The hydrolysis of epoxides catalyzed by inorganic ammonium salts in water: kinetic evidence for hydrogen bond catalysis.

Naturally-occurring inorganic ammonium ions have been recently reported as efficient catalysts for some organic reactions in water, which contributes to the understanding of the chemistry in some natural environments (soils, seawater, atmospheric aerosols, …) and biological systems, and is also potentially interesting for green chemistry as many of their salts are cheap and non-toxic. In this work, the effect of NH4+ ions on the hydrolysis of small epoxides in water was studied kinetically. The presence of NH4+ increased the hydrolysis rate by a factor of 6 to 25 compared to pure water and these catalytic effects were shown not to result from other ions, counter-ions or from acid or base catalysis, general or specific. The small amounts of amino alcohols produced in the reactions were identified as the actual catalysts by obtaining a strong acceleration of the reactions when adding these compounds directly to the epoxides in water. Replacing the amino alcohols by other strong hydrogen-bond donors, such as trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) gave the same results, demonstrating that the kinetics of these reactions was driven by hydrogen-bond catalysis. Because of the presence of many hydrogen-bond donors in natural environments (for instance amines and hydroxy-containing compounds), hydrogen-bond catalysis is likely to contribute to many reaction rates in these environments.

Gas chromatography-mass spectroscopy optimization by computer simulation, application to the analysis of 93 volatile organic compounds in workplace ambient air.

GC-MS optimization method including both advantages from chromatographic separation and mass spectrometric detection was designed for a set of 93 volatile organic compounds. Only a few experiments were necessary to determine the thermodynamic retention parameters for all compounds on a RTX-VMS column. From these data, computer simulation was used in order to predict the retention times of the compounds in temperature programmed gas chromatography. Then, an automatic selection of ions from the NIST database was performed and compared to the optimum conditions (full separation of VOC). This simulation-selection procedure was used to screen a numerous set of GC and MS conditions in order to quickly design a GC-MS method whatever the set of compounds considered.

Evaluation of adsorbents for volatile methyl siloxanes sampling based on the determination of their breakthrough volume.

Volatile methyl siloxanes (VMS) have been detected in many different atmospheres such as biogas, sewage sludge, landfill gas, gasoline and ambient air. In these different atmospheres, their presence can involve several contamination problems and negative effects in industrial processes, their identification and quantification become a real challenge. Up to now there is no standardized procedure for VMS quantification, the sampling step remaining the major obstacle. Sampling gas through sorbent tube followed by analysis on TD-GC-MS is one of the reliable possibilities. It gathers sampling and preconcentration in one step and allows discrimination between all VMS, despite the difficulty to choose the appropriate adsorbent in order to avoid loss of analytes during sampling. In this context, this work deals with the comparison of different types of adsorbents based on the determination of the VMS breakthrough volume (BV). Although Tenax TA is the most widely used adsorbent, experiments show low BV values for the lightest VMS. At 25°C, the BV of TMS and L2 are, respectively, 0.2 and 0.44 L g(-1) which can contribute to an underestimation in concentration during their quantification. Carbosieve SIII usually used for C2-C5, did not adsorb light VMS as it was expected, and breakthrough volume obtained for VMS are more than ten times less than the values obtained for Tenax. On other hand, Chromosorb 106 and Carboxen 1000 in association with Carbotrap C and Carbotrap proved to be appropriated for VMS sampling, due to the high breakthrough volumes obtained for the lightest compounds comparing to the other adsorbents. The BVs of TMS for Carboxen 1000 and Chromosorb 106 are 1.2 × 10(4) and 39 L g(-1), respectively, and 49 × 10(4) and 1142 L g(-1) for L2, respectively.

Hydrocarbon removal from bilgewater by a combination of air-stripping and photocatalysis.

In order to prevent hydrocarbon discharge at sea from the bilge of ships, the International Maritime Organization (IMO) enacted the MARPOL 73/78 convention in which effluents are now limited to those with maximum oil content of 15 ppmv. Thus, photocatalysis and air-stripping were combined for the hydrocarbon removal from a real oily bilgewater sample and an original monitoring of both aqueous and gaseous phases was performed by GC/MS to better understand the process. Our results show that the hydrocarbon oil index [HC] can be reduced to its maximum permissible value of 15 ppmv (MARPOL) in only 8.5h when photocatalysis and air-stripping are used together in a synergistic way, as against 17 h when photocatalysis is used alone. However, this air-assisted photocatalytic process emits a large quantity of volatile organic compounds (VOC) and, within the first four hours, ca. 10% of the hydrocarbon removal in the aqueous phase is actually just transferred into the gaseous one. Finally, we highlight that the n-alkanes with a number of carbon atoms higher than 15 (N(C)>15) are those which most decrease the rate of [HC] removal.

