scholarly journals Experimental and Numerical Study of Capillary Driven Flow in Vane-type Tank under Normal Gravity and Microgravity Conditions

2020 ◽  
Author(s):  
Ning Weng ◽  
Qinggong Wang ◽  
Yuying Wang ◽  
Jinyin Huang ◽  
Letian Yao ◽  
...  
Keyword(s):  
Normal Gravity ◽  
Numerical Study ◽  
Microgravity Conditions

Reaction and phase separation mechanisms during synthesis of alloys by thermite type combustion reactions

2003 ◽  
Vol 18 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Cheryl Lau ◽  
Alexander S. Mukasyan ◽  
Arvind Varma
Keyword(s):  
Phase Separation ◽  
Normal Gravity ◽  
Metal Alloy ◽  
Fundamental Study ◽  
Separation Mechanisms ◽  
Segregation Process ◽  
Microgravity Conditions ◽  
Gravity Driven ◽  
Orthopedic Applications

Combustion of the thermite system is a promising approach for synthesis of alloys (e.g., Co-based) that are widely used in orthopedic applications. This process typically involves formation of two liquids (oxide and metal alloy), followed by their phase separation. The latter is generally believed to be controlled solely by gravity-driven buoyancy. To verify this hypothesis, a fundamental study of phase separation during alloy synthesis was conducted in both normal gravity and microgravity conditions. It was shown that a non-gravity-driven mechanism primarily controls the segregation process. Quenching experiments identified the reaction and phase separation mechanisms in the investigated systems.

scholarly journals Transcriptomic analysis of DNA damage response in zebrafish embryos under simulated microgravity

2021 ◽  
Author(s):  
Subhrajit Barua ◽  
Elia Brodsky ◽  
Harpreet Kaur ◽  
Aleksei Komissarov
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Simulated Microgravity ◽  
Normal Gravity ◽  
Enrichment Analysis ◽  
Differentially Expressed ◽  
Pathway Enrichment Analysis ◽  
Zebrafish Embryos ◽  
Damage Response ◽  
Microgravity Conditions

Objective: The objective of this study is to study the transcriptome of zebrafish embryos subjected to simulated microgravity and explore affected biological pathways, especially DNA damage response (DDR). The research question is whether simulated microgravity can have an impact on the basic biology of cell division, DNA repair, inflammation, and other vital cellular mechanisms. To validate that such experiments can yield relevant insights into human health and microgravity, we will correlate the found effects of simulated microgravity on zebrafish embryos with the reported effects of spaceflight on astronauts. Methods: 12 wild-type zebrafish embryos of both sexes, and of 3 to 12 months of age were microinjected with 2 nL (1 μg/μL) poly I:C or mock PBS buffer (0.5% phenol red, 240 mM KCl, and 40 mM HEPES at pH 7.4) using a microinjector followed by subjecting them immediately to the simulated microgravity conditions generated by RCCS or the normal gravity conditions in a cell culture dish. RNA-SEQ was performed on the samples according to the standard protocol. Raw gene counts data were obtained from the public domain (NASA Gene Labs) and subjected to further downstream analyses. Differential gene expression was performed using DESeq2. The results were annotated using pathway enrichment analysis (GSEA) on the KEGG pathway database and compared with the result of the NASA twin study. Result: Similar to previously published analysis, we found that a significant number of genes were differentially expressed under simulated microgravity conditions. We identified a total of 7542 genes out of 16532 when comparing expression between the groups: simulated microgravity and normal gravity (padj. value <0.05, log2 fold change in between -2 and 2). Out of these genes, 4504 were found to be up-regulated while 3038 were down-regulated compared to controls. Pathway enrichment analysis revealed that simulated microgravity has an effect on vital basic biological processes like DNA repair, peptide transport, and metabolism. Various other well-known signalling pathways like Notch signalling, wnt signalling, and p53 signalling were also significantly altered. These pathways are known to play an important role in DDR. To explore if the same pathways were also altered in humans, we explored the NASA twin study data and found that DDR was also significantly affected in the astronaut but due to ionizing radiation. Upon further investigation, we found that 62 genes belonging to the DDR pathway were mutually differentially expressed in Scott Kelly and the zebrafish embryos. However, there were 29 significantly differentially expressed genes belonging to the DDR pathway in zebrafish embryos that were not found to be differentially expressed in Scott Kelly. Out of these 29 genes, 14 were specific to zebrafish. Upon further investigation, we found that the DDR pathway is affected differently in simulated microgravity as compared to ionizing radiation. Conclusion: Simulated microgravity alters numerous biological pathways in zebrafish embryos, including DDR. But the nature of it is different from that of real spaceflight induced DDR. These observations should be investigated further to actually understand the nature of DNA damage response during spaceflights.

scholarly journals Effect of the coefficient of restitution and friction in the granular Leidenfrost effect in the absence of gravity. A numerical study

