Atomic-Scale Mechanisms of MoS2 Oxidation for Kinetic Control of MoS2/MoO3 Interfaces.

Oxidation of transition metal dichalcogenides (TMDs) occurs readily under a variety of conditions. Therefore, understanding the oxidation processes is necessary for successful TMD handling and device fabrication. Here, we investigate atomic-scale oxidation mechanisms of the most widely studied TMD, MoS2. We find that thermal oxidation results in α-phase crystalline MoO3 with sharp interfaces, voids, and crystallographic alignment with the underlying MoS2. Experiments with remote substrates prove that thermal oxidation proceeds via vapor-phase mass transport and redeposition, a challenge to forming thin, conformal films. Oxygen plasma accelerates the kinetics of oxidation relative to the kinetics of mass transport, forming smooth and conformal oxides. The resulting amorphous MoO3 can be grown with subnanometer to several-nanometer thickness, and we calibrate the oxidation rate for different instruments and process parameters. Our results provide quantitative guidance for managing both the atomic scale structure and thin-film morphology of oxides in the design and processing of TMD devices.

Giant and Controllable Photoplasticity and Photoelasticity in Compound Semiconductors.

We show that the wide-band gap compound semiconductors ZnO, ZnS, and CdS feature large photoplastic and photoelastic effects that are mediated by point defects. We measure the mechanical properties of ceramics and single crystals using nanoindentation, and we find that elasticity and plasticity vary strongly with moderate illumination. For instance, the elastic stiffness of ZnO can increase by greater than 40% due to blue illumination of intensity 1.4 mW/cm^{2}. Above-band-gap illumination (e.g., uv light) has the strongest effect, and the relative effect of subband gap illumination varies between samples-a clear sign of defect-mediated processes. We show giant optomechanical effects can be tuned by materials processing, and that processing dependence can be understood within a framework of point defect equilibrium. The photoplastic effect can be understood by a long-established theory of charged dislocation motion. The photoelastic effect requires a new theoretical framework which we present using density functional theory to study the effect of point defect ionization on local lattice structure and elastic tensors. Our results update the longstanding but lesser-studied field of semiconductor optomechanics, and suggest interesting applications.

Time-resolved photoluminescence studies of perovskite chalcogenides.

Chalcogenides in the perovskite and related crystal structures ("chalcogenide perovskites" for brevity) may be useful for future optoelectronic and energy-conversion technologies inasmuch as they have good excited-state, ambipolar transport properties. In recent years, several studies have suggested that semiconductors in the Ba-Zr-S system have slow non-radiative recombination rates. Here, we present a time-resolved photoluminescence (TRPL) study of excited-state carrier mobility and recombination rates in the perovskite-structured material BaZrS3, and the related Ruddlesden-Popper phase Ba3Zr2S7. We measure state-of-the-art single crystal samples, to identify properties free from the influence of secondary phases and random grain boundaries. We model and fit the data using a semiconductor physics simulation, to enable more direct determination of key material parameters than is possible with empirical data modeling. We find that both materials have Shockley-Read-Hall recombination lifetimes on the order of 50 ns and excited-state diffusion lengths on the order of 5 µm at room temperature, which bodes well for ambipolar device performance in optoelectronic technologies including thin-film solar cells.

[CURB-65 as a predictor of 30-day mortality in patients hospitalized with COVID-19 in Ecuador: COVID-EC study]. / CURB-65 como predictor de mortalidad a 30 días en pacientes hospitalizados con COVID-19 en Ecuador: estudio COVID-EC.

OBJECTIVE: This article aims to assess the utility of CURB-65 in predicting 30-day mortality in adult patients hospitalized with COVID-19. METHODS: This work is a cohort study conducted between March 1 and April 30, 2020 in Ecuador. RESULTS: A total of 247 patients were included (mean age 60 ± 14 years, 70% men, overall mortality 41.3%). Patients with CURB-65 ≥ 2 had a higher mortality rate (57 vs. 17%, p < .001) that was associated with other markers of risk: advanced age, hypertension, overweight/obesity, kidney failure, hypoxemia, requirement for mechanical ventilation, or onset of respiratory distress. CONCLUSIONS: CURB-65 ≥ 2 was associated with higher 30-day mortality on the univariate (Kaplan-Meier estimator) and multivariate (Cox regression) analysis.

Growth Kinetics and Atomistic Mechanisms of Native Oxidation of ZrSxSe2-x and MoS2 Crystals.

