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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Projections for future radiocarbon content in dissolved inorganic carbon in hardwater lakes: a retrospective approach

Inland water bodies contain significant amounts of carbon in the form of dissolved inorganic carbon (DIC) derived from a mixture of modern atmospheric and pre-aged sources, which needs to be considered in radiocarbon-based dating and natural isotope tracer studies. While reservoir effects in hardwater lakes are generally considered to be constant through time, a comparison of recent and historical DI14C data from 2013 and 1969 for Lake Constance reveals that this is not a valid assumption. We hypothesize that changes in atmospheric carbon contributions to lake water DIC have taken place due to anthropogenically forced eutrophication in the 20th century. A return to more oligotrophic conditions in the lake led to reoxygenation and enhanced terrigenous organic matter remineralization, contributing to lake water DIC. Such comparisons using DI14C measurements from different points in time enable nonlinear changes in lake water DIC source and signature to be disentangled from concurrent anthropogenically induced changes in atmospheric 14C. In the future, coeval changes in lake dynamics due to climate change are expected to further perturb these balances. Depending on the scenario, Lake Constance DI14C is projected to decrease from the 2013 measured value of 0.856 Fm to 0.54–0.62 Fm by the end of the century

A comparison of medetomidine and its active enantiomer dexmedetomidine when administered with ketamine in mice

Medetomidine-ketamine (MK) and dexmedetomidine-ketamine (DK) are widely used to provide general anaesthesia in laboratory animals, but have not been compared directly in many of these species, including rodents. This study aimed to compare the onset and depth of anaesthesia, and changes in vital signs, after intraperitoneal (IP) or subcutaneous (SC) administration of ketamine (75 mg kg-1) combined with medetomidine (1 mg kg-1) or dexmedetomidine (0.5 mg kg-1) using a randomised semi-crossover design with >= 48 hours between treatments in 10 male and 10 female mice. Each mouse was anaesthetised twice using the same administration route (IP or SC): once with each drug-ketamine combination. Anaesthetised mice were monitored on a heating pad without supplemental oxygen for 89 minutes; atipamezole was administered for reversal. The times that the righting reflex was lost post-injection and returned post-reversal were analysed using general linear models. Tail-pinch and pedal reflexes were examined using binomial generalized linear models. Pulse rate (PR), respiratory rate (fr), and arterial haemoglobin saturation (SpO2) were compared using generalized additive mixed models. There were no significant differences among treatments for the times taken for loss and return of the righting reflex, or response of the tail-pinch reflex. The pedal withdrawal reflex was abolished more frequently with MK than DK over time (P = 0.021). The response of PR and SpO2 were similar among treatments, but fr was significantly higher with MK than DK (P <= 0.0005). Markedly low SpO2 concentrations occurred within 5 minutes post-injection (83.8 +/- 6.7 %) in all treatment groups and were most severe after 89 minutes lapsed (66.7 +/- 7.5 %). No statistical differences were detected in regards to administration route (P <= 0.94). This study failed to demonstrate clinical advantages of the enantiomer dexmedetomidine over medetomidine when combined with ketamine to produce general anaesthesia in mice. At the doses administered, deep surgical anaesthesia was not consistently produced with either combination; therefore, anaesthetic depth must be assessed before performing surgical procedures. Supplemental oxygen should always be provided during anaesthesia to prevent hypoxaemia

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. R&#xC9;SUM&#xC9; La transition min&#xE9;ralis&#xE9;e entre les Formations de Goldenville et d'Halifax du groupe de Meguma a &#xE9;t&#xE9;i p&#xE9;n&#xE9;tr&#xE9;e par de la granodiorite et du monzogranite du complexe de Liscomb, pr&#xE8;s d'Eastville, Nouvelle-&#xC9;cosse. Des &#xE9;tudes chimiques des roches et des min&#xE9;raux des &#xE9;chantillons provenant de trous de forage et d'affleurements de surface permettent une documentation de la nature chimique du sous-sol et une &#xE9;valuation pr&#xE9;liminaire de l'ampleur de l'interaction entre les masses granitiqucs et leurs roches h&#xF4;tes m&#xE9;tas&#xE9;dimentaires. La quantit&#xE9; de Mg(Mg+Fe) a g&#xE9;n&#xE9;ralement augment&#xE9; tandis que le Mn a diminu&#xE9; dans la biotite et la chlorite avec les niveaux accrus de m&#xE9;tamorphisme apparus vers la zone de contact avec le complexe de Liscomb, dans la partie orientate du secteur cartographique. Le Fe et le Mn, deux &#xE9;l&#xE9;ments de transition ayant un comportement chimique semblable, ont &#xE9;t&#xE9; mobilis&#xE9;s et incorpores dans des min&#xE9;raux m&#xE9;tamorphiques 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 cristallis&#xE9;s lorsque la temp&#xE9;rature a chut&#xE9;; ils repr&#xE9;sentent vraisemblablement un type x&#xE9;nocristique fortement modifi&#xE9; Des sch&#xE9;mas discriminants standard confirment que les roches m&#xE9;tas&#xE9;dimentaires de Meguma se sont d&#xE9;pos&#xE9;es sur une marge continentale et que les intrusions granitiqucs se sont form&#xE9;es au moment de la fusion de la cro&#xFB;te lors de la collision des continents. La d&#xE9;tection d'une signature d'&#xE9;l&#xE9;ments traces caract&#xE9;ristiques due &#xE0; la transition entre les formations de Goldenville et d'Halifax, pr&#xE8;s d'Eastville, r&#xE9;v&#xE8;le l'assimilation de roches encaissantes de Meguma par les intrusions granitiques de Liscomb. M&#xEA;me si cela ne constitue pas une preuve certaine, le contraste marqu&#xE9; entre les rapports de Pb/Zn dans les roches m&#xE9;tas&#xE9;dimentaires 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 &#xE9;t&#xE9; soumises &#xE0; un processus p&#xE9;trog&#xE9;nltique diff&#xE9;rent. [Traduit par la r&#xE9;daction

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

The Angular Momentum Evolution of Very Low Mass Stars

We present theoretical models of the angular momentum evolution of very low mass stars (0.1 - 0.5 M_sun) and solar analogues (0.6 - 1.1 M_sun). We investigate the effect of rotation on the effective temperature and luminosity of these stars. We find that the decrease in T_eff and L can be significant at the higher end of our mass range, but becomes negligible below 0.4 M_sun. Formulae for relating T_eff to mass and v_rot are presented. We compare our models to rotational data from young open clusters of different ages to infer the rotational history of low mass stars, and the dependence of initial conditions and rotational evolution on mass. We find that the qualitative conclusions for stars below 0.6 M_sun do not depend on the assumptions about internal angular momentum transport, which makes these low mass stars ideal candidates for the study of the angular momentum loss law and distribution of initial conditions. We find that neither models with solid body nor differential rotation can simultaneously reproduce the observed stellar spin down in the 0.6 to 1.1 M_sun mass range and for stars between 0.1 and 0.6 M_sun. The most likely explanation is that the saturation threshold drops more steeply at low masses than would be predicted with a simple Rossby scaling. In young clusters there is a systematic increase in the mean rotation rate with decreased temperature below 3500 K (0.4 M_sun). This suggests either inefficient angular momentum loss or mass-dependent initial conditions for stars near the fully convective boundary. (abridged)Comment: To appear in the May 10, 2000 Ap

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