Phase transitions in K3AlF6

Phase transitions in the elpasolite-type K₃AlF₆ complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures , and . The α-K₃AlF₆ phase is stable below T₁ and crystallizes in a monoclinic unit cell with a=18.8588(2)Å, b=34.0278(2)Å, c=18.9231(1)Å, β=90.453(1)° (a=2a_c−c_c, b=4b_c, c=a_c+2c_c; a_c, b_c, c_c—the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T₁ and T₂. The γ polymorph is stable in the T₂<T<T₃ temperature range and has an orthorhombic unit cell with a=36.1229(6)Å, b=17.1114(3)Å, c=12.0502(3)Å (a=3a_c−3c_c, b=2b_c, c=a_c+c_c) at 250 °C and space group Fddd. Above T₃ the cubic δ polymorph forms with a_c=8.5786(4)Å at 400 °C and space group . The similarity between the K₃AlF₆ and K₃MoO₃F₃ compounds is discussed.     

Generic pairs of SU-rank 1 structures

For a supersimple SU-rank 1 theory T we introduce the notion of a generic elementary pair of models of T (generic T-pair). We show that the theory T^* of all generic T-pairs is complete and supersimple. In the strongly minimal case, T^* coincides with the theory of infinite dimensional pairs, which was used in (S. Buechler, Pseudoprojective strongly minimal sets are locally projective, J. Symbolic Logic 56(4) (1991) 1184–1194) to study the geometric properties of T. In our SU-rank 1 setting, we use T^* for the same purpose. In particular, we obtain a characterization of linearity for SU-rank 1 structures by giving several equivalent conditions on T^*, find a “weak” version of local modularity which is equivalent to linearity, show that linearity coincides with 1-basedness, and use the generic pairs to “recover” projective geometries over division rings from non-trivial linear SU-rank 1 structures.     

Cathode strip chamber for CMS ME1/1 endcap muon station

Seventy-six serial ME1/1 cathode strip chambers have been produced in Dubna. These chambers are the coordinate detectors of the first muon station of the CMS detector at CERN. This paper describes the design of the chamber, its main mechanical parameters, and the results of the cosmic ray test. The text was submitted by the authors in English.     

Ultra-Thin Gold Cluster Films by Langmuir–Blodgett-Techniques

The extraordinary electronic properties of the full-shell cluster Au₅₅(PPh₃)₁₂Cl₆ and its ligand modified derivatives make them one of the most attractive building blocks in future nanoelectronics. The reason is the ability to act as a single electron switch or transistor at room temperature. As a consequence of this knowledge, further developments to organize these quantum dots in two dimensions are necessary. In this study, the Langmuir–Blodgett (LB) technique has been applied to generate extended two-dimensionally organized arrangements of Au₅₅(PPh₃)₁₂Cl₆, Au₅₅[(cyclopentyl)₇Si₈O₁₂(CH₂)₃SH]₁₂Cl₆ and of Au₅₅(PhSH) _x Cl₆. Film formation was performed by spreading dichloromethane or pentane solutions of the clusters onto the water surface in a LB trough, followed by compression by means of a film balance. From the π-A isotherms exact cluster dimensions could be calculated from monolayers, except for Au₅₅[(cyclopentyl)₇Si₈O₁₂(CH₂)₃SH]₁₂Cl₆, the size of which resulted as too small. The reason is to be seen in the formation cluster double layers. Brewster angle microscopy (BAM) investigations of the thin films on the water surface, atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies of transferred films clearly demonstrated formation of densely packed monolayers and of double layers, respectively. These extended mono- and double layers are now available for electric investigations and the construction of layered systems. Those works are in progress. Dedicated to Professor Ilya Moiseev on the occasion of his 75th birthday.     

Monte Carlo phase diagram for diblock copolymer melts

A partial phase diagram is constructed for diblock copolymer melts using lattice-based Monte Carlo simulations. This is done by locating the order-disorder transition (ODT) with the aid of a recently proposed order parameter and identifying the ordered phase over a wide range of copolymer compositions (0.2相似文献   

Strong non-Noetherity of polynomial reduction

It is a well-known result by A. Reeves and B. Sturmfels that the reduction modulo a marked set of polynomials is Noetherian if and only if the marking is induced from an admissible term ordering. For finite sets of polynomials with a nonadmissible ordering, there is a constructive proof of the existence of an infinite reduction sequence, although a finite one might still be possible. On the base of our specialized software for combinatorics of monomial orderings, we have found some examples for which there is no finite reduction sequence. This is what we call “strong” non-Noetherity. Bibliography: 3 titles.     

Electropolymerization of pyrrole in acetonitrile as affected by the nature of substitute and deposition potential

We apply chronoamperometry and cyclic voltammetry to trace the effect of the deposition potential on morphological and redox properties of N-substituted polypyrrole films on platinum and ITO in acetonitrile solutions. The goal of these experiments is to check whether certain principle trends observed in the course of the film growth can be used to monitor the deposition process and to control the features of the fabricated polymer. We use STM for morphology characterization, and estimate the film thickness from its redox response in background solution. For titanocene-substituted pyrrole, we compare current transients data on the anodic electropolymerization and the monomer reduction, in order to estimate the mass transport contribution to the polymerization current within various time domains (0.1 ms–1,000 s). On the basis of all these observations, we conclude on the existence of four characteristic regions of deposition current transients and assign them to certain steps in the oligomers formation and the film growth. The region of the current growth is discussed as well in terms of traditional nucleation models.     

Synthesis and Pharmacological Evaluation of Novel 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole Derivatives as Promising Anxiolytic and Analgesic Agents

A number of novel 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole derivatives 2 were obtained by alkylation mainly in the 1H-tautomeric form of 2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole or its 8,9-dimethyl-substituted analog 4-chlorobenzyl bromide, 4-chloroacetic acid fluoroanilide, and 4-tert-butylphenacyl bromide in neutral medium. Compounds 3 were cyclized and synthesized earlier with 11-phenacyl-substituted diazepino[1,2-a]benzimidazoles upon heating in conc. HBr. The chemical structures of the compounds were clarified by using the ¹H Nuclear Magnetic Resonance Spectroscopy (¹H-NMR) technique. Anxiolytic properties were evaluated using the elevated plus maze (EPM) and open field (OF) tests. The analgesic effect of compounds was estimated with the tail flick (TF) and hot plate (HP) methods. Besides, possible the influence of the test compounds on motor activities of the animals was examined by the Grid, Wire, and Rotarod tests. Compounds 2d and 3b were the most active due to their prominent analgesic and anxiolytic potentials, respectively. The results of the performed in silico analysis showed that the high anxiolytic activity of compound 3b is explained by the combination of a pronounced interaction mainly with the benzodiazepine site of the GABA_A receptor with a prominent interaction with both the specific and allosteric sites of the 5-HT_2A receptor.