Repeatable method of thermal stress fracture test of brittle materials

Method heats specimens slowly and with sufficient control so that the critical temperature gradient in the specimens cannot occur before temperature equilibrium is reached

New stellar encounters discovered in the second Gaia data release

Passing stars may play an important role in the evolution of our solar system. We search for close stellar encounters to the Sun among all 7.2 million stars in Gaia-DR2 that have six-dimensional phase space data. We characterize encounters by integrating their orbits through a Galactic potential and propagating the correlated uncertainties via a Monte Carlo resampling. After filtering to remove spurious data, we find 694 stars that have median (over uncertainties) closest encounter distances within 5 pc, all occurring within 15 Myr from now. 26 of these have at least a 50% chance of coming closer than 1 pc (and 7 within 0.5 pc), all but one of which are newly discovered here. We further confirm some and refute several other previously-identified encounters, confirming suspicions about their data. The closest encounter in the sample is Gl 710, which has a 95% probability of coming closer than 0.08 pc (17 000 AU). Taking mass estimates from Gaia astrometry and multiband photometry for essentially all encounters, we find that Gl 710 also has the largest impulse on the Oort cloud. Using a Galaxy model, we compute the completeness of the Gaia-DR2 encountering sample as a function of perihelion time and distance. Only 15% of encounters within 5 pc occurring within +/- 5 Myr of now have been identified, mostly due to the lack of radial velocities for faint and/or cool stars. Accounting for the incompleteness, we infer the present rate of encounters within 1 pc to be 19.7 +/- 2.2 per Myr, a quantity expected to scale quadratically with the encounter distance out to at least several pc. Spuriously large parallaxes in our sample from imperfect filtering would tend to inflate both the number of encounters found and this inferred rate. The magnitude of this effect is hard to quantify.Comment: 12 pages. Accepted to A&A. Added to this version: section 3.2 and Fig. 8 (CMD) with discussion of astrometric quality metrics; full versions of tables 2 and 3 as ancillary dat

Non-local thermodynamic equilibrium stellar spectroscopy with 1D and 3D models - II. Chemical properties of the Galactic metal-poor disc and the halo

From exploratory studies and theoretical expectations it is known that simplifying approximations in spectroscopic analysis (LTE, 1D) lead to systematic biases of stellar parameters and abundances. These biases depend strongly on surface gravity, temperature, and, in particular, for LTE vs. non-LTE (NLTE) on metallicity of the stars. Here we analyse the [Mg/Fe] and [Fe/H] plane of a sample of 326 stars, comparing LTE and NLTE results obtained using 1D hydrostatic models and averaged models. We show that compared to the NLTE benchmark, all other three methods display increasing biases towards lower metallicities, resulting in false trends of [Mg/Fe] against [Fe/H], which have profound implications for interpretations by chemical evolution models. In our best NLTE model, the halo and disc stars show a clearer behaviour in the [Mg/Fe] - [Fe/H] plane, from the knee in abundance space down to the lowest metallicities. Our sample has a large fraction of thick disc stars and this population extends down to at least [Fe/H] ~ -1.6 dex, further than previously proven. The thick disc stars display a constant [Mg/Fe] ~ 0.3 dex, with a small intrinsic dispersion in [Mg/Fe] that suggests that a fast SN Ia channel is not relevant for the disc formation. The halo stars reach higher [Mg/Fe] ratios and display a net trend of [Mg/Fe] at low metallicities, paired with a large dispersion in [Mg/Fe]. These indicate the diverse origin of halo stars from accreted low-mass systems to stochastic/inhomogeneous chemical evolution in the Galactic halo.Comment: 15 pages, accepted for publication in Ap

Galaxy And Mass Assembly (GAMA): end of survey report and data release 2

The Galaxy And Mass Assembly (GAMA) survey is one of the largest contemporary spectroscopic surveys of low redshift galaxies. Covering an area of ˜286 deg2 (split among five survey regions) down to a limiting magnitude of r < 19.8 mag, we have collected spectra and reliable redshifts for 238 000 objects using the AAOmega spectrograph on the Anglo-Australian Telescope. In addition, we have assembled imaging data from a number of independent surveys in order to generate photometry spanning the wavelength range 1 nm-1 m. Here, we report on the recently completed spectroscopic survey and present a series of diagnostics to assess its final state and the quality of the redshift data. We also describe a number of survey aspects and procedures, or updates thereof, including changes to the input catalogue, redshifting and re-redshifting, and the derivation of ultraviolet, optical and near-infrared photometry. Finally, we present the second public release of GAMA data. In this release, we provide input catalogue and targeting information, spectra, redshifts, ultraviolet, optical and near-infrared photometry, single-component Sérsic fits, stellar masses, Hα-derived star formation rates, environment information, and group properties for all galaxies with r < 19.0 mag in two of our survey regions, and for all galaxies with r < 19.4 mag in a third region (72 225 objects in total). The data base serving these data is available at http://www.gama-survey.org/

Contrasting levels of fructose and urea added to an annual ryegrass based diet: effects on microbial protein synthesis, nutrient digestibility and fermentation parameters in continuous culture fermenters

