STRESS FIELD IN A SHEAR ZONE, AND FORMATION OF THE MAIN FAULT

Using the analytical approximation method, we calculated stress field parameters for cases with different relative positions of Riedel shears and loads required for shearing. Considering an internal friction angle of 30°, and the distance between adjacent shears exceeding 0.7 of the characteristic shear length, we estimated the Coulomb stress that can lead to fracturing. In the areas between the shears, it is below the shear strength value. This means that if an increase in the external load is lacking, there are no prerequisites for the formation of new fractures that may connect adjacent shears. If the shears are spaced closer to each other (i.e. at distances less than 0.7 of the shear length), the shear strength is exceeded in the areas between them, and new shears can occur there and connect the Riedel shears to each other. Therefore, in observations of a natural system of Riedel shears, it becomes possible to assess whether this system is sufficiently stable in its current status, or, in case of a critical increase in the Coulomb stress in the areas between adjacent shears, the equilibrium can be easily disturbed, and there is a possibility that the main fault forms in the strike-slip zone under study

ПОЛЕ НАПРЯЖЕНИЙ ВНУТРИ ЗОНЫ СДВИГА И ОБРАЗОВАНИЕ МАГИСТРАЛЬНОГО РАЗЛОМА

Using the analytical approximation method, we calculated stress field parameters for cases with different relative positions of Riedel shears and loads required for shearing. Considering an internal friction angle of 30°, and the distance between adjacent shears exceeding 0.7 of the characteristic shear length, we estimated the Coulomb stress that can lead to fracturing. In the areas between the shears, it is below the shear strength value. This means that if an increase in the external load is lacking, there are no prerequisites for the formation of new fractures that may connect adjacent shears. If the shears are spaced closer to each other (i.e. at distances less than 0.7 of the shear length), the shear strength is exceeded in the areas between them, and new shears can occur there and connect the Riedel shears to each other. Therefore, in observations of a natural system of Riedel shears, it becomes possible to assess whether this system is sufficiently stable in its current status, or, in case of a critical increase in the Coulomb stress in the areas between adjacent shears, the equilibrium can be easily disturbed, and there is a possibility that the main fault forms in the strike-slip zone under study.При помощи приближенного аналитического метода проведены расчеты параметров напряженного состояния массива для разных вариантов взаимного расположения сколов Риделя при нагрузке, необходимой для образования этих сколов. Результаты вычислений при значении угла внутреннего трения 30° показывают, что при расстоянии между соседними сколами, превышающем 0.7 характерной длины скола, кулоновское напряжение, отвечающее за разрушение материала, в промежутках между сколами оказывается ниже предела прочности. Это означает, что без увеличения внешней нагрузки отсутствуют предпосылки для образования новых нарушений, соединяющих соседние сколы. Если же сколы расположены ближе друг к другу, чем 0.7 длины скола, то на участках массива между ними превышен предел прочности. Соответственно, там должны возникнуть новые сколы, соединяющие сколы Риделя между собой. Таким образом, при наблюдении природной системы сколов Риделя появляется возможность оценить, является ли эта система достаточно устойчивой в ее текущем виде, или же, ввиду критического повышения кулоновского напряжения в участках массива между соседними сколами, равновесие может быть легко нарушено, и в изучаемой сдвиговой зоне образуется магистральный разлом

