thick domain wall. The use of numerical techniques for solving the equations of the massive modes is useful for matching possible phenomenological measurements in the gravitational law as a probe to warped extra dimensions.

  2. Experimental concept for examination of biological effects of magnetic field concealed by gravity.

    PubMed

    Yamashita, M; Tomita-Yokotani, K; Hashimoto, H; Takai, M; Tsushima, M; Nakamura, T

    2004-01-01

    Space is not only a place to study biological effects of gravity, but also provides unique opportunities to examine other environmental factors, where the biological actions are masked by gravity on the ground. Even the earth's magnetic field is steadily acting on living systems, and is known to influence many biological processes. A systematic survey and assessment of its action are difficult to conduct in the presence of dominant factors, such as gravity. Investigation of responses of biological systems against the combined environment of zero-gravity and zero-magnetic field might establish the baseline for the analysis of biological effects of magnetic factors. We propose, in this paper, an experimental concept in this context, together with a practical approach of the experiments, both in orbit and on the ground, with a thin magnetic shielding film. Plant epicotyl growth was taken as an exemplar index to evaluate technical and scientific feasibility of the proposed system concept. PMID:15880894

  3. Cosmological stability bound in massive gravity and bigravity

    SciTech Connect

    Fasiello, Matteo; Tolley, Andrew J. E-mail: andrew.j.tolley@case.edu

    2013-12-01

    We give a simple derivation of a cosmological bound on the graviton mass for spatially flat FRW solutions in massive gravity with an FRW reference metric and for bigravity theories. This bound comes from the requirement that the kinetic term of the helicity zero mode of the graviton is positive definite. The bound is dependent only on the parameters in the massive gravity potential and the Hubble expansion rate for the two metrics. We derive the decoupling limit of bigravity and FRW massive gravity, and use this to give an independent derivation of the cosmological bound. We recover our previous results that the tension between satisfying the Friedmann equation and the cosmological bound is sufficient to rule out all observationally relevant FRW solutions for massive gravity with an FRW reference metric. In contrast, in bigravity this tension is resolved due to different nature of the Vainshtein mechanism. We find that in bigravity theories there exists an FRW solution with late-time self-acceleration for which the kinetic terms for the helicity-2, helicity-1 and helicity-0 are generically nonzero and positive making this a compelling candidate for a model of cosmic acceleration. We confirm that the generalized bound is saturated for the candidate partially massless (bi)gravity theories but the existence of helicity-1/helicity-0 interactions implies the absence of the conjectured partially massless symmetry for both massive gravity and bigravity.

  4. Zero-Based Budgeting Redux.

    ERIC Educational Resources Information Center

    Geiger, Philip E.

    1993-01-01

    Zero-based, programmatic budgeting involves four basic steps: (1) define what needs to be done; (2) specify the resources required; (3) determine the assessment procedures and standards to use in evaluating the effectiveness of various programs; and (4) assign dollar figures to this information. (MLF)

  5. Graphs and Zero-Divisors

    ERIC Educational Resources Information Center

    Axtell, M.; Stickles, J.

    2010-01-01

    The last ten years have seen an explosion of research in the zero-divisor graphs of commutative rings--by professional mathematicians "and" undergraduates. The objective is to find algebraic information within the geometry of these graphs. This topic is approachable by anyone with one or two semesters of abstract algebra. This article gives the

  6. Graphs and Zero-Divisors

    ERIC Educational Resources Information Center

    Axtell, M.; Stickles, J.

    2010-01-01

    The last ten years have seen an explosion of research in the zero-divisor graphs of commutative rings--by professional mathematicians "and" undergraduates. The objective is to find algebraic information within the geometry of these graphs. This topic is approachable by anyone with one or two semesters of abstract algebra. This article gives the…

  7. Questioning Zero and Negative Numbers

    ERIC Educational Resources Information Center

    Wilcox, Virginia B.

    2008-01-01

    After experiencing a Developing Mathematical Ideas (DMI) class on the construction of algebraic concepts surrounding zero and negative numbers, the author conducted an interview with a first grader to determine the youngster's existing level of understanding about these topics. Uncovering young students' existing understanding can provide focus…

  8. Stepping Back from Zero Tolerance

    ERIC Educational Resources Information Center

    Browne-Dianis, Judith

    2011-01-01

    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

  9. Stepping Back from Zero Tolerance

    ERIC Educational Resources Information Center

    Browne-Dianis, Judith

    2011-01-01

    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…

  10. The ATLAS zero degree calorimeter

    SciTech Connect

    White, S.

    2009-10-17

    In May of 2009 the ATLAS zero degree calorimeter was installed in its initial configuration and integrated into the ATLAS trigger/daq. The detector was designed to measure Global characteristics of events - particularly in PbPb collisions - through the measurement of energy and position of very forward neutral particles. Here we discuss the design and tests - particularly of radiation hardness.

  11. Energy in first order 2 +1 gravity

    NASA Astrophysics Data System (ADS)

    Corichi, Alejandro; Rubalcava-García, Iraís

    2015-08-01

    We consider Λ =0 three-dimensional gravity with asymptotically flat boundary conditions. This system was studied by Ashtekar and Varadarajan within the second-order formalism—with metric variables—who showed that the Regge-Teitelboim formalism yields a consistent Hamiltonian description where, surprisingly, the energy is bounded from below and from above. The energy of the spacetime is, however, determined up to an arbitrary constant. The natural choice was to fix that freedom such that Minkowski spacetime has zero energy. More recently, Marolf and Patiño started from the Einstein-Hilbert action supplemented with the Gibbons-Hawking term and showed that, in the (2 +1 ) decomposition of the theory, the energy is shifted from the Ashtekar-Varadarajan analysis in such a way that Minkowski spacetime possesses a negative energy. In this contribution we consider the first-order formalism, where the fundamental variables are a s o (2 ,1 ) connection waIJ and a triad eaI . We consider two actions. A natural extension to 3 dimensions of the consistent action in 4 D Palatini gravity is shown to be finite and differentiable. For this action, the (2 +1 ) decomposition (that we perform using two methods) yields a Hamiltonian boundary term that corresponds to energy. It assigns zero energy to Minkowski spacetime. We then put forward a totally gauge invariant action and show that it is also well defined and differentiable. Interestingly, it turns out to be related, on shell, to the 3D Palatini action by an additive constant in such a way that its associated energy is given by the Marolf-Patiño expression. Thus, we conclude that, from the perspective of the first-order formalism, Minkowski spacetime can consistently have either zero, or a negative energy equal to -1 /4 G , depending on the choice of consistent action employed as starting point.

  12. Venus Gravity Handbook

    NASA Technical Reports Server (NTRS)

    Konopliv, Alexander S.; Sjogren, William L.

    1996-01-01

    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.

  13. Gravity and Biology

    NASA Technical Reports Server (NTRS)

    Morey-Holton, Emily R.

    1996-01-01

    Gravity has been the most constant environmental factor throughout the evolution of biological species on Earth. Organisms are rarely exposed to other gravity levels, either increased or decreased, for prolonged periods. Thus, evolution in a constant 1G field has historically prevented us from appreciating the potential biological consequences of a multi-G universe. To answer the question 'Can terrestrial life be sustained and thrive beyond our planet?' we need to understand the importance of gravity on living systems, and we need to develop a multi-G, rather than a 1G, mentality. The science of gravitational biology took a giant step with the advent of the space program, which provided the first opportunity to examine living organisms in gravity environments lower than could be sustained on Earth. Previously, virtually nothing was known about the effects of extremely low gravity on living organisms, and most of the initial expectations were proven wrong. All species that have flown in space survive in microgravity, although no higher organism has ever completed a life cycle in space. It has been found, however, that many systems change, transiently or permanently, as a result of prolonged exposure to microgravity.

  14. Tethered gravity laboratories study

    NASA Technical Reports Server (NTRS)

    Lucchetti, F.

    1990-01-01

    The scope of the study is to investigate ways of controlling the microgravity environment of the International Space Station by means of a tethered system. Four main study tasks were performed. First, researchers analyzed the utilization of the tether systems to improve the lowest possible steady gravity level on the Space Station and the tether capability to actively control the center of gravity position in order to compensate for activities that would upset the mass distribution of the Station. The purpose of the second task was to evaluate the whole of the experiments performable in a variable gravity environment and the related beneficial residual accelerations, both for pure and applied research in the fields of fluid, materials, and life science, so as to assess the relevance of a variable g-level laboratory. The third task involves the Tethered Variable Gravity Laboratory. The use of the facility that would crawl along a deployed tether and expose experiments to varying intensities of reduced gravity is discussed. Last, a study performed on the Attitude Tether Stabilizer concept is discussed. The stabilization effect of ballast masses tethered to the Space Station was investigated as a means of assisting the attitude control system of the Station.

  15. Global height datum unification: a new approach in gravity potential space

    NASA Astrophysics Data System (ADS)

    Ardalan, A. A.; Safari, A.

    2005-12-01

    The problem of “global height datum unification” is solved in the gravity potential space based on: (1) high-resolution local gravity field modeling, (2) geocentric coordinates of the reference benchmark, and (3) a known value of the geoid’s potential. The high-resolution local gravity field model is derived based on a solution of the fixed-free two-boundary-value problem of the Earth’s gravity field using (a) potential difference values (from precise leveling), (b) modulus of the gravity vector (from gravimetry), (c) astronomical longitude and latitude (from geodetic astronomy and/or combination of (GNSS) Global Navigation Satellite System observations with total station measurements), (d) and satellite altimetry. Knowing the height of the reference benchmark in the national height system and its geocentric GNSS coordinates, and using the derived high-resolution local gravity field model, the gravity potential value of the zero point of the height system is computed. The difference between the derived gravity potential value of the zero point of the height system and the geoid’s potential value is computed. This potential difference gives the offset of the zero point of the height system from geoid in the “potential space”, which is transferred into “geometry space” using the transformation formula derived in this paper. The method was applied to the computation of the offset of the zero point of the Iranian height datum from the geoid’s potential value W 0=62636855.8 m2/s2. According to the geometry space computations, the height datum of Iran is 0.09 m below the geoid.

  16. Gravity field modelling and gravimetry

    NASA Astrophysics Data System (ADS)

    Krynski, Jan

    2015-12-01

    The summary of research activities concerning gravity field modelling and gravimetric works performed in Poland in the period of 2011-2014 is presented. It contains the results of research on geoid modelling in Poland and other countries, evaluation of global geopotential models, determination of temporal variations of the gravity field with the use of data from satellite gravity space missions, absolute gravity surveys for the maintenance and modernization of the gravity control in Poland and overseas, metrological aspects in gravimetry, maintenance of gravimetric calibration baselines, and investigations of the nontidal gravity changes. The bibliography of the related works is given in references.

  17. Stabilization of dielectric liquid bridges by electric fields in the absence of gravity

    NASA Astrophysics Data System (ADS)

    Gonzalez, H.; Castellanos, A.; Barrero, A.; McCluskey, F. M. J.

    1989-09-01

    The stability of liquid bridges in zero gravity conditions under the influence of an ac electric field tangential to the interface is examined. A static analysis was carried out to find the bifurcation surfaces as a function of the three relevant nondimensional parameters: the slenderness or ratio of height to diameter of the cylindrical bridge, the ratio of dielectric constants of the two fluids used, and a nondimensional quantity proportional to the applied voltage. An experimental study using silicone and ricinus oil to approximate zero gravity conditions fully confirmed quantitatively the theoretical results.

  18. New massive gravity and AdS(4) counterterms.

    PubMed

    Jatkar, Dileep P; Sinha, Aninda

    2011-04-29

    We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS(4)). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS(4) Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS(3) gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory. PMID:21635026

  19. Approaches to Validation of Models for Low Gravity Fluid Behavior

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  20. New Massive Gravity and AdS{sub 4} Counterterms

    SciTech Connect

    Jatkar, Dileep P.; Sinha, Aninda

    2011-04-29

    We show that the recently proposed Dirac-Born-Infeld extension of new massive gravity emerges naturally as a counterterm in four-dimensional anti-de Sitter space (AdS{sub 4}). The resulting on-shell Euclidean action is independent of the cutoff at zero temperature. We also find that the same choice of counterterm gives the usual area law for the AdS{sub 4} Schwarzschild black hole entropy in a cutoff-independent manner. The parameter values of the resulting counterterm action correspond to a c=0 theory in the context of the duality between AdS{sub 3} gravity and two-dimensional conformal field theory. We rewrite this theory in terms of the gauge field that is used to recast 3D gravity as a Chern-Simons theory.

  1. Vacuum tunneling in gravity

    NASA Astrophysics Data System (ADS)

    Cho, Y. M.; Pak, D. G.

    2011-08-01

    Topologically non-trivial vacuum structures in gravity models with Cartan variables (vielbein and contortion) are considered. We study the possibility of vacuum spacetime tunneling in Einstein gravity assuming that the vielbein may play a fundamental role in quantum gravitational phenomena. It has been shown that in the case of RP3 space topology, the tunneling between non-trivial topological vacuums can be realized by means of Eguchi-Hanson gravitational instanton. In the Riemann-Cartan geometric approach to quantum gravity, the vacuum tunneling can be provided by means of contortion quantum fluctuations. We define a double self-duality condition for the contortion and give explicit self-dual configurations which can contribute to vacuum tunneling amplitude.

  2. Gravity and Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Blencowe, Miles

    The emergence of the macroscopic classical world from the microscopic quantum world is commonly understood to be a consequence of the fact that any given quantum system is open, unavoidably interacting with unobserved environmental degrees of freedom that will cause initial quantum superposition states of the system to decohere, resulting in classical mixtures of either-or alternatives. A fundamental question concerns how large a macroscopic object can be placed in a manifest quantum state, such as a center of mass quantum superposition state, under conditions where the effects of the interacting environmental degrees of freedom are reduced (i.e. in ultrahigh vacuum and at ultralow temperatures). Recent experiments have in fact demonstrated manifest quantum behavior in nano-to-micron-scale mechanical systems. Gravity has been invoked in various ways as playing a possible fundamental role in enforcing classicality of matter systems beyond a certain scale. Adopting the viewpoint that the standard perturbative quantization of general relativity provides an effective description of quantum gravity that is valid at ordinary energies, we show that it is possible to describe quantitatively how gravity as an environment can induce the decoherence of matter superposition states. The justification for such an approach follows from the fact that we are considering laboratory scale systems, where the matter is localized to regions of small curvature. As with other low energy effects, such as the quantum gravity correction to the Newtonian potential between two ordinary masses, it should be possible to quantitatively evaluate gravitationally induced decoherence rates by employing standard perturbative quantum gravity as an effective field theory; whatever the final form the eventual correct quantum theory of gravity takes, it must converge in its predictions with the effective field theory description at low energies. Research supported by the National Science Foundation (NSF) and the Foundational Questions Institute (FQXi).

