8,210 research outputs found
Structure and dynamics in glass-formers: predictability at large length scales
Dynamic heterogeneity in glass-formers has been related to their static
structure using the concept of dynamic propensity. We re-examine this
relationship by analyzing dynamical fluctuations in two atomistic glass-formers
and two theoretical models. We introduce quantitative statistical indicators
which show that the dynamics of individual particles cannot be predicted on the
basis of the propensity, nor by any structural indicator. However, the spatial
structure of the propensity field does have predictive power for the spatial
correlations associated with dynamic heterogeneity. Our results suggest that
the quest for a connection between static and dynamic properties of
glass-formers at the particle level is vain, but they demonstrate that such
connection does exist on larger length scales.Comment: 7 pages; 4 figs - Extended, clarified versio
Collective modes in relativistic npe matter at finite temperature
Isospin and density waves in neutral neutron-proton-electron (npe) matter are
studied within a relativistic mean-field hadron model at finite temperature
with the inclusion of the electromagnetic field. The dispersion relation is
calculated and the collective modes are obtained. The unstable modes are
discussed and the spinodals, which separate the stable from the unstable
regions, are shown for different values of the momentum transfer at various
temperatures. The critical temperatures are compared with the ones obtained in
a system without electrons. The largest critical temperature, 12.39 MeV, occurs
for a proton fraction y_p=0.47. For y_p=0.3 we get =5 MeV and for
y_p>0.495 MeV.
It is shown that at finite temperature the distillation effect in asymmetric
matter is not so efficient and that electron effects are particularly important
for small momentum transfers.Comment: 10 pages, 6 figure
Light clusters and the pasta phase
The effects of including light clusters in nuclear matter at low densities
are investigated within four different parametrizations of relativistic models
at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase)
are described for neutral nuclear matter with fixed proton fractions. We
discuss the effect of the density dependence of the symmetry energy, the
temperature and the proton fraction on the non-homogeneous matter forming the
inner crust of proto-neutron stars. It is shown that the number of nucleons in
the clusters, the cluster proton fraction and the sizes of the Wigner Seitz
cell and of the cluster are very sensitive to the density dependence of the
symmetry energy.Comment: 14 pages, 14 figures; Accepted for publication in Phys. Rev.
Core excitation in Ozone localized to one of two symmetry-equivalent chemical bonds - molecular alignment through vibronic coupling
Core excitation from terminal oxygen O in O is shown to be an
excitation from a localized core orbital to a localized valence orbital. The
valence orbital is localized to one of the two equivalent chemical bonds. We
experimentally demonstrate this with the Auger Doppler effect which is
observable when O is core-excited to the highly dissociative
O1s7a state. Auger electrons emitted from the atomic oxygen
fragment carry information about the molecular orientation relative to the
electromagnetic field vector at the moment of excitation. The data together
with analytical functions for the electron-peak profiles give clear evidence
that the preferred molecular orientation for excitation only depends on the
orientation of one bond, not on the total molecular orientation. The
localization of the valence orbital "7a" is caused by mixing of the valence
orbital "5b" through vibronic coupling of anti-symmetric stretching mode
with b-symmetry. To the best of our knowledge, it is the first discussion
of the localization of a core excitation of O. This result explains the
success of the widely used assumption of localized core excitation in
adsorbates and large molecules
Instabilities in asymmetric nuclear matter
The existence of phase transitions from liquid to gas phases in asymmetric
nuclear matter (ANM) is related with the instability regions which are limited
by the spinodals. In this work we investigate the instabilities in ANM
described within relativistic mean field hadron models, both with constant and
density dependent couplings at zero and finite temperatures. In calculating the
proton and neutron chemical potentials we have used an expansion in terms of
Bessel functions that is convenient at low densities. The role of the isovector
scalar -meson is also investigated in the framework of relativistic
mean field models and density dependent hadronic models. It is shown that the
main differences occur at finite temperature and large isospin asymmetry close
to the boundary of the instability regions.Comment: 13 pages, 5 figures; to appear in Phys. Rev.
