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  • 1
    Electronic Resource
    Electronic Resource
    Interstitial nitrogen induced by low-energy ion beam nitridation of AIII–BV semiconductor surfaces (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6066-6069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitridation of GaAs, InAs, and InSb by low-energy N2+ ion bombardment at room temperature was studied by near-edge x-ray absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy measurements. The formation of thin surface nitride layers, consisting mostly of GaN or InN but also containing minor amounts of mixed nitrides, was observed. Besides the nitride-related features, sharp peaks in the NEXAFS due to π* resonance at 401.0 eV and correlated peaks at 403.8 eV in N 1s core level spectra were detected. Both spectral features could be assigned to the presence of interstitial nitrogen, most likely molecular nitrogen. It was found that the amount of interstitial nitrogen in the surface layer strongly depends on the AIII–BV semiconductor system and may be affected by modification of the conditions during low energy ion bombardment. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1415765
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  • 2
    Electronic Resource
    Electronic Resource
    Approximation of the plasma inhomogeneity by broad-beam measurements and simulation : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 678-680 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In broad-beam ion sources an inhomogeneous plasma distribution has a strong effect on both the maximum extractable ion current and the broad-beam profile. An approximate plasma distribution function is determined by fitting calculated accelerator-grid currents to corresponding experimental data, thus efficiently replacing complicated and expensive plasma probe measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150258
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  • 3
    Electronic Resource
    Electronic Resource
    Modeling of broad beam ion sources : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1147-1149 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Our approach to ion beam modeling breaks down the complex interplay of competing elementary processes into a series of independent consecutive steps. Thus, both in methodological development and computational modeling, the main effort can be directed towards the processes which are of greatest relevance in the context given. Moreover, employment of the special software available allows for comprehensive and efficient optimization of multigrid ion sources for low ion beam divergence and long lifetime, even in a personal computer environment. Here, for our Kaufman-type two-grid ion source RR-ISQ 76 some ion beam characteristics in their dependence on geometrical two-grid configuration are calculated and discussed, first of all in terms of shape and area of the plasma sheath. These dependencies are used to optimize this particular ion source for a low beam divergence. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148652
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  • 4
    Electronic Resource
    Electronic Resource
    Diffraction of high-energy synchrotron radiation (invited) (abstract) : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1614-1614 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Diffraction of high-energy synchrotron radiation at energies above 100 keV combines advantages of conventional x-ray diffraction and neutron diffraction. For hard x rays absorption in matter is weak with typical mean free paths of several millimeters. Bulk properties are studied on large samples. With a three-crystal diffractometer an excellent k-space resolution of about 10−5 A(ring)−1 transversal and 10−4 A(ring)−1 longitudinal is achieved. In this contribution the particularities of hard x rays, the instrumental setup, and the k-space resolution are discussed and presented. The potential of the new method will be demonstrated on two examples: magnetic diffraction from MnF2 and the structural phase transition of SrTiO3. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146465
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  • 5
    Electronic Resource
    Electronic Resource
    Broad-beam modeling and experiments for electric spacecraft propulsion : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 732-734 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: At IOM Leipzig, we developed an efficient grid erosion simulation code. In our approach to ion beam extraction and grid erosion occurring in a multi-grid multi-aperture ion thruster we break down the complex interplay of pertinent elementary processes into consecutive steps. On the basis of ion optical and short-time grid-erosion measurements on a small broad-beam ion source, a comprehensive experimental validation of this code has been done. The good agreement between measured and simulated data furnishes confidence in the methodology. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150277
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  • 6
    Electronic Resource
    Electronic Resource
    Familial dyskeratotic comedones (1999)
    Oxford BSL : Blackwell Science Ltd
    British journal of dermatology 140 (1999), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report a 49-year-old white woman having asymptomatic hyperkeratotic comedone-like lesions on her legs, arms and trunk. Her sister is similarly affected, but less severely. The clinical and histopathological features indicated a diagnosis of familial dyskeratotic comedones, a rare autosomal dominant condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2133.1999.02835.x
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  • 7
    Electronic Resource
    Electronic Resource
    In situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 526-532 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ infrared (IR) spectroscopy and visible-light (VIS) spectroscopic ellipsometry over the spectral range from 700 to 2000 cm−1 and 1.5–3.5 eV, respectively, were used to investigate the optical behavior of boron nitride (BN) thin films at temperatures from room temperature (RT) to 600 °C. The polycrystalline hexagonal (h) and mixed-phase h- and cubic (c)-BN thin films were deposited by magnetron sputtering on [001] silicon. We observe a reversible moisture incorporation process in as-grown h-BN samples. When stored in normal ambient, the h-BN thin films absorb water into thin-film micropores. When annealed in ultrahigh vacuum or a dry nitrogen atmosphere, the samples expel moisture but retain their microstructure. This is observable by reduction of the thin-film refractive indices in accordance with changes in the IR lattice resonance behavior. The optical properties of high c-BN content thin films remain unchanged during annealing. And both intrinsic h- and c-BN thin-film VIS refractive indices are nearly temperature independent, at least up to 600 °C. Therefore, RT BN optical constants can be used for feedback loop control in in situ thin-film growth at temperatures up to 600 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368083
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  • 8
    Electronic Resource
    Electronic Resource
    Infrared ellipsometry on hexagonal and cubic boron nitride thin films (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1668-1670 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared spectroscopic ellipsometry (IRSE) over the wavelength range from 700 to 3000 cm−1 has been used to study and distinguish the microstructure of polycrystalline hexagonal and cubic boron nitride thin films deposited by magnetron sputtering onto (100) silicon. The IRSE data are sensitive to the thin-film layer structure, phase composition, and average grain c-axes orientations of the hexagonal phase. We determine the amount of cubic material in high cubic boron nitride content thin films from the infrared optical dielectric function using an effective medium approach. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118655
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of aperture displacement in broad-beam ion extraction systems : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 928-930 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Low-energy broad-beam ion sources cover a wide range of applications. Geometrical perturbations of the axial-symmetric extraction channels by off-axis shifts of the accelerator grid holes give rise to an ion beamlet tilt which under certain conditions is dependent on the beamlet current. In this study, the characteristics of the beamlet deflection are presented which were obtained by a three-dimensional trajectory simulation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428785
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  • 10
    Electronic Resource
    Electronic Resource
    Neuronal Control of MHC Class II Inducibility in Rat Astrocytes and Microglia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 8 (1996), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We analysed the inducibility of major histocompatibility complex (MHC) class II molecules of astrocytes and microglia in organotypic hippocampus slice cultures of Lewis rats. Treatment with interferon-γ (IFN-γ) resulted in the induction of MHC class II molecules on microglia preferentially in the injured marginal zones of the slice culture, but only sporadically in areas containing intact neuronal architecture. In astrocytes, inducibility of MHC class II molecules was even more strictly controlled. IFN-γ treatment induced MHC class II expression only in the slice culture zones containing degenerated neurons, and not in the presence of functional neurons. After suppression of spontaneous neuronal activity of the slice culture by the sodium channel blocker tetrodotoxin, MHC class II molecules on astrocytes could be induced by IFN-γ in areas with intact neuronal architecture, and microglia cells exhibited a higher level of expression. These data suggest that loss of neurons could result in MHC class II inducibility of glial cells, and thus in increased immune reactivity of nervous tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1996.tb01552.x
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