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Search Results: 1 - 10 of 2661 matches for " Takumi Yamada "
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Pulmonary Vein Isolation with a Multielectrode Basket Catheter
Takumi Yamada
Indian Pacing and Electrophysiology Journal , 2007,
Abstract: Pulmonary vein (PV) isolation (PVI) techniques have evolved as a curative treatment of atrial fibrillation (AF) since PVI guided by circumferential mapping with a circular catheter was initially proposed. A multielectrode basket catheter (MBC) is also useful for PVI because of some advantages; (1) an MBC provides some information about the PV anatomy on the fluoroscopic image, (2) an MBC can utilize the non-fluoroscopic navigation system, (3) an MBC enables the direct three-dimensional mapping around the PV ostium and antrum, (4) the distal electrodes of the MBC can be used to monitor some activation changes within the PV in real time and thereby indicate the effects of ablation at the ostium and antrum as radiofrequency lesions are created. PVI with an MBC is an effective and safe procedure to cure AF by integrating the PV anatomy and electrophysiology in combination with a non-fluoroscopic three-dimensional navigation system for the ablation catheter.
Post-Newtonian effects on Lagrange's equilateral triangular solution for the three-body problem
Takumi Ichita,Kei Yamada,Hideki Asada
Physics , 2010, DOI: 10.1103/PhysRevD.83.084026
Abstract: Continuing work initiated in earlier publications [Yamada, Asada, Phys. Rev. D 82, 104019 (2010), 83, 024040 (2011)], we investigate the post-Newtonian effects on Lagrange's equilateral triangular solution for the three-body problem. For three finite masses, it is found that the equilateral triangular configuration satisfies the post-Newtonian equation of motion in general relativity, if and only if all three masses are equal. When a test mass is included, the equilateral configuration is possible for two cases: (1) one mass is finite and the other two are zero, or (2) two of the masses are finite and equal, and the third one is zero, namely a symmetric binary with a test mass. The angular velocity of the post-Newtonian equilateral triangular configuration is always smaller than the Newtonian one, provided that the masses and the side length are the same.
Determination of light quark masses from the electromagnetic splitting of pseudoscalar meson masses computed with two flavors of domain wall fermions
Blum, Thomas;Doi, Takumi;Hayakawa, Masashi;Izubuchi, Taku;Yamada, Norikazu
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevD.76.114508
Abstract: We determine the light quark masses from lattice QCD simulations incorporating the electromagnetic interaction of valence quarks. The meson masses are calculated on lattice QCD configurations generated by the RBC Collaboration for two flavors of dynamical domain wall fermions, which are combined with QED configurations generated via quenched non-compact lattice QED. The electromagnetic part of the pion mass splitting is found to be $m_{\pi^+}-m_{\pi^0}=4.12(21)$ MeV, where only the statistical error is quoted, and similarly for the kaon, 1.443(55) MeV. Our results for the light quark masses are $m_u^{\rm\bar{MS}}$(2 GeV)=$3.02(27)(19)$ MeV, $m_d^{\rm\bar{MS}}$(2 GeV)=$5.49(20)(34)$ MeV, and $m_s^{\rm\bar{MS}}$(2 GeV)=$119.5(56)(74)$ MeV, where the first error is statistical and the second systematic. By averaging over $\pm e$ to cancel ${\cal O}(e)$ noise exactly on each combined gauge field configuration, we are able to work at physical $\alpha=1/137$ and obtain very small statistical errors. In our calculation, several sources of systematic error remain, including finite volume, non-zero lattice spacing, chiral extrapolation, quenched QED, and quenched strange quark, which may be more significant than the errors quoted above.
Atrial Tachycardia Originating from the Cavo-Tricuspid Isthmus May Exhibit Narrow P Waves
Takumi Yamada,Thomas McElderry,James D. Allred,Harish Doppalapudi
Indian Pacing and Electrophysiology Journal , 2010,
Abstract: An 83-year-old man underwent electrophysiological testing for focal atrial tachycardia (AT) exhibiting narrow P waves with negative deflections in the inferior leads. Catheter ablation at the cavo-tricuspid isthmus (CTI) successfully eliminated the AT. The propagation map during AT and pacing study from the successful ablation site demonstrated that the atrial activation throughout the CTI did not produce significant P wave deflections. Consequently, during AT, the left atrial activation time determined the P wave duration. This case demonstrates that AT originating from the CTI may exhibit narrow P waves which can be misinterpreted as AT originating from the inter-atrial septum.
