206 research outputs found
Lattice QCD Study for the Interquark Force in Three-Quark and Multi-Quark Systems
We study the three-quark and multi-quark potentials in SU(3) lattice QCD.
From the accurate calculation for more than 300 different patterns of 3Q
systems, the static ground-state 3Q potential is found
to be well described by the Coulomb plus Y-type linear potential (Y-Ansatz)
within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type flux-tube
formation is actually observed on the lattice in maximally-Abelian projected
QCD. For about 100 patterns of 3Q systems, we perform the accurate calculation
for the 1st excited-state 3Q potential by diagonalizing
the QCD Hamiltonian in the presence of three quarks, and find a large
gluonic-excitation energy of about 1 GeV, which gives a physical reason of
the success of the quark model. is found to be reproduced
by the ``inverse Mercedes Ansatz'', which indicates a complicated bulk
excitation for the gluonic-excitation mode. We study also the tetra-quark and
the penta-quark potentials in lattice QCD, and find that they are well
described by the OGE Coulomb plus multi-Y type linear potential, which supports
the flux-tube picture even for the multi-quarks. Finally, the narrow decay
width of penta-quark baryons is discussed in terms of the QCD string theory.Comment: Invited talk at Int. Conference on Quark Confinement and the Hadron
Spectrum 6, Sardinia, Italy, 21-25 Sep 200
Magnetic field-induced one-magnon Raman scattering in the magnon Bose-Einstein condensation phase of TlCuCl
We report the observation of the -symmetric one-magnon Raman peak
in the magnon Bose-Einstein condensation phase of TlCuCl. Its Raman shift
traces the one-magnon energy at the magnetic point, and its intensity
is proportional to the squared transverse magnetization. The appearance of the
one-magnon Raman scattering originates from the exchange magnon Raman process
and reflects the change of the magnetic-state symmetry. Using the bond-operator
representation, we theoretically clarify the Raman selection rules, being
consistent with the experimental results.Comment: 6 pages, 4 figure
Molecular aggregation : the design and synthesis of three-dimensional self-assembling systems
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1995.Includes bibliographical references.by Maria F. Tymoschenko.M.S
Energetics of Forced Thermal Ratchet
Molecular motors are known to have the high efficiency of energy
transformation in the presence of thermal fluctuation.
Motivated by the surprising fact, recent studies of thermal ratchet models
are showing how and when work should be extracted from non-equilibrium
fluctuations.
One of the important finding was brought by Magnasco where he studied the
temperature dependence on the fluctuation-induced current in a ratchet
(multistable) system and showed that the current can generically be maximized
in a finite temperature.
The interesting finding has been interpreted that thermal fluctuation is not
harmful for the fluctuation-induced work and even facilitates its efficiency.
We show, however, this interpretation turns out to be incorrect as soon as we
go into the realm of the energetics
[Sekimoto,J.Phys.Soc.Jpn.66,1234-1237(1997)]: the efficiency of energy
transformation is not maximized at finite temperature, even in the same system
that Magnasco considered. The maximum efficiency is realized in the absence of
thermal fluctuation. The result presents an open problem whether thermal
fluctuation could facilitate the efficiency of energetic transformation from
force-fluctuation into work.Comment: 3pages, 4sets of figure
Efficient implementation of selective recoupling in heteronuclear spin systems using Hadamard matrices
We present an efficient scheme which couples any designated pair of spins in
heteronuclear spin systems. The scheme is based on the existence of Hadamard
matrices. For a system of spins with pairwise coupling, the scheme
concatenates intervals of system evolution and uses at most pulses
where . Our results demonstrate that, in many systems, selective
recoupling is possible with linear overhead, contrary to common speculation
that exponential effort is always required.Comment: 7 pages, 4 figures, mypsfig2, revtex, submitted April 27, 199
Structural and photophysical characterisation of coordination and optical isomers of mononuclear ruthenium(II) polypyridyl 1,2,4-triazole complexes
