Trichloroethylene,tetrachloroethylene and carbon tetrachloride in an urban atmosphere: mixing ratios and temporal patterns

The measurement of halogenated hydrocarbons in the atmosphere is a matter of great interest owing to their adverse effects on the human health and the environment. This work is focused on the measurement of three toxic chlorinated hydrocarbons: trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CTC). Moreover, CTC is a greenhouse gas and an ozone depleting gas, restricted under the Montreal Protocol. Owing to their low reactivity, the target chlorinated hydrocarbons are considered to be persistent and, thus, many measurements only address their mean mixing ratios (a concentration measure expressed as mol/mol). Consequently, most of the reported data have low temporal resolution as daily, seasonal or yearly mean mixing ratios, obtained with few measurements. In the study reported in this paper hourly measurements were performed for a long period of time: almost two years for TCE and PCE, and one year for CTC. The main objective was to study the temporal variability of the chlorinated hydrocarbons with high temporal resolution in order to identify their main sources and to enhance the understanding of their atmospheric processes. During the measurement period, March 2007–February 2008 with N?=?3290 valid data, CTC showed a mean mixing ratio of 0.16?ppbv (SD?=?0.13) with lower temporal variability than the majority of non-methane hydrocarbons (NMHCs), being very well mixed in the urban atmosphere owing to its long lifetime. TCE and PCE mean mixing ratios for the May 2006–February 2008 period, were 0.13?ppbv (SD?=?0.42, N?=?4601) and 0.25?ppbv (SD?=?0.54, N?=?4709) respectively, with a larger temporal variability. The study of the sources of TCE and PCE reveals that both compounds have industrial and/or commercial origin, but with different main sources.     

Biocompatible inorganic nanoparticles for [18F]-fluoride binding with applications in PET imaging

A wide selection of insoluble nanoparticulate metal salts was screened for avid binding of [(18)F]-fluoride. Hydroxyapatite and aluminium hydroxide nanoparticles showed particularly avid and stable binding of [(18)F]-fluoride in various biological media. The in vivo behaviour of the [(18)F]-labelled hydroxyapatite and aluminium hydroxide particles was determined by PET-CT imaging in mice. [(18)F]-labelled hydroxyapatite was stable in circulation and when trapped in various tissues (lung embolisation, Subcutaneous and intramuscular), but accumulation in liver via reticuloendothelial clearance was followed by gradual degradation and release of [(18)F]-fluoride (over a period of 4 h) which accumulated in bone. [(18)F]-labelled aluminium hydroxide was also cleared to liver and spleen but degraded slightly even without liver uptake (Subcutaneous and intramuscular). Both materials have properties that are an attractive basis for the design of molecular targeted PET imaging agents labelled with (18)F.     

Thermodynamic analysis of polymerization-induced phase separation of a polystyrene in epoxy/monoamine–diamine systems. Effect of monoamine–diamine proportion on the phase diagram

Polymerization-induced phase separation of a polystyrene in various epoxy-amine systems where the amino groups were provided by a monoamine and a diamine mixed in different proportions was thermodynamically studied. A model based on the Flory–Huggins theory extended by Koningsveld and Staverman approach where the interaction parameter was dependent on temperature, composition and conversion, and polydispersity of the components was considered, was used. A general equation for the evolution during polymerization of the epoxy-amine species distributions according to the monoamine–diamine ratio was derived from the Stockmayer distribution. The interaction parameters continuously decreased with conversion. Phase diagrams of the blends were obtained and the critical composition was between 5 and 6 vol.% PS in all blends.     

Could marine aerosol contribute to deteriorate building materials from interior areas of lighthouses? An answer from the analytical chemistry point of view

In this work, a multianalytical methodology based on a combination of spectroscopic techniques such as Raman spectroscopy and micro energy dispersive X‐ray fluorescence spectroscopy, and soluble salt analysis by means of ion chromatography followed by a correlation analysis of these data was applied, in order to identify the nature of the deterioration compounds present in different building materials located on inner rooms from the ground floor of the Igueldo lighthouse (San Sebastian, Basque Country, North of Spain), and in order to prove if marine aerosol could contribute to cause deterioration processes in this kind of materials. The main deterioration compounds identified were sulfate and nitrate salts. Taking into consideration the positioning of some materials, a gypsum plaster covering them could be the sulfate source responsible of the crystallisation process of a wide variety of sulfate salts. Nevertheless, in some areas were no gypsum plaster remains are present, ammonium sulfate crystallisations were identified. The presence of this kind of sulfate could suggest a possible sulfate input coming from the migration of ammonium sulfate (among other sulfate salts) carried on marine aerosol, which can be deposited on the facade of the lighthouse and migrate to its inner areas. The possible source of nitrates that could cause the crystallisation of a wide variety of nitrate salts identified in this work could be the infiltration of ammonium nitrates coming from seagull droppings from outdoor to indoor areas. Copyright © 2013 John Wiley & Sons, Ltd.     

