Oxygen-vacancy-induced magnetism in anti-perovskite topological Dirac semimetal Ba3SnO.

The thermodynamic, structural, magnetic and electronic properties of the pristine and intrinsic vacancy-defect-containing topological Dirac semimetal Ba3SnO are studied using first-principles density functional theory calculations. The thermodynamic stability of Ba3SnO has been evaluated with reference to its competing binary phases Ba2Sn, BaSn and BaO. Subsequently, valid limits of the atomic chemical potentials derived from the thermodynamic stability were used for assessing the formation of Ba, Sn and O vacancy defects in Ba3SnO under different synthesis environments. Based on the calculated defect-formation energies, we find that the charge-neutral oxygen vacancies are the most favourable type of vacancy defect under most chemical environments. The calculated electronic properties of pristine Ba3SnO show that inclusion of spin-orbit coupling in exchange-correlation potentials computed using generalized gradient approximation yields a semimetallic band structure exhibiting twin Dirac cones along the Γ-X path of the Brillouin zone. The effect of spin-polarization and spin-orbit coupling on the physical properties of intrinsic vacancy defects containing Ba3SnO has been examined in detail. Using Bader charges, electron localization function (ELF), electronic density of states (DOS) and spin density, we show that the isolated oxygen vacancy is a magnetic defect in anti-perovskite Ba3SnO. Our results show that the origin of magnetism in Ba3SnO is the accumulation of unpaired charges at the oxygen vacancy sites, which couple strongly with the 5d states of the Ba atom. Owing to the metastability observed in earlier theoretically predicted magnetic topological semimetals, the present study reveals the important role of intrinsic vacancy defects in giving rise to magnetism and also provides opportunities for engineering the electronic structure of a Dirac semimetal.

Role of Thermal Equilibrium Dynamics in Atomic Motion during Nonthermal Laser-Induced Melting.

This study shows that initial atomic velocities as given by thermodynamics play an important role in the dynamics of phase transitions. We tracked the atomic motion during nonthermal laser-induced melting of InSb at different initial temperatures. The ultrafast atomic motion following bond breaking can in general be governed by two mechanisms: the random velocity of each atom at the time of bond breaking (inertial model), and the forces acting on the atoms after bond breaking. The melting dynamics was found to follow the inertial model over a wide temperature range.

Superior Anchoring of Sodium Polysulfides to the Polar C2N 2D Material: A Potential Electrode Enhancer in Sodium-Sulfur Batteries.

Despite the high theoretical specific energy in rechargeable sodium-sulfur batteries, the shuttle effect severely hampers its capacity and reversibility, which could be overcome by introducing an anchoring material. We, herein, use first-principles calculations to study the low-cost, easily synthesized, environmentally friendly, and stable two-dimensional polar nitrogenated holey graphene (C2N) and nonpolar polyaniline (C3N) to investigate their performance as anchoring materials and the mechanism behind the binding to identify the best candidate to improve the performance of sodium-sulfur batteries. We gain insight into the interaction, including the lowest-energy configurations, binding energies, binding nature, charge transfer, and electronic properties. Sodium primarily contributes to binding with the nanosheets, which is in accordance with their characteristics as anchoring materials. Sodium polysulfides (NaPSs) and the S8 cluster adsorb at the pores of C2N, where there are six electron lone pairs, one for each N atom. The polar C2N binds the NaPSs much strongly than the nonpolar C3N. In contrast to C3N, the charge population substantially modifies by adsorbing NaPSs on C2N, with a substantial charge transfer from the sulfur atoms. The calculated work function of 6.04 eV for pristine C2N, comparable with the previously reported values, decreases on adsorption of the NaPSs formed from battery discharging. We suggest that the inclusion of C2N into sulfur electrodes could also improve their issue with poor conductivity.

Renal effects of norepinephrine-induced variations in mean arterial pressure after liver transplantation: A randomized cross-over trial.

