Very-large-scale motions in rough-bed open-channel flow

Acknowledgements The study has been supported by two EPSRC/UK grants, ‘High-resolution numerical and experimental studies of turbulence-induced sediment erosion and near-bed transport’ (EP/G056404/1) and ‘Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification’ (EP/K041169/1). Discussions with I. Marusic and comments of three anonymous reviewers are greatly appreciated.Peer reviewedPublisher PD

Double-averaged velocity and stress distributions for hydraulically-smooth and transitionally-rough turbulent flows

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Geochemical characterization of the mineralized transition between the Goldenville and Halifax formations and the interaction with adjacent granitoid intrusions of the Liscomb Complex, Nova Scotia

The mineralized transition between the Goldenville and Halifax formations of the Meguma Group was intruded by granodiorite and monzogranite of the Liscomb Complex near Eastville, Nova Scotia. Mineral and whole-rock chemical studies of samples from drillholes and surface exposures allow documentation of the chemical nature and a preliminary assessment of the magnitude of interaction between the granitoid bodies and their metasedimentary host rocks. Mg/(Mg+Fe) broadly increased, whereas Mn decreased in biotite and chlorite with increasing grades of metamorphism toward the contact with the Liscomb Complex in the eastern section of the map area. Fe and Mn, two transition elements with similar chemical behaviour, were mobilized and incorporated into Fe-rich contact metamorphic minerals such as almandine garnet and staurolite. Garnet in the granodiorite shows reversals in zoning, with Mg and Fe decreasing sharply and Mn increasing at the rim. Reversely zoned garnet crystallized with falling temperature and likely represents a highly modified xenocrystic type. Standard discriminant diagrams confirm that the Meguma metasedimentary rocks were deposited on a continental margin and that the granitoid intrusions formed as crustal melts during continental collision. Assimilation of Meguma country rock by the Liscomb granitoid intrusions is indicated by the detection of a characteristic trace element signature imparted by the transition between the Goldenville and Halifax formations near Eastville. Although not certain proof, the strong contrast between Pb/Zn ratios in the Meguma metasedimentary rocks and the Liscomb granodiorite (-0.45) and the rest of the South Mountain Batholith (1.19-2.26) suggests a variant petrogenetic process for the two granitoid bodies. RÉSUMÉ La transition minéralisée entre les Formations de Goldenville et d'Halifax du groupe de Meguma a étéi pénétrée par de la granodiorite et du monzogranite du complexe de Liscomb, près d'Eastville, Nouvelle-Écosse. Des études chimiques des roches et des minéraux des échantillons provenant de trous de forage et d'affleurements de surface permettent une documentation de la nature chimique du sous-sol et une évaluation préliminaire de l'ampleur de l'interaction entre les masses granitiqucs et leurs roches hôtes métasédimentaires. La quantité de Mg(Mg+Fe) a généralement augmenté tandis que le Mn a diminué dans la biotite et la chlorite avec les niveaux accrus de métamorphisme apparus vers la zone de contact avec le complexe de Liscomb, dans la partie orientate du secteur cartographique. Le Fe et le Mn, deux éléments de transition ayant un comportement chimique semblable, ont été mobilisés et incorpores dans des minéraux métamorphiques de contact riches en Fe comme les grenats d'almandine et la staurolite. Les grenats a l'intericur de la granodiorite affichent des inversions de zonation avec une diminution soudaine du Mg et du Fe et une augmentation du Mn le long de la frange du secteur. Les grenats de zonation inverse se sont cristallisés lorsque la température a chuté; ils représentent vraisemblablement un type xénocristique fortement modifié Des schémas discriminants standard confirment que les roches métasédimentaires de Meguma se sont déposées sur une marge continentale et que les intrusions granitiqucs se sont formées au moment de la fusion de la croûte lors de la collision des continents. La détection d'une signature d'éléments traces caractéristiques due à la transition entre les formations de Goldenville et d'Halifax, près d'Eastville, révèle l'assimilation de roches encaissantes de Meguma par les intrusions granitiques de Liscomb. Même si cela ne constitue pas une preuve certaine, le contraste marqué entre les rapports de Pb/Zn dans les roches métasédimentaires de Meguma et la granodiorite de Liscomb (— 0,45) ainsi que le reste du batholithe de South Mountain (1,19-2,26), permet de supposer que les deux masses granitiques ont été soumises à un processus pétrogénltique différent. [Traduit par la rédaction

Drag forces on a bed particle in open-channel flow : Effects of pressure spatial fluctuations and very-large-scale motions

The study has been supported by two EPSRC/UK grants, ‘High-resolution numerical and experimental studies of turbulence-induced sediment erosion and near-bed transport’ (EP/G056404/1) and ‘Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification’ (EP/K041088/1). I.M. also acknowledges the support of the Australian Research Council.Peer reviewedPublisher PD

An assessment of diet overlap of two mesocarnivores in the North-West Province, South Africa

We used scat analysis to study the diet of two sympatric medium-sized carnivores: brown hyaena and black-backed jackal, in the NorthWest Province of South Africa. Seven major dietary categories were identified from the scats, with mammal remains being most common for both species. Brown hyaena scats contained more large mammal remains, which together with the presence of invertebrates (in 50% of all brown hyaena scats), suggests that they mainly scavenged. Jackal scats contained a higher proportion of small mammal remains, suggesting that jackals actively hunted more often than brown hyaenas did. The diets differed significantly between the two species, even though diet overlap was fairly high (0.79). Further analysis, albeit based on small sample sizes, suggests that diet of these mesopredators differ between protected reserves with apex predators and unprotected areas without apex predators, thus confounding generalizations. Further studies are therefore required to investigate possible mesopredator release when apex predators are absent

Warm dust in the terrestrial planet zone of a sun-like Pleiad: collisions between planetary embryos?

Only a few solar-type main sequence stars are known to be orbited by warm dust particles; the most extreme is the G0 field star BD+20 307 that emits ~4% of its energy at mid-infrared wavelengths. We report the identification of a similarly dusty star HD 23514, an F6-type member of the Pleiades cluster. A strong mid-IR silicate emission feature indicates the presence of small warm dust particles, but with the primary flux density peak at the non-standard wavelength of ~9 micron. The existence of so much dust within an AU or so of these stars is not easily accounted for given the very brief lifetime in orbit of small particles. The apparent absence of very hot (>~1000 K) dust at both stars suggests the possible presence of a planet closer to the stars than the dust. The observed frequency of the BD+20 307/HD 23514 phenomenon indicates that the mass equivalent of Earth's Moon must be converted, via collisions of massive bodies, to tiny dust particles that find their way to the terrestrial planet zone during the first few hundred million years of the life of many (most?) sun-like stars. Identification of these two dusty systems among youthful nearby solar-type stars suggests that terrestrial planet formation is common.Comment: ApJ in press, 19 pages including 3 figures and 2 tables, minor changes to the tables and figure

Security-first thinking and educational practices for young children in foster care in Sweden and England: A think piece

While the education of looked after children has attracted considerable policy attention in Europe and North America, and globally the early education of preschool aged children is the subject of substantial investment, the early education of young children in foster care is neglected in both research and policy. This paper is a cross-national think piece to stimulate research and debate about young children in foster care. We present findings from two studies, one in England and one in Sweden, exploring foster carers’ views and practices with young children. We argue that there is a perceived tension, in foster care policy and practice, between education and emotional wellbeing such that young children's attachment relationships and sense of security is privileged over their engagement in educational practices. Attachment relationships are a necessary but insufficient condition for optimal development of fostered children