12,911 research outputs found
Do Consumers Really Use Food Labels?
Ordered Probit models are used to estimate the probabilities of consumers reading food labels for harmful ingredients and for using labels to assist with food purchasing decisions. Demographics, health concerns, attitudes, and eating habits are shown to influence the likelihood of using food labels. Effects from over 25 variables are ranked in terms of their relative impacts on the use of food labels. Dieting, concerns about calories, foreign foods, and many other variable effects on the use of food labels are shown.Consumer/Household Economics,
Novel Higgs decay signals in R-parity violating models
In supersymmetric models the lightest Higgs boson may decay with a sizable
branching ratio into a pair of light neutralinos. We analyze such decays within
the context of the minimal supersymmetric standard model with R-parity
violation, where the neutralino itself is unstable and decays into Standard
Model fermions. We show that the R-parity violating couplings induce novel
Higgs decay signals that might facilitate the discovery of the Higgs boson at
colliders. At the LHC, the Higgs may be observed, for instance, through its
decay -via two neutralinos- into final states containing missing energy and
isolated charged leptons such as , and .
Another promising possibility is the search for the displaced vertices
associated with the neutralino decay. We also point out that Higgs searches at
the LHC might additionally provide the first evidence of R-parity violation.Comment: 15 pages, 7 figures. Corrected affiliation
Spatial and temporal localization of light in two dimensions
Quasi-resonant scattering of light in two dimensions can be described either
as a scalar or as a vectorial electromagnetic wave. Performing a scaling
analysis we observe in both cases long lived modes, yet only the scalar case
exhibits Anderson localized modes together with extremely long mode lifetimes.
We show that the localization length of these modes is influenced only by their
position, and not their lifetime. Investigating the reasons for the absence of
localization, it appears that both the coupling of several polarizations and
the presence of near-field terms are able to prevent long lifetimes and
Anderson localization.Comment: 5 pages, 4 figures and Supplementary Informatio
Obtaining pressure versus concentration phase diagrams in spin systems from Monte Carlo simulations
We propose an efficient procedure for determining phase diagrams of systems
that are described by spin models. It consists of combining cluster algorithms
with the method proposed by Sauerwein and de Oliveira where the grand canonical
potential is obtained directly from the Monte Carlo simulation, without the
necessity of performing numerical integrations. The cluster algorithm presented
in this paper eliminates metastability in first order phase transitions
allowing us to locate precisely the first-order transitions lines. We also
produce a different technique for calculating the thermodynamic limit of
quantities such as the magnetization whose infinite volume limit is not
straightforward in first order phase transitions. As an application, we study
the Andelman model for Langmuir monolayers made of chiral molecules that is
equivalent to the Blume-Emery-Griffiths spin-1 model. We have obtained the
phase diagrams in the case where the intermolecular forces favor interactions
between enantiomers of the same type (homochiral interactions). In particular,
we have determined diagrams in the surface pressure versus concentration plane
which are more relevant from the experimental point of view and less usual in
numerical studies
Agriculture Productivity Growth: Is the Current Trend on the Track to Poverty Reduction?
In this study we evaluate the effect of annual productivity growth in agriculture over the 1991-2001 period on poverty in eleven developing countries. We compare this with the optimal pattern of productivity growth of comparable cost with the sole goal of maximizing poverty reduction. This comparison reveals that regional agricultural development is a viable option in the fight for poverty reduction.Food Security and Poverty,
Tools for Quantum Algorithms
We present efficient implementations of a number of operations for quantum
computers. These include controlled phase adjustments of the amplitudes in a
superposition, permutations, approximations of transformations and
generalizations of the phase adjustments to block matrix transformations. These
operations generalize those used in proposed quantum search algorithms.Comment: LATEX, 15 pages, Minor changes: one author's e-mail and one reference
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Quantum phases of bosons in double-well optical lattices
We study the superfluid to Mott insulator transition of bosons in a
two-legged ladder optical lattice, of a type accessible in current experiments
on double-well optical lattices. The zero-temperature phase diagram is mapped
out, with a focus on its dependence upon interchain hopping and the tilt
between double wells. We find that the unit-filling Mott phase exhibits a
non-monotonic behavior as a function of the tilt parameter, producing a
reentrant phase transition between Mott insulator and superfluid phases.Comment: 5 pages, 5 figure
Magnetic defects promote ferromagnetism in Zn1-xCoxO
Experimental studies of Zn1-xCoxO as thin films or nanocrystals have found
ferromagnetism and Curie temperatures above room temperature and that p- or
n-type doping of Zn1-xCoxO can change its magnetic state. Bulk Zn1-xCoxO with a
low defect density and x in the range used in experimental thin film studies
exhibits ferromagnetism only at very low temperatures. Therefore defects in
thin film samples or nanocrystals may play an important role in promoting
magnetic interactions between Co ions in Zn1-xCoxO. The electronic structures
of Co substituted for Zn in ZnO, Zn and O vacancies, substituted N and
interstitial Zn in ZnO were calculated using the B3LYP hybrid density
functional in a supercell. The B3LYP functional predicts a band gap of 3.34 eV
for bulk ZnO, close to the experimental value of 3.47 eV. Occupied minority
spin Co 3d levels are at the top of the valence band and unoccupied levels lie
above the conduction band minimum. Majority spin Co 3d levels hybridize
strongly with bulk ZnO states. The neutral O vacancy and interstitial Zn are
deep and shallow donors, respectively. The Zn vacancy is a deep acceptor and
the acceptor level for substituted N is at mid gap. The possibility that p- or
n-type dopants promote exchange coupling of Co ions was investigated by
computing total energies of magnetic states of ZnO supercells containing two Co
ions and an oxygen vacancy, substituted N or interstitial Zn in various charge
states. The neutral N defect and the singly-positively charged O vacancy are
the only defects which strongly promote ferromagnetic exchange coupling of Co
ions at intermediate range.Comment: 9 pages, 11 figure
Complex Hybrid Inflation and Baryogenesis
We propose a hybrid inflation model with a complex waterfall field which
contains an interaction term that breaks the U(1) global symmetry associated to
the waterfall field charge. We show that the asymmetric evolution of the real
and imaginary parts of the complex field during the phase transition at the end
of inflation translates into a charge asymmetry. The latter strongly depends on
the vev of the waterfall field, which is well constrained by diverse
cosmological observations.Comment: 4 RevTex pages, no figures. Changes made in response to referee's
comments; matches version published in Phys.Rev.Let
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