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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4411-4420 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method to deduce energy distributions of defects in the band gap of a semiconductor by measuring the complex admittance of a junction is proposed. It consists of calculating the derivative of the junction capacitance with respect to the angular frequency of the ac signal corrected by a factor taking into account the band bending and the drop of the ac signal over the space charge region of the junction. Numerical modeling demonstrates that defect distributions in energy can be reconstructed by this method with high accuracy. Defect distributions of polycrystalline Cu(In,Ga)Se2 thin films are determined by this method from temperature dependent admittance measurements on heterojunctions of Cu(In,Ga)Se2 with ZnO that are used as efficient thin film solar cells. © 1996 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)
    Review of Scientific Instruments 67 (1996), S. 2490-2495 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Results of a pilot study with a spectro-streak apparatus applying a grating microspectrometer with a self-focusing reflection grating are reported. The microspectrometer chip (dimensions: 17×6.4 mm2; 125 μm effective thickness of the three-layer x-ray resist system), fabricated with the versatile LIGA technique, has been adapted to a picosecond streak camera. Performance tests have been carried out with a fluorescent probe exhibiting a dynamic Stokes shift of the exciplex fluorescence band due to solvation of the charge transfer dipole within about 400 ps. The use of a LIGA microspectrometer in ultrafast spectroscopy proved to be of advantage in time-resolved studies of complex luminescence spectra where a moderate spectral resolution is required and a large spectral range must be covered. © 1996 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 69 (1996), S. 2888-2890 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy was measured on Cu(In,Ga)(S,Se)2 thin film and single crystal heterojunctions. The emission rates of defects for various near-stoichiometric compositions follow a Meyer–Neldel rule, showing increasing attempt-to-escape frequencies with increasing defect depth. Defects in highly (In,Ga)-rich material showed lower attempt-to-escape frequencies and follow a separate Meyer–Neldel relation. Repetitive air annealing of a CuInSe2 heterojunction revealed a shift of the depth and capture cross section of an observed defect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 25-27 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of a postdeposition anneal on the structure and dielectric properties of epitaxial BaxSr1−xTiO3 (BST) thin films (x=0.35–0.65) have been measured. The films were grown by pulsed laser deposition on LaAlO3 (001) substrates. The films were single phase and (001) oriented with a lattice parameter larger than the bulk. The dielectric properties of the x=0.35 film exhibited a broad temperature dependence and a peak at 168 K, which is 36 K below the peak observed in bulk BST (x=0.35). Annealing films for 8 h in flowing oxygen at 900 °C caused the lattice parameter to decrease and dielectric properties to become more like the bulk. Annealing also resulted in an increased electric field dependent dielectric tuning without increased dielectric loss. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 7 (1995), S. 0 
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Several Miocene basins are developed on a mosaic of deformed Mesozoic carbonate platforms and ophiolitic units in the Antalya region of south-west Turkey. Two of these, the Manavgat and Köprü basins, show contrasting orientations and stratigraphies. The Manavgat basin is orientated broadly SE-NW and contains a succession of shallow-water reef carbonates overlain by a thick sequence of deeper-water marls. The upper part of the succession consists of sandstones, siltstones and conglomerates, mainly deposited by gravity processes. The stratigraphy of the N-S Köprü basin can be subdivided into a western part, which consists of coarse fan delta-conglomerates with local patch reefs, and an eastern part with thinly bedded sandy turbidites. Tooi marks indicate north to south flow in the north of the basin, but a southeasterly direction in the area of intersection with the Manavgat basin in the south-east. In the light of alternative regional hypotheses, it is thought that early Miocene basin initiation is related to coeval southeastward thrusting of the Mesozoic Lycian Nappes. Flexural loading is inferred to have resulted in block faulting of the foreland and this exploited pre-existing lines of structural weakness, dating from early Mesozoic rifting. mid-Miocene relative sea- level rise may relate to global eustacy, and/or regional tectonic subsidence. Finally, late Miocene renewed coarse clastic input (locally very coarse) and basin infilling reflect tectonic uplift to the north, possibly related to continuing Africa-Eurasia convergence in the region.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Scandinavian journal of immunology 43 (1996), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Natural killer (NK) cells in HIV-infected patients have a reduced ability to generate non-MHC restricted cytotoxicity to a variety of target cells. The authors investigated antibodies to NK cells in HIV-infected patients and evaluated effects of these antibodies to NK cell numbers and function. Antibodies to NK cells were determined in 160 HIV-infected patients and 35 healthy controls. Flow cytometric whole blood methods were developed to detect antibodies to NK cells. Antibodies to asialo-GM1 were detected by TLC immunostaining. The presence of antibodies to NK cells was demonstrated in plasma of about one-third (54/160) of HIV-infected patients but rarely in controls (2/35). Autoantibodies bound to NK cells in vivo and were detected by a strong increase of surface immunoglobulin (Ig) on NK cells of HIV-infected patients. Anti-NK cell antibodies were warmreactive antibodies rather of IgG than of IgM phenotype. The prevalence of specific antibodies to asialo-GM1 was low (12.5%). Numbers of circulating NK cells did not differ significantly between antibody positive (99.5/μl) and antibody negative (141/μl) patients (P = 0.3). However, pre-incubation of healthy donors' NK cells with autoantibody positive plasma significantly inhibited cytotoxicity to K562 leukaemic cells (P = 0.002). Autoantibodies to NK cells in HIV-infected patients are present in the plasma of one-third of HIV-infected patients and are bound to NK cells in vivo. There is evidence that these autoantibodies can induce NK cell defects similar to those seen in vivo
