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Search Results: 1 - 10 of 400 matches for " Takatoshi Kasai "
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Systematic investigations of deep sub-barrier fusion reactions using an adiabatic approach
Takatoshi Ichikawa
Physics , 2015,
Abstract: To describe fusion hindrance observed in fusion reactions at extremely low incident energies, I propose a novel extension of the standard CC model by introducing a damping factor that describes a smooth transition from sudden to adiabatic processes. I demonstrate the performance of this model by systematically investigating various deep sub-barrier fusion reactions. I extend the standard CC model by introducing a damping factor into the coupling matrix elements in the standard CC model. I adopt the Yukawa-plus-exponential (YPE) model as a basic heavy ion-ion potential, which is advantageous for a unified description of the one- and two-body potentials. For the purpose of these systematic investigations, I approximate the one-body potential with a third-order polynomial function based on the YPE model. Calculated fusion cross sections for the medium-heavy mass systems of $^{64}$Ni + $^{64}$Ni, $^{58}$Ni + $^{58}$Ni, and $^{58}$Ni + $^{54}$Fe, the medium-light mass systems of $^{40}$Ca + $^{40}$Ca, $^{48}$Ca + $^{48}$Ca, and $^{24}$Mg + $^{30}$Si, and the mass-asymmetric systems of $^{48}$Ca + $^{96}$Zr and $^{16}$O + $^{208}$Pb are consistent with the experimental data. The astrophysical S factor and logarithmic derivative representations of these are also in good agreement with the experimental data. Since the results calculated with the damping factor are in excellent agreement with the experimental data in all systems, I conclude that the smooth transition from the sudden to adiabatic processes occurs and that a coordinate-dependent coupling strength is responsible for the fusion hindrance. In all systems, the potential energies at the touching point $V_{\rm Touch}$ strongly correlate with the incident threshold energies for which the fusion hindrance starts to emerge, except for the medium-light mass systems.
Relationship between Advanced Glycation End Products and Plaque Progression in Patients with Acute Coronary Syndrome: The JAPAN-ACS Sub-study
Yoshifumi Fukushima, Hiroyuki Daida, Takeshi Morimoto, Takatoshi Kasai, Katsumi Miyauchi, Sho-ichi Yamagishi, Masayoshi Takeuchi, Takafumi Hiro, Takeshi Kimura, Yoshihisa Nakagawa, Masakazu Yamagishi, Yukio Ozaki, Masunori Matsuzaki, JAPAN-ACS Investigators
Cardiovascular Diabetology , 2013, DOI: 10.1186/1475-2840-12-5
Abstract: Intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI) was undertaken, followed by the initiation of statin treatment (either 4 mg/day of pitavastatin or 20 mg/day of atorvastatin), in patients with ACS. In the 208 JAPAN-ACS subjects, PV using IVUS in non-culprit segment > 5 mm proximal or distal to the culprit lesion and, serum levels of AGEs and soluble RAGE (sRAGE) were measured at baseline and 8–12 months after PCI.At baseline, no differences in the levels of either AGEs or sRAGE were found between patients with DM and those without DM. The levels of AGEs decreased significantly with statin therapy from 8.6 ± 2.2 to 8.0 ± 2.1 U/ml (p < 0.001), whereas the levels of sRAGE did not change. There were no significant correlations between changes in PV and the changes in levels of AGEs as well as sRAGE. However, high baseline AGEs levels were significantly associated with plaque progression (odds ratio, 1.21; 95% confidence interval, 1.01 - 1.48; p = 0.044) even after adjusting for DM in multivariate logistic regression models.High baseline AGEs levels were associated with plaque progression in the JAPAN-ACS trial. This relationship was independent of DM. These findings suggest AGEs may be related to long-term glucose control and other oxidative stresses in ACS.NCT00242944Recent advances in plaque imaging have enabled the quantitative measurement of plaque volume (PV) and their characteristics[1,2]. Several clinical trials have observed significant plaque regression after treatment with HMG CoA-reductase inhibitors (statins) using intravascular ultrasound (IVUS) [3-6].Using IVUS, the Japan Assessment of Pitavastatin and Atorvastatin in Acute Coronary Syndrome (JAPAN–ACS) trial has demonstrated that early aggressive statin therapy (either pitavastatin or atorvastatin) in patients with acute coronary syndrome (ACS) significantly reduces PV of non-culprit coronary lesions during the first 8–12 months after ACS [7]. In this trial, the regression o
Remote-Plasma-Assisted Deposition of Pentacene Layer Using Atomic-Hydrogen  [PDF]
Satoshi Yamauchi, Takatoshi Minakuchi, Miyuki Onodera
Journal of Crystallization Process and Technology (JCPT) , 2014, DOI: 10.4236/jcpt.2014.41002
Abstract:

Pentacene thin layers were deposited on Si with the native oxide at 80°C by remote-plasma-assisted deposition (RPAD) using hydrogen-plasma cell to supply atomic hydrogen radicals. The deposition rate was increased by RPAD comparing to that by non-excited hydrogen gas supply whereas thermal evaporation rate of pentacene from crucible was same in the both process. DFM and XRD studies showed the grain laterally grew in the thin film phase with the size above 10 μm by RPAD. First-principles molecular orbital calculations suggested pentacene is evaporated from crucible as the trimer or larger cluster but atomic hydrogen penetrated into the cluster enhances cracking of pentacene clusters to the monomer.

