Showing papers by "Karlsruhe Institute of Technology published in 2002"

Ontology Learning for the Semantic Web

Abstract: The Semantic Web relies heavily on formal ontologies to structure data for comprehensive and transportable machine understanding. Thus, the proliferation of ontologies factors largely in the Semantic Web's success. The authors present an ontology learning framework that extends typical ontology engineering environments by using semiautomatic ontology construction tools. The framework encompasses ontology import, extraction, pruning, refinement and evaluation.

A multipath model for the powerline channel

Abstract: The development of powerline communication (PLC) systems for Internet, voice, and data services requires measurement-based models of the transfer characteristics of the mains network suitable for performance analysis by simulation. This paper presents an analytic model describing complex transfer functions of typical powerline networks using only a small set of parameters. The model is based on physical signal propagation effects in mains networks including numerous branches and impedance mismatching. Besides multipath propagation accompanied by frequency-selective fading, signal attenuation of typical power cables increasing with length and frequency is considered. A verification of the model at a test network, as well as its use for definition of attenuation profiles and reference channels, demonstrate the practical value of the proposed model.

Analysis and modeling of impulsive noise in broad-band powerline communications

Abstract: Contrary to many other communication channels, the powerline channel does not represent an additive white Gaussian noise environment. In the frequency range from several hundred kilohertz up to 20 MHz, it is mostly dominated by narrow-band interference and impulsive noise. In particular, the impulsive noise introduces significant time variance into the powerline channel. Spectral analysis and time-domain analysis of impulsive noise give some figures of the power spectral density as well as distributions of amplitude, impulse width, and "interarrival" times in typical powerline scenarios. Furthermore, the impulse rate and the disturbance ratio of the scenarios are examined. Finally, a statistical model of the time behavior of random impulsive noise based on a partitioned Markov chain is developed, which is suitable for implementation in computer-based communication system simulations.

Measuring Similarity between Ontologies

Abstract: Ontologies now play an important role for many knowledge-intensive applications for which they provide a source of precisely defined terms However, with their wide-spread usage there come problems concerning their proliferation Ontology engineers or users frequently have a core ontology that they use, eg, for browsing or querying data, but they need to extend it with, adapt it to, or compare it with the large set of other ontologies For the task of detecting and retrieving relevant ontologies, one needs means for measuring the similarity between ontologies We present a set of ontology similarity measures and a multiple-phase empirical evaluation

Driving Current through Single Organic Molecules

Abstract: We investigate electronic transport through two types of conjugated molecules. Mechanically controlled break junctions are used to couple thiol end groups of single molecules to two gold electrodes. Current-voltage characteristics ( IVs) of the metal-molecule-metal system are observed. These IVs reproduce the spatial symmetry of the molecules with respect to the direction of current flow. We hereby unambiguously detect an intrinsic property of the molecule and are able to distinguish the influence of both the molecule and the contact to the metal electrodes on the transport properties of the compound system.

Ant colony optimization for resource-constrained project scheduling

Abstract: An ant colony optimization (ACO) approach for the resource-constrained project scheduling problem (RCPSP) is presented. Several new features that are interesting for ACO in general are proposed and evaluated. In particular, the use of a combination of two pheromone evaluation methods by the ants to find new solutions, a change of the influence of the heuristic on the decisions of the ants during the run of the algorithm, and the option that an elitist ant forgets the best-found solution are studied. We tested the ACO algorithm on a set of large benchmark problems from the Project Scheduling Library. Compared to several other heuristics for the RCPSP, including genetic algorithms, simulated annealing, tabu search, and different sampling methods, our algorithm performed best on average. For nearly one-third of all benchmark problems, which were not known to be solved optimally before, the algorithm was able to find new best solutions.

Ionic Liquids: Solvents for the Electrodeposition of Metals and Semiconductors

Abstract: In a wider sense, ionic liquids are molten salts that melt below 100 °C. As their name suggests, they are solely composed of ions and many combinations of organic and/or inorganic cations and anions exist. Depending on the systems they can reach electrochemical windows of more than 4 V and thus they give access to a number of elements that cannot be electrodeposited from aqueous solutions, such as the light and refractory metals, as well as elemental and compound semiconductors. Presumably, ionic liquids will become important for electrochemical nanotechnology.

