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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Backreflection x-ray standing waves (BRXSW) and crystal truncation rod (CTR) scatterings have been used to probe the structure of heteroepitaxial CaSrF2 crystals on GaAs(111)B substrate. Coupled with the film-thickness information obtained from x-ray Fresnel reflectivity data, the combined x-ray standing wave and BRXSW data suggest one or both of the F and As layers missing from the heteroepitaxial interface. The CTR data support a missing F layer and interface (Ca, Sr) atoms occupying the T sites on GaAs(111) surface.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An ultrahigh vacuum (UHV) diffractometer has been designed for studies of surface structures using the grazing-angle x-ray standing-wave method. The design is featured by a horizontal plane of diffraction for use at a vertical-wiggler source of synchrotron radiation. A sample is horizontally mounted in an UHV chamber (4×10−7 Pa) placed on crossed swivels, which control the glancing-incidence angle of x rays on the sample surface with a 50-μrad accuracy. The chamber accepts a sample from a transportation vessel under high vacuum. A beryllium window allows x-ray fluorescence to reach a semiconductor detector at short access. The whole assembly sits on a high-precision rotary table, regulating the sample Δθ angle with a reproducibility of better than 0.5 μrad required for control of the x-ray field profile. The system has been successfully applied to an accurate determination of the in-plane ordering of As atoms on a Si(111) surface with a 1×1 structure. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The x-ray-diffraction results reported here are from the first high-resolution triple-crystal experiments to be performed at the Australian National Beamline Facility at the Photon Factory. The heart of the facility is a multipurpose two-axis high-resolution vacuum diffractometer (BIGDIFF) Z. Barnea et al., Rev. Sci. Instrum. 63, 1069 (1992) capable of use for high-resolution powder diffraction (using both conventional scintillation detectors and imaging plates), protein crystallography, reflectometry, as well as single-crystal diffractometry. The present experiments were conducted on BIGDIFF in triple-crystal diffraction mode with a monolithic channel-cut Si monochromator (supplied by Professor M. Hart), a single-crystal Si sample, and a four-reflection monolithic channel-cut Si analyzer crystal. The Si(111) sample is a part of a wafer which had been implanted with 100 keV B+ ions (doses 1×1015 and 5×1015 cm−2) through a one-dimensional 0.5 μm thick oxide strip pattern with a 5.83 μm period and 4 μm open region. The triple-crystal data were collected in the form of two-dimensional intensity maps in the vicinity of the 111 Bragg peak, varying the sample rotation (ω) and the analyzer/scintillation detector rotation (2θ). The first results were collected in air both with the as-described sample and after the oxide layer had been removed. Certain slice scans (one-dimensional sections of the two-dimensional intensity maps) were also collected with a vacuum of 1 Torr and reveal considerable improvement in signal to background.The data will be compared with a recent similar study A. Yu. Nikulin et al., J. Appl. Cryst. 27, 338 (1994) performed on BL-14B at the Photon Factory. The new data collected in air indicate that lattice distortion may be mapped with a resolution of approximately 160 A(ring), to a depth of approximately 1.0 μm, providing valuable quantitative information on ion diffusion in such implanted materials. The slice scans collected in vacuum indicate that a depth resolution of 50 A(ring) is certainly achievable using BIGDIFF. The data show the excellent potential of BIGDIFF for extremely good signal to noise and very high resolution in such experiments, and the advantages of working entirely in vacuum. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1192-1195 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new counting system for charged particles, which is suitable for the counting of pulse trains arriving in a short time, was constructed. The system is composed of a microchannel-plate intensifier, a CCD camera, a frame buffer, a particle counter, and a personal computer. Ion (or electron) pulses incident on the microchannel plate are amplified and then converted to photoradiating spots on a fluorescent screen. The image of the bright spots on the screen is taken by the camera and stored in the frame buffer. The computer processes the stored data and counts the number of bright spots. The performance of the system was examined by applying it to the detection of ions generated by a pulse laser. More than 300 photoions generated by one laser pulse (pulse width: 30 ns) were successfully counted, indicating that the peak counting rate of the system exceeds 1010 cps.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Design features of a proposed high-resolution, high-speed powder diffractometer for operation at a synchrotron source are described. A key feature of the design is the use of imaging plates to record an almost complete range of data including both the high-angle and the small-angle scattering regime. The x-ray optics involve the use of a condensing-collimating channel-cut monochromator (CCCC) to achieve narrow parallel beams with cross sections of the order of 50 μm in the plane of diffraction, so that geometrical aberrations are very low and the beam cross section is well matched to the spatial resolution of the imaging plate detector. Angular resolution in 2θ of the diffractometer is easily variable, and designed to range from 0.01° upwards. Optional translation of the detector perpendicular to the incident-beam direction makes it possible to obtain time-resolved data. Applications of the instrument include high-resolution powder data collection for Rietveld analysis, studies of dynamic phenomena such as chemical reactions and phase transformations, particle-size determination, texture analysis, residual-stress measurements, single-crystal studies of the truncation-rod effect and surface scattering, microdiffraction, combined high-angle and small-angle scattering measurements, and studies of multilayer structures. As an illustration of the sort of results attainable with the proposed system, we present an oscillation photograph of the crystal-truncation rod effect for a Si wafer which was recorded at a synchrotron source using an imaging plate as the detector.