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Two anions (dodecylbenzenesulfonate anion and stearate anion) are employed to synthesize intercalated layered double hydroxides (LDH) by co-precipitation method. Then the intercalated LDHs are incorporated in the casting solutions of [...]

Abstract: Amorphous chromium-containing solid nanoparticles and hollow spheres were formed as the intermediate product during the synthesis of [Cr.sub.2][O.sub.3] by gamma radiolysis of dichromate solution. Scanning transmission X-ray microscopy (STXM) [...]

Abstract: Based on the backbone of the nitrogen-rich triazole and tetrazole structure, their N-OH derivatives were designed to improve the properties of energetic materials. This work introduces five novel nitrogen-rich [...]

Phenol, a known water pollutant, was electrochemically oxidized on a steel/Ir[O.sub.2]-[Sb.sub.2][O.sub.3] novel anode. Since the oxidation mechanisms vary based on the anode material, a mechanisms study of electrooxidation of phenol on it was conducted. The phenol oxidation was carried out at 20 mA/[cm.sup.2] constant current density with a pH 11.00 [Na.sub.2]S[O.sub.4] medium at room temperature. During 6 h of electrolysis, samples were tested for chemical oxygen demand removal efficiency of the anode. The steel/Ir[O.sub.2]-[Sb.sub.2][O.sub.3] anode showed 76.3% chemical oxygen demand removal efficiency. Both 4-nitroso-N,N-dimethylaniline and the HC[O.sub.3.sup.-]/C[O.sub.3.sup.2-] radical scavenger tests confirmed the formation and presence of the hydroxyl radicals in the system. Therefore, it was concluded that the hydroxyl radicals that are generated on the anode surface are the main cause for the oxidation mechanism. Moreover, ICE, HPLC, and UV-vis absorbance and cyclic voltammetry results confirmed the presence of catechol and benzoquinone as intermediates and the reaction mechanism. Key words: benzoquinone, catechol, oxidation mechanisms, phenol, steel/Ir[O.sub.2]-[Sb.sub.2][O.sub.3] anode. Le phenol, un polluant de l'eau connu, a ete oxyde sur une nouvelle anode d'acier/Ir[O.sub.2]-[Sb.sub.2][O.sub.3]. Comme les mecanismes d'oxydation dependent du materiau qui constitue l'anode, nous avons mene une etude des mecanismes de l'electro-oxydation du phenol. L'oxydation du phenol a ete effectuee sous une densite de courant constant de 20 mA/[cm.sup.2] a pH 11.00 dans une solution de [Na.sub.2]S[O.sub.4] a temperature ambiante. Au cours de l'electrolyse, nous avons analyse des echantillons preleves pendant 6 h afin d'evaluer le rendement d'epuration de la demande chimique en oxygene de l'anode. L'anode d'acier/Ir[O.sub.2]-[Sb.sub.2][O.sub.3] a produit un rendement d'epuration de la demande chimique en oxygene de 76,3%. Les tests de reduction de la 4-nitroso-N,N-dimethylaniline et de piegeage de radicaux HC[O.sub.3.sup.-]/C[O.sub.3.sup.2-] ont tous deux confirme la formation et la presence de radicaux hydroxyle dans le systeme. Par consequent, nous avons conclu que le mecanisme d'oxydation est principalement attribuable aux radicaux hydroxyle qui sont generes a la surface de l'anode. En outre, les resultats d'efficacite du courant instantane, de chromatographie liquide a haute performance a detection par absorbance dans l'UV-vis et de voltamperometrie cyclique ont confirme la presence de catechol et de benzoquinone comme intermediaires, ainsi que le mecanisme de reaction. [Traduit par la Redaction] Mots-cles: benzoquinone, catechol, mecanismes d'oxydation, phenol, anode acier/Ir[O.sub.2]-[Sb.sub.2][O.sub.3]., Introduction Phenol ([C.sub.6][H.sub.5]OH) is a known hazardous aromatic hydrocarbon that is produced through both natural and anthropogenic processes. (1) Recently, phenolic compounds have been detected in ground and surface water [...]

