During the preparation of versatile tables for the secondary extinction factor Y(μ) of cylindrical and spherical mosaic crystals expressed as functions of the Bragg angle θ, absorption coefficient times radius μρ and reduced radius τ(0) = σ(0)ρ [σ(0) = (2π)(1/2)Q/η], or of θ, τ(0) and ξ(0) = μ/σ(0), five kinds of Student's Tn probability functions T1, T2, T3, T4, T∞ for describing the mosaic distribution of crystals have been tested. T1 is Lorentzian (L) and T∞ is close to Gaussian (G). The influence of these different mosaic distributions upon the reflection power ratio, the integrated reflection power ratio (the area under the rocking curve) and the extinction factor Y(μ) in cylindrical crystals has been thoroughly investigated. For a weakly absorbing cylindrical crystal with τ(0) = 30, the value of Y(μ) for the T2 distribution turns out to be nearly two times the value for G, but the difference between these distributions becomes small when ξ(0) > 1. The L distribution has been found to be unsuitable for describing the mosaic distribution. The determination of different types of mosaic distribution from the rocking curves is discussed based on these results. Finally T2, T4 and the G distribution have been found to be acceptable for the calculation of secondary extinction factor tables for cylindrical and spherical crystals.
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http://dx.doi.org/10.1107/S0108767310032927 | DOI Listing |
Philos Trans R Soc Lond B Biol Sci
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BirdLife International, David Attenborough Building, Pembroke Street, Cambridge CB2 3QZ, UK.
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View Article and Find Full Text PDFZool Res
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Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610299, China.
Assessing the threat status of species in response to global change is critical for biodiversity monitoring and conservation efforts. However, current frameworks, even the IUCN Red List, often neglect critical factors such as genetic diversity and the impacts of climate and land-use changes, hindering effective conservation planning. To address these limitations, we developed an enhanced extinction risk assessment framework using lizards as a model.
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Department of Biological Sciences, Northern Kentucky University.
Treating substance use disorders is difficult as individuals often resume substance use during abstinence. One potential factor contributing to the recurrence of substance use is incubation of drug craving. Specifically, individuals report higher levels of craving when presented with drug-paired stimuli across abstinence, although this effect is largely absent in opioid-dependent individuals.
View Article and Find Full Text PDFEnviron Sci Pollut Res Int
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South African Institute for Aquatic Biodiversity, Makhanda, 6140, South Africa.
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