Numerical simulation of the turbulent convective buoyant flow of sodium over a backward- facing step

A forced convective and a buoyancy-aided turbulent liquid sodium flow over a backward-facing step with a constant heat flux applied on the indented wall is simulated. Linear eddy viscosity models are used for the Reynolds stresses. Turbulent heat fluxes are modelled with a single gradient diffusion hypotheses with two different approaches to evaluate the turbulent Prandtl number. Moreover, the influence of turbulence on heat transfer to sodium is also assessed through simulations with zero turbulent thermal diffusivity. The results are compared with DNS data from literature. The velocity and turbulent kinetic energy profiles predicted by all models are in good agreement with the DNS data. The local Nusselt number trend is qualitatively well captured, however, its magnitude is underestimated by all models for the mixed convection case. For forced convection, the heat transfer is overestimated by all heat flux models. The simulation with neglected turbulent heat transfer shows the best overall agreement for the forced convection case. For the mixed convection best agreement is obtained using a correlation to locally evaluate the turbulent thermal diffusivity

Numerical simulation of the turbulent convective buoyant flow of sodium over a backward- facing step

A forced convective and a buoyancy-aided turbulent liquid sodium flow over a backward-facing step with a constant heat flux applied on the indented wall is simulated. Linear eddy viscosity models are used for the Reynolds stresses. Turbulent heat fluxes are modelled with a single gradient diffusion hypotheses with two different approaches to evaluate the turbulent Prandtl number. Moreover, the inuence of turbulence on heat transfer to sodium is also assessed through simulations with zero turbulent thermal diffusivity. The results are compared with DNS data from literature. The velocity and turbulent kinetic energy profiles predicted by all models are in good agreement with the DNS data. The local Nusselt number trend is qualitatively well captured, however, its magnitude is underestimated by all models for the mixed convection case. For forced convection, the heat transfer is overestimated by all heat flux models. The simulation with neglected turbulent heat transfer shows the best overall agreement for the forced convection case. For the mixed convection best agreement is obtained using a correlation to locally evaluate the turbulent thermal diffusivity

The sub-stellar birth rate from UKIDSS

We present a new sample of mid-L to mid-T dwarfs with effective temperatures of 11001700 K selected from the UKIDSS Large Area Survey (LAS) and confirmed with infrared spectra from X-shooter/Very Large Telescope. This effective temperature range is especially sensitive to the formation history of Galactic brown dwarfs and allows us to constrain the form of the sub-stellar birth rate, with sensitivity to differentiate between a flat (stellar like) birth rate and an exponentially declining form. We present the discovery of 63 new L and T dwarfs from the UKIDSS LAS DR7, including the identification of 12 likely unresolved binaries, which form the first complete sub-set from our programme, covering 495 square degrees of sky, complete to J = 18.1. We compare our results for this sub-sample with simulations of differing birth rates for objects of masses 0.10-0.03 M-circle dot and ages 1-10 Gyr. We find that the more extreme birth rates (e. g. a halo type form) can likely be excluded as the true form of the birth rate. In addition, we find that although there is substantial scatter we find a preference for a mass function, with a power-law index a in the range -1 <alpha <0 that is consistent (within the errors) with the studies of late T dwarfs.Peer reviewe

Method for computing variances of estimates derived from the Health Interview Survey

A method for computing variances of estimates derived from the health interview survey[by Judy A. Bean].Public Health Service publication no. 1000, ser. 2, no. 38.Includes bibliographical references.1970500686

Assessing the genetic and molecular basis of resistance to Fusarium verticillioides in maize