  3. The Grip of Gravity

    NASA Astrophysics Data System (ADS)

    Gondhalekar, Prabhakar

    2001-09-01

    Gravity is one of the most inexplicable forces of nature, controlling everything, from the expansion of the Universe to the ebb and flow of ocean tides. The search for the laws of motion and gravitation began more than two thousand years ago, a quest that Prabhakar Gondhalekar recounts in The Grip of Gravity. Beginning with Aristotle and concluding with Planck, Gondhalekar outlines a 'genealogy' of gravity and lucidly explains how previous explanations have shaped the most recent development in the field, string theory. In this work, physicist and astronomer Gondhalekar describes experiments, both planned and proposed, and clearly explains natural phenomena like ocean tides, seasons, ice ages, the formation of planets, stars, and exotic objects like black holes and neutron stars, which are all controlled by gravity. Including anecdotes and thumb-nail sketches of the personalities involved, The Grip of Gravity provides an introduction to the foundation of modern physics and shows how the current developments in string theory may lead to a new and radical interpretation of gravity. Prabhakar Gondhalekar is an Honorary Fellow in the Department of Physics and Astronomy, University College, London. Until his retirement in 1998, he was the head of the Space Astronomy Group at the Rutherford Appleton Laboratory, where he had been a researcher for 18 years. His research has included a number of topics in galactic and extragalactic astronomy, with his major work focusing on the interstellar medium and active galactic nuclei. Gondhalekar has been awarded Royal Society, Leverhulme Trust, and NATO Research Fellowships to do research in universities in the United States and Israel.

  4. Seeking the Light: Gravity Without the Influence of Gravity

    NASA Technical Reports Server (NTRS)

    Sack, Fred; Kern, Volker; Reed, Dave; Etheridge, Guy (Technical Monitor)

    2002-01-01

    All living things sense gravity like humans might sense light or sound. The Biological Research In Canisters (BRIC-14) experiment, explores how moss cells sense and respond to gravity and light. This experiment studies how gravity influences the internal structure of moss cells and seeks to understand the influences of the spaceflight environment on cell growth. This knowledge will help researchers understand the role of gravity in the evolution of cells and life on earth.

  5. Quantum-gravity fluctuations and the black-hole temperature

    NASA Astrophysics Data System (ADS)

    Hod, Shahar

    2015-05-01

    Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the discrete quantum spectrum suggested by Bekenstein with the continuous semi-classical spectrum suggested by Hawking? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quantized black-hole radiation spectrum. Remarkably, it is shown that this characteristic temperature of the discrete (quantized) black-hole radiation agrees with the well-known Hawking temperature of the continuous (semi-classical) black-hole spectrum.

  6. Role of Gravity Waves in Determining Cirrus Cloud Properties

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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).

  7. Asymptotically safe Lorentzian gravity.

    PubMed

    Manrique, Elisa; Rechenberger, Stefan; Saueressig, Frank

    2011-06-24

    The gravitational asymptotic safety program strives for a consistent and predictive quantum theory of gravity based on a nontrivial ultraviolet fixed point of the renormalization group (RG) flow. We investigate this scenario by employing a novel functional renormalization group equation which takes the causal structure of space-time into account and connects the RG flows for Euclidean and Lorentzian signature by a Wick rotation. Within the Einstein-Hilbert approximation, the β functions of both signatures exhibit ultraviolet fixed points in agreement with asymptotic safety. Surprisingly, the two fixed points have strikingly similar characteristics, suggesting that Euclidean and Lorentzian quantum gravity belong to the same universality class at high energies. PMID:21770628

  8. Resummation of Massive Gravity

    SciTech Connect

    Rham, Claudia de; Gabadadze, Gregory; Tolley, Andrew J.

    2011-06-10

    We construct four-dimensional covariant nonlinear theories of massive gravity which are ghost-free in the decoupling limit to all orders. These theories resume explicitly all the nonlinear terms of an effective field theory of massive gravity. We show that away from the decoupling limit the Hamiltonian constraint is maintained at least up to and including quartic order in nonlinearities, hence excluding the possibility of the Boulware-Deser ghost up to this order. We also show that the same remains true to all orders in a similar toy model.

  9. Gauge/Gravity Duality

    ScienceCinema

    Polchinski, Joseph [Kavli Institute for Theoretical Physics

    2010-09-01

    Gauge theories, which describe the particle interactions, are well understood, while quantum gravity leads to many puzzles. Remarkably, in recent years we have learned that these are actually dual, the same system written in different variables. On the one hand, this provides our most precise description of quantum gravity, resolves some long-standing paradoxes, and points to new principles. On the other, it gives a new perspective on strong interactions, with surprising connections to other areas of physics. I describe these ideas, and discuss current and future directions.

  10. Nonlinear magnetohydrodynamics from gravity

    NASA Astrophysics Data System (ADS)

    Hansen, James; Kraus, Per

    2009-04-01

    We apply the recently established connection between nonlinear fluid dynamics and AdS gravity to the case of the dyonic black brane in AdS4. This yields the equations of fluid dynamics for a 2+1 dimensional charged fluid in a background magnetic field. We construct the gravity solution to second order in the derivative expansion. From this we find the fluid dynamical stress tensor and charge current to second and third order in derivatives respectively, along with values for the associated transport coefficients.

  11. Asymptotically Safe Lorentzian Gravity

    SciTech Connect

    Manrique, Elisa; Rechenberger, Stefan; Saueressig, Frank

    2011-06-24

    The gravitational asymptotic safety program strives for a consistent and predictive quantum theory of gravity based on a nontrivial ultraviolet fixed point of the renormalization group (RG) flow. We investigate this scenario by employing a novel functional renormalization group equation which takes the causal structure of space-time into account and connects the RG flows for Euclidean and Lorentzian signature by a Wick rotation. Within the Einstein-Hilbert approximation, the {beta} functions of both signatures exhibit ultraviolet fixed points in agreement with asymptotic safety. Surprisingly, the two fixed points have strikingly similar characteristics, suggesting that Euclidean and Lorentzian quantum gravity belong to the same universality class at high energies.

  12. Gauge/Gravity Duality

    NASA Astrophysics Data System (ADS)

    Ammon, Martin; Erdmenger, Johanna

    2015-04-01

    Part I. Prerequisites: 1. Elements of field theory; 2. Elements of gravity; 3. Symmetries in quantum field theory; 4. Introduction to superstring theory; Part II. Gauge/Gravity Duality: 5. AdS/CFT correspondence; 6. Tests of the AdS/CFT correspondence; 7. Integrability and scattering amplitudes; 8. Further examples of AdS/CFT; 9. Holographic renormalisation group flows; 10. Duality with D-branes in supergravity; 11. Finite temperature and density; Part III. Applications: 12. Linear response and hydrodynamics; 13. QCD and holography: confinement and chiral symmetry breaking; 14. QCD and holography: finite temperature and density; 15. Strongly coupled condensed matter systems; Appendixes; References; Index.

  13. Loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Chiou, Dah-Wei

    2015-12-01

    This paper presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) — a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and systematic derivations, it aims to provide a general picture of LQG, placing emphasis on the fundamental ideas and their significance. The canonical formulation of LQG, as the central topic of the paper, is presented in a logically orderly fashion with moderate details, while the spin foam theory, black hole thermodynamics, and loop quantum cosmology are covered briefly. Current directions and open issues are also summarized.

  14. Maglev Facility for Simulating Variable Gravity

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  15. Disposable remote zero headspace extractor

    DOEpatents

    Hand, Julie J.; Roberts, Mark P.

    2006-03-21

    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.

  16. Majorana Zero Modes in Graphene

    NASA Astrophysics Data System (ADS)

    San-Jose, P.; Lado, J. L.; Aguado, R.; Guinea, F.; Fernández-Rossier, J.

    2015-10-01

    A clear demonstration of topological superconductivity (TS) and Majorana zero modes remains one of the major pending goals in the field of topological materials. One common strategy to generate TS is through the coupling of an s -wave superconductor to a helical half-metallic system. Numerous proposals for the latter have been put forward in the literature, most of them based on semiconductors or topological insulators with strong spin-orbit coupling. Here, we demonstrate an alternative approach for the creation of TS in graphene-superconductor junctions without the need for spin-orbit coupling. Our prediction stems from the helicity of graphene's zero-Landau-level edge states in the presence of interactions and from the possibility, experimentally demonstrated, of tuning their magnetic properties with in-plane magnetic fields. We show how canted antiferromagnetic ordering in the graphene bulk close to neutrality induces TS along the junction and gives rise to isolated, topologically protected Majorana bound states at either end. We also discuss possible strategies to detect their presence in graphene Josephson junctions through Fraunhofer pattern anomalies and Andreev spectroscopy. The latter, in particular, exhibits strong unambiguous signatures of the presence of the Majorana states in the form of universal zero-bias anomalies. Remarkable progress has recently been reported in the fabrication of the proposed type of junctions, which offers a promising outlook for Majorana physics in graphene systems.

  17. Zero-Copy Objects System

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    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.

  18. Gravity Wave Excitation from Ocean Waves and Tsunamis, and Propagation Via Ray Tracing into the Thermosphere

    NASA Astrophysics Data System (ADS)

    Vadas, S.; Makela, J. J.; Fisher, D. J.

    2014-12-01

    In this poster, we discuss new solutions which describe the excitation of acoustic gravity waves from a moving surface ocean wave. We then describe a new method by which to ray trace the gravity waves into the thermosphere. We show that the ray traced-solutions equal theexact Fourier-Laplace solutions in the limit that the winds are zero,the temperature is constant, and thermospheric dissipation is turned off. We then apply these solutions to the gravity waves excited by a moving ocean wave using realisitic wind, temperature and thermospheric dissipation. Finally, we apply these results to a recently-observedtsunami.

  19. Traversable wormholes and non-singular black holes from the vacuum of quadratic gravity

    NASA Astrophysics Data System (ADS)

    Duplessis, Francis; Easson, Damien A.

    2015-08-01

    We present new traversable wormhole and nonsingular black hole solutions in pure, scale-free R2 gravity. These exotic solutions require no null energy condition violating or "exotic" matter and are supported only by the vacuum of the theory. It is well known that f (R ) theories of gravity may be recast as dual theories in the Einstein frame. The solutions we present are found when the conformal transformation required to move to the dual frame is singular. For quadratic R2 gravity, the required conformal factor is identically zero for spacetimes with R =0 . Solutions in this case are argued to arise in the strong coupling limit of general relativity.

  20. OFO experimental techniques and preliminary conclusions - Is artificial gravity needed during prolonged weightlessness.

    NASA Technical Reports Server (NTRS)

    Gualtierotti, T.; Bracchi, F.

    1972-01-01

    The technique of single unit recording from body systems generating electrical pulses coherent with their basic function (CNS, muscles, sense organs) has been proved feasible during the OFO A orbital flight, an automatic physiological experiment. The results of recording 155 hours of orbital flight of pulses from the nerve fibres of four vestibular gravity sensors in two bull frogs indicate that the vestibular organ adjusts to zero g. As all the other biological changes observed during orbit are due to lack of exercise, it is concluded that artificial gravity might not be necessary during prolonged space missions or on low gravity celestial bodies.

  1. Adhesion Casting In Low Gravity

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Cronise, Raymond J.

    1996-01-01

    Adhesion casting in low gravity proposed as technique for making new and improved materials. Advantages of low-gravity adhesion casting, in comparison with adhesion casting in normal Earth gravity, comes from better control over, and greater uniformity of, thicknesses of liquid films that form on and adhere to solid surfaces during casting.

  2. Spaceborne Gravity Gradiometers

    NASA Technical Reports Server (NTRS)

    Wells, W. C. (Editor)

    1984-01-01

    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.

  3. Revamped braneworld gravity

    SciTech Connect

    Bao Ruoyu; Park, Minjoon; Carena, Marcela; Santiago, Jose; Lykken, Joseph

    2006-03-15

    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.

  4. Revamped braneworld gravity

    SciTech Connect

    Bao, Ruoyu; Carena, Marcela; Lykken, Joseph; Park, Minjoon; Santiago, Jose; /Fermilab

    2005-11-01

    Gravity in five-dimensional braneworld backgrounds often exhibits problematic features, including kinetic ghosts, strong coupling, and the 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 DGP-like crossover behavior in a general warped setup.

  5. Loop Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Piguet, O.

    2014-09-01

    In this talk, I give a short general introduction to Loop Quantum Gravity (LQG), beginning with some motivations for quantizing General Relativity, listing various attempts and then focusing on the case of LQG. Work supported in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq (Brazil).

  6. Gravity and crustal structure

    NASA Technical Reports Server (NTRS)

    Bowin, C. O.

    1976-01-01

    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.

  7. Variable gravity research facility

    NASA Technical Reports Server (NTRS)

    Allan, Sean; Ancheta, Stan; Beine, Donna; Cink, Brian; Eagon, Mark; Eckstein, Brett; Luhman, Dan; Mccowan, Daniel; Nations, James; Nordtvedt, Todd

    1988-01-01

    Spin and despin requirements; sequence of activities required to assemble the Variable Gravity Research Facility (VGRF); power systems technology; life support; thermal control systems; emergencies; communication systems; space station applications; experimental activities; computer modeling and simulation of tether vibration; cost analysis; configuration of the crew compartments; and tether lengths and rotation speeds are discussed.

  8. A Trick of Gravity

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2010-01-01

    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.

  9. Artificial Gravity Research Plan

    NASA Technical Reports Server (NTRS)

    Gilbert, Charlene

    2014-01-01

    This document describes the forward working plan to identify what countermeasure resources are needed for a vehicle with an artificial gravity module (intermittent centrifugation) and what Countermeasure Resources are needed for a rotating transit vehicle (continuous centrifugation) to minimize the effects of microgravity to Mars Exploration crewmembers.

