Transport implications of Fermi arcs in the pseudogap phase of the cuprates

We derive the fermionic contribution to the longitudinal and Hall conductivities within a Kubo formalism, using a phenomenological Greens function which has been previously developed to describe photoemission data in the pseudogap phase of the cuprates. We find that the in-plane electrical and thermal conductivities are metallic-like, showing a universal limit behavior characteristic of a d-wave spectrum as the scattering rate goes to zero. In contrast, the c-axis resistivity and the Hall number are insulating-like, being divergent in the same limit. The relation of these results to transport data in the pseudogap phase is discussed.Comment: 3 pages, 2 figure

Josephson current noise above Tc in superconducting tunnel junctions

Tunnel junction between two superconductors is considered in the vicinity of the critical temperature. Superconductive fluctuations above Tc give rise to the noise of the ac Josephson current although the current itself is zero in average. As a result of fluctuations, current noise spectrum is peaked at the Josephson frequency, which may be considered as precursor of superconductivity in the normal state. Temperature dependence and shape of the Josephson current noise resonance line is calculated for various junction configurations.Comment: 8 pages, 2 figure

Magnetoconductivity of low-dimensional disordered conductors at the onset of the superconducting transition

Magnetoconductivity of the disordered two- and three-dimensional superconductors is addressed at the onset of superconducting transition. In this regime transport is dominated by the fluctuation effects and we account for the interaction corrections coming from the Cooper channel. In contrast to many previous studies we consider strong magnetic fields and various temperature regimes, which allow to resolve the existing discrepancies with the experiments. Specifically, we find saturation of the fluctuations induced magneto-conductivity for both two- and three-dimensional superconductors at already moderate magnetic fields and discuss possible dimensional crossover at the immediate vicinity of the critical temperature. The surprising observation is that closer to the transition temperature weaker magnetic field provides the saturation. It is remarkable also that interaction correction to magnetoconductivity coming from the Cooper channel, and specifically the so called Maki-Thompson contribution, remains to be important even away from the critical region.Comment: 4 pages, 1 figur

Coulomb drag in quantum circuits

We study drag effect in a system of two electrically isolated quantum point contacts (QPC), coupled by Coulomb interactions. Drag current exhibits maxima as a function of QPC gate voltages when the latter are tuned to the transitions between quantized conductance plateaus. In the linear regime this behavior is due to enhanced electron-hole asymmetry near an opening of a new conductance channel. In the non-linear regime the drag current is proportional to the shot noise of the driving circuit, suggesting that the Coulomb drag experiments may be a convenient way to measure the quantum shot noise. Remarkably, the transition to the non-linear regime may occur at driving voltages substantially smaller than the temperature.Comment: 6 pages, 2 figure

Relaxation and edge reconstruction in integer quantum Hall systems

The interplay between the confinement potential and electron-electron interactions causes reconstructions of Quantum Hall edges. We study the consequences of this edge reconstruction for the relaxation of hot electrons injected into integer quantum Hall edge states. In translationally invariant edges, the relaxation of hot electrons is governed by three-body collisions which are sensitive to the electron dispersion and thus to reconstruction effects. We show that the relaxation rates are significantly altered in different reconstruction scenarios.Comment: 8 pages, 3 figure

Protein retention on plasma-treated hierarchical nanoscale gold-silver platform

Dense arrays of gold-supported silver nanowires of about 100 nm in diameter grown directly in the channels of nanoporous aluminium oxide membrane were fabricated and tested as a novel platform for the immobilization and retention of BSA proteins in the microbial-protective environments. Additional treatment of the silver nanowires using low-temperature plasmas in the inductively-coupled plasma reactor and an atmospheric-pressure plasma jet have demonstrated that the morphology of the nanowire array can be controlled and the amount of the retained protein may be increased due to the plasma effect. A combination of the neutral gold sublayer with the antimicrobial properties of silver nanowires could significantly enhance the efficiency of the platforms used in various biotechnological processes

Оценка влияния схемы «винт в кольце» на взлетные характеристики летательного аппарата

Проаналізовано деякі аспекти розрахунку аеродинамічних характеристик літального апарата з поворотними гвинтами на кінцях крила. Проведено порівняння двох вибраних компонувальних схем. Приведено графічні залежності змін аеродинамічних коефіцієнтів, тягових характеристик гвинтів двох вибраних схем на всіх етапах зльоту літака.Air transport is the fastest means of transportation. However, for example, doubling cruising speed of flight increases its average ground speed only 10-15%. This is because a lot of time spent on such regimes as takeoff, landing, maneuvering on the ground, and so on. Since the bulk of air traffic is carried away from the 300 to 1000 km, take off and landing can be up to 50% of the length of the flight. So one of the ways to solve pressing tasks outlined is to build an aircraft that combines quality, speed horizontal flight aircraft and helicopters take off and landing. For the first time the technique of calculating aerodynamic characteristics of the aircraft vertical takeoff and landing small size for rational choice of its parameters in order to achieve the required performance testing. We consider a model airplane with rotary screws at the ends of the wings. This combination provides the benefits of a helicopter, namely the possibility of vertical takeoff and landing and hovering at a certain height in the air, with the benefits of the plane - much greater speed and flight range. The main problem of this aircraft is to ensure the stability and controllability during mode transition from vertical to horizontal flight and vice versa. To determine the required parameters propulsion Comparative calculations generated by aircraft with different layout schemes. Research of mass characteristics to determine the advantages and disadvantages of each scheme. The materials performed the study, the results of calculations of aerodynamic characteristics of the designed aircraft vertical takeoff and landing at different tilt angles of attack and thrust vector and at a speed of zero to switch to horizontal flight.Проанализированы некоторые аспекты расчета аэродинамических характеристик летательного аппарата с поворотными винтами на концах крыла. Проведено сравнение двух выбранных компоновочных схем. Приведены графические зависимости изменения аэродинамических коэффициентов, тяговых характеристик винтов двух выбранных схем на всех этапах взлета самолета