Effects of the Li-evaporation on the Czochralski growth of γ-LiAlO2

Two-inch-diameter γ-LiAlO₂ single crystals were grown from the melt by Czochralski method. The crystals were examined by optical methods, high-resolution X-ray diffraction and transmission electron microscopy (TEM). Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the Li/Al ratio in the residual melts. The Li-evaporation from both melt and grown crystal is the main problem in the γ-LiAlO₂ growth and has to be controlled by acting on the vertical temperature gradient. Shallow gradients increase the Li-evaporation from the crystal surface resulting in boules with a milky rim. On the other hand, steep gradients may induce cracks in the boule and enhance the Li₂O escape from melt with consequent variation of the composition. ICP-OES investigations reveal that melt compositions can vary in the range from 46.5 to 50 mol% Li₂O to obtain transparent LiAlO₂ crystals. Beyond this value, the formation of inclusions inside the crystals is probable. We have established an optimized growth assembly, which allows remaining the melt composition stoichiometric. The as-grown crystals exhibit defects like subgrains, twins and a core of voids and fine-grained inclusions. The latter could be characterized by TEM as submicron LiAl₅O₈ crystallites.     

Bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneaminato]palladium(II) complexes and their radical intermediates generated by PbO2 and PPh3

New bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneminato]palladium(II) [Pd(L ^x )₂] complexes bearing HO and MeO substituents on the salicyaldehyde moiety were prepared, and their spectroscopic properties, as well as redox reactivity towards PbO₂ and PPh₃, examined by e.s.r. and u.v. spectroscopy. The complexes display charge-transfer bands in the 670–692 nm range in polar solvents, which are assigned to the d(Pd) * (chelated quinoid) transition. One-electron oxidation of Pd(L ^x )₂ produces Pd^II-stabilized radicals in which the unpaired electrons are localized on the phenoxy fragments and do not couple with the two radical centers. The complexes are easily reduced with PPh₃ via intramolecular electron-transfer from ligand to metal to give various radical intermediates and Pd. All detected radical species have been characterized by e.s.r. spectroscopy.     

Preparation and testing for homogeneity of spiked strawberry and cabbage candidate reference materials

Strawberry and cabbage candidate reference materials (RMs) have been prepared by our laboratory during 1992–1993. Fresh materials have been homogenized and spiked with known concentrations of pesticides representing compounds commonly used for strawberries and cabbages. The candidate RMs have been then freeze-dried, homogenized, bottled under a stream of nitrogen and stored frozen at –20°C. Homogeneity and stability of the candidate RMs have been studied during the storage period. Homogeneity of the candidate RMs for 5 g samples has been within 10%. Homogeneity and stability studies have been carried out using the conventional multiresidue method of Luke et al. [1]. Instrumental analysis have been performed by gas chromatography mass spectrometry (GC-MS) employing selected ion monitoring (SIM).     

The totally symmetric Raman stretching vibration v(Mo-Mo) of quadruple molybdenum–molybdenum bonds varies linearly with the mass of molybdenum and its ligands

The electronic (400-800nm), i.r. and Raman (20-400cm-1) spectra of several hexahalo-di(aquo)dimolybdate(II) anions, Mo2X6(H2O)22− (X=Cl, Cl/Br, Br and I) containing quadruple metal-metal bonds have been investigated. The electronic spectra of the solid compounds at 300K show intense bands in the visible region (510-580nm) assigned to the expected delta delta transitions. From the i.r. and Raman spectra the skeletal and stretching modes in these binuclear anions have been identified. The metal-metal v(MoMo) stretching vibrational wavenumbers vary linearly as a function of the total mass, including molybdenum and its ligands. From this relationship, the mass of the ligands and that of the unknown material have been determined and compared with analytical results. In conclusion, the results are in very good agreement. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nonlocal fractional elliptic equations and applications

The L_p-coercive properties of a nonlocal fractional elliptic equation is studied. Particularly, it is proved that the fractional elliptic operator generated by this equation is sectorial in L_p space and also is a generator of an analytic semigroup. Moreover, by using the L_p-separability properties of the given elliptic operator the maximal regularity of the corresponding nonlocal fractional parabolic equation is established.     

