River networks of southern Africa: Scaling laws governing their geometry and deviations from scaling

in Geochemistry, Geophysics, Geosystems (2005), 6(9),

Africa is tectonically and hypsometrically different to all other continents and therefore provides a unique natural laboratory for the study of river network geometry. Southern Africa is one of the more ... [more ▼]

Africa is tectonically and hypsometrically different to all other continents and therefore provides a unique natural laboratory for the study of river network geometry. Southern Africa is one of the more unusual geomorphological regions of this continent, hence our interest in the geometry of the rivers draining this region. The 14 river basins analyzed here come from the larger networks of the Orange and Limpopo rivers, as well as from the southernmost section of the continent where rivers meander through an exhumed belt of folded Paleozoic mountains. Basic scaling laws, such as Horton’s laws and Hack’s law, hold for the rivers studied here, but the parameters governing these relationships vary between networks. A strong inverse correlation between Horton’s ratio of stream numbers and mean source stream slope is observed. We believe this is the first time such a relation has been reported. Horton’s ratio of basin areas is proportional to that of stream numbers but always greater than it; this contradicts existing models that equate the two parameters. An expression for the ratio of stream lengths in terms of the ratio of stream numbers is derived theoretically and verified for the available data. The parameter governing Hack’s law, h, varies not only between networks but also with scale inside each network. Existing models provide up to four scaling regimes. Given the spatial resolution of this study, the two regimes at the middle scales are visible here. These are termed the short-range and randomness regimes, with a crossover occurring at a drainage area of approximately 800 km2 . The values for h in the smaller short-range regime have an inverse correlation with the roughness of the topography. Observed values for h imply basins appear more elongated with increasing area; this would be more pronounced in rivers draining a smooth topography. In the randomness regime the values of h are lower, mostly between 0.5 and 0.6, with a weak positive correlation to topography roughness. This range of h corresponds to self-similar basins, but a more detailed analysis of individual stream fractality is necessary before such a conclusion can be made. [less ▲]

Les langues dans les offres d'emploi du Luxemburger Wort 1984-2004

Report (2005)

Der Einfluss von Expertise auf den Prozess der schulischen Leistungsbeurteilung

in Zeitschrift für Entwicklungspsychologie und Padagogische Psychologie (2005), 37

Two experiments investigated the effects of information processing goals on the recall of information about pupils and on achievement judgments. In Experiment 1 teachers (experts) were presented with case ... [more ▼]

Two experiments investigated the effects of information processing goals on the recall of information about pupils and on achievement judgments. In Experiment 1 teachers (experts) were presented with case reports about pupils. The reports were either read under the instruction (a) to form an impression of the personality of the described pupils or (b) to predict their future development. Afterwards subjects had to recall the case reports and to rate the academic achievement of the described pupils. Experiment 2 was a replication with university freshmen (laymen) as subjects. Depending on their processing goal, experts switched their processing of pupil information from top-down strategies involving the activation of prototypical categories about pupil personalities to bottom-up processing which consists of integrating the features of the individual case. Thus, processing goals appear as moderators in teachers’ judgments. [less ▲]

Self-organizing mixture models

in Neurocomputing (2005), 63

We present an expectation-maximization (EM) algorithm that yields topology preserving maps of data based on probabilistic mixture models. Our approach is applicable to any mixture model for which we have ... [more ▼]

We present an expectation-maximization (EM) algorithm that yields topology preserving maps of data based on probabilistic mixture models. Our approach is applicable to any mixture model for which we have a normal EM algorithm. Compared to other mixture model approaches to self-organizing maps (SOMs), the function our algorithm maximizes has a clear interpretation: it sums data log-likelihood and a penalty term that enforces self-organization. Our approach allows principled handling of missing data and learning of mixtures of SOMs. We present example applications illustrating our approach for continuous, discrete, and mixed discrete and continuous data. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

Representation of the Union's citizens by the European Parliament

in European Constitutional Law Review (2005), (1), 73-78

As it is obviously impossible for the modern ‘demos’ to assemble in order to take political decisions, democratic representation is an inevitable tool in large democracies. Representatives have to stand ... [more ▼]

As it is obviously impossible for the modern ‘demos’ to assemble in order to take political decisions, democratic representation is an inevitable tool in large democracies. Representatives have to stand for and to act for the people as a whole. Accordingly, the principle of representative or parliamentary democracy is a fundamental constitutional principle shared by all the Member States of the Union. Democracy doubtlessly works on the national level; the Member States' decisional powers, however, are fading with the constant transfer of competences towards the European level. This leads to a system of European ‘multi-level governance’ with wide consequences for the linkage between the represented peoples of the Member States and their representatives on both national and European levels. [less ▲]

Review of M. Robson and P. Stockwell. Language in Theory

in BELL. Belgian Essays on Language and Literature (2005), 3

Education and Pragmatism

Book published by Sense Publisher (2005)

Tauschprozesse Kulturwissenschaftliche Verhandlungen des Ökonomischen

Book published by Transcript (2005)

On the Income Dependence of Equivalence Scales

in Journal of Public Economics (2005), 89(5-6), 967-996

Household consumption exhibits economies of scale as the number of household members increases. We collect survey data from two countries, Germany and France, in order to obtain direct subjective ... [more ▼]

Household consumption exhibits economies of scale as the number of household members increases. We collect survey data from two countries, Germany and France, in order to obtain direct subjective estimates of household consumption economies of scale, and, in particular, to examine an additional dimension: whether household consumption economies of scale change as living standards go up. Our data from both countries indicate strongly that household economies of scale increase as the living standard goes up. We discuss the robustness of our survey method and compare our results to these of alternative estimation methods in the literature. [less ▲]

Le maintien du rire : les polices à Bruxelles

in Jaumain, Serge; Piette, Valérie (Eds.) L’Humour s’en va-t-en guerre. Bruxelles et la caricature en 14-18 (2005)