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To gain new structural insights into phase D and superhydrous B, two phases of potential mantle water reservoir, we have applied a range of one- (1D) and two-dimensional (2D) [sup.1]H and [sup.29]Si NMR techniques, as well as Raman spectroscopy, to samples synthesized at 24 GPa and 900~1100 [degrees]C. These data have revealed that phase D is characterized by disordered and varying local structures around both Si and H. The [sup.29]Si NMR spectra of phase D contain a nearly symmetric, broad peak near-177.7 ppm, attributable to octahedral Si with local structural disorder. The high-resolution [sup.1]H CRAMPS spectra of phase D contain a main broad peak near 12.6 ppm with shoulders near 10 and 7 ppm, suggesting a distribution of hydrogen bonding distances. For superhydrous B, our comprehensive 2D [sup.1]H and [sup.29]Si NMR results have clearly revealed that it contains dissimilar hydrogen (H1-H2) pairs and one tetrahedral Si site, consistent with space group Pnn2. Keywords: Phase D, superhydrous B, NMR, Raman, order/disorder, space group

The HIV-1 integrase (IN) inhibition process that targets divalent metal ion cofactors is analyzed. It is shown that HIV-1 IN needs divalent metal cations to achieve phosphodiester bond cleavage of DNA.

The role of M[g.sup.2+] on a calcium sensor protein from Entamoeba histolytica (EhCaBP) containing four C[a.sup.2+] -binding sites is reported to carry out various signal transduction processes. It is demonstrated that the presence of M[g.sup.2+] leads to a finer tuning of the range of C[a.sup.2+] concentration required for the protein to switch its conformation from a closed state to an open state in order to carry out various signal transduction processes.

Various x-ray diffraction experiments are employed to study the microscopic-scale structures of 0.72Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-0.28PbTi[O.sub.3] relaxor ferroelectrics in a high external dc field during phase transition. The results clearly prove that a change in the temperature also leads to a major change in the dominating cluster's orientation, as well as their interaction direction.

Commercially available anhydrous Mg[(Cl[O.sub.4]).sub.2] is described as a new and extremely efficient catalyst for synthesis of [alpha]-aminophosphonate by a three-component, one pot reaction. The observation of Mg[(Cl[O.sub.4]).sub.2]-catalyzed [alpha]-aminophosphonate synthesis indicates the simultaneous involvement of the carbonyl compound, the amine, and phosphite in the transition state.

The structural and optical properties of single crystal [Zn.sub.1-x][Mg.sub.x]O nanorods (0

Ab-initio thermophysical properties and isotopic separative effects in Mg[Cr.sub.2][O.sub.4] were computed with the CRYSTAL03 code. All calculations were carried out within the LCAO approach (Linear Combination of Atomic Orbitals) by using the Hartree-Fock and the hybrid B3LYP density functional methods. Vibrational frequencies have been computed at the long-wavelength limit corresponding to the center of the Brillouin zone (k [left arrow] 0). Since thermodynamic functions depend on the phonon dispersion relation, the ab-initio based vibrational analysis of the optical modes has been coupled with the semiempirical Kieffer model for the acoustic modes, which is based on a sine wave dispersion equation. All computed magnitudes (zero point energy, internal energy, Helmholtz free energy, optical vibrational modes, thermal corrections to internal energy, enthalpy and Gibbs free energy, thermal pressure, bulk modulus and its P and T derivatives, entropy, isochoric and isobaric heat capacity, and isotopic separative effects) are consistent with direct observations and/or reasonable estimates, within the accuracy of the method. The computed separative effects are similar to those observed in other [Cr.sup.3+]-bearing substances. The crystal field seems to have no influence on the separative effect for an isotopomeric couple with respect to an isolated gaseous couple with [Cr.sup.3+] as central cation. Keywords: Ab-initio thermochemistry, picrochromite, Cr-isotopes, Cr-fractionation, vibrational properties, thermal physics

Synthesis of active fold and palladium nanoparticles supported on MgO nanocubes and ZnO nanobelts and transition-metal-containing MgO nanobelts is presented by combining evaporation and deposition-precipitation techniques. The high activity and stability of the Au/CeO2 and Pd/CeO2 nanoparticle catalysts deposited on the MgO cubes are remarkable implying that a variety of efficient catalysts could be designed and tested using this approach.

