Formation of Warped Disks by Galactic Fly-by Encounters. I. Stellar Disks

Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and test the `fly-by scenario' of warp formation, in which impulsive encounters between galaxies are responsible for warped disks. Based on N-body simulations, we investigate the morphological and kinematical evolution of the stellar component of disks when galaxies undergo fly-by interactions with adjacent dark matter halos. We find that the so-called `S'-shaped warps can be excited by fly-bys and sustained for even up to a few billion years, and that this scenario provides a cohesive explanation for several key observations. We show that disk warp properties are governed primarily by the following three parameters; (1) the impact parameter, i.e., the minimum distance between two halos, (2) the mass ratio between two halos, and (3) the incident angle of the fly-by perturber. The warp angle is tied up with all three parameters, yet the warp lifetime is particularly sensitive to the incident angle of the perturber. Interestingly, the modeled S-shaped warps are often non-symmetric depending on the incident angle. We speculate that the puzzling U- and L-shaped warps are geometrically superimposed S-types produced by successive fly-bys with different incident angles, including multiple interactions with a satellite on a highly elongated orbit.Comment: 16 pages, 13 figures, 3 tables. Accepted for publication in Ap

The Influence Of Job Insecurity On Career Commitment And Attitude In Multinational Corporations

As the perception of lifelong work shifts into lifelong career in the job insecurity market, the career development of employees through professional and competitive career management has become more important than being loyal to a lifelong work. Furthermore, in the case of multinational corporations, such as differentiation from the head office policy, cultural differences in labor relations, and the liquidity of business withdrawal, such a feature has a higher possibility of job insecurity than general companies. Therefore, the purpose of this study is to verify empirically how job insecurity influences career commitment and career attitude through individual, job and career characteristics as intermediation with the members of multinational corporations as objectives. For this purpose, a total of 366 questionnaire data that targeted 27 multinational corporations were collected and analyzed. The result shows that the job insecurity of multinational corporations affects individual characteristic rather than job or career characteristic, and it is confirmed that individual characteristic has an effect on career commitment and career attitude. In the end, multinational corporations, unlike ordinary domestic companies, need active organizational career development program that corresponds to an open corporate culture as well as innovative and open systems and policies that balance both internal and external networking activities in terms of human resource management of corporations

Cyclophilin A Cpr1 Protein Modulates the Response of Antioxidant Molecules to Menadione-induced Oxidative Stress in Saccharomyces cerevisiae KNU5377Y

AbstractObjectivesThe cellular function of cyclophilin A (CypA) differs between organisms, even though CypA is conserved in both prokaryotes and eukaryotes. The purpose of this study was to elucidate the role of activated CypA isoform CPR1 in the antioxidative mechanisms of Saccharomyces cerevisiae under menadione (MD)-induced oxidative stress.MethodsFour S. cerevisiae strains, KNU5377Y (kwt) and BY4741 (bwt), and their isogenic cpr1Δ mutant strains (kc1 and bc1), were treated with MD, at a concentration ranging between 0.25 and 0.4 mM. Cpr1-mediated antioxidative effects were analyzed by measuring the levels of cellular glutathione (GSH) and ascorbate (AsA)-like molecules in yeast.ResultsGSH and AsA-like reductant molecule concentrations were more reduced in the presence of MD in the kc1 strain than in the kwt strain; whereas, there was no significant difference between the bwt and bc1 strains under the same conditions. In kc1 strain samples, we observed a reduction in the expression of proteins related both to GSH synthesis and the recycling system, and simultaneously, downregulation of GSH synthetase and GSH reductase activities were also evident. Oxidative stress in the kc1 strain was alleviated by the application of the GSH and AsA analog.ConclusionThese results indicate that activated Cpr1 modulates the response of antioxidant molecules involved in cellular redox homeostasis of KNU5377Y during oxidative stress induced by MD