7,639 research outputs found
A new quasi-exactly solvable problem and its connection with an anharmonic oscillator
The two-dimensional hydrogen with a linear potential in a magnetic field is
solved by two different methods. Furthermore the connection between the model
and an anharmonic oscillator had been investigated by methods of KS
transformation
Nonuniversal finite-size scaling in anisotropic systems
We study the bulk and finite-size critical behavior of the O symmetric
theory with spatially anisotropic interactions of non-cubic symmetry
in dimensions. In such systems of a given universality class,
two-scale factor universality is absent in bulk correlation functions, and
finite-size scaling functions including the Privman-Fisher scaling form of the
free energy, the Binder cumulant ratio and the Casimir amplitude are shown to
be nonuniversal. In particular it is shown that, for anisotropic confined
systems, isotropy cannot be restored by an anisotropic scale transformation.Comment: 8 pages, 1 figure, accepted for publication in Phys. Rev. E and
modifications of tex
Quantification of the influences of aggregate shape and sampling method on the overestimation of ITZ thickness in cementitious materials
The microstructure of the interfacial transition zone (ITZ) surrounding the aggregate in a cementitious composite is quite different from that of the bulk matrix, because of its distinct physical nature including relatively high porosity and low rigidity. The thickness and volume fraction of the ITZ play a major role in determining the transport and mechanical behavior of cementitious composites. However, the ITZ thickness may be overestimated when undertaking sectional plane analysis of these composites. Analysis of Platonic particles has previously shown that the sphericity of the particle is an important parameter in determining the overestimation of the ITZ thickness, but this raises the question of whether sphericity is sufficient to uniquely characterize the influence of aggregate shape. This paper investigates the influence of particle shape on overestimation of ITZ thickness for aggregate shapes which have the same sphericity values as Platonic particles; specifically, spheroids of differing geometries. A normal line sampling algorithm, which is designed to replicate the practical experimental process used in ITZ determination, is employed to obtain the apparent ITZ thickness. The influences of particle shape, sampling method and particle size distribution are investigated in terms of the overestimation of the ITZ volume fraction, and the effective diffusivity within three-phase composites, using the differential effective medium approximation
Selectron Studies at e-e- and e+e- Colliders
Selectrons may be studied in both e-e- and e+e- collisions at future linear
colliders. Relative to e+e-, the e-e- mode benefits from negligible backgrounds
and \beta threshold behavior for identical selectron pair production, but
suffers from luminosity degradation and increased initial state radiation and
beamstrahlung. We include all of these effects and compare the potential for
selectron mass measurements in the two modes. The virtues of the e-e- collider
far outweigh its disadvantages. In particular, the selectron mass may be
measured to 100 MeV with a total integrated luminosity of 1 fb^-1, while more
than 100 fb^-1 is required in e+e- collisions for similar precision.Comment: 16 pages, 11 figure
A branch-and-price algorithm for solving the cutting strips problem
After giving a suitable model for the cutting strips problem, we present a branch-and-price algorithm for it by combining the column generation technique and the branch-and-bound method with LP relaxations. Some theoretical issues and implementation details about the algorithm are discussed, including the solution of the pricing subproblem, the quality of LP relaxations, the branching scheme as well as the column management. Finally, preliminary computational experience is reported
Results of the MRI substudy of the intravenous magnesium efficacy in stroke trial
<p><b>Background and Purpose:</b>Although magnesium is neuroprotective in animal stroke models, no clinical benefit was confirmed in the Intravenous Magnesium Efficacy in Stroke (IMAGES) trial of acute stroke patients. The Magnetic
Resonance in IMAGES (MR IMAGES) substudy investigated the effects of magnesium on the imaging surrogate
outcome of infarct growth.</p>
<p><b>Methods:</b> IMAGES trial patients in participating centers were randomized to receive either intravenous magnesium or placebo within 12 hours of stroke onset. Infarct growth was defined as volume difference between baseline diffusion-weighted imaging and day 90 fluid-attenuated inversion recovery image lesions. Patients who died were imputed the largest infarct growth observed.</p>