Determination of light quark masses from the electromagnetic splitting of pseudoscalar meson masses computed with two flavors of domain wall fermions
Thomas Blum,Takumi Doi,Masashi Hayakawa,Taku Izubuchi,Norikazu Yamada
Physics , 2007, DOI: 10.1103/PhysRevD.76.114508
Abstract: We determine the light quark masses from lattice QCD simulations incorporating the electromagnetic interaction of valence quarks. The meson masses are calculated on lattice QCD configurations generated by the RBC Collaboration for two flavors of dynamical domain wall fermions, which are combined with QED configurations generated via quenched non-compact lattice QED. The electromagnetic part of the pion mass splitting is found to be $m_{\pi^+}-m_{\pi^0}=4.12(21)$ MeV, where only the statistical error is quoted, and similarly for the kaon, 1.443(55) MeV. Our results for the light quark masses are $m_u^{\rm\bar{MS}}$(2 GeV)=$3.02(27)(19)$ MeV, $m_d^{\rm\bar{MS}}$(2 GeV)=$5.49(20)(34)$ MeV, and $m_s^{\rm\bar{MS}}$(2 GeV)=$119.5(56)(74)$ MeV, where the first error is statistical and the second systematic. By averaging over $\pm e$ to cancel ${\cal O}(e)$ noise exactly on each combined gauge field configuration, we are able to work at physical $\alpha=1/137$ and obtain very small statistical errors. In our calculation, several sources of systematic error remain, including finite volume, non-zero lattice spacing, chiral extrapolation, quenched QED, and quenched strange quark, which may be more significant than the errors quoted above.
The isospin breaking effect on baryons with Nf=2 domain wall fermions
Takumi Doi,Thomas Blum,Masashi Hayakawa,Taku Izubuchi,Norikazu Yamada
Physics , 2006,
Abstract: We study the isospin breaking effect on octet baryons. Using the two-flavor dynamical domain-wall QCD configurations combined with the quenched non-compact QED configurations, the electromagnetic mass splittings between isomultiplets (p, n), (Sigma^+, Sigma^0, Sigma^-), (Xi^0, Xi^-) are investigated. We evaluate the main source of statistical fluctuations in the two-point correlation function, and find that the elimination of O(e) fluctuation (e: the QED charge) is essential to extract the signal. Preliminary results for $m_p - m_n$ as well as other mass splittings are presented. Possible origin of systematic uncertainty is also discussed.
Isospin symmetry breaking effects in the pion and nucleon masses
Ran Zhou,Thomas Blum,Takumi Doi,Masashi Hayakawa,Taku Izubuchi,Norikazu Yamada
Physics , 2008,
Abstract: We investigate the electromagnetic mass splittings in the pseudoscalar meson and nucleon systems by combining 2+1 flavor domain wall fermion gauge configurations, generated by the RBC and UKQCD collaborations, and quenched, non-compact, lattice QED configurations. We analyze finite volume effects by using $16^3\times 32$ and $24^3\times 64$ lattices.
Fermented Brown Sugar Residue Prolongs the Caenorhabditis elegans Lifespan via DAF-16  [PDF]
Takumi Satoh, Kazuichi Sakamoto
Food and Nutrition Sciences (FNS) , 2017, DOI: 10.4236/fns.2017.89061
Abstract: Purification of biomass ethanol from the products of brown sugar yeast-fermentation produces a large amount of residue. This fermentation residue contains abundant brown sugar-derived nutrients and is mainly used as compost or livestock feed. However, the in vivo physiological effects of oral residue ingestion are not known. The purpose of this study was to elucidate the physiological action and molecular mechanism of fermented brown sugar residue in nematode stress tolerance, aging, and lifespan using Caenorhabditis elegans. Fermented brown sugar residue was divided into two layers, supernatant and precipitate, and each was given to nematodes. Analysis of motility and survival rate under thermal stress revealed reduced mobility and increased survival rate following treatment with fermented brown sugar residue. The survival rate of nematodes under 1% H2O2 was markedly increased by the residue and mitochondrial membrane depolarization was induced and mitochondrial radical oxygen species levels increased. Furthermore, aging dependent reduction of motility was suppressed, and the average life span of nematodes was extended by treatment with fermented brown sugar residue. Moreover, the effects of fermented brown sugar residue on stress tolerance, lifespan elongation, and decreased aging dependent momentum reduction were lost in the daf-16 mutant. Taken together, our results show that the various physiological actions of fermented brown sugar residue, including stress tolerance and lifespan extension, occur via DAF-16.
