ALBERT

Description: MicroRNA (miRNA) is a non-coding small RNA composed of 20 to 24 nucleotides that influences plant root development. This study analyzed the miRNA expression in Arabidopsis root tip cells using Illumina sequencing and real-time PCR before (sample 0) and 15 min after (sample 15) a 3-D clinostat rotational treatment was administered. After stimulation was performed, the expression levels of seven miRNA genes, including Arabidopsis miR160, miR161, miR394, miR402, miR403, miR408, and miR823, were significantly upregulated. Illumina sequencing results also revealed two novel miRNAsthat have not been previously reported, The target genes of these miRNAs included pentatricopeptide repeat-containing protein and diadenosine tetraphosphate hydrolase. An overexpression vector of Arabidopsis miR408 was constructed and transferred to Arabidopsis plant. The roots of plants over expressing miR408 exhibited a slower reorientation upon gravistimulation in comparison with those of wild-type. This result indicate that miR408 could play a role in root gravitropic response.

Description: Gravitropism in plants is one of the most controversial issues. In the most wildly accepted starch-statolith hypothesis the sedimentation movement of amyloplasts in the gravisensing columella cells primarily triggers the asymmetric distribution of auxin which leads to the differential growth of the plant root. It has been gradually recognized that the inhomogeneous structures in statocytes arising from intracellular components such as cytoskeletons significantly affect the complex movements of amyloplasts and the final gravimorphogenesis. In this letter, we implement a diffusive dynamics measurement and inplanta microrheological analysis of amyloplasts in the wild-type plants and actin cytoskeleton mutants for the first time. We found that the intracellular environment of columella cells exhibits the spatial heterogeneity and the cage-confinement on amyloplasts which is the typically characteristics in colloidal suspensions. By comparing the distinct diffusive dynamics of amyloplasts in different types of plants with the behaviors of colloidal systems in different states, we quantitatively characterized the influence of the actin organization dominated intracellular envoronments on the amyloplast movements. Furthermore, the cage-confinement strength was measured by calculating the spatial fluctuation of local apparent viscosity within the columella cells. Finally, a linear association between the initial mechanical stimulation in the columella cells the subsequent intercellular signal transduction and the final gravity response was observed and a possible gravity sensing mechanism was suggested. It suggests the existence of a potential gravity-sensing mechanism that dictates a linear frustration effect of the actin cytoskeleton on the conversion of the mechanical stimulation of amyloplasts into gravitropic signals.

Description: Clinostats and centrifuges are widely used to create simulated microgravity or hypergravity, respectively, in order to study the impact of gravity on biosystems. Here, we used a clinostat and a centrifuge in alternating modes of operation in order to create a simulated parabolic flight like g -profile. To our knowledge, it is the first time that both devices were run in connection. In order to test the method, we investigated the production of reactive oxygen species of immune cells (macrophages) during oxidative burst in an on-line kinetic approach, which has been extensively studied under real (parabolic flight) and simulated microgravity (clinostat) as well as under hypergravity conditions (centrifuge). Our results indicate that clinostat and centrifuge can be operated in an alternating way to simulate the repetitive changes of gravity during parabolic flight. Although the switch from one gravity level to the other could not be carried out as quickly as it takes place during actual parabolic flight due to technical and operational reasons, it can be concluded that running experiments in a clinostat aboard a centrifuge on ground are suitable for studying gravity-related phenomena.

Description: Ground-Based Facilities (GBF) are essetial tools to understand the physical and biological effects of the absence of gravity and they are necessary to prepare and complement space experiments. It has been shown previously that a real microgravity environment induces the dissociation of cell proliferation from cell growth in seedling root meristems, which are limited populations of proliferating cells. Plant cell cultures are large and homogeneous populations of proliferating cells, so that they are a convenient model to study the effects of altered gravity on cellular mechanisms regulating cell proliferation and associated cell growth. Cell suspension cultures of the Arabidopsis thaliana cell line MM2d were exposed to four altered gravity and magnetic field environments in a magnetic levitation facility for 3 hours, including two simulated microgravity and Mars-like gravity levels obtained with different magnetic field intensities. Samples were processed either by quick freezing, to be used in flow cytometry for cell cycle studies, or by chemical fixation for microscopy techniques to measure parameters of the nucleolus. Although the trend of the results was the same as those obtained in real microgravity on meristems (increased cell proliferation and decreased cell growth), we provide a technical discussion in the context of validation of proper conditions to achieve true cell levitation inside a levitating droplet. We conclude that the use of magnetic levitation as a simulated microgravity GBF for cell suspension cultures is not recommended.

Description: Research on Artificial Gravity (AG) created by linear acceleration or centrifugation has a long history and could significantly contribute to realize long-term human spaceflight in the future. Employing centrifuges plays a prominent role in human physiology and gravitational biology. This article gives a short review about the background of Artificial Gravity with respect to hypergravity (including partial gravity) and provides information about actual ESA ground-based facilities for research on a variety of biosystems such as cells, plants, animals or, particularly, humans.

Description: Microgravity represents an adverse abiotic environment, which causes rearrangements in cellular organelles and changes in the energy metabolism of cells. Plastids and mitochondria are two subcellular energy organelles that are responsible for major metabolic processes, including photosynthesis, oxidative phosphorylation, ß -oxidation, and the tricarboxylic acid cycle. In our previous study performed on board the Chinese spacecraft SZ-8, we evaluated the global changes exerted by microgravity on the proteome of Arabidopsis thaliana cell cultures by comparing the microgravity-exposed samples with the controls either under 1 g centrifugation in space or 1 g ground conditions. Here, we report additional data from this space experiment that highlights the plastid and mitochondria proteins that responded to space flight conditions. We observed that 43 plastidial proteins and 50 mitochondrial proteins changed their abundances under microgravity in space. The major changes in both plastids and mitochondria involved proteins that functions in a suite of redox antioxidant and metabolic pathways. These results suggested that these antioxidant and metabolic changes in plastids and mitochondria could be important components of the adaptive strategy in plants subjected to microgravity in space.

Description: Owing to the development of the space exploration activities, the in-orbit management of fluids such as the transportation of propellant liquid in microgravity becomes the important direction of microgravity fluid research, and one of main problems is the stability behaviors of free surface flow in capillary channel of PMD. In the present study, an experiment set-up of the fluid transport with two different capillary channels has been developed on the Beijing Drop Tower platform. Both symmetrical and asymmetrical flow channels, with the same cross-sectional areas and lengths and different cross-sectional geometries were used and HFE-7500 is chosen as test liquid. 10 times of the drop-down experiments were performed for investigation of the capillary flow characters in different volumetric flow rates, and the three main patterns of capillary flows: subcritical flow, critical flow and supercritical flow were found in experiments, these patterns are distinguished by the movement of the point of lowest surface over time. Meanwhile, the critical flow rates at which free surface becomes instable observed in our experiments are (1) 2.7 ±0.2ml/s for the critical flow rate of asymmetrical channel; and (2) 2.2 ±0.2ml/s for symmetrical channel flow, respectively.

Description: The present work attempts to model the case of combined gravitational and capillary motion of condensate for an axisymmetric fin under steady and transient fin operation conditions. The focus here is to examine the structure of the mathematical problem and to develop suitable numerical techniques rather than yield information on the macroscopic condensate flow rate and fin efficiency. The problem is formulated starting from general conditions and is simplified step by step by introducing corresponding assumptions. The particular fin shape of a paraboloid from revolution is chosen and the equations are properly non-dimensionalized. A vast reduction of the number of problem parameters is achieved in this way. The cases of isothermal fin, steady state operation and dynamic operation are treated separately using specialized numerical solution techniques developed for each case in order to improve computational efficiency and accuracy. Typical results of fin temperature and condensate film thickness are presented and discussed.

Description: Thermocapillary convection has always been a hot topic of great importance in either crystal growth or thin films science. A space experiment about thermocapillary convection in an open cylindrical annuli pool will be done on SJ-10 satellite. A payload for space experiment has been established, which includes a cylindrical annuli thermocapillary convection system, a thermocouple temperature controlling system and measurement system, a thermal infrared imager, a high-precision displacement sensor, and an experiment controlling system. Some experiments have been done on the ground in order to compare with the results of space experiment. Some results from the ground experiment are shown, such as temperature oscillation, surface oscillation, and flow pattern transfer.

Description: The work reports some new experimental and theoretical results regarding the abnormal behaviors of liquid flows taking place in a thin liquid wedge situated under an as symmetric temperature gradient. These experimental results, obtained using particle image velocimetry (PIV) technique, are additional to those having been reported previously by the same research group. More specifically, a tangential directional flow can be induced when a sufficiently thin liquid wedge confined in two fluidic interfaces is heated or cooled at a point. The flows caused by point heating are in direction toward the thinner region of the liquid wedge whereas those caused by point cooling flow in the opposite direction, toward the thicker region. In theory, these flows are here interpreted as driven by thermodynamic mechanisms rather than by usual thermo-capillary effects. Theoretical results show that the presence of the flow is necessary for such a point-heated/cooled liquid wedge to evolve toward the minimum of interfacial energy. Under the free-force boundary conditions, the flow velocity predicted in theory is in good agreement with the experimental data in direction, scale of order, and variation behaviors with changing experimental conditions.

Description: Deployable aerobrakes for Earth re-entry capsules may offer many advantages in the near future, including the opportunity to recover on Earth scientific payloads from the Space with reduced risks and costs with respect to conventional systems. Such capsules can be accommodated in the selected launcher in folded configuration optimizing the available volume and, when planned by the mission profile, the aerobrake can be deployed in order to increase the surface exposed to the hypersonic flow and therefore to reduce the ballistic parameter. This can offer as main advantage the opportunity to perform an aerodynamic de-orbit of the system without the need of a dedicated propulsive subsystem and an atmospheric re-entry with reduced aerothermal and mechanical loads making possible the use of relatively lightweight and cheap thermal protection system materials. To ensure the recovery of the capsule, the deployable surface can be modulated to obtain the aerodynamic control of the de-orbit trajectory in order to correctly target the capsule towards the selected landing site for post-flight analyses and operations. The main objective of the work is to present a number of feasible mission profiles for orbital platforms to/from Low Earth Orbit aimed in particular at scientific experiments in microgravity conditions. In addition, a suborbital scenario for a technological demonstrator, useful to experimentally verify the system applicability before the design of orbital missions, is also presented and discussed.

Description: The geometry of the packing structure can affect the flow pattern and considerably influence the mass transfer efficiency between liquid film and gas phase. Therefore, it is necessary to investigate the flow patterns and factors that determine the efficiency of mass transfer and heat transfer. In this study, different packing structures, namely, sinusoidal, triangular, and rectangular corrugated plates, are investigated. Computational fluid dynamic simulations based on the volume-of-fluid method are performed by using the open-source software OpenFOAM to study the liquid film flow over these corrugation plates. The free-surface area between the liquid and gas has been found to reach its maximum when the resonance phenomenon occurs. According to the simulation results the triangular corrugated plate has the largest free-surface area among the three types under the same conditions for a certain Reynolds number. The results also indicated that the pattern of film flow on the sinusoidal and triangular corrugated plates is similar; the rectangular type is not good as the other two types. It is useful to choose a suitable packing structure when considering the manufacturing process and cost The research results provide a theoretical basis for the study of heat and mass transfer used in industry applications.

Description: This paper introduces the GeoFlow missions that were performed under microgravity conditions on board the Columbus Laboratory in the International Space Station (ISS) from the scientific operations standpoint. A brief introduction to the three GeoFlow experiments: GeoFlow, GeoFlow-2 and GeoFlow-2b is given, being their main purpose to capture some essential features of the Earth mantle convection. The major scientific requirements of each of the experiments are presented as an introduction for the scientific operations preparation and concept development description. Then, the activities performed in order to execute each of the experiments are presented in detail, focusing on the resolution of the several issues encountered during the mission. The outcomes and lessons learned from such long and complex missions close this paper.

