Exchange interaction and oscillations of the magnetization of the electron gas in a quantum cylinder

The exchange energy of the electron gas on a cylindrical surface in a constant magnetic field has been calculated. Analytical formulas describing the contribution of the exchange interaction into oscillations of the magnetization of the electron gas in a quantum cylinder have been obtained. It is shown that the magnetic response of the system exhibits Aharonov-Bohm oscillations for both degenerate and Boltzmann electron gases.     

Integrals over moduli spaces, ground ring, and four-point function in minimal Liouville gravity

Directly evaluating the correlation functions in 2D minimal gravity requires integrating over the moduli space. For degenerate fields, the higher equations of motion of the Liouville field theory allow converting the integrand to a derivative, which reduces the integral to boundary terms and the so-called curvature contribution. The latter is directly related to the vacuum expectation value of the corresponding ground-ring element. The action of this element on the cohomology related to a generic matter primary field is evaluated directly in terms of the operator product expansions of the degenerate fields. This allows constructing the ground-ring algebra and evaluating the curvature term in the four-point function. We also analyze the operator product expansions of the Liouville “logarithmic primaries” and calculate the relevant logarithmic terms. Based on this, we obtain an explicit expression for the four-point correlation number of one degenerate and three generic matter fields. We compare this integral with the numbers obtained from the matrix models of 2D gravity and discuss some related problems and ambiguities. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 147, No. 3, pp. 339–371, June, 2006.     

Structural and end‐group effects on bulk and surface properties of hyperbranched poly(urea urethane)s

The hydroxy end groups of aromatic and aliphatic hyperbranched poly‐(urea urethane)s prepared with an AA* + B*B₂ one‐pot method were modified with phenylisocyanate, butylisocyanate, and stearylisocyanate. The success of the modification reaction was verified with ¹H NMR and IR spectroscopy. Linear model poly‐(urea urethane)s were prepared, too, for comparison. The bulk properties of OH functionalized hyperbranched poly(urea urethane)s, compared with those of linear analogues and modified hyperbranched poly(urea urethane)s, were studied with differential scanning calorimetry, thermogravimetric analysis, and temperature‐dependent Fourier transform infrared measurements. Transparent and smooth thin films could be prepared from all polymer samples and were examined with a light microscope, a microglider, and an atomic force microscope. The properties of the polymer surface were examined by measurements of the contact angle and zeta potential. For all samples, the properties were mainly governed by the strong interactions of the urea and urethane units within the backbone, whereas the influence of the nature of the end groups and of the branched structure was reduced in comparison with other hyperbranched polymer systems. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3376–3393, 2005     

On resonance phototunneling and photoelectric properties ofpInSb-nCdTe heterojunction

Photoelectric properties and current-voltage characteristics of_pInSb-_nCdTe heterojunction have been studied as a function of_nCdTe layer thickness. Spectral dependence of photoconductivity has been found, as well as the junction field penetration domain in_nCdTe. Various mechanisms of charge separation are considered: resonance phototunneling mechanism, and absorption mechanism with further tunneling through the barrier, which explains the character of spectral dependence for the photoconductivity both beyond the maximum of spectral dependence and beyond edge of fundamental absorption for_pInSb. By the photoconductivity fall-off we have determined the concentration of impurity N_D, which stays in good agreement with the N_D value determined from measurements of field penetration depth. Possibilities of extending the photosensitivity to higher wavelengths range are discussed, by variation of impurities concentrations N_A and N_D, and by means of the external electrical field.     

Multielemental analysis of metallurgical samples by thermal neutron activation

Instrumental neutron activation analysis (INAA) was applied to investigated a total of 16 samples of raw materials, intermediate and final products involved in metallurgical processes in Romanian Iron and Stell works Sidex Galatzy: iron ores and pellets from different regions of the world, cast iron, slag and steels. A series of chemical elements was determined in the analyzed samples: Al, As, Ce, Co, Cr, Fe, La, Mn, Na, Sc, Sm, V, W. A qualitative discussion regarding the passing of from elements with different chemical affinity for oxygen compared to that of iron, from the raw materials to slag or to finite products is presented.     

Conformal geometry of surfaces in Lorentzian space forms

We study the conformal geometry of an oriented space-like surface in three-dimensional Lorentzian space forms. After introducing the conformal compactification of the Lorentzian space forms, we define the conformal Gauss map which is a conformally invariant two parameter family of oriented spheres. We use the area of the conformal Gauss map to define the Willmore functional and derive a Bernstein type theorem for parabolic Willmore surfaces. Finally, we study the stability of maximal surfaces for the Willmore functional.Dedicated to Professor T.J. WillmoreSupported by an FPPI Postdoctoral Grant from DGICYT Ministerio de Educación y Ciencia, Spain 1994 and by a DGICYT Grant No. PB94-0750-C02-02     

Novel synthesis of thieno[2,3‐b]pyridine and substituted 2‐thienylthiourea derivatives as antibiotic agents

Derivatives of thieno[2,3‐b]pyridine, 2‐thienylthiourea, 2‐thienylurea, 2‐thienylacetamide incorporating the 2‐phthalimidomethyl moiety have been synthesized. The synthesized compounds were then investigated for antibacterial activity against Escherichia coli, Bacillus subtilis and Staphylococcus aureus. The compounds were also investigated for antifungal activity against Aspergillus niger and Fusarium oxysporium. The structures of the newly synthesized compounds have been established on the basis of their analytical and spectral data.