A new insight on the role of Mg in calcite

Magnesium is a key determinant in calcite (CaCO₃) mineralization having a notable significance upon the carbonate growth. Magnesium is also present in CaCO₃ mineral scale formation which is a persistent and expensive problem in oil and gas production. In the present work, we attempt to treat CaCO₃ calcite mineral bulk inducing different concentrations of Mg impurity. The study is done using a quantum‐chemical computer code based on the Hartree–Fock method. It is found that small Mg impurity concentrations produce a significant distortion of the defect‐closest O atoms thus developing local microstructures being distinct to those of the original calcite structure. This structural alteration is accompanied by the electron density redistribution from the O 2p_z atomic orbitals (AOs) toward the O 2p_x and 2p_y AOs for impurity nearest oxygens. On the other hand, the high Mg impurity concentrations make the chemical bonding in calcite more ionic. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Unprecedented coexistence of a spirooxazine and its four transoid photomerocyanines

The synthesis of the 5′-hydroxy-1,3,3-trimethylspiro[indoline-2,3′-[3H]naphtho[1,2-b][1,4]oxazine] is reported. Equilibrium in the dark between closed and open forms has been proved by NMR spectroscopy.     

COURBURE ET TORSION DANS LES ALGÈBRES DE CLIFFORD

Clifford Algebras generalize curvature and torsion in R(p; q) (p and q are positive integers and p + q = n dimension of the space). General formulas are obtained. We study the special case q = 0. Moreover if n = 3 we obtain Frenet formulas.

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Résumé Les algébres de Clifford généralisent la courbure et la torsion dans R(p; q) (p q nombres positifs entiers et p + q = n, dimension de l’espace). On obtient aisément des formules générales. Nous étudions le cas particulier q = 0. Si en outre n = 3 on retrouve les formules de Frenet.

     

Non localization of free electrons

Using a formula derived from the Dirac equation, written in Clifford algebra, we prove that either in relativistic or in corpuscular (quantum) mechanics (Bohm, Vigier) free electrons cannot be localized. This makes the corpuscular hypothesis unacceptable, disproving the possibility of a subquantum field.     

Proprietes electroniques et electrogalvaniques du seleniure d'argent β: Domaine d'existence

A study of the electronic and electrogalvanic properties of β silver selenide has been performed on polycrystalline samples whose non-stoichiometry is controlled by eoulometric titration with the cell Ag/RbAg₄I₅/Ag_2+? Se/Pt. The adoption of an electronic model according to which the Frenkel defects of the silver sublattice are completely ionised allows us to compute independently the non-stoichiometry with the two formulaes δ = [Ag^o_i] ? [V'_Ag] and δ = n ? p. The homogeneity range has been drawn at positive temperatures and the formation enthalpy of the Frenkel defects is H'_F = 0,40 eV.