Monte Carlo Simulation of the Three-dimensional Ising Spin Glass

We study the 3D Edwards-Anderson model with binary interactions by Monte Carlo simulations. Direct evidence of finite-size scaling is provided, and the universal finite-size scaling functions are determined. Using an iterative extrapolation procedure, Monte Carlo data are extrapolated to infinite volume up to correlation length \xi = 140. The infinite volume data are consistent with both a continuous phase transition at finite temperature and an essential singularity at finite temperature. An essential singularity at zero temperature is excluded.Comment: 5 pages, 6 figures. Proceedings of the Workshop "Computer Simulation Studies in Condensed Matter Physics XII", Eds. D.P. Landau, S.P. Lewis, and H.B. Schuettler, (Springer Verlag, Heidelberg, Berlin, 1999

Invited - Spiking neuron circuits in ULSIC vs TFT technologies

Recent advances on computing systems have enabled increasing success of algorithms using artificial intelligence. Researchers are now exploring new computational paradigms and materials to enable computing at the level of the device, allowing increased privacy and also reduction in energy. One of the most promising techniques is to realize circuits that imitate how neurons in biological brains function. Spike-based neural networks have been shown to hold more computational power than other neuromorphic architectures and their integration into mainstream computing is projected to herald a new age of computational power. Integrating neuron circuits with the functionality of materials used in flexible electronics is likely to open up a large field of applications, most notably for sensors for continuous health monitoring. In traditional MOFET technologies, spiking neuron circuits are typically operated in the deep subthreshold in order to take advantage of the exponential dependence of Vg to achieve the spiking action and also to optimize energy consumption. Nevertheless, this gives rise to some challenging problems when implemented in flexible technologies where the desire for using low cost and low temperature processes leads to lower mobility and much greater variability in device processing. Please click Download on the upper right corner to see the full abstract

Energetics of oxygen-octahedra rotations in perovskite oxides from first principles

We use first-principles methods to study oxygen-octahedra rotations in ABO3 perovskite oxides. We focus on the short-period, perfectly antiphase or in-phase, tilt patterns that characterize most compounds and control their physical (e.g., conductive, magnetic) properties. Based on an analytical form of the relevant potential energy surface, we discuss the conditions for the stability of polymorphs presenting different tilt patterns, and obtain numerical results for a collection of thirty-five representative materials. Our results reveal the mechanisms responsible for the frequent occurrence of a particular structure that combines antiphase and in-phase rotations, i.e., the orthorhombic Pbnm phase displayed by about half of all perovskite oxides and by many non-oxidic perovskites. The Pbnm phase benefits from the simultaneous occurrence of antiphase and in-phase tilt patterns that compete with each other, but not as strongly as to be mutually exclusive. We also find that secondary antipolar modes, involving the A cations, contribute to weaken the competition between different tilts and play a key role in their coexistence. Our results thus confirm and better explain previous observations for particular compounds. Interestingly, we also find that strain effects, which are known to be a major factor governing phase competition in related (e.g., ferroelectric) perovskite oxides, play no essential role as regards the relative stability of different rotational polymorphs. Further, we discuss why the Pbnm structure stops being the ground state in two opposite limits, for large and small A cations, showing that very different effects become relevant in each case. Our work thus provides a comprehensive discussion on these all-important and abundant materials, which will be useful to better understand existing compounds as well as to identify new strategies for materials engineering

4D Spin Glasses in Magnetic Field Have a Mean Field like Phase

By using numerical simulations we show that the 4D $J=\pm 1$ Edwards Anderson spin glass in magnetic field undergoes a mean field like phase transition. We use a dynamical approach: we simulate large lattices (of volume $V$) and work out the behavior of the system in limit where both $t$ and $V$ go to infinity, but where the limit $V \to \infty$ is taken first. By showing that the dynamic overlap $q$ converges to a value smaller than the static one we exhibit replica symmetry breaking. The critical exponents are compatible with the ones obtained by mean field computations.Comment: Physrev format, 5 ps figures include

