480 research outputs found
Adherence to Antibiotic Prophylaxis in Children with Vesicoureteral Reflux
Vesicoureteral reflux (VUR) affects approximately 1% of children and may predispose a child with a bladder infection to develop pyelonephritis and renal scarring. To prevent these potential sequelae, one accepted treatment option for VUR includes low-dose continuous antibiotic prophylaxis (CAP) to maintain urine sterility until the condition resolves. Despite the widespread use of CAP, little data exists regarding adherence to long-term antibiotic therapy. Not only will poor adherence to CAP potentially preclude the intended benefit, but also nonadherence with antibiotic regimens may carry untoward effects including unnecessary treatment changes for presumed antibiotic failure, emergence of resistant organisms, and compromised clinical trial outcomes. We present an overview of medication adherence in children with VUR, discuss possible consequences of nonadherence to antibiotic prophylaxis, and suggest ways to improve adherence. We raise awareness of issues related to nonadherence relevant to healthcare providers, investigators, and the community
The possibility of a metal insulator transition in antidot arrays induced by an external driving
It is shown that a family of models associated with the kicked Harper model
is relevant for cyclotron resonance experiments in an antidot array. For this
purpose a simplified model for electronic motion in a related model system in
presence of a magnetic field and an AC electric field is developed. In the
limit of strong magnetic field it reduces to a model similar to the kicked
Harper model. This model is studied numerically and is found to be extremely
sensitive to the strength of the electric field. In particular, as the strength
of the electric field is varied a metal -- insulator transition may be found.
The experimental conditions required for this transition are discussed.Comment: 6 files: kharp.tex, fig1.ps fig2.ps fi3.ps fig4.ps fig5.p
Metal-insulator transitions in cyclotron resonance of periodic nanostructures due to avoided band crossings
A recently found metal-insulator transition in a model for cyclotron
resonance in a two-dimensional periodic potential is investigated by means of
spectral properties of the time evolution operator. The previously found
dynamical signatures of the transition are explained in terms of avoided band
crossings due to the change of the external electric field. The occurrence of a
cross-like transport is predicted and numerically confirmed
Duality Relation among Periodic Potential Problems in the Lowest Landau Level
Using a momentum representation of a magnetic von Neumann lattice, we study a
two-dimensional electron in a uniform magnetic field and obtain one-particle
spectra of various periodic short-range potential problems in the lowest Landau
level.We find that the energy spectra satisfy a duality relation between a
period of the potential and a magnetic length. The energy spectra consist of
the Hofstadter-type bands and flat bands. We also study the connection between
a periodic short-range potential problem and a tight-binding model.Comment: 6 pages, 3 figures, final version to appear in PR
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Shorter Disease Duration Is Associated With Higher Rates of Response to Vedolizumab in Patients With Crohn's Disease But Not Ulcerative Colitis.
Background & aimsPatients with Crohn's disease (CD), but not ulcerative colitis (UC), of shorter duration have higher rates of response to tumor necrosis factor (TNF) antagonists than patients with longer disease duration. Little is known about the association between disease duration and response to other biologic agents. We aimed to evaluate response of patients with CD or UC to vedolizumab, stratified by disease duration.MethodsWe analyzed data from a retrospective, multicenter, consortium of patients with CD (n = 650) or UC (n = 437) treated with vedolizumab from May 2014 through December 2016. Using time to event analyses, we compared rates of clinical remission, corticosteroid-free remission (CSFR), and endoscopic remission between patients with early-stage (≤2 years duration) and later-stage (>2 years) CD or UC. We used Cox proportional hazards models to identify factors associated with outcomes.ResultsWithin 6 months initiation of treatment with vedolizumab, significantly higher proportions of patients with early-stage CD, vs later-stage CD, achieved clinical remission (38% vs 23%), CSFR (43% vs 14%), and endoscopic remission (29% vs 13%) (P < .05 for all comparisons). After adjusting for disease-related factors including previous exposure to TNF antagonists, patients with early-stage CD were significantly more likely than patients with later-stage CD to achieve clinical remission (adjusted hazard ratio [aHR], 1.59; 95% CI, 1.02-2.49), CSFR (aHR, 3.39; 95% CI, 1.66-6.92), and endoscopic remission (aHR, 1.90; 95% CI, 1.06-3.39). In contrast, disease duration was not a significant predictor of response among patients with UC.ConclusionsPatients with CD for 2 years or less are significantly more likely to achieve a complete response, CSFR, or endoscopic response to vedolizumab than patients with longer disease duration. Disease duration does not associate with response vedolizumab in patients with UC
Simple deterministic dynamical systems with fractal diffusion coefficients
We analyze a simple model of deterministic diffusion. The model consists of a
one-dimensional periodic array of scatterers in which point particles move from
cell to cell as defined by a piecewise linear map. The microscopic chaotic
scattering process of the map can be changed by a control parameter. This
induces a parameter dependence for the macroscopic diffusion coefficient. We
calculate the diffusion coefficent and the largest eigenmodes of the system by
using Markov partitions and by solving the eigenvalue problems of respective
topological transition matrices. For different boundary conditions we find that
the largest eigenmodes of the map match to the ones of the simple
phenomenological diffusion equation. Our main result is that the difffusion
coefficient exhibits a fractal structure by varying the system parameter. To
understand the origin of this fractal structure, we give qualitative and
quantitative arguments. These arguments relate the sequence of oscillations in
the strength of the parameter-dependent diffusion coefficient to the
microscopic coupling of the single scatterers which changes by varying the
control parameter.Comment: 28 pages (revtex), 12 figures (postscript), submitted to Phys. Rev.
Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars
We report 370 measures of 170 components of binary and multiple star systems,
obtained from speckle imaging observations made with the Differential Speckle
Survey Instrument at Lowell Observatory's Discovery Channel Telescope in 2015
through 2017. Of the systems studied, 147 are binary stars, 10 are seen as
triple systems, and 1 quadruple system is measured. Seventy-six high-quality
non-detections and fifteen newly resolved components are presented in our
observations. The uncertainty in relative astrometry appears to be similar to
our previous work at Lowell, namely linear measurement uncertainties of
approximately 2 mas, and the relative photometry appears to be uncertain at the
0.1 to 0.15 magnitude level. Using these measures and those in the literature,
we calculate six new visual orbits, including one for the Be star 66 Oph, and
two combined spectroscopic-visual orbits. The latter two orbits, which are for
HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the
components at the level of 2 percent or better, and independent distance
measures that in one case agrees with the value found in the Gaia DR2, and in
the other disagrees at the 2- level. We find that HD 22451 consists of
an F6V+F7V pair with orbital period of days and masses of
and . For HD 185501, both stars
are G5 dwarfs that orbit one another with a period of days,
and the masses are and . We
discuss the details of both the new discoveries and the orbit objects
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