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1

Zero-gravity movement studies  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

2

Space truss zero gravity dynamics  

NASA Technical Reports Server (NTRS)

The Structural Dynamics Branch of the Air Force Flight Dynamics Laboratory in cooperation with the Reduced Gravity Office of the NASA Lyndon B. Johnson Space Center (JSC) plans to perform zero-gravity dynamic tests of a 12-meter truss structure. This presentation describes the program and presents all results obtained to date.

Swanson, Andy

1989-01-01

3

Zero-gravity aerosol behavior  

NASA Technical Reports Server (NTRS)

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

Edwards, H. W.

1981-01-01

4

Modeling of zero gravity venting  

NASA Technical Reports Server (NTRS)

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

Merte, H., Jr.

1984-01-01

5

Zero-gravity quantity gaging system  

NASA Technical Reports Server (NTRS)

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

1989-01-01

6

Zero-gravity slosh analysis  

NASA Astrophysics Data System (ADS)

Experimental results were used to anchor a newly developed three-dimensional, finite-difference hydrodynamics code that was designed to simulate large amplitude slosh in a container moving in a zero-g environment. The results of this anchoring are presented along with a brief description of the SOLA-SLOSH code of Hirt el al. (1983), a description of the experiment, and a description of how the code was used to model pointing errors of a liquid-filled spacecraft during its space maneuvers.

Eastes, T. W.; Chang, Y. M.; Hirt, C. W.; Sicilian, J. M.

7

Zero gravity tissue-culture laboratory  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

8

Containing Hair During Cutting In Zero Gravity  

NASA Technical Reports Server (NTRS)

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

Haines, Richard F.

1992-01-01

9

Zero Gravity Research Facility User's Guide  

NASA Technical Reports Server (NTRS)

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.

Thompson, Dennis M.

1999-01-01

10

On the Specification of the Gravity Model of Trade: Zeros, Excess Zeros and Zero-Inflated Estimation  

Microsoft Academic Search

Conventional studies of bilateral trade patterns specify a log-normal gravity equation for empirical estimation. However, the log-normal gravity equation suffers from three problems: the bias created by the logarithmic transformation, the failure of the homoscedasticity assumption, and the way zero values are treated. These problems normally result in biased and inefficient estimates. Recently, the Poisson specification of the trade gravity

Martijn Burger; Frank van Oort; Gert-Jan Linders

2009-01-01

11

Size Gap for Zero Temperature Black Holes in Semiclassical Gravity  

E-print Network

We show that a gap exists in the allowed sizes of all zero temperature static spherically symmetric black holes in semiclassical gravity when only conformally invariant fields are present. The result holds for both charged and uncharged black holes. By size we mean the proper area of the event horizon. The range of sizes that do not occur depends on the numbers and types of quantized fields that are present. We also derive some general properties that both zero and nonzero temperature black holes have in all classical and semiclassical metric theories of gravity.

Paul R. Anderson; Courtney D. Mull

1998-06-16

12

Passive zero-gravity leg restraint  

NASA Technical Reports Server (NTRS)

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.

Miller, Christopher R. (inventor)

1989-01-01

13

The response of single human cells to zero-gravity  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

14

Zero Gravity Cryogenic Vent System Concepts for Upper Stages  

Microsoft Academic Search

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

Alain Ravex; Robin Flachbart; Barney Holt

1999-01-01

15

Zero-Gravity Fuel-Cell Product-Water Accumulator  

NASA Technical Reports Server (NTRS)

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.

Barrera, Thomas P.

1989-01-01

16

Acceleration display system for aircraft zero-gravity research  

NASA Technical Reports Server (NTRS)

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.

Millis, Marc G.

1987-01-01

17

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

NASA Technical Reports Server (NTRS)

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.

Parang, Masood; Salah-Eddine, Adel

1987-01-01

18

The response of single human cells to zero gravity  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

19

Liquid jet impingement normal to a disk in zero gravity  

NASA Technical Reports Server (NTRS)

An experimental and analytical investigation was conducted to determine the free surface shapes of circular jets impinging normal to sharp-edged disks in zero gravity. Experiments conducted in a zero gravity drop tower yielded three distinct flow patterns which were classified in terms of the relative effects of surface tension and inertial forces. An order of magnitude analysis was conducted indicating regions where viscous forces were not significant when computing free surface shapes. The free surface analysis was simplified by transforming the governing potential flow equations and boundary conditions into the inverse plane. The resulting nonlinear equations were solved numerically and comparisons were made with the experimental data for the inertia dominated regime.

Labus, T. L.; Dewitt, K. J.

1978-01-01

20

Crew efficiency on first exposure to zero-gravity  

NASA Technical Reports Server (NTRS)

Activation task performance of Skylab crews showed improved efficiency as experience was gained in weightlessness living. During three activation intervals, less than 12 man-hours were lost due to reduced efficiency (including the effects of motion sensitivity) while almost 200 man-hours of productive work were delivered. Work rate improved for tasks in which simulation and training time were extensive and for tasks which allowed zero-gravity operations to be optimized.

Garriott, O. K.; Doerre, G. L.

1977-01-01

21

Development of a compact dilution refrigerator for zero gravity operation  

NASA Technical Reports Server (NTRS)

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

Roach, Pat R.; Helvensteijn, Ben

1990-01-01

22

Dichotomous behavior of capillary surfaces in zero gravity  

NASA Technical Reports Server (NTRS)

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

Concus, Paul; Finn, Robert

1990-01-01

23

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

NASA Technical Reports Server (NTRS)

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

Miyagawa, I.

1974-01-01

24

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

25

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

SciTech Connect

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)

Foster, Michael; Pearlman, Howard [Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)

2006-10-15

26

Ocular Blood Flow Measured Noninvasively in Zero Gravity  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

27

Zero-Gravity Vortex Vent and PVT Gaging System  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

28

Adiabatic demagnetization refrigerator for use in zero gravity  

NASA Technical Reports Server (NTRS)

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.

Dingus, Michael L.

1988-01-01

29

Steady State Detached Solidification of Water at Zero Gravity  

NASA Technical Reports Server (NTRS)

Steady-state detached solidification of water was calculated using the Moving Meniscus Model. Similar to the experimental observation of many materials in microgravity, detached solidification of water is predicted to occur in a sealed ampoule at zero gravity under proper conditions. For steady detachment, the freezing rate must exceed a critical value, Henry's constant of the dissolved gas must be below a critical value, the temperature of the top of the water must be below a critical value, the contact angle of water on the ampoule wall must exceed a critical value, and the diffusion coefficient must exceed a critical value. Each critical value depends on the physical properties and the other operating conditions. Thus different results are obtained for InSb and water. The critical gas pressure above the melt for water is much smaller than for InSb, the critical freezing rate is larger for water, and the critical contact angle of the melt on the ampoule wall is larger for water. For the gases examined here, the solubilities of Ar, N2 and Ne in water are sufficient for detachment to occur, while the solubility of He is not.

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

2001-01-01

30

Steady State Detached Solidification of Water at Zero Gravity  

NASA Technical Reports Server (NTRS)

Steady-state detached solidification of water was calculated using the Moving Meniscus Model. Similar to the experimental observation of many materials in microgravity, detached solidification of water is predicted to occur in a sealed ampoule at zero gravity under proper conditions. For steady detachment, the freezing rate must exceed a critical value, Henry's constant of the dissolved gas must be below a critical value, the temperature of the top of the water must be below a critical value, the contact angle of water on the ampoule wall must exceed a critical value, and the diffusion coefficient must exceed a critical value. Each critical value depends on the physical properties and the other operating conditions. Thus different results are obtained for InSb and water. The critical gas pressure above the melt for water is much smaller than for InSb, the critical freezing rate is larger for water, and the critical contact angle of the melt on the ampoule wall is larger for water. For the gases examined here, the solubilities of Ar, N2 and Ne in water are sufficient for detachment to occur, while the solubility of He is not.

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

2003-01-01

31

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

32

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

NASA Technical Reports Server (NTRS)

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.

Merte, H., Jr.

1986-01-01

33

Vortex motion phase separator for zero gravity liquid transfer  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

34

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

NASA Technical Reports Server (NTRS)

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

Parang, Masood

1986-01-01

35

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING PARABOLIC FLIGHTS  

E-print Network

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were assessed in this study to assess the heart rate variability (HRV) and blood pres- sure variability (BPV). Due to gravity

36

Zero Potts models coupled to two-dimensional quantum gravity  

NASA Astrophysics Data System (ADS)

The critical exponents that have been calculated for the Ising and Potts models coupled to two-dimensional quantum gravity correspond to annealed averages in the language of solid state physics. Using the replica trick and the approach of DDK we calculate the critical exponents for the Ising and q = 3, 4 state Potts models coupled to quenched two-dimensional quantum gravity.

Johnston, D. A.

1992-03-01

37

Assessment of geophysical flows for zero-gravity simulation  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

38

The Dirac point electron in zero-gravity Kerr--Newman spacetime  

E-print Network

Dirac's wave equation for a point electron in the topologically nontrivial maximal analytically extended electromagnetic Kerr--Newman spacetime is studied in a zero-gravity limit; here, "zero-gravity" means $G\\to 0$, 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; 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. Some of our results extend to a generalization of the zero-$G$ Kerr--Newman spacetime with different electric-monopole-to-magnetic-dipole-moment ratio.

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

2014-11-11

39

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

NASA Technical Reports Server (NTRS)

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.

Eisner, M. (editor)

1975-01-01

40

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

41

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

NASA Technical Reports Server (NTRS)

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.

Glover, K. E.

1976-01-01

42

On Calculating the Zero-Gravity Surface Figure of a Mirror  

NASA Technical Reports Server (NTRS)

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

Bloemhof, Eric E.

2010-01-01

43

Extracting Zero-Gravity Surface Figure of a Mirror  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

44

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

45

Velocity profiles, stresses, and Bagnold scaling of sheared granular system in zero gravity  

E-print Network

Velocity profiles, stresses, and Bagnold scaling of sheared granular system in zero gravity Oleh, therefore reducing the shear in the system. Next, we present stress distributions both for controlled volume and for controlled stress configurations. We discuss the dependence of solid volume fraction on shear rate under

Kondic, Lou

46

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING PARABOLIC FLIGHTS  

E-print Network

HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were to reduce postflight orthostatic intolerance. Key words: parabolic flight; heart rate; blood pressure

47

STS-42 Payload Specialist Merbold inside KC-135 during zero gravity flight  

NASA Technical Reports Server (NTRS)

STS-42 Payload Specialist Ulf D. Merbold (upside down) tumbles with fellow German Space Agency (DFVLR) scientist in the fuselage of KC-135 NASA 930 during a zero gravity flight the week of 05-16-88. Merbold is representing the European Space Agency (ESA) on the International Microgravity Laboratory 1 (IML-1) mission aboard Discovery, Orbiter Vehicle (OV) 103.

1988-01-01

48

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

NASA Technical Reports Server (NTRS)

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.

Eisner, M. (editor)

1974-01-01

49

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

50

Study on processing immiscible materials in zero gravity  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

51

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

PubMed

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

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

2000-10-01

52

A study of immiscible liquids, liquid behavior at zero gravity, and dynamic contact lines and angles  

NASA Astrophysics Data System (ADS)

The work reported here covers three topics that were investigated as part of preparation for a space based experiment. The intention of the proposed experiment was to study the relationship between container geometry and interface geometry for a free liquid surface at zero gravity.A mathematical theory proposed by Paul Concus and Robert Finn in 1974 and recently developed by Finn yields explicit geometrical criteria for the position of the free surface of a liquid at zero gravity in a cylindrical container of specified cross section. It is possible to find geometrical criteria that promise a particular liquid location. A unified graphical presentation of four geometries is given that can be used directly for the design of containments for liquids at zero gravity. As one application of these design curves, a container was built and tested in a series of 2 second droptower experiments at NASA Lewis Research Center.It was apparent that the space based experiment would require use of sophisticated optical instrumentation that would be most effective if a pair of immiscible liquids were used rather than a single liquid under its vapor. This work identifies 121 transparent immiscible liquid pairs that have properties compatible with optical instrumentation based on laser-induced fluorescence. Physical data such as specific gravity, index of refraction, viscosity, flash point, and toxicity were found in the literature. Compatibility with plexiglas (PMMA), contact angles of the internal meniscus on glass and PMMA, meniscus formation times, and clearing times were measured. A useful noninvasive technique for determining interfacial tensions is explained and used.The contact angle is a critical parameter in the consideration of liquid behavior at zero gravity, therefore, a technique, based on laser light refraction, was developed to objectively measure it. Dynamic contact line experiments were conducted at various velocities, both advancing and receding, using one of the 121 immiscible liquid pairs (nonane/formamide) in contact with glass.

Smedley, Gregory Todd

53

a Study of Immiscible Liquids, Liquid Behavior at Zero Gravity, and Dynamic Contact Lines and Angles  

NASA Astrophysics Data System (ADS)

The work reported here covers three topics that were investigated as part of preparation for a space based experiment. The intention of the proposed experiment was to study the relationship between container geometry and interface geometry for a free liquid surface at zero gravity. A mathematical theory proposed by Paul Concus and Robert Finn in 1974 and recently developed by Finn yields explicit geometrical criteria for the position of the free surface of a liquid at zero gravity in a cylindrical container of specified cross section. It is possible to find geometrical criteria that promise a particular liquid location. A unified graphical presentation of four geometries is given that can be used directly for the design of containments for liquids at zero gravity. As one application of these design curves, a container was built and tested in a series of 2 second drop-tower experiments at NASA Lewis Research Center. It was apparent that the space based experiment would require use of sophisticated optical instrumentation that would be most effective if a pair of immiscible liquids were used rather than a single liquid under its vapor. This work identifies 121 transparent immiscible liquid pairs that have properties compatible with optical instrumentation based on laser-induced fluorescence. Physical data such as specific gravity, index of refraction, viscosity, flash point, and toxicity were found in the literature. Compatibility with plexiglas (PMMA), contact angles of the internal meniscus on glass and PMMA, meniscus formation times, and clearing times were measured. A useful non-invasive for determining interfacial tensions is explained and used. The contact angle is a critical parameter in the consideration of liquid behavior at zero gravity, therefore, a technique, based on laser light refraction, was developed to objectively measure it. Dynamic contact line experiments were conducted at various velocities, both advancing and receding, using one of the 121 immiscible liquid pairs (nonane/formamide) in contact with glass.

Smedley, Gregory Todd

1990-01-01

54

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

55

Anomalous heat transport by the piston effect in supercritical fluids under zero gravity  

Microsoft Academic Search

The response to a boundary heating of a very compressible, low-diffusivity, supercritical fluid (CO2) under zero gravity is studied by solving numerically the full nonlinear one-dimensional Navier-Stokes equations. Both short (acoustic) and long (diffusion) time scales are investigated. A new mechanism of heat transport is seen, where the thermal energy is transformed into kinetic energy in a hot expanding boundary

B. Zappoli; D. Bailly; Y. Garrabos; B. Le Neindre; P. Guenoun

1990-01-01

56

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

NASA Technical Reports Server (NTRS)

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

Lal, R. B.

1975-01-01

57

Zero-Gravity Emulation of Satellites in Presence of Uncalibrated Sensors and Model Uncertainties  

Microsoft Academic Search

Recently, an alternative to the standard passive zero gravity emulation testbeds is developed which uses robotic technology. It is comprised of a manipulator whose end-effector rigidly grasps a satellite mock up, a six-axis force\\/moment (F\\/M) sensor placed at the interface of the satellite and the manipulator, and a control system. Despite significant advan- tages of the approach there exist practical

Mohamad Talebpour; Mehrzad Namvar

58

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

NASA Technical Reports Server (NTRS)

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

Dewitt, R. L.

1978-01-01

59

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

NASA Technical Reports Server (NTRS)

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

1979-01-01

60

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

NASA Technical Reports Server (NTRS)

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.

Keanini, R. G.; Rubinsky, B.

1990-01-01

61

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

SciTech Connect

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

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

1984-01-01

62

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

PubMed

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

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

2012-12-01

63

Indications for Criticality at Zero Curvature in a 4d Regge Model of Euclidean Quantum Gravity  

E-print Network

We re-examine the approach to four-dimensional Euclidean quantum gravity based on the Regge calculus. A cut-off on the link lengths is introduced and consequently the gravitational coupling and the cosmological constant become independent parameters. We determine the zero curvature, $ =0$, line in the coupling constant plane by numerical simulations. When crossing this line we find a strong, probably first order, phase transition line with indications of a second order endpoint. Beyond the endpoint the transition through the $ =0$ line appears to be a crossover. Previous investigations, using the Regge or the Dynamical Triangulation approach, dealt with a limit in which the first order transition prevails.

Wolfgang Beirl; Bernd A. Berg

2003-08-30

64

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

65

Zero  

E-print Network

You shall not find any new physics, because all physical events are interpreted well-known particles (leptons, quarks, photons, gluons, W-bosons, Z-boson) and forces which have long known (electroweak, gravity, strong interactions). Contents: 1. Pointlike events and probability. 2. Leptons' moving equations and masses. 3. Fermion-antifermion asommetry. 4. Electroweak equations. 5. Chromatic states and gluons. 6. Asimptotic freedom, confinement, Newton's gravity. 7. Dark energy and dark matter. 8. Events and particles. 9. Conclusion.

G. Quznetsov

2011-06-12

66

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

67

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

NASA Technical Reports Server (NTRS)

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.

McCrory, Jean L.

1997-01-01

68

Assessment of zero gravity effects on space worker health and safety  

NASA Technical Reports Server (NTRS)

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

1980-01-01

69

Assessment of zero gravity effects on space worker health and safety  

SciTech Connect

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

Not Available

1980-11-01

70

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

71

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

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

72

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

73

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

74

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

75

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

76

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

77

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

PubMed

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

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

2012-05-01

78

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

79

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

NASA Technical Reports Server (NTRS)

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

Musacchia, X. J.

1974-01-01

80

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

81

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

NASA Technical Reports Server (NTRS)

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.

1979-01-01

82

Dynamic and quantitative phase-contrast imaging of living cells under simulated zero gravity by digital holographic microscopy and superconducting magnet  

NASA Astrophysics Data System (ADS)

The experiment of dynamic and quantitative phase-contrast imaging of living cells in simulated zero gravity environment were performed by using digital holographic microscopy (DHM) combined with a superconducting magnet (SM). The SM with large gradient high magnetic field was used to simulate zero gravity by levitating biological living samples. The proposed DHM system provided highly efficient and versatile means for dynamically and quantitatively phase-contrast imaging MC3T3-E1 cells. To our knowledge, the phase images of living cells undergoing modifications and division under simulated zero gravity were firstly obtained by using DHM-SM prototype.

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

2012-09-01

83

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)

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.

Dintenfass, L.

1985-01-01

84

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

SciTech Connect

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.

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

1988-03-01

85

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

86

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

87

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

NASA Technical Reports Server (NTRS)

We describe here some of our recent mathematical work, which forms a basis for the Interface Configuration Experiment scheduled for USML-2. The work relates to the design of apparatus that exploits microgravity conditions for accurate determination of contact angle. The underlying motivation for the procedures rests on a discontinuous dependence of the capillary free surface interface S on the contact angle gamma, in a cylindrical capillary tube whose section (base) omega contains a protruding corner with opening angle 2 alpha. Specifically, in a gravity-free environment, omega can be chosen so that, for all sufficiently large fluid volume, the height of S is uniquely determined as a (single-valued) function mu(x,y) entirely covering the base; the height mu is bounded over omega uniformly in gamma throughout the range absolute value of (gamma -(pion/2)) less than or equal to alpha, while for absolute value of (gamma - (pion/2)) greater than alpha fluid will necessarily move to the corner and uncover the base, rising to infinity (or falling to negative infinity) at the vertex, regardless of volume. We mention here only that procedures based on the phenomenon promise excellent accuracy when gamma is close pion/2 but may be subject to experimental error when gamma is close to zero (orpion), as the 'singular' part of the domain over which the fluid accumulates (or disappears) when a critical angle gamma theta is crossed then becomes very small and may be difficult to observe. We ignore the trivial case gamma is equal to pion/2 (planar free surface), to simplify the discussion.

Concus, Paul; Finn, Robert

1994-01-01

88

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

PubMed

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

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

2004-11-01

89

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

PubMed Central

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

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

90

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

NASA Technical Reports Server (NTRS)

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

Sanchez, Merri J.

2000-01-01

91

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

NASA Technical Reports Server (NTRS)

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

Spuckler, C. M.

1981-01-01

92

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

NASA Technical Reports Server (NTRS)

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

2002-01-01

93

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

94

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

NASA Technical Reports Server (NTRS)

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

Bailey, J. A.

1976-01-01

95

Effects of Local Detachment of a Melt from Ampoule Walls, Crystal Vibration, and Magnetic Field at Crystal Growth under Zero Gravity  

Microsoft Academic Search

A numerical investigation of the melt flow and heat and mass transfer is carried out at the crystal growth under zero gravity, when the melt detachment from ampoule walls, crystal vibration, and various magnetic fields are active. Specific features of the melt flow are demonstrated depending on the size of a detachment zone adjacent to the crystallization boundary. The velocity

A. I. Feonychev; G. A. Dolgikh

2004-01-01

96

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

97

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

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

98

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

NASA Technical Reports Server (NTRS)

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

Tipton, Charles M.