Universal Finite Size Scaling Functions in the 3D Ising Spin Glass

We study the three-dimensional Edwards-Anderson model with binary interactions by Monte Carlo simulations. Direct evidence of finite-size scaling is provided, and the universal finite-size scaling functions are determined. Monte Carlo data are extrapolated to infinite volume with an iterative procedure up to correlation lengths xi \approx 140. The infinite volume data are consistent with a conventional power law singularity at finite temperature Tc. Taking into account corrections to scaling, we find Tc = 1.156 +/- 0.015, nu = 1.8 +/- 0.2 and eta = -0.26 +/- 0.04. The data are also consistent with an exponential singularity at finite Tc, but not with an exponential singularity at zero temperature.Comment: 4 pages, Revtex, 4 postscript figures include

Theory of Phase Ordering Kinetics

The theory of phase ordering dynamics -- the growth of order through domain coarsening when a system is quenched from the homogeneous phase into a broken-symmetry phase -- is reviewed, with the emphasis on recent developments. Interest will focus on the scaling regime that develops at long times after the quench. How can one determine the growth laws that describe the time-dependence of characteristic length scales, and what can be said about the form of the associated scaling functions? Particular attention will be paid to systems described by more complicated order parameters than the simple scalars usually considered, e.g. vector and tensor fields. The latter are needed, for example, to describe phase ordering in nematic liquid crystals, on which there have been a number of recent experiments. The study of topological defects (domain walls, vortices, strings, monopoles) provides a unifying framework for discussing coarsening in these different systems.Comment: To appear in Advances in Physics. 85 pages, latex, no figures. For a hard copy with figures, email [email protected]

Sources of Klebsiella and Raoultella species on dairy farms: Be careful where you walk

Klebsiella spp. are a common cause of mastitis, milk loss, and culling on dairy farms. Control of Klebsiella mastitis is largely based on prevention of exposure of the udder to the pathogen. To identify critical control points for mastitis prevention, potential Klebsiella sources and transmission cycles in the farm environment were investigated, including oro-fecal transmission, transmission via the indoor environment, and transmission via the outdoor environment. A total of 305 samples was collected from 3 dairy farms in upstate New York in the summer of 2007, and included soil, feed crops, feed, water, rumen content, feces, bedding, and manure from alleyways and holding pens. Klebsiella spp. were detected in 100% of rumen samples, 89% of water samples, and approximately 64% of soil, feces, bedding, alleyway, and holding pen samples. Detection of Klebsiella spp. in feed crops and feed was less common. Genotypic identification of species using rpoB sequence data showed that Klebsiella pneumoniae was the most common species in rumen content, feces, and alleyways, whereas Klebsiella oxytoca, Klebsiella variicola, and Raoultella planticola were the most frequent species among isolates from soil and feed crops. Random amplified polymorphic DNA-based strain typing showed heterogeneity of Klebsiella spp. in rumen content and feces, with a median of 4 strains per 5 isolates. Observational and bacteriological data support the existence of an oro-fecal transmission cycle, which is primarily maintained through direct contact with fecal contamination or through ingestion of contaminated drinking water. Fecal shedding of Klebsiella spp. contributes to pathogen loads in the environment, including bedding, alleyways, and holding pens. Hygiene of alleyways and holding pens is an important component of Klebsiella control on dairy farms

