Improving market institutions and urban food supplies for the urban poor: a comparative study of Nigeria and Zambia.

This study examines the systems which govern the marketing opportunities for informal urban and peri-urban cultivators, and for rural producers, in our two study countries, Nigeria and Zambia and it explores the mechanisms of marketing food in urban areas. Our literature review illustrates how little is known about how these formal and informal regulatory systems currently operate. For example, the positive contribution of both urban-based and rural-based traders in providing an essential service to urban consumers has not been adequately analysed

Internal Energy of the Potts model on the Triangular Lattice with Two- and Three-body Interactions

We calculate the internal energy of the Potts model on the triangular lattice with two- and three-body interactions at the transition point satisfying certain conditions for coupling constants. The method is a duality transformation. Therefore we have to make assumptions on uniqueness of the transition point and that the transition is of second order. These assumptions have been verified to hold by numerical simulations for q=2, 3 and 4, and our results for the internal energy are expected to be exact in these cases.Comment: 9 pages, 4 figure

Why is timing of bird migration advancing when individuals are not?

Recent advances in spring arrival dates have been reported in many migratory species but the mechanism driving these advances is unknown. As population declines are most widely reported in species that are not advancing migration, there is an urgent need to identify the mechanisms facilitating and constraining these advances. Individual plasticity in timing of migration in response to changing climatic conditions is commonly proposed to drive these advances but plasticity in individual migratory timings is rarely observed. For a shorebird population that has significantly advanced migration in recent decades, we show that individual arrival dates are highly consistent between years, but that the arrival dates of new recruits to the population are significantly earlier now than in previous years. Several mechanisms could drive advances in recruit arrival, none of which require individual plasticity or rapid evolution of migration timings. In particular, advances in nest-laying dates could result in advanced recruit arrival, if benefits of early hatching facilitate early subsequent spring migration. This mechanism could also explain why arrival dates of short-distance migrants, which generally return to breeding sites earlier and have greater scope for advance laying, are advancing more rapidly than long-distance migrants

On the duality relation for correlation functions of the Potts model

We prove a recent conjecture on the duality relation for correlation functions of the Potts model for boundary spins of a planar lattice. Specifically, we deduce the explicit expression for the duality of the n-site correlation functions, and establish sum rule identities in the form of the M\"obius inversion of a partially ordered set. The strategy of the proof is by first formulating the problem for the more general chiral Potts model. The extension of our consideration to the many-component Potts models is also given.Comment: 17 pages in RevTex, 5 figures, submitted to J. Phys.

Potts-Percolation-Gauss Model of a Solid

We study a statistical mechanics model of a solid. Neighboring atoms are connected by Hookian springs. If the energy is larger than a threshold the "spring" is more likely to fail, while if the energy is lower than the threshold the spring is more likely to be alive. The phase diagram and thermodynamic quantities, such as free energy, numbers of bonds and clusters, and their fluctuations, are determined using renormalization-group and Monte-Carlo techniques.Comment: 10 pages, 12 figure

Numerical Latent Heat Observation of the q=5 Potts Model

Site energy of the five-state ferromagnetic Potts model is numerically calculated at the first-order transition temperature using corner transfer matrix renormalization group (CTMRG) method. The calculated energy of the disordered phase $U^{+}$ is clearly different from that of the ordered phase $U^{-}$. The obtained latent heat $L = U^{-} - U^{+}$ is 0.027, which quantitatively agrees with the exact solution.Comment: 2 pages, Latex(JPSJ style files are included), 2 ps figures, submitted to J. Phys. Soc. Jpn.(short note

A systematic review of electronic patient records using the meta-narrative approach: Empirical findings and methodological challenges.