Matioliite, ideally NaMg[Al.sub.5][(P[O.sub.4]).sub.4][(OH).sub.6] x 2[H.sub.2]O, occurs as a secondary hydrothermal mineral in the Gentil mine granite pegmatite, Mendes Pimentel Co., Minas Gerais, Brazil. Some crystals are zoned to more Fe-rich compositions with an [Fe.sup.2+]:Mg ratio of approximately 1:1, corresponding to an intermediate member of the burangaite-matioliite solid-solution series. Matioliite is intimately associated with fluorapatite, crandallite, and zoned gormanite-souzalite cystals. The mineral forms prismatic to tabular crystals, up to 1 mm long. Matioliite is transparent and displays a vitreous luster; it is blue to colorless with a white streak. It is non-fluorescent. Mohs hardness is about 5. Calculated density is 2.948 g/[cm.sup.3]. Matioliite is biaxial negative, [[eta].sub.[alpha]] = 1.597(2), [[eta].sub.[beta]] = 1.627(2), [[eta].sub.[gamma]] = 1.632(1) (white light), 2V (meas.) = 43(2)[degrees], 2V (calc.) = 44[degrees], dispersion r > v, orientation X = b, Z ^ c = 6[degrees]. Pleochroism is Y > X > Z, X = light blue to colorless, Y = blue, Z = colorless. The empirical formula is [([Na.sub.0.94][Ca.sub.0.01]).sub.[summation]0.95 [([Mg.sub.0.88][Fe.sup.2+.sub.0.11][Mn.sub.0.01].sub.[summation]1.00] [([Al.sub.4.84][Fe.sup.3+.sub.0.13]).sub.[summation]4.97] [(P[O.sub.4]).sub.4.03][(OH).sub.5.76] x 2[H.sub.2]O. The mineral is monoclinic, space group C2/c, a = 25.075(1) [Angstrom], b = 5.0470(3) [Angstrom], c = 13.4370(7) [Angstrom], [beta] = 110.97(3)[degrees], V = 1587.9(4) [[Angstrom].sup.3], Z = 4. Crystal-structure determination was carried out and showed it is isostructural with burangaite, dufrenite, and natrodufrenite. Both the description and the name were approved by the CNMMN-IMA (Nomenclature Proposal 2005-011). The 'magnesium analog of burangaite' described from the Gold Quarry mine, Carlin-trend, Eureka County, Nevada; 'burangaite' from Hochgosch, Millstatter See-Rucken, Karnten, Austria; and 'burangaite' described from Corrego Pomarolli, Linopolis, Divino das Laranjeiras, Minas Gerais, Brazil, are probably matioliite. Keywords: Matioliite, new mineral, crystal structure, burangaite, chemical composition, Gentil mine, Mendes Pimentel, Brazil

The NMR solution structures of the binary complex of HPPK with the MgATP analogue MgAMPCPP and the ternary complex with MgAMPCPP and the HP analogue 7,7-dimethyl-6-hydroxymethylpterin are reported. Results indicate that in the binary complex HPPK.MgAMPCPP, loop 2 and 3 can assume multiple conformations in slow exchange on the NMR chemical shift as evidenced by multiple sets of NMR signals.

The production of the ternary polar intermetallic phase [Mg.sub.5.231(8)][Sm.sub.0.231(8)][Sb.sub.4] from solid state reactions at 700-850 degrees Celsius in sealed Ta or Nb containers when the synthetic conditions took into account its characteristic incongruent melting point is reported. The results present the first example of a superstructure of a[Mg.sub.3][Sb.sub.2]-like structure with a doubled c axis induced by ordering a mixture of the larger divalent Sm and Mg ions separately within alternate layers of octahedral sites.