Incidence of combined burns and major trauma in England and Wales

Introduction: Within the United Kingdom’s major trauma networks, limited consideration is given to the management of concomitant burns and trauma injuries, prominently highlighted in the arrangement of specialist services for major trauma and burns care. The majority of the literature regarding this topic, based almost exclusively on North American studies, predicts between 5 and 7% of all patients admitted to burns centres will suffer from concomitant (non-thermal) trauma injuries, in addition to their burn injuries. The aim of this study is to understand the epidemiology and outcomes for patients sustaining burns and trauma injuries in England and Wales. Methods: A retrospective review of patients sustaining concomitant burns and trauma injuries was made over a 71-month period from January 2010 to November 2016, using the national trauma registry for England and Wales, the Trauma Audit and Research Network database, identifying all patients with injury codes for burns and trauma (AIS >3). Data collected comprised patient demographic information, burn injury percentages, details of trauma injuries, details of hospital stay, and patient outcome. Comparison of information was made against the total burns and total trauma cohort to form a base standard for burns and trauma injuries, respectively. Results: Over the period analysed, 188 patients were found to have concomitant burns and trauma injuries. The patients were stratified according to age and the percentage of total body surface area burned. Hospital length of stay for concomitant burns and trauma patients was found to be higher than that of patients with isolated burns injuries. Mortality rates, although low overall, were found to be relatively higher for patients with concomitant burns and trauma injuries. Conclusions: This study demonstrated the rarity of this combination of injury pattern, in particular the occurrence of severe burns in the presence of major trauma, in UK. Improvements in burns care and trauma care hopefully contributes to the higher level of survival in concomitantly injured patients against data from previous literature. However, the synergistic effect of burns and trauma injuries appears to impact on the course of such patients, although larger scale analysis is required to determine the true prognostic factors

Development of Thiophene Compounds as Potent Chemotherapies for the Treatment of Cutaneous Leishmaniasis Caused by Leishmania major

Leishmania major (L. major) is a protozoan parasite that causes cutaneous leishmaniasis. About 12 million people are currently infected with an annual incidence of 1.3 million cases. The purpose of this study was to synthesize a small library of novel thiophene derivatives, and evaluate its parasitic activity, and potential mechanism of action (MOA). We developed a structure–activity relationship (SAR) study of the thiophene molecule 5A. Overall, eight thiophene derivatives of 5A were synthesized and purified by silica gel column chromatography. Of these eight analogs, the molecule 5D showed the highest in vitro activity against Leishmania major promastigotes (EC50 0.09 ± 0.02 µM), with an inhibition of the proliferation of intracellular amastigotes higher than 75% at only 0.63 µM and an excellent selective index. Moreover, the effect of 5D on L. major promastigotes was associated with generation of reactive oxygen species (ROS), and in silico docking studies suggested that 5D may play a role in inhibiting trypanothione reductase. In summary, the combined SAR study and the in vitro evaluation of 5A derivatives allowed the identification of the novel molecule 5D, which exhibited potent in vitro anti-leishmanial activity resulting in ROS production leading to cell death with no significant cytotoxicity towards mammalian cells

Research Article (PLOS ONE) Efficacy of a low-cost bubble CPAP system in treatment of respiratory distress in a neonatal ward in Malawi

Background: Respiratory failure is a leading cause of neonatal mortality in the developing world. Bubble continuous positive airway pressure (bCPAP) is a safe, effective intervention for infants with respiratory distress and is widely used in developed countries. Because of its high cost, bCPAP is not widely utilized in low-resource settings. We evaluated the performance of a new bCPAP system to treat severe respiratory distress in a low resource setting, comparing it to nasal oxygen therapy, the current standard of care.Methods: We conducted a non-randomized convenience sample study to test the efficacy of a low-cost bCPAP system treating newborns with severe respiratory distress in the neonatal ward of Queen Elizabeth Central Hospital, in Blantyre, Malawi. Neonates weighing >1,000 g and presenting with severe respiratory distress who fulfilled inclusion criteria received nasal bCPAP if a device was available; if not, they received standard care. Clinical assessments were made during treatment and outcomes compared for the two groups. Findings 87 neonates (62 bCPAP, 25 controls) were recruited. Survival rate for neonates receiving bCPAP was 71.0% (44/62) compared with 44.0% (11/25) for controls. 65.5% (19/29) of very low birth weight neonates receiving bCPAP survived to discharge compared to15.4% (1/13) of controls. 64.6% (31/48) of neonates with respiratory distress syndrome (RDS) receiving bCPAP survived to discharge, compared to 23.5% (4/17) of controls. 61.5% (16/26) of neonates with sepsis receiving bCPAP survived to discharge, while none of the seven neonates with sepsis in the control group survived.Interpretation: Use of a low-cost bCPAP system to treat neonatal respiratory distress resulted in 27% absolute improvement in survival. The beneficial effect was greater for neonates with very low birth weight, RDS, or sepsis. Implementing appropriate bCPAP devices could reduce neonatal mortality in developing countries