CD44 is required for two consecutive steps in HGF/c-Met signaling

Abstract: The tyrosine kinase receptor c-Met and its ligand HGF/SF, ezrin, and splice variants of CD44 have independently been identified as tumor metastasis-associated proteins. We now show that these proteins cooperate. A CD44 isoform containing variant exon v6 sequences is strictly required for c-Met activation by HGF/SF in rat and human carcinoma cells, in established cell lines as well as in primary keratinocytes. CD44v6-deficient tumor cells were unable to activate c-Met unless they were transfected with a CD44v6-bearing isoform. Antibodies to two v6-encoded epitopes inhibited autophosphorylation of c-Met by interfering with the formation of a complex formed by c-Met, CD44v6, and HGF/SF. In addition, signal transduction from activated c-Met to MEK and Erk required the presence of the cytoplasmic tail of CD44 including a binding motif for ERM proteins. This suggests a role for ERM proteins and possibly their link to the cortical actin cytoskeleton in signal transfer.

Computing iceberg concept lattices with TITANIC

Abstract: We introduce the notion of iceberg concept lattices and show their use in knowledge discovery in databases. Iceberg lattices are a conceptual clustering method, which is well suited for analyzing very large databases. They also serve as a condensed representation of frequent itemsets, as starting point for computing bases of association rules, and as a visualization method for association rules. Iceberg concept lattices are based on the theory of Formal Concept Analysis, a mathematical theory with applications in data analysis, information retrieval, and knowledge discovery. We present a new algorithm called TITANIC for computing (iceberg) concept lattices. It is based on data mining techniques with a level-wise approach. In fact, TITANIC can be used for a more general problem: Computing arbitrary closure systems when the closure operator comes along with a so-called weight function. The use of weight functions for computing closure systems has not been discussed in the literature up to now. Applications providing such a weight function include association rule mining, functional dependencies in databases, conceptual clustering, and ontology engineering. The algorithm is experimentally evaluated and compared with Ganter's Next-Closure algorithm. The evaluation shows an important gain in efficiency, especially for weakly correlated data.

Multi-sensor context-awareness in mobile devices and smart artifacts

Abstract: The use of context in mobile devices is receiving increasing attention in mobile and ubiquitous computing research. In this article we consider how to augment mobile devices with awareness of their environment and situation as context. Most work to date has been based on integration of generic context sensors, in particular for location and visual context. We propose a different approach based on integration of multiple diverse sensors for awareness of situational context that can not be inferred from location, and targeted at mobile device platforms that typically do not permit processing of visual context. We have investigated multi-sensor context-awareness in a series of projects, and report experience from development of a number of device prototypes. These include development of an awareness module for augmentation of a mobile phone, of the Mediacup exemplifying context-enabled everyday artifacts, and of the Smart-Its platform for aware mobile devices. The prototypes have been explored in various applications to validate the multi-sensor approach to awareness, and to develop new perspectives of how embedded context-awareness can be applied in mobile and ubiquitous computing.

Deconvolution of electrochemical impedance spectra for the identification of electrode reaction mechanisms in solid oxide fuel cells

Abstract: The polarization processes occurring at the electrode–electrolyte interfaces of solid oxide fuel cells (SOFC) were investigated by electrochemical impedance spectra measured at single cells under realistic operating conditions. The approach presented is based on distributions of relaxation times which are the basic quantity of interest in electrochemical impedance data analysis. A deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra. In contrast to nonlinear least squares curve fit of equivalent circuit models, no a priori circuit choice has to be made. Even more importantly, the excellent resolving capacity allows the untangling of the impedance contributions of up to three physically distinct processes within one frequency decade. With the method, processes with the highest polarization losses can be identified and targeted to improve cell performance. Based on the distributions, a general strategy for the identification of the reaction mechanisms is given. The evaluation of the distributions in terms of peak parameters is illustrated by a physical model for oxygen reduction at the SOFC cathode–electrolyte interface. The method is expected to find many applications in electrochemistry beyond the field of solid oxide fuel cell development.