A thorough understanding of native oxides is essential for designing semiconductor devices. Here, we report a study of the rate and mechanisms of spontaneous oxidation of bulk single crystals of ZrSxSe2-x alloys and MoS2. ZrSxSe2-x alloys oxidize rapidly, and the oxidation rate increases with Se content. Oxidation of basal surfaces is initiated by favorable O2 adsorption and proceeds by a mechanism of Zr-O bond switching, that collapses the van der Waals gaps, and is facilitated by progressive redox transitions of the chalcogen. The rate-limiting process is the formation and out-diffusion of SO2. In contrast, MoS2 basal surfaces are stable due to unfavorable oxygen adsorption. Our results provide insight and quantitative guidance for designing and processing semiconductor devices based on ZrSxSe2-x and MoS2 and identify the atomistic-scale mechanisms of bonding and phase transformations in layered materials with competing anions.

Opto-Mechanics Driven Fast Martensitic Transition in Two-Dimensional Materials.

Diffusional phase-change materials, such as Ge-Sb-Te alloys, are used in rewritable nonvolatile memory devices. But the continuous pursuit of readout/write speed and reduced energy consumption in miniaturized devices calls for an optically driven, diffusionless phase change scheme in ultrathin materials. Inspired by optical tweezers, in this work, we illustrate theoretically and computationally that a linearly polarized laser pulse with selected frequency can drive an ultrafast diffusionless martensitic phase transition of two-dimensional ferroelastic materials such as SnO and SnSe monolayers, where the unit-cell strain is tweezed as a generalized coordinate that affects the anisotropic dielectric function and electromagnetic energy density. At laser power of 2.0 × 1010 and 7.7 × 109 W/cm2, the transition potential energy barrier vanishes between two 90°-orientation variants of ferroelastic SnO and SnSe monolayer, respectively, so displacive domain switching can occur within picoseconds. The estimated adiabatic thermal limit of energy input in such optomechanical martensitic transition (OMT) is at least 2 orders of magnitude lower than that in Ge-Sb-Te alloy.

Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition.

Advances in solid-state and atomic physics are exposing the hidden relationships between conventional and exotic states of quantum matter. Prominent examples include the discovery of exotic superconductivity proximate to conventional spin and charge order, and the crossover from long-range phase order to preformed pairs achieved in gases of cold fermions and inferred for copper oxide superconductors. The unifying theme is that incompatible ground states can be connected by quantum phase transitions. Quantum fluctuations about the transition are manifestations of the competition between qualitatively distinct organizing principles, such as a long-wavelength density wave and a short-coherence-length condensate. They may even give rise to 'protected' phases, like fluctuation-mediated superconductivity that survives only in the vicinity of an antiferromagnetic quantum critical point. However, few model systems that demonstrate continuous quantum phase transitions have been identified, and the complex nature of many systems of interest hinders efforts to more fully understand correlations and fluctuations near a zero-temperature instability. Here we report the suppression of magnetism by hydrostatic pressure in elemental chromium, a simple cubic metal that demonstrates a subtle form of itinerant antiferromagnetism formally equivalent to the Bardeen-Cooper-Schrieffer (BCS) state in conventional superconductors. By directly measuring the associated charge order in a diamond anvil cell at low temperatures, we find a phase transition at pressures of approximately 10 GPa driven by fluctuations that destroy the BCS-like state but preserve the strong magnetic interaction between itinerant electrons and holes. Chromium is unique among stoichiometric magnetic metals studied so far in that the quantum phase transition is continuous, allowing experimental access to the quantum singularity and a direct probe of the competition between conventional and exotic order in a theoretically tractable material.

Order parameter fluctuations at a buried quantum critical point.

Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe(2) at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.

Confirmation of oxidative stress and fatty acid disturbances in two further Papillon-Lefèvre syndrome families with identification of a new mutation.

BACKGROUND: We have previously reported oxidative and fatty acids disturbances in one Papillon-Lefèvre syndrome (PLS) family. This Mendelian condition characterized by palmar plantar keratosis and severe aggressive periodontitis, is caused by mutations in the cathepsin C (CTSC) gene. In this study, we have analysed two further unrelated PLS families to confirm this association. METHODS: Mutations were identified by direct sequencing of CTSC. Biochemical analyses were performed in probands and their relatives in order to determine plasma levels of vitamin E, CoQ10 , lipid hydroperoxides (HP) and fatty acid patterns. RESULTS: Pathogenic CTSC mutations were identified in both families including a new mutation (c504C>G). Both probands showed low levels of vitamin E and CoQ10 , and high levels of lipid HP, and also very low levels of docohexaenoic acid. CONCLUSIONS: The previously reported oxidative and fatty acids disturbances were confirmed as a feature of this condition in two further families. There are low levels of antioxidant markers and high levels of oxidative markers, in addition of low levels of some anti-inflammatory fatty acids in persons suffering PLS and some of their relatives.

