High pressure study of structural and electronic properties of magnesium telluride

The full-potential linear muffin-tin orbital method (FP-LMTO) within the local density approximation (LDA) is used to calculate the electronic band structures and the total energies of MgTe in its stable (NiAs-B8) and high pressure phases. The latter provide us with the ground state properties such us lattice parameter, bulk modulus and its pressure derivatives. The transition pressure at which this compound undergoes the structural phase transition from the NiAs to CsCl phase is calculated. The energy band gaps and their volume and pressure dependence in the stable NiAs-B8 phase are investigated. The ground state properties, the transition pressure are found to agree with the experimental and other theoretical results. The elastic constants at equilibrium in both NiAs and CsCl structure are also determined.     

Empirical estimation of the proportional hazard premium for heavy-tailed claim amounts

The asymptotic normality of the sample proportional hazard premium for heavy-tailed claim amounts with infinite variance cannot be obtained by classical results for L-statistics. In this paper, we propose an alternative estimator for this class of premiums and we establish its asymptotic normality.     

Biotreatment on Cellulose Fluff Pulp: Quaternary Ammonium Salts Finish and Grafting with β-cyclodextrin

For its potential performances to be expanded, cellulose needs to be processed in different ways. Therefore, an object of the present work was to provide a chemical modification of cellulose through: a specific finish with two quaternary ammonium salts (namely Aliquat 336 and Aliquat 1529, respectively). Chemical grafting of β-cyclodextrin derivative (β-CD) onto fibers followed by the inclusion of benzoic acid in the grafted CD cavities as a probe chemical. Physicochemical properties and performances of the untreated and treated fibers have been determined with infrared spectra, microscopy, swelling measurements, antimicrobial finishing tests, and dye adsorption. Our results show that cellulose fibers can be efficiently modified with no significant changes in its structural and surface properties; the treated fibers show an attractive behavior in swelling, dye adsorption and antibacterial activity.     

FP-LMTO calculations of the structural,elastic, thermodynamic,and electronic properties of the ideal-cubic perovskite BiGaO3

Using the first-principles full-potential linear muffin-tin orbital method within the local density approximation, we have studied the structural, elastic, thermodynamic, and electronic properties of the ideal-cubic perovskite BiGaO₃. It is found that this compound has an indirect band gap. The valence band maximum (VBM) is located at Γ-point, whereas the conduction band minimum (CBM) is located at X-point. The pressure and volume dependences of the energy band gaps have been calculated. The elastic constants at equilibrium are also determined. We derived the bulk and shear moduli, Young’s modulus, and Poisson’s ratio. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of the bulk modulus, heat capacities, and Debye temperature with pressure and temperature are successfully obtained.     

Synthesis,crystal structure and spectral characteristics of highly fluorescent chalcone-based coumarin in solution and in polymer matrix

A new coumarin chalcone 3-((2E)-3-(2-hydroxyphenyl) prop-2-enoyl)-4-hydroxy-2(H)-chromen-2-one was synthesized using the Claisen Schmidt reaction by the condensation of 3-acetyl-4-hydroxycoumarin and 2-hydroxybenzaldehyde using a mild organic base. This novel compound was characterized by ¹H NMR, FT-IR and UV–vis spectroscopy. Single crystal X-ray diffraction investigation at low temperature (T=120 K) shows that this compound exhibits an intramolecular O3–H…O hydrogen bond, the coumarin ring and the phenyl group are nearly coplanar and the crystal packing is stabilized by intermolecular O3–H…O contacts and π–π stacking interactions. This ortho-hydroxyphenyl-4-hydroxycoumarin chalcone exhibits a strong blue-green emission under visible light excitation at 470 nm. The fluorescence behaviors of this compound doped in poly(methyl methacrylate) (PMMA) were investigated.     

