Magnitude Of Gravity Research Articles

Effect of a magnetic field gradient on the crystallization of hen lysozyme

The effect of microgravity on protein crystal growth is an interesting, but highly controversial, issue. We superimposed the magnetic force on gravity and studied its effect on the crystal growth of hen egg-white lysozyme. The magnetic force was used similarly to the centrifugal force in a space shuttle to virtually change the level of gravity. We observed that the number of crystals increased or decreased, respectively, when 5% of the additional force was applied in the same or in the opposite direction to normal gravity. Our result indicates that the magnitude of gravity can in fact affect the studied protein crystal growth, and that a magnetic force has the potential ability of controlling gravity.

Subsurface distribution and tectonic setting of the late-Variscan granites in the northwestern Bohemian Massif

Integrative gravity modelling reveals the 3D shape, subsurface extent and basal morphology of the late-Variscan granites in the northwestern Bohemian Massif. The combination of the results with structural and geochronological data enables the interpretation of the morphogenesis and the tectonic setting of the granite emplacement. For the subsurface shaping two gravity methods were used: the Linsser filtering and the 2.5D density modelling. The Linsser filtering enables tomographic analyses of the gravity field in successive depth levels. The 2.5D density models were computed by the GRAVMAG program (version 1.5, British Geological Survey) which interprets gravity data vs. geological cross sections. At depth, the granites show steep- and flat-sided, wedge-like plutons which are generally elongated in north–northwest–south–southeast direction. The maximum basal depths between 3 and 8 km occur along the root zones indicated by high gravity magnitudes. The western- and easternmost granites (e.g. Leuchtenberg, Bor) are deeply eroded, whereas the granites in the central part (e.g. Falkenberg, Rozvadov) are greatly buried in the metamorphic host rocks. In the northern Oberpfalz, the plutons show a west-sided basal asymmmetry, and in the western Bohemia, in contrast, the plutons have an east-sided basal asymmetry. The steep pluton flanks parallel north–northwest–south–southeast gravity gradients which result from the high density contrast of the granites and host rocks. The density contrasts are caused by steep faults which enabled the emplacement of the granites. The shape, basal morphology, depth and volume of the plutons presume a genetic link between magma intrusion and shear deformation. However, the orientation of the plutons 15–20° off the trend of the major faults and structural data suggest emplacement into opening fractures along initially transtensional faults owing to the Lower to Upper Carboniferous extension in the northwestern Bohemian Massif.

Effects of Natural Convection on Self-Ignition of Solid Fuel Heated by External Radiation.

The effects of natural convection on self-ignition of solid fuel heated by external radiation were studied numerically. The numerical model includes thermal heating and subsequent degradation reactions in the solid phase with heat and mass transport of evolved degradation products into an atmosphere containing oxygen. The combustible fuel component of the product gas is mixed with oxygen to produce premixed gas and the heating of the gas accelerates the oxidation in the gas phase leading to spontaneous ignition. The induced natural convection was found to play a key role in the heat and mass transport, and hence in the time-dependent process leading to ignition. In the numerical calculation the magnitude of gravity was changed continuously to study its effects on the ignition time and ignition point. Effects of oxygen concentration in the atmosphere were also studied.

Performance of a centrifugal phytotron

It is possible to cultivate plants under an artificial gravity field generated by a centrifugal device in space. In order to determine an optimal magnitude of gravity, there is a need to investigate the relationship between plant growth and gravity, including not only reduced gravity but also gravity greater than 1G. A prototype centrifugal phytotron was designed and fabricated in order to investigate the relationship between plant growth and increased gravity. This device enables us to cultivate plants over the long term by controlling environmental conditions in the phytotron such as temperature, relative humidity, CO 2 concentration and light intensity. The results of our experiment indicate that plant seeds can germinate and grow even under an artificial gravity which changes sinusoidally from 2G to 4G

Artificial gravity

The use of artificial gravity in extended space flight is reviewed. Topics examined include synergistic factors, gravity loading, gravity magnitude, uniformity of gravity field, and effects of slow rotation.

