112 research outputs found
The kinetic temperature of Barnard 68
We have observed the nearby isolated globule Barnard 68 (B68) in the
(J,K)=(1,1) and (2,2) inversion lines of ammonia. The gas kinetic temperature
derived from these is T=10+-1.2 K. The observed line-widths are almost thermal:
DV=0.181+-0.003 km/s (DVtherm=0.164+-0.010 km/s), supporting the earlier
hypothesis that B68 is in hydrostatic equilibrium. The kinetic temperature is
an input parameter to the physical cloud model put forward recently, and we
discuss the impact of the new value in this context.Comment: 4 pages, 2 figures, accepted for publication in A&A (Letters
Evolution of interdisciplinarity in biodiversity science
The study of biodiversity has grown exponentially in the last thirty years in response to demands for greater understanding of the function and importance of Earth's biodiversity and finding solutions to conserve it. Here, we test the hypothesis that biodiversity science has become more interdisciplinary over time. To do so, we analyze 97,945 peerâreviewed articles over a twentyâtwoâyear time period (1990â2012) with a continuous time dynamic model, which classifies articles into concepts (i.e., topics and ideas) based on word coâoccurrences. Using the model output, we then quantify different aspects of interdisciplinarity: concept diversity, that is, the diversity of topics and ideas across subdisciplines in biodiversity science, subdiscipline diversity, that is, the diversity of subdisciplines across concepts, and network structure, which captures interactions between concepts and subdisciplines. We found that, on average, concept and subdiscipline diversity in biodiversity science were either stable or declining, patterns which were driven by the persistence of rare concepts and subdisciplines and a decline in the diversity of common concepts and subdisciplines, respectively. Moreover, our results provide evidence that conceptual homogenization, that is, decreases in temporal ÎČ concept diversity, underlies the observed trends in interdisciplinarity. Together, our results reveal that biodiversity science is undergoing a dynamic phase as a scientific discipline that is consolidating around a core set of concepts. Our results suggest that progress toward addressing the biodiversity crisis via greater interdisciplinarity during the study period may have been slowed by extrinsic factors, such as the failure to invest in research spanning across concepts and disciplines. However, recent initiatives such as the Intergovernmental ScienceâPolicy Platform on Biodiversity and Ecosystem Services (IPBES) may attract broader support for biodiversityârelated issues and hence interdisciplinary approaches to address scientific, political, and societal challenges in the coming years
Meat consumersâ opinion regarding unhealthy pigs: should they be treated with antibiotics or euthanized on farm?
The aim of this study was to investigate the opinions of meat consumers (n = 1780) on on-farm management of unhealthy pigs, whether support for treatment with antibiotics varies according with chance of recovery, and the effect of knowledge on the use of antibiotics on these opinions. Most participants believed that the use of antibiotics was the best solution for unhealthy pigs, and this was associated with a low level of knowledge about antibiotics. Increasing the probability of recovery after treatment increased support for treating pigs with antibiotics. However, the majority of participants rejected the consumption of meat from animals housed in âhospital pensâ. After price, concern with food safety was the second main factor that influenced participantsâ choice when buying meat. Support for the use of antibiotics to deal with unhealthy pigs in âhospital pensâ, as well as for consumption of the meat from these animals, was higher among participants involved in agriculture. This shows that consumers are unaware of the potential negative repercussions for animal welfare associated with banning or reducing the use of antibiotics in livestock production, which is an important concern for the industr
Dust emissivity in the Submm/Mm: SCUBA and SIMBA observations of Barnard 68
We have observed the dark cloud Barnard 68 with SCUBA at 850 um and with
