Dynamical effects induced by long range activation in a nonequilibrium reaction-diffusion system

We both show experimentally and numerically that the time scales separation introduced by long range activation can induce oscillations and excitability in nonequilibrium reaction-diffusion systems that would otherwise only exhibit bistability. Namely, we show that the Chlorite-Tetrathionate reaction, where autocatalytic species diffuses faster than the substrates, the spatial bistability domain in the nonequilibrium phase diagram is extended with oscillatory and excitability domains. A simple model and a more realistic model qualitatively account for the observed behavior. The latter model provides quantitative agreement with the experiments.Comment: 19 pages + 9 figure

Turing Instability in a Boundary-fed System

The formation of localized structures in the chlorine dioxide-idodine-malonic acid (CDIMA) reaction-diffusion system is investigated numerically using a realistic model of this system. We analyze the one-dimensional patterns formed along the gradients imposed by boundary feeds, and study their linear stability to symmetry-breaking perturbations (Turing instability) in the plane transverse to these gradients. We establish that an often-invoked simple local linear analysis which neglects longitudinal diffusion is inappropriate for predicting the linear stability of these patterns. Using a fully nonuniform analysis, we investigate the structure of the patterns formed along the gradients and their stability to transverse Turing pattern formation as a function of the values of two control parameters: the malonic acid feed concentration and the size of the reactor in the dimension along the gradients. The results from this investigation are compared with existing experiments.Comment: 41 pages, 18 figures, to be published in Physical Review

Existencia y unicidad de solución y comportamiento asintótico para la ecuación de onda con condición de frontera del tipo Neumann y disipación localmente distribuido

En este trabajo se estudia la existencia y unicidad de solución de la ecuación de la onda con condiciones de frontera del tipo Neumann, con disipación localmente distribuida usando el método de Faedo Galerkin. Además analiza el decaimiento no exponencial de la energía asociado al sistema planteado. Se hacen las estimativas correspondientes basándose en propiedades del espacio donde se encuentra la solución de la ecuación, así como los teoremas correspondientes al sistema estudiado.Tesi

Exposure to Candida albicans Polarizes a T-Cell Driven Arthritis Model towards Th17 Responses, Resulting in a More Destructive Arthritis

BACKGROUND: Fungal components have been shown very effective in generating Th17 responses. We investigated whether exposure to a minute amount of C. albicans in the arthritic joint altered the local cytokine environment, leading to enhanced Th17 expansion and resulting in a more destructive arthritis. METHODOLOGY: Chronic SCW arthritis was induced by repeated injection with Streptococcus pyogenes (SCW) cell wall fragments into the knee joint of C57Bl/6 mice, alone or in combination with the yeast of C. albicans or Zymosan A. During the chronic phase of the arthritis, the cytokine levels, mRNA expression and histopathological analysis of the joints were performed. To investigate the phenotype of the IL-17 producing T-cells, synovial cells were isolated and analyzed by flowcytometry. PRINCIPAL FINDINGS: Intra-articular injection of either Zymosan A or C. albicans on top of the SCW injection both resulted in enhanced joint swelling and inflammation compared to the normal SCW group. However, only the addition of C. albicans during SCW arthritis resulted in severe chondrocyte death and enhanced destruction of cartilage and bone. Additionally, exposure to C. albicans led to increased IL-17 in the arthritic joint, which was accompanied by an increased synovial mRNA expression of T-bet and RORgammaT. Moreover, the C. albicans-injected mice had significantly more Th17 cells in the synovium, of which a large population also produced IFN-gamma. CONCLUSION: This study clearly shows that minute amounts of fungal components, like C. albicans, are very potent in interfering with the local cytokine environment in an arthritic joint, thereby polarizing arthritis towards a more destructive phenotype

Corrigendum: Bacillus Calmette–Guérin-Induced Trained Immunity Is Not Protective for Experimental Influenza A/Anhui/1/2013 (H7N9) Infection in Mice

Avian influenza A of the subtype H7N9 has been responsible for almost 1,600 confirmed human infections and more than 600 deaths since its first outbreak in 2013. Although sustained human-to-human transmission has not been reported yet, further adaptations to humans in the viral genome could potentially lead to an influenza pandemic, which may have severe consequences due to the absence of pre-existent immunity to this strain at population level. Currently there is no influenza A (H7N9) vaccine available. Therefore, in case of a pandemic outbreak, alternative preventive approaches are needed, ideally even independent of the type of influenza virus outbreak. Bacillus Calmette–Guérin (BCG) is known to induce strong heterologous immunological effects, and it has been shown that BCG protects against non-related infection challenges in several mouse models. BCG immunization of mice as well as human induces trained innate immune responses, resulting in increased cytokine responses upon subsequent ex vivo peripheral blood mononuclear cell restimulation. We investigated whether BCG (Statens Serum Institut-Denmark)-induced trained immunity may protect against a lethal avian influenza A/Anhui/1/2013 (H7N9) challenge. Here, we show that isolated splenocytes as well as peritoneal macrophages of BCG-immunized BALB/c mice displayed a trained immunity phenotype resulting in increased innate cytokine responses upon ex vivo restimulation. However, after H7N9 infection, no significant differences were found between the BCG immunized and the vehicle control group at the level of survival, weight loss, pulmonary influenza A nucleoprotein staining, or histopathology. In conclusion, BCG-induced trained immunity did not result in protection in an oseltamivir-sensitive influenza A/Anhui/1/2013 (H7N9) challenge mouse model