685 research outputs found
On U_q(SU(2))-symmetric Driven Diffusion
We study analytically a model where particles with a hard-core repulsion
diffuse on a finite one-dimensional lattice with space-dependent, asymmetric
hopping rates. The system dynamics are given by the
\mbox{U[SU(2)]}-symmetric Hamiltonian of a generalized anisotropic
Heisenberg antiferromagnet. Exploiting this symmetry we derive exact
expressions for various correlation functions. We discuss the density profile
and the two-point function and compute the correlation length as well
as the correlation time . The dynamics of the density and the
correlations are shown to be governed by the energy gaps of a one-particle
system. For large systems and depend only on the asymmetry. For
small asymmetry one finds indicating a dynamical exponent
as for symmetric diffusion.Comment: 10 pages, LATE
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Evidence for involvement of both IKCa and SKCa channels in hyperpolarizing responses of the rat middle cerebral artery
Endothelium-derived hyperpolarizing factor responses in the rat middle cerebral artery are blocked by inhibiting IKCa channels alone, contrasting with peripheral vessels where block of both IKCa and SKCa is required. As the contribution of IKCa and SKCa to endothelium-dependent hyperpolarization differs in peripheral arteries, depending on the level of arterial constriction, we investigated the possibility that SKCa might contribute to equivalent hyperpolarization in cerebral arteries under certain conditions. METHODS: Rat middle cerebral arteries (approximately 175 microm) were mounted in a wire myograph. The effect of KCa channel blockers on endothelium-dependent responses to the protease-activated receptor 2 agonist, SLIGRL (20 micromol/L), were then assessed as simultaneous changes in tension and membrane potential. These data were correlated with the distribution of arterial KCa channels revealed with immunohistochemistry. RESULTS: SLIGRL hyperpolarized and relaxed cerebral arteries undergoing variable levels of stretch-induced tone. The relaxation was unaffected by specific inhibitors of IKCa (TRAM-34, 1 micromol/L) or SKCa (apamin, 50 nmol/L) alone or in combination. In contrast, the associated smooth-muscle hyperpolarization was inhibited, but only with these blockers in combination. Blocking nitric oxide synthase (NOS) or guanylyl cyclase evoked smooth-muscle depolarization and constriction, with both hyperpolarization and relaxation to SLIGRL being abolished by TRAM-34 alone, whereas apamin had no effect. Immunolabeling showed SKCa and IKCa within the endothelium. CONCLUSIONS: In the absence of NO, IKCa underpins endothelium-dependent hyperpolarization and relaxation in cerebral arteries. However, when NOS is active SKCa contributes to hyperpolarization, whatever the extent of background contraction. These changes may have relevance in vascular disease states where NO release is compromised and when the levels of SKCa expression may be altered
Electronic correlation effects and the Coulomb gap at finite temperature
We have investigated the effect of the long-range Coulomb interaction on the
one-particle excitation spectrum of n-type Germanium, using tunneling
spectroscopy on mechanically controllable break junctions. The tunnel
conductance was measured as a function of energy and temperature. At low
temperatures, the spectra reveal a minimum at zero bias voltage due to the
Coulomb gap. In the temperature range above 1 K the Coulomb gap is filled by
thermal excitations. This behavior is reflected in the temperature dependence
of the variable-range hopping resitivity measured on the same samples: Up to a
few degrees Kelvin the Efros-Shkovskii ln law is obeyed,
whereas at higher temperatures deviations from this law are observed,
indicating a cross-over to Mott's ln law. The mechanism of
this cross-over is different from that considered previously in the literature.Comment: 3 pages, 3 figure
Transport of interface states in the Heisenberg chain
We demonstrate the transport of interface states in the one-dimensional
ferromagnetic Heisenberg model by a time dependent magnetic field. Our analysis
is based on the standard Adiabatic Theorem. This is supplemented by a numerical
analysis via the recently developed time dependent DMRG method, where we
calculate the adiabatic constant as a function of the strength of the magnetic
