First Measurement of Discrimination between Helium and Electron Recoils in Liquid Xenon for Low-Mass Dark Matter Searches.

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading α particles from ^{210}Po with a gold foil situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events.

Study of dielectric breakdown in liquid xenon with XeBrA: The xenon breakdown apparatus.

Maintaining the electric fields necessary for the current generation of noble liquid time projection chambers (TPCs), with drift lengths exceeding 1 m, requires a large negative voltage applied to their cathode. Delivering such high voltage is associated with an elevated risk of electrostatic discharge and electroluminescence, which would be detrimental to the performance of the experiment. The Xenon Breakdown Apparatus (XeBrA) is a 5-l, high voltage test chamber built to investigate the contributing factors to electrical breakdown in noble liquids. In this work, we present the main findings after conducting scans over stressed electrode areas, surface finish, pressure, and high voltage ramp speed in the medium of liquid xenon. Area scaling and surface finish were observed to be the dominant factors affecting breakdown, whereas no significant changes were observed with varying pressure or ramp speed. A general rise in both the anode current and photon rate was observed in the last 30 s, leading up to a breakdown, with a marked increase in the last couple of seconds. In addition, the position of breakdowns was reconstructed with a system of high-speed cameras and a moderate correlation with the Fowler-Nordheim field emission model was found. Tentative evidence for bubble nucleation being the originating mechanism of breakdown in the liquid was also observed. We deem the results presented in this work to be of particular interest for the design of future, large TPCs, and practical recommendations are provided.

Results of a Search for Sub-GeV Dark Matter Using 2013 LUX Data.

The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a bremsstrahlung photon or a so-called "Migdal" electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. We report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4-5 GeV/c^{2} using 1.4×10^{4} kg day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. This analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.

Search for Neutrinoless Double-Beta Decay with the Upgraded EXO-200 Detector.

Results from a search for neutrinoless double-beta decay (0νßß) of ^{136}Xe are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by EXO-200, the energy resolution of the detector has been improved to σ/E=1.23%, the electric field in the drift region has been raised by 50%, and a system to suppress radon in the volume between the cryostat and lead shielding has been implemented. In addition, analysis techniques that improve topological discrimination between 0νßß and background events have been developed. Incorporating these hardware and analysis improvements, the median 90% confidence level 0νßß half-life sensitivity after combining with the full data set acquired before the upgrade has increased twofold to 3.7×10^{25} yr. No statistically significant evidence for 0νßß is observed, leading to a lower limit on the 0νßß half-life of 1.8×10^{25} yr at the 90% confidence level.

Challenging present concepts in compression therapy: static stiffness index is not consistent and not clinically relevant.

Once a circumferential force is delivered to a limb by a compression device, assuming the tension within the device remains constant, any change in the total force is dependent upon a change in circumference of the limb, with the rate of change (excluding fabric creep) being dependent on the stress strain curve of the device. This article addresses the pre-conceived and well-accepted principle that interface compression delivered by a compression device substantially increases with the position of the limb, based on the positions of sitting (non-weight bearing) to standing and/or during muscle activity (ankle dorsiflexion). Using engineering parameters and clinical measurements, the authors demonstrate that changes in interface pressure are minimal if any, and that the current concept should be modified accordingly. Declaration of interest: This study was sponsored by Carolon. L. Reid, and S. Kravitz are employees of Carolon. M. Hegarty-Craver has received monetary compensation as a researcher for Carolon.

Simulated pressure changes in multilayer, multicomponent wrap systems when transitioning from rest to standing.

OBJECTIVE: The objective of this paper was to investigate the pressure applied to the lower leg by multilayer, multicomponent wrap systems, in different positions Method: The stretch profiles of five multilayer, multicomponent wrap systems were tested, three 2-layer and two 4-layer systems. These were quantified in the laboratory using a tensile testing device. The circumference of the lower leg was measured on healthy participants in three locations (ankle, B1 level, and calf) in three different postures (rest, dorsiflexion, and standing). RESULTS: The largest changes in circumference were used to simulate the pressure changes under the multilayer, multicomponent products using Laplace's Law. While the pressure differences were large for the zinc plaster product, pressure changes ranged from 5-10mmHg for the other, more elastic products. Additionally, it was noted that the leg decreased in circumference at the B1 level and calf for the majority of participants when transitioning from sitting to standing. This decrease in size results in a decrease in bandage tension and applied pressure. CONCLUSION: These results show that the sub-bandage pressure is not significantly affected by changes in posture when used as intended, within the therapeutic range. DECLARATION OF INTEREST: This study was sponsored by Carolon. L. Reid, and S. Kravitz are employees of Carolon and E. Grant is a Member of the Board. M. Hegarty-Craver and C. Kwon have received monetary compensation as researchers for Carolon.

