1,319 research outputs found

    The magnetic exciton of EuS revealed by resonant inelastic x-ray scattering

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    We report the valence-to-core resonant inelastic x-ray scattering (RIXS) of EuS measured at the L3 edge of Eu. The obtained data reveal two sets of excitations: one set is composed of a hole in the S 3p bands and an electron excited to extended Eu 5d band states, the other is made up from a hole in the Eu 4f states and an electron in localized Eu 5d states bound to the 4f hole by its Coulomb potential. The delocalized excitations arise from the dipole-allowed 5d to 2p emissions, whereas the localized excitations result from the dipole-forbidden (quadrupole-allowed) 4f to 2p emissions. Both these emission channels have a comparable intensity thanks to a small number of occupied 5d states (approximately 0.6) combined with a large number of occupied 4f states (seven). We identify the localized electron-hole pairs with the "magnetic excitons" suggested in the past as an interpretation of the sharp features seen in the optical absorption spectra. Our observations provide a direct experimental evidence of these excitons which has been missing up to now.Comment: 7 pages, 4 figures, supplemental material (PDF, 8 pages) added as an ancillary fil

    Hydrodynamic model for three-phase internal- and external-loop airlift reactors

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    A mathematical model predicting the hydrodynamic behaviour of three-phase airlift reactors, working with low-density solids and with high solids loading, was developed. The model allows for the prediction of local gas holdup and liquid velocity in airlift bioreactors. Model was validated for an external-loop airlift reactor and an internal-loop airlift reactor with an enlarged degassing zone, being a good agreement obtained between calculated and experimental data.Fundação para a Ciência e a Tecnologia (FCT) Junta Nacional de Investigação Científica e Tecnológica (JNICT) - PRAXIS 2/2.1/BIO/1061/95 Instituto de Biotecnologia e Química Fina (IBQF) - GGP XXI/BD/2937/9

    Modelling design of multiphase bubble-bed reactors for advanced food-industry applications

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    An EC project (IC15-CT98-0904 / PL979021) under this title commenced November 1998 courtesy of Dr Jindrich Zahradnik, sadly since deceased. In dedication to his memory overviewed here are contributions from the four partners whose lead investigators appear as authors (plus coordinator as corresponding author) with principals and researchers recognised in cited literature. A website (www.copernicus.aston.ac.uk) has been launched to disseminate major individual components and collaborations facilitated by study exchanges, also envisaged exploitation by industries. Drawing on this material we outline partners' established expertise and its unification under EC umbrella funding. To avoid confusion on due credit for contributions, references are designated by first letters of the above-named authors. At risk of appearing to favour ones' own wares, we humbly refer readers to our cited papers for contextual commentaries

    Pedigree analysis of Czech Holstein calves with schistosoma reflexum

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    <p>Abstract</p> <p>Background</p> <p>Schistosoma reflexum (SR) is congenital syndrome briefly characterized by visceral eventration, severe dorsoflexion and ankylosis of the spine and arthrogryposis. A genetic etiology has been proposed, but conclusive evidence has not yet been provided.</p> <p>Methods</p> <p>Pedigree analysis was carried out in 29 cases of SR in Czech Holsteins and Holstein crosses. Genetic relationship was evaluated and inbreeding coefficients calculated. Pedigrees of 15 Czech Holsteins fathering non-SR affected calves were used for comparison.</p> <p>Results</p> <p>Twenty-one cases occurred in one pedigree founded by three sires while three SR calves occurred in another pedigree with a common grandfather. The sex ratio between affected males and females was 11:6. Affected calves shared common ancestors different from those shared by the unaffected calves. The inbreeding coefficient in the SR affected calves was not increased compared to unaffected calves.</p> <p>Conclusions</p> <p>The findings are consistent with SR being inherited autosomal recessively. Further studies are however needed to confirm this and therefore a breeding trial is recommended where a suspected heterozygous sire is mated to closely related females.</p

    Miyabeacin: A new cyclodimer presents a potential role for willow in cancer therapy

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    Willow (Salix spp.) is well known as a source of medicinal compounds, the most famous being salicin, the progenitor of aspirin. Here we describe the isolation, structure determination, and anti-cancer activity of a cyclodimeric salicinoid (miyabeacin) from S. miyabeana and S. dasyclados. We also show that the capability to produce such dimers is a heritable trait and how variation in structures of natural miyabeacin analogues is derived via cross-over Diels-Alder reactions from pools of ortho-quinol precursors. These transient ortho-quinols have a role in the, as yet uncharacterised, biosynthetic pathways around salicortin, the major salicinoid of many willow genotypes
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