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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3188-3190 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. © 1999 American Institute of Physics.
    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 84 (1998), S. 1196-1203 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical-field profiles in wide-band-gap AlxGa1−xN/InxGa1−xN multiple-quantum well (MQW) separate-confinement heterostructure (SCH) laser diodes (LDs) were calculated using a 2×2 transfer-matrix approach that accommodates complex refractive indices. The refractive indices of AlxGa1−xN and InxGa1−xN were approximated by shifting the refractive index of GaN according to the band-gap energy of the solid solution. Current LDs were analyzed and show reasonable optical confinement. Optimization of the SCH waveguide for a three MQW active region was performed by varying the waveguide and cladding layer thicknesses. For 0.8μm thick Al0.10Ga0.90N cladding layers, waveguides on sapphire and SiC substrates had a maximum confinement factor of ∼3.3%. Layers outside of the waveguide strongly affected the optical field for thin (∼0.4 μm) cladding layer thicknesses and resulted in resonant coupling of the light out of the waveguide. Sapphire substrates were found to enhance light confinement, while SiC substrates were found to reduce optical confinement as the cladding layer thickness is reduced. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 67-69 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dispersion of the ordinary and extraordinary indices of refraction for wurtzite AlxGa1−xN epitaxial layers with x=0.00, 0.04, 0.08, 0.11, and 0.20 in the range of wavelengths 457〈λ〈980 nm were measured via a prism-coupled waveguide technique. The quantitative accuracy of x is ±10% and the accuracy of the refractive indices is ∼±0.01. The dispersion is found to be well described by a 1st-order Sellmeier dispersion formula. A simple functional form is presented that allows calculation of the refractive indices as functions of x and λ. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Histopathology 21 (1992), S. 0 
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Eleven colloid cysts of the third ventricle were investigated by immunohistochemistry using 16 mono- and polyclonal antibodies. Colloid cyst epithelium, choroid plexus epithelium and ependyma showed different immunohistochemical profiles. In particular, antibodies to different cytokeratins and to transthyretin revealed considerable and constant differences of immunoreactivity. Therefore, common derivation of the three tissues seems unlikely. Our findings are interpreted in favour of the non-neuroepithelial origin of third ventricular colloid cysts.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The closely related synaptic vesicle membrane proteins synaptophysin and synaptoporin are abundant in the hippocampal formation of the adult rat. But the prenatal hippocampal formation contains only synaptophysin, which is first detected at embryonic day 17 (E17) in perikarya and axons of the pyramidal neurons. At E21 synaptophysin immunoreactivity extends into the apical dendrites of these cells and in newly formed terminals contacting these dendrites. The transient presence of synaptophysin in axons and dendrites suggests a functional involvement of synaptophysin in fibre outgrowth of developing pyramidal neurons. Synaptoporin expression parallels the formation of dentate granule cell synaptic contacts with pyramidal neurons: the amount of hippocampal synaptoporin, determined in immunoblots and by synaptoporin immunostaining of developing mossy fibre terminals, increases during the first postnatal week. Moreover, in the adult, synaptoporin is found exclusively in the mossy fibre terminals present in the hilar region of the dentate gyrus and the regio inferior of the cornu ammonis. In contrast, synaptophysin is present in all synaptic fields of the hippocampal formation, including the mossy fibre terminals, where it colocalizes with synaptoporin in the same boutons. Our data indicate that granule neuron terminals differ from all other terminals of the hippocampal formation by the presence of both synaptoporin and synaptophysin. This difference, observed in the earliest synaptic contacts in the postnatal hippocampus and persisting into adult life, suggests distinct functions of synaptoporin in these nerve terminals.