BACKGROUND: Acute kidney injury is commonly seen after liver transplantation. The optimal perioperative target mean arterial pressure (MAP) for renal filtration, perfusion and oxygenation in liver recipients is not known. The effects of norepinephrine-induced changes in MAP on renal blood flow (RBF), oxygen delivery (RDO2 ), glomerular filtration rate (GFR) and renal oxygenation (=renal oxygen extraction, RO2 Ex) were therefore studied early after liver transplantation. METHODS: Ten patients with an intra- and post-operative vasopressor-dependent systemic vasodilation were studied early after liver transplantation during sedation and mechanical ventilation. To achieve target MAP levels of 60, 75 and 90 mm Hg, the norepinephrine infusion rate was randomly and sequentially titrated. At each target MAP, data on cardiac index (CI), RBF and GFR were obtained by transpulmonary thermodilution (PiCCO), the renal vein thermodilution technique and renal extraction of chromium ethylenediaminetetraaceticacid (51 Cr-EDTA), respectively. Renal oxygen consumption (RVO2 ) and extraction (RO2 Ex) were calculated according to standard formulas. RESULTS: At a target MAP of 75 mm Hg, CI (13%), RBF (18%), RDO2 (24%), GFR (31%) and RVO2 (20%) were higher while RO2 Ex was unchanged compared to a target MAP of 60 mm Hg. Increasing MAP from 75 up to 90 mm Hg increased RVR by 38% but had no further effects on CI, RBF, RDO2 or GFR. CONCLUSIONS: In patients undergoing liver transplantation, RBF and GFR are pressure-dependent at MAP levels below 75 mm Hg. Our results suggest that MAP should probably be targeted to approximately 75 mm Hg for optimal perioperative renal filtration, perfusion and oxygenation in patients undergoing liver transplantation.

X-ray illumination of the ejecta of supernova 1987A.

When a massive star explodes as a supernova, substantial amounts of radioactive elements--primarily (56)Ni, (57)Ni and (44)Ti--are produced. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.

Monitoring the anaesthetist in the operating theatre - professional competence and patient safety.

This article about competence and patient safety in anaesthesia was inspired by a statement in the 2015 AAGBI guidelines on monitoring during anaesthesia: 'the presence of an appropriately trained and experienced anaesthetist is important for patient safety during anaesthesia'. The review starts with a structured description of competence, presenting five dimensions of it; the first two dimensions are identical with the two classical attributes of competence, practical skills and theoretical knowledge. Concerning skills, the value of aiming for a high level of proficiency early in a traning programme is pointed out, and deliberate practice is given as an example of a pedagogical model where aiming for excellence is a core idea. For theoretical knowledge, the value of a deep approach to learning physiology and basic sciences is stressed. The third dimension (anaesthetists' non-technical skills), represents skills necessary for good team-work in the operating theatre. The two last dimensions of competence are the understanding of work and intuitive expert knowing. Understanding work means being aware of what the work is about, appreciating the different aspects of the anaesthetist's job. Intuitive expert knowing, lastly, concerns the tacit dimension of knowledge and skills, which enables professional experts to quickly find a working solution for most clinical problems. The final part of the review is about the 'when' and 'how' of competence assessment. The main message is the importance of assessing the competence of clinically active anaesthetists regularly during their whole career.

Patient Experiences of Life Years After Severe Civilian Lower Extremity Trauma With Vascular Injury.

OBJECTIVE: Severe lower limb trauma with arterial injury is often devastating for the individual. Many studies describe how to manage these injuries when they occur. Short-term functional outcome is quite well described, but the patients are often young, and their suffering is physical, mental, and social from a lifelong perspective. The aim of this study was to report patient experiences of their lives several years after their accidents, and to explore mechanisms of how to improve management. METHOD: The Swedvasc registry was searched for participants from 1987 to 2011, living in the region of Uppsala, Sweden. Some amputated participants were added from the Walking Rehabilitation Center. There were five reconstructed patients with an intact limb, and three with amputations. In depth interviews were conducted and systematically analyzed, using A Giorgi's descriptive phenomenological method. RESULTS: Eight patients participated, five with reconstructed and three with amputated limbs. Life affecting functional impairments were described by all patients. The patients undergoing amputation had received more structured follow up and support through the Walking Rehabilitation Center. The satisfaction with the cosmetic result was poorer than expected. All patients had developed strategies of how to cope with their impairments and stated they now lived "normal lives." CONCLUSIONS: Despite substantial physical, psychological, and cosmetic impairments years after severe lower limb trauma, the participants described life as "normal" and mainly satisfactory. Transition to the new situation could have been facilitated by more frequent and continuous follow up after discharge from hospital, in particular among the non-amputated patients who tend to be lost to follow up. Findings also indicate that family members have to be acknowledged, strengthened, and supported.

Dispersion and monochromatization of x-rays using a beryllium prism.

We demonstrate experimentally and numerically that an x-ray prism made of beryllium can be used to disperse and monochromatize x-rays. A polished beryllium cuboid was employed as refractive and dispersive optics. The results of a proof-of-principle experiment and methods of performance optimization are presented. The spatial separation of undulator harmonics and their subsequent selection using a slit are described. A numerical study, assuming realistic beam and beamline parameters, suggests that undulator harmonics can be spatially separated in the range from 3 keV to beyond 20 keV, while maintaining throughput above 50%. Refractive optics is particularly suitable for low-repetition-rate sources such as free-electron lasers and other LINAC-based short-pulse sources.

