Structural peculiarities and electrical properties of multicomponent oxide crystals. Alkali ion conductors

Electrical and dielectric properties of anisotropic, “pure” and rare earth doped, K₅Bi(MoO₄)₄ (KBMO), β-BaB₂O₄ (BBO), and CsLiB₆O₁₀ (CLBO) single crystals are studied. Cationic conductivity by alkali ions is found in these crystals. Anisotropy of their electrical and dielectric properties is examined. Relations between the structure and transport mechanisms are discussed. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 6, pp. 679–686. The article is published in the original. Published by report at IX Conference “Fundamental Problems of Solid State Ionics”, Chernogolovka, 2008.     

The relationship between the kinetic data of the low-temperature thermolysis and the heats of explosion of inorganic azides

The primary chemical processes of the thermal decomposition and detonation change of inorganic azides possessing explosive character is considered by means of the linear relationship between the activation energies, E, of the initial stage of low-temperature thermolysis, and the heats of explosion of these substances. Also, the possibility of applying E values in the estimation of the initiation capability of azides is considered.     

Production of fructosyltransferase in mechanically stirred and air-lift bioreactors

Aureobasidium pullulans cells were cultivated in a 3 dm³ stirred bioreactor to optimize the production of fructosyltransferase (FTase). Batch experiments were focused on the influence of the initial sucrose concentration (150–350 g dm^?3), sodium nitrate concentration (10–25 g dm^?3), and stirring rate (180–540 min^?1) on the process. It was found that the FTase specific activity per cell mass was positively influenced by the conditions that impeded the cell growth such as higher sucrose concentrations or lower oxygen transfer rates. Higher content of inorganic nitrogen substrate slightly increased the overall FTase production. The presence of fructose moiety-containing saccharides in the cultivation medium was observed to be indispensable for FTase production. An addition of a concentrated sucrose solution in the 40th cultivation hour therefore essentially resumed the FTase production. Finally, scale-up experiments were performed in 12 dm³ and 100 dm³ mechanically stirred bioreactors and in 20 dm³ and 60 dm³ air-lift bioreactors.     

Partitioning of organic compounds in phases imitating the headgroup and core regions of phospholipid bilayers

Solvation free energies of drugs, peptides, and other small molecules in the core and headgroup regions of phospholipid bilayers determine their conformations, accumulation, and transport properties. The transfer free energy includes the energy terms for the formation of a cavity for the solute, the interactions of the solute with phospholipids, electrostatic interactions of the solute with the membrane, and dipole potentials and entropy terms. The interaction energies with phospholipids can be estimated by correlating the partitioning in surrogate solvent systems and in the bilayer. As the headgroup surrogate, we use diacetylphosphatidylcholine (DAcPC), the acetylated headgroup of the most abundant mammalian phospholipid, phosphatidylcholine, which forms a homogeneous solution with acceptable viscosity when mixed with water in ratios similar to those in the fully hydrated bilayer. The two-phase system of n-hexadecane (C16) as the core surrogate and hydrated DAcPC was used to monitor partitioning of 16 nonionizable compounds. On the bilogarithmic scale, the C16/DAcPC partition coefficients correlate neither with those in the C16/water and 1-octanol/water systems nor with their difference, which is frequently used as a parameter of hydrogen bonding for prediction of the bilayer location of the solutes. The C16/DAcPC system provides a satisfactory emulation of the solvation properties of the bilayer regions, as reflected in correct predictions of the bilayer location for those of the studied chemicals, for which this information is available.     

Spectrally and Time-Resolved Fluorescence Imaging of 22-NBD-Cholesterol in Human Peripheral Blood Mononuclear Cells in Chronic Kidney Disease Patients

The interaction of the fluorescent probe 22-NBD-cholesterol with membranes of human peripheral blood mononuclear cells (PBMC) was tested by time- and spectrally resolved fluorescence imaging to monitor the disturbance of lipid metabolism in chronic kidney disease (CKD) and its treatment with statins. Blood samples from healthy volunteers (HV) and CKD patients, either treated or untreated with statins, were compared. Spectral imaging was done using confocal microscopy at 16 spectral channels in response to 458 nm excitation. Time-resolved imaging was achieved by time-correlated single photon counting (TCSPC) following excitation at 475 nm. The fluorescence of 22-NBD-cholesterol was mostly integrated into plasmatic membrane and/or intracellular membrane but was missing from the nuclear region. The presence of two distinct spectral forms of 22-NBD-cholesterol was uncovered, with significant variations between studied groups. In addition, two fluorescence lifetime components were unmasked, changing in CKD patients treated with statins. The gathered results indicate that 22-NBD-cholesterol may serve as a tool to study changes in the lipid metabolism of patients with CKD to monitor the effect of statin treatment.     