Deamination of adenine is one of several forms of premutagenic lesions occurring in DNA. In the present study, mechanisms for the deamination reaction of adenine with [OH.sup.-]/n[H.sub.2]O(n = 0,1,2,3)and 3[H.sub.2]O were investigated. HF/6-31G(d), B3LYP/6-31G(d), MP2/6-31G(d), and B3LYP/6-31+G(d) levels of theory were employed to search for and optimize all geometries. Energies were calculated at the G3MP2B3 and CBS-QB3 levels of theory. The effect of solvent (water) was computed using the polarizable continuum model (PCM). Intrinsic reaction coordinate (IRC) calculations were performed for all transition states. Five pathways were investigated for the deamination reaction of adenine with [OH.sup.-]/n[H.sub.2]O and 3[H.sub.2]O. The first four pathways (A-D) are initiated by deprotonation at the amino group of adenine by [OH.sup.-], while pathway E is initiated by tautomerization of adenine. For all pathways the next two steps involve formation of a tetrahedral intermediate followed by dissociation to products via a 1,3-proton shift. Deamination with a single [OH.sup.-] has a high activation barrier (190 kJ [mol.sup.-1] using the G3MP2B3 level) for the rate-determining step. The addition of one water molecule reduces this barrier by 68 kJ [mol.sup.-1] at the G3MP2B3 level. Adding additional water molecules decreases the overall activation energy of the reaction, but the effect becomes smaller with each additional water molecule. The most plausible mechanism is pathway E, the deamination reaction of adenine with 3[H.sub.2]O, with an overall G3MP2B3 activation energy of 139 and 137 kJ [mol.sup.-1] for the gas phase and PCM, respectively. This barrier is lower than that for the deamination with [OH.sup.-]/3[H.sup.2]O by 6 and 2kJ [mol.sup.-1] for the gas phase and PCM, respectively. Keywords: deamination, adenine, 1,3-proton shift, optimized structures, deprotonation. Resume : La desamination de l'adenine est une des multiples formes prises par les lesions premutagenes pouvant se produire dans l'ADN. Dans le present travail, on a etudie les mecanismes de la reaction de desamination de l'adenine avec du [OH.sup.-]/n[H.sup.2]O (n = 0, 1, 2 et 3) et 3[H.sup.2]O. Dans la recherche et l'optimisation de toutes les geometries, on a fait appel a des calculs aux niveaux HF/3-31G(d), B3LYP/6-31G(d), MP2/6-31G(d) et B3LYP/6-31+G(d) de la theorie. Les energies ont ete calculees aux niveaux G3MP2B3 et CBS-QB3 de la theorie. On a calcule l'effet du solvant (eau) en utilisant le modele du continuum polarisable (MCP). On a effectue des calculs de coordonnees reactionnelles intrinseques (CRI) pour tous les etats de transition. On a examine cinq voies reactionnelles pour la reaction de desamination de l'adenine avec [OH.sup.-]/n[H.sub.2]Oet3[H.sup.2]O. Les quatre premieres voies (A- D) sont initiees par la deprotonation du groupe amino de l'adenine par le [OH.sup.-], alors que la voie E est initiee par une tautomerisation de l'adenine. Pour l'ensemble des cinq voies reactionnelles, les deux etapes suivantes impliquent la formation d'un intermediaire tetraedrique, suivie par la dissociation en produits par le biais d'un deplacement 1,3 de proton. Sur la base des calculs au niveau G3MP2B3 la barriere d'activation de l'etape cinetiquement determinante de la desamination avec un seul [OH.sup.-] est elevee, a 190 kJ [mol.sup.-1]. L'addition d'une molecule d'eau reduit cette barriere par 68 kJ [mol.sup.-1] (au niveau G3MP2B3). L'addition de molecules d'eau supplementaires diminue l'energie d'activation totale de la reaction, mais l'effet diminue avec l'addition de chaque molecule d'eau additionnelle. Le mecanisme le plus plausible est la voie E, la reaction de desamination de l'adenine avec 3[H.sub.2]O, avec une energie d'activation globale au niveau G3MP2B3 de 139 et de 137 kJ [mol.sup.-1] respectivement pour la phase gazeuse et le modele du continuum polarisable (MCP). La barriere est inferieure a celle pour la desamination avec [OH.sup.-]/3[H.sub.2]O par 6 et 2kJ [mol.sup.-1] respectivement pour la phase gazeuse et le MCP. [Traduit par la Redaction] Mots-cles: desamination, adenine, deplacement 1,3 de proton, structure optimisee, deprotonation., Introduction Extensive knowledge and understanding of genetic material and its physicochemical properties is one of the natural goals of science. One of the essential components of genetic material is adenine [...]

