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  • Author or Editor: P. Gill x
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Résumé  

On décrit la méthode pour le dosage du hafnium dans des aciers étalons. Cette méthode consiste en une combinaison de l'analyse par activation neutronique avec un procédé d'extraction par solvant, l'agent d'extraction étant le di (2 ethylhexyl) phosphate. Enfin, on procède à une extraction en retour dans de l'acide fluorhydrique 2N juste avant la mesure d'activité. La mesure est faite au moyen d'un détecteur Ge(Li) 60 cc associé à un analyseur 2048 canaux. La méthode d'analyse ainsi décrite permet une détermination rapide du hafnium avec, une précision de l'ordre de 3 à 4% pour les dosages de routine.

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Abstract  

Simultaneous TG (thermogravimetric analysis)-DTA (differential thermal analysis) measures both differential temperatures and weight changes in a material as a function of temperature or time in a controlled atmosphere. Simultaneous measurement of these two material properties not only improves productivity but also simplifies interpretation of the results. The complementary information obtained allows differentiation between endothermic and exothermic events which have no associated weight loss (e.g. melting and crystallization) and those which involve a weight loss (e.g. degradation). The combined evaluation also assures identical experimental and sampling conditions for both measurements, thereby eliminating those sources of uncertainty. This paper briefly describes a new simultaneous TG-DTA instrument with emphasis on how the measurements are made and with several typical applications

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Abstract  

Traditionally, Modulated DSC (MDSC®) [1] has been used to simultaneously measure the heat capacity and heat flow of a sample in a single experiment. As first proposed by Readinget at. in 1992 [2], this complex heat capacity signal (Cp *) can be further deconvoluted into components which are in-phase (C′p) or out-of phase (C′p with the imposed temperature modulation. The vector sum of these components, respectively termed the reversing Cp and kinetic Cp, is equal to the aforementioned complex Cp (Cp *). Recent research has centered around the analysis of these signals and their inclusion into MDSC experiments. For most polymer systems, the contribution of the kinetic Cp is negligible, except at the melt. This signal does contain a small peak at the Tg of PET, but the significance of this peak is to date not clear. Examples of further applications will be presented and discussed, as well as the derivation and interpretation of novel MDSC signals.

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Abstract  

Modulated DSCTM (MDSC) is a new, patent-pending extension to conventional DSC which provides information about the reversing and nonreversing characteristics of thermal events, as well as the ability to directly measure heat capacity. This additional information aids interpretation and allows unique insights into the structure and behaviour of materials., A number of examples of its use are described.

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Indiscriminate use of antibiotics in apicultural practices may lead to contamination of otherwise healthy and naturally produced honey. Contamination not only affects honey quality but also pose significant health risks to consumers. In this context, one hundred raw honey samples from India were analysed for presence of antibiotic residues. For determination of oxytetracycline and erythromycin, high performance liquid chromatography and for chloramphenicol, enzyme immunoassay based validated procedures were used. Oxytetracycline and erythromycin with concentrations above maximum tolerance limits were detected in 24% and 2% samples, respectively. None of the samples contained chloramphenicol residues. Although, total dietary intake of detected antibiotics through honey was found to be <1% of their acceptable daily intake values, the presence of antibiotics in honey is an alarming health concern for people following customary honey feeding. The outcomes underline the need of inter-sectoral approaches to create awareness among beekeepers regarding health risks associated with residues of antibiotics in honey and merits of approved apicultural practices. Therefore, to meet global food safety requirements, continual residue monitoring schemes along with enlightenment of beekeepers on scientific beehive management and risks associated with incautious apicultural practices are of vital importance.

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