256 research outputs found
Access Denied? Exploring the Causes of the Low Representation of Women in Senior Executive Positions within Procurement
What's Needed to Develop Strategic Purchasing in Healthcare?:Policy Lessons from a Realist Review
SIMULTANEOUS OBSERVATIONS OF GIANT PULSES FROM THE CRAB PULSAR, WITH THE MURCHISON WIDEFIELD ARRAY AND PARKES RADIO TELESCOPE: IMPLICATIONS FOR THE GIANT PULSE EMISSION MECHANISM
We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes, and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5σ and 6.5σ, respectively. We detected 51% of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of -3.6 > α > -4.9 (S[subscript v] ∝ v[superscript α]). We present a Monte Carlo analysis supporting the conjecture that the giant pulse emission in the Crab is intrinsically broadband, the less than 100% correlation being due to the relative sensitivities of the two instruments and the width of the spectral index distribution. Our observations are consistent with the hypothesis that the spectral index of giant pulses is drawn from normal distribution of standard deviation 0.6, but with a mean that displays an evolution with frequency from −3.00 at 1382 MHz, to −2.85 at 192 MHz
Beyond intentional trust:supplier opportunism and management control mechanisms in public sector procurement and contracting
Standoff detection of bacterial spores by field deployable coherent Raman spectroscopy
: Vibrational spectroscopies offer great potential for standoff detection of chemical and biological warfare agents, avoiding contamination to the operator and equipment. Among them, particularly promising is Coherent anti-Stokes Raman scattering (CARS) spectroscopy, using synchronized pump/Stokes laser pulses to set up a vibrational coherence of target molecules at a laser focus, which is read by further interaction with a probe pulse, resulting in the emission of a coherent beam detectable at a distance. CARS has previously demonstrated the capability to detect bacterial spores based on the Raman spectrum of the characteristic molecule calcium dipicolinate (CaDPA); however, a complex and bulky laser technology, which is only suitable for a laboratory environment, was employed. Here we develop a broadband CARS setup based on a compact, industrial grade ytterbium laser system. We demonstrate high signal-to-noise ratio detection of Bacillus atrophaeus spores at a concentration of 105 cfu/mm2, at a standoff distance of 1 m, and an acquisition time of 1 s. Our system, which combines chemical specificity and sensitivity along with improved ruggedness and portability, paves the way to a new generation of instruments for real-world standoff detection of chemical and biological threats
A trial-based economic evaluation of 2 nurse-led disease management programs in heart failure
Clinical practice guidelines for the treatment of low back pain suggest the inclusion of a biopsychosocial approach in which patient self-management is prioritized. While many physiotherapists recognise the importance of evidence-based practice, there is an evidence practice gap that may in part be due to the fact that promoting self-management necessitates change in clinical behaviours. Evidence suggests that a patient’s motivation and maintenance of self-management behaviours can be positively influenced by the clinician’s use of an autonomy supportive communication style. Therefore, the aim of this study was to develop and pilot-test the feasibility of a theoretically derived implementation intervention to support physiotherapists in using an evidence-based autonomy supportive communication style in practice for promoting patient self-management in clinical practice
VLBA Observations of Sub-Parsec Structure in Mrk 231: Interaction between a Relativistic Jet and a BAL Wind
We report on the first high frequency VLBI observations of the nearby broad
absorption line quasar (BALQSO), Mrk 231. Three epochs of observations were
achieved at 15 GHz and 22 GHz, two of these included 43 GHz observations as
well. The nuclear radio source is resolved as a compact double. The core
component experienced a strong flare in which the flux density at 22 GHz
increased by (45 mJy) in three months. Theoretical models of the flare
imply that the emission is likely enhanced by very strong Doppler boosting of a
highly relativistic ejecta with a kinetic energy flux, . Combining our data with two previous epochs of 15 GHz data,
shows marginal evidence for the slow advance of the secondary component
(located pc from the core) over a 9.4 year span. We estimate
that the long term time averaged kinetic energy flux of the secondary at
. Low frequency VLBA observations
indicate that the secondary is seen through a shroud of free-free absorbing gas
with an emission measure of . The
steep spectrum secondary component appears to be a compact radio lobe that is