The reaction mechanisms of vinyl acetate with OH radicals in the atmosphere have been studied using the density functional theory method. The geometry parameters and frequencies of all of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis sets. The single-point energy calculations are carried out at the MPWB1K/6311+G(3df,2pd)level. The detailed profiles of the potential energy surfaces for the reactions are constructed. Two OH addition and three H abstraction reaction pathways are considered for the reaction of vinyl acetate with OH radicals. The theoretical study shows that the most energetically favorable isomer is that of OH addition to the terminal carbon positions (C1 atom). The Å-ester rearrangement, which is characteristic of ester oxidation processes, is confirmed to be thermodynamically and kinetically favorable. The main products of the OH-initiated atmospheric oxidation of vinyl acetate are formaldehyde, formic acetic anhydride, and acetic acid. Key words: vinyl acetate, OH radicals, reaction mechanism, quantum chemical calculation. On a etudie les mecanismes reactionnels de l'acetate de vinyle avec les radicaux OH de l'atmosphere en faisant appel a la theorie de la fonctionnelle de la densite. On a calcule les parametres geometriques et les frequences des points stationnaires au niveau MPWBK1K de la theorie avec des ensembles de base 6-31G(d,p). Les calculs d'energie ponctuelle ont ete faits au niveau MPWB1K/6-311+G(3df,pd). On a construit les profils detailles des surfaces d'energie potentielle des reactions. On a considere l'addition de deux OH et l'enlevement de trois H comme voies reactionnelles pour la reaction de l'acetate de vinyle avec les radicaux OH. L'etude theorique montre que l'isomere le plus favorable d'un point de vue energetique est celui correspondant a l'addition d'un OH sur les positions carbonees terminales (C1). On a pu confirmer que le rearrangement de l'[alfa]-ester, qui est caracteristique des processus d'oxydation d'ester, est le plus favorable tant d'un point de vue thermodynamique que cinetique. Les produits principaux qui resultent d'une oxydation atmospherique de l'acetate de vinyle, initiee par un radical OH, sont le formaldehyde, l'anhydride mixte de l'acide formique et acetique et l'acide acetique. Mots-cles: acetate de vinyle, radicaux OH, mecanisme reactionnel, calculs de chimie quantique., Introduction Vinyl acetate (VA) ([C[H3.sub.]C(O)OCH=C[H.sub.2]]) is a synthetic unsaturated ester and has a wide variety of industrial applications. The major use of VA is to produce polyvinyl alcohol, polyvinyl acetate, [...]

The behavior of structural OH in clinopyroxene (augite and omphacite) during successive heating has been investigated by in situ micro-FTIR measurements under temperatures ranging from room temperature to 500[degrees]C at 100[degrees]C increment. The first group of OH band (3620-3640 [cm.sup.-1]) exhibits a systematic decrease of peak position upon successive heating, while the other two groups (3520-3535 and 3450-3465 [cm.sup.-1]) show only little change. Both augite and omphacite display a decrease of integral absorbance of OH fundamental stretching vibration upon successive heating. The IR spectra of OH band are reversible when the temperature decreases from 500[degrees]C to room temperature, suggesting that changes in IR indicate changes in molecular state of OH. Based on: (1) the decreases of integral absorbance of OH bands with increasing temperature, and (2) comparison with Paterson's relationship (Paterson 1982), we suggest that OH absorption coefficients are temperature dependent, so it is necessary to apply different absorption coefficients when determining OH content from Beer-Lambert law at different temperatures and sample temperatures should be reported in quantitative IR studies Keywords: IR, varying temperature, OH, clinopyroxene DOI: 10.2138/am.2010.3501

