Ensemble inequivalence, bicritical points and azeotropy for generalized Fofonoff flows

We present a theoretical description for the equilibrium states of a large class of models of two-dimensional and geophysical flows, in arbitrary domains. We account for the existence of ensemble inequivalence and negative specific heat in those models, for the first time using explicit computations. We give exact theoretical computation of a criteria to determine phase transition location and type. Strikingly, this criteria does not depend on the model, but only on the domain geometry. We report the first example of bicritical points and second order azeotropy in the context of systems with long range interactions.Comment: 4 pages, submitted to Phys. Rev. Let

Allergen recognition in the origin of asthma

Allergic respiratory diseases such as bronchial asthma are believed to result directly from the repeated local expression in airway tissues of T helper (Th) 2-polarized T cell immunity to inhaled allergens. Recent evidence suggests that these T cell responses are typically primed in utero and subsequently reshaped during postnatal allergen exposure via immune deviation, leading to the eventual emergence of stable allergen-specific T cell memory which is polarized towards the Th1 (normal) or Th2 (atopic) phenotype. The underlying Th1/Th2 switching process is influenced by a number of host and environmental factors that are poorly understood. Prominent amongst these are factors that affect the kinetics of maturation of immune competence during the early postnatal period. In particular, there is mounting evidence that the immunological milieu at the materno-fetal interface is naturally skewed towards the Th2 phenotype (possibly an evolutionary adaptation to protect the placenta against the toxic effects of Th1 cytokines). Furthermore, this bias appears to be preserved for varying periods into infancy, which may account for the presence of a high risk 'window' for allergic sensitization in early postnatal life. It is hypothesized that the principal impetus for postnatal development of a normal Th1/Th2 balance (and hence closure of the high risk sensitization window) is provided via contact with Th1-stimulatory commensal and pathogenic micro-organisms at the body's major mucosal surfaces

Preparation of interstitial lung cells by enzymatic digestion of tissue slices: preliminary characterization by morphology and performance in functional assays

A technique is reported here for the quantitative extraction of live cells from the lung interstitium; it involves the incubation of slices of perfused lung in a mixture containing optimal concentrations of collagenase, DNAse, and fetal calf serum, followed by the simultaneous recovery and fractionation of cells released from the tissue matrix on a six-step discontinuous percoll gradient. Yields in the order of 10(8) viable cells per gram of lung were routinely achieved with tissues from rat, mouse and guinea-pig. Preliminary characterization of these cells has been performed in the rat by histological techniques (Giemsa staining, transmission electron microscopy), cytochemistry (acid phosphatase, esterase, peroxidase), by the capacity to bind monoclonal antibodies directed at lymphocyte surface markers, and by a range of functional tests. The cells comprised, on average, 32% macrophages, 44% lymphocytes (T and B cells and large granular lymphocytes), with small numbers of eosinophils, mast cells and epithelial cells. Transmission electron microscopy revealed minimal ultrastructural damage to extracted cells, with such functions as phagocytosis, FcR activity, mitogen responsiveness, antigen presentation, and NK-cell activity, being readily demonstrable. In addition, these activities segregated into defined areas of the six-step density gradient

Violent relaxation in two-dimensional flows with varying interaction range

Understanding the relaxation of a system towards equilibrium is a long-standing problem in statistical mechanics. Here we address the role of long-range interactions in this process by considering a class of two-dimensional flows where the interaction between fluid particles varies with the distance