632 research outputs found

    Does Experience with Sagebrush In utero and Early in Life Influence the Use of Sagebrush by Sheep?

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    Learning from mother begins early in the developmental process and can have lifelong effects when it comes to forage preferences. Recent research suggests that mothers are a powerful and positive influence before birth. Pregnancy is not an incubation period buy a staging period for well-being and disease later in life. Better understanding the developmental processes which take place in utero and the effects they have later in life may help us create management plans that utilize grazing animals to their full potential as landscape manipulators. Using in utero and early-life programming as a management tool is a relatively new concept, but offers a faster approach than genetic selection to respond to environmental contingencies in the short-term. Experiences in utero and early in life may have marked effects on the ability of herbivores to consume toxin-containing plants such as sagebrush. This is because environmental experiences cause epigenetic alterations in consumers which are translated into neurological, morphological, and physiological changes that influence foraging behavior. This change in behavior can reduce the competitive ability of toxin-containing plants in the community and allow for greater primary production and diversity. However, information regarding herbivores\u27 exposure early in life to plant toxins and their subsequent physiological and behavioral responses is limited. Moreover, no information is available on early life experiences to toxin-containing shrubs like sagebrush and their subsequent influence on feeding behavior by herbivores. Thus, the objective of my research was to explore how experience in utero and early life with sagebrush affected intake of and preference for sagebrush by sheep later in life

    Guy's Hospital. Notes Respecting Mr. B. Cooper

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    Physical characterisation of southern massive star-forming regions using Parkes NH3_3 observations

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    We have undertaken a Parkes ammonia spectral line study, in the lowest two inversion transitions, of southern massive star formation regions, including young massive candidate protostars, with the aim of characterising the earliest stages of massive star formation. 138 sources from the submillimetre continuum emission studies of Hill et al., were found to have robust (1,1) detections, including two sources with two velocity components, and 102 in the (2,2) transition. We determine the ammonia line properties of the sources: linewidth, flux density, kinetic temperature, NH3_3 column density and opacity, and revisit our SED modelling procedure to derive the mass for 52 of the sources. By combining the continuum emission information with ammonia observations we substantially constrain the physical properties of the high-mass clumps. There is clear complementarity between ammonia and continuum observations for derivations of physical parameters. The MM-only class, identified in the continuum studies of Hill et al., display smaller sizes, mass and velocity dispersion and/or turbulence than star-forming clumps, suggesting a quiescent prestellar stage and/or the formation of less massive stars.Comment: 20 pages, 9 Figures, 1 appendix (to appear in full online only, a sample appendix in the paper); 7 tables. Accepted by MNRA

    First-Time Market Steer

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    The target audience for this fact sheet is 4-H youth who are thinking about or have recently purchased their first 4-H steer. This fact sheet is a simple outline that will give them more information on selection, feeding, housing, basic care, and grooming

    First-Time Market Hog

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    This fact sheet is for 4-H youth who are thinking about or have recently purchased their first 4-H hog. This fact sheet is a simple outline that will give them more information on selection, feeding, housing, basic care, and grooming

    The molecular environment of massive star forming cores associated with Class II methanol maser emission

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    Methanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7 GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.Comment: 5 pages, 1 figure, IAU Symposium 242 Conference Proceeding

    An uncertainty principle for star formation -- III. The characteristic emission time-scales of star formation rate tracers

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    We recently presented a new statistical method to constrain the physics of star formation and feedback on the cloud scale by reconstructing the underlying evolutionary timeline. However, by itself this new method only recovers the relative durations of different evolutionary phases. To enable observational applications, it therefore requires knowledge of an absolute 'reference time-scale' to convert relative time-scales into absolute values. The logical choice for this reference time-scale is the duration over which the star formation rate (SFR) tracer is visible because it can be characterised using stellar population synthesis (SPS) models. In this paper, we calibrate this reference time-scale using synthetic emission maps of several SFR tracers, generated by combining the output from a hydrodynamical disc galaxy simulation with the SPS model SLUG2. We apply our statistical method to obtain self-consistent measurements of each tracer's reference time-scale. These include Hα{\alpha} and 12 ultraviolet (UV) filters (from GALEX, Swift, and HST), which cover a wavelength range 150-350 nm. At solar metallicity, the measured reference time-scales of Hα{\alpha} are 4.32−0.23+0.09{4.32^{+0.09}_{-0.23}} Myr with continuum subtraction, and 6-16 Myr without, where the time-scale increases with filter width. For the UV filters we find 17-33 Myr, nearly monotonically increasing with wavelength. The characteristic time-scale decreases towards higher metallicities, as well as to lower star formation rate surface densities, owing to stellar initial mass function sampling effects. We provide fitting functions for the reference time-scale as a function of metallicity, filter width, or wavelength, to enable observational applications of our statistical method across a wide variety of galaxies.Comment: 24 pages, 18 figures, 7 tables (including Appendices); published in MNRA

    High Angular Resolution JHK Imaging of the Centers of the Metal-Poor Globular Clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92)

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    The Canada-France-Hawaii Telescope (CFHT) Adaptive Optics Bonnette (AOB) has been used to obtain high angular resolution JHK images of the centers of the metal-poor globular clusters NGC5272 (M3), NGC6205 (M13), NGC6287, and NGC6341 (M92). The color-magnitude diagrams (CMDs) derived from these data include the upper main sequence and most of the red giant branch (RGB), and the cluster sequences agree with published photometric measurements of bright stars in these clusters. The photometric accuracy is limited by PSF variations, which introduce systematic errors of a few hundredths of a magnitude near the AO reference star. The clusters are paired according to metallicity, and the near-infrared CMDs and luminosity functions are used to investigate the relative ages within each pair. The near-infrared CMDs provide the tightest constraints on the relative ages of the classical second parameter pair NGC5272 and NGC6205, and indicate that these clusters have ages that differ by no more than +/- 1 Gyr. These results thus support the notion that age is not the second parameter. We tentatively conclude that NGC6287 and NGC6341 have ages that differ by no more than +/- 2 Gyr. However, the near-infrared spectral energy distributions of stars in NGC6287 appear to differ from those of stars in outer halo clusters, bringing into question the validity of this age estimate.Comment: 22 pages, 17 figures. To be published in the Astronomical Journa
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