Showing papers by "University of Bremen published in 1982"
TL;DR: The authors analytically explores the properties of simple differential-difference equations that represent dynamic processes with feedback dependent on prior states of the system and shows that very complex time dependent behaviors may arise from these processes.
Abstract: This paper analytically explores the properties of simple differential-difference equations that represent dynamic processes with feedback dependent on prior states of the system. Systems with pure negative and positive feedback are examined, as well as those with mixed (positive/negative) feedback characteristics. Very complex time dependent behaviors may arise from these processes. Indeed, the same mechanism may, depending on system parameters and initial conditions, produce simple, regular, repetitive patterns and completely irregular random-like fluctuations.
121 citations
TL;DR: The cAMP molecule seemed to be bound by these specific hydrogen bonds to the 5' and 3' oxygen, the 2' hydroxyl, and an ion pair interaction between the negative charge in equatorial position and a positively charged amino acid side chain.
Abstract: cAMP binding to the 'stable' cAMP-binding sites in the regulatory subunit of the cAMP-dependent protein kinase type I was investigated using a set of 18 selected derivatives. All the tested analogues were competitive with [3H]cAMP and inhibitor constants from 12 nM to 20 microM with the free regulatory subunit were determined. The cAMP molecule seemed to be bound by these specific hydrogen bonds to the 5' and 3' oxygen, the 2' hydroxyl, and an ion pair interaction between the negative charge in equatorial position and a positively charged amino acid side chain. The adenine base is rather unspecifically bound with no hydrogen bonds involved. This binding specificity of the 'stable' site is similar to the requirement for dissociation as determined by the activation of the kinase by a respective analogue. This indicates that occupation of the 'stable' sites leads to activation of the protein kinase. The presence of the catalytic subunit reduced the affinity of most analogues. The binding of one derivative with the negative charge fixed in the axial position is not influenced by the addition of the catalytic subunit and ATP. A plausible model for a conformational change during the activation process in the 'stable' site is discussed.
108 citations
TL;DR: In this paper, a submartingale type inequality for a martingale integral with values in a Hilbert space was proved for a fixed time interval (0,T) under the assumption that there is a β≧0 such that the integral is stable under some additional assumption on U t s.
Abstract: On a fixed time interval [0,T] we consider where M is a square integrable martingale with values in a Hilbert space K,Φ s (ω) suitable operators from K to H, another Hilbert space, and U t s is a mild evolution operator on H. Under the assumption that there is a β≧0 such that we prove a submartingale type inequality for that integral. As applicatins we show that it has a continuous version, if M has, or is cadlage if M is calage, and we prove that it is stable under some additional assumption on U t s Finally we ontain an existence and uniquenss theorem for an SPDE.
100 citations
TL;DR: In this article, the authors discuss controllability for stochastic systems and derive necessary and sufficient algebraic conditions for the control of the state and the output of white and colored noise linear systems.
56 citations
TL;DR: In this article, the pH-Abhagigkeit der 13 C-NMR-Spektren von Aminoure 2-Methylalanin (α-Aminoiso-buttersaure, Aib) was untersucht.
52 citations
TL;DR: It is concluded that ACTH-like neuropeptides might physiologically be involved in the plastic processes underlying functional recovery from CNS lesions.
50 citations
TL;DR: A considerable number of tectal cells showed a change of stimulus preference if the stimulus velocity was changed, and no clear correlation between response types and anatomical distribution within the tectum layers could be found.
Abstract: In the optic tectum of Bufo bufo the activity of single neurons was recorded during the presentation of moving visual stimuli. The location of the recorded cells was marked iontophoretically by means of alcian blue dye. A total of 132 cells were studied, most of which showed clear differences within their responses to a square and to rectangles oriented either horizontally or vertically. The cells were found primarily within the tectum layers 8 and 6. The majority of them preferred the square to the horizontal bar, and this stimulus to the vertical one. Another group responded best to the horizontal rectangle. Relatively few cells were found in which the vertical stimulus was preferred to the horizontal one. A considerable number of tectal cells showed a change of stimulus preference if the stimulus velocity was changed. No clear correlation between response types and anatomical distribution within the tectum layers could be found.
