Hall helps Ohm: some corrections to negative-U centers approach to transport properties of YBa2_2Cu3_3Ox_x and La2−x_{2-x}Srx_xCuO4_4

For broad oxygen and strontium doping ranges, temperature dependences (T-dependences) of the normal state resistivity \rho(T) of YBa_2Cu_3O_x (YBCO) and La_(2-x)Sr_xCuO_4 (LSCO) are calculated and compared to experiments. Holes transport was taken in the \tau-approximation, where \tau(T,\epsilon) is due to acoustic phonons. Besides, T-dependence of the chemical potential \mu(T) and effective carrier mass m* ~10-100 free electron masses, obtained by negative-U centers modelling the T-dependence of the Hall coefficient, were used to calculate \rho(T). In addition, it is demonstrated that anisotropy of the cuprates does not affect the calculated T-variation of neither Hall coefficient nor \rho, but only rescale their magnitudes by factors depending on combinations of m_ab and m_c.Comment: 4th International Conference Fundamental Problems of High-Temperature Superconductivity, Moscow-Zvenigorod (October 3-7, 2011) Submitted to J. Supercond. Nov. Magn.: after revision. Extension for Supercond. Sci. Technol. 24 075026 (2011), DOI: 10.1088/0953-2048/24/7/075026 Contains: 2 pages, 3 figure

Glass-metal nanocomposites with planar waveguides for biosensor applications

Abstract At the present time, optical properties of media containing nanoparticles (NPs) of noble metals is a subject of large number of studies [1]. The possibility of light excitation of localized surface plasmon resonance (LSPR) in metal NPs radically changes properties of dielectric media, due to optical absorption of visible range. The spectral position of LSPR can be controlled by modifying parameters of nanocomposite, giving a possibility to use this kind of media in device applications. Considerable attention is also drawn to nonlinear properties of such composites, particularly due to its high-speed nonlinear response Presented paper concerns the development of biosensor platform based on silver nanoparticles, synthesized in glasses of two types: in UV irradiated photo-thermo-refractive glasses and in sodium-borosilicate glasses treated in water atmosphere. Glasses with silver nanoparticles are good candidates for creation of biosensors employing the phenomenon of LSPR effect with planar waveguides circuits for excitation and for detection of plasmon resonance shift Two methods of creation of optical waveguides are examined such as thermal diffusion and ionexchange. The exploitation of planar waveguides in subsurface region allows inputting the light into the sensible part of the glass and facilitates the registration of the optical response of the glass. Two methods of optical waveguide creation are examined: by thermal diffusion and ionexchange. The configuration of localized surface plasmon resonance based biosensor is presented and discussed. The immobilization scheme of D-galactose/D-glucose binding protein on the glass is also presented

Study of semi-polar gallium nitride grown on m-sapphire by chloride vapor-phase epitaxy

In this study, we analyzed the result of the influence of the non-polar plane of a sapphire substrate on the structural, morphological, and optical properties and Raman scattering of the grown epitaxial GaN film. It was found that selected technological conditions for the performed chloride-hydride epitaxy let us obtain the samples of structurally qualitative semi-polar wurtzite gallium nitride with (11¯22) orientation on m-sapphire. Using a set of structural and spectral methods of analysis the structural, morphological, and optical properties of the films were studied and the value of residual bi-axial stresses was determined. A complex of the obtained results means a high structural and optical quality of the epitaxial gallium nitride film. Optimization of the applied technological technique in the future can be a promising approach for the growth of the qualitative GaN structures on m-sapphire substrates

Periodic actin structures in neuronal axons are required to maintain microtubules

Axons are the cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly-spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily-conserved, ubiquitous, highly-ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organisation and function, combining versatile Drosophila genetics with super-resolution microscopy and various functional readouts. Analyses with 11 different actin regulators and 3 actin-targeting drugs suggest PMS to contain short actin filaments which are depolymerisation resistant and sensitive to spectrin, adducin and nucleator deficiency - consistent with microscopy-derived models proposing PMS as specialised cortical actin. Upon actin removal we observed gaps in microtubule bundles, reduced microtubule polymerisation and reduced axon numbers suggesting a role of PMS in microtubule organisation. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilising protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerisation contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration

Warm-up spectroscopy of quadrupole-split nuclear spins in n-GaAs epitaxial layers

12 pages, 9 figuresThe efficiency of the adiabatic demagnetization of nuclear spin system (NSS) of a solid is limited, if quadrupole effects are present. Nevertheless, despite a considerable quadrupole interaction, recent experiments validated the thermodynamic description of the NSS in GaAs. This suggests that nuclear spin temperature can be used as the universal indicator of the NSS state in presence of external perturbations. We implement this idea by analyzing the modification of the NSS temperature in response to an oscillating magnetic field at various frequencies, an approach termed as the warm-up spectroscopy. It is tested in a n-GaAs sample where both mechanical strain and built-in electric field may contribute to the quadrupole splitting, yielding the parameters of electric field gradient tensors for 75As and both Ga isotopes, 69Ga and 71Ga