Microgravity Science and Technology最新文献

Animal cells can growth in three-dimensional (3D) systems, which provide an excellent opportunity to study natural interactions between cells and their extracellular matrix (ECM) in vivo. In this particular study, a human liver carcinoma cell line (HepG2) was cultured in two different systems: a rotary cell culture system (RCCS) and a continuous stirred tank reactor (CSTR). By simulating microgravity, both reactors facilitated the formation of HepG2 cells into spheroid structures without the need for additional support materials. The HepG2 spheroids exhibited over 80% viability for up to 10 days in both the RCCS and the CSTR. The RCCS provided more suitable conditions for generating well-formed HepG2 spheroids within a 14-day period, whereas the CSTR allowed for more efficient oxygen delivery to the spheroid cells, resulting in higher cell viability despite larger spheroid diameters (200–300 µm). At the end of production, the urea amounts were observed as 8.1 nmol well⁻¹, and 9.5 nmol well⁻¹ in the CSTR, and the RCCS, respectively. For the first 6 days, the spheroids in the RCCS produced more albumin (1.18 ± 0.003 ng mL⁻¹), then, on the 8th day, it was 1.22 ± 0.015 ng mL⁻¹ in the CSTR. The monolayer HepG2 cells and HepG2 spheroids exhibited IC₅₀ values of 250–500 mM and 1300–2200 mM against ethanol, respectively. These findings highlight the remarkable potential of bioreactors in producing animal cell lines in 3D systems, providing valuable insights into cellular behavior and paving the way for the scalable production of intricate tissue constructs.

The effect of the temporal variation of the hydraulic gradient on the transport of the impurity pulses in a porous column has been studied experimentally. The measurements were made using horizontal columns with different porosity and therefore different permeability. The temporal changes in the hydraulic gradient as well as the intensity of the bulk flow were organized by changing the vertical position of the outlet valve. Only harmonic fluctuations of the filtration flow intensity have been taken into account. It was shown that the effect of the time-varying flow rate is only noticeable when concentration convection develops against the background of the main advective flow. Changing the period and amplitude of the flow pulsations caused by changing the hydraulic gradient at the ends of the column will only change the impurity transport rate, not the amount of impurity leached.

In this paper, we study 2D stationary regimes of mixed convection in a square cavity with a moving lid. All walls of the cavity are considered as solid; the side walls are assumed to be perfectly thermally insulated, while the top and bottom walls are isothermal, the temperature of the bottom wall is higher. The impact of a smooth change in the velocity of the upper wall of on the convective stability of air within a square cavity is investigated both analytically, using low-mode approximation, and numerically, by the finite difference method. Calculations are performed for Grashof numbers up to values thirty times greater than the critical one. It have been shown that for each supercritical Grashof number there is a critical Reynolds number (Re_c) such that with a smooth change in the Reynolds number within the interval (-Re_c< Re < Re_c) the flow is continuously transformed, changing the structure from normal single-vortex to anomalous double-vortex and vice versa. If, with a change in the Reynolds number, the limits of the specified interval are exceeded, a hysteresis transition from the anomalous flow to the normal one is observed. These findings provide new insights into the complex interplay between thermal and inertial forces in convective flows. Understanding these flow structures and transitions could improve the knowledge of combustion processes.

Inertial waves in a rotating confined fluid can focus on closed trajectories, known as wave attractors. These regimes are not eigenmodes and are related only to the frequency dependence of the wave vector. This paper presents an experimental investigation of the cylindrical cavity shape’s effect on the attractor’s spatial structure. We considered three different configurations: i) a circular cylinder with both conical axisymmetric ends; ii) a cylinder with one straight end and the other end inclined to the plane of the cross-section; iii) both ends of the cylinder are inclined parallel. The major observed difference is the azimuthal flow structure. In the axisymmetric case, the shape of the wave attractor is independent of the azimuthal coordinate, and the instantaneous vorticity field represents a system of nested rings in the cross-section. If one of the cavity ends has a constant slope, wave focusing appears in the meridional plane passing near the direction specified by the geometry. The three-dimensional law of wave reflection from inclined boundaries causes meridional trapping, which is important in real geo- and astrophysical systems with complex boundary topography.

Both Singular Value Decomposition (SVD) and Artificial Neural Networks (ANNs) can be powerful tools for image processing. Here they are applied in the context of the “Effect of Marangoni Convection on Heat Transfer in Phase Change Materials” (MarPCM) microgravity experiment [Porter et al. (Acta Astronautica 210, 212–223, 2023)], which investigates the use of thermocapillary (Marangoni) convection to expedite melting of organic Phase Change Materials (PCMs) in cuboidal and cylindrical domains. The processing of the cylindrical “melting bridge” experimental images is particularly challenging due to the converging lens effect caused by the curved interface and the refractive index of the liquid PCM. A combination of SVD and ANNs is used to propose an algorithm to process these images. The network is trained on a set of synthetic images of the melting bridge, generated via ray-tracing [Martinez et al. (Advances in Space Research 72, 1915–1928, 2023)] then projected onto the eigenmodes associated with the largest singular values of the image database, which includes snapshots of the melting process in all representative cases. Two optimal algorithm architectures are described, characterized by the number of SVD modes considered in the projection and the hyperparameters of the ANN. The performance of the algorithm is analyzed in terms of its ability to associate images with the correct liquid fraction. The processing strategy is tested by applying it to images obtained from ground experiments using the scientific prototype of the MarPCM cuboidal cell.

