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Search Results: 1 - 10 of 212004 matches for " Joshua L. Bryant "
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Contact Toxicity and Residual Efficacy of Indoxacarb against the European Earwig (Dermaptera: Forficulidae)
Susan C. Jones,Joshua L. Bryant
Insects , 2012, DOI: 10.3390/insects3030593
Abstract: Indoxacarb (Arilon 20WG) was evaluated against a nuisance pest, the European earwig ( Forficula auricularia), and was found to be an effective contact toxicant with residual activity on substrates commonly encountered in urban environments. Within 16 h of being directly sprayed with indoxacarb, ≥90% of earwigs from two populations were either ataxic, moribund, or dead, and 100% displayed these symptoms of severe intoxication at 1 d. Brief exposure (5 min or 1 h) to dried residues on either a porous (pine wood) or non-porous (ceramic tile) substrate also was sufficient to cause severe intoxication of earwigs within 1 d. In all bioassays, indoxacarb-treated earwigs showed no signs of recovery during the 21-d observation period. In outdoor urban habitats, intoxicated earwigs would be more vulnerable to desiccation, predation, or pathogens leading to higher mortality than in a laboratory setting.
Land application of spent gypsum from ditch filters: phosphorus source or sink?  [PDF]
Karen L. Grubb, Joshua M McGrath, Chad J. Penn, Ray B. Bryant
Agricultural Sciences (AS) , 2011, DOI: 10.4236/as.2011.23048
Abstract: Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25oC, and samples were collected at 1, 7, and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concen-trations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.
Behavioral Responses of the Bed Bug to Permethrin-Impregnated ActiveGuard? Fabric
Susan C. Jones,Joshua L. Bryant,Scott A. Harrison
Insects , 2013, DOI: 10.3390/insects4020230
Abstract: ActiveGuard? Mattress Liners have been used to control house dust mites, and they also are commercially available as an integrated pest management tool for use against bed bugs ( Cimex lectularius). The aim of our study was to evaluate responses of numerous populations of the bed bug to the permethrin-impregnated fabric, with particular regard to contact toxicity, repellency, and feeding inhibition. Continuous exposure to ActiveGuard fabric resulted in rapid intoxication for three of four populations, with 87 to 100% of moderately pyrethroid-resistant and susceptible bed bugs succumbing by 1 d. In comparison, a highly resistant population reached 22% mortality at 10 d. Video data revealed that bed bugs readily traversed ActiveGuard fabric and spent a considerable amount of time moving about and resting on it during a 12-h period. ActiveGuard fabric was non-repellent to bed bugs from five tested populations. Furthermore, significantly fewer bed bugs successfully fed to repletion through ActiveGuard fabric than through blank fabric for the five populations. With just 30 min of feeding exposure, mortality ranged from 4% to 83%, depending upon the bed bug strain. These laboratory studies indicate that ActiveGuard liners adversely affected bed bugs from diverse populations.
Effect of Land Application of Phosphorus-Saturated Gypsum on Soil Phosphorus in a Laboratory Incubation
Karen L. Grubb,Joshua M. McGrath,Chad J. Penn,Ray B. Bryant
Applied and Environmental Soil Science , 2012, DOI: 10.1155/2012/506951
Abstract: Agricultural drainage ditches can deliver high loads of phosphorus (P) to surface water. Installation of filter structures containing P sorbing materials (PSMs), including gypsum, is an emerging practice that has shown promise to reduce these P loads. The objective of this study was to evaluate what effect soil amendment with gypsum would have on soil P concentrations and forms in a laboratory incubation experiment. Gypsum was saturated at two levels with P, and applied to a silt loam and a sandy loam at two rates. The treated soils were incubated in the laboratory at 25°C, and samples were collected on eight dates between 0 and 183 days after amendment. Spent gypsum application did not significantly increase soil water-extractable or Mehlich 3 P when applied at typical agronomic rates. This appears to be a viable strategy to remove P from agricultural drainage waters but does not appear to provide any additional P fertilizer value. 1. Introduction Accelerated eutrophication of the Chesapeake Bay has been identified as a priority natural resource concern [1]. According to the Chesapeake Bay Program Watershed Model Phase 4.3 agricultural sources account for 45% of the total phosphorus (P) delivered to the Chesapeake Bay [2]. The Delmarva Peninsula is comprised of the nine counties of the eastern shore of Maryland, Accomack and Northampton counties in Virginia, and the state of Delaware. The Delmarva Peninsula is home to a large concentration of poultry production, leading to a regional surplus of phosphorus (P). In the past, poultry manure was land applied based on crop nitrogen (N) requirements. However, because the P?:?N ratio found in manure is much higher than the P?:?N ratio required by plants, excessive P application has occurred resulting in elevated soil P concentrations [3]. The lower portion of the Delmarva Peninsula is dominated by coarse textured soils, shallow groundwater tables, and agricultural drainage ditches. Phosphorus leaching to groundwater is greatly increased in sandy soils with limited capacity to retain P, in soils with high P saturation, and in ditch drained soils containing preferential flow pathways [4]. This combination of hydrology and agricultural practices has led to P loading to surface water through shallow subsurface pathways and environmental quality issues [5]. One possible way to reduce phosphorus loss is to use by-product materials that can sorb phosphorus [6]. Phosphorus sorption is the process of adsorption and precipitation of P from dissolved to solid forms [7]. Phosphorus sorbing materials (PSMs) can provide a
The Political Ecology of Environmental Management in the Developing World
Bryant, Raymond L.
