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  • 1
    Electronic Resource
    Electronic Resource
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 429-437 
    Details
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We systematically investigate the difference between both actively and passively mode-locked lasers with Gain-at-the-End (GE) and Gain-in-the-Middle (GM) at the example of Nd:YLF lasers. The GE laser generates pulse widths approximately three times shorter than a comparable GM cavity. This is due to enhanced Spatial Hole Burning (SHB) which effectively flattens the saturated gain and allows for a larger lasing bandwidth compared to a GM cavity. We first investigate enhanced SHB by measuring the cw mode spectrum, where we have observed that the mode spacing in GE cavities depends primarily on the crystal length. This was also confirmed for a Nd:LSB crystal, where the pump absorption length was significantly shorter than the crystal length. In mode-locked operation, pulse widths of 4 ps for passive mode locking and 5 ps for active mode locking are demonstrated with GE cavities, compared to 11 ps for passive and 17 ps for active mode locking with GM cavities. Additionally, the time-bandwidth product for the GE cavity is approximately twice the ideal product for a sech2 pulse shape and cannot be improved by dispersion compensation alone, while the GM cavity has nearly ideal time-bandwidth-limited performance. The results for the GM cavity compare well to existing theories taking into account the added effect of pump-power-dependent gain bandwidth which increases the bandwidth of Nd: YLF from 360 to 〉 500 GHz. In a following paper [1] (called Part II) a rigorous theoretical treatment of the effects due to SHB will be presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081271
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  • 2
    Electronic Resource
    Electronic Resource
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 569-579 
    Details
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In Part I of this paper [1] experimental results were presented and discussed. In this part, we investigate theoretically the dynamics of end-pumped solid-state lasers due to enhanced spatial hole burning. This becomes possible by a fast numerical implementation of the saturated gain in the presence of strong spatial hole burning that allows to treat the multimode case for an arbitrary pumping level. We find for a wide range of laser parameters that the mode spacing of the cw running modes is essentially determined by the length of the gain medium and only weakly depends on the absorption depth of the pump transition. It is shown that spatial hole burning can lead to a completely flat saturated gain profile over half of the gain bandwidth. In mode-locked lasers, the flat gain due to spatial hole burning results in shorter pulses. But the pulses are neither Gaussian-nor sech-shaped as they are in actively or passively mode-locked lasers without spatial hole burning. Further, we show that soliton-like pulse shaping can be used to restore a transform-limited sech-shaped pulse in an end-pumped solid-state laser while exploiting the full gain bandwidth of the laser material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01091215
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in gallbladder motor function during the female cycle — a risk factor leading to gallstone formation? (1982)
    Springer
    Journal of molecular medicine 60 (1982), S. 1357-1362 
    Details
    ISSN: 1432-1440
    Keywords: Gallbladder motor function ; Gallstone formation ; Gallbladder ultrasonography ; Gallbladder contraction ; Gallbladder refilling ; Gallensteinentstehung ; Gallenblasenkontraktion ; Motorische Gallenblasenfunktion ; Gallenblasenfüllung ; Ultraschalldiagnostik
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 8 Frauen mit stabilem Zyklus wurden mittels Sonographie das Gallenblasenvolumen bestimmt und in der Progesteron- sowie der Östrogenphase des Zyklus die Gallenblasenkontraktion nach oraler Reizmahlzeit und die spontane Wiederauffüllung der entleerten Gallenblase quantitativ untersucht. Zur Volumenberechnung wurde die Formel eines Drehellipsoids verwandt, die sich im Modellversuch als hinreichend exakt erwiesen hatte. Die intraindividuellen Vergleichsuntersuchungen zeigten in der Progesteronphase (21. oder 22. Tag) gegenüber der östrogenphase (12. oder 13. Tag) statistisch gesicherte größere Nüchternvolumina, höhere Residualvolumina nach Kontraktion und eine langsamere Gallenblasenentleerung sowie eine verzögerte Wiederauffüllung der entleerten Gallenblase. Dem hormonal modifizierten Kontraktionsverhalten und der unterschiedlich ablaufenden Gallenblasenfüllung könnte im Rahmen der Gallensteinentstehung eine wesentliche Bedeutung zukommen.
