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Search Results: 1 - 10 of 867 matches for " Ryohei Fukuda "
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Effects of Triple-$α$ and $^{12}\rm C(α,γ)^{16}O$ Reaction Rates on the Supernova Nucleosynthesis in a Massive Star of 25 $M_{\odot}$
Yukihiro Kikuchi,Masa-aki Hashimoto,Masaomi Ono,Ryohei Fukuda
Physics , 2014,
Abstract: We investigate effects of triple-$\alpha$ and $^{12}\rm C(\alpha,\gamma) ^{16}O$ reaction rates on the production of supernova yields for a massive star of 25 $M_{\odot}$. We combine the reaction rates to examine the rate dependence, where the rates are considered to cover the possible variation of the rates based on experiments on the earth and theories. We adopt four combinations of the reaction rates from two triple-$\alpha$ reaction rates and two $^{12}\rm C(\alpha,\gamma)^{16}O$ ones. First, we examine the evolution of massive stars of 20 and 25 $M_{\odot}$ whose helium cores correspond to helium stars of 6 and 8 $M_{\odot}$, respectively. While the 25 $M_{\odot}$ stars evolve to the presupernova stages for all combinations of the reaction rates, evolutionary paths of the 20 $M_{\odot}$ stars proceed significantly different way for some combinations, which are unacceptable for progenitors of supernovae. Second, we perform calculations of supernova explosions within the limitation of spherical symmetry and compare the calculated abundance ratios with the solar system abundances. We can deduce some constraints to the reaction rates. As the results, a conventional rate is adequate for a triple-$\alpha$ reaction rate and a rather higher value of the reaction rate within the upper limit for the experimental uncertainties is favorable for a $^{12}\rm C(\alpha,\gamma)^{16}O$ rate.
Purification and properties of S-hydroxymethylglutathione dehydrogenase of Paecilomyces variotii no. 5, a formaldehyde-degrading fungus
Ryohei Fukuda, Kazuhiro Nagahama, Kohsai Fukuda, Keisuke Ekino, Takuji Oka, Yoshiyuki Nomura
AMB Express , 2012, DOI: 10.1186/2191-0855-2-32
-Process Nucleosynthesis in MHD Jet Explosions of Core-Collapse Supernovae
Motoaki Saruwatari,Masa-aki Hashimoto,Ryohei Fukuda,Shin-ichiro Fujimoto
Journal of Astrophysics , 2013, DOI: 10.1155/2013/506146
Abstract: We investigate the -process nucleosynthesis during the magnetohydrodynamical (MHD) explosion of a supernova in a helium star of 3.3? , where effects of neutrinos are taken into account using the leakage scheme in the two-dimensional (2D) hydrodynamic code. Jet-like explosion due to the combined effects of differential rotation and magnetic field is able to erode the lower electron fraction matter from the inner layers. We find that the ejected material of low electron fraction responsible for the -process comes out from just outside the neutrino sphere deep inside the Fe-core. It is found that heavy element nucleosynthesis depends on the initial conditions of rotational and magnetic fields. In particular, the third peak of the distribution is significantly overproduced relative to the solar system abundances, which would indicate a possible -process site owing to MHD jets in supernovae. 1. Introduction Study of the -process has been developed considerably keeping pace with the terrestrial experiments of nuclear physics far from the stability line of nuclides [1]. In particular, among the three peaks, which correspond to the elements of , , and , in the abundance pattern for the solar system -elements, the transition from the second to third peak elements has been stressed by nuclear physicists [2]. Although supernovae could be one of the astrophysical sites of the -process [2, 3], explosion mechanism is not still completely resolved, where supernova explosions are originated from the gravitational collapse of massive stars of ? [4, 5]. However it is unclear whether neutron-rich elements could be ejected or not during the shock wave propagation. As far as the one-dimensional calculations, almost all realistic numerical simulations concerning the collapse-driven supernovae of ? have failed to explode the outer layer above the Fe-core due to drooping of the energetic shock wave propagation [6, 7]. Although there exist calculations for 8 and 11? stars to explode, the explosion energies are very weak [8–15]. Therefore, a plausible site/mechanism of the -process has not yet been clarified. On the other hand, models of magnetorotational explosion (MRE) for core-collapse supernovae have been presented as a supernova mechanism [16–19] since both rapid rotations and/or strong magnetic fields could be resulted for neutron stars after the explosions. Furthermore, MRE with a realistic magnetic field configuration has been investigated [20–22]. In their series of papers, it has been shown that magnetorotational instability plays a critical role concerning the
The Effects of Opening Trade on Regional Inequality in a Model of Scale-Invariant Growth and Foot-Loose Capital  [PDF]
Katsufumi Fukuda
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.25078
Abstract: We consider a semi endogenous R & D growth model with international trade, foot-loose capital, and local and international knowledge spillovers in a closed economy and also international knowledge spillovers in an open economy. We show that by opening trade two regions diverge (converge) with (not) sufficiently high intertemporal knowledge spillover in the R & D sector and elasticity of substitution between modern goods, and not sufficiently high (sufficiently high) richer country A’s share of firm owned.
Periodontal Disease Bacteria Specific to Tonsil in IgA Nephropathy Patients Predicts the Remission by the Treatment
Yasuyuki Nagasawa, Kenichiro Iio, Shinji Fukuda, Yasuhiro Date, Hirotsugu Iwatani, Ryohei Yamamoto, Arata Horii, Hidenori Inohara, Enyu Imai, Takeshi Nakanishi, Hiroshi Ohno, Hiromi Rakugi, Yoshitaka Isaka
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0081636
Abstract: Background Immunoglobulin (Ig)A nephropathy (IgAN) is the most common form of primary glomerulonephritis in the world. Some bacteria were reported to be the candidate of the antigen or the pathogenesis of IgAN, but systematic analysis of bacterial flora in tonsil with IgAN has not been reported. Moreover, these bacteria specific to IgAN might be candidate for the indicator which can predict the remission of IgAN treated by the combination of tonsillectomy and steroid pulse. Methods and Findings We made a comprehensive analysis of tonsil flora in 68 IgAN patients and 28 control patients using Denaturing gradient gel electrophoresis methods. We also analyzed the relationship between several bacteria specific to the IgAN and the prognosis of the IgAN. Treponema sp. were identified in 24% IgAN patients, while in 7% control patients (P = 0.062). Haemophilus segnis were detected in 53% IgAN patients, while in 25% control patients (P = 0.012). Campylobacter rectus were identified in 49% IgAN patients, while in 14% control patients (P = 0.002). Multiple Cox proportional-hazards model revealed that Treponema sp. or Campylobactor rectus are significant for the remission of proteinuria (Hazard ratio 2.35, p = 0.019). There was significant difference in remission rates between IgAN patients with Treponema sp. and those without the bacterium (p = 0.046), and in remission rates between IgAN patients with Campylobacter rectus and those without the bacterium (p = 0.037) by Kaplan-Meier analysis. Those bacteria are well known to be related with the periodontal disease. Periodontal bacteria has known to cause immune reaction and many diseases, and also might cause IgA nephropathy. Conclusion This insight into IgAN might be useful for diagnosis of the IgAN patients and the decision of treatment of IgAN.
Error Correction of Enumerative Induction of Deterministic Context-free L-system Grammar
Ryohei Nakano
IAENG International Journal of Computer Science , 2013,
Khovanov homology and Rasmussen's s-invariants for pretzel knots
Ryohei Suzuki
Mathematics , 2006,
Abstract: We calculated the rational Khovanov homology of some class of pretzel knots, by using the spectral sequence constructed by P. Turner. Moreover, we determined the Rasmussen's s-invariant of almost of pretzel knots with three pretzels.
Infinite Sparse Block Model with Text Using 2DCRP
Ryohei Hisano
Statistics , 2015,
Abstract: A fundamental step in understanding the topology of a network is to uncover its latent block structure. To estimate the latent block structure with more accuracy, I propose an extension of the sparse block model, incorporating node textual information and an unbounded number of roles and interactions. The latter task is accomplished by extending the well-known Chinese restaurant process to two dimensions. Inference is based on collapsed Gibbs sampling, and the model is evaluated on both synthetic and real-world interfirm buyer-seller network datasets.
Heterostructure Solar Cells Based on Sol-Gel Deposited SnO2 and Electrochemically Deposited Cu2O  [PDF]
Akito Fukuda, Masaya Ichimura
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.46A001

