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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1861-1862 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic InGaAs lasers with cw operating lifetimes exceeding 5000 h are reported for the first time. The device structure, grown by low-pressure metalorganic chemical vapor deposition, incorporates a single In0.37Ga0.63As strained-layer quantum well in a GaAs/AlGaAs graded-index separate confinement heterostructure. These devices are remarkable for their immunity to sudden failure and for their (gradual) degradation rates which are comparable to the best GaAs lasers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 37 (1997), S. 366-371 
    ISSN: 1432-2102
    Keywords: Key words Magnetic resonance imaging • Myocardial perfusion • Ultrafast imaging • Contrast medium ; Schlüsselwörter Magnetresonanztomographie • Myokardperfusion • Schnelle MR Bildgebung • Kontrastmittel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die bildgebende Magnetresonanztomographie (MRT) kann die Passage des mit Kontrastmittel angereicherten Blutes durch den Herzmuskel nachweisen und erlaubt sogar eine quantitative Beurteilung der Myokardperfusion. Der klinische Einsatz dieser Methode ist verzögert einerseits durch die Schwierigkeit der Bildauswertung, andererseits dadurch, daß mit herkömmlichen Techniken nur eine Schicht pro Herzschlag abgebildet werden kann. Neue Entwicklungen sowohl der Kernzspintomographen wie auch der Strategien zur beschleunigten Bildaufnahme ermöglichen die Beurteilung der Perfusion über den gesamten Herzmuskel mit einer Auflösung im Bereich von 2 mm. Als Beispiel einer solchen Abbildungstechnik wird eine schnelle (130 ms pro Bild) segmentierte Gradientenechoplanarsequenz mit vorangehendem Sättigungspuls diskutiert und Resultate in einem Infarktpatienten vorgestellt. Der klinische Nutzen der MRT-gestützten Bestimmung der Perfusion zur Diagnose von Koronarerkrankungen wird durch die Vielfältigkeit der MRT-Methoden zur Bestimmung von Herzfunktionsparametern verstärkt.
    Notes: Summary Magnetic resonance imaging detects the flow of contrast – enhanced blood and even allows the quantitative assessment of myocardial perfusion. The clinical application of this method is being held back by the difficulties in image evaluation and the limitation of standard techniques to the acquisition of a single slice per heart beat cycle. Recent developments in scanner hardware as well as in image acquisition techniques open up the possibility of assessing myocardial perfusion over the entire heart with a spatial resolution in the range of 2 mm. As an example of such a new scanning strategy, a segmented gradient-echo recalled echo planar imaging sequence with preceding saturation is discussed and results in a patient with an infarction are presented. The clinical use of perfusion assessment covering the entire heart for the diagnosis of coronary artery disease is enhanced by the flexibility of magnetic resonance imaging for the assessment of functional cardiac parameters.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 262 (1999), S. 268-274 
    ISSN: 1617-4623
    Keywords: Key words Transposase ; Transposon ; Tc1 ; Tc3 ; Caenorhabditis elegans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Caenorhabditis elegans transposons Tc1 and Tc3 are able to transpose in heterologous systems such as human cell lines and zebrafish. Because these transposons might be useful vectors for transgenesis and mutagenesis of diverse species, we determined the minimal cis requirements for transposition. Deletion mapping of the transposon ends shows that fewer than 100 bp are sufficient for transposition of Tc3. Unlike Tc1, Tc3 has a second, internal transposase binding site at each transposon end. We found that these binding sites play no major role in the transposition reaction, since they can be deleted without reduction of the transposition frequency. Site-directed mutagenesis was performed on the conserved terminal base pairs at the Tc3 ends. The four terminal base pairs at the ends of the Tc3 inverted repeats were shown to be required for efficient transposition. Finally, increasing the length of the transposon from 1.9 kb to 12.5 kb reduced the transposition frequency by 20-fold, both in vivo and in vitro.
    Type of Medium: Electronic Resource
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