1991-01-01

99

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

100

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

NASA Astrophysics Data System (ADS)

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

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

2000-04-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

102

GRAVITY  

NSDL National Science Digital Library

3rd Grade Science Standard 4: Students will understand that objects near Earth are pulled toward Earth by gravity Objective 2: Describe the effects of gravity on the motion of an object In this activity we will learn how gravity effects the motion of an object. We will do this by finding out what gravity is and watching experiments on gravity. Finally, we will conduct our own experiment to see first hand how gravity effects everything around us. So, what is gravity? Is it a term that you have heard before? What does it do? Why is it so important? Why do we need to know how it works? If you\\'ve ever wondered what the answers to these questions are, then you\\'re in ...

Ms. Hendricks

2007-11-06

103

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

104

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

105

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

NASA Technical Reports Server (NTRS)

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

Wolf, David A.; Schwarz, Ray P.

1991-01-01

106

Liouville gravity from Einstein gravity  

E-print Network

We show that Liouville gravity arises as the limit of pure Einstein gravity in 2+epsilon dimensions as epsilon goes to zero, provided Newton's constant scales with epsilon. Our procedure - spherical reduction, dualization, limit, dualizing back - passes several consistency tests: geometric properties, interactions with matter and the Bekenstein-Hawking entropy are as expected from Einstein gravity.

D. Grumiller; R. Jackiw

2007-12-28

107

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

NASA Technical Reports Server (NTRS)

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

Straube, Timothy Milton

1993-01-01

108

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

NASA Technical Reports Server (NTRS)

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

Darbro, W.

1978-01-01

109

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

NASA Technical Reports Server (NTRS)

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

Chen, Yongkang; Callahan, Michael; Weislogel, Mark

2013-01-01

110

Simulation of a cometary conglomerate of frozen gases and dust in a zero-gravity environment: A critical evaluation of possible space experiments  

NASA Technical Reports Server (NTRS)

It is proposed to use the Shuttle (OFT experiments) or eventually Spacelab to study, in the absence of gravity the low velocity accretion and the bulk properties of icy conglomerates simulating cometary material and their sedimentation and bulk properties in very small acceleration fields. Their behavior when exposed to the direct solar flux is also under consideration.

Delsemme, A. H.

1976-01-01

111

Ground Zero.  

ERIC Educational Resources Information Center

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)

Vail, Kathleen

1995-01-01

112

Space travel and gravity  

Microsoft Academic Search

Space travelling is not possible for human because, by the time, we cross Jupiter, our bones dissolve as there is zero gravity and, by developing a gravity chamber in the space ship itself we will be able to travel in space for generations and explore the universe.

P. Karmakar; Greeninavin

2010-01-01

113

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)

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.

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

1975-01-01

114

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

115

Hungry Zero  

NSDL National Science Digital Library

The definition of the Zero Property of Multiplication will be presented and discussed, along with a review of other vocabulary necessary for this lesson (factors, products, "groups of", Commutative Property). The students will be taken through a guided lesson, showing them and explaining to them the process of multiplying by 0. This will be followed by independent practice for the students, including a peer review of said practice. The lesson will conclude with a whole class review of the Zero Property of Multiplication. At each step along the way, the teacher will be monitoring student progress and decide on a reteaching worksheet, continued independent practice, or an enrichment exercise.

Joe Szewczyk

2012-06-26

116

Zero Energy Travel  

E-print Network

It is fundamentally possible to travel with zero energy based on Newton Laws of Motion. According to the first law of motion, a body will continue to travel for infinite distance unless it is acted upon by another force. For a body in motion, the force which stops perpetual motion is friction. However, there are many circumstances that friction is zero, for example in space, where there is vacuum. On earth, gravity makes objects to be in constant contact with each other generating friction but technology exists to separate them in the air using powerful magnetic forces. At low speeds, the friction caused by air is minimal but we can create vacuum even on land for high speed travel. Another condition for travelling is for it to stop at its destination. On land, we can recover the kinetic energy back into electrical energy using brushless permanent magnet generators. These generators can also convert electric energy into kinetic energy in order to provide motion. This article reviews technologies that will allow us to travel with zero energy. It is easier to do it on land but in the air, it is not obvious.

Othman Ahmad; Aroland Kiring; Ali Chekima

2012-10-17

117

“Patient Zero”:  

PubMed Central

Summary This article contextualizes the production and reception of And the Band Played On, Randy Shilts’s popular history of the initial recognition of the American AIDS epidemic. Published over twenty-five years ago, the book and its most notorious character, “Patient Zero,” are in particular need of a critical historical treatment. The article presents a more balanced consideration—a “patient’s view”—of Gaétan Dugas’s experience of the early years of AIDS. I oppose the assertion that Dugas, the so-called Patient Zero, ignored incontrovertible information about the condition and was intent on spreading his infection. Instead I argue that scientific ideas in 1982 and 1983 about AIDS and the transmissibility of a causative agent were later portrayed to be more self-evident than they were at the time. The article also traces how Shilts’s highly selective—and highly readable—characterization of Dugas rapidly became embedded in discussions about the need to criminalize the reckless transmission of HIV. PMID:24769806

McKay, Richard A.

2014-01-01

118

Electrophoresis in space at zero gravity  

NASA Technical Reports Server (NTRS)

Early planning for manufacturing operations in space include the use of electrophoresis for purification and separation of biological materials. Greatly simplified electrophoresis apparatus have been flown in the Apollo 14 and 16 missions to test the possibility of stable liquid systems in orbit. Additionally, isoelectric focusing and isotachophoresis are of particular interest as they offer very high resolution and have self-sharpening boundaries. The value of possible space electrophoresis is substantial. For example, present technology permits large fractionation of only a few of blood proteins many fractions, and separated cell populations are needed for research.

Bier, M.; Snyder, R. S.

1974-01-01

119

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

NASA Technical Reports Server (NTRS)

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

1974-01-01

120

Zero Energry Travel  

E-print Network

It is fundamentally possible to travel with zero energy based on Newton Laws of Motion. According to the first law of motion, a body will continue to travel for infinite distance unless it is acted upon by another force. For a body in motion, the force which stops perpetual motion is friction. However, there are many circumstances that friction is zero, for example in space, where there is vacuum. On earth, gravity makes objects to be in constant contact with each other generating friction but technology exists to separate them in the air using powerful magnetic forces. At low speeds, the friction caused by air is minimal but we can create vacuum even on land for high speed travel. Another condition for travelling is for it to stop at its destination. On land, we can recover the kinetic energy back into electrical energy using brushless permanent magnet generators. These generators can also convert electric energy into kinetic energy in order to provide motion. This article reviews technologies that will allo...

Ahmad, Othman; Chekima, Ali

2011-01-01

121

Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production  

E-print Network

#12;Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward Zero Carbon Energy Production Toward

Narasayya, Vivek

122

Multiple zeros of polynomials  

NASA Technical Reports Server (NTRS)

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

Wood, C. A.

1974-01-01

123

Zero Tolerance in Schools.  

ERIC Educational Resources Information Center

Questions the effectiveness of the widespread use of zero-tolerance policies enacted by school boards to punish students who violate weapon and drug rules. Suggests that enforcement of zero-tolerance policies has not been equitable. Reviews proposal for alternative to zero tolerance. (PKP)

Henault, Cherry

2001-01-01

124

Gravity Waves  

Atmospheric Science Data Center

article title:  Gravity Waves Ripple over Marine Stratocumulus Clouds   ... when a pebble is thrown into a still pond, such "gravity waves" sometimes appear when the relatively stable and stratified air masses ... Oct 29, 2003 Images:  Gravity Waves location:  Indian Ocean thumbnail:  ...

2013-04-19

125

Droplet burning at zero G  

NASA Technical Reports Server (NTRS)

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

Williams, F. A.

1978-01-01

126

Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li  

E-print Network

Gravity inversion using a binary formulation Richard A. Krahenbuhl* and Yaoguo Li Gravity contrast that gives rise to zero gravity response on the surface. As a result, part of the salt structure structure using gravity data can be divided into two general categories. The first are interface inversions

127

Venus gravity  

NASA Technical Reports Server (NTRS)

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

Reasenberg, Robert D.

1993-01-01

128

Gravity Fountains  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2007-01-01

129

Isometrodynamics and Gravity  

E-print Network

Isometrodynamics (ID), the gauge theory of the group of volume-preserving diffeomorphisms of an "inner" D-dimensional flat space, is tentatively interpreted as a fundamental theory of gravity. Dimensional analysis shows that the Planck length l_P - and through it \\hbar and \\Gamma - enters the gauge field action linking ID and gravity in a natural way. Noting that the ID gauge field couples solely through derivatives acting on "inner" space variables all ID fields are Taylor-expanded in "inner" space. Integrating out the "inner" space variables yields an effective field theory for the coefficient fields with l_P^2 emerging as the expansion parameter. For \\hbar goint to zero only the leading order field does not vanish. This classical field couples to the matter Noether currents and charges related to the translation invariance in "inner" space. A model coupling this leading order field to a matter point source is established and solved. Interpreting the matter Noether charge in terms of gravitational mass Newton's inverse square law is finally derived for a static gauge field source and a slowly moving test particle. Gravity emerges as potentially related to field variations over "inner" space and might microscopically be described by the ID gauge field or equivalently by an infinite string of coefficient fields only the leading term of which is related to the macroscopical effects of gravity.

Christian Wiesendanger

2009-07-25

130

Regge Gravity from Spinfoams  

NASA Astrophysics Data System (ADS)

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

Magliaro, Elena; Perini, Claudio

2013-02-01

131

Tolerating Zero Tolerance?  

ERIC Educational Resources Information Center

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…

Moore, Brian N.

2010-01-01

132

Zero Energy Use School.  

ERIC Educational Resources Information Center

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

Nelson, Brian, Ed.; And Others

133

The Zero Program  

ERIC Educational Resources Information Center

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…

Roland, Erling; Midthassel, Unni Vere

2012-01-01

134

Zero-mode waveguides  

DOEpatents

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.

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

2007-02-20

135

Gravity investigations  

SciTech Connect

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.

Healey, D.L. [Geological Survey, Denver, CO (USA)

1983-12-31

136

Zeroing in on Supersymmetric Radiation Amplitude Zeros  

SciTech Connect

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.

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

2012-02-15

137

Linearisation instability of gravity waves?  

E-print Network

Gravity waves in irrotational dust spacetimes are characterised by nonzero magnetic Weyl tensor $H_{ab}$. In the linearised theory, the divergence of $H_{ab}$ is set to zero. Recently Lesame et al. [Phys. Rev. D {\\bf 53}, 738 (1996)] presented an argument to show that, in the exact nonlinear theory, $div H=0$ forces $H_{ab}=0$, thus implying a linearisation instability for gravity waves interacting with matter. However a sign error in the equations invalidates their conclusion. Bianchi type V spacetimes are shown to include examples with $div H=0\

Roy Maartens

1996-09-30

138

Einstein Gravity from Conformal Gravity  

E-print Network

We show that that four dimensional conformal gravity plus a simple Neumann boundary condition can be used to get the semiclassical (or tree level) wavefunction of the universe of four dimensional asymptotically de-Sitter or Euclidean anti-de Sitter spacetimes. This simple Neumann boundary condition selects the Einstein solution out of the more numerous solutions of conformal gravity. It thus removes the ghosts of conformal gravity from this computation. In the case of a five dimensional pure gravity theory with a positive cosmological constant we show that the late time superhorizon tree level probability measure, $|\\Psi [ g ]|^2$, for its four dimensional spatial slices is given by the action of Euclidean four dimensional conformal gravity.

Juan Maldacena

2011-06-09

139

Starting From Ground Zero  

ERIC Educational Resources Information Center

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)

Fischer, William B.; Stauffer, Robert A.

1978-01-01

140

Zero-G Condensing Heat Exchanger with Integral Disinfection  

NASA Technical Reports Server (NTRS)

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

Burke, Kenneth A. (Inventor)

2012-01-01

141

zeroBio  

NSDL National Science Digital Library

Elliott Kimmel may have created zeroBio for the students of London, Ontario's Central Secondary School, but high school biology students anywhere would benefit tremendously from a visit to this extensive collection of biology learning resources. In addition to functioning as an online biology textbook, zeroBio offers dissection photos for a number of specimens, multimedia presentations, self-quizzing flashcards for organic chemistry, downloadable worksheets, interactive quizzes, games, puzzles, and more.

Kimmel, Elliott

142

The Dark Gravity model predictions for Gravity Probe B  

E-print Network

The previous version of this article gave erroneous predictions. The correct uptodate predictions can be found in the section devoted to gravitomagnetism in the living review of the Dark Gravity theory: gr-qc/0610079 The most natural prediction is zero frame dragging and the same geodetic effect as predicted by GR. However, a straightforward extension of the theory could lead to the same frame-dragging as in GR.

Frederic Henry-Couannier

2007-10-23

143

Improved Airborne Gravity Results Using New Relative Gravity Sensor Technology  

NASA Astrophysics Data System (ADS)

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

Brady, N.

2013-12-01

144

Gravity Calculator  

NSDL National Science Digital Library

The gravity calculator calculates the gravitational force between two masses. Also included is a visualization of the typical measurement of gravitational force (weight) in different environments (stationary and free fall).

Brendan Cannell, Ronnie Johnson, The Shodor Education Foundation, Inc.

145

Gravity brake  

DOEpatents

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.

Lujan, Richard E. (Santa Fe, NM)

2001-01-01

146

A Regularization of Quantum Gravity  

E-print Network

We re-examine results of the Liouville theory and provide arguments that a {\\it negative} bare cosmological constant is essential to define two-dimensional quantum gravity. From this we are naturally led to a regularization of quantum gravity within the Regge approach such that it is described by small fluctuations around equilateral triangles, whose average link length approaches zero in the continuum limit. We investigate a model based on this idea numerically and present evidence for the desired long-range correlations. Interestingly, the approach might generalize to higher dimensions. The picture of an inflated balloon, which is often used to demonstrate the properties of an expanding classical universe, seems to be valuable to understand quantum gravity as well.

Wolfgang Beirl; Bernd A. Berg

2001-03-09

147

Role of gravity in preparative electrophoresis  

NASA Technical Reports Server (NTRS)

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.

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

148

The Zero program.  

PubMed

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 student bullying by increasing the school's ability to uncover and stop bullying, and eventually to prevent it. The Zero program was launched in 2003, but the work that led to it goes back to the first national steps against bullying in 1983. The program extends over sixteen months as teachers develop their awareness of bullying and their competence in addressing it. Students and parents are involved in the program as well. The role of the school leadership is very important. More than 360 Norwegian schools have carried out the program. PMID:22504789

Roland, Erling; Midthassel, Unni Vere

2012-01-01

149

Three-dimensional loop quantum gravity: coupling to point particles  

Microsoft Academic Search

We consider the coupling between three-dimensional gravity with zero cosmological constant and massive spinning point particles. First, we study the classical canonical analysis of the coupled system. Then, we go to the Hamiltonian quantization generalizing loop quantum gravity techniques. We give a complete description of the kinematical Hilbert space of the coupled system. Finally, we define the physical Hilbert space

Karim Noui; Alejandro Perez

2005-01-01

150

Zero Tolerance versus Privacy.  

ERIC Educational Resources Information Center

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

Dowling-Sendor, Benjamin

2000-01-01

151

On Topological 1D Gravity. I  

E-print Network

In topological 1D gravity, the genus zero one-point function combined with the gradient of the action function leads to a spectral curve and its special deformation. After quantization, the partition function is identified as an element in the bosonic Fock space uniquely specified by the Virasoro constraints.

Jian Zhou

2014-12-04

152

Simulating Gravity  

ERIC Educational Resources Information Center

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…

Pipinos, Savas

2010-01-01

153

Massive gravity  

NASA Astrophysics Data System (ADS)

The concept of mass has been central in many areas of physics. Gravitation is not an exception, and it has been one of the long-standing questions whether the graviton, a spin-2 particle that mediates gravity, can have a non-vanishing mass or not. This question is relevant from not only theoretical but also phenomenological viewpoints, since a nonzero graviton mass may lead to late-time acceleration of the universe and thus may be considered as an alternative to dark energy. In 2010, de Rham, Gabadadze and Tolley proposed the first example of a fully nonlinear massive gravity theory and showed that the so called Boulware-Deser ghost, which had been one of the major obstacles against a stable nonlinear theory of massive gravity since 1972, can be removed by construction. Since then, nonlinear massive gravity has been attracting significant interest among physicists and cosmologists. The nonlinear theory of massive gravity provides a theoretical framework in which properties of the remaining five physical degrees of freedom of massive gravity can be studied. As always with any low-energy effective theories, one of the first tasks would be to identify good and bad backgrounds. Depending on the choice of backgrounds, some of the five degrees of freedom may become strongly coupled, may exhibit instantaneous propagation, or may lead to ghost/gradient instabilities. A related subject is to seek interesting solutions such as those relevant for astrophysical objects and those describing self-accelerating cosmology. Those solutions will allow us to study phenomenological and cosmological implications of the theory. Yet another important task would be to seek a possible (partial) UV completion that can be applied beyond the regime of validity of the low-energy effective theory that we currently know of. We invited articles to cover those important subjects in massive gravity. Given the recent rapid developments in the field, however, it must be noted that this focus issue should be best considered as a snapshot. We still hope that the collection of articles provides readers with guidance to the research at the frontier and ideally expedites further progress in the field. Shinji MukohyamaGuest Editor

Mukohyama, Shinji

2013-09-01

154

Venipuncture and intravenous infusion access during zero-gravity flight  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

155

Dental equipment test during zero-gravity flight  

NASA Technical Reports Server (NTRS)

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

Young, John; Gosbee, John; Billica, Roger

1991-01-01

156

Neural-Thyroid Interaction on Skeletal Isomyosin in Zero Gravity  

NASA Technical Reports Server (NTRS)

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

Baldwin, Kenneth M.

2000-01-01

157

Fluid mass sensor for a zero gravity environment  

NASA Technical Reports Server (NTRS)

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

Fogal, G. L. (inventor)

1976-01-01

158

Zero-gravity atmospheric Cloud Physics Experiment Laboratory; Programmatics report  

NASA Technical Reports Server (NTRS)

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.

1974-01-01

159

A Zero-Gravity Cup for Drinking Beverages in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

160

Type Zero Copper Proteins  

PubMed Central

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 Ĺ). 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

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

2009-01-01

161

Gravity and positional homeostasis of the cell  

NASA Astrophysics Data System (ADS)

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 ?m 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.

Nace, George W.

162

Is nonrelativistic gravity possible?  

SciTech Connect

We study nonrelativistic gravity using the Hamiltonian formalism. For the dynamics of general relativity (relativistic gravity) the formalism is well known and called the Arnowitt-Deser-Misner (ADM) formalism. We show that if the lapse function is constrained correctly, then nonrelativistic gravity is described by a consistent Hamiltonian system. Surprisingly, nonrelativistic gravity can have solutions identical to relativistic gravity ones. In particular, (anti-)de Sitter black holes of Einstein gravity and IR limit of Horava gravity are locally identical.

Kocharyan, A. A. [School of Mathematical Sciences, Monash University, Clayton 3800 (Australia)

2009-07-15

163

You and Gravity  

NSDL National Science Digital Library

In this assignment you will learn all about gravity, and how it affects you. Today we are going to talk about Gravity. Let's see what Bill Nye the Science Guy says about gravity. Bill Nye and Gravity Bill Nye showed us what gravity is. but now we need to define it. What is gravity? Why do we need it? What would happen if there was no gravity? Go through each ...

Miss Rounds

2010-04-30

164

Quasilocalization of gravity on a brane by resonant modes.  

PubMed

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

Csáki, C; Erlich, J; Hollowood, T J

2000-06-26

165

Gravity WebQuest  

NSDL National Science Digital Library

Learn more about gravity! 1 .So, what is gravity? What does it do? Why is it so important? Use your worksheet and fill write down the things it tells you about gravity. Gravity info 2. Now, let's go back to that same website and imagine what would happen if the force of gravity was turned off. ...

Mrs. Benson

2010-01-26

166

Inertial waste separation system for zero G WMS  

NASA Technical Reports Server (NTRS)

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.

1971-01-01

167

Fat Fisher zeroes  

NASA Astrophysics Data System (ADS)

We show that it is possible to determine the locus of Fisher zeroes in the thermodynamic limit for the Ising model on planar ("fat") ?4 random graphs and their dual quadrangulations by matching up the real part of the high and low temperature branches of the expression for the free energy. The form of this expression for the free energy also means that series expansion results for the zeroes may be obtained with rather less effort than might appear necessary at first sight by simply reverting the series expansion of a function g( z) which appears in the solution and taking a logarithm. Unlike regular 2D lattices where numerous unphysical critical points exist with non-standard exponents, the Ising model on planar ?4 graphs displays only the physical transition at c=exp(-2 ?)=1/4 and a mirror transition at c=-1/4 both with KPZ/DDK exponents ( ?=-1, ?=1/2, ?=2). The relation between the ?4 locus and that of the dual quadrangulations is akin to that between the (regular) triangular and honeycomb lattices since there is no self-duality.

Janke, W.; Johnston, D. A.; Stathakopoulos, M.

