Effect of Gravity on the Macroscopic Advancing Contact Angle of Sessile Drops

A series of experiments were conducted in a reduced gravity (near‐free‐fall) environment (g = 0) and on ground (g = 1) to study the effect of gravity on the advancing contact angles of sessile drops. The reduced net acceleration force was produced by parabolic flights. The ground experiments were conducted for various three‐phase contact‐line advancing rates whereas the reduced gravity experiments were conducted for only one advancing rate due to the short duration of reduced gravity. The experimental results show that for water sessile drops on Teflon‐coated silicon wafers, the advancing contact angle in the reduced gravity environment is less than that of the advancing contact angle in 1g (126°) by about 5° for the same three‐phase contact line advancing rates.     

Fire safety research in microgravity: How to detect smoke and flames you cannot see

Any design requiring the application of technology contains a challenge to achieve a safe design. Manned space flight requires the highest degree of attention to crew safety, thus understanding and recognizing all potential risks involved. An important area of concern is establishing design criteria for a reliable fire detection and suppression system. This has been a main target when designing the European pressurized manned module Columbus Attached Laboratory as part of the international space station. This paper describes experiments performed to investigate the behavior of fires and the fluid dynamics of suppression agents in microgravity by means of parabolic flight maneuvers as an aid for the development of a design of a fire detection and suppression system for the manned Columbus Attached Laboratory.Reprinted fromHazard Prevention: Journal of the System Safety Society, Fourth Quarter, Volume 30, No. 4, 1994, with permission from the author.This paper was presented at the Twelfth International System Safety Society Conference in New Orleans, Louisiana, on July 5 through 10, 1994.     

Antibody-based Detection of <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 and <Emphasis Type="Italic">Salmonella enterica</Emphasis> Serovar Typhimurium Grown in Low-shear Modeled Microgravity

With the advent of prolonged spaceflights, it is important to determine if antibody-based assays can be used to monitor food and water for bacterial contaminants. In the present work, a ground-based high aspect ratio vessel (HARV) was used to determine if low shear modeled microgravity (LSMMG) alters antibody-binding to E. coli O157:H7 and Salmonella enterica serovar Typhimurium. Antibody–bacteria binding was similar under LSMMG and normal gravity because there was no difference in amount of captured bacteria measured by colony forming units (CFU) between assays conducted in the HARV and a conventional roller flask. The ability of E. coli O157:H7 and Salmonella Typhimurium grown in LSMMG to bind specific antibodies was also studied. After incubations of 4, 18 or 36 h in the HARV or a shaking incubator, bacteria were harvested for enzyme-linked immunosorbent assays (ELISA). In the E. coli O157:H7 ELISA using a goat polyclonal primary antibody, LSMMG did not alter the linear range of detection (10⁵–10⁷ cells/ml) nor the signal to noise ratio at any bacterial concentration. Although insignificant changes in signal to noise ratios were evident, LSMMG did not alter the range of detection (10⁵–10⁷ cells/ml) for Salmonella Typhimurium in ELISAs using either a polyclonal or a monoclonal antibody. These results suggest that immunoassays may be used in spacecrafts because LSMMG does not have significant deleterious effects on antibody-binding to bacteria nor does it significantly alter surface antigens necessary for antibody-based methods.     

Rac1/Wave2/Arp3 Pathway Mediates Rat Blood-Brain Barrier Dysfunction under Simulated Microgravity Based on Proteomics Strategy

The blood-brain barrier (BBB) is critical to maintaining central nervous system (CNS) homeostasis. However, the effects of microgravity (MG) on the BBB remain unclear. This study aimed to investigate the influence of simulated MG (SMG) on the BBB and explore its potential mechanism using a proteomic approach. Rats were tail-suspended to simulate MG for 21 days. SMG could disrupt the BBB, including increased oxidative stress levels, proinflammatory cytokine levels, and permeability, damaged BBB ultrastructure, and downregulated tight junctions (TJs) and adherens junctions (AJs) protein expression in the rat brain. A total of 554 differentially expressed proteins (DEPs) induced by SMG were determined based on the label-free quantitative proteomic strategy. The bioinformatics analysis suggested that DEPs were mainly enriched in regulating the cell–cell junction and cell–extracellular matrix biological pathways. The inhibited Ras-related C3 botulinum toxin substrate 1 (Rac1)/Wiskott–Aldrich syndrome protein family verprolin-homologous protein 2 (Wave2)/actin-related protein 3 (Arp3) pathway and the decreased ratio of filamentous actin (F-actin) to globular actin contributed to BBB dysfunction induced by SMG. In the human brain microvascular endothelial cell (HBMECs), SMG increased the oxidative stress levels and proinflammatory cytokine levels, promoted apoptosis, and arrested the cell cycle phase. Expression of TJs and AJs proteins were downregulated and the distribution of F-actin was altered in SMG-treated HBMECs. The key role of the Rac1/Wave2/Arp3 pathway in BBB dysfunction was confirmed in HBMECs with a specific Rac1 agonist. This study demonstrated that SMG induced BBB dysfunction and revealed that Rac1/Wave2/Arp3 could be a potential signaling pathway responsible for BBB disruption under SMG. These results might shed a novel light on maintaining astronaut CNS homeostasis during space travel.     

