Exploring the contributions of liquid-phase sulfur chemistry to the mass-independent sulfur fractionation of the Archean rock record

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 30-32).Archean sulfur mass-independent fractionation (S-MIF) has been widely recognized as one of the strongest indicators for the rise of atmospheric oxygen in the Early Proterozoic. A decade after its discovery, the wide-ranging implications of Archean sulfur MIF have been discussed extensively and despite a number of recent studies on the gas-phase chemistry of sulfur, no definite overall picture has emerged to date as to the precise origin and preservation of the Archean mass-independent sulfur signal. The interpretation of the Archean sulfur MIF as a strong constraint for atmospheric oxygen levels, however, requires a dominant atmospheric source of sulfur MIF. This study was aimed at investigating the potential contribution of the poorly explored mass-independent effects from liquid-phase sulfur chemistry and focused on sulfur isotope fractionation during liquid-phase photolytic breakdown of phenacylphenylsulfone (PPS) as a model system for initial investigation. Results confirm that MIF in this system is caused by the magnetic 33S isotope and excludes other mechanisms such as nuclear volume effects or vibronic coupling that would produce concomitant MIF in the 32S-34_3-3S triad. This provides a starting point for discussing the implications of magnetic isotope effects as a mechanism for mass-independent isotope fractionation in the chemical evolution of the sulfur cycle and suggests that liquid-phase processes such as the photolysis of PPS cannot constitute the principal source of mass-independent sulfur fractionation in the Archean.by Sebastian Hermann Kopf.S.M

Case report of an exercise training and nutritional intervention plan in a patient with A350P mutation in DES gene.

Performing a supplementation intervention with creatine and protein, in conjunction with low-intensity endurance and resistance exercise is safe and has a positive effect on the quality of life in a patient with desminopathy

