Calcul ab initio de l'interaction d'une molécule d'azote avec un ion Na+. Comparaison avec les données expérimentales du spectre infrarouge de N2 adsorbé dans la zéolithe NaA

In order to compare theoretical results to some experimental data from infrared spectra of N2 adsorbed in NaA zeolite, we present here an ab initio quantum calculation of the couple N2-Na+. After determining its equilibrium geometry, we calculate the frequency shift of the N-N vibration and its transition dipolar moment induced by the présence of the sodium cation. The results agree quite well with the experimental data and with those obtained from empirical interaction potentials.Pour retrouver un certain nombre de grandeurs expérimentales tirées des spectres infrarouges de la molécule d'azote adsorbée dans la zéolithe NaA, nous présentons ici un calcul quantique ab initio sur le couple N 2-Na+. Après avoir déterminé sa géométrie d'équilibre nous calculons le glissement de la fréquence de vibration N-N et son moment dipolaire de transition induit par la présence du cation. Les résultats obtenus sont en bon accord avec l'expérience ainsi qu'avec ceux déterminés à partir de potentiels empiriques d'interaction

Safety and quality of food contact materials. Part 1: Evaluation of analytical strategies to introduce migration testing into good manufacturing practice

The results of a research project (EU AIR Research Programme CT94-1025) aimed to introduce control of migration into good manufacturing practice and into enforcement work are reported. Representative polymer classes were defined on the basis of chemical structure, technological function, migration behaviour and market share. These classes were characterized by analytical methods. Analytical techniques were investigated for identification of potential migrants. High-temperature gas chromatography was shown to be a powerful method and H-1-magnetic resonance provided a convenient fingerprint of plastic materials. Volatile compounds were characterized by headspace techniques, where it was shown to be essential to differentiate volatile compounds desorbed from those generated during the thermal desorption itself. For metal trace analysis, microwave mineralization followed by atomic absorption was employed. These different techniques were introduced into a systematic testing scheme that is envisaged as being suitable both for industrial control and for enforcement laboratories. Guidelines will be proposed in the second part of this paper

European guidelines on microscopic colitis: United European Gastroenterology (UEG) and European Microscopic Colitis Group (EMCG) statements and recommendations

INTRODUCTION: Microscopic colitis is a chronic inflammatory bowel disease characterised by normal or almost normal endoscopic appearance of the colon, chronic watery, non-bloody diarrhoea and distinct histological abnormalities, which identify three histological subtypes, the collagenous colitis, the lymphocytic colitis and the incomplete microscopic colitis. With ongoing uncertainties and new developments in the clinical management of microscopic colitis, there is a need for evidence-based guidelines to improve the medical care of patients suffering from this disorder. METHODS: Guidelines were developed by members from the European Microscopic Colitis Group and United European Gastroenterology in accordance with the Appraisal of Guidelines for Research and Evaluation II instrument. Following a systematic literature review, the Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the certainty of the evidence. Statements and recommendations were developed by working groups consisting of gastroenterologists, pathologists and basic scientists, and voted upon using the Delphi method. RESULTS: These guidelines provide information on epidemiology and risk factors of microscopic colitis, as well as evidence-based statements and recommendations on diagnostic criteria and treatment options, including oral budesonide, bile acid binders, immunomodulators and biologics. Recommendations on the clinical management of microscopic colitis are provided based on evidence, expert opinion and best clinical practice. CONCLUSION: These guidelines may support clinicians worldwide to improve the clinical management of patients with microscopic colitis