47 citations
TL;DR: Six groups could be distinguished which preferred the square stimulus but differred strongly in their responses to rectangles oriented either vertically or horizontally, and two of these groups showed stimulus preference inversion if the stimulus velocity was changed.
Abstract: In the tectum opticum ofHydromantes italicus neurons were recorded extracellularly which responded selectively to moving visual stimuli. Part of the recorded cells were marked iontophoretically by means of alcian-blue dye for anatomical localization. Out of a total of 110 neurons six groups could be distinguished which preferred the square stimulus but differred strongly in their responses to rectangles oriented either vertically or horizontally. Two of these groups showed stimulus preference inversion if the stimulus velocity was changed. These response patterns displayed characteristic differences with those known in other amphibia, well corresponding to differences in the prey catching behaviours.
41 citations
TL;DR: Computer analysis of a modified version of a model oscillator is used to simulate phase response curves such as are obtained in circadian systems, and the consequences for interpreting the molecular mechanism of circadian clocks on the basis ofphase response curves to various treatments are discussed.
39 citations
TL;DR: In this paper, the main sources of nitrate in man are food and drinking water, and the problem of high nitrate content is mainly one of drinking water generation from ground water.
04 Oct 1982
TL;DR: This paper summarizes some recent results on graph languages generated by edge replacement and shows that their languages are fixed points of their productions and that they can be generated by language operations from finite graph languages.
Abstract: Edge replacement systems provide a simple mechanism to generate graph languages. They generalize context-free (string) grammars to the case of graphs. This paper summarizes some recent results on graph languages generated by edge replacement. Especially, we show that our languages are fixed points of their productions (considered as equations) and that they can be generated by language operations (substitution and iteration) from finite graph languages.
TL;DR: The paper reports also on results of MSC coding of speech, where both the strategy of adaptive quantization and of adaptive prediction were included in coder design.
Abstract: This paper deals with the application of multipath search coding (MSC) concepts to the coding of stationary memoryless and correlated sources and of speech signals at a rate of one bit per sample. We have made use of three MSC classes: 1) codebook coding (vector quantization), 2) tree coding, and 3) trellis coding. This paper explains the performances of these coders and compares them both with those of conventional coders and with rate-distortion bounds. Figs. 2 and 3 demonstrate the potentials of MSC coding strategies. The paper reports also on results of MSC coding of speech, where both the strategy of adaptive quantization and of adaptive prediction were included in coder design.
TL;DR: In this article, the authors derived the signal as well as the noise power spectrum of the induced voltage at the read head by generalizing the theory of the signal behaviour, and the theoretical result turned out to agree quite well with the experimental one.
Abstract: The modulation noise and the special case, dc erased noise in magnetic recording are discussed theoretically, taking account of two main causes at the same stage, i.e. the magnetic properties such as the inhomogeneous distribution of the particles on the tape, and the mechanical properties such as the head-to-tape space variations arising from the tape surface roughness. We derive the signal as well as the noise power spectrum of the induced voltage at the read head. This is done by generalizing the theory of the signal behaviour. The theoretical result turned out to agree quite well with the experimental one. The modulation noise power spectrum can be interpreted to consist of two parts, i.e. the steep peak due to the mechanical causes near the recorded signal wavenumber and the broad peak due to magnetic causes.
TL;DR: The synthesis of benzylpenicillin (BP) after mixing phenyl-acetyl-glycine (PAG), 6-aminopenicillanic acid (6-APA) and free or immobilized penicillin amidase (E.C.5.1.3.11) was studied as a function of pH and ionic strength.
TL;DR: Using Plummer et al.'s [11] rate equations on the dissolution and deposition of CaCO3 in H2O CO2 systems, we have calculated deposition rates of Ca CO3 to stalagmites in caves which are covered by glaciers or bare karst.