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2373-2375 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Synchrotron radiation obtained from the 6-T vertical-wiggler source at the Photon Factory has been used to study dynamical x-ray diffraction in a nearly perfect germanium crystal under total external reflection conditions. A specially designed goniometer has allowed independent control of the glancing angle and the deviation angle from exact Bragg incidence. The rocking-curve profiles observed from slightly asymmetric Bragg planes as a function of glancing angle were found to be quite different for both the diffracted and specular beams. These profiles show unusual features arising from the excitation or de-excitation of the wave fields in shallow surface layers of the bulk crystal. Furthermore, GeK fluorescence signals measured during the Bragg reflection showed characteristic modulations, demonstrating the feasibility of new standing-wave experiments for determination of interface structures.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2311-2314 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A cylindrical position-sensitive x-ray gas detector has been designed, which allows a complete powder pattern to be recorded simultaneously from a specimen placed at the center of the detector circle. It covers an angular range 2θ of 120° at a 25-cm radius and works in the self-quenching streamer mode of gas ionization to provide 0.06° resolution in 2θ. Powder line positions can be determined with an accuracy of ±0.05°. The quality of detected patterns is well suited to profile analysis. Tests made at a classical x-ray source showed that recorded line profiles are describable by asymmetric Pearson VII functions. The designed instruments have successfully been applied to in situ powder data collection from a BaBiO3−x specimen at high temperatures and subsequent structure refinement by profile-fitting techniques. These features make the detector most suitable to the studies of fast structure changes like phase transitions with synchrotron radiation.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2540-2542 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The position and chemical state of S atoms have been investigated for the Al/S-passivated GaAs(111)A and (111)B samples using the soft x-ray standing wave technique and synchrotron radiation photoemission spectroscopy. The x-ray standing wave results indicate that the S atoms at the Al/S/GaAs(111) interface are significantly more disordered than the S atoms at the S/GaAs(111) surface. The position of the S atoms does not change upon the Al deposition. The synchrotron radiation photoemission spectra suggest that the Ga atoms bonded to S atoms before the Al deposition exchange with Al atoms upon deposition.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 57 (2003), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have studied the expression of a human homologue of mafB (maf-1), a member of the family of large maf transcription factors. In support of the suggested key role that mafB expression plays in differentiating macrophages, we found mafB to be expressed at a very high level in monocytic U937 and THP-1 cell lines. However, we show here that mafB transcription is not restricted to myeloid cells but can also be detected in lymphoid cells, indicating transcriptional plasticity during haematopoiesis. In conclusion, strong proliferative signals mediated by T-cell activation and interleukins (IL-4 and IL-12) downregulate the mafB messenger RNA transcript level when resting naïve CD4+ T-helper cells enter the differentiation pathway in vitro.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary Eosinophilic pustular folliculitis (EPF) is characterized clinically by pruritic grouped follicular papules and pustules on the trunk, limbs, and face, and. Histologically by follicular infiltration with eoslnophils. The blood eosinophil count is elevated in most patients. Oral minocycline. Nonsteroidal anti-inflammatory drugs, diamino diphenyl sulphone and corticosteroids may induce remission. We report two Japanese men with EPF who responded poorly to the usual therapy. Intravenous injections of recombinant interferon-γ (riFN-γ). 5 × 105 to 2 × 106 Japan Reference Unit (JRU) (1 JRU roughly corresponds to 4 NIH units) daily for 7 days, cleared the skin lesions and returned the peripheral eosinophil counts to normal in both patients. However, the lesions recurred 2–3 days after rIFN-γ was stopped. Both patients have received intravenous rIFN-γ once or twice a week for nearly 1 year without systemic side-effects. Reverse transcripta sepolymerase chain reaction revealed a decreased expression of interleukin 5 (IL-S) mRNA in peripheral mononuclear cells after the rIFN-γ therapy. rIFN-γ may become the treatment of choice in recalcitrant EPF, although further studies are needed. It may work by interfering with the immunological function of type 2 T-helper cells, including IL-5 production responsible for the growth and differentiation of eosinophils.
    Type of Medium: Electronic Resource
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