Spectroscopic investigation of the high-current phase of a pulsed GMAW process

International audienceWhile metal vapours have an important impact on the efficiency of the pulsed gas metal arc welding process, only a few papers are focused on this effect. In this paper, methods based on emission spectroscopy are performed to improve the understanding of the physical phenomena occurring during the high-current pulse. Boltzmann plots applied to iron lines, the Stark broadening of the 696.5 nm argon line and composition calculations assuming local thermodynamic equilibrium are used to determine characteristic parameters of the plasma. It is observed that the central part of the arc is mainly composed of iron. The percentage of iron increases quickly at the beginning of the high-current pulse, and slowly decreases, when the central part broadens. During the high-current phase the temperature profile has a minimum value of around 8000 K at the axis of the arc while the argon envelope of the central part reaches temperatures of approximately 13.000 K. High percentage of iron and high radiation of the plasma at the centre can explain the measured shape of the temperature profile

Color vision loss among styrene-exposed workers neurotoxicological threshold assessment

Styrene represents nowadays one of the most used organic solvent. The current exposure limit proposed for this chemical differs significantly from country to country: the Threshold Limit Value - Time Weighted Average (TLV-TWA) proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) is 50 ppm while the German, Finnish and Swedish occupational exposure limit is 20 ppm. Nevertheless, effects on the nervous system were recently reported in workers exposed at TWA styrene levels below the current TL V. Neuro-optic pathways have been sh own to be particularly vulnerable to organic solvent exposure. Analysis and measurements of visual functions can provide important information on early neurotoxic effects. Previous studies support the hypothesis that styrene exposure can induce a dose-dependent color vision loss. The aim of this study is to assess a threshold level below which no detectable effect occurs for color vision. We applied a sub-application of the change point problem in two-phase regression considering one phase as a constant line. In accordance with this model the maximum-likelihood technique was used as a method to examine the dose-effect relationship between externa I styrene exposure and chromatic discrimination. The present article presents a joint analysis of data from two previously published studies, one carried out in Canada and the other in Italy. The age and seniority of the workers from both countries were remarkably similar, as were the process type, the chemicals used and the work-tasks oi exposed subjects. The mathematical method presented here shows the existence of a statistically significant threshold. This finding shows that, in fiberglass-reinforced plastics industry, visual color impairment could be significantly detected above 4 ppm (upper limit of the confidence interval at 5% = 26 ppm). The exact clinical meaning of this effect, and also the progress of the impairment in exposed workers, is still to be assessed in further studies. The results of our study support the need of a reduction of the occupational limits for styrene in workplaces to values close to or lower than German, Finnish or Swedish exposure limits

Head circumference at birth and maternal factors related to cord blood total IgE.

International audienceBACKGROUND: A recent study reported an association between a large head circumference at birth and adult total IgE. However, no study has yet looked at the relation between head circumference and cord blood IgE. OBJECTIVES: To assess the relationship between child's cord blood total IgE and head circumference at birth taking parental allergy and smoking habits as well as placental calcifications into account. METHODS: Two samples of unselected newborns and their mothers with uncomplicated pregnancies were studied: 235 in study A with data on parental allergy and 99 in study B with data on placental calcifications. RESULTS: In both studies, cord blood IgE was significantly related to large head circumference at birth (0.07 vs 0.15 IU/mL for newborns /= 37 cm, respectively, P = 0. 03 for study A and 0.09 vs 0.28 IU/mL, P = 0.04 for study B). Cord blood IgE was unrelated to parental smoking habits. Maternal IgE significantly increased in mothers exposed to both active and passive smoking during pregnancy compared with other pregnant women. High cord blood IgE were associated with high maternal IgE (r = 0. 38; P < 0.001). Multiple linear regression showed that large head circumference, maternal IgE and clinical manifestations of maternal, but not paternal, allergy were independently related to cord blood IgE (study A). Large head circumference and placental calcifications were independently related to a higher cord blood IgE level (study B). CONCLUSIONS: Besides the role of genetic factors, results on the preferential role of maternal vs paternal allergy and associations to large head circumference and placental calcifications support the hypothesis of the role of environmental factors during pregnancy on the level of cord blood IgE