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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 143-147 (Oct. 1993), p. 567-572 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6178-6185 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnSexTe1−x epilayers were investigated by means of luminescence, reflectivity, and temperature dependence in the concentration range 0〈x〈0.4. The studied ZnSexTe1−x epilayers with thicknesses of about 1.5 μm were grown on GaAs substrates by metalorganic vapor phase epitaxy. It was found that the luminescence and reflectivity spectra of the mixed crystals are strongly affected by the compositional disorder. A continuous transition from the recombination through free and bound exciton states to the recombination of excitons localized by the compositional fluctuations of the mixed crystal was observed in the concentration region of about x=0.25. The position of the excitonic band edge was derived from the photoluminescence excitation spectra and from temperature dependence of the emission spectra.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2581-2583 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two sharp and intense emission bands with the maxima of 2.185 and 2.150 eV and a weak phonon coupling were investigated in the heteroepitaxial ZnTe layers. The study of the ZnTe layers grown on different substrates with thicknesses of 0.5–3.2 μm has shown that this luminescence is produced in the interface region that contains a high density of structural defects. The temperature dependence of these bands reveals the excitonic character of the recombination. We propose that the observed bands originate from the recombination of excitons localized at structural defects such as dislocations and associated defects.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 551-557 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new method is developed for calculating the correlation function of the random deformation in heteroepitaxic layers and superlattices from measurements of iso-intensity contours of diffuse X-ray scattering. The method is based on the optical coherence approach and kinematical diffraction theory. Structural models have been found that enable the correlation functions to be calculated for various types of randomly placed defects (mosaic blocks and random elastic deformation). The applicability of the method has been demonstrated by measuring the diffuse X-ray scattering from a ZnTe layer grown on a GaAs substrate. The parameters characterizing the defects were obtained from a comparison of the calculated correlation function with theoretical models.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-0130
    Keywords: Split vascularized fibula ; Vascularized periosteal flap ; Bone defects ; Reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new principle in reconstructive surgery is presented: “The immediate reconstruction of a missing bone segment with a primary osteoperiosteal tube that will secondarily be transformed into a complete osseous tube. ” In 5 out of 7 baboons, a bone tube with an almost normal bone cavity was achieved after 16 to 28 weeks. In 2 cases, we failed to reconstruct the tube because of an intraoperative fault and postoperative plate fracture with subsequent destruction of the vascularized periosteal flap. On the basis of this study, we describe a new concept in reconstruction of segmental bone defects of the lower extremity. The osteoperiosteal tube is formed by the combination of two successful experimental and clinical techniques: the vascularized fibular transfer which is modified by splitting the bone graft longitudinally, and transfer of vascularized periosteum (“concept of the substitution of a missing bone segment by an organ-like tube”). In the most stressed marginal region of the bone defect, there is vascularized cortical bone from the longitudinally split fibular graft and an increasing amount of lamellar bone being produced under the vascularized periosteal flap. By splitting the graft, nutrition depends entirely on the periosteal blood supply. The “concept of the dual blood supply” was initially described by Berggren et al. and Papanastasiou et al. [4, 18]. The significance of the “concept of the vascularized periosteum transfer for reconstruction of a segmental bone defect” is well illustrated. Only in cases where the vascularized periosteal flap was intact and securely sutured to the fibulae graft and the two tibia stumps could a bone tube be reconstructed. The arrangement of both vascularized grafts as an osteoperiosteal tube exemplify the “concept of the given space” as described by Stock et al. [26]. Inside the osteoperiosteal tube, a “consolidation chamber” is created in which all the factors required for bone formation can be concentrated. Comparison of the results of successfully reconstructed bone tubes with the solid bone column in the defect of the baboon where no bone tube could be reconstructed underline the “concept of combination of different vascularized grafts for reconstruction of segmental bone defects in long bone defects of the lower extremity.”
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European radiology 3 (1993), S. 453-458 
    ISSN: 1432-1084
    Keywords: Liver ; Liver neoplasms ; Hepatocellular carcinoma ; MR studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nineteen patients with 28 histologically proven hepatocellular carcinomas (HCCs) were examined using T1- and T2-weighted spin-echo sequences and dynamic gadopentetate dimeglumine-enhanced magnetic resonance imaging (MRI) performed by fast T1-weighted gradient-echo sequence (100/5/80°) which was performed before and repeatedly (12 sets of images) after intravenous bolus injection of gadopentetate dimeglumine (Gd-DTPA) over a period of 10 min. Enhancement of HCC was heterogeneous in 24 lesions (85.7%). Intra-lesional non-enhancing areas were seen in 18 cases (64%). A late-enhancing pseudocapsule was seen in 12 lesions (42.9%). In addition, two groups were distinguished in the examined HCCs: 16 lesions (57.1%) showed stronger enhancement compared to liver parenchyma with maximum positive lesion-to-liver contrast on the 15-s images, while 12 lesions (42.9%) had an enhancement less than normal liver with a maximum negative contrast on the 15-s images. We conclude that the morphologic features most frequently encountered in HCC on dynamic Gd-DTPA-enhanced MRI are inhomogeneity of enhancement, intra-lesional non-enhancing areas, and relatively late enhancement of a pseudocapsule. Taking the degree of enhancement to be representative of the degree of vascularity, we also conclude that HCC can appear either hypervascular or hypovascular in the early phase of the dynamic study.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 376 (1991), S. 257-263 
    ISSN: 1435-2451
    Keywords: Parenteral nutrition ; LCT-fat ; Yoshida sarcoma ; Tumor growth ; Nitrogen balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einer experimentellen Untersuchung an Sprague-Dawley-Ratten wurden die Auswirkungen von parenteral zugeführten LCT-Fetten auf das Tumorwachstum des Yoshida-Sarkoms in seiner Aszites form überprüft. Dabei wurden 4 Gruppen mit je 10 tumortragenden (TTR) and 10 nicht tumortragenden Ratten (NTTR) gebildet, denen parenteral LCT-Fette in unterschiedlicher Dosierung (Gruppe 1–3) zugeführt, bzw. die enteral ad libitum ernährt wurden (Gruppe 4). Es zeigt sich, daß die tumortragenden Ratten (TTR) cine höhere Stickstoffretention aufwiesen, als die nicht tumortragenden Ratten (NTTR). Dabei fiel auf, daß die NTTR einen höheren Stickstoffgehalt in der Muskulatur hatten. Der Stickstoffanteil nahm dabei mit zunehmendem Fettanteil ab. Die Betrachtung des Sarkoms ergab, daß sich sowohl der Stickstoffgehalt des Aszites, wie auch die Menge and die Zellzahl des Tumors umgekehrt proportional zur Menge des parenteral zugeführten Fettes verhielt. Für den Wirt konnten wir zeigen, daß er die zugeführten Energiemengen nicht unmittelbar für sich verwerten konnte. Der Tumor wächst nicht proportional mit der ihm zugeführten Energie, sondern muß sich vom Katabolismus des Wirtes ernähren.