Description: A three-dimensional VOSET method is used along with the adaptive mesh refinement (AMR) method to simulate the behaviors of a bubble departing from the outside wall of a horizontal square-cross-section tube in microgravity under the influence of nonuniform electric fields. The effects of gravity, electric field intensity, fluid permittivity, and bubble initial position on the bubble detachment and rising are investigated and analyzed. Computational results show that the gravity and electric fields have significant influences on the bubble detachment and rising velocity and rising trajectory. Decrease in gravity results in the decrease in the buoyancy exerted on the bubble, considerably mitigating the rising capability of the bubble and delaying the bubble detachment. Imposing a nonuniform electric field, which exhibits physically the strongest intensity in regions near the tube wall, can supply an additional driving force as a replacement of the buoyancy to accelerate the bubble detachment and rising. It is also shown that a larger electric field intensity or larger ratio of liquid permittivity to gas permittivity leads to a larger deformation, easier detachment, and larger rising velocity, of the bubble. The nonuniformity of the electric fields can also affect the bubble motion trajectory and result in the asymmetric deformation of the bubble.

Description: Ground-based simulators of microgravity such as fast rotating 2-D clinostats are valuable tools to study gravity related processes. We describe here a versatile g -value-adjustable 2-D clinostat that is suitable for plant analysis. To avoid seedling adaptation to 1 g after clinorotation, we designed chambers that allow rapid fixation. A detailed protocol for fixation, RNA isolation and the analysis of selected genes is described. Using this clinostat we show that mRNA levels of LONG HYPOCOTYL 5 (HY5), MIZU-KUSSEI 1 (MIZ1) and microRNA MIR163 are down-regulated in 5-day-old Arabidopsis thaliana roots after 3 min and 6 min of clinorotation using a maximal reduced g -force of 0.02 g , hence demonstrating that this 2-D clinostat enables the characterization of early transcriptomic events during root response to microgravity. We further show that this 2-D clinostat is able to compensate the action of gravitational force as both gravitropic-dependent statolith sedimentation and subsequent auxin redistribution (monitoring D R 5 r e v :: G F P reporter) are abolished when plants are clinorotated. Our results demonstrate that 2-D clinostats equipped with interchangeable growth chambers and tunable rotation velocity are suitable for studying how plants perceive and respond to simulated microgravity.

Description: An experimental study on ignition and combustion of single coal particles under different O 2 concentrations was conducted at both normal (1-g) and microgravity ( μ -g) in the first time. The surface and centre temperatures of the bituminous coal particle with initial diameter of ∼ 2.0mm were measured by the monochromatic imaging technique using a short wavelength infrared (SWIR) camera and an embedded fine thermocouple respectively. Results revealed that at μ -g, ignition of the tested coal particles was homogeneous. O 2 concentration significantly affects the shape, ignition temperature and ignition delay time of the volatile flames. A mathematical model considering thermal conduction inside the coal particle was developed to describe the ignition process of single particle, adopting the volatile matter flammability limit as the homogeneous ignition criterion. The predicted ignition temperatures were slightly lower but closer to μ -g data. And the predicted variation trends of ignition temperature and delay time under different O 2 concentrations agreed well with the μ -g experimental results.

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper provides an historical perspective of the involvement of Prof. J.C. Legros in microgravity research during aircraft parabolic flights. Prof. Legros conducted 27 experiments during 33 campaign of microgravity research organised by the European Space Agency. Nearly all fields of fluid physics were investigated in microgravity by this indefatigable scientist. This paper gives a non-exhaustive summary of some experiments conducted by Prof. Legros during these 33 campaigns.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Although several researches have reported potential gender differences in adaptations during microgravity, the musculoskeletal alterations of different genders are still under debate. Besides, there were few researches which involved recovery phase after reloading. In the present study, we investigated the musculoskeletal alterations of rats hindlimb via tail-suspension in both genders, and analyzed the serum sex hormone at the same time. Thirty-two Sprague Dawley rats were equally divided by gender into four groups randomly: control of male (CONM), tail-suspension of male (TSM), control of female (CONF) and tail-suspension of female (TSF). The experiment consisted two phases, which were 21 days of tail suspension phase and 21 days’ reloading phase, and parameters of bone, muscle and serum were tested at the end point of each phase. The results indicated that during tail suspension phase, male rats showed a greater and earlier bone loss and microstructure deterioration compared with females, but they could maintain muscle strength much better. In addition, during reloading phase, male rats showed a slower bone recovery and some parameters could not recover until the end, while loss in muscle mass and strength in both genders could recover to control level.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The regimes of joint flows of the evaporating liquid and vapor-gas mixture in a 3D rectangular channel are studied with the help of a partially invariant solution for the convection equations. The effects of thermodiffusion and diffusive thermal conductivity in the gas–vapor phase are additionally taken into account in the governing equations and under interface conditions. A numerical simulation of the 3D fluid flows is carried out for the liquid–gas system like ethanol–nitrogen and HFE-7100–nitrogen under microgravity conditions. The influence of the thermal load, liquid layer thickness and heat-transfer liquid type on the structure of the fluid flows and evaporation characteristics is investigated. The solution allows one to describe the formation of longitudinal thermocapillary rolls observed in the experiments. The evaporative mass flow rate depends essentially on the thermophysical properties of the working liquid. Spatial size and a shape of thermal patterns are determined by the applied thermal load and they can be varied with the change in the liquid layer thickness. Topological structure of the flows (double or quadruple vortex composition) is defined by the combined influence of the thermocapillary and convective mechanisms and phase transition effects. The results discussed in the paper provide motivation for the development of a classification of the 3D flow regimes similar to the Napolitano’s classification for 2D flows.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Microgravity and vacuum are two main environments in outer space. In the microgravity environment, vibration is a typical phenomenon, and it will induce a reciprocating sliding contact between a journal and a bearing in a clearance joint. In vacuum environment, the adhesion effects are severe, and the friction forces are much higher than the ground environment. Nanoscale textures can reduce the contact area and trap the wear particles, which are beneficial to the friction reduction. Most of the current studies focus on the single-pass sliding contact. Actually, considering the roughness of the contact surfaces, a multi-asperity tip should be more reasonable. In this paper, vibration induced reciprocating sliding contacts between nanoscale multi-asperity tips and a textured surface are investigated using a multiscale method, and the material is FCC copper. Six rigid tips are modelled with different cylindrical asperities and slid on the textured surface. Corresponding to the tips, the average friction forces are compared, and the effects of the tip radii are analyzed. The total average friction forces of the textured surface are compared with the case of a smooth surface, and the mechanism of the friction reduction is discussed. The results showed that the total average friction forces decrease as the increase of the asperity radii, and the textured surface can reduce friction forces effectively compared with the smooth surface. This work could contribute to reducing friction by designing the tip and the textured surface in vibration induced reciprocating sliding contacts under microgravity, which will be beneficial to prolong the life of components on the spacecraft.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Analysis of three different equations of state suitable for describing fluids near the thermodynamic critical point is performed. Numerical simulation of the piston effect (adiabatic heating) with the use of the equations of state is carried out. The range of temperature distances to the critical point in which the calculated time of the piston effect is equal to the analytical time is defined. The reasons of discrepancy between the calculated and analytical times of the piston effect beyond the range defined is discussed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, a linear stability analysis is performed for both monotonic and oscillatory modes within a horizontal polymer solution layer, which solely the solvent evaporates into air. The approach is based on general thermodynamic principles and also on the physics of the gas phase and its interactions with the liquid phase. Due to evaporation, the solvent mass fraction changes and cooling occurs at the liquid-gas interface. This can trigger solutal and thermal Rayleigh-Bénard-Marangoni instabilities in the system. For the monotonic mode, the effects of composition dependent diffusion coefficient and dynamic viscosity on the onset of Rayleigh-Bénard-Marangoni convection are studied. Moreover, the effect of different total heights of the liquid-gas system on the behavior of convection onset is considered. The results show that a variable diffusion coefficient and a variable viscosity can notably change the onset of instability for a polyisobutylene (PIB)/toluene solution. Our model for the monotonic mode is also satisfactorily compared with an experimental study. For the oscillatory mode, where the relaxation time is also composition dependent, we observe that very thin layers will be susceptible to an oscillatory instability when drying occurs in the system. Finally, an approximate model is derived exploiting the fact that the solutal Marangoni is by far the most dominant instability mechanism here. A negligible difference with respect to the full model confirms the predominance of the solutal Marangoni mechanism.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We use a lubrication-type approach to investigate the dynamics of moving contact lines observed during droplet evaporation in the constrained vapor bubble experimental set-up. The effects of capillarity, viscous flow, and disjoining pressure are considered, while gravity is neglected. The disjoining pressure is described by a two-component model. Direct comparisons to the experimental recordings of receding contact line dynamics for n-butanol in a quartz cuvette are made.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Concentration-induced convection of a binary metal melt in a rectangular crucible has been studied numerically in the case of a mixture with a eutectic phase diagram. The calculations are performed for realistic parameters which correspond to the pair of metals Sn-Pb. A solid rod with non-wettable boundaries and a non-uniform longitudinal temperature distribution on the surface is immersed into the melt vertically at the center of the crucible. The condition of complete non-wetting allows us to consider the interface between the melt and the rod to be free. The temperature non-uniformity leads to inhomogeneity of the surface tension. As a result, the thermocapillary force generates a steady convective flow first on the surface of the rod and then in the volume. Due to this motion, the heavy component of the alloy is transferred along the rod’s surface to the butt-end. At the boundary patches with the excess of concentration it has been extracted into the volume by means of the desorption mechanism. In the presence of weak convection in the volume, this component is partially accumulated near the bottom of the crucible under the butt-end. Thus, there takes place a process of separation of heavy admixture for the two-component metal melts.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Liquid degassing takes place in several space processes (cooling and lubrication of hardware, combustion of liquid propellants etc.) during launching and re-orbiting of rockets and workstations. The present work studies the effect of hypergravity acceleration on the two phase flow that is developed during the degassing of a liquid jet. Liquid is initially saturated with dissolved gas at 200 kPa and 400 kPa and is then injected at the bottom of a liquid column having its top open to atmospheric pressure. Due to the sudden decompression inside the column, the liquid jet becomes supersaturated with dissolved gas, thus triggering the formation of degassing bubbles within its volume. The local liquid flow pattern inside the column is tracked by recording the motion of bubbles. Experiments are conducted at 1 g, 2 g and 8 g accelerations, using the Large Diameter Centrifuge (LDC) facility of the Technology Center (ESTEC) of the European Space Agency (ESA). The liquid flow behavior registered at varying hypergavity conditions is quite interesting. For an injection pressure of 200 kPa the liquid velocity magnitude increases with acceleration level possibly because of the inertial shear force. Increasing the injection pressure to 400 kPa, not only the magnitude, but also the direction of liquid velocity varies possibly due to the larger effect of Coriolis force induced by the increased liquid velocities.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The capillary driven seepage in porous media under microgravity conditions is investigated. Experiments on the flow of a liquid in an inhomogeneous artificial porous medium are presented. A non-stationary mathematical model of the flow of a multiphase fluid in a sample of a porous medium is described. The experimental data are compared with the results of a three-dimensional numerical simulation of the multiphase seepage process. The behavior of the imbibition front when passing through a boundary of medias with different permeability is investigated.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉One cause of thrombocytopenia in astronauts after spaceflight is decreased platelet production. To increase our understanding of thrombopoiesis in humans while in space, we investigated the effects of simulated microgravity, achieved using a random positioning machine (RPM), on megakaryoblastic cells (MEG-01 cell line). Exposure of MEG-01 cells to simulated microgravity for up to one week significantly increased cellular apoptosis compared to the static group (1 g-control). Flow cytometry analysis of the cell cycle revealed a significant increase in the percentage of cells in the G0/G1 phase after one week of RPM-exposure compared to the static group. Additionally, after one week, a difference in morphology was detected between the cells of the static group and the cells exposed to microgravity conditions. The expression of the CD33 surface marker was significantly decreased after a one week of microgravity exposure compared to the 1 g-control. We, therefore, concluded that in MEG-01 cells, simulated microgravity induces apoptosis, inhibits cell cycle progression of cells from G0/G1 into S phase, decreases cell proliferation, and decreases the expression of surface markers. We believe that, with insufficient physiological compensation, these changes under microgravity conditions may lead to disorders of megakaryocytes differentiation and/or decreased platelet production. It should also be noted that the human cell line MEG-01 could be a useful model for studying the effects of simulated microgravity on platelet production because of their ability to generate platelet-like particles.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉An influence of a spatial temperature modulation of the heat release/consumption at the interface on nonlinear convective flows in the 47v2 silicone oil - water system, has been investigated. Two types of boundary conditions on lateral walls: periodic boundary conditions corresponding to laterally infinite two-layer system and rigid heat-insulated lateral walls corresponding to the closed cavity, have been considered. It is shown that the spatial modulation can change the sequence of bifurcations and lead to the appearance of new oscillatory regimes. Specifically, pulsating traveling waves changing the direction of propagation, as well as regimes corresponding to period doubling, period-four and period-eight bifurcations, have been obtained.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The model of water vapor condensation on a composite V-shaped surface with multi wettability gradients was built and the condensation process with different gravity was studied by molecular dynamics to find out whether this model could control the condensation mode and accelerate the condensate drainage from the micro-perspective. With the absence of gravity, the simulation results indicated that the condensation mode could be controlled as a dropwise condensation. What’s more, the movement of condensate nano-droplet also could be controlled, which was helpful for increasing the efficiency of condensate drainage. The temperature of hot wall was largest while it was smallest for cold wall. The temperature of water was in the middle. The result was in accordance with the law of energy conservation. However, the condensation process was different with the effect of gravity. It can be concluded that the condensation process was much quicker with greater gravity, leading to the larger condensation rate. The temperature of cold wall and water were larger than that of hot wall, especially for greater gravity. It was because the part of energy generated by gravity transferred to the thermal energy of water and cold wall, and the other part transferred to the kinetic energy of water. The gravitational potential energy and kinetic energy increased with greater gravity, while the thermal energy increased first and then decreased, corresponding well with the final temperature of condensation process with different gravity. The results will provide a microcosmic mechanism for space experiment and guidance for space system drainage.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The influence of gravity (including 0 G, 0.16 G, 0.38 G, 1 G and 1.8 G) on the antisolvent crystallization of 〈em〉L〈/em〉-histidine was investigated in a self-designed micro-channel crystallizer on a zero-G flight, which was successfully launched on June 13th, 2018. The stable form of 〈em〉L〈/em〉-histidine was obtained under microgravity, while only the metastable form can be observed in the ground experiments with the same inlet conditions. The possible reason is the extremely ordered flow field of the system in microgravity environment. A large amount of small particles aggregated at 1.8 G due to the enhanced micromixing, which favors nucleation. Bigger particles crystalized at Moon gravity (0.16 G) without the excessive consumption of the supersaturation by explosive nucleation and with moderate convection of the system. It is concluded that both nucleation and crystal growth were influenced by the micromixing status in the system due to the altered gravity extent.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper presented a linear-stability analysis on thermocapillary-buoyancy convection in radially heated annular pool filled in 5cSt silicone oil / HT-70 two-layer fluids. The influences of the aspect ratio, radius ratio and thickness ratio on the flow stability were discussed. Results indicate that the system is most unstable when the thickness ratio is close to 0.375. Flow bifurcation appears when the thickness ratio varies from 0.625 to 0.875. Three corresponding destabilization mechanisms were revealed. Effect of buoyancy convection and the upper boundary condition on the flow stability were also analyzed. The upper rigid wall can enhance the flow stability in the annular two-layer system, especially when the thickness ratio is near 0.75. Furthermore, the buoyancy can greatly reduce the flow stability comparing with that under the microgravity condition.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In order to investigate the dynamics of quasi-static bubble formation from a submerged orifice, this paper developed an axisymmetric VOSET method with continuum surface force (CSF) model which can accurately capture the moving phase interface of gas-liquid flow. Test case shows that numerical results are in good agreement with experimental results from the literature. The effects of gas flow rate, orifice size, surface tension, contact angle, liquid density, and gravitational acceleration on bubble shape, departure time and departure volume are investigated and analyzed. It is found that increase in orifice size, surface tension, and contact angle results in the increase in the capillary force resisting bubble detachment, which leads to larger departure time and departure volume. But there is a critical contact angle, and contact angle has no significance effect on the process of bubble formation and detachment, when it is smaller than the critical value. Buoyancy force promoting bubble detachment increases with the increase of liquid density and gravitational acceleration, which results in smaller departure time and departure volume. Also, the forming process of the neck shape of bubble bottom at the bubble detachment stage is observed, and the results show that the position of the smallest part of the neck approximately equals to the orifice radius 〈em〉R〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper reports on a study of bubble motion in a regularly spaced pore structure under microgravity using the lattice Boltzmann method (LBM). Initially, a single bubble’s motion is derived; then the simulation is extended for two-bubble dynamics. By considering a gas-liquid two-phase flow, the interaction force (namely the fluid-fluid cohesive force and fluid-solid adhesive force) is derived using the Shan-Chen model with multicomponent single relaxation. This determines the interaction forces governing a single bubble’s dynamics in the porous structure. Then the primary parameters that influence bubble motion are studied, such as the bubble’s diameter, distance between adjacent cells, arrangement between cells, and the effects of flow-field characteristics on single-bubble motion. The simulation developed for single-bubble motion provides the basis for studying a two-bubble system’s motion trajectory and coalescence behavior. By employing the aforementioned analysis, the proposed approach optimizes porous media’s structural parameters under microgravity, resulting in increased bubble movement speed and an enhanced two-phase flow in porous media.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Lockheed Martin has developed a patented solution for increasing payload power on communications satellites which introduces a coupled East-West radiator assembly with deployable radiators. The deployable radiators are deployed in integration and test phases to provide equipment access. The equipment is mounted onto internal structural panels and is thermally coupled to both east and west radiators by flexible heat pipes which have dual condensers. Coupling to both east and west radiators provides greater average heat dissipation. This application is uniquely demanding for the flexible heat pipes due to heat transport, operating temperatures, pressure cycling and deployment cycling. This paper describes derivation of requirements for the flexible heat pipes for the radiator assembly, and qualification testing to verify that the heat pipe design will work as intended. A structural qualification unit was subjected to thermal cycling, pressure cycling, vibration, flex cycling and ultimately burst testing. The qualification unit was modified following burst test into a single condenser unit. It was then charged and subjected to thermal performance testing. The test results verify that the flexible heat pipe design meets all requirements for the East-West radiator assembly.〈/p〉

