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Search Results: 1 - 10 of 2490 matches for " Toru Kimura "
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Conditions for Gravitational Instability in Protoplanetary Disks
Shigeo S. Kimura,Toru Tsuribe
Physics , 2012, DOI: 10.1093/pasj/64.5.116
Abstract: Gravitational instability is one of considerable mechanisms to explain the formation of giant planets. We study the gravitational stability for the protoplanetary disks around a protostar. The temperature and Toomre's Q-value are calculated by assuming local equilibrium between viscous heating and radiative cooling (local thermal equilibrium). We assume constant $\alpha$ viscosity and use a cooling function with realistic opacity. Then, we derive the critical surface density $\Sigma_{\rm{c}}$ that is necessary for a disk to become gravitationally unstable as a function of $r$. This critical surface density $\Sigma_{\rm c}$ is strongly affected by the temperature dependence of the opacity. At the radius $r_{\rm c}\sim 20$AU, where ices form, the value of $\Sigma_{\rm c}$ changes discontinuously by one order of magnitude. This $\Sigma_{\rm c}$ is determined only by local thermal process and criterion of gravitational instability. By comparing a given surface density profile to $\Sigma_{\rm c}$, one can discuss the gravitational instability of protoplanetary disks. As an example, we discuss the gravitational instability of two semi-analytic models for protoplanetary disks. One is the steady state accretion disk, which is realized after the viscous evolution. The other is the disk that has the same angular momentum distribution with its parent cloud core, which corresponds to the disk that has just formed. As a result, it is found that the disks tend to become gravitationally unstable for $r\ge r_{\rm c}$ because ices enable the disks to become low temperature. In the region closer to the protostar than $r_{\rm c}$, it is difficult for a typical protoplanetary disk to fragment because of the high temperature and the large Coriolis force. From this result, we conclude that the fragmentation near the central star is possible but difficult.
A Study on Diagnostic Assist Systems of Chronic Obstructive Pulmonary Disease from Medical Images by Deep Learning  [PDF]
Toru Kimura, Takashi Kawakami, Akihiro Kikuchi, Ryosuke Ooev, Masaki Akiyama, Hiroyuki Horikoshi
Journal of Computer and Communications (JCC) , 2018, DOI: 10.4236/jcc.2018.61003
Abstract:
In this paper, we propose new diagnostic assist systems of medical images using deep learning algorithms. Specifically, we aim to develop a diagnostic support system for the very early stage of chronic obstructive pulmonary disease (COPD) based on the CT images. It is said that COPD is a disease that develops due to long-term smoking, and it is said that there are a large number of latent onset reserve forces. By discovering this COPD in the very early period 0 and improving the living conditions, subsequent severity can be avoided in many cases, so a system that will help diagnosis by professional radiologists is needed. We show the some experimental results examined by the constructed system.
Hepatic Arterial Infusion Chemotherapy for Advanced Hepatocellular Carcinoma in Japan
Hiroki Nishikawa,Yukio Osaki,Ryuichi Kita,Toru Kimura
Cancers , 2012, DOI: 10.3390/cancers4010165
Abstract: Transcatheter methods such as transcatheter arterial chemoembolization (TACE) and hepatic arterial infusion chemotherapy (HAIC) have an important role in the treatment for advanced hepatocellular carcinoma (HCC). Recently, sorafenib, an inhibitor of tyrosine kinases, has been found to obtain survival benefits in patients with HCC, leading to major advances in the treatment of advanced HCC. However, it is associated with a low tumor response rate, minimal survival advantage, and high rates of adverse events. On the other hand, high rates of objective treatment response with HAIC for advanced HCC have been reported, although convincing evidence of it contributing to overall survival in HAIC has been lacking. In Japan, HAIC still tends to be the preferred method for the treatment of advanced HCC, even in patients with poor liver function. However, the choice of chemotherapeutic agents in TACE/HAIC for HCC varies between institutions. In this review, based on studies reported to date in the literature, we refer to current knowledge regarding the chemotherapeutic agents used for TACE/HAIC for HCC in Japan and consider the future perspectives for HAIC for this cancer.
