Essai de détermination de l'age et de la vitesse d'altération d'un sol ferrallitique camerounais à l'aide de la méthode du déséquilibre radioactif uranium-thorium

Wir schlagen eine neue Methode zur Berechnung der «Verwitterungsgesch windigkeit » eines Bodens vor, die auf dem radioaktiven Uranium -Thorium Ungleichgewicht beruht. Die Anwendung dieser Methode auf einen ferrallitischen Boden aus Kamerun erlaubt es uns die Geschwindigkeit mit der seine Verwitterungsfront fortschreitet auf 7.10⁻³ cm/Jahr zu bestimmen.A new method for calculating the «weathering rate» of a soil is proposed which is based on the uranium-thorium radioactive desequilibrium. The application of this method to a ferrallitic soil from Cameroon permits the authors to value the progression rate of its weathering face as 7.10⁻³ cm/year.Nous proposons une nouvelle méthode de calcul de la «vitesse d'altération» d'un sol, basée sur le déséquilibre radioactif uranium-thorium. L'application de cette méthode à un sol fenrallitique du Cameroun nous permet d'estimer la vitesse de progression de son front d'altération à 7.10⁻³ cm/an.Boulad Adel Paul, Muller Jean-Pierre, Bocquier Gérard. Essai de détermination de l'âge et de la vitesse d'altération d'un sol ferrallitique camerounais à l'aide de la méthode du déséquilibre radioactif uranium-thorium. In: Sciences Géologiques. Bulletin, tome 30, n°3, 1977. Sédimentologie et géochimie de la surface. pp. 175-188

Modal expansion for the 2D Green's function in a non-orthogonal coordinates system.

We present an efficient modal method to calculate the two-dimensional Green's function for electromagnetics in curvilinear coordinates. For this purpose the coordinate transformation based differential method, introduced for the numerical analysis of surface-relief gratings, is directly used with perfectly matched layers (PMLs). The covariant formalism Maxwell's equations, very convenient for the non-orthogonal coordinates formulation, also gives an unified analysis of PMLs. Numerical results for a line source placed above a perfectly conducting corrugated surface are presented

Selection for litter size in pigs. II. Efficiency of closed and open selection lines*

A selection experiment on litter size in the pig was carried on for seventeen generations in an Inra experimental herd. The founder population was made up of 10 males and 120 females from the Large White breed. Selection was first performed for ten generations in a closed line, compared to a control line derived from the same founder population. Selection was carried on within sire family on the total number of piglets born in the first two litters of the dam (TB1 + TB2). After ten generations, the selection criterion became dam TB1 only. The control line was then discontinued and a panel of frozen semen from the 11th generation boars was created for later comparisons. The selected line was opened to gilt daughters of hyperprolific boars and sows, at a rate of 1/8 per generation, and the same selection procedure was applied irrespective of the origin of the gilt. During the whole experiment, the number of ova shed (OS) and the number of live embryos (LE) at 30 days in the 3rd pregnancy were recorded. These two parts of the experiment were analysed using REML estimation of genetic parameters and a BLUP-Animal Model in order to estimate the responses to selection. Significant heritabilities for TB1, TB2, OS and LE were obtained, i.e. 0.10, 0.05, 0.43 and 0.19, respectively. Significant common environment variances and covariances were estimated for nearly all traits. Significantly positive BLUP responses per generation were observed from G0 to G17 for TB1 (+0.086), TB2 (+0.078), OS (+0.197) and LE (+0.157). However, the responses were 3- to 4-fold higher in the G12–G17 interval compared to G0–G11, and they were also in fair agreement with previous estimates based on standard least-squares procedures, using the control line and the control frozen semen panel. Since G11, the selection intensity was increased by nearly 80 p. cent compared to the previous generations, and the proportion of hyperprolific ancestry increased up to 65 p. cent in the sows of the last generation. The total genetic gain of about 1.4 piglets at birth per litter could be shared between a gain due to immigration, of about 0.8 piglets per litter, and a within-line selection gain of about 0.6 piglets. Thus by combining selection and immigration in the second part of the experiment, advantage could be taken from both the genetic superiority of the immigrants and the higher internal selection intensity made possible by immigration