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.     

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.     

Holographic spectrum dividers for the UV spectral range

We have theoretically and experimentally studied the possibility of using nonlinear recording of holographic mirrors for creating a spectrum divider capable of spatially separating wavelengths in the spectral region of 290–330 nm.     

Image contrast enhancement for two-photon fluorescence microscopy in a turbid medium

Image contrast enhancement is investigated for two-photon excitation fluorescence images of a microscopic sample that is buried underneath a turbid medium. The image contrast, which deteriorates rapidly with sample depth because of scattering loss, is enhanced by an increase in the average excitation power of the focused Gaussian (the TEM(00) mode) beam according to a compensation relation that has been derived by use of a Monte Carlo analysis of the scattering problem. A correct increase in the excitation power results in a detected fluorescence signal that remains invariant with sample depth. The scheme is demonstrated on images of DAPI-stained nuclei cells viewed underneath a suspension of 0.105-mum-diameter polystyrene spheres.     

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.     

Bulge-Forming miRNases Cleave Oncogenic miRNAs at the Central Loop Region in a Sequence-Specific Manner

The selective degradation of disease-associated microRNA is promising for the development of new therapeutic approaches. In this study, we engineered a series of bulge-loop-forming oligonucleotides conjugated with catalytic peptide [(LeuArg)₂Gly]₂ (BC–miRNases) capable of recognizing and destroying oncogenic miR-17 and miR-21. The principle behind the design of BC–miRNase is the cleavage of miRNA at a three-nucleotide bulge loop that forms in the central loop region, which is essential for the biological competence of miRNA. A thorough study of mono- and bis-BC–miRNases (containing one or two catalytic peptides, respectively) revealed that: (i) the sequence of miRNA bulge loops and neighbouring motifs are of fundamental importance for efficient miRNA cleavage (i.e., motifs containing repeating pyrimidine–A bonds are more susceptible to cleavage); (ii) the incorporation of the second catalytic peptide in the same molecular scaffold increases the potency of BC–miRNase, providing a complete degradation of miR-17 within 72 h; (iii) the synergetic co-operation of BC–miRNases with RNase H accelerates the rate of miRNA catalytic cleavage by both the conjugate and the enzyme. Such synergy allows the rapid destruction of constantly emerging miRNA to maintain sufficient knockdown and achieve a desired therapeutic effect.     

Mo/Ni and Ni/Ta–W–N/Ni thin-film contact layers for (Bi,Sb)<Subscript>2</Subscript>Te<Subscript>3</Subscript>-based intermediate-temperature thermoelectric elements

We have examined the possibility of utilizing thin-film contact layers for producing reliable Ohmic contacts to proposed intermediate-temperature (Bi,Sb)₂Te₃-based thermoelectric materials with improved thermoelectric properties, which allow the working temperature range to be extended to 600 K. Three contact configurations have been produced by ion-plasma magnetron sputtering: a single Ni layer, Mo/Ni bilayer, and Ni/Ta–W–N/Ni three-layer system. It has been shown that reliable contacts can be produced using Mo/Ni and Ni/Ta–W–N/Ni layers, which prevent interdiffusion between the materials to be joined and ensure good adhesion to the thermoelectric element.