20,169 research outputs found
Non-equilibrium phonon dynamics in trapped ion systems
We propose a concrete experiment to probe the non-equilibrium local dynamics
of the one-dimensional Bose-Hubbard model using a trapped ion system consisting
of a linear chain of few Ba^+ ions prepared in a state of transverse motional
mode which corresponds to a fixed number of phonons per ion. These phonons are
well-known to be described by an effective Bose-Hubbard model. We propose a
protocol which leads to a sudden local sign reversal of the on-site interaction
strength of this Hubbard model at one of the sites and demonstrate that the
subsequent non-equilibrium dynamics of the model can be experimentally probed
by measuring the time-dependent phonon number in a specific motional state of
the Ba+ ions. We back our experimental proposal with exact numerical
calculation of the dynamics of a Bose-Hubbard model subsequent to a local
quench.Comment: The submission contains 5 pages and 4 figure
Signatures of charmonium modification in spatial correlation functions
We study spatial correlation functions of charmonium in 2+1 flavor QCD using
an improved staggered formulation. Contrary to the temporal correlation
functions the spatial correlation functions exhibit a strong temperature
dependence above the QCD transition temperature. Above this temperature they
are sensitive to temporal boundary conditions. Both features become significant
at a temperature close to 1.5 Tc and suggest corresponding modifications of
charmonium spectral functions.Comment: 12 pages, LaTeX, 3 figure
Bi-quadratic magnetoelectric coupling in underdoped La_2CuO_{4+x}
The recent discovery of relaxor ferroelectricity and magnetoelectric effect
in lightly doped cuprate material La_2CuO_{4+x} has provided a number of
questions concerning its theoretical description. It has been argued using a
Ginzburg-Landau free energy approach that the magnetoelectric effect can be
explained by the presence of bi-quadratic interaction terms in the free energy.
Here, by using the same free energy functional, we study the variety of
behavior which can emerge in the electric polarization under an external
magnetic field. Subsequently, we discuss the role of Dzyaloshinskii-Moriya
interaction in generating this magnetoelectric response. This work is
particularly relevant for such relaxor systems where the material-dependent
parameters would be affected by changes in e.g. chemical doping or cooling
rate.Comment: 8 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1112.152
Dynamical phase transition of a 1D transport process including death
Motivated by biological aspects related to fungus growth, we consider the
competition of growth and corrosion. We study a modification of the totally
asymmetric exclusion process, including the probabilities of injection
and death of the last particle . The system presents a phase transition
at , where the average position of the last particle
grows as . For , a non equilibrium stationary state
exists while for the asymptotic state presents a low density
and max current phases. We discuss the scaling of the density and current
profiles for parallel and sequential updates.Comment: 4 pages, 5 figure
A COMPARATIVE STUDY OF THE ULTRASTRUCTURE OF MICROVILLI IN THE EPITHELIUM OF SMALL AND LARGE INTESTINE OF MICE
A comparative analysis of the fine structure of the microvilli on jejunal and colonic epithelial cells of the mouse intestine has been made. The microvilli in these two locations demonstrate a remarkably similar fine structure with respect to the thickness of the plasma membrane, the extent of the filament-free zone, and the characteristics of the microfilaments situated within the microvillous core. Some of the core microfilaments appear to continue across the plasma membrane limiting the tip of the microvillus. The main difference between the microvilli of small intestine and colon is in the extent and organization of the surface coat. In the small intestine, in addition to the commonly observed thin surface "fuzz," occasional areas of the jejunal villus show a more conspicuous surface coat covering the tips of the microvilli. Evidence has been put forward which indicates that the surface coat is an integral part of the epithelial cells. In contrast to the jejunal epithelium, the colonic epithelium is endowed with a thicker surface coat. Variations in the organization of the surface coat at different levels of the colonic crypts have also been noted. The functional significance of these variations in the surface coat is discussed
Aspartate transcarbamylase from Leishmania donovani. A discrete, nonregulatory enzyme as a potential chemotherapeutic site
Leishmania donovani is a protozoal pathogen that belongs to the kinetoplastida order. Unlike in other eucaryotic systems, the first three enzymes of the de novo pyrimidine biosynthetic pathway are not components of a multifunctional protein system. The three enzyme activities in the crude extract were separated on a Sephacryl S-200 column. Aspartate carbamoyltransferase (EC 2.1.3.2) has been purified to apparent homogeneity. The enzyme has an approximate molecular weight of 135,000 and seems to be a tetramer of equivalent subunits of molecular weight 35,000. The enzyme shows strictly hyperbolic kinetics with both the substrates under a variety of conditions and is not inhibited by nucleotide phosphates. Km for carbamyl phosphate is 3.1 × 10-4 M and for aspartate is 7.6 × 10-3 M. Apparently, the enzyme has no regulatory role in pyrimidine biosynthesis. N-(Phosphonoacetyl)-L-aspartic acid is a powerful competitive inhibitor (Ki = 5 × 10-7 M) for this enzyme with carbamyl phosphate as substrate. This inhibitor completely inhibits the growth of the vector form of organism at 60 μM and significantly affects the growth of the pathogenic form in a macrophage assay system. The potency of the inhibitor is comparable with allopurinol which is undergoing human clinical trial as an antileishmanial drug
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