Arbor : Ciencia, Pensamiento y Cultura , 2008, DOI: 10.3989/arbor.2008.i729.157
Abstract: This paper addresses selected aspects of environmental management in the developing world through the prism of a political ecology perspective. It begins with a brief overview of the evolution of political ecology. It then turns to two case studies from South- East Asia in order to explore spaces of confrontation and spaces of cooperation – spaces that encompass key elements of historical and contemporary environmental management in the developing world. In the process, the paper underlines the multifaceted politics of transaction that takes place in a world that can never be transformed simply through apolitical calls to “save nature”. Este artículo aborda diversos aspectos clave de la gestión ambiental en el mundo en desarrollo desde la perspectiva de la ecología política. Comienza con un breve repaso de la evolución de la ecología política. Posteriormente se abordan dos casos de estudio en el Sudeste de Asia con el fin de explorar espacios de confrontación y espacios de cooperación que aglutinan elementos clave de la historia y la actualidad de la gestión ambiental en el mundo en desarrollo. En este proceso el artículo concluye que las multifacéticos políticas de transacción que tienen lugar en el mundo no pueden ser transformadas simplemente a través de apolíticas llamadas a “salvar la naturaleza”.
Real hypersurfaces in unimodular complex surfaces
Robert L. Bryant
Mathematics , 2004,
Abstract: A unimodular complex surface is a complex 2-manifold X endowed with a holomorphic volume form. A strictly pseudoconvex real hypersurface M in X inherits not only a CR-structure but a canonical coframing as well. In this article, this canonical coframing on M is defined, its invariants are discussed and interpreted geometrically, and its basic properties are studied. A natural evolution equation for strictly pseudoconvex real hypersurfaces in unimodular complex surfaces is defined, some of its properties are discussed, and several examples are computed. The locally homogeneous examples are determined and used to illustrate various features of the geometry of the induced structure on the hypersurface.
SO(n)-invariant special Lagrangian submanifolds of C^{n+1} with fixed loci
Robert L. Bryant
Mathematics , 2004,
Abstract: Let SO(n) act in the standard way on C^n and extend this action in the usual way to C^{n+1}. It is shown that a nonsingular special Lagrangian submanifold L in C^{n+1} that is invariant under this SO(n)-action intersects the fixed line C in a nonsingular real-analytic arc A (that may be empty). If n>2, then A has no compact component. Conversely, an embedded, noncompact nonsingular real-analytic arc A in C lies in an embedded nonsingular special Lagrangian submanifold that is SO(n)-invariant. The same existence result holds for compact A if n=2. If A is connected, there exist n distinct nonsingular SO(n)-invariant special Lagrangian extensions of A such that any embedded nonsingular SO(n)-invariant special Lagrangian extension of A agrees with one of these n extensions in some open neighborhood of A. The method employed is an analysis of a singular nonlinear PDE and ultimately calls on the work of Gerard and Tahara to prove the existence of the extension.
Gradient Kahler Ricci Solitons
Robert L. Bryant
Mathematics , 2004,
Abstract: Some observations about the local and global generality of gradient Kahler Ricci solitons are made, including the existence of a canonically associated holomorphic volume form and vector field, the local generality of solutions with a prescribed holomorphic volume form and vector field, and the existence of Poincare coordinates in the case that the Ricci curvature is positive and the vector field has a fixed point.
Conformal geometry and 3-plane fields on 6-manifolds
Robert L. Bryant
Mathematics , 2005,
Abstract: The purpose of this note is to provide yet another example of the link between certain conformal geometries and ordinary differential equations, along the lines of the examples discussed by Nurowski in math.DG/0406400. In this particular case, I consider the equivalence problem for 3-plane fields D on 6-manifolds M that satisfy the nondegeneracy condition that D+[D,D]=TM I give a solution of the equivalence problem for such D (as Tanaka has previously), showing that it defines a so(4,3)-valued Cartan connection on a principal right H-bundle over M where H is the subgroup of SO(4,3) that stabilizes a null 3-plane in R^{4,3}. Along the way, I observe that there is associated to each such D a canonical conformal structure of split type on M, one that depends on two derivatives of the plane field D. I show how the primary curvature tensor of the Cartan connection associated to the equivalence problem for D can be interpreted as the Weyl curvature of the associated conformal structure and, moreover, show that the split conformal structures in dimension~6 that arise in this fashion are exactly the ones whose so(4,4)-valued Cartan connection admits a reduction to a spin(4,3)-connection. I also discuss how this case has features that are analogous to those of Nurowski's examples.
Geodesically reversible Finsler 2-spheres of constant curvature
Robert L. Bryant
Mathematics , 2004,
Abstract: A Finsler space is said to be geodesically reversible if each oriented geodesic can be reparametrized as a geodesic with the reverse orientation. A reversible Finsler space is geodesically reversible, but the converse need not be true. In this note, building on recent work of LeBrun and Mason, it is shown that a geodesically reversible Finsler metric of constant flag curvature on the 2-sphere is necessarily projectively flat. As a corollary, using a previous result of the author, it is shown that a reversible Finsler metric of constant flag curvature on the 2-sphere is necessarily a Riemannian metric of constant Gauss curvature, thus settling a long-standing problem in Finsler geometry.
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