730 research outputs found
Lattice Dirac fermions in a non-Abelian random gauge potential: Many flavors, chiral symmetry restoration and localization
In the previous paper we studied Dirac fermions in a non-Abelian random
vector potential by using lattice supersymmetry. By the lattice regularization,
the system of disordered Dirac fermions is defined without any ambiguities. We
showed there that at strong-disorder limit correlation function of the fermion
local density of states decays algebraically at the band center. In this paper,
we shall reexamine the multi-flavor or multi-species case rather in detail and
argue that the correlator at the band center decays {\em exponentially} for the
case of a {\em large} number of flavors. This means that a
delocalization-localization phase transition occurs as the number of flavors is
increased. This discussion is supported by the recent numerical studies on
multi-flavor QCD at the strong-coupling limit, which shows that the phase
structure of QCD drastically changes depending on the number of flavors. The
above behaviour of the correlator of the random Dirac fermions is closely
related with how the chiral symmetry is realized in QCD.Comment: Version appears in Mod.Phys.Lett.A17(2002)135
Three Phases in the 3D Abelian Higgs Model with Nonlocal Gauge Interactions
We study the phase structure of the 3D nonlocal compact U(1) lattice gauge
theory coupled with a Higgs field by means of Monte-Carlo simulations. The
nonlocal interactions among gauge variables are along the temporal direction
and mimic the effect of local coupling to massless particles. We found that in
contrast to the 3D local abelian Higgs model which has only one phase, the
present model exhibits the confinement, Higgs, and Coulomb phases separated by
three second-order transition lines emanating from a triple point. This result
is quite important for studies on electron fractionalization phenomena in
strongly-correlated electron systems. Implications to them are discussed
Pseudo- Three-Dimensional Analysis of Cyclic Deformation of Ground Subject to Seismic Liquefaction
A Numerical tool was developed to evaluate the effects of differential movement which occurs at the ground surface during earthquakes. A special emphasis is placed on liquefaction of subsoils. A complicated three-dimensional analysis was avoided by using a pseudo-three-dimensional method of finite element analysis which runs on an element mesh of the ground surface topography as seen from the sky. The present analysis takes into account the nonlinear stress-strain behavior of soils, the ground softening due to pore pressure development, and the irregularity in the topography. The proposed method was applied to several cases in which buried pipelines were damaged by seismic liquefaction. The calculated results showed that the differential movement of the ground in cyclic manners is not significant. Thus, it seems that those pipeline failures were induced not by the cyclic ground movement but by the monotonic or permanent displacement which accumulated to several meters
Beneficial effects of green tea: A literature review
The health benefits of green tea for a wide variety of ailments, including different types of cancer, heart disease, and liver disease, were reported. Many of these beneficial effects of green tea are related to its catechin, particularly (-)-epigallocatechin-3-gallate, content. There is evidence from in vitro and animal studies on the underlying mechanisms of green tea catechins and their biological actions. There are also human studies on using green tea catechins to treat metabolic syndrome, such as obesity, type II diabetes, and cardiovascular risk factors
Natriuretic peptides in embryonic stem cell-derived cardiomyocytes and their receptors in the CNS.
The natriuretic peptides (NPs) are a family of related hormones that play important roles inthe cardiovascular homeostasis, cell growth and neuroendocrine functions. Recently, theyhave emerged as potentially important clinical biomarkers in heart failure. The heartsecretes two major natriuretic peptides: atrial natriuretic peptide (ANP) and brainnatriuretic peptide (BNP), while C-type natriuretic peptide (CNP) is mainly secretedfrom the brain and blood vessels. The physiological effects of NPs are initiated bybinding to natriuretic peptide receptors (NPRs), which are widely distributed inseveral organs. This review describes: the expression of natriuretic peptides in thecardiomyocytes differentiated from ES cells and their role in the cardiomyocytedevelopment. We also describe the detailed distribution of NPRs in the centralnervous system and their possible functions in various brain regions
Discovery of a novel restriction endonuclease by genome comparison and application of a wheat-germ-based cell-free translation assay: PabI (5âČ-GTA/C) from the hyperthermophilic archaeon Pyrococcus abyssi
To search for restriction endonucleases, we used a novel plant-based cell-free translation procedure that bypasses the toxicity of these enzymes. To identify candidate genes, the related genomes of the hyperthermophilic archaea Pyrococcus abyssi and Pyrococcus horikoshii were compared. In line with the selfish mobile gene hypothesis for restrictionâmodification systems, apparent genome rearrangement around putative restriction genes served as a selecting criterion. Several candidate restriction genes were identified and then amplified in such a way that they were removed from their own translation signal. During their cloning into a plasmid, the genes became connected with a plant translation signal. After in vitro transcription by T7 RNA polymerase, the mRNAs were separated from the template DNA and translated in a wheat-germ-based cell-free protein synthesis system. The resulting solution could be directly assayed for restriction activity. We identified two deoxyribonucleases. The novel enzyme was denoted as PabI, purified and found to recognize 5âČ-GTAC and leave a 3âČ-TA overhang (5âČ-GTA/C), a novel restriction enzyme-generated terminus. PabI is active up to 90°C and optimally active at a pH of around 6 and in NaCl concentrations ranging from 100 to 200 mM. We predict that it has a novel 3D structure
Integrable Impurity Model with Spin and Flavour: Model Inspired by Resonant Tunneling in Quantum Dot
We introduce an integrable impurity model in which both electrons and
impurity have spin and flavour degrees of freedom. This model is a
generalization of the multi-channel Kondo model and closely related with
resonant tunneling through quantum dot. The Hamiltonian is exactly diagonalized
by means of the Bethe ansatz.Comment: 1 reference is adde
Quasi-excitations and superconductivity in the t-J model on a ladder
We study the t-J model on a ladder by using slave-fermion-CP^1 formalism
which is quite useful for study of lightly-doped high-T_c cuprates. By
integrating half of spin variables, we obtain a low-energy effective field
theory whose spin part is nothing but CP^1 sigma model. We especially focus on
dynamics of composite gauge field which determines properties of
quasi-excitations. Value of the coefficient of the topological term strongly
influences gauge dynamics and explaines why properties of quasi-excitations
depend on the number of legs of ladder. We also show that superconductivity
appears as a result of short-range antiferromagnetism and order parameter has
d-wave type symmetry.Comment: Latex, 28 pages and 1 figur
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