3,320 research outputs found

    Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate

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    We determine the frequency dependence of four independent CdWO4_4 Cartesian dielectric function tensor elements by generalized spectroscopic ellipsometry within mid-infrared and far-infrared spectral regions. Single crystal surfaces cut under different angles from a bulk crystal, (010) and (001), are investigated. From the spectral dependencies of the dielectric function tensor and its inverse we determine all long wavelength active transverse and longitudinal optic phonon modes with AuA_u and BuB_u symmetry as well as their eigenvectors within the monoclinic lattice. We thereby demonstrate that such information can be obtained completely without physical model line shape analysis in materials with monoclinic symmetry. We then augment the effect of lattice anharmonicity onto our recently described dielectric function tensor model approach for materials with monoclinic and triclinic crystal symmetries [Phys. Rev. B, 125209 (2016)], and we obtain excellent match between all measured and modeled dielectric function tensor elements. All phonon mode frequency and broadening parameters are determined in our model approach. We also perform density functional theory phonon mode calculations, and we compare our results obtained from theory, from direct dielectric function tensor analysis, and from model lineshape analysis, and we find excellent agreement between all approaches. We also discuss and present static and above reststrahlen spectral range dielectric constants. Our data for CdWO4_4 are in excellent agreement with a recently proposed generalization of the Lyddane-Sachs-Teller relation for materials with low crystal symmetry [Phys. Rev. Lett. 117, 215502 (2016)].Comment: arXiv admin note: text overlap with arXiv:1512.0859

    Anisotropy and phonon modes from analysis of the dielectric function tensor and inverse dielectric function tensor of monoclinic yttrium orthosilicate

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    We determine the frequency dependence of the four independent Cartesian tensor elements of the dielectric function for monoclinic symmetry Y2_2SiO5_5 using generalized spectroscopic ellipsometry from 40-1200 cm1^{-1}. Three different crystal cuts, each perpendicular to a principle axis, are investigated. We apply our recently described augmentation of lattice anharmonicity onto the eigendielectric displacement vector summation approach [A. Mock et al., Phys. Rev. B 95, 165202 (2017)], and we present and demonstrate the application of an eigendielectric displacement loss vector summation approach with anharmonic broadening. We obtain excellent match between all measured and model calculated dielectric function tensor elements and all dielectric loss function tensor elements. We obtain 23 Au_{\mathrm{u}} and 22 Bu_{\mathrm{u}} symmetry long wavelength active transverse and longitudinal optical mode parameters including their eigenvector orientation within the monoclinic lattice. We perform density functional theory calculations and obtain 23 Au_{\mathrm{u}} symmetry and 22 Bu_{\mathrm{u}} transverse and longitudinal optical mode parameters and their orientation within the monoclincic lattice. We compare our results from ellipsometry and density functional theory and find excellent agreement. We also determine the static and above reststrahlen spectral range dielectric tensor values and find a recently derived generalization of the Lyddane-Sachs-Teller relation for polar phonons in monoclinic symmetry materials satisfied [M. Schubert, Phys. Rev. Lett. 117, 215502 (2016)]

    Natural law in American jurisprudence: Calder vs. Bull and Corfield v. Coryell and their progeny

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    This dissertation seeks to answer the question of whether and to what extent principles of natural law have figured in Supreme Court jurisprudence in the last two centuries. In the last quarter-century, scholars and judicial analysts have displayed a renewed interest in natural law reasoning and whether justices do or should take cognizance of natural law considerations. The issue became prominent during the 1991 confirmation hearings of Clarence Thomas, who had written and spoken favorably of natural law as a guiding principle in constitutional adjudication. Two cases and their progeny figure herein. In Calder v. Bull (1798), Supreme Court Justices Samuel Chase and James Iredell discussed whether principles of natural justice placed limits on legislatures beyond which they could not go, or whether judges could rely only on specific constitutional restraints in evaluating legislative acts. In Corfield v. Coryell (1823), Justice Bushrod Washington explained that the Constitution’s Privileges and Immunities Clause protects those rights that are “fundamental,” and many subsequent commentators and courts have given this statement a natural rights gloss. This work contributes to existing Supreme Court literature by tracing the entire history of Calder and Corfield, the two cases most frequently cited for potentially having natural law implications. The paper considers each citation as it is relevant to the natural law debate; cases are excluded only because they are cited for another point. For example, cases that cite Calder for its holding that the Constitution’s Ex Post Facto clause only applies to criminal cases are not considered. The paper concludes that natural law considerations now figure in Supreme Court jurisprudence only in a mediated sense. While several Eighteenth and Nineteenth Century opinions, including Corfield itself, accept natural law principles as interpretative guides, natural law as a free-standing source of adjudication has faded from Supreme Court jurisprudence. Concomitantly, the Privileges and Immunities Clause as a source of rights has been largely discarded in favor of a substantive due-process jurisprudence, with the Court adopting a gradual, common-law type of approach in determining the constitutional limits of government interference with Americans’ rights