ИССЛЕДОВАНИЕ ВЗАИМОДЕЙСТВИЯ ТРЕЩИН СДВИГА НА ОСНОВЕ ПРИБЛИЖЕННОГО АНАЛИТИЧЕСКОГО РЕШЕНИЯ ЗАДАЧИ ТЕОРИИ УПРУГОСТИ

The article describes a method yielding approximate analytical solutions under the theory of elasticity for a set of interacting arbitrarily spaced shear fractures. Accurate analytical solutions of this problem are now available only for the simplest individual cases, such as a single fracture or two collinear fractures. A large amount of computation is required to yield a numerical solution for a case considering arbitrary numbers and locations of fractures, while this problem has important practical applications, such as assessment of the state of stress in seismically active regions, forecasts of secondary destruction impacts near systems of large faults, studies of reservoir properties of the territories comprising oil and gas provinces.In this study, an approximate estimation is obtained with the following simplification assumptions: (1) functions showing shear of fractures’ borders are determined similar to the shear function for a single fracture, and (2) boundary conditions for the fractures are specified in the integrated form as mean values along each fracture. Upon simplification, the solution is obtained through the system of linear algebraic equations for unknown values of tangential stress drop. With this approach, the accuracy of approximate solutions is consistent with the accuracy of the available data on real fractures.The reviewed examples of estimations show that the resultant stress field is dependent on the number, size and location of fractures and the sequence of displacements of the fractures’ borders.В работе представлен метод построения приближенного аналитического решения задачи теории упругости для множества взаимодействующих произвольно расположенных трещин скола. Точное аналитическое решение подобной задачи до сих пор известно лишь для простейших частных случаев (одиночная трещина, две коллинеарные трещины), а для нахождения численного решения в произвольном случае количества и расположения трещин требуется выполнить большой объем вычислений. Между тем данная задача имеет практически важные приложения, такие как оценка напряженного состояния сейсмически активных районов, прогноз возникновения вторичных разрушений вблизи систем крупных разрывов, исследование коллекторских свойств массивов в областях формирования нефтегазоносных залежей.Приближенность созданного аналитического решения достигается рядом упрощающих предположений, первое из которых определяет задание вида функций смещения бортов трещин, аналогичного виду функции смещения для одиночной трещины, второе – задание краевых условий на трещинах в интегральной форме, в виде средних значений по длине трещины. Эти упрощения приводят к тому, что решение задачи сводится к системе линейных алгебраических уравнений относительно неизвестных значений сброшенных на трещинах касательных напряжений (stress drop). При этом точность полученного приближенного решения согласуется с точностью данных о реальных трещинах, известных на практике.Приведенные в качестве примеров результаты расчетов показывают зависимость конечного поля напряжений от числа, размеров и расположения трещин, а также от очередности возникновения смещений их бортов

Трифторацетат кальция: новый структурный тип

Objectives. The study was devoted to considering the features of the synthesis and crystal structure of calcium trifluoroacetate Ca2(CF3COO)4·8CF3COOH and investigating the products of its thermal behavior.Methods. The compositions of the proposed structural form were characterized by various physicochemical methods (X-ray diffraction, IR spectroscopy), and the products of thermal decomposition were determined under dynamic vacuum conditions.Results. The reaction between calcium carbonate and 99% trifluoroacetic acid yielded a new structural type of calcium trifluoroacetate Ca2(CF3COO)4·8CF3COOH (I) in the form of colorless prismatic crystals unstable air. X-ray diffraction results confirmed the composition I: space group P21, with unit cell parameters: a = 10.0193(5) Å, b = 15.2612(7) Å, c = 16.3342(8) Å, β = 106.106(2)°, V = 2399.6(2) Å3, Z = 2. The structure is molecular, constructed from Ca2(CF3COO)4·8CF3COOH dimers. The end molecules of the trifluoroacetic acid were involved in the formation of intramolecular hydrogen bonds with oxygen atoms of the bidentate bridging anions CF3COO−. There were strongly pronouncedsymmetric and asymmetric absorption bands of COO and CF3-groups in the IR spectrum of the resulting compound in the range of 1200–1800 cm−1. The definite peak of the oscillation of the OH-group at 3683 cm−1 corresponds to the trifluoroacetic acid molecules present in the structure. The broadpeak of the valence oscillations in the range of 3300–3500 cm−1 is caused by the presence of intramolecular hydrogen bonds. Decomposition began at 250°C and 10−2 mm Hg with calcium fluoride CaF2 as the final decomposition product.Conclusions. We obtained a previously undescribed calcium–trifluoroacetic acid complex whose composition can be represented by Ca2(CF3COO)4·8CF3COOH. The crystal island structure is a dimeric molecule where the calcium atoms are bound into dimers by four trifluoroacetate groups. The complex was deposited in the Cambridge Structural Data Bank with a deposit number CCDC 2081186. Although the compound has a molecular structure, thermal decomposition leads to the formation of calcium fluoride characterized by a small particle size, which may further determine its applications.Цели. Работа посвящена рассмотрению особенностей синтеза и кристаллического строения трифторацетата кальция Ca2(CF3COO)4·8CF3COOH, а также изучению продуктов его термического поведения.Методы. Соединение охарактеризовано различными физико-химическими методами (рентгеноструктурный анализ, ИК-спектроскопия), установлены продукты термического разложения в условиях динамического вакуума.Результаты. Взаимодействием карбоната кальция с 99% трифторуксусной кислотой синтезирован новый структурный тип трифторацетата кальция Ca2(CF3COO)4·8CF3COOH (I) в виде неустойчивых на воздухе бесцветных призматических кристаллов. Строение I установлено по результатам рентгеноструктурного анализа: пространственная группа Р21, параметры элементарной ячейки: a = 10.0193(5) Å, b = 15.2612(7) Å, c = 16.3342(8) Å, β = 106.106(2)°, V = 2399.6(2) Å3, Z = 2. Структура молекулярная, построена из димеров Ca2(CF3COO)4·8CF3COOH. Торцевые молекулы трифторуксусной кислоты участвуют в образовании внутримолекулярных водородных связей с атомами кислорода бидентатных мостиковых анионов CF3COO−. На ИК-спектре полученного соединения в диапазоне 1200–1800 см−1 присутствуют ярко выраженные симметричные и асимметричные полосы поглощения СОО и CF3-групп. Четкий пик колебания OH-группы на 3683 см−1 соответствует присутствующим в структуре молекулам трифторуксусной кислоты. Широкий пик валентных колебаний в области 3300–3500 см−1 обусловлен наличием внутримолекулярных водородных связей. При давлении 10−2 мм рт.ст. разложение начинается при 250 °С, конечным продуктом разложения является фторид кальция CaF2.Выводы. Нами получен ранее не описанный комплекс кальция с трифторуксусной кислотой, состав которого может быть представлен формулой Ca2(CF3COO)4·8CF3COOH, кристаллическая островная структура которого представляет собой димерную молекулу, а атомы кальция связаны в димеры четырьмя трифторацетатными группами. Комплекс задепонирован в Кембриджском банке структурных данных, номер депонирования – CCDC 2081186. Соединение имеет молекулярное строение, термическое разложение приводит к образованию фторида кальция, характеризующегося небольшим размером частиц, что может в дальнейшем обусловить его применение