A study prepared Mg2NiH4 thin films by activated reactive evaporation in a molecular beam epitaxy system equipped with an atomic hydrogen source. The optical band gap of the in situ deposited Mg2NiH4 hydride, 1.75 eV, is in good agreement with that of Mg2NiH4 which was formed ex situ by hydrogenation of metallic Pd capped Mg2Ni films.

The structural and optical properties of magnesium-substituted zinc oxide ([Zn.sub.1-x][Mg.sub.x]O) nanocrystals synthesized by low temperature are studied. The results have concluded that due to phase segregation, the formation of the shell of [Mg.sub.2][(OH).sub.2] on the ZnO leads to quenching of the green emission, but this shell formation does not have much effect on the near band edge photoluminescence.

The Ti-Mg-dichloromethylene complexes derived from the oxidative addition of C[CI.sub.4] to the Mg-Ti[CI.sub.4] bimetallic species serve as a novel class of ambiphilic dichlorocarbenoid equivalents. Ti-Mg-dichlorocarbenoid is highly selective and also, it seems highly reactive in both alkene cyclopropanations and carbonyl dichloromethylenations.

The first magnesium and zinc boraamidinate (bam) complexes are synthesized via metathetical reactions between dilithio atoms and Grignard reagents or MCl2 (M=Mg, Zn). The results show that the bam anionic radical [PhB(N(super t)Bu)(sub 2)](super .-) can be stabilized by coordination to a variety of early main-group metal centers to provide neutral radicals whose relative stabilities are compared and discussed.

Metal cation complexes (M=Mg, Al, Ca) are produced in a cold molecular beam environment and studied with infrared photo dissociation spectroscopy in the carbonyl stretch region. The structures and spectra of these complexes are also investigated with density functional theory and spectroscopy and theory are consistent with structures having the metal action binding on the oxygen of the carbonyl for all three complexes.

The M=O bonds associated with cation vacancies in the lattice of both Mg2.5VMoO8 and Mg2.5VMoO8 are characterized by Raman spectroscopy and single-crystal X-ray diffraction. The results provide evidence that cation vacancies in Mg2.5VMoO8 and Mg2.5VMO8 stabilize a M=O species that is similar to the M=O species found on oxide surfaces.

The phases LiMgCa(sub 10)Sb(sub 9), Mg(sub 2)Ca(sub 10)Sb(sub 9), and Li(sub 1.38(2))Sb(sub 9) are synthesized by high-temperature solid-state means and characterized by single-crystal means and property measurements. The LiMgCa(sub 10)Sb(sub 9) compound is correspondingly diamagnetic and presumably a semiconductor.

The band structures of wurtzite ZnO are calculated by the empirical pseudopotential method (EPM). The eight parameters of the Zn and O atomic preudopotential form factors are obtained.

The kinetics of the Fe-Mg intracrystalline exchange reaction in [P2.sub.1]/c pigeonite ([Wo.sub.10][En.sub.47][Fs.sub.43]) free of exsolved augite, from the Parana rhyodacite sample BTS308, was studied by single-crystal X-ray diffraction (XRD). Isothermal disordering annealing experiments, with oxygen fugacity controlled at the IW buffer, were performed on two crystals at 650, 700, 750, and 800 [degrees]C until the Fe-Mg exchange equilibrium was reached. The XRD data were collected from the two untreated crystals and after each annealing experiment. Structure refinements were carried out taking into account the recently discovered stronger preference of Mn for the M2 site compared to [Fe.sup.2+]. The linear regression of In [k.sup.*.sub.D] vs. 1/T yielded the following equation: In [k.sup.*.sub.D] = -2925([+ or -] 110)/T(K) + 0.574([+ or -] 0.111); ([R.sup.2] = 0.997) The [T.sub.c] values calculated using this equation were 566 ([+ or -] 6) and 571 ([+ or -]6) [degrees]C for the two crystals. Analysis of the kinetic data was performed according to Mueller's model, which allowed retrieval of the disordering rate constants [C.sub.0][K.sup.+.sub.dis] for all four temperatures. The Arrhenius relation: In [K.sup.+.sub.dis] = In [K.sub.0] - Q/(RT) = 20.45( [+ or -] 1.91) - 25191 ([+ or -] 1900)/T(K); ([R.sup.2] = 0.989) yielded an activation energy of 50.03 ([+ or -]3) kcal/mol for the Fe-Mg exchange process. Cooling time constants, calculated at the QMF buffer conditions of the host rock were, for the two crystals, [eta] = 0.94 x [10.sup.-1] [K.sup.-1] [year.sup.-1] and [eta] = 1.10 x [10.sup.-1] [K.sup.-1] [year.sup.-1] and gave cooling rates on the order of 10 [degrees]C/h consistent with very fast lava cooling.

