Microgravity Science and Technology最新文献

The article analyzes how long-duration space missions’ effect on the heart rate variability parameters and invariable blood proteins. The results are discussed taking into correlation between them. Seven Russian cosmonauts took part in the research during their missions to the International Space Station. Samples of dry blood drops were collected as part of the space experiment ''OMICs-DBS'', electrocardiogram samples were collected as part of the space experiment "Cardiovector". We have established a linear relationship between the concentrations of the following proteins: complement C1q subcomponent subunit A (encoded by the C1QA gene), complement C1r subcomponent (encoded by the C1R gene), fibrinogen gamma chain (encoded by the FGG gene),galectin-3 (encoded by the LGALS3 gene), interstitial collagenase or matrix metalloproteinase-1 (encoded by the MMP-1 gene), pigment epithelium-derived factor (encoded by the PEDF gene) and frequency-domain heart rate variability (HRV) parameters at some stages of space flight. Three proteins were associated with of total power parameters, and either positively correlated with the low-frequency (LF) domain as in the case of the C1QA (complement C1q subcomponent subunit A) or negatively - LGALS3, MMP-1 (galectin-3, matrix metalloproteinase-1) correlated with the high-frequency domain (HF). One of the proteins, the PEDF (pigment epithelium-derived factor), positively correlated with the HF, which correspondingly reflected the effect of vagal modulation on the SA node. The Complement C1r subcomponent had positive correlations with both HF and LF. The FGG (fibrinogen gamma chain) was negatively correlated with both individual components of the frequency-domain (HF, ms2 and LF ms2) also its total power. We assume that such statistical relationships reflect the tension of regulatory mechanisms, which is consistent with classical studies of autonomic regulation in space flight.

The studies on bubble pinch − off deviates to some degree from the actual situation due to limitations in theoretical assumptions and experimental conditions, and physical details such as satellite bubbles inside the bubble cannot be observed. Even some of the published experimental results are divergent. To fully understand the dynamics of bubble pinch − off, the authors applied the volume of fluid (VOF) method to investigate the effect of liquid − phase viscosity on bubble pinch − off, and analyzed the pinch − off process and the surrounding flow field. It was found that in low − viscosity liquids, the process of bubble pinch − off is relatively fast and the position corresponding to R_min varies only in the axial direction; and satellite bubbles during pinch − off shows vertical distribution, which enter the upper and lower parts with the jet after bubble pinch − off. In intermediate and high viscosity liquids, a gas line is formed after bubble pinch − off, and the length and duration of the gas line increase with an increase in liquid − phase viscosity; and the position corresponding to R_min moves not only radially inward, but also axially upward. In liquids of different viscosities, the strength of annular flow and the radial pressure drop are different, which leads to different phenomena of bubble pinch − off.

This paper presents the experimental results of a high-temperature heat pipe with fins at horizontal. The heat pipe tube is designed to Φ25 × 410 mm, two wraps of 100 mesh screen, and filling mass of 15 g sodium. The height and thickness of the fins are 13 mm and 1 mm, and the gap distance between two fins is 5 mm. The wall material of the tube container and fins both are stainless steel. In order to compare the impact of the fins on the startup performance of the heat pipe, a plain-tube high-temperature heat pipe without fins which has the same dimensions is also comparatively experimented. The experimental results show that the finned heat pipe can start successfully and its end of condenser behaves bright red color, which is roughly in accordance with the results of the plain-tube heat pipe. The comparative results also show that the startup time of full startup and the temperature difference between evaporator and condenser after fully starting for the finned heat pipe and plain-tube heat pipe are similarly same. However, adding fins in condenser have a great effect on the temperature rise-rate during starting process and the quasi-steady or equilibrium temperature after startup between the results of two heat pipes.

