Higher-order topological superconductivity from repulsive interactions in kagome and honeycomb systems

We discuss a pairing mechanism in interacting two-dimensional multipartite lattices that intrinsically leads to a second order topological superconducting state with a spatially modulated gap. When the chemical potential is close to Dirac points, oppositely moving electrons on the Fermi surface undergo an interference phenomenon in which the Berry phase converts a repulsive electron-electron interaction into an effective attraction. The topology of the superconducting phase manifests as gapped edge modes in the quasiparticle spectrum and Majorana Kramers pairs at the corners. We present symmetry arguments which constrain the possible form of the electron-electron interactions in these systems and classify the possible superconducting phases which result. Exact diagonalization of the Bogoliubov-de Gennes Hamiltonian confirms the existence of gapped edge states and Majorana corner states, which strongly depend on the spatial structure of the gap. Possible applications to vanadium-based superconducting kagome metals AV$_3$Sb$_3$ (A=K,Rb,Cs) are discussed.

Lagrangian eddy tracking reveals the Eratosthenes anticyclonic attractor in the eastern Levantine Basin

Statistics of anticyclonic eddy activity and eddy trajectories in the Levantine Basin over the 2000–2018 period are analyzed using the DYNED-Atlas database, which links automated mesoscale eddy detection by the Angular Momentum Eddy Detection and Tracking Algorithm (AMEDA) algorithm to in situ oceanographic observations. This easternmost region of the Mediterranean Sea, delimited by the Levantine coast and Cyprus, has a complex eddying activity, which has not yet been fully characterized. In this paper, we use Lagrangian tracking to investigate the eddy fluxes and interactions between different subregions in this area. The anticyclonic structure above the Eratosthenes Seamount is identified as hosting an anticyclone attractor, constituted by a succession of long-lived anticyclones. It has a larger radius and is more persistent (staying in the same position for up to 4 years with successive merging events) than other eddies in this region. Quantification of anticyclone flux shows that anticyclones that drift towards the Eratosthenes Seamount are mainly formed along the Israeli coast or in a neighboring area west of the seamount. The southeastern Levantine area is isolated, with no anticyclone transfers to or from the western part of the basin, defining the effective attraction basin for the Eratosthenes anticyclone attractor. Co-localized in situ profiles inside eddies provide quantitative information on their subsurface physical anomaly signature, whose intensity can vary greatly with respect to the dynamical surface signature intensity. Despite interannual variability, the so-called Eratosthenes anticyclone attractor stores a larger amount of heat and salt than neighboring anticyclones, in a deeper subsurface anomaly that usually extends down to 500 m. This suggests that this attractor could concentrate heat and salt from this subbasin, which will impact the properties of intermediate water masses created there.

Topological changes in telechelic micelles: flowers versus stars

Micellization and morphology of spherical telechelic micelles formed by tri-block copolymers with short solvophobic end blocks at low concentrations is discussed within scaling arguments and Single Chain Mean Field Theory (SCMFT). In ultra-dilute regime, individual telechelic polymer chains can exist in solution in two distinct states: open linear chain conformation with two free ends and closed loop conformation, when two ends are connected by the effective attraction between two solvophobic ends. At concentrations below gelation point, closed loops tend to form micelles comprised mostly of loops in flower-like micelles, while linear polymers in open conformations tend to form star-shaped aggregates with one hydrophobic dangling end. Resulting two kinds of micelles have remarkably different topology and dimensions, while the transition between them can be driven by the entropy, namely conformation changes between domination of the looped and linear conformations. As a result, the transition between two types of micelles lies in a narrow interaction parameters range. Thus, these topological micelles are very sensitive to the changes in external environment and they can serve as a very sensitive stimuli-responsive smart materials.

