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  • 1
    Electronic Resource
    Electronic Resource
    Phase dependence of Kikuchi patterns. I. Theory (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 104-109 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Thermal diffuse scattering in high-energy electron diffraction is analysed using the Einstein model of lattice vibrations. An expression for the intensity distribution in the Kikuchi pattern is obtained which includes thickness-dependent terms (i.e. a dependent-Bloch-wave theory is used) and the effects of a general crystal structure. The corresponding two-beam limit is shown to consist of four distinct terms, two of which depend on the phase of the structure factor. One of these is found to be non-zero only for non-centrosymmetric crystals and for relatively thin crystals. It leads to an asymmetric Kikuchi band, even in a symmetrical scattering geometry. This asymmetry may be used to determine the polarity of non-centrosymmetric crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388009304
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  • 2
    Electronic Resource
    Electronic Resource
    Absorptive form factors for high-energy electron diffraction (1990)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 202-208 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The thermal diffuse scattering contribution to the absorptive potential in high-energy electron diffraction is calculated in the form of an absorptive contribution to the atomic form factor. To do this, the Einstein model of lattice vibrations is used, with isotropic Debye-Waller factors. The absorptive form factors are calculated as a function of scattering vector s and temperature factor M on a grid which enables polynomial interpolation of the results to be accurate to better than 2% for much of the ranges 0 ≤ Ms2 ≤ 6 and 0 ≤ M ≤ 2 Å2. The computed values, together with an interpolation routine, have been incorporated into a Fortran subroutine which calculates both the real and absorptive form factors for 54 atomic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389011906
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  • 3
    Electronic Resource
    Electronic Resource
    A density-matrix approach to coherence in high-energy electron diffraction (1992)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 48 (1992), S. 215-221 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: It is shown that a density-matrix formalism may be used to analyse various aspects of coherence in high-energy electron diffraction theory. This approach is demonstrated by two examples: an analysis of the coherence between two Bloch waves generated by diffuse scattering as a function of crystal thickness (the dependent-to-independent Bloch-wave `transition') and an analysis of the coherence between electrons which are diffusely scattered in different directions and their contribution to high-resolution images.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767391010413
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  • 4
    Electronic Resource
    Electronic Resource
    Inversion of convergent-beam electron diffraction patterns (1992)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 48 (1992), S. 555-562 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The problem of recovering the structure factors that contribute to a zone-axis convergent-beam diffraction pattern is discussed. It is shown that an automated matching procedure that minimizes the sum-of-squares difference between experimental and simulated patterns is effective whether one is refining accurate structure factors in a known crystal or attempting ab initio structure determination. The details of the minimization method are analysed and it is shown that a quasi-Newton method that uses analytically derived gradients is particularly effective when several structure factors are varied. The inversion method for ab initio structure determination is tested on the [110] axis of GaP, using simulated patterns as ideal 'experimental' data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767392001843
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  • 5
    Electronic Resource
    Electronic Resource
    Smooth parabolas in transmission electron diffraction patterns (1994)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 357-366 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Perturbation theory is used to analyse the geometry of various diffracted features in large-angle high-energy electron diffraction patterns taken in transmission. Particular attention is paid to smooth parabolic features and their straight-line envelopes. It is shown that the features lie in positions determined by a `modified Bragg condition' that takes account of dynamical interactions in the crystal. The results have considerable bearing on the interpretation of almost identical resonance features seen in reflection high-energy electron diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767393012942
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of dependent to independent Bloch wave transition in Kikuchi patterns (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 342-346 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The transition from dependent to independent Bloch waves in high-energy electron diffraction theory is demonstrated by observing the disappearance of subsidiary fringes in Kikuchi patterns as the crystal thickness is increased. Comparison is made between experimental and computed Kikuchi band profiles in Si. It is shown that the subsidiary fringes provide a method for thickness determination in zone axis convergent-beam electron diffraction patterns from relatively thin crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389001054
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  • 7
    Electronic Resource
    Electronic Resource
