Stochastic analysis of chemical reactions in multi-component interacting systems at criticality

We numerically and analytically investigate the behavior of a non-equilibrium phase transition in the second Schl\"ogl autocatalytic reaction scheme. Our model incorporates both an interaction-induced phase separation and a bifurcation in the reaction kinetics, with these critical lines coalescing at a bicritical point in the macroscopic limit. We construct a stochastic master equation for the reaction processes to account for the presence of mutual particle interactions in a thermodynamically consistent manner by imposing a generalized detailed balance condition, which leads to exponential corrections for the transition rates. In a non-spatially extended (zero-dimensional) setting, we treat the interactions in a mean-field approximation, and introduce a minimal model that encodes the physical behavior of the bicritical point and permits the exact evaluation of the anomalous scaling for the particle number fluctuations in the thermodynamic limit. We obtain that the system size scaling exponent for the particle number variance changes from $\beta_0 = 3/2$ at the standard non-interacting bifurcation to $\beta = 12/7$ at the interacting bicritical point. The methodology developed here provides a generic route for the quantitative analysis of fluctuation effects in chemical reactions occurring in multi-component interacting systems.Comment: 10 pages, 4 figures, 0 tabl

Integrin CD11b activation drives anti-tumor innate immunity

Myeloid cells are recruited to damaged tissues where they can resolve infections and tumor growth or stimulate wound healing and tumor progression. Recruitment of these cells is regulated by integrins, a family of adhesion receptors that includes integrin CD11b. Here we report that, unexpectedly, integrin CD11b does not regulate myeloid cell recruitment to tumors but instead controls myeloid cell polarization and tumor growth. CD11b activation promotes pro-inflammatory macrophage polarization by stimulating expression of microRNA Let7a. In contrast, inhibition of CD11b prevents Let7a expression and induces cMyc expression, leading to immune suppressive macrophage polarization, vascular maturation, and accelerated tumor growth. Pharmacological activation of CD11b with a small molecule agonist, Leukadherin 1 (LA1), promotes pro-inflammatory macrophage polarization and suppresses tumor growth in animal models of murine and human cancer. These studies identify CD11b as negative regulator of immune suppression and a target for cancer immune therapy

Togo: Thorny transition and misguided aid at the roots of economic misery

The parliamentary elections of October 2007, the first free Togolese elections since decades, were meant to correct at least partially the rigged presidential elections of 2005. Western donors considered it as a litmus test of despotic African regimes’ propensity to change towards democratization and economic prosperity. They took Togo as model to test their approach of political conditionality of aid, which had been emphasised also as corner stone of the joint EU-Africa strategy. Empirical findings on the linkage between democratization and economic performance are challenged in this paper because of its basic data deficiencies. It is open to question, whether Togo’s expected economic consolidation and growth will be due to democratization of its institutions or to the improved external environment, notably the growing competition between global players for African natural resources

Fences in our heads: a discourse analysis of the korup resettlement stalemate

The resettlement of people from human-inhabited protected areas (HIPAs) is a contentious point in the people-and-parks debate. This article illustrates the setbacks that can arise from conservation-and-development projects where these two realms of local reality are separated through resettlement schemes, rather than integrated. We rely on a comprehensive social, ecological, economic, and legal cost-benefit and risk analysis of the Korup National Park's resettlement program in Cameroon. After 23 years, in 2003, this program had reached a stalemate, with skyrocketing costs and near-closure of policy alternatives. The article suggests that ideology and policy combined to generate conservation failure, while inhibiting institutional learning and managers' ability to opt out of failing policies. We identify a nexus of three factors at the root of these problems: (a) legal fencing; (b) implicit policies; and (c) self-serving scientific myths. In the Congo Basin, where the architecture of protected areas was built around the tenets of "fortress conservation," legal reform is clearly needed to enable effective community conservation. We argue, nonetheless, that negotiated alternatives remain feasible even within the current legal strictures. Progress requires, however, that managers move away from past exclusionary policies and engage in genuine co-management work within HIPAs