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Search Results: 1 - 10 of 120918 matches for " T. T. Takahashi "
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Lattice QCD study of $g_A^{N^*N^*}$ with two flavors of dynamical quarks
T. T. Takahashi,T. Kunihiro
Physics , 2007, DOI: 10.1142/S0217732308029332
Abstract: We report the first lattice QCD result of the axial charge of N(1535), $g_A^{N^*N^*}$. The measurement is performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at $\beta$=1.95 and the mean-field improved clover quark action with the hopping parameters, $\kappa$=0.1375, 0.1390 and 0.1400. In order to avoid the signal contaminations by N(1650) lying just 100 MeV above N(1535), we construct 2$\times$2 correlation matrices and diagonalize them so that clear signal separation can be found. The wraparound contributions in the correlator, which can be another source of signal contamination, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N(1535) takes small values as $g_A^{N^*N^*}\sim 0.2$, independent of quark masses, in the pion-mass range of 0.7 to 1.1 GeV.
Detailed analysis of the gluonic excitation in the three-quark system in lattice QCD
T. T. Takahashi,H. Suganuma
Physics , 2004, DOI: 10.1103/PhysRevD.70.074506
Abstract: We study the excited-state potential and the gluonic excitation in the static three-quark (3Q) system using SU(3) lattice QCD with $16^3\times 32$ at $\beta$=5.8 and 6.0 at the quenched level. For about 100 different patterns of spatially-fixed 3Q systems, we accurately extract the excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ together with the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ by diagonalizing the QCD Hamiltonian in the presence of three quarks. The gluonic excitation energy $\Delta E_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$ is found to be about 1 GeV at the typical hadronic scale. This large gluonic-excitation energy is conjectured to give a physical reason of the success of the quark model for low-lying hadrons even without explicit gluonic modes. We investigate the functional form of $\Delta E_{\rm 3Q}$ in terms of the 3Q location. The lattice data of $\Delta E_{\rm 3Q}$ are relatively well reproduced by the ``inverse Mercedes Ansatz'' with the ``modified Y-type flux-tube length'', which indicates that the gluonic-excitation mode is realized as a complicated bulk excitation of the whole 3Q system.
Decalcified choroidal osteoma found in the retina
Yoshikawa T, Takahashi K
Clinical Ophthalmology , 2012, DOI: http://dx.doi.org/10.2147/OPTH.S37952
Abstract: alcified choroidal osteoma found in the retina Case report (1422) Total Article Views Authors: Yoshikawa T, Takahashi K Published Date November 2012 Volume 2012:6 Pages 1823 - 1825 DOI: http://dx.doi.org/10.2147/OPTH.S37952 Received: 10 September 2012 Accepted: 16 October 2012 Published: 02 November 2012 Tadanobu Yoshikawa, Kanji Takahashi Department of Ophthalmology, Kansai Medical University, Hirakata Hospital, Osaka, Japan Abstract: Choroidal osteoma is a benign tumor of the choroid. Herein, we report a rare case of decalcified choroidal osteoma found in the retina. A 27-year-old woman presented with visual loss. Her best-corrected visual acuity was 20/50 OS. Ophthalmoscopy of the left eye revealed a yellow-white calcified region accompanied by a decalcified region of four disc diameters in size. After 6 years, spectral-domain optical coherence tomography showed a tumor projected strongly upwards from the choroid and partially through the retina with serous retinal detachment, with both a lamellar appearance and mound-like area. The calcified region became more contractive than was observed on the first visit. Conversely, the decalcified region was wider than was observed on the first visit. Her best-corrected visual acuity was 20/400 OS. Choroidal osteoma was worsened by progression of decalcification. The decalcified choroidal osteoma resulted in poor visual acuity, and projected strongly upward from the choroid and into the retina.
Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles
T. Furukawa,Y. Takahashi
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2011, DOI: 10.5194/acp-11-4289-2011
Abstract: Atmospheric aerosols have both a direct and an indirect cooling effect that influences the radiative balance at the Earth's surface. It has been estimated that the degree of cooling is large enough to weaken the warming effect of carbon dioxide. Among the cooling factors, secondary organic aerosols (SOA) play an important role in the solar radiation balance in the troposphere as SOA can act as cloud condensation nuclei (CCN) and extend the lifespan of clouds because of their high hygroscopic and water soluble nature. Oxalic acid is an important component of SOA, and is produced via several formation pathways in the atmosphere. However, it is not certain whether oxalic acid exists as free oxalic acid or as metal oxalate complexes in aerosols, although there is a marked difference in their solubility in water and their hygroscopicity. We employed X-ray absorption fine structure spectroscopy to characterize the calcium (Ca) and zinc (Zn) in aerosols collected at Tsukuba in Japan. Size-fractionated aerosol samples were collected for this purpose using an impactor aerosol sampler. It was shown that 10–60% and 20–100% of the total Ca and Zn in the finer particles (<2.1 μm) were present as Ca and Zn oxalate complexes, respectively. Oxalic acid is hygroscopic and can thus increase the CCN activity of aerosol particles, while complexes with various polyvalent metal ions such as Ca and Zn are not hygroscopic, which cannot contribute to the increase of the CCN activity of aerosols. Based on the concentrations of noncomplexed and metal-complexed oxalate species, we found that most of the oxalic acid is present as metal oxalate complexes in the aerosols, suggesting that oxalic acid does not always increase the hygroscopicity of aerosols in the atmosphere. Similar results are expected for other dicarboxylic acids, such as malonic and succinic acids. Thus, it is advisable that the cooling effect of organic aerosols should be estimated by including the information on metal oxalate complexes and metal complexes with other dicarboxylic acids in aerosols.