    Absorption in high-energy electron diffraction from non-centrosymmetric crystals (1990)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 208-214 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The influence of absorptive potentials on high-energy electron diffraction amplitudes is analysed, with an emphasis on effects which are specific to diffraction from non-centrosymmetric crystals. It is shown that the phase difference which then exists between the elastic and absorptive potential coefficients can give rise to a significant asymmetry between +g and -g reflections. This phase difference is calculated for a number of important III-V semiconductors. In many diffraction calculations it is assumed that the phase difference is zero - it is argued here that such calculations cannot be truly quantitative. The inclusion of absorption by perturbation theory is shown to be valid, but only if the change in the eigenvectors as well as the eigenvalues is taken into account. It is shown that within two-beam theory the +g, -g asymmetry in non-centrosymmetric crystals arises purely from changes in the eigenvectors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389011918
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  • 8
    Electronic Resource
    Electronic Resource
    The refractive development of the eye of the American kestrel (Falco sparverius): a new avian model (1992)
    Springer
    Journal of comparative physiology 170 (1992), S. 565-574 
    Details
    ISSN: 1432-1351
    Keywords: Eye ; Refractive error ; Development ; Kestrel ; Myopia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Most measures of avian visual performance are carried out on commonly available domestic species such as the chicken, and most of the data on avian induced refractive error deals with chickens. Raptors are predatory birds in which good visual resolving ability is particularly important. Behavioral studies indicate that the eyes of raptors have two to three times the resolving ability of the human eye. The domestic chicken is precocial at hatching whereas most raptors are semi-altricial. This study was an effort to determine if the effect of early visual deprivation on the refractive development of the chicken eye can be reproduced in the American kestrel, a species which is not domesticated and in which the need for acute vision is particularly important. Visual deprivation was achieved by unilaterally applying translucent plastic goggles over the eyes of kestrels two days after hatching. Refractive error was measured using a retinoscope and trial lenses. Ocular growth was monitored by A-scan ultrasonography, and frozen ocular sections of sacrificed birds. The effect of the experimental manipulation on the contralateral control eye and body weight was evaluated each day over a 42-day period. The goggles did not significantly affect the normal changes in body weight or the normal pattern of ocular growth and refractive development in the untreated eyes. An analysis of the refractive state changes as a result of form deprivation was made each week for 6 weeks after hatching on both the treated and untreated eyes in a separate group of experimental birds. Visual form deprivation caused a significant myopic shift in refractive error and a significant increase in the vitreous chamber depth in the treated eyes at 3 and 6 weeks of age. However, the amount of myopia produced is much less than that induced in chicks, and in certain cases hyperopia is produced. The kestrels recover from myopia and hyperopia within 10 days of goggle removal, after 3 to 4 weeks of deprivation. This study is the first indication that chickens may not be a representative bird model for studying form deprivation myopia. First, myopia is not always produced in kestrels in response to form deprivation. Second, kestrels are severely myopic at hatching and therefore, the direction of emmetropization is opposite to that found in hatchling chicks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199333
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  • 9
    Electronic Resource
    Electronic Resource
    Secondary poisoning hazard of fenthion to American kestrels (1991)
    Springer
    Archives of environmental contamination and toxicology 21 (1991), S. 84-90 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The possibility that fenthion, an organophosphorus pesticide, could represent a secondary poisoning hazard to birds of prey was tested, using American kestrels (Falco sparverius) and house sparrows (Passer domesticus) as representative models of a naturally occurring predator-prey interaction. Fourteen kestrels were presented with live sparrows exposed previously to perches containing Rid-A-Bird 1100® solution (11% fenthion active ingredient). Eleven kestrels died within twenty-four h after consuming one fenthion-exposed sparrow. Two kestrels died after consumption of a second fenthion-exposed sparrow on day 2, and a final kestrel died after partially consuming a third fenthion-exposed sparrow on day 3. Brain cholinesterase (ChE) activity in kestrels was depressed to levels diagnostic of poisoning by a ChE-inhibiting compound. The majority of fenthion contamination of sparrows was external, with the highest amounts measured on the feet. The detection of fenthion residues in kestrel gastro-intestinal tracts confirmed secondary fenthion poisoning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01055561
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of dietary sodium fluoride on internal organs, breast muscle, and bones in captive American kestrels (Falco sparverius) (1992)
    Springer
    Archives of environmental contamination and toxicology 22 (1992), S. 242-246 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract In 1982, 29 7-day-old American kestrel (Falco sparverius) chicks from captive stock were randomly assigned to one of three dietary regimens: (1) 10 birds were fed daily with cockerel mash (0 ppm of F-: control birds); (2) 10 birds were fed daily with cockerel mash containing 1,120 ppm of F-; (3) 9 birds were fed daily with cockerel mash containing 2,240 ppm of F-. Growth of the kestrels was not significantly affected by NaF in their diet. No significant differences were found among the 3 groups for length of duodenum, jejunum and ileum. Rectum was longer as more fluoride was added to the diet. Weights of adrenals, brain, gizzard, spleen, heart, kidneys, liver, pancreas, and pectoral muscle were not significantly affected by treatment, although kidneys, spleen and adrenals tended to become lighter. Percent bone ash was significantly (P〈0.05) increased, while bone breaking strength was significantly (P〈0.05) decreased by treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213292
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