20,632 research outputs found
An alternative approach for the dynamics of polarons in one dimension
We developed a new method based on functional integration to treat the
dynamics of polarons in one-dimensional systems. We treat the acoustical and
the optical case in an unified manner, showing their differences and
similarities. The mobility and diffusion coefficients are calculated in the
Markovian approximation in the strong coupling limit.Comment: 57 page
Applications of quantum integrable systems
We present two applications of quantum integrable systems. First, we predict
that it is possible to generate high harmonics from solid state devices by
demostrating that the emission spectrum for a minimally coupled laser field of
frequency to an impurity system of a quantum wire, contains multiples
of the incoming frequency. Second, evaluating expressions for the conductance
in the high temperature regime we show that the caracteristic filling fractions
of the Jain sequence, which occur in the fractional quantum Hall effect, can be
obtained from quantum wires which are described by minimal affine Toda field
theories.Comment: 25 pages of LaTex, 4 figures, based on talk at the 6-th international
workshop on conformal field theories and integrable models, (Chernogolovka,
September 2002
Breathers in the elliptic sine-Gordon model
We provide new expressions for the scattering amplitudes in the
soliton-antisoliton sector of the elliptic sine-Gordon model in terms of cosets
of the affine Weyl group corresponding to infinite products of q-deformed gamma
functions. When relaxing the usual restriction on the coupling constants, the
model contains additional bound states which admit an interpretation as
breathers. These breather bound states are unavoidably accompanied by Tachyons.
We compute the complete S-matrix describing the scattering of the breathers
amonst themselves and with the soliton-antisoliton sector. We carry out various
reductions of the model, one of them leading to a new type of theory, namely an
elliptic version of the minimal D(n+1)-affine Toda field theory.Comment: 20 pages, Latex, one eps-figur
Outcome of renal grafts after simultaneous kidney/ pancreas transplantation
Nineteen patients with endstage renal failure due to Type 1 (insulin-dependent) diabetes mellitus received simultaneous pancreas/kidney transplants using bladder drainage technique. Another group of 25 Type 1 diabetic patients received pancreas/kidney transplants by the duct occlusion technique. We observed a higher incidence of rejection episodes in the patients of the bladder drainage group than those in the duct occlusion group, 14 of 19 patients (74%) vs 7 of 25 (28%) respectively. Anti CD3 antibodies (Orthoclone, OKT3) as a part of induction treatment was used more often in the bladder drainage group (58%) than in the control group (20%)
Sistemas de produção: conceitos e definições no contexto agrícola.
Introdução. Definições e exemplificações de sistemas: Sistema de cultivo, Sistema de produção, Sistema em monocultura ou produção isolada; Sistema em sucessão de culturas; Sistema em consorciação de culturas ou policultivo; Sistema em integração: lavoura-pecuária, lavoura-floresta, pecuária-floresta, lavoura-pecuária-floresta. Ausência de interação. Interação entre sistemas de cultivo/criação conduzidos em diferentes áreas físicas. Interação entre sistemas de cultivo/criação conduzidos em um mesmo espaço físico. Sistema agrícola: sistema de sucessão soja - milho/trigo em SPD na região de Londrina-PR; sistema de sucessão soja - milho/sorgo em SPD na região de Rio Verde-GO; sistema de rotação soja-trigo (ano 1); soja-aveia ou nabo forrageiro (ano 2); milho-nabo forrageiro-trigo (ano 3); e soja-aveia (ano 4), em SPD na região de Passo Fundo-RS. sistema de sucessão soja ? milho/algodão em SPD na região de Sapezal-MT; sistema de sucessão soja - girassol/sorgo em SPD na região de Campo Novo do Parecis-MT; sistema de integração arroz irrigado-azevém para pastejo, na região de Pelotas-RS. sistema de sucessão de cana-de-açúcar com cultivo de amendoim durante o período de reforma do canavial na região de Sertãozinho-SP. sistema de sucessão de cana-de-açúcar com cultivo de Crotalaria spectabilis durante o período de reforma do canavial na região de Coruripe-AL. Bioma. Considerações finais.bitstream/item/69333/1/Doc-335-OL.pd
Spin-excitations of the quantum Hall ferromagnet of composite fermions
The spin-excitations of a fractional quantum Hall system are evaluated within
a bosonization approach. In a first step, we generalize Murthy and Shankar's
Hamiltonian theory of the fractional quantum Hall effect to the case of
composite fermions with an extra discrete degree of freedom. Here, we mainly
investigate the spin degrees of freedom, but the proposed formalism may be
useful also in the study of bilayer quantum-Hall systems, where the layer index
may formally be treated as an isospin. In a second step, we apply a
bosonization scheme, recently developed for the study of the two-dimensional
electron gas, to the interacting composite-fermion Hamiltonian. The dispersion
of the bosons, which represent quasiparticle-quasihole excitations, is
analytically evaluated for fractional quantum Hall systems at \nu = 1/3 and \nu
= 1/5. The finite width of the two-dimensional electron gas is also taken into
account explicitly. In addition, we consider the interacting bosonic model and
calculate the lowest-energy state for two bosons. Besides a continuum
describing scattering states, we find a bound-state of two bosons. This state
is interpreted as a pair excitation, which consists of a skyrmion of composite
fermions and an antiskyrmion of composite fermions. The dispersion relation of
the two-boson state is evaluated for \nu = 1/3 and \nu = 1/5. Finally, we show
that our theory provides the microscopic basis for a phenomenological
non-linear sigma-model for studying the skyrmion of composite fermions.Comment: Revised version, 14 pages, 4 figures, accepted to Phys. Rev.