Description: The capillary driven flow in cylindrical interior corners satisfying the Concus-Finn condition was investigated under microgravity. The governing equation of capillary driven flow in cylindrical interior corners was established, and the approximate analytical solution was obtained. The relationship between liquid’s front position and time was derived, which was then compared with the results of drop tower experiments and numerical simulation using the FLOW-3D software. The influence of different parameters on the interior corner flow was studied. The results showed that the meniscus height decreased as contact angle increased, and increased as the radius of rounded wall increased. The influence of decreasing the contact angle on a rounded wall was greater than that on a straight wall. Our findings can be referred to designing tanks or choosing the suitable solution in the space fluid management.

Description: Microgravity induces alterations in the functioning of immune cell; however, the underlying mechanisms have not yet been identified. In this study, hemocytes (blood cells) of the blue mussel Mytilus edulis were investigated under altered gravity conditions. The study was conducted on the ground in preparation for the BIOLAB TripleLux-B experiment, which will be performed on the International Space Station (ISS). On-line kinetic measurements of reactive oxygen species (ROS) production during the oxidative burst and thus cellular activity of isolated hemocytes were performed in a photomultiplier (PMT)-clinostat (simulated microgravity) and in the 1 g operation mode of the clinostat in hypergravity on the Short-Arm Human Centrifuge (SAHC) as well as during parabolic flights. In addition to studies with isolated hemocytes, the effect of altered gravity conditions on whole animals was investigated. For this purpose, whole mussels were exposed to hypergravity (1.8 g) on a multi-sample incubator centrifuge (MuSIC) or to simulated microgravity in a submersed clinostat. After exposure for 48 h, hemocytes were taken from the mussels and ROS production was measured under 1 g conditions. The results from the parabolic flights and clinostat studies indicate that mussel hemocytes respond to altered gravity in a fast and reversible manner. Hemocytes (after cryo-conservation) exposed to simulated microgravity ( μ g), as well as fresh hemocytes from clinorotated animals, showed a decrease in ROS production. Measurements during a permanent exposure of hemocytes to hypergravity (SAHC) show a decrease in ROS production. Hemocytes of mussels measured after the centrifugation of whole mussels did not show an influence to the ROS response at all. Hypergravity during parabolic flights led to a decrease but also to an increase in ROS production in isolated hemocytes, whereas the centrifugation of whole mussels did not influence the ROS response at all. This study is a good example how ground-based facility experiments can be used to prepare for an upcoming ISS experiment, in this case the TRIPLE LUX B experiment.

Description: To understand the boiling crisis mechanism, one can take advantage of the slowing down of boiling at high pressures, in the close vicinity of the liquid-vapor critical point of the given fluid. To preserve conventional bubble geometry, such experiments need to be carried out in low gravity. We report here two kinds of saturated boiling experiments. First we discuss the spatial experiments with SF 6 at 46 ∘ C. Next we address two ground-based experiments under magnetic gravity compensation with H 2 at 33 K. We compare both kinds of experiments and show their complementarity. The dry spots under vapor bubbles are visualized by using transparent heaters made with metal oxide films. We evidence two regimes of the dry spots growth: the regime of circular dry spots and the regime of chain coalescence of dry spots that immediately precedes the heater dryout. A recent H 2 experiment is shown to bridge the gap between the near-critical and low pressure boiling experiments.

Description: Flow boiling in micro-channels and mini-channels has received significant attention due to its capability for dissipating highflux heat, especially in the thermal management of high precision electronics. A heat sink with narrow rectangular mini-channels is designed to investigate flow boiling in the mini-channels, including the effect of gravity. It contains 14 parallel channels with a cross section, of 1×4mm 2 , of which the hydraulic diameter is 1.6mm. The cooling capability, the temperature uniformity, and the temperature stability of the flow boiling in minichannels are investigated with R22, with total mass flow flux ranges from 35 to 70kg/m 2 s. The results show that the cooling capability of the heat- sink is up to 340W(∼ 3.0W/cm 2 ), and the temperature difference is below 4 ∘ C(even down to 2 ∘ C) on the heat sink. The temperature uniformity isn’t quite sensitive to heat flux. The instability has not been observed in the present researches.

Description: The lift force acting on a flat body near the boundary of a container filled with liquid is investigated. The container makes tangential translational oscillations. Experimental measurement of the force is performed by the method of dynamic body suspension in the gravity field. It is found that the repulsive force acts on the body near the wall. Thereby in the container subjected to horizontal translational oscillations the body, which is denser than the liquid, repulses from the bottom. In the suspended state the body makes tangential oscillations without touching the container wall. Herein the body weight is balanced by the lift force. The hysteresis is observed between the critical transition of the body in suspended state and return to the boundary. It is found that with decrease of liquid viscosity the lift force grows and the hysteresis disappears. The theoretical model of vibrational suspension of the body in the gravity field is presented. The problem is solved in the approximation of high frequency and small amplitude of vibration. It is shown that the time-averaged repulsive force acts on both the heavy and the light bodies at a distance comparable to the thickness of the Stokes layer. The conditions of retention of the flat body in the suspended state depending on the relative density and relative thickness of the solid are found. The experimental results agree satisfactorily with the theoretical calculations in the limit of high frequencies.