<p><b>Results:</b> Among the 90 patients included in the primary analysis, there was no difference in infarct growth (median absolute growth, P=0.639; median percentage growth, P=0.616; proportion with any growth, P=0.212) between the
46 treated with magnesium and 44 with placebo. Infarct growth correlated with NIHSS score change from baseline to
day 90. There was a trend showing baseline serum glucose correlated with infarct growth with magnesium treatment,
but not in the placebo group. The mismatch frequency was reduced from 73% to 47% by increasing the mismatch
threshold from >20% to >100% of core volume.</p>
<p><b>Conclusions:</b> Infarct growth, confirmed here as a surrogate for clinical progression, was similar between magnesium and placebo treatment, paralleling the main IMAGES trial clinical outcomes. Glucose was a covariate for infarct growth with magnesium treatment. A more stringent mismatch threshold to define penumbra more appropriately would have
excluded half of the patients in this 12-hour time window stroke study.</p>
Increasing levels of circulating Th17 cells and interleukin-17 in rheumatoid arthritis patients with an inadequate response to anti-TNF-α therapy
Introduction: The objective of this study was to investigate the effects of tumor necrosis factor (TNF)-alpha inhibitors on circulating T helper-type 17 (Th17) cells and Th17-related cytokines in patients with rheumatoid arthritis (RA). Methods: The frequencies of circulating Th17 cells and serum levels of Th17-related cytokines were determined using flow cytometry analysis and ELISA, respectively, in 48 RA patients both before (baseline) and six months after anti-TNF-alpha therapy. Therapeutic response was evaluated using European League Against Rheumatism (EULAR) response criteria. Results: Significantly higher baseline frequencies of circulating Th17 cells and serum levels of interleukin (IL)-6, IL17, IL-21, IL-23 and TNF-alpha were observed in active RA patients than in 12 healthy controls (all P < 0.001). After anti-TNF-alpha therapy, 36 patients (75%) were EULAR responders (20 good responders and 16 moderate responders) and 12 (25.0%) were non-responders. The mean levels of circulating Th17 cells and IL-17 significantly decreased (1.13% vs. 0.79%; 43.1 pg/ml vs. 27.8 pg/ml; respectively, both P < 0.001) in parallel with clinical remission in responders. Levels of IL-6, IL-21, IL-23 and TNF-alpha were significantly decreased after anti-TNF-alpha therapy in responders. In contrast, the mean levels of circulating Th17 cells and IL-17 significantly increased after anti-TNF-alpha therapy (2.94% vs. 4.23%; 92.1 pg/ml vs. 148.6 pg/ml; respectively, both P < 0.05) in non-responders. Logistic regression analysis identified a high baseline level of IL-17 as a significant predictor of poor therapeutic response. Conclusions: The beneficial effect of anti-TNF-alpha therapy might involve a decrease in Th17-related cytokines in responders, whereas rising levels of circulating Th17-cells and IL-17 were observed in patients with an inadequate response to anti-TNF-alpha therapy
The Random-bond Potts model in the large-q limit
We study the critical behavior of the q-state Potts model with random
ferromagnetic couplings. Working with the cluster representation the partition
sum of the model in the large-q limit is dominated by a single graph, the
fractal properties of which are related to the critical singularities of the
random Potts model. The optimization problem of finding the dominant graph, is
studied on the square lattice by simulated annealing and by a combinatorial
algorithm. Critical exponents of the magnetization and the correlation length
are estimated and conformal predictions are compared with numerical results.Comment: 7 pages, 6 figure
Optical Resonances in Reflectivity near Crystal Modes with Spatial Dispersion
We study the effect of spatial dispersion of crystal modes on optical
properties such as the reflectivity . As an example for isotropic media, we
investigate the simplest model for phonons in ionic crystals and compare with
previous results for highly anisotropic plasmons, which are now understood from
a more general point of view. As a consequence of the wave vector dependence of
the dielectric function small changes in the lineshape are predicted. Beyond
that, if the frequency of minimal is near a pole of the dispersionless
dielectric function, the relative amplitude of dips in with normal and
anomalous dispersion differ significantly, if dissipation and disorder are low.Comment: 4 pages, 7 eps figures, minor change
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