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Sol-gel-based zirconia (Zr[O.sub.2]) and silica (Si[O.sub.2]) were obtained in situ via hydrolysis-polycondensation of metal alkoxide precursors in membranes of poly(3-hydroxybutyrate) (PHB). What followed was an assessment of thermal and spectroscopic effects from the insertion of the inorganic network in the PHB matrix. The findings exhibited a dependence of both the concentration and the chemical nature of the precursor on the properties of the as-formed inorganic-organic hybrids. The results also indicated that positive nucleating effects, a reduction of the crystallite size and a variation in thermal transitions correlate with spectroscopic data from the alpha and beta crystal forms of the PHB matrix, as well as the crystallization data obtained through polarized light microscopy., INTRODUCTION The sol-gel method was developed during the 1960s due to a demand for faster and more secure synthetic routes in the nuclear industry [I). Since then, this versatile process [...]

The glass transition is the freezing of a liquid into a solid state without evident structural order. Although glassy materials are well characterized experimentally, the existence of a phase transition into the glass state remains controversial Here, we present numerical evidence for the existence of a novel first-order dynamical phase transition in atomistic models of structural glass formers. In contrast to equilibrium phase transitions, which occur in configuration space, this transition occurs in trajectory space, and it is controlled by variables that drive the system out of equilibrium. Coexistence is established between an ergodic phase with finite relaxation time and a nonergodic phase of immobile molecular configurations. Thus, we connect the glass transition to a true phase transition, offering the possibility of a unified picture of glassy phenomena.

Natural surface coatings from Cayuga Lake, New York with components Fe oxide, Mn oxide, Chlorella vulgaris, and Leptothrix discophora cells are collected and studied for the adsorption of Pb in relation to a pH range of 5-8. The results are compared to the predicted results of a Kurbatov-based additive model, and graphed for Pb binding to the biofilm components at different pH levels.

Studying the reductive separation of manganese oxide by Fe(II) in simulated conditions of acid mine drainage is analyzed by using X-ray absorption synchrotron spectroscopy and a flow-through reaction cell. In affected natural environments by acid mine drainage complex intermediate solid phase formation on mineral surfaces that undergo reductive dissolution can influence the release rate of metals to solution.

This study examines the effects of metal-adsorptive materials on long-contaminated mineral soil. The study concludes that the metal-specific effects occurred in the reduction of soluble concentrations of reactive oxides.

Investigations into the effects of permanent charge on the acid-base properties of surface complexation models materials whose charges are disributed uniformly on the surface follow the Guoy-Chapman model where the surface potential is treated as a function of surface charge and ionic strength. For porous materials whose charge is distributed both on the internal and external surfaces, permanent charge follows the Poisson-Boltzmann model where surface potential is treated as a function of internal charge, ionic strength and surface charge.

The ability of different organic compounds to catalyze chromium(VI) reduction reactions was investigated in the presence and absence of oxide surfaces. The results showed that surface-catalyzed Cr(VI) reduction by titanium dioxide has the highest efficiency. Likewise, geothite also displayed quite high catalytic reactivity, but less than that of titanium dioxide.

The difference between the protons added and removed in dissolution of oxide minerals rather than the number of protons required to form an activated complex gives the proton rate order. The mechanism explains similar values of the rate order and metal valence and the similarity between rates of water ligand lability in dissolved complexes and metal desorption. The assignment of ligand functional groups to metal-coordination sites indicates that ligand-promoted dissolution is often dependent on adsorbed proteins.

The formation yields of OH radicals from the gas-phase reactions of O3 with different alkenes were investigated using gas chromatography and in situ Fourier transform infrared absorption spectroscopy. Cyclohexanone and cyclohexanol were obsrved as products when cyclohexane was present, thus indicating the formation of OH radicals from O3 reactions.

The aqueous suspension of the mixed oxides Al(OH)3/SiO2 and Fe(OH)3/SiO2 was studied using transmission electron microscopy to determine the influence of oxide interaction on their adsorption characteristics. The results showed that the interaction between Al(OH)3 and SiO2 was stronger than that observed in Fe(OH)3 and SiO2. In addition, there was enhanced Cd+ and Ca2+ adsorption.

A short description is provided, on the present knowledge of endoperoxides: preparation and thermal and photolytic decomposition, with a special emphasis on the structural requirements to favor cycloreversion. The profitable use of this property, in the development of highly reversible photochromic systems, and of specific sources or traps of oxygen in aqueous media is also described.

The real-time observations of reactions for a number of systems, including the island growth of surface oxide on the Cu (110) are focused. It is further observed that scanning tunneling microscopy allows the direct observation of these reactions on the surface of the atomic scale.

Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at [...]

Dislocations in oxides such as cerium dioxide, a solid electrolyte for fuel cells, have a property that is the opposite of what researchers expected, according to new analysis at Massachusetts [...]

Iodine oxide was detected in the boundary layer at Mace Head, Ireland in May 1997, suggesting that iodine chemistry occurs in the troposphere. IO produces O(sub2) and halogen atoms when reacting with itself or with halogen oxides BrO and C1O. IO can have a major impact on the boundary-layer photochemistry at levels of 6 p.p.t., and further investigations will establish the conditions that result in IO.

M. Zhang and P. Boolchand argue that properties of the glassy state in systems like Si[O.sub.2] and [([Na.sub.2]O).sub.χ] [(Te[O.sub.2]).sub.1-χ] can be understood in terms of a constrained network picture (1). [...]