Absolute negative conductivity and zero-resistance states in two-dimensional electron systems: A plausible scenario

We present a model that provides a plausible explanation of the effect of zero-resistance and zero-conductance states in two-dimensional electron systems subjected to a magnetic field and irradiated with microwaves observed in a number of experiments and of the effect’s main features. The model is based on the concept of absolute negative conductivity associated with photon-assisted scattering of electrons on impurities. It is shown that the main features of the effect can be attributed to the interplay of different electron scattering mechanisms.     

Maxwell’s equations in the Majorana representation in a locally isotropic chiral medium

Maxwell’s equations in the Majorana representation are generalized to the case of a chiral medium. A relation between the dynamic variables and the parameters of a chiral medium is found. An expression for the current density 4-vector is obtained for the medium under consideration.     

Muon spin resonance and repolarization in amorphous silicon monoxide (a-SiO)

Studies of the muonium fractions in the amorphous oxide a-SiO have been carried out by RF resonance at TRIUMF, Canada and LF repolarization techniques at RAL, U.K. The resonance measurements confirm the presence of the interstitial Mu centre in this intermediate oxide of silicon. Analysis of the data gathered at RAL, using a recently-developed fitting technique, reveals that the Mu^* state is present here as well, but with lower relative fractions than in a-Si. However, as in the latter material, but in contrast to c-Si, this bond-centre species appears to be stable up to room temperature.     

Specular reflectance of cold-rolled aluminum surfaces

The specular reflectance of cold-rolled aluminum surface is studied using a fiber optic system. An approximation for the determination of surface roughness is presented.     

Fe2+/Fe3+ ratios in bottom sediments of some lakes in British Columbia,Canada

Fe²⁺/Fe³⁺ ratio versus sediment depth values have been determined for ten lakes in British Columbia. The values often reflect the local topography of the lakes, the weathering history of the deposited minerals, and the diagenesis of the minerals after deposition in the lake.     

Asymptotic expansions of integrals of two Bessel functions via the generalized hypergeometric and Meijer functions

Asymptotic expansions of certain finite and infinite integrals involving products of two Bessel functions of the first kind are obtained by using the generalized hypergeometric and Meijer functions. The Bessel functions involved are of arbitrary (generally different) orders, but of the same argument containing a parameter which tends to infinity. These types of integrals arise in various contexts, including wave scattering and crystallography, and are of general mathematical interest being related to the Riemann—Liouville and Hankel integrals. The results complete the asymptotic expansions derived previously by two different methods — a straightforward approach and the Mellin-transform technique. These asymptotic expansions supply practical algorithms for computing the integrals. The leading terms explicitly provide valuable analytical insight into the high-frequency behavior of the solutions to the wave-scattering problems.     

Analysis of fragrance compounds in blood samples of mice by gas chromatography, mass spectrometry, GC/FTIR and GC/AES after inhalation of sandalwood oil.

After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and alpha-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: alpha-santalol 6.1 ng/mL, beta-santalol 5.3 ng/mL and alpha-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with alpha-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively.     

Likelihood Ratio Tests for Principal Components

A particular class of tests for the principal components of a scatter matrix Σ is proposed. In the simplest case one wants to test whether a given vector is an eigenvector of Σ corresponding to its largest eigenvalue. The test statistics are likelihood ratio statistics for the classical Wishart model, and critical values are obtained parametrically as well as nonparametrically without making any assumptions on the eigenvalues of Σ. Still, the tests have asymptotic properties similar to those of classical procedures and are asymptotically admissible and optimal in some sense.