微重力锻炼平台造型设计探析

目的在研发设计空间站跑步机时,需要时刻利用微重力环境对样机进行实验验证。由此,工程师提出了微重力锻炼平台机械原理方案。微重力运动锻炼平台是一个在地面重力环境下模拟微重力环境的系统,可分别模拟航天员空间站微重力走跑训练和月球表面行走技能。为了让机械方案变成可供锻炼者使用的器材,就需要对其进行造型研究,以得出微重力运动锻炼平台竖直跑带长度、宽度以及显示屏距跑带的水平距离的人机工程尺寸,同时还要得出符合锻炼者审美的外观造型与配色方案。方法通过对空间站跑步机原理样机的研究分析,以人机工程学理论为指导,进行了平台的相关人机工程数据设计。通过对固定脚、立柱的形态与尺寸设计,对跑台的装饰设计,对肢体悬挂系统支架的包装设计,使得微重力锻炼平台的形态结构更加安全、稳定、均衡。结论锻炼平台的造型设计必须严格按照人机工程学原理进行,才能保证其安全性与合理性。     

微重力条件下Pd40Ni40P20合金凝固组织中磷原子的分布

在中国返地卫星上研究了Ｐｄ（４０）Ｎｉ（４０）Ｐ（２０）合金凝固样品中磷原子的分布行为。发现与重力条件下凝固样品相比，微重力条件下样品凝固组织中初生相的含磷量较低，而共晶区域内的平均磷含量较高。另外，微重力条件下样品显微组织中共晶区域内具有Ｐｄ－Ｎｉ固溶体晶格类型的相的形态和溶质原子磷含量均发生了明显的变化。讨论了微重力及重力凝固条件下溶质原子的分配原则，并对合金凝固过程中溶质原子磷的分布行为进行了分析。     

Effect of Marangoni number on thermocapillary convection and free-surface deformation in liquid bridges

Floating zone technique is a crucible-free process for growth of high quality single crystals. Unstable thermocapillary convection is a typical phenomenon during the process under microgravity. Therefore, it is very important to investigate the instability of thermocapillary convection in liquid bridges with deformable free-surface under microgravity. In this works, the Volume of Fluid(VOF) method is employed to track the free-surface movement. The results are presented as the behavior of flow structure and temperature distribution of the molten zone. The impact of Marangoni number(Ma) is also investigated on free-surface deformation as well as the instability of thermocapillary convection. The free-surface exhibits a noticeable axisymmetric(but it is non-centrosymmetric) and elliptical shape along the circumferential direction. This specific surface shape presents a typical narrow ‘neck-shaped' structure with convex at two ends of the zone and concave at the mid-plane along the axial direction. At both θ = 0° and θ = 90°, the deformation ratio ξ increases rapidly with Ma at first, and then increases slowly. Moreover, the hydrothermal wave number m and the instability of thermocapillary convection increase with Ma.     

硅酸铋(BSO)晶体的空间生长

BSO晶体首次在飞船上进行了空间晶体生长.本文对空间和地面生长的BSO晶体进行了X射线摇摆曲线、位错腐蚀和透过率的测试.实验结果表明:在微重力环境下能明显提高BSO晶体的光学质量.     

沸石和磷酸盐分子筛晶体的空间生长

沸石晶体是应用领域最广的分子筛材料.基于这一原因,长期以来人们几乎把"沸石"一词等同于分子筛.沸石晶体不仅可应用于催化、吸附、分离等过程,还可用于微型激光器、非线性光学材料及纳米器件等新兴领域.因此,分子筛材料的合成和晶体生长引起科学界和工业部门越来越浓厚的研究兴趣.1982年美国联合碳化物公司首次合成了新型磷酸铝分子筛,打破了分子筛由硅氧四面体和铝氧四面体组成的传统观念,此后许多AlPO4-n分子筛不断涌现.由于在地面上难以生长出较大尺度的沸石晶体,因而,自20世纪80年代以来,沸石晶体的合成已成为空间材料科学的研究热点之一.前苏联、欧洲、日本和美国已在空间完成了多次沸石和磷酸铝晶体生长试验.本文将首先介绍微重力环境对于分子筛晶体生长的有利条件.然后,简述国际上已完成的空间实验,包括:前苏联PHOTO返回卫星实验、欧洲和日本CASIMIR飞行实验、欧洲EURECA空间飞行平台实验、美国STS航天飞机实验、国际空间站(ISS)实验.最后综述空间实验的主要研究结果.     

风速对微小重力下粉粒体空气输送影响的研究

研究了一种在太空生产中的材料输送方式.通过数值仿真得出以下结论：采用管道空气输送能够减小压力损失从而提高能源利用率;对于不同种类的被输送物质,都可以找到合适的输送条件,既能够最大限度地减小动力,又不至于因为动力不足而无法输送;管道内粒子的运动轨迹几乎完全取决于气流.