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  • 1
    ISSN: 1432-0711
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Zusammenfassung Die Diskussion und das Vorlegen von Erfahrungsberichten im Arbeitskreis hat ergeben, daß eine Früherkennung des Endometriumcarcinoms mit geeigneten morphologischen Methoden grundsätzlich möglich ist. In mehreren Publikatonen wird von einer hohen Erfolgsrate in der Ausbeute des zytologisch aufgearbeiteten intrakavitär gewonnenen Materials gesprochen, die in einzelnen günstig gelagerten Fällen mehr als 90% erreicht. Hier handelt es sich ausschließlich um Testergebnisse vieler Geräte, die unter optimalen Bedingungen erhoben worden sind. Der Arbeitskreis äußerte die Meinung, daß dieses Ergebnis unter ambulanten Bedingungen zum gegenwärtigen Zeitpunkt kaum erreicht werden kann. Die Ursache dafür sind beeinflussende variable Faktoren, die die Auswertbarkeit des intrakavitär gewonnenen Materials einschränken, in manchen Fällen sogar unmöglich machten. Hierzu gehören u. a. Arbeitsgänge wie Materialgewinnung, die Materialverarbeitung oder das Einschätzen von besonderen anatomischen Gegebenheiten. In diesen Zusammenhang gehört auch die möglichst klare und eindeutige Beschreibung und Interpretation des morphologischen Befundes, was wiederum eine zentrale Einrichtung mit geschultem und erfahrenen Personal erfordert. Solange diese Erfordernisse nicht erfüllt sind, werden diese Methoden als Screeningverfahren im Rahmen der Früherkennung des Endometriumcarcinoms noch nicht allgemein praktikabel sein.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1433-1443 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The intermixing of GaAs/(Ga,Al)As heterointerfaces by Ga+ implantation and annealing has been investigated. The damage accumulation in a GaAs/AlAs superlattice turned out to be less rapid than in a GaAs/GaAlAs quantum-well structure. Low-temperature photoluminescence (PL) spectroscopy of a GaAs/AlAs superlattice could be performed for doses as high as 1 × 1016 ions/cm2. The photoluminescence spectra exhibited several emission bands on the high energy side. The number and energy of these blue shifted peaks were found to depend on the implanted dose and as confirmed by secondary ion mass spectrometry, they could be interpreted as the emission of several quantum wells of the superlattice, disordered with different mixing rates. Two regimes were evidenced; while the depth extension of the disordering has been directly related to the post-implantation defects distribution in the high dose regime, some diffusion of these defects during annealing has been pointed out in the low dose regime. Cross-sectional transmission electron microscopy observations have confirmed the influence of the structure of the implanted sample on damage accumulation. Moreover, the decrease of the PL intensity after annealing could be related to the presence of extended residual defects in the implanted layers. The study of the influence of annealing time at 760 °C, has shown that the photoluminescence intensity can be progressively recovered, while the intermixing saturates rapidly.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4833-4842 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The damage generation and its annealing behavior in GaAs/(Ga,Al)As quantum wells after Ga+ implantation at room temperature is investigated by transmission electron microscopy. Its relations with the disordering of the layered structures is explored by low temperature photoluminescence spectroscopy. We find that at low doses the intermixing is activated during annealing through the diffusion of point defects, while at high doses the disordering is produced by cascade mixing. A strong segregation of the defects in the GaAs layers is observed. During implantation of a GaAs/Ga0.65Al0.35As single quantum well, the GaAs quantum-well layer accumulates damage more rapidly than the Ga0.65Al0.35As barriers. At high dose this leads to a differential amorphization of the two compounds. Using the critical damage energy density model, the amorphization thresholds of GaAs and Ga0.65Al0.35As are estimated around 26 eV/molecule and 960 eV/molecule, respectively, in our conditions of implantation. The influence of barriers in AlAs is studied. AlAs is more resistant to amorphization than Ga0.65Al0.35As and delays the amorphization of the GaAs quantum-well layer. This effect is attributed to the in situ recombination of point defects during irradiation in AlAs material as well as to some intermixing of the layers. After annealing it appears that defects can easily diffuse in Al rich materials but are trapped in GaAs. It is concluded that the ability of AlAs to prevent damage accumulation in GaAs quantum wells and to drain off the defects during annealing can be exploited for device applications. The general trends for an optimized GaAs/GaAlAs quantum well dedicated to mixing applications such as the fabrication of quantum-well wires by masked implantation is finally proposed.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5012-5015 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present the structure of a GaAs/GaAlAs quantum well, which can promote strong mixing rates upon high-dose implantation, with good recovery of the electronic properties after annealing. This structure is employed to fabricate quantum-well wires by Ga+ masked implantation. Low-temperature photoluminescence measurements reveal large lateral modulations of the effective band gap ((approximately-greater-than)178 meV), and small lateral interdiffusion lengths (10 nm). A simple calculation shows that one-dimensional quantization energies between 11 and 20 meV can be expected in these structures.