Grain marketing policy changes and spatial efficiency of maize and wheat markets in Ethiopia

"In the context of on-going market reform in developing countries, there is a need for an improvement in the existing methods of spatial market efficiency analysis in order to better inform the debate toward designing and implementing new grain marketing policies, institutions, and infrastructure that facilitate the emergence of a well developed and competitive grain marketing system. The standard parity bounds model (PBM), while it overcomes many weaknesses of the conventional methods of spatial market efficiency analysis, it does not allow for the test of structural changes in spatial market efficiency as a result of policy changes. In this paper, building on the standard PBM, we develop an extended parity bounds model (EPBM). The EPBM is a stochastic gradual switching model with three trade regimes. The EPBM is estimated by maximum likelihood procedure and allows for tracing the time path and structural change in spatial market efficiency conditions due to the policy changes. We applied the EPBM to analyze the effect of grain marketing policy changes on spatial efficiency of maize and wheat markets in Ethiopia. The results show that the effect of policy changes on spatial market efficiency is not significant statistically in many cases; there is high probability of spatial inefficiency in maize and wheat markets before and after the policy changes. The implication of these results is that maize and wheat markets are characterized by periodic gluts and shortages, which can undermine the welfare of producers, grain traders and consumers. It is also observed that the nature of spatial inefficiency for maize and wheat markets is different implying that the two commodities might require different policy responses in order to improve spatial market efficiency. Maize traders made losses most of the time while wheat traders made excess profits most of the time covered by the study." Authors' AbstractStochastic analysis ,structural change ,

Primary neurons that express the L2/HNK-1 carbohydrate during early development in the zebrafish

In zebrafish, many nerve pathways in both the CNS and periphery are pioneered by a small and relatively simple set of ‘primary’ neurons that arise in the early embryo. We now have used monoclonal antibodies to show that, as they develop, primary neurons of several functional classes express on their surfaces the L2/HNK-1 tetrasaccharide that is associated with a variety of cell surface adhesion molecules. We have studied the early labeling patterns of these neurons, as well as some non-neural cells, and found that the time of onset and intensity of immunolabeling vary specifically according to cell type. The first neuronal expression is by Rohon-Beard and trigeminal ganglion neurons, both of which are primary sensory neurons that mediate touch sensitivity. These cells express the epitope very strongly on their growth cones and axons, permitting study of their development unobscured by labeling in other cells. Both types initiate axogenesis at the same early time, and appear to be the first neurons in the embryo to do so. Their peripheral neurites display similar branching patterns and have similar distinctive growth cone morphologies. Their central axons grow at the same rate along the same longitudinal fiber pathway, but in opposite directions, and where they meet they appear to fasciculate with one another. The similarities suggest that Rohon-Beard and trigeminal ganglion neurons, despite their different positions, share a common program of early development. Immunolabeling is also specifically present on a region of the brain surface where the newly arriving trigeminal sensory axons will enter the brain. Further, the trigeminal expression of the antigen persists in growth cones during the time that they contact an individually identified central target neuron, the Mauthner cell, which also expresses the epitope. These findings provide descriptive evidence for possible roles of L2/HNK-1 immunoreactive molecules in axonal growth and synaptogenesis

Cell-cell interactions during the migration of an identified commissural growth cone in the embryonic grasshopper

Journal ArticleOne of the fascicles of the posterior commissure of the embryonic grasshopper is pioneered by an individually identifiable neuron named Q1. Q1 initially grows along a longitudinal pathway established by another pioneer neuron, MPl, and then crosses to the midline, where it meets and fasciculates with the axon of the contralateral Q1

Growth cone dynamics during the migration of an identified commissural growth cone

Journal ArticleWe have used time-lapse video microscopy to study the behavior of a neuron, 01, that pioneers the posterior commissure of the embryonic grasshopper. Our goal is to use time-lapse video as a tool to acquire a precise picture of normal development over time, and thereby identify stereotypic activities that might indicate important interactions necessary for proper formation of the commissure

Seeing a c-theorem with holography

There is no known model in holography exhibiting a $c$-theorem where the central charges of the dual CFT are distinct. We examine a holographic model of RG flows in a framework where the bulk gravity theory contains higher curvature terms. The latter allows us to distinguish the flow of the central charges $a$ and $c$ in the dual field theories in four dimensions. One finds that the flow of $a$ is naturally monotonic but that of $c$ is not. Extending the analysis of holographic RG flows to higher dimensions, we are led to formulate a novel c-theorem in arbitrary dimensions for a universal coefficient appearing in the entanglement entropy of the fixed point CFT's.Comment: 5 pages, 1 figure, v2: minor change

High Resolution Aperture Synthesis Observations of Molecular Gas in NGC1068

We have obtained high resolution (2.9″∼260 pc) aperture synthesis imaging of NGC 1068 in the CO J = 1 → 0 line made with the Owens Valley mm Interferometer. The major features seen in CO are: (1) the inner spiral arms of molecular gas at ∼15″ radius (1.5 kpc) which originate from the ends of the central stellar bar, and (2) a compact source (∼3″) coincident with the Seyfert 2 nucleus. The components within 2 kpc of the galactic nucleus account for approximately 30% of the total molecular gas content in NGC 1068. The spiral arm CO emission is resolved into 38 discrete complexes which closely correlate with regions of strong Hα and 10 μm emission. The sizes of these structures range up to 500 pc and their masses derived from the CO line flux are 2×10^7−7×10^8M⊙. Somewhat smaller mass estimates are obtained from the virial theorem using the observed CO linewidths and sizes, suggesting that these complexes may be self-gravitating

Symmetry and Surface Symmetry Energies in Finite Nuclei

A study of properties of the symmetry energy of nuclei is presented based on density functional theory. Calculations for finite nuclei are given so that the study includes isospin dependent surface symmetry considerations as well as isospin independent surface effects. Calculations are done at both zero and non-zero temperature. It is shown that the surface symmetry energy term is the most sensitive to the temperature while the bulk energy term is the least sensitive. It is also shown that the temperature dependence terms are insensitive to the force used and even more insensitive to the existence of neutron skin. Results for a symmetry energy with both volume and surface terms are compared with a symmetry energy with only volume terms along the line of $\beta$ stability. Differences of several MeV are shown over a good fraction of the total mass range in $A$. Also given are calculations for the bulk, surface and Coulomb terms.Comment: 11 pages, 2 figures, Added a new tabl