Local structure of DNA toroids reveals curvature-dependent intermolecular forces

In viruses and cells, DNA is closely packed and tightly curved thanks to polyvalent cations inducing an effective attraction between its negatively charged filaments. Our understanding of this effective attraction remains very incomplete, partly because experimental data is limited to bulk measurements on large samples of mostly uncurved DNA helices. Here we use cryo electron microscopy to shed light on the interaction between highly curved helices. We find that the spacing between DNA helices in spermine-induced DNA toroidal condensates depends on their location within the torus, consistent with a mathematical model based on the competition between electrostatic interactions and the bending rigidity of DNA. We use our model to infer the characteristics of the interaction potential, and find that its equilibrium spacing strongly depends on the curvature of the filaments. In addition, the interaction is much softer than previously reported in bulk samples using different salt conditions. Beyond viruses and cells, our characterization of the interactions governing DNA-based dense structures could help develop robust designs in DNA nanotechnologies.

Financial instruments of the enterprises. Monograph

Over the past decades, developed countries have seen an increasing trend in the importance of the debt finance market in financing investment. With the globalization of global financial markets, this trend has also been evident in emerging markets. However, for domestic companies, the domestic stock market has not yet become a reliable source of capital mobilization, and most enterprises rely on their own funds or attract financial resources in the form of various forms of bank lending. At the same time, the possibilities of effective attraction of investment resources directly in the domestic banking market are limited, as real borrowing rates for many enterprises of the non-oil sector of the economy are significantly higher than the profitability of their business. Different financial instruments of enterprises have different yield orders. If some of them are minimally profitable and perform the function of saving capital, others multiply it by times. The choice of investment strategy determines which securities will fall into the portfolio, in what proportion they will be presented. В течение последних десятилетий в развитых странах наблюдается тенденция роста значимости рынка долговых финансовых инструментов в финансировании инвестиций. В условиях глобализации мировых финансовых рынков данная тенденция проявилась и на формирующихся рынках. Однако для отечественных компаний внутренний фондовый рынок пока не стал надежным источником мобилизации капитала, и большинство предприятий полагается на собственные средства или привлекает финансовые ресурсы в виде различных форм банковского кредитования.

Electrostatically assisted macroion association

A model system of highly asymmetric polyelectrolyte with directional short-range attractive interactions was studied by canonical Monte Carlo computer simulations. Comparison of MC data with previously published theoretical results shows good agreement. For moderate values of binding energies, which matches those of molecular docking, a dynamic equilibrium between free and dimerized macroions is observed. Fraction of dimerized macroions depends on macroion concentration, binding energy magnitude, and on the valency of small counterions. Divalent counterions induce an effective attraction between macroions and enhance dimerization. This effect is most notable at low to moderate macroion concentrations.

Sociological monitoring of vocational guidance preferences of future applicants as an element of management of the formation of the shipbuilding educational infrastructure

В работе рассматриваются профориентационные предпочтения старшеклассников Санкт-Петербурга и Ленинградской области с целью создания более эффективного управления формированием инфраструктуры вузов РФ, готовящих кадры для судостроительной промышленности. Социологический мониторинг осуществлялся силами социологической лаборатории, межвузовского центра по образованию в области истории и философии науки и техники, с привлечением бакалавров и магистров кафедры философии и социологии морского технического университета. Для большей эффективности исследования при обработке социологических данных использовались методы многомерного статистического анализа и k-групповых средних. В ходе работы было подтверждено, что для более эффективного привлечения абитуриентов вузам судостроительного профиля необходимо сохранять, поддерживать и развивать многообразие направлений подготовки, включая и гуманитарные, с упором на собственно судостроительные специальности. Для сохранения контингента обучающихся и привлечения новых необходимо также развивать систему дополнительного образования. The article considers the vocational guidance preferences of senior students in St. Petersburg and Leningrad region in order to create a more effective management of infrastructure formation of universities of the Russian Federation training personnel for the shipbuilding industry. The sociological monitoring was carried out by the sociological laboratory and the interuniversity centre for education in the field of history and phylosophy of science and technology with the involvement of bachelors and masters students of the department of phylosophy and sociology at St. Petersburg State Marine Technical University. To make the research more effective the methods of multivariable statistical analysis were used for processing of sociological data and k-group averages. In the course of research, it was confirmed that for more effective attraction of applicants to the university of shipbuilding profile it is necessary to preserve, maintain and develop a variety of training directions including humanities with an emphasis on the actual shipbuilding specialties. To maintain the number of trainees and attract new ones it is also necessary to develop a system of the additional education.