2001-11-01

168

Zero Sound from Holography  

E-print Network

Quantum liquids are characterized by the distinctive properties such as the low temperature behavior of heat capacity and the spectrum of low-energy quasiparticle excitations. In particular, at low temperature, Fermi liquids exhibit the zero sound, predicted by L. D. Landau in 1957 and subsequently observed in liquid He-3. In this paper, we ask a question whether such a characteristic behavior is present in theories with holographically dual description. We consider a class of gauge theories with fundamental matter fields whose holographic dual in the appropriate limit is given in terms of the Dirac-Born-Infeld action in AdS_{p+1} space. An example of such a system is the N=4 SU(N_c) supersymmetric Yang-Mills theory with N_f massless N=2 hypermultiplets at strong coupling, finite baryon number density, and low temperature. We find that these systems exhibit a zero sound mode despite having a non-Fermi liquid type behavior of the specific heat. These properties suggest that holography identifies a new type of quantum liquids.

A. Karch; D. T. Son; A. O. Starinets

2008-06-24

169

NOVA: Absolute Zero  

NSDL National Science Digital Library

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

170

Zero-dimensional magnetite  

NASA Astrophysics Data System (ADS)

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

Arredondo, Melissa Gayle

171

Zero Emission Coal  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

172

Graviresponses of osteocytes under altered gravity  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

173

Gravity Launch  

NSDL National Science Digital Library

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

American Association for the Advancement of Science

2009-01-01

174

How Much Gravity Is Needed to Establish the Perceptual Upright?  

PubMed Central

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

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

2014-01-01

175

How much gravity is needed to establish the perceptual upright?  

PubMed

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

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

2014-01-01

176

Airglow response to vertically standing gravity waves  

NASA Technical Reports Server (NTRS)

There is currently much interest in fluctuations of airglow emissions caused by atmospheric gravity waves. The fluctuations of brightness tend to be found in phase (or occasionally in antiphase) with the fluctuations of measured temperature, whereas current theory tends to anticipate substantial phase differences. We suggest here that the discrepancy results from failure of the common theoretical assumption that the relevant gravity waves are dominated by a single upgoing component: that, instead, there is an accompanying downgoing component of comparable magnitude, produced by reflection. In the case of total reflection, simple, steady state chemistry and vertical viewing, the phase difference is necessarily zero (or 180 deg).

Hines, Colin O.; Tarasick, David W.

1994-01-01

177

Nowhere-Zero Flow Polynomials  

Microsoft Academic Search

In this article, we introduce certain flow polynomials associated with digraphs and use them to study nowhere-zero flows from a commutative algebraic perspective.Using Hilbert's Nullstellensatz, we establish a relation between nowhere-zero flows and dual flows.For planar graphs this gives a relation between nowhere-zero flows and flows of their planar duals.It also yields an appealing proof that every bridgeless triangulated graph

Shmuel Onn

2003-01-01

178

Asymptotic Zero Distribution 1 Asymptotic Zero Distribution of  

E-print Network

Tni mi(z) = niX k=;mi akzk that lie in the angle 1 argz of Tni mi(z) of modulus > 1 and there are at most o(mi) zeros of modulus but a negligible proportion of the zeros of the Tni mi(z)'s accumulate on the circles jzj= r and jzj= R

Pritsker, Igor

179

Zero emission coal  

SciTech Connect

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

Ziock, H.; Lackner, K.

2000-08-01

180

Zero-installation, zero-maintenance, zero-cost portal for database-related educational use  

Microsoft Academic Search

In keeping with the special anniversary theme of ITI 2008 conference ldquoComputer at the Universityrdquo, this paper describes the Teradata University Network (TUN). TUN is a web-based educational resource that uses a zero cost - zero installation - zero maintenance model to provide tools, datasets, and other materials for teaching both traditional and emerging database-related topics at universities world-wide. In

Nenad Jukic; Paul Gray; Boris Jukic

2008-01-01

181

Gravity data of Nevada  

USGS Publications Warehouse

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

Ponce, David A.

1997-01-01

182

First order gravity on the light front  

NASA Astrophysics Data System (ADS)

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.

Alexandrov, Sergei; Speziale, Simone

2015-03-01

183

Precision zero-home locator  

DOEpatents

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

Stone, William J. (Kansas City, MO)

1986-01-01

184

Precision zero-home locator  

DOEpatents

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

Stone, W.J.

1983-10-31

185

Zero knowledge proofs of identity  

Microsoft Academic Search

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

U. Fiege; Amos Fiat; Adi Shamir

1987-01-01

186

Zero-tracking adaptive filters  

Microsoft Academic Search

A new type of adaptive filter is proposed which can directly estimate and track its own zeros. The adaptation algorithm adapts the zeros of the filter and hence, indirectly, the filter coefficients. To first order in the adaptation parameter, the new algorithm is equivalent to the usual LMS algorithm, and thus it shares the same convergence properties with the latter.

SOPHOCLES J. ORFANIDIS; LOY MAUGH VAIL

1986-01-01

187

Zero Waste, Renewable Energy & Environmental  

E-print Network

Zero Waste, Renewable Energy & Environmental Stewardship - Connecting loose ends: Thermal Recycling Technology · Bottom Ash · Finding Solutions #12;Arguments given against WTE: Excerpts of an article 07 business, namely "zero waste" and "clean production." #12;Arguments given against WTE: People who think we

Columbia University

188

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

SciTech Connect

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.

Maziashvili, Michael, E-mail: maziashvili@gmail.com [Particle Physics and Cosmology Group, Ilia State University, 3/5 Cholokashvili Ave., Tbilisi 0162, Georgia (United States)

2013-03-01

189

Critical regimes of internal gravity wave generation  

E-print Network

The problem of constructing an asymptotic representation of the solution of the internal gravity wave field exited by a source moving at a velocity close to the maximum group velocity of the individual wave mode is considered. For the critical regimes of individual mode generation the asymptotic representation of the solution obtained is expressed in terms of a zero-order Macdonald function. The results of numerical calculations based on the exact and asymptotic formulas are given.

Vitaly V. Bulatov; Yuriy V. Vladimirov; Vasily A. Vakorin

2005-11-27

190

On the structure of the topological phase of two-dimensional gravity  

Microsoft Academic Search

The topological phase of two-dimensional gravity is re-examined. The correlation functions of the naturally occuring operators in the minimal topological model are computed, using topological methods, in genus zero and genus one. The genus-zero results agree with recent results obtained in exact solutions of ``matrix models'', suggesting that the two approaches to two-dimensional gravity are equivalent. The coupling of two-dimensional

Edward Witten

1990-01-01

191

Plane Symmetric Solutions in f(R) Gravity  

E-print Network

The modified theories of gravity, especially the f(R) theory, have attracted much attention in recent years. In this context, we explore static plane symmetric vacuum solutions using the metric approach of this theory. The field equations are solved using the assumption of constant scalar curvature which may be zero or non-zero. We have found a total of three plane symmetric solutions. The correspondence of these solutions with the well-known solutions in General Relativity is given.

M. Sharif; M. Farasat Shamir

2009-12-08

192

Gravity-induced stresses in finite slopes  

USGS Publications Warehouse

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.

Savage, W.Z.

1994-01-01

193

Analytical Study of Gravity Effects on Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

194

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

195

Sensitivity of Simulated Climate to Conservation of Momentum in Gravity Wave Drag Parameterization  

Microsoft Academic Search

The Canadian Middle Atmosphere Model is used to examine the sensitivity of simulated climate to conservation of momentum in gravity wave drag parameterization. Momentum conservation requires that the parameterized gravity wave momentum flux at the top of the model be zero and corresponds to the physical boundary condition of no momentum flux at the top of the atmosphere. Allowing momentum

Tiffany A. Shaw; Michael Sigmond; Theodore G. Shepherd; John F. Scinocca

2009-01-01

196

Chiral Gravity, Log Gravity and Extremal CFT  

E-print Network

We show that the linearization of all exact solutions of classical chiral gravity around the AdS3 vacuum have positive energy. Non-chiral 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 CFT. Moreover we show that log gravity contains chiral gravity within it as a decoupled charge superselection sector. We normally 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.

Alexander Maloney; Wei Song; Andrew Strominger

2009-03-26

197

Chiral gravity, log gravity, and extremal CFT  

SciTech Connect

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.

Maloney, Alexander [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Song Wei [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190 (China); Center for the Fundamental Laws of Nature Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States); Strominger, Andrew [Center for the Fundamental Laws of Nature Jefferson Physical Laboratory, Harvard University, Cambridge, Massachusetts 02138 (United States)

2010-03-15

198

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

199

The behavior of surface tension on steady-state rotating fluids in the low gravity environments  

NASA Technical Reports Server (NTRS)

The effect of surface tension on steady-state rotating fluids in a low gravity environment is studied. All the values of the physical parameters used in these calculations, except in the low gravity environments, are based on the measurements carried out by Leslie (1985) in the low gravity environment of a free-falling aircraft. The profile of the interface of two fluids is derived from Laplace's equation relating the pressure drop across an interface to the radii of curvature which has been applied to a low gravity rotating bubble that contacts the container boundary. The interface shape depends on the ratio of gravity to surface tension forces, the ratio of centrifugal to surface tension forces, the contact radius of the interface to the boundary, and the contact angle. The shape of the bubble is symmetric about its equator in a zero-gravity environment. This symmetry disappears and gradually shifts to parabolic profiles as the gravity environment becomes non-zero. The location of the maximum radius of the bubble moves upward from the center of the depth toward the top boundary of the cylinder as gravity increases. The contact radius of interface to the boundary r0 at the top side of cylinder increases and r0 at the bottom side of the cylinder decreases as the gravity environment increases from zero to 1 g.

Hung, R. J.; Leslie, Fred W.

1987-01-01

200

Talking About Gravity  

NSDL National Science Digital Library

The purpose of this assessment probe is to elicit students' ideas about gravity. The probe is designed to determine whether students recognize that gravity is a universal force that exists everywhere in space, regardless of whether air is present.

Francis Eberle

2005-01-01

201

Towards noncommutative gravity  

E-print Network

In this short article accessible for non-experts I discuss possible ways of constructing a non-commutative gravity paying special attention to possibilities of realizing the full diffeomorphism symmetry and to relations with 2D gravities.

D. V. Vassilevich

2009-02-17

202

Urine specific gravity test  

MedlinePLUS

Urine specific gravity is a laboratory test that measures 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 ...

203

NUT-charged black holes in Gauss-Bonnet gravity  

SciTech Connect

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.

Dehghani, M.H. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Department of Physics, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, 35 Caroline Street North, Waterloo, Ontario (Canada); Mann, R.B. [Department of Physics, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, 35 Caroline Street North, Waterloo, Ontario (Canada)

2005-12-15

204

Holographic Superconductor/Insulator Transition at Zero Temperature  

E-print Network

We analyze the five-dimensional AdS gravity coupled to a gauge field and a charged scalar field. Under a Scherk-Schwarz compactification, we show that the system undergoes a superconductor/insulator transition at zero temperature in 2+1 dimensions as we change the chemical potential. By taking into account a confinement/deconfinement transition, the phase diagram turns out to have a rich structure. We will observe that it has a similarity with the RVB (resonating valence bond) approach to high-Tc superconductors via an emergent gauge symmetry.

Tatsuma Nishioka; Shinsei Ryu; Tadashi Takayanagi

2010-01-20

205

Grasping objects autonomously in simulated KC-135 zero-g  

NASA Technical Reports Server (NTRS)

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

Norsworthy, Robert S.

1994-01-01

206

Motion in Quantum Gravity  

E-print Network

We tackle the question of motion in Quantum Gravity: what does motion mean at the Planck scale? Although we are still far from a complete answer we consider here a toy model in which the problem can be formulated and resolved precisely. The setting of the toy model is three dimensional Euclidean gravity. Before studying the model in detail, we argue that Loop Quantum Gravity may provide a very useful approach when discussing the question of motion in Quantum Gravity.

Karim Noui

2010-03-31

207

Physics of Artificial Gravity  

NASA Technical Reports Server (NTRS)

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.

Bukley, Angie; Paloski, William; Clement, Gilles

2006-01-01

208

Quantum Physics Einstein's Gravity  

E-print Network

Quantum Physics confronts Einstein's Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 13 October 2001 #12; Quantum Physics confronts Einstein's Gravity and with Einstein's theory of gravity (the general relativity) is still the single biggest theoretical problem

Visser, Matt

209

Stephen Hawking Quantum Gravity  

E-print Network

Stephen Hawking and Quantum Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 4 Nov 2000 #12; Stephen Hawking and Quantum Gravity Abstract: Through research, Stephen Hawking has captured a place in the popular imagina- tion. Quantum gravity in its various

Visser, Matt

210

Spherically symmetric static vacuum solutions in Mimetic gravity  

E-print Network

In this paper we analyze spherically symmetric static vacuum solutions with various topologies in mimetic gravity. When the Einstein's tensor is different from zero, a new class of solutions different from the Schwarzschild one emerges from the theory. We analyze the feature of the new solutions and we study the planar motion for the spherical case.

Myrzakulov, Ratbay

2015-01-01

211

Instanton representation of Plebanski gravity. Euclidean signature minisuperspace solution  

E-print Network

Using the action for the instanton representation of Plebanski gravity (IRPG), we construct minisuperspace solutions restricted to diagonal variables. We have treated the Euclidean signature case with zero cosmological constant, depicting a gravitational analogy to free particle motion. This paper provides a testing ground for the IRPG for a simple case, which will be extended to the full theory in future work.

Eyo Eyo Ita III

2012-06-11

212

Analysis Of Transfer Of Cryogens In Low Gravity  

NASA Technical Reports Server (NTRS)

Report discusses calculations of thermodynamic aspects of refilling tanks with cryogenic liquids in low or zero gravity. Calculations required to design prototype system resupplying cryogenic propellant liquids to re-usable spacecraft not returning to Earth. Equations and computer programs developed for thermodynamic analysis used to extrapolate important design information from orbiting small-scale versions of system.

Defelice, David M.; Aydelott, John C.

1993-01-01

213

Zero modes on zero-angle grain boundaries in graphene  

NASA Astrophysics Data System (ADS)

Electronic states confined to zero-angle grain boundaries in single-layer graphene are analyzed using topological band theoretic arguments. We identify a hidden chiral symmetry which supports symmetry-protected zero modes in projected bulk gaps. These branches occupy a finite fraction of the interface-projected Brillouin zone and terminate at bulk gap closures, manifesting topological transitions in the occupied manifolds of the bulk systems that are joined at an interface. These features are studied by numerical calculations on a tight-binding lattice and by analysis of the geometric phases of the bulk ground states.

Phillips, Madeleine; Mele, E. J.

2015-03-01

214

Net zero building energy conservation  

NASA Astrophysics Data System (ADS)

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

Kadam, Rohit

215

Science Gravity Unit  

NSDL National Science Digital Library

3rd grade new unit on gravity National Standard: Standard 4, objective 1. Objective: Students will understand that objects near the earth are pulled towards the earth by gravity. Demonstrate that gravity is a force. Does anyone know what is going to happen if I let go of this ball? Why do you think that will happen? Today we are going to answer these questions by talking about gravity! I want you to go to this website and take notes while you read about gravity. ology click on "meet ...

Ms. Pace

2009-11-09

216

Zero-G Workstation Design  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

217

The D-Zero Experiment  

NSDL National Science Digital Library

The D-Zero Experiment is a worldwide collaboration of physics researchers centrally located at the Fermilab National Accelerator Laboratory's Tevratron Collider. The experiment focuses on the fundamental nature of matter, with particular attention paid to "precise studies of interactions of protons and antiprotons at the highest available energies." Researchers will be especially interested in the results section within which they can access summaries of new results, D-Zero results presented at 1999 summer conferences, Run II Fermilab Supersymmetry/ Higgs Workshop documents and summaries, and documents of work conducted by various Physics Groups working in specialized areas. The site also offers a technical section featuring information on experiment upgrades and computing, as well as contact information for experiment collaborators. Note, some areas are restricted to D-Zero collaboration members.

218

Homes fit for zero: Dwellings in a zero-carbon  

E-print Network

.9kWp 14% Solar pv 1kW 15% µCHP 3kW 30% µCHP Thermal demand reduction measures Electricity demand-academic reports #12;Core research themes Building performance simulation/modelling Low and zero-carbon buildings involvement (PhD) Fuel poverty and refurbishment campaigns Whole life analysis of building components (RAEng

Painter, Kevin

219

THE ZERO MODES AND ZERO RESONANCES OF MASSLESS DIRAC OPERATORS  

E-print Network

of stability of Coulomb systems with magnetic fields. (For the precise definition of zero modes, see Definition their main concern is Lieb­ Thirring inequality for the Pauli operator with a strong magnetic fields and, #12 # = (# 1 , # 2 , # 3 ) is the triple of 4 � 4 Dirac matrices, D = 1 i # x , and Q(x) = # q jk (x) # is a 4

220

Quantization of emergent gravity  

NASA Astrophysics Data System (ADS)

Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as space-time admits a symplectic structure, in other words, a microscopic space-time becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC space-time, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing space-time itself, leading to a dynamical NC space-time. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background-independent formulation where space-time and matter fields are equally emergent from a universal vacuum of quantum gravity.

Yang, Hyun Seok

2015-02-01

221

(abstract) Venus Gravity Field  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

222

Quantization of Emergent Gravity  

E-print Network

Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC spacetime, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing spacetime itself, leading to a dynamical NC spacetime. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.

Hyun Seok Yang

2014-12-24

223

ZERI: Zero Emissions Research Initiative  

NSDL National Science Digital Library

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

224

Asymptotic Safety in quantum gravity  

NASA Astrophysics Data System (ADS)

Asymptotic Safety (sometimes also referred to as nonperturbative renormalizability) is a concept in quantum field theory which aims at finding a consistent and predictive quantum theory of the gravitational field. Its key ingredient is a nontrivial fixed point of the theory's renormalization group flow which controls the behavior of the coupling constants in the ultraviolet (UV) regime and renders physical quantities safe from divergences. Although originally proposed by Steven Weinberg to find a theory of quantum gravity the idea of a nontrivial fixed point providing a possible UV completion can be applied also to other field theories, in particular to perturbatively nonrenormalizable ones. The essence of Asymptotic Safety is the observation that nontrivial renormalization group fixed points can be used to generalize the procedure of perturbative renormalization. In an asymptotically safe theory the couplings do not need to be small or tend to zero in the high energy limit but rather tend to finite values: they approach a nontrivial UV fixed point. The running of the coupling constants, i.e. their scale dependence described by the renormalization group (RG), is thus special in its UV limit in the sense that all their dimensionless combinations remain finite. This suffices to avoid unphysical divergences, e.g. in scattering amplitudes. The requirement of a UV fixed point restricts the form of the bare action and the values of the bare coupling constants, which become predictions of the Asymptotic Safety program rather than inputs. As for gravity, the standard procedure of perturbative renormalization fails since Newton's constant, the relevant expansion parameter, has negative mass dimension rendering general relativity perturbatively nonrenormalizable. This has driven the search for nonperturbative frameworks describing quantum gravity, including Asymptotic Safety which -- in contrast to other approaches -- is characterized by its use of quantum field theory methods, without depending on perturbative techniques, however.

Nink, Andreas; Reuter, Martin; Saueressig, Frank

2013-06-01

225

Modelling bivariate count series with excess zeros  

Microsoft Academic Search

Bivariate time series of counts with excess zeros relative to the Poisson process are common in many bioscience applications. Failure to account for the extra zeros in the analysis may result in biased parameter estimates and misleading inferences. A class of bivariate zero-inflated Poisson autoregression models is presented to accommodate the zero-inflation and the inherent serial dependency between successive observations.

Andy H. Lee; Kui Wang; Kelvin K. W. Yau; Philip J. W. Carrivick; Mark R. Stevenson

2005-01-01

226

Resolving Zero Anaphora in Japanese  

Microsoft Academic Search

The paper presents a computational theory for resolving Japanese zero anaphora, based on the notion of ., 1990] in that the resolution works by matching one empathy hierarchy against another, which makes it possible to deal with discourses with no explicit topic and those with cataphora [Halliday and Hassan, 1990].The theory is formalized through the definite clause grammar (DCG) formalism

Tadashi Nomoto; Yoshihiko Nitta

1993-01-01

227

Stepping Back from Zero Tolerance  

ERIC Educational Resources Information Center

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

Browne-Dianis, Judith

2011-01-01

228

Zero-Sum Flows in Regular Graphs  

Microsoft Academic Search

For an undirected graph G, a zero-sum flow is an assignment of non-zero real numbers to the edges, such that the sum of the values of all edges incident with each vertex\\u000a is zero. It has been conjectured that if a graph G has a zero-sum flow, then it has a zero-sum 6-flow. We prove this conjecture and Bouchet’s Conjecture

S. Akbari; A. Daemi; O. Hatami; A. Javanmard; A. Mehrabian

2010-01-01

229

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

PubMed

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

Godin, Oleg A

2014-03-01

230

A possibility to solve the problems with quantizing gravity  

E-print Network

It is generally believed that quantum gravity is necessary to resolve the known tensions between general relativity and the quantum field theories of the standard model. Since perturbatively quantized gravity is non-renormalizable, the problem how to unify all interactions in a common framework has been open since the 1930s. Here, I propose a possibility to circumvent the known problems with quantizing gravity, as well as the known problems with leaving it unquantized: By changing the prescription for second quantization, a perturbative quantization of gravity is sufficient as an effective theory because matter becomes classical before the perturbative expansion breaks down. This is achieved by considering the vanishing commutator between a field and its conjugated momentum as a symmetry that is broken at low temperatures, and by this generates the quantum phase that we currently live in, while at high temperatures Planck's constant goes to zero.