Effect of Growing Soybean Plants Under Continuous Light on Leaf Photosynthetic Rate and Other Characteristics Concerning Biomass Production
Minobu Kasai
Journal of Agronomy , 2008,
Abstract: The present study investigated various characteristics concerning photosynthetic source capacity and biomass production of intact soybean plants grown under daily 10 h photoperiod as controls or under continuous light without darkness as CL plants from sowing. It was shown that while total photosynthetic source capacity and total dry matter production were larger in CL plants than in control plants, photosynthetic rate per unit leaf area and dry matter production of reproductive organs (pods) were smaller in CL plants than in control plants. It was also shown that CL plants had similar leaf intercellular CO2 concentration despite having lower leaf stomatal conductance and had lower activation state of Rubisco and similar content of leaf Rubisco as compared to control plants. With leaf microsomal membranes, three phosphatase activities, which have been found to increase under limitation of inorganic phosphate, were shown to be higher in CL plants than in control plants. Content of starch, a major photosynthetic end product in leaf was higher in CL plants than in control plants, showing that CL plants were subjected to a surplus source, an imbalance of photosynthetic source/sink balance. There are previous findings that inorganic phosphate stimulates the activation of Rubisco by promoting the binding of activator CO2 to the uncarbamylated inactive Rubisco. There is also evidence for the accumulation of starch in leaf under limitation of inorganic phosphate. Therefore, these results suggest that under continuous light that gives a surplus source, although plant total photosynthetic capacity and total biomass production are likely to increase, the efficiency of plant photosynthetic matter production is likely to decrease because of a lowered activation state of Rubisco that is likely to result from the limitation of inorganic phosphate. It is thus suggested that for the efficient improvement of plant biomass production, well-balanced improvement of source and sink would be essential.
An analytical approximation of the growth function in Friedmann-Lema?tre universes
Masumi Kasai
Physics , 2010,
Abstract: We present an analytical approximation formula for the growth function in a spatially flat cosmology with dust and a cosmological constant. Our approximate formula is written simply in terms of a rational function. We also show the approximate formula in a dust cosmology without a cosmological constant, directly as a function of the scale factor in terms of a rational function. The single rational function applies for all, open, closed and flat universes. Our results involve no elliptic functions, and have very small relative error of less than 0.2 per cent over the range of the scale factor $1/1000 \la a \lid 1$ and the density parameter $0.2 \la \Omega_{\rmn{m}} \lid 1$ for a flat cosmology, and less than $0.4$ per cent over the range $0.2 \la \Omega_{\rmn{m}} \la 4$ for a cosmology without a cosmological constant.
Strategy for Designing Self-Assembling Peptides to Prepare Transparent Nanofiber Hydrogel at Neutral pH
Hidenori Yokoi,Takatoshi Kinoshita
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/537262
Abstract: This study examined the formation of nanofiber hydrogels at neutral pH for 16 types of peptides with different net charges, hydrophobicities, and degrees of polymerization. The peptides formed various hydrogels depending on the arrangement of charged amino acids in the antiparallel β-sheet structure. Circular dichroism (CD) measurement, atomic force microscopy (AFM), visible light spectroscopy, and dynamic viscoelasticity measurement showed that the formation of transparent nanofiber hydrogels in peptides requires at least 2 additional positively or negatively charged amino acids per peptide. When designing the amino acid sequence, it is important to consider both the net charge and position of the charged amino acids, and it should be ensured that basic amino acids do not face other basic ones in the antiparallel β-sheet structure. Peptides that had charged amino acids clustered at the center of the nanofiber formed rigid gels.
