2,570 research outputs found
Ab-initio calculations for the beta-tin diamond transition in Silicon: comparing theories with experiments
We investigate the pressure-induced metal-insulator transition from diamond
to beta-tin in bulk Silicon, using quantum Monte Carlo (QMC) and density
functional theory (DFT) approaches. We show that it is possible to efficiently
describe many-body effects, using a variational wave function with an optimized
Jastrow factor and a Slater determinant. Variational results are obtained with
a small computational cost and are further improved by performing diffusion
Monte Carlo calculations and an explicit optimization of molecular orbitals in
the determinant. Finite temperature corrections and zero point motion effects
are included by calculating phonon dispersions in both phases at the DFT level.
Our results indicate that the theoretical QMC (DFT) transition pressure is
significantly larger (smaller) than the accepted experimental value. We discuss
the limitation of DFT approaches due to the choice of the exchange and
correlation functionals and the difficulty to determine consistent
pseudopotentials within the QMC framework, a limitation that may significantly
affect the accuracy of the technique.Comment: 13 pages, 9 figures, submitted to the Physical Review B on October 2
Vector meson production in pp collisions at âs = 7TeV measured with the ALICE detector
Vector mesons are key probes of the hot and dense state of strongly interacting matter produced in heavy-ion collisions. Their dileptonic decay channel is particularly suitable for these studies, since dileptons have negligible final-state interactions in QCD matter. A measurement of the Ï and Ï differential cross sections was performed by the ALICE experiment in pp collisions at âs = 7TeV, through
their decay in muon pairs, for pT > 1GeV/c and 2.5 < y < 4
Vector meson production at âs = 7TeV and at âs = 2.76 TeV measured with the ALICE detector
Vector mesons are key probes of the hot and dense state of strongly interacting matter produced in heavy ion collisions. Their dilepton decay channel is particularly suitable for these studies, since dileptons have negligible final state interactions in QCD matter. We present the absolute production cross sections of Ï and Ï mesons measured with the ALICE muon spectrometer in the rapidity range 2.5 < y < 4 in pp collisions at âs = 7TeV and at âs = 2.76TeV, and the Ï/(Ï+Ï) ratio measured in Pb-Pb collisions at âsNN = 2.76TeV
UK Renal Registry 18th Annual Report: Chapter 3 Demographic and Biochemistry Profile of Kidney Transplant Recipients in the UK in 2014: National and Centre-specific Analyses.
There was a 2% fall in overall renal transplant numbers in 2014, with a significant fall in kidney donation from donors after circulatory death (10%). In 2014, death-censored renal transplant failure rates in prevalent patients were similar to previous years at 2.4% per annum. Transplant patient death rates remained stable at 2.3 per 100 patient years. The median age of incident and prevalent renal transplant patients in the UK was 50.6 and 53.3 years respectively. The median eGFR of prevalent renal transplant recipients was 52.5 ml/min/1.73 m2. The median eGFR of patients one year after transplantation was 57.4 ml/min/1.73 m2 post live transplant, 53.6 ml/min/1.73 m2 post brainstem death transplant and 50.1 ml/min/1.73 m2 post circulatory death transplant. In 2014, 13% of prevalent transplant patients had eGFR ,30 ml/min/1.73 m2. The median decline in eGFR slope beyond the first year after transplantation was â0.48 ml/min/1.73 m2/year.In 2014, malignancy (26%) and infection (24%) remained the commonest causes of death in patients with a functioning renal transplant
Electromagnetic analysis and performance comparison of fully 3D-printed antennas
In this work, the possibility of directly prototyping antennas by exploiting additive manufacturing 3D-printing technology is investigated. In particular, the availability of printable filaments with interesting conductive properties allows for printing of even the antenna conductive elements. Three samples of a 2.45 GHz microstrip patch antenna have been 3D-printed by using different approaches and materials, and their performance evaluated and compared. In particular, the same dielectric substrate printed in polylactic acid (PLA) has been adopted in all cases, whilst copper tape and two different conductive filaments have been used to realize the conductive parts of the three antenna samples, respectively. Even if an expected radiation efficiency reduction has been observed for the conductive filament case, the comparative analysis clearly demonstrates that 3D-printing technology can be exploited to design working fully-printed antennas, including the conductive parts
Topical tacrolimus and vitiligo: our experience in sixty cases
