How Highly Pathogenic Avian Influenza (H5N1) Has Affected World Poultry-Meat Trade

In 2003, outbreaks of the highly pathogenic avian influenza (HPAI) H5N1 virus had a major negative impact on the global poultry industry. Initially, import demand for both uncooked and cooked poultry declined substantially, due to consumers’ fear of contracting avian influenza by eating poultry meat. Consumer fears adversely affected poultry consumption in many countries, leading to lower domestic prices, decreased production, and lower poultry meat exports. These reductions proved to be short-lived, as prices, consumption, production, and exports returned to preoutbreak levels in a relatively short time. As consumers gained confidence that poultry was safe if properly handled and cooked, world demand for cooked poultry increased. The cooked poultry share of total cooked and uncooked global exports nearly doubled from 2004 to 2006. In 2006, the world poultry industry was again under pressure due to HPAI H5N1 outbreaks, this time in Europe. By the end of the year, however, world poultry meat output had reached a new high, although, for some European countries, it was slightly below the 2005 level.highly pathogenic avian influenza, HPAI H5N1, cooked poultry meat, uncooked poultry meat, poultry exports, domestic poultry prices, export poultry prices, poultry consumption, poultry production, International Relations/Trade, Livestock Production/Industries,

DERIVED FEED DEMAND FOR EGYPT'S POULTRY AND EGG SECTOR TO 2010--POLICIES AND IMPLICATIONS

Egypt's derived feed demand for poultry and eggs and its dependency on world feed markets was econometrically projected to 2010. Results reveal a poultry industry as highly dependent on imports, where dependency rate will approach 100 percent for soybeans and 48 percent for yellow corn in 2010.International Relations/Trade,

IMPACT OF SANITARY AND PHYTO-SANITARY AGREEMENTS ON WORLD TRADE OF POULTRY, AND POULTRY PRODUCTS

Replaced with revised version of paper 07/29/04.Food Consumption/Nutrition/Food Safety, International Relations/Trade,

Equivariant semidefinite lifts and sum-of-squares hierarchies

A central question in optimization is to maximize (or minimize) a linear function over a given polytope P. To solve such a problem in practice one needs a concise description of the polytope P. In this paper we are interested in representations of P using the positive semidefinite cone: a positive semidefinite lift (psd lift) of a polytope P is a representation of P as the projection of an affine slice of the positive semidefinite cone $\mathbf{S}^d_+$. Such a representation allows linear optimization problems over P to be written as semidefinite programs of size d. Such representations can be beneficial in practice when d is much smaller than the number of facets of the polytope P. In this paper we are concerned with so-called equivariant psd lifts (also known as symmetric psd lifts) which respect the symmetries of the polytope P. We present a representation-theoretic framework to study equivariant psd lifts of a certain class of symmetric polytopes known as orbitopes. Our main result is a structure theorem where we show that any equivariant psd lift of size d of an orbitope is of sum-of-squares type where the functions in the sum-of-squares decomposition come from an invariant subspace of dimension smaller than d^3. We use this framework to study two well-known families of polytopes, namely the parity polytope and the cut polytope, and we prove exponential lower bounds for equivariant psd lifts of these polytopes.Comment: v2: 30 pages, Minor changes in presentation; v3: 29 pages, New structure theorem for general orbitopes + changes in presentatio

Equivariant semidefinite lifts of regular polygons

Given a polytope P in $\mathbb{R}^n$, we say that P has a positive semidefinite lift (psd lift) of size d if one can express P as the linear projection of an affine slice of the positive semidefinite cone $\mathbf{S}^d_+$. If a polytope P has symmetry, we can consider equivariant psd lifts, i.e. those psd lifts that respect the symmetry of P. One of the simplest families of polytopes with interesting symmetries are regular polygons in the plane, which have played an important role in the study of linear programming lifts (or extended formulations). In this paper we study equivariant psd lifts of regular polygons. We first show that the standard Lasserre/sum-of-squares hierarchy for the regular N-gon requires exactly ceil(N/4) iterations and thus yields an equivariant psd lift of size linear in N. In contrast we show that one can construct an equivariant psd lift of the regular 2^n-gon of size 2n-1, which is exponentially smaller than the psd lift of the sum-of-squares hierarchy. Our construction relies on finding a sparse sum-of-squares certificate for the facet-defining inequalities of the regular 2^n-gon, i.e., one that only uses a small (logarithmic) number of monomials. Since any equivariant LP lift of the regular 2^n-gon must have size 2^n, this gives the first example of a polytope with an exponential gap between sizes of equivariant LP lifts and equivariant psd lifts. Finally we prove that our construction is essentially optimal by showing that any equivariant psd lift of the regular N-gon must have size at least logarithmic in N.Comment: 29 page

