1,710 research outputs found
The ADA Reasonable Accommodations Requirement and the Development of University Services Policies: Helping or Hindering Students with Learning Disabilities?
An Analysis of Differential Taxation as a Method of Maintaining Agricultural and Open Space Land Uses
Dispersal Dynamics of the Bivalve Gemma Gemma in a Patchy Environment
The purpose of this study was to analyze the dispersal dynamics of the ovoviviparous bivalve Gemma gemma (hereafter referred to as Gemma) in an environment disturbed by the pit-digging activities of horseshoe crabs, Limulus polyphemus. Gemma broods its young and has no planktonic larval stage, so all dispersal is the result of juvenile and adult movement. Animal movement was measured using natural crab pits, hand-dug simulated crab pits, and cylindrical bottom traps in the intertidal zone at Tom\u27s Cove, Virginia, USA.
This study demonstrated that horseshoe crabs create localized patches with reduced densities of Gemma, that all sizes and ages of Gemma quickly disperse into these low density patches, and that the mechanism of dispersal is passive bedload and suspended load transport. Freshly excavated natural pits had significantly lower Gemma densities than did undisturbed background sediment, but there were no significant differences in total density of other species, number of species, and species diversity (H\u27). Equitability (J\u27) was greater in pits than in controls because of the reduced abundance of Gemma, the numerically dominant species. Newly dug simulated crab pits also had significantly lower Gemma densities than controls and returned to control levels by the next day. Density recovery trajectories for individually marked pits showed consistent responses in summer and fall, but not in winter when low Gemma abundance resulted in greater variability among pits.
Significant positive correlations between the volume of sediment and the number of Gemma collected per bottom trap support the hypothesis that Gemma dispersal is a passive transport phenomenon. Assuming no active, density-dependent movement, the product of the Gemma density frequency distribution in undisturbed background sediment and the frequency distribution of sediment volume collected per trap created a predicted Gemma frequency distribution in traps that matched the actual distribution. Absolute dispersal rates and relative dispersal rates (absolute dispersal rate divided by background density in undisturbed sediment) into pits and traps were greater in summer than winter. Dispersal rate results suggest that increased horseshoe crab disturbance in summer may cause an increase in Gemma transport. Because Gemma individuals are dispersed by hydrodynamic action, it was expected that small, young individuals would be most easily transported in the bedload. There was, however, little evidence that movement into pits and traps was size- or age-selective.
Most recent benthic dispersal research has focused on the large-scale movement and settlement patterns of invertebrate larvae. The results from this study illustrate that dispersal of bottom-dwelling juveniles and adults plays an important role in regulating the local distribution and abundance of Gemma. Previous workers have shown that young Gemma live in dense aggregations and that growth and fecundity are reduced at such high densities, leading to population crashes. This study demonstrated a mechanism by which Gemma disperses into low-density patches where intraspecific competition may be mitigated, possibly resulting in enhanced individual reproductive success and population fitness
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Soluble levels of receptor for advanced glycation endproducts and dysfunctional high-density lipoprotein in persons infected with human immunodeficiency virus: ACTG NWCS332.
The role of high-density lipoprotein (HDL) function and advanced glycation end products (AGEs) in HIV-related atherosclerotic cardiovascular disease (CVD) is unclear. Both glycation and oxidation (HDLox) are major modifications of HDL that can alter its composition and function. Therefore, we explored the longitudinal association of HDLox with progression of glycation, as evaluated by measurement of circulating forms of receptor for AGE that predict morbidity (soluble Receptors for Advanced Glycation Endproducts [sRAGE], endogenous secretory Receptors for Advanced Glycation Endproducts [esRAGE]), in people with HIV-1 (PWH; HIV-1) and uninfected (HIV-1) individuals.We retrospectively assessed if levels of plasma sRAGE and esRAGE and HDL function (reduced antioxidant function is associated with increased HDL lipid hydroperoxide content; HDLox) in a subset of participants (n = 80) from a prospective 3-year study (AIDS Clinical Trials Group A5078). Primary outcomes were baseline and yearly rates of change over 96 of 144 weeks (Δ) in HDLox in HIV-1 versus uninfected HIV-1 controls (noted as HIV-1).Higher baseline levels of sRAGE in PWH on effective anti-retroviral therapy and with low CVD risk, but not in HIV-1 persons, were independently associated with higher HDLox. EsRAGE, but not sRAGE, had consistent inverse relationships with ΔHDLox in both HIV-1 and HIV-1 persons at baseline. In HIV-1 but not in HIV-1 persons, ΔHDLox had positive and inverse relationships with ΔRAGE and ΔesRAGE, respectively.Glycation and oxidation of HDL may contribute to impaired HDL function present in PWH
Notes and Comments: The Young and Frericks Cases: Re-Examining Traditional Theories of Manufacturer Liability for Product Defects
The expanding scope of product liability raised questions concerning the status of prior legal concepts in the area of design defects. The author discusses the present position of the law and the continued viability of the familiar latent-patent test of liability in Maryland
Notes and Comments: The Young and Frericks Cases: Re-Examining Traditional Theories of Manufacturer Liability for Product Defects
The expanding scope of product liability raised questions concerning the status of prior legal concepts in the area of design defects. The author discusses the present position of the law and the continued viability of the familiar latent-patent test of liability in Maryland
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