Reaction Diffusion Models in One Dimension with Disorder

We study a large class of 1D reaction diffusion models with quenched disorder using a real space renormalization group method (RSRG) which yields exact results at large time. Particles (e.g. of several species) undergo diffusion with random local bias (Sinai model) and react upon meeting. We obtain the large time decay of the density of each specie, their associated universal amplitudes, and the spatial distribution of particles. We also derive the spectrum of exponents which characterize the convergence towards the asymptotic states. For reactions with several asymptotic states, we analyze the dynamical phase diagram and obtain the critical exponents at the transitions. We also study persistence properties for single particles and for patterns. We compute the decay exponents for the probability of no crossing of a given point by, respectively, the single particle trajectories ($\theta$) or the thermally averaged packets ($\bar{\theta}$). The generalized persistence exponents associated to n crossings are also obtained. Specifying to the process $A+A \to \emptyset$ or A with probabilities $(r,1-r)$, we compute exactly the exponents $\delta(r)$ and $\psi(r)$ characterizing the survival up to time t of a domain without any merging or with mergings respectively, and $\delta_A(r)$ and $\psi_A(r)$ characterizing the survival up to time t of a particle A without any coalescence or with coalescences respectively. $\bar{\theta}, \psi, \delta$ obey hypergeometric equations and are numerically surprisingly close to pure system exponents (though associated to a completely different diffusion length). Additional disorder in the reaction rates, as well as some open questions, are also discussed.Comment: 54 pages, Late

Strengthening clinical cancer research in the United Kingdom

BACKGROUND: In 1999, 270 000 cases of cancer were registered in the United Kingdom, placing a large burden on the NHS. Cancer outcome data in 1999 suggested that UK survival rates were poorer than most other European countries. In the same year, a Department of Health review noted that clinical trials accrual was poor (<3.5% of incident cases) and hypothesised that increasing research activity might improve outcomes and reduce the variability of outcomes across England. Thus, the National Cancer Research Network (NCRN) was established to increase participation in cancer clinical research.METHODS: The NCRN was established in 2001 to provide a robust infrastructure for cancer clinical research and improvements in patient care. Remit of NCRN is to coordinate, support and deliver cancer clinical research through the provision of research support staff across England. The NCRN works closely with similar networks in Scotland, Wales and the Northern Ireland. A key aim of NCRN is to improve the speed of research and this was also assessed by comparing the speed of study delivery of a subset of cancer studies opening before and after NCRN was established.RESULTS: Patient recruitment increased through NCRN, with almost 32 000 (12% of annual incident cases) cancer patients being recruited each year. Study delivery has improved, with more studies meeting the recruitment target - 74% compared with 39% before NCRN was established.CONCLUSION: The coordinated approach to cancer clinical research has demonstrated increased accrual, wide participation and successful trial delivery, which should lead to improved outcomes and care. British Journal of Cancer (2011) 104, 1529-1534. doi: 10.1038/bjc.2011.69 www.bjcancer.com Published online 1 March 2011 (C) 2011 Cancer Research U

Innovation in Entrepreneurship Education: Developing Competitive Advantages for MBA Students

For the last decade entrepreneurship education has grown to become a major discipline in several universities and colleges, particularly in the United States, Europe, and other developed nations. Nevertheless, comprehensive entrepreneurship programs are starting to be implemented in higher-education institutions across emergent economies as well. Everywhere around the world, entrepreneurship students need to gain skills and knowledge that can help them get started and have better opportunities to succeed with their ventures. At CETYS Universidad, a private non-for-profit school in Mexico, an Entrepreneurship Concentration MBA program was designed and developed around the Entrepreneurial Life Cycle and Entrepreneurship Process frameworks. The program is intended to build entrepreneurship competencies in MBA students, nurture an innovative mindset, and help them increase their entrepreneurial self-confidence and capabilities. It is the first program of its kind to be offered in the northwest region of the country, and one of the few in Mexico. RESUMEN Durante la última década, la educación empresarial ha crecido hasta convertirse en una disciplina importante en varias universidades y colegios, particularmente en los Estados Unidos, Europa y otras naciones desarrolladas. Sin embargo, los programas integrales de emprendimiento también están comenzando a implementarse en instituciones de educación superior en economías emergentes. En todo el mundo, los estudiantes de emprendimiento necesitan adquirir habilidades y conocimientos que puedan ayudarlos a comenzar y tener mejores oportunidades para tener éxito con sus empresas. En CETYS Universidad, una escuela privada sin fines de lucro en México, se diseñó y desarrolló un programa de MBA de Concentración en Emprendimiento en torno a los marcos de Ciclo de Vida Emprendedor y Proceso de Emprendimiento. El programa está destinado a desarrollar competencias empresariales en los estudiantes de MBA, fomentar una mentalidad innovadora y ayudarlos a aumentar su confianza en sí mismos y sus capacidades empresariales. Es el primer programa de este tipo que se ofrece en la región noroeste del país y uno de los pocos en México.First editio

Cyclic Guanidines as Efficient Organocatalysts for the Synthesis of Polyurethanes

A systematic survey of basic/nucleophilic organocatalysts for the polyaddition in bulk of polyols, PEG-600, and PTMO-650, to isophorone diisocyanate (IPDI) has been performed. Guanidines were shown to be very efficient catalysts for the urethane linkage formation. Bicyclic penta-alkylated guanidines such as MTBD led to polyurethane molecular weight and dispersity that are in the range of those observed with tin-based catalysts such as DBTDL. Tetra-alkylated guanidine such as TBD was shown to be a weaker catalyst as compared to pentaalkylated guanidines, as a result of its high reactivity toward isocyanate, resulting in the formation of a less nucleophilic urea. Although the mechanism has not yet been firmly established, these experiments suggest that a nucleophilic-catalysis mechanism, involving the attack of one of the nitrogen of the guanidine onto the unsaturated system of the isocyanate, should not be totally ruled out with such strong Bronsted base catalysts

Recent achievements in facilitated transport membranes for separation processes

Membrane separation processes have been extensively used for some important industrial separations, substituting traditional methods. However, some applications require the development of new membranes. In this work, we discuss recent progress achieved in this field, focusing on gas and liquid separation using facilitated transport membranes. The advantages of using a carrier species either in a liquid membrane or fixed in a polymer matrix to enhance both the flux and the selectivity of the transport are summarized. The most probable transport mechanisms in these membranes are presented and the improvements needed to spread this technology are also discussed. As examples, we discuss our very successful experiences in air fractioning, olefin/paraffin separation and sugar recovery using liquid and fixed carrier membranes