Nature of bonding and electronic structure in MgB2, a boron intercalation superconductor

Chemical bonding and electronic structure of MgB2, a boron-based newly discovered superconductor, is studied using self-consistent band structure techniques. Analysis of the transformation of the band structure for the hypothetical series of graphite - primitive graphite - primitive graphite-like boron - intercalated boron, shows that the band structure of MgB2 is graphite-like, with pi-bands falling deeper than in ordinary graphite. These bands possess a typically delocalized and metallic, as opposed to covalent, character. The in-plane sigma-bands retain their 2D covalent character, but exhibit a metallic hole-type conductivity. The coexistence of 2D covalent in-plane and 3D metallic-type interlayer conducting bands is a peculiar feature of MgB2. We analyze the 2D and 3D features of the band structure of MgB2 and related compounds, and their contributions to conductivity.Comment: 4 pages in revtex, 3 figures in 4 separate EPS file

Indication of Superconductivity at 35 K in Graphite-Sulfur Composites

We report magnetization measurements performed on graphite--sulfur composites which demonstrate a clear superconducting behavior below the critical temperature T$_{c0}$ = 35 K. The Meissner-Ochsenfeld effect, screening supercurrents, and magnetization hysteresis loops characteristic of type-II superconductors were measured. The results indicate that the superconductivity occurs in a small sample fraction, possibly related to the sample surface.Comment: published versio

Using ion beam analysis and computer tomography for study the control rods of reactor protection system

The work is to develop methods for studying the Control Rods of Reactor Protection System (CR RPS). The isotopic and elemental content powder of boron carbide, the elemental content of alloy of shell of control rods, density and uniformity of the distribution of the absorber in the rod was studied. For investigate isotopic and elemental content was used PIGE and PIXE. A method has been developed and the isotopic composition of B₄C has been experimentally studied on the basis of the registration of γ-radiation excited in the proton reactions of the nuclei of isotopes ¹⁰B, ¹¹B, ¹²C. A method for analyzing the mass content in samples of boron carbide and 42HNM alloy was created for the range of elements from Al to W. The possibilities of research of integrity of a cover of control rods and density and uniformity of distribution in it of an absorber by a method of a computer tomography are studied.Розроблено методи дослідження стрижнів системи захисту реактора (СЗР). Досліджено ізотопний та елементний склади порошку карбіду бору, елементний склад сплаву оболонки керуючих стрижнів, щільність і рівномірність розподілу поглинача в стрижні. Для дослідження ізотопного та елементного вмісту використовували МІЯР та ХРВ. Розроблено метод та експериментально досліджено ізотопний склад B₄C на основі реєстрації γ-випромінювання, що збуджується в протонних реакціях ядер ізотопів ¹⁰B, ¹¹B, ¹²C. Створено метод аналізу масового вмісту в зразках карбіду бору та сплаву 42ХНМ для діапазону елементів від Al до W. Розглянуто можливості дослідження цілісності та щільності оболонки керуючих стрижнів та рівномірності розподілу в ній поглинача методом комп’ютерної томографії

Clinical Study Perioperative Avulsion of a Left Internal Mammary Artery Graft in a Patient with Syphilis

Avulsion of a graft after coronary artery bypass grafting surgery is a rare but very serious complication which leads to massive bleeding and possible life-threatening cardiac tamponade. In this paper we report a very rare case of a left internal mammary artery graft avulsion on the day of surgery in a patient with syphilis

Long-term outcomes of reconstructive procedures on coronary arteries for diffuse coronary atherosclerosis without endarterectomy

