4,757 research outputs found
Fouling of European freshwater bivalves (Unionidae) by the invasive zebra mussel (Dreissena polymorpha)
1. The zebra mussel (Dreissena polymorpha) is well known for its invasive success and its
ecological and economic impacts. Of particular concern has been the regional extinction of
North American freshwater mussels (Order Unionoida) on whose exposed shells the zebra
mussels settle. Surprisingly, relatively little attention has been given to the fouling of
European unionoids.
2. We investigated interspecific patterns in fouling at six United Kingdom localities
between 1998 and 2008. To quantify the effect on two pan-European unionoids (Anodonta
anatina and Unio pictorum), we used two measures of physiological status: tissue
mass : shell mass and tissue glycogen content.
3. The proportion of fouled mussels increased between 1998 and 2008, reflecting the recent,
rapid increase in zebra mussels in the U.K. Anodonta anatina was consistently more heavily
fouled than U. pictorum and had a greater surface area of shell exposed in the water
column.
4. Fouled mussels had a lower physiological condition than unfouled mussels. Unlike
tissue mass : shell mass ratio, tissue glycogen content was independent of mussel size,
making it a particularly useful measure of condition. Unio pictorum showed a stronger
decline in glycogen with increasing zebra mussel load, but had a broadly higher condition
than A. anatina at the time of study (July).
5. Given the high conservation status and important ecological roles of unionoids, the
increased spatial distribution and fouling rates by D. polymorpha in Europe should receive
more attention.Malacological Society of London Research Grant was provided to FP to support this study. Howard Baylis and Barrie Fuller (Zoology Department, University of Cambridge) facilitated the glycogen assays. Many thanks to Philine zu Ermgassen, Rebecca Mant, Anna McIvor, Nicole Spann and Alexandra Zieritz for field and lab assistance. Special thanks to David Strayer, Alan Hildrew and an anonymous referee for helpful suggestions on the manuscript
Topological field theories in n-dimensional spacetimes and Cartan's equations
Action principles of the BF type for diffeomorphism invariant topological
field theories living in n-dimensional spacetime manifolds are presented. Their
construction is inspired by Cuesta and Montesinos' recent paper where Cartan's
first and second structure equations together with first and second Bianchi
identities are treated as the equations of motion for a field theory. In
opposition to that paper, the current approach involves also auxiliary fields
and holds for arbitrary n-dimensional spacetimes. Dirac's canonical analysis
for the actions is detailedly carried out in the generic case and it is shown
that these action principles define topological field theories, as mentioned.
The current formalism is a generic framework to construct geometric theories
with local degrees of freedom by introducing additional constraints on the
various fields involved that destroy the topological character of the original
theory. The latter idea is implemented in two-dimensional spacetimes where
gravity coupled to matter fields is constructed out, which has indeed local
excitations.Comment: LaTeX file, no figure
Effects of climate change on aquaculture site selection at a temperate estuarine system
Aquaculture is one of the food industries that most evolved in recent years in response to increased human demand for seafood products, which has led to a progressive stock threat in nature. With a high seafood consumption per capita, Portugal has been exploring its coastal systems to improve the cultivation of fish and bivalve species with high commercial value. In this context, this study aims to propose the use of a numerical model as a tool to assess the impact of climate change on aquaculture site selection in a temperate estuarine system (Sado estuary). Therefore, the Delft3D model was calibrated and validated, showing good accuracy in predicting the local hydrodynamics, transport, and water quality. Furthermore, two simulations for the historical and future conditions were performed to establish a Suitability Index capable of identifying the most appropriate sites to exploit two bivalve species (one clam and one oyster), considering both winter and summer seasons. Results suggest that the estuary's northernmost region presents the best conditions for bivalves' exploitation, with more suitable conditions during summer than winter due to the higher water temperature and chlorophyll-a concentrations. Regarding future projections, the model results suggest that environmental conditions will likely benefit the production of both species due to the increase in chlorophyll-a concentration along the estuary.publishe
Concurrent Training Followed by Detraining: Does the Resistance Training Intensity Matter?
