Effect of the Sc/Zr ratio on the corrosion resistance of Al-Mg cast alloys

The results of investigations of the corrosion resistance of Al-Mg-Sc-Zr alloys with varying Mg content and different Sc/Zr ratios are presented. The objects of investigations were the Al-Mg-Sc-Zr alloys with total Sc + Zr content of 0.32 wt%. The concentration of Sc and Zr in the alloys varied with the increments of 0.02 wt%. The alloys were produced by induction casting. The effect of annealing temperature on the microhardness and electrical resistivity of the Al-Mg-Sc-Zr alloys was investigated. Corrosion tests were carried out in a medium simulating intergranular corrosion in aluminum alloys. Electrochemical studies and mass loss tests were performed. An increase in the Sc concentration and a decrease in the Zr one were shown to result in an increase in the corrosion rate. The primary Al3(ScxZr1-x) particles were found to have the main effect on the corrosion resistance of Al-Mg-Sc-Zr alloys. The dependence of the corrosion current on the annealing temperature of the Al-Mg-Sc-Zr alloy was found to have a non-monotonous character (with a maximum).Comment: 29 pages, 2 tables, 11 figures, 58 reference

Tungstate Based Ceramics Obtained By Spark Plasma Sintering Method – Possible Material for Consolidation of Radioactive Wastes’ Components

The Spark Plasma Sintering method was used to produce high-density ceramics from tungstates SrWO4 and NaNd(WO4)2 with scheelite structure. These compounds are proposed as possible matrices for the consolidation of radwaste components. Powder samples were obtained by coprecipitation method and studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). After sintering, the samples retained their phase identity (scheelite structure). The total duration of sintering was ∼ 13-15 min, the relative density was reached ∼ 92, 99%. Keywords: Tungstates, RW, Spark Plasma Sintering, high density, microstructur

Investigation of the effect of the grain sizes on the dynamic strength of the fine-grained alumina ceramics obtained by Spark Plasma Sintering

The results of dynamic strength tests of the alumina ceramics with various grain sizes are presented. The ceramics were obtained by Spark Plasma Sintering (SPS) of industrial submicron and fine Al2O3 powders. The heating up was performed with the rate of 10 oC/min; the grain sizes in the ceramics was controlled by varying the SPS temperature and the heating rate as well as by varying the initial sizes of the Al2O3 particles in the powders. The ceramics had a high density (over 98%) and a uniform fine-grained microstructure (the mean grain sizes varied from 0.8 to 13.4 mkm). The dynamic compressing tests were carried out by modified Kolsky method with using split Hopkinson pressure bar. The tests were performed at room temperature using a 20-mm PG-20 gas gun with the strain rate of ~10^3 s-1. The dependence of the dynamic ultimate strength of alumina on the grain size was found for the first time to have a non-monotonous character (with a maximum). The maximum value of the dynamic ultimate compression strength (SY = 1060 MPa) was provided at the mean grain size of ~2.9-3 mkm. The reduction of SY for alumina in the range of submicron grain sizes was shown to originate from the reduction of the relative density of the ceramics sintered at lower SPS temperatures.Comment: 16 pages, 1 table, 6 figures, 28 reference

Cytokine profile in community-acquired pneumonia in children

Community-acquired pneumonia (CAP) is one of the most common acute infectious diseases. To date, the incidence of CAP among children was decreased significantly worldwide, mainly due to increasing use of effective preventive measures. Nevertheless, CAP remains a common cause of childhood morbidity and mortality. Pneumonia may develop at any age, but most often it occurs in young children, who are more likely to have a more severe course of pneumonia. Currently, early diagnosis and prognosis of the disease severity in children is an urgent issue. It was found that, in most cases, a panel of conventional biomarkers, including the number of leukocytes, procalcitonin, CRP is not sufficient for the diagnosis of pediatric CAP. There is a demand for new biological markers which, along with clinical evaluation, may significantly improve diagnostics and management of CAP in children, thus reducing the risk of adverse outcomes associated with this disease. Such markers could be found among the cytokines, which are active participants in the CAP pathogenesis. The aim of this study was to determine the level of several cytokines in blood serum of children with CAP and to assess changes in the cytokine profile depending on the patient’s age and severity of the disease. The study included 117 children aged 1 to 18 years with a diagnosis of CAP confirmed by X-ray examination. The comparison group included 28 healthy children who did not have CAP or other signs of acute respiratory viral infection at the time of examination, being free of any chronic pathology requiring outpatient observation. A number of cytokines were determined quantitatively in blood serum, i.e., IL-1β, IFNγ, IL-2, IL-4, IL-6, IL-10, TNFα, IFNλ2 (IL-28A), IFNλ3 (IL-28B), IL-8, MCP-1, IL-17AF, GM-CSF using test systems based on the “sandwich” method of solid-phase ELISA using peroxidase labeling. As a result, it was found that the content of IL-6, IL-17AF, IL-1β, IFNγ, MCP-1, IFNλ2 (IL-28A), IFNλ3 (IL-28B), GM-CSF was significantly higher in the group of children with severe community-acquired pneumonia. The levels of certain cytokines, e.g., IL-6, IFNλ2 (IL-28A), IFNλ3 (IL-28B), GM-CSF varied depending on the age of patients, thus, probably, reflecting the degree of immune system activation in the children of different age groups

