Microwave Properties of Ba(0.6)K(0.4)BiO(3) Crystals

We report on field-induced variations of the microwave surface resistance at 9.6 GHz of Ba(0.6)K(0.4)BiO(3) crystals. Energy losses have been investigated as a function of the static magnetic field in the range of temperatures 4.2 K - Tc. By analyzing the experimental results in the framework of the Coffey and Clem model we determine the temperature dependence of the first-penetration field, upper critical field and depinning frequency. The results show that the pinning energy of this bismuthate superconductor is weaker than those of cuprates.Comment: 6 pages, 8 embedded figure

Non-cubic layered structure of Ba(1-x)K(x)BiO3 superconductor

Bismuthate superconductor Ba(1-x)K(x)BiO3 (x=0.27-0.49, Tc=25-32K) grown by an electrolysis technique was studied by electron diffraction and high-resolution electron microscopy. The crystalline structure thereof has been found to be non-cubic, of the layered nature, and non-centrosymmetric, with the lattice parameters a ~ ap, c ~ 2ap (ap is a simple cubic perovskite cell parameter) containing an ordered arrangement of barium and potassium. The evidence for the layered nature of the bismuthate superconductor removes the principal crystallographic contradiction between bismuthate and cuprate high-Tc superconductors.Comment: 4 pages, 3 figures, to be published in Physical Review B as a Rapid Communicatio

Observation of a Transition from BCS to HTSC-like Superconductivity in Ba_{1-x}K_xBiO_3 Single Crystals

A study of temperature dependences of the upper critical field B_{c2}(T) and surface impedance Z(T)=R(T)+iX(T) in Ba_{1-x}K_xBiO_3 single crystals that have transition temperatures in the range 6 x>0.4) reveals a transition from BCS to unusual type of superconductivity. B_{c2}(T) curves corresponding to the crystals that have T_c>20 K have positive curvature (like in some HTSC), and those of the crystals with T_c<15 K fall on the usual Werthamer-Helfand-Hohenberg curve. R(T) and X(T) dependences of the crystals with T_c~30 K and T_c~11 K are respectively linear (like in HTSC) and exponential (BCS) in the temperature range T << T_c. The experimental results are discussed in connection with the extended saddle point model by Abrikosov.Comment: 5 pages, 5 figure

Colloidal analogs of molecular chain stoppers

Self-assembly of nanoparticles in polymer-like chains bears a strong similarity to polymerization reactions, in which monomer units are brought together by directional noncovalent interactions. Based on this similarity, the molecular concepts of polymer chemistry can be applied to achieve controllable nanoparticle assembly. On the other hand, the ability to visualize nanoparticle assemblies and to exploit characterization tools used in nanoscience offers a unique way to study polymerization reactions. Here we explore this twofold strategy for an exemplary system including the self-assembly of bifunctional metal nanorods in the presence of monofunctional nanoparticles (chain stoppers). The approach provided insight into the polymerization kinetics, side reactions, the distribution of species in the system, and the design rules for the synthesis of molecular chain stoppers

Myocardial revascularization in patients with acute coronary syndrome in the context of COVID-19 pandemic: a single-center prospective cohort study

Aim. To assess the outcomes of myocardial revascularization (MR) and identify risk factors for early postoperative complications in patients with coronary artery disease (CAD) with acute coronary syndrome (ACS) in the context of coronavirus disease 2019 (COVID-19) pandemic.Material and methods. The study included 769 patients aged 67,0±4,4 years with CAD with ACS in the period from April to October 2020. In an expedited manner, percutaneous transluminal coronary angioplasty (n=699) and on pump coronary artery bypass grafting (CABG) (n=70) were performed. All patients underwent a COVID-19 rapid tests. After MR, the following outcomes were recorded: adverse cardiovascular events and other complications; various surgical interventions; bilateral COVID-19 pneumonia; death. The follow-up period lasted 30 days.Results. During the hospitalization, COVID-19 was detected in 5,3% of patients (n=41). Among them, bilateral multisegmental pneumonia developed in 48,8%. Among infected patients, COVID-19-related mortality in the early postoperative period was 9,8%. The all-cause mortality rate was 0,7%. On pump CABG significantly increases the risk of developing COVID-19 pneumonia (odds ratio (OR), 23,2; 95% confidence interval (CI) 14,2-35,4; p&lt;0,001). After MR, COVID-19 pneumonia was associated with respiratory (OR, 7,6; 95% CI, 4,3-11,5; p=0,001) and heart failure (OR, 4,2; 95% CI, 2,9-8,6; p=0,001), atrial fibrillation (OR, 8,3; 95% CI, 4,1-13,9; p=0,001), as well as with all-cause mortality (OR, 10,3; 95% CI, 5,2-16,7; p=0,005). Recurrent transmural myocardial infarction in patients with CAD was associated with heart failure after MR (OR, 7,1; 95% CI, 2,4-12,6; p=0,012).Conclusion. Conducting on pump CABG in patients with CAD with ACS is the leading trigger for developing COVID-19 pneumonia, which, during hospitalization after MR, was associated not only with respiratory complications, but also with impaired heart function, which significantly increases the death risk in this category of patients

