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  • 42.55  (2)
  • Cell & Developmental Biology  (1)
  • Control angiography  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 61 (1995), S. 429-437 
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 61 (1995), S. 569-579 
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Langenbeck's archives of surgery 355 (1981), S. 517-517 
    ISSN: 1435-2451
    Schlagwort(e): Polyurethane graft ; Microporosity ; Control angiography ; Scanning electronic microscopy ; Polyurethanprothesen ; Mikroporosität ; Kontrollangiographie ; Rasterelektronenmikroskopie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die neuen Kunststoffprothesen bestehen aus Polyúrethan, das nach einem speziellen Sprühverfahren verarbeitet wird. Die Prothesen sind längs- und querelastisch sowie mikroporös. In tierexperimentellen Untersuchungen wurden 20mal die terminale Aorta, 24mal die arteria carotis communis und 12mal die arteria femoralis superficialis ersetzt. Die Tiere wurden in regelmäßigen Abst↭den angiographiert. Nach Tötung erfolgten rasterelektronenmikroskopische und histologische Untersuchungen. Von 20 Aortentransplantaten blieben 18 bis zum Zeitpunkt der Tötung, bzw. bis heute offen. In Carotisposition scheinen sich die Transplantate nicht zu bewähren.
    Notizen: Summary The new plastic graft consists of polyurethane manufactured in a special spray process. These grafts are elastic both transversally and longitudinally and are microporous. In experiments on animals, the abdominal aorta was substituted 20 times, the common carotid artery 24 times, and the superficial femoral artery 12 times. The animals were regularly subjected to angiographical examinations. After they were killed, they were examined histologically and by means of a scanning electronic microscope. Of the 20 abdominal grafts, 18 have remained open to date. Carotis grafts, however, seemed to fail.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 212 (1985), S. 345-352 
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Previous studies have shown that sexual activity increases the weight of the accessory sex glands significantly, while the organ weights correlate inversely with the assayable androgen receptor concentrations in the prostate of sexually active versus sexually resting rats. In an effort to determine the structural basis of this phenomenon, the ventral prostates of adult rats kept with female rats for 4-6 months (HE-rats) were compared to those kept in groups of 5 males in one cage (HO-rats) for the same period. As an estimate of the secretory function of the gland the concentration of prostatic binding protein (PBP) was determined in prostatic cytosols using a highly specific ELISA. Catecholamines were measured by means of HPLC and subsequent electrochemical detection. Morphological studies included immunocytochemistry of PBP, visualization of adrenergic nerves, stereological analysis of stromal and glandular compartments of the prostate, and electron microscopy of the epithelium.The main findings were as follows: (1) The prostates of HE-rats were 35% heavier than those of the HO-rats. (2) The content in secretion was in the same range in both HE-rats and HO-rats (1.5 and 1.44 mg PBP per 1 mg DNA). (3) Immunocytochemistry and electron microscopy demonstrated a very homogeneous secretion within the glandular lumen of HO-rats with a diminished amount of secretory material within the glandular cells.In HE-rats the glandular lumina were clearly larger in diameter and intraluminal secretion was less homogeneously stained. The height of the epithelium was increased and the individual secretory cells contained several secretory granules. Within the prostatic stroma the profiles of adrenergic nerves were more numerous in HE-rats, and a greater total amount of noradrenaline was present. At the fine structural level signs of enhanced membrane turnover, such as lysosomal structures, were prominent in prostatic epithelium of HE-rats, while in HO-rats mostly dense bodies were observed. The results indicate that sexual activity results in the functional adaption (activity hypertrophy) of the prostate as a result of nerve-associated control of glandular activity.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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