Palaeoecological evidence of changes in vegetation and climate during the Holocene in the pre-Polar Urals, northeast European Russia

This study investigated Holocene tree-line history and climatic change in the pre-Polar Urals, northeast European Russia. A sediment core from Mezhgornoe Lake situated at the present-day alpine tree-line was studied for pollen, plant macrofossils, Cladocera and diatoms. A peat section from Vangyr Mire in the nearby mixed mountain taiga zone was analysed for pollen. The results suggest that the study area experienced a climatic optimum in the early Holocene and that summer temperatures were at least 2°C warmer than today. Tree birch immigrated to the Mezhgornoe Lake area at the onset of the Holocene. Mixed spruce forests followed at ca. 9500-9000 14C yr BP. Climate was moist and the water level of Mezhgornoe Lake rose rapidly. The hypsithermal phase lasted until ca. 5500-4500 14C yr BP, after which the mixed forest withdrew from the Mezhgornoe catchment as a result of the climate cooling. The gradual altitudinal downward shift of vegetation zones resulted in the present situation, with larch forming the tree-line

SELECTION OF A PROTOTYPE BRAIN DEFORMATION MODEL FOR USE IN THE TASK OF DISPLACEMENT PREDICTING FROM MRI IMAGES

This paper discusses the problem of glial brain tumors and ways to solve this problem

Об агрегативной устойчивости латексов, стабилизованных смесью ионных и неионных ПАВ

The colloid properties of styrene-butadiene latex stabilysed by the mixture of anionic alkylsulphonat (AS) and non-ionic oxiethylated fat alcohole (OC-20) were investigated. Addition of little amounts (less than 0,2 mol. Part) of AS into the mixture was founed to lead to the non-additive changes in particle sizes, influence the thickness of adsorbtion layers, Z-potencial and latex viskosity. It was shown that an agregative stability of the latex in the presents of different destabilizating factors (addition of electrolites, increasing of temperature, freezing, mechanical stiring) can be controlled, depending of their practical use, by changing the emulsifier mixture composition. For example, by changing the AS content in the composition one can reach the different thermosensibility of latex.Изучены коллоидно-химические свойства бутадиен-стирольных латексов, стабилизованных смесями анионактивного алкилсульфоната натрия (АС) и неионного оксиэтилированного жирного спирта (ОС-20). Присутствие небольших (до 0,2 мол. доли) количеств АС в смеси приводит к неаддитвному изменению размеров глобул, толщины адсорбционных защитных слоев, ξ- потенциала, вязкости латексов. Показано, что агрегативную устойчивость изученных латексов, к различного рода воздействиям (введению электролитов, нагреванию, замораживанию, перемешиванию) можно регулировать в соответствии и их целевым назначением изменением состава смеси эмульгаторов. Например, изменение количества АС в смеси обеспечивает различную степень теплочувствительности латекса

Thiacalix[4]arenes with triple bonds at the lower rim: Synthesis and structure

Reaction of thiacalixarenes with propargyl bromide in the presence of potassium or cesium carbonates leads mainly to mixture of the corresponding tetrasubstituted derivatives adopting 1,3-alternate and partial cone conformations. Sodium salts like carbonate and hydride are not effective as the base for the etherification of lower rim of thiacalix[4]- arenes by propargyl bromide. It was established that propargyl derivatives of thiacalix[4]arenes are in conformational exchange between forms due rotation of one aryl ring. © ISUCT Publishing

Combined Use of 2-D NMR Correlation Experiments, GIAO DFT 13C Chemical Shifts and 1-D NOESY Methods in Regioisomeric and Conformational Structure Determination of Cyclophanes in Solution

The combined application of two-dimensional nuclear magnetic resonance (2-D NMR) correlation experiments and gauge-including atomic orbital (GIAO) 13C NMR chemical shift calculations allowed reliable and simple determination of regioisomeric structure of heterocyclic substituents on the calix[4]arene lower rim. Moreover, the 1-D double pulsed field gradient nuclear Overhauser effect technique allows quick and efficient measurement of small nuclear Overhauser effects and, in doing so, establishes a 3-D structure of calix[4]arene simply and unequivocally. In general, these methods may find application in the regio- and stereoisomeric structure determination of complicated macrocyclic compounds. © 2011 Springer-Verlag

Molecular tectonics: Grid and porous coordination networks based on combinations of iron thiocyanate and pyridyl appended derivatives of tetrathiacalix[4]arene and tetramercaptotetrathiacalix[4]arene

