Investigation of long term drift of an intraocular pressure sensor

Microsystem Technologies - “Zero drift” behavior of an optical intraocular pressure sensor is studied using an analytical model based on the deflection of a circular membrane. Results...     

Semantical investigations into nonmonotonic and probabilistic logics

Different forms of semantics have been proposed for conditionals of the form “Usually, if A then B”, ranging from quantitative probability distributions to qualitative approaches using plausibility orderings, possibility distributions, or conditional objects. Atomic-bound systems, also called big-stepped probabilities, allow qualitative reasoning with probabilities, aiming at bridging the gap between qualitative and quantitative argumentation and providing a model for the nonmonotonic reasoning system P. By using Goguen and Burstall’s notion of institutions for the formalization of logical systems, we elaborate precisely which formal connections exist among big-stepped probabilities, standard probabilities, and qualitative logics. Based on our investigations, we also develop two variants of conditional objects, one of them having a simpler semantics while still providing a model for system P.     

Analysis of time-dependent flow-sensitive PC-MRI data

Many flow visualization techniques, especially integration-based methods, are problematic when the measured data exhibit noise and discretization issues. Particularly, this is the case for flow-sensitive phase-contrast magnetic resonance imaging (PC-MRI) data sets which not only record anatomic information, but also time-varying flow information. We propose a novel approach for the visualization of such data sets using integration-based methods. Our ideas are based upon finite-time Lyapunov exponents (FTLE) and enable identification of vessel boundaries in the data as high regions of separation. This allows us to correctly restrict integration-based visualization to blood vessels. We validate our technique by comparing our approach to existing anatomy-based methods as well as addressing the benefits and limitations of using FTLE to restrict flow. We also discuss the importance of parameters, i.e., advection length and data resolution, in establishing a well-defined vessel boundary. We extract appropriate flow lines and surfaces that enable the visualization of blood flow within the vessels. We further enhance the visualization by analyzing flow behavior in the seeded region and generating simplified depictions.     

Rigid body dynamics with a scalable body,quaternions and perfect constraints

In this paper, we present a formulation of the quaternion constraint for rigid body rotations in the form of a standard perfect bilateral mechanical constraint, for which the associated Lagrangian multiplier has the meaning of a constraint force. First, the equations of motion of a scalable body are derived. A scalable body has three translational, three rotational, and one uniform scaling degree of freedom. As generalized coordinates, an unconstrained quaternion and a displacement vector are used. To the scalable body, a perfect bilateral constraint is added, restricting the quaternion to unit length and making the body rigid. This way a quaternion based differential algebraic equation (DAE) formulation for the dynamics of a rigid body is obtained, where the 7×7 mass matrix is regular and the unit length restriction of the quaternion is enforced by a mechanical constraint. Finally, the equations of motion in the form of a DAE are linked to the Newton–Euler equations of motion of a rigid body. The rigid body DAE formulation is useful for the construction of (energy) consistent integrators.     

Coverage-biased random exploration of large models and application to testing

This paper presents several randomised algorithms for generating paths in large models according to a given coverage criterion. Using methods for counting combinatorial structures, these algorithms can efficiently explore very large models, based on a graphical representation by an automaton or by a product of several automata. This new approach can be applied to random exploration in order to optimise path coverage and can be generalised to take into account other coverage criteria, via the definition of a notion of randomised coverage satisfaction. Our main contributions are a method for drawing paths uniformly at random in composed models, i.e. models that are given as products of automata, first without and then with synchronisation; a new efficient approach to draw paths at random taking into account some other coverage criterion. Experimental results show promising agreement with theoretical predictions and significant improvement over previous randomised approaches. This work opens new perspectives for future studies of statistical testing and model checking, mainly to fight the combinatorial explosion problem.     

Digital repository: preservation environment and policy implementation

Distributed digital repositories can be used to address critical issues of long-term digital preservation and disaster management for large data centers. A policy-driven system provides an ideal solution for managing distributed repositories that require high flexibility and high configurability. Recent studies demonstrate that the integrated Rule-Oriented Data System, a peer-to-peer server middleware, provides the requisite dynamic extensibility needed to manage time-varying policies, automate validation of assessment criteria, manage ingestion processes, manage access policies, and manage preservation policies. The policy management can be implemented underneath existing digital library infrastructure such as Fedora.     

