The ATP-dependent generation of membrane potential by sub-bacterial vesicles from the marine bacterium, Vibrio alginolyticus

AbstractAddition of ATP leads to the accumulation of the permeant anion PCB− by sub-bacterial vesicles from Vibrio alginolyticus. This accumulation is caused by Δψ generation by ATPase, the effect being inhibited by CCCP, gramicidin D and DCCD. Δψ values may be increased by incubation of sub-bacterial vesicles at room temperature and with the protein fraction isolated according to Beechey et al. [(1975) Biochem. J. 148, 533–537] from another portion of the sub-bacterial vesicles. Δψ generation is observable only in the presence of Mg2+ at high concentrations (optimum ≈ 30 mM). Proceeding from experimental data we assume that Mg2+ reduces passive H+ conductivity of the vesicle membranes. Thus, a Δψ-generating ATPase has been shown for the first time in V. alginolyticus membranes

Stress concentration in ultra-thin coating with undulated surface profile

The uniaxial loading of an isotropic film-substrate system with a sinusoidal surface profile and planar interface is considered under plain strain conditions. We for- mulate the corresponding boundary value problem involving two-dimensional constitutive equations for bulk materials and one-dimensional equations for membrane-type surface and interface with the extra elastic constants as well as the residual surface stresses. The mixed boundary conditions consist of the generalized Young–Laplace equations and rela- tions describing the continuous of displacements across the surface and interphase regions. Using the linear perturbation technique combined with the Goursat–Kolosov complex po- tentials and the superposition principle, the original boundary value problem is reduced to the analytical solution of the integral equations system

Interfacial stresses in bimaterial composites with nanosized interface relief

The paper compares analytical and numerical solutions for two-dimensional solid mechanics problems of elastic bimaterial composites with a nanosized interface relief that arises on a boundary between two bulk layers and on an interface of a nearly circular inclusion. It is supposed that the uniform stress state takes place at infinity. Here, we use Gurtin–Murdoch model in which interphase domains are represented as negligibly thin layers ideally adhering to the bulk phases. Static boundary conditions at the interface are formulated according to the generalized Laplace–Young law. To solve corresponding boundary value we use first-order boundary perturbation method based on Goursat–Kolosov complex potentials. To examine the perturbation results, we use a finite element calculations

КОМПЛЕКСНИЙ АНАЛІЗ ІНВЕСТИЦІЙНОЇ ПРИВАБЛИВОСТІ ПІДПРИЄМСТВ В КОНТЕКСТІ ФІНАНСОВОГО ЗАБЕЗПЕЧЕННЯ РОЗВИТКУ ПІДПРИЄМСТВ

The article presents the preconditions and the subject field of the complex analysis of the investment attractiveness of enterprises, oriented on the formation of information that satisfies the interests of various interest groups. The methodical approach to the complex analysis of investment attractiveness of enterprises is proposed, which is based on an integrated assessment, which combines indicators of investment attractiveness assessment in three levels: countries, regions, enterprises. The results of the approbation of the proposed approach to a comprehensive analysis of investment attractiveness on the example of enterprises of the Lugansk region are presented and factors are to be considered when making decisions regarding investing and forming parameters of the strategy of financial regulation of enterprise development. The system of indicators of investment attractiveness of the region is refined and the expediency of using the methods of rating analysis using the indices of investment attractiveness of the countries is substantiated. On the basis of the analysis of direct foreign investment inflows, the ranking of Lugansk region is determined and conclusions are drawn regarding the investment attractiveness of the region.В статье раскрыты предпосылки и предметное поле комплексного анализа инвестиционной привлекательности предприятий, ориентированного на формирование информации, которая удовлетворяет интересы различных заинтересованных групп. Предложенный методический подход к комплексному анализу инвестиционной привлекательности предприятий основывается на интегральной оценке, объединяющей индикаторы оценки инвестиционной привлекательности по трем уровням: страны, регионы, предприятия. Приведены результаты апробации предложенного подхода к комплексному анализу инвестиционной привлекательности на примере предприятий Луганского региона и выявлены факторы, которые необходимо учитывать при принятии решений об инвестировании и формировании параметров стратегии финансового регулирования развития предприятий. Уточнена система показателей инвестиционной привлекательности региона и обоснована целесообразность использования методов рейтингового анализа с использованием индексов инвестиционной привлекательности стран. На основе анализа поступления прямого иностранного инвестирования определен рейтинг Луганской области и сделаны выводы относительно инвестиционной привлекательности региона.В статті розкрито передумови та предметне поле комплексного аналізу інвестиційної привабливості підприємств, орієнтованого на формування інформації, яка задовольняє інтереси різних зацікавлених груп. Запропоновано методичний підхід до комплексного аналізу інвестиційної привабливості підприємств, який базується на інтегральній оцінці, що поєднує індикатори оцінки інвестиційної привабливості за трьома рівнями: країни, регіони, підприємства. Наведено результати апробації запропонованого підходу до комплексного аналізу інвестиційної привабливості на прикладі підприємств Луганського регіону та виявлено фактори, які необхідно враховувати при прийнятті рішень щодо інвестування та формування параметрів стратегії фінансового регулювання розвитку підприємств. Уточнена система показників інвестиційної привабливості регіону та обґрунтовано доцільність методів рейтингового аналізу з використанням індексів інвестиційної привабливості країн. На основі аналізу надходження прямого іноземного інвестування визначено рейтинг Луганської області та зроблені висновки щодо інвестиційної привабливості регіону

