First L-band Interferometric Observations of a Young Stellar Object: Probing the Circumstellar Environment of MWC 419

We present spatially-resolved K- and L-band spectra (at spectral resolution R = 230 and R = 60, respectively) of MWC 419, a Herbig Ae/Be star. The data were obtained simultaneously with a new configuration of the 85-m baseline Keck Interferometer. Our observations are sensitive to the radial distribution of temperature in the inner region of the disk of MWC 419. We fit the visibility data with both simple geometric and more physical disk models. The geometric models (uniform disk and Gaussian) show that the apparent size increases linearly with wavelength in the 2-4 microns wavelength region, suggesting that the disk is extended with a temperature gradient. A model having a power-law temperature gradient with radius simultaneously fits our interferometric measurements and the spectral energy distribution data from the literature. The slope of the power-law is close to that expected from an optically thick disk. Our spectrally dispersed interferometric measurements include the Br gamma emission line. The measured disk size at and around Br gamma suggests that emitting hydrogen gas is located inside (or within the inner regions) of the dust disk.Comment: Accepted for publication in Ap

Investigating situated cultural practices through cross-sectoral digital collaborations: policies, processes, insights

The (Belfast) Good Friday Agreement represents a major milestone in Northern Ireland's recent political history, with complex conditions allowing for formation of a ‘cross-community’ system of government enabling power sharing between parties representing Protestant/loyalist and Catholic/nationalist constituencies. This article examines the apparent flourishing of community-focused digital practices over the subsequent ‘post-conflict’ decade, galvanised by Northern Irish and EU policy initiatives armed with consolidating the peace process. Numerous digital heritage and storytelling projects have been catalysed within programmes aiming to foster social processes, community cohesion and cross-community exchange. The article outlines two projects—‘digital memory boxes’ and ‘interactive galleon’—developed during 2007–2008 within practice-led PhD enquiry conducted in collaboration with the Nerve Centre, a third-sector media education organisation. The article goes on to critically examine the processes involved in practically realising, and creatively and theoretically reconciling, community-engaged digital production in a particular socio-political context of academic-community collaboration

Stellar and Molecular Radii of a Mira Star: First Observations with the Keck Interferometer Grism

Using a new grism at the Keck Interferometer, we obtained spectrally dispersed (R ~ 230) interferometric measurements of the Mira star R Vir. These data show that the measured radius of the emission varies substantially from 2.0-2.4 microns. Simple models can reproduce these wavelength-dependent variations using extended molecular layers, which absorb stellar radiation and re-emit it at longer wavelengths. Because we observe spectral regions with and without substantial molecular opacity, we determine the stellar photospheric radius, uncontaminated by molecular emission. We infer that most of the molecular opacity arises at approximately twice the radius of the stellar photosphere.Comment: 12 pages, including 3 figures. Accepted by ApJ

Simple Models Outperform More Complex Big-Leaf Models of Daily Transpiration in Forested Biomes

Transpiration makes up the bulk of total evaporation in forested environments yet remains challenging to predict at landscape-to-global scales. We harnessed independent estimates of daily transpiration derived from co-located sap flow and eddy-covariance measurement systems and applied the triple collocation technique to evaluate predictions from big leaf models requiring no calibration. In total, four models in 608 unique configurations were evaluated at 21 forested sites spanning a wide diversity of biophysical attributes and environmental backgrounds. We found that simpler models that neither explicitly represented aerodynamic forcing nor canopy conductance achieved higher accuracy and signal-to-noise levels when optimally configured (rRMSE = 20%; R2 = 0.89). Irrespective of model type, optimal configurations were those making use of key plant functional type dependent parameters, daily LAI, and constraints based on atmospheric moisture demand over soil moisture supply. Our findings have implications for more informed water resource management based on hydrological modeling and remote sensing.publishedVersio

Heavy Element Enrichment of a Jupiter-mass Protoplanet as a Function of Orbital Location

We calculate heavy element enrichment in a Jupiter-mass protoplanet formed by disk instability at various radial distances from the star, considering different disk masses and surface density distributions. Although the available mass for accretion increases with radial distance (a) for disk solid surface density (sigma) functions sigma=sigma_0*a^(-alpha) with alpha < 2, the accretion timescale is significantly longer at larger radial distances. Efficient accretion is limited to the first ~ 1E5 years of planetary evolution, when the planet is extended and before gap opening and type II migration take place. The accreted mass is calculated for disk masses of 0.01, 0.05 and 0.1 M_sun with alpha = 1/2, 1, and 3/2. We show that a Jupiter-mass protoplanet can accrete 1 to 110 M_earth of heavy elements, depending on the disk properties. Our results explain the large variation in heavy element enrichment found in extra-solar giant planets. Since higher disk surface density is found to lead to larger heavy element enrichment, our model results are consistent with the correlation between heavy element enrichment and stellar metallicity. Our calculations also suggest that Jupiter could have formed at a larger radial distance than its current location while still accreting the mass of heavy elements predicted by interior models. We conclude that in the disk instability model the final composition of a giant planet is strongly determined by its formation environment. The heavy element abundance of a giant planet does not discriminate between its origin by either disk instability or core accretion.Comment: accepted for publication in The Astrophysical Journa

The Effects of Microbial Inoculation on Short-to-Long Fermentation and Aerobic Stability of Grass-Legume Silage Ensiled in Big Bales

Wilted (35.9 % DM and 2.6% WSC) moderately difficult to ensile grass-legume mixture (red clover, alfalfa and timothy 50:20:30) was ensiled in cylindrical big bales (1.2 m hight and 1.2 m diameter) with a weight about 700 kg. The crop was ensiled for 8, 32 and 120 days with or without a microbial inoculation (SiloSolve® FC containing Lactococcus lactis DSM 11037/1k2081 and Lactobacillus buchneri DSM 22501/1k20738 applied at 1.5×105 CFU g-1 forage). Ten bales per treatment were prepared for each fermentation period. After each period of ensiling the big bales were opened, sampled, and tested for fermentation parameters, yeast and mould counts and aerobic stability. Weight loss during fermentation and aerobic exposure were recorded and DM losses were calculated. After 8 days of fermentation, the addition of SiloSolve® FC showed only significant positive effects on pH, acetic and butyric acid, while after 32 and 120 days of fermentation periods, significant improvements of adding SiloSolve® FC were observed across all parameters investigated. The results show that SiloSolve® FC is an effective treatment to reduce ammonia, ethanol, and butyric acid production, to control yeast and mould growth, and to improve acetic acid levels with a resulting improved aerobic stability of grass-legume mixture fermented in big bales. Total lactic acid bacteria increased significantly and an appreciable decrease number of yeasts were detected in the inoculated silage at all fermentation time points and after aerobic exposure if compared with untreated silage. Reduction in yeast and mould population during anaerobic phase of silage fermentation and during silage aerobic exposure period appears to be the main reason for the improvement aerobic stability of the inoculated silage. Improved fermentation, reduced DM loss during fermentation and during aerobic exposure periods lead to increase nutritive value of the inoculated silage