Changes In Gravitational Acceleration Research Articles

Surface Deformation Monitoring Using Time-lapse Microgravity Method in Central and East Lombok Regencies

Surface deformation is a natural occurrence on the surface of the earth. The deformation can be in the form of subsidence or uplifting of the land surface. In this research, an time-lapse microgravity method will be applied to monitor surface deformation that occurs in Central Lombok and East Lombok Districts. The method of time-lapse microgravity is repetitive gravity measurement at the same point with a certain time interval, the measured magnitude is a change in the value of the acceleration of gravity and the microGal scale. Measurements were made in August 2016, April 2018, and June 2019. The measured value of the change in gravitational acceleration is the superposition of the changes caused by subsurface and surface sources. Separation of the two values is carried out using striping filter, which takes into account the ratio of density, thickness, and depth of the surface and subsurface layers. Land subsidence occurred during the period August 2016 to April 2018 and land uplifting occurred during the April 2018 to June 2019 period. This land subsidence occurred due to natural compacting and minor tectonic activity (small earthquakes that were not felt) while land uplifting was occurred due to major tectonic activities, in the form of the Lombok Earthquake in July to September 2018.

Challenges to the central nervous system during human spaceflight missions to Mars.

Space travel presents a number of environmental challenges to the central nervous system, including changes in gravitational acceleration that alter the terrestrial synergies between perception and action, galactic cosmic radiation that can damage sensitive neurons and structures, and multiple factors (isolation, confinement, altered atmosphere, and mission parameters, including distance from Earth) that can affect cognition and behavior. Travelers to Mars will be exposed to these environmental challenges for up to 3 years, and space-faring nations continue to direct vigorous research investments to help elucidate and mitigate the consequences of these long-duration exposures. This article reviews the findings of more than 50 years of space-related neuroscience research on humans and animals exposed to spaceflight or analogs of spaceflight environments, and projects the implications and the forward work necessary to ensure successful Mars missions. It also reviews fundamental neurophysiology responses that will help us understand and maintain human health and performance on Earth.

Barometric formulas: various derivations and comparisons to environmentally relevant observations

Three different lines of thinking (mechanical, mixed thermodynamical-mechanical, statistical thermodynamic) are presented to derive the noted barometric formula, which gives the altitude dependence of the pressure of a gas in a gravity field. It is shown that the first two methods can be extended to non-isothermal cases, whereas statistical thermodynamics relies on the concept of thermal equilibrium and its usefulness is limited to the isothermal barometric formula. The temperature changes in the gravity field are taken into account by two different methods: simple conservation of energy, and a more refined line of thought based on the adiabatic expansion of an ideal gas. The changes in gravitational acceleration are also considered in further refinements. Overall, six different formulas are derived and their usefulness is tested on the atmosphere of the Earth. It is found that none of the formulas is particularly useful above an altitude of 20 km because radiation effects make the temperature changes in the atmosphere difficult to predict by simple theories. Finally, the different components of air are also considered separately in the context of the barometric formula, and it is shown that the known composition changes of the atmosphere are primarily caused by photochemical processes and not by the gravity field.Graphical abstract

Responses of Bioconvection of Tetrahymena thermophila to Partial Gravity Created by Aircraft Flight.

Bioconvection is a form of collective pattern formation driven by negative gravitaxis of swimming microorganisms. In bioconvection, the interaction between individual swimmers results in self-organization leading to the development of a macroscopic structure typically 100-1000 times greater than an individual microorganism. To gain insight into the role of gravity in this self-organization phenomenon, we investigated the bioconvective behavior of the ciliate Tetrahymena thermophila under short-term partial gravity, i.e., gravitational acceleration < 1 g, achieved by quasiparabolic flight maneuvers of an aircraft. The bioconvective responses of T. thermophila were assessed by observing the collective motion simultaneously in two separate scales, which we call macroscale and microscale, using a newly designed "dual-objective" device with two different magnifications. Microscale analysis revealed that the magnitude of gravikinesis, i.e., active regulation of the propulsive thrust, decreased almost linearly with changes in gravitational acceleration, while gravitactic characteristics, assessed by the distribution of the swimming direction, did not change significantly during partial gravity. Macroscale analysis demonstrated that downward plumes of convection pattern gradually shortened from the lower end, and disappeared under partial gravity. The sustained time of the plumes decreased almost linearly with changes in gravitational acceleration. The response of downward plumes to partial gravity may be attributable to the accumulation of cells into blobs in downward migration, which increases the rate of downward migration enough to exceed the rate of upward movement, which is enhanced due to gravikinesis. This suggests that gravity may act on cells involved in collective pattern formation differently than on free-swimming cells.

