Ion migration in high-T c superconductors and the nature of the conducting state ind-wave superconductors

The available experimental data on the ion migration in superconducting Y-123 and Bi-2223 films under the effect of high transport currents are summarized. Irrespective of structural perfection, electrostimulated diffusion of heavy ions and oxygen gives rise to the formation of new, stable phases and partial degradation of superconductivity. A model taking into account the proximity of the superconducting, structural, and magnetic transitions in high-T _c materials is used to explain ion migration as the response of the system of ions and coherentd electrons to the external electric field. Thed-wave symmetry superconducting state is shown to possess combined, rotational + translational invariance, rotational symmetry being due to the motion of electrons in the curl field of the ions, playing the role of topological defects.     

Designing an effective management system for enterprises: Concepts and verification

In this article lean and agile manufacturing are considered as separate organizational strategies of enterprise management. Therefore, a model of these strategies for business situations as well as assigning modern concepts and methods of management to these strategies and business segments has been proposed. This model, called LABDM (lean agile business development model), has been provisionally verified in small‐ and medium‐sized enterprises from the gas engineering industry in the Wielkopolska province in Poland. In 17 enterprises of this industry the use of modern concepts and methods of management have been studied. With the help of the rough sets theory, a set of concepts and methods that are crucial for the effective enterprises has been identified. By comparing these concepts and methods to the LABDM, the model's rationality is proven. In conclusion, the LABDM can be used as a tool when considering a lean or agile strategy, and modern concepts and methods that are associated with these strategies. © 2008 Wiley Periodicals, Inc.     

Effect of solvation of metal cations on modification of synthetic fibres with them

It was found that in order to increase the amount of cations bound by a fibre, it is necessary to convert the cation from the hydrate form into complexes containing substances that have a plasticizing effect on the polymer as ligands. Based on the results of a study of solvation and complexation in modification of polyester fibres with chromium(III) cations, the basic factors that affect chemisorption of chromium (III) cations by the fibres are reported. __________ Translated from Khimicheskie Volokna, No. 2, pp. 22–24, March–April, 2008.     

Synthesis and Interfacial Activity of Novel Heterogemini Sulfobetaines in Aqueous Solution

Three new heterogemini sulfobetaines and their chloride salts were synthesised. The interfacial activities of the obtained chlorides in aqueous solution were studied by equilibrium and dynamic surface tension measurements. The critical micelle concentration, surface excess concentration, minimum area per surfactant molecule and standard Gibbs energy of adsorption as well as micelle lifetime and diffusion coefficient were determined. The adsorption properties and micelle lifetime of these compounds significantly depend on the length of alkyl chain. The critical micelle concentration decreases with increasing chain length of the compounds considered. The values of the diffusion coefficient of N‐alkyl‐N‐methyl‐N‐(3‐sulfopropyl)‐6‐(N‐alkyl‐N‐methylamino)hexylammonium chloride tend to decrease as the concentration is increased.     

Miyaura Borylation and One‐Pot Two‐Step Homocoupling of Aryl Chlorides and Bromides under Solvent‐Free Conditions

Solvent‐free protocols for Miyaura borylation and the one‐pot, two‐step homocoupling of aryl halides are reported for the first time. Bis(dibenzylideneacetone)palladium(0) [Pd(dba)₂] is an optimal source of palladium for Miyaura borylation, while for one‐pot two‐step homocoupling palladium(II) acetate [Pd(OAc)₂] gives highest yields. Aryl bromides are coupled most efficiently using the DPEphos ligand. Chlorides are coupled using XPhos. The developed protocols are robust, versatile and easily reproducible on a large scale.

     

Chemical composition and structure of the shell of fly ash non-perforated cenospheres produced from the combustion of the Kuznetsk coal (Russia)