An apparatus to manipulate and identify individual Ba ions from bulk liquid Xe.

We describe a system to transport and identify barium ions produced in liquid xenon, as part of R&D towards the second phase of a double beta decay experiment, nEXO. The goal is to identify the Ba ion resulting from an extremely rare nuclear decay of the isotope (136)Xe, hence providing a confirmation of the occurrence of the decay. This is achieved through Resonance Ionization Spectroscopy (RIS). In the test setup described here, Ba ions can be produced in liquid xenon or vacuum and collected on a clean substrate. This substrate is then removed to an analysis chamber under vacuum, where laser-induced thermal desorption and RIS are used with time-of-flight mass spectroscopy for positive identification of the barium decay product.

Research into fabrics used in compression therapy and assessment of their impact on treatment regimens.

UNLABELLED: The objective of this paper is to provide a definition for interface compression that uses essential principles of engineering science. This definition discusses factors that influence the amount of applied pressure, including the size of the limb, the amount of fabric tension (graduated pressure profile), the number of layers, and the material creep characteristics. Laplace's law has been applied to compression therapy. Tension-extension profiles have been derived for different types of compression fabric to demonstrate the effects of resistance and friction. Force-time profiles have been derived for different types of fabric compression systems to demonstrate the effects of creep (creep is defined generally as the irreversible deformation of a material over time in the presence of a constantly applied load). Here, the fabric compression systems were applied to a test-bed that supplied a constant force to the fabric; creep was taken as the loss of compression (pressure) over time. Laplace's law has been interpreted for compression therapy. The amount of fabric tension is determined by the extent to which it is stretched during application, as well as by changes in the size of the limb. The fabric's relative elasticity, which is quantified by the rigidity index and is related to the slope of the tension-extension profile, dictates the amount that the applied force changes with extension. Compression systems that use multiple layers of fabric are generally more resistive to stretching than single-layer systems. Friction acting between the layers, as well as the added force from each layer, serves to increase the overall compression of these systems. As the applied force rises, the amount of pressure supplied by the fabric increases. However, when the same force (or fabric extension) is used, the applied pressure is less when distributed over a larger surface area. In other words, as the circumference of the limb increases, the pressure decreases. This is the driving principle behind graduated compression. In addition to the changes in fabric tension resulting from extension, the creep characteristics of the material affect the amount of compression provided throughout the wear cycle. The factors influencing interface compression are multi-faceted. Based upon the interpretation of the material properties of compression fabrics (tension-extension profile, number of fabric layers, and creep), new therapeutic guidelines have been established, and others clarified. DECLARATION OF INTEREST: This study was sponsored by Carolon. L. Reid, and S. Kravitz are employees of Carolon and E. Grant is a Member of the Board. M. Hegarty-Craver and C. Kwon have received monetary compensation as researchers for Carolon.

Design of a compartmentalized shotgun assembler for the human genome.

Two different strategies for determining the human genome are currently being pursued: one is the "clone-by-clone" approach, employed by the publicly funded project, and the other is the "whole genome shotgun assembler" approach, favored by researchers at Celera Genomics. An interim strategy employed at Celera, called compartmentalized shotgun assembly, makes use of preliminary data produced by both approaches. In this paper we describe the design, implementation and operation of the "compartmentalized shotgun assembler".

The sequence of the human genome.

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

A whole-genome assembly of Drosophila.

We report on the quality of a whole-genome assembly of Drosophila melanogaster and the nature of the computer algorithms that accomplished it. Three independent external data sources essentially agree with and support the assembly's sequence and ordering of contigs across the euchromatic portion of the genome. In addition, there are isolated contigs that we believe represent nonrepetitive pockets within the heterochromatin of the centromeres. Comparison with a previously sequenced 2.9- megabase region indicates that sequencing accuracy within nonrepetitive segments is greater than 99. 99% without manual curation. As such, this initial reconstruction of the Drosophila sequence should be of substantial value to the scientific community.