Effects of acute plasma volume expansion on renal perfusion, filtration, and oxygenation after cardiac surgery: a randomized study on crystalloid vs colloid.

BACKGROUND: In the present randomized study, we evaluated the differential effects of a colloid and a crystalloid fluid on renal oxygen delivery (RD(O2)), glomerular filtration (GFR), renal oxygen consumption ((RV(O2))), and the renal oxygen supply-demand relationship (i.e., renal oxygenation) after cardiac surgery with cardiopulmonary bypass. METHODS: Thirty patients with normal preoperative renal function, undergoing uncomplicated cardiac surgery, were studied in the intensive care unit in the early postoperative period. Patients were randomized to receive a bolus dose of either a crystalloid (Ringers-acetate 20 ml kg(-1), n=15) or a colloid solution (Venofundin) 10 ml kg(-1), n=15). Systemic haemodynamics were measured via a pulmonary artery catheter. Renal blood flow and GFR were measured by the renal vein retrograde thermodilution technique and by renal extraction of 51Cr-EDTA (=filtration fraction). Arterial and renal vein blood samples were obtained for measurements of renal oxygen delivery (RD(O2)) and RV(O2). Renal oxygenation was estimated from the renal oxygen extraction. RESULTS: Despite an increase in cardiac index and renal blood flow with both fluids, neither of the fluids improved RD(O2), because they both induced haemodilution. The GFR increased in the crystalloid (28%) but not in the colloid group. The crystalloid increased the filtration fraction (24%) and renal oxygen extraction (23%), indicating that the increase in GFR, the major determinant of RV(O2), was not matched by a proportional increase in RD(O2). CONCLUSIONS: Neither the colloid nor the crystalloid improved RD(O2) when used for postoperative plasma volume expansion. The crystalloid-induced increase in GFR was associated with impaired renal oxygenation, which was not seen with the colloid. CLINICAL TRIAL REGISTRATION: NCT01729364.

Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole.

Reconstructive vascular surgery and the extent of tissue damage due to diabetic foot ulcers relates to risk of new ulceration in patients with PAD.

OBJECTIVE: There is limited information regarding new ulceration following the healing of ischaemic foot ulcers in diabetic patients. Our aim is to study new ulcerations in the same foot as the previous ulcer(s) in patients with diabetes and severe peripheral artery disease (PAD). METHOD: Patients with diabetes and severe PAD who healed from previous ulcer(s) (Wagner grade 1-5, at or below the ankle), were recruited for the prospective study from the time of healing of their ulcer. Patients were followed up regarding new ulceration, and their treatments and ulcer status noted either directly or on examination of medical records. RESULTS: We analysed the data on 602 patients with diabetes and severe PAD with healed foot ulcers, either primarily (n=443, 74%) or after minor amputation (n=159, 26%). Of these 51% (n=305) had revascularisation before healing from the previous ulcer, 34% (n=202) developed a new ulcer on the same foot within 15 months (range 0-106). Amputation was required by 22% (n=45) of patients, with a new ulcer on the same foot. The median survival time of all patients (n=602) was 54 months. By regression analysis, a low maximal Wagner grade for the previous ulcer and reconstructive vascular surgery was related to a decreased risk of developing new ulcers in the same foot. CONCLUSION: Patients with diabetes and ischaemic foot ulcers have a high-risk for developing new ulcers and amputation in the same foot after healing. The extent of tissue involvement in the previous ulcer and reconstructive vascular surgery affected the risk for development of new ulcers.

Time-resolved X-ray diffraction investigation of the modified phonon dispersion in InSb nanowires.

The modified phonon dispersion is of importance for understanding the origin of the reduced heat conductivity in nanowires. We have measured the phonon dispersion for 50 nm diameter InSb (111) nanowires using time-resolved X-ray diffraction. By comparing the sound speed of the bulk (3880 m/s) and that of a classical thin rod (3600 m/s) to our measurement (2880 m/s), we conclude that the origin of the reduced sound speed and thereby to the reduced heat conductivity is that the C44 elastic constant is reduced by 35% compared to the bulk material.

Early revascularization after admittance to a diabetic foot center affects the healing probability of ischemic foot ulcer in patients with diabetes.

