Surface segregation in high-entropy alloys from alchemical machine learning

High-entropy alloys (HEAs), containing several metallic elements in near-equimolar proportions, have long been of interest for their unique mechanical properties. More recently, they have emerged as a promising platform for the development of novel heterogeneous catalysts, because of the large design space, and the synergistic effects between their components. In this work we use a machine-learning potential that can model simultaneously up to 25 transition metals to study the tendency of different elements to segregate at the surface of a HEA. We use as a starting point a potential that was previously developed using exclusively crystalline bulk phases, and show that, thanks to the physically-inspired functional form of the model, adding a much smaller number of defective configurations makes it capable of describing surface phenomena. We then present several computational studies of surface segregation, including both a simulation of a 25-element alloy, that provides a rough estimate of the relative surface propensity of the various elements, and targeted studies of CoCrFeMnNi and IrFeCoNiCu, which provide further validation of the model, and insights to guide the modeling and design of alloys for heterogeneous catalysis

Some methodological foundation of an innovation theory

Market economy in the era of post-industrial areas of development the main focus in order to achieve the planned economic growth, it is advisable puts on the concept of "innovation", taking as a basis for the introduction of new human activities constituent elements that contribute to improving the resulting total of all of society as a whole

Grain Boundaries: Atomic Structure Prediction, Phase Transitions and Effect on Strength of Polycrystals

В настоящей работе демонстрируется влияние границ зерен на свойства поликристаллических минералов на примере Σ5 (310) [001] границы в периклазе (MgO). Используя комбинацию специально адаптированного под эти цели эволюционного алгоритма USPEX и современных межатомных потенциалов на основе машинного обучения, исследуется конфигурационное пространство указанной межзеренной границы и прогнозируются ее возможные фазовые состояния.In this work, we demonstrate the effect of grain boundaries on the properties of polycrystalline minerals on the example of the ∑5(310)[001] grain boundary in periclase (MgO). Using the combination of extended evolutionary algorithm USPEX and modern machine-learning interatomic potentials, we explore the configuration space of the specified grain boundary and predict its possible phase-like states

Undamped electrostatic plasma waves

Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named {\it corner modes}. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the $(k,\omega_{_R})$ plane ($\omega_{_R}$ being the real part of the wave frequency and $k$ the wavenumber), away from the well-known `thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower $k$-values and chopping the tail shifts them toward higher $k$-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.Comment: 11 pages, 10 figure

Criticality in a Vlasov-Poisson system - a fermionic universality class

A model Vlasov--Poisson system is simulated close the point of marginal stability, thus assuming only the wave-particle resonant interactions are responsible for saturation, and shown to obey the power--law scaling of a second-order phase transition. The set of critical exponents analogous to those of the Ising universality class is calculated and shown to obey the Widom and Rushbrooke scaling and Josephson's hyperscaling relations at the formal dimensionality $d=5$ below the critical point at nonzero order parameter. However, the two-point correlation function does not correspond to the propagator of Euclidean quantum field theory, which is the Gaussian model for the Ising universality class. Instead it corresponds to the propagator for the fermionic {\it vector} field and to the {\it upper critical dimensionality} $d_c=2$. This suggests criticality of collisionless Vlasov-Poisson systems as representative of the {\it universality class} of critical phenomena of {\it a fermionic} quantum field description.Comment: 10 pages, 6 figures, Submitted to Phys. Rev.

BARIATRIC SURGERIES AND CORRECTION OF METABOLIC DISORDERS IN PATIENTS WITH MORBID OBESITY

The article presents the results of bariatric surgeries carried out in the clinic in patients with morbid obesity. We traced both the nearest and remote results after treatment, the loss of body weight in dynamics, relief of the manifestations of "metabolic syndrome" as well as we estimated the quality of life of patients in pre-and postoperative period