Complex Feeding Tracks of the Sessile Herbivorous Insect Ophiomyia maura as a Function of the Defense against Insect Parasitoids
Yoshiko Ayabe, Takatoshi Ueno
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032594
Abstract: Because insect herbivores generally suffer from high mortality due to their natural enemies, reducing the risk of being located by natural enemies is of critical importance for them, forcing them to develop a variety of defensive measures. Larvae of leaf-mining insects lead a sedentary life inside a leaf and make conspicuous feeding tracks called mines, exposing themselves to the potential risk of parasitism. We investigated the defense strategy of the linear leafminer Ophiomyia maura Meigen (Diptera: Agromyzidae), by focusing on its mining patterns. We examined whether the leafminer could reduce the risk of being parasitized (1) by making cross structures in the inner area of a leaf to deter parasitoids from tracking the mines due to complex pathways, and (2) by mining along the edge of a leaf to hinder visually searching parasitoids from finding mined leaves due to effective background matching of the mined leaves among intact leaves. We quantified fractal dimension as mine complexity and area of mine in the inner area of the leaf as interior mine density for each sample mine, and analyzed whether these mine traits affected the susceptibility of O. maura to parasitism. Our results have shown that an increase in mine complexity with the development of occupying larvae decreases the probability of being parasitized, while interior mine density has no influence on parasitism. These results suggest that the larval development increases the host defense ability through increasing mine complexity. Thus the feeding pattern of these sessile insects has a defensive function by reducing the risk of parasitism.
Damping of Quantum Vibrations Revealed in Deep Sub-barrier Fusion
Takatoshi Ichikawa,Kenichi Matsuyanagi
Physics , 2013,
Abstract: We demonstrate that when two colliding nuclei approach each other, their quantum vibrations are damped near the touching point. We show that this damping is responsible for the fusion hindrance phenomena measured in the deep sub-barrier fusion reactions. To show those, we for the first time apply the random-phase-approximation (RPA) method to the two-body $^{16}$O + $^{16}$O and $^{40}$Ca + $^{40}$Ca systems. We calculate the octupole transition strengths for the two nuclei adiabatically approaching each other. The calculated transition strength drastically decreases near the touching point, strongly suggesting the vanishing of the quantum couplings between the relative motion and the vibrational intrinsic degrees of freedom of each nucleus. Based on this picture, we also calculate the fusion cross section for the $^{40}$Ca + $^{40}$Ca system using the coupled-channel method with the damping factor simulating the vanishing of the couplings. The calculated results reproduce well the experimental data, indicating that the smooth transition from the sudden to adiabatic processes indeed occurs in the deep sub-barrier fusion reactions.
A Universal Damping Mechanism of Quantum Vibrations in Deep Sub-Barrier Fusion Reactions
Takatoshi Ichikawa,Kenichi Matsuyanagi
Physics , 2015, DOI: 10.1103/PhysRevC.92.021602
Abstract: We demonstrate the damping of quantum octupole vibrations near the touching point when two colliding nuclei approach each other in the mass-asymmetric $^{208}$Pb + $^{16}$O system, for which the strong fusion hindrance was clearly observed. We, for the first time, apply the random-phase approximation method to the heavy-mass asymmetric di-nuclear system to calculate the transition strength $B$(E3) as a function of the center-of-mass distance. The obtained $B$(E3) strengths are substantially damped near the touching point, because the single-particle wave functions of the two nuclei strongly mix with each other and a neck is formed. The energy-weighted sums of $B$(E3) are also strongly correlated with the damping factor which is phenomenologically introduced in the standard coupled-channel calculations to reproduce the fusion hindrance. This strongly indicates that the damping of the quantum vibrations universally occurs in the deep sub-barrier fusion reactions.
Calculations of Branching Ratios for Radiative-Capture, One-Proton, and Two-Neutron Channels in the Fusion Reaction $^{209}$Bi+$^{70}$Zn
Takatoshi Ichikawa,Akira Iwamoto
Physics , 2010, DOI: 10.1143/JPSJ.79.074201
Abstract: We discuss the possibility of the non-one-neutron emission channels in the cold fusion reaction $^{70}$Zn + $^{209}$Bi to produce the element Z=113. For this purpose, we calculate the evaporation-residue cross sections of one-proton, radiative-capture, and two-neutron emissions relative to the one-neutron emission in the reaction $^{70}$Zn + $^{209}$Bi. To estimate the upper bounds of those quantities, we vary model parameters in the calculations, such as the level-density parameter and the height of the fission barrier. We conclude that the highest possibility is for the 2n reaction channel, and its upper bounds are 2.4$%$ and at most less than 7.9% with unrealistic parameter values, under the actual experimental conditions of [J. Phys. Soc. Jpn. {\bf 73} (2004) 2593].
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