SIMBA at 1.2 mm. The submillimetre and millimetre dust emission correlate well
with the extinction map of Alves, Lada and Lada (2001).The A_V/850um
correlation is clearly not linear and suggests lower temperatures for the dust
in the inner core of the cloud. Assuming a model for the temperature gradient,
we derive the cloud-averaged dust emissivities (normalised to the V-Band
extinction efficiency) at 850 um and 1.2 mm. We find k_850um/k_V = 4.0 +/- 1.0
x 10^-5 and k_1.2mm/k_V = 9.0 +/- 3.0 x 10^-6. These values are compared with
other determinations in this wavelength regime and with expectations for models
of diffuse dust and grain growth in dense clouds.Comment: 8 pages, 4 figures, A&A accepted (Letter), referee forma
The NH2D/NH3 ratio toward pre-protostellar cores around the UCHII region in IRAS 20293+3952
The deuterium fractionation, Dfrac, has been proposed as an evolutionary
indicator in pre-protostellar and protostellar cores of low-mass star-forming
regions. We investigate Dfrac, with high angular resolution, in the cluster
environment surrounding the UCHII region IRAS 20293+3952. We performed high
angular resolution observations with the IRAM Plateau de Bure Interferometer
(PdBI) of the ortho-NH2D 1_{11}-1_{01} line at 85.926 GHz and compared them
with previously reported VLA NH3 data. We detected strong NH2D emission toward
the pre-protostellar cores identified in NH3 and dust emission, all located in
the vicinity of the UCHII region IRAS 20293+3952. We found high values of
Dfrac~0.1-0.8 in all the pre-protostellar cores and low values, Dfrac<0.1,
associated with young stellar objects. The high values of Dfrac in
pre-protostellar cores could be indicative of evolution, although outflow
interactions and UV radiation could also play a role.Comment: 5 pages, 3 figures. Accepted for publication in Astronomy and
Astrophysics Letter
ISOPHOT far-infrared serendipity sky survey
The ISOPHOT Serendipity Survey utilizes the slew time between ISO's pointed observations with strip scanning measurements of the sky in the far-IR at 170 micrometers . The slews contain information about two fundamentally different types of objects, namely unresolved galactic and extragalactic far-IR sources as well as extended regions of galactic cirrus emission. Since the structure of the obtained data is almost unique, the development of dedicated software to extract astrophysically interesting parameters for the crossed sources is mandatory. Data analysis is currently in its early stages and concentrates on the detection of point sources. First results from an investigation of a high galactic latitude field near the North Galactic Pole indicate that the detection completeness with respect to previously known IRAS sources will be almost 100 percent for sources with f(subscript 100micrometers > 2 Jy, dropping below approximately equals 50 percent for f(subscript 100micrometers < 1.5 Jy. Nevertheless, even faint sources down to a level of f(subscript 170micrometers approximately equals 1 Jy can be detected. Since the majority of the detected point sources are galaxies, the Serendipity Survey will result in a large database of approximately equals 2000 galaxies
Reliability of NH3 as the temperature probe of cold cloud cores
The temperature is a central parameter affecting the chemical and physical
properties of dense cores of interstellar clouds and their evolution to star
formation. The chemistry and the dust properties are temperature dependent and
the interpretation of observation requires the knowledge of the temperature and
its variations. Measurement of the gas kinetic temperature is possible with
molecular line spectroscopy, the ammonia molecule, NH3, being the most commonly
used tracer. We want to determine the accuracy of the temperature estimates
derived from ammonia spectra. The normal interpretation of NH3 observations
assumes that all the hyperfine line components are tracing the same gas volume.
In the case of temperature gradients they may be sensitive to different layers
and cause errors in the optical depth and gas temperature estimates. We examine
a series of spherical cloud models, 1.0 and 0.5 M_Sun Bonnor-Ebert spheres,
with different radial temperature profiles. We calculate synthetic NH3 spectra
and compare the derived column densities and temperatures to the true values.