Microgravity, the near absence of gravity experienced in space, is a major health concern for astronauts, leading to significant bone loss. This weakens their skeletal system, impacting performance during missions and hindering post-mission rehabilitation. To address this challenge, this paper explores the potential of advanced cellular research and regenerative medicine for mitigating bone loss in astronauts. We analyze the biological mechanisms affecting bone turnover markers and their implications for space travel. By examining key studies on the effects of spaceflight on bone structure in rodents and humans, we highlight the complex relationship between bone density and the microgravity environment. While acknowledging limitations like limited spaceflight simulators and the early stage of extraterrestrial research facilities, we propose a strategic shift towards advanced cellular research specifically tailored to microgravity. This approach focuses on understanding how microgravity disrupts bone formation and resorption at the cellular level. Tailor-made cellular laboratories are crucial for this research. These specialized labs would simulate microgravity and incorporate advanced technology to study the behavior and function of bone-forming cells (osteoblasts) and stem cells under these conditions. By investigating cellular mechanisms and potential therapeutic targets, this research holds promise for developing novel bone regeneration strategies for astronauts. This could involve stimulating bone formation or promoting the activity of stem cells to repair and strengthen bones in space. The success of this approach relies on collaboration between clinical applications and molecular signaling research. It also underscores the need for a skilled team of scientist-astronauts to conduct in vivo bone regeneration research under microgravity conditions. This multifaceted approach has the potential to not only improve astronaut health and well-being, but also pave the way for a sustainable human presence in space. Furthermore, advancements in cellular therapies for bone health under microgravity could have applications on Earth for treating conditions like osteoporosis.

This paper investigates the instability of FC-72 vapor–liquid interface in a rectangular channel under different gravity conditions employing short-term microgravity experimental systems designed based on the drop tower platform. Visual observations and numerical simulations were conducted to monitor the behavior of vapor–liquid interface. The study reveals significant fluctuations, with liquid climbing along both sides of the channel after drop cabin releases. Higher initial liquid levels result in increased maximum liquid phase heights and decreased minimum values, with noticeable fluctuations. In microgravity, the maximum height gradually rises with significant fluctuations, while minimum height remains relatively stable. Increasing contact angle leads to reduced variation in maximum and minimum heights, with a distinctive upward slope of vapor–liquid interface observed at a 90° contact angle. The temporal evolution of vapor–liquid interface observed in simulations closely aligns with experimental findings. This study highlights the importance of considering various factors in designing experiments involving fluid systems with low surface tension, particularly in aerospace applications, and calls for further research to develop more sophisticated models and techniques for understanding and controlling vapor–liquid interface instability.

Proton Exchange Membrane Fuel Cell (PEMFC) technology has been receiving more attention recently and can play a more expanded role in space missions with low gravity or microgravity. The liquid water generation in the Gas Diffusion Layer (GDL) of a Proton Exchange Membrane Fuel Cell (PEMFC) increases the resistance to oxygen flow toward the catalyst layer. Water flooding inside the GDL can affect the PEMFC performance especially at higher current densities. Therefore, a good understanding of the effect of liquid water amount in the GDL is crucial to water management and, subsequently, to the performance of the fuel cell. The purpose of the present study is to investigate the effect of the microstructure characteristics of the GDL on the water flooding and liquid water distribution inside the GDL. A one-dimensional theoretical model has been developed. Results indicate that the porosity gradient has a significant effect on the liquid water saturation and the performance of the PEM fuel cell.

An integration of both passive and active techniques to enhance the heat exchange has emerged as a promising research area over the past few decades. Our present investigation focuses on the heat exchange due to thermal convection in a square cavity driven by a channel, utilizing ternary hybrid nanofluid. The governing equations were derived from the averaged formulations describing thermal vibrational convection, illustrated using the vorticity of the mean velocity and stream functions relevant to both the mean and fluctuating flows. The influence of vibration on the system is quantified using a dimensionless vibration factor, denoted as Gershuni number (Gs), which is proportional to the ratio of the mean vibrational buoyancy force to the product of momentum and thermal diffusivities. All computations were conducted with fixed values of the Prandtl number (Pr = 6.1) and Reynolds number (Re = 100). The influence of physical parameters, including the Grashof number ((10^3 le Gr le 10^6) ), Gershuni number ((10^3 le Gs le 10^6)), and volume fraction of nanomaterials ((0% le Phi le 4%)), particularly under two scenarios: microgravity ((Gr= 0)) and terrestrial conditions, on the streamlines for both the mean and fluctuating flows, isotherms, and mean Nusselt number are discussed graphically. Numerical results indicate that an increase of Grashof number boosts heat exchange by 250% under buoyancy effects. Elevating nanomaterial volume fractions enhances thermal conductivity, increasing heat exchange by 30%. However, heightened thermal vibration reduces heat exchange.

