Electronic structure, phase stability and chemical bonding in Th2_2Al and Th2_2AlH4_4

We present the results of theoretical investigation on the electronic structure, bonding nature and ground state properties of Th$_2$Al and Th$_2$AlH$_4$ using generalized-gradient-corrected first-principles full-potential density-functional calculations. Th$_2$AlH$_4$ has been reported to violate the "2 \AA rule" of H-H separation in hydrides. From our total energy as well as force-minimization calculations, we found a shortest H-H separation of 1.95 {\AA} in accordance with recent high resolution powder neutron diffraction experiments. When the Th$_2$Al matrix is hydrogenated, the volume expansion is highly anisotropic, which is quite opposite to other hydrides having the same crystal structure. The bonding nature of these materials are analyzed from the density of states, crystal-orbital Hamiltonian population and valence-charge-density analyses. Our calculation predicts different nature of bonding for the H atoms along $a$ and $c$. The strongest bonding in Th$_2$AlH$_4$ is between Th and H along $c$ which form dumb-bell shaped H-Th-H subunits. Due to this strong covalent interaction there is very small amount of electrons present between H atoms along $c$ which makes repulsive interaction between the H atoms smaller and this is the precise reason why the 2 {\AA} rule is violated. The large difference in the interatomic distances between the interstitial region where one can accommodate H in the $ac$ and $ab$ planes along with the strong covalent interaction between Th and H are the main reasons for highly anisotropic volume expansion on hydrogenation of Th$_2$Al.Comment: 14 pages, 9 figure

Approach to diagnosis and pathological examination in bronchial Dieulafoy disease: a case series

<p>Abstract</p> <p>Background</p> <p>There are limited series concerning Dieulafoy disease of the bronchus. We describe the clinical presentation of a series of 7 patients diagnosed with Dieulafoy disease of the bronchus and provide information about the pathological diagnosis approach.</p> <p>Patients and methods</p> <p>A retrospective review of patients who underwent surgery for massive and unexplained recurrent hemoptysis in a referral center during a 11-year period.</p> <p>Results</p> <p>Seven heavy smoker (49 pack years) patients (5 males) mean aged 54 years experienced a massive hemoptysis (350–1000 ml) unrelated to a known lung disease and frequently recurrent. Bronchial contrast extravasation was observed in 3 patients, combining both CT scan and bronchial arteriography. Efficacy of bronchial artery embolization was achieved in 40% of cases before surgery. Pathological examination demonstrated a minute defect in 3 cases and a large and dysplasic superficial bronchial artery in the submucosa in all cases.</p> <p>Conclusion</p> <p>Dieulafoy disease should be suspected in patients with massive and unexplained episodes of recurrent hemoptysis, in order to avoid hazardous endoscopic biopsies and to alert the pathologist if surgery is performed.</p

Conversion of Vertical Banded Gastroplasty to Roux-en-Y Gastric Bypass Results in Restoration of the Positive Effect on Weight Loss and Co-morbidities: Evaluation of 101 Patients

BACKGROUND: Vertical banded gastroplasty (VBG) is a widely used restrictive procedure in bariatric surgery. However, the re-operation rate after this operation is high. In the case of VBG failure, a conversion to Roux-en-Y gastric bypass (RYGBP) is an option. A study was undertaken to evaluate the results of the conversion from VBG to RYGBP. METHODS: 101 patients had conversion from VBG to RYGBP. Patients were separated into 3 groups, based on the indication for conversion: weight regain (group 1), excessive weight loss (group 2) and severe eating difficulties (group 3). Data for the study were collected by retrospective analysis of prospectively recorded data. RESULTS: Weight regain (group 1) was the reason for conversion in 73.3% of patients. Staple-line disruption was the most important cause for the weight regain (74.3%). Excessive weight loss (group 2) affected 14% of patients and was caused by outlet stenosis in 78.6% of patients. The remaining 13% had severe eating difficulties as a result of outlet stenosis (46.1%), pouch dilatation (30.8%) and pouch diverticula (23.1%). Mean BMI before conversion to RYGBP was 40.5, 22.3 and 29.8 kg/m2 in group 1, 2 and 3, respectively. Minor or major direct postoperative complications were observed in 2.0% to 7.0%. Long-term complications were more frequent, and consisted mainly of anastomotic stenosis (22.7%) and incisional hernia (16.8%). Follow-up after conversion was achieved in all patients (100%), with a mean period of 38 +/- 29 months. BMI decreased from 40.5 to 30.1 kg/m2, increased from 22.3 to 25.3 kg/m2. and decreased slightly from 29.8 to 29.0 kg/m2 in group 1, 2 and 3, respectively. All patients in group 3 noticed an improvement in eating difficulties. CONCLUSION: Complications after conversion from failed VBG to RYGBP are substantial and need to be considered. However, the conversion itself is a successful operation in terms of effect on body weight and treating eating difficulties after VBG

Overview of large area triple-GEM detectors for the CMS forward muon upgrade

In order to cope with the harsh environment expected from the high luminosity LHC, the CMS forward muon system requires an upgrade. The two main challenges expected in this environment are an increase in the trigger rate and increased background radiation leading to a potential degradation of the particle ID performance. Additionally, upgrades to other subdetectors of CMS allow for extended coverage for particle tracking, and adding muon system coverage to this region will further enhance the performance of CMS

