707 research outputs found
Timing of Favorable Conditions, Competition and Fertility Interact to Govern Recruitment of Invasive Chinese Tallow Tree in Stressful Environments
The rate of new exotic recruitment following removal of adult invaders (reinvasion pressure) influences restoration
outcomes and costs but is highly variable and poorly understood. We hypothesize that broad variation in average
reinvasion pressure of Triadica sebifera (Chinese tallow tree, a major invader) arises from differences among habitats in
spatiotemporal availability of realized recruitment windows. These windows are periods of variable duration long enough to
permit establishment given local environmental conditions. We tested this hypothesis via a greenhouse mesocosm
experiment that quantified how the duration of favorable moisture conditions prior to flood or drought stress (window
duration), competition and nutrient availability influenced Triadica success in high stress environments. Window duration
influenced pre-stress seedling abundance and size, growth during stress and final abundance; it interacted with other
factors to affect final biomass and germination during stress. Stress type and competition impacted final size and biomass,
plus germination, mortality and changes in size during stress. Final abundance also depended on competition and the
interaction of window duration, stress type and competition. Fertilization interacted with competition and stress to
influence biomass and changes in height, respectively, but did not affect Triadica abundance. Overall, longer window
durations promoted Triadica establishment, competition and drought (relative to flood) suppressed establishment, and
fertilization had weak effects. Interactions among factors frequently produced different effects in specific contexts. Results
support our ‘outgrow the stress’ hypothesis and show that temporal availability of abiotic windows and factors that
influence growth rates govern Triadica recruitment in stressful environments. These findings suggest that native seed
addition can effectively suppress superior competitors in stressful environments. We also describe environmental scenarios
where specific management methods may be more or less effective. Our results enable better niche-based estimates of
local reinvasion pressure, which can improve restoration efficacy and efficiency by informing site selection and optimal
Management
Hybrid photonic-bandgap accelerating cavities
In a recent investigation, we studied two-dimensional point-defected photonic
bandgap cavities composed of dielectric rods arranged according to various
representative periodic and aperiodic lattices, with special emphasis on
possible applications to particle acceleration (along the longitudinal axis).
In this paper, we present a new study aimed at highlighting the possible
advantages of using hybrid structures based on the above dielectric
configurations, but featuring metallic rods in the outermost regions, for the
design of extremely-high quality factor, bandgap-based, accelerating
resonators. In this framework, we consider diverse configurations, with
different (periodic and aperiodic) lattice geometries, sizes, and
dielectric/metal fractions. Moreover, we also explore possible improvements
attainable via the use of superconducting plates to confine the electromagnetic
field in the longitudinal direction. Results from our comparative studies,
based on numerical full-wave simulations backed by experimental validations (at
room and cryogenic temperatures) in the microwave region, identify the
candidate parametric configurations capable of yielding the highest quality
factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added;
minor changes in the tex
The use of thermographic imaging to evaluate therapeutic response in human tumour xenograft models
YesNon-invasive methods to monitor tumour growth are an important goal in cancer drug development. Thermographic imaging systems offer potential in this area, since a change in temperature is known to be induced due to changes within the tumour microenvironment. This study demonstrates that this imaging modality can be applied to a broad range of tumour xenografts and also, for the first time, the methodology’s suitability to assess anti-cancer agent efficacy. Mice bearing subcutaneously implanted H460 lung cancer xenografts were treated with a novel vascular disrupting agent, ICT-2552, and the cytotoxin doxorubicin. The effects on tumour temperature were assessed using thermographic imaging over the first 6 hours post-administration and subsequently a further 7 days. For ICT-2552 a significant initial temperature drop was observed, whilst for both agents a significant temperature drop was seen compared to controls over the longer time period. Thus thermographic imaging can detect functional differences (manifesting as temperature reductions) in the tumour response to these anti-cancer agents compared to controls. Importantly, these effects can be detected in the first few hours following treatment and therefore the tumour is observable non-invasively. As discussed, this technique will have considerable 3Rs benefits in terms of reduction and refinement of animal use.University of Bradfor
Emergent global patterns of ecosystem structure and function from a mechanistic general ecosystem model
Anthropogenic activities are causing widespread degradation of ecosystems worldwide, threatening the ecosystem services upon which all human life depends. Improved understanding of this degradation is urgently needed to improve avoidance and mitigation measures. One tool to assist these efforts is predictive models of ecosystem structure and function that are mechanistic: based on fundamental ecological principles. Here we present the first mechanistic General Ecosystem Model (GEM) of ecosystem structure and function that is both global and applies in all terrestrial and marine environments. Functional forms and parameter values were derived from the theoretical and empirical literature where possible. Simulations of the fate of all organisms with body masses between 10 µg and 150,000 kg (a range of 14 orders of magnitude) across the globe led to emergent properties at individual (e.g., growth rate), community (e.g., biomass turnover rates), ecosystem (e.g., trophic pyramids), and macroecological scales (e.g., global patterns of trophic structure) that are in general agreement with current data and theory. These properties emerged from our encoding of the biology of, and interactions among, individual organisms without any direct constraints on the properties themselves. Our results indicate that ecologists have gathered sufficient information to begin to build realistic, global, and mechanistic models of ecosystems, capable of predicting a diverse range of ecosystem properties and their response to human pressures
Evaluation of Hungarian Wines for Resveratrol by Overpressured Layer Chromatography
A method, including solid phase extraction sample preparation, overpressured layer chromatographic separation and subsequent densitometric evaluation, was developed for measurement of total resveratrol (cis- and trans-isomers) content of wine. The amount of resveratrol was determined in wine samples from different winemaking regions of Hungary. The total resveratrol was high in Hungarian red wines (3.6–11 mg/L), and much lower in white ones (0.04–1.5 mg/L)
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