37,511 research outputs found
Pseudoscalars Mesons in Hot, Dense Matter
Phase transitions in hot and dense matter and the in--medium behavior of
pseudoscalar mesons () are investigated, in the framework of the three flavor Nambu--Jona-Lasinio
model, including the 't Hooft interaction, which breaks the symmetry.
Three different scenarios are considered: zero density and finite temperature,
zero temperature and finite density in quark matter with different degrees of
strangeness, and finite temperature and density. At T=0, the role of strange
valence quarks in the medium is discussed, in connection with the phase
transition and the mesonic behavior. It is found that the appearance of strange
quarks, above certain densities, leads to meaningful changes in different
observables, especially in matter with \betaT-\rho$ plane is analyzed in connection with possible signatures
of restoration of symmetries.Comment: 33 pages, 12 figures, PRC versio
Effective restoration of chiral and axial symmetries at finite temperature and density
The effective restoration of chiral and axial symmetries is investigated
within the framework of the SU(3) Nambu-Jona-Lasinio model. The topological
susceptibility, modeled from lattice data at finite temperature, is used to
extract the temperature dependence of the coupling strength of the anomaly. The
study of the scalar and pseudoscalar mixing angles is performed in order to
discuss the evolution of the flavor combinations of pairs and its
consequences for the degeneracy of chiral partners. A similar study at zero
temperature and finite density is also realized.Comment: 5 pages, 1 figure. Talk given at Strange Quark Matter 2004, Cape
Town, South Africa, 15-20 September, 200
Quantum Topology Change in (2 + 1)d
The topology of orientable (2 + 1)d spacetimes can be captured by certain
lumps of non-trivial topology called topological geons. They are the
topological analogues of conventional solitons. We give a description of
topological geons where the degrees of freedom related to topology are
separated from the complete theory that contains metric (dynamical) degrees of
freedom. The formalism also allows us to investigate processes of quantum
topology change. They correspond to creation and annihilation of quantum geons.
Selection rules for such processes are derived.Comment: LaTeX file, 33 pages, 10 postscript figures, some typos corrected,
references updated, and other minor change
Avoided crossings in mesoscopic systems: electron propagation on a non-uniform magnetic cylinder
We consider an electron constrained to move on a surface with revolution
symmetry in the presence of a constant magnetic field parallel to the
surface axis. Depending on and the surface geometry the transverse part of
the spectrum typically exhibits many crossings which change to avoided
crossings if a weak symmetry breaking interaction is introduced. We study the
effect of such perturbations on the quantum propagation. This problem admits a
natural reformulation to which tools from molecular dynamics can be applied. In
turn, this leads to the study of a perturbation theory for the time dependent
Born-Oppenheimer approximation
Adubação nitrogenada para pastagens do gênero Brachiaria em solos do Cerrado.
Introdução; Gênero Brachiaria; Matéria orgânica do solo e sua relação com a disponibilidade de N; Adições de nitrogênio ao sistema solo-pastagem; Importância da adubação nitrogenada em pastagens; Concentrações de nitrogênio e estimativa do teor de clorofila; Dinâmica do nitrogênio em pastagens; Perdas de nitrogênio do sistema solo-pastagem; Eficiência e recuperação do nitrogênio; Eficiência do nitrogênio na produção animal; Recomendação de adubação nitrogenada; Recomendação de adubação nitrogenada para o gênero Brachiaria de acordo com a fertilidade do solo; Recomendação de adubação nitrogenada para o gênero Brachiaria de acordo com o sistema de pastejo; Formas de aplicação de nitrogênio para pastagens; Considerações finais.bitstream/CNPAF/25514/1/doc_192.pd
Motor‐evoked potentials reveal a motor‐cortical readout of evidence accumulation for sensorimotor decisions
Many everyday activities require time-pressured sensorimotor decision making. Traditionally, perception, decision, and action processes were considered to occur in series, but this idea has been successfully challenged, particularly by neurophysiological work in animals. However, the generality of parallel processing requires further elucidation. Here, we investigate whether the accumulation of a decision can be observed intrahemispherically within human motor cortex. Participants categorized faces as male or female, with task difficulty manipulated using morphed stimuli. Transcranial magnetic stimulation, applied during the reaction-time interval, produced motor-evoked potentials (MEPs) in two hand muscles that were the major contributors when generating the required pinch/grip movements. Smoothing MEPs using a Gaussian kernel allowed us to recover a continuous time-varying MEP average, comparable to an EEG component, permitting precise localization of the time at which the motor plan for the responding muscle became dominant. We demonstrate decision-related activity in the motor cortex during this perceptual discrimination task, suggesting ongoing evidence accumulation within the motor system even for two independent actions represented within one hemisphere
