Phase-coherent transport in InN nanowires of various sizes

We investigate phase-coherent transport in InN nanowires of various diameters and lengths. The nanowires were grown by means of plasma-assisted molecular beam epitaxy. Information on the phase-coherent transport is gained by analyzing the characteristic fluctuation pattern in the magneto-conductance. For a magnetic field oriented parallel to the wire axis we found that the correlation field mainly depends on the wire cross section, while the fluctuation amplitude is governed by the wire length. In contrast, if the magnetic field is oriented perpendicularly, for wires longer than approximately 200 nm the correlation field is limited by the phase coherence length. Further insight into the orientation dependence of the correlation field is gained by measuring the conductance fluctuations at various tilt angles of the magnetic field.Comment: 5 pages, 5 figure

Interface dependence of the Josephson-current fluctuations in short SNS junctions

We discuss the dependence of the Josephson current correlations in mesoscopic superconductor/normal-conductor/superconductor (SNS) devices on the transparency of the superconductor/normal-conductor (SN) interfaces. Focusing on short junctions we apply the supersymmetry method to construct an effective field theory for mesoscopic SNS devices which is evaluated in the limit of highly and weakly transparent interfaces. We show that the two-point Josephson-current correlator differs by an universal factor 2 in these two cases.Comment: 5 pages, 1figure, version accepted by PR

Andreev reflection and strongly enhanced magnetoresistance oscillations in GaInAs/InP heterostructures with superconducting contacts

We study the magnetotransport in small hybrid junctions formed by high-mobility GaInAs/InP heterostructures coupled to superconducting (S) and normal metal (N) terminals. Highly transmissive superconducting contacts to a two-dimensional electron gas (2DEG) located in a GaInAs/InP heterostructure are realized by using a Au/NbN layer system. The magnetoresistance of the S/2DEG/N structures is studied as a function of dc bias current and temperature. At bias currents below a critical value, the resistance of the S/2DEG/N structures develops a strong oscillatory dependence on the magnetic field, with an amplitude of the oscillations considerably larger than that of the reference N/2DEG/N structures. The experimental results are qualitatively explained by taking Andreev reflection in high magnetic fields into account.Comment: 5 pages, 5 figure

Localized patterns and hole solutions in one-dimension extended sytem

The existence, stability properties, and bifurcation diagrams of localized patterns and hole solutions in one-dimensional extended systems is studied from the point of view of front interactions. An adequate envelope equation is derived from a prototype model that exhibits these particle-type solutions. This equation allow us to obtain an analytical expression for the front interaction, which is in good agreement with numerical simulations.Comment: 7 pages, 3 figure

Monte Carlo Modeling of Spin FETs Controlled by Spin-Orbit Interaction

A method for Monte Carlo simulation of 2D spin-polarized electron transport in III-V semiconductor heterojunction FETs is presented. In the simulation, the dynamics of the electrons in coordinate and momentum space is treated semiclassically. The density matrix description of the spin is incorporated in the Monte Carlo method to account for the spin polarization dynamics. The spin-orbit interaction in the spin FET leads to both coherent evolution and dephasing of the electron spin polarization. Spin-independent scattering mechanisms, including optical phonons, acoustic phonons and ionized impurities, are implemented in the simulation. The electric field is determined self-consistently from the charge distribution resulting from the electron motion. Description of the Monte Carlo scheme is given and simulation results are reported for temperatures in the range 77-300 K.Comment: 18 pages, 7 figure

Measurement of Rashba and Dresselhaus spin-orbit magnetic fields

Spin-orbit coupling is a manifestation of special relativity. In the reference frame of a moving electron, electric fields transform into magnetic fields, which interact with the electron spin and lift the degeneracy of spin-up and spin-down states. In solid-state systems, the resulting spin-orbit fields are referred to as Dresselhaus or Rashba fields, depending on whether the electric fields originate from bulk or structure inversion asymmetry, respectively. Yet, it remains a challenge to determine the absolute value of both contributions in a single sample. Here we show that both fields can be measured by optically monitoring the angular dependence of the electrons' spin precession on their direction of movement with respect to the crystal lattice. Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We apply our method to GaAs/InGaAs quantum-well electrons, but it can be used universally to characterise spin-orbit interactions in semiconductors, facilitating the design of spintronic devices

Transitional cell carcinoma of the bladder : histopathological and biological factors and prognosis

The main purpose of the studies reported in this thesis has been to determine the extent to which the behaviour of TCC can be predicted by histopathological and biological characteristics. The potential additional prognostic value of these factors was evaluated by combining them with other prognostic factors in multivariate analysis. In chapter 2 a two grade system of histological grading .. using simple histological criteria, is proposed. The interobserver variability of the WHO grading system and the two grade system is tested. The extent to which patient survival and progression free survival correlated with the two grade system, is evaluated. The additional value of grading is tested by combining it with other prognostic factors such as stage, age and mitotic index in multivariate analysis. In chapter 3 BM expression in TCC is described in an attempt to evaluate its use for the histopathological identification of microinvasion. Furthermore the usefulness of BM staining for the prediction of the clinical behaviour of TCC is assessed in comparison with grading, staging and ploidy. In chapter 4 the use of a two grade morphometrical grading system for prediction of the clinical behaviour of TCC is described. Also the heterogeneity in the WHO grade II tumours is evaluated using morphometry. In chapter 5 a study is reported in which it is determined whether image cytometry can provide useful parameters which can be used in the prediction of TCC behaviour. Special attention is given to the potential value of rare incidents, e.g. occasional cells with a very high DNA content. In chapter 6 a study is described concerning numerical chromosome aberrations in TCC as assessed by counting chromosomes in metaphase spreads. The modal number of chromosomes and the chromosomal range are used as potential prognostic factors in comparison with histological parameters. In chapter 7 "classical" metaphase chromosome counting is compared with interphase cytogenetics, especially in tumours having diploid and hyperdiploid DNA content. In chapter 8 The findings of these studies are discussed and general conclusions are draw

Covariant Lagrange multiplier constrained higher derivative gravity with scalar projectors

We formulate higher derivative gravity with Lagrange multiplier constraint and scalar projectors. Its gauge-fixed formulation as well as vector fields formulation is developed and corresponding spontaneous Lorentz symmetry breaking is investigated. We show that the only propagating mode is higher derivative graviton while scalar and vector modes do not propagate. Despite to higher derivatives structure of the action, its first FRW equation is the first order differential equation which admits the inflationary universe solution.Comment: Physics Letters B published version. LaTeX 12 page