The change with temperature of IR absorption bands in OH in muscovite was studied using unpolarized in-situ high-temperature infrared microspectroscopy. The molar absorption coefficient eat 3628 [cm.sup.-1] for OH in muscovite at room temperature (20[degrees]C) has been determined to be 127 [+ or -] 6 L/mol x cm. Using the orientation factor [gamma] = 0.47 for the angle between OH vector and [c.sup.*] axis (75 [+ or -] 5[degrees]), the true molar absorption coefficient [epsilon] at 3628 [cm.sup.-1] is determined to be 270 [degrees] 10 L/mol x cm at 20[degrees]C. Integral molar absorptivities are also determined from 20 to 650[degrees]C showing no weight loss. The value decreases from 7060 [+ or -] 190 L/mol x [cm.sup.2] at 20[degrees]C to 5190 [+ or -] 270 L/mol x [cm.sup.2] at 650[degrees]C (26% decrease). OH orientation of muscovite sample measured by polarized IR microspectroscopy at 20[degrees]C showed that the angle between the projection of OH vector to (001) plane (the OH' vector) and b axis is 30.5[degrees] at 20[degrees]C and did not change greatly at higher temperatures until 650[degrees]C. The tilting of OH dipoles toward the [c.sup.*] axis from 75[degrees] to about 43[degrees] while keeping the same angles along b axis would explain the observed decrease in integral molar absorptivities at higher temperatures, but further studies are needed to clarify the OH behavior at high temperatures. Keywords: Muscovite, OH, in-situ high-temperature IR microspectroscopy, integral molar absorptivity, OH orientation DOI: 10.2138/am.2010.3235

The tereochemical determination and the preparation of 1-(4-(4-((1R,5R,6R)-6-hydroxy-3-oxa-8-azabicyclo[3.2.1]octan-8-yl)-6-morpholino-1,3,5-triazin-2-yl)phenyl)-3-(pyridine-4-yl)urea, an active metabolite of the potent PI3 kinase inhibitor PKI-179, is described. Mosher's method is used for determining the absolute stereochemistry of the enantiomer, thus establishing the stereochemistry of the active metabolite.

Negatively charged analytes must be derivatized prior to gas chromatography-isotope ratio mass spectrometry (GCIRMS), with stringent control of isotope fractionation. Current methods require offline sample preparation. This study tests for the first time trimethylsulfonium hydroxide (TMSH) as online methylation agent prior to isotope analysis, addressing the herbicides bentszone and MCPA. Fully automated derivatization was achieved in a temperature-programmable GC injector, where reactants were injected into a packed liner, solvents were removed by split flow, and subsequent flash heating triggered the dedvatization, thereby transferring derivatives onto the chromatographic column. Stoichiometric addition of TMSH resulted in complete conversion giving accurate and reproducible nitrogen isotope values of bentazone. In contrast, reproducible carbon isotope analysis required TMSH in [greater than or equal to]250-fold excess. Contrary to expectations, [[delta].sup.13]C values became more negative at smaller TMSH excess. This indicates that elevated methyl group concentrations in the pore space of the injection liner facilitated close-to-equilibrium rather than kinetic isotope fractionation resulting in reproducible derivatization conditions. [[delta].sup.13]C results under these conditions compared favorably with liquid chromatography-IRMS: low standard deviations (0.3%0 for GC-IRMS, 0.1%o for LCIRMS) and a comparable offset of 1%o compared to elemental analyzer-IRMS demonstrate that both methods represent expedient ways for online isotope analysis of anionic target compounds. 10.1021/ac902750s

