Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Spectroscopic constraints on CH3OH formation: CO mixed with CH3OH ices towards young stellar objects

Contains fulltext : 149321.pdf (publisher's version ) (Open Access

Inoculaçao com lactobacillus plantarum da microbiotica em silagem de capim-nombaça

The objective was to follow the development of populations of lactic bacteria (LBA), enterobacteria (ENT) and moulds and yeast (MaY), pH and ammonia nitrogen (N-NH3) variations, bromatologic composition and acid organic contents of mombaça grass (Pannicum maximum) silages innoculated with Lacto-bacillus plantarum provided from epiphytic microbiota. The experimental design was completely randomized, in a factorial scheme with four innoculum concentrations (0, 104, 105 and 106 cfu/g of roughage) and five opening periods (1, 3, 7, 14 and 28 days), with three repetitions. There was a rapid pH fall in all innoculant concentrations. The N-NH3 production stablished from the 7th day, with lower values to innoculated treatments. Greater LBA concen-trations were observed in innoculated treatments up to the 7th fermentation day. Related to ENT, it was observed a reduction of its population in the innoculated treatments, up to the 3rd day of ensilage. The greater dry matter level and hemicellulosis levels was observed in the silage with innoculant concentration of 106. There was observed increment of lactic acid contents e reduction of acetic acid content owing to ino-culation. The innoculation with Lactobacillus plantarum from epiphytic microbiota improve the fermentation profile concerning pH, N-NH3, lactic acid e acetic acid values, favours the lactic bacteria development and promotes lower dry matter losses in mombaça grass silageObjetivou-se com este trabalho acompanhar o desenvolvimento das populações de bactérias láticas (BAL), enterobactérias (ENT) e mofos e leveduras (MeL), variações no pH e nitrogênio amoniacal (N-NH3), composição bromatológica e teores de ácidos orgânicos de silagens de capim-mombaça (Panicum maximum) inoculado com Lactobacillus plantarum proveniente da microbiota epifítica. O delineamento foi inteira-mente casualizado, em um esquema fatorial com quatro concentrações de inoculante (0, 104, 105, e 106 ufc/g de forragem) e cinco períodos de aberturas (1, 3, 7, 14 e 28 dias), com três repetições. Ocorreu uma rápida queda do pH em todas as concentrações de inoculante. A produção de N-NH3 estabilizou-se a partir do 7° dia, com menores valores para os tratamentos inoculados. Observaram-se maiores concen-trações de BAL para os tratamentos inoculados até o sétimo dia de fermentação. Com relação às ENT, observou-se uma redução de sua população nos tratamentos inoculados, até o terceiro dia de ensilagem. O maior teor de MS e de hemicelulose foi observado para silagem com concentração 106 de inoculante. Houve aumento dos teores de ácido lático e diminuição dos teores de ácido acético, em conseqüência da inoculação. A inoculação com Lactobacillus plantarum da microbiota epifítica melhora o perfil fermentativo de acordo com os valores de pH, NH3, ácido lático e ácido acético, favorece o desenvolvimento de bactérias láticas e promove menores perdas de matéria seca na silagem de capim-mombaç