  10. Hawaii Gravity Model

    SciTech Connect

    Nicole Lautze

    2015-12-15

    Gravity model for the state of Hawaii. Data is from the following source: Flinders, A.F., Ito, G., Garcia, M.O., Sinton, J.M., Kauahikaua, J.P., and Taylor, B., 2013, Intrusive dike complexes, cumulate cores, and the extrusive growth of Hawaiian volcanoes: Geophysical Research Letters, v. 40, p. 3367–3373, doi:10.1002/grl.50633.

  11. Cosmological tests of gravity

    SciTech Connect

    Jain, Bhuvnesh; Khoury, Justin

    2010-07-15

    Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the universe. We review recent developments in modified gravity theories, focusing on higher-dimensional approaches and chameleon/f(R) theories. We classify these models in terms of the screening mechanisms that enable such theories to approach general relativity on small scales (and thus satisfy solar system constraints). We describe general features of the modified Friedman equation in such theories. The second half of this review describes experimental tests of gravity in light of the new theoretical approaches. We summarize the high precision tests of gravity on laboratory and solar system scales. We describe in some detail tests on astrophysical scales ranging from {approx} kpc (galaxy scales) to {approx} Gpc (large-scale structure). These tests rely on the growth and inter-relationship of perturbations in the metric potentials, density and velocity fields which can be measured using gravitational lensing, galaxy cluster abundances, galaxy clustering and the integrated Sachs-Wolfe effect. A robust way to interpret observations is by constraining effective parameters, such as the ratio of the two metric potentials. Currently tests of gravity on astrophysical scales are in the early stages - we summarize these tests and discuss the interesting prospects for new tests in the coming decade.

  12. Low gravity phase separator

    NASA Technical Reports Server (NTRS)

    Smoot, G. F.; Pope, W. L.; Smith, L. (Inventor)

    1977-01-01

    An apparatus is described for phase separating a gas-liquid mixture as might exist in a subcritical cryogenic helium vessel for cooling a superconducting magnet at low gravity such as in planetary orbit, permitting conservation of the liquid and extended service life of the superconducting magnet.

  13. Unidexterous versus ambidexterous gravities

    SciTech Connect

    Amorim, R.; Das, A.

    1996-09-01

    The process of soldering two unidexterous gravities of opposite chiralities is considered at a quantum level, by using the field-antifield formalism with a Pauli-Villars regularization scheme. The resulting effective theory gives rise to a diffeomorphism anomaly which is compared with the original W2 anomalies. {copyright} {ital 1996 The American Physical Society.}

  14. The Gravity Problem

    ERIC Educational Resources Information Center

    Oberlin, Lynn

    1974-01-01

    Discusses the problem of gravity as it relates to distance from the center of the earth, and reports contradictory explanations from different source books. Uses this example to illustrate that science should not be taught from a single source, such as a textbook. (JR)

  15. Gravity-Off-loading System for Large-Displacement Ground Testing of Spacecraft Mechanisms

    NASA Technical Reports Server (NTRS)

    Han, Olyvia; Kienholz, David; Janzen, Paul; Kidney, Scott

    2010-01-01

    Gravity-off-loading of deployable spacecraft mechanisms during ground testing is a long-standing problem. Deployable structures which are usually too weak to support their own weight under gravity require a means of gravity-off-loading as they unfurl. Conventional solutions to this problem have been helium-filled balloons or mechanical pulley/counterweight systems. These approaches, however, suffer from the deleterious effects of added inertia or friction forces. The changing form factor of the deployable structure itself and the need to track the trajectory of the center of gravity also pose a challenge to these conventional technologies. This paper presents a novel testing apparatus for high-fidelity zero-gravity simulation for special application to deployable space structures such as solar arrays, magnetometer booms, and robotic arms in class 100,000 clean room environments

  16. Direct Numerical Simulations of Rayleigh-Taylor instability with gravity reversal

    NASA Astrophysics Data System (ADS)

    Livescu, Daniel; Wei, Tie

    2012-11-01

    In order to study the variable acceleration effects on the development of Rayleigh-Taylor instability (RTI), two unit problems are proposed: reversing the gravity and setting the gravity to zero in the turbulent stage of classical RTI. Data from high resolution Direct Numerical Simulations, covering the range of Atwood numbers from 0.04 to 0.9, are used to examine the modifications in the layer structure and turbulence properties following the change in gravity. After gravity reversal, the density inversion regions lead to new local RTI development, which efficiently mixes the large scales of the flow. This also introduces a strong directionality in the alignment of vorticity and strain rate eigenvectors. In addition, the turbulent transport reacts much faster to the change in gravity compared to the mean density. This renders the popular gradient diffusion hypothesis inappropriate for such flows, which pose significant challenges for engineering turbulence models.

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

    NASA Technical Reports Server (NTRS)

    Hill, D.; Downing, Robert S.

    1987-01-01

    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.

  18. Finite Zero Point Gravitational Energy in the Context of Modified Dispersion Relations

    NASA Astrophysics Data System (ADS)

    Garattini, Remo; Mandanici, Gianluca

    2015-01-01

    We compute the Zero Point Energy in a spherically symmetric background distorted at high energy as predicted by Gravity's Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. We find that the ordinary divergences can here be handled by an appropriate choice of the rainbow's functions, in contrast to what happens in other conventional approaches.

  19. National Geodetic Survey Gravity Network

    NASA Astrophysics Data System (ADS)

    Moose, R. E.

    1986-12-01

    In 1966, the U.S. National Gravity Base Network was established through the cooperative efforts of several government agencies and academic institutions involved in nationwide gravity observations. The network was reobserved between 1975 and 1979 by the National Geodetic Survey (NGS) using field procedures designed to give high-quality gravity differences. The report discusses the adjustment and the areas where apparent gravity change was observed. NGS plans to densify and maintain this network and to improve the accuracy of the station values by additional high-quality relative ties and by making observations with a new, absolute gravity meter in each of the states.

  20. Plants and gravity. Special issue

    NASA Technical Reports Server (NTRS)

    Kiss, J. Z. (Principal Investigator)

    2002-01-01

    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.

  1. Industrial processes influenced by gravity

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon

    1988-01-01

    In considering new directions for low gravity research with particular regard to broadening the number and types of industrial involvements, it is noted that transport phenomena play a vital role in diverse processes in the chemical, pharmaceutical, food, and biotech industries. Relatively little attention has been given to the role of gravity in such processes. Accordingly, numerous industrial processes and phenomena are identified which involve gravity and/or surface tension forces. Phase separations and mixing are examples that will be significantly different in low gravity conditions. A basis is presented for expanding the scope of the low gravity research program and the potential benefits of such research is indicated.

  2. Propulsion Investigation for Zero and Near-Zero Emissions Aircraft

    NASA Technical Reports Server (NTRS)

    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

    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.

  3. OBSERVED POLARIZATION OF BROWN DWARFS SUGGESTS LOW SURFACE GRAVITY

    SciTech Connect

    Sengupta, Sujan; Marley, Mark S. E-mail: Mark.S.Marley@NASA.go

    2010-10-20

    Light scattering by atmospheric dust particles is responsible for the polarization observed in some L dwarfs. Whether this polarization arises from an inhomogeneous distribution of dust across the disk or an oblate shape induced by rotation remains unclear. Here, we argue that the latter case is plausible and, for many L dwarfs, the more likely one. Furthermore, evolutionary models of mature field L dwarfs predict surface gravities ranging from about 200 to 2500 m s{sup -2} (corresponding to masses of {approx}15-70 M {sub Jupiter}). Yet comparison of observed spectra to available synthetic spectra often does not permit more precise determination of the surface gravity of individual field L dwarfs, leading to important uncertainties in their properties. Since rotationally induced non-sphericity, which gives rise to non-zero disk-integrated polarization, is more pronounced at lower gravities, polarization is a promising low gravity indicator. Here, we combine a rigorous multiple scattering analysis with a self-consistent cloudy atmospheric model and observationally inferred rotational velocities and find that the observed optical polarization can be explained if the surface gravity of the polarized objects is about 300 m s{sup -2} or less, potentially providing a new method for constraining L dwarf masses.

  4. Instruction Manual: ZBB. Zero Base Budgeting.

    ERIC Educational Resources Information Center

    Sidman, Bernard; Linstone, Robert T.

    This guide to zero base budgeting (ZBB) offers information intended to be useful to those implementing this system in schools. Beginning with an explanation of zero base budgeting, the paper then enumerates the advantages of such a system. Zero base budgeting design is then explained as well as the assumptions that underlie the system. Suggested…

  5. 40 CFR 180.5 - Zero tolerances.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 24 2014-07-01 2014-07-01 false Zero tolerances. 180.5 Section 180.5... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Definitions and Interpretative Regulations § 180.5 Zero tolerances. A zero tolerance means that no amount of the pesticide chemical may remain on the...

  6. Zero Tolerance: Advantages and Disadvantages. Research Brief

    ERIC Educational Resources Information Center

    Walker, Karen

    2009-01-01

    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…

  7. 40 CFR 180.5 - Zero tolerances.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Definitions and Interpretative Regulations § 180.5 Zero tolerances. A zero tolerance means that no amount of the pesticide chemical may remain on the raw agricultural commodity when it is offered for shipment. A zero tolerance for a pesticide chemical in or on...

  8. 40 CFR 180.5 - Zero tolerances.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Definitions and Interpretative Regulations § 180.5 Zero tolerances. A zero tolerance means that no amount of the pesticide chemical may remain on the raw agricultural commodity when it is offered for shipment. A zero tolerance for a pesticide chemical in or on...

  9. 40 CFR 180.5 - Zero tolerances.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Definitions and Interpretative Regulations § 180.5 Zero tolerances. A zero tolerance means that no amount of the pesticide chemical may remain on the raw agricultural commodity when it is offered for shipment. A zero tolerance for a pesticide chemical in or on...

  10. 40 CFR 180.5 - Zero tolerances.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 25 2012-07-01 2012-07-01 false Zero tolerances. 180.5 Section 180.5 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Definitions and Interpretative Regulations § 180.5 Zero tolerances. A zero tolerance means...

  11. Gravity from the Ground Up

    NASA Astrophysics Data System (ADS)

    Schutz, Bernard

    2003-12-01

    Preface; 1. Gravity on Earth: the inescapable force; 2. And then came Newton: gravity takes center stage; 3. Satellites: what goes up doesn't always come down; 4. The Solar System: a triumph for Newtonian gravity; 5. Tides and tidal forces: the real signature of gravity; 6. Interplanetary travel: the cosmic roller-coaster; 7. Atmospheres: keeping planets covered; 8. Gravity in the Sun: keeping the heat on; 9. Reaching for the stars: the emptiness of outer space; 10. The colors of stars: why they are black (bodies); 11. Stars at work: factories for the Universe; 12. Birth to death: the life cycle of the stars; 13. Binary stars: tidal forces on a huge scale; 14. Galaxies: atoms in the Universe; 15. Physics near the speed of light: Einstein stands on Galileo's shoulders; 16. Relating to Einstein: logic and experiment in relativity; 17. Spacetime geometry: finding out what is not relative; 18. Einstein's gravity: the curvature of spacetime in the Solar System; 19. Einstein's recipe: fashioning the geometry of gravity; 20. Neutron stars: laboratories of strong gravity; 21. Black holes: gravity's one-way street; 22. Gravitational waves: gravity speaks; 23. Gravitational lenses: bringing the Universe into focus; 24. Cosmology: the study of everything; 25. Big Bang: the seed from which we grew; 26. Einstein's Universe: the geometry of cosmology; 27. Ask the Universe: cosmic questions at the frontiers of gravity; Appendix A. Useful constants: values used in this book; Appendix B. Background: what you need to know before you start.

  12. Quantum gravity from noncommutative spacetime

    NASA Astrophysics Data System (ADS)

    Lee, Jungjai; Yang, Hyun Seok

    2014-12-01

    We review a novel and authentic way to quantize gravity. This novel approach is based on the fact that Einstein gravity can be formulated in terms of a symplectic geometry rather than a Riemannian geometry in the context of emergent gravity. An essential step for emergent gravity is to realize the equivalence principle, the most important property in the theory of gravity (general relativity), from U(1) gauge theory on a symplectic or Poisson manifold. Through the realization of the equivalence principle, which is an intrinsic property in symplectic geometry known as the Darboux theorem or the Moser lemma, one can understand how diffeomorphism symmetry arises from noncommutative U(1) gauge theory; thus, gravity can emerge from the noncommutative electromagnetism, which is also an interacting theory. As a consequence, a background-independent quantum gravity in which the prior existence of any spacetime structure is not a priori assumed but is defined by using the fundamental ingredients in quantum gravity theory can be formulated. This scheme for quantum gravity can be used to resolve many notorious problems in theoretical physics, such as the cosmological constant problem, to understand the nature of dark energy, and to explain why gravity is so weak compared to other forces. In particular, it leads to a remarkable picture of what matter is. A matter field, such as leptons and quarks, simply arises as a stable localized geometry, which is a topological object in the defining algebra (noncommutative ★-algebra) of quantum gravity.

  13. Zero-Brane Quantum Mechanics

    SciTech Connect

    Kabat, D.; Pouliot, P.

    1996-08-01

    We consider low energy, nonrelativistic scattering of two Dirichlet zero-branes as an exercise in quantum mechanics. For weak string coupling and sufficiently small velocity, the dynamics is governed by an effective U(2) gauge theory in 0+1 dimensions. At low energies, {ital D}-brane scattering can reliably probe distances much shorter than the string scale. The only length scale in the quantum mechanics problem is the eleven-dimensional Planck length. This provides evidence for the role of scales shorter than the string length in the weakly coupled dynamics of type IIA strings. {copyright} {ital 1996 The American Physical Society.}

  14. Zero-G experiments in two-phase fluids flow regimes

    NASA Technical Reports Server (NTRS)

    Heppner, D. B.; King, C. D.; Littles, J. W.

