Competition between two forms of ordering in finite Coulomb clusters

The lowest-energy state of spherical clusters made up of single-species charged particles in a three-dimensional confining potential is investigated by molecular dynamics simulations for a system size of 5 x 10(3) to 1.2 x 10(5). The energy per particle is compared between shell-structured clusters and spherical finite-bcc lattices with relaxed surfaces. The shell structure in the interior is the lowest-energy configuration for ion numbers lower than about 10(4), while for higher ion numbers, an interior with bcc ordering surrounded by a few shells on the outside has lower energy. The formation of a small bcc lattice (nucleation) in the shell-structured cluster of 2 x 10(4) ions is observed.     

Temperature sensitivity of Ge-B-SiO(2) waveguide Bragg gratings on a crystallized glass substrate

Waveguide Bragg gratings were fabricated by plasma-enhanced chemical-vapor deposition followed by irradiation with KrF excimer laser light through a phase mask. The period of the Bragg grating was 0.53 mum, and the Bragg wavelength was ~1.53 mum . The temperature dependence of the Bragg wavelength was 11 pm/ degrees C for a 10GeO(2) -90SiO(2)(mol.%) core waveguide on a Si substrate, and the Bragg wavelength shift was successfully reduced to 5.0pm/ degrees C by use of a 14GeO(2)-12B(2)O(3)-74SiO(2) (mol.%) core and a crystallized glass substrate with a thermal-expansion coefficient of -2.0x10(-6)(/ degrees C) .     

q-Painlevé Systems Arising from q-KP Hierarchy

A system of q-Painlevé type equations with multi-time variables t ₁,...,t _M is obtained as a similarity reduction of the N-reduced q-KP hierarchy. This system has affine Weyl group symmetry of type . Its rational solutions are constructed in terms of q-Schur functions.     

Pheromone synthesis: Part CVII? - synthesis of 2,6-dimethyloctyl formate, a potent mimic of the aggregation pheromone of the flour beetles

A mixture of the four stereoisomers of 2.6-dimethyloctyl formate was synthesized, and found to be a potent mimic of (4R,8R)-4,8-dimethyldecanal, the aggregation pheromone of the flour beetles,Tribolium castaneum andTribolium confusum. For Part CVI, see Mori K and Puapoomchareon P 1988Liebigs Ann. Chem. 175     

Tetrahedral metal complexes of [MW12O40]-type (MAlIII, ZnII) with dodecatungstate as tetrahedral ligand

Tetrabutylammonium salts of 12-heteropolytungstates with central metal ions in a tetrahedral oxygen environment, MW₁₂O₄₀ (MAl, Zn), have been prepared and their spectroscopic data (IR, UV and MCD) presented. IR studies in acetonitrile solution suggest that the tetrahedral structure around AlO₄ moiety is largely distorted, whereas the ZnO₄ moiety retains excellent tetrahedral symmetry.     

Effects on spontaneous emission on dynamic characteristics of semiconductor lasers

Dynamic characteristics of semiconductor lasers are calculated with single-mode rate equations, taking into account spontaneous emission factor β and bias current     

Overtone intensities in resonance Raman scattering

A model calculation of resonance Raman scattering tensors has been carried out for a diatomic molecule with a harmonic potential for the ground state and a linear repulsive potential for the excited state. Expressions for scattering tensors have been obtained by using a series of recurrence formulas induced from the Green function of the nuclear hamiltonian of the repulsive potential of the excited state and nuclear wavefunctions for the harmonic potential. The relative scattering intensities of overtones depend on the gradient of the repulsive potential curve and are interpreted in terms of the overlap integrals between nuclear wavefunctions of upper and lower states.     

A facile access to α-phenylselenenyl carbonyl compounds by electrochemical oxidation

A novel α-phenylselenenylation of carbonyl compounds has been performed by electrolysis of a solution of ketones, diphenyl diselenide, tetraethylammonium bromide, and magnesium bromide in polar solvents (MeOH, AcOH, MeCN). The electrolysis enables us to prepare the desired seleno-carbonyl compounds without employing strong bases and the activated selenenyl reagents PhSeX.     

Crystal growth of Co ferrite on fine acicular γ-Fe2O3 particles

Highly coercive magnetic powder was obtained by growing cobalt ferrite on the surface of γ-Fe₂O₃ particles in highly alkaline suspensions containing cobalt and ferrous ions in a Co/Fe molar ratio = $\text{1}\text{2}$. The mechanism of the growth and the structure of cobalt ferrite on γ-Fe₂O₃ were studied by X-ray diffraction and electron diffraction techniques. Results show that crystals of cobalt ferrite CoFe₂O₄ with a spinel type crystal structure of lattice constant 8.415 Å grew epitaxially on γ-Fe₂O₃. The acicular direction of the epitaxially grown Co-γ-Fe₂O₃ as well as γ-Fe₂O₃ was in the [$\text{1}$01] direction. It was found that from the lattice constant value and the half width of X-ray diffraction peaks, the lattice constant epitaxially grown Co γ-Fe₂O₃ may be attributed to two kinds of crystals, viz., seed γ-Fe₂O₃ ($\text{a = 8.35 ～ 8.37}\text{A}\text{?}$) which was partly reduced to Fe₃O₄, and surface layer CoFe₂O₄ ($\text{a = 8.415}\text{A}\text{?}$). The crystal growth in the interface between the seed crystals and the growth layer was affected by the crystal structure of the seed crystals. The lattice constant of CoFe₂O₄ which was located in the vicinity of the interface was almost equal to that of the seed crystals.     

Etude de l'autodiffusion sous pression dans le ceriumδ

After the study of self-diffusion in δ cerium under atmospheric pressure in which a mechanism of activated interstitials was assumed (a mechanism which implies a negative activation volume, as in the case with ε plutonium), it was logical to confirm our hypotheses by studying self-diffusion under higher pressures.As expected, the coefficient of self-diffusion was found to rise with pressure, the activation volume remaining negative throughout: ΔV < ?2 cm³/mol or - 10% mol vol.