Decomposition and stability of multifronts and multipulses

Selle S. Decomposition and stability of multifronts and multipulses. Bielefeld (Germany): Bielefeld University; 2009.In der Arbeit werden zeitabhängige Reaktions-Diffusions-Systeme in einer Raumdimension betrachtet, welche Multipuls- oder Multifront-Lösungen besitzen. Es wird eine numerische Methode entwickelt, die die Lösung in ihre einzelnen Pulse oder Fronten zerlegt und zusätzlich die Geschwindigkeiten und die Positionen der einzelnen Pulse oder Fronten berechnet. Es wird gezeigt, dass die Methode numerisch gut anwendbar ist, und es wird weiter ein Stabiltätsresultat für Multipulse und Multifronten bewiesen, falls der Abstand zwischen den Pulsen oder Fronten immer hinreichend groß ist und sie nur leicht miteinander interagieren.In this thesis we consider time dependent reaction diffusion systems in one space dimension that have multiple pulse or front solutions. We develop a new numerical method that decomposes the solutions into their single pulses or fronts and in addition one computes the speeds and the positions of the single pulses and fronts. We show that the method is numerically feasible and prove stability results for the multiple pulse and front solutions if the distance of the pulses or fronts is sufficiently large and they interact only through their small tails

Freezing multipulses and multifronts

Beyn W-J, Selle S, Thümmler V. Freezing multipulses and multifronts. SIAM Journal on Applied Dynamical Systems. 2008;7(2):577-608.We consider nonlinear time dependent reaction diffusion systems in one space dimension that exhibit multiple pulses or multiple fronts. In an earlier paper two of the authors developed the freezing method that allows us to compute a moving coordinate frame in which, for example, a traveling wave becomes stationary. In this paper we extend the method to handle multifronts and multipulses traveling at different speeds. The solution of the Cauchy problem is decomposed into a finite number of single waves, each of which has its own moving coordinate system. The single solutions satisfy a system of partial differential algebraic equations coupled by nonlinear and nonlocal terms. Applications are provided to the Nagumo and the FitzHugh-Nagumo systems. We justify the method by showing that finitely many traveling waves, when patched together in an appropriate way, solve the coupled system in an asymptotic sense. The method is generalized to equivariant evolution equations and is illustrated by the complex Ginzburg-Landau equation

City2020+ : assessing climate change impacts for the city of Aachen related to demographic change and health ; a progress report

The research initiative CITY 2020+ assesses the risks and opportunities for residents in urban built environments under projected demographic and climate change for the year 2020 and beyond, using the city of Aachen as a case study. CITY 2020+ develops strategies, options and tools for planning and developing sustainable future city structures. The investigation focuses on how urban environment, political structure and residential behaviour can best be adapted, with attention to the interactions among structural, political, and sociological configurations and their impacts on human health. The interdisciplinary research is organized in three clusters. Within the first cluster, strategies of older people exposed to heat stress, and their networks as well as environmental health risks according to atmospheric conditions are examined. The second cluster addresses governance questions, urban planning and building technologies as well as spatial patterns of the urban heat island. The third cluster includes studies on air quality related to particulate matter and a historical perspective of city development concerning environmental issues and climate variability. However, it turns out that research topics that require an interdisciplinary approach are best addressed not by pre-structuring the work into related sub-projects but through combining them according to shared methodological approaches. Examples illustrating this rather practical approach within ongoing research are presented in this paper

Tumor-derived GDF-15 blocks LFA-1 dependent T cell recruitment and suppresses responses to anti-PD-1 treatment

Abstract Immune checkpoint blockade therapy is beneficial and even curative for some cancer patients. However, the majority don’t respond to immune therapy. Across different tumor types, pre-existing T cell infiltrates predict response to checkpoint-based immunotherapy. Based on in vitro pharmacological studies, mouse models and analyses of human melanoma patients, we show that the cytokine GDF-15 impairs LFA-1/β2-integrin-mediated adhesion of T cells to activated endothelial cells, which is a pre-requisite of T cell extravasation. In melanoma patients, GDF-15 serum levels strongly correlate with failure of PD-1-based immune checkpoint blockade therapy. Neutralization of GDF-15 improves both T cell trafficking and therapy efficiency in murine tumor models. Thus GDF-15, beside its known role in cancer-related anorexia and cachexia, emerges as a regulator of T cell extravasation into the tumor microenvironment, which provides an even stronger rationale for therapeutic anti-GDF-15 antibody development