Fatigue variation of surface properties of silumin subjected to electron-beam treatment

The analysis of structure-phase states modification of silumin subjected to electron beam treatment with the following fatigue loading up to the failure is carried out by methods of transmission electron diffraction microscopy. The tribology and strength properties of silumin surface after electron beam treatment and fatigue tests are studied and hardness decrease, wear coefficient and friction coefficient increase with the growth of cycles number are revealed. The possible reasons of the tribology and strength properties of silumin surface layers decrease are discussed

Fractography of Fatigue Fracture Surface in Silumin Subjected to Electron-Beam Processing

The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 [mu]m located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 [mu]m in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life

Degradation of structure and properties of rail surface layer at long-term operation

The microstructure evolution and properties variation of the surface layer of rail steel after passed 500 and 1000 million tons of gross weight (MTGW) have been investigated. The wear rate increases to 3 and 3.4 times after passed 500 and 1000 MTGW, respectively. The corresponding friction coefficient decreases by 1.4 and 1.1 times. The cementite plates were destroyed and formed the cementite particles of around 10-50 nm in size after passed 500 MTGW. The early stage dynamical recrystallization was observed after passed 1000 MTGW. The mechanisms for these have been suggested. The large number of bend extinction contours is revealed in the surface layer. The internal stress field is evaluated

Fractography of Fatigue Fracture Surface in Silumin Subjected to Electron-Beam Processing

The surface modification of the eutectic silumin with high-intensity pulsed electron beam has been carried out. Multi-cycle fatigue tests were performed and irradiation mode made possible the increase in the silumin fatigue life more than 3.5 times was determined. Studies of the structure of the surface irradiation and surface fatigue fracture of silumin in the initial (unirradiated) state and after modification with intense pulsed electron beam were carried out by methods of scanning electron microscopy. It has been shown, that in mode of partial melting of the irradiation surface the modification process of silicon plates is accompanied by the formation of numerous large micropores along the boundary plate/matrix and microcracks located in the silicon plates. A multi-modal structure (grain size within 30-50 μm with silicon particles up to 10 [mu]m located on the boundaries) is formed in stable melting mode, as well as subgrain structure in the form of crystallization cells from 100 to 250 [mu]m in size). Formation of a multi-modal, multi-phase, submicro- and nanosize structure assisting to a significant increase in the critical length of the crack, the safety coefficient and decrease in step of cracks for loading cycle was the main cause for the increase in silumin fatigue life

Tailoring the electron and hole Land\'e factors in lead halide perovskite nanocrystals by quantum confinement and halide exchange

The tunability of the optical properties of lead halide perovskite nanocrystals makes them highly appealing for applications. Both, halide anion exchange and quantum confinement pave the way for tailoring their band gap energy. For spintronics applications, the Land\'e g-factors of electrons and hole are of great importance. By means of the empirical tight-binding and $\textbf{k}\cdot\textbf{p}$ methods, we calculate them for nanocrystals of the class of all-inorganic lead halide perovskites CsPb$X_3$ ($X = \text{I},\,\text{Br},\,\text{Cl}$). The hole g-factor as function of the band gap follows the universal dependence found for bulk perovskites, while for the electrons a considerable modification is predicted. Based on the $\textbf{k}\cdot\textbf{p}$ analysis we conclude that this difference arises from the interaction of the bottom conduction band with the spin-orbit split electron states. The model predictions are confirmed by experimental data for the electron and hole g-factors in CsPbI3 nanocrystals placed in a glass matrix, measured by time-resolved Faraday ellipticity in a magnetic field at cryogenic temperatures

MIP/Aquaporin 0 Represents a Direct Transcriptional Target of PITX3 in the Developing Lens

The PITX3 bicoid-type homeodomain transcription factor plays an important role in lens development in vertebrates. PITX3 deficiency results in a spectrum of phenotypes from isolated cataracts to microphthalmia in humans, and lens degeneration in mice and zebrafish. While identification of downstream targets of PITX3 is vital for understanding the mechanisms of normal ocular development and human disease, these targets remain largely unknown. To isolate genes that are directly regulated by PITX3, we performed a search for genomic sequences that contain evolutionarily conserved bicoid/PITX3 binding sites and are located in the proximity of known genes. Two bicoid sites that are conserved from zebrafish to human were identified within the human promoter of the major intrinsic protein of lens fiber, MIP/AQP0. MIP/AQP0 deficiency was previously shown to be associated with lens defects in humans and mice. We demonstrate by both chromatin immunoprecipitation and electrophoretic mobility shift assay that PITX3 binds to MIP/AQP0 promoter region in vivo and is able to interact with both bicoid sites in vitro. In addition, we show that wild-type PITX3 is able to activate the MIP/AQP0 promoter via interaction with the proximal bicoid site in cotransfection experiments and that the introduction of mutations disrupting binding to this site abolishes this activation. Furthermore, mutant forms of PITX3 fail to produce the same levels of transactivation as wild-type when cotransfected with the MIP/AQP0 reporter. Finally, knockdown of pitx3 in zebrafish affects formation of a DNA-protein complex associated with mip1 promoter sequences; and examination of expression in pitx3 morphant and control zebrafish revealed a delay in and reduction of mip1 expression in pitx3-deficient embryos. Therefore, our data suggest that PITX3 is involved in direct regulation of MIP/AQP0 expression and that the alteration of MIP/AQP0 expression is likely to contribute to the lens phenotype in cataract patients with PITX3 mutations

