3,440 research outputs found
Economic Issues of Invasive Pests and Diseases and Food Safety
The problem of invasive pests and diseases has become more urgent and far more complex today than in the recent past. Increased trade and movement of people, and the opening up of new trade routes have increased opportunities for the spread of invasive species. In addition, mono-cropping systems of cultivation; globalization; increased resistance of pests to pesticides and food safety and environmental concerns have all contributed to the growing complexity of the problem on hand. The economic dimensions of the problem can be viewed from at least two perspectives. First, with regard to the spread and impact of invasive species, particularly how best to provide more comprehensive assessments of impacts of invasions, so as to improve the cost effectiveness and efficiency of publicly funded programs aimed at eradication, control or mitigation of invasive pests and diseases. Second, from the perspective of incorporating more economic analysis and use of economic instruments in designing sanitary and phytosanitary measures. The paper explores some of these issues from an economic perspective. It concludes that incorporating more economic analysis in matters related to biological invasions is desirable, but presents a challenge to economists. Measurement requires data, and success in measurement will require that economists and biological scientists work closer together than they have in the past.sanitary and phytosanitary measures, SPS, invasive species, WTO, economic impact of invasive species, Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety, International Relations/Trade,
Collider phenomenology of Higgs bosons in Left-Right symmetric Randall-Sundrum models
We investigate the collider phenomenology of a left-right symmetric
Randall-Sundrum model with fermions and gauge bosons in the bulk. We find that
the model is allowed by precision electroweak data as long as the ratio of the
(unwarped) Higgs vev to the curvature scale is . In that region
there can be substantial modifications to the Higgs properties. In particular,
the couplings to and are reduced, the coupling to gluons is enhanced,
and the coupling to can receive shifts in either direction. The
Higgs mass bound from LEP II data can potentially be relaxed to GeV.Comment: 21 pages, 11 figures. Minor changes to numerics; replaced with
published versio
Stationary and Transient Work-Fluctuation Theorems for a Dragged Brownian Particle
Recently Wang et al. carried out a laboratory experiment, where a Brownian
particle was dragged through a fluid by a harmonic force with constant velocity
of its center. This experiment confirmed a theoretically predicted work related
integrated (I) Transient Fluctuation Theorem (ITFT), which gives an expression
for the ratio for the probability to find positive or negative values for the
fluctuations of the total work done on the system in a given time in a
transient state. The corresponding integrated stationary state fluctuation
theorem (ISSFT) was not observed. Using an overdamped Langevin equation and an
arbitrary motion for the center of the harmonic force, all quantities of
interest for these theorems and the corresponding non-integrated ones (TFT and
SSFT, resp.) are theoretically explicitly obtained in this paper. While the
(I)TFT is satisfied for all times, the (I)SSFT only holds asymptotically in
time. Suggestions for further experiments with arbitrary velocity of the
harmonic force and in which also the ISSFT could be observed, are given. In
addition, a non-trivial long-time relation between the ITFT and the ISSFT was
discovered, which could be observed experimentally, especially in the case of a
resonant circular motion of the center of the harmonic force.Comment: 20 pages, 3 figure
An assessment of Evans' unified field theory II
Evans developed a classical unified field theory of gravitation and
electromagnetism on the background of a spacetime obeying a Riemann-Cartan
geometry. In an accompanying paper I, we analyzed this theory and summarized it
in nine equations. We now propose a variational principle for Evans' theory and
show that it yields two field equations. The second field equation is algebraic
in the torsion and we can resolve it with respect to the torsion. It turns out
that for all physical cases the torsion vanishes and the first field equation,
together with Evans' unified field theory, collapses to an ordinary Einstein
equation.Comment: 11 pages of late
A Model for the Stray Light Contamination of the UVCS Instrument on SOHO
We present a detailed model of stray-light suppression in the spectrometer
channels of the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO
spacecraft. The control of diffracted and scattered stray light from the bright
solar disk is one of the most important tasks of a coronagraph. We compute the
fractions of light that diffract past the UVCS external occulter and
non-specularly pass into the spectrometer slit. The diffracted component of the
stray light depends on the finite aperture of the primary mirror and on its
figure. The amount of non-specular scattering depends mainly on the
micro-roughness of the mirror. For reasonable choices of these quantities, the
modeled stray-light fraction agrees well with measurements of stray light made
both in the laboratory and during the UVCS mission. The models were constructed
for the bright H I Lyman alpha emission line, but they are applicable to other
spectral lines as well.Comment: 19 pages, 5 figures, Solar Physics, in pres
Convexity of reduced energy and mass angular momentum inequalities
In this paper, we extend the work in
\cite{D}\cite{ChrusLiWe}\cite{ChrusCo}\cite{Co}. We weaken the asymptotic
conditions on the second fundamental form, and we also give an norm
bound for the difference between general data and Extreme Kerr data or Extreme
Kerr-Newman data by proving convexity of the renormalized Dirichlet energy when
the target has non-positive curvature. In particular, we give the first proof
of the strict mass/angular momentum/charge inequality for axisymmetric
Einstein/Maxwell data which is not identical with the extreme Kerr-Newman
solution.Comment: 27 page
Density functional theory of phase coexistence in weakly polydisperse fluids
The recently proposed universal relations between the moments of the
polydispersity distributions of a phase-separated weakly polydisperse system
are analyzed in detail using the numerical results obtained by solving a simple
density functional theory of a polydisperse fluid. It is shown that universal
properties are the exception rather than the rule.Comment: 10 pages, 2 figures, to appear in PR
Gallavotti-Cohen theorem, Chaotic Hypothesis and the zero-noise limit
The Fluctuation Relation for a stationary state, kept at constant energy by a
deterministic thermostat - the Gallavotti-Cohen Theorem -- relies on the
ergodic properties of the system considered. We show that when perturbed by an
energy-conserving random noise, the relation follows trivially for any system
at finite noise amplitude. The time needed to achieve stationarity may stay
finite as the noise tends to zero, or it may diverge. In the former case the
Gallavotti-Cohen result is recovered, while in the latter case, the crossover
time may be computed from the action of `instanton' orbits that bridge
attractors and repellors. We suggest that the `Chaotic Hypothesis' of
Gallavotti can thus be reformulated as a matter of stochastic stability of the
measure in trajectory space. In this form this hypothesis may be directly
tested
Ethnic Concerns and Latino Party Identification [post-print]
The accelerated growth of the Latino population in the United States has made Latinos a coveted addition to each major political party\u27s base. In this paper we examine the influence of ethnic concerns on the party identification of Latinos in the U.S. In contrast to previous studies, we account for Latinos’ perceptions of the political parties’ concern for their ethnic interests, allowing such interests to be self-defined. In a multinomial logit analysis of pooled data from three surveys of Latinos taken in 1999, 2004, and 2006, we find such perceptions do affect Latino partisanship, along with variables such as nativity and country of origin or ancestry. We also find a tendency toward independence among Latinos. Finally, we find movement toward the Democratic Party in 2004, once ethnic concerns are taken into account. One implication of the findings is that the party that can best persuade Latinos of their concern for their interests is the party most likely to gain their loyalties; indeed, the parties must earn those loyalties
Fluctuation formula for nonreversible dynamics in the thermostated Lorentz gas
We investigate numerically the validity of the Gallavotti-Cohen fluctuation
formula in the two and three dimensional periodic Lorentz gas subjected to
constant electric and magnetic fields and thermostated by the Gaussian
isokinetic thermostat. The magnetic field breaks the time reversal symmetry,
and by choosing its orientation with respect to the lattice one can have either
a generalized reversing symmetry or no reversibility at all. Our results
indicate that the scaling property described by the fluctuation formula may be
approximately valid for large fluctuations even in the absence of
reversibility.Comment: 6 pages, 6 figure
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