Comparative analysis of 2 resonance frequency measurement devices: Osstell Mentor and Osstell ISQ.

OBJECTIVE: Comparing reliability of Osstell Mentor and Osstell ISQ in implant stability measurement, and assessing whether their measurements are comparable. MATERIALS AND METHOD: Implant stability was measured with both devices on 58 implants in 15 patients. Six measurements were completed with each device with 2 different transducers (3 measurements with each transducer), that is, 12 measurements for each implant. RESULTS: Mean implant stability quotient (ISQ) value with Osstell ISQ was 72.59, 72.47, and 73.17 in the first measurements, respectively. With Osstell Mentor, the results were 72.43, 72.60, and 73.26, respectively; mean ranges were 3.37, 3.60, and 3.75, respectively. However, mean value with Osstell ISQ and Osstell Mentor was 72.87 and 72.04, respectively. The intraclass correlation coefficient was 0.98. This means an almost perfect degree of concordance between both devices. CONCLUSIONS: Resonance frequency analysis systems in Osstell Mentor and Osstell ISQ show almost perfect reproducibility and repeatability.

Direct measurement of antiferromagnetic domain fluctuations.

Measurements of magnetic noise emanating from ferromagnets owing to domain motion were first carried out nearly 100 years ago, and have underpinned much science and technology. Antiferromagnets, which carry no net external magnetic dipole moment, yet have a periodic arrangement of the electron spins extending over macroscopic distances, should also display magnetic noise. However, this must be sampled at spatial wavelengths of the order of several interatomic spacings, rather than the macroscopic scales characteristic of ferromagnets. Here we present a direct measurement of the fluctuations in the nanometre-scale superstructure of spin- and charge-density waves associated with antiferromagnetism in elemental chromium. The technique used is X-ray photon correlation spectroscopy, where coherent X-ray diffraction produces a speckle pattern that serves as a 'fingerprint' of a particular magnetic domain configuration. The temporal evolution of the patterns corresponds to domain walls advancing and retreating over micrometre distances. This work demonstrates a useful measurement tool for antiferromagnetic domain wall engineering, but also reveals a fundamental finding about spin dynamics in the simplest antiferromagnet: although the domain wall motion is thermally activated at temperatures above 100 K, it is not so at lower temperatures, and indeed has a rate that saturates at a finite value-consistent with quantum fluctuations-on cooling below 40 K.

Signatures of quantum criticality in pure Cr at high pressure.

The elemental antiferromagnet Cr at high pressure presents a new type of naked quantum critical point that is free of disorder and symmetry-breaking fields. Here we measure magnetotransport in fine detail around the critical pressure, Pc approximately 10 GPa, in a diamond anvil cell and reveal the role of quantum critical fluctuations at the phase transition. As the magnetism disappears and T-->0, the magnetotransport scaling converges to a non-mean-field form that illustrates the reconstruction of the magnetic Fermi surface, and is distinct from the critical scaling measured in chemically disordered CrV under pressure. The breakdown of itinerant antiferromagnetism only comes clearly into view in the clean limit, establishing disorder as a relevant variable at a quantum phase transition.

Interval gastric cancer: A call to attentiveness and action.

INTRODUCTION AND AIMS: Endoscopy is the most effective method for identifying gastric adenocarcinoma (GAC). Interval gastric cancer (IGC) is GAC that is diagnosed 2-3 years after a normal endoscopy. Its characteristics are unknown in the Colombian environment. The clinical, histopathologic, and endoscopic characteristics were evaluated, along with the presentation rate, proton pump inhibitor (PPI) use, and IGC survival rate, and compared with other types of GAC. METHODS: A retrospective, analytic study was conducted on a prospective cohort. It evaluated 513 patients with GAC treated at our institution, within the time frame of January 2012 and June 2018. The patients had endoscopic diagnosis of GAC and endoscopy within the past three years that was negative for tumor. RESULTS: A total of 513 patients diagnosed with GAC were evaluated. Forty-two of the patients had IGC (8.2%): 9 early lesions and 33 advanced lesions (79%). The IGCs were smaller (31 vs. 41 mm; P < .01), as well as flatter and more depressed (P < .01). There was no association with PPI use, but there was an association with a history of gastrectomy and anastomosis (P = .02), as well as the absence of red flags (P < .003). The most frequent locations were the gastric body (52%) and the antrum (26%). Overall two-year survival was similar between IGC and GAC (37.1 vs. 39.3%, P = .72). CONCLUSION: A total of 8.2% of recently diagnosed GAC were cases of IGC. The presence of anastomosis and the absence of red flags were related to IGC. Overall survival was poor and there were no differences from the other types of GAC detected.

