New results from H.E.S.S. observations of galaxy clusters

Clusters of galaxies are believed to contain a significant population of cosmic rays. From the radio and probably hard X-ray bands it is known that clusters are the spatially most extended emitters of non-thermal radiation in the Universe. Due to their content of cosmic rays, galaxy clusters are also potential sources of VHE (>100 GeV) gamma rays. Recently, the massive, nearby cluster Abell 85 has been observed with the H.E.S.S. experiment in VHE gamma rays with a very deep exposure as part of an ongoing campaign. No significant gamma-ray signal has been found at the position of the cluster. The non-detection of this object with H.E.S.S. constrains the total energy of cosmic rays in this system. For a hard spectral index of the cosmic rays of -2.1 and if the cosmic-ray energy density follows the large scale gas density profile, the limit on the fraction of energy in these non-thermal particles with respect to the total thermal energy of the intra-cluster medium is 8% for this particular cluster. This value is at the lower bounds of model predictions.Comment: 4 pages, one figure, invited talk at the 2nd Heidelberg workshop: "High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", January 13 - 16, 2009, to be published in Int. J. Mod. Phys.

Tumescent Injections in Subcutaneous Pig Tissue Disperse Fluids Volumetrically and Maintain Elevated Local Concentrations of Additives for Several Hours, Suggesting a Treatment for Drug Resistant Wounds.

PurposeBolus injection of fluid into subcutaneous tissue results in accumulation of fluid at the injection site. The fluid does not form a pool. Rather, the injection pressure forces the interstitial matrix to expand to accommodate the excess fluid in its volume, and the fluid becomes bound similar to that in a hydrogel. We seek to understand the properties and dynamics of externally tumesced (swollen) subcutaneous tissue as a first step in assessing whether tumescent antibiotic injections into wounds may provide a novel method of treatment.MethodsSubcutaneous injections of saline are performed in live and dead pigs and the physical properties (volume, expansion ratio, residence time, apparent diffusion constant) of the resulting fluid deposits are observed with diffusion-weighted magnetic resonance imaging, computed tomography, and 3D scanning.ResultsSubcutaneous tissue can expand to a few times its initial volume to accommodate the injected fluid, which is dispersed thoroughly throughout the tumescent volume. The fluid spreads to peripheral unexpanded regions over the course of a few minutes, after which it remains in place for several hours. Eventually the circulation absorbs the excess fluid and the tissue returns to its original state.ConclusionsGiven the evidence for dense fluid dispersal and several-hour residence time, a procedure is proposed whereby tumescent antibiotic injections are used to treat drug-resistant skin infections and chronic wounds that extend into the subcutaneous tissue. The procedure has the potential to effectively treat otherwise untreatable wounds by keeping drug concentrations above minimum inhibitory levels for extended lengths of time

Contrasting population genetic patterns within the white-throated sparrow genome (Zonotrichia albicollis)

<p>Abstract</p> <p>Background</p> <p>The level of nucleotide diversity observed across the genome is positively correlated with the local rate of recombination. Avian karyotypes are typified by large variation in chromosome size and the rate of recombination in birds has been shown to be negatively correlated with chromosome size. It has thus been predicted that nucleotide diversity is negatively correlated with chromosome size in aves. However, there is limited empirical evidence to support this prediction.</p> <p>Results</p> <p>Here we sequenced 27 autosomal and 12 sex chromosome-linked loci in the white-throated sparrow (<it>Zonotrichia albicollis</it>) to quantify and compare patterns of recombination, linkage disequilibrium (LD), and genetic diversity across the genome of this North American songbird. Genetic diversity on the autosomes varied up to 8-fold, with the lowest diversity observed on the macrochromosomes and the highest diversity on the microchromosomes. Genetic diversity on the sex chromosomes was reduced compared to the autosomes, the most extreme difference being a ~300-fold difference between the W chromosome and the microchromosomes. LD and population structure associated with a common inversion polymorphism (ZAL2/2^m) in this species were found to be atypical compared to other macrochromosomes, and nucleotide diversity within this inversion on the two chromosome arrangements was more similar to that observed on the Z chromosome.</p> <p>Conclusions</p> <p>A negative correlation between nucleotide diversity and autosome size was observed in the white-throated sparrow genome, as well as low levels of diversity on the sex chromosomes comparable to those reported in other birds. The population structure and extended LD associated with the ZAL2/2^mchromosomal polymorphism are exceptional compared to the rest of the white-throated sparrow genome.</p

Systematic review and meta-analysis of mouse models of diabetes-associated ulcers

Mouse models are frequently used to study diabetes-associated ulcers, however, whether these models accurately simulate impaired wound healing has not been thoroughly investigated. This systematic review aimed to determine whether wound healing is impaired in mouse models of diabetes and assess the quality of the past research. A systematic literature search was performed of publicly available databases to identify original articles examining wound healing in mouse models of diabetes. A meta-analysis was performed to examine the effect of diabetes on wound healing rate using random effect models. A meta-regression was performed to examine the effect of diabetes duration on wound healing impairment. The quality of the included studies was also assessed using two newly developed tools. 77 studies using eight different models of diabetes within 678 non-diabetic and 720 diabetic mice were included. Meta-analysis showed that wound healing was impaired in all eight models. Meta-regression suggested that longer duration of diabetes prior to wound induction was correlated with greater degree of wound healing impairment. Pairwise comparisons suggested that non-obese diabetic mice exhibited more severe wound healing impairment compared with db/db mice, streptozotocin-induced diabetic mice or high-fat fed mice at an intermediate stage of wound healing (p<0.01). Quality assessment suggested that the prior research frequently lacked incorporation of key clinically relevant characteristics. This systematic review suggested that impaired wound healing can be simulated in many different mouse models of diabetes but these require further refinement to become more clinically relevant