S. Hossenfelder

2013-09-04

231

Generalized Scale Invariant Gravity  

E-print Network

We generalize the scale invariant gravity by allowing a negative kinetic energy term for the classical scalar field. This gives birth to a new scalar-tensor theory of gravity, in which the scalar field is in fact an auxiliary field. For a pure gravity theory without matter, the scale symmetric phase represents an equivalent class of gravity theories, which the Einstein gravity plus a cosmological constant belongs to under a special gauge choice. The one-loop quantum correction of the theory is calculated by using the Vilkovisky-DeWitt's method. We find that the scale symmetry is broken dynamically, and that the Einstein gravity is the ground state of the broken phase. We also briefly discuss the consequent cosmological implications. It is shown that the time-delay experiment restricts the present universe to be very close to the ground state.

Shih-Yuin Lin; Kin-Wang Ng

1997-08-20

232

Quantum massive conformal gravity  

E-print Network

We first find the linear approximation of the second plus fourth order derivatives massive conformal gravity action. Then we reduce the linearized action to three separated second order derivatives terms, which allows us to quantize the massive conformal gravity fields by using the usual first order canonical quantization method. Finally, using the correct conformal normalization of the massive conformal gravity states, we show that the theory is unitary.

Faria, F F

2015-01-01

233

Loop Quantum Gravity  

Microsoft Academic Search

The problem of finding the quantum theory of the gravitational field, and\\u000athus understanding what is quantum spacetime, is still open. One of the most\\u000aactive of the current approaches is loop quantum gravity. Loop quantum gravity\\u000ais a mathematically well-defined, non-perturbative and background independent\\u000aquantization of general relativity, with its conventional matter couplings. The\\u000aresearch in loop quantum gravity

Carlo Rovelli

1997-01-01

234

Dark gravity and cosmology  

E-print Network

The previous version of this article was a first attempt to confront the Dark Gravity theory to cosmological data. However, more recent developments lead to the conclusion that the cosmological principle is probably not valid in Dark Gravity so that this kind of analysis is at best very premature. A more recent and living review of the Dark Gravity theory can be found in gr-qc/0610079

F. Henry-Couannier; A. Tilquin; C. Tao; A. Ealet

2007-10-24

235

Riding the Gravity Wave  

NSDL National Science Digital Library

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

2014-09-18

236

Gravity and Muscles  

NSDL National Science Digital Library

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

2012-06-26

237

Modified entropic gravity revisited  

NASA Astrophysics Data System (ADS)

Inspired by Verlinde's idea, some modified versions of entropic gravity have been suggested. Extending them in a unified formalism, herein we derive the generalized gravitational equations accordingly. From gravitational equations, the energy-momentum conservation law and cosmological equations are investigated. The covariant conservation law of energy-momentum tensor severely constrains viable modifications of entropic gravity. A discrepancy arises when two independent methods are applied to the homogeneous isotropic universe, posing a serious challenge to modified models of entropic gravity.

Wang, Tower

2014-09-01

238

Unified theory of nonlinear electrodynamics and gravity  

SciTech Connect

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

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

2011-01-15

239

Effects of gravity and pressure on laminar coflow methaneair diffusion flames at pressures from 1 to 60 atmospheres  

E-print Network

Effects of gravity and pressure on laminar coflow methane­air diffusion flames at pressures from 1 to 60 atmospheres Marc R.J. Charest , Clinton P.T. Groth, �mer L. Gülder University of Toronto January 2011 Available online 12 February 2011 Keywords: High pressure combustion Zero-gravity combustion

Groth, Clinton P. T.

240

Consideration of the relationship between Kepler and cyclotron dynamics leading to prediction of a nonmagnetohydrodynamic gravity-driven  

E-print Network

of a nonmagnetohydrodynamic gravity-driven Hamiltonian dynamo P. M. Bellan Applied Physics, Caltech, Pasadena, California of a specific flux surface. Suitably charged dust grains can have zero canonical angular momentum reduces the amount of centrifugal force required to balance the inward force of gravity and so achieve

Bellan, Paul M.

241

Extended gravity from noncommutativity  

E-print Network

We review the first order theory of gravity (vierbein formulation) on noncommutative spacetime studied in [1, 2]. The first order formalism allows to couple the theory to fermions. This NC action is then reinterpreted (using the Seiberg-Witten map) as a gravity theory on commutative spacetime that contains terms with higher derivatives and higher powers of the curvature and depend on the noncommutativity parameter \\theta. When the noncommutativity is switched off we recover the usual gravity action coupled to fermions. The first nontrival corrections to the usual gravity action coupled to fermions are presented in a manifest Lorentz invariant form.

Paolo Aschieri

2012-07-20

242

Hybrid Zero-capacity Channels  

E-print Network

There are only two known kinds of zero-capacity channels. The first kind produces entangled states that have positive partial transpose, and the second one - states that are cloneable. We consider the family of 'hybrid' quantum channels, which lies in the intersection of the above classes of channels and investigate its properties. It gives rise to the first explicit examples of the channels, which create bound entangled states that have the property of being cloneable to the arbitrary finite number of parties. Hybrid channels provide the first example of highly cloneable binding entanglement channels, for which known superactivation protocols must fail - superactivation is the effect where two channels each with zero quantum capacity having positive capacity when used together. We give two methods to construct a hybrid channel from any binding entanglement channel. We also find the low-dimensional counterparts of hybrid states - bipartite qubit states which are extendible and possess two-way key.

Sergii Strelchuk; Jonathan Oppenheim

2012-07-04

243

Warped brane worlds in critical gravity  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

244

Gribov ambiguity in asymptotically AdS three-dimensional gravity  

SciTech Connect

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.

Anabalon, Andres [Departamento de Ciencias, Facultad de Artes Liberales, Facultad de Ingenieria y Ciencias, Universidad Adolfo Ibanez, Vina Del Mar (Chile); Canfora, Fabrizio [Centro de Estudios Cientificos (CECS), Casilla 1469, Valdivia (Chile); Giacomini, Alex; Oliva, Julio [Instituto de Fisica, Facultad de Ciencias, Universidad Austral de Chile, Valdivia (Chile)

2011-03-15

245

The ethics of zero tolerance  

Microsoft Academic Search

Zero tolerance” has become the international “buzz word” of the secondary building administrator. As school violence has increased so have the legislative and regulatory policy-making mandates calling for increased disciplinary consequences for inappropriate student behavior. Ethical problem-solving and decision-making have taken a back seat to reactive discipline by school officials. Media publicity has forced proactive principals to become reactive impulsive

Kevin Gorman; Patrick Pauken

2003-01-01

246

Disposable remote zero headspace extractor  

DOEpatents

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

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

2006-03-21

247

Particle cloud combustion in reduced gravity  

NASA Technical Reports Server (NTRS)

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

Berlad, A. L.

1988-01-01

248

Black Hole Remnant from Gravity's Rainbow  

E-print Network

In this work, we investigate black hole (BH) physics in the context of gravity rainbow. We investigate this through rainbow functions that have been proposed by Amelino-Camelia, et el. in [arXiv:0806.0339, hep-th/9605211]. This modification will give corrections to both the temperature and the entropy of BH and hence it changes the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. It prevents BH from total evaporation, predicting the existence of BH remnant which may resolve the catastrophic behavior of Hawking radiation as the BH mass approaches zero.

Ahmed Farag Ali

2014-05-12

249

The Zero Exemplar Distance Problem  

NASA Astrophysics Data System (ADS)

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

Jiang, Minghui

250

Zero-Copy Objects System  

NASA Technical Reports Server (NTRS)

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

Burleigh, Scott C.

2011-01-01

251

Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

252

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

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

Lucchetti, F.

1989-01-01

253

Demonstrating Reduced Gravity.  

ERIC Educational Resources Information Center

Describes the construction of the Reduced-Gravity Demonstrator, which can be used to illustrate the effects of gravity on a variety of phenomena, including the way fluids flow, flames burn, and mechanical systems behave. Presents experiments, appropriate for classroom use, to demonstrate how the behavior of common physical systems change when…

Pearlman, Howard; And Others

1996-01-01

254

Specific Gravity Urobilinogen  

E-print Network

Date Lot # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen Bilirubin Blood / Hemoglobin HCG: Method Lot # Acetest® (Ketone): Lot # Clinitest® (Glucose): Lot # Ictotest®(Bilirubin # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen Bilirubin Blood / Hemoglobin HCG

Rodriguez, Carlos

255

Counterterms in Lovelock Gravity  

E-print Network

In this paper, we introduce the counterterms that remove the non-logarithmic divergences of the action in third order Lovelock gravity. We do this by defining the cosmological constant in such a way that the asymptotic form of the metric have the same form in Lovelock and Einstein gravities. Thus, we employ the counterterms of Einstein gravity and show that the power law divergences in the action of Lovelock gravity can be removed by suitable choice of coefficients. We find that the dependence of these coefficients on the dimension in Lovelock gravity is the same as in Einstein gravity. We also introduce the finite energy-momentum tensor and employ these counterterms to calculate the finite action and mass of the black hole solutions of third order Lovelock gravity. We calculate the thermodynamic quantities and show that the entropy calculated through the use of Gibbs-Duhem relation is consistent with the obtained entropy by Wald's formula. We, also, find that in contrast to Einstein gravity in which there ex...

Mehdizadeh, M R; Zangeneh, M Kord

2015-01-01

256

Demonstrating Reduced Gravity  

NASA Technical Reports Server (NTRS)

A miniature drop tower, Reduced-Gravity Demonstrator is developed to illustrate the effects of gravity on a variety of phenomena including the way fluids flow, flames burn, and mechanical systems (such as pendulum) behave. A schematic and description of the demonstrator and payloads are given, followed by suggestions for how one can build his (her) own.

Pearlman, Howard; Stocker, Dennis; Gotti, Daniel; Urban, David; Ross, Howard; Sours, Thomas

1996-01-01

257

The Great Gravity Escape  

NSDL National Science Digital Library

Students use water balloons and a length of string to understand how the force of gravity between two objects and the velocity of a spacecraft can balance to form an orbit. They see that when the velocity becomes too great for gravity to hold the spacecraft in orbit, the object escapes the orbit and travels further away from the planet.

2014-09-18

258

Anti-gravity device  

NASA Technical Reports Server (NTRS)

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

Palsingh, S. (inventor)

1975-01-01

259

Gravity Probe B  

NSDL National Science Digital Library

This broadcast reports on Gravity Probe B, a satellite designed to test the frame dragging prediction of Einstein's theory of general relativity, where a spinning object such as the Earth will push spacetime in front of it. Gravity Probe B uses gyroscopes which will shift direction while orbiting the Earth (if general relativity is correct). The broadcast contains comments from a scientist who has worked on the Gravity Probe B mission for over 44 years. There is a brief explanation of the difference between the behavior of gravity in Newtonian physics and general relativity. The broadcast also discusses why it took so long to build the satellite (a dozen technologies had to be invented first), the cost involved, and whether the plug would be pulled on the mission; however, Gravity Probe B was finally launched on April 20, 2004. The broadcast is 30 minutes in length.

260

Bilateral, Zero-Impedance Static Semiconductor Switch  

NASA Technical Reports Server (NTRS)

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

Doughman, C. L.

1968-01-01

261

Containment of a silicone fluid free surface in reduced gravity  

NASA Technical Reports Server (NTRS)

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

Pline, A.; Jacobson, T.

1988-01-01

262

Complete Classification of 1+1 Gravity Solutions  

E-print Network

A classification of the maximally extended solutions for 1+1 gravity models (comprising e.g. generalized dilaton gravity as well as models with non-trivial torsion) is presented. No restrictions are placed on the topology of the arising solutions, and indeed it is found that for generic models solutions on non-compact surfaces of arbitrary genus with an arbitrary non-zero number of holes can be obtained. The moduli space of classical solutions (solutions of the field equations with fixed topology modulo gauge transformations) is parametrized explicitly.

T. Kloesch; T. Strobl

1997-11-25

263

Propulsion Investigation for Zero and Near-Zero Emissions Aircraft  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

264

Bayesian Analysis of Zero-Inflated Distributions  

Microsoft Academic Search

In this paper zero-inflated distributions (ZID) are studied from the Bayesian point of view using the data augmentation algorithm. This type of discrete model arises in count data with excess of zeros. The zero-inflated Poisson distribution (ZIP) and an illustrative example via MCMC algorithm are considered.

Josemar Rodrigues

2003-01-01

265

Probability around the Quantum Gravity. Part 1: Planar Pure Gravity  

E-print Network

Probability around the Quantum Gravity. Part 1: Planar Pure Gravity V.A.Malyshev \\Lambda September 17, 1998 Abstract In this paper we study stochastic dynamics which leaves quantum gravity equilibrium science and biology. At the same time the paper can serve an intro­ duction to quantum gravity

266

Applications of standard gravity and conformal gravity  

Microsoft Academic Search

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

James G. O'Brien

2010-01-01

267

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

NASA Astrophysics Data System (ADS)

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.

Garattini, Remo; Mandanici, Gianluca

2015-01-01

268

Effects of background gravity stimuli on gravity-controlled behavior  

NASA Technical Reports Server (NTRS)

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

Mccoy, D. F.

1976-01-01

269

Vacuum energy: quantum hydrodynamics vs quantum gravity  

E-print Network

We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.

G. E. Volovik

2005-09-09

270

Toroidal solutions in Horava Gravity  

E-print Network

Recently a new four-dimensional non relativistic renormalizable theory of gravity was proposed by Horava. This gravity reduces to Einstein gravity at large distances. In this paper by using the new action for gravity we present different toroidal solutions to the equations of motion. Our solutions describe the near horizon geometry with slow rotating parameter.

Ahmad Ghodsi

2011-02-24

271

Science 101: What Is Gravity?  

NSDL National Science Digital Library

We all know lots of sayings about gravity. "What goes up must come down." "You fail to understand the gravity of the situation." Gravity is the name we give to the phenomenon that any two masses, like you and the earth, that attract each other. This brief introduction to gravity will help elementary educators teach the concept with confidence.

George Nelson

2004-09-01

272

Gravity in Gauge Mediation  

E-print Network

We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for mu and Bmu generation. Gravity sector can include stabilized moduli.

Zygmunt Lalak; Stefan Pokorski; Krzysztof Turzynski

2008-08-18

273

Gravity in Gauge Mediation  

E-print Network

We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for mu and Bmu generation. Gravity sector can include stabilized moduli.

Lalak, Zygmunt; Turzynski, Krzysztof

2008-01-01

274

Zero-G experiments in two-phase fluids flow regimes  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

275

[Low Fidelity Simulation of a Zero-Y Robot  

NASA Technical Reports Server (NTRS)

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

Sweet, Adam

2001-01-01

276

Modeling Candle Flame Behavior In Variable Gravity  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

277

Minimal Liouville Gravity correlation numbers from Douglas string equation  

E-print Network

We continue the study of $(q,p)$ Minimal Liouville Gravity with the help of Douglas string equation. We generalize the results of \\cite{Moore:1991ir}, \\cite{Belavin:2008kv}, where Lee-Yang series $(2,2s+1)$ was studied, to $(3,3s+p_0)$ Minimal Liouville Gravity, where $p_0=1,2$. We demonstrate that there exist such coordinates $\\tau_{m,n}$ on the space of the perturbed Minimal Liouville Gravity theories, in which the partition function of the theory is determined by the Douglas string equation. The coordinates $\\tau_{m,n}$ are related in a non-linear fashion to the natural coupling constants $\\lambda_{m,n}$ of the perturbations of Minimal Lioville Gravity by the physical operators $O_{m,n}$. We find this relation from the requirement that the correlation numbers in Minimal Liouville Gravity must satisfy the conformal and fusion selection rules. After fixing this relation we compute three- and four-point correlation numbers when they are not zero. The results are in agreement with the direct calculations in Minimal Liouville Gravity available in the literature \\cite{Goulian:1990qr}, \\cite{Zamolodchikov:2005sj}, \\cite{Belavin:2006ex}.

Alexander Belavin; Boris Dubrovin; Baur Mukhametzhanov

2014-09-11

278

A Vacuum Solution with Torsion in Higher-Derivative Gravity  

E-print Network

In this paper, we provide a vacuum solution with torsion in quadratic Riemann-curvature gravity. Physically, the solution means that vacuum can have a nonzero vacuum field with large torsion. We show that the Einstein-Hilbert action can be derived if we expand the quadratic curvature of the Lagrangian in a torsion-free Riemannian space-time around a nonzero vacuum field. We also show that the cosmological constant caused by a nonzero vacuum field is equal to zero.

Kouzou Nishida

2012-09-02

279

New energy definition for higher-curvature gravities  

Microsoft Academic Search

We propose a novel but natural definition of conserved quantities for gravity models of quadratic and higher order in curvature. Based on the spatial asymptotics of curvature rather than of metric, it avoids the more egregious problems - such as zero-energy 'theorems' and failure in flat backgrounds--in this fourth-derivative realm. In D>4, the present expression indeed correctly discriminates between second-derivative

Bayram Tekin; S. Deser

2007-01-01

280

New energy definition for higher-curvature gravities  

Microsoft Academic Search

We propose a novel but natural definition of conserved quantities for gravity models of quadratic and higher order in curvature. Based on the spatial asymptotics of curvature rather than of metric, it avoids the more egregious problems---such as zero-energy ``theorems'' and failure in flat backgrounds---in this fourth-derivative realm. In D>4, the present expression indeed correctly discriminates between second-derivative Gauss-Bonnet and

S. Deser; Bayram Tekin

2007-01-01

281

Introduction to Massive Gravity  

NASA Astrophysics Data System (ADS)

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.

de Rham, Claudia

282

Exercise in artificial gravity  

E-print Network

Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility ...

Edmonds, Jessica Leigh

2005-01-01

283

Causal Newton Gravity Law  

E-print Network

The equations of the relativistic causal Newton gravity law for the planets of the solar system are studied in the approximation when the Sun rests at the coordinates origin and the planets do not iteract between each other.

Yury M. Zinoviev

2012-01-17

284

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

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.

Lucchetti, F.

1989-01-01

285

Magnetic bearings with zero bias  

NASA Technical Reports Server (NTRS)

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

Brown, Gerald V.; Grodsinsky, Carlos M.

1991-01-01

286

What Is Gravity?  

ERIC Educational Resources Information Center

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…

Nelson, George

2004-01-01

287

Partial gravity habitat study  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

288

Applications of standard gravity and conformal gravity  

NASA Astrophysics Data System (ADS)

In this Thesis, we explore a number of interesting problems in the study of gravitation. First, we explore the open question of the validity of alternative theories of gravitation through applying the Conformal Gravity theory to galactic rotation curve data. The Curves generated are fits that require no Dark Matter of external fitting parameters, and are of a universal nature with striking results. Next, we apply the standard linearized Einstein Gravity to the Ring Laser of Mallett to calculate the gravitational Faraday effect produced by the setup. Third, we apply the mathematics of general relativity to the field of transformation optics to yield a straight forward way to compute the geodesics for light rays traveling through transformative media. Lastly, we explore the standard gravitational formulation of covarientizing a space-time perfect fluid. We show that the calculation when performed in a curved space time using an incoherent averaging procedure does not return the standard perfect fluid form of the energy momentum tensor.

O'Brien, James G.

289

Quantum gravity in large dimensions  

NASA Astrophysics Data System (ADS)

Quantum gravity is investigated in the limit of a large number of space-time dimensions d, using as an ultraviolet regularization the simplicial lattice path integral formulation. In the weak field limit the appropriate expansion parameter is determined to be 1/d. For the case of a simplicial lattice dual to a hypercube, the critical point is found at kc/?=1/d (with k=1/8?G) separating a weak coupling from a strong coupling phase, and with 2d2 degenerate zero modes at kc. The strong coupling, large G, phase is then investigated by analyzing the general structure of the strong coupling expansion in the large d limit. Dominant contributions to the curvature correlation functions are described by large closed random polygonal surfaces, for which excluded volume effects can be neglected at large d, and whose geometry we argue can be approximated by unconstrained random surfaces in this limit. In large dimensions the gravitational correlation length is then found to behave as |log((kc-k)|1/2, implying for the universal gravitational critical exponent the value ?=0 at d=?.

Hamber, Herbert W.; Williams, Ruth M.

2006-02-01

290

Asymptotic safety of gravity and the Higgs boson mass  

E-print Network

There are indications that gravity is asymptotically safe. The Standard Model (SM) plus gravity could be valid up to arbitrarily high energies. Supposing that this is indeed the case and assuming that there are no intermediate energy scales between the Fermi and Planck scales we address the question of whether the mass of the Higgs boson $m_H$ can be predicted. For a positive gravity induced anomalous dimension $A_\\lambda>0$ the running of the quartic scalar self interaction $\\lambda$ at scales beyond the Planck mass is determined by a fixed point at zero. This results in $m_H=m_{\\rm min}=126$ GeV, with only a few GeV uncertainty. This prediction is independent of the details of the short distance running and holds for a wide class of extensions of the SM as well. For $A_\\lambda 0$ is favored by explicit computations existing in the literature.

Mikhail Shaposhnikov; Christof Wetterich

2010-01-12

291

New massive gravity and AdS(4) counterterms.  

