Almost Flat Planar Diagrams

We continue our study of matrix models of dually weighted graphs. Among the attractive features of these models is the possibility to interpolate between ensembles of regular and random two-dimensional lattices, relevant for the study of the crossover from two-dimensional flat space to two-dimensional quantum gravity. We further develop the formalism of large $N$ character expansions. In particular, a general method for determining the large $N$ limit of a character is derived. This method, aside from being potentially useful for a far greater class of problems, allows us to exactly solve the matrix models of dually weighted graphs, reducing them to a well-posed Cauchy-Riemann problem. The power of the method is illustrated by explicitly solving a new model in which only positive curvature defects are permitted on the surface, an arbitrary amount of negative curvature being introduced at a single insertion.Comment: harvmac.tex and pictex.tex. Must be compiled "big". Diagrams are written directly into the text in pictex command

Working with farmers for agricultural innovation and climate adaptation

The CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS), in common with other CGIAR research programs, understands that farmers are at the centre of agricultural innovation and adaptation. This publication describes some of the many ways in which CCAFS works with farmers and farmers’ organizations to solve problems generated by climate change. Recognizing the importance of participatory knowledge systems involving farmers, scientists, and other stakeholders in responding effectively to climate change, this document seeks to provide an overview of the many ways CCAFS collaborations with farming communities work in practice – and how this can serve as a springboard for more effective dialogue and planning, leading ultimately to better outcomes for farming in a climate-constrained world

Branched Coverings and Interacting Matrix Strings in Two Dimensions

We construct the lattice gauge theory of the group G_N, the semidirect product of the permutation group S_N with U(1)^N, on an arbitrary Riemann surface. This theory describes the branched coverings of a two-dimensional target surface by strings carrying a U(1) gauge field on the world sheet. These are the non-supersymmetric Matrix Strings that arise in the unitary gauge quantization of a generalized two-dimensional Yang-Mills theory. By classifying the irreducible representations of G_N, we give the most general formulation of the lattice gauge theory of G_N, which includes arbitrary branching points on the world sheet and describes the splitting and joining of strings.Comment: LaTeX2e, 25 pages, 4 figure

Exact solution of discrete two-dimensional R2^{2} gravity

We exactly solve a special matrix model of dually weighted planar graphs describing pure two-dimensional quantum gravity with a R^2 interaction in order to study the intermediate regimes between the gravitating and flat metric. The flat space is modeled by a regular square lattice, while localized curvature is being introduced through defects of the lattice. No ``flattening'' phase transition is found with respect to the R^2 coupling: the infrared behaviour of the system is that of pure gravity for any finite R^2 coupling. In the limit of infinite coupling, we are able to extract a scaling function interpolating between pure gravity and a phase of a dilute gas of curvature defects on a flat background. We introduce and explain some novel techniques concerning our method of large N character expansions and the calculation of Schur characters on big Young tableaux

Advances in large N group theory and the solution of two-dimensional R2^{2} gravity

We review the recent exact solution of a matrix model which interpolates between flat and random lattices. The importance of the results is twofold: Firstly, we have developed a new large N technique capable of treating a class of matrix models previously thought to be unsolvable. Secondly, we are able to make a first precise statement about two-dimensional R^2 gravity. These notes are based on a lecture given at the Cargese summer school 1995. They contain some previously unpublished results

Detecting variable (V), diversity (D) and joining (J) gene segment recombination using a two-colour fluorescence system

<p>Abstract</p> <p>Background</p> <p>Diversity of immunoglobulins and the T cell antigen receptors is achieved via the recombination activating gene (RAG)-mediated rearrangement of variable (V), diversity (D) and joining (J) gene segments, and this underpins the efficient recognition of a seemingly limitless array of antigens. Analysis of V(D)J recombination activity is typically performed using extrachromosomal recombination substrates that are recovered from transfected cells and selected using bacterial transformation. We have developed a two-colour fluorescence-based system that simplifies detection of both deletion and inversion joining events mediated by RAG proteins.</p> <p>Results</p> <p>This system employs two fluorescent reporter genes that differentially mark unrearranged substrates and those that have undergone RAG-mediated deletion or inversion events. The recombination products bear the hallmarks of true V(D)J recombination and activity can be detected using fluorescence microscopy or flow cytometry. Recombination events can be detected without the need for cytotoxic selection of recombination products and the system allows analysis of recombination activity using substrates integrated into the genome.</p> <p>Conclusions</p> <p>This system will be useful in the analysis and exploitation of the V(D)J recombination machinery and suggests that similar approaches could be used to replace expression of one gene with another during lymphocyte development.</p

Fabrication of monodisperse poly(dl- lactic acid) microparticles using drop microfluidics

Monodisperse poly(dl-lactic acid) particles with a diameter between 11 and 121 μm were fabricated by drop microfluidics/solvent evaporation method using flow focusing glass capillary device. In the dripping regime, the ratio of droplet diameter to orifice diameter was in the range of 0.37−1.34 and was inversely proportional to the 0.39 power of the ratio of the continuous phase flow rate to dispersed phase flow rate

Fabrication of biodegradable poly(lactic acid) particles in flow focusing glass capillary devices

Fabrication of biodegradable poly(lactic acid) particles in flow focusing glass capillary device

Emulsion templating of poly(lactic acid) particles: droplet formation behavior

Monodisperse poly(dl-lactic acid) (PLA) particles of diameters between 11 and 121 ?m were fabricated in flow focusing glass microcapillary devices by evaporation of dichloromethane (DCM) from emulsion droplets at room temperature. The dispersed phase was 5% (w/w) PLA in DCM containing 0.1−2 mM Nile red and the continuous phase was 5% (w/w) poly(vinyl alcohol) in reverse osmosis water. Particle diameter was 2.7 times smaller than the diameter of the emulsion droplet template indicating very low particle porosity. Monodisperse droplets have only been produced under dripping regime using a wide range of dispersed phase flow rates (0.002−7.2 cm3h-1), continuous phase flow rates (0.3−30 cm3h-1) and orifice diameters (50−237 ?m). In the dripping regime, the ratio of droplet diameter to orifice diameter was inversely proportional to the 0.39 power of the ratio of the continuous phase flow rate to dispersed phase flow rate. Highly uniform droplets with a coefficient of variation (CV) below 2 % and a ratio of the droplet diameter to orifice diameter of 0.5−1 were obtained at flow rate ratios of 4−25. Under jetting regime, polydisperse droplets (CV > 6 %) were formed by detachment from relatively long jets (between 4 and 10 times longer than droplet diameter) and a ratio of the droplet size to orifice size was 2−5