A series of beta-diiminato complexes of the form (BDI-3)MX where (BDI-3)=[CH(CMeNC6H4-2-OMe)2]; M=Zn, Mg; X=O(super i)Pr, O(super t)Bu, or N(SiMe3)2 is synthesized. The (BDI-3) ligand is bidentate in (BDI-3)ZnN(SiMe3)2 and tetradentate in (BDI-3)MgN(SiMe3)2.

The study is conducted to determine two-component signal transduction as a predominant information processing mechanism in prokaryotes and is present in single-cell eukaryotes and higher plants. The result reveals that solution structures of the apo and activated DctD receiver domain derived from small angle scattered data and corroborate the previously proposed model for how receiver domains regulates the downstream domains.

The reaction of dialkylmagnesium with alkylzinc triisopropylsilylamide leads to a ligand exchange reaction and the formation of magnesium bis(triisopropysilylamide) that can be crystallized after the addition of 1,2-bis(dimethylamino)ethane (TMEDA). The tetracoordinate nitrogen atoms show rather long Mg-N bond lengths of 210.7 pm due to the bridging position of the triisopropylsilylamide anion.

Structural and electronic properties of (100)-oriented MgSO4 and MgSO4.H2O surfaces and the adsorption of water on the latter are investigated theoretically with a combination of ab initio and semiempirical methods. The molecular adsorption of water on the MgSO4.H2O surface leads to only small shifts of the electronic energy levels.

The homoleptic Mg-phosphinimide complexes [[Mg.sub.2]([micro]-NP-t-B[u.sub.3]).sub.2] [(NP-t-B[u.sub.3]).sub.2] (1) and [[Mg.sub.3][([micro]-NP-i-[Pr.sub.3]).sub.4] [(NP-i[Pr.sub.3]).sub.2] (2) were obtained from the reaction of 2 equiv, of the phosphinimines HNP[R.sub.3] (R = t-Bu, i-Pr) with Mg[Bu.sub.2]. Spectroscopic and crystallographic studies confirmed the dimeric and trimeric structures of compounds 1 and 2, respectively. Key words: magnesium, phosphinimides, homoleptic, crystal stuctures. Resume : On a obtenu les complexes homoleptiques Mg-phosphinimides [Mg.sub.2][([micro]-NP-t-[Bu.sub.3]).sub.2][(NP-t-[Bu.sub.3]).sub.2] (1) et [Mg.sub.3][([micro]NP-i-[Pr.sub.3]).sub.4] [(NP-i-[Pr.sub.3]).sub.2] (2) par reaction de 2 equiv. des phosphinimides HN[Pr.sub.3] (R = t-Bu, i-Pr) avec du Mg[Bu.sub.2]. Les etudes spectroscopiques et cristallographiques ont permis de confirmer la nature dimere et trimere des structures des composes 1 et 2, respectivement. Mots cles : magnesium, phosphinimides, homoleptique, structures cristallines. [Traduit par la Redaction]

The ratio of Cu and Ga are changed to acquire four electrons in order to tune the primitive composition of the ternary Mg2Cu6Ga5 phase to a quasicrystalline approximant. However, these efforts produce the Mg35Cu24Ga53 compound consisting of a three-dimensional cubic network, whose synthesis, structure and bonding analysis are presented.

