1,678 research outputs found
Studying use and risks of medicines in children: a European approach
In recent years there has been increasing awareness on the gap in knowledge on the safety and efficacy of medicines used in children. The work as described in this thesis is based on large observational studies across Europe and aimed to study the use and risks of medicines in children and adolescents. First we studied prescriptions patterns of several classes of medic
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Session B4: New Insights into Schooling Behavior in Response to Flow
Abstract:
Gregarious behaviour is found throughout the animal kingdom. Although many fish species live in groups during a certain period of their life cycle, rarely has this collective behaviour been incorporated in fish passage studies, which tend to focus on individual behaviour of target species. Near fish passes, local hydrodynamics are highly variable, potentially affecting school cohesion. Since schooling has several drivers, such as antipredatory benefits and energy savings mechanisms, a loss of school integrity might be a reason fish passes act as an ecological trap for fish species that live in schools. An understanding of how hydrodynamics, encountered near fish passes, affect school cohesion and schooling behaviour is needed. A ‘back-to-basics’ study was executed that explored the response of fish schools to hydrodynamics in an experimental setting. The Common Minnow (Phoxinus phoxinus) was chosen, since it is a strong schooling species and abundant in English rivers. Minnows are quite similar in morphology and swimming movements to the important (migratory) salmonids and could therefore serve as a proxy. Movements of schools of two individuals were recorded in flowing and standing water, and their individual trajectories extracted from video data. Results show that minnows switch from a tandem configuration in standing water to a close side-by-side configuration in flowing water. Modelling work revealed that in this side-by-side configuration, energy savings could not be realised. It was concluded that fish aim to maximize information transfer when encountering flow and therefore have to rely on vision more than their lateral line system as the effectiveness of the latter is disturbed by the flow conditions. These findings suggest that passage of schooling fish is highly dependent on flow characteristics as these determine the success of collective movement and navigation through fish passes
CSNE: Conditional Signed Network Embedding
Signed networks are mathematical structures that encode positive and negative
relations between entities such as friend/foe or trust/distrust. Recently,
several papers studied the construction of useful low-dimensional
representations (embeddings) of these networks for the prediction of missing
relations or signs. Existing embedding methods for sign prediction generally
enforce different notions of status or balance theories in their optimization
function. These theories, however, are often inaccurate or incomplete, which
negatively impacts method performance.
In this context, we introduce conditional signed network embedding (CSNE).
Our probabilistic approach models structural information about the signs in the
network separately from fine-grained detail. Structural information is
represented in the form of a prior, while the embedding itself is used for
capturing fine-grained information. These components are then integrated in a
rigorous manner. CSNE's accuracy depends on the existence of sufficiently
powerful structural priors for modelling signed networks, currently unavailable
in the literature. Thus, as a second main contribution, which we find to be
highly valuable in its own right, we also introduce a novel approach to
construct priors based on the Maximum Entropy (MaxEnt) principle. These priors
can model the \emph{polarity} of nodes (degree to which their links are
positive) as well as signed \emph{triangle counts} (a measure of the degree
structural balance holds to in a network).
Experiments on a variety of real-world networks confirm that CSNE outperforms
the state-of-the-art on the task of sign prediction. Moreover, the MaxEnt
priors on their own, while less accurate than full CSNE, achieve accuracies
competitive with the state-of-the-art at very limited computational cost, thus
providing an excellent runtime-accuracy trade-off in resource-constrained
situations
Cloning and expression analysis of a blue copperbinding protein gene from Dasypyrum Villosum
Adifferentially expressed fragment EST145 was isolated by suppression subtractive hybridization (SSH) method. Using EST145 as the probe, a blue copper-binding protein gene designated as DvBCB was screened from Dasypyrum villosum cDNA Library. The DvBCB gene was 845 bp in length with an open reading frame (ORF) which encoded a 178-amino acid polypeptide and contained the deduced functional sites: H66, C107, H112 and M121. Northern blot analysis showed that, the expression of DvBCB gene was enhanced in leaves after inoculation with Erysiphe graminis; reached a peak level at 24 h and decreased to constitutive level at 72 h after inoculation in resistant Gh21 line. The expression level in susceptible mutant M14S line was slightly lower than that in the resistant Gh21 line at all stages after inoculation, and the peak could not appear in M14S line. The function of DvBCB gene might include lignification of cell wall or scavenging of reactive oxygen species (ROS) during powdery mildew attack.Key words: Dasypyrum villosum, powdery mildew, suppression subtractive hybridization, blue copper-binding protein gene
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Development and application of an agent based model for glass eel selective tidal stream transport
Temperate eel populations have been in severe decline due to anthropogenic influences. In Europe, acts of regulation are in place for the sustainable management of the European eel (A. anguilla) population, through annual assessment of commercial landings and recruitment trends. Recruitment of juvenile eels into estuaries and subsequent rivers is thought to occur through usage of the flood, ebb and slack tides (Selective Tidal Stream Transport, STST) and other environmental variables. However, instalment of estuarine barriers is known to affect upstream migration with adverse consequences for the population.
