13 research outputs found
Bogoliubov - de Gennes versus Quasiclassical Description of Josephson Structures
The applicability of the quasiclassical theory of superconductivity in
Josephson multi-layer structures is analyzed. The quasiclassical approach is
compared with the exact theory based on the Bogoliubov - de Gennes equation.
The angle and energy resolved (coarse-grain) currents are calculated using both
techniques. It is shown that the two approaches agree in geometries
after the coarse-grain averaging. A quantitative discrepancy, which exceeds the
quasiclassical accuracy, is observed when three or more interfaces are present.
The invalidity of the quasiclassical theory is attributed to the presence of
closed trajectories formed by sequential reflections on the interfaces.Comment: revtex4,12 pages, 12 figure
Quasiclassical theory of superconductivity: a multiple interface geometry
The purpose of the paper is to suggest a new method which allows one to study
multiple coherent reflection/transmissions by partially transparent interfaces
(e.g. in multi-layer mesoscopic structures or grain boundaries in high-Tc's) in
the framework of the quasiclassical theory of superconductivity. It is argued
that typically the trajectory of the particle is a simply connected tree (no
loops) with knots, i.e. the points where interface scattering events occur and
ballistic pieces of the trajectory are mixed. A linear boundary condition for
the 2-component trajectory "wave function" which factorizes matrix (retarded)
Green's function, is formulated for an arbitrary interface, specular or
diffusive. To show the usage of the method, the current response to the vector
potential (the total superfluid density rho_s) of a SS' sandwich with the
different signs of the order parameter in S and S', is calculated. In this
model, a few percent of reflection by the SS' interface transforms the
paramagnetic response (rho_s < 0) created by the zero-energy Andreev bound
states near an ideal interface (see Fauchere et al. PRL, 82, 3336 (1999),
cond-mat/9901112), into the usual diamagnetic one (rho_s >0).Comment: Extended abstract submitted to "Electron Transport in Mesoscopic
Systems", Satellite conference to LT22, Goteborg, 12-15 August, 1999. 2 pages
Minor changes + the text height problem fixe
XY model in small-world networks
The phase transition in the XY model on one-dimensional small-world networks
is investigated by means of Monte-Carlo simulations. It is found that
long-range order is present at finite temperatures, even for very small values
of the rewiring probability, suggesting a finite-temperature transition for any
nonzero rewiring probability. Nature of the phase transition is discussed in
comparison with the globally-coupled XY model.Comment: 5 pages, accepted in PR
Remote in vivo stress assessment of aquatic animals with microencapsulated biomarkers for environmental monitoring
Remote in vivo scanning of physiological parameters is a major trend in the development of new tools for the fields of medicine and animal physiology. For this purpose, a variety of implantable optical micro- and nanosensors have been designed for potential medical applications. At the same time, the important area of environmental sciences has been neglected in the development of techniques for remote physiological measurements. In the field of environmental monitoring and related research, there is a constant demand for new effective and quick techniques for the stress assessment of aquatic animals, and the development of proper methods for remote physiological measurements in vivo may significantly increase the precision and throughput of analyses in this field. In the present study, we apply pH-sensitive microencapsulated biomarkers to remotely monitor the pH of haemolymph in vivo in endemic amphipods from Lake Baikal, and we compare the suitability of this technique for stress assessment with that of common biochemical methods. For the first time, we demonstrate the possibility of remotely detecting a change in a physiological parameter in an aquatic organism under ecologically relevant stressful conditions and show the applicability of techniques using microencapsulated biomarkers for remote physiological measurements in environmental monitoring
Vertex overload breakdown in evolving networks
We study evolving networks based on the Barabasi-Albert scale-free network
model with vertices sensitive to overload breakdown. The load of a vertex is
defined as the betweenness centrality of the vertex. Two cases of load
limitation are considered, corresponding to that the average number of
connections per vertex is increasing with the network's size ("extrinsic
communication activity"), or that it is constant ("intrinsic communication
activity"). Avalanche-like breakdowns for both load limitations are observed.
In order to avoid such avalanches we argue that the capacity of the vertices
has to grow with the size of the system. An interesting irregular dynamics of
the formation of the giant component (for the intrinsic communication activity
case is also studied). Implications on the growth of the Internet is discussed.Comment: To appear in Phys. Rev.