TL;DR: The phase response curves of circadian rhythms toward pulses of various chemical and physical perturbations are standardized and compared in Gonyaulax, Phaseolus, Kalanchoe, Trifolium, and Aplysia, finding that the phasing of the phase response curve is subject to variability of the boundary conditions of the different laboratories and seems to depend on the strength, direction, and modality of the perturbing pulse.
Abstract: The phase response curves of circadian rhythms toward pulses of various chemical and physical perturbations are standardized and compared in Gonyaulax, Phaseolus, Kalanchoe, Trifolium , and Aplysia . The time of maximal phase shift, in many of these curves clustered around a given time of day, especially in Gonyaulax and Aplysia . This could be interpreted as being due to a converging effect of these modalities on a single function that is decisive for the mechanism of the circadian clock. Since many of the treatments that result in significant phase response curves (e.g., light pulses, hormones, temperature pulses, changes of ion concentration, etc.) have also been shown in independent studies to be capable of affecting protein synthesis, it is possible that these treatments may all affect circadian rhythmicity by virtue of their direct or indirect effect on protein synthesis. There is also a number of treatments which give phase response curves that are not clustered, especially in Phaseolus . This means either that our original assumption is incorrect or that these treatments impinge on sensitive components of the clock other than protein synthesis. It is emphasized, however, that the phasing of a phase response curve on one hand is subject to variability of the boundary conditions in the different laboratories and on the other hand seems to depend on the strength, direction, and modality of the perturbing pulse.
01 Jan 1982
TL;DR: In this article, a phanomenologisch orientierte Soziologie, die zu solchen Fragen anregt, findet keine Antworten Ihr Interesse richtet sich auf das Wie des Objekt-and Themawerdens, nicht auf die Frage, was konkret Thema wird (vgl etwa Schutz 1971) Methodologisch weniger skrupulos, aber fur die Beantwortung der Themafrage w
Abstract: Warum fallen uns Eigentumskriminalitat, Prostitution, Drogenkonsum, Homosexualitat usw auf? Warum berichten Tageszeitungen uber diese Devianzen? Warum meinen wir, es “gabe” sie? Die phanomenologisch orientierte Soziologie, die zu solchen Fragen anregt, findet keine Antworten Ihr Interesse richtet sich auf das Wie des Objekt- und Themawerdens, nicht auf die Frage, was konkret Thema wird (vgl etwa Schutz 1971) Methodologisch weniger skrupulos, aber fur die Beantwortung der Themafrage wohl besser nutzbar scheinen sozialgeschichtliche Rekonstruktionen des Themas “Verbrechen” zu sein Ihnen zufolge ist staatlich organisierte Herrschaft das dieses Thema konstituierende Merkmal von Gesellschaften (vgl Hess, Stehr 1987) Mit der Entstehung von Staaten seien subjektive Interessen — Interessen an der Abschopfung des Mehrprodukts der Produzenten — in subjektive Rechte umgewandelt worden Die Sanktionen, die den Verstosen gegen diese Rechte gefolgt seien, seien von besonderer Legitimitat gewesen — das Ergebnis der erfolgreichen Generalisierung partikularer Interessen, die den Staat begrundet oder sich seiner bemachtigt hatten Dadurch erhalt — dieser These zufolge — abweichendes Verhalten einen dramatischen Bedeutungszuwachs Es ist das falsche, das bose Verhalten, das sich gegen das Ganze richtet und deswegen bestraft werden mus
01 Jan 1982
TL;DR: In this article, the conditions générales d'utilisation (http://www.numdam.org/legal.php) of the agreement with the séminaire de probabilités (Strasbourg) are discussed.
Abstract: © Springer-Verlag, Berlin Heidelberg New York, 1982, tous droits réservés. L’accès aux archives du séminaire de probabilités (Strasbourg) (http://portail. mathdoc.fr/SemProba/) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/legal.php). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.
TL;DR: A series of faujasite supported catalysts with monomodal dispersed phases of nickel, palladium, and platinum, exhibiting narrow particle size distributions, are chracterized by X.p.s. as discussed by the authors.
