Tuning the structural and dynamical properties of a dipolar Bose-Einstein condensate: Ripples and instability islands

It is now well established that the stability of aligned dipolar Bose gases can be tuned by varying the aspect ratio of the external harmonic confinement. This paper extends this idea and demonstrates that a Gaussian barrier along the strong confinement direction can be employed to tune both the structural properties and the dynamical stability of an oblate dipolar Bose gas aligned along the strong confinement direction. In particular, our theoretical mean-field analysis predicts the existence of instability islands immersed in otherwise stable regions of the phase diagram. Dynamical studies indicate that these instability islands, which can be probed experimentally with present-day technology, are associated with the going soft of a Bogoliubov--de Gennes excitation frequency with radial breathing mode character. Furthermore, we find dynamically stable ground state densities with ripple-like oscillations along the radial direction. These structured ground states exist in the vicinity of a dynamical radial roton-like instability.Comment: 9 pages, 11 figure

Pneumoperitoneum, pneumoretroperitoneum, pneumomediastinum and extensive subcutaneous emphysema in a patient with ulcerative colitis: a case report.

Abstract INTRODUCTION: Pneumo-mediastinum and subcutaneous emphysema are rare presentations of lower gastrointestinal tract perforation. PRESENTATION OF CASE: We are presenting the case of a middle aged man diagnosed with UC who presented with dyspnea and subcutaneous emphysema, attributed to multiple perforations including the stomach and colon. CASE DISCUSSION: Patients with ulcerative colitis (UC) are at an increased risk of perforations due to friability of colonic mucosa given the chronic inflammation and relapsing flares. Chronic use of steroids further predisposes to stress ulcers. These pathologies sometimes coexist and identification of each is crucial for the appropriate treatment plan. CONCLUSION: The case allows for a learning opportunity focusing on coexisting pathologies which may be differentiated based on anatomical knowledge and patient presentation. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserve

Enhanced uptake of water by oxidatively processed oleic acid

International audienceA quartz crystal microbalance apparatus has been used to measure the room temperature uptake of water vapour by thin films of oleic acid as a function of relative humidity, both before and following exposure of the films to various partial pressures of gas phase ozone. A rapid increase in the water-sorbing ability of the film is observed as its exposure to ozone is increased, followed by a plateau region in which additional water is taken up more gradually. In this fully-processed region the mass of water taken up by the film is about 4 times that of the unprocessed film. Infrared spectra of the films, measured after variable exposures to ozone, show dramatic increases in both the "free" and hydrogen-bonded O-H stretching regions, and a decrease in the intensity of olefinic features. These results are consistent with the formation of an oxygenated polymeric product or products, as well as the gas phase products previously identified

Ultrasound speckle noise reduction by radio-frequency data filtering

Ultrasound is a commonly used imaging modality for the examination of several pathologies due to its non-invasiveness, affordability and easiness of use. However, ultrasound images are degraded by an intrinsic artefact called 'speckle', which is the result of the constructive and destructive coherent summation of the ultrasound echoes. This paper aims to generate B-mode images out of radio-frequency (RF) data following standard procedures, a series of steps such as envelope detection, log-compression and scan conversion. Some low pass filters will be applied to RF data in order to achieve B-mode images with high quality by speckle noise reduction.info:eu-repo/semantics/publishedVersio

Inhomogeneous magnetism in single crystalline Sr3_3CuIrO6+δ_{6+\delta}: Implications to phase-separation concepts

The single crystalline form of an insulator, Sr$_3$CuIrO$_{6+\delta}$, is shown to exhibit unexpectedly more than one magnetic transition (at 5 and 19 K) with spin-glass-like magnetic susceptibility behaviour. On the basis of this finding, viz., inhomogeneous magnetism in a chemically homogeneous material, we propose that the idea of "phase- separation" described for manganites [1] is more widespread in different ways. The observed experimental features enable us to make a comparison with the predictions of a recent toy model [2] on {\it magnetic} phase separation in an insulating environment.Comment: 4 pages, 4 figure

Confucianism and its contexts: new research in Confucian political learning

This introduction to the special issue explains why political theorists should be interested in Confucianism and what we have to gain by considering Confucian learning in its broader historical and political contexts

Stochastic Newton Sampler: The R Package sns

The R package sns implements the stochastic Newton sampler (SNS), a MetropolisHastings Markov chain Monte Carlo (MCMC) algorithm where the proposal density function is a multivariate Gaussian based on a local, second-order Taylor-series expansion of log-density. The mean of the proposal function is the full Newton step in the NewtonRaphson optimization algorithm. Taking advantage of the local, multivariate geometry captured in log-density Hessian allows SNS to be more efficient than univariate samplers, approaching independent sampling as the density function increasingly resembles a multivariate Gaussian. SNS requires the log-density Hessian to be negative-definite everywhere in order to construct a valid proposal function. This property holds, or can be easily checked, for many GLM-like models. When the initial point is far from density peak, running SNS in non-stochastic mode by taking the Newton step - augmented with line search - allows the MCMC chain to converge to high-density areas faster. For high-dimensional problems, partitioning the state space into lower-dimensional subsets, and applying SNS to the subsets within a Gibbs sampling framework can significantly improve the mixing of SNS chains. In addition to the above strategies for improving convergence and mixing, sns offers utilities for diagnostics and visualization, sample-based calculation of Bayesian predictive posterior distributions, numerical differentiation, and log-density validation