To evaluate anthropogenic impact (e.g. estuarine barriers) on recruitment and aid in the improvement of population assessment, we present an Agent-Based Model (ABM) for the upstream migration of glass eels/ elvers through estuaries. A systematic review of the impacts of environmental factors based on a meta-analysis of the literature provided the behavioural parameters of the agents. The ABM is coupled to a hydrodynamic model of the Thames Estuary (UK) and simulations are validated with catchment data from different sampling sites along this waterway.
Results from the meta-analysis show that the predominant mechanisms for upstream migration include drifting with the flood tide and remaining in the substratum during ebb tide, whereas exploitation of the slack tide is debatable. Water temperature, the salinity gradient, and the moon phase are the most reported environmental variables affecting STST/ migration. Based on this, the ABM proved to be successful in predicting upstream migration along the Thames while explaining the efficiency of STST. Finally, the ABM is applied The Milford Haven Waterway (UK), which is heavily exploited by human activities, to provide information on possible recruitment success here and illustrate its functionality in the context of estuarine barrier management
Introductory clifford analysis
In this chapter an introduction is given to Clifford analysis and the underlying Clifford algebras. The functions under consideration are defined on Euclidean space and take values in the universal real or complex Clifford algebra, the structure and properties of which are also recalled in detail. The function theory is centered around the notion of a monogenic function, which is a null solution of a generalized Cauchy–Riemann operator, which is rotation invariant and factorizes the Laplace operator. In this way, Clifford analysis may be considered as both a generalization to higher dimension of the theory of holomorphic functions in the complex plane and a refinement of classical harmonic analysis. A notion of monogenicity may also be associated with the vectorial part of the Cauchy–Riemann operator, which is called the Dirac operator; some attention is paid to the intimate relation between both notions. Since a product of monogenic functions is, in general, no longer monogenic, it is crucial to possess some tools for generating monogenic functions: such tools are provided by Fueter’s theorem on one hand and the Cauchy–Kovalevskaya extension theorem on the other hand. A corner stone in this function theory is the Cauchy integral formula for representation of a monogenic function in the interior of its domain of monogenicity. Starting from this representation formula and related integral formulae, it is possible to consider integral transforms such as Cauchy, Hilbert, and Radon transforms, which are important both within the theoretical framework and in view of possible applications
Wildlife resources of the West African savanna
The wild fauna in Africa is a renewable resource and its overexploitation has led to the depletion of animal populations. This thesis focusses on the ecological characterization of the ungulate community of the West African savanna, with special reference to the Biosphere Reserve 'Boucle du Baoulé' in Mali, and makes a contribution to the ecological knowledge required for the conservation and management of West African savanna ecosystems.Part I contains background information on the environment of the West African savanna and its use by man, and it gives a description of the study area.Part II describes phenological patterns, production and quality for different groups of herbaceous plants, shrubs and trees and analyses the vegetation of the West African savanna as a source of food for the different ungulate species. Choice of habitat, diet composition, energy and protein requirements in relation to the metabolic weight of animal species are investigated as they are necessary for the analysis of the mechanisms of ecological separation of ungulates.In Part III the ecological carrying capacity of the West African savanna in the Baoulé is estimated by calculating dry-season stocking rates on the basis of the availability of quality forage. Results are compared with other approaches for the assessment of the ecological carrying capacity in the West African savanna zone and in other savanna ecosystems, elsewhere in Africa and in Australia.Using information on the ungulate community and the ecological carrying capacity of the West African savanna, in Part IV management options for the conservation and management of wild ungulate populations are suggested
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