Premartensitic Transition in Ni2+xMn1-xGa Heusler Alloys

The temperature dependencies of the resistivity and magnetization of a series of Ni2+XMn1-XGa (X = 0 - 0.09) alloys were investigated. Along with the anomalies associated with ferromagnetic and martensitic transitions, well-defined anomalies were observed at the temperature of premartensitic transformation. The premartensitic phase existing in a temperature range 200 - 260 K in the stoichiometric Ni2MnGa is suppressed by the martensitic phase with increasing Ni content and vanishes in Ni2.09Mn0.91Ga composition

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ АДСОРБЦІЙНОГО ЗАБРУДНЕННЯ В ЗАВАНТАЖЕННІ ЗНЕЗАЛІЗНЮВАЛЬНИХ ФІЛЬТРІВ

In the article the scheme of immobilization and transformation of iron forms is presented for underground water deferrization. The clarification block of the general model of physico-chemical deferrization of water is presented, taking into account the nonlinear effects of mass exchange. Separately the block of nonlinear problem of adsorption and transformation of iron oxide is considered. Using the method of dynamic averaging of the desired characteristic, approximate solutions are obtained. Executed the quantitativeanalysis of changes of the relative concentrations of free and adsorbed ferrous iron and the discrepancy between the corresponding exact and approximate solutions is estimated. The accumulation of adsorbed iron in the download is calculated.В статье приведена схема иммобилизации и трансформации форм железа при обезжелезивании подземных вод. Представлен осветительный блок общей модели физико-химического обезжелезивания воды с учетом нелинейных эффектов массообмена. Отдельно рассмотрен блок нелинейной задачи адсорбции и трансформации закиси железа. Используя метод динамического осреднения искомой характеристики, полученные приближенные ее решения.Проведен количественный анализ изменений относительных концентраций свободного и адсорбированного двухвалентного железа и оценено расхождение между соответствующими точными и приближенными решениями. Рассчитано накопления адсорбированного железа в загрузке.В статті наведено схему іммобілізації та трансформації форм заліза при знезалізненні підземних вод. Представлено освітлювальний блок загальної моделі фізико-хімічного знезалізнення води з врахуванням нелінійних ефектів масообміну. Окремо розглянутий блок нелінійної задачі адсорбції і трансформації закису заліза. Використовуючи метод динамічного осереднення шуканої характеристики, отримані наближені її розв’язки. Проведений кількісний аналіз змін відносних концентрацій вільного і адсорбованого двовалентного заліза та оцінена розбіжність між відповідними точними та наближеними розв’язками. Розраховано накопичення адсорбованого заліза в завантаженні

Premartensitic transition driven by magnetoelastic interaction in bcc ferromagnetic Ni2MnGaNi_{2}MnGa

We show that the magnetoelastic coupling between the magnetization and the amplitude of a short wavelength phonon enables the existence of a first order premartensitic transition from a bcc to a micromodulated phase in $Ni_{2}MnGa$. Such a magnetoelastic coupling has been experimentally evidenced by AC susceptibility and ultrasonic measurements under applied magnetic field. A latent heat around 9 J/mol has been measured using a highly sensitive calorimeter. This value is in very good agreement with the value predicted by a proposed model.Comment: 4 pages RevTex, 3 Postscript figures, to be published in Physical Review Letter

Influence of intermartensitic transitions on transport properties of Ni2.16Mn0.84Ga alloy

Magnetic, transport, and x-ray diffraction measurements of ferromagnetic shape memory alloy Ni$_{2.16}$Mn$_{0.84}$Ga revealed that this alloy undergoes an intermartensitic transition upon cooling, whereas no such a transition is observed upon subsequent heating. The difference in the modulation of the martensite forming upon cooling from the high-temperature austenitic state [5-layered (5M) martensite], and the martensite forming upon the intermartensitic transition [7-layered (7M) martensite] strongly affects the magnetic and transport properties of the alloy and results in a large thermal hysteresis of the resistivity $\rho$ and magnetization $M$. The intermartensitic transition has an especially marked influence on the transport properties, as is evident from a large difference in the resistivity of the 5M and 7M martensite, $(\rho_{\mathrm{5M}} - \rho_{\mathrm{7M}})/\rho _{\mathrm{5M}} \approx 15$, which is larger than the jump of resistivity at the martensitic transition from the cubic austenitic phase to the monoclinic 5M martensitic phase. We assume that this significant difference in $\rho$ between the martensitic phases is accounted for by nesting features of the Fermi surface. It is also suggested that the nesting hypothesis can explain the uncommon behavior of the resistivity at the martensitic transition, observed in stoichiometric and near-stoichiometric Ni-Mn-Ga alloys.Comment: 7 pages, 6 figures, REVTEX

