Today, predictive methods like Quantitative Structure-Activity Relationships
(QSARs) play an important role in setting the priorities for risk assessment of
chemicals. However, when a large number of compounds (>200) have to be
considered, limitations arise on which physico-chemical variables to use. In
this paper, a fast and easy way of chemically characterising compounds has
been investigated. A QSAR is a regression model that relates the variation in
the biological activity (y-matrix) within a homogenous series of compounds to
their chemical and structural properties (x-matrix). The descriptor variable
matrix (x) may be constructed from a multitude of variables indicating either
the presence or absence of predefined structural fragments. The present paper
investigates the possibilities and limitations of using such a derived x-matrix
in cases of QSARs and environmental modelling. The approach is used in two
examples, which both gave positive results.
Zinc ashes, muffle furnace fragments and lead slags from non-ferrous industries were applied to pave roads in the North of Belgium. From an inventory it appeared that there are at least 490 km of such roads. In our survey the materials on these roads were characterised. The total metal concentration, the availability and the leaching as a function of time were determined. It appeared that these materials contain high concentrations of heavy metals, some of which are readily available. The high leaching of some metals makes them as such unsuitable as secondary construction material. Methods for the application of these materials for road construction were examined where the materials replaced part of the sand and gravel fraction in lean concrete and in bituminous mixtures, or where they replaced the sand in sand-cement mixtures, all these to be used for road foundations, cycle tracks, etc. When lead slags were applied in lean concrete, a material was obtained complying with the standards for secondary construction materials and with sufficient compressive strength for road foundations. When zinc ashes or muffle fragments were used to replace sand in sand-cement mixtures, again a suitable construction material was obtained. The other combinations tried out were rather unsuccessful, because of high metal leaching and/or poor compressive strength.
Une expérience de croisement de bovins de races Holstein Frisonne, Brown Swiss et Ankole a été réalisée durant les années 1978-1988 dans l'élevage de Lushebere dans la région de Masisi, Kivu-Nord, Zaïre. Des effets additifs de la race Holstein Frisonne supérieure et des effets d'hétérosis individuels du croisement Holstein Frisonne x Ankolé ont été trouvés en ce qui concerne les rendements laitiers. Les effets d'hétérosis individuels du croisement Brown Swiss x Ankole ont contribué à l'augmentation de la production laitière. Le coefficient d'héritabilité s'est révélé faible (0,14) pour le rendement laitier, correspondant au caractère le plus important économiquement. Les raisons principales pourraient être liées à la sélection à long terme du phénotype, en particulier en ce qui concerne la race Ankole, mais également aux possibilités limitées, pour les races européennes, d'exprimer leur potentiel génétique en raison de l'absence d'alimentation à base de concentrés. En ayant pour objectif la réalisation d'un croisement à long terme, reposant sur la simulation de races synthétiques nouvelles, on a montré qu'il convenait de poursuivre les croisements avec des proportions de race Holstein Frisonne comprises entre 77,5 et 80 % et de race Ankole comprises entre 20 et 22,5 %
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.