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2009.03.049 Byline: Hyock Joo Kwon (1), Lina Abi-Mosleh (2), Michael L. Wang (2), Johann Deisenhofer (1)(3), Joseph L. Goldstein (2), Michael S. Brown (2), Rodney E. Infante (2) Keywords: CELLBIO Abstract: LDL delivers cholesterol to lysosomes by receptor-mediated endocytosis. Exit of cholesterol from lysosomes requires two proteins, membrane-bound Niemann-Pick C1 (NPC1) and soluble NPC2. NPC2 binds cholesterol with its isooctyl side chain buried and its 3[beta]-hydroxyl exposed. Here, we describe high-resolution structures of the N-terminal domain (NTD) of NPC1 and complexes with cholesterol and 25-hydroxycholesterol. NPC1(NTD) binds cholesterol in an orientation opposite to NPC2: 3[beta]-hydroxyl buried and isooctyl side chain exposed. Cholesterol transfer from NPC2 to NPC1(NTD) requires reorientation of a helical subdomain in NPC1(NTD), enlarging the opening for cholesterol entry. NPC1 with point mutations in this subdomain (distinct from the binding subdomain) cannot accept cholesterol from NPC2 and cannot restore cholesterol exit from lysosomes in NPC1-deficient cells. We propose a working model wherein after lysosomal hydrolysis of LDL-cholesteryl esters, cholesterol binds NPC2, which transfers it to NPC1(NTD), reversing its orientation and allowing insertion of its isooctyl side chain into the outer lysosomal membranes. Author Affiliation: (1) Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA (2) Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA (3) Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA Article History: Received 6 January 2009; Revised 10 February 2009; Accepted 23 March 2009 Article Note: (miscellaneous) Published: June 25, 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2008.08.005 Byline: Dorian Prato-Garcia, Ruben Vasquez-Medrano, Margarita Hernandez-Esparza Keywords: CPC; Fenton; Ferrioxalate solar phototreatment; Phenol; Advanced oxidation processes Abstract: In this work, the performance of advanced oxidation solar assisted photochemical treatments of synthetic phenolic type wastewaters was studied at natural pH conditions, and with phenol concentrations in the range of 180-733mg/L. The photochemical treatment was mediated with ferrioxalate and peroxide in two CPC (compound parabolic collector) photoreactors of different volumes and operation conditions (batch and with closed flow). Phenol transformation efficiencies of 100% and total COD reduction percentages of 85% were reached within the first hour of phototreatment, having as final product an aromatics free effluent, in both types of reactors. The ferrioxalate type complexes using mass ratios of oxalate/phenol=1.5, oxalate/Fe.sup.3+ =15 and H.sub.2O.sub.2/phenol5.0 showed to be very effective in the treatment of these effluents, even at pH conditions close to neutrality, pH region in which the Fenton type processes begin to lose efficiency due to the precipitation of iron as a hydroxide. Author Affiliation: Engineering and Chemical Science Department, Universidad Iberoamericana, A.C., Prolongacion Paseo de la Reforma 880, Lomas de Santa Fe, C.P. 01210, Distrito Federal, Mexico Article History: Received 19 February 2008; Revised 8 August 2008; Accepted 11 August 2008 Article Note: (miscellaneous) Communicated by: Associate Editor Gion Calzaferri

The toxicity characteristic leaching procedure (TCLP) is normally used to evaluate if sludge should be managed as hazardous waste. This study examines immobilization mechanisms of arsenic onto arsenic-iron hydroxide sludge, the byproduct of arsenic removal by coagulation with ferric chloride. The leaching mechanism of arsenic from the sludge due to the TCLP is also investigated. Microscopic characterization techniques including scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the sludge samples with the As-to-Fe ratios of 0.07 to 0.15 before and after the TCLP. SEM-EDS and FT-IR results suggested that arsenic-iron hydroxide sludge be ferric hydroxide, whose surface is inner or outer spherically sorbed by arsenic, rather than the precipitate of insoluble iron-arsenic compounds such as Fe[(AsO).sub.4]. This is also confirmed by XRD results, which revealed that none of such crystalline iron-arsenic compounds were detected in the arsenic-iron hydroxide sludge. Therefore, adsorption among other possible arsenic immobilization mechanisms, namely, precipitation, coprecipitation, and occlusion, is supposed to play the major role. Due to the TCLP, the arsenic concentrations ranging from 0.26 to 2.54 mg/L were leached out of the sludge samples with the As-to-Fe ratios ranging from 0.07 to 0.15, respectively. The changes of FT-IR patterns of the sludge after the TCLP suggested that during the TCLP, desorption and resorption of arsenic occurs. The relationship between arsenic in TCLP leachate and that remaining in the leached sludge can be modeled by Langmuir isotherm, an adsorption isotherm. This indicates that desorption and resorption of arsenic onto the leached sludge is the main phenomenon controlling arsenic leachability due to the TCLP. CE Database subject headings: Sludge; Waste management; Leaching; Arsenic.

