Study of the conditional flexibility effect of compressed chord on the overall stability of corrugated beams

In this paper, the calculation of cut corrugated beams loaded with uniformly distributed load in the plane of the wall, with a wall height of 333 and 500 mm (54 sizes), chord width from 160 to 400 mm and chord thickness from 6 to 30 mm for general stability in accordance with Building Codes (BC) 294.1325800.2017 is made. A geometric criterion has been defined which defines the boundaries of the load-carrying capacity of Russian corrugated beams between the flat bending form stability and the strength of the normal section under the action of the bending moment in the plane of the wall

Engineering methodology for calculation of corrugated beams for bending and torsion. Flat bend form stability

An engineering design procedure for calculating bending with torsion in corrugated beams, including finding the critical load of general stability, implemented in the commonly used MS Excel spreadsheet and verified in the LIRA-SAPR software package, has been proposed. The method makes it possible to take into account the beams section variability and corrugation parameters, to estimate the loading eccentricity effect, availability of supporting ribs and reinforcements of the compressed chord from the bending plane. Calculation results of particular design solutions for corrugated beams with definition of critical loads at transverse bending are given. Results of test calculation of a bent channel beam with calculation of stress-strain state parameters and its verification with the LIRA-SAP software package are given

Silver-doped Calcium Phosphate bone cements with antibacterial properties

Calcium phosphate bone cements (CPCs) with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag) through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt %) was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP) phase into the dicalcium phosphate dihydrate (DCPD) took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO₃)₃ was detected and Ag (met.) was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt %) the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content

Study of thermal effects of silicate-containing hydroxyapatites

The possibility of modifications of hydroxyapatite silicate ions, from the extracellular fluid prototype solution under near-physiological conditions has been studied. Formation of silicon-structured hydroxyapatite with different extent of substitution of phosphate groups in the silicate group has been established through chemical and X-ray diffraction analyses, FTIR spectroscopy and optical microscopy. The results obtained are in agreement and suggest the possibility of substitution of phosphate groups for silicate groups in the hydroxyapatite structure when introducing different sources of silica, tetraethoxysilane and sodium silicate, in the reaction mixture. Growth in the amount of silicon in Si-HA results in the increase in the thermal stability of the samples. The greatest mass loss occurs at temperatures in the range of 25-400 °С that is caused by the removal of the crystallization and adsorption water and volatile impurities. It is shown that the modified apatites are of imperfect structure and crystallize in a nanocrystalline state

Transcatheter mitral valve edge-to-edge repair in patients with severe mitral regurgitation: data from the MitraClip Russia Trial

Aim. To study the immediate and short-term outcomes of transcatheter mitral valve edge-to-edge repair with the MitraClip NT in patients with severe mitral regurgitation as part of the MitraClip Russia prospective single-center study.Material and methods. The study included 16 patients (men, 10; women, 6) with mean age of 70,1±2,1 years (mean Euroscore II, 6,90±5,56%; STS, 6,33±3,94%). Immediate technical success was defined as successful access, delivery, and removal of the device, and adequate placing the clip(s) to reduce the mitral regurgitation to grade 2 or below without the need for device- or procedure-related reintervention.Results. Immediate technical success was achieved in all patients. The average number of implanted clips per 1 patient was 1,7. In 1 patient (6,3%), a clip was attached to one mitral leaflet, which required an non-scheduled implantation of a second clip. In hospital mortality was 6,3%: a 92-year-old patient on the 3rd day after the operation had a sudden cardiac arrest followed by coma, hemispheric ischemic stroke and death on the 6th day. An autopsy revealed an iatrogenic atrial septal defect. Echocardiography performed on the 10th and 30th day after surgery showed a decrease in mitral regurgitation grade in 15 patients, while grade 3 residual mitral regurgitation did not reveal in any patient.Conclusion. Transcatheter mitral valve edge-to-edge repair with the MitraClip is a minimally invasive method for treating severe symptomatic mitral regurgitation (degenerative and functional). The results demonstrate high immediate efficacy and an acceptable safety profile in high surgical risk patients. Based on the analysis of death causes, the authors conclude that it is necessary to include initial pulmonary hypertension above 75 mm Hg as a relative contraindication to this procedure. The study limitations are the small sample size and short follow-up period

Исследование свойств композитного материала для СВЧ-применений на основе PTFE с различной концентрацией и размером частиц керамического наполнителя