Eco-Innovation Influencers: Unveiling the Role of Lean Management Principles Adoption
This study analyzes the determinant factors of eco-innovation, considering business units with dierent levels of technological intensity (high technology versus low technology). It aims, in the first instance, to complement the approach on the determinants of eco-innovation in the existent literature by incorporating the novelty related to the analysis of the eects arising from the adoption of the lean management principles. Specifically, it aims to analyze the eects of the previously referred to determinant factors both on the economic performance and on the innovative performance of Portuguese industrial and service companies with dierent levels of technological intensity (high-tech versus low-tech). The conceptual model presented is of an innovative nature, since it includes four groups of determinant factors present in the literature, namely technology, market, public policies, and cooperation relationships, and adds a fifth group of determinant factors still to be explored empirically concerning the adoption of lean management principles. In the empirical approach, five research hypotheses arising from the literature review are tested, using secondary data collected from the Community Innovation Survey (CIS)\u2014CIS 2010 for a total sample of 334 companies, made up of 95 high-tech companies and 239 low-tech companies. The conceptual model is tested using a logistic regression method, which indicated a suitable accuracy and reliability for the purposes of empirical tests. The empirical evidence confirms that most of the groups of determinants previously identified in the literature have a significant influence on eco-innovation. In addition, the empirical evidence obtained here indicates a positive and significant eect of lean management principles on eco-innovation
Água de chuva para consumo humano e produção de alimentos.
Água no Brasil e no Semi-Árido; tecnologias para captação de água de chuva
Captação de água de chuva: sustentabilidade ambiental no semi-árido brasileiro.
Este curso trata de introduzir o conceito de sustentabilidade ambiental nos programas de Pesquisa, Desenvolvimento e Informação (PD&I) que envolvem as tecnologias de Captação de Água de Chuva. O acervo tecnológico hoje existente de convivência com adversidade agroecológica do semi-árido brasileiro é uma realidade, especialmente no tocante a captação, armazenamento e uso das águas pluviais para o consumo doméstico, face ao êxito do Programa cisternas do Ministério de Desenvolvimento Social, em parceria com a "Articulação do Semi-Árido - ASA". Entretanto, acredita-se que os atores envolvidos no processo, necessitam oferecer um segundo passo, tendo como princípio básico quatro linhas de gestão das águas. A primeira que aborde água potável para cada família (já em execução), a segunda considere a água comunitária, a terceira se preocupe com a água utilizada na agricultura familiar e a quarta atenda estrategicamente a água emergencial, visando a segurança alimentar por meio do acesso e manejo sustentáveis da terra e das águas de usos múltiplos. Para formatar as quatro linhas de gestão das águas, este curso considera o conceito de desenvolvimento sustentável no sentido de garantir para as gerações futuras os recursos naturais escassos do semi-árido brasileiro e a sua convivência, relevante para a região. Assim, disserta-se em um primeiro momento o acervo tecnológico hoje existente, seguido da base conceitual sobre indicadores de sustentabilidade ambiental a qualquer bacia, sub-bacia e/ou micro-bacia hidrográfica de regiões áridas e semi-áridas, exemplificando-se, finalmente, as experiências práticas, já realizadas, utilizando-se a metodologia proposta para a convivência com o semi-árido brasileiro.1 CD-RO
Coeficiente de escoamento superficial em diferentes áreas de captação de água de chuva.
Técnicas de captação e armazenamento de água de chuva são alternativas estruturais eficientes que podem amenizar o problema de escassez ou falta de água no Semiárido brasileiro, seja para o consumo humano de famílias rurais dispersas ou para reduzir os riscos da instabilidade climática no segmento da produção agrícola. Entre essas técnicas, a cisterna calçadão é uma das mais utilizadas, principalmente, a partir de 2007, quando contou com incentivos do governo federal, por meio do Programa Uma Terra e Duas Águas (P1+2). Neste programa, considera-se para a cisterna uma capacidade de armazenamento de 52 m3 e uma área de captação de água de chuva de 200 m2, independendo das médias históricas de precipitação. Assim, este estudo objetivou determinar o coeficiente de escoamento superficial de diferentes coberturas utilizadas como áreas de captação de água de chuva, situadas em campo experimental da Embrapa Semiárido. Os tipos de áreas de captação analisados foram cimentada, cobertura de polietileno e solo nu. Os dados foram coletados entre janeiro de 2010 a dezembro de 2012, observando-se que a área com cobertura de lona de polietileno foi a mais eficiente quanto ao volume escoado; no entanto, sua durabilidade foi de apenas dois anos
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