Subcooled flow boiling in horizontal and vertical macro-channel under Earth-gravity and hyper-gravity conditions

This is an experimental study on highly subcooled flow boiling of water for assessing the effect of gravitational acceleration on flow boiling heat transfer. The experiments are conducted in a macro-channel 3 mm high, 40 mm wide and 120 mm long at water mass fluxes of 330, 630 and 830 kg/m2 s and heat fluxes in the range 200–900 kW/m2. Increased gravitational accelerations, from 1.8 to 9 times the Earth-gravity are achieved with the use of a ∼3 m radius centrifuge (Large Diameter Centrifuge, ESTEC/European Space Agency). Two distinct channel inclinations are examined; horizontal, where the gravitational acceleration is normal to the boiling surface, and vertical, where the gravitational acceleration is parallel to the boiling surface and opposite to flow direction. Experiments at hyper-gravity conditions show that for the horizontal channel inclination, flow boiling heat transfer coefficient increases, whereas for the vertical channel inclination it decreases. The observed deviations lie approximately between +15% and −40% from the Earth-g value. An interpretation of the present results is attempted based on the effect of liquid-phase natural and forced convection combined with the effect of buoyancy at vapor bubbles. The tendency of the heat transfer coefficient experimental data with respect to changes in gravitational acceleration allows the development of a gravity-modified version of the well-known two phase model of Liu-Winterton, by incorporating a linearly dependent gravity multiplier.

Microelectromechanical system gravimeters as a new tool for gravity imaging.

A microelectromechanical system (MEMS) gravimeter has been manufactured with a sensitivity of 40 ppb in an integration time of 1 s. This sensor has been used to measure the Earth tides: the elastic deformation of the globe due to tidal forces. No such measurement has been demonstrated before now with a MEMS gravimeter. Since this measurement, the gravimeter has been miniaturized and tested in the field. Measurements of the free-air and Bouguer effects have been demonstrated by monitoring the change in gravitational acceleration measured while going up and down a lift shaft of 20.7 m, and up and down a local hill of 275 m. These tests demonstrate that the device has the potential to be a useful field-portable instrument. The development of an even smaller device is underway, with a total package size similar to that of a smartphone.This article is part of a discussion meeting issue 'The promises of gravitational-wave astronomy'.

Field Tests of a Portable MEMS Gravimeter.

Gravimeters are used to measure density anomalies under the ground. They are applied in many different fields from volcanology to oil and gas exploration, but present commercial systems are costly and massive. A new type of gravity sensor has been developed that utilises the same fabrication methods as those used to make mobile phone accelerometers. In this study, we describe the first results of a field-portable microelectromechanical system (MEMS) gravimeter. The stability of the gravimeter is demonstrated through undertaking a multi-day measurement with a standard deviation of ms. It is then demonstrated that a change in gravitational acceleration of ms can be measured as the device is moved between the top and the bottom of a 20.7 m lift shaft with a signal-to-noise ratio (SNR) of 14.25. Finally, the device is demonstrated to be stable in a more harsh environment: a ms gravity variation is measured between the top and bottom of a 275-m hill with an SNR of 15.88. These initial field-tests are an important step towards a chip-sized gravity sensor.

Cell Wall Assembly and Intracellular Trafficking in Plant Cells Are Directly Affected by Changes in the Magnitude of Gravitational Acceleration

Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of gravity on the metabolism and cellular functioning of non-specialized plant cells, we investigated a rapidly growing plant cell devoid of known statoliths and without gravitropic behavior, the pollen tube. The effects of hyper-gravity and omnidirectional exposure to gravity on intracellular trafficking and on cell wall assembly were assessed in Camellia pollen tubes, a model system with highly reproducible growth behavior in vitro. Using an epi-fluorescence microscope mounted on the Large Diameter Centrifuge at the European Space Agency, we were able to demonstrate that vesicular trafficking is reduced under hyper-gravity conditions. Immuno-cytochemistry confirmed that both in hyper and omnidirectional gravity conditions, the characteristic spatial profiles of cellulose and callose distribution in the pollen tube wall were altered, in accordance with a dose-dependent effect on pollen tube diameter. Our findings suggest that in response to gravity induced stress, the pollen tube responds by modifying cell wall assembly to compensate for the altered mechanical load. The effect was reversible within few minutes demonstrating that the pollen tube is able to quickly adapt to changing stress conditions.