Impact of alcohol consumption on winter sports-related injuries.

INTRODUCTION: This study was carried out to evaluate data about trauma-related winter sports, including risk factors such as high speed, gender, age, alcohol consumption, details about the accident and snow conditions. METHODS: A retrospective review was conducted to determine the injury patterns and crash circumstances in holiday skiers and snowboarders. The data recorded were obtained from the database of the Pre-Hospital Emergency Registry of six skiing areas in the Dolomite mountains during the winter seasons November 2004-May 2009, injury data for major traumas from Ski Patrol Injury reports (helicopter, ambulance or ski slopes' patrol reports), and intrahospital Emergency Department data. Alcohol concentration in blood was detected in 200 individuals suffering from major trauma. RESULTS: A total of 4550 injured patients, predominantly male (69%), mean age 22 years (range 16-72), were included in the observational analysis. Knee, wrist and shoulder injuries were frequently associated with major thoracic, abdominal or head traumas (64% of cases). Suboptimal technical level, high speed, low concentration, snow or weather conditions, faulty equipment and protective devices were among the various causes of accidents. The analysis revealed that high alcohol blood concentration was present in 43% of 200 patients. CONCLUSIONS: Even though the major causes of accidents were excessive speed, excessive fatigue, technical errors and bad weather conditions, alcohol abuse was often discovered. Random sampling and a non-systematic detection of alcohol blood levels likely led to an underestimation of alcohol consumption-related injuries. It is recommended that investigations into alcoholic intoxication in injured skiers should be carried out on a large scale.

Long-term evaluation of cognitive function and cerebral metabolism in liver transplanted patients.

INTRODUCTION: Patients with liver cirrhosis without overt hepatic encephalopathy (OHE) show alterations of cognitive function and metabolism which seem to not be fully reversible after liver transplantation (OLT), but the long-term outcomes have not be studied. METHODS: Fourteen cirrhotic subjects including alcoholic (n = 4), viral (n = 4), mixed (n = 5), and cholestatic (n = 2) without OHE were evaluated for OLT as well as 8 age-matched normal controls. All subjects underwent cerebral positron emission tomography (PET) with 18F-fluorodeoxyglucose to quantify cerebral glucose metabolism and neuropsychological evaluation to test memory, intelligence, and cerebral frontal functions. Transplanted patients underwent repeat evaluations at 1 and 10 years after liver transplantation. RESULTS: Compared with the controls patients with liver cirrhosis showed significantly reduced cerebral glucose metabolism in all cerebral cortical and subcortical regions. This observation correlated with the presence of alterations in neuropsychological tests evaluating memory, frontal tasks, and visuospatial memory. Among 12 patients who were transplanted, 10 underwent repeat neuropsychological evaluation at 1 year; in addition 5 underwent PET). At 10 years the 7 living patients had repeat neuropsychological evaluation. One year after OLT, transplanted patients showed significant amelioration of cerebral glucose metabolism in all cerebral regions with significant improvements in neuropsychological tests, despite 20% of patients showing residual defects in frontal tasks. The cognitive function did not further improve at 10 years after OLT. CONCLUSION: Patients with liver cirrhosis show altered cerebral function and metabolism that revert after successful liver transplantation, but with residual mild deficits in cerebral frontal functions, which seem to not improve in the long term.

Heparin-like effect in liver disease and liver transplantation.

Liver cirrhosis is characterized by impairment of primary and secondary hemostasis but it is not clear how this impairment is related to the bleeding problems seen in cirrhosis. This delicate hemostatic balance can be perturbed by numerous conditions, such as variceal bleeding, renal failure, or infection/sepsis, which may lead to worsening of coagulation status to date. The role of endogenous heparinoids (glycosaminoglycans) in the coagulopathy of patients who have cirrhosis has been demonstrated by thromboelastography with the addition of heparinase I in patients who have recent variceal bleeding and infection. The heparin-like effect has also been demonstrated to be part of the coagulopathy seen after reperfusion in patients who have cirrhosis and are undergoing liver transplant. Therapeutic implications of these findings are not clear at the moment and the use of drugs able to cleave heparinoids should be explored.

Photocatalytic degradation of pesticide methomyl: determination of the reaction pathway and identification of intermediate products.