PubMed

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

Jatkar, Dileep P; Sinha, Aninda

2011-04-29

292

Approaches to Validation of Models for Low Gravity Fluid Behavior  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

293

Gravity Before Einstein and Schwinger Before Gravity  

NASA Astrophysics Data System (ADS)

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

Trimble, Virginia L.

2012-05-01

294

Center for Gravity, Electrical & Magnetic Studies  

E-print Network

Center for Gravity, Electrical & Magnetic Studies Colorado School of Mines CGEMGravity&Magnetics for the sponsors of the Gravity & Magnetics Research Consortium © Gravity and Magnetics Research Consortium, 2009

295

Gravity and Orbits  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

2007-03-21

296

Role of Gravity Waves in Determining Cirrus Cloud Properties  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

297

Complex spectrally arbitrary zero–nonzero patterns  

Microsoft Academic Search

In this article, we highlight interesting properties of complex spectrally arbitrary zero–nonzero patterns. In particular, we investigate irreducible complex spectrally arbitrary zero–nonzero patterns for which all Jacobians are zero at every nilpotent realization. We also study complex spectrally arbitrary patterns whose corresponding directed graph does not contain a two-cycle. Lastly, we provide a complete list of all 3?×?3 and 4?×?4

J. J. McDonald; A. A. Yielding

2012-01-01

298

Complex spectrally arbitrary zero–nonzero patterns  

Microsoft Academic Search

In this article, we highlight interesting properties of complex spectrally arbitrary zero–nonzero patterns. In particular, we investigate irreducible complex spectrally arbitrary zero–nonzero patterns for which all Jacobians are zero at every nilpotent realization. We also study complex spectrally arbitrary patterns whose corresponding directed graph does not contain a two-cycle. Lastly, we provide a complete list of all 3?×?3 and 4?×?4

J. J. McDonald; A. A. Yielding

2011-01-01

299

Brane-world gravity  

E-print Network

The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+d-dimensional spacetime (the "bulk"), with standard-model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (~ TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. General relativity cannot describe gravity at high enough energies and must be replaced by a quantum gravity theory, picking up significant corrections as the fundamental energy scale is approached. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity "leaks" into the bulk, behaving in a truly 1+3+d-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting testable implications for high-energy astrophysics, black holes and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review discusses the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models.

Roy Maartens

2004-04-29

300

NASA Net Zero Energy Buildings Roadmap  

SciTech Connect

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.

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

2014-10-01

301

Short-cut to new anomalies in gravity duals to logarithmic conformal field theories  

E-print Network

Various massive gravity theories in three dimensions are conjecturally dual to logarithmic conformal field theories (LCFTs). We summarise the status of these conjectures. LCFTs are characterised by the values of the central charges and the so-called "new anomalies". We employ a short-cut to calculate these new anomalies in generalised massive gravity and in the recently proposed higher-derivative gravity theories with holographic c-theorem. Both cases permit LCFTs exhibiting intriguing features, like rank three Jordan cells or non-zero central charges. Finally, as an example we discuss in some detail the partially massless version of new massive gravity, a theory with several special properties that we call "partially massless gravity".

Daniel Grumiller; Niklas Johansson; Thomas Zojer

2011-08-16

302

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

303

Zero Degree Calorimeter for CMS  

NASA Astrophysics Data System (ADS)

In 2007 the Large Hadron Collider (LHC) at CERN in Geneva will start to collide protons and lead ions together at extremely high energies. The purpose of the proton-proton running is to study the origin of mass. The purpose of the ion running is to recreate the first few moments of the universe. The Compact Muon Solenoid, or CMS, is one of the experiments at LHC. I am currently working with the Nuclear Physics Team at the University of Kansas on part of CMS, called the Zero Degree Calorimeter (ZDC). I use a simulation toolkit, Geant4, which uses the object-oriented nature of C++ code to allow users to build simulations of particle collisions. Neutrons hit the ZDC and collide with tungsten plates to produce a shower of particles. The ZDC uses tungsten plates to change the neutrons into charged particles, and optical fibers to gather Cerenkov photons that are created. The current goal is to convert as much energy that comes into the ZDC as possible into light energy, and determine the most effective design for the calorimeter. I will present estimates of the ZDC performance for both proton-proton and heavy ion running.

Lehnherr, Megan

2004-10-01

304

Maglev Facility for Simulating Variable Gravity  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

305

Lorentz violation and gravity  

NASA Astrophysics Data System (ADS)

This work explores the theoretical and experimental aspects of Lorentz violation in gravity. A set of modified Einstein field equations is derived from the general Lorentz-violating Standard-Model Extension (SME). Some general theoretical implications of these results are discussed. The experimental consequences for weak-field gravitating systems are explored in the Earth- laboratory setting, the solar system, and beyond. The role of spontaneous Lorentz-symmetry breaking is discussed in the context of the pure-gravity sector of the SME. To establish the low-energy effective Einstein field equations, it is necessary to take into account the dynamics of 20 coefficients for Lorentz violation. As an example, the results are compared with bumblebee models, which are general theories of vector fields with spontaneous Lorentz violation. The field equations are evaluated in the post- newtonian limit using a perfect fluid description of matter. The post-newtonian metric of the SME is derived and compared with some standard test models of gravity. The possible signals for Lorentz violation due to gravity-sector coefficients are studied. Several new effects are identified that have experimental implications for current and future tests. Among the unconventional effects are a new type of spin precession for a gyroscope in orbit and a modification to the local gravitational acceleration on the Earth's surface. These and other tests are expected to yield interesting sensitivities to dimensionless gravity- sector coefficients.

Bailey, Quentin G.

2007-08-01

306

Venus Gravity Handbook  

NASA Technical Reports Server (NTRS)

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

Konopliv, Alexander S.; Sjogren, William L.

1996-01-01

307

Tethered gravity laboratories study  

NASA Technical Reports Server (NTRS)

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.

Lucchetti, F.

1990-01-01

308

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

NASA Technical Reports Server (NTRS)

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

Hill, D.; Downing, Robert S.

1987-01-01

309

The effects of gravity on flammability  

NASA Technical Reports Server (NTRS)

The effects of weightlessness and increased gravity on flammability and flame propagation are discussed. The test equipment and procedures for determining gravity effects are described. Comparisons are made between flammability under normal gravity conditions and occurrences under altered gravity conditions

Pearce, J. P.; Kimzey, J. H.; Pippen, D. L.

1971-01-01

310

On the no-gravity limit of gravity  

E-print Network

We argue that Relative Locality may arise in the no gravity $G\\rightarrow0$ limit of gravity. In this limit gravity becomes a topological field theory of the BF type that, after coupling to particles, may effectively deform its dynamics. We briefly discuss another no gravity limit with a self dual ground state as well as the topological ultra strong $G\\rightarrow\\infty$ one.

J. Kowalski-Glikman; M. Szczachor

2012-12-21

311

Macroscopic quantization of gravity  

E-print Network

The moon is receding from earth at an average rate of 3.8 cm/yr [6][7][9][12].This anomaly cannot be attributed to the well-known tidal exchange of angular momentum between earth and moon [8]. A secular change in the astronomical unit AU is definitely a concern, it is reportedly increasing by about 15 cm/yr [9][10], in this letter; the concept of macroscopic quantization of gravity is introduced to account for these anomalies on theoretical basis. Interestingly, it was found useful in measuring the speed of gravity! What is more interesting is the fact that this concept is based on solid well known classical physics with no modifications to any standard model. It was found that the speed of gravity cg is in the range 10^4 c < cg < 10^5 c.

M. Y. Amin

2010-01-09

312

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:? Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.? Explain how an object orbits a planet in terms of trajectories and free fall.? Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

313

Marginal models for zero inflated clustered data  

Microsoft Academic Search

Over the last decade or so, there has been increasing interest in 'zero inflated' (ZI) regression models to account for 'excess' zeros in data. Examples include ZI poisson (ZIP), ZI binomial (ZIB), ZI negative binomial and ZI tobit models. Recently, extensions of these models to the clustered data case have begun to appear. For example, Hall considered ZIP and ZIB

Daniel B Hall; Zhengang Zhang

2004-01-01

314

Research on Zero-Coding Optimization  

Microsoft Academic Search

It is difficulty to get the most reasonable project artificially when the number of the encoding sequences is bigger so a method of computer simulation is introduced. Base on the mathematics model of the zero-coding, the reciprocal of the contrast D, the general number of bright lines, the general number of reticles, and the influence on the zero-coding due to

Hu Xinyu; Ye Binqiang; Wang Zuwen

2007-01-01

315

Zero-Knowledge Proofs of Identity  

Microsoft Academic Search

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

Uriel Feige; Amos Fiat; Adi Shamir

1988-01-01

316

Electrometer has automatic zero bias control  

NASA Technical Reports Server (NTRS)

Zero biasing circuit in a vibrating reed type electrometer counterbalances residual potential. It charges a capacitor to the residual potential and connects that capacitor in series with the vibrating reed so that the voltages cancel. This enables the electrometer to read zero output potential in the absence of an input current.

1965-01-01

317

Chaotic temperature dependence at zero temperature.  

E-print Network

Chaotic temperature dependence at zero temperature. A.C.D. van Enter Center for Theoretical Physics; Abstract We present a class of examples of nearest­neighbour, bounded­spin models, in which the low­temperature Gibbs measures do not converge as the temperature is lowered to zero, in any dimension. 1 Introduction

318

Random Complex Zeroes and Random Nodal Lines  

E-print Network

In these notes, we describe the recent progress in understanding the zero sets of two remarkable Gaussian random functions: the Gaussian entire function with invariant distribution of zeroes with respect to isometries of the complex plane, and Gaussian spherical harmonics on the two-dimensional sphere.

Fedor Nazarov; Mikhail Sodin

2010-03-22

319

Zero Stiffness Tensegrity Structures M. Schenk a  

E-print Network

words, they remain neutrally stable, require no external work to de- form, and hence have zero stiffness-stress. These structures require specific external loads or states of self-stress to exhibit zero stiffness. The key-standing prestressed pin-jointed structures, which are in general both statically and kinematically indeterminate

Guest, Simon

320

Zero-voltage and zero-current-switching half bridge DC\\/DC converter  

Microsoft Academic Search

This paper introduces an improved zero-voltage and zero-current-switching half bridge (ZV-ZCS HB) DC\\/DC converter for medium and high-power applications. The soft switching is obtained by adding only small capacitors. The operation principle and design procedure are presented together with an analysis of the total losses in the switch. By using the proposed operation principle and design procedure zero-voltage-zero-current switching and

Vencislav Valchev; Dimitre Yudov; J. Batchvarov; A. Van den Bossche; J. Melkebeek

2002-01-01

321

Voltage fed zero-voltage zero-current switching PWM DC-DC converter  

Microsoft Academic Search

A new zero-voltage zero-current switching full-bridge phase-shifted PWM converter with controlled output rectifier is presented in this paper. IGBT switches are used in the high-frequency inverter of the DC-DC converter. Zero-voltage turn-on and zero-current turn-off for all power switches of the inverter is achieved for full load range from no-load to short circuit by using new secondary energy recovery clamp

Jaroslav Dudrik; V. Ruscin

2008-01-01

322

Zero-Voltage- and Zero-Current-Switching Full-Bridge Converter With Secondary Resonance  

Microsoft Academic Search

A zero-voltage- and zero-current-switching full-bridge (FB) converter with secondary resonance is presented and analyzed. The primary side of the converter is composed of FB insulated-gate bipolar transistors, which are driven by phase-shift control. The secondary side is composed of a resonant tank and a half-wave rectifier. Without an auxiliary circuit, zero-voltage switching (for leading-leg switches) and zero-current switching (for lagging-leg

Eung-Ho Kim; Bong-Hwan Kwon

2010-01-01

323

External Resource: Gravity Assist Simulator  

NSDL National Science Digital Library

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

1900-01-01

324

Position from gravity  

NASA Technical Reports Server (NTRS)

Procedures for obtaining position from surface gravity observations are reviewed and their relevance assessed in the context of the application of modern geodetic techniques to programs of Earth and ocean physics. Solutions based on the use of surface layer techniques, the discrete value approach, and the development from Green's theorem are stated in summary, the latter being extended to order e cubed in the height anomaly. The representation of the surface gravity field which is required in order that this accuracy may be achieved is discussed. Interim techniques which could be used in the absence of such a representation are also outlined.

Mather, R. S.

1973-01-01

325

Consistency of Semiclassical Gravity  

E-print Network

We discuss some subtleties which arise in the semiclassical approximation to quantum gravity. We show that integrability conditions prevent the existence of Tomonaga-Schwinger time functions on the space of three-metrics but admit them on superspace. The concept of semiclassical time is carefully examined. We point out that central charges in the matter sector spoil the consistency of the semiclassical approximation unless the full quantum theory of gravity and matter is anomaly-free. We finally discuss consequences of these considerations for quantum field theory in flat spacetime, but with arbitrary foliations.

D. Giulini; C. Kiefer

1994-09-08

326

Problems of Massive Gravities  

E-print Network

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 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 timelike/causal curves). We extend previous no-go results to the entire three-parameter range of massive gravity theories. It is also argued that bimetric models suffer a similar fate.

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

2014-10-08

327

Loop Quantum Gravity  

E-print Network

This article 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 article, 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.

Dah-Wei Chiou

2014-12-14

328

Experimental Observation of Lee-Yang Zeros  

NASA Astrophysics Data System (ADS)

Lee-Yang zeros are points on the complex plane of physical parameters where the partition function of a system vanishes and hence the free energy diverges. Lee-Yang zeros are ubiquitous in many-body systems and fully characterize their thermodynamics. Notwithstanding their fundamental importance, Lee-Yang zeros have never been observed in experiments, due to the intrinsic difficulty that they would occur only at complex values of physical parameters, which are generally regarded as unphysical. Here we report the first observation of Lee-Yang zeros, by measuring quantum coherence of a probe spin coupled to an Ising-type spin bath. The quantum evolution of the probe spin introduces a complex phase factor and therefore effectively realizes an imaginary magnetic field. From the measured Lee-Yang zeros, we reconstructed the free energy of the spin bath and determined its phase transition temperature. This experiment opens up new opportunities of studying thermodynamics in the complex plane.

Peng, Xinhua; Zhou, Hui; Wei, Bo-Bo; Cui, Jiangyu; Du, Jiangfeng; Liu, Ren-Bao

2015-01-01

329

Topological zero modes at nonzero chemical potential  

NASA Astrophysics Data System (ADS)

We give analytical and numerical solutions for the zero modes of the Dirac operator in topological SU(2) gauge backgrounds at nonzero chemical potential. Continuation from imaginary to real chemical potential is used to systematically derive analytical zero modes for calorons at arbitrary holonomy and, in particular limits, for instantons and dyons (magnetic monopoles). For the latter a spherical ansatz is explored as well. All the zero modes exhibit stronger peaks at the core and negative regions in their densities. We discuss the structure of the corresponding overlap matrix elements. For discretized calorons on the lattice we consider the staggered operator and show that it does possess (quartet quasi)zero modes, whose eigenmodes agree very well with the continuum profiles, for zero as well as nonzero chemical potential.

Bruckmann, Falk; Rödl, Rudolf; Sulejmanpasic, Tin

2013-09-01

330

Multilevel zero-inflated Poisson regression modelling of correlated count data with excess zeros  

Microsoft Academic Search

Count data with excess zeros relative to a Poisson distribution are common in many biomedical applica- tions. A popular approach to the analysis of such data is to use a zero-inflated Poisson (ZIP) regression model. Often, because of the hierarchical study design or the data collection procedure, zero-inflation and lack of independence may occur simultaneously, which render the standard ZIP

Andy H. Lee; Kui Wang; Jane A. Scott; Kelvin K. W. Yau; Geoffrey J. McLachlan

2006-01-01

331

Feasibility of Achieving a Zero-Net-Energy, Zero-Net-Cost Homes  

Microsoft Academic Search

A green building competition, to be known as the Energy Free Home Challenge (EFHC), is scheduled to be opened to teams around the world in 2010. This competition will encourage both design innovation and cost reduction, by requiring design entries to meet 'zero net energy' and 'zero net cost' criteria. For the purposes of this competition, a 'zero net energy'

S. Al-Beaini; S. Borgeson; B. Coffery; D. Gregory; K. Konis; C. Scown; J. Simjanovic; B. Strogen; I. Walker

2009-01-01

332

Introduction to Loop Quantum Gravity  

E-print Network

The questions I have been asked during the 5th International School on Field Theory and Gravitation, have compelled me to give an account of the premises that I consider important for a beginner's approach to Loop Quantum Gravity. After a description of some general arguments and an introduction to the canonical theory of gravity, I review the background independent approach to quantum gravity, giving only a brief survey of Loop Quantum Gravity.

Simone Mercuri

2010-01-08

333

5, 1102911054, 2005 Convective gravity  

E-print Network

ACPD 5, 11029­11054, 2005 Convective gravity waves at mid-latitudes Y. G. Choi et al. Title Page Discussions Wind-profiler observations of gravity waves produced by convection at mid-latitudes Y. G. Choi1­11054, 2005 Convective gravity waves at mid-latitudes Y. G. Choi et al. Title Page Abstract Introduction

Paris-Sud XI, Université de

334

6, 19532001, 2006 Imaging gravity  

E-print Network

ACPD 6, 1953­2001, 2006 Imaging gravity waves in lower stratospheric AMSU-A radiances S. D under a Creative Commons License. Atmospheric Chemistry and Physics Discussions Imaging gravity waves.eckermann@nrl.navy.mil) 1953 #12;ACPD 6, 1953­2001, 2006 Imaging gravity waves in lower stratospheric AMSU-A radiances S. D

Boyer, Edmond

335

CFT, Integrable Models Liouville Gravity  

E-print Network

CFT, Integrable Models And Liouville Gravity Chernogolovka 2009 Sunday June 28, 2009. Conference as one of components of their L, A pairs. #12;CFT, Integrable Models And Liouville Gravity Chernogolovka Gravity Chernogolovka, 2009 Tuesday June 30, 2009. CONFERENCE HALL 09:30­10:10 Herman Boos (Wuppertal

Fominov, Yakov

336

Gravity Recovery and Climate Experiment  

NSDL National Science Digital Library

The Gravity Recovery and Climate Experiment (GRACE) mission uses twin satellites to make detailed measurements of Earth's gravity field. GRACE materials include a description of the mission, research projects, and personnel. There are also links to news articles, publications, datasets, and software tools for processing gravity data.

337

Linearized Torsion Waves in a Tensor-Tensor Theory of Gravity  

E-print Network

We investigate a linearized tensor-tensor theory of gravity with torsion and a perturbed torsion wave solution is discovered in background Minkowski spacetime with zero torsion. Furthermore, gauge transformations of any perturbed tensor field are derived in general background non-Riemannian geometries. By calculating autoparallel deviations, both longitudinal and transverse polarizations of the torsion wave are discovered.

Chih-Hung Wang

2007-12-12

338

Chern--Simons Gravity from 3+1 Dimensional Gravity  

E-print Network

In the context of a Poincar\\'e gauge theoretical formulation, pure gravity in 3+1-dimensions is dimensionally reduced to gravity in 2+1-dimensions with or without cosmological constant $\\Lambda$. The dimensional reductions are consistent with the gauge symmetries, mapping ISO(3, 1) gauge transformations into ISO(2,1) ones. One of the reductions leads to Chern-Simons-Witten gravity. The solutions of 2+1-gravity with $\\Lambda\\le 0$ (in particular the black-hole solution recently found by Banados, Teitelboim and Zanelli) and those of 1+1-dimensional Liouville gravity, are thus mapped into 3+1-dimensional vacuum solutions.

G. Grignani; G. Nardelli

1992-11-09

339

From Classical To Quantum Gravity: Introduction to Loop Quantum Gravity  

E-print Network

We present an introduction to the canonical quantization of gravity performed in loop quantum gravity, based on lectures held at the 3rd quantum geometry and quantum gravity school in Zakopane in 2011. A special feature of this introduction is the inclusion of new proposals for coupling matter to gravity that can be used to deparametrize the theory, thus making its dynamics more tractable. The classical and quantum aspects of these new proposals are explained alongside the standard quantization of vacuum general relativity in loop quantum gravity.

Kristina Giesel; Hanno Sahlmann

2013-01-02

340

Even-dimensional topological gravity from Chern-Simons gravity  

E-print Network

It is shown that the topological action for gravity in 2n-dimensions can be obtained from the 2n+1-dimensional Chern-Simons gravity genuinely invariant under the Poincare group. The 2n-dimensional topological gravity is described by the dynamics of the boundary of a 2n+1-dimensional Chern-Simons gravity theory with suitable boundary conditions. The field $\\phi^{a}$, which is necessary to construct this type of topological gravity in even dimensions, is identified with the coset field associated with the non-linear realizations of the Poincare group ISO(d-1,1).