Radiofrequency ablation during continuous saline infusion can extend ablation margins
Toru Ishikawa,Tomoyuki Kubota,Ryoko Horigome,Naruhiro Kimura
World Journal of Gastroenterology , 2013, DOI: 10.3748/wjg.v19.i8.1278
Abstract: AIM: To determine whether fluid injection during radiofrequency ablation (RFA) can increase the coagulation area. METHODS: Bovine liver (1-2 kg) was placed on an aluminum tray with a return electrode affixed to the base, and the liver was punctured by an expandable electrode. During RFA, 5% glucose; 50% glucose; or saline fluid was infused continuously at a rate of 1.0 mL/min through the infusion line connected to the infusion port. The area and volume of the thermocoagulated region of bovine liver were determined after RFA. The Joule heat generated was determined from the temporal change in output during the RFA experiment. RESULTS: No liquid infusion was 17.3 ± 1.6 mL, similar to the volume of a 3-cm diameter sphere (14.1 mL). Mean thermocoagulated volume was significantly larger with continuous infusion of saline (29.3 ± 3.3 mL) than with 5% glucose (21.4 ± 2.2 mL), 50% glucose (16.5 ± 0.9 mL) or no liquid infusion (17.3 ± 1.6 mL). The ablated volume for RFA with saline was approximately 1.7-times greater than for RFA with no liquid infusion, representing a significant difference between these two conditions. Total Joule heat generated during RFA was highest with saline, and lowest with 50% glucose. CONCLUSION: RFA with continuous saline infusion achieves a large ablation zone, and may help inhibit local recurrence by obtaining sufficient ablation margins. RFA during continuous saline infusion can extend ablation margins, and may be prevent local recurrence.
Effect of Pegylated Interferon Therapy After Curative Treatment of Hepatitis C Virus-Related Hepatocellular Carcinoma - A Case Report
Hiroki Nishikawa,Yukio Osaki,Ryuichi Kita,Toru Kimura
Journal of Gastroenterology and Hepatology Research , 2012, DOI: 10.6051/j.issn.2224-3992.2012.01.032
Abstract: The 5-year recurrence rate of hepatocellular carcinoma (HCC) isknown to be as high as 60-100% even if radically treated by radiofrequencyablation (RFA) or surgery. Accordingly it is required to treatbackground liver disease after radical treatment of HCC. A 50s malewith hepatitis C virus-related HCC (Genotype1b, 300KIU/mL) underwentRFA followed by pegylated interferon (PEG-IFN) α-2b and ribavirincombination therapy. Although the patient had an early virologicalresponse (EVR), he experienced a relapse. The patient was treated withlow-dose Peg-IFNα2a administration (90μg/2-4 weeks) for persistentlynormal alanine aminotransferase (ALT) and was followed up.Peg-IFN-α2a administration was initiated at doses of 90μg. HCVRNA test becomes negative after single dose, and then the patientremained negative HCV RNA result and normal ALT level. Afterthree months, recurrence of HCC 1.5 cm in size located at segment 2of the liver was observed and treated with RFA. After that, Peg-IFN-α2a administration was restarted and he had persistently negativeHCV RNA result, normal ALT level, and normal alpha-fetoprotein(AFP) level. Six months after the end of IFN treatment, his HCVRNAtest was negative, that is to say, he obtained a sustained virologicalresponse (SVR). Moreover, there has been no evidence ofHCC recurrence for 24 months after the second treatment of RFA.The HCC patient with genotype 1b and high viral load was treatedwith radical RFA followed by low-dose Peg-IFNα2a, and his HCVRNA level became negative, and he obtained an SVR, and ALT andAFP levels became normal. It was speculated that the Peg-IFN-α2alow-dose administration might contribute to preventing subsequentrecurrence of HCC.
