CONTROL OF A MOBILE PEST: THE IMPORTED FIRE ANT

Crop Production/Industries,

BT COTTON REFUGE POLICY

Since cotton producers do not own legal rights to kill insect populations that are susceptible to insecticides, individual producers may have no incentive to account for future, insecticide-resistance productivity losses arising from their pest-management decisions. As a result, the collective actions of producers may increase the rate of resistance development relative to the rate that maximizes social welfare. Concerns regarding insect-pest development of resistance to Bt cotton prompted the Environmental Protection Agency to establish legal limits on the proportion of total acres individual producers may plant, representing the first attempt to regulate the development of insecticide resistance and the first instance of the use of refuge as a policy instrument. Ever since Carlson and Castle first pointed out the resource characteristics of insecticide susceptibility, pest management in the presence of increasing resistance has been viewed as an exhaustible resource allocation problem, and many studies have examined efficient insecticide use in this setting. Resistance management studies found in the economics literature, however, have examined single-insect single-insecticide problems almost exclusively. The majority of genetic and entomological studies have followed suit. Since cotton producers routinely use multiple insecticides and insecticide mixtures to manage multiple insect pests, and since simulation and empirical evidence suggests that toxin mixtures can affect the rate of resistance development to component toxins, the standard model may not be well suited for the examination of refuge policies under cotton production settings. Static refuge policies that maximize the present value of profit flows attainable by producers over five- and 10-year planning horizons are examined using a deterministic, operational model that accounts for short- and long-run features of production and resistance development. The model accounts for the development of resistance in two cotton insect pests to Bt cotton and a popular conventional insecticide, and relationships between refuge policy, insecticide resistance, producer profit and producer behavior in Louisiana. The model is used to examine relationships between resistance simulation model parameters and refuge policies and comparative advantages between treated and untreated refuge policies.Agricultural and Food Policy,

THE ESTIMATION OF COTTON COSTS IN THE SOUTHEAST

Crop Production/Industries,

INFORMATION QUALITY, TECHNOLOGY DEPRECIATION, AND BT COTTON ADOPTION IN THE SOUTHEAST

In 1996, Bt cotton became one of the first genetically engineered crops to be available commercially. This study focuses on the various sources and quality of information about Bt cotton profitability available to farmers in the Southeast and assesses the relative importance of such information in the farmers' adoption decisions. A model of the individual decision to adopt is developed to incorporate two recent theories of the role of information quality (the "effective information" hypothesis and the "popularity" hypothesis) as well as the effect of current technology depreciation. The data show some support for all three factors as determinants of adoption.Crop Production/Industries,

The Electromagnetic Self-Energy Contribution to M_p - M_n and the Isovector Nucleon Magnetic Polarizability

We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham's formula is corrected and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find \delta M_{p-n}^\gamma = 1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input from lattice QCD to constrain this polarizability as: \beta_{p-n} = -0.87(85) x 10^{-4} fm^3.Comment: 5 pages, version accepted for publication in PR

Electromagnetic Self-Energy Contribution to M-p-M-n and the Isovector Nucleon Magnetic Polarizability

We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham\u27s formula is corrected, and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find delta M-p-n(gamma) = 1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input from lattice QCD to constrain this polarizability as: beta(p-n) = -0.87(85) x 10(-4) fm(3)

Characterization of a large sex determination region in Salix purpurea L. (Salicaceae).

Dioecy has evolved numerous times in plants, but heteromorphic sex chromosomes are apparently rare. Sex determination has been studied in multiple Salix and Populus (Salicaceae) species, and P. trichocarpa has an XY sex determination system on chromosome 19, while S. suchowensis and S. viminalis have a ZW system on chromosome 15. Here we use whole genome sequencing coupled with quantitative trait locus mapping and a genome-wide association study to characterize the genomic composition of the non-recombining portion of the sex determination region. We demonstrate that Salix purpurea also has a ZW system on chromosome 15. The sex determination region has reduced recombination, high structural polymorphism, an abundance of transposable elements, and contains genes that are involved in sex expression in other plants. We also show that chromosome 19 contains sex-associated markers in this S. purpurea assembly, along with other autosomes. This raises the intriguing possibility of a translocation of the sex determination region within the Salicaceae lineage, suggesting a common evolutionary origin of the Populus and Salix sex determination loci

Non-perturbative Gluons and Pseudoscalar Mesons in Baryon Spectroscopy

We study baryon spectroscopy including the effects of pseudoscalar meson exchange and one gluon exchange potentials between quarks, governed by $\alpha_s$. The non-perturbative, hyperspherical method calculations show that one can obtain a good description of the data by using a quark-meson coupling constant that is compatible with the measured pion-nucleon coupling constant, and a reasonably small value of $\alpha_s$.Comment: 12 pages; Submitted to Phys. Rev. C. Rapid Communication

The transposable elements of the Drosophila melanogaster euchromatin: a genomics perspective.

BACKGROUND: Transposable elements are found in the genomes of nearly all eukaryotes. The recent completion of the Release 3 euchromatic genomic sequence of Drosophila melanogaster by the Berkeley Drosophila Genome Project has provided precise sequence for the repetitive elements in the Drosophila euchromatin. We have used this genomic sequence to describe the euchromatic transposable elements in the sequenced strain of this species. RESULTS: We identified 85 known and eight novel families of transposable element varying in copy number from one to 146. A total of 1,572 full and partial transposable elements were identified, comprising 3.86% of the sequence. More than two-thirds of the transposable elements are partial. The density of transposable elements increases an average of 4.7 times in the centromere-proximal regions of each of the major chromosome arms. We found that transposable elements are preferentially found outside genes; only 436 of 1,572 transposable elements are contained within the 61.4 Mb of sequence that is annotated as being transcribed. A large proportion of transposable elements is found nested within other elements of the same or different classes. Lastly, an analysis of structural variation from different families reveals distinct patterns of deletion for elements belonging to different classes. CONCLUSIONS: This analysis represents an initial characterization of the transposable elements in the Release 3 euchromatic genomic sequence of D. melanogaster for which comparison to the transposable elements of other organisms can begin to be made. These data have been made available on the Berkeley Drosophila Genome Project website for future analyses.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are