Impaired Cognitive Function and Altered Hippocampal Synapse Morphology in Mice Lacking Lrrtm1, a Gene Associated with Schizophrenia
Noriko Takashima, Yuri S. Odaka, Kazuto Sakoori, Takumi Akagi, Tsutomu Hashikawa, Naoko Morimura, Kazuyuki Yamada, Jun Aruga
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022716
Abstract: Recent genetic linkage analysis has shown that LRRTM1 (Leucine rich repeat transmembrane neuronal 1) is associated with schizophrenia. Here, we characterized Lrrtm1 knockout mice behaviorally and morphologically. Systematic behavioral analysis revealed reduced locomotor activity in the early dark phase, altered behavioral responses to novel environments (open-field box, light-dark box, elevated plus maze, and hole board), avoidance of approach to large inanimate objects, social discrimination deficit, and spatial memory deficit. Upon administration of the NMDA receptor antagonist MK-801, Lrrtm1 knockout mice showed both locomotive activities in the open-field box and responses to the inanimate object that were distinct from those of wild-type mice, suggesting that altered glutamatergic transmission underlay the behavioral abnormalities. Furthermore, administration of a selective serotonin reuptake inhibitor (fluoxetine) rescued the abnormality in the elevated plus maze. Morphologically, the brains of Lrrtm1 knockout mice showed reduction in total hippocampus size and reduced synaptic density. The hippocampal synapses were characterized by elongated spines and diffusely distributed synaptic vesicles, indicating the role of Lrrtm1 in maintaining synaptic integrity. Although the pharmacobehavioral phenotype was not entirely characteristic of those of schizophrenia model animals, the impaired cognitive function may warrant the further study of LRRTM1 in relevance to schizophrenia.
Restoration of Dioxin-Induced Damage to Fetal Steroidogenesis and Gonadotropin Formation by Maternal Co-Treatment with α-Lipoic Acid
Takayuki Koga, Takumi Ishida, Tomoki Takeda, Yuji Ishii, Hiroshi Uchi, Kiyomi Tsukimori, Midori Yamamoto, Masaru Himeno, Masutaka Furue, Hideyuki Yamada
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040322
Abstract: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an endocrine disruptor, causes reproductive and developmental toxic effects in pups following maternal exposure in a number of animal models. Our previous studies have demonstrated that TCDD imprints sexual immaturity by suppressing the expression of fetal pituitary gonadotropins, the regulators of gonadal steroidogenesis. In the present study, we discovered that all TCDD-produced damage to fetal production of pituitary gonadotropins as well as testicular steroidogenesis can be repaired by co-treating pregnant rats with α-lipoic acid (LA), an obligate co-factor for intermediary metabolism including energy production. While LA also acts as an anti-oxidant, other anti-oxidants; i.e., ascorbic acid, butylated hydroxyanisole and edaravone, failed to exhibit any beneficial effects. Neither wasting syndrome nor CYP1A1 induction in the fetal brain caused through the activation of aryl hydrocarbon receptor (AhR) could be attenuated by LA. These lines of evidence suggest that oxidative stress makes only a minor contribution to the TCDD-induced disorder of fetal steroidogenesis, and LA has a restorative effect by targeting on mechanism(s) other than AhR activation. Following a metabolomic analysis, it was found that TCDD caused a more marked change in the hypothalamus, a pituitary regulator, than in the pituitary itself. Although the components of the tricarboxylic acid cycle and the ATP content of the fetal hypothalamus were significantly changed by TCDD, all these changes were again rectified by exogenous LA. We also provided evidence that the fetal hypothalamic content of endogenous LA is significantly reduced following maternal exposure to TCDD. Thus, the data obtained strongly suggest that TCDD reduces the expression of fetal pituitary gonadotropins to imprint sexual immaturity or disturb development by suppressing the level of LA, one of the key players serving energy production.
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