Showing papers by "University of Bremen published in 1979"

The Influence of External Real and White Noise on the LOTKA‐VOLTERRA Model

Abstract: The behaviour of a marginally stable predator‐prey system, the LOTKA‐VOLTERRA model is analyzed under the influence of parameter fluctuations. The cases of white and real noise are studied separately. It is shown that for white noise no stationary solution exists, but even for time tending to infinity explosion occurs only with zero probability. In the case of real noise the class of noise processes that permit a stationary solution is characterized by their spectral density. It turns out that this class consists of all stationary processes that do not contain the eigenfrequencies of the LOTKA‐VOLTERRA system. It is shown that for all other real noise processes a resonance phenomenon occurs and the solutions grow unboundedly. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA

A model for the chemical interactions of adenosine 3':5'-monophosphate with the R subunit of protein kinase type I. Refinement of the cyclic phosphate binding moiety of protein kinase type I.

Abstract: The cAMP receptor site in the regulatory subunit of adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase type I was mapped using analogues of cAMP in which the ribose phosphate moiety was systematically modified. Electronical alteration of the cyclophosphate ring at the 3' and 5' positions by sulfur and nitrogen decreased the affinity of these analogues towards the kinase. Substituents at these positions are not tolerated. Testing the separated diastereomers of derivatives in which one of the exocyclic oxygens at the phosphorus has been substituted by sulfur, it was found that one diastereoisomer is preferentially recognized. Based on these results it is proposed that the hydrophylic cyclic phosphate-ribose moiety of cAMP is bound to the kinase via its 3' and 5'-oxygens, the 2'-hydroxy group and the negative charge in a fixed position. Based on our and other published results it is further proposed, that the adenine moiety is bound in a hydrophobic cleft without any hydrogen bond interactions. The chemical interactions between cAMP and the R subunit of protein kinase type I differ from those found for the binding of cAMP to the chemoreceptor of Dictyostelium discoideum [18].

Identification by combined gas chromatography-mass spectrometry of phaseic acid and dihydrophaseic acid and characterization of further abscisic acid metabolites in pea seedlings.

Abstract: Seven day old seedlings of Pisum sativum L., cv. Kleine Rheinlanderin, were wilted for 3 days. After partially removing the roots, they were rewatered and at the same time radioactive abscisic acid([1-14C]ABA, spec. activity 1.7·108d s-1mmol-1) was applied for 1 h via the xylem of the roots. After 24 h, 4 days, and 12 days the seedlings were extracted and the metabolites of ABA were analyzed by means of thin-layer and gas chromatography in combination with mass spectrometry, autoradiography, and scintillation counting. Phaseic acid (PA) and dihydrophaseic acid (DPA) were identified as metabolites of ABA. The presence of another ABA-metabolite was also demonstrated. From its mass spectrum it has been postulated that this metabolite is 4′-desoxy-ABA. In addition to these substances, several other metabolites, which are more polar than ABA and its known degradation products, were present in the seedlings. The quantity and number of these unknown metabolites increased with time.

Associations between atopic diseases and the polymorphic systems ABO, Kidd, Inv and red cell acid phosphatase.

Abstract: In 239 German patients with atopic conditions (atopic dermatitis, hay fever, allergic rhinitis, bronchial asthma, and acute urticaria) the phenotype and gene distribution of 15 genetic blood polymorphisms (ABO, MNSs, Rhesus, P, Kell, Duffy, Kidd, Hp, Gc, Gm, Inv, aP, PGM1, EsD, and 6-PGD) were analyzed and compared with those in 151 selected controls (individuals clinically free of allergic conditions and without allergy in the family history). The incidence of blood group antigens A and B was somewhat higher in patients than in controls. These observations are in accordance with the results of previous studies in other populations. In addition, our observation favor the hypothesis that there are also associations between the phenotypes Jk (a-b+), Inv(1) and red cell acid phosphatase aP a and aP AP on the one hand and atopic disposition on the other. The possible reasons for these associations are discussed.

Essentially complete TO-spaces

Abstract: For a topological space X (a), (b), (c), (d) are equivalent: (a) X is an essentially complete To-space. (b) (i) X is sober; (ii) X is an upper semi-lattice with o with regard to its induced partial order such that the binary sup: X × X → X is continuous. (c) (i) X is a To-space; (ii) X is a complete lattice in its induced partial order such that for every set I the I-indexed sup: XI → X is continuous (d) (i) For every ordinary proper filter F on X there is a unique x ∈ X with X=conv\(\dot x^ - _1 \). —The essential hull λ X of a To-space X can be constructed as a space of “convergence sets”. —Suitably topologizing a poset (X, ≤) one obtains (i) Frink's ideal completion, (ii) MacNeille's completion as the lattice underlying .

