603 research outputs found
Maize (Zea mays L.) kernel development, suitability for dry-grind ethanol production, and susceptibility to aflatoxin accumulation in relation to late-season water stress
Worldwide, water stress during vegetative and reproductive development of cereal species is a primary constraint to crop yield. In maize ( Zea mays L.), environmental stresses such as high temperature and drought affect yield by reducing the number and mean dry weight of harvested seeds per unit area. Total grain yield is of great economic concern, and increasing yield under optimal and stress conditions has historically received the most attention by public and private breeding programs. But environmental effects on grain quality is of equal importance as maize production becomes more focused on end-user traits specifically for utilization in markets such as dry-grind ethanol, wet-milling, and enhanced animal feeds. While these traits have demonstrated great economic potential, the variability in their corresponding properties as a result of adverse environmental conditions during grain development is not well understood. Further development and utilization of valuable enduser traits will require a greater understanding of kernel development and composition during environmental stress
Assessing long-term viability of glyphosate-resistant technology as a foundation for cropping systems
The introduction of glyphosate-resistant (GR) crops in the late 1990s changed the way producers used herbicides to control weeds. Since the introduction of GR crops producers have relied on glyphosate alone for weed control instead of utilizing multiple modes of action for weed control. This over-reliance resulted in several weed species developing resistance to glyphosate. This has resulted in organizations from the public and private sector questioning the sustainability of GR cropping systems. Researchers from Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina established 156 onarm trials to determine the sustainability of GR cropping systems. The objectives of this study were: to determine the economics of a university weed resistance best management practice (BMP) versus a producers’ normal production practice; to evaluate when a producer that is risk neutral (profit maximizing) or risk averse should adopt a weed resistance BMP; and to compare the influences of using a university weed resistance BMP to a producer’s normal production practice on the 27 most common weed species in Mississippi. In all instances, the university weed resistance BMP utilized multiple modes of action in conjunction with glyphosate. A university weed resistance BMP can provide the same level of control on 27 of the most common weeds in Mississippi that a producer has become accustomed to with a glyphosate alone system, while delaying or controlling GR weeds. A university weed resistance BMP resulted in an increase in weed control cost, but similar yields and economic returns when compared to a producer’s normal production practice. Rotating a GR crop with a different GR crop resulted in higher economic returns when compared to a continuous GR cropping system or a GR crop followed by a non-GR crop rotation. Producers are often reluctant to adopt a weed resistance BMP because of the perceived increased cost for weed control. A risk neutral or risk averse producer should adopt a weed resistance BMP and feel confident that their decision will provide weed control equivalent to a glyphosate alone weed control program before resistance developed, delay or control GR weeds and be economically sound
Black hole quasinormal modes using the asymptotic iteration method
In this article we show that the asymptotic iteration method (AIM) allows one
to numerically find the quasinormal modes of Schwarzschild and Schwarzschild de
Sitter (SdS) black holes. An added benefit of the method is that it can also be
used to calculate the Schwarzschild anti-de Sitter (SAdS) quasinormal modes for
the case of spin zero perturbations. We also discuss an improved version of the
AIM, more suitable for numerical implementation.Comment: 10 pages, LaTeX; references added; substantially expanded versio
Graviton emission from simply rotating Kerr-de Sitter black holes: Transverse traceless tensor graviton modes
In this article we present results for tensor graviton modes (in seven
dimensions and greater, ) for greybody factors of Kerr-dS black holes
and for Hawking radiation from simply rotating (n+4)-dimensional Kerr black
holes. Although there is some subtlety with defining the Hawking temperature of
a Kerr-dS black hole, we present some preliminary results for emissions
assuming the standard Hawking normalization and a Bousso-Hawking-like
normalization.Comment: 12 pages, 18 figure
Angular Eigenvalues of Higher-Dimensional Kerr-(A)dS Black Holes with Two Rotations
In this paper, following the work of Chen, L\"u and Pope, we present the
general metric for Kerr-(A)dS black holes with two rotations. The corresponding
Klein-Gordon equation is separated explicitly, from which we develop
perturbative expansions for the angular eigenvalues in powers of the rotation
parameters with .Comment: 10 pages, no figures. To appear in the proceedings of 2011 Shanghai
Asia-Pacific School and Workshop on Gravitatio
Bulk dominated fermion emission on a Schwarzschild background
Using the WKBJ approximation, and the Unruh method, we obtain semi-analytic
expressions for the absorption probability (in all energy regimes) for Dirac
fermions on a higher dimensional Schwarzschild background. We present an
analytic expression relating the absorption probability to the absorption
cross-section, and then use these results to plot the emission rates to third
order in the WKBJ approximation. The set-up we use is sufficiently general such
that it could also easily be applied to any spherically symmetric background in
-dimensions. Our results lead to the interesting conclusion that for
bulk fermion emission dominates brane localised emission. This is an example
contrary to the conjecture that black holes radiate mainly on the brane.Comment: 13 pages, 3 figure
Split fermion quasi-normal modes
In this paper we use the conformal properties of the spinor field to show how
we can obtain the fermion quasi-normal modes for a higher dimensional
Schwarzschild black hole. These modes are of interest in so called split
fermion models, where quarks and leptons are required to exist on different
branes in order to keep the proton stable. As has been previously shown, for
brane localized fields, the larger the number of dimensions the faster the
black hole damping rate. Moreover, we also present the analytic forms of the
quasi-normal frequencies in both the large angular momentum and the large mode
number limits.Comment: 11 pages, 7 figures, version 2 added reference
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