Evaluating the acute effect of compression socks for recovery between exercise bouts

The current study aimed to investigate the acute application of compression socks for recovery after a strenuous bout of lower-body exercise. 58 active young adults (29 females, 29 males) performed ankle range of motion, calf circumference, isometric strength, calf endurance and perceived muscle soreness measures at baseline, and up to 48 hours following a strenuous bout of lower-body exercise. During the 30-minute recovery period, participants were randomly assigned an experimental leg (compression sock - COMP) and a control leg (passive recovery - CON). No significant group x time interactions were recorded (p > .05) and effect sizes were mostly trivial, except for a small decrease in perceived muscle soreness in COMP compared to CON immediately post-recovery (d = -0.29). For both groups, calf circumference increased, and calf endurance was reduced following exercise (p < .001), while perceived muscle soreness increased significantly over the follow-up period compared to baseline (p < .001). The application of compression socks for 30-minutes following intense calf exercise had little effect on physical measures but may result in a small decrease in perceived muscle soreness immediately following their use for recovery. These garments could be a viable recovery option for athletes with a short timeframe in between training bouts

Capturing the Perceived Phantom Limb through Virtual Reality

poster abstractPhantom limb is the sensation amputees may feel where the missing limb (occasionally an organ) is still attached to the body and is still moving as it would if it were there. Between 50-80% amputees report neuropathic pain, also known as phantom limb pain (PLP). Recent studies suggest that providing sensory input to the stump or amputation area may modulate how PLP can be related to neuroplastic changes in the cortex. However, there is still little understanding of why PLP occurs and there are no fully effective, long-term treatments available. Part of the problem is the difficulty for amputees to describe the sensations of their phantom limbs due to the lack of a physical limb as well as phantom limbs that are in positions that are impossible to attain. This project aims to develop an effective 3D tool with the Maya 3D animation software and the Unity game engine. The tool will then be used for those with phantom limb syndrome to communicate the sensations accurately and easily through various hand positions using a model arm with a user friendly interface. The 3D model arm will be able to mimic the phantom sensation, being able to go beyond normal joint extensions of a regular arm. This way we can have a true 3D visual of how the amputee with phantom limb feels if it is abnormal. Testing the effectiveness of the tool will involve a pilot study with able-bodied volunteers. The non-dominant limb of the volunteers will be hidden behind a blind. After putting their limb in a random position, they will attempt to capture the limb on the 3D model. The actual position and captured position will be compared to determine the reproducibility and accuracy of the virtual limb. By taking advantage of computer graphics, virtual reality and computerized image capture technologies we are hoping to achieve a far less challenging way to quickly and accurately capture the position and striking feelings of the phantom limb sensation

De-Aliasing Through Over-Integration Applied to the Flux Reconstruction and Discontinuous Galerkin Methods

High-order methods are quickly becoming popular for turbulent flows as the amount of computer processing power increases. The flux reconstruction (FR) method presents a unifying framework for a wide class of high-order methods including discontinuous Galerkin (DG), Spectral Difference (SD), and Spectral Volume (SV). It offers a simple, efficient, and easy way to implement nodal-based methods that are derived via the differential form of the governing equations. Whereas high-order methods have enjoyed recent success, they have been known to introduce numerical instabilities due to polynomial aliasing when applied to under-resolved nonlinear problems. Aliasing errors have been extensively studied in reference to DG methods; however, their study regarding FR methods has mostly been limited to the selection of the nodal points used within each cell. Here, we extend some of the de-aliasing techniques used for DG methods, primarily over-integration, to the FR framework. Our results show that over-integration does remove aliasing errors but may not remove all instabilities caused by insufficient resolution (for FR as well as DG)

A Survey of the Isentropic Euler Vortex Problem Using High-Order Methods

The flux reconstruction (FR) method offers a simple, efficient, and easy to implement method, and it has been shown to equate to a differential approach to discontinuous Galerkin (DG) methods. The FR method is also accurate to an arbitrary order and the isentropic Euler vortex problem is used here to empirically verify this claim. This problem is widely used in computational fluid dynamics (CFD) to verify the accuracy of a given numerical method due to its simplicity and known exact solution at any given time. While verifying our FR solver, multiple obstacles emerged that prevented us from achieving the expected order of accuracy over short and long amounts of simulation time. It was found that these complications stemmed from a few overlooked details in the original problem definition combined with the FR and DG methods achieving high-accuracy with minimal dissipation. This paper is intended to consolidate the many versions of the vortex problem found in literature and to highlight some of the consequences if these overlooked details remain neglected