Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde

It has been recently reported by Palmisano et al. (2015) [1] that the oxidation of 2-methoxybenzyl alcohol (2-MBA) to 2-methoxybenzaldehyde (2-MBAD) proceeds in water under near-UV light with an unexpected catalytic effect of 2-MBAD. In order to investigate the catalytic role of aldehyde in photolytic oxidation of ortho-substituted benzyl alcohols (OSBAs), reactivity runs were carried out with 2-methylbenzyl alcohol (2-MeBA), 2-nitrobenzyl alcohol (2-NBA), 2-hydroxybenzyl alcohol (2-HBA) and 2-chlorobenzyl alcohol (2-ClBA) in the absence and in the presence of their corresponding aldehyde. None of those alcohols showed a measurable oxidation rate even in the presence of their aldehydes but 2-NBA was oxidised very fast, although no corresponding carbonyl product was obtained. The possible catalytic role of 2-MBAD was investigated for the photolytic oxidation of 4-methoxybenzyl alcohol (4-MBA), 4-nitrobenzyl alcohol (4-NBA), 2-ClBA, 2-HBA, 2-MeBA and ferulic acid (FA). The results showed that 2-MBAD acts as a catalyst only for 4-MBA, 2-HBA and FA. The photocatalytic oxidation of OSBAs in the presence of powdered TiO2 has been also carried out in order to investigate the mutual influences, if any, between homogeneous and heterogeneous processes. The reactivity runs were carried out with TiO2 photocatalyst in water and under near-UV irradiation; a home-prepared (HP) TiO2 sample was used along with Degussa P25. HP catalyst showed the best performance: the 2-MBA half-life time was 5 times smaller and the selectivity to aldehyde 13 times higher than in the presence of Degussa P25

Influence of laser beam fluence distribution on the LIBS signal stability

NRC publication: Ye

Potentiel accru du Laser \ue0 Fibre pour l\u2019analyse Quantitative des \uc9l\ue9ments d\u2019alliages dans l\u2019acier

Les alliages de Fer sont des mat\ue9riaux m\ue9talliques relativement peu on\ue9reux dont les performances m\ue9caniques satisfont de nombreuses exigences qui peuvent atteindre des niveaux tr\ue8s \ue9lev\ue9es. La pr\ue9sence d\u2019\ue9l\ue9ments d\u2019alliages conduit, dans la plupart des cas, \ue0 des modifications de la strucutre et du comportement m\ue9canique des m\ue9taux. L'importance de v\ue9rifier la composition chimique des alliages m\ue9talliques a augment\ue9 au fil des ans pour garantir la qualit\ue9 des produits exp\ue9diers (tuyau, fil, plaque, feuille et t\uf4les d'acier) et ainsi minimiser les co\ufbts reli\ue9s au retour de marchandise et de r\ue9usinage. La spectrom\ue9trie laser-plasma (LIBS : \u201cLaser-Induced Breakdown Spectroscopy\u201d) est une technique analytique bien connue qui permet la d\ue9tection de la plupart des \ue9l\ue9ments du tableau p\ue9riodique avec des limites de d\ue9tection de l\u2019ordre de la partie par million massique (ppm m/m) et ceci sur tous types d\u2019\ue9chantillons qu\u2019ils soient liquides, solides ou gazeux. Sa simplicit\ue9 de mise en \u153uvre, sa rapidit\ue9 et sa versatilit\ue9 en font une technique tr\ue8s attractive avec un fort potentiel pour les applications n\ue9cessitant un contr\uf4le en ligne. La forte \ue9mergence sur le march\ue9 des lasers Ytterbium de grande puissance et compacte permettent d\u2019obtenir sur la cible des densit\ue9s de puissance de l\u2019ordre de 100 MW/cm2. Cette densit\ue9 est suffisante et sup\ue9rieure au seuil d\u2019ablation du mat\ue9riau ainsi qu\u2019au seuil de claquage (i.e. cr\ue9ation du plasma). Lorsque de telles sources sont coupl\ue9es \ue0 des spectrom\ue8tres de haute r\ue9solution, ceci permet d\u2019effectuer des mesures LIBS sur des alliages d\u2019acier. Des courbes de calibrations pour le Mn, Ni, Cr, Si , Cu, V et Ti ont \ue9t\ue9 obtenus avec une reproductibilit\ue9 sur la mesure site \ue0 site de l\u2019ordre de 1%.NRC publication: Ye

Primary stroke prevention worldwide: translating evidence into action

Stroke is the second leading cause of death and the third leading cause of disability worldwide and its burden is increasing rapidly in low-income and middle-income countries, many of which are unable to face the challenges it imposes. In this Health Policy paper on primary stroke prevention, we provide an overview of the current situation regarding primary prevention services, estimate the cost of stroke and stroke prevention, and identify deficiencies in existing guidelines and gaps in primary prevention. We also offer a set of pragmatic solutions for implementation of primary stroke prevention, with an emphasis on the role of governments and population-wide strategies, including task-shifting and sharing and health system re-engineering. Implementation of primary stroke prevention involves patients, health professionals, funders, policy makers, implementation partners, and the entire population along the life course