Character of electron reflection at a normal metal-Peierls semiconductor boundary

The reflection of electrons incident from a normal metal on the boundary of the metal with a quasi-one-dimensional conductor containing a charge-density wave (CDW) is investigated theoretically. It is shown that the reflection is not of an Andreev character, as it was suggested earlier, but rather of a Bragg character. This is due to the fact that the CDW is actually an electronic crystal, and its wave vector is a reciprocal lattice vector of the electronic crystal. The ratio of the intensities of the standard and Bragg reflection depends on the phase of the CDW.Comment: 9 pages, no figures, revte

Results of experiments for the detection of lunar ionosphere carried out on the first moon's artificial satellite /Luna-10/

Lunik X experiments to detect lunar ionospher

Infrared band intensities of 1,2-dibromoethane in solutions: Electrostatic effect and influence of hydrogen bonding on the conformational equilibrium

The conformational equilibrium of 1,2-dibromoethane (DBE) in various media (vapor phase, liquid, and solutions in n-hexane, carbon tetrachloride, toluene, carbon disulfide, bromoform, acetone, nitromethane, deuterated acetonitrile and deuterated dimethylsulfoxide) has been studied by IR absorption spectra. The enthalpy differences between trans (t) and gauche (g) conformers (ΔHo) were determined from the dependencies of 1n(It/Ig) upon T-1, where It and Ig are the integrated intensities of the bands, belonging to different conformers. The values RT · 1n(It/Ig) and (R · 1n (It/Ig) + ΔHo/T) obtained at 296 K were used as measures of the free enthalpy (ΔGo) and entropy differences of the conformers (ΔSo) respectively, when considering their changes with solvent. To minimize the errors due to solvent and temperature effects on the IR-band absorption coefficients, four different band pairs of trans and gauche conformers were investigated. Good correlations between ΔGo, ΔHo and the function of dielectric permitivity of the medium (0.5 -( -1)/(2 + 1))1/2 were observed for all solvents except toluene. Significant changes of ΔSo with the media have been found: they cover more than 1.5 cal mol-1 K-1 when going from the vapor phase to polar solvents. The ΔSo values correlate with ΔHo ones (compensation effect); the slope of the dependence (ΔΔSo/ΔΔHo) = (1.0 ± 0.3) · 10-3 K-1 is close to those determined earlier for 1,2-dichloro- and bromofluoro-ethanes, trans-1,2-dichlorocyclohexane and o-iodophenol. The overall integrated intensities in the CH2-stretching (αA/B(str), 3200-2700, cm-1) and deformational (αA/B(def), 1550-1300, cm-1) regions were measured for neat DBE and its solutions in CCl4, CD3CN and (CD3)2SO. The αA/B(str) value noticeably increases when going from CCl4 to proton acceptor solvents, while the αA/B(def) does not depend on the solvent. These results are interpreted within the framework of the formation of weak hydrogen bonds between CH2-groups of DBE and proton acceptor groups of the solvents. The enthalpies of specific interaction of DBE with CD3CN and (CD3)2SO were estimated using the 'intensity rule'. These values are about 1 kcal mol-1. Nevertheless, poor correlation between ΔHo, ΔGo and basicity parameters of the solvents indicate the minor effect of the H-bond formation on the conformational equilibrium of DBE

High-frequency oscillations in low-dimensional conductors and semiconductor superlattices induced by current in stack direction

A narrow energy band of the electronic spectrum in some direction in low-dimensional crystals may lead to a negative differential conductance and N-shaped I-V curve that results in an instability of the uniform stationary state. A well-known stable solution for such a system is a state with electric field domain. We have found a uniform stable solution in the region of negative differential conductance. This solution describes uniform high-frequency voltage oscillations. Frequency of the oscillation is determined by antenna properties of the system. The results are applicable also to semiconductor superlattices.Comment: 8 pages, 3 figure

Reaction of benzoyl and trichloroacetyl isocyanates with some three-membered heterocycles

1. Benzoyl isocyanate reacts with epichlorohydrin and thioepichlorohydrin to give linear isomers. 2. The benzoyl and trichloroacetyl isocyanates react with cyclohexene sulfide to give both cyclic and linear isomers. 3. Benzoyl isocyanate reacts with propylene sulfide to give both the cyclic and the linear isomer. © 1972 Consultants Bureau, a division of Plenum Publishing Corporation

Magnetic field and plasma inside and outside of the Martian magnetosphere

Simultaneous magnetic and plasma measurements, carried out by wide angle plasma detectors in the Mars environment, are compared in order to identify regions with significantly different physical properties. Magnetograms and ion spectra indicate changes in the magnetopause and magnetosphere of Mars that are associated with the dynamic pressure effect of the solar wind

Dependence of the intensity of 2,4,6-trinitrotoluene-induced mutagenesis on the physiological state of salmonella typhimurium tester strains

The dependence of the mutagenic potential of 2,4,6-trinitrotoluene (TNT) on the growth phase of the Salmonella typhimurium tester strains TA100 and TA98 is shown. The mutagenic potential proved to be maximal for log-phase cultures, being higher with strain TA100 than TA98. The amount of TNT absorbed by bacteria in the first minutes of contact varied, depending on culture age, and was the largest at the beginning of the exponential growth phase. A direct relation between the number of microbial cells and the amount of TNT absorbed from the medium was shown. The analysis of infrared (IR) spectra of cells after a 3-min contact with TNT, demonstrated that, at physiological temperatures, 2.4% of the original amount of TNT was present in cells of the tester strain in an unaltered form, while, at a lowered temperature, this value was 10.3%. Thus, the retardation of physiological processes in the cell changes the intensity of mutagen absorption and transformation. It is emphasized that an accurate assessment of mutagenicity should take into account the physiological state of tester bacteria

Low-temperature conductivity of quasi-one-dimensional conductors: Luttinger liquid stabilized by impurities

A new non-Fermi-liquid state of quasi-one-dimensional conductors is suggested in which electronic system exists in a form of collection of bounded Luttinger liquids stabilized by impurities. This state is shown to be stable towards interchain electron hopping at low temperatures. Electronic spectrum of the system contains zero modes and collective excitations of the bounded Luttinger liquids in the segments between impurities. Zero modes give rise to randomly distributed localized electronic levels, and long-range interaction generates the Coulomb gap in the density of states at the Fermi energy. Mechanism of conductivity at low temperatures is phonon-assisted hopping via zero-mode states. At higher voltages the excitations of Luttinger liquid are involved in electron transport, and conductivity obeys power-law dependence on voltage. The results provide a qualitative explanation for recent experimental data for NbSe3 and TaS3 crystals.Comment: 12 pages, 1 figur