The Landé factors of electrons and holes in lead halide perovskites: universal dependence on the band gap

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI3, MAPb(Br0.5Cl0.5)3, MAPb(Br0.05Cl0.95)3, FAPbBr3, FA0.9Cs0.1PbI2.8Br0.2, MA=methylammonium and FA=formamidinium) and all-inorganic (CsPbBr3) lead halide perovskites, determined by pump-probe Kerr rotation and spin-flip Raman scattering in magnetic fields up to 10 T at cryogenic temperatures. Further, we use first-principles density functional theory (DFT) calculations in combination with tight-binding and k ⋅ p approaches to calculate microscopically the Landé factors. The results demonstrate their universal dependence on the band gap energy across the different perovskite material classes, which can be summarized in a universal semi-phenomenological expression, in good agreement with experiment

Изучение возможности коррекции поведенческих нарушений у крыс со стереотаксической моделью болезни Альцгеймера

Relevance. Alzheimer's disease (AD) is a neurodegenerative disease, the drug therapy of which can only slow the progression of the disease, due to the variety of existing pathogenetic processes. A possible effective approach to the correction of symptoms can be the use of compounds with a complex mechanism of action — phosphorylacetohydrazides, capable of simultaneously acting on different parts of the pathological process, the most effective representative of which is the compound 2-chloroethoxy-para-N-dimethylaminophenyl phosphorylacetohydrazide (CAPAH). Target. To study the possibility of correcting cognitive and behavioral disorders in rats with a stereotaxic model of AD using the CAPAH compound, which affects different parts of the pathological process. Methods. 24 female Wistar rats were used in the work. AD was modeled in rats by stereotaxic bilateral injection of β-amyloid into the hippocampal region in a phosphate buffer solution, then on day 11, CAPACH (10 mg/kg) was administered intraperitoneally for 10 days, after which tests were performed using the ≪Elevated Plus Maze≫, ≪Open Field≫ and ≪Morris Water Maze≫. Statistical processing was carried out in the GraphPad Prism 8.0.1 program using one-way ANOVA analysis. Results. Multiple administration of CAPAH contributed to a decrease in the level of anxiety in the ≪Elevated Plus Maze≫ method, increasing the time spent in open arms by 4.6 times (p < 0.05) compared to rats without treatment. In the ≪Morris Water Maze≫ and ≪Open Field≫ tests, normalization of memory and motor activity processes was observed, respectively, the platform search time and the number of crossed lines did not differ from those of control animals. Conclusion. CAPAH reduces anxiety and memory processes in rats with a stereotaxic model of Alzheimer's disease caused by the introduction of β-amyloid into the hippocampus.Актуальность. Болезнь Альцгеймера (БА) — нейродегенеративное заболевание, лекарственная терапия которого способна лишь замедлить прогрессирование болезни, что обусловлено многообразием имеющихся патогенетических процессов. Возможным эффективным подходом к коррекции симптомов может стать применение соединений с комплексным механизмом действия — фосфорилацетогидразидов, способных одновременно воздействовать на разные звенья патологического процесса, наиболее эффективным представителем которых является соединение 2-хлорэтокси-пара-N-диметиламинофенил фосфорилацетогидразид (КАПАХ). Цель. Изучить возможность коррекции когнитивных и поведенческих нарушений у крыс со стереотаксической моделью БА с использованием соединения КАПАХ, воздействующего на разные звенья патологического процесса. Методы. В работе были использованы 24 самки крыс линии Wistar. БА моделировали у крыс путём стереотаксического билатерального введения в область гиппокампа β-амилоида в растворе фосфатного буфера, затем на 11-й день внутрибрюшинно вводили КАПАХ (10 мг/кг) в течение 10 дней, после чего проводили тестирование на установках ≪Приподнятый крестообразный лабиринт≫, ≪Открытое поле≫ и ≪Водный лабиринт Морриса≫. Статистическую обработку осуществляли в программе GraphPad Prism 8.0.1 с применением однофакторного анализа ANOVA. Результаты. Многократное введение КАПАХ способствовало снижению уровня тревожности в методе ≪Приподнятый крестообразный лабиринт≫, увеличивая время пребывания в открытых ≪рукавах≫ в 4,6 раза (р < 0,05) по сравнению с крысами без лечения. В тестах ≪Водный лабиринт Морриса≫ и ≪Открытое поле≫ наблюдалась нормализация процессов памяти и двигательной активности, соответственно, время поиска платформы и количество пересечённых линий не отличались от показателей контрольных животных. Вывод. КАПАХ уменьшает состояние тревожности и процессы памяти у крыс со стереотаксической моделью болезни Альцгеймера, вызванной введением β-амилоида в область гиппокампа

