Dissipation function of the first-order phase transformation in VO2 ceramics by internal-friction measurements

In order to apply the concept of the dissipation function during the first-order phase transition (FOPT) in solids, we measured the internal friction Q-1 and shear modulus μ for a range of frequencies of polycrystalline ceramics VO2 as the sample passed through a FOPT across the temperature range of 300–420 K. The experiment was repeated for different temperature variation rate Ṫ. We have found that for each frequency, a maximum of Q-1 and a minimum of μ occurred at the same temperature Tp when Ṫ was kept constant. The numerical values of the dissipation function ΔGR plus other FOPT parameters have been deduced using Q-1 data. The general trend of ΔGR-T and other results are found to be consistent with known physical aspects.published_or_final_versio

Quenching and reactivation of electroluminescence by charge trapping and detrapping in Si-implanted silicon nitride thin film

In this brief, quenching of electroluminescence (EL) from Si-implanted silicon nitride (SNR) thin film under a forward bias has been observed. The quenching phenomenon is shown to be due to charge trapping in the defect states involved in the radiative recombination. The composite EL bands have different quenching rates, causing a change in the EL spectrum shape by the EL quenching. Release of the trapped charges by a low-temperature annealing at 120 °C or an application of a reverse gate bias can partially recover the quenched EL both in the intensity and spectrum shape. The quenching phenomenon poses a serious challenge to the application of Si-implanted SNR thin films in light-emitting devices. © 2009 IEEE.published_or_final_versio

Evolution of electroluminescence from multiple Si-implanted silicon nitride films with thermal annealing

Influence of thermal annealing on electroluminescence (EL) from multiple-Si-implanted silicon nitride films has been investigated. A reduced injection current and an enhanced EL intensity have been obtained simultaneously by increasing the annealing temperature, which results in a higher EL quantum efficiency. In addition, four emission bands are identified, and their peak energies, intensities, and full widths at half maxima are found to change with annealing temperature. A model is proposed to illustrate the carrier transport, the mechanisms of the four emission bands, and the evolution of the EL bands with annealing as well. The two major bands and the minor ultraviolet band are explained in terms of the recombination of the injected electrons in either the silicon dangling-bond (≡ Si 0) states or the nitride conduction band with the injected holes in either the band tail states above the nitride valence band or the valence band itself, while the minor near infrared band is attributed to the Si nanocrystals formed in the thin film. © 2009 American Institute of Physics.published_or_final_versio

Formation of P In defect in annealed liquid-encapsulated Czochralski InP

Fourier transform infrared spectroscopy measurements have been carried out on liquid-encapsulated Czochralski-grown undoped InP wafers, which reproducibly become semi-insulating upon annealing in an ambient of phosphorus at 800-900°C. The measurements reveal a high concentration of hydrogen complexes in the form V InH 4 existing in the material before annealing in agreement with recent experimental studies. It is argued that the dominant and essential process producing the semi-insulating behavior is the compensation produced by an EL 2-like deep donor phosphorus antisite defect, which is formed by the dissociation of the hydrogen complexes during the process of annealing. The deep donor compensates acceptors, the majority of which are shallow residual acceptor impurities and deep hydrogen associated V In and isolated V In levels, produced at the first stage of the dissociation of the V InH 4 complex. The high concentration of indium vacancies produced by the dissociation are the precursor of the EL 2-like phosphorus antisite. These results show the importance of hydrogen on the electrical properties of InP and indicate that this largely results from low formation energy of the complex V InH 4 in comparison with that of an isolated V In. © 1998 American Institute of Physics.published_or_final_versio

Strain- and Adsorption-Dependent Electronic States and Transport or Localization in Graphene

The chapter generalizes results on influence of uniaxial strain and adsorption on the electron states and charge transport or localization in graphene with different configurations of imperfections (point defects): resonant (neutral) adsorbed atoms either oxygen- or hydrogen-containing molecules or functional groups, vacancies or substitutional atoms, charged impurity atoms or molecules, and distortions. To observe electronic properties of graphene-admolecules system, we applied electron paramagnetic resonance technique in a broad temperature range for graphene oxides as a good basis for understanding the electrotransport properties of other active carbons. Applied technique allowed observation of possible metal-insulator transition and sorption pumping effect as well as discussion of results in relation to the granular metal model. The electronic and transport properties are calculated within the framework of the tight-binding model along with the Kubo-Greenwood quantum-mechanical formalism. Depending on electron density and type of the sites, the conductivity for correlated and ordered adsorbates is found to be enhanced in dozens of times as compared to the cases of their random distribution. In case of the uniaxially strained graphene, the presence of point defects counteracts against or contributes to the band-gap opening according to their configurations. The band-gap behaviour is found to be nonmonotonic with strain in case of a simultaneous action of defect ordering and zigzag deformation. The amount of localized charge carriers (spins) is found to be correlated with the content of adsorbed centres responsible for the formation of potential barriers and, in turn, for the localization effects. Physical and chemical states of graphene edges, especially at a uniaxial strain along one of them, play a crucial role in electrical transport phenomena in graphene-based materials.Comment: 16 pages, 10 figure