Expression of SLC2A9 Isoforms in the Kidney and Their Localization in Polarized Epithelial Cells
Toru Kimura, Michi Takahashi, Kunimasa Yan, Hiroyuki Sakurai
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084996
Abstract: Background Many genome-wide association studies pointed out that SLC2A9 gene, which encodes a voltage-driven urate transporter, SLC2A9/GLUT9 (a.k.a. URATv1), as one of the most influential genes for serum urate levels. SLC2A9 is reported to encode two splice variants: SLC2A9-S (512 amino acids) and SLC2A9-L (540 amino acids), only difference being at their N-termini. We investigated isoform-specific localization of SLC2A9 in the human kidney and role of N-terminal amino acids in differential sorting in vitro. Methodology/Principal Findings Isoform specific antibodies against SLC2A9 were developed and human kidney sections were stained. SLC2A9-S was expressed in the apical side of the collecting duct while SLC2A9-L was expressed in the basolateral side of the proximal tubule. GFP fused SLC2A9s were expressed in MDCK cells and intracellular localization was observed. SLC2A9-S was expressed at both apical and basolateral membranes, whereas SLC2A9-L was expressed only at the basolateral membrane. Although SLC2A9-L has a putative di-leucine motif at 33th and 34th leucine, deletion of the motif or replacement of leucine did not affect its subcellular localization. When up to 16 amino acids were removed from the N-terminal of SLC2A9-S or when up to 25 amino acids were removed from the N-terminal of SLC2A9-L, there was no change in their sorting. Deletion of 20 amino acids from SLC2A9-S was not expressed in the cell. More than 30 amino acids deletion from SLC2A9-L resulted in expression at both apical and basolateral membranes as well as in the lysosome. When amino acids from 25th and 30th were changed to alanine in SLC2A9-L, expression pattern was the same as wild-type. Conclusions/Significance SLC2A9-L was expressed in the basolateral membrane of kidney proximal tubules in humans and this isoform is likely to responsible for urate reabsorption. N-terminal amino acids unique to each isoform played an important role in protein stability and trafficking.
The Role for the Inner Disk in Mass Accretion to the Star in the Early Phase of Star Formation
Takuya Ohtani,Shigeo S. Kimura,Toru Tsuribe,Eduard I. Vorobyov
Physics , 2014, DOI: 10.1093/pasj/psu098
Abstract: A physical mechanism that drives FU Orionis-type outbursts is reconsidered. We study the effect of inner part of a circumstellar disk covering a region from near the central star to the radius of approximately $5$ AU (hereafter, the inner disk). Using the fluctuated mass accretion rate onto the inner disk $\dot{M}_{\rm out}$, we consider the viscous evolution of the inner disk and the time variability of the mass accretion rate onto the central star $\dot{M}_{\rm in}$ by means of numerical calculation of an unsteady viscous accretion disk in a one-dimensional axisymmetric model. First, we calculate the evolution of the inner disk assuming an oscillating $\dot{M}_{\rm out}$. It is shown that the time variability of $\dot{M}_{\rm in}$ does not coincide with $\dot{M}_{\rm out}$ due to viscous diffusion. Second, we investigate the properties of spontaneous outbursts with temporally constant $\dot{M}_{\rm out}$. Outburst occur only in a limited range of mass accretion rates onto the inner disk $10^{-10}<\dot{M}_{\rm out}< 3\times 10^{-6}~{\rm M}_{\odot} {\rm yr}^{-1}$ due to gravo-magneto limit cycle (GML). Finally, we discuss the case with a combination of episodic $\dot{M}_{\rm out}$ and accretion outbursts cause by the GML in the inner disk. The GML can drive accretion outbursts onto the star even for the case of fluctuating $\dot{M}_{\rm out}$, although fluctuations of $\dot{M}$ decay during transmitting the inner disk inwards. We newly identified two modes of outburst which are spontaneous one and stimulated one. In a stimulated mode of outburst, $\dot{M}_{\rm out}$ does appear directly in $\dot{M}_{\rm in}$ (the latter defining the stellar accretion luminosity). In a spontaneous mode of outburst, $\dot{M}_{\rm out}$ appears as the interval between outbursts.
Effect of Environmental and Lifestyle Factors on Hypertension: Shimane COHRE Study
Tsuyoshi Hamano, Yoshinari Kimura, Miwako Takeda, Masayuki Yamasaki, Minoru Isomura, Toru Nabika, Kuninori Shiwaku
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049122
Abstract: Background In recent years there has been increasing evidence of an association between residential remoteness and hypertension (HTN); however, no study has examined the effects of residential remoteness-lifestyle associations on HTN. The objective of this study was to evaluate the effects of residential remoteness, as measured by road network distance and elevation, and lifestyle associations, including access to daily products as a measure of car use, on HTN in a rural region in Japan. Method This is a cross-sectional population based study. We analyzed data from the Shimane COHRE study conducted from 2006 to 2009 in the rural mountainous regions of Japan. After excluding missing data, we conducted a logistic regression analysis of the data for 1,348 individuals and examined the effects of residential remoteness and lifestyle associations, including road network distance, elevation and access to daily products as a measure of car use, on the prevalence of HTN. Principal Findings In participants without access to car use, the odds ratios for self-reported HTN (i.e. taking antihypertensive medication) were significantly increased in those living in moderate (odds ratio (OR): 2.21, 95% confidence interval (CI): 1.19–4.08) and far (OR: 2.55, 95% CI: 1.00–6.51) road distances, whereas there were no significant associations in participants with access to car use. There were no significant associations between elevation and HTN for participants either with or without access to car transportation. Conclusions Our findings show that specific residential remoteness-hypertension associations vary according to access to daily products as a measure of car use in a rural mountainous area of Japan. These results advance the understanding and importance of considering residential environment, “where people live,” in establishing health policy.