Objective. This study evaluated the long-term clinical and angiographic outcomes of coronary artery reconstruction for a diffusely diseased coronary artery without endarterectomy.Material and Methods. We retrospectively reviewed 660 consecutive patients (mostly men (89.5%), mean age 68.3 ± 7.4 years) who underwent coronary artery bypass grafting in combination with coronary artery reconstruction between 2003 and 2016. 558 operated on patients (84.5%) were followed up for a mean of 94.3 ± 31.2 months.Results. Long-term survival was 83.2% (95% confidence interval: 74.5–89.3); freedom from cardiac death was 97.4 ± 1.2%; and freedom from major adverse cardiac and cerebrovascular events was 64.7 ± 4.1%. Independent predictors of long-term mortality were age at surgery (< 70 years, p < 0.001), chronic obstructive pulmonary disease (p = 0.007), peripheral arterial disease (p = 0.002), diabetes mellitus (p = 0.013) and chronic kidney disease (p = 0.034). The arterial graft patency rate was 95.2%, and the vein graft patency rate was 75.4%.Conclusion. Coronary artery bypass grafting in conjunction with coronary artery reconstruction without endarterectomy confers satisfactory long-term clinical outcomes with high probability of freedom from cardiac death and angina pectoris, good rates of angiographic patency of arterial grafts and favorable rates of vein graft patency

Selection of optimal endarterectomy technique in the left anterior descending artery for diffuse coronary atherosclerosis

Aim. To determine the optimal method for performing coronary artery endarterectomy (СE) based on immediate and long-term outcomes of coronary artery bypass grafting (CABG) in combination with open or closed CE in the left anterior descending artery (LAD).Material and methods. This retrospective study included 103 patients who underwent CABG in combination with closed CE and 204 after open CE in the LAD during the period from 2003 to 2016. In both groups, the patient age was comparable (65 years [56; 69] vs 67 years [58; 72] (p=0,263)). There were more men (88,3% vs 81,4% (p=0,421). The mean follow-up period was 94 months [38; 180]. Long-term outcomes were assessed in 86,4% (n=89) and 83,8% (n=171) of patients from the closed and open CE groups, respectively (p=0,141). Angiographic data were studied in 75,3% and 67,3% of patients, respectively (p=0,441).Results. In the closed and open CE groups, in-hospital mortality was 4,8% and 1,5% (p=0,0012), incidence of perioperative myocardial infarction — 11,6% vs 2,5%, (p<0,001), survival rate after 7,8 years — 81,3±5,1% and 84,4±3,2% (p=0,342), respectively. The patency of arterial shunts was significantly higher in the open CE group — 93,1% vs 80,6% (p=0,004). At the same time, the patency of venous shunts in the long-term period between the groups was comparable — 70,1% vs 73,7% (p=0,314).Conclusion. Open CE in combination with CABG provides better immediate outcomes compared to closed CE. Long-term survival and freedom from angina between the groups were comparable. In the long-term period, the patency of internal thoracic artery after open CE is better than after the closed technique. Open CE is a safe and effective method to achieve complete myocardial revascularization in patients with severe diffuse LAD atherosclerosis

ТЕРМОДИФФУЗИЯ В МЕТАЛЛАХ ПРИ ИМПУЛЬСНОМ НЕРАЗРУШАЮЩЕМ ЛАЗЕРНОМ ВОЗДЕЙСТВИИ

The changes in the elemental composition of two-layer target when affected by the radiation of a G0R-100M ruby laser operating in the free oscillation regime were studied. The radiation flux density was varied from 104 до 5-105 Вт/см-2. The elemental composition of the target before and after irradiation was investigated by means of an ElvaX X-ray spectrometer. The investigations showed that affecting a thin layer (several ^m) nickel layer covering a titanium sample, the concentration of titanium in the surface stratum considerably (by a factor of 1.5 and more) increased. It is important that the titanium concentration with increasing the flux density of the operating irradiation increased monotonically in the mentioned space. The analogous phenomena on the laser irradiation effect on the back side of the thin cupper plate covered with nickel were observed. This testifies to the active metal diffusion from the target into the surface stratum in the zone of pulse heating of the investigated samples by means of laser radiation. Исследовано изменение элементного состава двухслойных мишеней под действием излучения рубинового лазера ГОР-100М в режиме свободной генерации с плотностью потока излучения от 104 до 5-105 Вт/см-2. Элементный состав мишени до и после облучения исследовался с использованием рентгеновского спектрометра ElvaX. Показано, что при воздействии на тонкий (несколько мкм) слой никеля, нанесенный на подложку из титана, после облучения концентрация титана в приповерхностном слое значительно (в 1,5 раза и более) увеличивалась. Существенно, что концентрация титана монотонно увеличивалась с ростом плотности потока воздействующего лазерного излучения в указанном интервале. Аналогичные явления наблюдались и при воздействии лазерного излучения на тыльную сторону тонкой медной пластины с покрытием из никеля. Это свидетельствует об активной диффузии металла из подложки в покрытие в зоне импульсного нагревания исследованных образцов лазерным излучением