field and the anisotropy of the interaction.Comment: minor revision, final version; 13 pages, 4 figure
Density Profile of the One-Dimensional Partially Asymmetric Simple Exclusion Process with Open Boundaries
The one-dimensional partially asymmetric simple exclusion process with open
boundaries is considered. The stationary state, which is known to be
constructed in a matrix product form, is studied by applying the theory of
q-orthogonal polynomials. Using a formula of the q-Hermite polynomials, the
average density profile is computed in the thermodynamic limit. The phase
diagram for the correlation length, which was conjectured in the previous
work[J. Phys. A {\bf 32} (1999) 7109], is confirmed.Comment: 24 pages, 6 figure
On Matrix Product Ground States for Reaction-Diffusion Models
We discuss a new mechanism leading to a matrix product form for the
stationary state of one-dimensional stochastic models. The corresponding
algebra is quadratic and involves four different matrices. For the example of a
coagulation-decoagulation model explicit four-dimensional representations are
given and exact expressions for various physical quantities are recovered. We
also find the general structure of -point correlation functions at the phase
transition.Comment: LaTeX source, 7 pages, no figure
Remarks on the multi-species exclusion process with reflective boundaries
We investigate one of the simplest multi-species generalizations of the one
dimensional exclusion process with reflective boundaries. The Markov matrix
governing the dynamics of the system splits into blocks (sectors) specified by
the number of particles of each kind. We find matrices connecting the blocks in
a matrix product form. The procedure (generalized matrix ansatz) to verify that
a matrix intertwines blocks of the Markov matrix was introduced in the periodic
boundary condition, which starts with a local relation [Arita et al, J. Phys. A
44, 335004 (2011)]. The solution to this relation for the reflective boundary
condition is much simpler than that for the periodic boundary condition
1981 Plant viruses
1, Clover viruses - 81HA6, 81MA9, 81BR14, 81BY12, 81BH5, 81AL38, 81ES39 OBJECTIVES: To determine the extent of the \u27Dinninup virus\u27 problem (sub. clover mottle). To further assess the incidence of red leaf virus to determine the incidence of bean yellow mosaic virus. To note the incidence of sub. clover stunt virus. A. BYDV: Survey of incidence - 81BU1, 81BU2, 81BR11, 81BR12, 81MA6, 81MA7, 81AL31, 81AL32, 81JE14, 81JE15, 81KA21, 81KA22, 81NA28, 81N031, 81ES38, 81E26. 2. Barley yellow dwarf virus. BYDV: Genotype x insecticide studies - 81MN14, 81MT29, 81E28, 81MN14. BYDV: differences amongst barley genotypes - 81C19, 81WH31, 81BA30. BYDV: Resistance and yield in CV.Shannon and CV. Proctor - 871BR13, 81MA8, 81AL36, 81JE17 Yield per plot and 100 seed weight - Albany 81AL36 Infection of BYDV in cereal genotypes at Manjimup ( 81MN13)
Matrix Product Eigenstates for One-Dimensional Stochastic Models and Quantum Spin Chains
We show that all zero energy eigenstates of an arbitrary --state quantum
spin chain Hamiltonian with nearest neighbor interaction in the bulk and single
site boundary terms, which can also describe the dynamics of stochastic models,
can be written as matrix product states. This means that the weights in these
states can be expressed as expectation values in a Fock representation of an
algebra generated by operators fulfilling quadratic relations which
are defined by the Hamiltonian.Comment: 11 pages, Late
Phase diagram of a generalized ABC model on the interval
We study the equilibrium phase diagram of a generalized ABC model on an
interval of the one-dimensional lattice: each site is occupied by a
particle of type \a=A,B,C, with the average density of each particle species
N_\a/N=r_\a fixed. These particles interact via a mean field
non-reflection-symmetric pair interaction. The interaction need not be
invariant under cyclic permutation of the particle species as in the standard
ABC model studied earlier. We prove in some cases and conjecture in others that
the scaled infinite system N\rw\infty, i/N\rw x\in[0,1] has a unique
density profile \p_\a(x) except for some special values of the r_\a for
which the system undergoes a second order phase transition from a uniform to a
nonuniform periodic profile at a critical temperature .Comment: 25 pages, 6 figure
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