    1975-01-01

    The two-phase flows studied were liquid and gas mixtures in a straight flow channel of circular cross-section. Boundaries between flow regimes have been defined for normogravity on coordinates of gas quality and total mass velocity; and, when combined with boundary expressions having a Froude number term, an analytical model was derived predicting boundary shifts with changes in gravity level. Experiments with air and water were performed, first in the normogravity environment of a ground laboratory and then in 'zero gravity' aboard a KC-135 aircraft flying parabolic trajectories. Data reduction confirmed regime boundary shifts in the direction predicted, although the magnitude was a little less than predicted. Pressure drop measurements showed significant increases for the low gravity condition.

  15. Gravity localization in sine-Gordon braneworlds

    NASA Astrophysics Data System (ADS)

    Cruz, W. T.; Maluf, R. V.; Sousa, L. J. S.; Almeida, C. A. S.

    2016-01-01

    In this work we study two types of five-dimensional braneworld models given by sine-Gordon potentials. In both scenarios, the thick brane is generated by a real scalar field coupled to gravity. We focus our investigation on the localization of graviton field and the behaviour of the massive spectrum. In particular, we analyse the localization of massive modes by means of a relative probability method in a Quantum Mechanics context. Initially, considering a scalar field sine-Gordon potential, we find a localized state to the graviton at zero mode. However, when we consider a double sine-Gordon potential, the brane structure is changed allowing the existence of massive resonant states. The new results show how the existence of an internal structure can aid in the emergence of massive resonant modes on the brane.

  16. f(R)-gravity from Killing tensors

    NASA Astrophysics Data System (ADS)

    Paliathanasis, Andronikos

    2016-04-01

    We consider f(R)-gravity in a Friedmann-Lemaître-Robertson-Walker spacetime with zero spatial curvature. We apply the Killing tensors of the minisuperspace in order to specify the functional form of f(R) and for the field equations to be invariant under Lie-Bäcklund transformations, which are linear in momentum (contact symmetries). Consequently, the field equations to admit quadratic conservation laws given by Noether’s theorem. We find three new integrable f(R)-models, for which, with the application of the conservation laws, we reduce the field equations to a system of two first-order ordinary differential equations. For each model we study the evolution of the cosmological fluid. We find that for each integrable model the cosmological fluid has an equation of state parameter, in which there is linear behavior in terms of the scale factor which describes the Chevallier, Polarski and Linder parametric dark energy model.

  17. Hardware development for Gravity Probe-B

    NASA Technical Reports Server (NTRS)

    Bardas, D.; Cheung, W. S.; Gill, D.; Hacker, R.; Keiser, G. M.

    1986-01-01

    Gravity Probe-B (GP-B), also known as the Stanford Relativity Gyroscope Experiment, will test two fundamental predictions of Einstein's General Theory of Relativity by precise measurement of the precessions of nearly perfect gyroscopes in earth orbit. This endeavor embodies state-of-the-art technologies in many fields, including gyroscope fabrication and readout, cryogenics, superconductivity, magnetic shielding, precision optics and alignment methods, and satellite control systems. These technologies are necessary to enable measurement of the predicted precession rates to the milliarcsecond/year level, and to reduce to 'near zero' all non-General Relativistic torques on the gyroscopes. This paper provides a brief overview of the experiment followed by descriptions of several specific hardware items with highlights on progress to date and plans for future development and tests.

  18. Black-hole thermodynamics in Lovelock gravity

    SciTech Connect

    Myers, R.C.; Simon, J.Z.

    1988-10-15

    The thermodynamic properties of black holes in Lovelock gravity are examined. In particular, the case of the Einstein Lagrangian plus the four-dimensional Euler density is discussed in detail. In five dimensions, one finds that the specific heat of a black hole becomes positive at small mass, allowing the black hole to achieve stable equilibrium with its environment and giving it an infinite lifetime. This behavior is not universal, however, but it always occurs in 2k+1 dimensions for a Lovelock theory including the 2k-dimensional Euler density. For theories including six-derivative or higher-order interactions, black holes with degenerate zero-temperature horizons are also possible.

  19. Hydrology and Gravity at the Membach Station, Belgium

    NASA Astrophysics Data System (ADS)

    van Camp, M.; Dassargues, A.; Vanclooster, M.; Crommen, O.; Petermans, T.; Vanneste, K.; Verbeeck, K.; Meurers, B.

    2005-12-01

    This paper investigates hydrological processes and their influence on gravity at the underground Membach station (eastern Belgium), where absolute (AG) and superconducting (SG) gravity measurements have been performed since 1996. Seasonal and short term effects are observed. The 3 μGal seasonal effect reflects long-wavelength component of annual continental water storage variations. The short-term effects consist of fast gravity decrease lasting minutes to a few days. These variations are anticorrelated with rainfall events in 80 % of the cases. The largest decrease was 4 muGal after a significant rainfall (150 mm in 3 days). Apart from rainfall, the Newtonian effect of vertical air mass distribution plays also an essential role (Meurers et al., this session). The gravity station was excavated in low-porosity argillaceous sandstone. Geophysical prospecting showed that the thickness of the weathered zone covering this bedrock can be highly variable between zero and 10 meters. In 2004, soil moisture and temperature probes were installed in the shallow upper 60 cm partially saturated soil, 45 m above the station. Based on a digital elevation model and geological studies, we investigated the soil moisture data and their relationships with high temporal resolution rainfall and gravity time series. This work can be essential to correct local effects that can mask regional effects such as changes in continental water storage. Local effects, indeed, could prevent the combination of satellite data (e.g. GRACE) with ground-based gravity measurements. On the other hand, studying the local seasonal variations also contributes to investigate the influence of the water storage variations in small river basins on the time dependent gravity field.

  20. Examination of Biological Effects of Magnetic Field Concealed by Gravity

    NASA Astrophysics Data System (ADS)

    Yamashita, M.; Tomita-Yokotani, K.; Hashimoto, H.; Nakamura, T.

    Response of biological systems against combined environment of zero-gravity and zero-magnetic field should be examined as the baseline to investigate biological effects of magnetic field that might be concealed by gravity. Space offers unique opportunities to conduct such study because long term microgravity is available for the scientific use. However, magnetic environment has been neither well controlled nor documented both in space and ground based experiments. Biological specimen is exposed to the various magnetic field of Earth during the revolutions in orbit. The profile of magnetic field varying in time depends on the orbital parameters and attitude of the space platform. Furthermore, the onboard 1 G control group is subjected to centrifugation spinning where magnetic field varies differently from the microgravity experiment group. It can not be accepted as the 1 G control in terms of magnetic environment. We propose experiment set up to shield exotic magnetic field experienced in orbiting space experiment platform. Thin film of amorphous metal or alloys has shielding capability, and is feasible to implement for space experimentation. In order to simulate zero-gravity and zero-magnetic field on ground, we developed a 3D- clinostat that equips a magnetic shielding layer for specimen. In order to evaluate effects of normal magnetic field of Earth, steady magnetic field is induced at the site of specimen inside the shield layer either in orbit or on 3D-clinostat. To fill the matrix of experimental design, 1 G control under the magnetic shielded condition, and 1 G control that is exposed to the normal field should be taken. Degree of magnetic shielding magnitude required for plant studies and other issues were examined by the preliminary experiments using a 3D-clinostat for the studies of etiolated seedlings.

  1. Plant gravity sensing

    NASA Technical Reports Server (NTRS)

    Sack, F. D.

    1991-01-01

    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.

  2. Local quantum gravity

    NASA Astrophysics Data System (ADS)

    Christiansen, N.; Knorr, B.; Meibohm, J.; Pawlowski, J. M.; Reichert, M.

    2015-12-01

    We investigate the ultraviolet behavior of quantum gravity within a functional renormalization group approach. The present setup includes the full ghost and graviton propagators and, for the first time, the dynamical graviton three-point function. The latter gives access to the coupling of dynamical gravitons and makes the system minimally self-consistent. The resulting phase diagram confirms the asymptotic safety scenario in quantum gravity with a nontrivial UV fixed point. A well-defined Wilsonian block spinning requires locality of the flow in momentum space. This property is discussed in the context of functional renormalization group flows. We show that momentum locality of graviton correlation functions is nontrivially linked to diffeomorphism invariance, and is realized in the present setup.

  3. That gravity thing

    NASA Astrophysics Data System (ADS)

    Jewess, Mike

    2009-05-01

    Your news article "New probe plots Earth's gravity field" (March p11) reports on the European Space Agency's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) – a satellite that will measure the Earth's gravitational field. It describes the way that g, the acceleration of free fall at the Earth's surface, varies with latitude; this variation is great enough to require adjustment of pendulum clocks between latitudes and also the recalibration of all balances that do not directly compare one mass with a reference mass. The article also notes that the spin of the (effectively fluid) Earth causes it to bulge at the equator, a realization that goes back to Newton's Principia.

  4. Gravity on Conformal Superspace

    NASA Astrophysics Data System (ADS)

    Kelleher, Bryan

    2003-11-01

    The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Taking this conformal nature seriously leads to a new theory of gravity which although very similar to general relativity has some very different features particularly in cosmology and quantisation. It should reproduce the standard tests of general relativity. The cosmology is studied in some detail. The theory is incredibly restrictive and as a result admits an extremely limited number of possible solutions. The problems of the standard cosmology are addressed and most remarkably the cosmological constant problem is resolved in a natural way. The theory also has several attractive features with regard to quantisation particularly regarding the problem of time.

  5. Antimatter gravity experiment

    SciTech Connect

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

    1990-01-01

    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.

  6. Gravity Behaves Like That?

    NASA Astrophysics Data System (ADS)

    Pazmino, John

    2007-02-01

    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.

  7. Gravity wave initiated convection

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1990-01-01

    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.

  8. Majorana Zero Modes in Graphene

    NASA Astrophysics Data System (ADS)

    San-Jose, Pablo; Lado, Jose L.; Aguado, Ramón; Guinea, Francisco; Fernández-Rossier, Joaquín

    A clear demonstration of topological superconductivity (TS) and Majorana zero modes remains one of the major pending goal in the field of topological materials. One common strategy to generate TS is through the coupling of an s-wave superconductor to a helical half-metallic system. Numerous proposals for the latter have been put forward in the literature, most of them based on semiconductors or topological insulators with strong spin-orbit coupling. Here we demonstrate an alternative approach for the creation of TS in graphene/superconductor junctions without the need of spin-orbit coupling. Our prediction stems from the helicity of graphene's zero Landau level edge states in the presence of interactions, and on the possibility, experimentally demonstrated, to tune their magnetic properties with in-plane magnetic fields. We show how canted antiferromagnetic ordering in the graphene bulk close to neutrality induces TS along the junction, and gives rise to isolated, topologically protected Majorana bound states at either end. We also discuss possible strategies to detect their presence. Remarkable progress has recently been reported in the fabrication of the proposed type of junctions, which offers a promising outlook for Majorana physics in graphene systems.

  9. Towards zero-power ICT

    NASA Astrophysics Data System (ADS)

    Gammaitoni, Luca; Chiuchiú, D.; Madami, M.; Carlotti, G.

    2015-06-01

    Is it possible to operate a computing device with zero energy expenditure? This question, once considered just an academic dilemma, has recently become strategic for the future of information and communication technology. In fact, in the last forty years the semiconductor industry has been driven by its ability to scale down the size of the complementary metal-oxide semiconductor-field-effect transistor, the building block of present computing devices, and to increase computing capability density up to a point where the power dissipated in heat during computation has become a serious limitation. To overcome such a limitation, since 2004 the Nanoelectronics Research Initiative has launched a grand challenge to address the fundamental limits of the physics of switches. In Europe, the European Commission has recently funded a set of projects with the aim of minimizing the energy consumption of computing. In this article we briefly review state-of-the-art zero-power computing, with special attention paid to the aspects of energy dissipation at the micro- and nanoscales.

  10. Towards zero-power ICT.

    PubMed

    Gammaitoni, Luca; Chiuchiú, D; Madami, M; Carlotti, G

    2015-06-01

    Is it possible to operate a computing device with zero energy expenditure? This question, once considered just an academic dilemma, has recently become strategic for the future of information and communication technology. In fact, in the last forty years the semiconductor industry has been driven by its ability to scale down the size of the complementary metal-oxide semiconductor-field-effect transistor, the building block of present computing devices, and to increase computing capability density up to a point where the power dissipated in heat during computation has become a serious limitation. To overcome such a limitation, since 2004 the Nanoelectronics Research Initiative has launched a grand challenge to address the fundamental limits of the physics of switches. In Europe, the European Commission has recently funded a set of projects with the aim of minimizing the energy consumption of computing. In this article we briefly review state-of-the-art zero-power computing, with special attention paid to the aspects of energy dissipation at the micro- and nanoscales. PMID:25961656

  11. Zero point energy of renormalized Wilson loops

    SciTech Connect

    Hidaka, Yoshimasa; Pisarski, Robert D.

    2009-10-01

    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.

  12. Dirac cone and double zero materials

    SciTech Connect

    Chan, C. T.; Huang Xueqin; Hang Zhihong; Zheng Huihuo; Lai Yun

    2011-10-03

    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.

  13. Mars Gravity Anomoly Map

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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.

  14. Gravity, Time, and Lagrangians

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2010-01-01

    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…

  15. Gravity gradient study

    NASA Technical Reports Server (NTRS)

    Bell, C. C.

    1971-01-01

    The results of the noise and drift test, and the comparison of the experimental simulation tests with the theoretical predictions, confirm that the rotating gravity gradiometer is capable of extracting information about mascon distributions from lunar orbit, and that the sensitivity of the sensor is adequate for lunar orbital selenodesy. The experimental work also verified analytical and computer models for the directional and time response of the sensor.

  16. Artificial gravity Mars spaceship

    NASA Technical Reports Server (NTRS)

    Clark, Benton C.

    1989-01-01

    Experience gained in the study of artificial gravity for a manned trip to Mars is reviewed, and a snowflake-configured interplanetary vehicle cluster of habitat modules, descent vehicles, and propulsion systems is presented. An evolutionary design is described which permits sequential upgrading from five to nine crew members, an increase of landers from one to as many a three per mission, and an orderly, phased incorporation of advanced technologies as they become available.

  17. [Low Fidelity Simulation of a Zero-Y Robot

    NASA Technical Reports Server (NTRS)

    Sweet, Adam

    2001-01-01

    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.

