4,741 research outputs found
Hamiltonian symplectic embedding of the massive noncommutative U(1) Theory
We show that the massive noncommutative U(1) theory is embedded in a gauge
theory using an alternative systematic way, which is based on the symplectic
framework. The embedded Hamiltonian density is obtained after a finite number
of steps in the iterative symplectic process, oppositely to the result proposed
using the BFFT formalism. This alternative formalism of embedding shows how to
get a set of dynamically equivalent embedded Hamiltonian densities.Comment: 16 pages, no figures, revtex4, corrected version, references
additione
Parasitofauna de Hoplias malabaricus Bloch, 1794 (Erythrinidae) do Estado do Amapá, Amazônia oriental, Norte do Brasil.
ENBRAPOA
Quantum pattern recognition with liquid-state nuclear magnetic resonance
A novel quantum pattern recognition scheme is presented, which combines the
idea of a classic Hopfield neural network with adiabatic quantum computation.
Both the input and the memorized patterns are represented by means of the
problem Hamiltonian. In contrast to classic neural networks, the algorithm can
return a quantum superposition of multiple recognized patterns. A proof of
principle for the algorithm for two qubits is provided using a liquid state NMR
quantum computer.Comment: updated version, Journal-ref adde
Proporções de concentrado e volumoso em rações para caprinos em crescimento.
Uma das principais deficiências dos rebanhos caprinos leiteiros no Brasil e, em especial, no semi-árido brasileiro, está relacionada com o manejo alimentar e nutricional dos animais, principalmente as categorias consideradas menos produtivas, como os machos em crescimento. O objetivo do presente estudo foi avaliar quatro relações de concentrado e volumoso na matéria seca de rações para caprinos em crescimento, tendo como volumoso o capim Elefante in natura, picado. Os tratamentos avaliados foram: 80:20; 60:40; 40:60 e 20:80% de concentrado e volumoso na matéria seca das rações. Foram utilizados 28 caprinos, machos, da raça Saanen com peso vivo inicial médio de 9,0 kg, distribuídos em quatro grupos, em baias coletivas, sendo que, cada baia continha sete animais. O delineamento experimental adotado foi o inteiramente casualizado com sete repetições. Foram observados maiores (P0,05) entre os tratamentos avaliados para o ganho de peso aos 30 dias. Assim, rações contendo 80% de concentrado e 20% de volumoso na matéria seca proporcionaram melhores desempenhos aos caprinos de origem leiteira, em fase de crescimento
Degradable particulate composite reinforced with nanofibres for biomedical applications
Nanofibre-based structures and their composites are increasingly being studied for many biomedical applications, including tissue
engineering scaffolds. These materials enable architectures resembling the extracellular matrix to be obtained. The search for optimized
supports and carriers of cells is still a major challenge for the tissue engineering field. The main purpose of this work is to develop a novel
composite structure that combines microparticles and nanofibres in reinforced polymeric microfibres. This innovative combination of
materials is obtained by melting extrusion of a particulate composite reinforced with chitosan nanofibre meshes (0.05 wt.%) produced
by the electrospinning technique. The reinforced microfibres were analysed by scanning electron microscopy and showed a considerable
alignment of the chitosan nanofibres along the longitudinal main axis of the microfibre composite structure. The tensile mechanical properties
revealed that the introduction of the nanofibre reinforcement in the particulate microfibre composite increased the tensile modulus
by up to 70%. The various structures were subjected to swelling and degradation tests immersed in an isotonic saline solution at 37 C.
The presence of chitosan nanofibres in the particulate microfibres enhances the water uptake by up to 24%. The combination of good
mechanical properties and enhanced degradability of the developed structures is believed to have great potential for various biomedical
applications, including three-dimensional fibre mesh scaffolds to be applied in the field of bone tissue engineering.This work was partially supported by the EU Integrated Project GENOSTEM (No. LSH503161) and by project Micro-Nano (POCI/CTM/48040/2002), financed by the Portuguese Foundation for Science and Technology (FCT). A.M. would like to thank FCT for his PhD grant (SFRH/BD/24382/2005)
A global analysis of Spitzer and new HARPS data confirms the loneliness and metal-richness of GJ 436 b
Context. GJ 436b is one of the few transiting warm Neptunes for which a
detailed characterisation of the atmosphere is possible, whereas its
non-negligible orbital eccentricity calls for further investigation.
