1,784 research outputs found

    Green Chemistry, Green Engineering and Eco-Innovation Towards a More Sustainable Petrochemical Industry: Determinants of Brazilian Petrochemical Companies´ Engagement in GCE-Based Eco-Innovation Processes

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    __Abstract__ It is the general wisdom, within the petrochemical industrial sector, that technological changes, for the development of cleaner products, processes and services, is a basic requirement for companies to achieve advanced states of environmental and economic sustainability in the 21st century. It is also agreed that to innovate is essential for this industry make the necessary advancements and to reconcile the firms´ interests of being profitable, in the short-term, with their long-term capacity to evolve with societal pressures to ensure worker‘s and consumer‘s health within a sustainable biosphere. Despite these corporate perspectives, companies´ decisions to engage in the process of change, through technological and management innovations, is contingent on a series of elements that determine companies‘ eco-innovative behavior. This thesis was designed to gain insight into the aspects and determinants that influence ecoinnovative behavior of companies in the Brazilian petrochemical sector. Drawing on Icel Ajzen´s Theory of Planned Behavior (TPB), on Montalvo Corral´s TPB-based structural descriptive innovation-directed behavioral model and on Franco Malerba´s Sectoral Systems of Innovation (SSI) framework as its major theoretical frameworks, this study was designed to obtain answers to these research questions: - What is the extent to which Brazilian petrochemical companies are willing to innovate based upon the Twelve Principles of the Green Chemistry and the Twelve Principles of Green Engineering (GCE) as approaches to more sustainable behavior? - How can their willingness to change be documented and explained and what are its main determinants? -What are the sector´s main agents, mechanisms and actions, which are integral to its implementation of GCE and to going beyond them in the future

    Simple Model For Resonant Tunneling Beyond The Effective-mass Approximation

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    We evaluate, within a single-band tight-binding model, the resonant transmission probability for a particle through a symmetric barrier-well-barrier potential structure. This is a simplified model of resonant tunneling through (Ga,Al)As-GaAs-(Ga,Al)As heterostructure. We examine both the cases of minimum of the band states at the center (direct-gap tunneling) and at the edge (indirect-gap tunneling) of the Brillouin zone for the barrier material. We show that only the lowest traveling-wave energy states, irrespective of their symmetry, dominate the tunneling. © 1987 The American Physical Society.35158126813

    Anomalous persistent photoconductivity in Cu2ZnSnS4 thin films and solar cells

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    A persistent photoconductivity effect (PPC) has been investigated in Cu2ZnSnS4 thin films and solar cells as a function of temperature. An anomalous increase of the PPC decay time with temperature was observed in all samples. The PPC decay time activation energy was found to increase when temperature rises above a crossover value, and also to grow with the increase of the sulfurization temperature and pressure. Both the anomalous behavior of the PPC decay time and the existence of two different activation energies are explained in terms of local potential fluctuations in the band edges of CZTS

    Clusters of Galaxies: New Results from the CLEF Hydrodynamics Simulation

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    Preliminary results are presented from the CLEF hydrodynamics simulation, a large (N=2(428)^3 particles within a 200 Mpc/h comoving box) simulation of the LCDM cosmology that includes both radiative cooling and a simple model for galactic feedback. Specifically, we focus on the X-ray properties of the simulated clusters at z=0 and demonstrate a reasonable level of agreement between simulated and observed cluster scaling relations.Comment: 7 pages, 4 figures, accepted for publication in Advances in Space Research (proceedings of the COSPAR 2004 Assembly, Paris

    Identifying and prioritising services in European terrestrial and freshwater ecosystems

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    Ecosystems are multifunctional and provide humanity with a broad array of vital services. Effective management of services requires an improved evidence base, identifying the role of ecosystems in delivering multiple services, which can assist policy-makers in maintaining them. Here, information from the literature and scientific experts was used to systematically document the importance of services and identify trends in their use and status over time for the main terrestrial and freshwater ecosystems in Europe. The results from this review show that intensively managed ecosystems contribute mostly to vital provisioning services (e.g. agro-ecosystems provide food via crops and livestock, and forests provide wood), while semi-natural ecosystems (e.g. grasslands and mountains) are key contributors of genetic resources and cultural services (e.g. aesthetic values and sense of place). The most recent European trends in human use of services show increases in demand for crops from agro-ecosystems, timber from forests, water flow regulation from rivers, wetlands and mountains, and recreation and ecotourism in most ecosystems, but decreases in livestock production, freshwater capture fisheries, wild foods and virtually all services associated with ecosystems which have considerably decreased in area (e.g. semi-natural grasslands). The condition of the majority of services show either a degraded or mixed status across Europe with the exception of recent enhancements in timber production in forests and mountains, freshwater provision, water/erosion/natural hazard regulation and recreation/ecotourism in mountains, and climate regulation in forests. Key gaps in knowledge were evident for certain services across all ecosystems, including the provision of biochemicals and natural medicines, genetic resources and the regulating services of seed dispersal, pest/disease regulation and invasion resistance

    Oropouche Virus Isolation, Southeast Brazil

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    An Oropouche virus strain was isolated from a novel host (Callithrix sp.) in Arinos, Minas Gerais State, southeastern Brazil. The virus was identified by complement fixation test and confirmed by reverse transcription–polymerase chain reaction. Phylogenetic analysis identified this strain as a genotype III isolate previously recognized only in Panama
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