Effect of novel porphyrazine photosensitizers on normal and tumor brain cells

Photodynamic therapy (PDT) is a clinically approved procedure for targeting tumor cells. Though several different photosensitizers have been developed, there is still much demand for novel photosensitizers with improved properties. In this study we aim to characterize the accumulation, localization and dark cytotoxicity of the novel photosensitizers developed in-house derivatives of porphyrazines (pz I-IV) in primary murine neuronal cells, as well as to identify the concentrations at which pz still effectively induces death in glioma cells yet is nontoxic to nontransformed cells. The study shows that incubation of primary neuronal and glioma cells with pz I-IV leads to their accumulation in both types of cells, but their rates of internalization, subcellular localization and dark toxicity differ significantly. Pz II was the most promising photosensitizer. It efficiently killed glioma cells while remaining nontoxic to primary neuronal cells. This opens up the possibility of evaluating pz II for experimental PDT for glioma

Защитное действие экстракта листьев черники в отношении эксайтотоксического действия глутамата на нейроны коры мозга крыс

The aqueous extract of blueberry leaves inhibits the glutamate-induced Ca2+ influx into the synaptosomes of rat brain neurons and the IC50 value of this process is close to the IC50 for MK-801, a well-known noncompetitive antagonist of glutamate NMDA subtype receptors. The aqueous extract of blueberry leaves protected the cultured neurons of the rat cerebral cortex from the neurotoxic effect of glutamate, and the inhibition intensity depended on the incubation time with the extract.Водный экстракт листьев черники ингибирует глутамат-индуцированный вход ионов Са2+ в синаптосомы нейронов мозга крыс, и IC50 этого процесса близка к IC50 для MK-801 – известного неконкурентного антагониста глутаматных рецепторов NMDA-подтипа. Водный экстракт листьев черники предохранял культивируемые нейроны коры мозга крысы от нейротоксического действия глутамата, причём выраженность ингибирования зависела от времени инкубации с экстрактом, на фоне которого действовал глутамат

Dynamics of a novel centromeric histone variant CenH3 reveals the evolutionary ancestral timing of centromere biogenesis

The centromeric histone H3 variant (CenH3) serves to target the kinetochore to the centromeres and thus ensures correct chromosome segregation during mitosis and meiosis. The Dictyostelium H3-like variant H3v1 was identified as the CenH3 ortholog. Dictyostelium CenH3 has an extended N-terminal domain with no similarity to any other known proteins and a histone fold domain at its C-terminus. Within the histone fold, α-helix 2 (α2) and an extended loop 1 (L1) have been shown to be required for targeting CenH3 to centromeres. Compared to other known and putative CenH3 histones, Dictyostelium CenH3 has a shorter L1, suggesting that the extension is not an obligatory feature. Through ChIP analysis and fluorescence microscopy of live and fixed cells, we provide here the first survey of centromere structure in amoebozoa. The six telocentric centromeres were found to mostly consist of all the DIRS-1 elements and to associate with H3K9me3. During interphase, the centromeres remain attached to the centrosome forming a single CenH3-containing cluster. Loading of Dictyostelium CenH3 onto centromeres occurs at the G2/prophase transition, in contrast to the anaphase/telophase loading of CenH3 observed in metazoans. This suggests that loading during G2/prophase is the ancestral eukaryotic mechanism and that anaphase/telophase loading of CenH3 has evolved more recently after the amoebozoa diverged from the animal linage