  18. Quantum gravity and renormalization

    NASA Astrophysics Data System (ADS)

    Anselmi, Damiano

    2015-01-01

    The properties of quantum gravity are reviewed from the point of view of renormalization. Various attempts to overcome the problem of non-renormalizability are presented, and the reasons why most of them fail for quantum gravity are discussed. Interesting possibilities come from relaxing the locality assumption, which also can inspire the investigation of a largely unexplored sector of quantum field theory. Another possibility is to work with infinitely many independent couplings, and search for physical quantities that only depend on a finite subset of them. In this spirit, it is useful to organize the classical action of quantum gravity, determined by renormalization, in a convenient way. Taking advantage of perturbative local field redefinitions, we write the action as the sum of the Hilbert term, the cosmological term, a peculiar scalar that is important only in higher dimensions, plus invariants constructed with at least three Weyl tensors. We show that the FRLW configurations, and many other locally conformally flat metrics, are exact solutions of the field equations in arbitrary dimensions d>3. If the metric is expanded around such configurations the quadratic part of the action is free of higher-time derivatives. Other well-known metrics, such as those of black holes, are instead affected in nontrivial ways by the classical corrections of quantum origin.

  19. Gravity slows light

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Ian

    2014-03-01

    The speed of light is measured as a constant number of metres per second. However, a meter is a measure of how far light travels in a second. That is, light always travels as far as it does in a second every second. This is a circular definition. When measured against other things, light speed must change. Gravity is usually described as a consequence of a curve in spacetime. The word ``space'' has two distinct meanings. In geometry, space is a continuous area. In relativity, ``space'' refers exclusively to geometric spaces measured with light. ``Time'' in a relativistic sense also refers exclusively to the passage of time as measured against light. So a curve in spacetime (a relativistic concept) is a gradual deviation in the thing we use to measure geometric spaces and the passage of time, i.e. the speed of light. I show how Newtonian gravity can explain observable phenomena if the speed of light is inversely proportional to the strength of the gravitational field. For example, we would also expect light to refract as it changes speed passing near massive bodies. Boundary conditions are also discussed, for example, very high gravity will slow light to a stop, making it impossible to measure anything against light, giving a gravitational singularity.

  20. Granular Superconductors and Gravity

    NASA Technical Reports Server (NTRS)

    Noever, David; Koczor, Ron

    1999-01-01

    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.

  1. Venus gravity fields

    NASA Technical Reports Server (NTRS)

    Sjogren, W. L.; Ananda, M.; Williams, B. G.; Birkeland, P. W.; Esposito, P. S.; Wimberly, R. N.; Ritke, S. J.

    1981-01-01

    Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

  2. Boundary Condtions of Gravity

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2014-05-01

    Our quantum mechanical derivation of the strong coupling using modified Newtonian inverse square logic in (1) and the fine structure constant (ALPHA) using Boltzmann expression in our book (2) come close to Einstein (1919) merging nuclear force with gravitation and retracting his cosmological constant. Its conflict with the inflationary aspect of the universe can be reconciled with the possibility that the light coming from the receding galaxies follow a curvilinear path increasing in length due to its ever increasing curvature without receding only in the radial direction. In (1), we implicitly show gravity as nothing but the cumulative effect of quantum mechanical forces, making G vary at different locations in the universe. The subsequent effects of gravitational variation would be on the curvature of the paths of the geodesics they create. Further investigation along these lines is warranted as we do not have unification, evidence of graviton, quantum gravity or anything else very concrete after a century of hard work. Strong coupling and ALPHA may be the boundary conditions of gravitational constants. Newtonian Gravity in Natural Units, Journal of Physical Science and Application 2 (7) (2012)265-268, [2] Quantum Consciousness - The Road to Reality by S. Goradia, 4/27/20.

  3. Zeros of Mittag-Leffler Functions

    NASA Astrophysics Data System (ADS)

    Puzio, Raymond; Hanneken, John; Achar, Narahari

    2004-11-01

    The Mittag-Leffler function E_α β, which is a generalization of the exponential and trigonometric functions, arises frequently in problems of fractional calculus and hence, to understand the theory of fractional differential equations, one needs to understand properties of this function. One property which is of interest is the nature of its zeros. The main results regarding zeros of E_α β when α is a real number lying between 1 and 3 may be summarized as follows: When 1 < α < 2, there is a finite number (possibly zero) of real zeros and an infinity of complex zeros. When 2 < α ≤ 3, there are a finite number (possibly zero) of complex zeros and an infinite number of real zeros. Furthermore, there are no complex zeros in a region of parameter space described approximately by 1 ≤ β < 0.67 - 0.51 α + 0.83 α^2. For large β (2 < α ≤ 3), the number of complex zeros goes as log β and the complex zeros are contained in a small region near the origin.

  4. Constraints on texture zero and cofactor zero models for neutrino mass

    SciTech Connect

    Whisnant, K.; Liao, Jiajun; Marfatia, D.

    2014-06-24

    Imposing a texture or cofactor zero on the neutrino mass matrix reduces the number of independent parameters from nine to seven. Since five parameters have been measured, only two independent parameters would remain in such models. We find the allowed regions for single texture zero and single cofactor zero models. We also find strong similarities between single texture zero models with one mass hierarchy and single cofactor zero models with the opposite mass hierarchy. We show that this correspondence can be generalized to texture-zero and cofactor-zero models with the same homogeneous costraints on the elements and cofactors.

  5. Spherically symmetric conformal gravity and ``gravitational bubbles''

    NASA Astrophysics Data System (ADS)

    Berezin, V. A.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2016-01-01

    The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the ``gravitational bubbles'', which is compact and with zero Weyl tensor. Thus, we obtained the pure vacuum curved space-times (without any material sources, including the cosmological constant) what is absolutely impossible in General Relativity. Such a phenomenon makes it easier to create the universe from ``nothing''. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly some features of non-vacuum solutions. Two of them are explicitly written, namely, the metrics à la Vaidya, and the electrovacuum space-time metrics.

  6. Conformal gravity and “gravitational bubbles”

    NASA Astrophysics Data System (ADS)

    Berezin, V. A.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2016-01-01

    We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson-Walker metrics. We called one of them the “gravitational bubbles”, which is compact and with zero Weyl tensor. These “gravitational bubbles” are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from “nothing”. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We describe the general structure of the energy-momentum tensor in the spherical conformal gravity and construct the vectorial equation that reveals clearly some features of non-vacuum solutions.

  7. Planckian axions and the Weak Gravity Conjecture

    NASA Astrophysics Data System (ADS)

    Bachlechner, Thomas C.; Long, Cody; McAllister, Liam

    2016-01-01

    Several recent works [1-3] have claimed that the Weak Gravity Conjecture (WGC) excludes super-Planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. We argue that in theories with N ≫ 1 axions, super-Planckian axion diameters D are readily allowed by the WGC. We clarify the non-trivial relationship between the kinetic matrix K — unambiguously defined by its form in a Minkowski-reduced basis — and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues f 1 2 ≤ ṡ ṡ ṡ ≤ f N 2 of K: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. In particular, even if one were to impose the condition f N < M pl, this would imply neither D < M pl nor D < √{N}{M}_{pl} . We then estimate the actions of instantons that fulfill the WGC. The leading instanton action is bounded from below by S≥ {S}{M}_{pl}/{f}_N , with {S} a fixed constant, but in the universal limit S≳ S√{N} {M}_{pl}/{f}_N . Thus, having f N > M pl does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. Finally, we argue that in effective axion-gravity theories, the zero-form version of the WGC can be satisfied by gravitational instantons that make negligible contributions to the potential.

  8. Locomotion in simulated microgravity: gravity replacement loads

    NASA Technical Reports Server (NTRS)

    McCrory, Jean L.; Baron, Heidi A.; Balkin, Sandy; Cavanagh, Peter R.

    2002-01-01

    BACKGROUND: When an astronaut walks or runs on a treadmill in microgravity, a subject load device (SLD) is used to return him or her back to the treadmill belt. The gravity replacement load (GRL) in the SLD is transferred, via a harness, to the pelvis and/or the shoulders. This research compared comfort and ground reaction forces during treadmill running in a microgravity locomotion simulator at GRLs of 60%, 80%, and 100% of body weight (BW). Two harness designs (shoulder springs only (SSO) and waist and shoulder springs (WSS)) were used. HYPOTHESES: 1) The 100% BW gravity replacement load conditions would be comfortably tolerated and would result in larger ground reaction forces and loading rates than the lower load conditions, and 2) the WSS harness would be more comfortable than the SSO harness. METHODS: Using the Penn State Zero Gravity Locomotion Simulator (ZLS), 8 subjects ran at 2.0 m x s(-1) (4.5 mph) for 3 min at each GRL setting in each harness. Subjective ratings of harness comfort, ground reaction forces, and GRL data were collected during the final minute of exercise. RESULTS: The 100% BW loading conditions were comfortably tolerated (2.3 on a scale of 0-10), although discomfort increased as the GRL increased. There were no overall differences in perceived comfort between the two harnesses. The loading rates (27.1, 33.8, 39.1 BW x s(-1)) and the magnitudes of the first (1.0, 1.4, 1.6 BW) and second (1.3, 1.7, 1.9 BW) peaks of the ground reaction force increased with increasing levels (60, 80, 100% BW respectively) of GRL. CONCLUSIONS: Subjects were able to tolerate a GRL of 100% BW well. The magnitude of the ground reaction force peaks and the loading rate is directly related to the magnitude of the GRL.

  9. Phenomenology in minimal theory of massive gravity

    NASA Astrophysics Data System (ADS)

    De Felice, Antonio; Mukohyama, Shinji

    2016-04-01

    We investigate the minimal theory of massive gravity (MTMG) recently introduced. After reviewing the original construction based on its Hamiltonian in the vielbein formalism, we reformulate it in terms of its Lagrangian in both the vielbein and the metric formalisms. It then becomes obvious that, unlike previous attempts in the literature of Lorentz-violating massive gravity, not only the potential but also the kinetic structure of the action is modified from the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory. We confirm that the number of physical degrees of freedom in MTMG is two at fully nonlinear level. This proves the absence of various possible pathologies such as superluminality, acausality and strong coupling. Afterwards, we discuss the phenomenology of MTMG in the presence of a dust fluid. We find that on a flat homogeneous and isotropic background we have two branches. One of them (self-accelerating branch) naturally leads to acceleration without the genuine cosmological constant or dark energy. For this branch both the scalar and the vector modes behave exactly as in general relativity (GR). The phenomenology of this branch differs from GR in the tensor modes sector, as the tensor modes acquire a non-zero mass. Hence, MTMG serves as a stable nonlinear completion of the self-accelerating cosmological solution found originally in dRGT theory. The other branch (normal branch) has a dynamics which depends on the time-dependent fiducial metric. For the normal branch, the scalar mode sector, even though as in GR only one scalar mode is present (due to the dust fluid), differs from the one in GR, and, in general, structure formation will follow a different phenomenology. The tensor modes will be massive, whereas the vector modes, for both branches, will have the same phenomenology as in GR.

  10. Horava gravity: Symmetries and Generalized Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Capasso, Dario

    In the search for a theory of Quantum Gravity a new proposal was recently made by P. Horava. The main feature of this new proposed theory is that it is power-counting renormalizable by construction, and could prove to be truly renormalizable, although more work is needed in this direction. The renormalizability of the theory is a central issue. Indeed, General Relativity does not have this property, implying that to construct its quantum version we need to "complete" the theory in the UV. Horava suggested a possible way to provide a UV completion of GR by giving up full spacetime reparametrization symmetry, which is one of the fundamental assumptions of GR, and adding appropriate higher order terms in the action. In this Thesis we review Horava's theory and analyze some of the issues related to the breaking of the spacetime structure. Specifically, we derive the general static spherically symmetric solutions for Horava's theory with a nonvanishing radial "shift" field gtr. Such "hedgehog" configurations are not considered in GR, since gtr can be mapped to zero with an appropriate reparametrization, but they are physically distinct solutions in Horava gravity where the reparametrization is not allowed by the reduced symmetry. These new solutions exhibit specific properties from the particle dynamics point of view and possess an extra gauge symmetry. We also study the deformed kinematics of point particles allowed by the reduced reparametrization symmetry. The main result is that particles can have generalized dispersion relations that include higher even powers of the momentum. We analyze the implications of this and provide some examples that may be converted into possible experimental tests for the deviations of this new theory of gravity from standard GR.

  11. Perturbations of nested branes with induced gravity

    SciTech Connect

    Sbisà, Fulvio; Koyama, Kazuya E-mail: kazuya.koyama@port.ac.uk

    2014-06-01

    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.

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

    PubMed

    Adam, John A

    2011-10-01

    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

  13. Zero-velocity magnetophoretic method for the determination of particle magnetic susceptibility.

    PubMed

    Watarai, Hitoshi; Duc, Hoang Trong Tien; Lan, Tran Thi Ngoc; Zhang, Tianyi; Tsukahara, Satoshi

    2014-01-01

    A simple zero-velocity method to determine the particle magnetic susceptibility by measuring the magnetophoretic velocity was proposed. The principle is that the magnetophoretic velocity of a particle in a liquid medium must be zero when the magnetic susceptibilities of the medium and the particle are equal, or the gravity force and the magnetophoretic force are balanced. By changing the medium magnetic susceptibility and measuring the magnetophoretic velocity of a particle, the particle magnetic susceptibility was determined from the medium magnetic susceptibility under the zero-velocity condition. The feasibility of the method was demonstrated for polystyrene particles using a Dy(III) solution in the horizontal migration mode and different organic solvents in the vertical migration mode. PMID:25007934

  14. Nonlinear modal resonances in low-gravity slosh-spacecraft systems

    NASA Technical Reports Server (NTRS)

    Peterson, Lee D.

    1991-01-01

    Nonlinear models of low gravity slosh, when coupled to spacecraft vibrations, predict intense nonlinear eigenfrequency shifts at zero gravity. These nonlinear frequency shifts are due to internal quadratic and cubic resonances between fluid slosh modes and spacecraft vibration modes. Their existence has been verified experimentally, and they cannot be correctly modeled by approximate, uncoupled nonlinear models, such as pendulum mechanical analogs. These predictions mean that linear slosh assumptions for spacecraft vibration models can be invalid, and may lead to degraded control system stability and performance. However, a complete nonlinear modal analysis will predict the correct dynamic behavior. This paper presents the analytical basis for these results, and discusses the effect of internal resonances on the nonlinear coupled response at zero gravity.