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 28 (1998), S. 397-419 
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Perovskite, ferroelectric and paraelectric, thin films exhibit outstanding dielectric properties, even at high frequencies (〉1 GHz). This feature makes films such as (Ba,Sr)TiO3 and Pb(Zr,Ti)O3 ideally suited for a wide range of capacitor applications, particularly decoupling capacitors and tunable microwave capacitors; the latter application has been fueled by the recent explosion in wireless communications. The successful implementation of these materials as high-frequency dielectrics requires a detailed understanding of both their processing and materials properties.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The solute-rich beta titanium alloy Ti-3Al-8V-6Cr-4Mo-4Zr was subjected to 1500 bar nitrogen pressure at elevated temperatures (500–920°C), leading to a diffusion layer with a high surface hardness. Microstructural, crystallographic and compositional analyses indicate that TiN (δ) and Ti2N (ε) are formed at temperatures exceeding 815°C. The increased concentration of nitrogen, which is a potent α-stabilizer in titanium, also causes α-Ti to form near the surface. The nitriding treatment does not significantly alter the tensile properties or fatigue limit in solution heat treated material. A subsequent ageing treatment of 72 h at 440°C and 16 h at 500°C reduces toughness significantly, allowing cracks induced by nitriding to propagate more easily into the bulk. Tensile ductility and fatigue performance of aged nitrided Ti-3Al-8V-6Cr—4Mo-4Zr are thus significantly lower than in the untreated reference condition.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Mehrschicht-Spiral-CT ; Mehrzeilen-Spiral-CT ; Aortenerkrankungen ; Key words Multi-slice helical CT ; Aortic diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Acute diseases of the central arteries require an immediate investigation. An efficient, fast and reliable diagnosis is necessary because of the high mortality, if the patient remains untreated. These requirements are perfectly fulfilled by the new CT-techniques. Methods. Suspected aortic diseases were examined with a new multi-slice helical CT. The thoracic or the abdominal aorta as well as the entire vascular tree from the supraaortic branches to the inguinal arteries were investigated with different CT protocols. The slice-thickness and the scan mode were changed while the total examination time was kept constant for the first two groups. In the third group a monophasic examination was compared to a biphasic one. Results. In the diagnosis of acute aortic diseases multi-slice helical CT proved to be a fast and reliable method with all scan protocols. The objective measurements of contrast homogeneity and image quality were comparable in the first two groups. The monophasic contrast medium injection protocol was superior to the biphasic administration mode. Conclusions. Multi-slice helical CT appears to be a very effective approach for the diagnosis of acute aortic diseases and seems to be the new gold standard.
    Notes: Zusammenfassung Akute Erkrankungen der Aorta im Körperstamm stellen eine lebensbedrohliche Situation für den betroffenen Patienten dar, so daß ein rasches Handeln zwingend erforderlich ist. Voraussetzung hierfür ist eine leistungsfähige, schnelle und zuverlässige Diagostik, die von der neuen CT-Technik in nahezu idealer Weise realisiert werden kann. Methoden: Bei klinischem Verdacht auf eine Aortenerkrankung wurden Untersuchungen mit einer neuen Mehrzeilen-Spiral-CT (MZ-SCT) durchgeführt. Die Aorta thoracalis, die Aorta abdominalis oder der gesamte Gefäßbaum von den supraaortalen Ästen bis zu den Inguinalarterien wurden mit verschiedenen Protokollen untersucht. In den ersten beiden Gruppen wurden bei konstanter Untersuchungszeit die Schichtdicke und die Tischvorschubgeschwindigkeit variiert. In der dritten Gruppe wurde eine monophasische mit einer biphasischen Untersuchung verglichen. Ergebnisse: In der Diagnostik von aortalen Erkrankungen erwies sich die MZ-SCT als schnelle und verläßliche Methode mit allen Protokollen. Die objektive Messung der Kontrasthomogenität und die subjektiven Abbildungsqualitäten waren in den ersten beiden Gruppen vergleichbar. Das monophasische Vorgehen war der biphasischen Untersuchung überlegen. Schlußfolgerung: Die MZ-SCT ist bei Anwendung geeigneter Untersuchungsprotokolle heute der Goldstandard in der Diagnostik akuter Aortenerkrankungen.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Probability theory and related fields 102 (1995), S. 519-545 
    ISSN: 1432-2064
    Keywords: 60H25 ; 35R60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary A long range contact process and a long range voter process are scaled so that the distance between sites decreases and the number of neighbors of each site increases. The approximate densities of occupied sites, under suitable tine scaling, converge to continuous space time densities which solve stochastic p.d.e.'s. For the contact process the limiting equation is the Kolmogorov-Petrovskii-Piscuinov equation driven by branching white noise. For the voter process the limiting equation is the heat equation driven by Fisher-Wright white noise.
    Type of Medium: Electronic Resource
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