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1444-1450 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Quantum wires were fabricated by selective intermixing of a GaAs/GaAlAs quantum well through masked Ga+ implantation and rapid thermal annealing. The evolution of the luminescence spectra of the wires with the width of the implantation masks, enabled us to characterize the lateral selectivity of our process as well as the degree of one-dimensional confinement. The lateral extent of the intermixing was estimated at 20 nm giving rise to an important penetration of aluminum into the wires. From numerical simulations of the spatial distribution of implantation-induced damage, it was concluded that some lateral diffusion of the defects occurred during annealing. However it has been possible to assess the confinement energies to be around 4 meV. The linewidth of the wires' emission turned out to increase with decreasing mask size, indicating the presence of some fluctuations of the confining potential along the wires. The roughness of the lateral definition of the wires was evaluated at 20 nm, of the same order of magnitude as the dimension of the intermixed region under the mask. Under these conditions optical excitation spectroscopy failed to detect the different one-dimensional subbands. Finally the potentialities of this method of fabrication of quantum wires are inspected.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2004-2014 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The inhibition and perturbations of surface photochemistry, due to the coupling of the excited state to the surface, are discussed as it pertains to CH3 Br adsorbed on nickel. Photofragmentation of CH3 Br was observed on a brominated Ni(111) surface, with the fragmentation process being strongly perturbed at low coverages. The perturbations are attributed to charge transfer processes. Direct photofragmentation was observed as well as a surface specific dissociative electron attachment channel. Cross section values are reported for fragmentation at 193 and 248 nm.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1280-1286 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An analysis of polycrystalline Au thin film interconnects of widths ranging from 850 to 25 nm, and lengths ranging from 1.0 μm to 20 nm which have been electrically stressed to the point of failure is presented. For the longer wires (widths 60–850 nm), the failure current density is typically found to be 1012 A m−2, essentially independent of the wire width, and then rapidly approaching zero for thinner wires. For the wider wires, failure occurs at the end towards the negative electrode; for narrow wires, failure tends to occur towards the center of the wire, as observed using scanning electron microscopy and atomic force microscopy. The mean time to failure for fixed current density is seen to decrease with decreasing wire width. The failure current density for a given wire width increases as the length decreases. An analysis of the temperature profile based on calculations of a simple model is presented which shows that this width-dependent behavior of narrow lines is not anticipated from the assumption of a homogeneous line subject to thermally-assisted electromigration alone. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2338-2342 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A high-throughput von Hámos-type Bragg crystal spectrometer is described that is operated with the Livermore electron beam ion trap. The spectrometer is employed to measure high-resolution x-ray spectra from highly charged heliumlike and neonlike ions. Data from heliumlike Ti20+ and Fe24+ and from neonlike Au69+ are presented to demonstrate the utility of the new instrument.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Measurements are presented on the contributions from dielectronic satellite transitions from upper configurations 1s2lnl', n≥3 to the characteristic x-ray emission of heliumlike Fe24+. The measurements were carried out on the electron beam ion trap at Livermore using high-resolution Bragg-crystal spectroscopy. By eliminating uncertainties in the location and magnitude of the satellite contributions inherent in theoretical predictions the measurements improve the use of the resonance line emission of heliumlike Fe24+ as a diagnostic of ion temperature and rotation velocity of high-temperature plasmas.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1466-1472 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the magnetic properties of flat permalloy cylinders by Lorentz transmission electron microscopy and micromagnetic simulations. The magnetization patterns during in situ magnetizing experiments have been imaged and they revealed that the magnetization reversal of the cylindrically shaped dots investigated is determined by the formation and annihilation of magnetic vortices. Furthermore, the experiments and micromagnetic simulations showed a dependence of the vortex annihilation field not only on the aspect ratio but also on the absolute thickness of the cylinders. The diameter of the cylindrical dots was varied between 150 and 1000 nm, and the thicknesses were 3, 5.5, 8.3, 15, and 20 nm, respectively. The formation of inhomogeneous magnetization patterns prior to vortex evolution was observed and by a comparison of the experimental to simulated Fresnel images these patterns can be identified as S- and C-like states. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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