On the construction of classical superstring field theories

This thesis describes the construction of classical superstring field theories based on the small Hilbert space. First we describe the traditional construction of perturbative superstring theory as an integral over the supermoduli space of type II world sheets. The geometry of supermoduli space dictates many algebraic properties of the string field theory action. In particular it allows for an algebraisation of the construction problem for classical superstring field theories in terms of homotopy algebras. Next, we solve the construction problem for open superstrings based on Witten’s star product. The construction is recursive and involves a choice of homotopy operator for the zero mode of the η-ghost. It turns out that the solution can be extended to the Neveu-Schwarz subsectors of all superstring field theories. The recursive construction involves a hierarchy of string products at various picture deficits. The construction is not entirely natural, but it is argued that different choices give rise to solutions related by a field redefinition. Due to the presence of odd gluing parameters for Ramond states the extension to full superstring field theory is non-trivial. Instead, we construct gauge-invariant equations of motion for all superstring field theories. The realisation of spacetime supersymmetry in the open string sector is highly non-trivial and is described explicitly for the solution based on Witten’s star product. After a field redefinition the non-polynomial equations of motion and the small Hilbert space constraint become polynomial. This polynomial system is shown to be supersymmetric. Quite interestingly, the supersymmetry algebra closes only up to gauge transformations. This indicates that only the physical phase space realizes N = 1 supersymmetry. Apart from the algebraic constraints dictated by the geometry of supermoduli space the equations of motion or action should reproduce the traditional string S-matrix. The S-matrix of a field theory is related to the minimal model of the associated homotopy algebra. Because of the recursive nature of the solution and its construction in terms of products of various picture deficits, it is possible to relate the S-matrices of various picture deficits and, therefore, relate the S-matrix calculated from the bosonic string products at highest picture deficit with the physical vertices at lowest picture deficit through a series of descent equations. For open superstrings one can go beyond the equations of motion. The presence of picture changing operators at internal Ramond lines imposes either a constraint on the Hilbert space or necessitates the introduction of an auxiliary string field at picture −3/2. Based on the full equations of motion for the open string field, an action principle is proposed and shown to be gauge-invariant.Diese Dissertation behandelt die Konstruktion von klassischen Superstringfeldtheorien basierend auf dem kleinen Hilbertraum. Zuerst wird die traditionelle Konstrukti- on der störungstheoretischen Superstringtheorie mittels Integration über den Supermodulraum von Typ-II-Weltflächen beschrieben. Die Geometrie dieses Modulraums bestimmt viele algebraische Eigenschaften der Stringfeldtheoriewirkung. Insbesondere ermöglicht sie es, das Konstruktionsproblem für klassische Superstringfeldtheorien zu algebraisieren. Als nächstes wird eine Lösung des Konstruktionsproblems für offene Superstrings ausgehend von Wittens Sternprodukt beschrieben. Diese Lösung ist rekursiv und hängt von der Wahl eines Homotopieoperators für die Nullmode des η-Geistfeldes ab. Die rekursive Konstruktion lässt sich auf die Neveu-Schwarz-Sektoren aller Superstringtheorien verallgemeinern. Im allgemeinsten Fall wird eine Hierarchie von Stringprodukten mit verschiedenen Picturedefiziten definiert. Obwohl die Konstruktion ist nicht ganz natürlich ist, gehen verschiedene Lösungen des Konstruktionspro- blems mittels Feldredefinition auseinander hervor. Für die Erweiterung auf Ramondsektoren ergibt sich eine weitere Komplikation durch die ungeraden Klebemoduli. Anstelle einer Wirkung werden lediglich eichinvariante Bewegungsgleichungen konstruiert. Der Lösungsraum der Bewegungsgleichungen für offene Superstrings ist superymmetrisch. Die Supersymmetrietransformationen werden explizit für offene Superstrings angegeben und es wird gezeig, dass die Kombination aus kleiner Hilbertraumbedingung und Bewegungsgleichungen in polynomielle Form gebracht werden kann und dass dieses erweiterte System supersymmetrisch ist. Die Supersymmetriealgebra schließt nur modulo Eichtransformationen, was darauf hindeutet, dass die N = 1 Supersymmetrie lediglich auf dem Lösungsraum realisiert ist. Eine wichtige Konsistenzbedingung für alle Superstringwirkungen ist die Äquivalenz der feldtheoretischen S-Matrix zur traditionellen störungstheoretischen S- Matrix. Die S-Matrix einer Feldtheorie ist eng mit dem minimalen Modell der as- soziierten Homotopiealgebra verknüpft. Durch die rekursive Konstruktion der Feldtheoriewirkung mittels Produkten bei verschiedenen Picturedefiziten ist es möglich die S-Matrizen bei unterschiedlichen Picturedefiziten durcheinander auszudrücken. Letztendlich führt dies zu einem Ausdruck der Superstring-S-Matrix durch die bosonische S-Matrix und Pictureänderungsoperatoren, die auf die externen Zustände wirken. Beim offenen Superstring ist es weiterhin möglich eine Wirkung für die vollständigen Bewegungsgleichungen zu finden. Die Präsenz der Pictureänderungsoperatoren in den internen Ramondlinien erfordert, dass man entweder den Hilbertraum einschränkt oder dass man ein Hilfsfeld bei Picture −3/2 einführt.Deutsche Übersetzung des Titels: Zur Konstruktion klassischer Stringfeldtheorie

The large core limit of spiral waves in excitable media: A numerical approach

We modify the freezing method introduced by Beyn & Thuemmler, 2004, for analyzing rigidly rotating spiral waves in excitable media. The proposed method is designed to stably determine the rotation frequency and the core radius of rotating spirals, as well as the approximate shape of spiral waves in unbounded domains. In particular, we introduce spiral wave boundary conditions based on geometric approximations of spiral wave solutions by Archimedean spirals and by involutes of circles. We further propose a simple implementation of boundary conditions for the case when the inhibitor is non-diffusive, a case which had previously caused spurious oscillations. We then utilize the method to numerically analyze the large core limit. The proposed method allows us to investigate the case close to criticality where spiral waves acquire infinite core radius and zero rotation frequency, before they begin to develop into retracting fingers. We confirm the linear scaling regime of a drift bifurcation for the rotation frequency and the core radius of spiral wave solutions close to criticality. This regime is unattainable with conventional numerical methods.Comment: 32 pages, 17 figures, as accepted by SIAM Journal on Applied Dynamical Systems on 20/03/1

