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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 26-30 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A double-crystal x-ray spectrometer (DCS) has been used to obtain high-resolution x-ray spectra of laser-produced plasmas. The DCS has a high dispersion, and thus can obtain highly resolved spectra in circumstances where the resolution of a conventional single-crystal Bragg spectrometer at comparable source-to-detector distances would be limited by the source size. In addition the DCS also yields unit-magnification one-dimensional spatial resolution in the direction perpendicular to the spectral direction. The instrument produces two spectra symmetrically disposed about a central wavelength, which makes it especially useful for measuring spectral line shifts. Analysis of the spectra from hydrogenic aluminium and helium-like chlorine indicates a resolving power (λ/Δλ) greater than 2500 and a spatial resolution better than 30 μm.
    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 63 (1992), S. 5012-5016 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A special crystal monolith was fabricated for absolute measurements of x-ray wavelength. It consists of two flat quartz plates, accurately cut relative to reflecting net planes, with a fixed distance between them. Absolute wavelengths (i.e., without use of reference lines) of L-shell laser produced spectra of Cu, Ge, As, etc. have been measured in the 7.5–8.5 A(ring) with an accuracy of Δλ/λ=10−5. Our Johann type x-ray spectrometer with a cylindrically bent quartz has been used to reveal line coincidences necessary for photopumping processes. In this scheme source-size influences are smaller, therefore, line profiles have been measured at a spectrometer resolution better than 5000. Because of its focusing in the sagittal plane, a von Hámos type x-ray spectrometer has been used to detect the small x-ray emission of subpicosecond laser-produced plasmas (E=2 mJ, t=100 fs). X-ray spectra of Al both Kα, Kβ lines and Heα-resonance line with its satellites. Finally, a multichannel x-ray microscope has been designed and fabricated. It consists of several two-dimensionally bent crystals where each of them images one x-ray line emitted by a laser-produced plasma. The spatial resolution of x-ray line images is about 5 μm, and the width of the spectral ranges is Δλ/λ=10−4 to 10−2. Thus, the spatial distribution of ions radiating in selected x-ray lines have been found being of interest in the study of population inversions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 26 (1993), S. 405-412 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Reflection curves of bent crystals were calculated using the Takagi–Taupin theory of dependence on bending radius, wavelength, crystal thickness and Bragg angle. The reflection properties of bent crystals were measured for bending radii down to 90 mm. Usually, for the measurement of rocking curves of crystals with large bending radii, the double-crystal diffractometer was used in parallel position (n, −n). A special achromatic diffractometer consisting of a plane and a bent crystal is proposed. It is used to measure rocking curves of bent crystals with small bending radii (R 〈 1 m). Experimental values show close agreement with the theory. The reflection properties are important for X-ray microscopy with two-dimensionally bent crystals and for X-ray spectroscopy with bent crystals.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 26 (1993), S. 845-845 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two errors in the paper by Härtwig, Hölzer, Wolf & Förster [J. Appl. Cryst. (1993), 26, 539–548] are corrected. On p. 540, the fifth line after equation (1) should read `δ1, δ2 and κ are small tilts of the crystals and the collimator, respectively'. In the reference list, the reference to Wilson (1958) should read Wilson, A. J. C. (1958). Proc. Phys. Soc. London, 72, 924–925.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 971-979 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Anisotropic elasticity theory is applied to calculations of the one- and two-dimensional curved crystals widely employed in X-ray optics. The expression for the displacement vector involved in the process of X-ray Bragg diffraction by a curved crystal is derived. The derivation takes into account the anisotropic elasticity effects for a crystal plate subjected to pure bending. Expressions for the angular deviation from the Bragg angle along the crystal surface are obtained for cylindrically, spherically and toroidally bent crystal geometries. The relationship between the radii of curvature of the crystal and the crystal's compliance tensor is discussed. It is shown that, for a given crystal, the occurrence of the anticlastic curvature effect directly depends on the crystal orientation. Bent silicon crystal plates with (200), (111) and (220) orientations are used to illustrate the influence of the anisotropic elasticity effects on the shape of the diffracting region on the crystal's surface.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 26 (1993), S. 539-548 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Single- and double-crystal spectrometer measurements of the Cu Kα doublet have been carried out after the selection of optimum measurement procedures and parameters. These include the influences of the X-ray-tube arrangement, horizontal and vertical divergences and the slow θ or λ dependence of the reflection curve. The influence of the apparatus function on the measured intensity distribution was minimized. The measured intensity profile could be approximated by a convolution of the instrumental function and the spectral line, with the inclusion of two additional terms. The intrinsic spectral line was fitted by Lorentz functions and, thus, described by 12 parameters. Good agreement between the results of the different measuring procedures and those of other authors is obtained. The apparent differences are discussed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1420-9071
    Keywords: Melatonin ; human-pineal gland ; aging ; sexual maturation ; SAD ; major depressive syndrome ; immunology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract During the last decade we have learned much on physiological changes in the secretion of the pineal hormone melatonin (MLT) in man. Reportedly, there is little or no MLT secreted before age 3 months. Then MLT production commences, becmes circadian, and reaches highest nocturnal levels at the age of 1–3 years. During all of childhood nocturnal peak levles drop progressively by 80% until adult levels are reached. This alteration appears to be the consequence of increasing body size in face of constant MLT production during childhood. The biological significance of this MLT alteration is presently unknown. Because of conceptual considerations, major depressive syndrome (MDS) and seasonal affective disorder (SAD) have been in the focus of pineal research for several years. Although in these disorders alterations in MLT levels could not be substantiated, light therapy, a consequence of this research, was discovered as an effective treatment for SAD and perhaps for MDS. In addition, there is some recent evidence for low MLT levels in schizophrenia. Finally, the potential effect of MLT in neuroimmunoendocrine interactions is presently explored. Reportedly, in vitro studies and animal experiments give evidence for a modulatory role of MLT in the immune response. However, the exact way of this possible action of MLT remains to be clarified. Clinical studies are too scant for a meaningful estimation of MLT's involvement in human neuroimmunoendocrine interactions.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0649
    Keywords: 42.55.Vc ; 32.30.Rj ; 52.25.Nr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Photo-resonant pumping of X-ray lasers requires close coincidence of a strong emission line with a suitable absorbing transition. We use a high-resolution crystal spectrometer to verify five coincidences, one of which has apparently not yet appeared in published work. All but one of the coincidences are found to lie within one linewidth. With respect to X-ray laser photo-pumping three of the five coincidences seem to be promising candidates.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-8760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results are presented of calculation of x-ray plasma images of glass shell targets with diagnostic additives Na, K, and Ca in the light of the intrinsic radiation of the resonance lines of H and He ions with Zn = 8, ii, 14, and 20, and also in the light of cw radiation in the wavelength range λ = 1-300 Å. The calculation results are compared with laser-plasma images obtained in experiments with the “Del'fin-l” thermonuclear facility. The temperature and density of the plasma, the rate of corona expansion, the target mass ablation rate, and the hydrodynamic coefficient of laser-energy transfer into kinetic energy of the ablating shell are determined. The plasma images obtained by backlighting the shell target with an auxiliary x-ray source are analyzed with account taken of the radiation refraction. The required energy, temporal, and spectral characteristics of the auxiliary source are determined.
    Type of Medium: Electronic Resource
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