Diffusion-controlled generation of a proton-motive force across a biomembrane

Respiration in bacteria involves a sequence of energetically-coupled electron and proton transfers creating an electrochemical gradient of protons (a proton-motive force) across the inner bacterial membrane. With a simple kinetic model we analyze a redox loop mechanism of proton-motive force generation mediated by a molecular shuttle diffusing inside the membrane. This model, which includes six electron-binding and two proton-binding sites, reflects the main features of nitrate respiration in E. coli bacteria. We describe the time evolution of the proton translocation process. We find that the electron-proton electrostatic coupling on the shuttle plays a significant role in the process of energy conversion between electron and proton components. We determine the conditions where the redox loop mechanism is able to translocate protons against the transmembrane voltage gradient above 200 mV with a thermodynamic efficiency of about 37%, in the physiologically important range of temperatures from 250 to 350 K.Comment: 26 pages, 4 figures. A similar model is used in arXiv:0806.3233 for a different biological system. Minor changes in the Acknowledgements sectio

Large temperature dependence of the Casimir force at the metal-insulator transition

The dependence of the Casimir force on material properties is important for both future applications and to gain further insight on its fundamental aspects. Here we derive a general theory of the Casimir force for low-conducting compounds, or poor metals. For distances in the micrometer range, a large variety of such materials is described by universal equations containing a few parameters: the effective plasma frequency, dissipation rate of the free carriers, and electric permittivity in the infrared range. This theory can also describe inhomogeneous composite materials containing small regions with different conductivity. The Casimir force for mechanical systems involving samples made with compounds that have a metal-insulator transition shows an abrupt large temperature dependence of the Casimir force within the transition region, where metallic and dielectric phases coexist.Comment: 23 pages, 9 figure

Nonuniform Self-Organized Dynamical States in Superconductors with Periodic Pinning

We consider magnetic flux moving in superconductors with periodic pinning arrays. We show that sample heating by moving vortices produces negative differential resistivity (NDR) of both N and S type (i.e., N- and S-shaped) in the voltage-current characteristic (VI curve). The uniform flux flow state is unstable in the NDR region of the VI curve. Domain structures appear during the NDR part of the VI curve of an N type, while a filamentary instability is observed for the NDR of an S type. The simultaneous existence of the NDR of both types gives rise to the appearance of striking self-organized (both stationary and non-stationary) two-dimensional dynamical structures.Comment: 4 pages, 2 figure

Quantum electrodynamics and photon-assisted tunnelling in long Josephson junctions

We describe the interaction between an electromagnetic field and a long Josephson junction (JJ) driven by a dc current. We calculate the amplitudes of emission and absorption of light via the creation and annihilation of quantized Josephson plasma waves (JPWs). Both, the energies of JPW quanta and the amplitudes of light absorption and emission, strongly depend on the junction's length and can be tuned by an applied dc current. Moreover, photon-assisted macroscopic quantum tunnelling in long Josephson junctions show resonances when the frequency of the outside radiation coincides with the current-driven eigenfrequencies of the quantized JPWs.Comment: 9 pages, 4 figure

Negative differential resistivity in superconductors with periodic arrays of pinning sites

We study theoretically the effects of heating on the magnetic flux moving in superconductors with a periodic array of pinning sites (PAPS). The voltage-current characteristic (VI-curve) of superconductors with a PAPS includes a region with negative differential resistivity (NDR) of S-type (i.e., S-shaped VI-curve), while the heating of the superconductor by moving flux lines produces NDR of N-type (i.e., with an N-shaped VI-curve). We analyze the instability of the uniform flux flow corresponding to different parts of the VI-curve with NDR. Especially, we focus on the appearance of the filamentary instability that corresponds to an S-type NDR, which is extremely unusual for superconductors. We argue that the simultaneous existence of NDR of both N- and S-type gives rise to the appearance of self-organized two-dimensional dynamical structures in the flux flow mode. We study the effect of the pinning site positional disorder on the NDR and show that moderate disorder does not change the predicted results, while strong disorder completely suppresses the S-type NDR.Comment: 10 pages, 1 table, 7 figure

Evolution of <I>Vibrio cholerae</I> El Tor and Detection of Their Gene-Variants in the Caucasus

, rstC genes), and 7 strains – to the genotype I. Genotypes I and II (genetically altered ones) are the hybrid variants of the El Tor biovar producing CT of the first type

Provision of the Preparedness and Management of Work of the Specialized Anti-Epidemic Team at the Premises of the Rospotrebnadzor Stavropol Anti-Plague Institute during the XXII Olympic and XI Paralympic Winter Games in Sochi

The paper contains the data on the management of work of the specialized anti-epidemic team (SAET) of the Stavropol Anti-Plague Institute during the XXII Olympic and XI Paralympic Winter Games (2014) in Sochi. Reviewed are the issues of SAET’s preparedness provision: staffing of the team, facility equipping, fitting with diagnostic preparations, professional training and development in view of the mass event mission - participation in interagency exercises, educational courses, seminars, and response drills. For the first time ever, SAET’s reinforced personnel comprised 60 specialists from research institutions and some other Rospotrebnadzor Organization. Provided was preparedness to perform laboratory diagnostics and indicate the agents of 82 nosological forms, including exotic ones. The team conducted investigations at the premises of the two facilities and bacteriological laboratory mounted on the trucks

Management of the Investigation and Detection of Legionellosis Agent in the Environmental Samples during the Preparation and Holding of the XXII Winter Olympics and XI Paralympics in Sochi

Provided are the data on the management and carrying out of the laboratory control over the hot-water supply systems of the sports venues and accommodation areas for the presence of Legionella pneumophila during the XXII Olympics and XI Paralympics in Sochi, 2014. Inspected have been 105 facilities. The samples from 37 of them showed positive. L. pneumophila DNA concentration varies between 2.19·102 and 3.92·107 genome equivalents (g.e.)/l. By means of bacteriological investigation detected have been legionella colonies in the water supply systems of 16 facilities, at one of the items - the loading is over 1·104 colony-forming units/l. Performed has been comparative analysis of the results obtained using PCR assay and bacteriological test. Based on the genotyping of 7 isolated strains serogroup 1 and 2 strains of 2-14 serogroups it is concluded that L. pneumophila strains circulating in the resort town Sochi are genetically heterogeneous