Behavior of packing materials in axially compressed chromatographic columns

The behavior of a packing material (Luna C18 from Phenomenex, Torrance, CA, USA) was studied during the consolidation of a column bed under axial compression stress. The kinetics of this consolidation, the permeability and efficiency of the columns obtained, and the reproducibility of these column properties were measured under different conditions. The consolidation process and the column properties are considerably affected by the friction between the packing material in the bed and the column wall. Clear evidence of this wall effect was demonstrated. The apparent permeability of columns consolidated under the same axial stress increases with increasing column length. The apparent modulus of elasticity of the beds increases with increasing column length. The shear resistance between the packed bed and the column wall was measured for columns of different lengths. It increases rapidly with increasing bed length. The column efficiency for thiourea (unretained) and phenyloctane (retention factor, k' approximately 1) was much poorer after recompression than after the first compression. It depended little on the compression stress. The effect of the column length was small.     

Adsorption isotherms and retention behavior of 1,1'-bis(2-naphthol) on CHIRIS AD1 and CHIRIS AD2 columns

The separation of the atropoisomers of 1,1'-bis(2-naphthol) was studied on CHIRIS AD1 and CHIRIS AD2, two Pirkle-type chiral stationary phases. Satisfactory selectivity was found only on CHIRIS AD2. The ternary mobile phases comprised hexane, dichloromethane and methanol. The effects of their composition and of the temperature on the retention under analytical conditions and on the single-component and competitive isotherms were investigated. The retention of the R- and S-isomers on CHIRIS AD1 and CHIRIS AD2 is controlled by the enthalpic contribution to adsorption, but the effect of the mobile phase on the retention should be attributed mainly to the entropic contribution. The adsorption of the less retained R-isomer is controlled by the achiral interactions, which are the same as for the S-isomer. The single-component and competitive isotherms of the R- and S-isomers are adequately described by the sum of a Langmuir term for the achiral contribution to adsorption and a linear-term characterising the selective or chiral adsorption of the S-isomer in the concentration range experimentally available, i.e. within the solubility limit of 1,1'-bis(2-naphthol).     

Asymptotic modeling of Signorini problem with Coulomb friction for a linearly elastostatic shallow shell

In 2002–2003, Paumier studied the Signorini problem with friction in the linear Kirchhoff–Love theory of plates using the convergence method. In 2008, Léger and Miara generalized this study to the case of linearized shallow shell but without friction. The purpose of this paper is to extend those results to the case of linearized shallow shell with a Coulomb friction law. Copyright © 2015 John Wiley & Sons, Ltd.     

Theoretical study of ground state and high-pressure phase of platinum carbide

We report local density-functional calculations using the full-potential linearized muffin-tin orbital method (FP-LMTO) for platinum carbide (PtC) in the, rock-salt (B1), zinc-blende (B3), wurtzite (B4), nickel-arsenide (B8) and PbO (B10) structures. The ground state properties such as the equilibrium lattice constant, elastic constants, the bulk modulus and its pressure derivative of PtC in these phases are determined and compared with available experimental and theoretical data.Our calculations show that the ground state phase of PtC to be zinc-blende (B3) structure at zero pressure and the nickel-arsenide (B8) structure is a high-pressure phase. The transition pressures at which this compound undergoes the structural phase transition from (B3) to (B8) and from (B3) to (B1) are found to be 34.25 and 51.28 GPa, respectively. The highest bulk modulus values in the nickel-arsenide (B8), zinc-blende (B3), rock-salt (B1) and PbO (B10) structures indicate that PtC is a hard material.     

[Yb(H2O)8][Cd3Cl9(H2O)]·6H2O

The title compound, namely octa­aqua­ytterbium(III) aqua­nona­chloro­tricadmate(II) hexa­hydrate, [Yb(H₂O)₈][Cd₃Cl₉(H₂O)]·6H₂O, was prepared by evaporation at 278 K from an aqueous solution of the ternary system YbCl₃–CdCl₂–H₂O and was characterized by elemental chemical analysis and by X‐ray powder and single‐crystal diffraction studies. The crystal structure can be viewed as being built from layers of double chains of CdCl₆ and CdCl₅(H₂O) octahedra separated by antiprismatic [Yb(H₂O)₈]³⁺ cations. The stabilization of the structure is ensured by O—H⋯O and O—H⋯Cl hydrogen bonds. A comparison with the structures of SrCd₂Cl₆·8H₂O and CeCd₄Cl₁₁·13H₂O is presented.