456 research outputs found
A Gelfand triple approach to Wigner and Husimi representations
The notion of Gelfand triples is applied to interpret mathematically a family of phase-space representations of quantum mechanics interpolating between the Wigner and Husimi representations. Gelfand triples of operators on Hilbert space, and Gelfand triples of functions on phase-space are introduced in order to get isomorphic correspondences between operators and their phase-space representations. The phasespace Gelfand triples are characterized by means of growth conditions on the analytic continuation of the functions. We give integral expressions for the sesquilinear forms belonging to the phase-space Gelfand triples. This provides mathematically rigorous phase-space analogues for quantum mechanical expectation values of bounded operators. 1
Evaluation of Brey's production/biomass model on the basis of along-term data set on a clam population
The Brey model is one of the most frequently used methods to obtain a quick estimate of the secondary production (P) of an area. It is based on an empirical relationship between the production/biomass (P/B) ratio and the (annual) mean weight (W) of the individuals of a population. Estimates of P/B by this model are frequently obtained by using only single measurements of W and B, thus circumventing tedious efforts required by conventional methods. The obtained P values of communities are sums of estimates made for individual species. Any constraints of the model can be fully understood only by evaluating it for single-species populations. Using an extensive data set obtained by monitoring a population of the bivalve Macoma balthica for 33 yr, we evaluated the model by comparing Brey model estimates of P and P/B with direct annual estimates. We corroborate the basis of the model by presenting a significant relationship between observed annual values of W and P/B. The model satisfactorily predicted P when late-winter (but not late-summer) assessments of W and B were used. The model underestimated P/B in the years with high mortality rates (Z), whereas it overestimated P/B in almost all other years. Z values were a better basis for predictions of P/B than Wvalues. The model could predict P/B well on the exclusive basis of W due to the significant correlation between W and Z (low Z values resulted in older and thus heavier individuals). Multi-year averages of model-predicted and observed P/B estimates were similar only when predictions were based on late-winter or annual (not on summer) estimates of W and B. In conclusion, the model cannot be recommended for precise and unbiased P estimates in a single species when no more than a once-only assessment of Wand B is available
Carbon Sequestration in Managed Temperate Coniferous Forests Under Climate Change
Management of temperate forests has the potential to increase carbon sinks and mitigate climate change. However, those opportunities may be confounded by negative climate change impacts. We therefore need a better understanding of climate change alterations to temperate forest carbon dynamics before developing mitigation strategies. The purpose of this project was to investigate the interactions of species composition, fire, management, and climate change in the Copper–Pine Creek valley, a temperate coniferous forest with a wide range of growing conditions. To do so, we used the LANDIS-II modelling framework including the new Forest Carbon Succession extension to simulate forest ecosystems under four different productivity scenarios, with and without climate change effects, until 2050. Significantly, the new extension allowed us to calculate the net sector productivity, a carbon accounting metric that integrates aboveground and belowground carbon dynamics, disturbances, and the eventual fate of forest products. The model output was validated against literature values. The results implied that the species optimum growing conditions relative to current and future conditions strongly influenced future carbon dynamics. Warmer growing conditions led to increased carbon sinks and storage in the colder and wetter ecoregions but not necessarily in the others. Climate change impacts varied among species and site conditions, and this indicates that both of these components need to be taken into account when considering climate change mitigation activities and adaptive management. The introduction of a new carbon indicator, net sector productivity, promises to be useful in assessing management effectiveness and mitigation activities
Increasing species richness of the macrozoobenthic fauna on tidal flats of the Wadden Sea by local range expansion and invasion of exotic species
The Normal College News, October 28, 1909
