483 research outputs found
Signal at subleading order in lattice HQET
We discuss the correlators in lattice HQET that are needed to go beyond the
static theory. Based on our implementation in the Schr\"odinger functional we
focus on their signal-to-noise ratios and check that a reasonable statistical
precision can be reached in quantities like and .Comment: 3 pages, Lattice2004(heavy), v2: corrected definition of X^{kin/spin
Relativistic diffusive motion in random electromagnetic fields
We show that the relativistic dynamics in a Gaussian random electromagnetic
field can be approximated by the relativistic diffusion of Schay and Dudley.
Lorentz invariant dynamics in the proper time leads to the diffusion in the
proper time. The dynamics in the laboratory time gives the diffusive transport
equation corresponding to the Juettner equilibrium at the inverse temperature
\beta^{-1}=mc^{2}. The diffusion constant is expressed by the field strength
correlation function (Kubo's formula).Comment: the version published in JP
Cell-cell communication mediated by the CAR subgroup of immunoglobulin cell adhesion molecules in health and disease
The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the nervous system. In this review we put our focus on the biological function of a less understood subgroup of Ig-like proteins composed of CAR (coxsackievirus and adenovirus receptor), CLMP (CAR-like membrane protein) and BT-IgSF (brain and testis specific immunoglobulin superfamily). The CAR-related proteins are type I transmembrane proteins containing an N-terminal variable (V-type) and a membrane proximal constant (C2-type) Ig domain in their extracellular region which are implicated in homotypic adhesion. They are highly expressed during embryonic development in a variety of tissues including the nervous system whereby in adult stages the protein level of CAR and CLMP decreases, only BT-IgSF expression increases within age. CAR-related proteins are concentrated at specialized cell-cell communication sites such as gap or tight junctions and are present at the plasma membrane in larger protein complexes. Considerable progress has been made on the molecular structure and interactions of CAR while research on CLMP and BT-IgSF is at an early stage. Studies on mouse mutants revealed biological functions of CAR in the heart and for CLMP in the gastrointestinal and urogenital systems. Furthermore, CAR and BT-IgSF appear to regulate synaptic function in the hippocampus
The IgSF cell adhesion protein CLMP and congenital short bowel syndrome (CSBS)
The immunoglobulin-like cell adhesion molecule CLMP is a member of the CAR family of cell adhesion proteins and is implicated in human congenital short-bowel syndrome (CSBS). CSBS is a rare but very severe disease for which no cure is currently available. In this review, we compare data from human CSBS patients and a mouse knockout model. These data indicate that CSBS is characterized by a defect in intestinal elongation during embryonic development and impaired peristalsis. The latter is driven by uncoordinated calcium signaling via gap junctions, which is linked to a reduction in connexin43 and 45 levels in the circumferential smooth muscle layer of the intestine. Furthermore, we discuss how mutations in the CLMP gene affect other organs and tissues, including the ureter. Here, the absence of CLMP produces a severe bilateral hydronephrosis—also caused by a reduced level of connexin43 and associated uncoordinated calcium signaling via gap junctions
Collision Thermalization of Nucleons in Relativistic Heavy-Ion Collisions
We consider a possible mechanism of thermalization of nucleons in
relativistic heavy-ion collisions. Our model belongs, to a certain degree, to
the transport ones; we investigate the evolution of the system created in
nucleus-nucleus collision, but we parametrize this development by the number of
collisions of every particle during evolution rather than by the time variable.
We based on the assumption that the nucleon momentum transfer after several
nucleon-nucleon (-hadron) elastic and inelastic collisions becomes a random
quantity driven by a proper distribution. This randomization results in a
smearing of the nucleon momenta about their initial values and, as a
consequence, in their partial isotropization and thermalization. The trial
evaluation is made in the framework of a toy model. We show that the proposed
scheme can be used for extraction of the physical information from experimental
data on nucleon rapidity distribution.Comment: 13 pages, 8 figure
Exact thermodynamics of an Extended Hubbard Model of single and paired carriers in competition
By exploiting the technique of Sutherland's species, introduced in
\cite{DOMO-RC}, we derive the exact spectrum and partition function of a 1D
extended Hubbard model. The model describes a competition between dynamics of
single carriers and short-radius pairs, as a function of on-site Coulomb
repulsion () and filling (). We provide the temperature dependence of
chemical potential, compressibility, local magnetic moment, and specific heat.
In particular the latter turns out to exhibit two peaks, both related to
`charge' degrees of freedom. Their origin and behavior are analyzed in terms of
kinetic and potential energy, both across the metal-insulator transition point
and in the strong coupling regime.Comment: 14 pages, 15 eps figure
Integrability of quantum chains: theory and applications to the spin-1/2 chain
In this contribution we review the theory of integrability of quantum systems
in one spatial dimension. We introduce the basic concepts such as the
Yang-Baxter equation, commuting currents, and the algebraic Bethe ansatz. Quite
extensively we present the treatment of integrable quantum systems at finite
temperature on the basis of a lattice path integral formulation and a suitable
transfer matrix approach (quantum transfer matrix). The general method is
carried out for the seminal model of the spin-1/2 chain for which
thermodynamic properties like specific heat, magnetic susceptibility and the
finite temperature Drude weight of the thermal conductivity are derived
Linearized Kompaneetz equation as a relativistic diffusion
We show that Kompaneetz equation describing photon diffusion in an
environment of an electron gas, when linearized around its equilibrium
distribution, coincides with the relativistic diffusion discussed in recent
publications. The model of the relativistic diffusion is related to soluble
models of imaginary time quantum mechanics. We suggest some non-linear
generalizations of the relativistic diffusion equation and their astrophysical
applications (in particular to the Sunyaev-Zeldovich effect).Comment: 12 page
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