OBJECTIVES: There is limited information about whether time from recognition of decreased perfusion to revascularization affects the probability of healing in a patient with a diabetic foot ulcer. The aim of the present study was to examine whether time to revascularization after referral to a multidisciplinary foot center was related to the outcome of foot ulcers in patients with diabetes and severe peripheral arterial disease (PAD). METHODS: Patients with diabetes, a foot ulcer, and a systolic toe pressure <45 mmHg or an ankle pressure <80 mmHg were prospectively included at the foot center, and considered for revascularization according to a preset protocol. All patients underwent invasive revascularization, either percutaneous transluminal angioplasty (PTA) or reconstructive vascular surgery. All patients had continuous follow-up until healing or death irrespective of the type of revascularization. RESULTS: A total of 478 patients were included (age 74 [range 66-80] years, 60% males), of whom 315 patients (66%) had PTA, and 163 (34%) had reconstructive surgery. Of the 478 patients, 217 (45%) healed primarily, 88 (19%) healed after a minor amputation, 76 (16%) healed after a major amputation and 92 patients (19%) died unhealed. The median time from inclusion in the study to revascularization was 8 weeks (3-18 weeks). Time to vascular intervention within 8 weeks (p < .001), maximum Wagner grade reached <3 (p < .001), absence of peripheral edema (p = .033), and presence of intermittent claudication (p = .001) were related to a higher probability of healing. CONCLUSIONS: Time to revascularization and extent of tissue damage were related to the probability of healing of ischemic foot ulcer in patients with diabetes over time. In the presence of a decreased perfusion in a patient with diabetes and a foot ulcer not only revascularization per se but also timing of revascularization is important for the possibility of healing without a major amputation.

Source attribution of human campylobacteriosis in Denmark.

SUMMARY This study assesses the contribution of different sources of human campylobacteriosis in Denmark using two different source-attribution approaches. In total, 794 non-human isolates and 406 isolates from human cases (domestic, travel related, and cases with unknown travel history) were collected. Isolates were characterized by multilocus sequence typing, flaA typing and susceptibility to antibiotics. Both models used indicate that the major burden of human campylobacteriosis in Denmark originates from the domestic broiler chicken reservoir. The second most important reservoir was found to be cattle. The Asymmetric Island model attributed 52% [95% credibility interval (CrI) 37-67] to Danish chicken, 17% (95% CrI 3-33) to imported chicken, and 17% (95% CrI 7-28) to cattle. Similarly, the Campylobacter source-attribution model apportioned 38% (95% CrI 28-47) to Danish chicken, 14% (95% CrI 10-18) to imported chicken, and 16% (95% CrI 7-25) to cattle. The addition of flaA type as an extra discriminatory typing parameter did not change the attribution of cases markedly.

Communication: Origin of the difference between carbon nanotube armchair and zigzag ends.

In this work, we have found that the difference between armchair and zigzag ends of carbon nanotubes (CNTs) does not pertain at close study for individual bonds and thus alternative strategies need to be developed to reach the ultimate goals in selective growth. Based on first-principles simulations, the difference between binding strengths for CNTs of different chirality was investigated using hydrogen dissociation energies at their passivated ends. When all H atoms are removed collectively we find the well-known difference: that armchair bonds are much weaker than zigzag ones, which is typically seen for both CNT ends and graphene edges. However, when individual H atoms are removed we find almost no difference in hydrogen dissociation energies, small difference in bond lengths, which by association means small difference in C-C and M-C binding energies. We show convincingly that the difference in binding energy between armchair and zigzag ends is due to a fragment stabilization effect that is only manifested when all (or several neighbouring) bonds are broken. This is because at armchair ends/edges neighbouring dangling bonds can pair-up to form C≡C triple bonds that constitute a considerable stabilization effect compared to the isolated dangling bonds at zigzag ends/edges. Consequently, in many processes, e.g., catalytic growth where bonds are normally created/broken sequentially, not collectively, the difference between armchair and zigzag ends/edges cannot be used to discriminate growth of one type over the other to achieve chiral selective growth. Strategies are discussed to realize chirality selective growth in the light of the results presented, including addition of C2-fragments to favor armchair tubes.

V4C3 MXene: a Type-II Nodal Line Semimetal with Potential as High-Performing Anode Material for Mg-Ion Battery.

