Transport in Bilayer Graphene: Calculations within a self-consistent Born approximation

The transport properties of a bilayer graphene are studied theoretically within a self-consistent Born approximation. The electronic spectrum is composed of $k$-linear dispersion in the low-energy region and $k$-square dispersion as in an ordinary two-dimensional metal at high energy, leading to a crossover between different behaviors in the conductivity on changing the Fermi energy or disorder strengths. We find that the conductivity approaches $2e^2/\pi^2\hbar$ per spin in the strong-disorder regime, independently of the short- or long-range disorder.Comment: 8 pages, 5 figure

Magneto-optical properties of multilayer graphenes

The magneto-optical absorption properties of graphene multilayers are theoretically studied. It is shown that the spectrum can be decomposed into sub-components effectively identical to the monolayer or bilayer graphene, allowing us to understand the spectrum systematically as a function of the layer number. Odd-layered graphenes always exhibit absorption peaks which shifts in proportion to sqrt(B), with B being the magnetic field, due to the existence of an effective monolayer-like subband. We propose a possibility of observing the monolayer-like spectrum even in a mixture of multilayer graphene films with various layers numbers.Comment: 9 pages, 7 figure

Tight--binding description of the quasiparticle dispersion of graphite and few--layer graphene

A universal set of third--nearest neighbour tight--binding (TB) parameters is presented for calculation of the quasiparticle (QP) dispersion of $N$ stacked $sp^2$ graphene layers ($N=1... \infty$) with $AB$ stacking sequence. The QP bands are strongly renormalized by electron--electron interactions which results in a 20% increase of the nearest neighbour in--plane and out--of--plane TB parameters when compared to band structure from density functional theory. With the new set of TB parameters we determine the Fermi surface and evaluate exciton energies, charge carrier plasmon frequencies and the conductivities which are relevant for recent angle--resolved photoemission, optical, electron energy loss and transport measurements. A comparision of these quantitities to experiments yields an excellent agreement. Furthermore we discuss the transition from few layer graphene to graphite and a semimetal to metal transition in a TB framework.Comment: Corresponding author: A. Gr\"uneis Tel.: +49 351 4659 519 e--mail: [email protected]

A Pulse Compression Ultrasonic Test Instrument and Its Applications

In recent years, so called “digital ultrasonic test instruments” have been commercially available. These conventional instruments employ electrical impulse excitation of ultrasonic probes. In this configuration, waveforms of ultrasonic pulses into a test object are determined only by the characteristics of probes. This means that variation of probe characteristics causes variation of evaluated results and reproducibility of evaluation is poor. Furthermore, some of the conventional instruments do not provide enough information required for quantitative nondestructive evaluation (QNDE) about a test object, since ultrasonic echo signals are A/D converted after an envelope detector in a receiver and only information of echo height and position is obtained

Magneto-Optical Studies of Exciton Effects in Layer-Type Semiconductors

Both experimental and theoretical works were performed with particular reference to a layer-type semiconductor, GaSe, for a coherent treatment of the exciton-like and the oscillatory Landau-like spectra appearing in a form of their combination in semiconductors in magnetic fields. The interband magneto-absorption and the Faraday rotation were measured in pulsed magnetic fields up to ～200 kOe at low temperatures. The theoretical analysis was based mainly on the exact solution for an extremely anisotropic semiconductor in the magnetic field of arbitrary intensity. The exciton effects are discussed in terms of the energy spectrum, the spectral intensity, and the spectral width by the use of the band parameters deduced from the experimental results

Deformed nuclear halos

Deformation properties of weakly bound nuclei are discussed in the deformed single-particle model. It is demonstrated that in the limit of a very small binding energy the valence particles in specific orbitals, characterized by a very small projection of single-particle angular momentum onto the symmetry axis of a nucleus, can give rise to the halo structure which is completely decoupled from the rest of the system. The quadrupole deformation of the resulting halo is completely determined by the intrinsic structure of a weakly bound orbital, irrespective of the shape of the core.Comment: LaTeX source (21 pages) and postscript file with figures (15 pages). Accepted to Nucl. Phys.

Inverse Correlation between Serum Levels of Selenoprotein P and Adiponectin in Patients with Type 2 Diabetes

Background: We recently identified selenoprotein P (SeP) as a liver-derived secretory protein that causes insulin resistance in the liver and skeletal muscle; however, it is unknown whether and, if so, how SeP acts on adipose tissue. The present study tested the hypothesis that SeP is related to hypoadiponectinemia in patients with type 2 diabetes. Methodology/Principal Findings: We compared serum levels of SeP with those of adiponectin and other clinical parameters in 36 patients with type 2 diabetes. We also measured levels of blood adiponectin in SeP knockout mice. Circulating SeP levels were positively correlated with fasting plasma glucose (r = 0.35, P = 0.037) and negatively associated with both total and high-molecular adiponectin in patients with type 2 diabetes (r = 20.355, P = 0.034; r = 20.367, P = 0.028). SeP was a predictor of both total and high-molecular adiponectin, independently of age, body weight, and quantitative insulin sensitivity index (b = 20.343, P = 0.022; b = 20.357, P = 0.017). SeP knockout mice exhibited an increase in blood adiponectin levels when fed regular chow or a high sucrose, high fat diet. Conclusions/Significance: These results suggest that overproduction of liver-derived secretory protein SeP is connected with hypoadiponectinemia in patients with type 2 diabetes

New Discrete Basis for Nuclear Structure Studies

A complete discrete set of spherical single-particle wave functions for studies of weakly-bound many-body systems is proposed. The new basis is obtained by means of a local-scale point transformation of the spherical harmonic oscillator wave functions. Unlike the harmonic oscillator states, the new wave functions decay exponentially at large distances. Using the new basis, characteristics of weakly-bound orbitals are analyzed and the ground state properties of some spherical doubly-magic nuclei are studied. The basis of the transformed harmonic oscillator is a significant improvement over the harmonic oscillator basis, especially in studies of exotic nuclei where the coupling to the particle continuum is important.Comment: 13 pages, RevTex, 6 p.s. figures, submitted to Phys. Rev.