Description: In order to understand the effect of surface evaporation on thermocapillary convection in an annular pool, a series of numerical simulation on thermocapillary convection of the fluids with Prandtl number from 0.01 to 50 in the pure vapor environment were carried out. The results show that thermocapillary convection is always coupled with the evaporation process on the free surface. With the increase of evaporation Biot number, the surface temperature decreases, and the evaporation mass flux near the hot wall increases obviously. However, near the cold wall, the evaporation mass flux increases first, and then decreases. When Marangoni number is small, the total evaporation mass rate at free surface increases with the increase of evaporation Biot number; when Marangoni number is larger, it increases first and then approaches a constant value. The aspect ratio of the annular pool has a positive influence on the thermocapillary convection strength and the total evaporation mass rate. With the increase of Prandtl number, the surface temperature rises gradually and the evaporative mass flux increases, and the thermocapillary convection cell moves gradually toward the outer wall and the free surface. This effect decreases with the increase of evaporation Biot number When evaporation Biot number is smaller, the total evaporation mass rate increases with the Prandtl number; when Biot number is larger, Prandtl number has little impact on the total evaporation mass rate.

Description: The difficulty of measuring the thermodiffusion coefficients by optical properties of water-ethanol binary mixtures of approximately 20 wt % of water has been highlighted by several authors in recent years. This is because the concentration derivative of the refractive index ( ∂ n / ∂ c ) p , T is near zero at this concentration. For this reason, we measured the thermodiffusion coefficients by means of density analysis using the thermogravitational column technique from 5 wt % to 50 wt % at 25 ∘ C. In addition, we measured the thermophysical properties such as density, dynamic viscosity, thermal expansion and mass expansion.

Description: Arabidopsis thaliana roots skew with minimal waving in the microgravity environment of the International Space Station. Root skewing and root waving have been studied on the ground as well as in spaceflight, but often using different media types. In this study, Arabidopsis seedlings were grown on nutrient media plates that were comprised of various gelling agents with varied hardness in order to better assess these media for spaceflight research experiments. ImageJ was used to quantify the root morphology of 8-dayold seedlings, while R was used to perform statistical analyses. Root growth was drastically different between Difco agar, agarose, and Phytagel. Additionally, root waving masked skewing in certain media. Regression analysis revealed overall patterns when organized by hardness but also revealed that differences in media type had more of an impact on root growth than hardness itself. Different arrangements of media around the root tip revealed that roots grown on the media surface were longer and had fewer waves per millimeter than roots grown embedded in media. The implications for spaceflight research are discussed.

Description: We report on different research and educational activities related to parabolic flights conducted in Barcelona since 2008. We use a CAP10B single-engine aerobatic aircraft flying out of Sabadell Airport and operating in visual flight conditions providing up to 8 seconds of hypogravity for each parabola. Aside from biomedical experiments being conducted, different student teams have flown in parabolic flights in the framework of the international contest ‘Barcelona Zero-G Challenge’, and have published their results in relevant symposiums and scientific journals. The platform can certainly be a good testbed for a proof-of-concept before accessing other microgravity platforms, and has proved to be excellent for motivational student campaigns.

Description: From the benchmark values of the diffusion and thermodiffusion coefficients of the tetralin, isobutylbenzene and n-dodecane ternary mixture, and the published optical contrast factors, we have evaluated the theoretical amplitudes of the two composition modes of the refractive-index fluctuations. Shadowgraph experiments have been performed on ground, where the current theory is expected to be correct only for large wave vectors. Two decay times have been observed experimentally. The fastest one being related to the thermal diffusivity of the mixture, while the slower one to mass diffusion. Hence, it has not been possible to distinguish the two eigenvalues of the mass diffusion matrix, a problem also encountered in traditional light-scattering with ternary mixtures of similar-size molecules. Thus, to compare the measured Intermediate Scattering Function with theory, we fix the amplitudes and decay rates to the benchmark values, use the wave number as a fitting parameter, and compare it to the experimental wave number. The good agreement between theory and experiments for the larger wave numbers validates the theory developed for the microgravity conditions.

Description: This article deals with problem to improve accuracy of microacceleration’s data estimated by board gauges by the example of a spacecraft with very elliptical orbit. There are discussed impartial difficulties of estimation in different parts of the elliptical orbit.

Description: In this article the interplay among different types of flow (i.e. induced by driving forces of a different nature) is presented as a possible and “natural” means to control convection patterning and strength in shallow rectangular cavities of finite extent (A =length/height =4) filled with a low Prandtl number liquid (silicon, Pr =0.01). A variety of results concerning the possible spatial structure of the “mixed” states of steady Buoyant, Marangoni and Vibrational convection are discussed with the express intent of supporting the optimization of future experiments to be performed onboard the International Space Station.

Description: Thermodiffusion experiments on isomassic binary mixture of decane and pentane in the liquid phase have been performed between 25 ∘ C and 50 ∘ C and for pressures from 1MPa until 20MPa. By dynamic analysis of the light scattered by concentration non-equilibrium fluctuations in the binary mixture we obtained the mass diffusion coefficients of the mixture at each temperature and pressure. For the first time we were able to apply similar analysis to thermal fluctuations thus getting a simultaneous measurement of the thermal diffusivity coefficient. While mass diffusion coefficients decrease linearly with the pressure, thermal diffusivity coefficients increase linearly. In principle the proposed method can be used also for measuring the Soret coefficients at the same time. However, for the present mixture the intensity of the optical signal is limited by the optical contrast factor. This affects our capability of providing a reliable estimate of the Soret coefficient by means of dynamic Shadowgraph. Therefore the mass diffusion coefficients measurements would need to be combined with independent measurements of the thermodiffusion coefficients, e.g. thermogravitational column, to provide Soret coefficients. The obtained values constitute the on-ground reference measurements for one of the mixture studied in the frame of the project SCCO-SJ10, which aims to measure the Soret coefficients of multicomponents mixtures under reservoir conditions. Microgravity experiments will be performed on the Chinese satellite SJ10 launched in April 2016.

Description: The article deals with the task to estimate microaccelerations caused by natural oscillations of big elastic elements after impulse firing of an orientation system engine. Offered estimation is useful for development of space-system engineering intended for realization of gravity-sensitive processes. It can be applied for taking a decision about appropriateness of one or another process on the board of spacecraft.

Description: As for alloy systems forming amorphous structure, it is very useful to pursue the diffusion mechanism of the eutectic alloys in the vicinity of the eutectic point to elucidate the amorphous developmental process. We therefore investigated interdiffusion coefficients in the liquid state of AuGe and AuSi alloy, which remarkably have the deep eutectic temperature. The diffusion experiments using a shear cell device were performed in the temperature range from 686 K to 1073 K. The acquired data seem to be reliable, because they were reproducible and overlapping well on fitting curves so that the convection would have been suppressed. As a result, the temperature dependence of the interdiffusion coefficients in the liquid AuGe alloy was expressed in the Arrhenius equation and no peculiarity in the diffusion mechanism was confirmed. The values of interdiffusion coefficient of this study would be highly appropriate considering the past experimental values of self-diffusion coefficients of AuSi alloy and the negative mixing enthalpy of the alloy system. In addition, the previous research on structure analysis in which the shoulder was not observed in the vicinity of the eutectic point supported our confirmation of the Arrhenius expression for the temperature dependence of the interdiffusion coefficients in the liquid AuGe.

Description: Evaporation of a macroscopic-scale sessile droplet on different hot isothermal substrates has been experimentally investigated, for the framework of planning space experiments onboard Chinese recoverable satellite to explore the interface effect, heat and mass transfer during the phase transition process. Undoubtedly, the evaporation phenomenon of a sessile drop on heated substrates is a complex problem which involves the behavior of triple line, heat transfer with thermal conduction and convection, mass transfer into the vapor phase. Therefore, preparations from scientific view have been carried out to validate setup of the space experiment modes. Based on the experiments performed in the terrestrial gravity, we found that the evolution of a water droplet could be separated into three stages, began with the constant contact area, then switched to the depin stage and ended up with the flushing stage. The average evaporation rate was measured and the thermal effects of different substrates were studied. Results revealed a linear variation of contact diameter with its average evaporation rate, which has the similar tendency with small drops. The varieties of the heat flux density during evaporating showed that droplet absorbed energy from the heated substrate, then with the help of the internal flow of thermocaplliry and buoyant convection, heat was transported to the liquid-vapor interface providing the energy for evaporation.

Description: Liquid bridges were flown aboard a Boeing 727-200 aircraft in a series of parabolic arcs that produced multiple periods of microgravity. During the microgravity portion of each arc, g eff , the effective total body acceleration due to external forces became negligibly small so that cylindrical liquid bridges could be suspended across two coaxial support posts. Near the bottom of each arc, g eff slowly increased to a maximum of 1.84g, causing the liquid bridges to deform and in some cases collapse. Although the physics of liquid bridges subject to varying total body force is well-established and has been analyzed extensively both theoretically and experimentally, specific hardware was designed to vary g eff in a precise way that overcomes the gravity-related limitations and high g-jitter associated with parabolic flights. Bridge-stability was examined for axial and lateral orientations with respect to g eff by measuring the slenderness ratio as a function of Bond number at the instant of bridge collapse. Results exhibit remarkable agreement with theory as well as with the experimental results obtained in a magnetic levitation-based experiment. The parabolic flight method offers technical originality and provides experimental insights for researchers in the microgravity field. Here we present hardware development, experimental considerations, and results, and demonstrate that parabolic flight is a viable alternative to extant techniques for quantitative experiments on fluids.

Description: Musculoskeletal disorders during and after spaceflight are considered as a serious health issue. In space, weight-bearing exercise recognized as the main countermeasure to bone loss, since many anti-resorptive medications have not yet been approved for spaceflight or have been unsuccessful in their limited application. We need to investigate a complementary or alternative way to prevent bone loss and muscle atrophy resulting from microgravity condition. Partial vibration was chosen because it is one of the most feasible ways to adopt safely and effectively. Moreover, although the influence of hind-limb suspension has been studied in both male and female rodents, only rarely are both genders evaluated in the same study. Thus, to further extend our knowledge, the present study performed comparative analysis between genders. A total of 36 12-week-old male and female Sprague-Dawley rats were used and were randomly assigned to control (CON), hind-limb suspension without vibration stimulus (HS), and hind-limb suspension with vibration stimulus (HV) groups. Hind-limb suspension has led to increasing the rate of bone loss and muscle atrophy regardless of gender. The rates of bone loss in male group obviously increased than that of female group. All structural parameters were showed significant difference between HS and HV ( p 〈 0.05) in male group whereas there are no significant differences in female group. In female, the muscle volume with treatment of partial vibration stimulus significantly increased which compared with that of hind-limb suspension ( p 〈 0.05) whereas there are no significant differences in male group. Thus partial vibration could prevent bone loss of tibia in males and muscle atrophy in females induced by hind-limb suspension. In other words, partial vibration has positive effects on damaged musculoskeletal tissues that differ based on gender.

Description: The transcriptome of Oryza sativa calli was analyzed on board the Chinese spaceship “Shenzhou 8” to study the effects of microgravity on plant signal transduction and secondary metabolism (as one of the experiments with SIMBOX on Shenzhou 8). Calli of Oryza sativa were pre-cultured for 4 days on ground and then loaded into the stationary platform or the rotating platform of a biological incubator, called SIMBOX, to grow in space under microgravity conditions or 1g-conditions, respectively. The calli were fixed by RNAlater after grew 324 h under microgravity. After 17 days, Shenzhou 8 returned to Earth carrying SIMBOX. Oryza sativa calli were recovered, and the RNA was extracted for transcriptome analysis. After comparing 1 gspaceflight controls-inflight controls with 1 g-ground controls, 157 probe sets with different expression levels (fold change ≥2, p〈0.05) were identified. When comparing spaceflight controls to 1 g-ground controls and to 1 g-inflight controls, 678 probe sets with different expression levels (fold change ≥2, p 〈0.05) were identified. The fact that the same 678 probe sets were identified in these two comparisons suggests that transcription was affected under microgravity conditions. MapMan analysis was used to classify 627 microgravity responsive (MR) transcripts. The MR transcripts were mainly involved in cell wall structure, the TCA cycle, primary metabolism, transcription, protein modification and degradation, hormone metabolism, calcium regulation, receptor like kinase activity and transport.