The 'Route from the Varangians to the Greeks': truth or fiction

The 'route from the Varangians to the Greeks' is widely known and often mentioned in research, popular science and educational literature. Much less often is it mentioned that the existence of the trade route is seriously doubted and needs additional evidence. The discussion about the actuality of a 'route from the Varangians to the Greeks' has intensified in the recent decade; it mostly involves historians who draw on chronicles, archive materials and literary sources. Although relevant geographical studies focus on small territories and have a limited scope, only they can give a definitive answer to the question of whether it was possible to sail the rivers of the East European Plain between the Baltic and Black Seas in the 8th-11th centuries AD. Of particular importance are studies on the watersheds marking the principal legs of the route. If the watersheds were traversable, the 'route from the Varangians to the Greeks' was navigable, and the impassability of watersheds would preclude navigation along the route. Methodologically, the study employs methods and approaches used in physiographical field studies, which have not been applied earlier to the watershed sections of the 'route from the Varangians to the Greeks'. The central result of the research is the reconstruction of the hydrological features and hydrographic situation of the watershed between the basins of the Neva (River Lovat) and the Western Dvina (River Usvyacha) during the existence of the 'route from the Varangians to the Greeks'. This reconstruction and the study of the watershed territories, the system of land communication routes and toponymic features of this territory conclusively demonstrate that the 'way from the Varangians to the Greeks', or the Baltic-Black Sea waterway, could actually exist

Effect of wood structure geometry during firebrand generation in laboratory scale and semi-field experiments

As the set of experiments result, statistically substantiated data were obtained on the laws of ignition of a model angular structure under conditions of a point source of heat exposure. The use of IR diagnostics made it possible to control the thermal picture in the experimental area, as well as to capture areas of the highest and lowest heating. In the Large Aerosol Chamber of IAO SB RAS, preliminary experiments were carried out on a “firebrand shower” model exposure, which is naturally occurring firebrands (flaming or glowing embers) with some types of construction materials (chipboards). The exposure of the samples to firebrands stream was provided using a firebrand generator of own original design. It was experimentally confirmed that particle size plays a significant role in the ignition of a building structure. If the characteristic particle size, which can be defined as the ratio of its volume to the surface area in contact with the wood, is less than a certain characteristic value, then the ignition mode with a sharp temperature maximum near the phase interface is not fulfilled. This can be explained by the prevailing heat removal into the external environment in comparison with the amount of heat coming from a heat gun and resulting from chemical reactions

Competing ideologies of Russia's civil society

Many analysts and public opinion makers in the West conflate the notions of Russia’s non-systemic liberal opposition and the country’s civil society. Indeed, despite garnering the support of a minority of Russia’s population, non-systemic liberal opposition represents a well-organized civic group with a clearly articulated agenda and the ability to take action. Yet, does Russia’s civil society end there? A closer look at the country’s politics shows that Russia has a substantial conservative-traditionalist faction that has also developed agenda for action and formulated opinions. This group is anti-liberal rather than illiberal ideologically and pro-strong state/pro a geopolitically independent Russia rather than pro-Kremlin politically. The interaction between liberal and conservative civic groups represents the battle of meanings, ideas, and ethics, and ultimately determines the future trajectory of Russia’s evolution. Thus, the analysis of Russia’s civil society must represent a rather more nuanced picture than a mere study of the liberal non-systemic opposition. This article will examine the complexity of Russia’s civil society scene with reference to the interplay between the liberal opposition and conservative majority factions. The paper will argue that such complexity stems from ideological value pluralism that falls far beyond the boundaries of the liberal consensus, often skewing our understanding of political practice in Russia