Dopants adsorbed as single atoms prevent degradation of catalysts

The design of catalysts with desired chemical and thermal properties is viewed as a grand challenge for scientists and engineers. For operation at high temperatures, stability against structural transformations is a key requirement. Although doping has been found to impede degradation, the lack of atomistic understanding of the pertinent mechanism has hindered optimization. For example, porous gamma-Al2O3, a widely used catalyst and catalytic support, transforms to non-porous alpha-Al2O3 at ~1,100C. Doping with La raises the transformation temperature to ~1,250C, but it has not been possible to establish if La atoms enter the bulk, adsorb on surfaces as single atoms or clusters, or form surface compounds. Here, we use direct imaging by aberration-corrected Z-contrast scanning transmission electron microscopy coupled with extended X-ray absorption fine structure and first-principles calculations to demonstrate that, contrary to expectations, stabilization is achieved by isolated La atoms adsorbed on the surface. Strong binding and mutual repulsion of La atoms effectively pin the surface and inhibit both sintering and the transformation to alpha-Al2O3. The results provide the first guidelines for the choice of dopants to prevent thermal degradation of catalysts and other porous materials.Comment: RevTex4, 4 pages, 4 JPEG figures, published in Nature Material

Current State of the Development of Next-Generation Vaccines against Ebola Virus Disease

Representative of Ebolavirus gender, Filoviridae family, Ebola virus is an etiological agent of particularly dangerous viral fever, the lethality of which comes up to 88 %. According to the leading specialists and experts in the sphere, vaccination is the most effective and cost-efficient method for the protection from epidemic spread. Objective of the review is to analyze current state of the development of next generation vaccines against Ebola fever. It is established that focus areas of the activities are the construction of vaccines on the basis of alpha-virus replicons, virus-like particles, and the development of DNA-vaccines and vector recombinant vaccines. The paper discusses the most significant achievements in the sphere of obtainment of potent therapies for prophylaxis as regards Ebola fever. To date manufactured, using various approaches, have been the next-generation vaccine preparations, for a number of which high protective capacity is demonstrated in the course of experiments on the nonhuman primates. The most advanced and prospective prototype is the vector recombinant vesicular stomatitis virus-based vaccine

Spectroscopic imaging of single atoms within a bulk solid

The ability to localize, identify and measure the electronic environment of individual atoms will provide fundamental insights into many issues in materials science, physics and nanotechnology. We demonstrate, using an aberration-corrected scanning transmission microscope, the spectroscopic imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that the spectroscopic information is spatially confined around the scattering atom. Furthermore we show how the depth of the atom within the crystal may be estimated.Comment: 4 pages and 3 figures. Accepted in Phys.Rev.Let

Environmental, biological and social factors contributing to new rises in COVID-19 morbidity in Russia

Morbidity surveys in certain regions during the COVID-19 pandemic have established that the infection spreads in a wave-like manner characterised with peaks and troughs in incidence. According to the analysis of COVID-19 epidemic development in Russia, surges in COVID-19 infections are mainly driven by seasonal factors, insufficient herd immunity, and emerging SARS-CoV-2 variants with increased transmissibility. The aim of the study was to analyse environmental, biological and social factors contributing to new rises in COVID-19 cases in Russia. The study covers the global epidemiological situation as of mid-2022 and the role of environmental, biological, and social factors in the spread of COVID-19 in the Russian Federation. The results suggest that new highly contagious SARS-CoV-2 variants and seasonality are the principal factors driving new rises in morbidity. The authors assume that the sixth and the seventh COVID-19 waves in Russia will be in line with the best case scenario, which predicts the spread of a SARS-CoV-2 variant with increased transmissibility and reduced virulence

Current State of the Development of Therapies for Emergency Prophylaxis and Treatment of Ebola Virus Disease

Nowadays vaccination of the population living in the endemic regions and widespread implementation of the potent therapies for the emergency prophylaxis and treatment into the clinical practice are regarded as the basic efficient and cost-effective measures for Ebola epidemic spread control. Objective of the review is to analyze current state of the development of aids for the immediate prophylaxis and treatment of Ebola fever. Focus area of the activities is the construction of drugs on the basis of virus-specific anti-bodies (including monoclonal), small interfering RNA, and anti-sense phosphordiamidate morpholine oligomers and interferons. The paper discusses the most significant achievements in this sphere

Conductivity of twin walls - surface junctions in ferroelastics: interplay of deformation potential, octahedral rotations, improper ferroelectricity and flexoelectric coupling

Electronic and structural phenomena at the twin domain wall-surface junctions in the ferroelastic materials are analyzed. Carriers accumulation caused by the strain-induced band structure changes originated via the deformation potential mechanism, structural order parameter gradient, rotostriction and flexoelectric coupling is explored. Approximate analytical results show that inhomogeneous elastic strains, which exist in the vicinity of the twin walls - surface junctions due to the rotostriction coupling, decrease the local band gap via the deformation potential and flexoelectric coupling mechanisms. This is the direct mechanism of the twin walls static conductivity in ferroelastics and, by extension, in multiferroics and ferroelectrics. On the other hand, flexoelectric and rotostriction coupling leads to the appearance of the improper polarization and electric fields proportional to the structural order parameter gradient in the vicinity of the twin walls - surface junctions. The "flexo-roto" fields leading to the carrier accumulation are considered as indirect mechanism of the twin walls conductivity. Comparison of the direct and indirect mechanisms illustrates complex range of phenomena directly responsible for domain walls static conductivity in materials with multiple order parameters.Comment: 35 pages, 11 figures, 3 table, 3 appendices Improved set of rotostriction coefficients are used in calculation