A general theory of tensor products of convex sets in Euclidean spaces

Positivity - We introduce both the notions of tensor product of convex bodies that contain zero in the interior, and of tensor product of 0-symmetric convex bodies in Euclidean spaces. We prove...     

Simulation of molecular fractionation and species distributions in phase separation of polystyrene-modified epoxy/monoamine–diamine blends

Molecular fractionation occurred at the beginning of phase separation in blends based on a polystyrene modifier and an epoxy system undergoing polymerization with a monoamine and a diamine mixed in different proportions was studied thermodynamically. The study was conducted by simulating in each separated phase the species distributions of components of the blend, the stoichiometric ratio, and the proportion of monoamine–diamine at cloud-point conditions. A model based on Flory–Huggins theory described in a previous paper Rico et al. [1] where the interaction parameters were dependent on temperature, composition, and conversion, χ(T,?,p), and where the polydispersity of the components was taken into account, was used for simulation. The effect of modifier proportion, monoamine–diamine ratio and polymerization temperature on molecular fractionation and species distribution was determined and analyzed. Explanations of the estimated trends were given on the basis of the thermodynamic model used.     

Selective oxidation of alkyl and aryl glyceryl monoethers catalysed by an engineered and immobilised glycerol dehydrogenase

Enzymes acting over glyceryl ethers are scarce in living cells, and consequently biocatalytic transformations of these molecules are rare despite their interest for industrial chemistry. In this work, we have engineered and immobilised a glycerol dehydrogenase from Bacillus stearothermophilus (BsGlyDH) to accept a battery of alkyl/aryl glyceryl monoethers and catalyse their enantioselective oxidation to yield the corresponding 3-alkoxy/aryloxy-1-hydroxyacetones. QM/MM computational studies decipher the key role of D123 in the oxidation catalytic mechanism, and reveal that this enzyme is highly enantioselective towards S-isomers (ee > 99%). Through structure-guided site-selective mutagenesis, we find that the mutation L252A sculpts the active site to accommodate a productive configuration of 3-monoalkyl glycerols. This mutation enhances the k_cat 163-fold towards 3-ethoxypropan-1,2-diol, resulting in a specific activity similar to the one found for the wild-type towards glycerol. Furthermore, we immobilised the L252A variant to intensify the process, demonstrating the reusability and increasing the operational stability of the resulting heterogeneous biocatalyst. Finally, we manage to integrate this immobilised enzyme into a one-pot chemoenzymatic process to convert glycidol and ethanol into 3-ethoxy-1-hydroxyacetone and (R)-3-ethoxypropan-1,2-diol, without affecting the oxidation activity. These results thus expand the uses of engineered glycerol dehydrogenases in applied biocatalysis for the kinetic resolution of glycerol ethers and the manufacturing of substituted hydroxyacetones.

Design and fabrication of a robust heterogeneous biocatalyts for the selective oxidation of alkyl/aryl glyceryl monoethers through the engineering and immobilization of glycerol dehydrogenases.     

On the cyclicity of weight-homogeneous centers

Let W be a weight-homogeneous planar polynomial differential system with a center. We find an upper bound of the number of limit cycles which bifurcate from the period annulus of W under a generic polynomial perturbation. We apply this result to a particular family of planar polynomial systems having a nilpotent center without meromorphic first integral.     

On a Normal Form for Non-Weakly Sequentially Continuous Polynomials on Banach Spaces

Let p be an m-homogeneous polynomial on a complex Banach space,and let (x_n)n be a bounded sequence such that when evaluatedin polynomials of degree less than m, it converges to zero,but p(x_n = 1. It is proved here that there exists a basic sequence(y_k)k equivalent to a subsequence , for which . 2000 MathematicsSubject Classification 46B99.     

Isomerization Reactions in Anionic Mesoionic Carbene‐Borates and Control of Properties and Reactivities in the Resulting CoII Complexes through Agostic Interactions

We present herein anionic borate‐based bi‐mesoionic carbene compounds of the 1,2,3‐triazol‐4‐ylidene type that undergo C?N isomerization reactions. The isomerized compounds are excellent ligands for Co^II centers. Strong agostic interactions with the “C?H”‐groups of the cyclohexyl substituents result in an unusual low‐spin square planar Co^II complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high‐spin tetrahedral Co^II center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single‐crystal EPR spectroscopy. We conclusively show here that the structure and properties of these Co^II complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene‐based ligands.