Revisiting the Impact of Bt Corn Adoption by U.S. Farmers

This study examines the impact of adopting Bt corn on farm profits, yields, and insecticide use. The study employs an econometric model that corrects for self-selection and simultaneity. The model is estimated using nationwide farm-level survey data for 2005. Regression analysis confirms that Bt adoption is associated with increased profits, yields and seeding rates. However, the results of this analysis suggest that Bt adoption is not significantly related to insecticide use. This result appears to be related to the fact that insect infestation levels were lower in 2005 than they were in earlier years.Genetically engineered corn, insect resistance, Bt corn, insecticide use, technology adoption, yields, Production Economics, Research and Development/Tech Change/Emerging Technologies,

Optical Cluster-Finding with An Adaptive Matched-Filter Technique: Algorithm and Comparison with Simulations

We present a modified adaptive matched filter algorithm designed to identify clusters of galaxies in wide-field imaging surveys such as the Sloan Digital Sky Survey. The cluster-finding technique is fully adaptive to imaging surveys with spectroscopic coverage, multicolor photometric redshifts, no redshift information at all, and any combination of these within one survey. It works with high efficiency in multi-band imaging surveys where photometric redshifts can be estimated with well-understood error distributions. Tests of the algorithm on realistic mock SDSS catalogs suggest that the detected sample is ~85% complete and over 90% pure for clusters with masses above 1.0*10^{14} h^{-1} M_solar and redshifts up to z=0.45. The errors of estimated cluster redshifts from maximum likelihood method are shown to be small (typically less that 0.01) over the whole redshift range with photometric redshift errors typical of those found in the Sloan survey. Inside the spherical radius corresponding to a galaxy overdensity of Delta=200, we find the derived cluster richness Lambda_{200} a roughly linear indicator of its virial mass M_{200}, which well recovers the relation between total luminosity and cluster mass of the input simulation.Comment: Accepted to ApJ. 13 pages, 9 figure

Wingtip mounted, counter-rotating proprotor for tiltwing aircraft

A tiltwing aircraft, capable of in-flight conversion between a hover and forward cruise mode, employs a counter-rotating proprotor arrangement which permits a significantly increased cruise efficiency without sacrificing either the size of the conversion envelope or the wing efficiency. A benefit in hover is also provided because of the lower effective disk loading for the counter-rotating proprotor, as opposed to a single rotation proprotor of the same diameter. At least one proprotor is provided on each wing section, preferably mounted on the wingtip, with each proprotor having two counter-rotating blade rows. Each blade row has a plurality of blades which are relatively stiff-in-plane and are mounted such that cyclic pitch adjustments may be made for hover control during flight

Conservation Tillage, Pesticide Use, and Biotech Crops in the U.S.A.

This paper presents the first part of an ongoing project whose objective is to present a long term relationship between conservation tillage, adoption of GE crops and pesticide use for major crops in the United States. In addition, the project aims to provide some innovative tests on causality using a panel data set. This paper presents preliminary results for soybeans.conservation tillage, biotechnology, genetically engineered crops, soybeans, herbicides, Environmental Economics and Policy, Farm Management, Production Economics,

The Cost of Increasing Adoption of Beneficial Nutrient-Management Practices

We estimate the cost of offsets tied to reductions in the use of nitrogen on U.S. cornfields under the proposed American Clean Energy and Security Act.offsets, nitrogen, corn, Agricultural and Food Policy, Crop Production/Industries, Environmental Economics and Policy,

Groups of two galaxies in SDSS: implications of colours on star formation quenching time-scales

We have devised a method to select galaxies that are isolated in their dark matter halo (N=1 systems) and galaxies that reside in a group of exactly two (N=2 systems). Our N=2 systems are widely-separated (up to $\sim$\,200\,$h^{-1}$\,kpc), where close galaxy-galaxy interactions are not dominant. We apply our selection criteria to two volume-limited samples of galaxies from SDSS DR6 with $M_{r}-5 \log_{10} h \leq$ -19 and -20 to study the effects of the environment of very sparse groups on galaxy colour. For satellite galaxies in a group of two, we find a red excess attributed to star formation quenching of 0.15\,$\pm$\,0.01 and 0.14\,$\pm$\,0.01 for the -19 and -20 samples, respectively, relative to isolated galaxies of the same stellar mass. Assuming N=1 systems are the progenitors of N=2 systems, an immediate-rapid star formation quenching scenario is inconsistent with these observations. A delayed-then-rapid star formation quenching scenario with a delay time of 3.3 and 3.7\,Gyr for the -19 and -20 samples, respectively, yields a red excess prediction in agreement with the observations. The observations also reveal that central galaxies in a group of two have a slight blue excess of 0.06\,$\pm$\,0.02 and 0.02\,$\pm$\,0.01 for the -19 and -20 samples, respectively, relative to N=1 populations of the same stellar mass. Our results demonstrate that even the environment of very sparse groups of luminous galaxies influence galaxy evolution and in-depth studies of these simple systems are an essential step towards understanding galaxy evolution in general.Comment: 17 pages, 11 figures, accepted to MNRA