We have used density functional theory simulations to explore the topological characteristics of a new MXene-like material, V4C3, and its oxide counterpart, assessing their potential as anode materials for Mg-ion batteries. Our research reveals that V4C3 monolayer is a topological type-II nodal line semimetal, protected by time reversal and spatial inversion symmetries. This type-II nodal line is marked by unique drumhead-like edge states that appear either inside or outside the loop circle, contingent upon the edge ending. Intriguingly, even with an increase in metallicity due to oxygen functionalization, the topological features of V4C3 remain intact. Consequently, the monolayer V4C3 has a topologically enhanced electrical conductivity that amplifies further upon oxygen functionalization. During the charging phase, a remarkable storage concentration led to a peak specific capacity of 894.73 mAh g-1 for V4C3, which only decreases to 789.33 mAh g-1 for V4C3O2. When compared to V2C, V4C3 displays a significantly lower specific capacity loss due to functionalization, demonstrating its superior electrochemical properties. Additionally, V4C3 and V4C3O2 exhibit moderate average open-circuit voltages (0.54 V for V4C3 and 0.58 V for V4C3O2) and energy barriers for intercalation migration (ranging between 0.29-0.63 eV), which are desirable for anode materials. Thus, our simulation results support V4C3 potential as an efficient anode material for Mg-ion batteries.

Dynamics of growing carbon nanotube interfaces probed by machine learning-enabled molecular simulations.

Carbon nanotubes (CNTs), hollow cylinders of carbon, hold great promise for advanced technologies, provided their structure remains uniform throughout their length. Their growth takes place at high temperatures across a tube-catalyst interface. Structural defects formed during growth alter CNT properties. These defects are believed to form and heal at the tube-catalyst interface but an understanding of these mechanisms at the atomic-level is lacking. Here we present DeepCNT-22, a machine learning force field (MLFF) to drive molecular dynamics simulations through which we unveil the mechanisms of CNT formation, from nucleation to growth including defect formation and healing. We find the tube-catalyst interface to be highly dynamic, with large fluctuations in the chiral structure of the CNT-edge. This does not support continuous spiral growth as a general mechanism, instead, at these growth conditions, the growing tube edge exhibits significant configurational entropy. We demonstrate that defects form stochastically at the tube-catalyst interface, but under low growth rates and high temperatures, these heal before becoming incorporated in the tube wall, allowing CNTs to grow defect-free to seemingly unlimited lengths. These insights, not readily available through experiments, demonstrate the remarkable power of MLFF-driven simulations and fill long-standing gaps in our understanding of CNT growth mechanisms.

Realization of either physisorption or chemisorption of 2H-tetraphenylporphyrin on the Cu(111) from density functional theory.

The adsorption of organic molecules to surfaces is a central issue to achieve fully-functional molecular devices, for which porphyrins are well-studied due to their chemical stability and functional diversity. Herein, we investigate both the physical and the chemical adsorption of the free-base tetraphenylporphyrin 2H-TPP on the Cu(111) surface within the framework of density functional theory and find that the most stable physisorbed configuration is more weakly bound by -0.31 eV than the chemisorbed configuration. We use the electron localization function to investigate the difference in binding mechanisms between strong physisorption and weak chemisorption. We have computed a reaction barrier of 0.12 eV in going from physical binding to chemical bonding to the surface, and a barrier of 50 meV in going between neighboring physical binding sites. Our results support the possibility of realizing free-base porphyrins either physisorbed or chemisorbed on Cu(111) depending on the deposition procedure and experimental conditions.

Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A.

The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy, finding narrow infrared emission lines of argon and sulfur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or a pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.

Genetic and environmental influences on adult attention deficit hyperactivity disorder symptoms: a large Swedish population-based study of twins.

BACKGROUND: Attention deficit hyperactivity disorder (ADHD) frequently persists into adulthood. Family and twin studies delineate a disorder with strong genetic influences among children and adolescents based on parent- and teacher-reported data but little is known about the genetic and environmental contribution to DSM-IV ADHD symptoms in adulthood. We therefore aimed to investigate the impact of genetic and environmental influences on the inattentive and hyperactive-impulsive symptoms of ADHD in adults. METHOD: Twin methods were applied to self-reported assessments of ADHD symptoms from a large population-based Swedish twin study that included data from 15 198 Swedish male and female twins aged 20 to 46 years. RESULTS: The broad heritability [i.e., A + D, where A is an additive genetic factor and D (dominance) a non-additive genetic factor] was 37% (A = 11%, D = 26%) for inattention and 38% (A = 18%, D = 20%) for hyperactivity-impulsivity. The results also indicate that 52% of the phenotypic correlation between inattention and hyperactivity-impulsivity (r = 0.43) was explained by genetic influences whereas the remaining part of the covariance was explained by non-shared environmental influences. These results were replicated across age strata. CONCLUSIONS: Our findings of moderate broad heritability estimates are consistent with previous literature on self-rated ADHD symptoms in older children, adolescents and adults and retrospective reports of self-rated childhood ADHD by adults but differ from studies of younger children with informant ratings. Future research needs to clarify whether our data indicate a true decrease in the heritability of ADHD in adults compared to children, or whether this relates to the use of self-ratings in contrast to informant data.