Thermal conductivity of NaCl loaded in regular arrays of nanovoids in a synthetic opal single crystal

Samples of opal + NaCl nanocomposites with 100 and 80% filling of first-order opal voids by sodium chloride have been prepared. Their effective thermal conductivities, κ_eff, were measured in the temperature interval 5–300 K. The lattice thermal conductivity of NaCl loaded in the opal voids, κ _ph ^op , was calculated from the measured κ_eff(T). The value of ph was found to be considerably smaller than the lattice thermal conductivity of bulk NaCl throughout the temperature interval studied. For T>20 K, this behavior of κ _ph ^op (T) is accounted for by the presence of specific defects that form in NaCl loaded in opal voids. For T<20 K, κ _ph ^op (T) is governed by boundary phonon scattering from bottlenecks in horn-shaped channels interconnecting the octahedral and tetrahedral first-order opal voids filled by sodium chloride. It was found that the value of κ _ph ^op (T) in this temperature region depends substantially on the dimensions of the bottlenecks, whose thicknesses are related to the amount of the cristobalite forming in a near-surface layer of the amorphous SiO₂ opal spheres in the course of preparation of the opal + NaCl nanocomposite.     

Thermal conductivity of HgSe loaded in the pore lattice of a synthetic opal single crystal

Samples of the opal + HgSe nanocomposite with 100% filling of the first-order opal pores by mercury selenide were prepared. The effective thermal conductivity κ_eff and electrical resistivity ρ_eff were measured in the temperature range T=5–200 K, and the thermopower coefficient α was measured in the interval 80–300 K. The coefficient α of HgSe in opal was shown to remain the same as that in bulk mercury selenide samples with similar carrier concentrations. The mechanism of carrier scattering in the HgSe loaded in opal also did not change. The total thermal conductivity κ _tot ⁰ and electrical resistivity ρ⁰ were isolated from κ_eff and ρ_eff, and the electronic (κ _e ⁰ ) and lattice (κ _ph ⁰ ) components of thermal conductivity of HgSe in opal were determined. The magnitude of κ _ph ⁰ was found to be considerably smaller than κ_ph of bulk HgSe with the same carrier concentration throughout the temperature interval studied (5–200 K). For T>20 K, this behavior of κ _ph ⁰ (T) is accounted for by the presence of specific impurities and defects forming in HgSe, and for T<20 K, by the onset of boundary scattering of phonons in the bottlenecks of the horn-shaped channels connecting first-order octahedral and tetrahedral opal pores loaded by mercury selenide.     

Synchrotron peak luminosity,black hole mass and Eddington ratio for SDSS flat-spectrum radio quasars

For a sample of 185 flat-spectrum radio quasars (FSRQs) constructed from the SDSS DR3 quasar catalog, we found a significant correlation between the synchrotron peak luminosity and both the black hole mass and Eddington ratio. This implies that the physics of its jet formation is not only tightly related with the black hole mass, but also with the accretion rate. We verify that the synchrotron peak luminosity can be a better indicator of jet emission than 5 GHz luminosity, through comparing the relationships between each of these two parameters and both black hole mass and Eddington ratio. The fundamental plane of black hole activity for our FSRQs is established as L _r ∝ L ^0.80±0.06_x M ^{−0.04±0.09}_bh with a weak dependence on black hole mass, however, the scatter is significant.

     

Structural and optical properties of Cu2ZnSn(S,Se)4 films obtained by magnetron sputtering of a Cu2ZnSn alloy target

Results of the study of structural and optical properties of Cu₂ZnSn(S,Se)₄ thin films obtained by sulfitation (selenization) of Cu₂ZnSn films which were sputtered by target direct current magnetron sputtering using a stoichiometric Cu₂ZnSn (99.99%) target are presented. It has been found that Cu₂ZnSn(S,Se)₄ thin films are polycrystalline with a grain size of ~60 nm. The optical bandgap of Cu₂ZnSnS₄ (E ^op _g = 1.65 eV) and Cu₂ZnSnSe₄ (R ^op _g = 1.2 eV) thin films have been determined.

     

On the theory of the diffraction of light by two parallel ultrasonic waves,one being then th harmonic of the other

Assuming the validity ofRaman andNath's preliminary theory, the amplitudes of the light diffracted by two parallel ultrasonic waves consisting of a fundamental tone and its n^th harmonic are compared in the following cases:

1. (1)

   the sound waves are superposed;

2. (2)

   the sound waves are situated side by side.

The diffraction patterns are approximately the same if the condition πnL/λ^*¦sin ?_s¦?1 is fulfilled, where sin?_s=?sλ/μ₀λ^*(s being an integer);λ is the wave-lenght of the incident light in vacuum, λ^* is the wave-lenght of the fundamental tone of the sound waves, μ₀ is the refractive index of the medium andL the width of the sound field. The good agreement between recent experiments ofMurty andRao in the arrangement of case (2) and theoretical results calculated in case (1) is thus justified. The theoretical confirmation of older experiments byPande, Pancholy andParthasarathy is thereby established at the same time.