Impact of intraoperative colonoscopy on anastomotic leakage detection and prevention in colorectal anastomosis for rectal cancer.

INTRODUCTION AND AIM: The value of leakage testing during colorectal resections to identify anastomotic leaks or bleeding has not been established. Our aim was to compare the impact of intraoperative colonoscopy (IOC) versus insufflation with a syringe, as leakage testing in lower anterior resection (LAR) for rectal cancer, with respect to the incidence of postoperative leakage (PL). MATERIALS AND METHODS: A retrospective study utilizing a prospective database of 426 patients with rectal cancer that underwent elective LAR, within the time frame of January 2015 and December 2019, was conducted. The anastomotic leak test was chosen by the surgeon. The incidence of postoperative leakage was compared between patients that underwent IOC and those that had the syringe leak test, utilizing the logistic regression analysis. Propensity score matching was included. RESULTS: There were no significant differences in the clinical characteristics or morbidity and mortality rates between the two groups. Four patients were excluded, leaving a patient total of 422. Seventy patients with IOC were compared with 352 that had the syringe leak test. The incidence of postoperative leakage was 5.7% in the IOC group and 12.2% in the control group (p = 0.001). After propensity score matching (n = 221), balancing the characteristics between the groups, the incidence of postoperative leakage was 5.7% in the IOC group and 13.9% in the syringe leak test group (p = 0.001). CONCLUSION: IOC was shown to be a safe method for evaluating the integrity of colorectal anastomosis and was associated with a higher percentage of protective stoma use, appearing to reduce the risk for PL.

CURB-65 as a predictor of 30-day mortality in patients hospitalized with COVID-19 in Ecuador: COVID-EC study.

OBJECTIVE: This article aims to assess the utility of CURB-65 in predicting 30-day mortality in adult patients hospitalized with COVID-19. METHODS: This work is a cohort study conducted between March 1 and April 30, 2020 in Ecuador. RESULTS: A total of 247 patients were included (mean age 60 ± 14 years, 70% men, overall mortality 41.3%). Patients with CURB-65 ≥ 2 had a higher mortality rate (57 vs. 17%, p < .001) that was associated with other markers of risk: advanced age, hypertension, overweight/obesity, kidney failure, hypoxemia, requirement for mechanical ventilation, or onset of respiratory distress. CONCLUSIONS: CURB-65  ≥ 2 was associated with higher 30-day mortality on the univariate (Kaplan-Meier estimator) and multivariate (Cox regression) analysis.

Relationship of serum cholesterol levels to atopy in the US population.

BACKGROUND: Cholesterol promotes Th2 immunity and allergic inflammation in rodents; whether this occurs in humans is unclear. Reports of both direct and inverse associations between serum cholesterol and atopy in different populations suggest that race and/or other demographic variables may modify these relationships. AIMS OF THE STUDY: To determine the relationships between levels of three serum cholesterol measures [total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C), and non-HDL-C] and atopy in a sample representative of the US population. METHODS: Cross-sectional study of 6854 participants aged > or =6 years from the 2005-2006 National Health and Nutrition Examination Survey. RESULTS: In the overall population, adjusted odds ratios (AORs) per two-standard deviation increase in TC and non-HDL-C for biochemical atopy (defined as > or =1 allergen-specific IgE to 19 allergens) were 1.17 [95% confidence interval (CI), 1.00-1.38] and 1.19 (95% CI, 1.03-1.39), respectively. Interactions by race were noted for the two relationships (interaction P = 0.004 and P = 0.009, respectively) with non-Hispanic Whites (NHWs) having direct relationships [TC: AOR 1.27 (95% CI, 1.03-1.57); non-HDL-C: AOR 1.27 (95% CI, 1.03-1.56)] and non-Hispanic Blacks (NHBs) inverse relationships [TC: AOR 0.77 (95% CI, 0.62-0.95); non-HDL-C: AOR 0.86 (95% CI, 0.69-1.08)]. The adjusted HDL-C-atopy relationship was nonsignificant for NHWs and inverse for NHBs [AOR 0.77 (95% CI, 0.61-0.96)]. Relationships were independent of body mass index and serum C-reactive protein and unmodified by corticosteroid or statin usage. Results were similar using current hay fever/allergy as the atopy outcome. CONCLUSIONS: There are marked inter-racial differences in the relationship between serum cholesterol and atopy in the US population.

