Geosituational modelling of coastal marine systems

The article summarizes years of experience of geosituational modelling of coastal marine systems in the Baltic Sea region and adjacent territories. Kaliningrad universities and academic institutions have done extensive research on the diversity of approaches and models of the regional geosituations as well as on identifying the most promising coastal marine areas. Some of the models presented in the present paper are qualitative, while others are empirical and statistical ones. However, the majority of the models can be referred to as forms of graphic and image mapping. The significance of the regional models lies in their specificity, a more detailed character (compared to the generalist ones) and the possibility of using them to back up managerial decisions in critical and emergency situations in order to minimize the negative effects of natural (storms, floods, earthquakes, etc.) and anthropogenic emergency situations. The authors developed a matrix classification attributable to a particular class of models for the situations leading to uncertain outcomes. The authors suggest using numerical methods combined with the empirical and statistical models for the assessment of the impact of industrial fishing on marine environment, minimizing the consequences of storms, floods and others factors. Special attention is paid to the modelling of climate change and geo-ecological consequences, as well as to atlas mapping and landscape planning. As a result of the geosituational analysis the authors got new insights into the solar-terrestrial links, marine-terrestrial ecosystems, global and regional processes related to climate change, oceanization, the vulnerability of natural systems under the increasing pressure of anthropogenic activities, and continuously increasing risks presented by industrial agriculture and other types of land use

Microbial landscape in hospital patients with new coronavirus disease (COVID-19), antibiotic resistance comparison vs. Pre-covid stage: a prospective study

Background. The new coronavirus infection has manifested untypically compared to other acute respiratory agents, posing a major challenge to researchers worldwide. Despite low incidence of bacterial complications, microbial coinfection plays an important role in the onset and development of severe COVID-19 to hamper diagnosis, treatment and prognosis.Objectives. A study of microbial landscape in secondary complications of COVID-19 and prevailing microbial-agent antibiotic resistance dynamics in COVID-19 vs. patients with pre-COVID community-acquired pneumonia.Methods. We analysed 1,113 bacterial sputum cultures in COVID-19 patients from 21 hospital of Krasnodar Krai. The study sample comprised 524 strains isolated from COVID-19 patients in bacteriological assays. The comparison sample included 643 positive sputum strains isolated from community-acquired pneumonia patients developing disease in outcome of acute respiratory infection in 2015–2018. The microbial aetiology landscape and strain antibiotic resistance have been compared in COVID-19 vs. patients with community-acquired pneumonia.Results. Gram-negative bacteria predominated in COVID-19 cultures (58%), followed by Gram-positive bacteria (15%) and fungi (27%). Acinetobacter baumannii (35%) and Klebsiella pneumoniae (33%) were about equally represented in Gram-negative flora, Pseudomonas aeruginosa (19%) and other microorganisms were half as common. Streptococcus pneumonia and Staphylococcus aureus accounted for 48 and 15% Gram-positive strains, respectively. Sputum-isolated fungi were mainly identifi ed as Candida albicans (89%). The Streptoccocus pneumoniae detection rate dropped to 7% in 2020 relative of other flora, which is 10 times less vs. pre-COVID rates, whilst the fungal rate increased dramatically. Antibiotic resistance increased in most isolated microbial strains.Conclusion. A Gram-negative-dominated aetiology of lower respiratory tract lesions, as well as higher risk of fungal and other opportunistic coinfections should be taken into account in patient treatment for a complicated coronavirus infection. A higher antibiotic resistance is induced by active indication-ignorant use of antibiotics, including pre-hospital treatment. A suitable treatment regimen in COVID-19 should avoid undue antibiotic prescriptions in every patient

Electronic band structure of a Tl/Sn atomic sandwich on Si(111)

A two-dimensional compound made of one monolayer of Tl and one monolayer of Sn on Si(111) has been found to have a sandwichlike structure in which the Sn layer (having the milk-stool arrangement) resides on the bulklike terminated Si(111) surface and the Tl layer (having the honeycomb-chained-trimer arrangement) is located above the Sn layer. The electronic band structure of the compound contains two spin-split surface-state bands, of which one is nonmetallic and the other is metallic. Near the Fermi level the metallic band is split with the momentum splitting Δk∥=0.037 Å−1 and energy splitting ΔEF=167 meV. The steep dispersion of the band when crossing the Fermi level corresponds to an electron velocity of ≈8.5×105 m/s, which is comparable to the value reported for graphene. The 2D Fermi contours have almost circular shape with spin texture typical for hexagonal surfaces

Single layer nickel disilicide on surface and as embedded layer

Single monolayers of various materials (e.g. graphene, silicene, bismuthene, plumbene, etc) have recently become fascinating and promising objects in modern condensed-matter physics and nanotechnology. However, growing a monolayer of non-layered material is still challenging. In the present report, it will be shown that single monolayer NiSi2 can be fabricated at Si(111) surface stabilized by either Tl, Pb or In monolayers. Nickel atoms were found to intercalate the stabilizing metal layers upon deposition and to reside in the interstitial sites inside the first silicon bilayer of bulk-like-terminated Si(111)1×1 surface. The interstitial positions almost coincide with the bulk NiSi2 atomic positions thus forming NiSi2 single layer. Atomic and electronic structure of formed systems is described in detail by means of a set of experimental techniques, including low-energy electron diffraction, scanning tunneling microscopy, angle-resolved photoemission spectroscopy and also first-principles density-functional-theory calculations. Quality of formed single monolayer NiSi2 was additionally confirmed by in situ four-probe transport measurements that show that single monolayer NiSi2 preserves a metallic-type conductivity down to 2.0 K. Moreover it was found that delta-type structure with atomic sheet of NiSi2 silicide embedded into a crystalline Si matrix can be fabricated using room-temperature overgrowth of a Si film onto the Tl stabilized NiSi2 surface layer. Confinement of the NiSi2 layer to a single atomic plane has been directly confirmed by high-resolution transmission electron microscopy