BRIX - An Easy-to-Use Modular Sensor and Actuator Prototyping Toolkit

Zehe S, Großhauser T, Hermann T. BRIX - An Easy-to-Use Modular Sensor and Actuator Prototyping Toolkit. In: Tenth Annual IEEE International Conference on Pervasive Computing and Communications, Workshop Proceedings. Lugano, Swizerland: IEEE; 2012: 817-822.In this paper we present BRIX, a novel modular hardware prototyping platform for applications in mobile, wearable and stationary sensing, data streaming and feedback. The system consists of three different types of compact stack- able modules, which can adapt to various applications and scenarios. The core of BRIX is a base module that contains basic motion sensors, a processor and a wireless interface. A battery module provides power for the system and makes it a mobile device. Different types of extension modules can be stacked onto the base module to extend its scope of functions by sensors, actuators and interactive elements. BRIX allows a very intuitive, inexpensive and expeditious prototyping that does not require knowledge in electronics or hardware design. In an example application, we demonstrate how BRIX can be used to track human body movements

Silica‐based core materials for thermal superinsulations in various applications

Vacuum insulation panels (VIP) are usually manufactured using standardized manufacturing processes based on empirical values and in most cases with any fumed silica as the main component of the core material. However, not all applications have the same requirements in terms of thermal conductivity and service life. Therefore, it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications cheaper core materials, like precipitated silica, would be a reasonable alternative. To replace the time-consuming series of measurements for this purpose, this work offers comprehensive parameter studies to determine the optimum product properties of precipitated silica, fumed silica, silica gel, and glass spheres for use in the building sector, in transport boxes, as a superinsulation at atmospheric pressure, and as a switchable VIP. As a result, not only the preferred materials but also their porosities and particle sizes are presented. For atmospheric pressure and construction applications, fumed silica has to be preferred. For the transport sector and switchable VIPs as well as certain special applications, precipitated silica and silica gel may well be reasonable alternatives

Population Dynamics of Borrelia burgdorferi in Lyme Disease

Many chronic inflammatory diseases are known to be caused by persistent bacterial or viral infections. A well-studied example is the tick-borne infection by the gram-negative spirochaetes of the genus Borrelia in humans and other mammals, causing severe symptoms of chronic inflammation and subsequent tissue damage (Lyme Disease), particularly in large joints and the central nervous system, but also in the heart and other tissues of untreated patients. Although killed efficiently by human phagocytic cells in vitro, Borrelia exhibits a remarkably high infectivity in mice and men. In experimentally infected mice, the first immune response almost clears the infection. However, approximately 1 week post infection, the bacterial population recovers and reaches an even larger size before entering the chronic phase. We developed a mathematical model describing the bacterial growth and the immune response against Borrelia burgdorferi in the C3H mouse strain that has been established as an experimental model for Lyme disease. The peculiar dynamics of the infection exclude two possible mechanistic explanations for the regrowth of the almost cleared bacteria. Neither the hypothesis of bacterial dissemination to different tissues nor a limitation of phagocytic capacity were compatible with experiment. The mathematical model predicts that Borrelia recovers from the strong initial immune response by the regrowth of an immune-resistant sub-population of the bacteria. The chronic phase appears as an equilibration of bacterial growth and adaptive immunity. This result has major implications for the development of the chronic phase of Borrelia infections as well as on potential protective clinical interventions