Estimating Lyapunov exponents in billiards

Dynamical billiards are paradigmatic examples of chaotic Hamiltonian dynamical systems with widespread applications in physics. We study how well their Lyapunov exponent, characterizing the chaotic dynamics, and its dependence on external parameters can be estimated from phase space volume arguments, with emphasis on billiards with mixed regular and chaotic phase spaces. We show that in the very diverse billiards considered here the leading contribution to the Lyapunov exponent is inversely proportional to the chaotic phase space volume, and subsequently discuss the generality of this relationship. We also extend the well established formalism by Dellago, Posch, and Hoover to calculate the Lyapunov exponents of billiards to include external magnetic fields and provide a software implementation of it

Real-Time Analysis of Large Astronomical Images

Forthcoming instruments designed for high-cadence large-area surveys, such as the Dark Energy Survey and Large Synoptic Survey Telescope, will generate several GB of data products every few minutes during survey operations. Since such surveys are designed to operate with minimal observer interaction, automated real-time analysis of these large images is necessary to ensure uninterrupted production of science-quality data. We describe a software infrastructure suite designed to support such surveys, focusing particularly on ImageHealth, a tool for near-real-time processing of large images. These image manipulation and analysis algorithms were applied to simulated data from the Dark Energy Survey, as well as observed data collected by the Y4KCam on the CTIO 1m telescope and the Mosaic camera on the Blanco telescope. The accuracy and speed of the ImageHealth code in particular were benchmarked against results from SourceExtractor, a standard image analysis tool ubiquitous in the astronomical community. ImageHealth is shown to provide comparable accuracy to SourceExtractor, but with significantly shorter execution time. Based on the importance of real-time analysis in reaching the Dark Energy Survey's science goals, ImageHealth and other aspects of this analysis package were incorporated (in modified form) into the Survey Image System Process Integration, the Dark Energy Camera software control environment. The original ImageHealth code, however, is completely instrument-independent, and is freely available for use within other observational data-taking environments.Comment: 7 pages, 3 figures, Accepted to Journal of Astronomical Instrumentation. Related software available online at the Astrophysics Source Code Library (http:/ascl.net

Dimensions of Discretion: Specifying the Object of Street-Level Bureaucracy Research

__Abstract__ At the street level of the state public policies get their final form and substance. This being so, discretion is a key concept. The goal of this article is to specify discretion as a research object in the study of street-level bureaucracy. Therefore the theoretical views on discretion prevalent in juridical and other disciplines are explored. Discretion appears to be a multi-faceted concept. This finding has consequences for the analysis of discretion in the explanation of what happens in street-level bureaucracies

The magic of good governance

__Abstract__ Governance is a widely used concept, in both the study and practice of public administration. Particularly in conjunction with the adjective good it serves as a normative standard against which the actual situation in countries across the world is claimed to be measured. In analytical terms, however, the concept shows shortcomings. It is, for instance, broad, and seems to imply or suggest consensus and uniformity. Yet these characteristics hardly seem to hinder an almost universal appeal and a widespread usage. Governance appears to function as a ‘magic concept’. Therefore, before it can be used in theory and research, considerable specification and elaboration are needed. At the same time its ‘magic’ character does make it useful, particularly in a rhetorical sense

The sustainable future of implementation research: On the development of the field and its paradoxes

__Abstract__ As fashionable as implementation studies were in the 1970s and 1980s, as en vogue it has become four decades later to consider implementation as a research theme of the past. It is clear that in the study of government new themes and concepts have been put on the agenda. In the ‘age of governance’ that study takes place under a variety of headings beyond ‘implementation’. At the same time a continued attention to what happens with policies-on-paper can be observed. In this special issue the development of implementation research as a scholarly field is assessed. A closer look reveals some paradoxes, but also steady advancement

Powers behind control: An essay on democracy

In contemporary Western democracies the role of government is not what it used to be. In the public discourse some authors claim to observe a ‘relocation of politics’, while others speak of a ‘democratic deficit’ in general. In this essay the relationship between democracy and governance is explored on a macro-level. The argument is that performance in the public domain and the decisions underlying it no longer in a direct way can be traced down to expressions of societal demands. This is because both the relationships between society and democracy and between politics and performance have become looser. In particular, the hierarchical relation between democracy and government has been replaced by a more horizontal pairing of democracy and governance. As the latter has multiple dimensions, entailing a range of activities performed at various spots by a variety of actors, it appears that democracy, as well, cannot appropriately get substance and form in a singular way anymore. Enhancing the visibility of who is involved in the processes leading to public decisions, combined with enlarging possibilities for accountability, ‘multi-localisation’ provides a conceptual perspective for rethinking contemporary democracy.Session 3: Institutional rearrangement of the public domai

Greenhouse gases in cold water filaments in the Arabian Sea during the Southwest Monsoon

The distribution of partial pressure of carbon dioxide and the concentrations of nitrous oxide and methane were investigated in a cold water filament near the coastal upwelling region off Oman at the beginning of the southwest monsoon in 1997. The results suggest that such filaments are regions of intense biogeochemical activity which may affect the marine cycling of climatically relevant trace gase

Leistungen der ökologischen Landwirtschaft zur Vermeidung von Stoffeinträgen in das Grund- und Oberflächenwasser im Vergleich zu konventioneller Bewirtschaftung

Stoffeinträge aus der Landwirtschaft in das Grund- und Oberflächenwasser stellen ein hohes Umweltrisiko dar. In einer systematischen Literaturübersicht wurden ökologische und konventionelle Landwirtschaft hinsichtlich der jeweiligen Belastungen des Grund- und Oberflächenwassers im Vergleich untersucht. Insgesamt wurden 96 Vergleichsstudien mit 308 Vergleichpaaren evaluiert. 63% der Vergleichpaare zeigen Vorteile des ökologischen Landbaus in Bezug auf Nitratausträge, genauso 90% der Vergleichspaare in Bezug auf Pestizidbelastungen. Im Schnitt (Median) können unter ökologischer Bewirtsvchaftung 28% weniger Nitratauswaschungen festgestellt werden als in der konventionellen Landwirtschaft, zudem werden keine Pestizide und vermutlich auch weniger Tierarzneimittel in das Grund- und Oberflächenwasser ausgewaschen. Hinsichtlich des Austrags von Phosphor ist die Datenlage unklar. Das System der ökologischen Landwirtschaft zeigt ein hohes Potential im Schutz von Grund- und Oberflächenwasser

France: A Strong State, Towards a Stronger Local Democracy?

In the political organization of France, the so-called 'Jacobean logic' plays an important role. It stands for a tendency towards centralisation and uniformity. However, since the 1980s there has been a process of decentralisation to sub-national authorities. Grenoble is an example of a city in which new ways of involving citizens in urban policies are being tried out. Since the 1960s government-citizens relations in Grenoble are structured via the local associations, and mainly on the neighbourhood level. The focus of the city government's recent strategy is to adapt the infrastructure of citizen participation to the conditions of modern urban life.This means, for example, that the associations are stimulated to take into account the level of the agglomeration, and that new forms of involving individual citizens have been established