The form of cancer that is prevalent among women is breast cancer and is responsible for a significant number of cancer-related deaths. Coriolus versicolor (CV) extract has demonstrated notable anti-cancer properties. Additionally, microgravity can influence various aspects of cancer cell behavior, including growth, migration, proliferation, survival, and apoptosis. This research aimed to assess the efficacy of polysaccharide peptide from CV in combination with doxorubicin under simulated microgravity (S-µg) conditions and without S-µg on 4T1 cancer cells. A number of 80 female inbred BALB/c mice were divided into 8 experiment groups, including Control, polysaccharide peptide from CV (T, 1 g/kg BW), doxorubicin injection (Dox, 0.5 mg/kg BW), Dox + T, S-µg (Mic), Mic + D, Mic + T, and Mic + D + T. Subsequently, tumor biomarkers and cell death were expressed using Western blot, TUNEL assay, immunohistochemistry, and H&E staining techniques. Exposure to S-µg reduced tumor growth compared to the control group, but its effect was less than that of the groups affected by polysaccharide peptide from CV and Dox. The Dox and CV combination could significantly (p < 0.001) inhibit 4T1 breast tumors’ growth. The Dox + T group exhibited a decrease in the tumors’ volume compared to control (p < 0.001). Meanwhile, it could effectively suppress tumor growth and Ki-67, VEGF, MMP-2, and MMP-9 expression. Also, Dox + T could increase the mean survival time of the tumor-bearing mice. Dox + T demonstrated a meaningful increase in cleavage of caspase-3, caspase-8, and caspase-9, confirming the occurrence of apoptosis (p < 0.001). Taking together, Dox + T can be a safe anti-cancer supplement that can cause direct apoptosis to the cancer cells.

Graphical Abstract

We present here an extensive analysis of the free surface dynamics driven by the thermocapillary effect in half-filled elliptical containers in microgravity. Depending on the cell ellipticity (delta ), which selects the preferred static equilibrium via surface energy, and on the applied thermal forcing (Delta T), interesting dynamics are found. Simulations show that the steady, thermally-driven position of the interface — perpendicular to (Delta T) — undergoes a pitchfork bifurcation at a critical (delta _textrm{cr}) that breaks the vertical reflection symmetry of the system. These results are supported by (leading order) estimates of the opposing thermocapillary and surface tension forces, predicting the linear dependence of (delta _textrm{cr}) on (Delta T). Finally, the free surface relaxation after switching off the thermal control is explored. As a whole, the present analysis indicates that one can combine thermocapillary flows and an adequate cell design to manipulate and control fluids in microgravity, with potential in a wide variety of applications.

We studied experimentally the dynamics of a thin film coating on a fiber with different inclined angles. This type of flow is asymmetric and accompanied by rich dynamics manifested via the formation and interaction of droplets. It is found that the dynamics of the coating flows exhibits three typical regimes, i.e., oscillatory flow, steady and unsteady pearl-like flows, at different flow rates. Interestingly, at a large inclined angle, the coating flow exhibits behaviors of droplets shedding in the convective regime at high flow rates. The steady and unsteady pearl-like flows correspond to the absolute and convective instabilities, respectively, and the oscillatory flow is due to the secondary instability of the travelling wave. From the viewpoint for nonlinear dynamics, the oscillatory wave is a solution of relative periodic orbit which has fixed temporal and spacial periods. We identified the transition boundaries between different flow regimes in the (theta -overline{Q }) plan.

A compact and lightweight sensor is always expected to be embedded with the traditional micro-vibration isolator in spacecraft. It helps to detect the subtle disturbances the isolator encounters and alerts for potential harm. In this work, we developed a self-sensing micro-vibration isolator using an electret transducer. The theoretical models of the electret-based self-sensing isolator are derived from Hamilton's principle to investigate the coupled dynamics of the system and guide a model-based design. Simulations via the finite element method were also conducted to verify and extend the effectiveness of the proposed model. The results show that the electret transducer is an excellent candidate for the embedded sensor of the micro-vibration isolator. With the proper size and appropriate deployment pattern, the electret sensors can precisely detect the translation and rotation of the unsprung load.

In this work we present an experiment in which we injected microspheres at low pressure into a capacitively coupled argon plasma chamber. The setup was located in the top point of the Einstein-Elevator drop tower in Hannover, Germany, where the microparticles reached their equilibrium position above the lower electrode during (1 , g). During the fall, the trajectories of the microparticles, which were driven by the electric force, the neutral drag force and some residual gravitational force, were recorded. In addition, simulations of the plasma conditions were performed with commercial software to determine the microparticle charges via an orbital motion limit theory approach, taking into account the charge exchange in ion-neutral collisions. Based on the calculated position dependence of the microparticle charges and the electric force, the electric field present in the plasma sheath region was finally determined.