Исследование поведенческих эффектов новых фосфорилированных тиосемикарбазидов в эксперименте

Relevance. It is known that the existing drug therapy for cognitive disorders is characterized by low rates of efficacy and safety, as well as symptomatic orientation. Therefore, the search for new drugs in this area is an urgent issue, the solution of which can be phosphorylated derivatives of thiosemicarbazides (PTC), which have a multitarget mechanism of action.Aim. Study of acute toxicity and behavioral effects of PTC in mice.Methods. The objects of study are 2 new compounds of the PTC series: 2-[2-(Diphenylphosphoryl)acetyl]hydrazinecarbothioamide (T7) and 2-[2-(Diphenylphosphoryl) acetyl]-N-phenylhydrazinecarbothioamide (T8). The reference drug is diphenylphosphorylacetic acid hydrazide (phosenazid). After determining the acute toxicity with a single intraperitoneal injection, the effect of PTK on the behavior of mice was studied in the models "Open field" (OP), "Elevated plus maze" (EPM), "Dark-light chamber" (DLC) and "Behavioral despair" (BD). For statistical analysis, the GraphPadPrism 8.0.1 program was used with the calculation of Student's t-test.Results. It has been established that new PTC are less toxic than fosenazid. Behavioral testing showed that i.m. administration of T8 in test "OP" contributed to an increase in exploratory (6 and 12 mg/kg) and motor (12 mg/kg) activity, the development of an anxiolytic effect in the tests "EPM" (12 mg/kg) and "DLC" (6 mg / kg), and in "BD" (12 mg / kg) antidepressant effect. With the intravenous administration of T7, an increase in motor activity in the “OP” (16 mg / kg) was noted.Conclusion. Compounds of a number of PTC are promising for further synthesis and development as potential drugs with a different spectrum of psychotropic activitys.Актуальность. Известно, что существующая лекарственная терапия когнитивных расстройств характеризуется невысокими показателями эффективности и безопасности, а также симптоматической направленностью. Поэтому изыскание новых лекарственных средств в данной сфере является актуальным вопросом, решением которого могут стать фосфорилированные производные тиосемикарбазидов (ФТК), обладающие мультитаргетным механизмом действия.Цель. Изучение острой токсичности и влияния на поведение мышей ФТК.Методы. Объекты исследования — 2 новых соединения ряда ФТК: 2-[2-(Дифенилфосфорил)ацетил]гидразинкарботиоамид (Т7) и 2-[2-(Дифенилфосфорил)ацетил]-N-фенилгидразинкарботиоамид (Т8). Препарат сравнения — гидразид дифенилфосфорилуксусной кислоты (фосеназид). После определения острой токсичности при внутрибрюшинном однократном введении, влияние ФТК на поведение мышей изучено на моделях «Открытое поле» (ОП), «Приподнятый крестообразный лабиринт» (ПКЛ), «Тёмно-светлая камера» (ТСК) и «Поведенческое отчаяние» (ПО). Для статистического анализа применяли программу GraphPadPrism 8.0.1 с вычислением t-критерия Стьюдента.Результаты. Установлено, что новые ФТК обладают меньшей токсичностью по сравнению с фосеназидом. Поведенческое тестирование показало, что в/б введение Т8 способствовало увеличению исследовательской (6 и 12 мг/кг) и двигательной (12 мг/кг) активности на модели ОП, развитию анксиолитического эффекта в тестах ПКЛ (12 мг/кг) и ТСК (6 мг/кг), а в тесте ПО (12 мг/кг) — антидепрессивного действия. При в/б введении Т7 отмечалось увеличение двигательной активности в тесте ОП (16 мг/кг).Вывод. Соединения ряда ФТК являются перспективными для дальнейшего синтеза и разработки в качестве потенциальных лекарственных препаратов с различным спектром психотропной активности

Linking Human Diseases to Animal Models Using Ontology-Based Phenotype Annotation

A novel method for quantifying the similarity between phenotypes by the use of ontologies can be used to search for candidate genes, pathway members, and human disease models on the basis of phenotypes alone