Signal-dependent regulation of splicing via phosphorylation of Sam68

Abstract: Evolution of human organismal complexity from a relatively small number of genes1,2—only approximately twice that of worm or fly—is explained mainly by mechanisms generating multiple proteins from a single gene, the most prevalent of which is alternative pre-messenger-RNA splicing1,3,4. Appropriate spatial and temporal generation of splice variants demands that alternative splicing be subject to extensive regulation, similar to transcriptional control. Activation by extracellular cues of several cellular signalling pathways can indeed regulate alternative splicing5,6,7,8. Here we address the link between signal transduction and splice regulation. We show that the nuclear RNA-binding protein Sam68 is a new extracellular signal-regulated kinase (ERK) target. It binds exonic splice-regulatory elements of an alternatively spliced exon that is physiologically regulated by the Ras signalling pathway, namely exon v5 of CD44. Forced expression of Sam68 enhanced ERK-mediated inclusion of the v5-exon sequence in mRNA. This enhancement was impaired by mutation of ERK-phosphorylation sites in Sam68, whereas ERK phosphorylation of Sam68 stimulated splicing of the v5 exon in vitro. Finally, Ras-pathway-induced alternative splicing of the endogenous CD44-v5 exon was abolished by suppression of Sam68 expression. Our data define Sam68 as a prototype regulator of alternative splicing whose function depends on protein modification in response to extracellular cues.

Web engineering

Abstract: Web Engineering is the application of systematic, disciplined and quantifiable approaches to development, operation, and maintenance of Web-based applications. It is both a pro-active approach and a growing collection of theoretical and empirical research in Web application development. This paper gives an overview of Web Engineering by addressing the questions: a) why is it needed? b) what is its domain of operation? c) how does it help and what should it do to improve Web application development? and d) how should it be incorporated in education and training? The paper discusses the significant differences that exist between Web applications and conventional software, the taxonomy of Web applications, the progress made so far and the research issues and experience of creating a specialisation at the master's level. The paper reaches a conclusion that Web Engineering at this stage is a moving target since Web technologies are constantly evolving, making new types of applications possible, which in turn may require innovations in how they are built, deployed and maintained.

OntoEdit: Collaborative Ontology Development for the Semantic Web

Abstract: Ontologies now play an important role for enabling the semantic web. They provide a source of precisely defined terms e.g. for knowledge-intensive applications. The terms are used for concise communication across people and applications. Typically the development of ontologies involves collaborative efforts of multiple persons. OntoEdit is an ontology editor that integrates numerous aspects of ontology engineering. This paper focuses on collaborative development of ontologies with OntoEdit which is guided by a comprehensive methodology.

Deconvolution of electrochemical impedance spectra for the identification of electrode reaction mechanisms in solid oxide fuel cells

Abstract: The polarization processes occurring at the electrode-electrolyte interfaces of solid oxide fuel cells (SOFC) were investigated by electrochemical impedance spectra measured at single cells under realistic operating conditions. The approach presented is based on distributions of relaxation times which are the basic quantity of interest in electrochemical impedance data analysis. A deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra. In contrast to nonlinear least squares curve fit of equivalent circuit models, no a priori circuit choice has to be made. Even more importantly, the excellent resolving capacity allows the untangling of the impedance contributions of up to three physically distinct processes within one frequency decade. With the method, processes with the highest polarization losses can be identified and targeted to improve cell performance. Based on the distributions, a general strategy for the identification of the reaction mechanisms is given. The evaluation of the distributions in terms of peak parameters is illustrated by a physical model for oxygen reduction at the SOFC cathode-electrolyte interface. The method is expected to find many applications in electrochemistry beyond the field of solid oxide fuel cell development.

User-Driven Ontology Evolution Management

Abstract: With rising importance of knowledge interchange, many industrial and academic applications have adopted ontologies as their conceptual backbone. However, industrial and academic environments are very dynamic, thus inducing changes to application requirements. To fulfill these changes, often the underlying ontology must be evolved as well. As ontologies grow in size, the complexity of change management increases, thus requiring a well-structured ontology evolution process. In this paper we identify a possible six-phase evolution process and focus on providing the user with capabilities to control and customize it. We introduce the concept of an evolution strategy encapsulating policy for evolution with respect to user?s requirements.

S-CREAM - Semi-automatic CREAtion of Metadata

Abstract: Richly interlinked, machine-understandable data constitute the basis for the Semantic Web. We provide a framework, S-CREAM, that allows for creation of metadata and is trainable for a specific domain. Annotating web documents is one of the major techniques for creating metadata on the web. The implementation of S-CREAM, OntoMat-Annotizer supports now the semi-automatic annotation of web pages. This semi-automatic annotation is based on the information extraction component Amilcare. OntoMat-Annotizer extract with the help of Amilcare knowledge structure from web pages through the use of knowledge extraction rules. These rules are the result of a learning-cycle based on already annotated pages.

