Une méthode générale d'estimation des paramètres génétiques dans un échantillon sélectionné, avec une application à une sélection sur un indice à trois caractères

L’estimation des paramètres génétiques d’une population, héritabilités et corrélations génétiques, à partir d’un échantillon repose sur de nombreuses hypothèses, qui concernent tant la population elle-même que l’échantillon qu’on en tire. La principale condition à laquelle doit satisfaire l’échantillon est d’être aléatoire, ce qui n’est pas le cas lorsque les individus mesurés, ou leurs parents, sont sélectionnés, situation fréquente chez les animaux d’élevage. Dans ce cas, les estimations obtenues par les techniques classiques de régression et d’analyse de variance peuvent être faussées et des corrections sont nécessaires pour tenir compte de la sélection. Lorsque la sélection se fait sur plusieurs caractères simultanément, combinés par exemple dans un indice de sélection, la correction repose sur la connaissance des variances-covariances des parents sélectionnés relativement à celles de la population non sélectionnée, selon une méthode générale décrite, en particulier, par AI TKEN (1934). Cette méthode inclut, comme cas particulier, les résultats de plusieurs travaux récents concernant les effets de la sélection sur un seul caractère. Cependant, la variance d’échantillonnage des estimations corrigées ainsi obtenues a une expression complexe. Un exemple numérique, concernant une sélection sur un indice à 3 caractères chez le Porc, est traité. Il montre un bon accord entre les estimées corrigées pour les effets de la sélection et les estimées tirées de l’échantillon non sélectionné.The estimation of genetic parameters rests on several hypotheses, concerning either the population considered itself or the sample drawn from it. In particular, random sampling has to be assumed, which is not the case when the individuals measured, or their parents, are selected, a frequent situation in farm animals. In this case, the usual estimates from regression and analysis of variance may be biassed. When selection is based on several traits, which for instance are combined into an index, the bias may be derived from the knowledge of the phenotypic variance-covariance matrix of the selected parents, according to a general method described, in particular, by AiruErt (1934). This method includes, as particular cases, several more recent results concerning the bias due to selection on one character. However, the sampling variances of the estimates so obtained have complex expressions. A numerical illustration is given, which concerns a three-trait index selection in the pig. The results show a good agreement between the estimates corrected for the bias due to selection and the estimates drawn from the unselected sample

A new tool based on faecal stanols can distinguish specific mammalian species in modern and past environments

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Structure and stimuli-responsiveness of all-DNA dendrimers: theory and experiment

We present a comprehensive theoretical and experimental study of the solution phase properties of DNA-based family of nanoparticles - dendrimer-like DNA molecules (DL-DNA). These charged DNA dendrimers are novel macromolecular aggregates, which hold high promise in targeted self-assembly of soft matter systems in the bulk and at interfaces. To describe the behavior of this family of dendrimers (with generations ranging from G1 to G7), we use a theoretical model in which base-pairs of a single DL-DNA molecule are modeled by charged monomers, whose interactions are chosen to mimic the equilibrium properties of DNA correctly. Experimental results on the sizes and conformations of DL-DNA are based on static and 1dynamic light scattering; at the same time, Molecular Dynamics simulations are employed to model the equilibrium properties of DL-DNA, which compare favorably with the findings from experiments while at the same time providing a host of additional information and insight into the molecular structure of the nanostructures. We also examine the salt-responsiveness of these macromolecules, finding that despite the strong screening of electrostatic interactions, brought about by the added salt, the macromolecules shrink only slightly, their size robustness stemming from the high bending rigidity of the DNA-segments. The study of these charged dendrimer systems is an important field of research in the area of soft matter due to their potential role for various interdisciplinary applications, ranging from molecular cages and carriers for drug delivery in a living organism to the development of dendrimer- and dendron-based ultra-thin films in the area of nanotechnology. These findings are essential to determine if DL-DNA is a viable candidate for the experimental realization of cluster crystals in the bulk, a novel form of solids with multiple site occupancy.Comment: 38 pages, 17 figure

Integral data analysis for resonance parameters determination

Neutron time-of-flight experiments have long been used to determine resonance parameters. Those resonance parameters have then been used in calculations of integral quantities such as Maxwellian averages or resonance integrals, and results of those calculations in turn have been used as a criterion for acceptability of the resonance analysis. However, the calculations were inadequate because covariances on the parameter values were not included in the calculations. In this report an effort to correct for that deficiency is documented: (1) the R-matrix analysis code SAMMY has been modified to include integral quantities of importance, (2) directly within the resonance parameter analysis, and (3) to determine the best fit to both differential (microscopic) and integral (macroscopic) data simultaneously. This modification was implemented because it is expected to have an impact on the intermediate-energy range that is important for criticality safety applications

Merger of Nuclear Data with Criticality Safety Calculations

In this paper we report on current activities related to the merger of differential/integral data (especially in the resolved-resonance region) with nuclear criticality safety computations. Techniques are outlined for closer coupling of many processes � measurement, data reduction, differential-data analysis, integral-data analysis, generating multigroup cross sections, data-testing, criticality computations � which in the past have been treated independently

Application of bio-based solvents for biocatalysed synthesis of amides with Pseudomonas stutzeri lipase (PSL)

Bio-based solvents were investigated for the biocatalysed amidation reactions of various ester-amine combinations by Pseudomonas stutzeri lipase (PSL). Reactions were undertaken in a range of green and potentially bio-based solvents including terpinolene, p-cymene, limonene, 2-methyl THF, ɣ-valerolactone, propylene carbonate, dimethyl isosorbide, glycerol triacetate and water. Solvent screenings demonstrated the importance and potential of using non-polar bio-based solvents for favouring aminolysis over hydrolysis; whilst substrate screenings highlighted the unfavourable impact of reactants bearing bulky para- or 4-substituents. Renewable terpene-based solvents (terpinolene, p-cymene, D-limonene) were demonstrated to be suitable bio-based media for PSL amidation reactions. Such solvents could provide a greener and more sustainable alternative to traditional petrochemical derived non-polar solvents. Importantly, once the enzyme (either PSL or CALB) binds with a bulky para-substituted substrate, only small reagents are able to access the active site. This therefore limits the possibility for aminolysis to take place, thereby promoting the hydrolysis. This mechanism of binding supports the widely accepted 'Ping Pong - Bi Bi' mechanism used to describe enzyme kinetics. The work highlights the need to further investigate enzyme activity in relation to para- or 4-substituted substrates. A priority in PSL chemistry remains a methodology to tackle the competing hydrolysis reaction