Thermal and Transport Behavior of Single Crystalline R2CoGa8 (R = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) Compounds

The anisotropy in electrical transport and thermal behavior of single crystalline R$_{2}$CoGa$_{8}$ series of compounds is presented. These compounds crystallize in a tetragonal structure with space gropup P4/mmm. The nonmagnetic counterparts of the series namely Y$_{2}$CoGa$_{8}$ and Lu$_{2}$CoGa$_{8}$show a behavior consistent with the low density of states at the fermi level. In Y$_{2}$CoGa$_{8}$, a possibility of charge density wave transition is observed at $\approx$ 30 K. Gd$_{2}$CoGa$_{8}$ and Er$_{2}$CoGa$_{8}$ show a presence of short range correlation above the magnetic ordering temperature of the compound. In case of Gd$_{2}$CoGa$_{8}$, the magnetoresistance exhibits a significant anisotropy for current parallel to {[}100{]} and {[}001{]} directions. Compounds with other magnetic rare earths (R = Tb, Dy, Ho and Tm) show the normal expected magnetic behavior whereas Dy$_{2}$CoGa$_{8}$ exhibits the possibility of charge density wave (CDW) transition at approximately same temperature as that of Y$_{2}$CoGa$_{8}$. The thermal property of these compounds is analysed on the basis of crystalline electric field (CEF) calculations.Comment: 10 Pages 14 Figures. Submitted to PR

Two-band effects in transport properties of MgB2

We present resistivity and thermal conductivity measurements on bulk samples, prepared either by a standard method or by a one-step technique. The latter samples, due to their high density and purity, show residual resistivity values as low as 0.5 mW cm and thermal conductivity values as high as 215 W/mK, higher than the single crystal ones. Thermal and electrical data of all the samples are analysed in the framework of the Bloch-Gruneisen equation giving reliable parameter values. In particular the temperature resitivity coefficient, obtained both from resistivity and thermal conductivity, in the dirty sample comes out ten time larger than in the clean ones. This result supports the hypothesis of ref. [1] that p and s bands conduct in parallel, prevailing p conduction in clean samples and s conduction in dirty samples .Comment: 8 pages, 5 figures, Presented at the BOROMAG workshop, June 17-19 2002, Genoa, Ital

A Fibreoptic Endoscopic Study of Upper Gastrointestinal Bleeding at Bugando Medical Centre in Northwestern Tanzania: a Retrospective Review of 240 Cases.

Upper gastrointestinal (GI) bleeding is recognized as a common and potentially life-threatening abdominal emergency that needs a prompt assessment and aggressive emergency treatment. A retrospective study was undertaken at Bugando Medical Centre in northwestern Tanzania between March 2010 and September 2011 to describe our own experiences with fibreoptic upper GI endoscopy in the management of patients with upper gastrointestinal bleeding in our setting and compare our results with those from other centers in the world. A total of 240 patients representing 18.7% of all patients (i.e. 1292) who had fibreoptic upper GI endoscopy during the study period were studied. Males outnumbered female by a ratio of 2.1:1. Their median age was 37 years and most of patients (60.0%) were aged 40 years and below. The vast majority of the patients (80.4%) presented with haematemesis alone followed by malaena alone in 9.2% of cases. The use of non-steroidal anti-inflammatory drugs, alcohol and smoking prior to the onset of bleeding was recorded in 7.9%, 51.7% and 38.3% of cases respectively. Previous history of peptic ulcer disease was reported in 22(9.2%) patients. Nine (3.8%) patients were HIV positive. The source of bleeding was accurately identified in 97.7% of patients. Diagnostic accuracy was greater within the first 24 h of the bleeding onset, and in the presence of haematemesis. Oesophageal varices were the most frequent cause of upper GI bleeding (51.3%) followed by peptic ulcers in 25.0% of cases. The majority of patients (60.8%) were treated conservatively. Endoscopic and surgical treatments were performed in 30.8% and 5.8% of cases respectively. 140 (58.3%) patients received blood transfusion. The median length of hospitalization was 8 days and it was significantly longer in patients who underwent surgical treatment and those with higher Rockall scores (P < 0.001). Rebleeding was reported in 3.3% of the patients. The overall mortality rate of 11.7% was significantly higher in patients with variceal bleeding, shock, hepatic decompensation, HIV infection, comorbidities, malignancy, age > 60 years and in patients with higher Rockall scores and those who underwent surgery (P < 0.001). Oesophageal varices are the commonest cause of upper gastrointestinal bleeding in our environment and it is associated with high morbidity and mortality. The diagnostic accuracy of fibreoptic endoscopy was related to the time interval between the onset of bleeding and endoscopy. Therefore, it is recommended that early endoscopy should be performed within 24 h of the onset of bleeding

Optical Properties of Single-Crystal Zinc

Measurements were made of the absorptivity of single crystals of zinc from 0.1 to 3.0 eV at 4.2K. Polarized radiation was used with the electric field vector parallel or perpendicular to the c axis of the crystal. New structure was found for E⃗ ⊥c^at about 0.15 eV; no low-energy structure was observed for E⃗ ∥c^. The low-energy interband transition is attributed to transitions near the point K in the Brillouin zone. The structure in the near-infrared and visible spectra is highly temperature dependent. Comparisons of the absorptivity and the conductivity are made between our 4.2-K data and the data of Rubloff for 77 and 300 K and with the calculations of Kasowski. Thermomodulation measurements on basal-plane samples are described which show the conductivity doublet as originating from two distinct infrared-absorption structures. The low-energy absorptivity is found to be nearly constant for E⃗ ∥c^. An optical effective-mass component m∗∥of 2.0m0 is computed from theories of the anomalous skin effect.This article is from Physical Review B 5 (1972): 2829, doi:10.1103/PhysRevB.5.2829. Posted with permission.</p

Resource quality determines the evolution of resistance and its genetic basis

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability: All the experimental data to support the findings of this study including all virus assay and development data is available at DataDryad. https://doi.org/10.5061/dryad.k98sf7m4g. The complete sequencing data in CRAM format is available from the European Bioinformatics Institute (EBI), under accession number PRJEB27964.Parasites impose strong selection on their hosts, but the level of any evolved resistance may be constrained by the availability of resources. However, studies identifying the genomic basis of such resource‐mediated selection are rare, particularly in non‐model organisms. Here, we investigated the role of nutrition in the evolution of resistance to a DNA virus (PiGV), and any associated trade‐offs in a lepidopteran pest species (Plodia interpunctella). Through selection experiments and whole genome re‐sequencing we identify genetic markers of resistance that vary between the nutritional environments during selection. We do not find consistent evolution of resistance in the presence of virus but rather see substantial variation among replicate populations. Resistance in a low nutrition environment is negatively correlated with growth rate, consistent with an established trade‐off between immunity and development, but this relationship is highly context dependent. Whole genome resequencing of the host shows that resistance mechanisms are likely to be highly polygenic and although the underlying genetic architecture may differ between high and low nutrition environments, similar mechanisms are commonly used. As a whole, our results emphasise the importance of the resource environment on influencing the evolution of resistance.Natural Environment Research Council (NERC)National Institutes of Health (NIH