2021 ◽  
Vol 249 ◽  
pp. 14016
Author(s):  
Daniel Schiochet Nasato ◽  
Heiko Briesen
Keyword(s):  
Coefficient Of Friction ◽  
Parametric Study ◽  
Granular Media ◽  
Numerical Study ◽  
Packing Fraction ◽  
Coefficient Of Restitution ◽  
Granular System ◽  
The Coefficient Of Friction ◽  
Leidenfrost Effect ◽  
Microgravity Conditions

In this study the granular Leidenfrost effect in the absence of gravity is investigated numerically by means of the discrete element method. Apart from identifying the phenomena, a parametric study to quantify the influence of the coefficient of restitution and friction in the packing fraction of the granular media is carried on numerically. Surprisingly, both the coefficient of restitution and the coefficient of friction exhibit an influence of the same magnitude in the packing fraction of the granular system, which has not been reported in experiments and simulation of granular Leidenfrost regime under gravity or microgravity conditions.

scholarly journals A computational study of soot formation and flame structure of coflow laminar methane/air diffusion flames under microgravity and normal gravity

2021 ◽  
Author(s):  
Armin Veshkini ◽  
Seth B. Dworkin
Keyword(s):  
Normal Gravity ◽  
Volume Fraction ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Numerical Study ◽  
Computational Study ◽  
Flame Structure ◽  
Chemical Kinetic ◽  
Surface Growth ◽  
Rate Of Increase

A numerical study is conducted of methane-air coflow diffusion flames at microgravity (μg) and normal gravity (lg), and comparisons are made with experimental data in the literature. The model employed uses a detailed gas phase chemical kinetic mechanism that includes PAH formation and growth, and is coupled to a sectional soot particle dynamics model. The model is able to accurately predict the trends observed experimentally with reduction of gravity without any tuning of the model for different flames. The microgravity sooting flames were found to have lower temperatures and higher volume fraction than their normal gravity counterparts. In the absence of gravity, the flame radii increase due to elimination of buoyance forces and reduction of flow velocity, which is consistent with experimental observations. Soot formation along the wings is seen to be surface growth dominated, while PAH condensation plays a more major role on centerline soot formation. Surface growth and PAH growth increase in microgravity primarily due to increases in the residence time inside the flame. The rate of increase of surface growth is more significant compared to PAH growth, which causes soot distribution to shift from the centerline of the flame to the wings in microgravity. Keywords: laminar diffusion flame,methane-air,microgravity, soot formation, numerical modelling

Modeling of Phosphate Ion Transfer to the Surface of Osteoblasts under Normal Gravity and Simulated Microgravity Conditions

2004 ◽  
Vol 1027 (1) ◽  
pp. 85-98 ◽  
Author(s):  
KARTHIK MUKUNDAKRISHNAN ◽  
PORTONOVO S. AYYASWAMY ◽  
MAKARAND RISBUD ◽  
HOWARD H. HU ◽  
IRVING M. SHAPIRO
Keyword(s):  
Simulated Microgravity ◽  
Normal Gravity ◽  
Ion Transfer ◽  
Phosphate Ion ◽  
Microgravity Conditions

Eddie Leonardi Memorial Lecture: “Natural Convection From Earth to Space”

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Victoria Timchenko
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Memorial Lecture ◽  
Numerical Studies ◽  
Fluid Properties ◽  
Microgravity Conditions

This lecture is dedicated to the memory of Professor Eddie Leonardi, formerly International Heat Transfer Conference (IHTC-13) Secretary, who tragically died at an early age on December 14, 2008. Eddie Leonardi had a large range of research interests: he worked in both computational fluid dynamics/heat transfer and refrigeration and air-conditioning for over 25 years. However starting from his Ph.D. ‘A numerical study of the effects of fluid properties on natural convection’ awarded in 1984, one of his main passions has been natural convection and therefore the focus of this lecture will be on what Eddie Leonardi has achieved in numerical and experimental investigations of laminar natural convective flows. A number of examples will be presented which illustrate important difficulties of numerical calculations and experimental comparisons. Eddie Leonardi demonstrated that variable properties have important effects and significant differences occur when different fluids are used, so that dimensionless formulation is not appropriate when dealing with flows of fluids with significant changes in transport properties. Difficulties in comparing numerical solutions with either numerically generated data or experimental results will be discussed with reference to two-dimensional natural convection and three-dimensional Rayleigh–Bénard convection. For a number of years Eddie Leonardi was involved in a joint US-French-Australian research program—the MEPHISTO experiment on crystal growth—and studied the effects of convection on solidification and melting under microgravity conditions. Some results of this research will be described. Finally, some results of experimental and numerical studies of natural convection for building integrated photovoltaic (BIPV) applications in which Eddie Leonardi had been working in the last few years will be also presented.

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