     

Molecular pseudopotential calculations V

The equilibrium geometries, nuclear distances, wave functions and energies for the XY ²₊ , X₂Y⁺, Y₂H⁺ (X=Li, Na, K; Y=Rb, Cs), resp. the X₂H⁺, X₂Y⁺ (X, Y=Cu, Ag, Au) triatomic alkali ions, resp. noble metal ions, further the dissociation energies for the X₂Y⁺→X⁺+XY; XY ²₊ →Y⁺+XY and Y₂H⁺→Y⁺+YH processes are determined with the pseudopotential method. The calculations were performed using the Hellmann-type analytical potential with simple floating-type one-centre wave function.

     

Low-frequency dispersion of the effective transverse conductivity in inhomogeneous media in strong magnetic field

On crystalline silicon specimens with a nonuniform carrier concentration distribution produced by an optical method, a dispersion of the effective transverse conductivity σ _⊥ ^eff (ω) is observed near the frequency ω≈ω_c=τ _⊥ ^?1 ≡ε/4πσ _⊥ ^eff . At ω<ω_c, an anomalous transverse effective conductivity is observed: σ _⊥ ^eff (ω) is greater than the transverse conductivity of a homogeneous specimen σ _⊥ ^h (ω) (in the frequency range studied in the experiment σ _⊥ ^h (ω) = const). Near ω≈ω_c, the conductivity σ _⊥ ^eff decreases, and, at ω>ω_c it coincides with σ _⊥ ^h .     

Relative tensor calculus and the tensor time derivative

A relative tensor calculus is formulated for expressing equations of mathematical physics. A tensor time derivative operator ▽ _b ^a is defined which operates on tensors λ^ia...ib. Equations are written in a rigid, flat, inertial or other coordinate system a, altered to relative tensor notation, and are thereby expressed in general flowing coordinate systems or materials b, c, d, .... Mirror tensor expressions for ▽ _b ^a λ^ic...id and ▽ _b ^a λ_ic...id exist in a relative geometry G if and only if a rigid coordinate system a exists in G, where ▽ _b ^a λ^ic = λ _,0c ^ic + λ^kev _ckc ^aic + λ _kc ^ic v _b ^ckc , ▽_jcλ^ic = λ _,jc ^ic + λ^kcΓ _{jc kc} ^ie , and v _b ^aic is the velocity of b relative to a with components in c. These operators are convenient in theoretical analyses and can be incorporated into machine programs for the numerical solution of physical problems.     

Effect of anion of lithium salt on the property of lithium salt-epoxidized natural rubber polymer electrolytes

Lithium salt, LiX (where X = BF ₄ ^? , I^?, CF₃SO ₃ ^? , COOCF ₃ ^? or ClO ₄ ^? ), was incorporated into epoxidized natural rubber (ENR). Thin films of LiX-ENR polymer electrolytes (PEs) were obtained via solvent casting method. These electrolytes were characterized using SEM/X-mapping, FTIR, differential scanning calorimeter, thermogravimetry analysis, and impedance spectroscopy. The trend in thermal stability and ionic conductivity of LiX-ENR PEs follow LiBF₄ > > LiCF₃SO₃ ~ LiCOOCF₃ > LiI > > LiClO₄. The LiClO₄ hardly dissociates and formed LiClO₄ aggregates within the polymer matrix that resulted in a PE with low thermal stability and low ionic conductivity. The LiCF₃SO₃, LiCOOCF₃, and LiI, however, exert moderate interactions with the ENR, and their respective PEs exhibit moderate ionic conductivity and thermal property. The occurrence of epoxide ring opening and complexation or cross-linking reactions in and between the ENR chains that involve BF ₄ ^? ions have produced a LiBF₄-ENR PE with superior thermal property and ionic conductivity as compared to other PEs studied in this work.     

Paramagnetische Resonanz des dreiwertigen Gadoliniums in YPO4, YVO4 und YAsO4

The EPR spectra of Gd³⁺-doped isostructural single crystals of YPO₄, YVO₄, and YAsO₄ have been measured in X-band at room temperature and at nitrogen and helium temperatures. The zero-field splitting can be described by the five crystal-field parametersb ₂ ⁰ ,b ₄ ⁰ ,b _6/0,b ₄ ⁴ , and b ₆ ⁴ fitted to a tetragonal spin-Hamiltonian corresponding to the point symmetry D_2d of the Gd³⁺ site. The values ofg and b ₂ ⁰ vary significantly with host lattice and with temperature.     

Messung von Lebensdauern und relativen Besetzungszahlen angeregter Zustände des Wasserstoffatoms mit der Methode der Ionenstrahlspektroskopie

H ⁺₂ ions or protons, accelerated to energies between 80 and 300 keV, are sent through a thin carbon target. Light emitted by the excited atoms moving out of the foil with a definite velocity is analyzed using interference filters and a cooled photomultiplier. Intensities of theH _α,H _β, andH _γ lines are measured as functions of the distance from the foil. The data is analyzed with a computer program, which yields (in agreement with theory) mean lives of the hydrogen atom excited states involved, and the relative initial state populations of states belonging to the same principal quantum number. There is no indication of cascading.