Aim. Vitiligo is an acquired hypomelanotic disorder characterized by circumscribed depigmented maculae on the skin. Current treatment procedures include narrow band UVB therapy, topical corticosteroids and imunomodulators. Aim of our study was to evaluate the efficacy and safety of topical tacrolimus in the treatment of vitiligo. Methods. Sixty patients (44 females, 22 males) with stable vitiligo were enrolled in our study. They did not show any benefits from topical corticosteroids, PUVA and NB-UVB therapy, so they were administered topical tacrolimus 0.1% twice a day and followed-up for 9 months. Results. At least a partial repigmentation was noticed with tacrolimus ointment in 46 patients after 9 months of therapy. Twenty-three of them obtained a good repigmentation, already evaluable at 3 months from the beginning of therapy and remaining the same at 6 and 9 months, respectively. The other 23 patients obtained an excellent repigmentation, evaluable only at 9 months from the beginning of therapy, while a poor repigmentation was observed at 3 and 6 months. Two patients discontinued therapy because of side effects, while the remaining 12 had no repigmentation at all. Conclusion. Topical tacrolimus could be considered an effective and safe therapy for vitiligo, expecially for patients who had no benefits from corticosteroids and/or phototherapy
Mitigating Sensor and Acquisition Method-Dependence of Fingerprint Presentation Attack Detection Systems by Exploiting Data from Multiple Devices
The problem of interoperability is still open in fingerprint presentation attack detection (PAD) systems. This involves costs for designers and manufacturers who intend to change sensors of personal recognition systems or design multi-sensor systems, because they need to obtain sensor-specific spoofs and retrain the system. The solutions proposed in the state of the art to mitigate the problem still require data from the target sensor and are therefore not exempt from the problem of obtaining new data. In this paper, we provide insights for the design of PAD systems thanks to an overview of an interoperability analysis on modern systems: hand-crafted, deep-learning-based, and hybrid. We investigated realistic use cases to determine the pros and cons of training with data from multiple sensors compared to training with single sensor data, and drafted the main guidelines to follow for deciding the most convenient PAD design technique depending on the intended use of the fingerprint identification/authentication system
Does off-pump coronary revascularization confer superior organ protection in re-operative coronary artery surgery? A meta-analysis of observational studies
Off-pump coronary artery bypass surgery (OPCAB) has been hypothesised to be beneficial in the high-risk patient population undergoing re-operative coronary artery bypass graft surgery (CABG). In addition, this technique has been demonstrated to provide subtle benefits in end-organ function including heart, lungs and kidney. The aims of this study were to assess whether OPCAB is associated with a lower incidence of major adverse cardiovascular and cerebrovascular events (MACCE) and other adverse outcomes in re-operative coronary surgery. Twelve studies, incorporating 3471 patients were identified by systematic literature review. These were meta-analysed using random-effects modelling. Primary endpoints were MACCE and other adverse outcomes including myocardial infarction, stroke, renal dysfunction, low cardiac output state, respiratory failure and atrial fibrillation. A significantly lower incidence of myocardial infarction, stroke, renal dysfunction, low cardiac output state, respiratory failure and atrial fibrillation was observed with OPCAB (OR 0.58; 95% CI (confidence interval) [0.39-0.87]; OR 0.37; 95% CI [0.17-0.79]; OR 0.39; 95% CI [0.24-0.63]; OR 0.14; 95% CI [0.04-0.56]; OR 0.36; 95% CI [0.24-0.54]; OR 0.41; 95% CI [0.22-0.77] respectively). Sub-group analysis using sample size, matching score and quality score was consistent with and reflected these significant findings. Off-pump coronary artery bypass grafting reduces peri-operative and short-term major adverse outcomes in patients undergoing re-operative surgery. Consequently we conclude that OPCAB provides superior organ protection and a safer outcome profile in re-operative CABG
Sheep α-globin gene sequences: Implications for their concerted evolution and for the down-regulation of the 3' genes
In sheep as in man and most other mammals, there are two α-globin genes (Iα and IIα), which are expressed at different levels, the upstream gene being the most efficient. In α-globin gene triplication and quadruplication, this trend is confirmed, i.e., the α-chain output of the downstream genes progressively decreases. In this study, we have determined the complete sequence of the cDNAs and of both the introns in a triple-α haplotype in which each gene could be recognized for the presence of distinct alleles. The sequence analysis reveals that the bodies of the three α-globin genes are essentially identical (99.9% homology) and moreover indicates that the down-regulation of additional α-globin genes in sheep is not the effect of sequence variation from the Cap to the Poly(A) addition sites. This striking similarity among α-genes is higher than that seen in other mammals and is probably sustained by particularly efficient mechanisms of gene conversion and cross-over fixation
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