1,022 research outputs found
Exact valence bond entanglement entropy and probability distribution in the XXX spin chain and the Potts model
By relating the ground state of Temperley-Lieb hamiltonians to partition
functions of 2D statistical mechanics systems on a half plane, and using a
boundary Coulomb gas formalism, we obtain in closed form the valence bond
entanglement entropy as well as the valence bond probability distribution in
these ground states. We find in particular that for the XXX spin chain, the
number N_c of valence bonds connecting a subsystem of size L to the outside
goes, in the thermodynamic limit, as = (4/pi^2) ln L, disproving a recent
conjecture that this should be related with the von Neumann entropy, and thus
equal to 1/(3 ln 2) ln L. Our results generalize to the Q-state Potts model.Comment: 4 pages, 2 figure
Resonances for coupled Bose-Einstein Condensates
We study some effects arising from periodic modulation of the asymmetry and
the barrier height of a two-well potential containing a Bose-Einstein
condensate. At certain modulation frequencies the system exhibits resonances,
which may lead to enhancement of the tunneling rate between the wells and which
can be used to control the particle distribution among the wells. Some of the
effects predicted for a two-well system can be carried over to the case of a
Bose-Einstein condensate in an optical lattice
A constrained Potts antiferromagnet model with an interface representation
We define a four-state Potts model ensemble on the square lattice, with the
constraints that neighboring spins must have different values, and that no
plaquette may contain all four states. The spin configurations may be mapped
into those of a 2-dimensional interface in a 2+5 dimensional space. If this
interface is in a Gaussian rough phase (as is the case for most other models
with such a mapping), then the spin correlations are critical and their
exponents can be related to the stiffness governing the interface fluctuations.
Results of our Monte Carlo simulations show height fluctuations with an
anomalous dependence on wavevector, intermediate between the behaviors expected
in a rough phase and in a smooth phase; we argue that the smooth phase (which
would imply long-range spin order) is the best interpretation.Comment: 61 pages, LaTeX. Submitted to J. Phys.
Factors influencing in vivo transduction by recombinant adeno-associated viral vectors expressing the human factor IX cDNA.
Long-term expression of coagulation factor IX (FIX) has been observed in murine and canine models following administration of recombinant adeno-associated viral (rAAV) vectors into either the portal vein or muscle. These studies were designed to evaluate factors that influence rAAV-mediated FIX expression. Stable and persistent human FIX (hFIX) expression (> 22 weeks) was observed from 4 vectors after injection into the portal circulation of immunodeficient mice. The level of expression was dependent on promoter with the highest expression, 10% of physiologic levels, observed with a vector containing the cytomegalovirus (CMV) enhancer/beta-actin promoter complex (CAGG). The kinetics of expression after injection of vector particles into muscle, tail vein, or portal vein were similar with hFIX detectable at 2 weeks and reaching a plateau by 8 weeks. For a given dose, intraportal administration of rAAV CAGG-FIX resulted in a 1.5-fold or 4-fold higher level of hFIX compared to tail vein or intramuscular injections, respectively. Polymerase chain reaction analysis demonstrated predominant localization of the rAAV FIX genome in liver and spleen after tail vein injection with a higher proportion in liver after portal vein injection. Therapeutic levels of hFIX were detected in the majority of immunocompetent mice (21 of 22) following intravenous administration of rAAV vector without the development of anti-hFIX antibodies, but hFIX was not detected in 14 immunocompetent mice following intramuscular administration, irrespective of strain. Instead, neutralizing anti-hFIX antibodies were detected in all the mice. These observations may have important implications for hemophilia B gene therapy with rAAV vectors
Analogy between a two-well Bose-Einstein condensate and atom diffraction
We compare the dynamics of a Bose-Einstein condensate in two coupled potential wells with atoms diffracting from a standing light wave. The corresponding Hamiltonians have an identical appearance, but with a different set of commutation rules. Well-known diffraction phenomena as Pendellosung oscillations between opposite momenta in the case of Bragg diffraction, and adiabatic transitions between momentum states are shown to have analogies in the two-well case. They represent the collective exchange of a fixed number of atoms between the wells
Phase dynamics of a multimode Bose condensate controlled by decay
The relative phase between two uncoupled BE condensates tends to attain a
specific value when the phase is measured. This can be done by observing their
decay products in interference. We discuss exactly solvable models for this
process in cases where competing observation channels drive the phases to
different sets of values. We treat the case of two modes which both emit into
the input ports of two beam splitters, and of a linear or circular chain of
