12,738 research outputs found
THE QUESTIONABLE NECESSITY OF CHANGING MAIZE INTERVENTION
The EU took clear steps to suppress and abandon the intervention of maize in 2006. Originally the measure should have been revised in the course of the “Health Check”. But the European Commission (EC) rendered the minimal quality requirement for maize stricter in the intervention period starting 1 November 2006. Later the EC proposed to finish the intervention of maize. According to that decision the intervention of maize exists in the marketing year of 2007/08 and 2008/09 with a quantity limitation but it finishes in the marketing year of 2009/10. The EC argues for the abandonment of maize intervention, because, intervention stocks of cereals have increased significantly after the accession of the 10 new member states (EU-10), and the balance of the maize market is at risk. This measure is aimed to get back the intervention to its original purpose, as a safety net. We prove in this study that the intervention stock of cereal has not significantly increased after the enlargement in 2004 and it is not a reason for finishing maize intervention. The intervention stock of maize has increased since 2004 but not so significantly that it could be a reason for the abandonment of maize intervention.cereal, intervention, maize, stock, Agricultural and Food Policy, Agricultural Finance,
Superconductivity in heavily boron-doped silicon carbide
The discoveries of superconductivity in heavily boron-doped diamond (C:B) in
2004 and silicon (Si:B) in 2006 renew the interest in the superconducting state
of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a
metallic phase from which upon further doping superconductivity can emerge.
Recently, we discovered superconductivity in a closely related system:
heavily-boron doped silicon carbide (SiC:B). The sample used for that study
consists of cubic and hexagonal SiC phase fractions and hence this lead to the
question which of them participates in the superconductivity. Here we focus on
a sample which mainly consists of hexagonal SiC without any indication for the
cubic modification by means of x-ray diffraction, resistivity, and ac
susceptibility.Comment: 9 pages, 5 figure
Electron Addition Spectrum in the Supersymmetric t-J Model with Inverse-Square Interaction
The electron addition spectrum A^+(k,omega) is obtained analytically for the
one-dimensional (1D) supersymmetric t-J model with 1/r^2 interaction. The
result is obtained first for a small-sized system and its validity is checked
against the numerical calculation. Then the general expression is found which
is valid for arbitrary size of the system. The thermodynamic limit of
A^+(k,omega) has a simple analytic form with contributions from one spinon, one
holon and one antiholon all of which obey fractional statistics. The upper edge
of A^+(k,omega) in the (k,omega) plane includes a delta-function peak which
reduces to that of the single-electron band in the low-density limit.Comment: 5 pages, 1 figure, accepted for publication in Phys. Rev. Let
A multi-layer phase field model for extracting multiple near-circular objects
This paper proposes a functional that assigns low `energy' to sets of subsets of the image domain consisting of a number of possibly overlapping near-circular regions of approximately a given radius: a `gas of circles'. The model can be used as a prior for object extraction whenever the objects conform to the `gas of circles' geometry, e.g. cells in biological images. Configurations are represented by a multi-layer phase field. Each layer has an associated function, regions being defined by thresholding. Intra-layer interactions assign low energy to configurations consisting of non-overlapping near-circular regions, while overlapping regions are represented in separate layers. Inter-layer interactions penalize overlaps. Here we present a theoretical and experimental analysis of the model
Estimates on Green functions of second order differential operators with singular coefficients
We investigate the Green functions G(x,x^{\prime}) of some second order
differential operators on R^{d+1} with singular coefficients depending only on
one coordinate x_{0}. We express the Green functions by means of the Brownian
motion. Applying probabilistic methods we prove that when x=(0,{\bf x}) and
x^{\prime}=(0,{\bf x}^{\prime}) (here x_{0}=0) lie on the singular hyperplanes
then G(0,{\bf x};0,{\bf x}^{\prime}) is more regular than the Green function of
operators with regular coefficients.Comment: 16 page
Green Function of the Sutherland Model with SU(2) internal symmetry
We obtain the hole propagator of the Sutherland model with SU(2) internal
symmetry for coupling parameter , which is the simplest nontrivial
case. One created hole with spin down breaks into two quasiholes with spin down
and one quasihole with spin up. While these elementary excitations are
energetically free, the form factor reflects their anyonic character. The
expression for arbitrary integer is conjectured.Comment: 13pages, Revtex, one ps figur
Effects of Rattling Phonons on the Quasiparticle Excitation and Dynamics in the Superconducting -Pyrochlore KOsO
Microwave penetration depth and surface resistance at 27 GHz are
measured in high quality crystals of KOsO. Firm evidence for
fully-gapped superconductivity is provided from . Below the second
transition at K, the superfluid density shows a step-like
change with a suppression of effective critical temperature .
Concurrently, the extracted quasiparticle scattering time shows a steep
enhancement, indicating a strong coupling between the anomalous rattling motion
of K ions and quasiparticles. The results imply that the rattling phonons help
to enhance superconductivity, and that K sites freeze to an ordered state with
long quasiparticle mean free path below .Comment: 5 pages, 5 figures, to be published in Phys. Rev. Let
Stochastic Quasilinear Evolution Equations in UMD Banach Spaces
In this work we prove the existence and uniqueness up to a stopping time for the stochastic counterpart of Tosio Kato\u27s quasilinear evolutions in UMD Banach spaces. These class of evolutions are known to cover a large class of physically important nonlinear partial differential equations. Existence of a unique maximal solution as well as an estimate on the probability of positivity of stopping time is obtained. An example of stochastic Euler and Navier–Stokes equation is also given as an application of abstract theory to concrete models
Density-functional theory of freezing of vortex-liquid in quasi two-dimensional superconductors
We present a theory of vortex liquid-to-solid transition in homogeneous quasi
2D superconductors. The free energy is written as a functional l of density of
zeroes of the fluctuating order parameter. The transition is weakly first-order
and well below the Hc2(T) line. Transition temperature, discontinuities of the
average Abrikosov ratio and of the average superfluid density, the Debay-Waller
factor and the latent heat are in good agreement with Monte Carlo simulations.
The density is only weakly modulated in the "vortex-solid" phase, consistent
with the density-wave behavior.Comment: 12 pages and 1 figure available upon request, LaTex Version 2.09,
submitted to Phys. Rev. Let
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