Association between the rs6950982 polymorphism near the SERPINE1 gene and blood pressure and lipid parameters in a high-cardiovascular-risk population: interaction with Mediterranean diet

The SERPINE1 (serpin peptidase inhibitor, clade E, member 1) gene, better known by its previous symbol PAI-1 (plasminogen activator inhibitor 1), has been associated with cardiovascular phenotypes with differing results. Our aim was to examine the association between the rs6950982 (G > A) near the SERPINE1 gene, blood pressure (BP) and plasma lipid concentrations as well as the modulation of the polymorphism effects by adherence to Mediterranean diet (AMD). We studied 945 high-cardiovascular-risk subjects. Biochemical, clinical, dietary and genetic data (rs6950982) were obtained. We also determined the common rs1799768 (4G/5G), for checking independent effects. AMD was measured by a validated questionnaire, and four groups were considered. rs6950982 (A > G) and rs1799768 (4G/5G) were only in moderate–low linkage disequilibrium (D′ = 0.719; r2 = 0.167). The most significant associations we obtained were with rs6950982 (A > G). In males, the G allele was nominally associated with higher diastolic BP (AA: 81.5 ± 10.9, AG: 82.1 ± 11.4, GG: 85.7 ± 10.5 mmHg; Padditive = 0.030) and systolic BP (AA + AG: 141.4 ± 6.9 mmHg vs. GG: 149.8 ± 8.0 mmHg; Precessive = 0.036). In the whole population, the rs6950982 was also associated with plasma lipids. Subject with the G allele presented higher total cholesterol (Padditive = 0.016, Precessive = 0.011), low-density lipoprotein cholesterol (Padditive = 0.032, Precessive = 0.031) and triglycerides (Padditive = 0.040, Precessive = 0.029). AMD modulated the effect of rs6950982 on triglyceride concentrations (P for interaction = 0.036). Greater AMD reduced the higher triglyceride concentrations in GG subjects. No significant interactions were found for the other parameters. The rs6950982 was associated with higher BP in men and higher triglycerides in the whole population, this association being modulated by AMD

Transthyretin Aggregation Pathway toward the Formation of Distinct Cytotoxic Oligomers

Characterization of small oligomers formed at an early stage of amyloid formation is critical to understanding molecular mechanism of pathogenic aggregation process. Here we identifed and characterized cytotoxic oligomeric intermediates populated during transthyretin (TTR) aggregation process. Under the amyloid-forming conditions, TTR initially forms a dimer through interactions between outer strands. The dimers are then associated to form a hexamer with a spherical shape, which serves as a building block to self-assemble into cytotoxic oligomers. Notably, wild-type (WT) TTR tends to form linear oligomers, while aTTR variant(G53A) prefers forming annular oligomers with pore-like structures. Structural analyses of the amyloidogenic intermediates using circular dichroism (CD) and solid-state NMR revealthatthe dimer and oligomers have a signifcant degree of native-like β-sheet structures (35–38%), but with more disordered regions (~60%)than those of nativeTTR.TheTTR variant oligomers are also less structured than WT oligomers. The partially folded nature of the oligomeric intermediates might be a common structural property of cytotoxic oligomers.The higher fexibility of the dimer and oligomers may also compensate for the entropic loss due to the oligomerization of the monomers

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Measurement and interpretation of same-sign W boson pair production in association with two jets in pp collisions at s = 13 TeV with the ATLAS detector

This paper presents the measurement of fducial and diferential cross sections for both the inclusive and electroweak production of a same-sign W-boson pair in association with two jets (W±W±jj) using 139 fb−1 of proton-proton collision data recorded at a centre-of-mass energy of √s = 13 TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed by selecting two same-charge leptons, electron or muon, and at least two jets with large invariant mass and a large rapidity diference. The measured fducial cross sections for electroweak and inclusive W±W±jj production are 2.92 ± 0.22 (stat.) ± 0.19 (syst.)fb and 3.38±0.22 (stat.)±0.19 (syst.)fb, respectively, in agreement with Standard Model predictions. The measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confdence level intervals on dimension-8 operators. A search for doubly charged Higgs bosons H±± that are produced in vector-boson fusion processes and decay into a same-sign W boson pair is performed. The largest deviation from the Standard Model occurs for an H±± mass near 450 GeV, with a global signifcance of 2.5 standard deviations

Combination of searches for heavy spin-1 resonances using 139 fb−1 of proton-proton collision data at s = 13 TeV with the ATLAS detector

A combination of searches for new heavy spin-1 resonances decaying into different pairings of W, Z, or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb−1 of proton-proton collisions at = 13 TeV collected during 2015–2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting quark pairs (qq, bb, , and tb) or third-generation leptons (τν and ττ) are included in this kind of combination for the first time. A simplified model predicting a spin-1 heavy vector-boson triplet is used. Cross-section limits are set at the 95% confidence level and are compared with predictions for the benchmark model. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The complementarity of the various analyses increases the sensitivity to new physics, and the resulting constraints are stronger than those from any individual analysis considered. The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up to 1.5 TeV in the case of production via vector-boson fusion