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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 24 (1985), S. 3890-3897 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression and phase variation of Neisseria gonorr-hoeae P.ll genes in Escherichia coli viere studied using TnphoA fusions. Fusions were created in the P.llc gene of N. gonorrhoeae JS3 using λTnphoA-1 and were characterized by restriction digestion and dideoxy sequencing. Three fusions were chosen for further study; Tnp7 (fusion junction at mature amino acid 7), Tnp57 (amino acid 57), Tnp66 (amino acid 66). All fusions were in frame with the P.llc coding sequence but were out of frame with the purported initiation codon. All fusion constructions were shown to phase vary in E. coli in an analogous fashion to that seen in N. gonorrhoeae, i.e. phase changes (in a recA background) at a frequency of c. 10−3 accompanied by an alteration at the DNA level of the number of coding repeats (CRs). In vitro mutagenesis of the fusion constructions indicated that expression of out of frame P.ll genes in E. coli was probably the result of ribosomal frameshifting within the run of ‘A’ residues immediately preceding the CR region and not due to low-level false initiation at codons other than the ATG initiation codon (as had previously been suggested). The mechanism for P.llc::phoA phase variation appears to be related to the ‘slipped-strand mispairing’ mechanism responsible for frameshift mutations in a number of other bacterial genes containing short, direct, tandem repeats.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Ein dreidimensionales hydrodynamisches Modell in randwert-angepaßten Koordinaten wurde entwickelt zur Berechnung der Zirkulation in Schelf- und Randmeeren. Die Impuls- und Kontinuitätsgleichungen werden in einem räumlich verschachtelten Gitter mit einem halbimpliziten finiten Differenzenverfahren für den externen Anteil der vertikal integrierten Strömung und einem expliziten Verfahren für den internen Anteil gelöst. Die Vertikalkoordinate wird nach Transformation mit der lokalen Wassertiefe mit einer Reihe permeabler Schichten approximiert. Die Impulsgleichung des internen Anteils wird explizit gelöst mit Ausnahme des vertikalen Diffusionsterms. Dieser wird implizit behandelt, um die Begrenzung durch den Zeitschritt zu vermeiden. Das Modell wurde in einer zweidimensionalen Version getestet und die Ergebnisse verglichen mit den analytischen Lösungen einer stehenden Welle in einem geschlossenen Becken, einer Gezeitenströmung in einem Ringkanal mit konstanter Tiefe und windinduzierter Strömung in einem elliptischen und zylindrischen Becken. Der Test des dreidimensionalen Modells berücksichtigt Wind und Massenaufbau in einem Rechteckbecken. Alle Simulationen zeigen eine sehr gute Übereinstimmung der Ergebnisse mit der analytischen Lösung.
    Abstract: Résumé Un modèle hydrodynamique tri-dimensionnelle avec un système de coordonnées adapté aux frontières a été développé pour simuler les courants côtiers et du plateau continental. Les équations de mouvement et de continuité sont résolues sur des grilles spatiales séparées et emboitées en utilisant un schema semi-implicite aux différences finies pour le courant barotrope et un schema explicite pour le courant barocline. La coordonnée verticale est adaptée à la prodondeur locale et est approximée en utilisant une série de couches perméables. Les équations de mouvement interne pour les vitesses baroclines sont résolues explicitement à l'exception des termes diffusifs verticaux qui utilisent un schema implicite pour pallier les contraintes de pas de temps. Le modèle a été testé en mode bi-dimensionnel en comparaison avec des solutions analytiques pour une onde stationnaire en bassin clos, pour un courant de marée en bassin annulaire de profondeur constante et pour un courant du au vent dans un bassin cylindrique de section elliptique. Des tests tri-dimensionnels du code de calcul en bassin rectangulaire font intervenir des variations de densité et de force du vent. Toutes ces simulations fournissent d'excellentes concordances avec les solutions analytiques.
    Notes: Summary A three dimensional hydrodynamic model has been developed in boundary fitted coordinates for application to shelf and coastal sea circulation. The momentum and continuity equations are solved on a space staggered grid system using a semi-implicit finite-difference solution algorithm for the exterior vertically averaged flow and an explicit procedure for the interior flow. The vertical coordinate, transformed by the local depth, is approximated by a series of permeable layers. The interior momentum equations are solved explicitly with the exception that the vertical diffusive terms employ an implicit specification to ease the time step restriction. The model has been tested in a two dimensional mode against analytic solutions for a standing wave in a closed basin, tidal flow in a annular basin with constant depth and wind driven flow in a elliptic cylindrical basin. Three dimensional tests of the code include wind and density forcing in a rectangular basin. All simulations show excellent agreement with the analytic solutions.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Ein dreidimensionales hydrodynamisches Modell in randwert-angepaßten Koordinaten zur Simulation von Strömung im Meer wird kurz beschrieben. Das Modell wird an einfachen Beispielen mit Gezeiten- und atmosphärischer Anregung getestet und die Ergebnisse werden mit analytischen Lösungen verglichen. Die zweidimensionale Version des Modells wird benutzt zur Berechnung von gezeiten- und sturmflutbedingten Wasserständen und Strömungen auf dem Norwegischen Festlandsockel. Die Simulation wird mit einer feinen und einer groben Gitterauflösung durchgeführt. Die berechneten Wasserstände und Strömungen werden mit Beobachtungen und Modellergebnissen des operationellen Modells des Norwegischen Meteorologischen Instituts verglichen.
