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Constraints on modified Gauss-Bonnet gravity during big bang nucleosynthesis
Kusakabe, Motohiko,Koh, Seoktae,Kim, K. S.,Cheoun, Myung-Ki American Physical Society 2016 Physical Review D Vol.93 No.4
<P>Modified gravity is considered to be one of the possible explanations of the accelerated expansions of the present and the early universe. We study the effects of modified gravity on big bang nucleosynthesis (BBN). If the effects of modified gravity are significant during the BBN epoch, they should be observed as changes of primordial light element abundances. We assume a f(G) term with the Gauss-Bonnet term G, during the BBN epoch. A power-law relation of df/dG proportional to t(p) where t is the cosmic time was assumed for the function f(G) as an example case. We solve time evolutions of physical variables during BBN in the f(G) gravity model numerically, and we analyzed the calculated results. It is found that a proper solution for the cosmic expansion rate can be lost in some parameter region. In addition, we show that calculated results of primordial light element abundances can be significantly different from observational data. Especially, observational limits on the primordial D abundance leads to the strongest constraint on the f(G) gravity. We then derive constraints on parameters of the f(G) gravity taking into account the existence of the solution of expansion rate and final light element abundances.</P>
Phototransduction and Visual Cycle in the Ascidian Tadpole Larva
Kusakabe, Takehiro,Nakashima, Yuki,Kusakabe, Rie,Horie, Takeo,Kawakami, Isao,Yoshida, Reiko,Inada, Kyoko,Nakagawa, Masashi,Tsuda, Motoyuki Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
Ascidians are lower chordates, and their tadpole-like larvae share a basic body plan with vertebrates. To study photoreceptive systems in ascidians, we have isolated and characterized cDNA clones for three opsins, five G protein ${\alpha}$ subunits (G${\alpha}$), catalytic and regulatory subunits of cGMP phosphodiesterase (PDE), and arrestin from the ascidian Ciona intestinalis tadpole larva. Ci-opsin1 and Ci-opsin2 are vertebrate-type opsins, while Ci-opsin3 is a retinal photoisomerase similar to retinochrome and mammalian RGR. Both Ci-opsin1 and arrestin are specifically localized in the photoreceptor cells of the ocellus, whereas Ci -opsin2 is not expressed in the photoreceptors, but is co-localized in another population of neurons in the brain with PDE (Ci-PDE9 and Ci-PDE$\delta$). Ci-opsin3 is present in the entire region of the brain. Though five different cDNAs encoding Ga have been cloned, no transducin-type G protein has been found yet. Interestingly, one of G${\alpha}$i isoform is conspicuously expressed in the entire region of the brain. The Ci-opsin3 gene expression was observed in a broad area of the brain vesicle as well as in the visceral ganglion. Genes encoding ascidian homologs of CRALBP and ${\beta}$-CD, whose function is required for the mammalian visual cycle, are co-expressed with Ci-opsin3 in the brain vesicle and visceral ganglion. Localization of Ci-opsin3, CRALBP, and ${\beta}$-CD in a broad area of the brain suggests that the brain of the ascidian larva has a visual cycle system similar to that of the vertebrate RPE. Based on these data, we discuss the evolution of vertebrate visual systems.
PREPARATION OF SUPPORTED PALLADIUM MEMBRANE AND SEPARATION OF HYDROGEN
Morooka, Shigeharu,Kusakabe, Katsuki,Aoki, Kanna,Yokoyama, Shuichi 한국화학공학회 1996 Korean Journal of Chemical Engineering Vol.13 No.5
Palladium acetate was sublimed at a reduced pressure at 400℃, carried into the macropores of the porous wall of an α-alumina support tube and was decomposed there. A thin palladium membrane which was thus formed showed a hydrogen permeance of 10^6 ㏖·m ²·s ¹·Pa ¹ and a hydrogen/nitrogen permselectivity higher than 1000. The membrane was stable against hydrogen embrittlement even when the permeation temperature was varied between 100 and 300℃, and it was stable to sulfur or chlorine. To test the ability of this system for the separation of hydrogen and deuterium. a palladium disk was used instead of the prepared membrane since a definite membrane thickness was necessary for calculation. When H₂ and D₂ permeated through the membrane independently, the H/D permselectivity was approximately 7 at 150-200℃ under a feed side pressure of 0.4 MPa and a permeate side pressure of 0.1 MPa. When a mixture of H₂ and D, was fed, the H/D permselectivity was reduced to 1.2-1.6.