TL;DR: In this paper, a low-passband insertion loss is achieved by large gap fin-lines and pure metal inserts mounted in the E-plane of rectangular waveguides requiring no supporting dielectrics, which combines the advantages of low-cost etching techniques and the low-loss performance of usual waveguide circuits.
Abstract: Low passband insertion-loss is achieved (1) by large-gap fin-lines, by which the high-Q potential increasing with gap-width is fully utilized, and (2) by pure metal inserts mounted in the E-plane of rectangular waveguides requiring no supporting dielectrics. This design combines the advantages of low-cost etching techniques and the low-loss performance of usual waveguide circuits. The theory described includes both higher-order mode interaction of the discontinuities and the finite thickness of dielectrics, metal fins as well as inserts. An optimizing computer program varies the filter parameters for a given number of resonators until the insertion loss yields a minimum in passband and an optimum in stopband. Data for optimized X-, Ka-, V-, E-, and W-band filters are given. Measurements verify the described theory. Measured minimum pass-band insertion losses are 0.3, 0.7, 1.5 dB for the fin-line filter for midband frequencies of about 12, 34, 75 GHz, and for the metal insert filter 0.1, 0.6, 0.5, and 0.7 dB at 12, 33, 63, and 76 GHz, respectively.
TL;DR: In this paper, a unified theory of first-order and higher-order necessary optimality conditions for abstract vector optimization problems in normed linear spaces is presented, from which nearly all known firstorder, second-order, and higherorder necessary conditions can be derived.
Abstract: In this paper, we present a unified theory of first-order and higher-order necessary optimality conditions for abstract vector optimization problems in normed linear spaces. We prove general multiplier rules, from which nearly all known first-order, second-order, and higher-order necessary conditions can be derived. In the last section, we prove higher-order necessary conditions for semi-infinite programming problems.
TL;DR: In this paper, the relative stabilities of topologically closed ring clusters H 8 Si 4 O 4, [H 8 Si 3 AlO 4 ] − and [H8 Si 2 Al 2 O 4 ]− have been investigated.
Abstract: Non-empirical molecular orbital studies on the relative stabilities of topologically closed ring clusters H 8 Si 4 O 4 , [H 8 Si 3 AlO 4 ] − and [H 8 Si 2 Al 2 O 4 ] − modelling building units of zeolite frameworks, have been carried out. According to the calculations, AlOAl type bridges are unstable in doubly negative charged species, but can be stabilized in the presence of cations. This stabilization effect increases with increasing cation charge. Several hypothetical bimolecular cluster equilibria are also discussed.
TL;DR: Partial correlation coefficient analysis showed water temperature to be the most important factor; the relationship between cadmium in G. tigrinus and in the river Weser turned out to be an imaginary correlation, considering the hypothesis of an increased elimination of Cadmium via exuvia in the summer population.
TL;DR: Afferent visual projections were demonstrated in three species of plethodontid salamanders by means of anterograde transport of horseradish peroxidase.
TL;DR: In this paper, the oscillatory and bistable behavior of the heterogeneous catalytic methanol oxidation on a Pd supported catalyst is explained in terms of the changing properties of the active metal phase due to its loading with carbon monoxidde and hydrogen.
Abstract: The oscillatory and bistable behavior of the heterogeneous catalytic methanol oxidation on a Pd supported catalyst is explained in terms of the changing properties of the active metal phase due to its loading with carbon monoxidde and hydrogen.
TL;DR: In this paper, a method of calculating the solution of Kramers' equation for two dimensional rotational brownian movement in a plane under the influence of a periodic potential is presented.
TL;DR: A comparison of particle size distributions from electron micrographs and oxygen chemisorption capacities on reduced platinum and palladium faujasite X confirms the existence of monodisperse metal phases of narrow aggregate size distribution and excludes a grape structure for the occluded metal particles.
Abstract: A comparison of particle size distributions from electron micrographs and oxygen chemisorption capacities on reduced platinum and palladium faujasite X confirms the existence of monodisperse metal phases of narrow aggregate size distribution and excludes a grape structure for the occluded metal particles. For reduced, monodisperse nickel faujasites a degree of reduction can be obtained by this comparison.