Modern methods for identification and quantification of cardiac glycosides

Scientific relevance. Cardiac glycosides have been used in medicine for over two centuries. Current studies suggest that biologically active substances from this group can be used to treat not only heart conditions but also viral infections, cancers, and other diseases. Therefore, quality control methods for cardiac glycosides are becoming increasingly relevant.Aim. Based on a review of Russian and international quality standards, as well as up-to-date scientific data, this study aimed to identify promising methods for the identification and quantification of cardiac glycosides in herbal drugs and herbal medicinal products, as well as to evaluate the possibility of substituting physicochemical methods for biological methods.Discussion. The methods that are currently used to standardise cardiac glycosides are either not selective or require laboratory animals (biological test systems). According to a study of pharmacopoeial methods for the identification of cardiac glycosides in herbal drugs and herbal medicinal products, chemical identification tests and thin-layer chromatography continue to be relevant. Quantitative testing of herbal drugs and extracts uses biological and non-selective (spectrophotometry) methods, whereas chromatography is described only in general and individual monographs for herbal drug preparations containing individual cardiac glycosides and medicinal products containing these preparations. Upon analysing quality standards and scientific publications, the authors identified potentially promising methods for the quantification of cardiac glycosides in herbal drugs, herbal drug preparations, and herbal medicinal products, namely chromatographic methods.Conclusions. Reverse-phase high-performance liquid cjromatography (HPLC) with spectrophotometric detection is the most suitable method for pharmacopoeial analysis. The development of an HPLC-based analytical procedure to determine the cardiac glycoside content will provide an opportunity to advance from biological or non-selective methods to more ethical and selective up-to-date techniques

Electronic Collective Modes and Superconductivity in Layered Conductors

A distinctive feature of layered conductors is the presence of low-energy electronic collective modes of the conduction electrons. This affects the dynamic screening properties of the Coulomb interaction in a layered material. We study the consequences of the existence of these collective modes for superconductivity. General equations for the superconducting order parameter are derived within the strong-coupling phonon-plasmon scheme that account for the screened Coulomb interaction. Specifically, we calculate the superconducting critical temperature Tc taking into account the full temperature, frequency and wave-vector dependence of the dielectric function. We show that low-energy plasmons may contribute constructively to superconductivity. Three classes of layered superconductors are discussed within our model: metal-intercalated halide nitrides, layered organic materials and high-Tc oxides. In particular, we demonstrate that the plasmon contribution (electronic mechanism) is dominant in the first class of layered materials. The theory shows that the description of so-called ``quasi-two-dimensional superconductors'' cannot be reduced to a purely 2D model, as commonly assumed. While the transport properties are strongly anisotropic, it remains essential to take into account the screened interlayer Coulomb interaction to describe the superconducting state of layered materials.Comment: Final version (minor changes) 14 pages, 6 figure

Clinical and functional features and quality of life in depressive disorders in patients undergoing pulmonary thromboendarterectomy

Aim. To conduct a comparative analysis of clinical and functional parameters and quality of life (QoL) in patients with chronic thromboembolic pulmonary hypertension (CTEPH), depending on the presence of a depressive disorder in long-term postoperative period.Material and methods. The study included 182 patients with CTEPH in the long term after surgery. Depending on the Patient Health Questionnaire 9 ( PHQ-9) data, all patients were divided into 2 groups: the 1st group — patients without depressive syndrome in the long-term postoperative period, the 2nd — patients with depressive syndrome. A comparative assessment of the initial clinical and functional characteristics, as well as QoL was carried out using the SF-36 questionnaire in both groups of patients. In patients who had a coronavirus disease 2019 (COVID-19), a comparative assessment using the Post-COVID-19 Functional Status (PCFS) scale was carried out.Results. Clinically relevant depressive syndrome in patients with CTEPH in the long term after surgery was registered in 25,3% of cases. In the 2nd group of patients, prior myocardial infarction (p=0,02), concomitant chronic cerebrovascular disease (p=0,01), as well as moderate and severe post-COVID-19 functional limitations according to the PCFS scale (p=0,004) were significantly more often recorded compared with the 1st group. In the 2nd group of patients, the level of QoL in almost all parameters was significantly lower in comparison with the 1st group (p&lt;0,05). Decreased QoL (score &lt;40) in the 2nd group concerned numerous parameters, including the physical and mental health components. In the 1st group of patients, reduced QoL was observed only in some physical parameters.Conclusion. The group of patients with CTEPH with depressive syndrome in the long-term postoperative period was characterized by a higher incidence of concomitant chronic cerebrovascular disease and a history of myocardial infarction compared with patients without depressive disorders. In the group of patients with depressive disorders, moderate and severe post-COVID-19 functional limitations according to the PCFS scale were more often observed. Depressive disorders in patients with CTEPH in the long-term postoperative period were accompanied by significantly reduced QoL parameters. Patients experienced the greatest difficulties both during normal daily activities and in professional activities

