The Remarkable Place of the UV-Curve in Economic Theory

The purpose of this paper is to provide an analysis of the impact the UV-curve had on economic theory and to provide an account of the subsequent radical changes in its place and role over the decades since its first appearance in 1958. The paper traces the historical development of the UV-curve and argues that the role of the UV-curve has changed from a measuring device to a graphical representation of full employment to an axiom necessary for matching models of unemployment. This changing role is best understood in the light of a paradigmatic change from Keynesianism to neoclassical search theory.UV-curve, Beveridge-curve, Theories of Unemployment, UV-analysis, Matching models, History of Economic Thought

The structure of finite meadows

A meadow is a commutative ring with a total inverse operator satisfying 0^{-1}=0. We show that the class of finite meadows is the closure of the class of Galois fields under finite products. As a corollary, we obtain a unique representation of minimal finite meadows in terms of finite prime fields.Comment: 12 page

Interactions between Behaviour and Genetics in Wild and Domestic Bird Populations

Personality traits can be favoured by both natural and artificial selection, if they result in increased fitness or productivity, and therefore play an important role in both wild and domestic populations. Here, we review how personality traits affect and are affected by natural and artificial selection by focusing on studies from both wild and domestic bird populations. Further, we will also explore how artificial selection affects personality and fitness traits in a domestic population. We will use the great tit (Parus major) and the laying hen (Gallus gallus domesticus) as our model species. When comparing the studies on behaviour genetics in great tits and laying hens, it is fascinating to see that two fields of study that seem quite far apart have so much in common

Multifunctional Land Use: An Accessibility Interpretation

The need for an efficient urban land use has generated much interest in new forms of urban architecture. In The Netherlands, at present an intensive discussion is taking place on so-called multifunctional land use. This concept aims to concentrate and combine several socio-economic functions in the same area, so as to save scarce space and to exploit economies of synergy. This paper tries to define multifunctional land use from the perspective of accessibility, since, from the viewpoint of spatial functionality, the appropriate demarcation should be based on transport costs and their impact on mutual interactions between actors. The interpretation of multifunctional land use in terms of accessibility is attractive since its avoids the demarcation problem implying the neglect of activities located outside the demarcated area. In order to incorporate the multifunctional character of accessibility, attention will also be paid to the multiplicity of interactions and to multipurpose trips. Addressing the notion of multifunctionality by means of accessibility is also relevant for the measurement of urbanisation economies. These will in this paper be replaced by accessibility economies, again in order not having to apply an arbitrary demarcation rule for metropolitan areas

Chemical potential in active systems: predicting phase equilibrium from bulk equations of state?

We derive a microscopic expression for a quantity $\mu$ that plays the role of chemical potential of Active Brownian Particles (ABPs) in a steady state in the absence of vortices. We show that $\mu$ consists of (i) an intrinsic chemical potential similar to passive systems, which depends on density and self-propulsion speed, but not on the external potential, (ii) the external potential, and (iii) a newly derived one-body swim potential due to the activity of the particles. Our simulations on active Brownian particles show good agreement with our Fokker-Planck calculations, and confirm that $\mu(z)$ is spatially constant for several inhomogeneous active fluids in their steady states in a planar geometry. Finally, we show that phase coexistence of ABPs with a planar interface satisfies not only mechanical but also diffusive equilibrium. The coexistence can be well-described by equating the bulk chemical potential and bulk pressure obtained from bulk simulations for systems with low activity but requires explicit evaluation of the interfacial contributions at high activity.Comment: Added new results in Section 3.4 and updated Discussion and Conclusio

AFROweeds: a collaborative and participative online network to enhance weed capacities in Africa

Weed competition cause high yield losses in African crop production systems. Conservative estimates show that even for rice alone weeds cost economies of sub-Saharan Africa (SSA) already a near $1.5 billion per year. For subsistence farmers in SSA there is only a limited range of affordable and effective control strategies. Due to the diversity of weed species, the complexity of crop – weed ecology and associated environmental and management interactions, as well as the socio-economic constraints of subsistence farming in Africa, few effective weed control strategies are developed so far. Moreover, even the limited number of control strategies, or component technologies currently available face limited dissemination and adoption among the (rice) farmer communities in SSA. The above described situation is largely the result of the sub-optimal capacities of agricultural research and development (R&D) organizations in SSA. The region has an extremely low ratio of trained weed scientists per farmer. Conversely, in the absence of weed scientists, students, R&D professionals or farmers looking for information on weeds, reliable, comprehensive and comprehensible sources are scant and scattered. The EU-ACP funded Afroweeds is an initiative of CIRAD and Africa Rice Center (AfricaRice) to link European and African botanists and weed scientists with the objective to enhance the regional capacities in these fields of expertise. Afroweeds is a network for professionals and students aimed at sharing knowledge on rice weeds. The modes operandi of Afroweeds is an open-access website (http://www.afroweeds.org/network). This online platform enables members to exchange information, discuss relevant issues and to access an increasingly extensive library of information and photos on weed species and management. The most eye-catching features of the Afroweeds collaborative platform are the extremely user-friendly weed species identification tools. They encompass image recognition software and a multiple-choice program (called 'plant robot') using schematic drawings of plant organs (e.g. leaves, flowers). Identification results can be cross-checked with a rich gallery of photos of fieldgrowing or herbarium specimen and information on ecology and biology, while the Afroweeds data base can also be consulted for effective management options. The strength of the Afroweeds collaborative site further lies in the fact that information and concerns can easily be shared with the other members of community for feed-back. By facilitating such exchange between actors who are otherwise isolated from each other, Afroweeds contributes towards spreading and enhancing knowledge on rice weeds and best weed management practices to improve the productivity of African rice-based cropping systems. (Texte intégral