Nachweis von Maillard-Produkten in Malzen, Bieren und Braucouleuren

Zusammenfassung Bei der Maillard-Reaktion reagieren primär reduzierende Zucker mit den freien Aminogruppen der Aminosäuren. Dabei entstehen aus Aldosen als erste stabile Zwischenprodukte die 1-Aminosäure-1-desoxy-ketosen (Amadori-Verbindungen). In Malzen konnten zehn Amadori-Verbindungen quantitativ bestimmt werden. Sie entstehen während des Darrens des Malzes. Aufgrund unterschiedlicher Darrbedingungen unterscheiden sich die Malztypen im Gehalt und im Muster dieser Substanzen. Während der Erhitzungsvorgänge beim Brauprozeß (Maischen, Würzekochung) werden die Amadori-Verbindungen etwa zur Hälfte abgebaut, dagegen sind bei der an schließenden Gärung keine Veränderungen zu beobachten. Aus dem Gehalt und dem Muster der Amadori-Verbindungen im Bier können somit Rückschlüsse auf das verwendete Malz gezogen werden. Bei der Herstellung von Braucouleuren werden Ammoniak bzw. Ammoniumverbindungen als Aminokomponenten eingesetzt. Die Couleure enthalten deshalb keine 1-Aminosäure-l-desoxy-ketosen, dafür aber Desoxyfructosazine, die bei der Reaktion von Zuckern mit Ammoniak entstehen. Diese Pyrazinderivate wurden in Braucouleuren in hohen Mengen (2–6 g/100 g) gefunden. Es wird eine Methode vorgestellt, mit der ein Zusatz von Braucouleuren zum Bier über die Bestimmung der Desoxyfructosazine eindeutig nachgewiesen werden kann.

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Detection of Maillard products in malts, beers, and brewing couleurs

During the Maillard reaction, the reducing sugars first react with the free amino groups of the amino acids. With aldoses, 1-amino-l-deoxyketoses (ketose-amino acids, Amadori compounds) are the first stable intermediates to be formed. In malts ten different Amadori compounds could be determined that formed during the kiln-drying of malt. Dependent on the kiln-drying conditions, the different types of malt contain different amounts and proportions of these compounds. During the brewing process (mashing, mash wort cooking) about half of the Amadori compounds are decomposed, whereas during fermentation no changes can be observed. Therefore the amount and composition of Amadori compounds detected in beer may indicate the type of malt used. During the production of brewing couleurs, ammonia or ammonium compounds react with sugars and deoxyfructosazines are formed. In brewing coleurs, relatively high amount of these pyrazine derivatives (2–6 g/100 g) could be found. An analytical method is described for the quantitative determination of deoxyfructosazines, indicating an addition of brewing couleur to beer.

     

Untersuchungen an Caramel Curiepunkt-Pyrolyse von Caramelzuckersirupen und andere strukturspezifische Untersuchungen

Zusammenfassung Es wird über die Curiepunkt-Pyrolyse handelsüblicher Caramelzuckersirup-Proben und die Identifizerung von über 80 Pyrolysefragmenten durch kombinierte Capillargaschromatographie/ Massenspektrometrie berichtet. Mit dieser Methode sind die Proben untereinander and gegenüber Couleuren differenzierbar. Mittels Ultrafiltration wurden die Komponenten einer intensiv braunen Probe in Fraktionen unterschiedlicher Molekülmasse getrennt and nach Pyrolyse miteinander verglichen. In einer niedermolekularen Fraktion wurden nach Permethylierung Laevoglucosan, 1,6-Anhydro--d-glucofuranose, Trehalose, Cellobiose, Maltose, Isomaltose und Gentiobiose Bowie einige Difructosedianhydride nachgewiesen.

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Investigations of caramel. Curiepoint pyrolysis of caramel syrups and other investigations of structure

Summary A report is given on the investigation of commercial caramel syrups by Curiepoint pyrolysis and the identification of more than 80 pyrolysis products by capillary gas chromatography mass spectrometry. This method enables the differentiation between different caramel syrups and, additionally, between caramel syrups and caramel colours. Compounds of different molecular masses have been examined in the same manner after they have been isolated from an intense brown caramel sample by ultrafiltration. In a fraction consisting of compounds with low molecular masses laevoglucosan, 1,6-anhydro--d-glucofuranose, trehalose, cellobiose, maltose, isomaltose, gentiobiose and some difructosedianhydrides were identified by GC/MS after permethylation.

