The influence of phonons on the optical properties and the conductivity of quasi-one-dimensional metals

The frequency dependent conductivity σ(ω) completely taking into account the interaction between electrons is studied. The shape and the temperature dependence of optical absorption near the frequency of a molecular phonon activated due to the interaction with electrons are found. For a system with attractive sign of the e-e backward scattering amplitude g₁<0 an absorption edge near the gap 2Δ in the electronic spectrum is studied. A low frequency conductivity is discussed. The properties under consideration depend essentially on the magnitudes of e-e interactions and are critical to the sign of g₁.     

Contribution of superconducting grains and grain boundaries to the magnetoresistance of ceramic YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7 − δ</Subscript> high-temperature superconductors in weak magnetic fields

The current-voltage characteristics of granular YBa₂Cu₃O_6.95 high-temperature superconductor samples have been measured at a temperature of 77.3 K in external transverse magnetic fields H _ext with a strength of up to H _ext ≈ 500 Oe for low transport current densities (0.1 A/cm² ≤ j ≤ 0.6 A/cm²). The current-voltage characteristics obtained have been used to construct dependences of the magnetoresistance ρ on the quantities j (ρ(j) _Hext=const) and H _ext(ρ(H _ext) _{j = const}). It has been revealed that the current and field dependences of the magnetoresistance exhibit anomalies at H _ext ≥ H _c1g , where H _c1g is the lower critical field of superconducting grains. A comparative analysis of the dependences ρ(j)H _{ext = const} and ρ(H _ext) _{j = const} has made it possible to develop concepts regarding the influence of the processes of redistribution of the magnetic field between grain boundaries and superconducting grains on the transport and galvanomagnetic properties of granular high-temperature superconductors. It has been established that the field dependences of the magnetoresistance exhibit specific features associated with the beginning of penetration of Josephson vortices into grain boundaries in the magnetic field H _c1J and with the breaking of a continuous chain of Josephson junctions in the magnetic field H _c2J .     

The retention of some azoles in reversed-phase liquid chromatography

The influence of the structure-related physicochemical properties of derivatives of nitrogen-containing heterocyclic compounds on their retention under the conditions of reversed-phase liquid chromatography was studied. The dependence of the chromatographic retention of azole derivatives on the composition of the mobile phase was determined. The presence of azole protonated forms was substantiated by conductometric data.     

Wadge Degrees of Infinitary Rational Relations

We show that, from the topological point of view, 2-tape Büchi automata have the same accepting power as Turing machines equipped with a Büchi acceptance condition. The Borel and the Wadge hierarchies of the class RAT _ω of infinitary rational relations accepted by 2-tape Büchi automata are equal to the Borel and the Wadge hierarchies of ω-languages accepted by real-time Büchi 1-counter automata or by Büchi Turing machines. In particular, for every non-null recursive ordinal α, there exist some -complete and some -complete infinitary rational relations. And the supremum of the set of Borel ranks of infinitary rational relations is an ordinal which is strictly greater than the first non-recursive ordinal . This very surprising result gives answers to questions of Simonnet [39] and of Lescow and Thomas [30,43]. This paper is an extended version of a conference paper which appeared in the Proceedings of the 23rd International Symposium on Theoretical Aspects of Computer Science, STACS 2006, [19].     

Synthesis and gas separation properties of metathesis polynorbornenes with different positions of one or two SiMe3 groups in a monomer unit

The metathesis polymerization of 5,5-bis(trimethylsilyl)norbornene, 2,3-bis(trimethylsilyl)norbornadiene, and exo,endo-3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]non-7-ene with the catalysts WCl₆/1,1,3,3-tetramethyl-1,3-disilacyclobutane, RuCl₃/EtOH, and the Grubbs Ru-carbene complex Cl₂(PCy₃)₂Ru=CHPh has been studied. New polymers with yields of up to 98% and M _w = (2?39) × 10⁵ are prepared. New metathesis copolymers of 5-trimethylsilylnorbonene with 5-(hydroxymethyl)norbornene and 5-(trimethylsiloxymethyl)norbornene are synthesized in the presence of the Cl₂(PCy₃)₂Ru=CHPh catalyst with yields of 78 and 98%. The gas-permeability study of the above series of the metathesis polymers containing one or two Me₃Si substituents in each monomer unit shows that the introduction of the second SiMe₃ group markedly improves their transport characteristics. A change in the character of the backbone (polynorbornadiene, polytricyclononene) has a small effect on the permeability of the polymers. The metathesis polynorbornene with two vicinal SiMe₃ groups exhibits higher gas-permeability coefficients than its isomer with germinal substituents. The homopolymer of 5-trimethylsilylnorbornene is characterized by better transport parameters than its copolymers with -OSiMe₃ and -OH substituents.     

Application of the Monte Carlo method for spectrometer calibration to determine the surface activity of radionuclides deposited on the ground

The results of efficiency calibration and verification of the in situ method with application of a handheld spectrometer with high-purity germanium detector are presented. The conducted studies show that the calibration of spectrometer efficiency with the use of the Monte Carlo method can be applied for measurement of the surface activity of radionuclides deposited on the ground with an uncertainty of not more than 22%.     

Causal loop diagrams as a de-escalation technique

Escalation of commitment, the tendency of decision makers to keep on investing in losing courses of action, has been shown to be a costly decision bias that affects many areas of decision making. Even though escalation is a widely studied phenomenon, there has been comparatively little research on how to avoid this bias. The present study focuses on de-escalation of commitment and proposes that causal loop diagrams (CLDs) can help to decrease escalating commitment to a failing course of action. By means of an experiment, this study shows that using a CLD decreases escalation tendencies.