The study of cell membrane structures under microgravity is crucial for understanding the inherent physiological and adaptive mechanisms relevant to overcoming challenges in human space travel and gaining deeper insight into the membrane-protein interactions at reduced gravity. However, the membrane dynamics under microgravity conditions is not unraveled yet. Moreover, the complexity of cells poses significant challenges when investigating the effects of microgravity on individual components, including cell membranes. Giant Unilamellar Vesicles (GUVs) serve as valuable cell-mimicking models and act as artificial cells, providing insights into the biophysics of membrane architecture. Herein, we have elucidated the membrane dynamics of artificial cells under simulated microgravity conditions. GUVs were synthesized in the size range of 20 ± 2.1 μm and their morphological changes were examined under simulated microgravity conditions using a random positioning machine. We observed that the well-defined spherical GUVs were transfigured and deformed into elongated structures under microgravity conditions. The membrane fluidity of GUVs increased sevenfold under microgravity conditions compared to GUVs under normal gravity conditions at 48 h. It is also noted that there is a reduction in the membrane microviscosity. The study sheds light on the membrane mechanics under microgravity conditions and contributes valuable insights to the broader understanding of membrane responses to microgravity and its implications for space exploration and biomedical applications.

With NASA and other space agencies planning for longer-duration spaceflights, such as missions to Mars, and the rise in space tourism, it is crucial to comprehend the impact of the space environment on human health. However, there is a lack of information on how spaceflight impacts cerebrovascular health. The absence of gravitational force negatively affected various physiological functions in astronauts, especially posing risks to the cerebrovascular system. Exposure to microgravity leads to fluid changes that impact cardiac function, arterial pressure, and cerebrovascular structural changes that may be the cause of cognitive impairment. Numerous experiments have simulated microgravity to study the damage caused by prolonged spaceflight and reported similar findings. Understanding the effect of simulated microgravity on cerebrovascular structure and function has important implications for cerebrovascular health on Earth and in space. Simulated microgravity has been shown to induce endothelial dysfunction, altering nitric oxide (NO) synthesis pathways and increasing oxidative stress. Dysregulation of the Renin-Angiotensin system, NADPH oxidases, K⁺ Channels, and L-type Ca²⁺ Channels contributes to vascular dysfunction, while mitochondrial complexes expression and Ca²⁺ concentration exacerbate oxidative stress. This knowledge is essential for creating effective countermeasures to protect astronaut health during extended space missions. Therapeutic interventions targeting mitochondrial ROS and NADPH oxidases showed promise in mitigating these effects. This review article delves into the significant challenges posed by extended spaceflight, focusing on the cerebrovascular systems. It also provides a comprehensive understanding of molecular mechanisms associated with microgravity-induced cerebrovascular dysfunction and potential therapeutic interventions, paving the way for safer and more effective space travel.

Graphical Abstract

To study the effect of micro-structured surface with wedge-shaped channel on pool boiling heat transfer performance of FC-72, four kinds of mixed wettability surfaces with area ratio of the micro-pillar region to the smooth channel region of approximately 1:1 were fabricated in this study (the surfaces were denoted as the Multi tip surface, Multi star surface, Less tip surface and Less star surface). The experimental results indicated that the CHF increases with the increase of liquid subcooling. The structural surface parameters will affect the bubble dynamics behavior and thus affect CHF. The effect of capillary wick suction on the mixed wetting surface first increases and then decreases. The capillary wick suction plays a significant role in the increase of CHF, and the capillary wick force on the Less tip surface with the best heat transfer performance is the largest. The Zuber model is modified by combining three factors to propose a critical heat flux model suitable for mixed wetting surfaces. With the increase of heat flux, the bubble detachment frequency decreases, the bubble detachment diameter increases and the nucleation site density basically shows exponential growth. Bubbles in the micro-pillar array region will be driven to slip onto the smooth channel due to energy difference and the bubbles in smooth channels will also migrate in the direction of wider smooth channels under the action of Laplace force.