526 research outputs found
Ground state properties of a confined simple atom by C fullerene
We numerically study the ground state properties of endohedrally confined
hydrogen (H) or helium (He) atom by a molecule of C. Our study is based
on Diffusion Monte Carlo method. We calculate the effects of centered and small
off-centered H- or He-atom on the ground state properties of the systems and
describe the variation of ground state energies due to the C parameters
and the confined atomic nuclei positions. Finally, we calculate the electron
distributions in plane in a wide range of C parameters.Comment: 23 pages, 9 figures. To appear in J.Phys. B: Atom. Mol. Op
Volatile and glycosidically bound composition of Loureiro and Alvarinho wines
Composition of Loureiro and Alvarinho wines from the Vinhos Verdes region,
respecting free volatile compounds as well as glycosidically bound aroma precursors,
was exhaustively determined by GC-MS after adsorption on XAD-2 resin. On the
whole, were identified and quantified 120 volatile compounds in the free fraction and
77 glycosidically bound compounds, belonging to C6-compounds, alcohols, fatty acids
ethyl esters, esters of organic acids, acetates, monoterpenic alcohols, monoterpenic
oxides and diols, C13-norisoprenoids, volatile phenols, volatile fatty acids and carbonyl
compounds. Globally, the wines of the two cultivars present similar composition on
volatiles. However, respecting varietal compounds, Loureiro wines are richer than
Alvarinho ones with regard to C6-compounds and monoterpenic compounds, occurring
the opposite for volatile phenols. It was also demonstrate that wines of both varieties
may benefit the aroma reserve, present as glycoconjugates, as it is susceptible of
being technologically explored. Linalool, Ho-trienol, α-terpineol, contributing with
fruity and floral notes, and β-damascenone mostly for Alvarinho, confering tropical
fruit notes, are the varietal compounds which may particularly influence the aroma of
these wines. Respecting fermentative compounds, Alvarinho is also particularly rich in
fatty acids ethyl esters related to lipid metabolism and acetates of fusel alcohols,
which can provide it a fruity character; Loureiro contains higher levels of esters of
organic acids and 2-phenylethanol, conferring fruity and floral notes. Sensory analysis
agree with chemical analyses showing a pronounced tree and tropical fruit character
for Alvarinho wines while Loureiro wines present more intense citrus fruit notes.Centre of Biological
Engineering of Universidade do Minho; Estação Vitivinícola Amândio
Galhano (EVAG); Solar de Serrade; EVAG; Comissão de Viticultura da Região dos Vinhos Verdes
Progress in Classical and Quantum Variational Principles
We review the development and practical uses of a generalized Maupertuis
least action principle in classical mechanics, in which the action is varied
under the constraint of fixed mean energy for the trial trajectory. The
original Maupertuis (Euler-Lagrange) principle constrains the energy at every
point along the trajectory. The generalized Maupertuis principle is equivalent
to Hamilton's principle. Reciprocal principles are also derived for both the
generalized Maupertuis and the Hamilton principles. The Reciprocal Maupertuis
Principle is the classical limit of Schr\"{o}dinger's variational principle of
wave mechanics, and is also very useful to solve practical problems in both
classical and semiclassical mechanics, in complete analogy with the quantum
Rayleigh-Ritz method. Classical, semiclassical and quantum variational
calculations are carried out for a number of systems, and the results are
compared. Pedagogical as well as research problems are used as examples, which
include nonconservative as well as relativistic systems
Active adaptive conservation of threatened species in the face of uncertainty
Adaptive management has a long history in the natural resource management literature, but despite this, few practitioners have developed adaptive strategies to conserve threatened species. Active adaptive management provides a framework for valuing learning by measuring the degree to which it improves long-run management outcomes. The challenge of an active adaptive approach is to find the correct balance between gaining knowledge to improve management in the future and achieving the best short-term outcome based on current knowledge. We develop and analyze a framework for active adaptive management of a threatened species. Our case study concerns a novel facial tumor disease affecting the Australian threatened species Sarcophilus harrisii: the Tasmanian devil. We use stochastic dynamic programming with Bayesian updating to identify the management strategy that maximizes the Tasmanian devil population growth rate, taking into account improvements to management through learning to better understand disease latency and the relative effectiveness of three competing management options. Exactly which management action we choose each year is driven by the credibility of competing hypotheses about disease latency and by the population growth rate predicted by each hypothesis under the competing management actions. We discover that the optimal combination of management actions depends on the number of sites available and the time remaining to implement management. Our approach to active adaptive management provides a framework to identify the optimal amount of effort to invest in learning to achieve long-run conservation objectives
Structure-property correlations in model composite materials
We investigate the effective properties (conductivity, diffusivity and elastic moduli) of model random composite media derived from Gaussian random fields and overlapping hollow spheres. The morphologies generated in the models exhibit low percolation thresholds and give a realistic representation of the complex microstructure observed in many classes of composites. The statistical correlation functions of the models are derived and used to evaluate rigorous bounds on each property. Simulation of the effective conductivity is used to demonstrate the applicability of the bounds. The key morphological features which effect composite properties are discussed
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