Description: Thisarticle deals with new classification of microaccelerations which appear in the indoor environment of spacecraft during its exploitation. This classification allows effective application of different methods to control mocroacceleration level in the area with technological equipment with the purpose of creating of facilities to conduct gravity-sensitive processes on a board of spacecraft.

Description: Immune dysfunction in astronauts is well documented after spaceflights. Microgravity is one of the key factors directly suppressing the function of immune system. However, it is unclear which subpopulations of immune cells including innate and adaptive immune cells are more sensitive to microgravity We herein investigated the direct effects of modeled microgravity (MMg) on different immune cells in vitro . Mouse splenocytes, thymocytes and bone marrow cells were exposed to MMg for 16 hrs. The survival and the phenotypes of different subsets of immune cells including CD4 + T cells, CD8 + T cells, CD4 + Foxp3 + regulatory T cells (Treg), B cells, monocytes/macrophages, dendritic cells (DCs), natural killer cells (NK) were determined by flow cytometry. After splenocytes were cultured under MMg for 16h, the cell frequency and total numbers of monocytes, macrophages and CD4 + Foxp3 + T cells were significantly decreased more than 70 %. MMg significantly decreased the cell numbers of CD8 + T cells, B cells and neutrophils in splenocytes. The cell numbers of CD4 + T cells and NK cells were unchanged significantly when splenocytes were cultured under MMg compared with controls. However, MMg significantly increased the ratio of mature neutrophils to immature neutrophils in bone marrow and the cell number of DCs in splenocytes. Based on the cell survival ability, monocytes, macrophages and CD4 + Foxp3 + Treg cells are most sensitive to microgravity; CD4 + T cells and NK cells are resistant to microgravity; CD8 + T cells and neutrophils are impacted by short term microgravity exposure. Microgravity promoted the maturation of neutrophils and development of DCs in vitro . The present studies offered new insights on the direct effects of MMg on the survival and homeostasis of immune cell subsets.

Description: A detailed statistical analysis of bubble dispersion in turbulent jets based on data from drop tower experiments is presented here. A stochastic model is also introduced in order to capture these statistics to a large extent, treating bubbles as passive tracers with a local diffusivity given by a k - ε description of the turbulence. Bubble-bubble and bubble-flow interactions are neglected. Simple scaling analysis suggests that this approach is justified sufficiently far downstream. It is also found that, although interactions cannot be neglected very close to the inlet, the model predictions for the overall spatial distribution of the bubble ensemble are compatible with data within experimental uncertainty, and within the limited statistics of the experiments. In addition, the velocity fluctuations from the same experiments are analyzed, obtaining the local standard deviation of bubble velocities. We also find good agreement between experimental data and the effective model. Slight deviations between the model predictions and the experimental data are found at the jet margins, concerning the dependence on Reynolds number of jet angle and the relative velocity fluctuations. Consequently, significant bubble-flow interactions seem to be confined at the boundaries of the jets.

Description: We present an experimental setup (OLGA: Oxygen Low Gravity Apparatus) designed to compensate, partially or totally, gravity forces in a sample of O 2 by means of magnetic forces. The compensation remains within 1 % in a 5 cm 3 volume and within 5 % in a 40 cm 3 volume. The experiments can be carried out at intermediate controlled gravity levels, between Earth (1g 0 ) and zero (0g 0 ) gravity by adjusting the magnetic field intensity. The setup can also be used to perform fast variations of gravity, with a time constant of 340ms, from -0.5g 0 maximum (overcompensation) to 0g 0 , or from 0g 0 to 0.4g 0 maximum. The sharp acceleration or deceleration of spacecrafts can thus be reproduced to investigate in detail for instance, the transient behavior of life support systems or, when properly rescaled, fuel in rocket tanks. Numerical simulations and experiments also show that high conductive materials (copper) near the cell can modify the magnetic forces during the transient and then the accelerations. In contrast, low conductive materials (titanium) have negligible effect.

Description: Due to gravitational stimulation, the lower part of a shoot base grows faster than the upper part, leading the shoot to curve upward. Though much research has been done on the mechanism of plant gravitropism, it still requires extensive elucidation. Recently, functional genomic strategies have been applied to study this mechanism in plants. The present study carried out a proteomic analysis to gain a better understanding of gravity stimulation in rice. Three-week-old rice seedlings were gravitropically stimulated and samples were harvested at 4 different time points: 0.5, 3, 6, and 9 h. Then, the total crude proteins were extracted from the lower and upper parts of the shoot base, separated by 2-DE, and silver stained. At each time point, proteins in the lower and upper parts were compared, and the differently expressed proteins were identified using MALDI TOF or ESI-MS/MS. After gravity stimulation, proteins involved in nine different functional categories were either up-regulated or down-regulated. Sugar metabolism, glycolysis, the tricarboxylic acid (TCA/citric) cycle, pyruvate metabolism, and transcription regulation-related proteins were regulated. Although the initiation of defense reactions mainly occurred in roots, some different defense mechanisms were also evoked in the aerial tissues. Interestingly, the abundance of some proteins changed drastically at only 0.5 h after reorientation: inosine monophosphate dehydrogenase (up to 6.49-fold higher in lower flanks at 0.5 h), ATP synthase D (4.25-fold), and ribulose-1,5 -bisphosphate carboxylase oxygenase (3.62-fold). These findings may aid in understanding the mechanism of the gravitropism.

Description: Microgravity or simulated microgravity promotes stem cell proliferation and inhibits differentiation. But, researchers have not yet been able to understand the underlying mechanism through which microgravity or simulated microgravity brings about stem cell proliferation and inhibition of differentiation. In this study, we investigated the effect of simulated microgravity (SMG) on MDA-MB-231 and MCF-7 human breast cancer cells using rotary cell culture system (RCCS). SMG induced a significant accumulation of these cancer cells in S phase of the cell cycle. But, compared with the static group, there was no effect on the overall growth rate of cells in the RCCS group. Furthermore, the expression of cyclin D1 was inhibited in the RCCS group, indicating that RCCS induced cell cycle arrest. In addition, RCCS also induced glycolytic metabolism by increasing the expression of adrenomedullin (ADM), but not HIF1 a . The addition of ADM further enhanced the effects of SMG, which was induced by RCCS. But, the addition of adrenomedullin antagonist (AMA) reversed these effects of SMG. Finally, our results proved that RCCS, which induced cells cycle arrest of breast cancer cells, enhanced glycolysis and upregulated the expression of ADM. But, this did not lead to an increase in hypoxia-inducible factor-1 a (HIF1 a ) expression. Thus, we have uncovered a new mechanism for understanding the Warburg effect in breast cancer cells, this mechanism is not the same as hypoxia induced glycolysis.

Description: The axial development of the void fraction, interfacial area concentration and Sauter mean bubble diameter profiles of adiabatic air-water bubbly flows in 5.0 and 3.0 mm-diameter pipes were measured using a stereo image processing method under two gravity conditions, vertical upward (normal gravity) and microgravity. The flow measurements were performed at four axial locations. The axial distances from the pipe inlet ( z ) normalized by the pipe diameter ( D ) were z / D = 5.5, 34, 72 and 110 for 5.0 mm-diameter pipe and z / D = 15, 62, 120 and 188 for 3.0 mm-diameter pipe. Data were collected for superficial gas and liquid velocities respectively in the ranges of 0.00434–0.0500 m/s and 0.205–0.754 m/s. The effect of gravity on the radial distribution of bubbles and the axial development of two-phase flow parameters is discussed in detail, based on the obtained database. The phase distributions in pipe cross-sections were classified into 3 basic patterns: core peak , intermediate peak and wall peak distributions, based on two normalized parameters: a normalized void peak position and a normalized void peak intensity. Phase distribution pattern maps under normal and microgravity conditions were generated for bubbly flows in 5.0 and 3.0 mm-diameter pipes. The data obtained in the current experiment are expected to contribute to the benchmarking of CFD simulation of void fraction and interfacial area concentration distribution patterns in forced convective pipe flow under microgravity conditions.

Description: The surface tension driven flow induced by the bidirectional temperature differences always exists in various natural processes and phenomena. However, the researchers have mainly focused on the flow resulted from a unidirectional temperature difference. In this paper, combined with a vertical heat transfer, the thermocapillary convection of the silicone oil (Prantal number, Pr = 6.7) in a shallow annular pool is investigated by numerical simulations. We have put emphases on analyzing the effect of the bottom heat flux on the thermocapillary convection driven by a horizontal temperature gradient for three cases, which are divided according to the Marangoni number. The simulation results reveal that a hydrothermal wave coverts into a shorter hydrothermal wave and finally into a chaotic state with the enhancement of the heat flux when an unsteady oscillatory flow takes place in the three cases. The difference lies in the fact that whether the punctate wave and basic flow exist or not, and the details are discussed in this paper. In addition, a small vertical heat transfer can stabilize the thermocapillary convection while the relatively larger bottom heat flux has a negative influence on the stability. This is the first report on this field according to our knowledge, and the obtained results are very different from the ones with unidirectional temperature difference.

Description: Thin wire, subcooled boiling experiments were performed onboard an aircraft flying a parabolic trajectory to provide microgravity conditions for improved observation of jet flow phenomena and their behavior in the absence of buoyant forces. A new type of nucleation jet flow was observed in microgravity. This new micro-bubble jet flow is seen at medium to high heat fluxes and is characterized by a region of the wire that forms multiple jet columns which contain micro-bubbles. These columns flow together and penetrate tens of millimeters into the bulk fluid. Bubble behavior on the wire was observed to progress from a dominance of larger isolated bubbles on the wire to a dominance of micro-bubble jet flows on the wire as heat flux was increased. There was also a transient transition from a few large isolated bubbles to micro-bubble jet flow dominance for a set heat flux. A cross correlation calculation provided velocities of micro-bubbles in the flow, which were in the range of 4-14 mm/s. These velocities were used with convection correlations to show that fluid flows induced by jet flows are a significant contributor to the subcooled boiling heat transfer in microgravity, but are not the primary contributor. Additionally, a relative bubble area analysis approximates the direct contribution of these jet flows to the overall heat dissipation. These micro-bubble jet flows, which are only observed on thin wires (not flat surfaces), and the convection currents they induce, have the potential to allow for sustained fluid motion to occur in microgravity.

Description: The influence of transient heat transfer in different condensation condition was investigated experimentally in the present paper. Getting condensation heat and mass transfer regularity and characteristics in space can provide theoretical basis for thermodynamic device such as heat pipes, loop heat pipes and capillary pumped loops as well as other fluid management engineering designing. In order to study the condensation process in space, an experimental study has been carried out on the ground for space experiment. The results show that transit heat transfer coefficient of film condensation is related to the condensation film width, the flow condition near the two phase interface and the pressure of the vapor and non-condensable gas in chamber. On the ground, the condensation heat flux on vertical surface is higher than it on horizontal surface. The transit heat flux of film condensation is affected by the temperature of superheated vapor, the temperature of condensation surface and non-condensable gas pressure. Condensation heat flux with vapor forced convection is many times more than it with natural convection. All of heat flux for both vapor forced convection and natural convection condensation in limited chamber declines dramatically over time. The present experiment is preliminary work for our future space experiments of the condensation and heat transfer process onboard the Chinese Spacecraft “TZ-1” to be launched in 2016.

Description: Microgravity is a major abiotic stress in space. Its effects on plants may depend on the duration of exposure. We focused on two different phases of microgravity responses in space. When higher plants are exposed to short-term (seconds to hours) microgravity, such as on board parabolic flights and sounding rockets, their cells usually exhibit abiotic stress responses. For example, Ca 2+ -, lipid-, and pH-signaling are rapidly enhanced, then the production of reactive oxygen species and other radicals increase dramatically along with changes in metabolism and auxin signaling. Under long-term (days to months) microgravity exposure, plants acclimatize to the stress by changing their metabolism and oxidative response and by enhancing other tropic responses. We conclude by suggesting that a systematic analysis of regulatory networks at the molecular level of higher plants is needed to understand the molecular signals in the distinct phases of the microgravity response and adaptation.

