Microgravity Science and Technology

Hashim, Ishak; Arifin, Norihan Md

doi: 10.1007/bf02870973pmid: N/A

We obtain explicit analytical expressions for the linear growth rates of the steady Bénard-Marangoni convection in a horizontal layer of electrically-conducting fluid with a deformable free upper surface in the presence of a uniform vertical magnetic field subjected to a constant temperature at its lower boundary. The leading order behavior of the marginal stability curve for the onset of steady Bénard-Marangoni convection is also given. The numerically-calculated linear growth rates showing the stabilizing effect of the magnetic field are presented.

Acero, F. J.; Ferrera, C.; Cabezas, M. G.; Montanero, J. M.

doi: 10.1007/bf02870975pmid: N/A

The equilibrium shape of a liquid bridge confined between two parallel solid supports of arbitrary shape is analyzed theoretically. The influence of the shape of the solid supports, the volume of the liquid bridge and the axial, lateral, and centrifugal forces acting on it are considered. The theoretical study is performed using three different techniques: (i) a numerical process for the minimization of the free energy associated with the fluid configuration, (ii) a second-order analytical expansion around the cylindrical solution to the Young-Laplace equation, and (iii) a finite-difference scheme to numerically integrate the Young-Laplace equation. The two numerical methods are in excellent agreement, indicating the degree of accuracy of the calculations, and there is also good agreement between the analytical expansion and the numerical solutions for moderately large values of the perturbation parameters.

Chacha, M.; Saghir, M. Z.; Viviani, A.

doi: 10.1007/bf02870976pmid: N/A

The phenomenon of mass flux in a mixture due to a temperature gradient is known as the Soret effect. Accurate experimental and theoretical models are needed for a better understanding and effective characterisation of situations involving coupled transport processes as in hydrocarbon reservoirs. This requires precise knowledge of the transport coefficients particularly the Fick and Soret diffusion coefficients. We have investigated the effect of residual-g and (very) low-frequency g-jitters encountered on-board spacecraft FOTON on mass-thermo-fluid dynamics in the presence of Soret effect. Results revealed that the diffusion process is slightly affected by the g-jitter on board the FOTON platform, which indicates that FOTON is a good platform to conduct near perfect microgravity environment.

Meissner, Klaus; Hanke, Wolfgang

doi: 10.1007/bf02870977pmid: N/A

The functional properties of neuronal tissue critically depend on cellular composition and intercellular comunication. A basic principle of such communication found in various types of neurons is the generation of action potentials (APs). These APs depend on the presence of voltage gated ion channels and propagate along cellular processes (e.g. axons) towards target neurons or other cells. It has already been shown that the properties of ion channels depend on gravity. To discover whether the properties of APs also depend on gravity, we examined the propagation of APs in earthworms (invertebrates) and isolated nerve fibres (i.e. bundles of axons) from earthworms under conditions of micro- and macro-gravity. In a second set of experiments we could verify our results on rat axons (vertebrates). Our experiments carried out during two parabolic flight campaigns revealed that microgravity slows AP propagation velocity and macrogravity accelerates the transmission of action potentials. The relevance for live-science related questions is considerable, taking into account that altered gravity conditions might affect AP velocity in man during space flight missions.