The aim of this study was to analyze the training and detraining (DT) effects of concurrent aerobic training and resistance training against 3 different external loads on strength and aerobic variables. Thirty-two men were randomly assigned to 4 groups: low-load (LLG, n = 9), moderate-load (MLG, n = 9), high-load (HLG, n = 8), and control group (CG, n = 6). Resistance training consisted of full squat (FS) with a low load (40-55% 1 repetition maximum [1RM]), a moderate load (55-70% 1RM), or a high load (70-85% 1RM) combined with jump and sprint exercises. Aerobic training was performed at 75% of the maximal aerobic speed for 15-20 minutes. The training period lasted for 8-week, followed by 4-week DT. Pretraining, post-training, and post-DT evaluations included 20-m running sprints (0-10 m: T10; 0-20 m: T20), shuttle run test, countermovement vertical jump (CMJ) test, and loading test (1RM) in FS. All the experimental groups showed improvements (p ≤ 0.05) in all the parameters assessed, except the LLG for T10 and the HLG for T20. The LLG, MLG, and HLG showed great changes in 1RM and V[Combining Dot Above]O2max compared with the CG (p ≤ 0.05), whereas the HLG and MLG showed a greater percentage change than the CG in T10 (p < 0.001) and CMJ (p ≤ 0.05). The 4-week DT period resulted in detrimental effects in all variables analyzed for all 3 experimental groups. In conclusion, our results suggest that strength training programs with low, moderate, or high external loads combined with low-intensity aerobic training could be effective for producing significant gains in strength and aerobic capacities. Moreover, the higher loads used increased gains in explosive efforts.info:eu-repo/semantics/publishedVersio
The relationship of anthropometrical characteristics and front crawl performance in male age-group swimmers
Swimming performance is affected by several factors including the swimming technique, the swimmer’s functional and metabolic characteristics and the level of training accomplishment. However, performance is also depending on the swimmer’s anthropometrical characteristics. The body shape, body size and body composition can play an important role to achieve higher performances
Measuring Morbidity Associated with Urinary Schistosomiasis: Assessing Levels of Excreted Urine Albumin and Urinary Tract Pathologies
Urinary schistosomiasis is a debilitating disease caused by a parasitic worm that dwells in the blood vessels, particularly those surrounding the human bladder wall. Although not directly associated with high patient mortality, this disease is linked to both short-term morbidity, e.g. visible blood in urine (acute), as well as long-term sequelae, e.g. urinary tract pathologies (chronic). Numerous control programmes based upon chemotherapy have been implemented in sub-Saharan Africa in an attempt to reduce the burden of disease inflicted, particularly in children. Although there are rapid tests to assess the prevalence of acute manifestations of disease (i.e. blood in urine), namely urine-reagent strips, monitoring of chronic manifestations (i.e. urinary tract pathologies) is still rather laborious, time-consuming and requires specialised equipment, e.g. portable ultrasonography, as well as highly trained staff. This study has attempted to evaluate associations between albuminuria (albumin in urine, a new application for the HemoCue photometer) and urinary tract pathologies, and consequently assess this new biochemical marker as a potential rapid proxy of chronic disease sequelae typical in children in areas where urinary schistosomiasis is of public health importance
Path Integrals, Density Matrices, and Information Flow with Closed Timelike Curves
Two formulations of quantum mechanics, inequivalent in the presence of closed
timelike curves, are studied in the context of a soluable system. It
illustrates how quantum field nonlinearities lead to a breakdown of unitarity,
causality, and superposition using a path integral. Deutsch's density matrix
approach is causal but typically destroys coherence. For each of these
formulations I demonstrate that there are yet further alternatives in
prescribing the handling of information flow (inequivalent to previous
analyses) that have implications for any system in which unitarity or coherence
are not preserved.Comment: 25 pages, phyzzx, CALT-68-188
Correction: Biofunctionalized pectin hydrogels as 3D cellular microenvironments
Correction for 'Biofunctionalized pectin hydrogels as 3D cellular microenvironments' by Sara C. Neves et al., J. Mater. Chem. B, 2015, 3, 2096–2108
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