8,894 research outputs found
From “boat to plate”: creating value through sustainable fish supply chain visibility
Environmental concerns about the scarcity of marine resources are critical driving forces for firms aiming to prepare their supply chains for sustainability. Building on previous work, this paper highlights the mplementation of good practices geared towards sustainable operations in the seafood department, which were pursued in an exploratory retailer case. Outcomes of the adopted environmentally and socially acceptable fish retailing strategies, ranged from traceability, to self-certification and eco-labelling. The consequences for business were, as follows: stronger collaboration and trust across the chain of custody, improvement of sponsors’ image and of consumers’ loyalty and, progress in the Greenpeace retailers’ evaluation ranking.info:eu-repo/semantics/publishedVersio
Tetragonal tungsten bronze compounds: relaxor vs mixed ferroelectric - dipole glass behavior
We demonstrate that recent experimental data (E. Castel et al J.Phys. Cond.
Mat. {\bf 21} (2009), 452201) on tungsten bronze compound (TBC)
BaPrNdFeNbO can be well explained in our model
predicting a crossover from ferroelectric () to orientational (dipole)
glass (), rather then relaxor, behavior. We show, that since a "classical"
perovskite relaxor like Pb(Mn Nb)O is never a
ferroelectric, the presence of ferroelectric hysteresis loops in TBC shows that
this substance actually transits from ferroelectric to orientational glass
phase with growth. To describe the above crossover theoretically, we use
the simple replica-symmetric solution for disordered Ising model.Comment: 5 two-column pages, 4 figure
Quenched disorder and spin-glass correlations in XY nematics
We present a theoretical study of the equilibrium ordering in a 3D XY nematic
system with quenched random disorder. Within this model, treated with the
replica trick and Gaussian variational method, the correlation length is
obtained as a function of the local nematic order parameter and the effective
disorder strength. These results clarify what happens in the limiting cases of
diminishing order parameter and disorder strength, that is near a phase
transition of a pure system. In particular, it is found that quenched disorder
is irrelevant as the order parameter tends to zero and hence does not change
the character of the continuous XY nematic to isotropic phase transition. We
discuss how these results compare with experiments and simulationsComment: 19 pages, 6 figures, corrected typo
One-step replica symmetry breaking solution of the quadrupolar glass model
We consider the quadrupolar glass model with infinite-range random
interaction. Introducing a simple one-step replica symmetry breaking ansatz we
investigate the para-glass continuous (discontinuous) transition which occurs
below (above) a critical value of the quadrupole dimension m*. By using a
mean-field approximation we study the stability of the one-step replica
symmetry breaking solution and show that for m>m* there are two transitions.
The thermodynamic transition is discontinuous but there is no latent heat. At a
higher temperature we find the dynamical or glass transition temperature and
the corresponding discontinuous jump of the order parameter.Comment: 10 pages, 3 figure
Decoherence of Semiclassical Wigner Functions
The Lindblad equation governs general markovian evolution of the density
operator in an open quantum system. An expression for the rate of change of the
Wigner function as a sum of integrals is one of the forms of the Weyl
representation for this equation. The semiclassical description of the Wigner
function in terms of chords, each with its classically defined amplitude and
phase, is thus inserted in the integrals, which leads to an explicit
differential equation for the Wigner function. All the Lindblad operators are
assumed to be represented by smooth phase space functions corresponding to
classical variables. In the case that these are real, representing hermitian
operators, the semiclassical Lindblad equation can be integrated. There results
a simple extension of the unitary evolution of the semiclassical Wigner
function, which does not affect the phase of each chord contribution, while
dampening its amplitude. This decreases exponentially, as governed by the time
integral of the square difference of the Lindblad functions along the classical
trajectories of both tips of each chord. The decay of the amplitudes is shown
to imply diffusion in energy for initial states that are nearly pure.
Projecting the Wigner function onto an orthogonal position or momentum basis,
the dampening of long chords emerges as the exponential decay of off-diagonal
elements of the density matrix.Comment: 23 pg, 2 fi
Sistemas de rotação de culturas para cevada, sob plantio direto, durante dez anos, em Guarapuava, PR.
bitstream/item/84002/1/CNPT-CIRCULAR-9-SISTEMAS-DE-ROTACAO-DE-CULTURAS-PARA-CEVADA-SOB-PLANTIO-DIRETO-DURANTE-DEZ-ANOS.pd
Caracterização química de frutos de novos genótipos de mamoeiro na Chapada do Apodi.
No Brasil, o mamoeiro é cultivado em praticamente todos os Estados, sendo a Bahia o maior produtor, seguido de Espirito Santo, Ceará e Rio Grande do Norte com 45,03%, 31,93%, 5,69% e 4,70% respectivamente (IBGE, 2013). O fruto é utilizado nas dietas alimentares por serem excelentes fontes de cálcio, vitaminas A e C e apresenta importância econômica para o agronegócio brasileiro
Bose Glass in Large N Commensurate Dirty Boson Model
The large N commensurate dirty boson model, in both the weakly and strongly
commensurate cases, is considered via a perturbative renormalization group
treatment. In the weakly commensurate case, there exists a fixed line under RG
flow, with varying amounts of disorder along the line. Including 1/N
corrections causes the system to flow to strong disorder, indicating that the
model does not have a phase transition perturbatively connected to the Mott
Insulator-Superfluid (MI-SF) transition. I discuss the qualitative effects of
instantons on the low energy density of excitations. In the strongly
commensurate case, a fixed point found previously is considered and results are
obtained for higher moments of the correlation functions. To lowest order,
correlation functions have a log-normal distribution. Finally, I prove two
interesting theorems for large N vector models with disorder, relevant to the
problem of replica symmetry breaking and frustration in such systems.Comment: 16 pages, 7 figure
Growth laws and self-similar growth regimes of coarsening two-dimensional foams: Transition from dry to wet limits
We study the topology and geometry of two dimensional coarsening foams with
arbitrary liquid fraction. To interpolate between the dry limit described by
von Neumann's law, and the wet limit described by Marqusee equation, the
relevant bubble characteristics are the Plateau border radius and a new
variable, the effective number of sides. We propose an equation for the
individual bubble growth rate as the weighted sum of the growth through
bubble-bubble interfaces and through bubble-Plateau borders interfaces. The
resulting prediction is successfully tested, without adjustable parameter,
using extensive bidimensional Potts model simulations. Simulations also show
that a selfsimilar growth regime is observed at any liquid fraction and
determine how the average size growth exponent, side number distribution and
relative size distribution interpolate between the extreme limits. Applications
include concentrated emulsions, grains in polycrystals and other domains with
coarsening driven by curvature
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