The logic of Probabilistic risk assessment versus decision levels

The emergence of risk analysis in relation to technological development is traced. The logical foundations of Probabilistic Risk Assessment as it is currently structured are examined and discussed with respect to levels of decision making and to the nature of different risks. It is shown that the static and synoptic nature of the PRA model is adequate for decision contexts which focus on technical content but inadequate for higher level decisions. Finally, six questions proposed for consideration by a SMiRT panel on decision-making are addressed.     

A non-linear analysis to detect the origin of PM10 concentrations in Northern Italy

This work presents the formalization and the application of the factor separation technique in order to investigate the impact of precursor emission and their nonlinear interaction (in particulate matter accumulation processes). By processing the simulations of a 3D multiphase modeling system, the factor separation methodology can support the Environmental Authority in quantifying the impact of precursor emissions on PM10 production and consequently in assessing the feasible efficiency of different emission control strategies over a considered domain. The case study proposed by this paper focuses on the Po Valley region (Northern Italy), characterized by critical PM10 levels claiming for sound emission reduction policies. The results show the heavy nonlinearities and the strong seasonal dependence in the formation of PM10, over the study domain. Furthermore the results highlight that peak PM10 concentrations are mainly related to primary PM emissions in urban areas, and gas emissions (mainly NOx and NH3) in rural areas.     

Frequency and significance of anti-gliadin and anti-endomysial antibodies in autoimmune hepatitis

Celiac disease has been associated with autoimmune disorders, but its frequency in autoimmune hepatitis is unknown. Sera from 157 patients with type 1 autoimmune hepatitis, 24 patients with type 2 autoimmune hepatitis, 62 patients with primary biliary cirrhosis, 30 patients with chronic hepatitis B, and 80 patients with chronic hepatitis C were tested for immunoglobulin A anti-endomysial antibodies by indirect immunofluorescence and immunoglobulin A and G antibodies to gliadin by enzyme immunoassay. Duodenal biopsy evaluation was recommended in patients seropositive for immunoglobulin A anti-endomysial antibodies. Immunoglobulin A anti-endomysial antibodies were present in eight of the 181 patients with autoimmune hepatitis (4%), including six with type 1 disease (4%) and two with type 2 disease (8%). Immunoglobulin A antibodies to gliadin were found in six of these eight patients, but they were also present in two others, including one patient with chronic hepatitis C. Five of the eight patients with immunoglobulin A antiendomysial antibodies, including three patients with no gastrointestinal symptoms, had duodenal biopsies and subtotal villous atrophy was present in all of them. No patient with primary biliary cirrhosis or chronic viral hepatitis had antiendomysial antibodies. The presence of celiac disease in autoimmune hepatitis is high (at least one in 36 patients) and it is predominantly asymptomatic. Screening with anti-endomysial and anti-gliadin antibodies should be performed and results confirmed with intestinal biopsy.     

Autoantibodies to tissue transglutaminase as predictors of celiac disease

Our aim was to study the prognostic value of growth hormone (GH) -stimulated insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) generation in patients with compensated [group 1 (N = 8) with a Child-Pugh (CP) score of 5-8] and decompensated postnecrotic liver cirrhosis [group 2 (N = 7) with a CP score of 9-12]. Serum levels of IGF-I, GH-binding protein (GHBP), and IGFBP-3 were measured before and 24 hr after a single subcutaneous injection of recombinant human GH (rhGH, 0.14 units/kg). Patients (mean age 56 years) were followed prospectively for three years. Six patients (40%) died during the follow-up period, of whom half had a CP score <9. Mean serum IGF-I levels 24 hr after rhGH injection (group 1 vs group 2, 17.4 +/- 6.8 vs 7.4 +/- 0.7 nmol/liter) predicted survival with 93% accuracy. Levels <10 nmol/liter portended a poor prognosis, with 15% survival at one year, whereas levels >10 nmol/liter had a 100% survival rate at one and two years, respectively. Baseline IGF-I (9.98 +/- 2.0 vs 6.38 +/- 0.8 nmol/liter), GHBP (9.2 +/- 3 vs 5.7 +/- 0.8%/50 microl), and IGFBP-3 serum levels at baseline (1.7 +/- 0.3 vs 0.86 +/- 0.2 mg/liter) and at 24 hr (2.04 +/- 0.38 vs 0.99 +/- 0.3 mg/liter) did not add to the predictive value of stimulated IGF-I levels at 24 hr and were less accurate in predicting the outcome in comparison to CP score (80%). We conclude that stimulated IGF-1 <10 nmol/liter may be a true predictor of a negative prognosis in patients with liver cirrhosis.     