     

Gaschromatographisch-massenspektrometrische Untersuchung der im Modellsystem Cystein/Methionin/Furfural unter R?stbedingungen gebildeten Aromastoffe

Zusammenfassung Das Modellsystem Cystein/Methionin/Furfural lieferte unter Röstbedingungen ein komplexes Reaktionsgemisch, das sich mittels Adsorptionschromatographie auf Kieselgel und Capillar-GC in ca. 130 Komponenten auftrennen ließ, von denen 85 capillargaschromatographisch-massenspektrometrisch charakterisiert wurden. Furfural und die aus Cystein und Methionin resultierenden reaktiven Abbauprodukte H₂S, Cysteamin und Methylmercaptan sind wichtige Precursor für heterocyclische Flavorkomponenten. Neben Furanen, (Furan)-aldiminen und schwefelsubstituierten Furanderivaten werden auchN-Furfurylpyrrole, Pyridine, Thiazole, Thiazoline, Thiazolidine, Thiophene sowie aliphatische Schwefelverbindungen und cyclische Methylenpolysulfide gebildet. Beim Kaffeerösten entsteht Furfural als eine der Furanhauptkomponenten und spielt bei der Genese wesentlicher Kaffeearomastoffe eine zentrale Rolle.

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Gaschromatographic-mass spectrometric investigation of aroma compounds from the reaction of cysteine and methionine with furfural under roasting conditions

Summary The model-system cysteine/methionine/furfural produced under roasting conditions a complex mixture of compounds which was separated by adsorption chromatography on silica gel, according to the increasing polarity of the components, into six fractions. The fractions were investigated by capillary gas chromatography with and without mass spectrometry. Of the approx. 130 compounds detected, 85 were identified and quantified. Furfural and the reactive degradation products H₂S, cysteamine and methylmercaptan, resulting from cysteine and methionine, are important precursors for heterocyclic flavor components. Besides furans, (furan)aldimines, and sulphur-substituted furan derivates, the following compounds are also formed:N-furfurylpyrroles, pyridines, thiazoles, thiazolines, thiazolidines, thiophenes, as well as aliphatic sulphur compounds and cyclic methylene polysulfides. During coffee roasting, furfural is produced as one of the major components of the furans and is essential for the formation of important coffee aroma constituents.

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Poster-Präsentation beim Deutschen Lebensmittelchemikertag in Bremen (14.–16. Sept. 1988)     

Bestimmung des Herbicids Glyphosat und dessen Hauptmetabolit Aminomethylphosphons?ure (AMPA) in Trinkwasser mit Hilfe der HPLC

Zusammenfassung Es wird eine Methode zur Bestimmung von Glyphosat und dessen Hauptmetabolit Aminomethylphosphonsäure (AMPA) in Trinkwasser beschrieben, die es erlaubt, den in der Schweiz geforderten Toleranzwert von 0,1 g/1 zu erreichen (Nachweisgrenze 0,02 g/l). Die Wasserprobe wird dabei direkt mit 9-Fluorenylmethyl-chloroformaat (FMOCCI) versetzt, um extrahierbare und gleichzeitig fluorescierende Derivate zu erhalten. Diese werden nach Ausschütteln mit einem organischen Lösungsmittelgemisch durch HPLC mit Fluorescenzdetektor bestimmt. In bisher 151 untersuchten Trinkwasserproben des Kantons Bern konnten weder Glyphosat noch AMPA nachgewiesen werden.

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Determination of glyphosate herbicide and its main metabolite aminomethylphosphonic acid (AMPA) in drinking water by HPLC

Summary A method for the determination of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) is described. With a detection limit of 0.02 g/l, the method suitably fulfills the requirements of the Swiss legislation (tolerance value of 0.1 g/l water). The compounds are derivatized directly in the original water sample with 9-fluorenylmethyl chloroformate (FMOCCI) in order to obtain extractable and fluorescent derivatives. These are extracted with organic solvents and determined by HPLC using a fluorescence detector. Neither of the compounds could be detected in 151 tap water samples from the Canton of Berne.