Minimal bases of polynomial modules, structural indices and Brunovsky-transformations

Abstract: Structural indices and state feedback of finite dimensional linear systems are analysed with the help of elementary module theory. The basic modules are polynomial and have a natural graduation. With respect to this graduation the concepts of minimal bases and degree preserving isomorphisms are introduced. Thus it becomes possible to give a module theoretic interpretation of the different definitions of structural indices. They are reduced to invariants of a special submodule of Km[s] which is also crucial for the understanding of Brunovsky-transformations. It is shown that the Brunovsky-transformations induce families of degree-preserving module isomorphisms. A detailed study of this fact leads to results concerning pole assignment via state feedback, classification of orbits of the Brunovsky-group and canonical forms.

Fractioned heart rate variability. Part II: Experiments on superimposition of components of stress.

Abstract: The part of heart rate variability, linked to non-physical stress, is explored in experiments changing systematically peripheral motor strain, speed and difficulty of mental tasks, taking into account the duration of the experimental session. The physiological reaction is fractioned into components of strain according to the mental load and the arousal model.

On the incidence of blood group O and Gm(-1) phenotypes in patients with malignant melanoma.

Abstract: Fifteen polymorphic systems of the blood (ABO, MNSs, Rhesus, P, Kell, Duffy, Kidd, Hp, Gc, Gm, Inv, aP, PGM1, EsD, and 6-PGD) were examined in 191 unrelated male and female patients suffering from malignant melanoma. These polymorphic systems were compared with the corresponding phenotype and gene frequencies of controls from the same geographical area (Rhineland-Palatinate). The only associations discovered were the ABO and Gm polymorphisms: The incidence of O and Gm(-1) phenotypes in patients is obviously higher than in controls. These observations agree with the findings in other population samples from Germany and Bulgaria.

Conversion of methanol to hydrocarbons over metal-zeolite catalysts

Abstract: Ni2+, Cr3+ and Pb2+ exchanged CaY zeolites including mixed forms like CrNiCaY and PbNiCaY were used to study methanol conversion. The selectivity of the reaction to olefin and paraffin formation depends on the type of samples, the activation of the catalyst and the reaction conditions.

Verfahren zur Reinigung von n-Pentan für die Gaschromatographie insbesondere mit EC-Detektoren

Abstract: Durch die Kombination von Destillation uber XAD-Harz und Nachbehandlung mit aktiviertem Magnesium werden bei einem Rucklaufverhaltnis von 1∶2 und bei Verwendung von Pentan minderer Qualitat (beispielsweise „technischer Qualitat”) alle ECD-aktiven organischen Verbindungen bis unterhalb der Nachweisgrenze entfernt. Die Ausbeute an gereinigtem Pentan betragt je nach Ausgangsqualitat mindestens 90%. Im weiteren ergibt sich uber diese Reinigungsprozedur in unseren Laboren die Moglichkeit des Losungsmittel-Recycling. Im Augenblick konnen ca. 80% der eingesetzten Losungsmittelmenge einer Wiederverwendung zuganglich gemacht werden. Das oben beschriebene Verfahren wird von uns mittlerweile seit einem Jahr eingesetzt. Nennenswerte Storungen traten bisher nicht auf [5].

Zielsetzungen und Instrumentarien der europäischen Verbraucherrechtspolitik: Eine Analyse von Entwicklungen im Bereich des Zivilrechts