Sparse sum-of-squares certificates on finite abelian groups

Let G be a finite abelian group. This paper is concerned with nonnegative functions on G that are sparse with respect to the Fourier basis. We establish combinatorial conditions on subsets S and T of Fourier basis elements under which nonnegative functions with Fourier support S are sums of squares of functions with Fourier support T. Our combinatorial condition involves constructing a chordal cover of a graph related to G and S (the Cayley graph Cay($\hat{G}$,S)) with maximal cliques related to T. Our result relies on two main ingredients: the decomposition of sparse positive semidefinite matrices with a chordal sparsity pattern, as well as a simple but key observation exploiting the structure of the Fourier basis elements of G. We apply our general result to two examples. First, in the case where $G = \mathbb{Z}_2^n$, by constructing a particular chordal cover of the half-cube graph, we prove that any nonnegative quadratic form in n binary variables is a sum of squares of functions of degree at most $\lceil n/2 \rceil$, establishing a conjecture of Laurent. Second, we consider nonnegative functions of degree d on $\mathbb{Z}_N$ (when d divides N). By constructing a particular chordal cover of the d'th power of the N-cycle, we prove that any such function is a sum of squares of functions with at most $3d\log(N/d)$ nonzero Fourier coefficients. Dually this shows that a certain cyclic polytope in $\mathbb{R}^{2d}$ with N vertices can be expressed as a projection of a section of the cone of psd matrices of size $3d\log(N/d)$. Putting $N=d^2$ gives a family of polytopes $P_d \subset \mathbb{R}^{2d}$ with LP extension complexity $\text{xc}_{LP}(P_d) = \Omega(d^2)$ and SDP extension complexity $\text{xc}_{PSD}(P_d) = O(d\log(d))$. To the best of our knowledge, this is the first explicit family of polytopes in increasing dimensions where $\text{xc}_{PSD}(P_d) = o(\text{xc}_{LP}(P_d))$.Comment: 34 page

Lab-frame observables for probing the top-Higgs interaction

We investigate methods to explore the CP nature of the $t\bar{t}h$ coupling at the LHC, focusing on associated production of the Higgs with a $t \bar{t}$ pair. We first discuss the constraints implied by low-energy observables and by the Higgs-rate information from available LHC data, emphasizing that they cannot provide conclusive evidence on the nature of this coupling. We then investigate kinematic observables that could probe the $t\bar{t}h$ coupling directly, in particular quantities that can be constructed out of just lab-frame kinematics. We define one such observable by exploiting the fact that $t \bar{t}$ spin correlations do also carry information about the CP-nature of the $t\bar{t}h$ coupling. Finally, we introduce a CP-odd quantity and a related asymmetry, able to probe CP violation in the $t\bar{t}h$ coupling and likewise constructed out of lab-frame momenta only.Comment: 32 pages, updated with latest data from ATLAS and references adde

Locking classical information

It is known that the maximum classical mutual information that can be achieved between measurements on a pair of quantum systems can drastically underestimate the quantum mutual information between those systems. In this article, we quantify this distinction between classical and quantum information by demonstrating that after removing a logarithmic-sized quantum system from one half of a pair of perfectly correlated bitstrings, even the most sensitive pair of measurements might only yield outcomes essentially independent of each other. This effect is a form of information locking but the definition we use is strictly stronger than those used previously. Moreover, we find that this property is generic, in the sense that it occurs when removing a random subsystem. As such, the effect might be relevant to statistical mechanics or black hole physics. Previous work on information locking had always assumed a uniform message. In this article, we assume only a min-entropy bound on the message and also explore the effect of entanglement. We find that classical information is strongly locked almost until it can be completely decoded. As a cryptographic application of these results, we exhibit a quantum key distribution protocol that is "secure" if the eavesdropper's information about the secret key is measured using the accessible information but in which leakage of even a logarithmic number of key bits compromises the secrecy of all the others.Comment: 32 pages, 2 figure

Review of En-Face Choroidal Imaging Using Spectral-Domain Optical Coherence Tomography

Investigations of choroidal vasculature have been of particular interest given choroidal vascular dysfunction are thought to be related with a number pathologic conditions such as central serous chorioretinopathy and various forms of AMD, including polypoidal choroidal vasculopathy. On the other hand, en face imaging of the choroid allows an exceptional alternative to histopathologic evaluation of the choroid, and can be used to quantify choroidal vascular structures. Our former study verified differences in the macular choroid in AMD and control patients previously noted on histopathologic studies. The use of phase-resolved approaches in larger population longitudinal studies reveal the sequence of RPE and choroidal changes in the pathogenesis of various AMD subtypes, which cannot be done using histopathology. Issues with lateral resolution of the OCT system in measuring choriocapillaris size could be solved by incorporating the axial dimension of the choriocapillaris into choriocapilaris diameter assessment (assuming the choriocapillaris are round in vivo), and by correcting for anisometric pixel resolution. Forthcoming studies are required to determine whether areas of choriocapillaris correlate with areas of RPD lesions