Causes and Consequences of Species Diversity in Forest Ecosystems

What are the causes and consequences of species diversity in forested ecosystems, and how is this species diversity being affected by rapid environmental and climatic change, movement of invertebrate and vertebrate herbivores into new biogeographic regions, and expanding human populations and associated shifts in land-use patterns? In this book, we explore these questions for assemblages of forest trees, shrubs, and understory herbs at spatial scales ranging from small plots to large forest dynamics plots, at temporal scales ranging from seasons to centuries, in both temperate and tropical regions, and across rural-to-urban gradients in land use

Precision determination of absolute neutron flux

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using a method of an alpha-gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performed to determine the mean de Broglie wavelength of the beam to a precision of 0.024 %. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058 %. We discuss the principle of the alpha-gamma method and present details of how the measurement was performed including the systematic effects. We also describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.Comment: 44 page

The Application of Half-Life in Clinical Decision Making: Comparison of the Pharmacokinetics of Extended-Release Topiramate (USL255) and Immediate-Release Topiramate

Objective: For extended-release drugs with multi-compartment kinetics, such as topiramate, effective half-life (t1/2eff) may be a more clinically relevant parameter than elimination half-life (t1/2z). Using topiramate as a real-life example, the objective was to compare these half-life values for immediate- and extended-release topiramate (TPM-IR and USL255, respectively) to understand how drug pharmacokinetics may impact drug dosing recommendations. Methods: The t1/2z and t1/2eff for USL255 and TPM-IR were compared using data from a phase I study (N = 36) of 200 mg USL255 administered once daily (QD) or TPM-IR twice daily (BID); effect of sampling duration on t1/2z was investigated. To further explore the relationship between half-life and dosing, steady-state PK was simulated for USL255 and TPM-IR. Results: As previously reported, mean t1/2z was similar between USL255 (80.2 h) and TPM-IR (82.8 h); TPM-IR t1/2z was ∼4 times longer than reported in the Topamax label (21 h). In contrast, USL255 displayed a 1.5 fold longer t1/2eff (55.7 vs 37.1 h for TPM-IR). When t1/2z was calculated from 48 to 336 h, values ranged from 28.8 to 82.8 h. Simulated steady-state PK profiles of USL255 QD exhibited reduced plasma fluctuations during a dosing interval vs TPM-IR QD or BID. Significance: As expected for the same moiety, t1/2z of USL255 and TPM-IR were similar; however, the longer t1/2eff for USL255 better approximates differences in recommend dosing (QD USL255 vs BID TPM-IR). Further, sampling duration impacted t1/2z, diminishing its predictive value for determining dose regimens; sampling-time differences may also explain t1/2z discrepancy between TPM-IR here versus Topamax label. As expected, steady-state simulations confirm that although TPM-IR has a long t1/2z, taking TPM-IR QD would lead to large plasma fluctuations. These data demonstrate that t1/2z may be less clinically meaningful than t1/2eff, and using t1/2z for some drugs may lead to erroneous conclusions regarding dosing regimens

Patterns in Southeast Florida Coral Reef Community Composition

The Southeast (SE) Florida coral reef system is the northern extension of the Florida reef tract. This high latitude system lies offshore a heavily populated and urbanized coast and therefore is affected by numerous environmental and anthropogenic stressors. Using annual monitoring data collected in 2004, the southeast lorida reef community was analyzed to investigate patterns in community composition in various habitat types. Data was collected by SCUBA divers who conducted a 30m2 belt transect survey at 24 sample sites offshore Broward County (SE), Florida. Sites ranged in depth range from six to 18 meters. The 24 sites occurred on five different reef habitat categories: ridge-shallow, colonized pavement-shallow, linear inner reef, linear middle reef, and linear outer reef. These sites were established for the Broward County Board of County Commissioners and Environmental Protection and Growth Management Department, Biological Resources Division, in order to monitor Broward County coral communities and sedimentation rates in relation to possible effects from a beach renourishment project. The assessment took place prior to the renourishment project