Vanadium-molybdenum phosphates supported by TiO2-anatase as new catalysts for selective oxidation of ethane to acetic acid

Dispersion of vanadium and molybdenum phosphates on titanium oxide (anatase) below the monolayer gives good catalysts for direct oxidation of ethane to acetic acid. By comparison with the dispersion of only vanadium phosphate, the higher selectivity to acetic acid for vanadium and molybdenum phosphates has been explained by an interaction between molybdenum and vanadium as it can be deduced from electron spin resonance and laser Raman spectroscopy studies.     

Structural reliability in the continuous feedback process for model validation and regulations improvement

The connections between structural reliability and system reliability are reviewed, emphasizing their intimate dependence. The problem of model validation is then outlined; the importance of data in this respect is analyzed.The role of structural reliability in the set-up of regulations and standards is shown to be the statistical analysis of the ‘safety margin’ provided by component design.Furthermore the importance is stressed of implementing a continuous feedback between analysis and operational data on individual structures in order to improve and update prior estimates and models.     

Relation entre les proprietes acides de graphites naturels et leur activite catalytique dans l'isomerisation de l'oxyde de styrene

The surface properties of two natural graphites have been investigated by catalytic activity in the isomerisation of styrene oxide to phenylacetaldehyde and by programmed thermodecomposition (TDP) combined with mass spectrometry gas analysis. The oxygen and water vapour influence has been studied in both cases.The two catalysts are respectively a natural Ceylon graphite (GC solid) with a 3.0 m²/g BET area and a natural Madagascar graphite (GM solid) which has been ground and has a 10.6 m²/g BET area (Table 1).The catalytic isomerisation runs were carried out at 305°C and the results are summarised in Table 2 for different gas mixture compositions. Oxygen directly favours the conversion (TTG) while water vapour mainly influences the selectivity (S).The thermodecomposition products of these solids are mainly CO and CO₂ as shown on Fig. 1. However the relative percentage of CO₂ which is related to the acidic properties of graphites (24) is very different, 16% of the BET area for the GC solid, but only 2% for the GM solid (Table 3). When the catalyst CC is pretreated at 300°C in oxygen instead of nitrogen, the TDP spectrum remains the same but the number of sites remarkably increases as shown in Table 4. Moreover the comparison of Tables 2 and 4 shows a parallelism between isomerisation activity and acidic properties. For this reason, we further investigated the influence of gaseous atmosphere by studying the TDP of the two graphites, first degassed at 850°C and then pretreated at 300°C with air or nitrogen in presence (or not) of water vapour. Important modifications are observed in the spectra (Figs. 2 and 3). Oxygen increases the total number of acid sites. The effect of water vapour is weaker. However, for the GM solid it increases the relative percentage of strong acid sites, i.e. desorbing at the lowest temperatures. For the GC solid, the effect is opposite.These results suggest that only a fraction of the acid functional groups is active for isomerisation, specifically those desorbing CO₂ near the reaction temperature. This assumption is also supported by the fact that a used catalyst presents such groups, while a fresh one does not, as shown on Fig. 4, which means that catalytic sites have been developed during reaction. Their number is increased when oxygen is present in the gaseous phase, and their stability is modified by the presence of water vapour.     

Vanadium–molybdenum phosphates supported by TiO2 for ethane oxidation to acetic acid: a correlation between the local environment of vanadium and the reactivity

Different complementary physicochemical tools have been used to explain the improvement of the catalytic performances for ethane oxidation into acetic acid induced by the addition of molybdenum as phosphate to vanadium phosphate deposited on TiO₂-anatase, at a coverage below the monolayer. Electron microscopy techniques have shown that the elements are dispersed on the support. Electron spin resonance, laser Raman and UV-visible spectroscopies have evidenced that the short range order around vanadium is modified by the presence of molybdenum. ⁵¹V NMR has shown that molybdenum favours the octahedral symmetry of vanadium. The acidic properties of the catalyst are improved by the adding effect of molybdenum and by the addition of water. This should explain a better desorption of acetic acid and the improvement of the corresponding yield. This confirms the importance of the atomic environment of vanadium-based oxides to control the mild oxidation of light alkanes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Impact of Climate Change on Salinization of Coastal Water Resources

Water Resources Management - A density-dependent numerical model was set up to quantify the actual and future (2050) salinization of a coastal aquifer in the Po Delta (Italy). SEAWAT 4.0 was used...