Superplastic behavior of ultrafine-grained Ti−6Al−4V ELI alloy produced by severe plastic deformation

This paper reports the results of investigation of mechanical behavior of the ultrafinegrained (UFG) Ti-6Al-4V alloy processed by equal-channel angular pressing (ECAP) and extrusion at temperatures in a range of 500−800°C. The UFG alloy reveals superplastic behavior at relatively low temperatures down to 600°C (elongation 240%). The features of microstructure change of the UFG alloy under superplastic straining conditions that contribute to additional strengthening of the alloy are shown

Microstructural features of failure surfaces and low-temperature mechanical properties of Ti-6Al-4V ELI ultra-fine grained alloy

Microstructural regularities of failure surfaces and low-temperature mechanical characteristics in quasistatic uniaxial tension and compression have been studied for ultra-fine grained structural states of Ti-6Al-4V ELI alloy processed by equal channel angular pressing. Values of the yield stress and uniform strain at 300, 77, and 4.2 K have been compared for structural states of the Ti-6Al-4V ELI alloy that differ in the average grain size and the morphology of α and β phases. Statistical distributions of dimple sizes on the failure surfaces have been studied for different structural states and temperatures.Исследованы особенности микроструктуры поверхностей излома и низкотемпературные механические свойства сверхмелкозернистого ELI-сплава Ti-6Al-4V, обработанного методом равноканального углового прессования, при квазистатическом одноосном растяжении и сжатии. Проведено сравнение значений предела текучести и однородной деформации, полученных при температурах 300, 77 и 4,2 К для разных структурных состояний ELI-сплава ТІ-6А1-4У с различным средним размером зерна и морфологией α- и β-фаз. Исследовано статистическое распределение размеров ямок на поверхностях излома при различных структурных состояниях и температурах

The course and outcomes of monochorial monoamniotic twin pregnancy

S.A. Kalashnikov1, A.G. Konoplyannikov1, K.Yu. Voskoboeva1, L.R. Semenova1, I.S. Kulakova2 1Pirogov Russian National Research Medical University, Moscow, Russian Federation 2Bashkir State Medical University, Ufa, Russian Federation Aim: to evaluate the course and outcomes of monochorial monoamniotic (MCMA) twin pregnancy. Patients and Methods: this prospective study included 34 patients (a mean age 31.8±4.3 years) with MCMA twins for assessing the course of pregnancy and perinatal outcomes. The authors evaluated such criteria as the timing of delivery and the prenatal management of MCMA-twin pregnancy, as well as the perinatal outcomes and mortality. Monitoring of the pregnant women with umbilical cord entanglement was started at 16 weeks of gestation and included ultrasound examination every two weeks and after 26–28 weeks of gestation — two or three times a week coupled with cardiotocography for fetal assessment. Results: the study demonstrated a high prevalence of cervical insufficiency which was found in 10 (29.4%) MCMA twin pregnancies at 18 to 28 weeks of gestation. The diagnosis of umbilical cord entanglement was established in 16 (47.1%) patients, twin-twin transfusion syndrome (TTTS) – in 2 (5.9%) patients, and twin anemia-polycythemia syndrome (TAPS) – in 1 (2.9%) patient. The reported antenatal losses were 6 of 68 (8.8%) of fetuses. There were 7 perinatal losses of 68 MCMA-twin pregnancies (10.3%). The antenatal and perinatal losses in MCMA twins were caused by the following specific complications: TTTS, cord entanglement and hypoxia due to the selective intrauterine growth restriction (sIUGR). A preterm operative delivery was used in 29 (85.2%) patients with MCMA twins. Five (14.7%) patients did not have complications and it was possible to prolong the pregnancy to 36 weeks. Caesarean sections were carried out almost for all the pregnant women (33 (97.1%)). Conclusion: the antenatal and perinatal losses in MCMA twins are caused by the specific complications. These findings prove that patients with complicated MCMA twin pregnancies need to have a careful monitoring in Level III perinatal centers. Planned caesarean sections are recommended for all MCMA twin pregnancies. If complications are detected, a preterm operative delivery closer to week 35 of gestation will enable to increase the fetal survival rates and thus to improve the perinatal outcomes. Uncomplicated MCMA twin pregnancies can be prolonged to week 36 for improving the condition of newborn babies at the time of delivery. Keywords: multifetal pregnancy, monochorial monoamniotic twin pregnancy, umbilical cord entanglement, neonatal outcome, twin-twin transfusion syndrome, selective intrauterine growth restriction, twin anemia-polycythemia syndrome. For citation: Kalashnikov S.A., Konoplyannikov A.G., Voskoboeva K.Yu. et al. The course and outcomes of monochorial monoamniotic twin pregnancy. Russian Journal of Woman and Child Health. 2023;6(1):6–12 (in Russ.). DOI: 10.32364/2618-8430-2023-6-1-6-12. </p

Epidemiology and Risk Factors of Osteosarcoma

© 2020, © 2020 Taylor & Francis Group, LLC. Osteosarcoma is a rare tumor diagnosed at any age; however younger age is a common risk factor. In addition, multiple factors are believed to contribute to higher rates of osteosarcoma, particularly race and gender. Although diagnosed worldwide, osteosarcoma is found to be more prevalent in Africa with high numbers of cases reported in Nigeria, Uganda, and Sudan. Additionally, higher rates are detected in African Americans, suggesting a genetic predisposition linked to race. This review focuses on identifying high risk factors of osteosarcoma with an emphasis on sarcoma epidemiology and risk factors in African countries

Cationic penetrating antioxidants switch off Mn cluster of photosystem II in situ

Mitochondria-targeted antioxidants (also known as ‘Skulachev Ions’ electrophoretically accumulated by mitochondria) exert anti-ageing and ROS-protecting effects well documented in animal and human cells. However, their effects on chloroplast in photosynthetic cells and corresponding mechanisms are scarcely known. For the first time, we describe a dramatic quenching effect of (10-(6-plastoquinonyl)decyl triphenylphosphonium (SkQ1) on chlorophyll fluorescence, apparently mediated by redox interaction of SkQ1 with Mn cluster in Photosystem II (PSII) of chlorophyte microalga Chlorella vulgaris and disabling the oxygen-evolving complex (OEC). Microalgal cells displayed a vigorous uptake of SkQ1 which internal concentration built up to a very high level. Using optical and EPR spectroscopy, as well as electron donors and in silico molecular simulation techniques, we found that SkQ1 molecule can interact with Mn atoms of the OEC in PSII. This stops water splitting giving rise to potent quencher(s), e.g. oxidized reaction centre of PSII. Other components of the photosynthetic apparatus proved to be mostly intact. This effect of the Skulachev ions might help to develop in vivo models of photosynthetic cells with impaired OEC function but essentially intact otherwise. The observed phenomenon suggests that SkQ1 can be applied to study stress-induced damages to OEC in photosynthetic organisms. © 2019, Springer Nature B.V