Independent analyses of several individual datasets obtained with Spitzer have
led to contradicting results attributed to the different techniques used to
treat the instrumental effects. Aims. We aim at investigating these previous
controversial results and developing our knowledge of the system based on the
full Spitzer photometry dataset combined with new Doppler measurements obtained
with the HARPS spectrograph. We also want to search for additional planets.
Methods. We optimise aperture photometry techniques and the photometric
deconvolution algorithm DECPHOT to improve the data reduction of the Spitzer
photometry spanning wavelengths from 3-24 {\mu}m. Adding the high precision
HARPS radial velocity data, we undertake a Bayesian global analysis of the
system considering both instrumental and stellar effects on the flux variation.
Results. We present a refined radius estimate of RP=4.10 +/- 0.16 R_Earth, mass
MP=25.4 +/- 2.1 M_Earth and eccentricity e= 0.162 +/- 0.004 for GJ 436b. Our
measured transit depths remain constant in time and wavelength, in disagreement
with the results of previous studies. In addition, we find that the
post-occultation flare-like structure at 3.6 {\mu}m that led to divergent
results on the occultation depth measurement is spurious. We obtain occultation
depths at 3.6, 5.8, and 8.0 {\mu}m that are shallower than in previous works,
in particular at 3.6 {\mu}m. However, these depths still appear consistent with
a metal-rich atmosphere depleted in methane and enhanced in CO/CO2, although
perhaps less than previously thought. We find no evidence for a potential
planetary companion, stellar activity, nor for a stellar spin-orbit
misalignment. [ABRIDGED]Comment: 25 pages, 26 figures, 8 tables, accepted for publication in A&
Relativistic Green functions in a plane wave gravitational background
We consider a massive relativistic particle in the background of a
gravitational plane wave. The corresponding Green functions for both spinless
and spin 1/2 cases, previously computed by A. Barducci and R. Giachetti
\cite{Barducci3}, are reobtained here by alternative methods, as for example,
the Fock-Schwinger proper-time method and the algebraic method. In analogy to
the electromagnetic case, we show that for a gravitational plane wave
background a semiclassical approach is also sufficient to provide the exact
result, though the lagrangian involved is far from being a quadratic one.Comment: Last paper by Professor Arvind Narayan Vaidya, 18 pages, no figure
Gauging the SU(2) Skyrme model
In this paper the SU(2) Skyrme model will be reformulated as a gauge theory
and the hidden symmetry will be investigated and explored in the energy
spectrum computation. To this end we purpose a new constraint conversion
scheme, based on the symplectic framework with the introduction of Wess-Zumino
(WZ) terms in an unambiguous way. It is a positive feature not present on the
BFFT constraint conversion. The Dirac's procedure for the first-class
constraints is employed to quantize this gauge invariant nonlinear system and
the energy spectrum is computed. The finding out shows the power of the
symplectic gauge-invariant formalism when compared with another constraint
conversion procedures present on the literature.Comment: revised version, to appear in Phys.Rev.
Ulvan: a new natural derived biomaterial obtained from renewable marine resources
[Excerpt] It is not hard to understand the commitment set in tissue engineering research and the effort to find better performing materials. The ultimate goal: an ideal scaffold with cell and tissue compliant mechanical properties that supports cellular attachment, growth and differentiation. In this study, a new natural derived polysaccharide–ulvan–found at the cell wall of green algae Ulva, the common sea lettuce, was investigated. The aim of this research work is to study and develop novel biomedical applications based on this polysaccharide, with special emphasis to tissue engineering. The polysaccharide ulvan, composed of sulphated rhamnose, xylose, glucoronic and iduronic acids, was isolated from Ulva batch by step extraction using hot water and precipitation with organic solvents. The obtained polysaccharide was then used to produce polymeric films by solvent casting.[...]info:eu-repo/semantics/publishedVersio
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