Search results for "MANIPULATION"
showing 10 items of 311 documents
Use of stable isotope analysis to evaluate the possible impact of fish migration on a lake biomanipulation
2007
1. A lake restoration project involving mass fish removals was started to improve further the water quality of a lake recovering from severe eutrophication. The effectiveness of such biomanipulation as a lake management option could be compromised if removed fish are rapidly replaced by large-scale immigration from a connected lake. 2. Stable isotope analysis (SIA) was used to examine the migrations of perch (Perca fluviatilis L.) and roach (Rutilus rutilus (L.)) between two connected lakes in central Finland, Jyvasjarvi and the larger Paijanne. Baseline δ15N signatures in primary consumers were significantly higher in Jyvasjarvi and this difference was reflected further up the food chain i…
Biomanipulating the drinking water reservoir of Estonia's capital city: Prospects for success
2008
The possibility of utilizing biomanipulation to improve the water quality of Tallinn's drinking water reservoir (Lake Ulemiste) was analysed on the basis of water quality data, test fishing by different methods, and earlier studies on aquatic plants, light climate and sediments. Eutrophic, polymictic Lake Ulemiste is characterized by a prevalence of high filamentous cyanobacteria biomass, rotifers in the zooplankton community, mature bream in the fish biomass, and a high density of planktivores (YOY perch). Several prerequisites for being a potential target for biomanipulation were identified, including (i) decreased external total phosphorus (TP) loading; and (ii) a sufficient stock of pis…
Can lake restoration by fish removal improve the status of profundal macroinvertebrate assemblages?
2013
Summary Removal of fish to restore lake pelagic food webs and water quality has been shown to increase the abundance of benthic invertebrates in shallow areas due to decreased predation pressure, while responses of profundal macroinvertebrate assemblages are less well documented. We used multivariate analyses and a Before-After-Control-Impact design to assess the impacts of fish removal (in total 101 000 kg of percid and cyprinid fish) on profundal macroinvertebrate species composition and abundance and ecological status in two basins of a eutrophic boreal lake. In the deeper main basin, macroinvertebrate community composition and classification of ecological status were not affected by fis…
Fluorescence and spin properties of defects in single digit nanodiamonds
2009
International audience; This article reports stable photoluminescence and high-contrast optically detected electron spin resonance (ODESR) from single nitrogen-vacancy (NV) defect centers created within ultrasmall, disperse nanodiamonds of radius less than 4 nm. Unexpectedly, the efficiency for the production of NV fluorescent defects by electron irradiation is found to be independent of the size of the nanocrystals. Fluorescence lifetime imaging shows lifetimes with a mean value of around 17 ns, only slightly longer than the bulk value of the defects. After proper surface cleaning, the dephasing times of the electron spin resonance in the nanocrystals approach values of some microseconds, …
A multivariate analysis of phytoplankton and food web changes in a shallow biomanipulated lake
1996
1. Phytoplankton dynamics, food chain changes and resilience in Lake Zwemlust, a shallow lake in The Netherlands, are described for the period 1986-94. 2. After biomanipulation in 1987, the lake moved through two alternative states, while the external nutrient loadings were maintained. A clear-water phase, mostly dominated by macrophytes, persisted from 1987 to 1991, and a rather turbid state, dominated by algae, occurred in the summers of 1992-94, after several consecutive and sustained perturbations affecting different parts of the food web in the lake. These two periods were characterized by different community structures. 3. The phytoplankton assemblage gradually changed in a pattern th…
A uniform quantificational logic for algebraic notions ofcontext
2002
A quantificational framework of formal reasoning is proposed, which emphasises the pattern of entering and exiting context. Contexts are modelled by an algebraic structure which reflects the order and manner in which context is entered into and exited from. The equations of the algebra partitions context terms into equivalence classes. A formal semantics is defined, containing models that map equivalence classes of certain context terms to sets of first order structures. The corresponding Hilbert system incorporates the algebraic equations as axioms asserted in context. In this way a uniform logic for arbitrary algebras of context is obtained. Soundness and completeness are proved. In semig…
Effet de l'environnement sur l'interaction entre les gammares (Crustacea : Amphipoda) et leurs parasites manipulateurs acanthocéphales
2016
Many parasites with complex life cycle have developed the ability to alter the phenotype of their hosts. It is recognized that such changes in appearance and behavior are responsible for an increase in the probability of predation of their intermediate hosts by their definitive hosts. This phenomenon of parasite manipulation can have numerous consequences at the scale of the ecosystem, modifying the interactions between host populations and altering their ecological role. However, manipulative parasites received little attention from an ecological point of view. Thus, the effect of the environment on the interaction between these parasites and their hosts, in particular in terms of manipula…
Rapid construction of algebraic axioms from samples
1991
Abstract An axiom is called reliable if it is confirmed in several places in a given sample of algebra. A very effective algorithm for enumerating such axioms is described.
Real quadrics in C n , complex manifolds and convex polytopes
2006
In this paper, we investigate the topology of a class of non-Kähler compact complex manifolds generalizing that of Hopf and Calabi-Eckmann manifolds. These manifolds are diffeomorphic to special systems of real quadrics Cn which are invariant with respect to the natural action of the real torus (S1)n onto Cn. The quotient space is a simple convex polytope. The problem reduces thus to the study of the topology of certain real algebraic sets and can be handled using combinatorial results on convex polytopes. We prove that the homology groups of these compact complex manifolds can have arbitrary amount of torsion so that their topology is extremely rich. We also resolve an associated wall-cros…
Grip Force Adjustments Reflect Prediction of Dynamic Consequences in Varying Gravitoinertial Fields
2018
International audience; Humans have a remarkable ability to adjust the way they manipulate tools through a genuine regulation of grip force according to the task. However, rapid changes in the dynamical context may challenge this skill, as shown in many experimental approaches. Most experiments adopt perturbation paradigms that affect only one sensory modality. We hypothesize that very fast adaptation can occur if coherent information from multiple sensory modalities is provided to the central nervous system. Here, we test whether participants can switch between different and never experienced dynamical environments induced by centrifugation of the body. Seven participants lifted an object …