Decalcified choroidal osteoma found in the retina
Yoshikawa T,Takahashi K
Clinical Ophthalmology , 2012,
Abstract: Tadanobu Yoshikawa, Kanji TakahashiDepartment of Ophthalmology, Kansai Medical University, Hirakata Hospital, Osaka, JapanAbstract: Choroidal osteoma is a benign tumor of the choroid. Herein, we report a rare case of decalcified choroidal osteoma found in the retina. A 27-year-old woman presented with visual loss. Her best-corrected visual acuity was 20/50 OS. Ophthalmoscopy of the left eye revealed a yellow-white calcified region accompanied by a decalcified region of four disc diameters in size. After 6 years, spectral-domain optical coherence tomography showed a tumor projected strongly upwards from the choroid and partially through the retina with serous retinal detachment, with both a lamellar appearance and mound-like area. The calcified region became more contractive than was observed on the first visit. Conversely, the decalcified region was wider than was observed on the first visit. Her best-corrected visual acuity was 20/400 OS. Choroidal osteoma was worsened by progression of decalcification. The decalcified choroidal osteoma resulted in poor visual acuity, and projected strongly upward from the choroid and into the retina.Keywords: osteoma, decalcification, choroidal osteoma
Removal of Z_3-symmetry breaking from Fermionic Determinants
Toru T. Takahashi
Physics , 2008,
Abstract: We consider prescriptions that are free from the direct charge-screening effects by quark loops and enable us to clarify the confining nature of a vacuum. We test two candidates for an order parameter, a Polyakov loop ($P$) evaluated in zero-triality backgrounds and fermionic determinants (${\mathcal D}_{1,2}$) with non-zero triality. Especially, ${\mathcal D}_{1,2}$ has very small fluctuations in comparison with a Polyakov loop in zero-triality sector, and seems to well reflect the characteristic of a vacuum. Such prescriptions could be still usable for the clarification of the confinement property of a vacuum.
Low-lying Dirac eigenmodes and monopoles in 3+1D compact QED
Toru T. Takahashi
Physics , 2008, DOI: 10.1088/1126-6708/2008/05/094
Abstract: We study the properties of low-lying Dirac modes in quenched compact QED at $\beta =1.01$, employing $12^3\times N_t$ ($N_t =4,6,8,10,12$) lattices and the overlap formalism for the fermion action. We pay attention to the spatial distributions of low-lying Dirac modes below and above the ``phase transition temperature'' $T_c$. Near-zero modes are found to have universal anti-correlations with monopole currents, and are found to lose their temporal structures above $T_c$ exhibiting stronger spatial localization properties. We also study the nearest-neighbor level spacing distribution of Dirac eigenvalues and find a Wigner-Poisson transition.
Low-lying Dirac eigenmodes and monopoles in 4D compact QED
Toru T. Takahashi
Physics , 2007, DOI: 10.1088/1126-6708/2007/11/047
Abstract: We study the properties of low-lying Dirac modes in quenched compact QED at $\beta$=0.99, 1.01 and 1.03, employing $12^3\times 12$ lattices and the overlap formalism for the fermion action. We pay special attention to the spatial distributions of the low-lying Dirac modes. Near-zero modes are found to have universal anti-correlations with monopole currents below/above the critical $\beta$. We also study the nearest-neighbor level spacing distribution of Dirac eigenvalues and find a signal of a Wigner-Poisson transition. We make a possible speculation on the chiral phase transition in 4D compact QED.
锆诱导的五元环化合物的新和成
席婵娟,TAKAHASHI,T
化学学报 , 2001,
Abstract: 由锆杂五元环化合物出发合成五元环有机化合物,只要求一个碳单元并且形成两个碳-碳链,从以下四个方面描述了利用锆杂环化物合成五元环有机化合物的新合成方法(1)CO或RNC的插入反应;(2)与丙炔酸酯的加成反应-峡谷次的Michael加成;(3)与碘代丙烯酸酯或碘代环烯酮的偶联加成反应-先偶联后Michael加成;(4)与酰氯的取代加成反应-先亲核取代后亲核加成,每类反应都含有数个简单反应类型。
Nuclear force in Lattice QCD
T. T. Takahashi,T. Doi,H. Suganuma
Physics , 2006, DOI: 10.1063/1.2220240
Abstract: We perform the quenched lattice QCD analysis on the nuclear force (baryon-baryon interactions). We employ $20^3\times 24$ lattice at $\beta=5.7$ ($a\simeq 0.19$ fm) with the standard gauge action and the Wilson quark action with the hopping parameters $\kappa=0.1600, 0.1625, 0.1650$, and generate about 200 gauge configurations. We measure the temporal correlators of the two-baryon system which consists of heavy-light-light quarks. We extract the inter-baryon force as a function of the relative distance $r$. We also evaluate the contribution to the nuclear force from each ``Feynman diagram'' such as the quark-exchange diagram individually, and single out the roles of Pauli-blocking effects or quark exchanges in the inter-baryon interactions.
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