Synthesis of two-dimensional TlxBi1-x compounds and Archimedean encoding of their atomic structure

Crystalline atomic layers on solid surfaces are composed of a single building block, unit cell, that is copied and stacked together to form the entire two-dimensional crystal structure. However, it appears that this is not an unique possibility. We report here on synthesis and characterization of the one-atomic-layer-thick TlxBi1−x compounds which display quite a different arrangement. It represents a quasi-periodic tiling structures that are built by a set of tiling elements as building blocks. Though the layer is lacking strict periodicity, it shows up as an ideally-packed tiling of basic elements without any skips or halting. The two-dimensional TlxBi1−x compounds were formed by depositing Bi onto the Tl-covered Si(111) surface where Bi atoms substitute appropriate amount of Tl atoms. Atomic structure of each tiling element as well as arrangement of TlxBi1−x compounds were established in a detail. Electronic properties and spin texture of the selected compounds having periodic structures were characterized. The shown example demonstrates possibility for the formation of the exotic low-dimensional materials via unusual growth mechanisms

Searching for stochastic gravitational waves using data from the two colocated LIGO Hanford detectors

Searches for a stochastic gravitational-wave background (SGWB) using terrestrial detectors typically involve cross-correlating data from pairs of detectors. The sensitivity of such cross-correlation analyses depends, among other things, on the separation between the two detectors: the smaller the separation, the better the sensitivity. Hence, a colocated detector pair is more sensitive to a gravitational-wave background than a noncolocated detector pair. However, colocated detectors are also expected to suffer from correlated noise from instrumental and environmental effects that could contaminate the measurement of the background. Hence, methods to identify and mitigate the effects of correlated noise are necessary to achieve the potential increase in sensitivity of colocated detectors. Here we report on the first SGWB analysis using the two LIGO Hanford detectors and address the complications arising from correlated environmental noise. We apply correlated noise identification and mitigation techniques to data taken by the two LIGO Hanford detectors, H1 and H2, during LIGO’s fifth science run. At low frequencies, 40–460 Hz, we are unable to sufficiently mitigate the correlated noise to a level where we may confidently measure or bound the stochastic gravitational-wave signal. However, at high frequencies, 460–1000 Hz, these techniques are sufficient to set a 95% confidence level upper limit on the gravitational-wave energy density of Ω(f) < 7.7 × 10[superscript -4](f/900  Hz)[superscript 3], which improves on the previous upper limit by a factor of ~180. In doing so, we demonstrate techniques that will be useful for future searches using advanced detectors, where correlated noise (e.g., from global magnetic fields) may affect even widely separated detectors.National Science Foundation (U.S.)United States. National Aeronautics and Space AdministrationCarnegie TrustDavid & Lucile Packard FoundationAlfred P. Sloan Foundatio

Atomic arrangement and electron band structure of Si(1 1 1)-ß-√3×√3-Bi reconstruction modified by alkali-metal adsorption: Ab initio study

Using ab initio calculations, atomic structure and electronic properties of Si(1 1 1)$sqrt{3} imes sqrt{3}$ -Bi surface modified by adsorption of 1/3 monolayer of alkali metals, Li, Na, K, Rb and Cs, have been explored. Upon adsorption of all metals, a similar atomic structure develops at the surface where twisted chained Bi trimers are arranged into a honeycomb network and alkali metal atoms occupy the ${{T}_{4}}$ sites in the center of each honeycomb unit. Among other structural characteristics, the greatest variation concerns the relative heights at which alkali metals reside with respect to Bi-trimer layer. Except for Li, the other metals reside higher than Bi layer and their heights increase with atomic number. All adsorbed surface structures display similar electron band structures of which the most essential feature is metallic surface-state band with a giant spin splitting. This electronic property allows one to consider the Si(1 1 1)$sqrt{3} imes sqrt{3}$ -Bi surfaces modified by alkali metal adsorption as a set of material systems showing promise for spintronic applications

Atomic arrangement and electron band structure of Si(1 1 1)-ß-√3×√3-Bi reconstruction modified by alkali-metal adsorption: Ab initio study

Using ab initio calculations, atomic structure and electronic properties of Si(1 1 1)$sqrt{3} imes sqrt{3}$ -Bi surface modified by adsorption of 1/3 monolayer of alkali metals, Li, Na, K, Rb and Cs, have been explored. Upon adsorption of all metals, a similar atomic structure develops at the surface where twisted chained Bi trimers are arranged into a honeycomb network and alkali metal atoms occupy the ${{T}_{4}}$ sites in the center of each honeycomb unit. Among other structural characteristics, the greatest variation concerns the relative heights at which alkali metals reside with respect to Bi-trimer layer. Except for Li, the other metals reside higher than Bi layer and their heights increase with atomic number. All adsorbed surface structures display similar electron band structures of which the most essential feature is metallic surface-state band with a giant spin splitting. This electronic property allows one to consider the Si(1 1 1)$sqrt{3} imes sqrt{3}$ -Bi surfaces modified by alkali metal adsorption as a set of material systems showing promise for spintronic applications