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

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

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

НАРУШЕНИЯ ФУНКЦИИ ВНЕШНЕГО ДЫХАНИЯ И ИХ ВЛИЯНИЕ НА КЛИНИЧЕСКИЙ ИСХОД У КАРДИОХИРУРГИЧЕСКИХ ПАЦИЕНТОВ

Goal: to investigate the frequency and specific features of respiratory disorders and their impact on the clinical course in the patients having coronary artery bypass graft operation. Materials. 454 patients expecting coronary artery bypass graft operation were enrolled into the prospective cohort study. External respiration function was evaluated prior to the surgery. Pathologic respiration patterns were assessed basing on forced expiratory volume per 1 second (FEV1 ) and forced vital lung capacity (FVLC). The pattern was evaluated as obstructive with the ratio of FEV1 /FVLC &lt; 0.70; and the restrictive pattern was the combination of FEV1 /FVLC≥ 0.70 and FVLC &lt; 80% of "must". Results. Obstructive and restrictive patterns were detected in 72 (15.8%) and 50 (11.0%) patients respectively. Out of 133 patients with compromised external respiration function chronic obstructive pulmonary disease was diagnosed only in 26 patients. Bronchial obstruction was related to the risk of auricular fibrillation, increase of duration of artificial pulmonary ventilation and prolonged hospital stay. Conclusion. It has been demonstrated that it is possible to improve clinical outcomes in the patients undergoing cardiac surgery through diagnostics of respiratory disorders, detection of risk groups and prevention of complications. Цель: изучить встречаемость и характеристики респираторных нарушений и их влияния на клиническое течение у пациентов при операциях коронарного шунтирования. Материал. В проспективное когортное исследование было включено 454 пациента, которым планировалось коронарное шунтирование. Оценку функции внешнего дыхания выполняли перед операцией. Патологический респираторный паттерн определяли на основании объема форсированного выдоха в 1-ю секунду (ОФВ1 ) и форсированной жизненной емкости легких (ФЖЕЛ). Критерием обструктивного паттерна являлось соотношение ОФВ1 /ФЖЕЛ &lt; 0,70, рестриктивного − комбинация ОФВ1 /ФЖЕЛ ≥ 0,70 и ФЖЕЛ &lt; 80% от «должного». Результаты. Обструктивный и рестриктивный паттерны были выявлены у 72 (15,8%) и 50 (11,0%) пациентов соответственно. Из 133 пациентов со снижением функции внешнего дыхания только 26 имели диагноз хронической обструктивной болезни легких. Бронхиальная обструкция была связана с риском развития фибрилляции предсердий, увеличением длительности искусственной вентиляции легких и срока госпитализации. Вывод. Продемонстрирована возможность улучшения клинических исходов у кардиохирургических пациентов путем диагностики респираторных нарушений, выявления групп риска и профилактики осложнений.

Results of a three-year follow-up and quality of life dynamics after pulmonary thromboendarterectomy

Aim. To evaluate the results of a three-year follow-up of patients with chronic thromboembolic pulmonary hypertension (CTEPH) and quality of life (QOL) dynamics after pulmonary thromboendarterectomy (PTE).Material and methods. The study included 125 patients with CTEPH aged 49,7± 11,9 years. Three-year follow-up included the recording of adverse cardiovascular events, surgeries, death during the period from the end of hospitalization and up to three years. The SF-36 questionnaire was used to assess physical and mental wellbeing before and three years after PTE. Multivariate linear regression was used to assess the factors affecting QOL in the long-term postoperative period.Results. During a three-year follow-up, adverse cardiovascular events was recorded in 1,9% of patients. One patient underwent coronary artery bypass graft surgery and one patient — cholecystectomy. Reoperative PTE was not carried out. The overall three-year survival rate was 90,4%.At baseline, patients with CTEPH had a low level of physical and mental well-being (&lt;40 points). Three years after the operation, these parameters significantly increased (p&lt;0,05), but did not exceed 50 points. Multivariate linear regression revealed an unfavorable effect of early postoperative residual pulmonary hypertension on the physical health three years after PTE. Other factors (age, sex, body weight, comorbidity, hospital acquired complications) did not affect the physical and emotional aspects of QOL.Conclusion. Three-year survival rate in patients with CTEPH after PTE was 90,4%. During the follow-up period, no recurrent thromboembolic events were recorded. Adverse cardiovascular events were recorded in 1,9% of patients. Three years after surgery, the physical and mental health increased in comparison with preoperative values, but did not exceed 50 points on the SF-36 questionnaire. The physical aspect of QOL after surgery is affected by early postoperative residual pulmonary hypertension

Carbon dioxide elimination pattern in assessing the risk of an unfavorable outcome in cardiac surgery

Aim. To assess the influence of resting partial pressure of end-tidal carbon dioxide (PetCO2) levels on the long-term results of cardiac surgery.Materials and methods. This prospective cohort study included 454 patients with coronary artery disease who underwent elective coronary artery bypass graft surgery. Before surgery, all patients underwent pulmonary function tests, including body plethysmography, lung diffusion capacity assessment and cardiopulmonary exercise testing with the determination of ventilatory and gas exchange parameters, including PetCO2 at rest. The endpoint was the 2-year survival rate after surgery.Results. Parameters characterizing the obstructive breathing pattern, the lung diffusion capacity, and resting PetCO2 levels had a significant predictor value in relation to long-term survival after cardiac surgery. Among the baseline clinical and functional characteristics, a significant influence on long-term results was shown by the EuroSCORE II (OR 1,69 (1,26-2,27), p=0,001). The highest sensitivity and specificity in relation to long-term mortality risk after coronary artery bypass grafting was shown by resting PetCO2 value equal to 31 mm Hg (area under the ROC curve 0,74 (0,64-0,86), p&lt;0,001).Conclusion. The resting PetCO2 level below 31 mm Hg in patients with coronary artery disease showed a significant effect on the increased long-term mortality risk after cardiac surgery, which is important for patients with exercise intolerance

DISORDERS OF EXTERNAL RESPIRATION AND THEIR IMPACT ON THE CLINICAL OUTCOME IN THE PATIENTS UNDERGOING CARDIAC SURGERY

Goal: to investigate the frequency and specific features of respiratory disorders and their impact on the clinical course in the patients having coronary artery bypass graft operation. Materials. 454 patients expecting coronary artery bypass graft operation were enrolled into the prospective cohort study. External respiration function was evaluated prior to the surgery. Pathologic respiration patterns were assessed basing on forced expiratory volume per 1 second (FEV1 ) and forced vital lung capacity (FVLC). The pattern was evaluated as obstructive with the ratio of FEV1 /FVLC &lt; 0.70; and the restrictive pattern was the combination of FEV1 /FVLC≥ 0.70 and FVLC &lt; 80% of "must". Results. Obstructive and restrictive patterns were detected in 72 (15.8%) and 50 (11.0%) patients respectively. Out of 133 patients with compromised external respiration function chronic obstructive pulmonary disease was diagnosed only in 26 patients. Bronchial obstruction was related to the risk of auricular fibrillation, increase of duration of artificial pulmonary ventilation and prolonged hospital stay. Conclusion. It has been demonstrated that it is possible to improve clinical outcomes in the patients undergoing cardiac surgery through diagnostics of respiratory disorders, detection of risk groups and prevention of complications