7,033 research outputs found
Vlasov analysis of relaxation and meta-equilibrium
The Hamiltonian Mean-Field model (HMF), an inertial XY ferromagnet with
infinite-range interactions, has been extensively studied in the last few
years, especially due to its long-lived meta-equilibrium states, which exhibit
a series of anomalies, such as, breakdown of ergodicity, anomalous diffusion,
aging, and non-Maxwell velocity distributions. The most widely investigated
meta-equilibrium states of the HMF arise from special (fully magnetized)
initial conditions that evolve to a spatially homogeneous state with well
defined macroscopic characteristics and whose lifetime increases with the
system size, eventually reaching equilibrium. These meta-equilibrium states
have been observed for specific energies close below the critical value 0.75,
corresponding to a ferromagnetic phase transition, and disappear below a
certain energy close to 0.68. In the thermodynamic limit, the -space
dynamics is governed by a Vlasov equation. For finite systems this is an
approximation to the exact dynamics. However, it provides an explanation, for
instance, for the violent initial relaxation and for the disappearance of the
homogeneous states at energies below 0.68.Comment: 7 pages, 2 figures. Contribution to the Proceedings of the 31st
Workshop of the International School of Solid State Physics ``Complexity,
Metastability and Nonextensivity'', held at the Ettore Majorana Foundation
and Centre for Scientific Culture, Erice, Sicily, Italy, July 2004. Edited by
C. Tsallis, A. Rapisarda and C. Bec
Second-generation bioethanol from industrial wood waste of South American species
There is a global interest in replacing fossil fuels with renewable sources of energy. The present review evaluates the significance of South-American wood industrial wastes for bioethanol production. Four countries have been chosen for this review, i.e., Argentina, Brazil, Chile, and Uruguay, based on their current or potential forestry industry. It should be noted that although Brazil has a global bioethanol market share of 25%, its production is mainly first-generation bioethanol from sugarcane. The situation in the other countries is even worse, in spite of the fact that they have regulatory frameworks in place already allowing the substitution of a percentage of gasoline by ethanol. Pines and eucalyptus are the usually forested plants in these countries, and their industrial wastes, as chips and sawdust, could serve as promising raw materials to produce second-generation bioethanol in the context of a forest biorefinery. The process to convert woody biomass involves three stages: pretreatment, enzymatic saccharification, and fermentation. The operational conditions of the pretreatment method used are generally defined according to the physical and chemical characteristics of the raw materials and subsequently determine the characteristics of the treated substrates. This article also reviews and discusses the available pretreatment technologies for eucalyptus and pines applicable to South-American industrial wood wastes, their enzymatic hydrolysis yields, and the feasibility of implementing such processes in the mentioned countries in the frame of a biorefinery.Fil: Vallejos, María Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Kruyeniski, Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; ArgentinaFil: Area, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Químicas y Naturales. Instituto de Materiales de Misiones; Argentin
Butane-1,4-diyl bis-(pyridine-3-carboxyl-ate)
Molecules of the title compound (alternative name: butane-1,4-diyl dinicotinate), C16H16N2O4, lie on a inversion centre, located at the mid-point of the central C—C bond of the aliphatic chain, giving one half-molecule per asymmetric unit. The butane chain adopts an all-trans conformation. The dihedral angle between the mean plane of the butane-3-carboxylate group [for the non-H atoms, maximum deviation = 0.0871 (15) Å] and the pyridine ring is 10.83 (7)°. In the crystal, molecules lie in planes parallel to (122). The structure features weak π–π interactions with a centroid–centroid distance of 3.9281 (11) Å
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