Effect of severe plastic deformation realized by rotary swaging on the mechanical properties and corrosion resistance of near-a-titanium alloy Ti-2.5Al-2.6Zr

The research aims to analyze the impact that severe plastic deformation arising during Rotary Swaging has on mechanical properties and corrosion resistance of a near-a-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M). The nature of corrosion decay in fine-grained alloys caused by hot salt corrosion is known to vary from pit corrosion to intercrystalline corrosion at the onset of recrystallization processes. Resistance to hot salt corrosion in a fine-grained titanium alloy Ti-2.5Al-2.6Zr is shown to depend on the structural-phase state of grain boundaries that varies during their migration as a result of covering corrosive doping elements (aluminum, zirconium) distributed in the crystal lattice of a titanium alloy.Comment: 37 pages, 15 figures, 39 reference

Corrosion fatigue crack initiation in ultrafine-grained near-a titanium alloy PT7M prepared by Rotary Swaging

The study focuses on corrosion fatigue processes taking place in an ultrafine-grained (UFG) near-a-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M) used in nuclear engineering. UFG structure formed with Rotary Swaging is found to increase resistance to corrosion fatigue. Parameters of the Basquin's equation are defined and the slope of the fatigue curve Sa-lg(N) is shown to depend (nonmonotonic dependence) on the UFG alloy annealing temperature. This effect can be explained with the patterns of microstructural evolution in a UFG alloy PT7M during annealing: (1) reduced density of lattice dislocations, (2) precipitation and dissolution of zirconium nanoparticles, (3) release of a''-phase particles causing internal stress fields along interphase (a-a'')-boundaries, and (4) intensive grain growth at elevated annealing temperatures. It is shown that the fatigue crack closure effect manifested as changing internal stress fields determined using XRD method may be observed in UFG titanium alloys.Comment: 54 pages, 2 tables, 19 figures, 64 referance

Effect of annealing on the corrosion-fatigue strength and hot salt corrosion resistance of fine-grained titanium near-{\alpha} alloy Ti-5Al-2V obtained by Rotary Swaging

The corrosion-fatigue strength in 3% aqueous NaCl solution and the resistance against hot salt corrosion (HSC) of the fine-grained near-a alloy Ti-5Al-2V (Russian analog of Grade 9 titanium alloy with increased aluminum content) has been studied. The properties of the Ti-5Al-2V alloy in the coarse-grained state, in the fine-grained after cold Rotary Swaging (RS), in partly recrystallized state, and in fully recrystallized one have been investigated. The mechanical properties of the alloy were characterized using compression tests and microhardness measurements. The effects of RS and of the annealing temperature and time on the character of corrosion destruction of the surface and on the composition of the products of the HSC were studied. RS was shown to result in an increase in the depth of the intergranular corrosion defects while the recrystallization annealing promotes the increasing of the corrosion resistance of the Ti-5Al-2V titanium alloy. The parameters of the Basquin equation for the corrosion-fatigue curves for the near-a Ti-5Al-2V alloy in the coarse-grained state, in the severely strained one, and after recrystallization annealing were determined for the first time. An effect of nonmonotonous dependencies of the slopes of the corrosion-fatigue curves for the strained near-a Ti-5Al-2V alloy on the recrystallization annealing temperature has been observed.Comment: 46 pages, 1 table, 19 figures, 64 reference

Investigation of the microstructure of the fine-grained YPO4_4:Gd ceramics with xenotime structure after Xe irradiation

The paper reports on the preparation of xenotime-structured ceramics by the Spark Plasma Sintering (SPS) method. Phosphates Y$_{0.95}$Gd$_{0.05}$PO$_4$ (YPO$_4$:Gd) were obtained by the sol-gel method. The synthesized nanopowders are collected in large agglomerates 10-50 mkm in size. Ceramics has a fine-grained microstructure and a high relative density (98.67%). The total time of the SPS process was approximately 18 min. High-density sintered ceramics YPO$_4$:Gd with a xenotime structure were irradiated with Xe$^{+26}$ ions (E = 167 MeV) to fluences of $1\times10^{12}$-$3\times 10^{13}$ cm$^{-2}$. Complete amorphization at maximum fluence was not achieved. As the fluence increases, an insignificant increase in the depth of the amorphous layer is observed. According to the results of grazing incidence XRD (GIXRD), with an increase in fluence from $1\times10^{12}$-$3\times 10^{13}$ cm$^{-2}$, an increase in the volume fraction of the amorphous structure from 20 to 70% is observed. The intensity of XRD peak 200 YPO$_4$:Gd after recovery annealing (700$^\circ$C, 18 h) reached a value of ~80% of the initial intensity I0.Comment: 16 pages, 10 figure