МУЛЬТИСПИРАЛЬНАЯ КОМПЬЮТЕРНАЯ ТОМОГРАФИЯ В ДИАГНОСТИКЕ ПАЦИЕНТОВ С ПАТОЛОГИЕЙ ВОСХОДЯЩЕГО ОТДЕЛА АОРТЫ В ДО- И ПОСЛЕОПЕРАЦИОННОМ ПЕРИОДЕ

This review presents current information on the diagnosis of patients with pathology of the ascending aorta in the pre and postoperative period using multispiral computed tomography. The authors paid attention to the importance of valuation of the valvular apparatus elements, the geometry of the root of the aorta (effective coaptation height, Henle triangles, aortic regurgitation area, etc.), the features of which are necessary for the surgeon to solve technical issues of the forthcoming operation. A comparison of the diagnostic value of multispiral computed tomography and transthoracic echocardiography with respect to the visualization of valvular structures is shown. The role of multispiral computed tomography in the planning of transcatheter aortic valve replacement and the determination of results after intervention is described. With the help of multispiral computed tomography, assessing the state of the ascending aorta, the aortic root and aortic valve elements, the surgeon has an opportunity to choose the optimal variant of the valve-preserving operation and to evaluate postoperative results in the preoperative period.В обзоре представлена актуальная информация о диагностике пациентов с патологией восходящего отдела аорты в до- и послеоперационном периоде с помощью мультиспиральной компьютерной томографии. Авторы уделили внимание важности оценки элементов клапанного аппарата, геометрии корня аорты (эффективная высота коаптации, треугольники Генле, площадь аортальной регургитации и др.), особенности которой необходимы хирургу для решения технических вопросов предстоящей операции. Показано сравнение диагностической ценности мультиспиральной компьютерной томографии и трансторакальной эхокардиографии в отношении визуализации клапанных структур. Описана роль мультиспиральной компьютерной томографии в планировании транскатетерного протезирования аортального клапана и определении результатов после интервенции. С помощью мультиспиральной компьютерной томографии, оценивая состояние восходящего отдела аорты, элементов корня аорты и аортального клапана, хирург в предоперационном периоде получает возможность выбора оптимального варианта клапаносохраняющей операции и оценки послеоперационных результатов

СЛУЧАЙ УСПЕШНОГО ХИРУРГИЧЕСКОГО ЛЕЧЕНИЯ КОНСТРИКТИВНОГО ПЕРИКАРДИТА ПОСЛЕ ТРАНСПЛАНТАЦИИ СЕРДЦА

Heart transplantation became a widespread and effective method of terminal heart failure treatment. Simultane- ously with accumulation of experience and knowledge, physicians face complications both specific and nonspe- cific for heart transplant patients – such as constrictive pericarditis. There are only several cases of constrictive pericarditis after heart transplantation described, and mortality among such patients is quite high. We present one case of constrictive pericaditis, that was diagnosed 11 months after the heart transplantation was performed. The subtotal pericardectomy was performed. Postoperatively, significant improvement in hemodynamic parame- ters – the decrease in CVP and LA pressure, the increase in end-diastollic LV size – indicated the effectiveness of procedure. Трансплантация сердца (ТС) стала общепринятым методом лечения терминальной стадии седечной не- достаточности во всем мире. Но одновременно с накоплением опыта врачи сталкиваются и с различными осложнениями, в том числе и традиционными для кардиохирургии – такими как констриктивный пери- кардит. В литературе описаны единичные наблюдения, при этом летальность в этой группе больных вы- сока. В нашем сообщении описан случай констриктивного перикардита, развившегося через 11 месяцев после трансплантации сердца. Больному была выполнена операция – субтотальная перикардэктомия. Значительное улучшение гемодинамических параметров (снижение ЦВД, увеличение КДР ЛЖ, сниже- ние АД ЛА) свидетельствовали о хорошем результате вмешательства.