Nelson Merino; Alfredo Perez; Patricio Salgado

2009-10-08

341

Geological appraisal over the Singhbhum-Orissa Craton, India using GOCE, EIGEN6-C2 and in situ gravity data  

NASA Astrophysics Data System (ADS)

The gravity field and derivatives generated with the high resolution EIGEN-6C2 gravity model which includes satellite gravity data of GOCE (Gravity field and steady-state Ocean Circulation Explorer) has been utilized for geological appraisal of the Singhbhum-Orissa Craton, India. The GOCE only field gravity data and in situ gravity data of the same area have been utilized for comparative assessment to validate the results derived by EIGEN-6C2 gravity data. The GOCE and EIGEN-6C2 Bouguer gravity data have been generated from GOCE and EIGEN-6C2 Free-air gravity data, respectively, after removing topography effect. The result shows that correlation coefficient and covariance between the Bouguer gravity anomaly distribution of in situ and EIGEN-6C2 data of the entire study area are 0.68 and 93.9 mgal2, respectively. The GOCE field compares well to the terrestrial derivative fields in the long-wavelength part of the signal. Further, EIGEN-6C2 and in situ Bouguer gravity data have been analyzed using the 1st and 2nd Vertical Derivatives, Analytical Signal and Tilt Derivative mapping techniques. Published geological and structural maps of the area have been overlapped over different derivative maps and the analytical signal map to analyze the correlation with the subsurface geology and geological structures of the area. Major distinct geological signatures, on different derivative maps and analytical signal map, are correlated well with the existing geological map. The TDR derived from the EIGEN-6C2 Bouguer anomaly has been used to map geologic contacts. The source boundaries and depths are determined from the zero contours, and the half distance between ±?/4 contours or the distance between zero and +?/4 or -?/4 contour of TDR, respectively. The gravity data generated from EIGEN-6C2 model provides sufficient resolution for understanding of the geological setting of the Singhbhum-Orissa Craton.

Pal, S. K.; Majumdar, T. J.

2015-03-01

342

CONSERVATION VOICES GRAVITY RULES  

E-print Network

CONSERVATION VOICES GRAVITY RULES By David R. Montgomery When it comes to runoff and erosion of life that we value today in this region, and pass them on to future generations, we need to not only headwater environments from degradation through wilderness and Wild & Scenic Rivers protection is a prudent

Montgomery, David R.

343

Gravity Content in Dreams  

Microsoft Academic Search

Flying and falling dreams are often listed among the most common of dreams. Aside from the pure form, in which the dreamer actually falls or flies, it is frequent to find situations in which the dreamer deals with actions or objects implying gravity functions, that is, climbing, floating through air or water, and going up or down on a ladder

Alfio Maggiolini; Anna Persico; Franca Crippa

2007-01-01

344

Specific Gravity Urobilinogen  

E-print Network

Date Lot # Specific Gravity pH Leukocytes Nitrite Protein Glucose Ketone Urobilinogen Bilirubin Blood / Hemoglobin HCG: Method Lot # Acetest® (Ketone): Lot # Clinitest® (Glucose): Lot # Ictotest®(Bilirubin Urobilinogen Bilirubin Blood / Hemoglobin HCG: Method Lot # Acetest® (Ketone): Lot # Clinitest® (Glucose): Lot

Rodriguez, Carlos

345

Statistical origin of gravity  

SciTech Connect

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

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

2010-06-15

346

The Flavor of Gravity  

SciTech Connect

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

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

2007-06-19

347

External Resource: Different Gravity  

NSDL National Science Digital Library

This article from NASA's Suited for Spacewalking An Activity Guide for Technology Education explains that gravity is an attractive force that all objects have for one another. It doesn't matter whether the object is a planet, a cannon ball, a feather, or

1900-01-01

348

Quantum Gravity and Turbulence  

E-print Network

We apply recent advances in quantum gravity to the problem of turbulence. Adopting the AdS/CFT approach we propose a string theory of turbulence that explains the Kolmogorov scaling in 3+1 dimensions and the Kraichnan and Kolmogorov scalings in 2+1 dimensions. In the gravitational context, turbulence is intimately related to the properties of spacetime, or quantum, foam.

Vishnu Jejjala; Djordje Minic; Y. Jack Ng; Chia-Hsiung Tze

2010-05-18

349

Low gravity phase separator  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

350

Semiclassical unimodular gravity  

SciTech Connect

Classically, unimodular gravity is known to be equivalent to General Relativity (GR), except for the fact that the effective cosmological constant ? has the status of an integration constant. Here, we explore various formulations of unimodular gravity beyond the classical limit. We first consider the non-generally covariant action formulation in which the determinant of the metric is held fixed to unity. We argue that the corresponding quantum theory is also equivalent to General Relativity for localized perturbative processes which take place in generic backgrounds of infinite volume (such as asymptotically flat spacetimes). Next, using the same action, we calculate semiclassical non-perturbative quantities, which we expect will be dominated by Euclidean instanton solutions. We derive the entropy/area ratio for cosmological and black hole horizons, finding agreement with GR for solutions in backgrounds of infinite volume, but disagreement for backgrounds with finite volume. In deriving the above results, the path integral is taken over histories with fixed 4-volume. We point out that the results are different if we allow the 4-volume of the different histories to vary over a continuum range. In this ''generalized'' version of unimodular gravity, one recovers the full set of Einstein's equations in the classical limit, including the trace, so ? is no longer an integration constant. Finally, we consider the generally covariant theory due to Henneaux and Teitelboim, which is classically equivalent to unimodular gravity. In this case, the standard semiclassical GR results are recovered provided that the boundary term in the Euclidean action is chosen appropriately.

Fiol, Bartomeu; Garriga, Jaume, E-mail: bfiol@ub.edu, E-mail: jaume.garriga@ub.edu [Departament de Física Fonamental i, Institut de Cičncies del Cosmos, Universitat de Barcelona, Martí i Franqučs 1, 08028 Barcelona (Spain)

2010-08-01

351

Artificial Gravity Research Plan  

NASA Technical Reports Server (NTRS)

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.

Cromwell, Ronita

2014-01-01

352

A Trick of Gravity  

ERIC Educational Resources Information Center

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

Newburgh, Ronald

2010-01-01

353

Spaceborne Gravity Gradiometers  

NASA Technical Reports Server (NTRS)

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

Wells, W. C. (editor)

1984-01-01

354

SO(3) massive gravity  

E-print Network

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

Chunshan Lin

2014-08-05

355

Gravity Probe B to test Einstein  

NASA Astrophysics Data System (ADS)

Gravity probe B, which has been proposed for a space shuttle launch in 1992, is a 2-ton spacecraft that has been under study for several years at the Marshall Space Flight Center, Huntsville, Ala. The heart of the spacecraft is a gyroscope, which consists o f a solid quartz golfball-sized sphere that serves as the rotor. Levitated in space by an electric field, the rotor would spin completely untouched at 170 cycles per second.The rotor is so nearly perfectly round that if it were expanded from its golfball size to the size of the earth, the highest imperfection on its surface would be only about 1.8 m (6 feet). To give the ball superconductivity, Marshall has developed a niobium coating for the rotor and has been instrumental in the development of an isothermal barrier—a large vacuum-bottlelike container that would provide near-absolute-zero temperatures for the gyroscope.

Bell, Peter M.

356

Black hole remnant from gravity's rainbow  

NASA Astrophysics Data System (ADS)

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

Farag Ali, Ahmed

2014-05-01

357

Flat Spacetime Vacuum in Loop Quantum Gravity  

E-print Network

We construct a state in the loop quantum gravity theory with zero cosmological constant, which should correspond to the flat spacetime vacuum solution. This is done by defining the loop transform coefficients of a flat connection wavefunction in the holomorphic representation which satisfies all the constraints of quantum General Relativity and it is peaked around the flat space triads. The loop transform coefficients are defined as spin foam state sum invariants of the spin networks embedded in the spatial manifold for the SU(2) quantum group. We also obtain an expression for the vacuum wavefunction in the triad represntation, by defining the corresponding spin networks functional integrals as SU(2) quantum group state sums.

A. Mikovic

2004-04-06

358

Hardware development for Gravity Probe-B  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

359

Nonlinear modal resonances in low-gravity slosh-spacecraft systems  

NASA Technical Reports Server (NTRS)

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.

Peterson, Lee D.

1991-01-01

360

GRAVITY detector systems  

NASA Astrophysics Data System (ADS)

GRAVITY is a second generation instrument for the VLT Interferometer, designed to enhance the near-infrared astrometric and spectro-imaging capabilities of VLTI. It will combine the AO corrected beams of the four VLT telescopes. The GRAVITY instrument uses a total of five eAPD detectors, four of which are for wavefront sensing and one for the Fringe tracker. In addition two Hawaii2RG are used, one for the acquisition camera and one for the spectrometer. A compact bath cryostat is used for each WFS unit, one for each of the VLT Unit Telescopes. Both Hawaii2RG detectors have a cutoff wavelength of 2.5 microns. A new and unique element of GRAVITY is the use of infrared wavefront sensors. For this reason SELEX-Galileo has developed a new high speed avalanche photo diode detector for ESO. The SAPHIRA detector, which stands for Selex Avalanche Photodiodes for Highspeed Infra Red Applications, has been already evaluated by ESO. At a frame rate of 1 KHz, a read noise of less than one electron can be demonstrated. A more detailed presentation about the performance of the SPAHIRA detector will be given at this conference 1. Each SAPHIRA detector is installed in an LN2 bath cryostat. The detector stage, filter wheel and optics are mounted on the cold plate of the LN2 vessel and enclosed by a radiation shield. All seven detector systems are controlled and read out by the standard ESO NGC controller. The NGC is a controller platform which can be adapted and customized for all infrared and optical detectors. This paper will discuss specific controller modifications implemented to meet the special requirements of the GRAVITY detector systems and give an overview of the GRAVITY detector systems and their performance.

Mehrgan, Leander H.; Finger, Gert; Accardo, Matteo; Lizon, Jean-Louis; Stegmeier, Joerg; Eisenhauer, Frank

2014-07-01

361

Industrial processes influenced by gravity  

NASA Technical Reports Server (NTRS)

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.

Ostrach, Simon

1988-01-01

362

Plants and gravity. Special issue  

NASA Technical Reports Server (NTRS)

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

Kiss, J. Z. (Principal Investigator)

2002-01-01

363

Entrainment in oscillatory zero-mean flow  

NASA Astrophysics Data System (ADS)

The dynamical processes associated with the stably stratified atmospheric boundary layer or in the ocean thermocline are less well understood than those of its convective counterparts. This is due to its complexity, and the fact that buoyancy reduces entrainment across density interfaces. We present results on a series of laboratory experiments where a sharp density interface generated by either salt concentration or heat, advances due to grid stirred turbulence. We parametrize the level of buoyancy at the density interface by a local Richardson number defined in terms of the density difference across the interface, which may be due to a temperature or salinity jump. L is the integral lengthscale and u' is the r.m.s. velocity scale. So Ri = C L/u 2. The laboratory experiments were designed to compare the entrainment produced by zero-mean turbulence in heat or salt density interfaces. In the experiment we used a small perspex box of 15 by 10 cm in base, a small mesh grid (M= 0.8 cm ) driven by a motor. So as to generate the density interface by disolving salt in the bottom layer of the water column or by heating the top layer, we added the top light layer, which had a density difference carefully set up by means of a sponge float. The grid was set to oscillate with fixed frequency and stroke at the begining of the experiment and the velocity of advance of the interface Ve was measured by looking at a Shadowgraph or by video recording. The turbulent parameters are derived from previous measurements as a function of the distance between the grid center and the interface z as: l = 0.1 z and the turbulent velocity údecays inversely proportinal to the distance z. There are several mechanisms that produce mixing across the density interface. And there is a dependence of the Prandtl number on the Entrainment law. The entrainment is a power function of the local Richardson number, and the value of the empirical exponent n(Ri,Pr) is compared with previous results. The relationship between the Flux Richardson number and the Gradient or local one and the ways in which the interface extracts energy from the turbulence source via internal waves Internal gravity (or buoyancy) waves are characteristic of the stable boundary layer and contribute to its transport processes, both directly, and indirectly via internal waveinduced turbulence. These proceses are able to control entrainment across strong density interfaces as those defined by Kings et al (1989) in the Antartica. A comparison of the range of entrainment values from laboratory experiments with those ocurring in nature, both in the atmosphere and ocean shows the importance of modeling correctly the integral lengthscales of the environmental turbulence.

Medina, P.; Sanchez, M. A.

2009-04-01

364

Zero-base budgeting and the library.  

PubMed

This paper describes the application of zero-base budgeting to libraries and the procedures involved in setting up this type of budget. It describes the "decision packages" necessary when this systmem is employed, as well as how to rank the packages and the problems which are related to the process. Zero-base budgeting involves the entire staff of a library, and the incentive engendered makes for a better and more realistic budget. The paper concludes with the problems which one might encounter in zero-base budgeting and the major benefits of the system. PMID:626795

Sargent, C W

1978-01-01

365

Quantum Gravity from Noncommutative Spacetime  

E-print Network

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 $\\star$-algebra) of quantum gravity.

Jungjai Lee; Hyun Seok Yang

2014-11-25

366

Quantum gravity from noncommutative spacetime  

NASA Astrophysics Data System (ADS)

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.

Lee, Jungjai; Yang, Hyun Seok

2014-12-01

367

Modified Gravity and Coupled Quintessence  

NASA Astrophysics Data System (ADS)

The distinction between modified gravity and quintessence or dynamical dark energy is difficult. Many models of modified gravity are equivalent to models of coupled quintessence by virtue of variable transformations. This makes an observational differentiation between modified gravity and dark energy very hard. For example, the additional scalar degree of freedom in f(R)-gravity or non-local gravity can be interpreted as the cosmon of quintessence. Nevertheless, modified gravity can shed light on questions of interpretation, naturalness and simplicity. We present a simple model where gravity is modified by a field dependent Planck mass. It leads to a universe with a cold and slow beginning. This cosmology can be continued to the infinite past such that no big bang singularity occurs. All observables can be described equivalently in a hot big bang picture with inflation and early dark energy.

Wetterich, Christof

368

Visual analysis of flow boiling at different gravity levels in 4.0 mm tube  

NASA Astrophysics Data System (ADS)

The aim of the present paper is to describe the results of flow boiling heat transfer at low gravity and compare them with those obtained at earth gravity, evaluating possible differences. The experimental campaigns at low gravity have been performed during the parabolic flight campaign of October-November 2013. The paper will show the analysis of differences between the heat transfer coefficients and vapour bubble parameters at normal and at zero gravity. The results of 4.0 mm tube are presented and discussed. With respect to terrestrial gravity, heat transfer is systematically lower at microgravity in the range of the experimental conditions. Heat transfer differences for the two gravity conditions are related to the different bubble size in each of them. The size of a bubble in flow boiling is affected by the gravity level, being larger at low gravity, unless inertial forces are largely predominant over buoyancy and other forces acting on the bubble itself when detaching from a heated wall. Vapour bubble parameters (bubble diameter, bubble length, width, and nose velocity) have been measured.

Valencia-Castillo, C. M.; Celata, G. P.; Saraceno, L.; Zummo, G.

2014-11-01

369

Effect of gravity on the stability and structure of lean hydrogen-air flames  

NASA Technical Reports Server (NTRS)

Detailed, time-dependent, 2D numerical simulations with full hydrogen-oxygen chemistry are used to investigate the effects of gravity on the stability and structure of laminar flames in lean, premixed hydrogen-air mixtures. The calculations show that the effects of gravity becomes more important as the lean flammability limit is approached. In a 12 percent hydrogen-air mixture, gravity plays only a secondary role in determining the multidimensional structure of the flame with the stability and structure of the flame controlled primarily by the thermo-diffusive instability mechanism. However, in leaner hydrogen-air mixtures gravity becomes more important. Upward-propagating flames are highly curved and evolve into a bubble rising upwards in the tube. Downward-propagating flames are flat or even oscillate between structures with concave and convex curvatures. The zero-gravity flame shows only cellular structures. Cellular structures which are present in zero gravity can be suppressed by the effect of buoyancy for mixtures leaner than 11 percent hydrogen. These observations are explained on the basis of an interaction between the processes leading to buoyancy-induced Rayleigh-Taylor instability and the thermo-diffusive instability.

Patnaik, G.; Kailasanath, K.

1991-01-01

370

[Dynamics of ECG voltage in changing gravity].  

PubMed

Comparative analysis of the QRS voltage response to gravity variations was made using the data about 26 normal human subjects collected in parabolic flights (CNERS-AIRBUS A300 Zero-G, n=23; IL-76MD, n=3) and during the tilt test (head-up tilt at 70 degrees for a min and head-down tilt at-15 degrees for 5 min, n=14). Both the parabolic flights and provocative tilt tests affected R-amplitude in the Z lead. During the hypergravity episodes it was observed in 95% of cases with the mean gain of 16% and maximal--56%. On transition to the horizontal position, the Rz-amplitude showed a rise in each subject (16% on the average). In microgravity, the Rz-amplitude reduced in 95% of the observations. The voltage decline averaged 18% and reached 49% at the maximum. The head-down tilt was conducive to Rz reduction in 78% of observations averaging 2%. Analysis of the ECG records under changing gravity when blood redistribution developed within few seconds not enough for serious metabolic shifts still revealed QRS deviations associated exclusively with the physical factors, i.e., alteration in tissue conduction and distance to electrodes. Our findings can stand in good stead in evaluation of the dynamics of predictive ECG parameters during long-term experiments leading to changes as in tissue conduction, so metabolism. PMID:16915811

Saltykova, M M; At'kov, O Iu; Capderou, A; Morgun, V V; Gusakov, V A; Khe?mets, G I; Konovalov, G A; Kondratiuk, L L; Kataev, Iu V; Voronin, L I; Kaspranski?, R R; Vaida, P

2006-01-01

371

Planckian Axions and the Weak Gravity Conjecture  

E-print Network

Several recent works 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 $N\\gg1$ axions, super-Planckian axion diameters $\\cal{D}$ are readily allowed by the WGC. We clarify the nontrivial 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 $f_1^2 \\le ... \\le f_N^2$ 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 $f_NM_{pl}$ 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 satisf...

Bachlechner, Thomas C; McAllister, Liam

2015-01-01

372

Spherically symmetric conformal gravity and "gravitational bubbles"  

E-print Network

The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equation 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. The second class is more general, 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 the same features of non-vacuum solutions. One of them, the metrics a la Vaidya, is explicitly written.

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

2014-12-09

373

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs  

NASA Technical Reports Server (NTRS)

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2006-01-01

374

Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLS  

NASA Technical Reports Server (NTRS)

A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water. The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles

Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Geiger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

2003-01-01

375

Super-reflection and cloaking based on zero index metamaterial  

Microsoft Academic Search

A zero index metamaterial (ZIM) can be utilized to block wave (super-reflection) or conceal objects completely (cloaking). The ``super-reflection'' device can be realized by a Mu zero (Epsilon zero) metamaterial with a perfect electric (magnetic) conductor inclusion of arbitrary shape and size for a transverse electric (magnetic) incident wave. In contrast, a Mu zero (Epsilon zero) metamaterial with a perfect

Jiaming Hao; Wei Yan; Min Qiu

2010-01-01

376

Rotating gravity currents. Part 1. Energy loss theory  

NASA Astrophysics Data System (ADS)

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.

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

2005-01-01

377

Zero-G Annular Flow and 1-G Stratified Flow Single Component Two-Phase Condensation Modeling  

NASA Astrophysics Data System (ADS)

Two-phase systems can achieve the same energy management in space as single-phase systems with the advantage of reduced mass, size, and pumping requirements. Designing the condenser of a two-phase thermal management system requires a better understanding of the behavior of condensing two-phase flow in zero-G than previously existed. Thus, a new model was developed for condensing zero-G annular flow, using the universal velocity profile, the Kármán momentum-heat transfer analogy and Wheeler's correlations for film thickness and interfacial friction factor in reduced gravity annular flow. The model was validated against reduced gravity experimental data collected aboard a KC-135 aircraft in 1991-1992 by NASA and Texas A&M University. Good agreement was found between the model and the experimental data. A new procedure was suggested for modeling condensing 1-G stratified flow. This procedure was found to underpredict experimental data by an average of 10%.

Baranek, Pascale; Marsden, Ken C.; Best, Frederick R.

1994-07-01

378

On zero energy states in graphene  

E-print Network

We obtain zero energy states in graphene for a number of potentials and discuss the relation of the decoupled Schr\\"odinger-like equations for the the spinor components with non relativistic $\\cal{PT}$ symmetric quantum mechanics.

C. -L. Ho; P. Roy

2014-10-02

379

Healthy Zero Energy Buildings ENVIRONMENTAL AREA RESEARCH  

E-print Network

contaminants, have also been associated with negative impacts on human health. Increasing ventilation rates perception, performance, and other human outcomes as affected by ventilation. Project Specifics· PerformHealthy Zero Energy Buildings ENVIRONMENTAL AREA RESEARCH PIER Environmental Research www

380

ASU Roadmap to Zero Waste Contact Information  

E-print Network

strides in the implementation of renewable energy and the reduction of greenhouse gas emissions. With our the collective actions of the entire ASU community to hit our target. Zero solid waste also is smart business

Zhang, Junshan

381

Partnerships to continue moving toward zero emissions  

E-print Network

development strategies; · Provides science-based information about the technological or state that is interested in supporting the market development of zero emission-edge yet accessible analytical resources to help create and implement market

California at Davis, University of

382

Topological zero modes at nonzero chemical potential  

E-print Network

We give analytical and numerical solutions for the zero modes of the Dirac operator in topological SU(2) gauge backgrounds at nonzero chemical potential. Continuation from imaginary to real chemical potential is used to systematically derive analytical zero modes for calorons at arbitrary holonomy and, in particular limits, for instantons and dyons (magnetic monopoles). For the latter a spherical ansatz is explored as well. All the zero mode exhibit stronger peaks at the core and negative regions in their densities. We discuss the structure of the corresponding overlap matrix elements. For discretized calorons on the lattice we consider the staggered operator and show that it does possess (quartet quasi-)zero modes, whose eigenmodes agree very well with the continuum profiles, also for nonzero chemical potential.

