Global asymptotic properties for a Leslie-Gower food chain model

We study global asymptotic properties of a continuous time Leslie-Gower food chain model. We construct a Lyapunov function which enables us to establish global asymptotic stability of the unique coexisting equilibrium state.Comment: 5 Pages, 1 figure. Keywords: Leslie-Gower model, Lyapunov function, global stabilit

Metabolic syndrome: what neurosurgeons should know

Journal ArticleThe term metabolic syndrome, first introduced in 1988, has evolved in concept since that time. While the strict definition is subject to ongoing debate, the syndrome generally involves glucose intolerance, obesity, dyslipidemia and high blood pressure, which increase the risk of developing cardiovascular disease. The complex pathophysiology underlying this syndrome similarly has yet to be agreed upon but can be attributed largely, although not entirely, to insulin resistance and dysfunctional glucose and fat metabolism. This multifactorial syndrome highlights the complex association between noninsulin-dependent diabetes mellitus, coronary artery disease, and hypertension. An overview of factors contributing to the pathogenesis of metabolic syndrome may help neurosurgeons gain an understanding of this increasingly encountered disorder. Insulin resistance and hyperinsulinemia are key pathophysiological components of metabolic syndrome. Glucose homeostasis requires that the feedback loop is maintained between insulinproducing pancreatic beta cells in response to a rise in serum glucose levels. In the setting of insulin resistance, the abnormally high levels of insulin produced in response to serum glucose elevations act not only to stimulate glucose uptake by muscles through a phosphatidylinositol 3-kinase pathway but also to induce mitogenic and proinflammatory effects via a MAP kinase pathway

Unstructured-grid methods development for unsteady aerodynamic and aeroelastic analyses

The current status of unstructured grid methods development in the Unsteady Aerodynamics Branch at NASA-Langley is described. These methods are being developed for unsteady aerodynamic and aeroelastic analyses. The flow solvers are highlighted which were developed for the solution of the unsteady Euler equations and selected results are given which show various features of the capability. The results demonstrate 2-D and 3-D applications for both steady and unsteady flows. Comparisons are also made with solutions obtained using a structured grid code and with experimental data to determine the accuracy of the unstructured grid methodology. These comparisons show good agreement which thus verifies the accuracy

Magnetic helicity in magnetohydrodynamic turbulence with a mean magnetic field

A computational investigation of magnetic helicity of the fluctuatingmagnetic fieldHm in ideal and freely decaying three‐dimensional (3‐D) magnetohydrodynamics (MHD) in the presence of a uniform mean magnetic field is performed. It is shown that for ideal 3‐D MHDHm, which is a rugged invariant in the absence of a mean magnetic field [Frisch et al., J. Fluid Mech. 77, 796 (1975)], decays from its initial value and proceeds to oscillate about zero. The decay of Hm is shown to result from the presence of a new ‘‘generalized’’ helicity invariant, which includes contributions from the uniform magnetic field. The loss of invariance of Hm will diminish the effects of inverse transfer of Hm on freely decaying turbulence. This is demonstrated in a discussion of the selective decay relaxation process

Halting indigenous biodiversity decline: ambiguity, equity, and outcomes in RMA assessment of significance

In New Zealand, assessment of ‘significance’ is undertaken to give effect to a legal requirement for local authorities to provide for protection of significant sites under the Resource Management Act (1991). The ambiguity of the statute enables different interests to define significance according to their goals: vested interests (developers), local authorities, and non-vested interests in pursuit of protection of environmental public goods may advance different definitions. We examine two sets of criteria used for assessment of significance for biological diversity under the Act. Criteria adapted from the 1980s Protected Natural Areas Programme are inadequate to achieve the maintenance of biological diversity if ranking is used to identify only highest priority sites. Norton and Roper-Lindsay (2004) propose a narrow definition of significance and criteria that identify only a few high-quality sites as significant. Both sets are likely to serve the interests of developers and local authorities, but place the penalty of uncertainty on non-vested interests seeking to maintain biological diversity, and are likely to exacerbate the decline of biological diversity and the loss of landscape-scale processes required for its persistence. When adopting criteria for assessment of significance, we suggest local authorities should consider whose interests are served by different criteria sets, and who will bear the penalty of uncertainty regarding biological diversity outcomes. They should also ask whether significance criteria are adequate, and sufficiently robust to the uncertainty inherent in the assessment of natural values, to halt the decline of indigenous biological diversity

Avitrol-treated bait for protection of grapes from house finch damage

In an effort to reduce damage by house finches (Carpodacus mexicanus) to grapes, field trials were undertaken in two red winegrape (Pinot Noir and Pinot Chardonnay) vineyards in California using prebait (rape seed and canary grass seed) followed by baiting with these same seeds treated with a hydrochloric acid and 4-aminopyridine (Avitrol) solution. Seed was placed in V-shaped troughs placed 1-3 feet above the vines; treated seed was blended in a ratio of 2 untreated seeds to 1 treated seed, and 3 parts canary grass seed to 1 part rape seed. Prebait seed was replaced with treated seed when estimated maximum house finch visitation occurred, and was exposed from 1 to 4 days, with removal when house finch feeding from troughs ceased; the prebait and treatment schedule was then repeated as necessary until harvest. Bird counts were made throughout the trial, and winegrape damage assessment was conducted. In one test vineyard, early in the trial damage in the treated plot was assessed at 3% while damage in the control plot was insignificant, and house finches abandoned the test site. In the other test vineyard, the treatment plot received 7% damage while the two control plots received 17% and 13% damage, respectively. As a result of the treatment, grape damage was reduced approximately 50% as compared to bird damage the previous year. Data support the conclusion that Avitrol-affected house finches may stimulate an avoidance reaction among other flock members

Liquefaction of H2 molecules upon exterior surfaces of carbon nanotube bundles

We have used molecular dynamics simulations to investigate interaction of H2 molecules on the exterior surfaces of carbon nanotubes (CNTs): single and bundle types. At 80 K and 10 MPa, it is found that charge transfer occurs from a low curvature region to a high curvature region of the deformed CNT bundle, which develops charge polarization only on the deformed structure. The long-range electrostatic interactions of polarized charges on the deformed CNT bundle with hydrogen molecules are observed to induce a high local-ordering of H2 gas that results in hydrogen liquefaction. Our predicted heat of hydrogen liquefaction on the CNT bundle is 97.6 kcal kg^-1. On the other hand, hydrogen liquefaction is not observed in the CNT of a single type. This is because charge polarization is not developed on the single CNT as it is symmetrically deformed under the same pressure. Consequently, the hydrogen storage capacity on the CNT bundle is much higher due to liquefaction than that on the single CNT. Additionally, our results indicate that it would also be possible to liquefy H2 gas on a more strongly polarized CNT bundle at temperatures higher than 80 K

AVIRIS ground data-processing system

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has been under development at JPL for the past four years. During this time, a dedicated ground data-processing system has been designed and implemented to store and process the large amounts of data expected. This paper reviews the objectives of this ground data-processing system and describes the hardware. An outline of the data flow through the system is given, and the software and incorporated algorithms developed specifically for the systematic processing of AVIRIS data are described