The integrated molar absorption coefficient of isolated and localized OH groups in selected minerals is theoretically investigated within the density functional theory framework. The overall decrease in absorption coefficient of stretching modes observed with increasing frequency is consistent with the experimental observations. It is related to a decrease in the magnitude of the hydrogen Born effective charge tensor projected along the OH bond as a function of increasing H-bonding. The scatter of theoretical data shows that the use of a general calibration of infrared absorbances in minerals cannot lead to accurate water contents. In contrast, the combination of theoretical modeling and experimental measurements should improve the determination of the hydrogen distribution among structurally distinct OH defects in nominally anhydrous minerals. Keywords: Infrared, spectroscopy, DFT, hydroxyl

Ab initio molecular dynamics simulations of hydroxide and hydronium ions are described near a hydrophobic interface, which has shown that both ions behave like amphiphilic surfactants that stick to a hydrophobic hydrocarbon surface with their hydrophobic side. The results have shown why hydrophobic surfaces in contact with water acquire a net negative charge, a phenomenon that has important implications for biology and polymer science.

Photoelectron-imaging spectroscopy, flowing afterglow-photoelectron spectroscopy and the flowing afterglow-selected ion flow tube technique and electronic structure calculations are used for studying the mechanism of the reaction of the hydroxide ion (H[O.sup.-]) with 1H-1,2,3-triazole. Deprotonation of 1H-1,2,3-triazole at the C5 position has initiated fragmentation of the ring structure to yield a minor product, the ketenimine anion.

The vibrational spectrum of [alpha]-AlOOH diaspore calculated at the B3LYP level of theory with a double-(symbol) quality Gaussian-type basis set by using the periodic ab initio CRYSTAL code is reported.

We report on temperature dependencies of infrared (IR) fundamental, combination, and overtone vibrations of hydroxyl species (OH) in nominally anhydrous minerals (e.g., titanite), ferroelectric crystals (K[Ta.sub.1] [sub.x][Nb.sub.x][O.sub.3], KTN), layer silicates (talc, mica, and pyrophyllite), and hydrous minerals such as apatite and synthetic hydrous/deuterated garnets [[Ca.sub.3][A1.sub.2][([O.sub.4][H.sub.4]).sub.3] and [Ca.sub.3][Al.sub.2][([O.sub.4][D.sub.4]).sub.3]] for the temperature range of 20-300 K. Data obtained by high- resolution FTIR spectroscopy show that increasing temperature generally leads to a decrease in the band height and band area of fundamental vibrations of hydroxyl species, whereas the combination and first-overtone bands commonly show different temperature dependencies. The results show that in the investigated temperature range, the variations of the band height and area for different OH bands (especially for combinations and overtones) on cooling or heating do not reflect changes in OH concentrations in the materials, but relate to temperature-dependent absorption coefficients. The observations imply that absorption coefficients calibrated at room temperature cannot necessarily be used for the determination of hydroxyl contents at other temperatures. Keywords: Infrared spectroscopy, low temperature, apatite, hydrous garnet, pyrophyllite, tale, sericite, titanite

Determination of OH number sensities outside of a platinum catalyst using cavity ringdown spectroscopy was carried out. The relative concentration of OH probed with LIF appeared to be lower compared that determined by CRDS which might be due to electron quenching as indicated by a shorter fluorescence lifetime.

Ab intio calculations with rate constants prediction were used to investigate the kinetics and mechanism of the reaction of the cyanomidyl radical (HNCN) with hydroxyl radical (OH). It was found that the primary intermediates formed HON(H)CN and HONCNH are stable in low temperature range and start dissociating when temperature is higher than 800 K giving rise to [H.sub.2]O and NCN as the primary products.

The kinetics and absolute rate constants of the gas-phase reaction of the hydroxymethyl radical (C[H.sub.2]OH) with molecular oxygen were studied using laser photolysis/near-IR absorption spectroscopy. The results showed slight negative temperature dependence in the measured temperature region.