  15. D-Zero Vacuum System

    SciTech Connect

    Wintercorn, S.J.; /Fermilab

    1986-04-07

    The system pumping speed was calculated by taking the reciprocal of the sum of the reciprocal pump speed and the reciprocal line conductances. The conductances of the pipe were calculated from the following formulas taken from the Varian vacuum manual. This report updates the original to reflect the pumping curves and basic vacuum system characteristics for the purchased components and installed piping of the D-Zero vacuum system. The system consists of two Edward's E2M275 two stage mechanical pumps, a Leybold-Heraeus WSU2000 Blower and three Varian 4' diffusion pumps (one for each cryostat). Individual pump and system pumping speed curves and a diagram of the system is included.

  16. Rotating gravity currents. Part 1. Energy loss theory

    NASA Astrophysics Data System (ADS)

    Martin, J. R.; Lane-Serff, G. F.

    2005-01-01

    A comprehensive energy loss theory for gravity currents in rotating rectangular channels is presented. The model is an extension of the non-rotating energy loss theory of Benjamin (J. Fluid Mech. vol. 31, 1968, p. 209) and the steady-state dissipationless theory of rotating gravity currents of Hacker (PhD thesis, 1996). The theory assumes the fluid is inviscid, there is no shear within the current, and the Boussinesq approximation is made. Dissipation is introduced using a simple method. A head loss term is introduced into the Bernoulli equation and it is assumed that the energy loss is uniform across the stream. Conservation of momentum, volume flux and potential vorticity between upstream and downstream locations is then considered. By allowing for energy dissipation, results are obtained for channels of arbitrary depth and width (relative to the current). The results match those from earlier workers in the two limits of (i) zero rotation (but including dissipation) and (ii) zero dissipation (but including rotation). Three types of flow are identified as the effect of rotation increases, characterized in terms of the location of the outcropping interface between the gravity current and the ambient fluid on the channel boundaries. The parameters for transitions between these cases are quantified, as is the detailed behaviour of the flow in all cases. In particular, the speed of the current can be predicted for any given channel depth and width. As the channel depth increases, the predicted Froude number tends to surd 2, as for non-rotating flows.

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

    PubMed

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

    2014-07-15

    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

  18. Geometric scalar theory of gravity

    SciTech Connect

    Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D.; Moschella, U. E-mail: eduhsb@cbpf.br E-mail: egoulart@cbpf.br E-mail: toniato@cbpf.br

    2013-06-01

    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.

  19. Cascading gravity is ghost free

    SciTech Connect

    Rham, Claudia de; Khoury, Justin; Tolley, Andrew J.

    2010-06-15

    We perform a full perturbative stability analysis of the 6D cascading gravity model in the presence of 3-brane tension. We demonstrate that for sufficiently large tension on the (flat) 3-brane, there are no ghosts at the perturbative level, consistent with results that had previously only been obtained in a specific 5D decoupling limit. These results establish the cascading gravity framework as a consistent infrared modification of gravity.

  20. Cosmological tests of modified gravity

    NASA Astrophysics Data System (ADS)

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein’s theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard Λ CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

  1. Astrophysical aspects of Weyl gravity

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    1991-01-01

    This paper discusses the astrophysical implications and applications of Weyl gravity, which is the theory resulting from the unique action allowed under the principle of local scale invariance in Einstein gravity. These applications include galactic dynamics, the mass-radius relation, the cosmological constant, and the 'Modified Newtonian Dynamics' proposed by Milgrom (1983). The relation of Weyl gravity to other scale-invariant theories is addressed.

  2. D-dimensional log gravity

    SciTech Connect

    Alishahiha, Mohsen; Fareghbal, Reza

    2011-04-15

    We study Einstein gravity in dimensions D{>=}4 modified by curvature squared at critical point where the theory contains only massless gravitons. We show that at the critical point a new mode appears leading to a logarithmic gravity in the theory. The corresponding logarithmic solution may provide a gravity description of logarithmic conformal field theories (CFT) in higher dimensions. We note also that for special values of the parameters of the theory, the model admits solutions with nonrelativistic isometries.

  3. Cosmological tests of modified gravity.

    PubMed

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years. PMID:27007681

  4. Gravity: Simple Experiments for Young Scientists.

    ERIC Educational Resources Information Center

    White, Larry

    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…

  5. [Biology of size and gravity].

    PubMed

    Yamashita, Masamichi; Baba, Shoji A

    2004-03-01

    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

  6. Active Response Gravity Offload System

    NASA Technical Reports Server (NTRS)

    Valle, Paul; Dungan, Larry; Cunningham, Thomas; Lieberman, Asher; Poncia, Dina

    2011-01-01

    The Active Response Gravity Offload System (ARGOS) provides the ability to simulate with one system the gravity effect of planets, moons, comets, asteroids, and microgravity, where the gravity is less than Earth fs gravity. The system works by providing a constant force offload through an overhead hoist system and horizontal motion through a rail and trolley system. The facility covers a 20 by 40-ft (approximately equals 6.1 by 12.2m) horizontal area with 15 ft (approximately equals4.6 m) of lifting vertical range.

  7. Conformal tensors via Lovelock gravity

    NASA Astrophysics Data System (ADS)

    Kastor, David

    2013-10-01

    Constructs from conformal geometry are important in low dimensional gravity models, while in higher dimensions the higher curvature interactions of Lovelock gravity are similarly prominent. Considering conformal invariance in the context of Lovelock gravity leads to natural, higher curvature generalizations of the Weyl, Schouten, Cotton and Bach tensors, with properties that straightforwardly extend those of their familiar counterparts. As a first application, we introduce a new set of conformally invariant gravity theories in D = 4k dimensions, based on the squares of the higher curvature Weyl tensors.

  8. Modified teleparallel theories of gravity

    NASA Astrophysics Data System (ADS)

    Bahamonde, Sebastian; Böhmer, Christian G.; Wright, Matthew

    2015-11-01

    We investigate modified theories of gravity in the context of teleparallel geometries. It is well known that modified gravity models based on the torsion scalar are not invariant under local Lorentz transformations while modifications based on the Ricci scalar are. This motivates the study of a model depending on the torsion scalar and the divergence of the torsion vector. We derive the teleparallel equivalent of f (R ) gravity as a particular subset of these models and also show that this is the unique theory in this class that is invariant under local Lorentz transformation. Furthermore one can show that f (T ) gravity is the unique theory admitting second-order field equations.

  9. Teleparallel equivalent of Lovelock gravity

    NASA Astrophysics Data System (ADS)

    González, P. A.; Vásquez, Yerko

    2015-12-01

    There is a growing interest in modified gravity theories based on torsion, as these theories exhibit interesting cosmological implications. In this work inspired by the teleparallel formulation of general relativity, we present its extension to Lovelock gravity known as the most natural extension of general relativity in higher-dimensional space-times. First, we review the teleparallel equivalent of general relativity and Gauss-Bonnet gravity, and then we construct the teleparallel equivalent of Lovelock gravity. In order to achieve this goal, we use the vielbein and the connection without imposing the Weitzenböck connection. Then, we extract the teleparallel formulation of the theory by setting the curvature to null.

  10. A Challenge to Entropic Gravity

    NASA Astrophysics Data System (ADS)

    Roveto, Jonathan; Munoz, Gerardo

    2012-03-01

    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.

  11. Bringing Gravity to Space

    NASA Technical Reports Server (NTRS)

    Norsk, P.; Shelhamer, M.

    2016-01-01

    This panel will present NASA's plans for ongoing and future research to define the requirements for Artificial Gravity (AG) as a countermeasure against the negative health effects of long-duration weightlessness. AG could mitigate the gravity-sensitive effects of spaceflight across a host of physiological systems. Bringing gravity to space could mitigate the sensorimotor and neuro-vestibular disturbances induced by G-transitions upon reaching a planetary body, and the cardiovascular deconditioning and musculoskeletal weakness induced by weightlessness. Of particular interest for AG during deep-space missions is mitigation of the Visual Impairment Intracranial Pressure (VIIP) syndrome that the majority of astronauts exhibit in space to varying degrees, and which presumably is associated with weightlessness-induced fluid shift from lower to upper body segments. AG could be very effective for reversing the fluid shift and thus help prevent VIIP. The first presentation by Dr. Charles will summarize some of the ground-based and (very little) space-based research that has been conducted on AG by the various space programs. Dr. Paloski will address the use of AG during deep-space exploration-class missions and describe the different AG scenarios such as intra-vehicular, part-of-vehicle, or whole-vehicle centrifugations. Dr. Clement will discuss currently planned NASA research as well as how to coordinate future activities among NASA's international partners. Dr. Barr will describe some possible future plans for using space- and ground-based partial-G analogs to define the relationship between physiological responses and G levels between 0 and 1. Finally, Dr. Stenger will summarize how the human cardiovascular system could benefit from intermittent short-radius centrifugations during long-duration missions.

  12. Bootstrapping gravity solutions

    NASA Astrophysics Data System (ADS)

    Aparício, João; Grumiller, Daniel; Lopez, Esperanza; Papadimitriou, Ioannis; Stricker, Stefan

    2013-05-01

    We construct an algorithm to determine all stationary axi-symmetric solutions of 3-dimensional Einstein gravity with a minimally coupled self-interacting scalar field. We holographically renormalize the theory and evaluate then the on-shell action as well as the stress tensor and scalar one-point functions. We study thermodynamics, derive two universal formulas for the entropy and prove that global AdS provides a lower bound for the mass of certain solitons. Several examples are given in detail, including the first instance of locally asymptotically flat hairy black holes and novel asymptotically AdS solutions with non-Brown-Henneaux behavior.

  13. The gravity apple tree

    NASA Astrophysics Data System (ADS)

    Espinosa Aldama, Mariana

    2015-04-01

    The gravity apple tree is a genealogical tree of the gravitation theories developed during the past century. The graphic representation is full of information such as guides in heuristic principles, names of main proponents, dates and references for original articles (See under Supplementary Data for the graphic representation). This visual presentation and its particular classification allows a quick synthetic view for a plurality of theories, many of them well validated in the Solar System domain. Its diachronic structure organizes information in a shape of a tree following similarities through a formal concept analysis. It can be used for educational purposes or as a tool for philosophical discussion.

  14. Gravity and Granular Materials

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Gottlieb, Robert G.

    1993-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  17. An inverse dynamic analysis on the influence of upper limb gravity compensation during reaching.

    PubMed

    Essers, J M N Hans; Meijer, Kenneth; Murgia, Alessio; Bergsma, Arjen; Verstegen, Paul

    2013-06-01

    Muscular dystrophies (MDs) are characterized by progressive muscle wasting and weakness. Several studies have been conducted to investigate the influence of arm supports in an attempt to restore arm function. Lowering the load allows the user to employ the residual muscle force for movement as well as for posture stabilization. In this pilot study three conditions were investigated during a reaching task performed by three healthy subjects and three MD subjects: a control condition involving reaching; a similar movement with gravity compensation using braces to support the forearm; an identical reaching movement in simulated zero-gravity. In the control condition the highest values of shoulder moments were present, with a maximum of about 6 Nm for shoulder flexion and abduction. In the gravity compensation and zero gravity conditions the maximum shoulder moments were decreased by more than 70% and instead of increasing during reaching, they remained almost unvaried, fluctuating around an offset value less than 1 Nm. Similarly, the elbow moments in the control condition were the highest with a peak around 3.3 Nm for elbow flexion, while the moments were substantially reduced in the remaining two conditions, fluctuating around offset values between 0 to 0.5 Nm. In conclusion, gravity compensation by lower arm support is effective in healthy subjects and MD subjects and lowers the amount of shoulder and elbow moments by an amount comparable to a zero gravity environment. However the influence of gravity compensation still needs to be investigated on more people with MDs in order to quantify any beneficial effect on this population. PMID:24187187

  18. Dynamics of Superfluid Helium in Low-Gravity

    NASA Technical Reports Server (NTRS)

    Frank, David J.

    1997-01-01

    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.

  19. Zero sound in dipolar Fermi gases

    SciTech Connect

    Ronen, Shai; Bohn, John L.

    2010-03-15

    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.

  20. Zero leakage separable and semipermanent ducting joints

    NASA Technical Reports Server (NTRS)

    Mischel, H. T.

    1973-01-01

    A study program has been conducted to explore new methods of achieving zero leakage, separable and semipermanent, ducting joints for space flight vehicles. The study consisted of a search of literature of existing zero leakage methods, the generation of concepts of new methods of achieving the desired zero leakage criteria and the development of detailed analysis and design of a selected concept. Other techniques of leak detection were explored with a view toward improving this area.

  1. NASA Net Zero Energy Buildings Roadmap

    SciTech Connect

    Pless, S.; Scheib, J.; Torcellini, P.; Hendron, B.; Slovensky, M.

    2014-10-01

    In preparation for the time-phased net zero energy requirement for new federal buildings starting in 2020, set forth in Executive Order 13514, NASA requested that the National Renewable Energy Laboratory (NREL) to develop a roadmap for NASA's compliance. NASA detailed a Statement of Work that requested information on strategic, organizational, and tactical aspects of net zero energy buildings. In response, this document presents a high-level approach to net zero energy planning, design, construction, and operations, based on NREL's first-hand experience procuring net zero energy construction, and based on NREL and other industry research on net zero energy feasibility. The strategic approach to net zero energy starts with an interpretation of the executive order language relating to net zero energy. Specifically, this roadmap defines a net zero energy acquisition process as one that sets an aggressive energy use intensity goal for the building in project planning, meets the reduced demand goal through energy efficiency strategies and technologies, then adds renewable energy in a prioritized manner, using building-associated, emission- free sources first, to offset the annual energy use required at the building; the net zero energy process extends through the life of the building, requiring a balance of energy use and production in each calendar year.

  2. Variable gravity Universe

    NASA Astrophysics Data System (ADS)

    Wetterich, C.