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GTP-binding rab proteins, present in synaptic vesicles and endocrine secretory granules, have been shown to be involved in the control of regulated exocytosis. We found rab3 proteins in immunoblots of diverse areas of the mouse central nervous system (spinal cord, olfactory bulb, hippocampus, cerebellum and neocortex). Immunohistochemical observations at light- and electron-microscopical levels in the hippocampus and other areas revealed rab3 proteins in virtually all synaptic fields and terminals of the areas investigated. In the retina, rab3A immunoreactivity was confined to the inner and outer plexiform layers. Ultrastructural examination revealed that rab3A was present in conventional terminals in the inner plexiform layer and in horizontal cell processes of the outer plexiform layer. In contrast ribbon synapses, which play a key role in transferring information from the photoreceptor cells to the central nervous system, were immunonegative. We also tested whether other proteins of the rab3 family are present in ribbon synapses. However, using an antibody recognizing rab3B and rab3C in addition to rab3A, we found no immunoreactivity in these synapses. Interestingly, we observed also no immunoreactivity for synaptosomal-associated protein 25 (SNAP-25) in ribbon synapses, but conventional synapses and horizontal cell processes were heavily stained. Our data show that the known rab3 and SNAP-25 isoforms, which are components of the secretory apparatus of conventional synapses, are absent from ribbon synapses of the retina. Our observations suggest different mechanisms of transmitter exocytosis in conventional and ribbon terminals.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Histopathology 29 (1996), S. 0 
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The biological behaviour of meningeal haemangiopericytomas was retrospectively studied using immunohistochemical staining with MIB1, a monoclonal antibody against the Ki-67 antigen, a nuclear protein related to cell proliferation. Paraffin-embedded material from 62 tumours from 40 patients were investigated. The proliferating compartment of the tumours was estimated by evaluating the MIB1 staining index, i.e. the percentage of MIB1 positive nuclei in at least 1000 counted tumour cells in representative areas. The staining index ranged from 1.24% to 39.01%. Statistical analysis revealed no significant correlation between the staining index and recurrence-free survival (χ2 = 0.3922, P = 0.5311). Long-term observation (〉100 months), however, revealed a tendency to longer survival in the group with a staining index less than 5%. According to our results, the MIB1 staining index does not contribute to the accuracy of predicting the clinical outcome of meningeal haemangiopericytomas.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1434-5196
    Keywords: Key words Internal cerebral vein thrombosis ; Sinovenous thrombosis ; Colitis ulcerosa ; Trauma ; Schlüsselwörter Hirnvenenthrombose ; Sinusthrombose ; Trauma ; Colitis ulcerosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Venöse Abflußstörungen des Gehirns werden mit unterschiedlicher Häufigkeit im Obduktionsgut aufgeführt. Neben entzündlichen Prozessen, hämorheologischen Störungen und Neoplasien kommen bei der forensischen Begutachtung traumatische Ursachen für die Genese von Thrombosen in Frage. Berichtet wird über eine 14 Jahre alt gewordene Schülerin, die 2 1/2 Tage nach einer tätlichen Auseinandersetzung verstarb. Anamnestisch wurde von einer Colitis ulcerosa berichtet. Initial waren weder äußere Verletzungen noch neurologische Auffälligkeiten erkennbar. In der Nacht wurde sie komatös in der Klinik aufgenommen. Die kranielle computertomographische Untersuchung zeigte eine zunehmende intraventrikuläre und intrazerebrale Blutung, Zeichen der venösen Stauung und ein Hirnödem. Die Patientin verstarb im dissoziierten Hirntod. Neuropathologisch fand sich eine in Organisation stehende Thrombose des Sinus sagittalis superior, die sich in die inneren Hirnvenen fortsetzte und die durch die entzündliche Darmerkrankung verursacht war. Eine traumatische Genese war somit auszuschließen.