Optical levitation of a droplet under a linear increase in gravitational acceleration

The optical levitation of a liquid droplet in the gas phase was investigated under a time-dependent change in the gravitational acceleration in an airplane following a specific flight profile. Through multiple trials under a linear increase in effective gravitational acceleration, we performed an experiment on the optical trapping of a droplet from 0.3 g 0 to 0.9 g 0, where g 0 = 9.8 m/s 2. During this change in the effective gravitational acceleration, the trapping position of a droplet with a radius of 14 μm was found to be lowered by ca. 100 μm. The essential feature of the change in the trapping position was reproduced by a theoretical calculation under the framework of ray optics. To the best of our knowledge, this study is the first to report on optical levitation under a time-dependent gravitational change.

A study of annular flow film characteristics in microgravity and hypergravity conditions

Annular flow is an important flow regime in many industrial applications. The need for a better understanding of this flow regime is driven by the desire to improve the design of many terrestrial and space-based systems. Gravity is a complicating factor in the studies and modeling of two-phase flows on earth. Experimental data on the annular flow film characteristics was collected in microgravity aboard the Novespace Zero-G Airbus microgravity simulator. The gravitational effect on the film thickness characteristics was examined by collecting data using an air-water mixture during the microgravity and pull-up (hypergravity) portions of each parabolic flight. Previously reported trends in annular flow average film thickness values for normal gravity are observed in microgravity and hypergravity conditions. The change in gravitational acceleration has little effect on the average film thickness and the film thickness time trace. However, the wave characteristics vary significantly.

Normal and microgravity experiment of oscillating lifted flames in coflow

Characteristics of oscillating lifted flames in coflow have been investigated experimentally with highly diluted propane in both normal gravities and microgravities to elucidate the oscillation mechanism. In normal gravity, oscillating lifted flames with the frequency of 2–5 Hz were observed in a certain range of fuel mole fraction and jet velocity for the jet Reynolds number smaller than 100. The oscillation frequency in terms of the Strouhal number, defined in terms of the stoichiometric laminar burning velocity, correlated well with jet velocity. This demonstrated the importance of the propagation characteristics of tribrachial flames at the base of lifted flames in the flame oscillation Microgravity experiments have been conducted after the oscillating lifted flames were stabilized in normal gravity. During the change in gravitational acceleration, the flames rapidly stabilized as nozzle attached flames and became stationary. This behavior confirmed that the lifted flame oscillation in normal gravity is due to the buoyancy driven instability. Numerical simulation has also been performed accounting the change in gravitational acceleration. The results successfully predicted the transition behavior from oscillating lifted flame in normal gravity to stationary nozzle attached flame in microgravity and the variation of flame shapes during the transition.

Inhibitory effect of hypergravity on photosynthetic carbon dioxide fixation in Euglena gracilis

Photosynthesis, the conversion of light energy into chemical energy, is a critical biological process, whereby plants synthesize carbohydrates from light, carbon dioxide (CO2) and water. The influence of gravity on this biological process, however, is not well understood. Thus, centrifugation was used to alter the gravity environment of Euglena gracilis grown on nutritive agar plates illuminated with red and blue light emitting diodes. The results showed that hypergravity (up to 10xg) had an inhibitory effect on photosynthetic CO2 fixation. Chlorophyll accumulation per cell was essentially unaffected by treatment; however, Chl a/Chl b ratios decreased in hypergravity when compared to 1xg controls. Photosynthesis in Euglena appears to have limited tolerance for even moderate changes in gravitational acceleration.

The kinetics of translocation and cellular quantity of protein kinase C in human leukocytes are modified during spaceflight.

Protein kinase C (PKC) is a family of serine/threonine kinases that play an important role in mediating intracellular signal transduction in eukaryotes. U937 cells were exposed to microgravity during a space shuttle flight and stimulated with a radiolabeled phorbol ester ([3H]PDBu) to both specifically label and activate translocation of PKC from the cytosol to the particulate fraction of the cell. Although significant translocation of PKC occurred at all g levels, the kinetics of translocation in flight were significantly different from those on the ground. In addition, the total quantity of [3H]PDBu binding PKC was increased in flight compared to cells at 1 g on the ground, whereas the quantity in hypergravity (1.4 g) was decreased with respect to 1 g. Similarly, in purified human peripheral blood T cells the quantity of PKCdelta varied in inverse proportion to the g level for some experimental treatments. In addition to these novel findings, the results confirm earlier studies which showed that PKC is sensitive to changes in gravitational acceleration. The mechanisms of cellular gravisensitivity are poorly understood but the demonstrated sensitivity of PKC to this stimulus provides us with a useful means of measuring the effect of altered gravity levels on early cell activation events.

Theoretical tides on a rigid, spherical moon

Theoretical tidal tilts and changes in gravitational acceleration make possible the determination of gross physical properties of the moon