Elephants classify human ethnic groups by odor and garment color

Animals can benefit from classifying predators or other dangers into categories, tailoring their escape strategies to the type and nature of the risk. Studies of alarm vocalizations have revealed various levels of sophistication in classification [1-5]. In many taxa, reactions to danger are inflexible, but some species can learn the level of threat presented by the local population of a predator [6-8] or by specific, recognizable individuals [9-10]. Some species distinguish several species of predator, giving differentiated warning calls and escape reactions; here we explore an animal’s classification of sub-groups within a species. We show that elephants distinguish at least two Kenyan ethnic groups, and can identify them by olfactory and color cues independently. In the Amboseli ecosystem, Kenya, Maasai warriors demonstrate virility by spearing elephants (Loxodonta africana), but Kamba agriculturalists pose little threat. Elephants showed greater fear when they detected the scent of garments previously worn by Maasai than by Kamba men, and reacted aggressively to the color associated with Maasai warriors. Elephants are therefore able to classify members of a single species into sub-groups that pose different degrees of danger

A heuristic approach application of network modelling

Thesis (M. Ing.) -- University of Stellenbosch, 1996.One copy microfiche.Full text to be digitised and attached to bibliographic record

Microeconometric Evaluation of Selected ESF-Funded ALMP-Programmes

The study evaluates different ESF-funded labour market programmes by comparing the labour market status at different points in time after the treatment. In order to solve the selection problem we employ a standard matching algorithm with a multi-dimensional distance measure. The effects of the analyzed programmes (wage subsidies, start-up subsidies and qualification measures for recipients of social welfare) are very heterogeneous. It can be observed that the direct integration into the regular labour market provides an advantage for the supported individuals. Its lasting effects, however, strongly depend on the group of persons being supported, the type of treatment and the employers’ financial share.In der Studie werden verschiedene ESF-geförderte Arbeitsmarktprogramme über einen Vergleich des Arbeitsmarktstatus zu verschiedenen Zeitpunkten nach der Teilnahme evaluiert. Um das Selektionsproblem zu lösen, wird ein Standard-Matching-Ansatz mit einem multidimensionalen Distanzmaß genutzt. Die Wirkungen der untersuchten Programme (Einstellungszuschüsse, Existenzgründungsförderung, Qualifizierungs- und Beschäftigungsmaßnahmen für Sozialhilfeempfänger) sind unterschiedlich. Zusammenfassend kann festgestellt werden, dass die direkte Integration in den regulären Arbeitsmarkt die Beschäftigungschancen der geförderten Personen verbessert. Letztendlich hängt die Wirkung allerdings davon ab, welche Personengruppe gefördert wird, welcher Maßnahmetyp eingesetzt wird und wie hoch die finanzielle Beteiligung des Arbeitgebers ist

Fluidized Capacitive Bioanode As a Novel Reactor Concept for the Microbial Fuel Cell

The use of granular electrodes in Microbial Fuel Cells (MFCs) is attractive because granules provide a cost-effective way to create a high electrode surface area, which is essential to achieve high current and power densities. Here, we show a novel reactor design based on capacitive granules: the fluidized capacitive bioanode. Activated carbon (AC) granules are colonized by electrochemically active microorganisms, which extract electrons from acetate and store the electrons in the granule. Electricity is harvested from the AC granules in an external discharge cell. We show a proof-of-principle of the fluidized capacitive system with a total anode volume of 2 L. After a start-up period of 100 days, the current increased from 0.56 A/m² with 100 g AC granules, to 0.99 A/m² with 150 g AC granules, to 1.3 A/m² with 200 g AC granules. Contact between moving AC granules and current collector was confirmed in a control experiment without biofilm. Contribution of an electro-active biofilm to the current density with recirculation of AC granules was limited. SEM images confirmed that a biofilm was present on the AC granules after operation in the fluidized capacitive system. Although current densities reported here need further improvement, the high surface area of the AC granules in combination with external discharge offers new and promising opportunities for scaling up MFCs