    Notes: Abstract Thromboses of the cerebral veins which occur at a frequency of 3.75 to 9.3% in autopsy material are caused by local or systemic inflammatory processes, hematological disorders, neoplasms or traumatic brain damage. We report on a 14-year-old girl who suffered from colitis ulcerosa during the last 4 years of life. Immediately after a brawl with a schoolboy she complained of headache and vertigo, but no physical abnormality was detected by the physician. She was admitted to the hospital after becoming comatose during the following night. On neurological examination she was comatous with a decerebrate state, the pupils were small and non-reactive to light, divergent ocular bulbi and bilateral extensor plantar responses. A cerebral computer tomogramm showed a cerebral edema and a hemorrhage in the left basal ganglia and both cerebral ventricles which subsequently increased to the right cerebral ganglia, the corpus callosum and the right cerebral hemisphere. Despite antiedematous therapy the girl died on the second day after the brawl. A neuropathology examination revealed thrombosis of the superior sagittal sinus extending to the internal cerebral veins and a bilateral hemorrhagic infarction of the thalamus and the basal ganglia with intraventricular hemorrhage. As the thrombus in the sagittal sinus showed signs of organisation, a postraumatic origin alone is improbable and a hemorrheological disorder due to colitis ulcerosa seemed to be the main cause.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-0350
    Keywords: Neonatal intracranial aneurysm ; Cerebral aneurysm in childhood ; Familial intracranial aneurysm ; Collagen type III ; Cerebral hemorrhage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 32-day-old boy died of recurring cerebral hemorrhages starting on the 4th day of life. Autopsy disclosed a remittingly ruptured saccular aneurysm of the anterior communicating artery. A 7-day-old brother of his had previously died of recurring subarachnoid hemorrhages as well. The young age of the patient, the site of the aneurysm, and its probably familial occurrence make this case a unique one. Nonaneurysmatic basal cerebral arteries showed remarkable histological changes partly resembling those seen in fibromuscular dysplasia, some of them probably representing preaneurysmatic alterations. A known underlying systemic disease could not be found, and immunohistochemical detection of type III collagen revealed no identifiable deficiency.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 9 (1993), S. 394-399 
    ISSN: 1433-0350
    Keywords: Lissencephaly ; Agyria ; Neuronal migration ; Miller-Dieker syndrome ; Walker-Warburg syndrome ; Congenital muscular dystrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neuropathological findings at autopsy in four cases of type I and three of type II lissencephaly are presented. Type I lissencephaly is characterized by agyriapachygyria with a markedly thickened cerebral cortex with four coarse histological layers. The normally myelinated white matter, often with neuronal heterotopias, is very narrow, and the gray-to-white matter ratio is inverted (about 4:1); there are no white-gray interdigitations. Claustrum and capsula extrema are absent. Ventricular dilatation is present, especially of the occipital horns. In the hypoplastic brain stem large olivary heterotopias can often be observed. Severe cerebellar malformations, obstructive hydrocephalus, severe eye abnormalities, and congenital muscular dystrophy are not seen. Clinically, type I lissencephaly presents as “isolated lissencephaly sequence” or as “Miller-Dieker syndrome” with characteristic facial dysmorphism. The long survival of 20 years achieved by one of our patients is very uncommon. Type II lissencephaly is characterized by widespread agyria. Usually, obstructive hydrocephalus is present with a thin cerebral mantle showing a slightly thickened cortex and a narrow, hypomyelinated white matter often with neuronal heterotopias (gray-to-white matter ratio about 1:1). The border between gray and white matter is blurred. Claustrum and capsula extrema are absent. Histologically, the cortex appears disorganized without layering; widespread leptomeningeal gliomesenchymal proliferations and glioneuronal heterotopias are present. Hydrocephalus is caused by obstruction of the subarachnoid space, aqueductal stenosis, and Dandy-Walker malformation. The latter is a typical finding in type II lissencephaly together with severe cerebellar cortical dysplasias. Aplasia of the olfactory nerves, gliotic fusion of the frontal lobes, and an occipital cephalocele may be found. Type II lissencephaly occurs in clinical syndromes with severe eye abnormalities and congenital muscular dystrophy (the so-called “Walker-Warburg syndrome”). The congenital muscular dystrophies have no dystrophin deficiency, as we were able to show immunohistochemically in the muscle biopsies of two further patients with this syndrome.
    Type of Medium: Electronic Resource
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