Universal relaxation function in nonextensive systems
We have derived the dipolar relaxation function for a cluster model whose
volume distribution was obtained from the generalized maximum Tsallis
nonextensive entropy principle. The power law exponents of the relaxation
function are simply related to a global fractal parameter and for
large time to the entropy nonextensivity parameter . For intermediate times
the relaxation follows a stretched exponential behavior. The asymptotic power
law behaviors both in the time and the frequency domains coincide with those of
the Weron generalized dielectric function derived from an extension of the Levy
central limit theorem. They are in full agreement with the Jonscher
universality principle. Moreover our model gives a physical interpretation of
the mathematical parameters of the Weron stochastic theory and opens new paths
to understand the ubiquity of self-similarity and power laws in the relaxation
of large classes of materials in terms of their fractal and nonextensive
properties.Comment: Two figures. Submitted for publicatio
Silages of agro-industrial by-products in lamb diets : effct on growth performance, carcass, meat quality and in vitro methane emissions
Research Areas: AgricultureABSTRACT - The use of agro-industrial by-products in animal feed is an opportunity to reduce imports, food waste and promote a clean and circular economy, turning worthless raw materials into high -quality and low-cost animal feeds, which does not compete with human food. This study aims to produce silages with by-products of carrot, sweet potato, potato, and tomato pomace and integrate them in lamb diets, replacing 50% of dry matter (DM) of a concentrate-based diet. Effects on growth performance, meat quality and methane production were evaluated. Three silages were produced using 350 g/kg tomato pomace, 200 g/kg wheat bran, 150 g/kg alfalfa hay and 300 g/kg potato (Psil) or 300 g/kg sweet potato (SPsil) or 300 g/kg carrot (Csil). Thirty-two lambs were housed individually and divided into four groups (8 animals/group) on the following diets: Control -850 g/kg concentrate and 150 g/kg hay; P -500 g/kg concentrate and 500 g/kg Psil in DM; SP - 500 g/kg concentrate and 500 g/kg SPsil in DM; C - 500 g/kg concentrate and 500 g/kg Csil in DM. The trial lasted 6 weeks after 1 week of adaptation. Methane production was assessed in vitro by the Ankom system, using as inoculum rumen content samples collected individually from 6 lambs on each diet at slaughter. Diet had no effect on DM intake, average daily gain and DM conversion ratio, averaging 1055 +/- 248 g, 320 +/- 61.1 g and 3.35 +/- 0.600, respectively. Also, carcass characteristics were not affected by the diet except for the lightness of subcutaneous fat which was increased by the silage diets (L* value, P = 0.016). The meat pa-rameters, pH, intramuscular fat, shear force, cooking losses and sensory attributes, were not affected by the diet. In meat color, the parameters a* and Chroma were highest in animals fed diet C, have an intermediate value with Control diet and are lowest with diets P and SP (P = 0.027 and P = 0.012, respectively). Diets had no impact on total methane emissions. The costs of the silage diets per kg live weight gain were lower than those of Control diet (P = 0.018). In summary, by-product silage can be a good option to replace concentrated feed in lamb diets without altering the growth performance and meat quality or methane production and thus contributing to the sustainability of livestock farms and the environment.info:eu-repo/semantics/publishedVersio
A design of selective solar absorber for high temperature applications
This study presents a design of multilayer solar selective absorber for high temperature applications. The optical stack of this absorber is composed of four layers deposited by magnetron sputtering on stainless steel substrates. The first is a back-reflector tungsten layer, which is followed by two absorption layers based on CrAlSiNx/ CrAlSiOyNx structure for phase interference. The final layer is an antireflection layer of SiAlOx. The design was theoretically modelled with SCOUT software using transmittance and reflectance curves of individual thin layers, which were deposited on glass substrates. The final design shows simultaneously high solar absorbance = 95.2 % and low emissivity ε= 9.8% (at 400 ºC) together with high thermal stability at 400 ºC, in air, and 600 ºC in vacuum for 650 h.The authors acknowledge the support of FCT in the framework of the Strategic Funding UID/FIS/04650/2013
and the financial support of FCT, POCI and PORL operational programs through the project POCI-01-0145-
FEDER-016907 (PTDC/CTM-ENE/2882/2014), co-financed by European community fund FEDER.info:eu-repo/semantics/publishedVersio
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