Introduction. The technology of printed circuit boards (PCBs) is widely used in modern electronic instrumentation. PCBs for the microwave frequency range are made based on foil composite materials, in particular, polytetrafluoroethylene (PTFE). At the moment, there is no domestic production of such a class of materials. Information concerning foreign manufacturing technologies in this field and the influence of the filler on the characteristics of the composite material remains confidential. Therefore, research into the properties of composite materials for microwave applications with properties similar to foreign analogues seems relevant.Aim. Experimental determination of the dependence of the electrical and mechanical properties of a composite material based on polytetrafluoroethylene depending on the concentration and size of the titanium dioxide fraction.Materials and methods. Experimental determination of the dependence of the electrical and mechanical properties of a composite material based on PTFE depending on the concentration and size of the titanium dioxide fraction.Results. The results of an experimental study of the mechanical properties and microwave parameters of experimental samples of composite material based on PTFE are presented, namely: composite material with 10 % content of ceramic titanium dioxide powders (fraction size 10, 49 and 126 µm); composite material with 5, 10 and 15 % content of ceramic titanium dioxide powder (fraction size 49 µm for polytetrafluoroethylene and 126 µm for titanium dioxide).Conclusion. The results obtained demonstrate prospects for using compositions based on PTFE and titanium dioxide powder as a basis for microwave materials. A correlation was established between the percentage of the introduced ceramic filler and the microwave parameters of the material. The studies demonstrated a slight difference in the microwave properties of the manufactured composite material samples with a different ratio between the particle sizes of titanium dioxide and PTFE. However, a significant decrease in their mechanical properties was observed.Введение. Технология печатных плат является наиболее распространенной в современном электронном приборостроении. Платы для СВЧ-диапазона частот изготавливаются на основе фольгированных композитных материалов, в частности на основе политетрафторэтилена. В данный момент отечественное производство подобного класса материалов отсутствует. Информация, касающаяся зарубежной технологии изготовления композитного материала и влияния наполнителя на его характеристики, является закрытой. Поэтому актуальной задачей является поиск и исследование свойств композитных материалов для СВЧ-применения со свойствами, аналогичными зарубежным аналогам.Цель работы. Экспериментальное определение зависимости электрических и механических свойств композитного материала на основе политетрафторэтилена от концентрации и размера фракции диоксида титана.Материалы и методы. Механические свойства образцов композитного материала измерялись методом гидростатического взвешивания. Исследовались прочность и относительное удлинение при разрыве с помощью разрывной машины РМИ-250. СВЧ-параметры определялись с помощью метода Николсона–Росса–Вейра.Результаты. Представлены результаты экспериментального исследования механических свойств и СВЧпараметров экспериментальных образцов композитного материала на основе политетрафторэтилена: с 10 %-м содержанием керамических порошков диоксида титана (размер фракции 10, 49 и 126 мкм); с 5, 10 и 15 %-м содержанием керамического порошка диоксида титана (размер фракций у политетрафторэтилена – 49 мкм и у диоксида титана – 126 мкм).Заключение. Результаты демонстрируют перспективность применения композиций на основе PTFE и порошка диоксида титана в качестве основы для СВЧ-материалов. Установлена корреляция между процентным содержанием вводимого керамического наполнителя и СВЧ-параметрами материала. Исследования продемонстрировали незначительное отличие в СВЧ-свойствах изготовленных образцов композитного материала при различном соотношении между размерами частиц диоксида титана и PTFE. Однако при этом наблюдается значительное снижение их механических свойств

Influence of Structural Disorder on the Magnetic Order in FeRhCr Alloys

Magnetic phase transitions in alloys are highly influenced by the sample preparation techniques. In the present research, electronic and magnetic properties of Fe48Cr3Rh49 alloys with varying cooling rates were studied, both experimentally and theoretically. The degree of crystalline ordering was found to depend on the cooling rate employed after annealing the alloy. Modeling of alloy structures with different degrees of crystalline ordering was carried out via strategic selection of substitution positions and distances between chromium atoms. Theoretical calculations revealed significant changes in magnetic and electronic properties of the alloy with different substitutions. A comprehensive analysis of the calculated and experimental data established correlations between structural characteristics and parameters governing the magnetic phase transition. In this study, we also developed a method for evaluating the magnetic properties of the alloys obtained under different heat treatments. The proposed approach integrates atom substitution and heat treatment parameters, offering precise control over alloy manufacturing to effectively tune their essential magnetic properties