El objetivo de este experimento fue evaluar los efectos de la adición de fructosa cristalina y urea a una dieta basada en raigrás anual sobre la síntesis de proteína microbiana, la fermentación y la digestibilidad de los nutrientes, usando fermentadores de flujo continuo. Se usaron seis fermentadores de flujo continuo en un arreglo factorial 3x2, con tres niveles de hidratos de carbono solubles (WSC) obtenidos por la adición de fructosa cristalina (21, 24 y 27 g.100 g MS1; LWSC, MWSC y HWSC, respectivamente) y dos niveles de proteína bruta (CP) obtenidos por la adición de urea (14,6 y 18,6 g.100 g MS1, LCP y HCP, respectivamente). Se corrieron sucesivamente cuatro períodos de 10d (7d para adaptación, 3d para muestreo). La síntesis de proteína microbiana se estimó por la relación purinas: N. Hubo una interacción significativa entre niveles de WSC y CP para síntesis de proteína microbiana (P&lt;0,001). El nivel de WSC no afectó el pH, la concentración de amonio ni la concentración de ácidos grasos volátiles (VFA). Niveles más altos de CP aumentaron la proporción de ácido acético y tendieron a aumentar la relación acético propiónico, mientras que el nivel de WSC no afectó las proporciones de VFA. Los tratamientos no afectaron la digestibilidad de los nutrientes. Concluimos que la adición de fructosa cristalina a dietas basadas en raigrás anual aumentó la síntesis de proteína microbiana a los niveles más altos de CP en la dieta.The objective of this experiment was to evaluate the effects of the addition of crystalline fructose and urea to an annual ryegrassbased diet on microbial protein synthesis, fermentation profile and nutrient apparent digestibility, using continuous culture fermenters. Six fermenters were used in a 3 x 2 factorial arrangement with three levels of water soluble carbohydrates (WSC) obtained by crystalline fructose addition (21, 24 and 27 g.100 g DM1; LWSC, MWSC and HWSC, respectively) and two levels of CP obtained by urea addition (14.6 and 18.6 g.100 g DM1, LCP and HCP, respectively). Four 10d periods were ran sequentially (7d for adaptation, 3d for sampling). Microbial protein synthesis was assessed by purine to N ratio. There was a positive interaction between WSC and CP level on microbial protein synthesis (P&lt;0.001). Water soluble carbohydrate level did not affect fermentation pH, ammonia concentration or total volatile fatty acids concentration (VFA). Greater CP levels also increased acetic acid proportion and tended to increase acetic to propionic acid ratio, whereas WSC level did not affect VFA proportions. Treatments did not affect nutrient digestibility. We conclude that the addition of crystalline fructose to annual ryegrass samples increased microbial protein synthesis at the greater levels of CP in diet

Heating and Trapping of Electrons in ECRIS from Scratch to Afterglow

Plasmas in Electron Cyclotron Resonance Ion Sources (ECRIS) are collisionless and can therefore be simulated by just following the motion of electrons in the confining static magnetic and oscillating microwave (MW) electric field of ECRIS. With a powerful algorithm the three-dimensional trajectories of 104 ECR-heated and confined electrons are calculated in a standard ECRIS with a deep minimum of |B| and a new ECRIS with a very flat minimum of |B|. The spatial electron (plasma) densities and electron energy densities deduced from these trajectories yield new and surprising insight in the performance of ECRIS. With computer animation we plan to present: The energy increase of certain electrons on extremely stable trajectories, the power dependence of the electron energy density up to the X-ray collapse, the time dependent build up of the electron density and energy density distributions, and the time evolution of these electron distributions under afterglow conditions

Use of anabolic implants in calves to increase weaning weight and backgrounding gains

The main component of the beef industry in South Carolina is cow/calf operations. Recent advances in implant technology are being utilized to help these producers increase weights at time of sale to feedlots. The objective of this study was to determine how the use of anabolic implants in steer calves at 4 mo of age and at weaning altered weight gain at two different farm locations in South Carolina. Steers ( year 1; n= 161, year 2 n=116) from Edisto REC and Simpson REC were randomly allotted into two treatment groups: 1) no implant or 2) implant at 4 mo of age plus implant at weaning. Weights were obtained at implanting, weaning, and the end of backgrounding. Real-time ultrasound measurements of the ribeye area and fat thickness were collected at the end of the backgrounding period. Data were analyzed with the treatment, location, year, and the interaction in the model. Implanting the steers increased (P\u3c0.001) average daily gains from implanting to weaning, weaning to the end of the backgrounding, and overall by 0.36, 0.15, 0.25 lb/hd/d respectively. Implanting also increased ribeye area by 0.34 in2. Weight and gains of the steers differed by location and year but there were no interactions between location, year, and implant treatment. The use of anabolic implants in steer calves at 4 mo of age and then again at weaning helped to increase weight gain, other desirable carcass traits and produced heavier steers for marketing

Use of anabolic implants in calves to increase weaning weight and backgrounding gains

The main component of the beef industry in South Carolina is cow/calf operations. Recent advances in implant technology are being utilized to help these producers increase weights at time of sale to feedlots. The objective of this study was to determine how the use of anabolic implants in steer calves at 4 mo of age and at weaning altered weight gain at two different farm locations in South Carolina. Steers ( year 1; n= 161, year 2 n=116) from Edisto REC and Simpson REC were randomly allotted into two treatment groups: 1) no implant or 2) implant at 4 mo of age plus implant at weaning. Weights were obtained at implanting, weaning, and the end of backgrounding. Real-time ultrasound measurements of the ribeye area and fat thickness were collected at the end of the backgrounding period. Data were analyzed with the treatment, location, year, and the interaction in the model. Implanting the steers increased (P\u3c0.001) average daily gains from implanting to weaning, weaning to the end of the backgrounding, and overall by 0.36, 0.15, 0.25 lb/hd/d respectively. Implanting also increased ribeye area by 0.34 in2. Weight and gains of the steers differed by location and year but there were no interactions between location, year, and implant treatment. The use of anabolic implants in steer calves at 4 mo of age and then again at weaning helped to increase weight gain, other desirable carcass traits and produced heavier steers for marketing