5,215 research outputs found
Comparison of two fluorescent whiteners, Calcofluor and Blankophor, for the detection of fungal elements in clinical specimens in the diagnostic laboratory
ABSTRACTFluorescent whiteners, such as Blankophor and Calcofluor white, bind to chitin and cellulose, and fluoresce when exposed to UV light. Detection of fungal elements from skin and nail samples was faster and more accurate using Blankophor compared with potassium hydroxide preparations and Calcofluor (sensitivity and specificity 100% and 86% vs. 83–90% and 84–88%, or 80% and 84%, respectively). Visibility was improved, and the procedures were simple, inexpensive and rapid, all of which are important considerations in a busy diagnostic laboratory
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Laboratory evaluation of stable isotope labeling of Culicoides (Diptera: Ceratopogonidae) for adult dispersal studies.
BackgroundStable isotope labeling is a promising method for use in insect mark-capture and dispersal studies. Culicoides biting midges, which transmit several important animal pathogens, including bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV), are small flies that develop in various semi-aquatic habitats. Previous Culicoides dispersal studies have suffered from the limitations of other labeling techniques, and an inability to definitively connect collected adult midges to specific immature development sites.ResultsAdult C. sonorensis were successfully labeled with 13C and 15N stable isotopes as larvae developing in a semi-aquatic mud substrate in the laboratory. High and low-dose isotope treatments for both elements significantly enriched midges above the background isotope levels of unenriched controls. Enrichment had no effect on C. sonorensis survival, though a slight (~ 5 day) delay in emergence was observed, and there was no significant effect of pool size on 13C or 15N enrichment levels.ConclusionsStable isotope labeling is life-long, and does not interfere with natural insect behaviors. Stable isotope enrichment using 13C or 15N shows promise for Culicoides dispersal studies in the field. This method can be used to identify adult dispersal from larval source habitat where a midge developed. It may be possible to detect a single enriched midge in a pool of unenriched individuals, though further testing is needed to confirm the sensitivity of this method
From spin to anyon notation: The XXZ Heisenberg model as a (or ) anyon chain
We discuss a relationship between certain one-dimensional quantum spin chains
and anyon chains. In particular we show how the XXZ Heisenberg chain is
realised as a (alternately ) anyon model. We find the
difference between the models lie primarily in choice of boundary condition.Comment: 13 page
Critical Behaviour of Mixed Heisenberg Chains
The critical behaviour of anisotropic Heisenberg models with two kinds of
antiferromagnetically exchange-coupled centers are studied numerically by using
finite-size calculations and conformal invariance. These models exhibit the
interesting property of ferrimagnetism instead of antiferromagnetism. Most of
our results are centered in the mixed Heisenberg chain where we have at even
(odd) sites a spin-S (S') SU(2) operator interacting with a XXZ like
interaction (anisotropy ). Our results indicate universal properties
for all these chains. The whole phase, , where the models change
from ferromagnetic to ferrimagnetic behaviour is
critical. Along this phase the critical fluctuations are ruled by a c=1
conformal field theory of Gaussian type. The conformal dimensions and critical
exponents, along this phase, are calculated by studying these models with
several boundary conditions.Comment: 21 pages, standard LaTex, to appear in J.Phys.A:Math.Ge
Conformal invariance studies of the Baxter-Wu model and a related site-colouring problem
The partition function of the Baxter-Wu model is exactly related to the
generating function of a site-colouring problem on a hexagonal lattice. We
extend the original Bethe ansatz solution of these models in order to obtain
the eigenspectra of their transfer matrices in finite geometries and general
toroidal boundary conditions. The operator content of these models are studied
by solving numerically the Bethe-ansatz equations and by exploring conformal
invariance. Since the eigenspectra are calculated for large lattices, the
corrections to finite-size scaling are also calculated.Comment: 12 pages, latex, to appear in J. Phys. A: Gen. Mat
Critical Behaviour of One-particle Spectral Weights in the Transverse Ising Model
We investigate the critical behaviour of the spectral weight of a single
quasiparticle, one of the key observables in experiment, for the particular
case of the transverse Ising model.Series expansions are calculated for the
linear chain and the square and simple cubic lattices. For the chain model, a
conjectured exact result is discovered. For the square and simple cubic
lattices, series analyses are used to estimate the critical exponents. The
results agree with the general predictions of Sachdev.Comment: 4 pages, 3 figure
A closer look at symmetry breaking in the collinear phase of the Heisenberg Model
The large limit of the square-lattice Heisenberg
antiferromagnet is a classic example of order by disorder where quantum
fluctuations select a collinear ground state. Here, we use series expansion
methods and a meanfield spin-wave theory to study the excitation spectra in
this phase and look for a finite temperature Ising-like transition,
corresponding to a broken symmetry of the square-lattice, as first proposed by
Chandra et al. (Phys. Rev. Lett. 64, 88 (1990)). We find that the spectra
reveal the symmetries of the ordered phase. However, we do not find any
evidence for a finite temperature phase transition. Based on an effective field
theory we argue that the Ising-like transition occurs only at zero temperature.Comment: 4 pages and 5 figure
Series Expansions for three-dimensional QED
Strong-coupling series expansions are calculated for the Hamiltonian version
of compact lattice electrodynamics in (2+1) dimensions, with 4-component
fermions. Series are calculated for the ground-state energy per site, the
chiral condensate, and the masses of `glueball' and positronium states.
Comparisons are made with results obtained by other techniques.Comment: 13 figure
Density Matrix Renormalisation Group Approach to the Massive Schwinger Model
The massive Schwinger model is studied, using a density matrix
renormalisation group approach to the staggered lattice Hamiltonian version of
the model. Lattice sizes up to 256 sites are calculated, and the estimates in
the continuum limit are almost two orders of magnitude more accurate than
previous calculations. Coleman's picture of `half-asymptotic' particles at
background field theta = pi is confirmed. The predicted phase transition at
finite fermion mass (m/g) is accurately located, and demonstrated to belong in
the 2D Ising universality class.Comment: 38 pages, 18 figures, submitted to PR
Ground state parameters, finite-size scaling, and low-temperature properties of the two-dimensional S=1/2 XY model
We present high-precision quantum Monte Carlo results for the S=1/2 XY model
on a two-dimensional square lattice, in the ground state as well as at finite
temperature. The energy, the spin stiffness, the magnetization, and the
susceptibility are calculated and extrapolated to the thermodynamic limit. For
the ground state, we test a variety of finite-size scaling predictions of
effective Lagrangian theory and find good agreement and consistency between the
finite-size corrections for different quantities. The low-temperature behavior
of the susceptibility and the internal energy is also in good agreement with
theoretical predictions.Comment: 6 pages, 8 figure
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