The degradation of pesticide methomyl in aqueous solution by UV-irradiation in the presence of TiO2 "Degussa P-25" has been studied. It was found that mineralisation to carbon dioxide, water, sulfate and ammonia took place during the process. The rate of photodecomposition of methomyl was measured using high performance liquid chromatography (HPLC), while its mineralization was followed using ion chromatography (IC), and total organic carbon (TOC) analysis. The identification of reaction intermediate products was carried out using coupled techniques HPLC-MS (electrospray ionization in positive mode) and a degradation pathway was proposed. Under our conditions, complete disappearance of 1.23 x 10(-4) mol l(-1) of pure pesticide occurred within 45 min of illumination and 80% TOC removal occurred in less than 4 h. Three main intermediates were identified resulting from (i) the rupture of the ester bond (or the N-O bond), (ii) the hydroxylation of methyl group borne by the nitrogen atom and (iii) the product resulting from the decarboxylation of the oxidized hydroxylated methyl group (photo-Kolbe reaction). In order to be sure that the photocatalytic results were consistent, hydrolysis and photolysis tests were performed. Photocatalysis proved to be an excellent new advanced oxidation technology (AOT) to eliminate methomyl present in water.

Experimental microkinetic approach of the photocatalytic oxidation of isopropyl alcohol on TiO2. Part 1. Surface elementary steps involving gaseous and adsorbed C3H(x)O species.

The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factor and activation energy). The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The deep oxidation (CO2 and H2O formation) of low concentrations of organic pollutants in air is one of the interests of the PCO. For IPA, literature data strongly suggest that acetone is the single route to CO2 and H2O and this explains that the present study is dedicated to the elementary steps involving gaseous and adsorbed C3H(x)O species. The microkinetic study shows that strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA, respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The kinetic parameters of the elementary steps determined in the present study are used in part 2 to provide a modeling of macroscopic kinetic data such as the turnover frequency (TOF in s(-1)) of the PCO using IPA/O2 gas mixtures.

Experimental microkinetic approach of the photocatalytic oxidation of isopropyl alcohol on TiO2. Part 2. from the surface elementary steps to the rates of oxidation of the C3H(x)O species.

The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of the PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factors and activation energies). These kinetic parameters are used to evaluate a priori the catalytic activity (turnover frequency, TOF, in s(-1)) of the solid that is compared to the experimental value. The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The microkinetic study shows that only strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The apparent rate constant (1.4 10(-3) s(-1)) of the Langmuir-Hinshelwood elementary step between IPA(sads) and the active oxygen containing species generated by the UV irradiation provides the TOF of the PCO for IPA/O2 gas mixtures. The kinetic parameters of the elementary steps determined by the experimental microkinetic approach allow us to provide a reasonable simulation of the experimental data (coverages of the adsorbed species and partial pressures of the gases of interest) recorded during a static PCO of IPA(sads) species.

Degradation of pentachlorophenol in cyclodextrin extraction effluent using a photocatalytic process.

This work evaluates a process for the elimination of pentachlorophenol (PCP) from effluents provided by a cyclodextrin-assisted flushing of contaminated soils. The effectiveness of photocatalytic degradation of PCP in several cyclodextrin (CD) solutions was evaluated using TiO2 as a photocatalyst. Effects of CD type on PCP degradation rate were studied at two pH values. A similar effect was observed for all CDs used on degradation rate of PCP and the decay of PCP was found to be less extensive at pH 11 than at pH 7. The kinetic orders of the photocatalytic reactions of PCP for all of the solutions have been determined. The first-order rate constants were found to be 0.0884, 0.0362, 0.0197 and 0.0053 min(-1) in CD solutions, respectively, at 0, 1, 2 and 5 mmol l(-1) of CD. Batch experiments were performed in order to study the CD extraction enhancement of PCP previously adsorbed on soil. The results show that the removal capacity of PCP from soil increases with CD concentration (from 0 to 5 mmol l(-1)). When the CD concentration was 5 mmol l(-1), an extraction of about 70% of PCP adsorbed on soil was observed, whereas only 37% was removed when water was used as the flushing solution. The optimal conditions for such a coupled method depend on the nature and concentration of the extracting agent and also on the photocatalytic experimental conditions. This work revealed that the coupling of cyclodextrin-enhanced solubilization and photocatalytic treatment is a promising method for contaminated soil remediation.

[Modification of an experimental model of chronic pancreatic and biliary fistula in the minipig (author's transl)]. / Modifiche di un modello sperimentale di fistola pancreatica e biliare cronica nel minipig.

An improvement in Corring's experimental model in the minipig is described. The model requires: -- a complete diversion of the biliopancreatic secretion and the possibility of its reintroduction into the duodenum; -- a particular anaesthesiological, technical and management problems taken up during the course of the research. Data are also given about basal pancreatic and biliary secretions in this particular experimental model.