СОВРЕМЕННЫЙ КОМПЛЕКСНЫЙ ПОДХОД К ХИРУРГИЧЕСКОМУ ЛЕЧЕНИЮ ЛЕГОЧНОЙ АРТЕРИАЛЬНОЙ ГИПЕРТЕНЗИИ, АССОЦИИРОВАННОЙ С ВРОЖДЕННЫМИ ПОРОКАМИ СЕРДЦА

Pulmonary arterial hypertension (PAH) is a common complication of congenital heart disease (CHD) occurring in left-to-right shunt. The progression of PAH is associated with delayed diagnosis and surgical treatment of congenital heart disease. An uncorrected left-to-right shunt in patients with CHD lead to histological changes of pulmonary vessels and reversal of the shunt may arise, with the development of Eisenmenger’s syndrome. Until recently, the surgical treatment of patients thought to be impossible, and few attempts to perform radical correction were associated with high in-hospital mortality. The main causes of the in-hospital mortality included acute right ventricular failure, pulmonary hypertension crisis and cardiac arrhythmias. The long-term survival of these patients was low, directly associated with the progression of residual pulmonary hypertension. The novel technique of a fenestrated double patch has been widely used abroad, but very rarely in Russia. Moreover, there is no standardized algorithm for selecting surgical approach in these patients as well as common approaches to the preoperative management and anesthetic protocol. The efficiency of specific therapies for residual pulmonary hypertension is poorly understood. Lack of research and experience in applying the fenestrated double patch in Russia for a population of children and adolescents who require combined treatment (surgical and specific therapy for pulmonary arterial hypertension) proved our research to be pivotal.Легочная артериальная гипертензия (ЛАГ) является частым осложнением врожденных пороков сердца (ВПС) с лево-правым сбросом. Развитие этого осложнения связано с несвоевременной диагностикой и хирургической коррекцией врожденной патологии сердца. Длительное существование врожденного порока сердца с лево-правым шунтом приводит к стадийному гистологическому изменению сосудов легких и формированию комплекса Эйзенменгера, появлению «перекрестного» сброса крови. До недавнего времени хирургическое лечение таких пациентов считалось невозможным, а немногочисленные попытки радикальной коррекции сопровождались высокой госпитальной летальностью. Основными причинами госпитальной летальности являлись: острая правожелудочковая недостаточность, кризы легочной гипертензии и нарушения ритма сердца. Отдаленная выживаемость таких пациентов была невысокой и обусловливалась прогрессированием резидуальной легочной гипертензии. Оригинальная методика двойной заплаты с фенестрой применялась за рубежом, но не нашла широкого распространения в России. Кроме того, до сих пор не существует стандартизированного алгоритма выбора хирургической тактики у таких пациентов, отсутствуют единые подходы к предоперационной подготовке, не разработан общепринятый протокол анестезиологического пособия, до конца не изучена эффективность специфической терапии резидуальной легочной гипертензии. Отсутствие публикаций и опыта применения методики двойной заплаты с фенестрой в России при наличии популяции детей и подростков, нуждающихся в комбинированном, хирургическом и специфическом лечении легочной артериальной гипертензии, постулировало наше исследование

ЭТАПНОЕ ХИРУРГИЧЕСКОЕ ЛЕЧЕНИЕ ПАЦИЕНТА С КОАРКТАЦИЕЙ АОРТЫ В СОЧЕТАНИИ С АБЕРРАНТНОЙ ПРАВОЙ ПОДКЛЮЧИЧНОЙ АРТЕРИЕЙ

We present the results of a staged surgical treatment of a subject with a rare congenital disorder – aortic coarctation in combination with an aberrant right subclavian artery. The choice of an implantation of the aberrant right subclavianartery into the right common carotid artery as the first stage of surgical reconstruction contributed to the prevention of the spinal complications connected with multiple clamping of two subclavian arteries in one-staged surgical treatment of aortic coarctation. It is concluded that the chosen method of the surgical correction is not standard and is characterized by a high level of technical complexity and allows to radically correct the complex congenital heart disease.Представлены результаты этапного хирургического лечения пациента с редкой врожденной патологией – коарктация аорты в сочетании с аберрантной правой подключичной артерией. Выбор в качестве первого этапа хирургической реконструкции имплантации аберрантной правой подключичной артерии в общую сонную артерию справа способствовал профилактике спинальных осложнений, связанных с симультивным пережатием двух подключичных артерий при одноэтапном хирургическом лечении коарктации аорты. Сделано заключение о том, что выбранный метод хирургической коррекции является нестандартным и характеризуется высоким техническим уровнем сложности, позволяет радикально корригировать сложный врожденный порок сердца