Diffuse-interface model for nanopatterning induced by self-sustained ion etch masking

We construct a simple phenomenological diffuse-interface model for composition-induced nanopatterning during ion sputtering of alloys. In simulations, this model reproduces without difficulties the high-aspect ratio structures and tilted pillars observed in experiments. We investigate the time evolution of the pillar height, both by simulations and by {\it in situ} ellipsometry. The analysis of the simulation results yields a good understanding of the transitions between different growth regimes and supports the role of segregation in the pattern-formation process.Comment: 10 pages, 3 figures; minor revisions with respect to first version; figures nicened; journal ref. adde

Comparison of four statistical methods for detection of a major gene in a progeny test design

In livestock improvement it is common to design a progeny test of sires in order to estimate their breeding values. The data recorded for these estimate are useful for the detection of major genes. They are the n.m performances Yij of m progeny j of n sires i. These data need to be corrected for the polygenic influence of the sire on its progeny (sire i effect Ui). Four statistical tests of the segregation of a major gene are compared. The first (ﺎSA for "segregation analysis") is the classical ratio of the likelihoods under Ho (no major gene) and H1 (a major gene is segregating). The parameters describing the population (means and standard deviations within genotype) are estimated by maximizing the marginal likelihood of the Yij. The other statistics studied are approximations of this ﺎSA statistic where the sire i effect (Ui) is considered as a fixed effect (ﺎ FE statistic) or, following Elsen et al. (1988) and Höschele (1988), where the parameters, and Ui, are estimated maximizing the joint likelihood of Ui and Yij (ﺎME and ﺎME2 statistics). Simulation studies were done in order to describe the distribution of these statistics. It is shown that ﺎSA and ﺎME1 are the most powerful test, followed by ﺎME2 whose relative loss of power ranged between 20 and 40%, depending on the H1 case studied, when 400 progeny are measured (n = m = 20). The segregation analysis, based on direct maximization of the likelihood, required 30 times more computation time than the ﺎME test using an EM algorithm.Il est fréquent, en sélection, de tester sur descendance, des mâles, afin d’estimer leur valeur génétique. Les données recueillies dans ce but peuvent être utilisées afin de mettre en évidence un gène majeur. Elles sont constituées des n.m performances Yij de m descendants j de n mâles i. Ces données doivent être corrigées pour l’effet polygénique du père (Ui) sur ses descendants. Quatre tests statistiques de mise en évidence d’un tel gène majeur sont comparés. Le premier (ﺎSA pour "segregation analysis") est le rapport classique des vraisemblances sous Ho (pas de gène majeur) et sous H1 (existence d’un gène majeur). Les paramètres caractéristiques de la population (moyennes et écarts types intragénotype) sont estimés en maximisant la vraisemblance marginale des Yij Les autres statistiques de tests sont des approximations de ﺎSA pour lesquelles, soit l’effet père Ui est considéré comme un effet fixé (test IFE) soit, comme proposé par Elsen et al. (1988) et Höschele (1988), les paramètres, et Ui, sont obtenus en maximisant la vraisemblance conjointe des Yij et des Ui (test ﺎME1 et ﺎME2 Nous avons réalisé des simulations afin de décrire les distributions de ces tests. ﺎSA et ﺎME1 sont les tests les plus puissants, suivi par ﺎME2 dont la perte relative de puissance varie entre 20 et 40% selon l’hypothèse H1 étudiées, quand 400 descendants sont mesurés (n = m =20). L’analyse de ségrégation, réalisée par maximisation directe de la vraisemblance, demande 30 fois plus de temps de calcul que les tests ﺎME réalisés l’aide d’un algorithme EM

Interface properties in dielectrics: A cross-section analysis by atomic force microscopy

International audienceEven if interfaces are more and more investigated their properties remain partially unknown, especially as regards their electronic properties. This is mainly related to the lack of characterization at relevant scale. In this context, electrical modes derivate from Atomic Force Microscopy appear well adapted. In this paper, a method to probe space charge at nanoscale is proposed. This method is based on surface potential measurement by Kelvin Probe Force Microscopy (KPFM) and post-processing technique based either on numerical derivation or Finite Element Method. Through these methods, densities of interface charges and injected charges were determined at different metal/dielectric interfaces

