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  • 1
    ISSN: 1432-1017
    Keywords: Key words Quartz crystal microbalance ; Cell adhesion ; Cell-substrate interaction ; RGD-sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The quartz crystal microbalance (QCM) has been widely accepted as a sensitive technique to follow adsorption processes in gas as well as in liquid environments. However, there are only a few reports about the use of this technique to monitor the attachment and spreading of mammalian cells onto a solid support in culture. Using a QCM-setup we investigated the time course of cell attachment and spreading as a function of seeding density for three widespread and frequently used cell lines (MDCK strains I and II and Swiss 3T3-fibroblasts). Results were found to be in good agreement with the geometrical properties of the individual cell types. The shifts of the resonance frequency associated with confluent cell layers on top of the quartz resonators were found to be dependent on the cell species [MDCK-I: (320±20) Hz; MDCK-II: (530±25) Hz; 3T3: (240±15) Hz] reflecting their individual influence on the shear oscillation of the resonator. These findings are discussed with respect to the basic models of materials in contact with an oscillating quartz resonator. We furthermore showed by inhibition-assays using soluble RGD-related peptides, that only specific, integrin mediated cell adhesion is detected using this QCM approach, whereas the sole presence of the cellular body in close vicinity to the resonator surface is barely detectable.
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  • 2
    ISSN: 1432-1017
    Keywords: Key words Impedance analysis ; MDCK-cells ; Quartz crystal microbalance (QCM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The viscoelastic behavior of epithelial cells (MDCK-I and MDCK-II) grown on AT-cut quartz crystals with a fundamental resonance at 5 MHz was investigated by impedance spectroscopy. Using the electromechanical model recently derived by Martin et al. [(1991) Anal Chem 63: 2272 – 2281] for Newtonian liquids in contact with shear wave resonators we quantified the viscous damping arising from the adherent cells by fitting the impedance data with a modified Butterworth-Van Dyke circuit in the region of the resonance frequency. Impedance spectroscopy was additionally performed in the frequency range from 1 Hz to 1 MHz to scrutinize the passive electrical properties of the epithelial cell layers using an additional platinum electrode. These data allow one to document the cell layers' integrity as well as the electrode coverage. We were able to confirm that the presence of a cell-layer mainly increases damping of the shear wave and does not exhibit a pure mass-load behavior. These findings were supported by the discovery that the inductance L in the electromechanical model was less influenced by the cell-layer than the resistance R. The apparent cell-viscosities determined by our method are 0.097 poise for MDCK-I and 0.142 poise for MDCK-II cell-layers. These low apparent viscosities may be explained in terms of a considerable spacing between the cells immobilized via their focal contacts and the quartz surface.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Informatik, Forschung und Entwicklung 15 (2000), S. 151-160 
    ISSN: 0949-2925
    Keywords: Schlüsselwörter: Realzeitsystem, Zeitverhalten, Test, Evolutionärer Test, Evolutionäre Algorithmen ; Keywords: Real-time system, Temporal behavior, Test, Evolutionary testing, Evolutionary computation ; CR Subject Classification: C.3, D.2.5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Abstract. The development of real-time systems is an essential industrial activity. Dynamic testing is the most important analytical method to assure the quality of real-time systems. It is the only means by which the run-time behavior of a system can be examined in its actual application environment. Existing software test methods generally concentrate on testing the functional correctness. They offer no support for examining the temporal behavior, though for the correct functioning of real-time systems the aspect of temporal correctness and functional correctness are equally important. This means that new approaches that concentrate on testing a system's temporal behavior need to be added to existing test procedures The temporal behavior is incorrect if the system is not capable of meeting specified temporal requirements within permitted input situations. In general, a violation means that outputs are produced too early or their computation takes too long, which means they are then produced to late. The tester's task is to find the input situations with the longest or shortest execution times in order to determine whether these violate the system's specified temporal frame. If the search for such input situations is interpreted as a problem of optimization, evolutionary algorithms can be used for the automatic search for the longest or shortest execution times. In this case the fitness function corresponds to the measured execution time. The individuals generated represent test data for the system under test. The use of evolutionary algorithms for testing is called evolutionary testing. A number of experiments have been carried out within the scope of this work in order to compare evolutionary testing with other test methods. All experiments show that evolutionary testing reaches longer and shorter execution times than have been found using random testing and systematic testing. Evolutionary testing therefore seems suitable for checking the temporal correctness of real-time software. A combination of evolutionary testing and systematic testing offers further opportunities to improve the test quality and is suggested in this paper as an effective test strategy for real-time systems.