Objective Currently, consensus is lacking on the relation between closure of atrial septal defect (ASD) and the incidence of atrial fibrillation (AF), which is a known complication in ASD patients. More importantly, studies reporting on the treatment applied for AF in ASD patients are scarce. The aims of this study were (1) to assess the incidence of AF in ASD patients, (2) to study the relation between closure and AF and (3) to evaluate applied treatment strategies. Methods A single-centre retrospective study in 173 patients with an ASD was performed. We analysed the incidence of AF, the relation of AF with closure, method of closure and the treatment success of therapies applied. Results Almost 20% of patients with an ASD developed AF, with a mean age of 59 (±14) years at first presentation of AF during a median clinical follow-up of 43 (29-59) years. Older age (OR 1.072; p<0.001) and a dilated left atrium (OR 3.727; p=0.009) were independently associated with new-onset AF. Closure itself was not independently associated with AF. First applied treatment strategy was rhythm control in 77%. Of the 18 patients treated with antiarrhythmic drugs 50% had at least 1 recurrence of AF. Conclusion No clear relation between closure of the ASD and AF could be assessed. This is the first study describing applied therapy for AF in ASD patients of which medical rhythm control was the most applied strategy with a disappointing efficacy
Expanding distribution of lethal amphibian fungus Batrachochytrium salamandrivorans in Europe
Emerging fungal diseases can drive amphibian species to local extinction. During 2010-2016, we examined 1,921 urodeles in 3 European countries. Presence of the chytrid fungus Batrachochytrium salamandrivorans at new locations and in urodeles of different species expands the known geographic and host range of the fungus and underpins its imminent threat to biodiversity
The level and distribution of methyl-esters influence the impact of pectin on intestinal T cells, microbiota, and Ahr activation
Pectins are dietary fibres that modulate T cell immunity, microbiota composition, and fermentation profiles, but how this is influenced by the degree of methyl-esterification (DM) and degree-of-blockiness (DB) of pectin is unknown. Here, we demonstrate that supplementation of DM19(high-DB), DM49(low-DB) and DM43(high-DB) pectins at a low dose increased the frequencies of intestinal T-helper (Th)1 and Th2 cells after 1 week of pectin supplementation in mice, whereas DM18(low-DB) did not. After 4 weeks of supplementation with those pectins, Th1 and Th2 frequencies returned to control levels, whereas RorÎłt+ regulatory T-cell frequencies increased. These structure-dependent effects could derive from induced shifts in microbiota composition that differed between DM18(low-DB) pectin and the other pectins. T-cell-modulating effects were not short-chain-fatty acid-dependent, but rather through an increase in Aryl-hydrocarbon-receptor-activating components. Thus, pectins with a specific combination of DM and DB have an impact on intestinal T cell-immunity in mice, when supplemented at a low dose
Toll-like receptor 2-modulating pectin-polymers in alginate-based microcapsules attenuate immune responses and support islet-xenograft survival
Encapsulation of pancreatic islets in alginate-microcapsules is used to reduce or avoid the application of life-long immunosuppression in preventing rejection. Long-term graft function, however, is limited due to varying degrees of host tissue responses against the capsules. Major graft-longevity limiting responses include inflammatory responses provoked by biomaterials and islet-derived danger-associated molecular patterns (DAMPs). This paper reports on a novel strategy for engineering alginate microcapsules presenting immunomodulatory polymer pectin with varying degrees of methyl-esterification (DM) to reduce these host tissue responses. DM18-pectin/alginate microcapsules show a significant decrease of DAMP-induced Toll-Like Receptor-2 mediated immune activation in vitro, and reduce peri-capsular fibrosis in vivo in mice compared to higher DM-pectin/alginate microcapsules and conventional alginate microcapsules. By testing efficacy of DM18-pectin/alginate microcapsules in vivo, we demonstrate that low-DM pectin support long-term survival of xenotransplanted rat islets in diabetic mice. This study provides a novel strategy to attenuate host responses by creating immunomodulatory capsule surfaces that attenuate activation of specific pro-inflammatory immune receptors locally at the transplantation site
Response to comment on 'Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity'
Lambert et al. question our retrospective and holistic epidemiological assessment of the role of chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that chytridiomycosis has affected at least 501 amphibian species
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