To fabricate a heterostructure solar cell using environmentally friendly materials and low cost techniques, tin oxide (SnO2) and cuprous oxide (Cu2O) were deposited by the sol-gel method and the electrochemical deposition, respectively. The SnO2 films were deposited from a SnCl2 solution containing ethanol and acetic acid. The Cu2O films were deposited using a galvanostatic method from an aqueous bath containing CuSO4 and lactic acid at a temperature of 40°C. The Cu2O/SnO2 heterostructure solar cells showed rectification and photovoltaic properties, and the best cell showed a conversion efficiency of 6.6 × 10-2 % with an open-circuit voltage of 0.29 V, a short-circuit current of 0.58 mA/cm2, and a fill factor of 0.39.

Bioremediation of Bisphenol A by Glycosylation with Immobilized Marine Microalga Amphidinium crassum
——Bioremediation of Bisphenol a by Immobilized Cells

Kei Shimoda, Ryohei Yamamoto, Hiroki Hamada
Advances in Chemical Engineering and Science (ACES) , 2011, DOI: 10.4236/aces.2011.13015
Abstract: Glycosylation of bisphenol A, which is an endocrine disrupting chemical, was investigated using immobilized marine microalga and plant cells from the viewpoint of bioremediation of bisphenol A. Immobilized marine microalga of Amphidinium crassum glucosylated bisphenol A to the corresponding glucoside. On the other hand, bisphenol A was glycosylated to its glucoside, diglycoside, gentiobioside, and gentiobiosylglucoside, which was a new compound, by immobilized plant cells of Catharanthus roseus.
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