Synthesis, structural, spectroscopic and reactivity properties of a new N-2,3,4-trifluorophenyl-3,5-di-tert-butylsalicylaldimine ligand and its Cu(II) and Pd(II) complexes

A new N-2,3,4-trifluorophenyl-3,5-di-tert-butylsalicylaldimine (1) complexes with Cu(II) (2) and Pd(II) (3) have been synthesized and characterized by X-ray crystallography, UV-Vis, IR, ¹H NMR and EPR spectroscopic techniques. The X-ray crystal structure of complex 2 reveals tetrahedrally distorted square-planar coordination geometry around Cu(II). The UV/Vis and EPR results indicate that the solid state geometry of 2 remains unchanged in solutions. Chemical oxidation of 3 with Ce(IV) in CHCl₃ generates relatively stable Pd(II)-phenoxyl radical complex (g = 2.0073). The results related with the chemical oxidation of 2 and 3 as well as the catalytic activity of 3 in the hydrogenation of PhNO₂ are presented.     

Are per capita incomes of MENA countries converging or diverging?

This study considers the issue of income convergence among the MENA (Middle East and North African) countries by using real per capita incomes over the period 1950-2006. We employed (Kapetanios et al. 2003) [21] unit root test by incorporating an additive constant and a trend component as Chong et al. (2008) [20] did in their study and found most of the MENA countries diverging during the sample period.     

Linear and nonlinear abstract equations with parameters

This paper focuses on nonlocal boundary value problems for linear and nonlinear abstract elliptic equations in Banach spaces. Here equations and boundary conditions contain certain parameters. The uniform separability of the linear problem and the existence and uniqueness of maximal regular solution of nonlinear problem are obtained in L_p spaces. For linear case the discreteness of spectrum of corresponding parameter dependent differential operator is obtained. The behavior of solution when the parameter approaches zero and its smoothness with respect to the parameter is established. Moreover, we show the estimate for analytic semigroups in terms of interpolation spaces. This fact can be used to obtain maximal regularity properties for abstract boundary value problems.     

Compact embedding in Besov spaces and B-separable elleptic operators

Necessary and sufficient conditions for compactness of sets in Banach space valued Besov class Bp,q s(Ω;E) is derived.The embedding theorems in Besov-Lions type spaces B l,s p,q(Ω;E0,E) are studied,where E0,E are two Banach spaces and E 0  E.The most regular class of interpolation space E α,between E 0 and E are found such that the mixed differential operator D α is bounded and compact from B p,q l,s (Ω;E 0,E) to B p,q s (Ω;E α) and Ehrling-Nirenberg-Gagliardo type sharp estimates established.By using these results the separability of differential operators with variable coefficients and the maximal B-regularity of parabolic Cauchy problem are obtained.In applications,the infinite systems of the elliptic partial differential equations and parabolic Cauchy problems are studied.     

A study of transglucosylation kinetic in an enzymatic synthesis of benzyl alcohol glucoside by α-glucosidase from S. cerevisiae

α-1,4-Glucosidase from Saccharomyces cerevisiae is an enzyme which is widely used in synthesis of different drugs. Glucosidase inhibitors are studied as potential drugs for prevention of HIV and diabetes. For understanding of these processes it is very important to have insights in the transglucosylation activity of this enzyme. In this paper the kinetics of transglucosylation reaction catalyzed by this enzyme in the synthesis of benzyl alcohol glucoside was studied and all relevant kinetic constants for this system are found. It was shown one additional property of transglycosylation reactions catalyzed by glycosidases—inhibition by both, glucose acceptor and glucose donor, and mechanisms for these inhibitions were proposed.