Characteristics of mukoviscisidosis in the southern regions of Russia

Introduction. Cystic fibrosis (CF) is a  hereditary disease with genetic heterogeneity and clinical polymorphism. Expanding the range of knowledge about the characteristics of the course of the disease in different regions is important to achieve the goal of improving the quality and life expectancy.Purpose. Comparative analysis of the features of the course of CF in the subjects of the Southern Federal District, Stavropol Territory.Methods. Data from the National Register of Patients of the RF MV 2016 were used. Results: there are clinical and genetic features between the regions of the Southern Federal District and the Stavropol Territory of the North Caucasus Federal District and in general with the Russian Federation. Analysis of the data showed differences in indicators: the proportion of patients aged ≥ 18 is the lowest in the Republic of Crimea (14.9%), in the Rostov region the lowest average age of patients (9.0 ± 6.3), and the lowest age of diagnosis 2.2 ± 3.1 years. Late terms of diagnosis were revealed in the Stavropol Territory (4.0 ± 8.0 years), but here there is one of the highest average age of CF patients (14.1 ± 11.5), the proportion of adult patients (23.3%) and the lowest allelic frequency of F508del, which is determined by the high number of patients with a “soft” genotype. There is a high proportion of patients with an undetermined genotype. A low proportion of two identified genetic variants of the CFTR gene is registered in patients of the Republic of Crimea. A low frequency of Burkholderia cepacia complex and Achromobacter spp was revealed, and a high infection with non-tuberculous mycobacteria was revealed in the Rostov region. FEV1 in children and adults was lower in Rostov Region and Stavropol Territory. In all regions, there is a discrepancy between the seeding of flora and azithromycin therapy and the severity of the genotype with the use of pancreatic enzymes.Conclusions. Analysis of the data of the registry, which allows substantiating the need to study the regional characteristics of the course of CF in order to differentiate the planning of measures to improve the quality of medical care for patients with CF

Риск развития кровотечений, требующих гемотрансфузии, после транскатетерной имплантации аортального клапана у пациентов с сопутствующей ишемической болезнью сердца

Introduction. Perioperative bleeding is a potentially life-threatening complication of surgical intervention. The incidence of perioperative bleeding during transcatheter aortic valve implantation (TAVI) reaches 6%. An increased risk of perioperative bleeding is noted in patients requiring constant antiplatelet therapy, which includes patients with concomitant coronary artery disease (CAD).Aim. The study of risk factors of bleeding, which require blood transfusion in candidates for TAVI with concomitant CAD.Materials and methods. A retrospective study. The patients with concomitant CAD who underwent TAVI from 2016 to 2021 with hemodynamically significant coronary artery stenosis (n = 270) were included in this study. The incidence of early postoperative bleeding requiring blood transfusions was analyzed. Risk factors of bleeding development were evaluated.Results. The average age of the patients was 77.7 ± 7.2 years, the number of male and female patients was comparable (45.9 and 54.1%).The majority of patients were diagnosed with chronic heart failure (90.4%), more than half of the patients suffered from pulmonary hypertension (51.9%). The incidence of bleeding that required blood transfusion was 9.3%. The risk factors of the bleeding were dual antiplatelet therapy, baseline anemia (hemoglobin less than 120 g/l), history of stroke, chronic renal failure and critical aortic stenosis. The risk factors were included in the predictive model.Conclusion. Bleeding requiring blood transfusion in patients with severe aortic stenosis and CAD after TAVR occurs in 9.3%. It can be partially predicted using the predictive model. The using of the predictive model may be useful in determining the predominant risk of thrombotic or bleeding events after surgery.Введение. Периоперационное кровотечение является потенциально жизнеугрожающим осложнением хирургического вмешательства.Встречаемость периоперационных кровотечений при транскатетерной имплантации аортального клапана (ТИАК) достигает 6%. Повышенный риск развития периоперационных кровотечений отмечается у пациентов, требующих постоянной антиагрегантной терапии, к которой относятся пациенты с сопутствующей ишемической болезнью сердца (ИБС).Цель. Изучить факторы риска развития кровотечений, требующих гемотрансфузии, у пациентов, госпитализированных для проведения ТИАК, при сопутствующей ИБС.Материалы и методы. Проведено ретроспективное исследование. Рассмотрены пациенты, перенесшие ТИАК в период с 2016 по 2021 г., при сопутствующей ИБС с гемодинамически значимым поражением коронарных артерий (n = 270). Изучена частота развития ранних послеоперационных кровотечений, требующих проведения гемотрансфузий. Выполнена оценка факторов риска развития кровотечений.Результаты. Средний возраст исследуемых составил 77,7 ± 7,2 года, количество пациентов мужского и женского пола было сопоставимо – 45,9 и 54,1%. У большинства пациентов была диагностирована хроническая сердечная недостаточность (90,4%), у половины – легочная гипертензия (51,9%). Частота развития кровотечений, потребовавших проведения гемотрансфузии, составила 9,3%. Повышение риска развития кровотечений, требующих гемотрансфузии, ассоциировано с наличием следующих факторов риска: двойная антиагрегантная терапия, исходная анемия (гемоглобин менее 120 г/л), инсульт в анамнезе, хроническая почечная недостаточность и критический аортальный стеноз. Полученные факторы риска включены в прогностическую модель.Заключение. У 9,3% пациентов с тяжелым аортальным стенозом и сопутствующей ИБС при проведении ТИАК развиваются кровотечения, требующие гемотрансфузии. Развитие кровотечения можно частично спрогнозировать с помощью предложенной в исследовании модели. Ее использование в клинической практике может быть полезным для определения превалирующего риска тромботических или геморрагических событий в послеоперационном периоде