Molecular and catalytic properties of phytate‐degrading enzymes (phytases)

Abstract: Summary Phytate-degrading enzymes catalyse the step-wise release of phosphate from phytate, the principle storage form of phosphorus in plant seeds and pollen.They are widespread in nature, occurring in plants and micro-organisms, as well as in some animal tissues. Phytate-degrading enzymes have been studied intensively in recent years because of the great interest in such enzymes for reducing phytate content in animal feed and food for human consumption.Phytate-degrading enzymes are also of interest for producing defined breakdown products of phytate for kinetic and physiological studies.Certain myo-inositol phosphates have been proposed to have novel metabolic effects and therefore, the physiological role of different myo-inositol phosphates is presently undergoing extensive research.Generally, phytase behaves like a monomeric enzyme with molecular masses between 40 and 70 kDa.Up to now, two main types of phytate-degrading enzymes have been identified; acid phytate-degrading enzymes with an pH optimum around pH 5 and alkaline phytate-degrading enzymes with an pH optimum around pH 8.Most of the so far described phytate-degrading enzymes belong to the acidic type, and their optimal pH ranges from 4.5 to 6.0. This review summarises the molecular features as well as catalytic properties of phytate-degrading enzymes and also discusses enzymatic phytate degradation.

On the knee in the energy spectrum of cosmic rays

Abstract: Results from direct and indirect measurements of cosmic rays are reviewed. Emphasis is given to the understanding of the knee in the energy spectrum. The data are compared to contemporary models for the knee. Implications on the present understanding of the origin of galactic cosmic rays are discussed.

Upper limits for neutrino oscillations ν ¯ μ → ν ¯ e from muon decay at rest

Abstract: The KARMEN experiment at the spallation neutron source ISIS used ${\overline{\ensuremath{ u}}}_{\ensuremath{\mu}}$ from ${\ensuremath{\mu}}^{+}$ decay at rest for the search of neutrino oscillations ${\overline{\ensuremath{ u}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{ u}}}_{e}$ in the appearance mode, with $p({\overline{\ensuremath{ u}}}_{e}{,e}^{+})n$ as a detection reaction of ${\overline{\ensuremath{ u}}}_{e}.$ In total, 15 candidates satisfy all conditions for the ${\overline{\ensuremath{ u}}}_{e}$ signature, in agreement with the background expectation of $15.8\ifmmode\pm\else\textpm\fi{}0.5$ events, yielding no indication for oscillations. A single event based likelihood analysis leads to upper limits on the oscillation parameters ${\mathrm{sin}}^{2}(2\ensuremath{\Theta})l1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ for $\ensuremath{\Delta}{m}^{2}g~100 {\mathrm{eV}}^{2}$ and $\ensuremath{\Delta}{m}^{2}l0.055 {\mathrm{eV}}^{2}$ for ${\mathrm{sin}}^{2}(2\ensuremath{\Theta})=1$ at 90% confidence. Thus, KARMEN does not confirm the LSND experiment and restricts significantly its favored parameter region for ${\overline{\ensuremath{ u}}}_{\ensuremath{\mu}}\ensuremath{\rightarrow}{\overline{\ensuremath{ u}}}_{e}.$

The building stock as a research object

Abstract: Activities related to refurbishment of the building stock as a percentage of all building work have been constantly growing in most central European countries over the last 20 years. The main argument in this paper is the need to improve knowledge about composition of the existing building stock, the dynamics of its transformation and to relate this to the different actors in property professions. A review is presented of traditional and new sectoral research approaches to partial or national building stocks to provide a context for assessing an integrated approach to the German building stock with methodological propositions for improving the synergy between different sectoral approaches. Detailed consideration is given to life cycle analysis, building product modelling, historical building research and new simulation techniques. Sustainability indicators and the integration of building stock, infrastructure and land use are discussed. Depuis une vingtaine d'annees, les activites liees a la rehabilitatio...