Successful Surgery of Severely Comorbid Cystic Pulmonary Hypoplasia

Background. Cystic pulmonary hypoplasia is a malformation of terminal bronchial tree as a cystic dilatation of various size at the level of subsegmental bronchi or bronchioles, which accounts for 60–80% of the overall malformation incidence.Materials and methods. We present a descriptive case of general clinical picture, diagnostic radiological examination and choosing a strategy for surgical diagnosis and treatment of cystic pulmonary hypoplasia. Patient K., 57 yo, was admitted to the Republican Clinical Tuberculosis Dispensary with fibroatelectasis of the right lung lower lobe and underlying subcompensated diabetes type II, inspected by a phthisiatrician, thoracic surgeon and referred for surgical treatment.Results and discussion. A careful history inspection and X­ray data in most cases suffice to successfully diagnose the congenital type of cystic pulmonary defects. Treatment in such patients is personalised, with preference towards surgical intervention. A correct diagnosis is usually conditioned by a detailed and careful examination of the lung morbid morphology during surgery.Conclusion. Modern instrumental methods, with multispiral computed tomography in particular, are key to correctly diagnose a malformation. Relevant case reports are of interest and importance to advance research into causative factors of the disease

Factors contributing to drug-resistant tuberculosis treatment outcome in five countries in the Eastern Europe and Central Asia region

Drug-resistant tuberculosis (DR-TB) is a global challenge and a major contributor of death from anti-microbial resistance. With the main aim to determine factors contributing to treatment outcomes observed among DR-TB patients in the countries in Eastern Europe and Central Asia (EECA), a multi-method study was conducted in: Azerbaijan, Belarus, Romania, Tajikistan and Ukraine. Both quantitative and qualitative methodologies were used for data collection and analysis. The quantitative approaches included a desk review of documents related to the DR-TB responses and an analysis of clinical records of DR-TB patients in selected health facilities of the five countries. Qualitative methods included in-depth interviews with national TB programme (NTP) managers, other healthcare providers and non-governmental organizations (NGOs) workers, as well as interviews and Focus Group Discussions (FGDs) with DR-TB patients. The desk review of 38 reports identified as the main challenges to address DR-TB financial and/or management issues and adverse events of the medicines. The most common recommendations related to treatment outcome focussed on general programme management, treatment regimen composition, clinical management and social support for the patients. In all the five countries the NTPs still have a vertical structure. Some integration into the primary health care system (PHC) already exists but further involvement of PHC facilities is feasible and recommended. Interviews with stakeholders indicated that alcoholism and homelessness and a lack of appropriate response to these issues remain as major challenges for a sub-set of patients. Civil society groups, NGOs and communities are substantially engaged in providing different services to DR-TB patients, especially in Ukraine, Romania and Tajikistan. Data from clinical records of 212 patients revealed that independent risk factors for unfavourable treatment outcome (death, loss to follow-up, failure) were culture-positivity at two months of treatment, history of treatment with second-line drugs and homelessness. More powerful, less toxic and shorter oral treatment regimens as well as comprehensive patient support are needed to improve treatment outcome of patients with DR-TB

Sr-Doped Molecular Hydrogen: Synthesis and Properties of SrH22_{22}

Recently, several research groups announced reaching the point of metallization of hydrogen above 400 GPa. Following the mainstream of extensive investigations of compressed polyhydrides, in this work we demonstrate that small (4 atom %) doping of molecular hydrogen by strontium leads to a dramatic reduction in the metallization pressure to about 200 GPa. Studying the high-pressure chemistry of the Sr-H system at 56-180 GPa, we observed the formation of several previously unknown compounds: C2/m-Sr$_3$H$_{13}$, pseudocubic SrH$_6$, SrH$_9$ with cubic F-43m Sr sublattice, and pseudotetragonal P1-SrH$_{22}$, the metal hydride with the highest hydrogen content discovered so far. Unlike Ca and Y, strontium forms molecular semiconducting polyhydrides, whereas calcium and yttrium polyhydrides are high-Tc superconductors with an atomic H sublattice. The latter phase, SrH$_{22}$ or Sr$_{0.04}$H$_{0.96}$, may be considered as a convenient model of the consistent bandgap closure and metallization of hydrogen. Using the impedance measurements in diamond anvil cells at 300-440 K, we estimated the direct bandgap of the Pm-3n-like compound P1-SrH$_6$ to be 0.44-0.51 eV at 150 GPa, and its metallization pressure to be 220 GPa. Together with the machine learning interatomic potentials, the impedance spectroscopy allowed us to estimate the diffusion coefficients of hydrogen D$_H$ = 1.0-2.8 E-10 m$^2$/s in SrH$_6$ and 1.2-2.1 E-9 m$^2$/s in P1-SrH$_{22}$ at 500-600 K.Comment: Supporting information was compressed and reduced by 2 times to 36 figure