© ISUCT Publishing. The combination of three pyridyl appended tetrathiacalix[4]arene (TCA) and tetramercaptotetrathiacalix[4]arene (TMTCA) derivatives in 1,3-alternate imposed conformation behaving as neutral tectons with octahedral FeII(NCS)2 complex as a metallatecton, leads to the formation of new coordination networks. Whereas the tecton 4, a tetrasubstituted TCA derivative (pyridyl in ortho position), leads to a 2D grid-like network, for the other two tectons 5 and 6, the formation of 3D diamond-like architectures is observed

The Problems of Applied Models of Classification of Objects on Mammograms in Breast Cancer Screening

This article discusses the problem of the methods used to classify objects on a mammogram

Chironomid Fauna of the Lakes from the Pechora River Basin (East of European part of Russian Arctic): Ecology and Reconstruction of Recent Ecological Changes in the Region

We investigated chironomid fauna of surface sediments and a short sediment core (Bol’shoy Kharbey Lake) from Pechora river basin, Northern Russia. Twenty three investigated lakes have thermokarst, glacial or floodplain origin and are characterised by low mineralization, mostly hydrocarbon-calcium type of water and low concentration of nutrients. Most of the lakes have circumneutral pH around ≤7 and only two lakes are slightly more acidic with pH ≤ 6. Ninety six chironomid taxa were identified in the surface sediments. Distribution of chironomids in the studied region is driven by continentality, mean TJuly and рН. Chironomid communities from the core of the B. Kharbei Lake demonstrate the highest similarity with the fauna of the deeper lakes of the glacial origin. The glacial lakes have the highest indices of continentality and the lowest winter temperatures within the investigated data set. The chironomid fauna of the glacial lakes is composed of the profundal, oligotrophic and cold-stenotherm taxa. The fauna of the floodplain and thermokarst lakes is more closely related to TJuly and is composed of littoral and phytophilic taxa of meso – or eutrophic waters and moderate temperature conditions. The fauna of the acidic thermokarst lakes considerably differs from the other lakes. Chironomid communities here are represented by tolerant to acidification taxa, and by the typically littoral and shallow water acid-tolerant taxa that apparently also can tolerate acidification. Studied sediment record covers ca last 200 years. The reconstructed TJuly during the entire period remain slightly below the modern temperatures. From 1970 reconstructed TJuly shows steady increase to the modern level. The reconstructed water depths (WDs) of the lake are higher than today till 1980. The highest WDs are reconstructed for ca 1970. After that the WDs gradually decrease to the modern level. Changes of the WDs are most probably related to changes in the precipitation rate

Molecular tectonics: On the formation of 1-D silver coordination networks by thiacalixarenes bearing nitrile groups

Two new p-tert-butylthiacalix[4]arene derivatives 2 and 3 decorated at the lower rim with four nitrile groups have been prepared and structurally characterised in the crystalline phase. The two ligands, differing by the length of the spacer between the calix moiety and the nitrile group, adopt the 1,3-alternate conformation in the solid state. The ligand 3 bearing four (CH2)3CN fragments behaves as a tecton in the presence of silver salts (AgX, X = BF4, PF6 or SbF6) and leads to the formation of analogous 1-D linear coordination networks. The tecton 3 acts as a bischelate unit and bridges consecutive silver cations adopting a tetrahedral coordination geometry. Anions and solvent molecules occupy the free space between networks and exhibit no specific interactions with the cationic architecture. © The Royal Society of Chemistry

Molecular tectonics: Anion control of dimensionality and connectivity in meta-pyridyl appended tetramercaptotetrathiacalix[4]arene based silver coordination networks

The combination of the same organic tecton 1, a meta-pyridyl appended tetramercaptotetrathiacalix[4]arene in 1,3-alternate conformation offering four pyridyl units and eight thioether groups, with three silver salts AgX (X = BF4 -, NO3 - and SbF6 -) leads, under identical conditions (concentration, temperature and solvent system), to the formation of different silver coordination networks. Both the connectivity and the dimensionality of the three silver coordination networks depend on the nature of the anion used as a counter ion. Whereas the weakly coordinating BF4 - anion does not participate in the formation of the non-tubular 1D coordination network, the coordinating NO 3 - anion is bound to the metal cation and this leads to the formation of a tubular 1D silver coordination network. In both cases, the eight S atoms of the tecton 1 do not take part in the binding of the cation. In marked contrast, when the SbF6 - anion is used as a counter ion, the organic tecton 1 behaves as a tetrakismonodentate through its four meta-pyridyl moieties and as a bischelating unit of the SCCS type leading thus to the formation of a porous 3D diamondoid-type network. © 2014 The Royal Society of Chemistry