associated with a working surface between the ram-pressure confined jet, and a
dense medium that is likely to be the source of the free-free absorption. The
properties of the dense gas are consistent with the temperatures, displacement
from the nucleus and the column density of total hydrogen commonly associated
with the BAL wind.Comment: To appear in Ap
High Sensitivity Array Observations of the z=1.87 Sub-Millimeter Galaxy GOODS 850-3
We present sensitive phase-referenced VLBI results on the radio continuum
emission from the z=1.87 luminous submillimeter galaxy (SMG) GOODS 850-3. The
observations were carried out at 1.4 GHz using the High Sensitivity Array
(HSA). Our sensitive tapered VLBI image of GOODS 850-3 at 0.47 x 0.34 arcsec
(3.9 x 2.9 kpc) resolution shows a marginally resolved continuum structure with
a peak flux density of 148 \pm 38 uJy/beam, and a total flux density of 168 \pm
73 uJy, consistent with previous VLA and MERLIN measurements. The derived
intrinsic brightness temperature is > 5 \pm 2 x 10^3 K. The radio continuum
position of this galaxy coincides with a bright and extended near-infrared
source that nearly disappears in the deep HST optical image, indicating a dusty
source of nearly 9 kpc in diameter. No continuum emission is detected at the
full VLBI resolution (13.2 x 7.2 mas, 111 x 61 pc), with a 4-sigma point source
upper limit of 26 uJy/beam, or an upper limit to the intrinsic brightness
temperature of 4.7 x 10^5 K. The extent of the observed continuum source at 1.4
GHz and the derived brightness temperature limits are consistent with the radio
emission (and thus presumably the far-infrared emission) being powered by a
major starburst in GOODS 850-3, with a star formation rate of ~2500 M_sun/yr.
Moreover, the absence of any continuum emission at the full resolution of the
VLBI observations indicates the lack of a compact radio AGN source in this
z=1.87 SMG.Comment: 19 pages, 4 figures, accepted for publication in A
IR and UV Galaxies at z=0.6 -- Evolution of Dust Attenuation and Stellar Mass as Revealed by SWIRE and GALEX
We study dust attenuation and stellar mass of star-forming
galaxies using new SWIRE observations in IR and GALEX observations in UV. Two
samples are selected from the SWIRE and GALEX source catalogs in the
SWIRE/GALEX field ELAIS-N1-00 ( deg). The UV selected sample
has 600 galaxies with photometric redshift (hereafter photo-z) and NUV (corresponding to \rm L_{FUV} \geq 10^{9.6} L_\sun).
The IR selected sample contains 430 galaxies with mJy
(\rm L_{dust} \geq 10^{10.8} L_\sun) in the same photo-z range. It is found
that the mean ratios of the z=0.6 UV galaxies are
consistent with that of their z=0 counterparts of the same . For
IR galaxies, the mean ratios of the z=0.6 LIRGs (\rm
L_{dust} \sim 10^{11} L_\sun) are about a factor of 2 lower than local LIRGs,
whereas z=0.6 ULIRGs (\rm L_{dust} \sim 10^{12} L_\sun) have the same mean
ratios as their local counterparts. This is consistent
with the hypothesis that the dominant component of LIRG population has changed
from large, gas rich spirals at z to major-mergers at z=0. The stellar
mass of z=0.6 UV galaxies of \rm L_{FUV} \leq 10^{10.2} L_\sun is about a
factor 2 less than their local counterparts of the same luminosity, indicating
growth of these galaxies. The mass of z=0.6 UV lunmous galaxies (UVLGs: \rm
L_{FUV} > 10^{10.2} L_\sun) and IR selected galaxies, which are nearly
exclusively LIRGs and ULIRGs, is the same as their local counterparts.Comment: 27 pages, 8 figures, to be published in the Astrophysical Journal
Supplement series dedicated to GALEX result
Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array
Recent observations with the Murchison Widefield Array at 185 MHz have serendipitously unveiled a heretofore unknown giant and relatively nearby (z = 0.0178) radio galaxy associated with NGC 1534. The diffuse emission presented here is the first indication that NGC 1534 is one of a rare class of objects (along with NGC 5128 and NGC 612) in which a galaxy with a prominent dust lane hosts radio emission on scales of ∼700 kpc. We present details of the radio emission along with a detailed comparison with other radio galaxies with discs. NGC 1534 is the lowest surface brightness radio galaxy known with an estimated scaled 1.4-GHz surface brightness of just 0.2 mJy arcmin[superscript −2]. The radio lobes have one of the steepest spectral indices yet observed: α = −2.1 ± 0.1, and the core to lobe luminosity ratio is <0.1 per cent. We estimate the space density of this low brightness (dying) phase of radio galaxy evolution as 7 × 10[superscript −7] Mpc[superscript −3] and argue that normal AGN cannot spend more than 6 per cent of their lifetime in this phase if they all go through the same cycle
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