Dynamical Renormalization Group Study for a Class of Non-local Interface Equations
We provide a detailed Dynamic Renormalization Group study for a class of
stochastic equations that describe non-conserved interface growth mediated by
non-local interactions. We consider explicitly both the morphologically stable
case, and the less studied case in which pattern formation occurs, for which
flat surfaces are linearly unstable to periodic perturbations. We show that the
latter leads to non-trivial scaling behavior in an appropriate parameter range
when combined with the Kardar-Parisi-Zhang (KPZ) non-linearity, that
nevertheless does not correspond to the KPZ universality class. This novel
asymptotic behavior is characterized by two scaling laws that fix the critical
exponents to dimension-independent values, that agree with previous reports
from numerical simulations and experimental systems. We show that the precise
form of the linear stabilizing terms does not modify the hydrodynamic behavior
of these equations. One of the scaling laws, usually associated with Galilean
invariance, is shown to derive from a vertex cancellation that occurs (at least
to one loop order) for any choice of linear terms in the equation of motion and
is independent on the morphological stability of the surface, hence
generalizing this well-known property of the KPZ equation. Moreover, the
argument carries over to other systems like the Lai-Das Sarma-Villain equation,
in which vertex cancellation is known {\em not to} imply an associated symmetry
of the equation.Comment: 34 pages, 9 figures. Journal of Statistical Mechanics: Theory and
Experiments (in press
Form factors of boundary fields for A(2)-affine Toda field theory
In this paper we carry out the boundary form factor program for the
A(2)-affine Toda field theory at the self-dual point. The latter is an
integrable model consisting of a pair of particles which are conjugated to each
other and possessing two bound states resulting from the scattering processes 1
+1 -> 2 and 2+2-> 1. We obtain solutions up to four particle form factors for
two families of fields which can be identified with spinless and spin-1 fields
of the bulk theory. Previously known as well as new bulk form factor solutions
are obtained as a particular limit of ours. Minimal solutions of the boundary
form factor equations for all A(n)-affine Toda field theories are given, which
will serve as starting point for a generalisation of our results to higher rank
algebras.Comment: 24 pages LaTeX, 1 figur
An Unexpected Association in a Patient with Heart Failure Presenting a Surgical Challenge
Bicuspid aortic valve (BAV) is the most common form of congenital heart disease and frequently leads to premature valvular dysfunction. BAV is associated with aortic wall abnormalities and a high prevalence of ascending aorta dilatation and coarctation of the aorta (CoA). Consequently, in patients with BAV a careful assessment of the valve, and also of the aortic root and the ascending aorta, should be performed. The most feared complication is aortic dissection, however, the actual incidence of this complication is low. We report the case of a 58-year-old man who presented with New York Heart Association class III heart failure. The work-up revealed BAV with severe stenosis and severe compromise of left ventricle systolic function. In addition, CoA in the isthmus region, and type B dissection of the aorta were diagnosed.info:eu-repo/semantics/publishedVersio
Dissipative dynamics of topological defects in frustrated Heisenberg spin systems
We study the dynamics of topological defects of a frustrated spin system
displaying spiral order. As a starting point we consider the SO(3) nonlinear
sigma model to describe long-wavelength fluctuations around the noncollinear
spiral state. Besides the usual spin-wave magnetic excitations, the model
allows for topologically non-trivial static solutions of the equations of
motion, associated with the change of chirality (clockwise or counterclockwise)
of the spiral. We consider two types of these topological defects, single
vortices and vortex-antivortex pairs, and quantize the corresponding solutions
by generalizing the semiclassical approach to a non-Abelian field theory. The
use of the collective coordinates allows us to represent the defect as a
particle coupled to a bath of harmonic oscillators, which can be integrated out
employing the Feynman-Vernon path-integral formalism. The resulting effective
action for the defect indicates that its motion is damped due to the scattering
by the magnons. We derive a general expression for the damping coefficient of
the defect, and evaluate its temperature dependence in both cases, for a single
vortex and for a vortex-antivortex pair. Finally, we consider an application of
the model for cuprates, where a spiral state has been argued to be realized in
the spin-glass regime. By assuming that the defect motion contributes to the
dissipative dynamics of the charges, we can compare our results with the
measured inverse mobility in a wide range of temperature. The relatively good
agreement between our calculations and the experiments confirms the possible
relevance of an incommensurate spiral order for lightly doped cuprates.Comment: 22 pages, 7 figures, final published versio
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