Protein Phosphatase 2A Interacts with the Na+,K+-ATPase and Modulates Its Trafficking by Inhibition of Its Association with Arrestin
Toru Kimura, WonSun Han, Philipp Pagel, Angus C. Nairn, Michael J. Caplan
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029269
Abstract: Background The P-type ATPase family constitutes a collection of ion pumps that form phosphorylated intermediates during ion transport. One of the best known members of this family is the Na+,K+-ATPase. The catalytic subunit of the Na+,K+-ATPase includes several functional domains that determine its enzymatic and trafficking properties. Methodology/Principal Findings Using the yeast two-hybrid system we found that protein phosphatase 2A (PP2A) catalytic C-subunit is a specific Na+,K+-ATPase interacting protein. PP-2A C-subunit interacted with the Na+,K+-ATPase, but not with the homologous sequences of the H+,K+-ATPase. We confirmed that the Na+,K+-ATPase interacts with a complex of A- and C-subunits in native rat kidney. Arrestins and G-protein coupled receptor kinases (GRKs) are important regulators of G-protein coupled receptor (GPCR) signaling, and they also regulate Na+,K+-ATPase trafficking through direct association. PP2A inhibits association between the Na+,K+-ATPase and arrestin, and diminishes the effect of arrestin on Na+,K+-ATPase trafficking. GRK phosphorylates the Na+,K+-ATPase and PP2A can at least partially reverse this phosphorylation. Conclusions/Significance Taken together, these data demonstrate that the sodium pump belongs to a growing list of ion transport proteins that are regulated through direct interactions with the catalytic subunit of a protein phosphatase.
Further evidence for a male-selective genetic association of synapse-associated protein 97 (SAP97) gene with schizophrenia
Akihito Uezato, Junko Kimura-Sato, Naoki Yamamoto, Yoshimi Iijima, Hiroshi Kunugi, Toru Nishikawa
Behavioral and Brain Functions , 2012, DOI: 10.1186/1744-9081-8-2
Abstract: We investigated seven SAP97 single nucleotide polymorphisms (SNPs) that displayed a significant association with schizophrenia in our preceding study in an independent Japanese population consisting of a total of 393 unrelated patients with schizophrenia (232 males and 161 females) and 393 unrelated control subjects (211 males and 182 females).The SNP rs9843659 showed a significant genotypic association with male patients in a recessive model (p = 0.037). The analysis of the combined data from the current and prior studies also demonstrated a significant association of this SNP (p = 0.0039). The meta-analysis for the allele frequency covering the two studies yielded an odds ratio of 1.38.The present study replicated the previously reported male-selective genetic association between the SAP97 polymorphism and schizophrenia. These findings further support the possible involvement of the SAP97 gene variation in the susceptibility to schizophrenia in males and in the genetic basis for sex differences in the disorder.Schizophrenia is a serious psychiatric disorder with a high prevalence of nearly 1% and a wide variety of mental dysfunctions that are only partially improved by the current antipsychotic drugs. It is well accepted that multiple susceptibility genes may be involved in the pathogenesis of schizophrenia [1], and the search for such genes has produced promising results [2]. To obtain a further insight into the genetic factors, we have investigated the possible association between schizophrenia and the genes that are related to the impaired N-methyl-D-aspartate (NMDA) receptor-mediated glutamate neurotransmission and the development-dependent onset of schizophrenia, because 1) NMDA receptor antagonists, such as phencyclidine (PCP) and ketamine, cause the psychotic symptoms indistinguishable from those of schizophrenia [3,4], 2) the onset of schizophrenia and the above psychotomimetic effects typically occur after puberty [5-9], and 3) in experimental animals, th
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