The MUSIC-algorithm and the factorization method in inverse scattering theory for inhomogeneous media

Abstract: We consider the scattering of time-harmonic plane waves by an inhomogeneous medium. The far field patterns u? of the scattered waves depend on the index of refraction 1 + q, the frequency, and directions and of observation and incidence, respectively. The inverse problem which is studied in this paper is to determine the support ? of q from the knowledge of u? (, ) for all , where the frequency is fixed (and known). Our new approach is based on the far field operator F which is the integral operator with kernel u? (, ). It depends on the data only and is therefore known (at least approximately). The MUSIC algorithm in signal processing uses the discrete version of F, i.e. the matrix F = (u? ( i, j)) N?N, and determines the locations of the point scatterers. The key idea in both cases is to factorize F and F in the forms where the operator S and the matrix S are 'more explicit' than F and F, respectively, and T, T are suitable isomorphisms. In a first theoretical result we show that the ranges of S and F# coincide, where F# is some suitable combination of the real and imaginary parts of F. In the finite dimensional case a simple argument from matrix theory yields that the ranges of S and F coincide. Since F# is known from the data we can decide for every function on the unit sphere whether it belongs to the range of S or not. We apply this test to the far field patterns of point sources and arrive at an explicit test whether a point z belongs to ? or not. We will demonstrate that this method also leads to a fast visualization of the obstacle.

Interference by toxic metal ions with DNA repair processes and cell cycle control: molecular mechanisms.

Abstract: Nickel, cadmium, cobalt, and arsenic compounds are well-known carcinogens to humans and experimental animals. Even though their DNA-damaging potentials are rather weak, they interfere with the nucleotide and base excision repair at low, noncytotoxic concentrations. For example, both water-soluble Ni(II) and particulate black NiO greatly reduced the repair of DNA adducts induced by benzo[a]pyrene, an important environmental pollutant. Furthermore, Ni(II), As(III), and Co(II) interfered with cell cycle progression and cell cycle control in response to ultraviolet C radiation. As potential molecular targets, interactions with so-called zinc finger proteins involved in DNA repair and/or DNA damage signaling were investigated. We observed an inactivation of the bacterial formamidopyrimidine-DNA glycosylase (Fpg), the mammalian xeroderma pigmentosum group A protein (XPA), and the poly(adenosine diphosphate-ribose)polymerase (PARP). Although all proteins were inhibited by Cd(II) and Cu(II), XPA and PARP but not Fpg were inhibited by Co(II) and Ni(II). As(III) deserves special attention, as it inactivated only PARP, but did so at very low concentrations starting from 10 nM. Because DNA is permanently damaged by endogenous and environmental factors, functioning processing of DNA lesions is an important prerequisite for maintaining genomic integrity; its inactivation by metal compounds may therefore constitute an important mechanism of metal-related carcinogenicity.

Construction, test and commissioning of the triple-gem tracking detector for compass

Abstract: The Small Area Tracking system of the COMPASS experiment at CERN includes a set of 20 large area, fast position-sensitive Gas Electron Multiplier detectors, designed to reliably operate in the harsh radiation environment of the experiment. We describe in detail the design, choice of materials, assembly procedures and quality controls used to manufacture the devices. The test procedure in the laboratory, the performance in test beams and in the initial commissioning phase in the experiment are presented and discussed.

The tracking detector of the KLOE experiment

Abstract: The design and construction of the large Drift Chamber for the KLOE experiment at the Frascati φ-factory, DAΦNE, are described. The relevant aspects of the various elements of the detector are reviewed together with a description of the track reconstruction program and of the calibration procedures. The performance of the detector based on measurements with cosmic rays and with e+e− colliding beams during DAΦNE commissioning is presented.

Authoring and annotation of web pages in CREAM

Abstract: Richly interlinked, machine-understandable data constitute the basis for the Semantic Web. We provide a framework, CREAM, that allows for creation of metadata. While the annotation mode of CREAM allows to create metadata for existing web pages, the authoring mode lets authors create metadata --- almost for free --- while putting together the content of a page.As a particularity of our framework, CREAM allows to create relational metadata, i.e. metadata that instantiate interrelated definitions of classes in a domain ontology rather than a comparatively rigid template-like schema asm Dublin Core. We discuss some of the requirements one has to meet when developing such an ontology-based framework, e.g. the integration of a metadata crawler, inference services, document management and a meta-ontology, and describe its implementation, viz. Ont-O-Mat, a component-based, ontology-driven Web page authoring and annotation tool.