Mechanism of copolymerization of acrylamide with a polymerizable surfactant

Associating polymers have been prepared by radical copolymerization in water of acrylamide with a micelleforming cationic polymerizable surfactant. To estimate the locus of initiation, the polymerizations were carried out in the presence of initiators and radical inhibitors of various solubilities (water-soluble or oil-soluble), and the decay of inhibitor concentration has been monitored by electron spin resonance spectroscopy. Conversion–time curves simultaneously determined. The experimental data have been interpreted by taking into account the concentration and lifetime of the different radical species (primary radicals, oligoradicals, inhibitors), their partitioning between the micelles and the aqueous continuous phase, and the dynamics of the micellar system. Analysis of the data provided some insight into the copolymerization mechanism of these micellar systems.     

New assignment algorithms for the multi-depot vehicle routing problem

This paper considers the design and analysis of algorithms for the multi-depot vehicle routing problem with time windows (MDVRPTW). Given the intrinsic difficulty of this problem class, approximation methods of the type ‘cluster first, route second’ (two-step approaches) seem to offer the most promise for practical size problems. After describing six heuristics for the cluster part (assignment of customers to depots) an initial computational study of their performance is conducted. Finding, as expected, that the heuristics with the best results (in terms of the routing results) are those with the largest computational efforts.     

New Cu(II), Co(II), and Ni(II) complexes with thieno[2,3-b]pyridine and 2-methylthieno[2,3-b]pyridine as ligands: Synthesis and crystal structures

Although thienopyridines attract attention because of their biological activities, they have not been used as ligands in coordination compounds. Thieno[2,3-b]pyridine was prepared by known procedures; by reduction of 2-nitrothiophene, and reaction of the resulting 2-thienyl ammonium salt with malondialdehyde tetramethylacetal in the presence of zinc chloride. The same procedure was used for the preparation of a new derivative, 2-methylthieno[2,3-b]pyridine, starting from 2-methyl-5-nitrothiophene. The thienopyridines were used in the synthesis of coordination compounds. Chlorides, isothiocyanates, acetates, and chloroacetates of copper(II), nickel(II), or cobalt(II) were used as starting salts. The prepared complexes were characterized by elemental analysis and FT IR. Structures of the four complexes were determined by single-crystal X-ray diffraction analysis. Presented at the 1st International Conference “Applied Natural Sciences” on the occasion of the 10th anniversary of the University of Ss. Cyril and Methodius, Trnava, 7–9 November 2007.     

Radical polymerization in homogenized butyl acrylate emulsion

The addition of a small amount of monomer strongly decreased the clouding temperature of nonionic emulsifier (Tween 20). The clouding temperature of the Tween 20 aqueous solution was independent of emulsifier concentration but it strongly varied in the presence of monomer. The decreased cloud temperature was attributed to the penetration of monomer molecules into the interfacial layer that increased the flocculation of microdroplets (monomer-swollen micelles). The surface tension of homogenized ((mini)emulsion) butyl acrylate aqueous emulsion was much smaller than that estimated at or above CMC of Tween 20. The polymerization rate vs. conversion curve of the (mini)emulsion deviates from the three rate intervals typical for the emulsion polymerisation. The shape of the rate-conversion curve reminds more the four rate intervals curve. Interval 2 is overlapped with the initial maximal rate and rate shoulder at higher conversion. The initial maximal polymerization rate (R_p,max,1) is attributed to the abrupt increase in polymer particles, the polymerization under monomer saturated condition and emulsifier containing peroxide groups (Tw_peroxid 20). The rate of emulsion polymerization of BA initiated by ammonium peroxodisulphate (APS) is ca. by one order of magnitude larger than that of blank polymerization (without APS). The second maximal rate (rate shoulder) can result from the gel effect. The more pronounced increase in R_p,max,1 with Tw 20 concentration supports the presence of peroxide groups. The slight dependence of R_p,max,2 on [Tw 20] for both APS and DBP (dibenzoyl peroxide) is discussed in terms of the depressed radical entry rate into the close packed surface later of polymer particles. The low activation energy is attributed to the decreased barrier for entering radicals into the polymer particles with increasing temperature. This is more pronounced with the accumulation of covalently bound emulsifier moieties (resulting from Tw_peroxid 20) at the particle surface. The ratio of the final number of polymer particles to the initial number of monomer droplets (N_p/N_drop) promotes the partial monomer droplet nucleation. The dye approach indicates that the degree of depletion of monomer droplets decreases from the classical emulsion polymerization to the polymerization in pre-homogenized emulsions and the emulsion polymerization with a prolonged-emulsification interval.