Description: Cell cultures of Arabidopsis thaliana ( A . t .) respond to changes in the gravitational field strength with fluctuations of the amount of cytosolic calcium (Ca 2+ ). In parabolic flight experiments, where hyper- and μ g phases follow each other, μ g clearly increased Ca 2+ , while hyper-g caused a slight reduction. Since the latter observation had not been reported before, we studied this effect in more detail. Using a special centrifuge for heavy items (ZARM, Bremen, Germany), we determined the hyper-g-dependent intracellular Ca 2+ level with transgenic cell lines expressing the Ca 2+ sensor, cameleon. This sensor exhibits a shift in fluorescence from 480 to 530 nm in response to Ca 2+ binding. The data show a drop in the intracellular Ca 2+ concentration with a threshold gravity of around 3 g. This is above hypergravity levels achieved during parabolic flights (1.8 g). The use of mutants with different sub-cellular targets of cameleon expression (nucleus, tonoplast, plasma membrane) gave the same results, i.e. Ca 2+ is obviously exported from several intracellular compartments.

Description: Using late larval stages of cichlid fish ( Oreochromis mossambicus ) we have shown earlier that the biomineralization of otoliths is adjusted towards gravity by means of a neurally guided feedback loop. Centrifuge experiments, e.g., revealed that increased gravity slows down otolith growth. Microgravity thus should yield an opposite effect, i.e., larger than normal otoliths. Consequently, late larval cichlids (stage 14, vestibular system operational) were subjected to real microgravity during the 12 days FOTON-M3 spaceflight mission (OMEGAHAB-hardware). Controls were kept at 1 g on ground within an identical hardware. Animals of another batch were subsequently clinorotated within a submersed fast-rotating clinostat with one axis of rotation (2d-clinostat), a device regarded to simulate microgravity. Temperature and light conditions were provided in analogy to the spaceflight experiment. Controls were maintained at 1 g within the same aquarium. After all experiments, animals had reached late stage 21 (fish can swim freely). Maintenance under real microgravity during spaceflight resulted in significantly larger than normal otoliths (both lapilli and sagittae, involved in sensing gravity and the hearing process, respectively). This result is fully in line with an earlier spaceflight study in the course of which otoliths from late-staged swordtails Xiphophorus helleri were analyzed. Clinorotation resulted in larger than 1 g sagittae. However, no effect on lapilli was obtained. Possibly, an effect was present but too light to be measurable. Overall, spaceflight obviously induces an adaptation of otolith growth, whereas clinorotation does not fully mimic conditions of microgravity regarding late larval cichlids.

Description: Results from International Space Station experiments on combustion of n-propanol/glycerol droplets are reported. The initial n-propanol mass fraction was 0.95 and droplets had initial diameters in the 2 – 5 mm range. Some droplets were fiber supported while others were free floating, and the environment was either an oxygen/nitrogen mixture at 1 atm or an oxygen/helium mixture at pressures of 1 and 3 atm. The droplets burned in a multi-stage manner where n-propanol was preferentially evaporated during the early stages of combustion. The resulting buildup of glycerol in the liquid at the droplet surface led to sudden droplet heating and flame contraction. The experimental data are evaluated to provide burning rates, radiometer outputs, and droplet diameters as functions of time. These data are used to calculate effective liquid species diffusivities, D, using asymptotic theory. The D values can be substantially larger than molecular diffusivities in some cases, indicative of the presence of strong convective mixing. It was found that support fibers can decrease D values and that high burning rates can substantially increase D. These variations are attributed to changes in droplet internal flow patterns.

Description: The ground-based facilities 2D clinostat (CN) and Random Positioning Machine (RPM) were designed to simulate microgravity conditions on Earth. With support of the CORA-ESA-GBF program we could use both facilities to investigate the impact of simulated microgravity on normal and malignant thyroid cells. In this review we report about the current knowledge of thyroid cancer cells and normal thyrocytes grown under altered gravity conditions with a special focus on growth behaviour, changes in the gene expression pattern and protein content, as well as on altered secretion behaviour of the cells. We reviewed data obtained from normal thyrocytes and cell lines (two poorly differentiated follicular thyroid cancer cell lines FTC-133 and ML-1, as well as the normal thyroid cell lines Nthy-ori 3-1 and HTU-5). Thyroid cells cultured under conditions of simulated microgravity (RPM and CN) and in Space showed similar changes with respect to spheroid formation. In static 1 g control cultures no spheroids were detectable. Changes in the regulation of cytokines are discussed to be involved in MCS (multicellular spheroids) formation. The ESA-GBF program helps the scientists to prepare future spaceflight experiments and furthermore, it might help to identify targets for drug therapy against thyroid cancer.

Description: Al base alloy can be used as model alloy of Ni base single crystal superalloy due to their similarity on microstructure, while its lower melt temperature can match the restricted temperature of furnace working in space. The crystal selection behavior Al base alloy during directional solidification is studied by Bridgman process. With rise of heating temperature and decrease of withdraw rate, the number of grains passed spiral selector reduces. At heating temperature 900 ∘ C and withdraw rate 2mm/min, an Al base single crystal alloy can be produced. At higher heating temperature more Mg segregates to dendrite stem, which cause smaller liquid volume fraction. At lower withdraw rate less Cu segregate to interdendrite region, which cause reduced constitutional undercooling. These two factors lead to the shrinkage of secondary dendrite arm, thus the efficiency of spiral selector is improved.

Description: A hybrid two-phase model, incorporating lattice Boltzmann method (LBM) and finite difference method (FDM), was developed to investigate the coalescence of two drops during their thermocapillary migration. The lattice Boltzmann method with a multi-relaxation-time (MRT) collision model was applied to solve the flow field for incompressible binary fluids, and the method was implemented in an axisymmetric form. The deformation of the drop interface was captured with the phase-field theory, and the continuum surface force model (CSF) was adopted to introduce the surface tension, which depends on the temperature. Both phase-field equation and the energy equation were solved with the finite difference method. The effects of Marangoni number and Capillary numbers on the drop’s motion and coalescence were investigated.

Description: An in-house developed code has been used to predict soot formation in a methane air co flow diffusion flame at normal gravity and at lower gravity levels of 0.5 G, and 0.0001 G (microgravity). There is an augmentation of soot formation at lower gravity levels because of lower buoyancy induced acceleration leading to an increased residence time. The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. The axial velocity under normal gravity and reduced gravity show negative values (relatively small in magnitude) near the wall at axial height beyond 15 cm; but axial velocity is never negative in microgravity condition. Peak value of soot volume fraction at 0.5 G and microgravity multiplies by a factor of ∼3 and ∼7, respectively of that at normal gravity. The zone of peak soot volume fraction shifts away from the axis towards the wings, as gravity level is lowered. In comparison to soot volume fraction, the factors of amplification of soot number density at reduced gravity and at microgravity are comparatively lower at 1.2 and 1.5 of that at normal gravity respectively. On the other hand, mean soot particle sizes at reduced gravity and microgravity increase to 1.5 and 2 times of that at normal gravity respectively.

Description: A heated-stage optical microscope has been developed for in-situ crystallization observation of ZBLAN glass. Traditional crystallization studies on most materials, including ZBLAN, are completed following high temperature heat treatment. The modern heated-stage microscope developed in this study permits high temperature sample microscopy data to be collected in real time. The heated stage has a high-end temperature limit of 520 ∘ C with a heating ramp rate of 2.2 ∘ C/second. The stage was also fitted with liquid nitrogen for rapid cooling and sample annealing up to −190 ∘ C. The stage was customized to fit a Keyence VHX-2000 digital microscope with a magnification range of 100X–1000X. The microscope also has the ability to image samples using Differential Interference Contrasts (DIC) microscopy, which is used to elucidate key crystalline features not apparent with traditional optical microscopy. Additionally, the experiment was constructed to be operated on a microgravity parabolic aircraft to study the effects of microgravity on the crystallization of ZBLAN.

Description: Flame spread and extinction phenomena over a thick PMMA in purely opposed and concurrent flows are investigated by conducting systematical experiments in a narrow channel apparatus. The present tests focus on low-velocity flow regime and hence complement experimental data previously reported for high and moderate velocity regimes. In the flow velocity range tested, the opposed flame is found to spread much faster than the concurrent flame at a given flow velocity. The measured spread rates for opposed and concurrent flames can be correlated by corresponding theoretical models of flame spread, indicating that existing models capture the main mechanisms controlling the flame spread. In low-velocity gas flows, however, the experimental results are observed to deviate from theoretical predictions. This may be attributed to the neglect of radiative heat loss in the theoretical models, whereas radiation becomes important for low-intensity flame spread. Flammability limits using oxygen concentration and flow velocity as coordinates are presented for both opposed and concurrent flame spread configurations. It is found that concurrent spread has a wider flammable range than opposed case. Beyond the flammability boundary of opposed spread, there is an additional flammable area for concurrent spread, where the spreading flame is sustainable in concurrent mode only. The lowest oxygen concentration allowing concurrent flame spread in forced flow is estimated to be approximately 14 % O 2 , substantially below that for opposed spread (18.5 % O 2 ).

Description: Effects of gravity on liquid crystal phase transitions (LCPT) in polydisperse aqueous suspensions of Mg 2 Al layered double hydroxide (LDHs) were studied under normal gravity condition. Samples with different suspension concentration (SC) were tested for 15 days and the relevant changes in samples were observed through crossed polarizers. Our results showed: (a) the samples were still isotropic (I) when SC 〈 23 wt%; (b) when 23 wt% 〈 SC 〈 30 wt%, a shear-induced birefringence appeared after preparation, and finally coexistence of four phases was reached, including an opaque isotropic top phase, a birefringent middle phase, a faint birefringence phase and a sediment layer of larger platelets resulting from the high polydispersity; (c) when SC 〉 30 wt%, the suspensions were in a gel state, and the gel network slowed down the LCPT. The above different behavior of phase transitions is apparently due to the concentration gradient and fractionation caused by gravity. This study provides guidance on how to select samples of LDHs suspensions for LCPT used in the upcoming experiment in the space program SJ-10 satellite.

Description: In order to understand the characteristics of pure solutocapillary flow in a shallow annular pool subjected to a constant radial solutal gradient, a series of three-dimensional numerical simulations were performed. The annular pool was filled with the toluene/n-hexane mixture fluid with the Schmidt number of 142.8. The inner and outer cylinders were respectively maintained at low and high solutal concentrations. Aspect ratio of the annular pool is fixed at ε = 0.15 or 0.05. Results indicate that the solutocapillary flow is steady and axisymmetric at a small solutal capillary Reynolds number. The surface fluid flows radially from the inner cylinder toward the outer cylinder and a return flow exists near the bottom. With the increase of the solutal capillary Reynolds number, an axisymmetric oscillatory flow firstly appears and then becomes a three-dimensional oscillatory flow at ε = 0.15. Whereas at ε = 0.05 a direct transition from the steady and axisymmetric flow to the three-dimensional oscillatory flow is observed. Three types of the flow instabilities are the standing wave, hydrosolutal wave and source/sink type wave instabilities. Furthermore, the physical mechanism of the flow destabilization is analyzed.

Description: In order to understand the characteristics of thermocapillary flow of a toluene/ n -hexane mixture with the Soret effect in a shallow annular pool, a series of three-dimensional numerical simulations were carried out. The shallow annular pool was heated from the outer cylinder and cooled at the inner cylinder. The initial toluene concentration in the toluene/ n -hexane mixture varied from 0 to 0.4467. Results indicate that the flow undergoes two transitions from the axisymmetric steady flow to the hydrothermal waves, and then to chaos with the increase of the thermocapillary Reynolds number. The critical thermocapillary Reynolds number for the incipience of the oscillatory flow decreases with the increase of the initial solute concentration. When the thermocapillary flow transits to a three-dimensional oscillatory flow, a concentration fluctuation is observed on the free surface, which is similar to the hydrothermal waves. However, compared with that of the temperature, the dimensionless fluctuation amplitude of the concentration is relatively weak. Furthermore, the fundamental oscillation frequency increases linearly with the initial solute concentration, but the wave number of the hydrothermal waves is almost unchangeable.