Bruckmann, Falk; Sulejmanpasic, Tin

2013-01-01

383

Topological zero modes at nonzero chemical potential  

E-print Network

We give analytical and numerical solutions for the zero modes of the Dirac operator in topological SU(2) gauge backgrounds at nonzero chemical potential. Continuation from imaginary to real chemical potential is used to systematically derive analytical zero modes for calorons at arbitrary holonomy and, in particular limits, for instantons and dyons (magnetic monopoles). For the latter a spherical ansatz is explored as well. All the zero mode exhibit stronger peaks at the core and negative regions in their densities. We discuss the structure of the corresponding overlap matrix elements. For discretized calorons on the lattice we consider the staggered operator and show that it does possess (quartet quasi-)zero modes, whose eigenmodes agree very well with the continuum profiles, also for nonzero chemical potential.

Falk Bruckmann; Rudolf Rodl; Tin Sulejmanpasic

2013-05-06

384

Locomotion in simulated microgravity: gravity replacement loads  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

385

Reggeon exchange from gauge/gravity duality  

NASA Astrophysics Data System (ADS)

We perform the analysis of quark-antiquark Reggeon exchange in meson-meson scattering, in the framework of the gauge/gravity correspondence in a confining background. On the gauge theory side, Reggeon exchange is described as quark-antiquark exchange in the t channel between fast projectiles. The corresponding amplitude is represented in terms of Wilson loops running along the trajectories of the constituent quarks and antiquarks. The paths of the exchanged fermions are integrated over, while the "spectator" fermions are dealt with in an eikonal approximation. On the gravity side, we follow a previously proposed approach, and we evaluate the Wilson-loop expectation value by making use of gauge/gravity duality for a generic confining gauge theory. The amplitude is obtained in a saddle-point approximation through the determination near the confining horizon of a Euclidean "minimal surface with floating boundaries", i.e., by fixing the trajectories of the exchanged quark and antiquark by means of a minimisation procedure, which involves both area and length terms. After discussing, as a warm-up exercise, a simpler problem on a plane involving a soap film with floating boundaries, we solve the variational problem relevant to Reggeon exchange, in which the basic geometry is that of a helicoid. A compact expression for the Reggeon-exchange amplitude, including the effects of a small fermion mass, is then obtained through analytic continuation from Euclidean to Minkowski space-time. We find in particular a linear Regge trajectory, corresponding to a Regge-pole singularity supplemented by a logarithmic cut induced by the non-zero quark mass. The analytic continuation leads also to companion contributions, corresponding to the convolution of the same Reggeon-exchange amplitude with multiple elastic rescattering interactions between the colliding mesons.

Giordano, Matteo; Peschanski, Robi

2011-10-01

386

Deflating the case for zero inflation  

Microsoft Academic Search

This paper analyzes the U.S. congressional proposal to instruct the Federal Reserve to, in the next five years, lower inflation to zero from its current rate of around 5 percent. The paper concludes that, when other policy options are considered, the zero inflation policy is not advisable. Its benefits would be very small--possibly negative--while its costs would probably be significant.

S. Rao Aiyagari

1990-01-01

387

Artificial or variable gravity attained by tether systems  

NASA Technical Reports Server (NTRS)

The simplest orbiting tethered system demands for stability that the mass centers of two end bodies be displaced above and below the position of zero acceleration. Therefore, the contents of the end bodies are subjected necessarily to acceleration fields or artificial gravity whose magnitudes depend on the dimensions and masses of the system. If the length of the tether changes, so do the fields. Even for a fixed tether length, the acceleration field at a location in the system may be somewhat variable unless special means are employed to maintain a constant value. These fundamental properties of a tethered system can be used to advantage if small or variable acceleration fields are desired for experimental or operational reasons. This potential use involves a few expressions from a formulation of tether system dynamics. Some of these formulae were collected for convenient use. Two and three body tethered equilibrium equations are explained. A special application of acceleration field control using a tether system is attainment of near-zero gravity. In this applicaition, even small variations about zero become a critical matter.

Lundquist, C. A.

1986-01-01

388

GRAVITY: the calibration unit  

NASA Astrophysics Data System (ADS)

We present in this paper the design and characterisation of a new sub-system of the VLTI 2nd generation instrument GRAVITY: the Calibration Unit. The Calibration Unit provides all functions to test and calibrate the beam combiner instrument: it creates two artificial stars on four beams, and dispose of four delay lines with an internal metrology. It also includes artificial stars for the tip-tilt and pupil guiding systems, as well as four metrology pick-up diodes, for tests and calibration of the corresponding sub-systems. The calibration unit also hosts the reference targets to align GRAVITY to the VLTI, and the safety shutters to avoid the metrology light to propagate in the VLTI-lab. We present the results of the characterisation and validtion of these differrent sub-units.

Blind, N.; Eisenhauer, F.; Haug, M.; Gillessen, S.; Lippa, Magdalena; Burtscher, L.; Hans, O.; Haussmann, F.; Huber, S.; Janssen, A.; Kellner, S.; Kok, Y.; Ott, T.; Pfuhl, O.; Sturm, E.; Weber, J.; Wieprecht, E.; Amorim, A.; Brandner, W.; Perrin, G.; Perraut, K.; Straubmeier, C.

2014-07-01

389

Plant gravity sensing  

NASA Technical Reports Server (NTRS)

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

Sack, F. D.

1991-01-01

390

Gravity Gets You Down  

NSDL National Science Digital Library

This site has students understanding that: 1) Without air resistance, all objects would fall at the same acceleration, regardless of mass. 2) Gravity is the force that causes objects to fall. 3) Air resistance, a type of friction, works against gravity to decrease the acceleration of a falling object. Included in this two day lesson plan are the objectives, needed materials, procedures, adaptations for older students, discussion questions, a rubric for assessment, extension activities, suggested reading, links to other sites, vocabulary, and academic standards. Students can click on a vocabulary word to hear its pronunciation and a sentence using the word. Teachers can link to Teaching Tools to create custom worksheets, puzzles, and quizzes. A printable version can be downloaded. Teachers can purchase the video, The Invisible Force, and download comprehension questions and answers.

DiscoverySchool.com

2007-12-12

391

Quantum Gravity and Inflation  

SciTech Connect

Using the Ashtekar-Sen variables of loop quantum gravity, a new class of exact solutions to the equations of quantum cosmology is found for gravity coupled to a scalar field, that corresponds to inflating universes. The scalar field, which has an arbitrary potential, is treated as a time variable, reducing the hamiltonian constraint to a time-dependent Schroedinger equation. When reduced to the homogeneous and isotropic case, this is solved exactly by a set of solutions that extend the Kodama state, taking into account the time dependence of the vacuum energy. Each quantum state corresponds to a classical solution of the Hamiltonian-Jacobi equation. The study of the latter shows evidence for an attractor, suggesting a universality in the phenomena of inflation. Finally, wavepackets can be constructed by superposing solutions with different ratios of kinetic to potential scalar field energy, resolving, at least in this case, the issue of normalizability of the Kodama state.

Alexander, S

2004-05-25

392

Hamiltonian spinfoam gravity  

NASA Astrophysics Data System (ADS)

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

Wieland, Wolfgang M.

2014-01-01

393

Cambridge Cosmology: Quantum Gravity  

NSDL National Science Digital Library

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

Thomas Hertog

394

Dark energy and gravity  

Microsoft Academic Search

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

T. Padmanabhan

2008-01-01

395

Viscosity in modified gravity  

E-print Network

A bulk viscosity is introduced in the formalism of modified gravity. It is shown that, on the basis of a natural scaling law for the viscosity, a simple solution can be found for quantities such as the Hubble parameter and the energy density. These solutions may incorporate a viscosity-induced Big Rip singularity. By introducing a phase transition in the cosmic fluid, the future singularity can nevertheless in principle be avoided.

Iver Brevik

2012-11-23

396

Gravity and Falling  

NSDL National Science Digital Library

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

Astronomical Society of the Pacific

2008-01-01

397

Free-Air Gravity  

NSDL National Science Digital Library

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

398

Covariant Loop Quantum Gravity  

NASA Astrophysics Data System (ADS)

Preface; Part I. Foundations: 1. Spacetime as a quantum object; 2. Physics without time; 3. Gravity; 4. Classical discretization; Part II. The 3D Theory: 5. 3D Euclidean theory; 6. Bubbles and cosmological constant; Part III. The Real World: 7. The real world: 4D Lorentzian theory; 8. Classical limit; 9. Matter; Part IV. Physical Applications: 10. Black holes; 11. Cosmology; 12. Scattering; 13. Final remarks; References; Index.

Rovelli, Carlo; Vidotto, Francesca

2014-11-01

399

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

NASA Technical Reports Server (NTRS)

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

Adams, Richard J.

1988-01-01

400

Massive Gravity from Higher Derivative Gravity with Boundary Conditions  

E-print Network

With an appropriate choice of parameters, a higher derivative theory of gravity can describe a normal massive sector and a ghost massless sector. We show that, when defined on an asymptotically de Sitter spacetime with Dirichlet boundary conditions, such a higher derivative gravity can provide a framework for a unitary theory of massive gravity in four spacetime dimensions. The resulting theory is free not only of higher derivative ghosts but also of the Boulware-Deser mode.

Minjoon Park; Lorenzo Sorbo

2012-10-29

401

Granular Superconductors and Gravity  

NASA Technical Reports Server (NTRS)

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

Noever, David; Koczor, Ron

1999-01-01

402

Cosmic strings in gravity  

NASA Astrophysics Data System (ADS)

We consider Kasner-type static, cylindrically symmetric interior string solutions in the theory of modified gravity. The physical properties of the string are described by an anisotropic energy-momentum tensor satisfying the condition ; that is, the energy density of the string along the -axis is equal to minus the string tension. As a first step in our study we obtain the gravitational field equations in the theory for a general static, cylindrically symmetric metric, and then for a Kasner-type metric, in which the metric tensor components have a power law dependence on the radial coordinate . String solutions in two particular modified gravity models are investigated in detail. The first is the so-called "exponential" modified gravity, in which the gravitational action is proportional to the exponential of the sum of the Ricci scalar and matter Lagrangian, and the second is the "self-consistent model", obtained by explicitly determining the gravitational action from the field equations under the assumption of a power law dependent matter Lagrangian. In each case, the thermodynamic parameters of the string, as well as the precise form of the matter Lagrangian, are explicitly obtained.

Harko, Tiberiu; Lake, Matthew J.

2015-02-01

403

Venus gravity fields  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

404

Economic and Financial Implications of the ZEROS Technology  

E-print Network

Value Calculations for Killeen ZEROS Project, 2011. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9 Pro Forma Income Statement for Robust Scenario Analysis... of Killeen ZEROS Project, 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 10 Pro Forma Cash Flow Budget for Robust Scenario Analysis of Killeen ZEROS Project, 2011...

Rister, M. Edward; Lacewell, Ronald D.; Sturdivant, Allen W.

405

The daily mean zero-flux plane during soil-controlled evaporation: A Green's function approach  

NASA Astrophysics Data System (ADS)

A solution is presented of the linearized Richards equation with inclusion of gravity and with appropriate boundary conditions describing the combined soil-controlled surface evaporation and the downward infiltration, following the application of a given amount of precipitation or irrigation. This solution is shown to agree with available field measurements, namely the evolution with time of the zero-flux plane depth and of the rate of soil-controlled evaporation from the bare soil surface. The problem is solved by means of the Green's function method; the result is general enough to be also applicable to flow problems in linear soils with boundary conditions substantially different from the ones considered herein.

Brutsaert, Wilfried

2014-12-01

406

Intertwining Operator Algebras, Genus-Zero Modular Functors and Genus-Zero Conformal Field Theories  

Microsoft Academic Search

We describe the construction of the genus-zero parts of conformal field theories in the sense of G. Segal from representations of vertex operator algebras satisfying certain conditions. The construction is divided into four steps and each step gives a mathematical structure of independent interest. These mathematical structures are intertwining operator algebras, genus-zero modular functors, genus-zero holomorphic weakly conformal field theories,

Yi-Zhi Huang

1995-01-01

407

Zero-Inflated Poisson and Zero-Inflated Negative Binomial Models Using the COUNTREG Procedure  

Microsoft Academic Search

Real-life count data are frequently characterized by overdispersion and excess zeros. Zero-inflated count models provide a parsimonious yet powerful way to model this type of situation. Such models assume that the data are a mixture of two separate data generation processes: one generates only zeros, and the other is either a Poisson or a negative binomial data-generating process. The result

Donald Erdman; Arthur Sinko

2008-01-01

408

A zero-voltage and zero-current switching three-level DC\\/DC converter  

Microsoft Academic Search

This paper presents a novel zero-voltage and zero-current switching (ZVZCS) three-level DC\\/DC converter. This converter overcomes the drawbacks presented by the conventional zero-voltage switching (ZVS) three-level converter, such as high circulating energy, severe parasitic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase-shift control with a

Francisco Canales; Peter Barbosa; Fred C. Lee

2002-01-01

409

A novel zero-voltage and zero-current-switching full-bridge PWM converter  

Microsoft Academic Search

A novel zero voltage and zero current switching full bridge pulse width modulation (ZVZCS-FB-PWM) converter is proposed and analyzed. An auxiliary circuit, which consists of a diode and auxiliary winding coupled with output inductor, are added to provide zero current switching (ZCS) conditions. The ZCS of lagging-leg switches is achieved by resetting the primary current with induced EMF of auxiliary

Xu Feng; Xu DianGuo; Liu YuXiu

2003-01-01

410

Dynamics of Superfluid Helium in Low-Gravity  

NASA Technical Reports Server (NTRS)

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

Frank, David J.

1997-01-01

411

Zero cosmological constant and nonzero dark energy from the holographic principle  

NASA Astrophysics Data System (ADS)

The first law of thermodynamics and the holographic principle applied to an arbitrary large cosmic causal horizon are shown to naturally demand a zero cosmological constant and a non-zero dynamical dark energy in the form of the holographic dark energy. A semiclassical analysis shows that the holographic dark energy has a parameter d = 1 and an equation of state comparable to current observational data if the entropy of the horizon saturates the Bekenstein-Hawking bound. This result indicates that quantum field theory should be modified on a large scale to explain the dark energy. The relations among the dark energy, the quantum vacuum energy and the entropic gravity are also discussed.

Lee, Jae-Weon

2013-09-01

412

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

413

Non-zero total correlation means non-zero quantum correlation  

E-print Network

We investigated the super quantum discord based on weak measurements. The super quantum discord is an extension of the standard quantum discord defined by projective measurements and also describes the quantumness of correlations. We provide some equivalent conditions for zero super quantum discord by using quantum discord, classical correlation and mutual information. In particular, we find that the super quantum discord is zero only for product states, which have zero mutual information. This result suggests that non-zero correlations can always be detected using the quantum correlation with weak measurements. As an example, we present the assisted state-discrimination method.

Bo Li; Lin Chen; Heng Fan

2014-04-01

414

Geometric scalar theory of gravity  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

415

Geometric scalar theory of gravity  

SciTech Connect

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

Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D. [Instituto de Cosmologia Relatividade Astrofisica ICRA - CBPF Rua Dr. Xavier Sigaud 150 - 22290-180 Rio de Janeiro - Brazil (Brazil); Moschella, U., E-mail: novello@cbpf.br, E-mail: eduhsb@cbpf.br, E-mail: Ugo.Moschella@uninsubria.it, E-mail: egoulart@cbpf.br, E-mail: jsalim@cbpf.br, E-mail: toniato@cbpf.br [Universitŕ degli Studi dell'Insubria - Dipartamento di Fisica e Matematica Via Valleggio 11 - 22100 Como - Italy (Italy)

2013-06-01

416

Low-gravity fluid flows  

NASA Technical Reports Server (NTRS)

The behavior of fluids in micro-gravity conditions is examined, with particular regard to applications in the growth of single crystals. The effects of gravity on fluid behavior are reviewed, and the advent of Shuttle flights are noted to offer extended time for experimentation and processing in a null-gravity environment, with accelerations resulting solely from maneuvering rockets. Buoyancy driven flows are considered for the cases stable-, unstable-, and mixed-mode convection. Further discussion is presented on g-jitter, surface-tension gradient, thermoacoustic, and phase-change convection. All the flows are present in both gravity and null gravity conditions, although the effects of buoyancy and g-jitter convection usually overshadow the other effects while in a gravity field. Further work is recommended on critical-state and sedimentation processes in microgravity conditions.

Ostrach, S.

1982-01-01

417

Artificial Gravity for Space Travel  

Microsoft Academic Search

This study presents magnetic concepts for artificial gravity and artificial balance on space travel. The magnetic pseudo gravity system could be constructed on any size manned spacecraft, low-gravity planet and moon. Qualitative analysis of the magnetic methods via soft ferrite, Fe oxide nano-particles and ferrofluids is elucidated. The magnetic method could ensure that weight-bearing bones of space travelers are continually

Shun-Wen Cheng

2007-01-01

418

D-dimensional log gravity  

SciTech Connect

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.

Alishahiha, Mohsen; Fareghbal, Reza [School of physics, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2011-04-15

419

Cascading gravity is ghost free  

SciTech Connect

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.

Rham, Claudia de [Departement de Physique Theorique, Universite de Geneve, 24 Quai E. Ansermet, CH-1211 Geneve (Switzerland); Khoury, Justin [Center for Particle Cosmology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6395 (United States); Tolley, Andrew J. [Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada)

2010-06-15

420

Entropic Gravity in Rindler Space  

E-print Network

We show that Rindler horizons are entropic screens and gravity is an entropic force in Rindler space by deriving the Verlinde entropy formula from the focusing of light due to a mass close to the horizon. Consequently, gravity is also entropic in the near horizon regions of Schwarzschild and de Sitter space-times. In different limits, the entropic nature of gravity in Rindler space leads to the Bekenstein entropy bound and the uncertainty principle.

Edi Halyo

2011-04-13

421

Primer on Gravity and Magnetics  

NSDL National Science Digital Library

This web page explains the goals and benefits of studying gravity and magnetic data to understand subsurface geology of the Earth. It discusses uses of gravity and magnetic measurements in providing information about the density of rocks, and explains how these measurements are useful in exploration for oil and gas and mineral deposits. The page uses gravity and magnetic maps and as well as figures to illustrate some of the concepts of interpretation, such as amplitude, frequency and anomalies.

Richard Gibson

422

Renormalizability of Topologically Massive Gravity  

E-print Network

We consider renormalizability of topologically massive gravity in three space-time dimensions. With a usual parametrization of the metric tensor, we establish the statement that topologically massive gravity is in fact renormalizable. In this proof, we make use of not only a recently found, new infrared regularization method of scalar mode but also a covariant ultraviolet regulator with a specific combination of higher derivative terms which is motivated by the new massive gravity in three dimensions.

Ichiro Oda

2009-08-14

423

Cascading Gravity is Ghost Free  

E-print Network

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.

Claudia de Rham; Justin Khoury; Andrew J. Tolley

2010-06-24

424

The lunar environment as a fractional-gravity biological laboratory.  

PubMed

A quarter of a century ago men stepped upon the lunar surface and established the possibility of human expansion beyond Earth. When humans return to the moon to occupy it with greater permanency, an applied lunar biological laboratory would provide a means of conducting experiments on the long-term effects of fractional gravity in animals and plants and provide necessary data to enhance the health, safety and well-being of lunar workers and inhabitants. In-depth studies can go beyond zero-g observations, on-orbit centrifuge studies, and ground-based research providing important insight into continuous 1/6-g effects on biological systems. Studies concentrating on development, gravity sensing, and adaptation/readaptation would provide preliminary data on whether long-term fractional gravity is detrimental or compromising to fundamental biological function. Food production research in 1/6-g would provide important information for on site application to improve the yield and quality of food (animal and plant) produced in the unique lunar environment. The purpose of this paper is to discuss some examples of the major gravitational biology areas that could be studied on the moon and applied to lunar population needs utilizing lunar biological facilities and continuous fractional gravity. PMID:11539524

Garshnek, V

1994-07-01

425

Self-accelerating massive gravity: Covariant perturbation theory  

NASA Astrophysics Data System (ADS)

We undertake a complete and covariant treatment for the quadratic Lagrangian of all of the degrees of freedom of massive gravity with a fixed flat fiducial metric for arbitrary massive gravity parameters around any isotropic self-accelerating background solution. Generically, three out of four Stückelberg degrees of freedom propagate in addition to the usual two tensor degrees of freedom of general relativity. The complete kinetic structure typically is only revealed at an order in the graviton mass that is equivalent to retaining curvature terms in a locally flat expansion. These results resolve several apparent discrepancies in the literature where zero degrees of freedom propagate in either special cases or approximate treatments as well as decoupling limit analyses which attempt to count longitudinal degrees of freedom.