    Notes: Summary The gallbladder volume of eight women with stable cycles was determined by sonography. Furthermore, gallbladder contraction — following an orally administered fatty meal and the spontaneous refilling of the empty gallbladder — was quantitatively examined. The formula of a rotation ellipsoid, which has been proven to be adequately accurate in in vitro studies, was used for calculating the gallbladder volume. In the gestagen phase (21st or 22nd day) the intraindividual studies showed greater fasting volumes, higher residual volumes after contraction, slower gallbladder emptying, and retarded refilling of the empty gallbladder as compared to the estrogen phase (12th or 13th day). The hormonally modified contraction behavior and the differing course of gallbladder filling may play a major role in the pathogenesis of gallstone formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01716215
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  • 4
    Electronic Resource
    Electronic Resource
    Wertigkeit moderner Verfahren zur Lokalisation von Phäochromocytomen (1979)
    Springer
    Journal of molecular medicine 57 (1979), S. 1209-1215 
    Details
    ISSN: 1432-1440
    Keywords: Pheochromocytoma localization ; Plasma catecholamines ; Adrenal phlebography ; Ultrasonography ; Computed tomography ; Phäochromocytomlokalisation ; Plasmakatecholamine ; Nebennierenphlebographie ; Sonographie ; Computer-Tomographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei sechs Patienten mit adrenalem Phäochromocytom erfolgte die Lokalisationsdiagnostik durch Ultraschalluntersuchung, Phlebographie der Nebennieren und selektiver Katecholaminbestimmung im Blut der Vena cava sowie der Nebennierenvenen. Durch die selektive Katecholaminbestimmung konnten alle Phäochromocytome lokalisiert werden, durch die Ultraschalluntersuchung fünf, durch die Phlebographie vier. Ein Phäochromocytom von 1,5 g Gewicht, das nur durch die selektive Katecholaminbe-stimmung, nicht aber durch Ultraschall oder Phlebographie lokalisiert wurde, konnte computertomographisch dargestellt werden. Um Fehldiagnosen bei der selektiven Katecholaminbestimmung zu vermeiden, darf vor der Blutentnahme aus den Nebennierenvenen kein Röntgenkontrastmittel injiziert werden, da dies zu einer erheblichen Adrenalin- oder Noradrenalinfreisetzung aus dem Nebennierenmark führen kann.
    Notes: Summary In six patients with adrenal pheochromocytoma the tumors were localized by ultrasonography, phlebography of the adrenal glands and by estimation of plasma catecholamines selectively obtained from the vena cava and the adrenal gland veins. All tumors were localized by selective catecholamine estimation, five by ultrasonography, and four by phlebography. The smallest pheochromocytoma of 1.5 g weight was only localized by selective catecholamine estimation but not by ultrasonography or phlebography. This tumor, however, had been visualized by computed tomography. To avoid diagnostic errors by selective catecholamine estimation, it is important to withdraw blood from the adrenal gland veins prior to the injection of any radiographic contrast media, since this may result in an extremely enhanced secretion of catecholamines from the adrenal medulla.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01489248
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  • 5
    Electronic Resource
    Electronic Resource
    Der Einfluß von Sonographie und Computer-Tomographie auf die operative Behandlung der akuten Pankreatitis (1982)
    Springer
    Langenbeck's archives of surgery 356 (1982), S. 141-149 
    Details
    ISSN: 1435-2451
    Keywords: Acute pancreatitis ; Computed tomography ; Ultrasound ; Operative treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die „stadiengerechte Therapie” der akuten Pankreatitis, die jedem Schweregrad der Erkrankung angemessen ist, besteht neben der konservativen Basistherapie und Intensivmedizin im richtigen Einsatz operativer Maßnahmen. Voraussetzung dafür ist die frühe Diagnose und Beurteilung des Schweregrades der akuten Pankreatitis. Neben klinischen und klinisch-chemischen Befunden und dem Verlauf unter konservativer Therapie ermöglichen die Sonographie und die Computer-Tomographie eine bessere Beurteilung der jeweiligen Verlaufsform. Die für die Klinik der Erkrankung so wichtigen morphologischen Veränderungen der Bauchspeicheldrüse und ihrer Umgebung werden durch diese neuartigen Untersuchungsmethoden transparenter. Wäh rend bei der leichten Pankreatitis die Sonographie als erstes morphologisches Untersuchungsverfahren eingesetzt wird, besteht bei den schweren Verlaufsformen eine klassische Indikation zur Computer-Tomographie. Durch Einsatz von Sonographie und Computer-Tomographie läßt sich die Indikation zur frühzeitigen oder verzögerten Operation der hämorrhagisch-nekrotisierenden Pankreatitis, die bisher nach klinischen Kriterien erfolgte, in den meisten Fällen exakter stellen.
    Notes: Summary Adequate stage-depending therapy of acute pancreatitis includes basic conservative treatment, intensive care measurements, and operative interventions depending on the grade of severity. Prerequisites are early diagnosis and accurate clinical assessment of the stage of severity. Beside clinical and laboratory findings, as well as the development of acute pancreatitis under conservative treatment, sonography and computed tomography allow a better prediction of the underlying morphological changes, thus leading to an exact staging of the patient's individual situation. Sonography is regarded a screening procedure of high accuracy in mild forms of acute pancreatitis. Computed tomography is the method of choice in all severe forms of this disease. The indication for immediate or delayed operative treatment of hemorrhagic necrotising pancreatitis, heretofore depending on clinical findings solely, is supported by these new-invasive diagnostic modalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01239461
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