    Notes: Zusammenfassung. Die Entwicklung von Realzeitsystemen ist eine wesentliche Aufgabe im industriellen Umfeld. Der dynamische Test ist die wichtigste analytische Qualitätssicherungsmethode für Realzeitsysteme. Der dynamische Test ist das einzige Verfahren, mit dem das Laufzeitverhalten der Systeme in der tatsächlichen Einsatzumgebung überprüft werden kann. Bestehende Testmethoden konzentrieren sich weitgehend auf den Test des funktionalen Verhaltens von Systemen. Sie bieten keine besondere Unterstützung für den Test des zeitlichen Verhaltens. Für die Korrektheit von Realzeitsystemen sind jedoch beide Aspekte gleichermaßen wichtig. Folglich müssen die bestehenden Methoden um neue Ansätze ergänzt werden, die auf die Prüfung des zeitlichen Verhaltens spezialisiert sind. Ein Fehler im Zeitverhalten von Realzeit-Systemen liegt dann vor, wenn es zulässige Eingabesituationen gibt, für die das System nicht in der Lage ist, die spezifizierten zeitlichen Anforderungen zu erfüllen. In den meisten Fällen ist dies darauf zurückzuführen, daßdas System eine Ausgabe zu früh macht oder daßdie Berechnung einer Ausgabe zu lange dauert und diese daher zu spät erfolgt. Aufgabe des Testers ist es folglich, die Eingabesituationen mit den längsten und kürzesten Ausführungszeiten zu finden, um zu überprüfen, ob die für das System spezifizierten Zeitschranken verletzt werden. Wird die Suche nach entsprechenden Eingabesituationen als Optimierungsproblem interpretiert, dann können evolutionäre Algorithmen verwendet werden, um die Eingaben mit den längsten und kürzesten Ausführungszeiten automatisch zu suchen. Die zu optimierende Zielfunktion entspricht hierbei den gemessenen Ausführungszeiten, die generierten Individuen repräsentieren Testdaten. Die Verwendung evolutionärer Algorithmen für den Test nennen wir evolutionären Test. Zum Vergleich des evolutionären Tests mit anderen Testmethoden wurden in dieser Arbeit mehrere Experimente durchgeführt. In allen Experimenten erreicht der evolutionäre Test längere bzw. kürzere Ausführungszeiten als durch Zufallstests oder systematische Tests gefunden werden. Der evolutionäre Test erscheint daher als gut geeignet für die Prüfung der zeitlichen Korrektheit von Realzeitsystemen. Die Kombination des evolutionären Tests mit systematischen Tests kann die Testqualität weiter verbessern und wird in diesem Papier als Teststrategie für Realzeitsysteme empfohlen.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Software quality journal 6 (1997), S. 127-135 
    ISSN: 1573-1367
    Keywords: Keywords: testing ; real-time systems ; genetic algorithms ; temporal behaviour ; embedded systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The development of real-time systems is an essential industrial activity whose importance is increasing. The most important analytical method to assure the quality of real-time systems is dynamic testing. Testing is the only method which examines the actual run-time behaviour of real-time software, based on an execution in the real application environment. Dynamic aspects like the duration of computations, the memory actually needed, or the synchronization of parallel processes are of major importance for the correct function of real-time systems and have to be tested. A comprehensive investigation of existing software test methods shows that they mostly concentrate on testing for functional correctness. They are not suited for an examination of temporal correctness which is essential to real-time systems. Very small systems show a wide range of different execution times. Therefore, existing test procedures must be supplemented by new methods, which concentrate on determining whether the system violates its specified timing constraints. In general, this means that outputs are produced too early or their computation takes too long. The task of the tester is to find the inputs with the longest or shortest execution times to check whether they produce a temporal error. If the search for such inputs is interpreted as a problem of optimization, genetic algorithms can be used to find the inputs with the longest or shortest execution times automatically. The fitness function is the execution time measured in processor cycles. Experiments using genetic algorithms on a number of programs with up to 1511 LOC and 843 integer input parameters have successfully identified new longer and shorter paths than had been found using random testing or systematic testing. Genetic algorithms are able therefore to check large programs and they show considerable promise in establishing the validity of the temporal behaviour of real-time software.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Real-time systems 15 (1998), S. 275-298 
    ISSN: 1573-1383
