Average degree conditions forcing a minor

Mader first proved that high average degree forces a given graph as a minor. Often motivated by Hadwiger's Conjecture, much research has focused on the average degree required to force a complete graph as a minor. Subsequently, various authors have consider the average degree required to force an arbitrary graph $H$ as a minor. Here, we strengthen (under certain conditions) a recent result by Reed and Wood, giving better bounds on the average degree required to force an $H$-minor when $H$ is a sparse graph with many high degree vertices. This solves an open problem of Reed and Wood, and also generalises (to within a constant factor) known results when $H$ is an unbalanced complete bipartite graph

Evaluating the Economic Impact of Countervailing Duties on United States Warm Water Shrimp Imports

Estimates of price and scale elasticities for U.S. consumed shrimp are derived using aggregate source country shrimp import data. It was assumed that supply was perfectly elastic and U.S. wholesalers determine the quantities imported from individual countries given the prices and preferences of U.S. consumers. Ex-ante analysis suggests that most countries levied with the countervailing duty experience declines in U.S. import demand while those countries not affected by the countervailing duty experience increases in import demand. Ex-post analysis shows the reverse to be true. Several countries impacted by the countervailing duty had increased import demand from the United States while Mexico, which was not affected by the countervailing duty, had decreased import demand. The results from aggregate level data suggest that imposing duties on specific companies within a country may not be effective if that company is not a monopoly producer or controls a significant share of the shrimp produced in that country.International Relations/Trade,

Fragmentation of Negative Ions from Carbohydrates: Part 2. Fragmentation of High-Mannose N-Linked Glycans

[M + NO3]− And [M + (NO3)2]2− ions were produced by electrospray from neutral high-mannose ([Man]5–9[GlcNAc]2, [Glc]1–3[Man]4–9[GlcNAc]2) N-linked glycans and their 2-aminobenzamide derivatives sprayed from methanol:water containing ammonium nitrate. Low energy collision-induced decomposition (CID) spectra of both types of ions were almost identical and dominated by cross-ring and C-type fragments, unlike the corresponding spectra of the positive ions that contained mainly B- and Y-type glycosidic fragments. This behavior could be rationalized by an initial proton abstraction from various hydroxy groups by the initially-formed anionic adduct. These negative ion spectra were more informative than the corresponding positive ion spectra and contained prominent ions that were diagnostic of structural features such as the composition of individual antennas that were not easily obtainable by other means. C-ions defined the sequence of the constituent monosaccharide residues. Detailed fragmentation mechanisms are proposed to account for many of the diagnostic ions

Seafood Safety and Trade

Food Consumption/Nutrition/Food Safety, International Relations/Trade,

A powerful test for linearity when the order of integration is unknown [Revised to become No. 07/06 above]

In this paper we propose a test of the null hypothesis of time series linearity against a nonlinear alternative, when uncertainty exists as to whether or not the series contains a unit root. We provide a test statistic that has the same limiting null critical values regardless of whether the series under consideration is generated from a linear I(0) or linear I(1) process, and is consistent against nonlinearity of either form, being asymptotically equivalent to the efficient test in each case. Finite sample simulations show that the new procedure has good size control and offers substantial power gains over the recently proposed robust linearity test of Harvey and Leybourne (2007).Nonlinearity testing; Wald tests; unit root tests; stationarity tests