Exact and approximate results for the Anderson impurity model

This paper provides exact and rigorous upper and lower bounds to the ground state energy of the Single Impurity Anderson Model in the limit of infiniteU. The upper bound approximates the ground state energy very well and the corresponding state may be used as a starting point for further investigations. The energy spectrum of the Single Impurity Anderson Model is calculated exactly for a special non-trivial model density of states describing the bare band electrons. All approaches introduced here are compared to this exact result and to other ground state energy calculations.     

Electrohydrodynamic instabilities in nematic liquid crystals under dichotomous parametric modulation

The onset of EHD instabilities in nematic liquid crystals driven by parametric modulation is investigated starting with the one-dimensional linear model of Dubois-Violette. The superposition of a constant electric field with a dichotomous (stochastic or periodic) field as well as the superposition of two dichotomous stochastic fields (pregaussian noise) are considered in detail. The experimentally observed discontinuous behaviour of the threshold (direct transition towards chaos) above a critical strength of the driving field and the dependence of the threshold curve on the correlation time of the noise can be explained qualitatively. Experiments to complete the phase diagram are proposed.     

Method for quantitative determination of allapinine in Aconitum leucostomum

Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 436–438, May–June, 1989.     

Linear optics of polarization sheets

We develop a theory in which thin films or monolayers of strongly polarizable molecules are described as linear polarization sheets. We show that this concept in combination with the transfer matrix method allows a transparent derivation of the transmission and reflection properties of a composite interface.     

High resolution Mössbauer spectroscopy with67Zn in metallic systems

The high energy resolution of the 93.3 keV Mössbauer transition in⁶⁷Zn is used to investigate changes of s-electron density at the Zn nucleus in Cu-Zn alloys with special emphasis on the α-phase and on Zn-metal itself. We observe the presence of short-range order in α-brass with only four different Cu-Zn configurations, instead of the expected binomial distribution. In Zn metal, no change of center shift was observed when crossing the superconducting phase transition. The tremendous anisotropy of the Lamb-Mössbauer factor, as well as the temperature shift found for hexagonal Zn metal, demonstrate that the 93.3 keV resonance is also extremely sensitive to lattice dynamical effects. Our results, as well as specific heat data, are quantitatively described by an extended Debye model characterized by two Debye temperatures, θ_⊥ and θ_‖, which correspond to the lattice vibrations perpendicular and parallel to thec axis, respectively.     

Lifetime measurements in Pt and the shape coexistence picture

Lifetimes for levels in the yrast band of ¹⁸⁴Pt have been measured up to spin 16⁺ using the recoil distance technique. The B(E2) values exhibit a marked increase in going from spin 2 to 10, consistent with a proposal that two bands of different deformations are mixing at low spin. This provides further support for shape coexistence occuring at low excitation energies in this region.     

Direct clean-up and analysis of ribonucleosides in physiological fluids

We describe the group-selective separation and quantification of unmodified, modified and hypermodified ribonucleosides in physiological fluids (urine, serum) by on-line multidimensional high-performance affinity chromatography (HPAC)-reversed-phase liquid chromatography (RPLC). The excretion levels and patterns of ribonucleosides such as N1-methyladenosine, N1-methylinosine, N2-methylguanosine, N2-dimethylguanosine, N6-carbamoylthreonyladenosine and 2-pyridone-5-carboxamido-N-ribofuranoside were determined in urines from a control group and from patients with different diseases. The HPAC-RPLC method applied represents a powerful tool, e.g. as a non-invasive screening test, a method to investigate disorders in ribonucleoside and/or RNA metabolism, a method for drug monitoring during nucleoside chemotherapy, and a method to study renal ribonucleoside reutilization.