     

Effect of the Lattice and Spin-Phonon Contributions on the Temperature Behavior of the Ground State Splitting of Gd<Superscript>3+</Superscript> in SrMoO<Subscript>4</Subscript>

The temperature behavior of the EPR spectra of the Gd³⁺ impurity center in single crystals of SrMoO₄ in the temperature range T = 99–375 K is studied. The analysis of the temperature dependences of the spin Hamiltonian b ₂ ⁰ (T) = b₂(F) + b₂(L) and P ₂ ⁰ (T) = P₂(F) + P₂(L) (for Gd¹⁵⁷) describing the EPR spectrum and contributing to the Gd³⁺ ground state splitting ΔE is carried out. In terms of the Newman model, the values of b₂(L) and P₂(L) depending on the thermal expansion of the static lattice are estimated; the b₂(F) and P₂(F) spin-phonon contributions determined by the lattice ion oscillations are separated. The analysis of b ₂ ⁰ (T) and P ₂ ⁰ (T) is evidence of the positive contribution of the spin-phonon interaction; the model of the local oscillations of the impurity cluster with close frequencies ω describes well the temperature behavior of b₂(F) and P₂(F).     

Low-temperature thermal conductivity of tellurium-doped bismuth

Phonon thermal conductivities κ₂₂ (?T ‖ C1) and κ₃₃ (? T ‖ C₃) of tellurium-doped bismuth with an electron concentration in the range 1.8 × 10¹⁹ ≤ n_L ≤ 1.4 × 10²⁰ cm^?3 were studied in the temperature interval 2 < T < 300 K. The temperature dependence of the phonon thermal conductivity obtained on doped bismuth samples of both orientations exhibits two maxima, one at a low temperature and the other at a high temperature. The effect of various phonon relaxation mechanisms on the dependence of both phonon thermal conductivity maxima on temperature, impurity concentration, and electron density is studied.     

Thermal conductivity in dirty superconducting alloys in high field

This paper discusses the thermal conductivityK of a dirty type II superconductor in the mixed state, for fields close to the upper critical field (H _e2 orH _e3) where the electronic component is dominant and easily separated. To order |Δ|², the conductivity depends only on the space average 〈|Δ|²〉. Our formula is a generalisation of earlier results byMaki andAmbegaokar andGriffin for gapless superconductors. The slope\(\left( {\frac{{\partial K}}{{\partial H}}} \right)_{Hc2} \) is proportional to the slope of the magnetization curve\(\left( {\frac{{\partial K}}{{\partial H}}} \right)_{Hc2} \), the ratio of these two slopes being a universal function of temperature. These results are very different from the predictions of the “effective gap” model.     

Z \to b\bar b andZ \to c\bar c as tests of the Standard Modelas tests of the Standard Model

We consider the decays $Z \to b\bar b$ and $Z \to c\bar c$ as tests of the Standard Model (SM). We find thatR _b =0.2141 andR _c =0.1719. Comparing with recent experimental measurements, we find thatR _b ^exp is too high by 3.9σ andR _c ^exp is too low by 2.4σ.     

An efficient basis set representation for calculating electrons in molecules

ABSTRACT

The method of McCurdy, Baertschy, and Rescigno, J. Phys. B, 37, R137 (2004) [1 C.W. McCurdy, M. Baertschy, and T.N. Rescigno, J. Phys. B 37, R137 (2004).[Crossref], [Web of Science ®] , [Google Scholar]] is generalised to obtain a straightforward, surprisingly accurate, and scalable numerical representation for calculating the electronic wave functions of molecules. It uses a basis set of product sinc functions arrayed on a Cartesian grid, and yields 1 kcal/mol precision for valence transition energies with a grid resolution of approximately 0.1 bohr. The Coulomb matrix elements are replaced with matrix elements obtained from the kinetic energy operator. A resolution-of-the-identity approximation renders the primitive one- and two-electron matrix elements diagonal; in other words, the Coulomb operator is local with respect to the grid indices. The calculation of contracted two-electron matrix elements among orbitals requires only O(Nlog?(N)) multiplication operations, not O(N⁴), where N is the number of basis functions; N = n³ on cubic grids. The representation not only is numerically expedient, but also produces energies and properties superior to those calculated variationally. Absolute energies, absorption cross sections, transition energies, and ionisation potentials are reported for 1- (He⁺, H⁺₂), 2- (H₂, He), 10- (CH₄), and 56-electron (C₈H₈) systems.     

Vacuum condensates in supersymmetric gluodynamics

We analyse the restrictions imposed by supersymmetric Ward identities on the dimension-six condensates in supersymmetric gluodynamics. It is shown that the system of the Ward identities admits a nonzero value for the four-fermion condensate \(\left\langle {\left( {\lambda \sigma _\mu T^a \bar \lambda } \right)^2 } \right\rangle _0 \) while 〈f ^abc F _μν ^a F _νρ ^b F _ρμ ^c 〉₀ must vanish.