FeCr₂S₄ in magnetic fields: possible evidence for a multiferroic ground state.

We report on neutron diffraction, thermal expansion, magnetostriction, dielectric, and specific heat measurements on polycrystalline FeCr2S4 in external magnetic fields. The ferrimagnetic ordering temperatures TC ≈ 170 K and the transition at TOO ≈ 10 K, which has been associated with orbital ordering, are only weakly shifted in magnetic fields up to 9 T. The cubic lattice parameter is found to decrease when entering the state below TOO. The magnetic moments of the Cr- and Fe-ions are reduced from the spin-only values throughout the magnetically ordered regime, but approach the spin-only values for fields >5.5 T. Thermal expansion in magnetic fields and magnetostriction experiments indicate a contraction of the sample below about 60 K. Below TOO this contraction is followed by a moderate expansion of the sample for fields larger than ~4.5 T. The transition at TOO is accompanied by an anomaly in the dielectric constant. The dielectric constant depends on both the strength and orientation of the external magnetic field with respect to the applied electric field for T < TOO. A linear correlation of the magnetic-field-induced change of the dielectric constant and the magnetic-field dependent magnetization is observed. This behaviour is consistent with the existence of a ferroelectric polarization and a multiferroic ground state below 10 K

Получение производных замещенных фенолов с потенциальной антимикробной активностью

Objectives. With the growing resistance of pathogenic microorganisms to antibiotics, the development of new antimicrobial drugs offering specific mechanisms of action becomes an urgent task. Only few antimicrobials offer a broad spectrum of activity against gram-positive and gram-negative bacteria, molds, and yeasts. In this regard, the purpose of the work was to develop methods for synthesizing biologically active derivatives of alkyl-substituted phenols (reactions at the hydroxy group) to study their biological effect.Methods. The synthesis of imidazole acetates of substituted phenols was carried out in two stages. At the first stage, the chloroacetyl derivative of the selected compounds was obtained, to which imidazole was then added. O-acylation reactions at the first stage of the synthesis were carried out under varying conditions. The first version of the synthesis was carried out using chloroacetyl chloride as an acylating agent together with a high-boiling solvent. In the second variant, chloroacetic anhydride was used, along with an attempt to replace the solvent with a low-boiling one. A thymol methoxy derivative was additionally synthesized by a known method using methyl iodide and varying the reaction parameters.Results. The parameters of chloroacetylation and methoxylation of aromatic alcohols were optimized with rational selection of solvents and the ratio of reagents in the reactions. Synthesized thymol (2-isopropyl-5-methylphenol) and propofol (2,6-isopropylphenol) derivatives contained imidazole as an additional pharmacophore with affinity for microorganism cell membrane proteins. A thymol methoxy derivative comprising an aromatic ether exhibiting increased hydrophobicity was also obtained. The synthesized compounds were characterized by NMR spectroscopy.Conclusions. Chloroacetyl derivatives of aromatic alcohols can be effectively synthesized by cooling the reaction mixture using an excess quantity of an acylating agent and increasing the reaction time (compared to literature data). The yield of thymol chloroacetate was 75%, while that of propofol chloroacetate was 30%. This can be explained by the sterically hindered reaction of the propofol alcohol group, which has isopropyl substituents at the second and sixth positions of the benzene ring.Цели. В связи с растущей резистентностью патогенных микроорганизмов к антибиотикам актуальной задачей является разработка новых противомикробных препаратов с уникальным механизмом действия. Немногие антимикробные препараты обладают широким спектром действия на грамположительные и грамотрицательные бактерии, плесени и дрожжи. В связи с этим, цель нашей работы – разработать способы синтеза биологически активных производных алкил-замещенных фенолов (реакций по гидроксигруппе) для исследования их биологического действия.Методы. Синтез имидазолацетатов замещенных фенолов проводился в две стадии. На первой стадии было получено хлорацетильное производное выбранных соединений, к которому далее присоединялся имидазол. Реакции O-ацилирования на первой стадии синтеза проводились в различных условиях. Первый вариант синтеза проводили с использованием хлорацетилхлорида в качестве ацилирующего агента и высококипящего растворителя. Во втором варианте использовали хлоруксусный ангидрид, и была предпринята попытка заменить растворитель на низкокипящий. Также было синтезировано метоксипроизводное тимола по известной методике, с применением метилйодида и варьирования параметров реакции.Результаты. Проведена оптимизация параметров хлорацетилирования и метоксилирования ароматических спиртов. Осуществлен подбор растворителей и соотношения реагентов в реакциях. Были синтезированы производные тимола (2-изопропил-5-метилфенола) и пропофола (2,6-изопропилфенола), содержащие имидазол в качестве дополнительного фармакофора, имеющего сродство к белкам клеточных мембран микроорганизмов. Также было получено метоксипроизводное тимола – ароматический простой эфир с повышенной гидрофобностью. Синтезированные соединения были охарактеризованы методом ЯМР-спектроскопии.Выводы. Синтез хлорацетильных производных ароматических спиртов при охлаждении реакционной массы с использованием избытка ацилирующего агента и увеличением времени реакции (по сравнению с литературными данными) является более предпочтительным. Выход хлорацетета тимола составил 75%, хлорацетата пропофола – 30%, что можно объяснить стерически затрудненным реагированием спиртовой группы пропофола, имеющего изопропильные заместители по 2 и 6 положениям бензольного кольца

Fabrication of the Ni[3]Al-based alloy formed by spark plasma sintering of VKNA powders