Maize (Zea mays L.) is a major cereal crop, the second most cultivated crop in the world. Maize is used for human consumption, livestock feed, and biofuel. In addition to its economic importance, maize has been a widely used model species for genetics and plant biology. Among the limitations to maize production and seed quality, the several diseases caused by Fusarium are severe and largely diffused. Maize research has been oriented towards distinguishing the levels of resistance to ear rot caused by Fusarium verticillioides, however, it has not yet been possible to clarify the model of genetic action of the resistance that could guide the selection of resistant genotypes. The Multi-parent Advance Generation Intercross (MAGIC) maize population was previously used to identify quantitative trait loci (QTL) for Fusarium seedling rot resistance using the rolled towel assay (RTA) that allows fast and reliable phenotyping at early developmental stages. Production of transcriptomic data specific to the infection phase may increase the precision by which candidate genes are identified. RNA-Seq approach was used to compare the genome-wide gene expression patterns in maize scutella and early germinating shoots in the eight MAGIC maize founder lines in mock and F. verticilloides treated seeds. The RTAs were performed at 48, 72, 96, 120, 168 hours post inoculation (hpi) under two conditions control and treated to identify the appropriate time point for the investigation of MAGIC maize founder lines transcriptome profiles. Twenty seeds were used for each RTA in both treatments, in the treated, the seeds were inoculated with 100 \u3bcl of a 3.5 x 106 ml-1 spore suspension of F. verticillioides ITEM10027 (MPVP 294). Real-time PCR was applied on plant and pathogen specific genes to identify the best time point for RNA extraction, which turned out to be 72 hpi. RNA was extracted from the scutella and early germinating shoots and a total of 48 cDNA libraries (8 genotypes x 2 conditions x 3 biological replicates) have been produced and subjected to sequencing. Transcriptomic data on the parental lines will be projected onto recombinant inbred lines reconstructed genomes and used to narrow down QTL intervals to their genetic determinants. The defense-related transcriptional changes will shed light on and related them to the specific genomic regions identified by QTL mapping

Parallaxes of southern extremely cool objects III : 118 L and T dwarfs

We present new results from the Parallaxes of Southern Extremely Cool dwarfs program to measure parallaxes, proper motions and multiepoch photometry of L and early T dwarfs. The observations were made on 108 nights over the course of 8 yr using the Wide Field Imager on the ESO 2.2m telescope. We present 118 new parallaxes of L and T dwarfs of which 52 have no published values and 24 of the 66 published values are preliminary estimates from this program. The parallax precision varies from 1.0 to 15.5mas with a median of 3.8mas. We find evidence for two objects with long term photometric variation and 24 new moving group candidates. We cross-match our sample to published photometric catalogues and find standard magnitudes in up to 16 pass-bands from which we build spectral energy distributions and H-R diagrams. This allows us to confirm the theoretically anticipated minimum in radius between stars and brown dwarfs across the hydrogen burning minimum mass. We find the minimum occurs between L2 and L6 and verify the predicted steep dependence of radius in the hydrogen burning regime and the gentle rise into the degenerate brown dwarf regime. We find a relatively young age of ~2 Gyr from the kinematics of our sample.Peer reviewedFinal Accepted Versio

Discovery of a new Y dwarf: WISE J030449.03-270508.3

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record [D. J. Pinfield, et al, Discovery of a new Y dwarf: WISE J030449.03−270508.3, MNRAS, Vol. 444 (2): 1931-1939, September 2014] is available online at: https://doi.org/10.1093/mnras/stu1540.We present a new Y dwarf, WISE J030449.03−270508.3, confirmed from a candidate sample designed to pick out low-temperature objects from the Wide-field Infrared Survey Explorer (WISE) data base. The new object is typed Y0pec following a visual comparison with spectral standards, and lies at a likely distance of 10–17 pc. Its tangential velocity suggests thin disc membership, but it shows some spectral characteristics that suggest that it may be metal poor and/or older than previously identified Y0 dwarfs. Based on trends seen for warmer late-type T dwarfs, the Y-band flux peak morphology is indicative of sub-solar metallicity, and the enhanced red wing of the J-band flux peak offers evidence for high gravity and/or low metallicity (with associated model trends suggesting an age closer to ∼10 Gyr and mass in the range 0.02–0.03 Mȯ). This object may thus be extending the population parameter space of the known Y0 dwarfs.Peer reviewe