A theoretical analysis of vertical flow equilibrium

The assumption of Vertical Equilibrium (VE) and of parallel flow conditions, in general, is often applied to the modeling of flow and displacement in natural porous media. However, the methodology for the development of the various models is rather intuitive, and no rigorous method is currently available. In this paper, we develop an asymptotic theory using as parameter the variable $$R_{{L}} = L/H\sqrt {k_{{V}} /k_{{H}} } $$ . It is rigorously shown that the VE model is obtained as the leading order term of an asymptotic expansion with respect to 1/R L 2 . Although this was numerically suspected, it is the first time that it is theoretically proved. Using this formulation, a series of special cases are subsequently obtained depending on the relative magnitude of gravity and capillary forces. In the absence of strong gravity effects, they generalize previous works by Zapata and Lake (1981), Yokoyama and Lake (1981) and Lake and Hirasaki (1981), on immiscible and miscible displacements. In the limit of gravity-segregated flow, we prove conditions for the fluids to be segregated and derive the Dupuit and Dietz (1953) approximations. Finally, we also discuss effects of capillarity and transverse dispersion.

Modeling three-dimensional solidification with magnetic fields and reduced gravity

Two interacting systems of partial differential equations governing three-dimensional laminar flow of an incompressible viscous fluid undergoing solidification or melting while under the influence of an externally applied magnetic field have been formulated and integrated numerically. The model includes effects of Joule heating, latent heat, and arbitrary magnitude and orientation of gravity and the magnetic field. It allows for arbitrary temperature-dependent physical properties within the melt and the solid phase. The mushy region is captured by varying viscosity orders of magnitude in the mushy region and by allowing latent heat of phase change to be an arbitrary function of temperature. The uniqueness of this approach is in the fact that both liquid and solid phases are treated as incompressible liquids with the solid phase having an extremely high viscosity. It was found numerically that the magnetic field strength and orientation can significantly influence flow field velocity and vorticity, amount of accrued solid, and the solid/liquid interface shape.

Using the free fall of objects under gravity for visual depth estimation

We performed an experiment that tested people’s ability to use the free fall of objects under gravity as a scale referent in a two-dimensional display. Subjects were presented with a two-dimensional computer animation of a fountain on a perspectival video background. Both rich and poor stimuli (i.e., fountains spraying many drops of water or only a single drop) were used. The task was to change the magnitude of simulated gravity so as to make the display appear “natural.” Results indicate that subjects reliably matched gravitational acceleration to apparent depth. Accuracy and reliability of the settings were higher for the rich stimuli than the poor stimuli, demonstrating the importance of complex stimuli for the human perceptual system.

Galactic hydrostatic equilibrium with magnetic tension and cosmic-ray diffusion

Three gravitational potentials differing in the content of dark matter in the Galactic plane are used to study the structure of the z-distribution of mass and pressure in the solar neighborhood. A P(0) of roughly (3.9 + or - 0.6) x 10 to the -12th dyn/sq cm is obtained, with roughly equal contributions from magnetic field, cosmic ray, and kinetic terms. This boundary condition restricts both the magnitude of gravity and the high z-pressure. It favors lower gravity and higher values for the cosmic ray, magnetic field, and probably the kinetic pressures than have been popular in the past. Inclusion of the warm H(+) distribution carries a significant mass component into the z about 1 kpc regime.

Buoyancy effects on flames spreading down thermally thin fuels

Experiments show that buoyancy influences the downward spread rate of flames consuming thermally thin fuel beds. For index cards (9.8 × 10 −3 cm half-thickness) and adding-machine tape (4.3 × 10 −3 cm half-thickness), an increase in the buoyancy level causes the spread rate to drop until no flame propagation is possible. A dimensionless spread rate is found to correlate with a Damköhler number. As the Damköhler number increases with decreasing buoyancy level brought about by an increase in pressure or a decrease in gravity, the dimensionless spread rate approaches unity. It is also found that a small change in orientation with respect to the vertical is equivalent to a change in the magnitude of gravity in the direction of spread, and power-law relations between the dimensional spread rate and pressure are only valid over a small pressure range.

Stimulus generalization of gravity.

In two experiments, squirrel monkeys were exposed to centrifugally generated, artificial gravity and trained to respond for food reinforcement at selected gravity (g) levels. Experiment I involved a single g value; in Exp. II, subjects were trained to discriminate among two or three g values. After training, generalization tests were administered over a 1.1-g to 2.1-g range. The major findings were as follows: (a) single-stimulus training yielded a linear relationship between percentage of responding and magnitude of gravity. (b) Two-valued discrimination training produced gradient peaks which were shifted from S(D) in a direction away from S(Delta). This effect was cancelled when S(D) was located equidistant between two S(Delta) stimuli. (c) Gradient form was independent of the S(D)-S(Delta) difference, but related to continuum location and/or intensity of discriminative stimuli.

Subjective vertical as a function of body position and gravity magnitude.

Subjective vertical as a function of body position and gravity magnitude.