The X-ray crystal structure of the N2 isomers of the Ru(bipy)2 complexes of Hphpztr (1) and Hpztr (2), (bipy = 2,2'-bipyridine, Hphpztr = 2-(5'-phenyl-4'H-[1,2,4]triazol-3'-yl)pyrazine and Hpztr = 2-(4'H-[1,2,4]triazol-3'-yl)pyrazine) are reported. The molecular structure obtained for 2 demonstrates an interesting structural aspect in the sharing of a single proton between two molecular units. The isolation of the Δ and Λ stereoisomers of 1 and [Ru(phen)2(pztr)]+ (phen = 1,10-phenanthroline) (3) by semipreparative HPLC is also reported. The compounds obtained are characterised by electronic spectroscopy and particular attention is paid to the photophysical properties of Δ and Λ isomers of 1 and 3, in chiral enantiopure and racemic solvents
Indispensable roles of OX40L-derived signal and epistatic genetic effect in immune-mediated pathogenesis of spontaneous pulmonary hypertension
<p>Abstract</p> <p>Background</p> <p>Pulmonary hypertension (PH) refers to a spectrum of diseases with elevated pulmonary artery pressure. Pulmonary arterial hypertension (PAH) is a disease category that clinically presents with severe PH and that is histopathologically characterized by the occlusion of pulmonary arterioles, medial muscular hypertrophy, and/or intimal fibrosis. PAH occurs with a secondary as well as a primary onset. Secondary PAH is known to be complicated with immunological disorders. The aim of the present study is to histopathologically and genetically characterize a new animal model of PAH and clarify the role of OX40 ligand in the pathogenesis of PAH.</p> <p>Results</p> <p>Spontaneous onset of PAH was stably identified in mice with immune abnormality because of overexpression of the tumor necrosis factor (TNF) family molecule OX40 ligand (OX40L). Histopathological and physical examinations revealed the onset of PAH-like disorders in the C57BL/6 (B6) strain of OX40L transgenic mice (B6.TgL). Comparative analysis performed using different strains of transgenic mice showed that this onset depends on the presence of OX40L in the B6 genetic background. Genetic analyses demonstrated a susceptibility locus of a B6 allele to this onset on chromosome 5. Immunological analyses revealed that the excessive OX40 signals in TgL mice attenuates expansion of regulatory T cells the B6 genetic background, suggesting an impact of the B6 genetic background on the differentiation of regulatory T cells.</p> <p>Conclusion</p> <p>Present findings suggest a role for the OX40L-derived immune response and epistatic genetic effect in immune-mediated pathogenesis of PAH.</p
Gac two-component system in Pseudomonas syringae pv. tabaci is required for virulence but not for hypersensitive reaction
Pseudomonas syringae pv. tabaci 6605 causes wildfire disease on host tobacco plants. To investigate the regulatory mechanism of the expression of virulence, Gac two-Component system-defective mutants, Delta gacA and Delta gacS, and a double mutant, Delta gacA Delta gacS, were generated. These mutants produced smaller amounts of N-acyl homoserine lactones required for quorum sensing, had lost swarming motility, and had reduced expression of virulence-related hrp genes and the algT gene required for exopolysaccharide production. The ability of the mutants to cause disease symptoms in their host tobacco plant was remarkably reduced, while they retained the ability to induce hypersensitive reaction (HR) in the nonhost plants. These results indicated that the Gac two-component system of P. syringae pv. tabaci 6605 is indispensable for virulence on the host plant, but not for HR induction in the nonhost plants.</p
Experimental investigation of a control scheme for a zero-detuning resonant sideband extraction interferometer for next-generation gravitational-wave detectors
Some next-generation gravitational-wave detectors, such as the American
Advanced LIGO project and the Japanese LCGT project, plan to use power recycled
resonant sideband extraction (RSE) interferometers for their interferometer's
optical configuration. A power recycled zero-detuning (PRZD) RSE
interferometer, which is the default design for LCGT, has five main length
degrees of freedom that need to be controlled in order to operate a
gravitational-wave detector. This task is expected to be very challenging
because of the complexity of optical configuration. A new control scheme for a
PRZD RSE interferometer has been developed and tested with a prototype
interferometer. The PRZD RSE interferometer was successfully locked with the
control scheme. It is the first experimental demonstration of a PRZD RSE
interferometer with suspended test masses. The result serves as an important
step for the operation of LCGT.Comment: 6 pages, 9 figrue
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