Распространенность новой коронавирусной инфекции COVID-19 у пациентов, перенесших легочную эндартерэктомию (по данным одноцентрового регистра)

Aim. To assess the prevalence and clinical and functional features of a new coronavirus infection (COVID-19) in patients who underwent pulmonary thromboendarterectomy (PTE) using data from a single-center registry. Methods. This study included 127 patients with chronic thromboembolic pulmonary hypertension who underwent PTE from January 2016 to March 2020 and were included in a follow-up group. The follow-up after surgery was 6 or more months. The prevalence of COVID-19 and clinical and functional properties of the cardiorespiratory system were assessed in the study group. Results. The average follow-up period after PTE in the study group was 2.5 ± 0.9 years. 14 (11%) deaths not associated with COVID-19 were reported during this period. 5 cases of COVID-19 were detected among the remaining 113 patients. In one case, the infection was asymptomatic, while other patients had the typical clinical symptoms and developed bilateral polysegmental pneumonia. No patients required mechanical ventilation or died of COVID-19. All patients who underwent PTE were compliant with anticoagulation therapy and PAH-specific therapy for residual pulmonary hypertension. No adjustment of PAH-specific and anticoagulation therapy was required during COVID-19. Conclusion. The prevalence of COVID-19 in patients who underwent PTE was 4.4%, no deaths were recorded. Outpatient follow-up and timely informing of patients undergoing PTE allow keeping the COVID-19 morbidity and mortality in the studied group at the general population level. Evaluation of the impact of chronic anticoagulants and PAH-specific therapy on the outcome of COVID-19 deserves further research.Целью исследования явилась оценка распространенности и клинико-функциональных особенностей новой коронавирусной инфекции (COVID-19) у пациентов, перенесших легочную эндартерэктомию (ЛЭЭ), на примере одноцентрового регистра. Материал и методы. В исследование включены пациенты (n = 127) с хронической тромбоэмболической легочной гипертензией, перенесшие в период с января 2016 по март 2020 г. ЛЭЭ и состоявшие в группе диспансерного наблюдения. Срок наблюдения после хирургического вмешательства составил ≥ 6 мес. Проведена оценка распространенности COVID-19 и клинико-функциональных особенностей кардиореспираторной системы у обследованных пациентов. Результаты. Средний срок наблюдения после ЛЭЭ составил 2,5 ± 0,9 года. Летальность, не ассоциированная с COVID-19, за этот период составила 14 (11 %) случаев, среди остальных пациентов (n = 113) выявлено 5 случаев COVID-19. В 1 случае течение инфекционного заболевания было бессимптомным, в остальных – с типичной клинической симптоматикой и развитием двусторонней полисегментарной пневмонии. Случаев, при которых потребовалась искусственная вентиляция легких, и летальных исходов не зарегистрировано. Все пациенты, перенесшие ЛЭЭ, соблюдали рекомендации по приему антикоагулянтов и при наличии резидуальной легочной гипертензии получали специфическую терапию. Во время лечения COVID-19 коррекция терапии не требовалась. Заключение. Заболеваемость COVID-19 в группе пациентов, перенесших ЛЭЭ, составила 4,4 %, летальных исходов не зарегистрировано. При диспансерном наблюдении и своевременном информировании пациентов, перенесших ЛЭЭ, уровень заболеваемости и смертности от COVID-19 может не превышать таковой в общей популяции. Требуются дальнейшее изучение и оценка влияния на клиническую картину и исход COVID-19 при постоянном приеме антикоагулянтов и специфических препаратов для лечения легочной артериальной гипертензии