    Notes: Summary In an experimental study with sprague-dawley-rats we tested the effect of parenteral substituted LCT-fats on tumor growth of the Yoshida sarcoma in its ascites form. Therefore we tested 4 groups with 10 tumor-bearing and 10 non-tumor-bearing rats. We added group 1–3 LCT-fats in different doses. Group 4 was fed enterally. We found that tumor-bearing rats had a higher nitrogen retention than non-tumor-bearing rats. Non-tumor-bearing rats showed a higher nitrogen concentration in the muscles. The portion of nitrogen increased with increasing portion of fat. The content of nitrogen in the ascites, the quantity and the number of tumor cells was reversed in proportion to the portion of fat. For the host we showed that he cannot make use of the energy directly. The tumor does not grow in proportion to the available energy but has to support itself from the catabolism of the host.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 165 (1991), S. 51-63 
    ISSN: 1615-6102
    Keywords: Bivalent structure ; Meiosis ; Microtubules ; Mitochondria ; Nuclear envelope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using ultrathin sections and electron microscopy, the structure of prophase I spermatocytes is described in the mothEphestia kuehniella Z. Some stages were also examined using light microscopy and antitubulin immunofluorescence microscopy. Changes in the mitochondrial inventory, the endomembranes, and the nuclear content during the progression of meiosis from pachytene to diakinesis have a bearing on the structure of prometaphase and metaphase I spermatocytes. In late diplotene, a short-lived system of cytoplasmic microtubules forms independently of the flagellar bases. Possibly mediated by these microtubules, mitochondria gather in a portion of the cell and fusion of individual mitochondria occurs. The clustering of mitochondria, which persists until the meiotic spindle has developed, may be the prerequisite for the bipartition of the chondriome during cytokinesis. After late pachytene, the mass of perinuclear endoplasmic reticulum and the number and size of the Golgi stacks also increase. These endomembranes give rise to the multi-layered membraneous envelope around the meiotic spindle and probably to the intraspindle membrane system. After late pachytene, the number of nuclear pores also increases and material export from the nucleus is apparent. The exchange is interpreted as an indicator for transcriptional activity in the late prophase I nucleus when the chromatin is transiently decondensed (diffuse stage). In the course of chromatin recondensation, the bivalents assume a speckled appearance in ultrathin sections. Metaphase I bivalents possess lighter staining equatorial material. This material is not stained with a DNA-specific fluorescent dye or with acetic orcein, which preferentially binds to chromatin. It is hypothesized that less dense core material becomes interspersed with chromatin during the diffuse stage and is involved in the maintenance of bivalent structure until the onset of anaphase I.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1615-6102
    Keywords: Asters ; Microtubules ; Mitosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using an antibody against tyrosinated tubulin and epifluorescence microscopy, mitosis was studied in three different microvessel endothelial cell types recently isolated from bovine corpus luteum. Dividing cells were flat and at certain stages individual microtubules could be followed for considerable lengths. The structure of the spindle apparatus and the course of mitosis were conventional. Microtubule asters were small from prophase until metaphase in all three cell types. However, whereas in two cell types telophase asters remained inconspicuous, prominent asters, of mostly straight microtubules, formed in telophase cells of a third cell type. Thus, aster size is heterogeneous between different endothelial cell types. Large microtubule asters are not regularly found in dividing cultured mammalian cells. The microendothelial cell types present themselves as appropriate systems for spindle research and especially for the study of aster microtubule dynamics and function.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 18 (1991), S. 409-412 
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.80.+s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The kinetics of cluster formation in supersonic jets is examined by numerical integration of the master equation system. Some general characteristics of cluster kinetics could be formulated. Excellent agreement between experimental curves of p-cresol (H2O)0, 1, 2, 3 formation as function of H2O pressure and the corresponding calculated curves were obtained assuming successive cluster formation. From the kinetic curves, an unambiguous assignment of cluster size was possible which agreed with mass-resolved REMPI measurements. The fit of the rate coefficients shows the formation of p-cresol (H2O)1 to be faster than p-cresol (H2O)2 and p-cresol (H2O)3.
    Type of Medium: Electronic Resource
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