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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8035-8038 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Strain relaxation and its effect on domain formation of epitaxial PbTiO3 thin films grown on MgO (001) substrates were investigated as a function of film thickness by two-dimensional reciprocal space mapping using synchrotron x-ray diffraction. Within a few hundreds of angstrom region, it was observed that c-domain abundance, α, was critically dependent on film thickness. As the film thickness increased further, α was saturated at a value of ∼0.75. The HK mesh scan on PbTiO3 (100) reflections revealed that directional tilting of a domains with four-fold symmetry began to develop as the film thickness exceeded 650 Å. Thermodynamic equilibrium relief of the coherency strain was evaluated based on Mattews–Blakslee criteria that determine thickness dependent misfit accommodation. This theoretical consideration with experimental results led us to conclude that the unrelaxed residual misfit strain has a significant effect on the domain formation, particularly in the region below the thickness of 1000 Å. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The international journal of advanced manufacturing technology 16 (2000), S. 739-747 
    ISSN: 1433-3015
    Schlagwort(e): Key words: Assembly modelling; Feature-based; Injection moulds; Object-oriented
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0942-0940
    Schlagwort(e): Keywords: Cromakalim; potassium channel; subarachnoid hemorrhage; vasospasm.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary ¶ Background. Delayed cerebral vasospasm remains an unpredictable and inadequately treated complication of aneurysmal subarachnoid hemorrhage (SAH). Recent evidence indicates that the potassium channel activator cromakalim is capable of limiting cerebral vasospasm in rabbits when administered immediately after experimental SAH (i.e. before spastic constriction has been initiated). However, the ultimate clinical value of cromakalim for treating vasospasm will depend in part on its effectiveness when administered after SAH-induced constriction has already been initiated. The present study examined the effects of cromakalim on vasospasm when treatment was initiated after SAH-induced constriction was underway.  Methods. New Zealand white rabbits were subjected to experimental SAH by injecting autologous blood into the cisterna magna. Cromakalim (0.03, 0.1 or 0.3 mg/kg) or vehicle was injected intravenously at 8 hour intervals beginning 24 hours post-SAH. Animals were killed by perfusion fixation 48 hours after SAH. Basilar arteries were removed and sectioned, and cross-sectional area was measured.  Findings. The average cross sectional areas of basilar arteries were reduced by 64% and 68% in the SAH-only and SAH+vehicle groups, respectively. Treatment with cromakalim dose-dependently attenuated SAH-induced constriction. The groups treated with 0.03, 0.1, and 0.3 mg/kg cromakalim exhibited average decreases in cross-sectional area of 57%, 42%, and 19%, respectively.  Interpretation. These findings indicate that cromakalim dose-dependently attenuates cerebral vasospasm when administered 24 hours after experimental SAH in the rabbit. The results suggest KATP channel activators, such as cromakalim, could be of benefit for reversing cerebral vasospasm after aneurysmal SAH.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1433-0350
    Schlagwort(e): Key words Arachnoid cyst ; Middle cranial fossa ; Fenestration ; Shunt-independent
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The best operative intervention for children with arachnoid cysts remains the subject of controversy. Recent reports stress that craniotomy for cyst fenestration is associated with a low incidence of morbidity and mortality and may leave the child shunt-independent. Among a total of 66 intracranial arachnoid cysts operated on in the authors’ department from 1985 to 1997, 44 cases (67%) were located in the middle cranial fossa. A higher incidence in the first decade of life (53 cases) and a marked male predominance (45 cases) were recognized. Headache, cranial deformities, symptoms of raised intracranial pressure, and seizures constituted the most frequent features of the clinical presentation. To determine which treatment provides the greatest benefit with the lowest incidence of complications, the records of the 44 patients with arachnoid cysts in the middle cranial fossa were reviewed. The mean age of these patients was 4.6 years (range 0–16 years). Different types of initial surgical procedures were performed. In 33 patients with middle cranial fossa arachnoid cysts (MCFAC) the initial surgery took the form of craniotomy with excision of the cyst walls and fenestration into the basal cisterns. Shunting procedures were performed in 9 patients: cysto-peritoneal shunts (CPS) were placed in 4 patients and ventriculo-peritoneal shunts (VPS), in 3 patients, and cyst excision was performed in addition to CPS in 2 patients. Excision of the cyst membrane alone without fenestration was performed in 2 patients. The initial treatment was successful in terms of reduced symptoms and decreased cyst size, with no additional treatment needed for the cyst, in 79% (26/33) of patients who had undergone excision of the cyst walls and fenestration into the basal cisterns, compared with 66% (6/9) of patients who had undergone shunting procedures. Cyst membrane excision was not successful in any of the patients who underwent this procedure alone. No significant difference in morbidity was noted between these different treatment options. On follow-up CT scan and MRI, cysts of types I and II (Galassi classification) exhibited a steady tendency to reduction or obliteration. These results confirm that radical excision of the outer and inner membranes of the cyst wall with fenestration into the basal cistern is a safe and effective shunt-independent procedure for MCFAC, especially for those of types I and II.
    Materialart: Digitale Medien
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