Antarctic springtime depletion of atmospheric mercury

Unlike other heavy metals that are inherently associated with atmospheric aerosols, mercury in ambient air exists predominantly in the gaseous elemental form. Because of its prolonged atmospheric residence time, elemental mercury vapor is distributed on a global scale. Recently, Canadian researchers have discovered that total gaseous mercury levels in the lower tropospheric boundary layer in the Canadian Arctic are often significantly depleted during the months after polar sunrise. A possible explanation may involve oxidation of elemental mercury, followed by adsorption and deposition of the oxidized form, leading to an increased input of atmospheric mercury into the Arctic ecosystem. Here we present the first continuous high-time-resolution measurements of total gaseous mercury in the Antarctic covering a 12-month period between January 2000 and January 2001 at the German Antarctic research station Neumayer (70 degrees 39' S, 8 degrees 15' W). We report that mercury depletion events also occur in the Antarctic after polar sunrise and compare our measurements with a data setfrom Alert, Nunavut, Canada. We also present indications that BrO radicals and ozone play a key role in the boundary-layer chemistry during springtime mercury depletion events in the Antarctic troposphere.     

Das digitale geologische Strukturmodell Bitterfeld als neuer Baustein in der Sanierungsforschung

Identification, assessment and remediation of a large-scale groundwater contamination requires a profound knowledge of the geological structure to predict the fate of contaminants in the subsurface. Within the SAFIRA-project, a model sector of the Bitterfeld/Wolfen area was chosen to transfer the structural geological data of the Tertiary and Quarternary aquifer units into a digital geological model. Using 125 selected drillholes as a base of 28 networked cross-sections, small-scale lithological and structural heterogeneities, in particular of the Quarternary layers, could be assigned to 31 litho-stratigraphic sedimentation units and depicted using a 10 × 10 m GIS grid. An assignment of hydraulic parameters to individual sedimentary bodies allows a combination with flow and transport models. The structural model was generated by combining gridding sections and additional point and lateral information of sediment distribution and allows -beyond visualisation purposes- volumetric calculations of distinct sedimentary units, which are relevant for an assessment of retardation processes in the remaining lignite seam. The present structural model is the base for a “Spatial Model Bitterfeld” and anables further investigations on the environmental impact of different scenarios.     

Comparison of analysis methods for package-induced stresses on moulded Hall sensors

Due to the piezoresistive and the piezo-Hall effect in semiconductor materials, Hall sensors show a strong temperature dependency and also a drift when subjected to temperature cycles Manic et al. (2000). Four factors mainly influence the mechanical stress in the sensitive layer. These are the geometry of the device, the differences of the coefficients of thermal expansion of the package materials, the temperature-dependent material properties and the time-dependent, viscous material properties. The objective of this investigation was to determine the mechanical stress in a moulded Hall sensor during the packaging process by finite-element simulation in comparison to experimental methods. It is shown that after each process-step the mechanical stress in the sensitive layer changes over time depending on the absolute value and the rate of the temperature change. Measurements of the inverse bending radius of glued and moulded chips show good agreement to the simulations.     

Entwicklung rechtssicherer Web-Anwendungen

A broad variety of juridical requirements has to be considered during the development of Web-applications. Disregard of these requirements holds severe financial dangers. A complete compilation of juridical requirements is complicated due to the multitude of juridical areas and the variety of Web-applications. Therefore, a development-driven juridical framework is suggested. From a software engineering point of view it is crucial to capture requirements at an early stage of development in order to avoid much higher costs at a later time. Thus, specialized conceptual modelling methods are examined with regard to their capability to model juridical requirements. A lack of methodical support is identified which is addressed by a systematic adaption and extension of the eW3DT method.     

Online-Literaturdatenbanken im Bereich der Wirtschaftsinformatik: Bereitstellung wissenschaftlicher Literatur und Analyse von Interaktionen der Wissensteilung

Knowledge sharing is fundamental for innovations in the scientific community. The paper examines how the interaction of knowledge sharing is supported by online services. With respect to business information systems, a survey of online literature databases is given, providing an aggregation of various publication sources, a direct access to publications, and which are available to the public. Furthermore, special analysis services are presented which describe competitive interactions of knowledge sharing via rankings on the one hand, and cooperative interactions of knowledge sharing via co-authorship evaluation on the other.     

PAC-Bayesian Compression Bounds on the Prediction Error of Learning Algorithms for Classification

We consider bounds on the prediction error of classification algorithms based on sample compression. We refine the notion of a compression scheme to distinguish permutation and repetition invariant and non-permutation and repetition invariant compression schemes leading to different prediction error bounds. Also, we extend known results on compression to the case of non-zero empirical risk.We provide bounds on the prediction error of classifiers returned by mistake-driven online learning algorithms by interpreting mistake bounds as bounds on the size of the respective compression scheme of the algorithm. This leads to a bound on the prediction error of perceptron solutions that depends on the margin a support vector machine would achieve on the same training sample.Furthermore, using the property of compression we derive bounds on the average prediction error of kernel classifiers in the PAC-Bayesian framework. These bounds assume a prior measure over the expansion coefficients in the data-dependent kernel expansion and bound the average prediction error uniformly over subsets of the space of expansion coefficients.Editor Shai Ben-David     

Eine Dienstgüte unterstützende Webservice-Architektur für flexible Geschäftsprozesse

Web services as a technology to enable distributed business processes gain in importance. However, the support of Quality of Service (QoS) is crucial in this context. Thus, we present an integrated web service architecture with comprehensive QoS support. The architecture we introduce in this paper supports the assessment of web services to assure that only web services will be used in critical business processes that satisfy the requirements defined by the user. The selection and execution of a certain web service depends on its QoS-properties that must be guaranteed in Service Level Agreements (SLAs). The compliance with SLAs is monitored by the system as well. Furthermore we introduce a prototypical implementation of our web service architecture.     

Modeling and querying moving objects in networks

Moving objects databases have become an important research issue in recent years. For modeling and querying moving objects, there exists a comprehensive framework of abstract data types to describe objects moving freely in the 2D plane, providing data types such as moving point or moving region. However, in many applications people or vehicles move along transportation networks. It makes a lot of sense to model the network explicitly and to describe movements relative to the network rather than unconstrained space, because then it is much easier to formulate in queries relationships between moving objects and the network. Moreover, such models can be better supported in indexing and query processing. In this paper, we extend the ADT approach by modeling networks explicitly and providing data types for static and moving network positions and regions. In a highway network, example entities corresponding to these data types are motels, construction areas, cars, and traffic jams. The network model is not too simplistic; it allows one to distinguish simple roads and divided highways and to describe the possible traversals of junctions precisely. The new types and operations are integrated seamlessly into the ADT framework to achieve a relatively simple, consistent and powerful overall model and query language for constrained and unconstrained movement.     

Arguments and Misunderstandings: Fuzzy Unification for Negotiating Agents

In this paper, we develop the notion of fuzzy unification and incorporate it into a novel fuzzy argumentation framework for extended logic programming. We make the following contributions: The argumentation framework is defined by a declarative bottom-up fixpoint semantics and an equivalent goal-directed top-down proofprocedure for extended logic programming. Our framework allows one to represent positive and explicitly negative knowledge, as well as uncertainty. Both concepts are used in agent communication languages such as KQML and FIPA ACL. One source of uncertainty in open systems stems from mismatches in parameter and predicate names and missing parameters. To this end, we conservatively extend classical unification and develop fuzzy unification based on normalised edit distance over trees.