The chemistry involved in the steam treatment of lignocellulosic materials

Pretreatment of lignocellulosic materials is essential for bioconversion because of the various physical and chemical barriers that greatly inhibit their susceptibility to bioprocesses such as hydrolysis and fermentation. The aim of this article is to review some of the most important pretreatment methods developed to date to enhance the conversion of lignocellulosics. Steam explosion, which precludes the treatment of biomass with high-pressure steam under optimal conditions, is presented as the pretreatment method of choice and its mode of action on lignocellulosics is discussed. The optimal pretreatment conditions for a given plant biomass are defined as those in which the best substrate for hydrolysis is obtained with the least amount of soluble sugars lost to side reactions such as dehydration. Therefore, pretreatment optimization results from a compromise between two opposite trends because hemicellulose recovery in acid hydrolysates can only be maximized at lower pretreatment severities, whereas the development of substrate accessibility requires more drastic pretreatment conditions in which sugar losses are inevitable. To account for this heterogeneity, the importance of several process-oriented parameters is discussed in detail, such as the pretreatment temperature, residence time into the steam reactor, use of an acid catalyst, susceptibility of the pretreated biomass to bioconversion, and process design.

Intensities of 4f-4f transitions in glass materials

In this article we review some of the basic aspects of rare earth spectroscopy applied to vitreous materials. The characteristics of the intra-atomic free ion and ligand field interactions, as well as the formalisms of the forced electric dipole and dynamic coupling mechanisms of 4f-4f intensities, are outlined. The contribution of the later mechanism to the 4f-4f intensities is critically discussed, a point that has been commonly overlooked in the literature of rare earth doped glasses. The observed correlation between the empirical intensity parameter W2 and the covalence of the ion first coordination shell is discussed accordingly to the theoretical predictions.

Biblioteca de l'EPSEVG: memòria estadística 2014 i recull d'actuacions clau

Preprint

Biblioteca de l’FME Memòria estadística i recull d’actuacions clau 2014

Memòria 2014 Biblioteca FME

Reforma i ampliació de la Biblioteca Montserrat Roig a Sant Feliu de Llobregat.

Award-winning

Memòria 2014 Biblioteca EPSEB

Preprint

Carta de serveis de la Biblioteca ETSAB per al PDI

Infografia de la carta de serveis de la Biblioteca ETSAB per al PDI: solucions per a la publicació de la recerca, edicions de llibres i revistes, gestió de la informació, etc.

Col·lecció local a la Biblioteca Pública: recomacions bàsiques

Normes per ajudar les biblioteques a organitzar el seu fons de col·lecció local. En l'article es fa una definició del que és col·lecció local i es donen un seguit de recomanacions bàsiques segons el tipus d'àrea que cobreixi, el tipus de material, el seu tractament i els seus serveis que aquesta secció ha d'oferir en la biblioteca pública.

Hydrology, light and the use of organic and inorganic materials as structuring factors of biological communities in Mediterranean streams

Hydrological disturbances, light availability and nutrients are the most relevant factors determining the structure of the biological communities in Mediterranean rivers. While some hydrological disturbances are able to induce catastrophic effects, which may cause a complete reset in physical and biological conditions, continued enrichment or changes in light availability are factors leading to the progressive shift in the communities of autotrophs and heterotrophs in the systems. Primary production in Mediterranean streams shows relevant seasonal changes which mainly follows the variations in light availability. In most forested streams, the algal community is shade-adapted. Nutrient enrichment (especially phosphorus) leads to marked increases in primary production, but this increase is not lineal and there is a saturation of algal biomass even in the most enriched systems. The heterotrophs (bacteria, fungi) are related to the pattern of DOC availability (which most depends on the seasonal discharge and leaf fall dynamics) and to the available substrata in the stream. It has been repeatedly observed that shorttime increases of extracellular enzyme activities are related to the accumulation of autochthonous (algal) and/or allochthonous (leaves) organic matter on the streambed during spring and summer, this being more remarkable in dry than in wetter years. Flow reduction favours detritus concentration in pools, and the subsequent increase in the density and biomass of the macroinvertebrate community. In Mediterranean streams collectors are accounting for the highest density and biomass, this being more remarkable in the least permanent systems, in accordance with the effect of floods on the organic matter availability. Nutrients, through the effect on the primary producers, also affect the trophic food web in the streams by favouring the predominance of grazers

Marques de Biblioteca: Llegat Ferrater Mora

A la mort de Ferrater Mora, i davant la notícia de la donació de la seva biblioteca a la UdG, es va encarregar un Ex-libris a Joan Brossa

Biblioteca del Convento San Carlos Borromeo de San Lorenzo

En febrero de 1813 la edificación del Convento de San Carlos Borromeo de San Lorenzo resguardó al cuerpo de granaderos al mando del coronel José de San Martín en su lucha contra el ejército español. Pero también fue el escenario en el que se produjo, en abril de 1819, el conocido "Armisticio de San Lorenzo" que se firmó entre representantes de las provincias de Buenos Aires, Santa Fe y Entre Ríos para acordar el cese de la hostilidad.

Memòria de la biblioteca : Any 2014.

Memòria de la Biblioteca de la Facultat de Nàutica de Barcelona de l'any 2014.

Biblioteca Rector Gabriel Ferraté. Memòria 2014

Preprint

Guia temàtica Biblioteca ETSAB: Àrees residencials de baixa densitat

Postprint (author’s final draft)

Guia temàtica Biblioteca ETSAB: Arquitectura i ciutat en la literatura

Postprint (author’s final draft)