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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 397-403 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An unusual new line has been observed in the low-temperature photoluminescence spectrum of GaAs/AlGaAs epilayers grown by liquid-phase epitaxy, which represents a unique probe of the heterointerface. A very strong, broad and asymmetric line is seen, with peak energy ranging from that of the bound exciton to that of the shallowest acceptor, increasing roughly linearly with the logarithm of the excitation power. The intensity is seen to exhibit a very strong temperature dependence as the temperature is varied from 1.4 K up to about 20 K where the line falls below the background luminescence intensity. Intensity and energy dependence of the luminescence as a function of the Al mole fraction on one side of the junction is also investigated. By employing a novel step-etching technique, this transition is shown to originate from the GaAs/AlGaAs heterojunction. A qualitative model is proposed to explain the observed data.
    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 57 (1985), S. 2896-2899 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoluminescence of Ge-doped AlxGa1−xAs and Sn-doped GaAs were investigated at 1.4 K. The ionization energy of Ge is strongly dependent on the Al composition in AlGaAs, and is in very poor agreement with the effective mass value. The ionization energy of Sn was found to be 110 meV in contrast with previously reported values. We also report a Sn acceptor bound excitation line at 1.507 eV in Sn-doped GaAs, and a broad luminescence band peaking at ∼1.5 eV in Ge-doped AlGaAs.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2309-2311 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the modulation characteristics of multiple quantum well tunneling injection lasers designed for 0.98 μm emission wavelength. Electrons are injected into the active region through a single barrier via tunneling. The active region has four quantum wells with different well widths. Improved high frequency performance, compared to similar separate confinement heterostructure lasers, has been demonstrated. The modulation response at 21 GHz is above 0 dB and the extrapolated −3 dB modulation bandwidth is ∼30 GHz under pulsed bias. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Der Pathologe 17 (1996), S. 213-218 
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Riesenaxonale Neuropathie ; Mikrofilamentallagerung ; Key words Giant axonal neuropathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We report a sporadic case of giant axonal neuropathy (GAN) starting in a 5-year-old boy with gait disturbance. At the age of 10 years he showed signs of a sensomotoric polyneuropathy and central neurological symptoms: intention tremor, nystagmus and visual disturbance. The boy also had curly hair. Sural nerve biopsy showed many giant axons with accumulation of microfilaments, which were also found in cytoplasma of Schwann cells, endothelial cells and fibrocytes. Similar changes were detected in endothelial cells of a muscle biopsy, which additionally displayed neurogenic atrophy and target fibers. Immunohistochemically, desmin, vimentin, heat shock protein 70, and ubiquitin were not detectable in giant axons, which, however, contained neurofilament protein 68, 200 and β -tubulin. Our case shows that careful ultrastructural examination of a muscle biopsy may point to the diagnosis of GAN.
    Notes: Zusammenfassung Wir berichten über einen sporadischen Fall von Riesenaxonneuropathie (RAN), die bei einem 5 jährigen Jungen mit einer progredienten Gangstörung begann. Auffällig waren außerdem stumpfe, gekräuselte Haare. Im Alter von 10 Jahren bestanden eine sensomotorische Polyneuropathie und zentral-neurologische Symptome: Visusminderung, sakkadierte Blickfolge und Intentionstremor. Die Biopsie des N. suralis bestätigt das Vorliegen einer Neuropathie und zeigt viele Risenaxone mit ultrastruktureller Anhäufung von Mikrofilamenten. Diese sind auch im Zytoplasma der Schwann-Zellen, Endothelzellen und Fibrozyten zu erkennen. Auch intramuskuläre Endothelzellen enthalten gleichartige Veränderungen; darüber hinaus ist im Muskel ein neurogenes Gewebsbild ausgebildet. Immunhistochemisch exprimieren die Axone Neurofilamentprotein 200 und 68 sowie β -Tubulin, jedoch weder Desmin, Vimentin, Heat-shock-Protein 70 oder Ubiquitin. Der Fall illustriert, daß die ultrastrukturelle Untersuchung einer Muskelbiopsie diagnostische Hinweise für eine RAN liefern kann.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 3033-3035 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0533