Interference effects in electronic transport through metallic single-wall carbon nanotubes

In a recent paper Liang {\it et al.} [Nature {\bf 411}, 665 (2001)] showed experimentally, that metallic nanotubes, strongly coupled to external electrodes, may act as coherent molecular waveguides for electronic transport. The experimental results were supported by theoretical analysis based on the scattering matrix approach. In this paper we analyze theoretically this problem using a real-space approach, which makes it possible to control quality of interface contacts. Electronic structure of the nanotube is taken into account within the tight-binding model. External electrodes and the central part (sample) are assumed to be made of carbon nanotubes, while the contacts between electrodes and the sample are modeled by appropriate on-site (diagonal) and hopping (off-diagonal) parameters. Conductance is calculated by the Green function technique combined with the Landauer formalism. In the plots displaying conductance {\it vs.} bias and gate voltages, we have found typical diamond structure patterns, similar to those observed experimentally. In certain cases, however, we have found new features in the patterns, like a double-diamond sub-structure.Comment: 15 pages, 4 figures. To apear in Phys. Rev.

Pairing of bosons in the condensed state of the boson-fermion model

A two component model of negative U centers coupled with the Fermi sea of itinerant fermions is discussed in connection with high-temperature superconductivity of cuprates, and superfluidity of atomic fermions. We examine the phase transition and the condensed state of this boson-fermion model (BFM) beyond the ordinary mean-field approximation in two and three dimensions. No pairing of fermions and no condensation are found in two-dimensions for any symmetry of the order parameter. The expansion in the strength of the order parameter near the transition yields no linear homogeneous term in the Ginzburg-Landau-Gor'kov equation and a zero upper critical field in any-dimensional BFM, which indicates that previous mean-field discussions of the model are flawed. Normal and anomalous Green's functions are obtained diagrammatically and analytically in the condensed state of a simplest version of 3D BFM. A pairing of bosons analogous to the Cooper pairing of fermions is found. There are three coupled condensates in the model, described by the off-diagonal single-particle boson, pair-fermion and pair-boson fields. These results negate the common wisdom that the boson-fermion model is adequately described by the BCS theory at weak coupling.Comment: 7 pages, 4 figure

Real space inhomogeneities in high temperature superconductors: the perspective of two-component model

The two-component model of high temperature superconductors in its real space version has been solved using Bogoliubov-de Gennes equations. The disorder in the electron and boson subsystem has been taken into account. It strongly modifies the superconducting properties and leads to local variations of the gap parameter and density of states. The assumption that the impurities mainly modify boson energies offers natural explanation of the puzzling positive correlation between the positions of impurities and the values of the order parameter found in the scanning tunnelling microscopy experiments.Comment: 19 pages, IOPP style include

Superfluid transition temperature in a trapped gas of Fermi atoms with a Feshbach resonance

We investigate strong coupling effects on the superfluid phase transition in a gas of Fermi atoms with a Feshbach resonance. The Feshbach resonance describes a composite quasi-Boson, which can give rise to an additional pairing interaction between the Fermi atoms. This attractive interaction becomes stronger as the threshold energy of the Feshbach resonance two-particle bound state is lowered. In a recent paper, we showed that in the uniform Fermi gas, this tunable pairing interaction naturally leads to a BCS-BEC crossover of the Nozi`eres and Schmitt-Rink kind, in which the BCS-type superfluid phase transition continuously changes into the BEC-type as the threshold energy is decreased. In this paper, we extend our previous work by including the effect of a harmonic trap potential, treated within the local density approximation (LDA). We also give results for both weak and strong coupling to the Feshbach resonance. We show that the BCS-BEC crossover phenomenon strongly modifies the shape of the atomic density profile at the superfluid phase transition temperature Tc, reflecting the change of the dominant particles going from Fermi atoms to composite Bosons. In the BEC regime, these composite Bosons are shown to first appear well above Tc. We also discuss the "phase diagram" above Tc as a function of the tunable threshold energy. We introduce a characteristic temperature T* describing the effective crossover in the normal phase from a Fermi gas of atoms to a gas of stable molecules.Comment: 43 pages, 13 figures (submitted to PRA