A novel application of Fiber Bragg Grating (FBG) sensors in MPGD

We present a novel application of Fiber Bragg Grating (FBG) sensors in the construction and characterisation of Micro Pattern Gaseous Detector (MPGD), with particular attention to the realisation of the largest triple (Gas electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of about 0.5 m2 active area each, employing three GEM foils per chamber, to be installed in the forward region of the CMS endcap during the long shutdown of LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM foils that are mechanically stretched in order to secure their flatness and the consequent uniform performance of the GE1/1 chamber across its whole active surface. So far FBGs have been used in high energy physics mainly as high precision positioning and re-positioning sensors and as low cost, easy to mount, low space consuming temperature sensors. FBGs are also commonly used for very precise strain measurements in material studies. In this work we present a novel use of FBGs as flatness and mechanical tensioning sensors applied to the wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used to determine the optimal mechanical tension applied and to characterise the mechanical tension that should be applied to the foils. We discuss the results of the test done on a full-sized GE1/1 final prototype, the studies done to fully characterise the GEM material, how this information was used to define a standard assembly procedure and possible future developments.Comment: 4 pages, 4 figures, presented by Luigi Benussi at MPGD 2015 (Trieste, Italy). arXiv admin note: text overlap with arXiv:1512.0848

Performance of a Large-Area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System

Gas Electron Multiplier (GEM) technology is being considered for the forward muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first implementation is planned for the GE1/1 system in the $1.5 < \mid\eta\mid < 2.2$ region of the muon endcap mainly to control muon level-1 trigger rates after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by 3,072 radial strips with 455 $\mu$rad pitch arranged in eight $\eta$-sectors. We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and tested it in 20-120 GeV hadron beams at Fermilab using Ar/CO$_{2}$ 70:30 and the RD51 scalable readout system. Four small GEM detectors with 2-D readout and an average measured azimuthal resolution of 36 $\mu$rad provided precise reference tracks. Construction of this largest GEM detector built to-date is described. Strip cluster parameters, detection efficiency, and spatial resolution are studied with position and high voltage scans. The plateau detection efficiency is [97.1 $\pm$ 0.2 (stat)]\%. The azimuthal resolution is found to be [123.5 $\pm$ 1.6 (stat)] $\mu$rad when operating in the center of the efficiency plateau and using full pulse height information. The resolution can be slightly improved by $\sim$ 10 $\mu$rad when correcting for the bias due to discrete readout strips. The CMS upgrade design calls for readout electronics with binary hit output. When strip clusters are formed correspondingly without charge-weighting and with fixed hit thresholds, a position resolution of [136.8 $\pm$ 2.5 stat] $\mu$rad is measured, consistent with the expected resolution of strip-pitch/$\sqrt{12}$ = 131.3 $\mu$rad. Other $\eta$-sectors of the detector show similar response and performance.Comment: 8 pages, 32 figures, submitted to Proc. 2014 IEEE Nucl. Sci. Symposium, Seattle, WA, reference adde

Development and performance of Triple-GEM detectors for the upgrade of the muon system of the CMS experiment

The CMS Collaboration is evaluating GEM detectors for the upgrade of the muon system. This contribution will focus on the R&D performed on chambers design features and will discuss the performance of the upgraded detector

Effects of iron-ore mining and processing on metal bioavailability in a tropical coastal lagoon

In water systems, water quality and geochemical properties of sediments determine the speciation of trace metals, metal transport, and sediment-water exchange, influencing metal availability and its potential effects on biota. Studies from temperate climates have shown that iron-ore mining and tailing wastewaters, besides being a source of trace metals, usually show high levels of dissolved ions and particulate suspended matter, thus having the potential of indirectly changing metal bioavailability. For the first time in the tropics, we identified the effects of iron-ore mining and processing on metal bioavailability in a coastal lagoon. With an extensive sampling scheme, we investigated the potential sources of metals; the links among metal levels in water, sediments, and invertebrates; and the contrasting effects on metal speciation and bioavailability. The metals Fe, Mn, Al, Cr, Zn, Cu, Ni, Pb, Cd, Hg, and As were measured in water, sediments (surface and profiles), and invertebrates from Mãe-Bá Lagoon and in the sites directly influenced by the mining operations (tailing dams and nearby rivers). In addition, samples from two other lagoons, considered pristine, were analyzed. The study area is located in the southeast of Brazil (Iron Quadrangle Region and a coastal area of Espírito Santo State). General water characteristics included pH, dissolved organic carbon, alkalinity, and anion composition. Water metal speciation was assessed by a speciation model (Chemical Equilibria in Aquatic Systems). Grain-size distribution, organic carbon, carbonate, and acid volatile sulfide (AVS) were determined in sediments. Statistical methods included comparison of means by Mann-Whitney test, ordination and correlation analyses, and analysis of regression for geochemical normalization of metals with grain size. The dissolved metal concentrations, the total metal levels in sediments, and the normalization based on the fine sediment fraction showed that the mining operations constitute potential sources of Fe, Mn, Cr, Cu, Ni, Pb, As, and Hg to Mãe-Bá Lagoon. However, trace metal availability was reduced because of increased pH, hardness, and sulfide content (356 μmol/g) in the sites influenced by the mining. The lagoon showed similar water chemistry as in the mining sites, with metal bioavailability further decreased by the presence of dissolved organic carbon and chloride. Although AVS levels in the lagoon were low (0.48-56 μmol/g), metal bioavailability was reduced because of the presence of organic matter. Metal levels in invertebrates confirmed the predicted low metal bioavailability in Mãe-Bá Lagoon. The lagoon was considered moderately contaminated only by Hg and As. The iron-ore mining and processing studied here constitute potential sources of metal pollution into the tropical lagoon. Contrary to expectations, however, it also contributes to reducing the overall metal bioavailability in the lagoon. These findings are believed to be useful for evaluating metal exposure in a more integrated way, identifying not only the sources of pollution but also how they can affect the components involved in metal speciation and bioavailability in water systems, leading to new insights