The synthesis and characterizations of sandwich structured layered materials through direct combination of oppositely charged building blocks, such as positively charged layered double hydroxide (LDH) nanosheets and negatively charged oxide nanosheets, are presented. The characterization has shown the layered structures fabricated via layer-by-layer self-assembly, in which LDH nanosheets and oxide sheets are alternately stacked.

A mixed quantum/classical molecular dynamics embedded cluster density functional theory (DFT) was used to study the structure of the singly occupied and the lower unoccupied molecular orbitals. It was found that a considerable fraction of the excess electron density resides in the frontal o 2p orbitals of oxygen atoms in the hydrating OH group.

Dielectric spectroscopy was used to study the rational molecular dynamics of water confined to layered oxide materials with brucite structure. A nonmonotonous temperature dependence of the relaxation rates were observed for layered double hydroxides NiAlMo or ZnAlMo and it was argued that the unusual temperature dependence of the observed relaxation process was not due to a substantial loss of water.

The lipid peroxidation is studied using a nonadenine model of linoleic acid. The oxidation is found to be terminal involving the mono-allylic methylene groups at the end for hydrogen abstraction.

The kinetics of the reaction of OH [C.sub.2][H.sub.2 are evaluated by using laser flash photolysis at 248 nm to generate OH radicals and laser-induced fluorescence to monitor OH removal. The dependence of the rate coefficients on temperature and on the vibrational quantum number has demonstrated that there is a significant contribution from nonreactive vibrational relaxation in which the potential energy well of the chemical adduct, HO[C.sub.2][H.sub.2] is not significantly sampled.

Ab initio calculations were used to investigate the reactions of S[O.sub.3] with H, O, and OH radicals and estimate their rate constants. The results have shown S[O.sub.3] O reaction to be insignificant during most conditions of interest, even in lean flames, S[O.sub.3] H is found to be the major consumption reaction for S[O.sub.3].

The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm was used to study the dissociation of methanol between 1591 and 2865 K. The values obtained for reaction C[H.sub.3]OH Kr -> C[H.sub.3] OH Kr and C[H.sub.3]OH Kr -> C[H.sub.2] [H.sub.2]O Kr were found to be in agreement with the result data for earlier experimental determination and also for OH C[H.sub.3] -> products.

Electrospray ionization is used to generate bare vanadium oxide and hydroxide cluster cations, [V.sub.m][O.sub.n.sup.+] and [V.sub.m][O.sub.n-1] [(OH).sup.+] (m = 1-4, n = 1-10), and mass spectrometric techniques are used to investigate the clusters with respect to their reactivity toward methanol. Many reaction channels like abstraction of a hydrogen atom, a methyl radical, or a hydroxymethyl radical, elimination of methane and adduct formation are observed.

A topochemical synthetic approach is described for transforming brucite-like [Co.sup.2+] -[Fe.sup.2+] into hydrotalcite-like C[o.sup.2+] -F[e.sup.3+] layered double hydroxides (LDHs) is described. The results have shown that after a normal ion-exchange process, [Co.sup.2+] -[Fe.sup.3+] LDHs accommodating perchlorate anions are exfoliated into unilamellar nanosheets in formamide by an ultrasonic treatment.

Single-crystal X-ray diffraction, FTIR and Raman spectroscopies and scanning electron microscopy are used to study a comprehensive structural characterization of the colorless and yellow forms of N-hydroxyphthalimide (NHP), the deuterated form (NDP), and the ethoxylated form (ethoxy-NHP). The study shows that the crystalline yellow form of NHP exhibits a strong absorption band at 575 nm whereas the colorless NHP form does not, however the various NHP forms decompose at temperatures considerably below the melting point.

Electron pulse radiolysis and transient absorption spectroscopy are used to measure the rate constants for the reactions of phenol with the hydroxyl radical in water from room temperature to 380 degree Celsius. The results have shown that it is possible to determine the rate constants for all the reactions involved in the kinetic scheme up to supercritical conditions.