Motloch, Pavel; Hu, Wayne

2014-11-01

426

Beables/Observables in Classical and Quantum Gravity  

E-print Network

Observables `are observed' whereas beables just `are'. Beables have more scope in the cosmological and quantum domains. Both are entities that form `brackets' with `the constraints' that are `equal to' zero. Moreover, a variety of notions of brackets, constraints and equalities are to be considered. I.e. Poisson, Dirac, commutator, histories, Schouten-Nijenhuis, double and Nambu brackets; first-class, gauge, linear and effective constraints; plain alias strong, weak and weak-effective equalities. The Dirac-Bergmann distinction in notions of gauge leads to further notions of beable, and is tied to some diffeomorphism-specific subtleties. Thus we cover a wide range of notions of beables/observables: Dirac, Kuchar, effective, Bergmann, histories, multisymplectic, master, Nambu and bi-. We also cover a wide range of classical and quantum theories of gravity: general relativity, loop quantum gravity, histories theory, supergravity and M-theory.

Anderson, Edward

2013-01-01

427

Gauss-Bonnet gravity renders negative tension braneworlds unstable  

SciTech Connect

We show that the addition of the Gauss-Bonnet term to Einstein gravity induces a tachyon mode in the spin two fluctuations of the Randall-Sundrum I model. We demonstrate that this instability is generically related to the presence of a flat negative tension brane, of codimension one, embedded in an anti-de Sitter background. In particular its presence is independent of Z{sub 2}-symmetry or compactness of the extra dimension. The gravitational tachyon mode persists for arbitrarily small but nonvanishing Gauss-Bonnet coupling. It is a bound state localized on the negative tension brane, much like the graviton zero-mode is localized on a positive tension one. We discuss the possible resolution of this instability by the inclusion of induced gravity terms on the branes or by an effective four-dimensional cosmological constant.

Charmousis, Christos; Dufaux, Jean-Francois [LPT, Universite de Paris-Sud, Bat. 210, 91405 Orsay CEDEX (France)

2004-11-15

428

Crustal structure beneath the southern Appalachians: nonuniqueness of gravity modeling  

USGS Publications Warehouse

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.

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

1983-01-01

429

International Space University variable gravity research facility design  

NASA Astrophysics Data System (ADS)

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.

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

1994-03-01

430

The International Space University's variable gravity research facility design  

NASA Astrophysics Data System (ADS)

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

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

1991-09-01

431

Utilization of Low Gravity Environment for Measuring Liquid Viscosity  

NASA Technical Reports Server (NTRS)

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

Antar, Basil N.; Ethridge, Edwin

1998-01-01

432

The International Space University's variable gravity research facility design  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

433

Entanglment assisted zero-error codes  

NASA Astrophysics Data System (ADS)

Zero-error information theory studies the transmission of data over noisy communication channels with strictly zero error probability. For classical channels and data, much of the theory can be studied in terms of combinatorial graph properties and is a source of hard open problems in that domain. In recent work, we investigated how entanglement between sender and receiver can be used in this task. We found that entanglement-assisted zero-error codes (which are still naturally studied in terms of graphs) sometimes offer an increased bit rate of zero-error communication even in the large block length limit. The assisted codes that we have constructed are closely related to Kochen-Specker proofs of non-contextuality as studied in the context of foundational physics, and our results on asymptotic rates of assisted zero-error communication yield non-contextuality proofs which are particularly `strong' in a certain quantitive sense. I will also describe formal connections to the multi-prover games known as pseudo-telepathy games.

Matthews, William; Mancinska, Laura; Leung, Debbie; Ozols, Maris; Roy, Aidan

2011-03-01

434

Stability of zero modes in parafermion chains  

NASA Astrophysics Data System (ADS)

One-dimensional topological phases can host localized zero-energy modes that enable high-fidelity storage and manipulation of quantum information. Majorana fermion chains support a classic example of such a phase, having zero modes that guarantee twofold degeneracy in all eigenstates up to exponentially small finite-size corrections. Chains of "parafermions"—generalized Majorana fermions—also support localized zero modes, but, curiously, only under much more restricted circumstances. We shed light on the enigmatic zero-mode stability in parafermion chains by analytically and numerically studying the spectrum and developing an intuitive physical picture in terms of domain-wall dynamics. Specifically, we show that even if the system resides in a gapped topological phase with an exponentially accurate ground-state degeneracy, higher-energy states can exhibit a splitting that scales as a power law with system size, categorically ruling out exact localized zero modes. The transition to power-law behavior is described by critical behavior appearing exclusively within excited states.

Jermyn, Adam S.; Mong, Roger S. K.; Alicea, Jason; Fendley, Paul

2014-10-01

435

ZERO EMISSION POWER GENERATION TECHNOLOGY DEVELOPMENT  

SciTech Connect

Clean Energy Systems (CES) was previously funded by DOE's ''Vision 21'' program. This program provided a proof-of-concept demonstration that CES' novel gas generator (combustor) enabled production of electrical power from fossil fuels without pollution. CES has used current DOE funding for additional design study exercises which established the utility of the CES-cycle for retrofitting existing power plants for zero-emission operations and for incorporation in zero-emission, ''green field'' power plant concepts. DOE funding also helped define the suitability of existing steam turbine designs for use in the CES-cycle and explored the use of aero-derivative turbines for advanced power plant designs. This work is of interest to the California Energy Commission (CEC) and the Norwegian Ministry of Petroleum & Energy. California's air quality districts have significant non-attainment areas in which CES technology can help. CEC is currently funding a CES-cycle technology demonstration near Bakersfield, CA. The Norwegian government is supporting conceptual studies for a proposed 40 MW zero-emission power plant in Stavager, Norway which would use the CES-cycle. The latter project is called Zero-Emission Norwegian Gas (ZENG). In summary, current engineering studies: (1) supported engineering design of plant subsystems applicable for use with CES-cycle zero-emission power plants, and (2) documented the suitability and availability of steam turbines for use in CES-cycle power plants, with particular relevance to the Norwegian ZENG Project.

Ronald Bischoff; Stephen Doyle

2005-01-20

436

Active Response Gravity Offload System  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

437

An Underlying Theory for Gravity  

E-print Network

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

Yuan K. Ha

2012-08-14

438

Born-Infeld Gravity Revisited  

E-print Network

In this paper we investigate the behavior of linearized gravitational excitation in the Born-Infeld Gravity in $AdS_3$ space. We obtain the linearized equation of motion and show that this higher order gravity propagate two gravitons, massless and massive, on the $AdS_3$ background. In contrast to the $R^2$ models, such as TMG or NMG, Born-Infeld Gravity does not have a critical point for any regular choice of parameters. So the logarithmic solution is not a solution of this model, due to this one can not find a logarithmic conformal field theory as a dual model for Born-Infeld Gravity.

M. R. Setare; M. Sahraee

2014-04-22

439

Dual gravity and E11  

E-print Network

We consider the equation of motion in the gravity sector that arises from the non-linear realisation of the semi-direct product of E11 and its first fundamental representation, denoted by l1, in four dimensions. This equation is first order in derivatives and at low levels relates the usual field of gravity to a dual gravity field. When the generalised space-time is restricted to be the usual four dimensional space-time we show that this equation does correctly describe Einstein's theory at the linearised level. We also comment on previous discussions of dual gravity.

Peter West

2014-11-04

440

Is Gravity an Entropic Force?  

E-print Network

The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde's example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde's argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This may provide a further support for the conclusion that gravity is not an entropic force.

Shan Gao

2011-07-16

441

Repulsive gravity in tension stars  

NASA Astrophysics Data System (ADS)

In stars, pressure opposes the attractive force of gravity. In general relativity, if the pressure is negative (a tension) and P is less than -1/3 rho(c)-squared, then the resulting gravity is repulsive. Such material is invoked in cosmology to give the inflation of the universe. In tension stars, this repulsive gravity is balanced by the tension. The simplest tension stars only exist in esoteric situations beyond the neck of an Einstein-Rosen bridge in Schwarzschild space. Here, tension material is confined within a massive shell of normal matter. The resulting object, while still repulsive inside, has an attractive exterior gravity and can, in principle, exist without horizons.

Katz, J.; Lynden-Bell, D.

1991-09-01

442

Zero-voltage-zero-current switching in high-output-voltage full-bridge PWM converters using the interwinding capacitance  

Microsoft Academic Search

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulsewidth-modulated (PWM) power converter is proposed. The new converter uses the interwinding capacitance and a small primary-side inductor to achieve a zero-current-zero-voltage turn off and a zero-current turn on of the passive-to-active leg transistors. The turn off of the active-to-passive leg transistors is with zero voltage, and the turn on is with

Djordje Garabandic; William G. Dunford; Mark Edmunds

1999-01-01

443

Zero-voltage-zero-current switching in high-output-voltage full bridge PWM converters using the interwinding capacitance  

Microsoft Academic Search

A novel zero-voltage and zero-current switching (ZVZCS) full-bridge (FB) pulse width modulated (PWM) converter is proposed. The new converter uses the interwinding capacitance and a small primary side inductor to achieve a zero-current-zero-voltage turn off and a zero-current turn on of the passive-to-active leg transistors. The turn off of the active-to-passive leg transistors is with zero-voltage and the turn on

Djordje Garabandic; W. G. Dunford; M. Edmunds

1998-01-01

444

Influence of zero gravity simulation on time course of mitosis in microplasmodia of physarum polycephalum  

NASA Astrophysics Data System (ADS)

Detrimental effects of weight lessness are no longer expected to hinder successful mitosis. Experiments in space and on the fast clinostat give no hints of this. Nevertheless we are thinking of a g sensitivity during the process of chromosome condensation and distribution. The time course of nuclear division in microplasmodia of the slime mold Physarum polycephalum was investigated under 0 g simulation on the fast rotating clinostat in comparison to 1 g controls. The result of this experiment is: A significant shortening of mitosis under 0 g simulation compared to 1 g controls.

Sobick, V.; Briegleb, W.

445

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

446

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

447

Proposal for the design of a zero gravity tool storage device  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

448

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

NASA Astrophysics Data System (ADS)

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

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

1991-01-01

449

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

450

Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity  

NASA Astrophysics Data System (ADS)

The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.

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

1990-09-01

451

Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity  

Microsoft Academic Search

The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure

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

1990-01-01

452

On a zero-gravity limit of the Kerr--Newman spacetimes and their electromagnetic fields  

E-print Network

We discuss the limit of vanishing $G$ (Newton's constant of universal gravitation) of the maximal analytically extended Kerr--Newman electrovacuum spacetimes {represented in Boyer--Lindquist coordinates}. We investigate the topologically nontrivial spacetime emerging in this limit and show that it consists of two copies of flat Minkowski spacetime glued at a timelike solid cylinder. As $G\\to 0$, the electromagnetic fields of the Kerr-Newman spacetimes converge to nontrivial solutions of Maxwell's equations on this background spacetime. We show how to obtain these fields by solving Maxwell's equations with singular sources supported only on a circle in a spacelike slice of the spacetime. These sources do not suffer from any of the pathologies that plague the alternate sources found in previous attempts to interpret the Kerr--Newman fields on the topologically simple Minkowski spacetime. We characterize the singular behavior of these sources and prove that the Kerr-Newman electrostatic potential and magnetic stream function are the unique solutions of the Maxwell equations among all functions that have the same blow-up behavior at the ring singularity.

A. Shadi Tahvildar-Zadeh

2014-11-16

453

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

SciTech Connect

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

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

1996-05-01

454

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

NASA Technical Reports Server (NTRS)

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

Concus, Paul; Finn, Robert

1996-01-01

455

N zero gravity, aboard the space shuttle Columbia's upcoming flight, Air Force Colonel  

E-print Network

. In recognition of the growing importance of the academia-biotechnology relationship, University Rector Professor. Danny Gazit #12;last year set up a steering committee, chaired by Gazit, to evaluate and advance all in the 20th century was about breaking down processes to their elemental parts like mitochondria in cells

Linial, Michal

456

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

457

Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity  

NASA Technical Reports Server (NTRS)

The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.

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

1990-01-01

458

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

NASA Technical Reports Server (NTRS)

A methodology for correcting raw pressure-drop data on the influence of acceleration on the instrumentation in two-phase flow thermal management systems is described. Such systems are now being considered as an alternative to conventional single-phase systems in future space missions because of the potential to reduce overall system mass, size, and pumping power requirements. Corrected pressure-drop measurements are presented and compared with predictions of two-phase flow pressure-drop models. A set of flow and acceleration conditions is defined for which the frictional pressure drop does not increase upon entry into 0-'g' pressure drop.

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

1991-01-01

459

KC-135 zero-gravity two-phase flow pressure drop experiments and modelling  

E-print Network

(kg/no) 1. 161 958 VISCOSITY (N/m2 s) 1. 8x10 s 90 x 10 SURFACE TENSION (N/m2) 0. 0644 PRESSURE (psia) TEMP ( C) 14. 7 25. 0 25 The flow conditions of the April 30, 1990 flight are listed in Table 5. Table 5. Texas A A M University...D e pmtrt (Pi)0. 19(Pg)0. 19(1 Pg)0. 7 Pg 41 [tt F = xo. 7 s (1-x)0 24 P 079 PD)-0. 25 f 0 079 [QD]-0. 2 S So g=(1-x) +x 2( ? ') pgfgo Then the two-phase pressure dmp is calculated: ~2 C = -(~)1 @A 2 dz (27) (28). 18 Note: this method...

Lambert, Anne

1990-01-01

460

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

461

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

462

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

463

The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity  

Microsoft Academic Search

A commanding encyclopedia of the history and principles of spaceflight-from earliest conceptions to faster-than-light galaxy-hopping Here is the first truly comprehensive guide to space exploration and propulsion, from the first musings of the Greeks to current scientific speculation about interstellar travel using \\

David Darling

2002-01-01

464

Zero gravity and cardiovascular homeostasis. The relationship between endogenous hyperprolactinemia and plasma aldosterone  

NASA Technical Reports Server (NTRS)

Prolactin, thyrotropin and aldosterone were measured by radioimmunoassay and plasma renin activity by the radioimmunoassay of angiotensin I in normal women before and after the intravenous injection of 200 micrograms of thyrotropin releasing hormone. Prolactin increased at 15 minutes following thyrotropin releasing hormone. Plasma renin activity was not different from control levels during the first hour following the administration of thyrotropin releasing hormone, nor did the plasma aldosterone concentration differ significantly from the control levels during this period. However, with upright posture, an increase in aldosterone and in plasma renin activity was noted, demonstrating a normal capacity to secrete aldosterone. Similarly, no change in aldosterone was seen in 9 patients with primary hypothyroidism given thyrotropin releasing hormone, despite the fact that the increase in prolactin was greater than normal. These data demonstrate that acutely or chronically elevated serum prolactin levels do not result in increased plasma aldosterone levels in humans.

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

1978-01-01

465

The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity  

NASA Astrophysics Data System (ADS)

A commanding encyclopedia of the history and principles of spaceflight-from earliest conceptions to faster-than-light galaxy-hopping Here is the first truly comprehensive guide to space exploration and propulsion, from the first musings of the Greeks to current scientific speculation about interstellar travel using "warp drives" and wormholes. Space buffs will delight in its in-depth coverage of all key manned and unmanned missions and space vehicles-past, present, and projected-and its clear explanations of the technologies involved. Over the course of more than 2,000 extensively cross-referenced entries, astronomer David Darling also provides fascinating insights into the cultural development of spaceflight. In vivid accounts of the major characters and historical events involved, he provides fascinating tales of early innovators, the cross-pollination that has long existed between science fiction and science fact, and the sometimes obscure links between geopolitics, warfare, and advances in rocketry.

Darling, David

2002-11-01

466

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

467

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

NASA Technical Reports Server (NTRS)

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

Ludwig, E.

1984-01-01

468

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

469

Growth of single crystals by vapor transport in zero-gravity environment, ground-based experiments  

NASA Technical Reports Server (NTRS)

Mass and heat transfer phenomena associated with the growth of single crystals by chemical vapor transport reactions were investigated. In this technique, a gaseous transport agent reacts with the solid source material to form exclusively gaseous products. The gas phase species migrate from the source to the condensation zone of the closed reaction ampoule where the reverse reaction occurs with formation of single crystals. The necessary concentration gradient is achieved by means of a temperature gradient.

Wiedemeier, H.

1978-01-01

470

Free-surface phenomena under low- and zero-gravity conditions  

NASA Technical Reports Server (NTRS)

An apparatus to measure contact angle was constructed to exploit the proposed internal-corner criterion. If 2 alfa is the internal angle between two intersecting vertical planes and gamma is the contact angle, a meniscus at the corner rises to a finite height if alfa + gamma pi/2 and to an infinite height if alfa + gamma pi/2. The apparatus operates by decreasing the angle alfa from pi/2 until the meniscus height changes abruptly. A number of liquids are tested on glass and plexiglas.

Coles, D.

1985-01-01

471

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

NASA Technical Reports Server (NTRS)

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

Rubin, A. L.

1977-01-01

472

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

NASA Technical Reports Server (NTRS)

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

Germain, A.

1981-01-01

473

Feasibility study for the manufacture of zero gravity pharmaceuticles, immunological, and viral agents  

NASA Technical Reports Server (NTRS)

The feasibility of extracting, isolating, purifying, separating, or preparing medical and biological products of high socio-economic value in space was studied. In particular, the study was designed to concentrate on the isolation or purification of virals, pharmaceutical and immunological agents by means of electrophoresis, as the Apollo 16 flight demonstrated that a mixed population of latex spheres (.2 and .8 microns) could be successfully separated by electrophoresis in space and without sedimentation with minimal convection. This prompted NASA scientists to look into the possibility of carrying out types of biochemical experiments that would utilize space for medical purposes.

1974-01-01

474

Proposal for a zero-gravity toilet facility for the space station  

NASA Technical Reports Server (NTRS)

This proposed toilet facility has a straightforward design. It has few moving parts and is easily maintained. Air and water flow provide sanitary movement of the waste. The toilet's chambers are coated with Teflon which, along with the water flow, makes it self-cleaning. An added disinfectant called Betadiene kills any bacteria that may form on the chamber walls. The chair is contoured to take into account the neutral body position and the necessary strain position for defecation. Restraints at the ankles, knees, and midsection hold the body in the chair. The waste is stored in discs of Gortex material which are inside a replaceable storage chamber. This chamber can be removed, capped and stored until eventual return to earth.

Fleri, Edgar L., Jr.; Galliano, Paul A.; Harrison, Mark E.; Johnson, William B.; Meyer, Gregory J.

1989-01-01

475

Low scale quantum gravity in gauge-Higgs unified models  

E-print Network

We consider the scale at which gravity becomes strong in linearized General Relativity coupled to the gauge-Higgs unified(GHU) model. We also discuss the unitarity of S-matrix in the same framework. The Kaluza-Klein(KK) gauge bosons, KK scalars and KK fermions in the GHU models can drastically change the strong gravity scale and the unitarity violation scale. In particular we consider two models GHU_SM and GHU_MSSM which have the zero modes corresponding to the particle content of the Standard Model and the Minimal Supersymmetric Standard Model, respectively. We find that the strong gravity scale could be lowered as much as 10^13 (10^14) GeV in the GHU_SM (GHU_MSSM) for one extra dimension taking 1 TeV as the compactification scale. It is also shown that these scales are proportional to the inverse of the number of extra dimensions d. In the d=10 case, they could be lowered up to 10^5 GeV for both models. We also find that the maximum compactification scales of extra dimensions quickly converge into one special scale M_O near Planck scale or equivalently into one common radius R_0 irrespectively of d as the number of zero modes increases. It may mean that all extra dimensions emerge with the same radius near Planck scale. In addition, it is shown that the supersymmetry can help to remove the discordance between the strong gravity scale and the unitarity violation scale.

Jubin Park

2015-01-19

476

Diffraction patterns in ferrofluids: Effect of magnetic field and gravity  

NASA Astrophysics Data System (ADS)

In this paper, we report the experimental observation of diffraction patterns in a ferrofluid comprising of Fe3O4 nanoparticles in hexane by a 10 mW He-Ne laser beam. An external dc magnetic field (0-2 kG) was applied perpendicular to the beam. The diffraction pattern showed a variation at different depths of the sample in both zero and applied magnetic field. The patterns also exhibit a change in shape and size as the external field is varied. This effect arises due to thermally induced self-diffraction under the influence of gravity and external magnetic field.

Radha, S.; Mohan, Shalini; Pai, Chintamani

2014-09-01

477

Probing Quantum Gravity Through Exactly Soluble Midi-Superspaces I  

E-print Network

It is well-known that the Einstein-Rosen solutions to the 3+1 dimensional vacuum Einstein's equations are in one to one correspondence with solutions of 2+1 dimensional general relativity coupled to axi-symmetric, zero rest mass scalar fields. We first re-examine the quanization of this midi-superspace paying special attention to the asymptotically flat boundary conditions and to certain functional analytic subtleties associated with regularization. We then use the resulting quantum theory to analyze several conceptual and technical issues of quantum gravity.

A. Ashtekar; M. Pierri

1996-06-28

478

Modified Gravity (MOG) Black Holes and their Observable Shadows  

E-print Network

The shadows cast by non-rotating and rotating modified gravity (MOG) black holes are determined by the two parameters mass $M$ and angular momentum $J=Ma$. The sizes of the shadows cast by the spherically symmetric static Schwarzschild-MOG and Kerr-MOG rotating black holes increase significantly as the free parameter $\\alpha$ is increased from zero. The Event Horizon Telescope (EHT) shadow image measurements can determine whether Einstein's general relativity is correct or whether it should be modified in the presence of strong gravitational fields.

Moffat, J W

2015-01-01

479

Discrete Quantum Gravity in the Regge Calculus Formalism  

SciTech Connect

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

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

2005-09-01