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

Typability in partial groupoids

Adapting a claim of M. Kracht, we establish a characterization of the typable partial applicative algebras.Comment: 5 page

Adapting weed management in rice to changing climates

This paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in rice in Africa. Elevated CO2 levels may have positive effects on rice competitiveness with C4 weeds, but these are generally outnumbered by C3 species in weed populations of rice in Africa. Moreover, higher temperatures and drought will favor C4 over C3 plants. Increased CO2 levels may also improve tolerance of rice against parasitic weeds, while invasiveness of such species may be stimulated by soil degradation and more frequent droughts or floods. Elevated CO2 may increase belowground relative to aboveground growth, in particular of perennial (C3) species, rendering mechanical control less effective or even counterproductive. Increased CO2 levels, rainfall and temperature may also reduce the effectiveness of chemical control. The implementation of climate change adaptation technologies, such as drought-tolerant germplasm and water-saving irrigation regimes, will also have consequences for rice–weed competition. Rainfed production systems are hypothesized to be most vulnerable to direct effects of climate change (e.g. changes in rainfall patterns) and are likely to face increased competition from C4 and parasitic weeds. Bioticstress- tolerant rice cultivars to be developed for these systems should encompass weed competitiveness and parasitic-weed resistance. In irrigated systems, indirect effects will be more important and weed management strategies should be diversified to lessen dependency on herbicides and mechanical control, and be targeted to perennial rhizotomous (C3) weeds. Water-saving production methods that replace the weed-suppressive flood water layer by intermittent or continuous periods of aerobic conditions, necessitate additional weed management strategies to address the inherent increases in weed competition

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

Increasing paddy yields and improving farm management: results from participatory experiments with good agricultural practices (GAP) in Tanzania

Rice is an increasingly important commodity in sub-Saharan Africa. In Tanzania, the rice yield gap is as high as 87%, due to a combination of production constraints and sub-optimal crop management. Reducing this yield gap may be partly achieved through the introduction and dissemination of good agricultural practices (GAP). We conducted 18 farmer-managed on-farm trials in Tanzania, to test a set of GAP components against conventional farmers' practices (FP) for two consecutive growing seasons in 2013 and 2014. The objectives were: (1) to understand farmers' capabilities in implementing GAP; (2) to acquire better insights into the merits, relevance and suitability of individual GAP components; and (3) to provide a case study showing that exposure to good practices combined with the farmers' own experimentations can serve to improve and, trigger a positive change in the participating farmers' crop management. Compared to the farmers' own practices, average yield increases of 1 t paddy ha−1 in 2013 and 2.7 t ha−1 in 2014 were achieved when following GAP. These yield advantages were mainly obtained by a higher panicle number, improved harvest index and improved weed control. Farmers experienced difficulties with land levelling, planting or sowing in lines and using rotary weeders, but they were convinced that these technologies are important to boost their rice yields. The case of Tanzania shows that paddy yields can be substantially improved by GAP and that adoption of GAP by smallholder rice farmers can be triggered by stimulating experimentations with such practices on their own farms

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