    2014-01-01

    For variable gravity models the strength of gravity, as measured by Newton's "constant" or the Planck mass, depends on the value of a scalar field, the cosmon. We discuss two simple four-parameter models with a quadratic or constant cosmon potential. They are compatible with all presently available cosmological observations, including inflation. The inflaton and the scalar field of quintessence are the same cosmon field. Dark energy constitutes a small, almost constant fraction of the energy density during the radiation- and matter-dominated epochs (early dark energy). In the present epoch we witness a transition to a new dark energy-dominated epoch. Our models are free of a big bang singularity. The stability of solutions generates an arrow of time. Our picture of the Universe is unusual, with a shrinking or static scale factor, while the masses of particles increase and the size of atoms shrinks. The evolution of the Universe can be very slow for all cosmological epochs including inflation, with typical time scale 1010 yr, and in sharp contrast to the usual big bang picture. The map to the equivalent Einstein frame with constant particle masses and expanding scale factor can be singular at the big bang.

  3. Modifications of gravity.

    PubMed

    Skordis, Constantinos

    2011-12-28

    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 ΛCDM, 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

  4. Modified gravity and cosmology

    NASA Astrophysics Data System (ADS)

    Clifton, Timothy; Ferreira, Pedro G.; Padilla, Antonio; Skordis, Constantinos

    2012-03-01

    In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, scalar-tensor, Einstein-æther, and Bimetric theories, as well as TeVeS, f(R), general higher-order theories, Hořava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher co-dimension braneworlds. We also review attempts to construct a Parameterised Post-Friedmannian formalism, that can be used to constrain deviations from General Relativity in cosmology, and that is suitable for comparison with data on the largest scales. These subjects have been intensively studied over the past decade, largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive and up-to-date introduction to the subject as a whole.

  5. Holographic entanglement entropy for the most general higher derivative gravity

    NASA Astrophysics Data System (ADS)

    Miao, Rong-Xin; Guo, Wu-zhong

    2015-08-01

    The holographic entanglement entropy for the most general higher derivative gravity is investigated. We find a new type of Wald entropy, which appears on entangling surface without the rotational symmetry and reduces to usual Wald entropy on Killing horizon. Furthermore, we obtain a formal formula of HEE for the most general higher derivative gravity and work it out exactly for some squashed cones. As an important application, we derive HEE for gravitational action with one derivative of the curvature when the extrinsic curvature vanishes. We also study some toy models with non-zero extrinsic curvature. We prove that our formula yields the correct universal term of entanglement entropy for 4d CFTs. Furthermore, we solve the puzzle raised by Hung, Myers and Smolkin that the logarithmic term of entanglement entropy derived from Weyl anomaly of CFTs does not match the holographic result even if the extrinsic curvature vanishes. We find that such mismatch comes from the `anomaly of entropy' of the derivative of curvature. After considering such contributions carefully, we resolve the puzzle successfully. In general, we need to fix the splitting problem for the conical metrics in order to derive the holographic entanglement entropy. We find that, at least for Einstein gravity, the splitting problem can be fixed by using equations of motion. How to derive the splittings for higher derivative gravity is a non-trivial and open question. For simplicity, we ignore the splitting problem in this paper and find that it does not affect our main results.

  6. Humans use internal models to estimate gravity and linear acceleration.

    PubMed

    Merfeld, D M; Zupan, L; Peterka, R J

    1999-04-15

    Because sensory systems often provide ambiguous information, neural processes must exist to resolve these ambiguities. It is likely that similar neural processes are used by different sensory systems. For example, many tasks require neural processing to distinguish linear acceleration from gravity, but Einstein's equivalence principle states that all linear accelerometers must measure both linear acceleration and gravity. Here we investigate whether the brain uses internal models, defined as neural systems that mimic physical principles, to help estimate linear acceleration and gravity. Internal models may be used in motor contro, sensorimotor integration and sensory processing, but direct experimental evidence for such models is limited. To determine how humans process ambiguous gravity and linear acceleration cues, subjects were tilted after being rotated at a constant velocity about an Earth-vertical axis. We show that the eye movements evoked by this post-rotational tilt include a response component that compensates for the estimated linear acceleration even when no actual linear acceleration occurs. These measured responses are consistent with our internal model predictions that the nervous system can develop a non-zero estimate of linear acceleration even when no true linear acceleration is present. PMID:10217143

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

    SciTech Connect

    Hwang, Jai-chan; Noh, Hyerim

    2005-03-15

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  9. The International Space University's variable gravity research facility design

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  10. Crustal structure beneath the southern Appalachians: nonuniqueness of gravity modeling

    USGS Publications Warehouse

    Hutchinson, Deborah R.; Grow, John A.; Klitgord, Kim D.

    1983-01-01

    Gravity models computed for a profile across the long-wavelength paired negative-positive Bouguer anomalies of the southern Appalachian Mountains show that the large negative anomaly can be explained by a crustal root zone, whereas the steep gradient and positive anomaly east of the root may be explained equally well by three different geometries: a suture zone, a mantle upwarp, or a shallow body. Seismic data support the existence of a mountain root but are inadequate to resolve differences among the three possible geometries for the positive anomaly. The presence of outcropping mafic and ultramafic rocks in the southern Appalachians and the inferred tectonic history of the Appalachian orogen are most consistent with the suture-zone model. Crust similar to continental crust probably exists beneath the Coastal Plain and inner continental shelf where the gravity anomalies return to near-zero values.

  11. The International Space University's variable gravity research facility design

    NASA Astrophysics Data System (ADS)

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

    1991-09-01

    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.

  12. International Space University variable gravity research facility design

    NASA Astrophysics Data System (ADS)

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

    1994-03-01

    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 will 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. This report describes the VGRF design that was developed by international participants specializing in the following areas: the politics of international cooperation; engineering, architecture; in-space physiological, materials, and life science experimentation; data communications; and business and management.

  13. Cosmological perturbations in massive gravity and the Higuchi bound

    SciTech Connect

    Fasiello, Matteo; Tolley, Andrew J. E-mail: andrew.j.tolley@case.edu

    2012-11-01

    In de Sitter spacetime there exists an absolute minimum for the mass of a spin-2 field set by the Higuchi bound m{sup 2} ≥ 2H{sup 2}. We generalize this bound to arbitrary spatially flat FRW geometries in the context of the recently proposed ghost-free models of Massive Gravity with an FRW reference metric, by performing a Hamiltonian analysis for cosmological perturbations. We find that the bound generically indicates that spatially flat FRW solutions in FRW massive gravity, which exhibit a Vainshtein mechanism in the background as required by consistency with observations, imply that the helicity zero mode is a ghost. In contradistinction to previous works, the tension between the Higuchi bound and the Vainshtein mechanism is equally strong regardless of the equation of state for matter.

  14. Capillary-gravity wave resistance in ordinary and magnetic fluids

    NASA Astrophysics Data System (ADS)

    Browaeys, J.; Bacri, J.-C.; Perzynski, R.; Shliomis, M. I.

    2001-01-01

    Wave resistance is the drag force associated to the emission of waves by a moving disturbance at a free fluid surface. In the case of capillary-gravity waves it undergoes a transition from zero to a finite value as the speed of the disturbance reaches a certain critical value. For the first time an experiment is designed in order to obtain the capillary-gravity wave resistance as a function of speed. The effect of viscosity is explored, and a magnetic fluid is used to extend the available range of critical speeds. The threshold values are in good agreement with the proposed theory. Contrary to the theoretical model, however, the measured wave resistance reveals a non-monotonic speed dependence after the threshold.

  15. Utilization of Low Gravity Environment for Measuring Liquid Viscosity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.; Ethridge, Edwin

    1998-01-01

    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.

  16. Gravity...It's So Attractive!

    ERIC Educational Resources Information Center

    Lewis, Carol

    1992-01-01

    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)

  17. Is There Gravity in Space?

    ERIC Educational Resources Information Center

    Bar, Varda; And Others

    1997-01-01

    Investigates students' ideas about gravity beyond the earth's surface. Presents a lesson plan designed to help students understand that gravity can act beyond Earth's atmosphere. Also helps students gain a more adequate intuitive understanding of how natural and artificial satellites stay in orbit. Reports that this strategy changed some students'…

  18. Quantum Corrections to Entropic Gravity

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Wang, Chiao-Hsuan

    2013-01-01

    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 ℏ 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 ℏ. Such deviation from the classical Newton's law may serve as a probe to the validity of entropic gravity.

  19. Quantum Corrections to Entropic Gravity

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Wang, Chiao-Hsuan

    2013-12-01

    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 ħ 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 ħ. Such deviation from the classical Newton's law may serve as a probe to the validity of entropic gravity.

  20. Reduced Gravity Zblan Optical Fiber

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  1. Born-Infeld-Horava gravity

    SciTech Connect

    Guellue, Ibrahim; Sisman, Tahsin Cagri; Tekin, Bayram

    2010-05-15

    We define various Born-Infeld gravity theories in 3+1 dimensions which reduce to Horava's model at the quadratic level in small curvature expansion. In their exact forms, our actions provide z{yields}{infinity} extensions of Horava's gravity, but when small curvature expansion is used, they reproduce finite z models, including some half-integer ones.

  2. Near-Surface Gravity Survey

    USGS Multimedia Gallery

    A USGS hydrologist prepares equipment to conduct a gravity survey to evaluate small variations in the earth's gravity field. The USGS Office of Groundwater Branch of Geophysics develops and tests new tools and field methods to support USGS analysis of groundwater flow systems....

  3. Quantum W sub 3 gravity

    SciTech Connect

    Schoutens, K. . Inst. for Theoretical Physics); Sevrin, A. ); van Nieuwenhuizen, P. . Theory Div. State Univ. of New York, Stony Brook, NY . Inst. for Theoretical Physics)

    1991-11-01

    We briefly review some results in the theory of quantum W{sub 3} gravity in the chiral gauge. We compare them with similar results in the analogous but simpler cases of d = 2 induced gauge theories and d = 2 induced gravity.

  4. Extensions of 2D gravity

    SciTech Connect

    Sevrin, A.

    1993-06-01

    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.

  5. Foam formation in low gravity

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  6. Conceptualization and design of a variable-gravity research facility

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The goal is to provide facilities for the study of the effects of variable-gravity levels in reducing the physiological stresses upon the humans of long-term stay time in zero-g. The designs studied include: twin-tethered two module system with a central despun module with docking port and winch gear; and rigid arm tube facility using shuttle external tanks. Topics examined included: despun central capsule configuration, docking clearances, EVA requirements, crew selection, crew scheduling, food supply and preparation, waste handling, leisure use, biomedical issues, and psycho-social issues.

  7. Discrete Quantum Gravity in the Regge Calculus Formalism

    SciTech Connect

    Khatsymovsky, V.M.

    2005-09-01

    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.

  8. Analog model for quantum gravity effects: phonons in random fluids.

    PubMed

    Krein, G; Menezes, G; Svaiter, N F

    2010-09-24

    We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model. PMID:21230759

  9. Zero-Base Budgeting:; An Institutional Experience.

    ERIC Educational Resources Information Center

    Alexander, Donald L.; Anderson, Roger C.

    Zero-base budgeting as it is used at Allegany College is described. Zero-based budgeting is defined as a budgeting and planning approach that requires the examination of every item in a budget request as if the request were being proposed for the first time. Budgets (decision packages) are first made up for decision units (i.e., a course for the…

  10. Teacher Perceptions of Division by Zero

    ERIC Educational Resources Information Center

    Quinn, Robert J.; Lamberg, Teruni D.; Perrin, John R.

    2008-01-01

    Dividing by zero can be confusing for students at all levels. If teachers are to provide clear and understandable explanations of this topic, they must possess a strong conceptual understanding of it themselves. In this article, the authors present qualitative data on fourth- through eighth-grade teachers' perceptions of division by zero. They…

  11. Join the ZERO TO THREE Policy Network

    ERIC Educational Resources Information Center

    Lally, J. Ronald; Lurie-Hurvitz, Erica; Cohen, Julie

    2006-01-01

    The authors describe the new ZERO TO THREE Policy Network, launched in 2005 to help the early childhood community get involved with public policy. The purpose of the ZERO TO THREE Policy Network is to engage infant-toddler professionals, researchers, and advocates in the public policy process and provide them with the tools and information they…

  12. Zero Tolerance Policies. ERIC Digest Number 146.

    ERIC Educational Resources Information Center

    McAndrews, Tobin

    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…

  13. Workshop: Promoting Sustainability Through Net Zero Strategies

    EPA Science Inventory

    In 2011, EPAs Office of Research and Development (ORD) signed an MOU with the U.S. Army to support the Armys Net Zero initiative. The 17 Net Zero pilot installations aim to produce as much energy as used; limit freshwater use and increase water reuse; and reduce the generation ...

  14. Student Dress Codes Using Zero Tolerance?

    ERIC Educational Resources Information Center

    Essex, Nathan L.

    2004-01-01

    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…

  15. Teacher Perceptions of Division by Zero

    ERIC Educational Resources Information Center

    Quinn, Robert J.; Lamberg, Teruni D.; Perrin, John R.

    2008-01-01

    Dividing by zero can be confusing for students at all levels. If teachers are to provide clear and understandable explanations of this topic, they must possess a strong conceptual understanding of it themselves. In this article, the authors present qualitative data on fourth- through eighth-grade teachers' perceptions of division by zero. They

  16. Workshop: Promoting Sustainability Through Net Zero Strategies

    EPA Science Inventory

    In 2011, EPA’s Office of Research and Development (ORD) signed an MOU with the U.S. Army to support the Army’s Net Zero initiative. The 17 Net Zero pilot installations aim to produce as much energy as used; limit freshwater use and increase water reuse; and reduce the generation ...

  17. Determining Absolute Zero Using a Tuning Fork

    ERIC Educational Resources Information Center

    Goldader, Jeffrey D.

    2008-01-01

    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…

  18. Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory

    SciTech Connect

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

    1987-06-15

    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.

  19. Superconducting gravity gradiometer for sensitive gravity measurements. I. Theory

    NASA Astrophysics Data System (ADS)

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

    1987-06-01

    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.

  20. Low gravity synthesis of polymers with controlled molecular configuration

    NASA Technical Reports Server (NTRS)

    Heimbuch, A. H.; Parker, J. A.; Schindler, A.; Olf, H. G.