Arabidopsis NSE4 Proteins Act in Somatic Nuclei and Meiosis to Ensure Plant Viability and Fertility

The SMC 5/6 complex together with cohesin and condensin is a member of the structural maintenance of chromosome (SMC) protein family. In non-plant organisms SMC5/6 is engaged in DNA repair, meiotic synapsis, genome organization and stability. In plants, the function of SMC5/6 is still enigmatic. Therefore, we analyzed the crucial d-kleisin component NSE4 of the SMC5/6 complex in the model plant Arabidopsis thaliana. Two functional conserved Nse4 paralogs (Nse4A and Nse4B) are present in A. thaliana, which may have evolved via gene subfunctionalization. Due to its high expression level, Nse4A seems to be the more essential gene, whereas Nse4B appears to be involved mainly in seed development. The morphological characterization of A. thaliana T-DNA mutants suggests that the NSE4 proteins are essential for plant growth and fertility. Detailed investigations in wild-type and the mutants based on live cell imaging of transgenic GFP lines, fluorescence in situ hybridization (FISH), immunolabeling and super-resolution microscopy suggest that NSE4A acts in several processes during plant development, such as mitosis, meiosis and chromatin organization of differentiated nuclei, and that NSE4A operates in a cell cycle-dependent manner. Differential response of NSE4A and NSE4B mutants after induced DNA double strand breaks (DSBs) suggests their involvement in DNA repair processes

The Effects of Latrepirdine on Amyloid-ß Aggregation and Toxicity

© 2016 - IOS Press and the authors. All rights reserved. Latrepirdine (DimebonTM) has been demonstrated to be a neuroprotective and cognition improving agent in neurodegenerative diseases that feature protein aggregation and deposition, such as Alzheimer's disease (AD). The accumulation of amyloid-ß (Aß) protein aggregates is a key event in the neurodegenerative process in AD. This study explores if latrepirdine modulation of protein aggregation contributes to its neuroprotective mechanism of action. Assessment of neuronal cell death showed that there was a significant reduction in lactate dehydrogenase release at an equimolar ratio of Aß:latrepirdine and with lower concentrations of latrepirdine. The ability of latrepirdine to alter the formation of Aß42 aggregates was assessed by thioflavin-T fluorescence, western immunoblotting and atomic force microscopy (AFM). Despite showing a reduction in thioflavin-T fluorescence with latrepirdine treatment, indicating a decrease in aggregation, immunoblotting and AFM showed a modest increase in both the formation and size of Aß aggregates. The discrepancies between thioflavin-T and the other assays are consistent with previous evidence that cyclic molecules can interfere with thioflavin-T binding of amyloid protein preparations. The ability of latrepirdine to modulate Aß aggregation appears to be independent of its neuroprotective effects, and is unlikely to be a mechanism by which latrepirdine offers protection. This study investigates the effect of latrepirdine on Aß aggregation, and presents evidence suggesting that caution should be applied in the use of thioflavin-T fluorescence based assays as a method for screening compounds for protein aggregation altering properties

Spindle Assembly Checkpoint Protein Dynamics Reveal Conserved and Unsuspected Roles in Plant Cell Division

Background: In eukaryotes, the spindle assembly checkpoint (SAC) ensures that chromosomes undergoing mitosis do not segregate until they are properly attached to the microtubules of the spindle. Methodology/Principal Findings: We investigated the mechanism underlying this surveillance mechanism in plants, by characterising the orthogolous SAC proteins BUBR1, BUB3 and MAD2 from Arabidopsis. We showed that the cell cycle-regulated BUBR1, BUB3.1 and MAD2 proteins interacted physically with each other. Furthermore, BUBR1 and MAD2 interacted specifically at chromocenters. Following SAC activation by global defects in spindle assembly, these three interacting partners localised to unattached kinetochores. In addition, in cases of 'wait anaphase', plant SAC proteins were associated with both kinetochores and kinetochore microtubules. Unexpectedly, BUB3.1 was also found in the phragmoplast midline during the final step of cell division in plants. Conclusions/Significance: We conclude that plant BUBR1, BUB3.1 and MAD2 proteins may have the SAC protein functions conserved from yeast to humans. The association of BUB3.1 with both unattached kinetochore and phragmoplast suggests that in plant, BUB3.1 may have other roles beyond the spindle assembly checkpoint itself. Finally, this study of the SAC dynamics pinpoints uncharacterised roles of this surveillance mechanism in plant cell division