Search

Elephant grass ( Pennisetum purpureum ) is a lignocellulosic material that has high potential for ethanol production in tropical countries due to their high availability and adaptability. Chemical and physicochemical pretreatments like alkaline delignification, diluted acid hydrolysis, steam explosion, alkaline peroxide and aqueous ammonia soaking were performed in order to determine their effect on the hydrolysis and the fermentability of the cellulosic fraction of this material. In an initial screening of the methods, the alkaline pretreatment with NaOH yielded the highest concentrations of reducing sugars (34.4 g/L) and ethanol (15.1 g/L). A more detailed study of the effect of the alkaline pretreatment conditions (temperature, solid to liquid ratio, NaOH concentration and residence time) on the fermentability of elephant grass was carried out. Results showed that under pretreatment conditions of 120 °C for 1 h with 2 wt.%. NaOH and a solid to liquid ratio of 1: 20 (wt.) the highest yield of ethanol was obtained, i.e., 26.1 g/L (141.5 mg ethanol/g dry biomass, 95% of theoretical yield). Furthermore, this pretreatment allowed the removal of most of the lignin present in this material, i.e., 88% lignin removal. Besides, this pretreatment allowed a high recovery of the cellulosic fraction in the solid.

Comentário

This dissertation explores the complex interactions between organizational structure and the environment. In Chapter 1, I investigate the effect of financial development on the formation of European corporate groups. Since cross-country regressions are hard to interpret in a causal sense, we exploit exogenous industry measures to investigate a specific channel through which financial development may affect group affiliation: internal capital markets. Using a comprehensive firm-level dataset on European corporate groups in 15 countries, we find that countrieswith less developed financial markets have a higher percentage of group affiliates in more capital intensive industries. This relationship is more pronounced for young and small firms and for affiliates of large and diversified groups. Our findings are consistent with the view that internal capital markets may, under some conditions, be more efficient than prevailing external markets, and that this may drive group affiliation even in developed economies. In Chapter 2, I bridge current streams of innovation research to explore the interplay between R&D, external knowledge, and organizational structure–three elements of a firm’s innovation strategy which we argue should logically be studied together. Using within-firm patent assignment patterns,we develop a novel measure of structure for a large sample of American firms. We find that centralized firms invest more in research and patent more per R&D dollar than decentralized firms. Both types access technology via mergers and acquisitions, but their acquisitions differ in terms of frequency, size, and i\ntegration. Consistent with our framework, their sources of value creation differ: while centralized firms derive more value from internal R&D, decentralized firms rely more on external knowledge. We discuss how these findings should stimulate more integrative work on theories of innovation. In Chapter 3, I use novel data on 1,265 newly-public firms to show that innovative firms exposed to environments with lower M&A activity just after their initial public offering (IPO) adapt by engaging in fewer technological acquisitions andmore internal research. However, this adaptive response becomes inertial shortly after IPO and persists well into maturity. This study advances our understanding of how the environment shapes heterogeneity and capabilities through its impact on firm structure. I discuss how my results can help bridge inertial versus adaptive perspectives in the study of organizations, by documenting an instance when the two interact.

Publicado

Título del tomo II: La pesca en todos los países : segunda parte de la caza Copia digital. España : Ministerio de Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria., 2021

La psicología positiva surge como alternativa a la psicología negativa. La perspectiva positiva tiene como objetivo realzar los recursos intra e interpersonales para favorecer el desarrollo óptimo de los seres humanos, grupos, organizaciones y sociedades. Esta tradición tiene una larga historia en el pensamiento filosófico-antropológico occidental y oriental. Este artículo concluye que la psicología positiva no es algo tan novedoso como muchos investigadores suponen.