The reactions of laser-ablated group 13 metal atoms with [H.sub.2[O.sub.22] and the products in solid argon are described. Vibrational frequencies of metal hydroxides, MOH, M[(OH).sub.2] and M[(OH).sub.3], where M = Al, Ga, In and Tl, are identified by using isotopic substitution in the infrared spectra and density theory calculations.

The rate constant for the self-recombination of hydroxyl radicals ([super .]OH) in aqueous solution giving [H.sub.2][O.sub.2] product is measured up to 350 degree Celsius by direct measurement of the [super .]OH radical transient optical absorption at 250nm. The results have shown that the 230 nm band is due to hydrogen-bonded OH, the 310 nm bond corresponding to 'free' OH and the absorption spectra of the [H.super..] atom and [H.sub.2][O.sub.2] shift toward the visible.

The quantum-mechanical electronic structure methods (CASSCF and CASPT2) are used to investigate the singlet and triplet potential energy surfaces (PESs) for the gas-phase bimolecular self-reaction of [HOO.sup..]. The decomposition of an intermediate into HOOH - [O.sub.2] involves an energy barrier of 45.2 kcal/mol at 0 K, leading to a conclusion that the single H-atom transfer on the triplet PES is the dominant pathway leading to HOOH + [O.sub.2].

A novel site-specific structure-activity relationship is developed for the site-specific addition of OH radicals to (poly)alkenes at 298 K. There is agreement for noncyclic (poly)alkenes, including conjugated structures while the SAR-predicted rate constants for cyclic (poly)alkenes are found to be generally within

The diffusion of OH, H[O.sub.2], and [O.sub.3] in He, and of OH in air, is examined by using a coated-wall flow tube reactor coupled to a chemical ionization mass spectrometry. It is shown that measured values for OH and H[O.sub.2] are in better agreement with measured values of their polar analogues ([H.sub.2]O and [H.sub.2][O.sub.2]) as compared to measured values of their nonpolar analogues (O and [O.sub.2]).

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.12.005 Byline: Biswajit Mukhopadhyay (a), Jon Sundquist (b), Rodney J. Schmitz (c) Keywords: Electrochemical process; Hexavalent chromium; Groundwater contamination; Groundwater remediation Abstract: The conventional chemical reduction-precipitation technique in the removal of Cr(VI) from contaminated groundwater involves a two-step process whereby Cr(VI) is first reduced to Cr(III) at an acidic pH by a reducing agent and in a subsequent step, Cr(III) is precipitated as insoluble hydroxide at an alkaline pH. In a variation of this method, Fe(II) is added electrochemically to the Cr(VI) containing water. From a pure iron electrode, Fe.sup.2+ ions are released into the solution and bring forth the reduction of Cr(VI). At the cathode, H.sub.2O is reduced whereby the OH.sup.- ions entering the solution keep the pH of the solution in the alkaline range. This latter fact greatly facilitates simultaneous reduction of Cr(VI) to Cr(III) and co-precipitation of hydroxides of trivalent Cr and Fe. On the basis of a set of experimental data, it is shown that this process is both thermodynamically and kinetically efficient, meaning, with the electrochemical method, rapid and nearly complete removal of Cr(VI) from a groundwater source with both high and low levels of Cr-contamination can be achieved. These factors make the electrochemical process superior to the conventional chemical process in remediation of Cr-contaminated groundwater. Author Affiliation: (a) Ecology and Environment, Inc. 1412 Main Street, Dallas, TX 75202, USA (b) Ecology and Environment, Inc. 368 Pleasantview Drive, Lancaster, NY 14086, USA (c) Andco Environmental Processes, Inc. 595 Commerce Drive, Buffalo, NY 14228, USA Article History: Received 18 January 2005; Revised 24 October 2005; Accepted 13 December 2005

A study of the mechanism of the gas-phase OH initiated oxidation of glycoaldehyde in the 233-296 K temperature range using a turbulent flow reactor coupled with a chemical ionization mass spectrometer is presented. Formaldehyde, C[O.sub.2], formic acid and glyoxal were observed at RT with the yields of 80, 34, 18 and 14% respectively, in the presence of oxygen and decrease of temperature to 233K led to significant change in the yields of stable products.