    Keywords: Real-time systems ; verification ; validation ; testing ; test strategy ; evolutionary testing ; evolutionary optimization ; evolutionary algorithm ; temporal behavior ; temporal correctness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Many industrial products are based on the use of embedded computer systems. Usually, these systems have to fulfil real-time requirements, and correct system functionality depends on their logical correctness as well as on their temporal correctness. In order to verify the temporal behavior of real-time systems, previous scientific work has, to a large extent, concentrated on static analysis techniques. Although these techniques offer the possibilty of providing safe estimates of temporal behavior for certain cases, there are a number of cases in practice for which static analysis can not be easily applied. Furthermore, no commercial tools for timing analysis of real-world programs are available. Therefore, the developed systems have to be thoroughly tested in order to detect existing deficiencies in temporal behavior, as well as to strengthen the confidence in temporal correctness. An investigation of existing test methods shows that they mostly concentrate on testing for logical correctness. They are not specialised in the examination of temporal correctness which is also essential to real-time systems. For this reason, existing test procedures must be supplemented by new methods which concentrate on determining whether the system violates its specified timing constraints. Normally, a violation means that outputs are produced too early, or their computation takes too long. The task of the tester therefore is to find the input situations with the longest or shortest execution times, in order to check whether they produce a temporal error. If the search for such inputs is interpreted as a problem of optimization, evolutionary computation can be used to automatically find the inputs with the longest or shortest execution times. This automatic search for accurate test data by means of evolutionary computation is called evolutionary testing. Experiments using evolutionary testing on a number of programs with up to 1511 LOC and 5000 input parameters have successfully identified new longer and shorter execution times than had been found using other testing techniques. Evolutionary testing, therefore, seems to be a promising approach for the verification of timing constraints. A combination of evolutionary testing and systematic testing offers further opportunities to improve the test quality, and could lead to an effective test strategy for real-time systems.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 100 (1967), S. 2474-2483 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Reaktionen von NF3 mit V2O5, CrO3, Cr2O3, MoO3, WO3, VCl3, CrCl3, Mo, W, VN, MoN und MoS2 werden studiert. V2O5 gibt bei 400° NO[VOF4] neben VOF3, Cr2O3 bei 430° ein Gemisch von Cr2O3 + CrF3, MoO3 bei 430° NO[MoO2F3] neben MoO2F2 und MoF6, WO3 bei 430° NO[WOF5] neben WF6. CrO3 reagiert bis zu seinem Zersetzungspunkt von 200° nicht. VCl3 setzt sich bei 70° zu VCl1.5F1.5, bei höheren Temperaturen zu VF3 und VCl4 bzw. VF5 und VCl4 um. Aus CrCl3 entsteht bei 480° reines CrF3. Aus Mo-Pulver erhält man bei 280° über MoF3 als Zwischenprodukt MoF6, aus W-Pulver bei 280° WF6. VN wandelt sich bei 200° teilweise, bei 400° vollständig in VF3 um, während MoN bei 260° über das Zwischenprodukt MoF3 in MoF6 übergeht. Aus MoS2 entstehen die gasförmigen Verbindungen MoF6, NSF, SF4 und SF6.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 474-480 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of new Thiazyltrifluoride Derivatives by Si-N Bond Cleavage Reactions. Preparation of N.N'-Bis(difluorophosphoryl)sulfur Difluoride DiimideBy Si-N bond cleavage reactions with thiazyltrifluoride NSF2-N(CH3)2 (3) and NSF2-N(C2H5)2 (4) were prepared. (CH3)3Si-N=SF2=N-Si(CH3)3 (1) react with SF4 to yield NSF2-N=SF2 (5), with P2O3F4 to give O=PF2-N=SF2=N-PF2=O (6) and small amounts of (CH3)3Si-N=SF2=N-PF2=O (7). By reaction of 1 with dimethylamine and piperidine [CH3)3Si-N=]2S[N(CH3)2]2 (8) and [(CH3)3Si-N=]2S(NC5H10)2 (9) are formed.
    Notes: Durch Si-N-Spaltungsreaktionen mit Thiazyltrifluorid wurden NSF2—N(CH3)2 (3) und NSF2—N(C2H5)2 (4) dargestellt. Aus (CH3)3Si—N=SF2=N—Si(CH3)3 1) entsteht mit SF4 NSF2—N=SF2 (5), mit P2O3F4 O=PF2-N=SF2=N-PF2=O (6) neben geringen Mengen (CH3)3Si—N=SF2=N—PF2—O(7). Die Reaktionen von 1 mit Dimethylamin und mit Piperidin führt zu [(CH3)3Si-N=]2S[N(CH3)2]2 (8) bzw. zu [(CH3)3Si-N=]2S(NC5H10)2 (9).
    Additional Material: 2 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 1791-1802 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions with Indole Derivatives, XXVI. The Steric Course of Methylene-Lactam Rearrangements in Rigid Policyclic SystemsThe four stereoisomeric, disubstituted indoloquinolizindines of type 12 have been prepared in a stereoselective manner and then treated according to the methylene-lactam rearrangement. In all cases the exocyclic double-bound with E-configuration is obtained. This type of configuration is found in many indole-alkaloids.
    Notes: Alle vier stereoisomeren, disubstituierten Indolochinolizidine des Typs 12 wurden mit Hilfe stereoselektiver Techniken dargestellt und der Methylen-Lactam-Umlagerung unterworfen. In allen Fällen wird die E-konfigurierte exocyclische Doppelbindung erhalten, ein Konfigurationstyp, der in vielen Indolalkaloiden angetroffen wird.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 82 (1970), S. 324-324 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 10
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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