    Coyote (\u3ci\u3eCanis latrans\u3c/i\u3e) diet in an urban environment: variation relative to pet conflicts, housing density, and season

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    Coyotes (Canis latrans Say, 1823) are highly successful in urbanized environments, but as they populate cities, conflict can occur and often manifests in the form of incidents with pets. To better understand whether coyotes view pets as prey or, alternatively, as competitors or a threat, we conducted a diet analysis of coyotes in the Denver metropolitan area (DMA) by analyzing scats. We also examined differences in diet between high- and low-density housing and among seasons. We found only small percentages of trash and domestic pets in the coyote diet. The presence of pets in the diet did not coincide with the increase of pet conflicts in the DMA in December and January, supporting the hypothesis that coyote conflict with pets is primarily driven by competition or a threat response. Coyotes relied mostly on native plant and animal species, and rodents and lagomorphs were the most prevalent diet items. Coyotes consumed rodents and non-native plants more often in high-density housing and deer, corn, and native plants more often in low-density housing. Coyotes also consumed more fruits and invertebrates during summer and autumn and more mammals and birds in winter and spring. As human–coyote conflicts increase in urban areas, understanding how coyotes and other urban-adapted carnivores use anthropogenic resources may provide insight that can be used to promote coexistence between humans and wildlife

    Burning characteristics of single particles of coal and wood mixtures for co-firing in an upward-flowing hot gas stream

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    This study presents the comparative burning behaviours of single solid particles of coal and biomass mixtures for co-firing. In this experimental investigation, a direct observation approach was used to investigate the ignition, flame characteristics and combustion times by means of high-speed photography at 7000 frames per second. Single particles were entrained into a hot gas stream at 1340 K and a rapid heating rate of 104–105 K/s. The apparent volatile flames from the prepared particle size groups were observed within 20–50 ms. To assess the effect of oxygen concentration, particles were burned for their flame characteristics in a range of 10%–40% O2. The test particles were sieved into three size groups (215–255 μm, 255–300 μm and 300–350 μm) to assess the effect of particle size. Special particles for the co-firing effect were collected individually from two types of mixed pellet: 20:80 and 50:50 coal/wood. Pure sub-bituminous coal and wood particles were also prepared in order to compare their combustion behaviours. In the experimental setup with a cross-injection configuration, sequential combustion processes were effectively and clearly described in terms of particle displacement with time. The experimental results showed distinguishable flame characteristics from single particles of coal, 50:50 coal/wood, 20:80 coal/wood and wood, including soot flame size and intensity. The impact of high coal-blending ratio caused an increase in the flame size and intensity and the ignition time was close to that of pure coal particles. Quantitative measurements of combustion events on co-firing particles were also discussed in relation to significant impacts of the particle size and the oxygen concentration

    Directly observed road safety compliance by Motor Cycle Riders after a 5- Year Road Safety Campaign in Naivasha, Kenya

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    Objective: To assess the extent of compliance with road safety regulations by  motorcycle riders following a five year road safety campaign in Naivasha town, Kenya.Design: A cross sectional study.Setting: Naivasha town, Nakuru county, Kenya.Results: A total of 9,280 MCs ferrying 13,733 people were observed. Less than 1% complied with all the four road safety  requirements. The overall helmet wearing compliance was 31%. MC driver helmet compliance was 42% which was five timeshigher than passenger helmet compliance. Female passengers were twice less likely to wear helmet than males.Conclusion: Despite the five-year road safety campaign, compliance among MC users remains low particularly among the passengers and more so female passengers. Does Kenya need to rethink the motor cycle road safety policy
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