modes. In these latter cases, the transitivity of relative phase becomes an
issue
Mechanics and rates of tidal inlet migration : modeling and application to natural examples
Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Earth Surface 121 (2016): 2118–2139, doi:10.1002/2016JF004035.Tidal inlets on barrier coasts can migrate alongshore hundreds of meters per year, often presenting great management and engineering challenges. Here we perform model experiments with migrating tidal inlets in Delft3D-SWAN to investigate the mechanics and rates of inlet migration. Model experiments with obliquely approaching waves suggest that tidal inlet migration occurs due to three mechanisms: (1) littoral sediment deposition along the updrift inlet bank, (2) wave-driven sediment transport preferentially eroding the downdrift bank of the inlet, and (3) flood-tide-driven flow preferentially cutting along the downdrift inlet bank because it is less obstructed by flood-tidal delta deposits. To quantify tidal inlet migration, we propose and apply a simple mass balance framework of sediment fluxes around inlets that includes alongshore sediment bypassing and flood-tidal delta deposition. In model experiments, both updrift littoral sediment and the eroded downdrift inlet bank are sediment sources to the growing updrift barrier and the flood-tidal delta, such that tidal inlets can be net sink of up to 150% of the littoral sediment flux. Our mass balance framework demonstrates how, with flood-tidal deltas acting as a littoral sediment sink, migrating tidal inlets can drive erosion of the downdrift barrier beach. Parameterizing model experiments, we propose a predictive model of tidal inlet migration rates based upon the relative momentum flux of the inlet jet and the alongshore radiation stress; we then compare these predicted migration rates to 22 natural tidal inlets along the U.S. East Coast and find good agreement.National Science Foundation Grant Number: EAR-14247282017-05-1
Diffraction and trapping in circular lattices
When a single two-level atom interacts with a pair of Laguerre-Gaussian beams
with opposite helicity, this leads to an efficient exchange of angular momentum
between the light field and the atom. When the radial motion is trapped by an
additional potential, the wave function of a single localized atom can be split
into components that rotate in opposite direction. This suggests a novel scheme
for atom interferometry without mirror pulses. Also atoms in this configuration
can be bound into a circular lattice
Large Vessel Vasculitis
2-[18F] fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has become part of the worldwide standard of care in oncology. For a decade, this functional imaging tool has also demonstrated important diagnostic results in inflammatory diseases, especially in large vessel vasculitis (LVV). Since clinical PET imaging is increasingly used in these two conditions, this chapter aims to assist imaging specialists and clinicians by getting acquainted with the PET imaging procedures and the current status in clinical practice for LVV. General background information, PET technical considerations (including patient preparation, imaging protocols, scoring methodology), diagnostic and prognostic performance, and response monitoring will be addressed, in line with recent international expert-based recommendations.Also, in the era of personalized medicine, new hybrid technologies such as PET/MR and PET radiotracers will be discussed.</sub
On a neck, on a spit : controls on the shape of free spits
© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth Surface Dynamics 4 (2016): 193-210, doi:10.5194/esurf-4-193-2016.We investigate the controls upon the shape of freely extending spits using a one-contour-line model of shoreline evolution. In contrast to existing frameworks that suggest that spits are oriented in the direction of alongshore sediment transport and that wave refraction around the spit end is the primary cause of recurving, our results suggest that spit shoreline shapes are perhaps best understood as graded features arising from a complex interplay between distinct morphodynamic elements: the headland updrift of the spit, the erosive "neck" (which may be overwashing), and the depositional "hook". Between the neck and the hook lies a downdrift-migrating "fulcrum point" which tends towards a steady-state trajectory set by the angle of maximum alongshore sediment transport. Model results demonstrate that wave climate characteristics affect spit growth; however, we find that the rate of headland retreat exerts a dominant control on spit shape, orientation, and progradation rate. Interestingly, as a spit forms off of a headland, the rate of sediment input to the spit itself emerges through feedbacks with the downdrift spit end, and in many cases faster spit progradation may coincide with reduced sediment input to the spit itself. Furthermore, as the depositional hook rests entirely beyond the maximum in alongshore sediment transport, this shoreline reach is susceptible to high-angle wave instability throughout and, as a result, spit depositional signals may be highly autogenic.This research was
supported by NSF grants EAR-0952146 and EAR-1424728
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