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Determining a technology's merit as a solution to Hungarian drinking water arsenic contamination goes beyond technical concerns: environmental and economic aspects also play very important roles. In an effort to address the current arsenic drinking water requirements in Hungary, life cycle analysis (LCA) methodology was applied on two example arsenic removal technologies, coagulation-filtration and adsorption, from cradle to grave. A distribution of 500 m³/day was assumed, along with a range of possible operation boundary conditions modelled solely for As treatment. Nine out of 10 considered impact categories tended to favour coagulation-filtration, however realistic variations in water chemistry and product characteristics led to some overlap of their environmental impact. Unlike other studies on water systems, electricity did not have a large direct impact; this was due to the focussed nature of this study on individual treatment technologies rather than an entire water supply system. Regeneration of the adsorption technology filter material was also observed to require nearly the same mass of materials for one regeneration as what was needed to support the coagulation-filtration technology for an entire year. Hazardous waste was surprisingly not reduced for adsorption compared to coagulation-filtration due to pre filtration requirements and an extra regeneration, even though adsorption shifts some of the environmental burden to the production phase. Additionally, cost analysis observes that coagulation-filtration is the cheaper of the two technologies; its highest cost is that of waste disposal, while the highest single expense modelled is that of the adsorption media cost. [ABSTRACT FROM AUTHOR]

Cross-linked protein crystals represent a new class of micro- and mesoporous materials with properties potentially useful in technologies as diverse as chiral separations and drug delivery. These applications require the generation of protein crystals in formats and sizes quite distinct from the traditional submillimeter single crystals favored by structural biologists. Here we report a high-yield method for forming monodisperse protein crystals with tunable dimensions ranging from 250 nm up to tens of micrometers. X-ray powder diffraction of these crystallites confirms that the hen egg white lysozyme crystals are identical in structure to that of the bulk tetragonal lysozyme (a = 79.05 Å; c = 37.96 Å).

Spherical PbSe semiconductor nanocrystals with near-infrared absorption of 1100−2520 nm (corresponding to diameters of 3−13 nm) were synthesized in a noncoordinating solvent (1-octadecene). The as-prepared PbSe semiconductor nanocrystals have very narrow size distributions (σ ≅ 5−7%) without any postsynthetic size selection. High-resolution transmission electron microscopy (TEM), electron diffraction, and X-ray diffraction show that the nanocrystalline particles are single domains of rock-salt PbSe. A water-soluble form of these materials was generated through simple surface treatments.

A large absorption resonance has been observed in the far-infrared spectrum of water confined within inverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in heptane. The amplitude and spectral position of this resonance depend on the size of the water pool. The origin of the THz absorption of these liquid pools is assigned to surface oscillations of the water pool, driven by the interfacial tension of the water−surfactant-oil interface. These data indicate a dramatic restructuring of the density of states of the liquid and are consistent with a theoretical model for the oscillatory modes of liquid droplets. The presence of a large excess in the vibrational density of states of confined water could have far-ranging implications in many biochemical and chemical processes where confined water is present.

Efficient materials for recording volume holograms are described that could potentially find application in archival data storage. These materials are prepared by mixing photopolymerizable vinyl monomers with a liquid epoxy resin and an amine hardener. A solid matrix is formed in situ as the epoxy cures at room temperature. The unreacted vinyl monomers are subsequently photopolymerized during hologram recording. A key feature of these materials is the separation of the epoxy and vinyl polymerizations. This separation allows for a large index contrast to be developed in holograms when components are optimized. The standard material described in this work consists of a low index matrix (n ≅ 1.46), comprised of diethylenetriamine and 1,4-butanediol diglycidyl ether, and a high index photopolymer mixture (n ≅ 1.60) of N-vinylcarbazole and N-vinyl-2-pyrrolidinone. This material is functional in thick formats (several millimeters), which enables narrow angular bandwidth and high diffraction efficiency. A dynamic range (M/#) up to 13 has been measured in these materials. Holographic performance is highly dependent on the amount of amine hardener used, as well as on photopolymer shrinkage.

¹H and ¹³C nuclear magnetic resonance (NMR) relaxation studies of thiophenol-capped CdS nanocrystals are presented. The transverse and longitudinal relaxation times were investigated as a function of nanocrystal radius, and the transverse relaxation time was also studied as a function of temperature. Both proton and carbon T2 values were found to increase with nanocrystal radius, contrary to initial expectations. This effect is explained in terms of motion of the thiophenol with respect to the nanocrystalline surface. Theoretical expressions for relaxation due to anisotropic motion are developed based on both bridging and terminal bonding configurations of the thiophenol ligands, and the data are fit to these models. The data are found to be consistent with thiophenol ligands bound in a terminal fashion to a single Cd atom. The temperature dependence of the proton T2 value is also suprising. T2 is found to decrease with increasing temperature, and the size of this change scales with the nanocrystal radius. This is explained in terms of an extra component of relaxation due to thermally excited electrons.