The relationship between the composition and structure of the shell of low-density non-perforated cenospheres of fly ashes from the combustion of coal from the Kuznetsk Basin (Russia) at temperatures of 1500 and 1650 °C has been investigated. Narrow fractions of cenospheres of constant composition have been separated from concentrates with the use of the technological scheme including stages of hydrodynamic gravitational separation, grain-size classification, and magnetic separation. It has been established that the concentrations of the major components of the chemical composition of the products obtained are related by linear regression equations. In particular, the aluminosilicate composition of the non-perforated cenospheres with a low Fe₂O₃ concentration (2.5-3.5 wt.%) is described by two general regression equations [SiO₂] = 80 − 0.7·[Al₂O₃] and SiO₂/Al₂O₃ = 5.54 − 0.12·[Al₂O₃] with correlation coefficients of −0.98 and −0.99, respectively. In this case, narrow fractions of products with different Fe₂O₃ contents are characterized by nearly constant SiO₂/Al₂O₃ ratios. The shell structure has been investigated using scanning electron microscopy. It has been revealed that the outer and inner surfaces of globules are covered by a film with a thickness of 30-50 nm. The surface of magnetic cenospheres contains heterogeneous regions with extended linear ferrospinel aggregates of crystallites with sizes ranging from 50 to 1000 nm. It has been shown that the size of globules and the thickness and porosity of the shell in each series depend on the composition of the melt from which they are formed and on its viscosity. Nonmagnetic cenospheres are formed from the high-silica K-Al-Si melt with the SiO₂/Al₂O₃ ratio varying over a wide range (1.6-3.6). Narrow fractions of magnetic cenospheres formed at low temperatures (1500 °C) are characterized by nearly constant SiO₂/Al₂O₃ ratios. Globules of this type are formed from two immiscible high-silica K-Al-Si and Fe-Al-Si melts.     

The effect of red pigment on the amyloidization of yeast proteins

The intensity of amyloid-bound thioflavine T fluorescence was studied in crude lysates of yeast strains carrying mutations in the ADE1 or ADE2 genes and accumulating the red pigment (a result of polymerization of aminoimidazoleribotide), and in white isogenic strains--either adenine prototrophs or carrying mutations at the first stages of purine biosynthesis. We found that the red pigment leads to a drop of amyloid content. This result, along with the data on separation of protein polymers of white and red strains in PAGE, suggests that the red pigment inhibits amyloid fibril formation. The differences in transmission of the thioflavine T fluorescence pattern by cytoduction and in blot-hybridization of pellet proteins of red and white [PSI(+) ] strains with Sup35p antibodies confirmed this conclusion. Purified red pigment treatment also led to a decrease of fluorescence intensity of thioflavine T bound to insulin fibrils and to yeast pellet protein aggregates from [PSI(+) ] strains. This suggests red pigment interaction with amyloid fibrils. Comparison of pellet proteins from red and white isogenic strains separated by 2D-electrophoresis followed by MALDI analysis has allowed us to identify 48 pigment-dependent proteins. These proteins mostly belong to functional classes of chaperones and proteins involved in glucose metabolism, closely corresponding to prion-dependent proteins that we characterized previously. Also present were some proteins involved in stress response and proteolysis. We suppose that the red pigment acts by blocking certain sites on amyloid fibrils that, in some cases, can lead in vivo to interfere with their contacts with chaperones and the generation of prion seeds.     

Activation Enthalpies of Deformation-Induced Lattice Defects in Severe Plastic Deformation Nanometals Measured by Differential Scanning Calorimetry

Samples of 99.99 pct pure copper and nickel of 99.998 pct purity were deformed by high-pressure torsion (HPT) at different hydrostatic pressures, to different shear strains. Activation enthalpies (Q) were determined by differential scanning calorimetry (DSC) using Kissinger’s method. For the one annealing peak found in HPT Cu, Q amounts to Q = 0.78 to 0.48 eV depending on the shear strain applied. In the case of Ni, the activation enthalpies of the two annealing peaks were determined as Q = 0.65 eV and Q = 0.95 eV, respectively, with no obvious dependence on shear strain, although this has been indicated by the annealing peak temperatures. Applying defect specific analyses of the annealing peaks, it turned out that the larger Q value represents the annihilation of dislocations and agglomerates, while the smaller one reflects the annihilation of single or double vacancies. Concerning the strain dependence of the larger Q, two possible explanations have been discussed: (1) the annihilation of dislocations assisted by the strain-dependent density of vacancy agglomerates and (2) the annihilation of dislocations enhanced by a strain-dependent level of long-range internal stresses. Because of closer correlations of Q with external and internal stresses at very high shear strains, explanation (2) has been favored.     

Effect of doping with Nb and Dy on the heat capacity of Si

The heat capacity of undoped Si and Si doped with Nb (10¹⁸ cm^-3) and Dy (10¹⁷ cm^-3) was measured by differential scanning calorimetry (DSM-2M and Mettler instruments). The phase transition from diamond Si to the high-pressure phase Si II was found to occur in undoped Si between 550 and 650 K. No phase transition was observed in Si doped with Nb or Dy, indicating that the dopants strengthen the Si lattice, thereby impeding structural changes.