The material based on Ni[3]Al intermetallic has been obtained from the industrial powder of a VKNA type by the method of spark plasma sintering. Materials sintering was conducted at the temperature of 1100 °С, compacting pressure of 20 MPa, and during soaking time equal to 5 minutes. The heating rate of samples amounted to 50 and 200 °С/min. It has been established that the material obtained by sintering at the rate of 50 °С/min possesses a maximum value of density (5.93 g/cm{3}) and a maximum level of bending strength (~ 400 MPa)

The exponential map for representations of Up,q(gl(2))U_{p,q}(gl(2))

For the quantum group $GL_{p,q}(2)$ and the corresponding quantum algebra $U_{p,q}(gl(2))$ Fronsdal and Galindo explicitly constructed the so-called universal $T$-matrix. In a previous paper we showed how this universal $T$-matrix can be used to exponentiate representations from the quantum algebra to get representations (left comodules) for the quantum group. Here, further properties of the universal $T$-matrix are illustrated. In particular, it is shown how to obtain comodules of the quantum algebra by exponentiating modules of the quantum group. Also the relation with the universal $R$-matrix is discussed.Comment: LaTeX-file, 7 pages. Submitted for the Proceedings of the 4th International Colloquium ``Quantum Groups and Integrable Systems,'' Prague, 22-24 June 199

Espon-Interstrat. Espon in Integrated Territorial Strategies.

The INTERSTRAT project’s overall aim is “to encourage and facilitate the use of ESPON 2013 Programme findings in the creation and monitoring of Integrated Territorial Development Strategies (ITDS) and to support transnational learning about the actual and potential contribution of ESPON to integrated policy-making.” We defined integrated territorial development as ‘the process of shaping economic, social and environmental change through spatially sensitive policies and programmes’

OSL-dating of the Pleistocene-Holocene climatic transition in loess from China, Europe and North America, and evidence for accretionary pedogenesis

Loess deposits intercalated by paleosols are detailed terrestrial archives of Quaternary climate variability providing information on the global dust cycle and landscape dynamics. Their paleoclimatic significance is often explored by quantifying their mineral magnetic properties due to their sensitivity to local/regional hydroclimate variability. Detailed chronological assessment of such regional proxy records around the climatic transitions allow a better understanding of how regional records react to major global climatic transitions such as the Pleistocene-Holocene climatic transition. Logs of high-resolution magnetic susceptibility and its frequency dependence were used as paleoclimatic proxies to define the environmental transition from the last glacial loess to the current interglacial soil as reflected in nine loess-paleosol sequences across the northern hemisphere, from the Chinese Loess Plateau, the southeastern European loess belt and the central Great Plains, USA. The onset of increase in magnetic susceptibility above typical loess values was used to assess the onset of, and developments during, the Pleistocene-Holocene climatic transition. High-resolution luminescence dating was applied on multiple grain-sizes (4–11 μm, 63–90 μm, 90–125 μm) of quartz extracts from the same sample in order to investigate the timing of Pleistocene-Holocene climatic transition in the investigated sites. The magnetic susceptibility signal shows a smooth and gradual increase for the majority of the sites from the typical low loess values to the interglacial ones. The initiation of this increase, interpreted as recording the initiation of the Pleistocene-Holocene climatic transition at each site, was dated to 14–17.5 ka or even earlier. Our chronological results highlight the need of combining paleoclimatic proxies (magnetic susceptibility) with absolute dating when investigating the Pleistocene-Holocene climatic transition as reflected by the evolution of this proxy in order to avoid chronostratigraphic misinterpretations in loess-paleosol records caused by simple pattern correlation. The detailed luminescence chronologies evidence the continuity of eolian mineral dust accumulation regardless of glacial or interglacial global climatic regimes. Coupled with magnetic susceptibility records this indicates that dust sedimentation and pedogenesis act simultaneously and result in a non-negligible accretional component in the formation of Holocene soils in loess regions across the Northern Hemisphere. The luminescence ages allowed the modeling of accumulation rates for the Holocene soil which are similar for European, Chinese and U.S.A. loess sites investigated and vary from 2 cm ka−1 to 9 cm ka−1. While accretional pedogenesis has often been implicitly or explicitly assumed in paleoclimatic interpretation of loess-paleosol sequences, especially in the Chinese Loess Plateau, our luminescence data add direct evidence for ongoing sedimentation as interglacial soils formed

Липоксигеназное окисление жирных кислот в растениях.

Lipid peroxidation is common to all biological systems, both appearing in developmentally and environmentally regulated processes of plants. The hydroperoxy polyunsaturated fatty acids, synthesized by the action of various highly specialized forms of lipoxygenases, are substrates of at least seven different enzymе families. Signaling compounds such as jasmonates, antimicrobial and antifungal compounds such as leaf aldehydes or divinyl ethers, and a plant-specific blend of volatiles including leaf alcohols are among the numerous productsПерекисное окисление является общим процессом для всех биологических систем, причем в растениях онo происходит под влиянием как природных механизмов развития, так и стимулов окружающей среды. Гидропероксиды полиненасыщенных жирных кислот, биосинтезируемые под действием различных специфичных изоформ липоксигеназ, представляют собой субстраты по меньшей мере для семи различных семейств ферментов. Среди множества продуктов ферментативных реакций ключевую роль играют сигнальные соединения растений, такие как жасмонаты, альдегиды, спирты и дивиниловые эфиры полиненасыщенных жирных кислот из листьев (антимикробные и антигрибковые соединения)