For high signal-to-noise observations, the estimated gas kinetic temperatures
are within ~0.3 K of the real mass averaged temperature and the column
densities are correct to within ~10%. When the S/N ratio of the (2,2) spectrum
decreases below 10, the temperature errors are of the order of 1K but without a
significant bias. When the density of the models is increased by a factor of a
few, the results begin to show significant bias because of the saturation of
the (1,1) main group. The ammonia spectra are found to be a reliable tracer of
the mass averaged gas temperature. Because the radial temperature profiles of
the cores are not well constrained, the central temperature could still differ
from this value. If the cores are optically very thick, there are no guarantees
of the accuracy.Comment: 7 pages, accepted to A&
Physical properties of dense cores in Orion B9
We aim to determine the physical and chemical properties of dense cores in
Orion B9. We observed the NH3(1,1) and (2,2), and the N2H+(3-2) lines towards
the submm peak positions. These data are used in conjunction with our LABOCA
870 micron dust continuum data. The gas kinetic temperature in the cores is
between ~9.4-13.9 K. The non-thermal velocity dispersion is subsonic in most of
the cores. The non-thermal linewidth in protostellar cores appears to increase
with increasing bolometric luminosity. The core masses are very likely drawn
from the same parent distribution as the core masses in Orion B North. Starless
cores in the region are likely to be gravitationally bound, and thus
prestellar. Some of the cores have a lower radial velocity than the systemic
velocity of the region, suggesting that they are members of the "low-velocity
part" of Orion B. The observed core-separation distances deviate from the
corresponding random-like model distributions. The distances between the
nearest-neighbours are comparable to the thermal Jeans length. The fractional
abundances of NH3 and N2H+ in the cores are ~1.5-9.8x10^{-8} and
~0.2-5.9x10^{-10}, respectively. The NH3 abundance appears to decrease with
increasing H2 column and number densities. The NH3/N2H+ column density ratio is
larger in starless cores than in cores with embedded protostars. The core
population in Orion B9 is comparable in physical properties to those in nearby
low-mass star-forming regions. It is unclear if the origin of cores could be
explained by turbulent fragmentation. On the other hand, many of the core
properties conform with the picture of dynamic core evolution. The Orion B9
region has probably been influenced by the feedback from the nearby Ori OB 1b
group, and the fragmentation of the parental cloud into cores could be caused
by gravitational instability.Comment: 17 pages, 11 figures, 7 tables. Accepted for publication in Astronomy
and Astrophysics. Version 2: minor language corrections adde
Effect of floor type on the performance, physiological and behavioural responses of finishing beef steers
peer-reviewedBackground:The study objective was to investigate the effect of bare concrete slats (Control), two types of mats [(Easyfix mats (mat 1) and Irish Custom Extruder mats (mat 2)] fitted on top of concrete slats, and wood-chip to simulate deep bedding (wood-chip placed on top of a plastic membrane overlying the concrete slats) on performance, physiological and behavioral responses of finishing beef steers. One-hundred and forty-four finishing steers (503Â kg; standard deviation 51.8Â kg) were randomly assigned according to their breed (124 Continental cross and 20 HolsteinâFriesian) and body weight to one of four treatments for 148Â days. All steers were subjected to the same weighing, blood sampling (jugular venipuncture), dirt and hoof scoring pre study (day 0) and on days 23, 45, 65, 86, 107, 128 and 148 of the study. Cameras were fitted over each pen for 72Â h recording over five periods and subsequent 10Â min sampling scans were analysed.
Results: Live weight gain and carcass characteristics were similar among treatments. The number of lesions on the hooves of the animals was greater (PÂ <Â 0.05) on mats 1 and 2 and wood-chip treatments compared with the animals on the slats. Dirt scores were similar for the mat and slat treatments while the wood-chip treatment had greater dirt scores. Animals housed on either slats or wood-chip had similar lying times. The percent of animals lying was greater for animals housed on mat 1 and mat 2 compared with those housed on concrete slats and wood chips. Physiological variables showed no significant difference among treatments.
Conclusions:
In this exploratory study, the performance or welfare of steers was not adversely affected by slats, differing mat types or wood-chip as underfoot material
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