ROTATIONAL-DYNAMICS OF SOLID C-70 - A NEUTRON-SCATTERING STUDY

PMID: 10011126PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.PMID: 10011126 This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K.We report the results of neutron-diffraction and low-energy neutron-inelastic-scattering experiments on high-purity solid C-70 between 10 and 640 K. Thermal hysteresis effects are found to accompany structural changes both on cooling and on heating. The observed diffuse scattering intensity does not change with temperature. At 10 K broad librational peaks are observed at 1.82(16) meV [full width at half maximum=1.8(5) meV]. The peaks soften and broaden further with increasing temperature. At and above room temperature, they collapse into a single quasielastic line. At 300 K, the diffusive reorientational motion appears to be somewhat anisotropic, becoming less so with increasing temperature. An isotropic rotational diffusion model, in which the motions of adjacent molecules are uncorrelated, describes well the results at 525 K. The temperature dependence of the rotational diffusion constants is consistent with a thermally activated process having an activation energy of 32(7) meV.This work at the University of Sussex at supported by the Science and Engineering Research Council, U.K

Occupancy of Freshwater Turtles Across a Gradient of Altered Landscapes

Turtles are one of the most threatened groups of vertebrates worldwide. In the northeastern United States, a legacy of centuries of dramatic landscape alteration has affected freshwater turtle populations, but the relationships between the current landscape and distributions and abundances of freshwater turtles remain poorly understood. We used a stratified random approach to select 88 small, isolated wetlands across a gradient of forest cover throughout Rhode Island, USA, and systematically sampled freshwater turtles in these wetlands. We report estimates of relative abundance and used a canonical correspondence analysis to investigate relationships between species relative abundance and environmental covariates. We also investigated which environmental covariates affect the occurrence and detection probabilities of each species. Eastern painted turtles (Chrysemys picta picta) and common snapping turtles (Chelydra serpentina) were widespread (occurring in 83% and 63% of wetlands, respectively) and relatively abundant. Spotted turtles (Clemmys guttata) were far less common, occurring in 8% of wetlands, and exhibited a positive association with shallow wetlands surrounded by forest. Non‐native red‐eared sliders (Trachemys scripta elegans) occurred in 10% of wetlands and exhibited a positive association with road density, likely reflecting a positive relationship between slider occurrence and human population density. Identifying landscape‐scale habitat features that are associated with the occurrence of sensitive species can improve the ability of biologists to identify and protect turtle populations

Evidence of vascular growth associated with laser treatment of normal canine myocardium.

BACKGROUND: Transmyocardial laser revascularization is a new therapy for patients with refractory angina. Although clinical studies suggest that transmyocardial laser revascularization decreases angina and may improve regional blood flow, the underlying mechanisms are not elucidated. We hypothesized that one mechanism may relate to stimulation of vascular growth in laser-treated regions. METHODS: Transmyocardial laser revascularization channels were made with holmium:yttrium-aluminum garnet or carbon dioxide lasers in eight normal canine hearts; animals were sacrificed 2 to 3 weeks later and examined for vascular density and for evidence of smooth muscle proliferation. RESULTS: The original channels were infiltrated by granulation tissue with associated vascularity. Vascular growth was stimulated immediately surrounding the channel remnant as evidenced by an increase in the number of vessels (approximately twice that of the control region) and an increase in the number of vascular cells staining positive for markers of cellular proliferation. CONCLUSIONS: Transmyocardial laser revascularization leads to local vascular growth as early as 2 weeks after treatment. It remains to be determined whether this mechanism contributes to increased regional blood flow or to clinical benefits associated with this novel form of therapy