Description: The effects of Bi addition on the properties of Sn-3.0Ag-0.5Cu molten alloy on Cu substrates are discussed using wettability and interface microstructure analysis. The changes of the contact angles between Sn-3.0Ag-0.5Cu- x Bi and Cu substrates with the spreading time are described by Dezellus model. It indicates that the spreading process is governed by the interfacial reaction during the dwelling time. The interface microstructure is observed to clarify the effects of reactions on the spreading behavior. It is found that Cu 6 Sn 5 is formed adjacent to the solder and Cu 3 Sn appears over the substrate with Bi added at 613K, indicating that Bi exists between the intermetallics and the addition of Bi can hinder the diffusion of copper towards the interior of the solder. Therefore the existence of Bi decreases the agglomeration of Cu-Sn grains. The growth of intermetallics is thus limited and the shape of intermetallics transforms from scallop to zigzag consequently. However, the segregation phenomenon appears when the additive amount of Bi is more than 5.5mass %, which could lead to the occurrence of fracture and degrade the performance of Sn-3.0Ag-0.5Cu- x Bi alloy. The results of the present study provide basic physical and chemical data for the application of lead-free solder in the future microgravity space environment.

Description: 〈h3〉Abstract〈/h3〉 〈p〉In order to understand the effect of Marangoni convection on the evaporation rate and the flow pattern, we performed a series of three-dimensional numerical simulations on evaporation process of sessile water droplet by introducing a kinetic model. Substrate temperature and the ratio of vapor pressure varied from 299 K to 308 K and from 0.92 to 0.99, respectively. The variation range of contact angle 〈em〉θ〈/em〉 was between 9.15° and 120°. Results show that the axisymmetric ring-shape temperature distribution on droplet free surface transforms into a serrated temperature distribution because of the enhancing Marangoni convection with the increase of substrate temperature. In addition, with the decrease of vapor pressure, the total evaporation rate on free surface will be increased and the Marangoni effect will be enhanced. The flow pattern is axisymmetric at 90〈sup〉o〈/sup〉 ≤ 〈em〉θ〈/em〉 ≤ 120〈sup〉o〈/sup〉 when the substrate temperature is fixed. However, it shifts to a multi-cellular pattern with the decrease of contact angle as a result of the competition between Marangoni flow and the evaporation. Additionally, the total evaporation rate increases with the increase of contact angle when contact angle is above 60〈sup〉o〈/sup〉, but when the contact angle is below 60〈sup〉o〈/sup〉, the trend is reverted. The temperature distribution becomes distinct at a small contact angle.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Clinostats and Random Positioning Machines (RPMs) are valuable devices for microgravity simulations in order to study fundamental gravity-dependent mechanisms on ground and in preparation for space flights. Both devices have different modes of operation, which have to be carefully considered and comprehensively discussed with respect to their potential impact on the quality of (simulated) microgravity. Here, we used the well-studied oxidative burst reaction of the immune cell (macrophage) model system, in order to compare clinorotation with random positioning. The RPM was used in a clinorotation mode, rotating the sample with 60 rpm around the horizontal axis and in the “random speed mode” (2-10 rpm) with and without random direction, thus, two axes rotating either bi- or unidirectionally. The production of Reactive Oxygen Species (ROS) during oxidative burst of the macrophages was visualized by the luminescence luminol assay. During clinorotation the cells responded with a reduction of the ROS production which is fully in line with earlier studies (clinostat, parabolic flight). In contrast, the exposure to the two random positioning modes showed that the oxidative burst response during RPM-exposure differs significantly from that observed during clinorotation, i.e. a jittering, more variant form of ROS production. We can conclude from our work, that the RPM is not suitable in its real random mode (with and without random direction; 2-10 rpm) to simulate the conditions of microgravity for the chosen system. We recommend that investigators using microgravity simulators should carefully choose the device and mode of operation specifically for their cellular system of interest.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Equations for thermal vibrational convection in a nonuniformly heated liquid with thermal density inversion subjected to high-frequency small-amplitude vibrations are obtained by averaging method. The problem of thermal vibrational convection in a horizontal cylinder filled with a liquid with quadratic temperature dependence of density is studied analytically on the basis of these equations for arbitrary orientations of temperature gradient, gravity and vibration axis. The heating is carried out in such a way that the point of temperature inversion of density is located at the cylinder axis. It is shown that by changing the direction of vibrations and their intensity, it is possible to control the structure and intensity of average flow.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The process of heat transfer in a closed domain of temperature-density inhomogeneous supercritical fluid (SCF) heated or cooled from the boundaries under weightlessness is studied numerically. The calculations near the thermodynamic critical point are carried out with the use of 1D equations of Navier-Stokes, mass conservation, energy balance, and van der Waals equation of state. It is obtained that when the critical point approaches the characteristic time of “piston effect”, τ〈sub〉PE〈/sub〉, in inhomogeneous SCF significantly increases in comparison with the homogeneous case. The larger temperature-density inhomogeneity and the closer the critical point, the longer time of “piston effect”. In addition the heating of the fluid causes the temperature-density inhomogeneity to be stronger, whereas cooling leads to the weakening of the inhomogeneity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉As technology becomes increasingly miniaturized, extremely localized heat dissipation leads to the challenge of how to keep these devices from overheating. A pulsating heat pipe (PHP) is an excellent cooling device based on the phase change of a working fluid. Experiments are performed to investigate the thermal performances of a Micro Pulsating Heat Pipe (MPHP) using different working fluids. The MPHP consists of 20 parallel channels made of a copper capillary tube with an internal diameter of 0.8 mm. The MPHP is filled with ethanol, deionized water and an aqueous solution of 1-butanol as working fluids, with different filling ratios (FRs) in the range 40–70 vol.%. The 1-butanol aqueous solution is known as a self-rewetting fluid, i.e. a dilute aqueous solution of alcohols with a number of carbon atoms higher than four (such as 1-butanol and pentanol). The surface tension of self-rewetting fluids decreases gradually with an increase in temperature, reaching a minimum around 60 °C, and subsequently increases gradually at higher temperatures. Therefore, at relatively high temperature self-rewetting fluids flow towards the regions at higher temperature due to the Marangoni effect. This flow should improve the boiling phenomenon, which is very important in the heat transfer mechanism of the MPHP. The experimental results indicate that, in the case of self-rewetting fluid, the stable oscillating motion in the MPHP arises at the heat load regime lower than that with water. In addition, the effective thermal conductivity of the MPHP with the highest concentration of self-rewetting fluid is higher than that with other fluids in the high heat load regime.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The development of the Marangoni instability in a two-layer film in the presence of a transverse temperature gradient and a heat release/consumption at the liquid-liquid interface, is investigated. The analysis is carried out in the lubrication approximation. Numerical simulations are performed by means of a finite-difference method. The multistability of the alternating roll patterns of different orientations and scales, has been found.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Metal screens are commonly used as components for fluid handling in spacecraft and rocket tank designs. In most cases the screen performs a passive separation of the gaseous from the liquid propellant phase. This means that the liquid is able to flow through the screen, causing a flow through screen pressure drop, while the gaseous phase is blocked due to the pressure jump across a curved liquid-gas interphase at the small screen pores. As long as the flow through screen pressure drop is smaller than the bubble point pressure, phase separation is possible and allows the provision of gas-free liquid for the spacecraft or rocket engine. The opposite, the separation of the liquid from the gaseous propellant phase, is more challenging. Liquid-gas phase separation means that the gaseous phase is allowed to enter the phase separation device while the liquid phase is blocked. The separation of the liquid from the gas is possible due to a double screen element, as the work of Conrath et al. (Int. J. Multiphase Flow 〈strong〉50〈/strong〉, 1–15, 〈span〉2013〈/span〉) and Behruzi et al. (〈span〉2013〈/span〉) has shown for storable liquids in Earth’s gravity and microgravity as well as for cryogenic liquids in Earth’s gravity. The liquid-gas phase separation of cryogenic liquids in microgravity however has not been investigated yet. Therefore, an experimental campaign consisting of six drop tests in microgravity using the drop tower at the University of Bremen, has been conducted. The experimental results confirm predicted governing physical phenomena and give evidence about further fluid mechanical and thermodynamical effects.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The flow regimes and pressure drop in a slit microchannel with a height of 164 μm and width of 10 mm are studied experimentally. The boundaries between the regimes are precisely determined using the developed procedure. The homogeneous flow model and the separated flow model are considered for determining the frictional pressure drop. Experimental data are compared with theoretical models. For the homogeneous flow model, the Dukler correlation gives good agreement with experimental data with a mean absolute error of 12%. A new correlation, which describes the experimental data with a mean absolute error of 8.1%, is proposed for the homogeneous flow model. For the separated flow model, the Hwang and Kim correlation gives the best agreement with a mean absolute error of 12.8%. The dependence of the pressure drop in the film flows (annular and stratified regimes) on the mass gas quality has been investigated. It is shown that the minimal pressure drop for the film flows is achieved in the stratified regime; thus, it is the most promising for the use in technical applications.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, an experimental study of boiling-up of a superheated water jet at an outflow through a short slit nozzle into the atmosphere in the presence of a passive swirler (twisted tape, wire winding) has been carried out in order to affect and control the jet behavior. The evolution of jet disintegration with increasing liquid superheat during the outflow both from the saturation line and at a fixed initial pressure has been traced. The characteristic structures and shapes of the flow have been identified. The relationship between the jet shape and various mechanisms of vaporization has been noted. For small superheats when outflowing from the saturation line, both unswirling jet shapes and swirling jet ones have looked the same. When a liquid outflows at a fixed initial pressure, a more structured parabolic jet profile with a decreasing opening angle is observed when the pressure increases. The differences have been revealed at moderate superheats, when the parabolic jet profile has been replaced by a trapezoidal jet one with increasing temperature along the isobars. It has been established that in the case of attainable superheats, the intensive process of boiling-up plays the main role in the flow formation. In this case the jet shape remained unchanged at outflows both from the saturation line and from the isobars. In the experiments conducted, manifestations of the two-phase jet instability, which have been in experiments with a passive swirler for a short cylindrical nozzle have not been observed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In order to reveal the impact mechanism of gravity acceleration on thermocapillary convection instability in two-layer system, the flow characteristics of two-layered thermocapillary convection in annular pool under various gravity levels is investigated by 3D numerical simulation, in which the outer and inner walls are differentially heated. The interface of fluids is assumed to be a flat non-deformable interface, where thermocapillary forces act on. The computational results show that, with the increase of gravitational acceleration the convective structure of the upper layer changes from multi-cell structure to singe cell structure, then to multi-cell structure; while in the lower layer the flow changes from multi-cell to single cell structure. The convection instability mode also is modified, and the wave number at the interface decreases from seven to six. The average oscillatory amplitude of azimuthal velocity decreases with the increase of gravitational acceleration.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The theory of long nonlinear oscillating wave packets (breathers) in a stratified fluid with a small density difference in a gravitational field is developed. The theory is based on the Gardner equation and its modifications, which are fully integrable with modern methods of the nonlinear wave theory. Examples of the breather generation are given and the conditions for their stability are discussed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The interface distribution and self-pressurization phenomenon are the most important problems in the storage of cryogenic liquid on orbit, which are difficult to be predicted and assessed exactly due to the complex non-equilibrium thermal behavior. In this paper, one 3-D CFD model based on volume of fluid (VOF) method is established to investigate the interface evolution and self-pressurization process in the liquid oxygen (LOX) tank in microgravity environment with various heat loads and gravitational accelerations. The validity of the model is verified by both the present ground experiments and the drop tower experiments from literature. The impact of microgravity on the gas-liquid interface distribution in the cryogenic tank is analyzed. Different from the ground condition, the distribution behavior of the gas-liquid two-phase fluid in microgravity is that the liquid is covering the tank wall, and the ullage is staying at the top of the tank surrounded by the liquid. Then the pressurization rate of the tank with different gravitational accelerations is obtained. The tank pressure rise rate increases with the reducing of the gravity. The results are beneficial to the optimal design of the cryogenic propellant tank.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper is addressing the challenge related to understanding the experimental results obtained by Taylor dispersion technique when working under high pressure with supercritical carbon dioxide (CO2). We discuss typical experimental problems that arise when using the Taylor dispersion method for measuring diffusion coefficients in the supercritical fluids. The diffusion coefficients of the two samples in supercritical carbon dioxide were measured along the isobars at different temperatures. The diffusion coefficients of ethanol in supercritical CO2 have been measured in the temperature range from 304.15 to 343 K along the isobar 〈em〉p〈/em〉 = 12.0 MPa. Experiments with the gaseous CH4/CO2 mixture with a mole fraction of CH4 = 0.2052 mol mol〈sup〉− 1〈/sup〉 have been conducted in the temperature range from 317.85K to 343.15 K along the isobar 〈em〉p〈/em〉 = 12.5 MPa. A comparative analysis of a diffusion behavior of these very different mixtures is presented.〈/p〉

Description: A series of experiments were performed to elucidate the influence of residence time of fuel vapor transport on the sooting behavior of microgravity ethanol droplet flames using the 2.2 sec drop-tower facilities at the NASA Glenn Research Center (GRC). In these experiments, the residence time of fuel vapor transport was adjusted by means of changes in initial droplet diameters (1.6 mm versus 1.9 mm) and oxygen concentrations (ranging from 21 % to 33 % mole fraction in argon atmospheric environments). As the flame temperature is increased, the measured soot volume fraction initially increased and then began to decrease after reaching a maximum value. Experimental results clearly indicate that the residence time can control the sooting behavior for microgravity droplet flames by mediating the competition among the fuel pyrolysis reactions, fragmentation of formed soot precursors, and oxidation of soot precursors and particles which eventually result in an interesting non-monotonic sooting behavior at elevated flame temperatures.