Density functional B3LYP/6- 31G method suits best for predicting structures of mg-Bc, McBchls and their 1:1 acetone complexes. It was found that complexation of pigments induced dark electronic states below the main soret transition. d

X-ray diffraction (XRD) and x-ray adsorption fine structure (XAFS) are used for examining the effect of exposure of a high magnetic field on the thermal decomposition behavior for Mg/Fe-layered double hydroxide (LDH) and the influence of high magnetic field on microstructures for Mg/Fe-LDH. The results have shown that [Fe.sup.3+] ions are substituted for [Al.sup.3+] in LDH and the application of heat treatment under 10 T to the decomposition of Mg/Fe-LDH has led to the synthesis of nanosized Mg[Fe.sub.2][O.sub.4] at lower temperatures.

The structure and magnetic properties of a series of [Fe.sub.3-x][Mg.sub.x][O.sub.4] (0

The examples of group 2 metal-gallium heterocycle complexes containing the first crystallographically characterized Ga-Mg and Ga-Ca bonds in molecular compounds are reported. These have the potential for use as a milder reagents for the transfer of the gallium heterocycles to less electropositive metals than the potassium salts of [:Ga{(ArNCH)2}(super -).

The crystal structure and magnetic properties of the MgO-only films are examined. The MgO-only films had smaller nanoscale FePt grains of 8.0 nm, higher out-of-plane coercivity of 10.0 kOe, a high remanence ratio approaching unity and a high magnetic anisotropy constant of 5*10(super 6) erg/cc.

The pattern formation of a forsterite ([Mg.sub.2]Si[O.sub.4])-chondrule in the melt droplet by using a phase-field method is described. The double structure has captured the distinctive features of barred-olivine textures seen in natural chondrules.

Positron annihilation and Raman spectroscopies are used for studying the defect properties of perovskite type materials ([Ba.sub.3]B' [Nb.sub.2][O.sub.9] (where B' = Mg, Zn, or Co)) with near-stichiometric compositions. The existence of an internal electric field between charged 1:1 nanoregions and the rest of material has created conditions for preferential positron annihilation that affect the obtained positron lifetime values.

Surface oxidation of the CoFe and CoFeB bottom electrodes is detected by using magnetometry measurements of exchange bias (EB) characterizations that have included the EB field, training effect, uncompensated spin density and enhanced coercivity. The variations in the parameters are related to the surface oxidation of the bottom electrode and the annealed samples have shown evidence for an oxygen migration back to the MgO tunnel barrier by annealing.

High-resolution [super 19]F magic angle spinning (MAS) NMR spectroscopy is used to study disorder and bonding in a crystalline solid, fluorine-substituted deuterated hydrous magnesium silicate which exhibit four distinct F sites. The existence of J couplings in fluorine is discussed in relation to both the nature of bonding in the solid state and the occurrence of 'through-space' [super 19]F-[super 19]F J couplings in solution which is similar to structural disorder and spin-spin interactions found in both synthetic and naturally occurring clinohumite samples.

Chiral [alpha]-chloro- or bromocarboxylic acids in the presence of KOt-Bu (or KHMDS) and Mg[(Ot-Bu).sub.2] is used to perform general inversion-stereospecific, N-selective alkylation of substituted 2-pyridones, amides and carbamates. Mechanistic evidence suggested that the reaction proceeds through 2-pyridone O-coordinated Mg carboxylate intermediates to yield the product through an intramolecular [S.sub.N]2 alkylation.

The electronic and magnetic properties of pure and Mn-doped armchair and zigzag ZnO nanotubes are analyzed by using density functional theory with the generalized gradient approximation. The studies have shown that large magnetic moments have appeared in Mn-doped ZnO nanotubes, which are due to the hybridization between the O 2p and Mn 3d states.