    1975-01-01

    Heterogeneous chemical systems have been studied for the synthesis of isotactic polypropylene in order to establish baseline parameters for the reaction process and to develop sensitive and accurate methods of analysis. These parameters and analytical methods may be used to make a comparison between the polypropylene obtained at one g with that of zero g (gravity). Baseline reaction parameters have been established for the slurry (liquid monomer in heptane/solid catalyst) polymerization of propylene to yield high purity, 98% isotactic polypropylene. Kinetic data for the slurry reaction showed that a sufficient quantity of polymer for complete characterization can be produced in a reaction time of 5 min; this time is compatible with that available on a sounding rocket for a zero-g simulation experiment. The preformed (activated) catalyst was found to be more reproducible in its activity than the in situ formed catalyst.

  1. Further studies of propellant sloshing under low-gravity conditions

    NASA Technical Reports Server (NTRS)

    Dodge, F. T.

    1971-01-01

    A variational integral is formulated from Hamilton's Principle and is proved to be equivalent to the usual differential equations of low-gravity sloshing in ellipsoidal tanks. It is shown that for a zero-degree contact angle the contact line boundary condition corresponds to the stuck condition, a result that is due to the linearization of the equations and the ambiguity in the definition of the wave height at the wall. The variational integral is solved by a Rayleigh-Ritz technique. Results for slosh frequency when the free surface is not bent-over compare well with previous numerical solutions. When the free surface is bent over, however, the results for slosh frequency are considerably larger than those predicted by previous finite-difference, numerical approaches: the difference may be caused by the use of a zero degree contact angle in the present theory in contrast to the nonzero contact angle used in the numerical approaches.

  2. On-chip zero-index metamaterials

    NASA Astrophysics Data System (ADS)

    Li, Yang; Kita, Shota; Muñoz, Philip; Reshef, Orad; Vulis, Daryl I.; Yin, Mei; Lončar, Marko; Mazur, Eric

    2015-11-01

    Metamaterials with a refractive index of zero exhibit physical properties such as infinite phase velocity and wavelength. However, there is no way to implement these materials on a photonic chip, restricting the investigation and application of zero-index phenomena to simple shapes and small scales. We designed and fabricated an on-chip integrated metamaterial with a refractive index of zero in the optical regime. Light refracts perpendicular to the facets of a prism made of this metamaterial, directly demonstrating that the index of refraction is zero. The metamaterial consists of low-aspect-ratio silicon pillar arrays embedded in a polymer matrix and clad by gold films. This structure can be fabricated using standard planar processes over a large area in arbitrary shapes and can efficiently couple to photonic integrated circuits and other optical elements. This novel on-chip metamaterial platform opens the door to exploring the physics of zero index and its applications in integrated optics.

  3. Problems of massive gravities

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    The method of characteristics is a key tool for studying consistency of equations of motion; it allows issues such as predictability, maximal propagation speed, superluminality, unitarity and acausality to be addressed without requiring explicit solutions. We review this method and its application to massive gravity (mGR) theories to show the limitations of these models' physical viability: Among their problems are loss of unique evolution, superluminal signals, matter coupling inconsistencies and micro-acausality (propagation of signals around local closed time-like curves (CTCs)/closed causal curves (CCCs)). We extend previous no-go results to the entire three-parameter range of mGR theories. It is also argued that bimetric models suffer a similar fate.

  4. Gravity waves from thunderstorms

    NASA Technical Reports Server (NTRS)

    Balachandran, N. K.

    1980-01-01

    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.

  5. A new gravity model

    NASA Astrophysics Data System (ADS)

    Kruglov, S. I.

    2015-08-01

    We propose a new model of modified gravity theory with the function . Constant curvature solutions corresponding to the flat and de Sitter spacetime are obtained. The Jordan and Einstein frames are considered; the potential and the mass of the scalar degree of freedom are found. We show that the flat spacetime is stable and the de Sitter spacetime is unstable. The slow-roll parameters , , and the -fold number of the model are evaluated in the Einstein frame. The index of the scalar spectrum power-law and the tensor-to-scalar ratio are calculated. Critical points of autonomous equations for the de Sitter phase and the matter dominated epoch are found and studied. We obtain the approximate solution of equations of motion which is the deviation from the de Sitter phase in the Jordan frame. It is demonstrated that the model passes the matter stability test.

  6. Phantom Crossing DGP Gravity

    SciTech Connect

    Hirano, Koichi; Komiya, Zen

    2010-08-12

    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.

  7. Transverse gravity versus observations

    NASA Astrophysics Data System (ADS)

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J. J.

    2009-07-01

    Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂μξμ = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

  8. Transverse gravity versus observations

    SciTech Connect

    Álvarez, Enrique; Faedo, Antón F.; López-Villarejo, J.J. E-mail: anton.fernandez@uam.es

    2009-07-01

    Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂{sub μ}ξ{sup μ} = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance.

  9. Lidar measurements of gravity waves in the middle atmosphere in southern hemisphere winter above New Zealand

    NASA Astrophysics Data System (ADS)

    Kaifler, Bernd; Kaifler, Natalie; Dörnbrack, Andreas; Ehard, Benedikt; Rapp, Markus

    2015-04-01

    The international Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign was carried out in New Zealand during austral winter 2014. Its aim was to extensively study gravity waves from their sources in the troposphere, along their propagation through the atmosphere to the regions of dissipation at high altitudes. New Zealand was chosen due to its proximity to the edge of the polar vortex and its orography where strong flows excite gravity waves, making it one of the world's gravity wave hotspots. During DEEPWAVE, a comprehensive set of instruments was operated to observe gravity waves. The DLR Rayleigh/Raman lidar was set up at NIWA station in Lauder on New Zealand's South Island in June 2014. The instrumented was operated whenever weather permitted. Temperature profiles are retrieved between 22 and 80 km with 10 min temporal and 1 km vertical resolution. In order to study variations in gravity wave propagation associated with the breakdown of the polar vortex, observations were continued beyond the DEEPWAVE campaign. In total 755 operation hours during 99 nights were accumulated between June and November 2014. We present statistics of gravity wave activity and wave parameters which we derived from this extensive dataset using filtering techniques and spectral analysis. In a first step, we characterize gravity wave activity using the gravity wave potential energy density. Then we study spectral properties of the waves using two-dimensional FFT of wave-induced temperature variances. We find that in the stratosphere, low-frequency waves with periods close to the inertial period are very common. Large-amplitude waves with periods of less than two hours occur at times mainly in the mesosphere. The distribution of observed phase speeds suggests that observed waves fall into three groups: one group with mean phase speeds of -3 km/h, one group with phase speeds close to zero, and a broad background. In addition to statistics, we show case studies of selected gravity wave events.

  10. AdS Chern-Simons gravity induces conformal gravity

    NASA Astrophysics Data System (ADS)

    Aros, Rodrigo; Díaz, Danilo E.

    2014-04-01

    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.

  11. New Bi-Gravity from New Massive Gravity

    NASA Astrophysics Data System (ADS)

    Akhavan, A.; Alishahiha, M.; Naseh, A.; Nemati, A.; Shirzad, A.

    2016-05-01

    Using the action of three dimensional New Massive Gravity (NMG) we construct a new bi-gravity in three dimensions. This can be done by promoting the rank two auxiliary field appearing in the expression of NMG's action into a dynamical field. We show that small fluctuations around the AdS vacuum of the model are non-tachyonic and ghost free within certain range of the parameters of the model. We study central charges of the dual field theory and observe that in this range they are positive too. This suggests that the proposed model might be a consistent three dimensional bi-gravity.

  12. Gravity quantized: Loop quantum gravity with a scalar field

    SciTech Connect

    Domagala, Marcin; Kaminski, Wojciech; Giesel, Kristina; Lewandowski, Jerzy

    2010-11-15

    ...''but we do not have quantum gravity.'' This phrase is often used when analysis of a physical problem enters the regime in which quantum gravity effects should be taken into account. In fact, there are several models of the gravitational field coupled to (scalar) fields for which the quantization procedure can be completed using loop quantum gravity techniques. The model we present in this paper consists of the gravitational field coupled to a scalar field. The result has similar structure to the loop quantum cosmology models, except that it involves all the local degrees of freedom of the gravitational field because no symmetry reduction has been performed at the classical level.

  13. Gravity-matter entanglement in Regge quantum gravity

    NASA Astrophysics Data System (ADS)

    Paunković, Nikola; Vojinović, Marko

    2016-03-01

    We argue that Hartle-Hawking states in the Regge quantum gravity model generically contain non-trivial entanglement between gravity and matter fields. Generic impossibility to talk about “matter in a point of space” is in line with the idea of an emergent spacetime, and as such could be taken as a possible candidate for a criterion for a plausible theory of quantum gravity. Finally, this new entanglement could be seen as an additional “effective interaction”, which could possibly bring corrections to the weak equivalence principle.

  14. Gravity Probe B Inspection

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The space vehicle Gravity Probe B (GP-B) is the relativity experiment developed at Stanford University to test two extraordinary predictions of Albert Einstein's general theory of relativity. The experiment will measure, very precisely, the expected tiny changes in the direction of the spin axes of four gyroscopes contained in an Earth-orbiting satellite at a 400-mile altitude. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system. They will measure how space and time are very slightly warped by the presence of the Earth, and, more profoundly, how the Earth's rotation very slightly drags space-time around with it. These effects, though small for the Earth, have far-reaching implications for the nature of matter and the structure of the Universe. GP-B is among the most thoroughly researched programs ever undertaken by NASA. This is the story of a scientific quest in which physicists and engineers have collaborated closely over many years. Inspired by their quest, they have invented a whole range of technologies that are already enlivening other branches of science and engineering. In this photograph, engineer Gary Reynolds is inspecting the inside of the probe neck during probe thermal repairs. GP-B is scheduled for launch in April 2004 and managed for NASA by the Marshall Space Flight Center. Development of the GP-B is the responsibility of Stanford University along with major subcontractor Lockheed Martin Corporation. (Image credit to Russ Leese, Gravity Probe B, Stanford University)

  15. Gravity Estimation from a Simulated GRACE Mission: Short vs. Long Arcs

    NASA Technical Reports Server (NTRS)

    Rowlands, David D.; Ray, Richard D.; Chinn, D. S.; Lemoine, F. G.; Smith, David E. (Technical Monitor)

    2001-01-01

    We present simulations of gravity estimation from a GRACE-like satellite mission: low-low intersatellite tracking with a precision of order 1 micron s(exp -1) yielding gravity fields of degree and order 120. We employ a unique parameterization of the intersatellite baseline vector which allows the gravity estimation to be performed (relatively) independently of the GPS (global positioning system) tracking data once sufficiently accurate orbits are obtained. This considerably simplifies data processing during the gravity estimation. During that process only certain components of the baseline parameterization need be adjusted; other components are uncorrelated with gravity and may be adopted unchanged from the initial GPS orbits. The technique is also amenable to very short arcs of data. We present comparisons of gravity estimation from 30 days of observations with arcs of length 15 minutes vs. arcs of one day. Our 'truth' field is the EGM96 (Earth Gravitational Model) model; our prior field is a degree-70 clone of EGM96, perturbed from it by amounts comparable to the standard errors of EGM96 (and identically zero for degrees 71-120). For a high inclination orbit, the short-arc analysis recovers low order gravity coefficients remarkably well, although higher order terms, especially sectorial terms, are understandably less accurate. The simulations suggest that either long or short arcs of GRACE data are likely to improve parts of the geopotential spectrum by several orders of magnitude. This is especially so for low order coefficients, which are markedly improved for all degrees through 120.

  16. Progress in the Determination of the Earth's Gravity Field

    NASA Technical Reports Server (NTRS)

    Rapp, Richard H. (Editor)

    1989-01-01

    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.

  17. Model selection for modified gravity.

    PubMed

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

    2011-12-28

    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

  18. Three Least-Squares Minimization Approaches to Interpret Gravity Data Due to Dipping Faults

    NASA Astrophysics Data System (ADS)

    Abdelrahman, E. M.; Essa, K. S.

    2015-02-01

    We have developed three different least-squares minimization approaches to determine, successively, the depth, dip angle, and amplitude coefficient related to the thickness and density contrast of a buried dipping fault from first moving average residual gravity anomalies. By defining the zero-anomaly distance and the anomaly value at the origin of the moving average residual profile, the problem of depth determination is transformed into a constrained nonlinear gravity inversion. After estimating the depth of the fault, the dip angle is estimated by solving a nonlinear inverse problem. Finally, after estimating the depth and dip angle, the amplitude coefficient is determined using a linear equation. This method can be applied to residuals as well as to measured gravity data because it uses the moving average residual gravity anomalies to estimate the model parameters of the faulted structure. The proposed method was tested on noise-corrupted synthetic and real gravity data. In the case of the synthetic data, good results are obtained when errors are given in the zero-anomaly distance and the anomaly value at the origin, and even when the origin is determined approximately. In the case of practical data (Bouguer anomaly over Gazal fault, south Aswan, Egypt), the fault parameters obtained are in good agreement with the actual ones and with those given in the published literature.

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  20. Running couplings in quantum theory of gravity coupled with gauge fields

    NASA Astrophysics Data System (ADS)

    Narain, Gaurav; Anishetty, Ramesh

    2013-10-01

    In this paper we study the coupled system of non-abelian gauge fields with higher-derivative gravity. Charge renormalization is investigated in this coupled system. It is found that the leading term in the gauge coupling beta function comes due to interaction of gauge fields with gravitons. This is shown to be a universal quantity in the sense that it doesn't depend on the gauge coupling and the gauge group, but may depend on the other couplings of the action (gravitational and matter). The coupled system is studied at one-loop. It is found that the leading term of gauge beta function is zero at one-loop in four dimensions. The effect of gauge fields on the running of gravitational couplings is investigated. The coupled system of gauge field with higher-derivative gravity is shown to satisfy unitarity when quantum corrections are taken in to account. Moreover, it is found that Newton constant goes to zero at short distances. In this renormalizable and unitary theory of gauge field coupled with higher-derivative gravity, the leading term of the gauge beta function, found to be universal for all gauge groups, is further studied in more detail by isolating it in the context of abelian gauge theories coupled with gravity in four dimensions. Using self-duality of abelian gauge theories in four dimensions, this term of the gauge beta function is shown to be zero to all loops. This is found to be independent of the gravity action, regularization scheme and gauge fixing condition. An explicit one-loop computation for arbitrary gravity action further demonstrates the vanishing of this term in the gauge beta function in four dimensions, independent of the regularization scheme and gauge fixing condition. Consequences of this are discussed.