170,197 research outputs found
Compte rendu de Jean C. Baudet : «Histoire de la chimie»
No full textBaudet (Jean C.), Histoire de la chimie. – Louvain-la-Neuve : De Boeck Supérieur, 2017. – viii, 354 p. – 1 vol. broché de 17 × 24 cm. – 32,00 €. – isbn 978-2-8073-0692-9
Compte rendu de Jean C. Baudet : «Histoire de la biologie et de la médecine»
No full textBaudet (Jean C.), Histoire de la biologie et de la médecine. – Louvain-la-Neuve : De Boeck Supérieur, 2018. – v, 361 p. – 1 vol. broché de 17 ×24 cm. – 29,00 €. – isbn 978-2-8073-1513-6
Evolution of the clay micro-structure in compression and shearing loading paths
No full textThe work presents a research approach in which the investigation of the macro-behaviour through element testing is systematically combined with the observation of processes and changes taking place at the micro-scale. The approach is aimed at identifying the main internal features which control, at the micro-scale, the material response, causing given behavioural facets, with the final purpose of assessing the influence of the different aspects of behaviour on model parameter values, hence supporting constitutive modelling and finding a relation between classes of behaviour and corresponding models and classes of clays.
The tested materials are two illitic stiff clays of marine origin, Pappadai clay and Lucera clay, that are investigated both when natural and when reconstituted in the laboratory. The microstructural analyses are carried out by means of different techniques: scanning electron microscopy is used to provide a qualitative investigation of the clay fabric and is combined with image processing, which allows to assess quantitatively the fabric orientation by means of a statistical analysis of the orientation of particles; the pore size distribution is analysed by means of mercury intrusion porosimetry, which provides information about the distribution of pores. The microstructure is first analysed for both Pappadai and Lucera clay at initial state, i.e., in the undisturbed state for the natural clay and after consolidation in consolidometer for the reconstituted clay. Then, the evolution of microstructure is explored after 1D and isotropic compression to states pre- and post- gross-yield, up to large pressures. A comparison is made between microstructures of specimens 1D and isotropically compressed to the same void ratio.
The evolution of both the natural and the reconstituted clay microstructure is also investigated under shearing loading paths, in both drained and undrained conditions.
The microstructural features underlying the macro-response exhibited by the clay are also compared with those recognized in the literature for other natural and reconstituted clays. The constitutive laws adopted by some advanced constitutive models to simulate the effects of structure are evaluated in the light of the observation and interpretation of the features and processes acting at the micro-scale and of their evolution under the different loading paths
Experimental study of the evolution of a velocity perturbation in fully developed turbulence
No full text
Extended self-similarity in the dissipation range of fully developed turbulence
No full textIn this letter we report further experimental evidence of extended self-similarity in the structure functions of the velocity field of fully developed turbulence. We study the behaviour of high-order structure functions close to the Kolmogorov scale r; where extended self-similarity is observed. © 1993 IOP Publishing Ltd
Cophylogeny reconstruction via an approximate bayesian computation
No full textDespite an increasingly vast literature on cophylogenetic reconstructions for studying host-parasite associations, understanding the common evolutionary history of such systems remains a problem that is far from being solved. Most algorithms for host-parasite reconciliation use an event-based model, where the events include in general (a subset of) cospeciation, duplication, loss, and host switch. All known parsimonious event-based methods then assign a cost to each type of event in order to find a reconstruction of minimum cost. The main problem with this approach is that the cost of the events strongly influences the reconciliation obtained. Some earlier approaches attempt to avoid this problem by finding a Pareto set of solutions and hence by considering event costs under some minimization constraints. To deal with this problem, we developed an algorithm, called Coala, for estimating the frequency of the events based on an approximate Bayesian computation approach. The benefits of this method are 2-fold: (i) it provides more confidence in the set of costs to be used in a reconciliation, and (ii) it allows estimation of the frequency of the events in cases where the data set consists of trees with a large number of taxa. We evaluate our method on simulated and on biological data sets. We show that in both cases, for the same pair of host and parasite trees, different sets of frequencies for the events lead to equally probable solutions. Moreover, often these solutions differ greatly in terms of the number of inferred events. It appears crucial to take this into account before attempting any further biological interpretation of such reconciliations. More generally, we also show that the set of frequencies can vary widely depending on the input host and parasite trees. Indiscriminately applying a standard vector of costs may thus not be a good strategy
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