    Keywords: Key words Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) ; Hereditary multi-infarct dementia ; Skin biopsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized clinically by recurrent cerebral infarcts, subcortical dementia and pseudobulbar palsy, and morphologically by a granular degeneration of cerebral and, to a lesser degree, extracerebral blood vessels. We present morphological findings in a further German family affected by CADASIL. The index case showed the typical periodic acid-Schiff-positive granular degeneration of vascular smooth muscle cells (VSMC) in cerebral vessels, which did not react with antibodies against various immunoglobulins or complement factors. Ultrastructurally, granular osmiophilic material (GOM) covered the VSMC in different cerebral regions as well as in extracerebral organs (muscle, nerve, skin, small and large intestine, liver, kidney and heart). Skin biopsy samples from other family members of the last two generations also revealed GOM irrespective of the clinical symptomatology (CADASIL, migraine only or asymptomatic). Patients in the third generation had higher amounts of GOM in skin vessels than did asymptomatic or migraine patients in the fourth generation. We conclude that skin biopsy is a useful and less-invasive screening method for the differential diagnosis of CADASIL.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 253 (1996), S. 367-370 
    ISSN: 1434-4726
    Keywords: Furosemide-induced ototoxicity ; Scala tympani ; Oxygen tension ; Auditory cortical-evoked potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of intravenous furosemide on the perilymphatic oxygen tension of the scala tympani (OT) in the guinea pig and the relationship between changes in OT and changes in auditory cortical-evoked reponses were studied, as well as changes in cochlear morphology. Furosemide in dosages of 25 mg/kg and 50 mg/kg caused a sharp decline in OT in addition to elevation of the threshold of auditory cortical-evoked responses. Ischemia of the cochlear stria vascularis was also found but without any damage of hair cells at the light microscopic level. Changes in OT were associated with transient threshold elevations and ischemia of the stria vascularis. Improvements in hearing were directly proportional to the recovery of OT.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 20 (1999), S. 755-770 
    ISSN: 1572-9567
    Keywords: chemical potential ; CVM ; free energy ; grand potential ; magnetic transition ; mixing entropy ; phase equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The phase equilibrium between structural phases with a magnetic transition is investigated using the CV-pair approximation of the cluster variation method (CVM). By the geometric analysis of the grand potential, it is demonstrated that the grand potential and effective chemical potential of the different structural phases with a magnetic transition can be separated into paramagnetic and magnetic terms. In addition, the molar grand potential-effective chemical potential curve can be obtained from the relevant molar energy diagram. A calculation method for the phase equilibrium between structural phases with a magnetic transition is proposed; this method is applied to the α/γ phase equilibrium in the Fe–Mn binary system, and the calculated phase diagram closely approximates the experimental diagram.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The protein journal 16 (1997), S. 733-738 
    ISSN: 1573-4943
    Keywords: Catalytic antibody ; transition-state analogue ; inhibitor ; screening ; ester hydrolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Monoclonal antibodies were raised against a β-naphthyl phosphonate hapten (1) to elicit antibodies capable of catalyzing the hydrolysis of β-naphthyl acetate (3). After cell fusion, potential catalytic antibody-producing hybridomas were selected, by use of a competitive inhibition assay on the basis of the binding activity for a short transition-state analogue (inhibitor 5), followed by use of high-performance liquid chromatography analysis for the hybridoma supernatants to screen the antibodies processing catalytic activities. It was shown that supernatants of 12 wells had high binding activity with inhibitor and of them, 7 had catalytic activities. After cloning by limiting dilution, we got two hybridoma clones producing monoclonal antibodies which catalyzed the hydrolysis of β-naphthyl acetate. This combination of competitive inhibition assay with high-performance liquid chromatography analysis represents an improved rapid approach for the screening of potential catalytic antibodies and significantly increases the possibility of obtaining efficient catalytic monoclonal antibodies. Further study of the catalytic antibodies revealed significant rate enhancement (K cat/K uncat ∼ 106) and specificity.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 33 (1998), S. 5773-5780 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract TiC whiskers with good quality and high yield are prepared by a modified chemical vapour deposition (CVD). The whisker morphology and factors affecting its formation have been investigated. Various whisker morphologies such as Wool-, Hassock-, Cluster-, bar-, Hedgehog-, and bamboo-like, are observed under different conditions. The morphologies of TiC whiskers are markedly affected by the gas flow rate and the C/Ti ratio, which is supposed to be related to concentration variation and the formation of Ni-Ti eutectic liquid phase. The growth characteristics of TiC whiskers are also affected by the stability of deposition parameters. It is found that in the course of whisker growth on nickel substrate, the well known VLS mechanism is not necessarily dominant. It is effective in the initial stage, but then might change to the VS mechanism with the dissipation of liquid droplets at the whisker tips. The deposition temperature plays an important role in changing from the VLS to the VS mechanism.
    Type of Medium: Electronic Resource
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