Systematic reviews are central to the enterprise of evidence-based medicine (EBM). However, traditional ‘Cochrane’ reviews have major limitations, especially when dealing with heterogeneous methodologies or an applied setting. The meta-narrative review (see Soc Sci Med 2005; 61: 417-30) is one of several new methods that seek to address pragmatic policy-level questions via broad-based literature reviews. Inspired by Kuhn, meta-narrative review takes a historical and paradigmatic approach to considering different areas of research activity. As an interpretive tool, the approach seeks distinct research traditions, each with its own meta-narrative. We then use these ‘stories of how research unfolded’ as a way of making sense of a diverse literature. Incommensurability between different traditions is seen not as a problem to be lamented or resolved but as a window to higher-order explanations about the nuances of empirical data and what these nuances mean for different applied situations. Having originally developed the meta-narrative method for a study of the diffusion of innovations in healthcare, we are now applying it in a review of the electronic patient record (EPR) in an organizational context. We have collated some 600 papers and books across multiple research traditions including health informatics, information systems research, computer-supported cooperative work (CSCW) and sociology. This very contemporary topic area is raising interesting methodological questions. For example, the EPR literature does not comprise as cleanly delineable traditions for four main reasons: 1. Information and communications technology research is a particularly fast-moving field, so paradigm shifts are relatively common (e.g. the rise of CSCW out of human-computer interaction research). 2. In the electronic age, it is easy for researchers to explore beyond their own discipline and ‘borrow’ theories, ideas and methods from elsewhere. Journal editors may commission overviews from experts in another tradition; authors may explicitly address an audience in another tradition. Research traditions can begin to converge (e.g. papers bringing together CSCW, information systems research and STS). 3. Some researchers are adept ‘boundary spanners’, writing for a number of different academic audiences and adapting their theoretical pedigree to fit (e.g. Marc Berg). 4. Some traditions are characterized not by a single unified paradigm but by active dialogue between competing paradigms (e.g. ‘hard’ versus ‘soft’ perspectives on knowledge management). This work contributes to the STS literature by critically questioning the nature of rigour in secondary research. The EBM movement values ‘Cochrane’ reviews because they meet positivist criteria (e.g. they are rational, objective, replicable, data-led, and transferable across contexts). In contrast, the meta-narrative review is interpretive, reflexive, problem-oriented and work-led, and makes no claim to either replicability or transferability. Rigour is redefined in terms of plausibility, authenticity and usefulness – raising the radical suggestion that the evidence base for key policy decisions can never be set in stone. Systematic reviews are central to the enterprise of evidence-based medicine (EBM). However, traditional ‘Cochrane’ reviews have major limitations, especially when dealing with heterogeneous methodologies or an applied setting. The meta-narrative review (see Soc Sci Med 2005; 61: 417-30) is one of several new methods that seek to address pragmatic policy-level questions via broad-based literature reviews. Inspired by Kuhn, meta-narrative review takes a historical and paradigmatic approach to considering different areas of research activity. As an interpretive tool, the approach seeks distinct research traditions, each with its own meta-narrative. We then use these ‘stories of how research unfolded’ as a way of making sense of a diverse literature. Incommensurability between different traditions is seen not as a problem to be lamented or resolved but as a window to higher-order explanations about the nuances of empirical data and what these nuances mean for different applied situations. Having originally developed the meta-narrative method for a study of the diffusion of innovations in healthcare, we are now applying it in a review of the electronic patient record (EPR) in an organizational context. We have collated some 600 papers and books across multiple research traditions including health informatics, information systems research, computer-supported cooperative work (CSCW) and sociology. This very contemporary topic area is raising interesting methodological questions. For example, the EPR literature does not comprise as cleanly delineable traditions for four main reasons: 1. Information and communications technology research is a particularly fast-moving field, so paradigm shifts are relatively common (e.g. the rise of CSCW out of human-computer interaction research). 2. In the electronic age, it is easy for researchers to explore beyond their own discipline and ‘borrow’ theories, ideas and methods from elsewhere. Journal editors may commission overviews from experts in another tradition; authors may explicitly address an audience in another tradition. Research traditions can begin to converge (e.g. papers bringing together CSCW, information systems research and STS). 3. Some researchers are adept ‘boundary spanners’, writing for a number of different academic audiences and adapting their theoretical pedigree to fit (e.g. Marc Berg). 4. Some traditions are characterized not by a single unified paradigm but by active dialogue between competing paradigms (e.g. ‘hard’ versus ‘soft’ perspectives on knowledge management). This work contributes to the STS literature by critically questioning the nature of rigour in secondary research. The EBM movement values ‘Cochrane’ reviews because they meet positivist criteria (e.g. they are rational, objective, replicable, data-led, and transferable across contexts). In contrast, the meta-narrative review is interpretive, reflexive, problem-oriented and work-led, and makes no claim to either replicability or transferability. Rigour is redefined in terms of plausibility, authenticity and usefulness – raising the radical suggestion that the evidence base for key policy decisions can never be set in stone

The Cooperative Participatory Evaluation of Renewable Technologies on Ecosystem Services (CORPORATES)

Publisher PD

Gas-plasma compressional wave coupling by momentum transfer

Pressure disturbances in a gas-plasma mixed fluid will result in a hybrid response, with magnetosonic plasma waves coupled to acoustic waves in the neutral gas. In the analytical and numerical treatment presented here, we demonstrate the evolution of the total fluid medium response under a variety of conditions, with the gas-plasma linkage achieved by additional coupling terms in the momentum equations of each species. The significance of this treatment lies in the consideration of density perturbations in such fluids: there is no 'pure' mode response, only a collective one in which elements of the characteristics of each component are present. For example, an initially isotropic gas sound wave can trigger an anisotropic magnetic response in the plasma, with the character of each being blended in the global evolution. Hence sound waves do not remain wholly isotropic, and magnetic responses are less constrained by pure magnetoplasma dynamics

Monte Carlo Simulations of Conformal Theory Predictions for the 3-state Potts and Ising Models

The critical properties of the 2D Ising and 3-state Potts models are investigated using Monte Carlo simulations. Special interest is given to measurement of 3-point correlation functions and associated universal objects, i.e. structure constants. The results agree well with predictions coming from conformal field theory confirming, for these examples, the correctness of the Coulomb gas formalism and the bootstrap method.Comment: 11 pages, 6 Postscript figures, uses Revte