    Abstract: Résumé Un modèle hydrodynamique tri-dimensionnel utilisant un système de coordonées adapté aux frontières permettant la simulation des courants océaniques est brièvement décrit. Le modèle est testé sur des cas simples avec le forçage de la marée et de l'atmosphére. Les résultats sont comparés aux solutions analytiques. Enfin la version bi-dimensionnelle du modèle est appliquée à la simulation des élévations du niveau (surcotes) liées à l'onde de marée et aux ondes de tempête et à celle des courants sur le plateau continental norvégien. Cette simulation est réalisée à la fois pour une grille grossière et une grille fine. Les surcotes et les courants simulés sont comparés à des observations ainsi qu'aux résultats obtenus du modèle opérationnel de l'Institut de Météorologie Norvégien.
    Notes: Summary A three dimensional boundary fitted coordinate hydrodynamic model for simulation of ocean currents is briefly described. The model is tested on simple test cases with tidal and atmospheric forcing and the results are compared with analytical solutions. Finally, the two-dimensional version of the model is applied for simulating tidal and storm surge elevation and currents on the Norwegian continental shelf. The simulation is carried out both for a coarse and fine grid. The simulated sea elevation and currents are compared with observations and model results from the operational model at the Norwegian Meteorological Institute.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pilus+ “wild-type” gonococci (Gc) frequently display gene conversion of their expressed complete pilin gene (CPG); a copy of DNA derived from one of the Gc genome's multiple silent partial pilin genes (PPG) is recombinationally-inserted into the CPG's central and 3′ portions with formation of a new, chimeric CPG. Expression of that new CPG leads to either 1) retention of pilus+ phenotype but change in pilin primary structure/antigenicity, or 2) phase change to pilus− phenotype capable of reverting. This study utilizes pilus revertants of P− rp±Gc and P+ colony morphotye variants spawned by P++ Gc to examine pilin gene conversion in strain MS11mk Gc in greater detail. Each revertant's and variant's expressed pilin gene's sequence (as pilin mRNA) was defined to learn whether their differences are due to gene conversion by different PPGs, or by varying stretches from the same PPG, or both. Gene conversion by PPG pilS1 copy 2 has been documented in Gc recovered from a human voluteer's urethra previously inoculated with pilus Gc (strain MS11). The pilus+ Gc isolated expressed structurally/antigenically distinct pilins.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As part of a process development campaign, studies have been conducted to determine the influence of induction temperature on the expression of two different malaria antigens, RN1 and RT2. Single-step temperature inductions, in which growth at 32.0°C is followed by a shift in temperature to a desired setpoint, show that there exists an optimum duration and temperature of induction which is product specific. Between an induction temperature of 39.5 and 44.5°C RN1 yield is constant at ca. 0.20 g/g total soluble protein (TSP). RT2 yield approaches 0.20 g/g TSP only at elevated induction temperatures. The optimum temperature of induction for RN1 production is 39.5°C, whereas, that for RT2 production is 41.0°C. Above the optimum temperature of induction antigen concentration decreases owing to decreases in biomass. Furthermore, the maximum concentration of these two antigens differ by a factor of four. With increasing temperature of induction the extent of proteolysis of the products also appears to increase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Proton magnetic resonance has been used to study water in Douglas fir and western red cedar. The free induction decay, when combined with a knowledge of chemical composition of the wood, gives an accurate measure of the absolute moisture content. Spin-lattice relaxation was found to be significantly different for the two species. In sapwood, three distinct spin - spin relaxation times, T2, were measured and assigned, with the help of anatomical data, to water in and on the cell wall, water in the ray and latewood tracheid lumens, and water in the earlywood tracheid lumens. This T2 behavior was explained by a model in which free water in a void exchanges with a small fraction of bound water on the lumen surface. The three T2's were almost independent of moisture content, suggesting physically separate compartments. The behavior of the three water components during drying was studied. The fiber saturation point could be determined from a single T2 measurement on a green sapwood sample. Magnetic resonance imaging of logs was investigated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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