Synchronous Behavior of Two Coupled Electronic Neurons

We report on experimental studies of synchronization phenomena in a pair of analog electronic neurons (ENs). The ENs were designed to reproduce the observed membrane voltage oscillations of isolated biological neurons from the stomatogastric ganglion of the California spiny lobster Panulirus interruptus. The ENs are simple analog circuits which integrate four dimensional differential equations representing fast and slow subcellular mechanisms that produce the characteristic regular/chaotic spiking-bursting behavior of these cells. In this paper we study their dynamical behavior as we couple them in the same configurations as we have done for their counterpart biological neurons. The interconnections we use for these neural oscillators are both direct electrical connections and excitatory and inhibitory chemical connections: each realized by analog circuitry and suggested by biological examples. We provide here quantitative evidence that the ENs and the biological neurons behave similarly when coupled in the same manner. They each display well defined bifurcations in their mutual synchronization and regularization. We report briefly on an experiment on coupled biological neurons and four dimensional ENs which provides further ground for testing the validity of our numerical and electronic models of individual neural behavior. Our experiments as a whole present interesting new examples of regularization and synchronization in coupled nonlinear oscillators.Comment: 26 pages, 10 figure

Stapled Porcine Pericardium Displays Lower Infectivity In Vitro Than Native and Sutured Porcine Pericardium.

Biological xenografts using tubulized porcine pericardium are an alternative to replace infected prosthetic graft. We recently reported an innovative technique using a stapled porcine pericardial bioconduit for immediate vascular reconstruction in emergency. The objective of this study is to compare the growth and adherence to grafts of bacteria and yeast incubated with stapled porcine pericardium, sutured or naked pericardium. One square centimeter of porcine pericardial patches, with or without staples or sutures, was incubated with 10 <sup>5</sup> colony forming units of Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Candida albicans for 1, 6, and 24 h. The medium was collected to quantify planktonic microorganisms, while grafts were sonicated to quantify adherent microorganisms. Dacron and Dacron Silver were analyzed in parallel as synthetic reference prostheses. Stapled porcine pericardium reduced the growth and the adherence of E coli (2- to 30-fold; P < 0.0005), S aureus (11- to 1000-fold; P < 0.0006), S epidermidis (>500-fold; P < 0.0001), and C albicans (12- to 50-fold; P < 0.0001) when compared to medium alone (growth) and pericardium or Dacron (adherence). Native and sutured porcine pericardium interfered with the growth and the adherence of E coli and C albicans, and Dacron with that of S epidermidis. As expected, Dacron Silver was robustly bactericidal. Stapled porcine pericardium exhibited a lower susceptibility to infection by bacteria and yeasts in vitro when compared to the native and sutured porcine pericardium. Stapled porcine pericardium might be a good option for rapid vascular grafting without increasing infectivity

Risk analysis of marine activities in the Belgian part of the North Sea (RAMA): final report

RAMA is a 2-year project (04/2004 - 04/2006) executed by two Belgian partners, Ecolas NV (Environmental Consultancy Agency) and the Maritime Institute (University of Ghent), and financed by the SPSD II research program, specific actions, of the Belgian Science Policy (BELPSO). RAMA aims to assess the environmental risks of spills by commercial shipping activities on the Belgian Part of the North Sea. Shipping patterns, transports of dangerous goods, probability of risks and the potential impact of spill incidents (oil & hazardous and noxious substances) will be assessed. The risk analysis within this project studies both the chances of a spill accident happening and the environmental impacts in case of an accident. The valorisation of the RAMA project will result in a thorough analysis of the current status of the shipping at the North Sea in relation to the issue of safety. The scope of the project will however go beyond the mere result of a fundamental risk analysis of the commercial shipping at the North Sea. It is also aiming at the formulation of recommendations to improve the safety level for the environment and at an optimization of response in the framework of the Belgian "North Sea Disaster Plan"