Description: The following paper deals with acoustic flame suppression mechanics in a microgravity environment with measurements taken from an Arduino-based sensor system and validation of the technique. A Zippo lighter is ignited in microgravity and then displaced from the base of the flame and suppressed using surface interactions with single tone acoustic waves to extinguished the flame. The analysis of data collected shows that the acoustic flame suppression measurementtechniques are effective to finding qualitative differences in extinguishing in microgravity and normal gravity. Further, the results suggest that the suppression may be more effective in a microgravity environment than in a normal (1g) environment and may be a viable method of extinguishing fires during space flight.

Description: In previous studies of granular flow, it has been found that gravity plays a compacting role, causing convection and stratification by density. However, there is a lack of research and analysis of the characteristics of different particles’ motion under normal gravity contrary to microgravity. In this paper, we conduct model experiments on sand flow using a model test system based on a drop tower under microgravity, within which the characteristics and development processes of granular flow under microgravity are captured by high-speed cameras. The configurations of granular flow are simulated using a modified MPS (moving particle simulation), which is a mesh-free, pure Lagrangian method. Moreover, liquid-gas-like phase transitions in the sand flow under microgravity, including the transitions to “escaped”, “jumping”, and “scattered” particles are highlighted, and their effects on the weakening of shear resistance, enhancement of fluidization, and changes in particle-wall and particle-particle contact mode are analyzed. This study could help explain the surface geology evolution of small solar bodies and elucidate the nature of granular interaction.

Description: 〈h3〉Abstract〈/h3〉 〈p〉Due to the reduced dimensions of electronic equipment and the need for thermal management of these equipment, In order to increase efficiency and longevity of component, heat sinks with micro aspects are very important. In this study, heat transfer of micro heat pipe has been studied experimentally. For this purpose, firstly the micro heat pipe that is suitable for industrial conditions and restrictions for the production of very small size triangular section was designed and built. According to the very small size of the primary copper tube, the manufacturing process requires precision and advanced technology. In such a way, at first the samples of fine copper tube available in the market was provided and during the process of heat and tension was brought, at the same time, to the desired thickness and diameter and then by using provided wedge the appropriate cross section is achieved. To apply thermal load, a set of various thermal flux was applied to the evaporator and temperature distribution achieved via five thermocouples which were installed on the body in accordance with the set-up and heat resistance was measured. Water and different solution mixture of water and ethanol were used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer. So that the effect of the double electric layer causes 20% drop in the thermal performance of heat pipe. However, when the operating fluid was normal water or a mixture of water and ethanol, the temperature difference between the evaporator and the condenser was higher than when pure water used. This was due to the fact that the dual electrical layer led to a disruption in the flow path inside the pipe. Micro heat pipe performance was affected due to the small size of the micro pipe as well as the ions in the fluid, causing a higher temperature difference between the evaporator and condenser sections.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The fluids behaviour within a spherical tank under microgravity conditions is investigated through a comparison between the original data from the FLUIDICS experiment carried out in the ISS and Direct Numerical Simulations for two-phase flows. The study case consists in the rotation of a spherical tank around a fixed axis. The tank is filled with a liquid with physical properties similar to those of liquid propellants and gases used in the space industry. Two tanks with different filling ratios have been tested in space. Cameras and sensors allow extracting the fluids dynamics and the temporal evolution of the force and torque exerted by the fluids on the tank wall. Several manoeuvres corresponding to different angular velocities and angular accelerations are submitted on both tanks. The velocity profile is divided into four phases: from zero, the angular velocity around the vertical axis increases linearly until it reaches the required constant value for which the fluids stabilise in the second phase, then the angular velocity decreases until it recovers zero. Numerical simulations are computed with the home-made code DIVA which is based on the Level Set method coupled with the Ghost Fluid Method. The force in the radial direction gives the value of the centrifugal force during the constant angular velocity phase. The average centrifugal force is well predicted by the simulations, the comparison with the experimental data exhibits errors lower than 3% for the half-filled tank. Considering the vertical torque, the effect of the Euler acceleration is clearly visible through the important peaks of opposite sign observed during the acceleration and the deceleration phases. Moreover, the oscillations of the gas bubble during the second phase can be observed from the torque evolution. Their magnitude decreases throughout time until the steady state is reached. The measured and predicted temporal evolutions match together until the magnitude of the oscillations reaches the noise level of the data. The bubble oscillations are much more damped for the tank containing a larger amount of liquid (75%). The frequency of these oscillations are investigated applying the Fourier transform of the torque signals and by looking at the videos taken during the experiment. Similar oscillation frequencies are observed with the experimental setup and the numerical simulations, even for the manoeuvre with the lower Bond numbers. We verify that the oscillation frequency increases with the angular velocity. Finally, the comparison exhibits that the numerical simulations provide an accurate prediction of the fluids behaviours in microgravity conditions for this range of Bond numbers.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In order to understand surface heat dissipation dependence of thermocapillary convection for moderate Prandtl number fluid in a deep annular pool, a series of three-dimensional numerical simulations have been carried out by using the finite volume method. The radius ratio and the aspect ratio of an annular pool are fixed at 0.5 and 1.0, respectively. The working fluid is 0.65cSt silicone oil with Prandtl number of 6.7. Surface heat dissipation Biot (〈em〉Bi〈/em〉) number is varied from 0 to 50. Results indicate that with the increase of Biot number, the radial temperature gradient near the inner cylindrical wall decreases, and near the outer cylindrical wall it increases, so the flow is enhanced. When 0 〈 〈em〉Bi〈/em〉 〈 10, with the increase of Marangoni number, the axisymmetric steady flow first transits to the standing wave, and then to the azimuthal waves. The standing wave should be attributed to Marangoni-Bénard instability. However, the azimuthal waves should be corresponded to hydraulic instability, which is mainly driven by the azimuthal motion of temperature fluctuation from the sudden change of flow direction near the bottom and the inner cylindrical wall. When 〈em〉Bi〈/em〉 ≥ 10, when the flow destabilizes, the axisymmetric steady flow transits directly to the azimuthal waves. With the increase of Biot number, the critical Marangoni number of the flow destabilization increases. Furthermore, the fundamental frequency and the wave number of three-dimensional oscillatory flow increase gradually with the increase of Biot number.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The purpose of a liquid acquisition device (LAD) is to separate liquid and vapor phases inside a spacecraft propellant storage tank in the reduced gravity and microgravity conditions of space so that vapor-free liquid can be extracted to the transfer line. A popular type of LAD called a screen channel LAD or gallery arm, uses a fine porous screen and surface tension forces of the liquid to allow pure liquid to flow through the screen while blocking vapor penetration. To analyze, size, and optimize the design of LADs for future in-space propellant transfer systems, models and data are required for the four fundamental influential factors for LAD systems, including bubble point, flow-through-screen pressure drop, wicking rate, and screen compliance for a wide variety of screen meshes. While there is sporadic data available for three of these parameters, there is no published quantitative data for screen compliance. During the transient startup of propellant transfer, the liquid must be accelerated from rest to the steady flow demand velocity, which causes the screen to deform or comply, so compliance data is required for accurate transient LAD analyses; most design codes only consider steady state analysis. This paper presents screen compliance experiments on 14 different screens, examining the effects of fineness of mesh, open area, and screen metal type on compliance. A basic equation of state is also developed and validated against the data which can be easily integrated into any transient LAD flow code to model propellant transfer.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper addresses the problem of designing an active disturbance rejection controller for a high accuracy drag-free satellite with cubic test mass. The uncertain model of the drag-free satellite is defined. The performance requirement imposed on the acceleration of the test mass is broken down into specification of drag-free and suspension loop because of the disturbance decoupling controller, which is based on the linear active disturbance rejection control technique. We derive two-degree internal model control structure of ADRC, which is used for robust stability verification. Search programs determine the parameters that satisfy system stability and the performance requirement. The design technique has shown to be robust to the perturbation of the system and good performance in disturbance suppressing. To check the design of the controller, an overall simulation is preformed, and the results confirmed that the controller is able to meet the system requirements.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Soret-Facet mission was conducted under microgravity conditions to measure the Soret coefficient (〈em〉S〈/em〉〈sub〉〈em〉T〈/em〉〈/sub〉) for salol/〈em〉tert〈/em〉-butyl alcohol using a two-wavelength Mach-Zehnder Interferometer (2-MZI). The 2-MZI is useful in the simultaneous measurement of temperature and concentration in binary mixtures. However, the simultaneous analysis of the 2-MZI had the limitation in accurate determination of 〈em〉S〈/em〉〈sub〉〈em〉T〈/em〉〈/sub〉 because of the uncertainties in the experimental values of coefficients of refractive indices. To reduce the uncertainties in the measurement of coefficients of refractive indices, this paper describes an alternative method to measure temperature and concentration individually, using the 2-MZI. This alternative method was applied to analyze the microgravity data of Soret-Facet mission and the changes of temperature and concentration were shown at each wavelength. The coefficients of refractive indices and 〈em〉S〈/em〉〈sub〉〈em〉T〈/em〉〈/sub〉 were corrected based on matching the two changes of temperature or concentration so that two or three of the following constraints were satisfied: fulfill the deviation ranges of coefficients; minimize the difference between two gradients; and match with thermocouples. This correction led to the reduction in dispersions of analyzed values in the simultaneous analysis, and clarified that it is necessary to improve not only the coefficients of refractive indices but also the ratio between phase changes in the simultaneous analysis. The results indicated that the separate analysis for the 2-MZI can estimate the coefficients of refractive indices and is useful for measuring the Soret coefficient in binary mixtures.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The experimental study of pure water pool boiling critical heat flux (CHF) on two platinum wires with 26 mm in length and 30 μm and 50 μm in diameters was conducted to investigate the effect of gravity on pool boiling CHF. The gravity level ranges from 1 to 3.5 g, and the saturation pressure ranges from 0.1 to 0.5 MPa. The hypergravity was generated by a centrifugal machine. The comparison between the experimental data under hypergravity and earth gravity shows that the difference between the pool boiling CHF under earth gravity and hypergravity is not significant in the experimental gravity range, almost within ±15% for gravity levels less than 3.5 g, and that generally the CHF under hypergravity is slightly higher than that under earth gravity. The pool boiling CHF experimental data are also used to assess 21 available correlations proposed for the pool boiling CHF under earth gravity to evaluate their applicability to hypergravity.〈/p〉