Diabetic foot disorders. A clinical practice guideline. For the American College of Foot and Ankle Surgeons and the American College of Foot and Ankle Orthopedics and Medicine.

Foot ulcerations, infections, and Charcot neuropathic osteoarthropathy are three serious foot complications of diabetes mellitus that can too frequently lead to gangrene and lower limb amputation. Consequently, foot disorders are one of the leading causes of hospitalization for persons with diabetes and can account for expenditures in the billions of dollars annually in the U.S. alone. Although not all foot complications can be prevented, dramatic reductions in their frequency have been obtained through the implementation of a multidisciplinary team approach to patient management. Using this concept, the authors present a Clinical Practice Guideline for diabetic foot disorders based on currently available evidence. The underlying pathophysiology and treatment of diabetic foot ulcers, infections, and the diabetic Charcot foot are thoroughly reviewed. Although these guidelines cannot and should not dictate the standard of care for all affected patients, they are intended to provide evidence-based guidance for general patterns of practice. The goal of a major reduction in diabetic limb amputations is certainly possible if these concepts are embraced and incorporated into patient management protocols.

Diabetic foot disorders: a clinical practice guideline. American College of Foot and Ankle Surgeons.

Foot ulcerations, infections, and Charcot neuropathic osteoarthropathy are three serious foot complications of diabetes mellitus that can too frequently lead to gangrene and lower limb amputation. Consequently, foot disorders are one of the leading causes of hospitalization for persons with diabetes and can account for expenditures in the billions of dollars annually in the U.S. alone. Although not all foot complications can be prevented, dramatic reductions in their frequency have been obtained through the implementation of a multidisciplinary team approach to patient management. Using this concept, the authors present a Clinical Practice Guideline for diabetic foot disorders based on currently available evidence. The underlying pathophysiology and treatment of diabetic foot ulcers, infections, and the diabetic Charcot foot are thoroughly reviewed. Although these guidelines cannot and should not dictate the standard of care for all affected patients, they are intended to provide evidence-based guidance for general patterns of practice. The goal of a major reduction in diabetic limb amputations is certainly possible if these concepts are embraced and incorporated into patient management protocols.

Microtags with 150-nm line gratings fabricated by use of extreme-ultraviolet lithography.

The microtag concept is an anticounterfeiting and security measure. Microtags are computer-generated holograms (CGH's) consisting of 150-nm lines arranged to form 300-nm-period gratings. The microtags that we describe were designed for readout at 442nm . The smallest microtag measures 56micromx80 microm when viewed at normal incidence. The CGH design process uses a modified iterative Fourier-transform algorithm to create either phase-only or phase-and-amplitude microtags. We also report on a simple and compact readout system for recording the diffraction pattern formed by a microtag. The measured diffraction patterns agree very well with predictions.

Synthetic infrared spectra.

We have designed, microfabricated, and characterized a diffractive optical element that reproduces the infrared spectrum of HF from 3600 to 4300 cm(-1) . The reflection-mode diffractive optic consists of 4096 lines, each 4.5mum wide, at 16 discrete depths relative to the substrate from 0 to 1.2 mum and was fabricated upon a silicon wafer by anisotropic reactive ion-beam etching in a four-mask-level process. We envisage the use of diffractive optical elements of this type as the basis for a new class of miniaturized, remote chemical sensor systems based on correlation spectroscopy.

Mass-producible microscopic computer-generated holograms: microtags.

We have developed a method for encoding phase and amplitude in microscopic computer-generated holograms (microtags) for security applications. An 8 x 8 cell phase-only and an 8 x 8 cell phase-and-amplitude microtag design has been exposed in photoresist by the extreme-ultraviolet (13.4-nm) lithography tool developed at Sandia National Laboratories. Each microtag measures 80 microm x 160 microm and contains features that are 0.2 microm wide. Fraunhofer zone diffraction patterns can be obtained from fabricated microtags without any intervening optics and compare favorably with predicted diffraction patterns.