[Eating behaviour and body image in a sample of adolescents from Sevilla]. / Conducta alimentaria e imagen corporal en una muestra de adolescentes de Sevilla.

OBJECTIVE: This study examined the presence of disordered eating behaviours and the influence that on them could have the degree of body dissatisfaction among adolescents. METHOD: By the Eating Attitudes Test-40 (EAT-40), the Sick Control On Fat Food (SCOFF) and the subscale of body dissatisfaction (BD) of the Eating Disorders Inventory-2 (EDI-2) a total of 841 students, aged 12-19, were studied. Eating behaviours, sex and age differences, and eating attitudes and behaviours related to the degree of body dissatisfaction were analized. RESULTS: We found that 21,29% had significant punctuations in the SCOFF and 7,13% in the EAT-40. There were significant sex-differences (13,93% and 3,23% in SCOFF and EAT-40 for males, 29,38% and 10,70% for women). With regard to previous studies, a decrease of the risk is observed in women and an increase in males. Major body dissatisfaction was observed among the 12 to 17-year-old girls, though sex-differences in eating alterations, can be mostly found between the ages of 14 and 16. Body dissatisfaction correlated positively and significantly to Body Mass Index, EAT-40 and SCOFF. CONCLUSION: In order to implement primary programs in the adolescent population it is necessary to explore the eating behaviours of risky and the degree of body dissatisfaction to be able to raise specifically the interventions to be carried out, involving teachers as primary agents for the work in the school context.

Near-infrared photonic phase-change properties of transition metal ditellurides.

We use the (Mo,W)Te2 system to explore the potential of transition metal dichalcogenides (TMDs) as phase-change materials for integrated photonics. We measure the complex optical constant of MoTe2 in both the 2H and 1T' phases by spectroscopic ellipsometry. We find that both phases have large refractive index, which is good for confined light-matter interaction volume. The change Δn between phases is of ℴ(1), which is large and comparable to established phase-change materials. However, both phases have large optical loss, which limits to figure of merit throughout the measured range. We further measure the NIR reflectivity of MoTe2 and Mo0.91W0.09Te2, in both the 2H and 1T' phases. The data show that the strong optical contrast between the 2H and 1T' structures persists even as the thermodynamic barrier between them is reduced by alloying. This bodes well for alloy design of phase-change materials.

Perioperative management of patients with cardiac implantable electronic devices. / Manejo perioperatorio de los pacientes con dispositivos cardíacos electrónicos implantables.

The use of implantable cardiac devices in people of all ages is increasing, especially in the elderly population: patients with pacemakers, cardioverter-defibrillators or cardiac resynchronization therapy devices regularly present for surgery for non-cardiac causes. This review was made in order to collect and analyze the latest evidence for the proper management of implantable cardiac devices in the perioperative period. Through a detailed exploration of PubMed, Academic Search Complete (EBSCO), ClinicalKey, Cochrane (Ovid), the search software UpToDate, textbooks and patents freely available to the public on Google, we selected 33 monographs, which matched the objectives of this publication.

Alpha-particle-induced p53 protein expression in a rat lung epithelial cell strain.

Other investigators have shown that both sparsely ionizing and UV radiation cause cell cycle arrest that is associated with increased expression of wild-type p53 protein. The effect of exposure to alpha-particles from 238Pu on the induction of the p53 protein has now been examined in cultured lung epithelial cells derived from male F344 rats. The number of cells having increased levels of p53 protein was determined by flow cytometry after the cells had been stained with a monoclonal antibody to p53. alpha-Particle irradiation caused a dose-dependent increase in p53 protein levels detectable at doses as low as 0.6 cGy, with no evidence of a threshold. An increase in p53 protein also occurred in X-irradiated cells. However, no increase was seen in cells exposed to less than 10 cGy of X-rays, indicating the existence of a relatively higher DNA damage threshold for sparsely ionizing radiation. In addition, more cells exposed to low doses of alpha radiation had increased p53 protein levels than would be predicted based on the number of nuclei expected to be traversed by an alpha-particle, suggesting that alpha-particles cause genetic damage by mechanisms in addition to direct interactions with DNA.