Abstract: Der Beitrag untersucht die europaische Verbraucherschutzpolitik im Bereich des Zivilrechts und konzentriert sich dabei auf das Verhaltnis der verbraucherpolitischen Programmatik zu den Handlungsinstrumentarien der europaischen Rechtspolitik. Der erste Untersuchungsschritt analysiert die konzeptionellen Grundlagen des verbraucherpolitischen Programms der EG von 1975 und der seither vorgelegten Entwurfe zur Produzentenhaftung, zum Werberecht, zu den Hausturgeschaften und zum Fernunterricht. Insgesamt entspricht die Entwicklung auf europaischer Ebene den auch national vorherrschenden Ansatzen: Die Verbraucherrechtspolitik erganzt die auf den Parallelprozes zwischen den Anbietern bezogene Wettbewerbsrechtspolitik durch Masnahmen, die sich auf die Austauschbeziehungen zwischen Produzenten und Konsumenten beziehen. Vorausgesetzt wird jeweils, das sich Konsumenteninteressen uber Marktprozesse durchsetzen mussen und deshalb Masnahmen, die durch die Kontrolle von Werbeaussagen, durch die Gewahrleistung eines okonomisch-rationalen Konsumentenverhaltens, durch Sanktionen gegen die Enttauschung berechtigter Erwartungen von Konsumenten die Funktionsfahigkeit der Marktprozesse verbessern, damit auch den Konsumenteninteressen entsprechen. Das wichtigste Mittel zur Umsetzung der europaischen Verbraucherpolitik bildet die Rechtsangleichung durch Richtlinien gem. Art. 100, 189 Abs. 3 EWG-V. Den Zielsetzungen einer marktbezogenen Verbraucherpolitik entspricht dieses Institut insofern, als es seinerseits als ein Instrument zur Gewahrleistung des «Funktionierens des Gemeinsamen Marktes» gehandhabt werden kann (vgl. Art. 3 h EWG-V). Diese Harmonie von Verbraucherpolitik und Rechtsangleichungspolitik ist jedoch nicht dauerhaft gewahrleistet. In der Verbraucherpolitik selbst erweist sich zunehmend, das bei dem Versuch, den Austauschprozes zwischen Produzenten und Konsumenten inhaltlich zu kontrollieren, dem Recht Steuerungsaufgaben zugemutet werden mussen. Dabei entsteht uberdies ein Bedurfnis, verbraucherpolitische Masnahmen mit anderen Politikbereichen zu koordinieren. Solchen Entwicklungen kann eine auf die Beseitigung von Handelshemmnissen und Wettbewerbsverzerrungen ausgerichtete Rechtsangleichung kaum angemessen Rechnung tragen. Die «Harmonisierung» der Verbraucherpolitik wird dadurch zu einer Aufgabe, die zusatzliche Koordinationsleistungen verlangt. Inhaltlich last sich diese Aufgabe mit den Zielen einer «harmonischen Entwicklung des Wirtschaftslebens» und einer «stetigen Besserung der Lebensbedingungen» in Verbindung bringen (vgl. Art. 2 und die Praambel des EWG-V). Als rechtliche Techniken, die zur Umsetzung einer derart fortentwickelten Verbraucherrechtspolitik zur Verfugung stehen, kommen neben der Festlegung materiell-rechtlicher Minimumstandards der Ausbau des Kollisionsrechts und die Bildung spezifischer, auf die Internationalisierung von Produktion und Absatz zugeschnittener Sachnormen in Betracht. Bislang sind allerdings Anzeichen fur eine zielstrebige Koordination dieser rechtlichen Techniken kaum zu entdecken.

Microwave filters with nonperiodic transmission characteristic

Abstract: A microwave filter with nonuniform-coupled transmission lines is suggested. In contrast to known transmission-line microwave filters the transmission characteristic does not change periodically with frequency. The synthesis procedure shown reduces the design problem to the known synthesis of directional couplers with nonuniform coupling factor. A table of calculated coupling factor values of the microwave filter with an equi-ripple passband of 0.05 dB up to 1 dB and an equi-ripple stopband of 60 dB is given. A practical design example shows good agreement with theoretical results.

Anatomy of Boolean-function simplification

Abstract: The existing methods for the simplification of Boolean functions are usually classified according to their mathematical background (e.g. consenus method) or their procedural tools (e.g. diagram methods) or are named in honour of scientists (e.g. Quine-McCluskey method). To make the methods more transparent, with respect to the judgment of their effectiveness in solving practical problems, it is suggested that they be classified according to the strategy of prime implicant generation. It is shown that the known methods can be assigned to one of the following basic strategies for the generation of prime implicants: (a) building-up from smaller implicants; (b) expansion of the function along literals or variables; (c) separation of the vector space into 1-subspaces and O-subspaces; (d) systematic inspection of all possible implicants; (e) heuristic methods. The strategy is shown to be a governing factor for the effectiveness of minimisation procedures, particularly if, owing to the complexity of the problems, only approximately minimal solutions can be obtained.

Existence and applications of monoidally closed structures in topological categories

Abstract: Introduction It is well known that a lot of fundamental mathematical constructions can be done in an arbitrary category if it is equipped with a monoidally closed structure. Hence our aim is to show, that in very general situations we can lift internal hom-functors and monoidal structures~ which deliver monoidally closed structures in many concrete cases. Since we can carry out our construction simply by cone-factorization techniques, this paper is also a contribution to the idea that the notion of cone-factorization is a fundamental for category theory. Obviously one can vary the factorizations and modify the cones in our construction in order to get similar results but other applications. We want to mention that following the same idea G. Greve has independently obtained similar results.