To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We have observed the G23 field of the Galaxy AndMass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase to validate the performance of the telescope and to characterise the detected galaxy populations. This observation covers ~48 deg2 with synthesised beam of 32.7 arcsec by 17.8 arcsec at 936MHz, and ~39 deg2 with synthesised beam of 15.8 arcsec by 12.0 arcsec at 1320MHz. At both frequencies, the root-mean-square (r.m.s.) noise is ~0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR versus radio luminosity relation, the ASKAP-detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical, and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for ~30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources aremore likely (~6%) to have an AGN than radio quiet galaxies (~1%), but the majority of AGN are not detected in radio at this sensitivity.
Introduction: Procedural skills training varies significantly across Canadian medical schools, and there is currently no standardized assessment tool to evaluate its benefits. This project aims to develop a curriculum that teaches 2nd-year medical students to perform and evaluate procedural skills. The goals of this program include decreasing anxiety, increasing confidence, and achieving competence for students and also allowing staff to judge the appropriate level of supervision when delegating learners to perform basic procedures in the team setting. Our curriculum incorporates, near-peer teaching as well as near peer formative assessment. Methods: Each of the twelve 2nd year participants completed a State Trait Anxiety Inventory and self-reported confidence questionnaire related to procedural skills. Students participated in four sessions taught by expert physicians over a five month period. A new skill was taught at each monthly workshop and an opportunity to practice previously taught skills was provided. Skills were assessed in a skills integration simulation OSCE, and the anxiety and confidence questionnaire was repeated. Results: Students who completed this pilot program showed a significant decrease in mean anxiety state (2.48 vs 1.74, p-value <0.001), while the control group did not (p-value = 0.408). When assessing confidence, students who completed this program showed increased self-assessed knowledge and confidence in each of the program's assessed skills. An increased level of competency was achieved in each skill by each student as assessed by the expert physicians. Conclusion: There is evidence to suggest that implementation of this procedural skills training model within the Canadian medical school curriculum may improve student anxiety, confidence, and competency for success in clerkship and could be the foundation for developing milestones for EPAs.
Introduction: In order to better characterize procedural skills curricula in Canada, a national survey was conducted. The objectives of the survey were: (i) to characterize procedural skills education currently employed in pre-clerkship and clerkship curricula; (ii) to determine what skills physician-educators think medical students should know upon graduation; and (iii) to identify physician-educator perceptions regarding the development of pre-clerkship procedural curriculum. Methods: A web-based survey was distributed to 201 clinician-educators across Canada's 17 medical schools. Respondents were directed to an individualized survey based on their self-identified roles at their institution. Respondents were asked demographic questions, what procedural skills are being taught and in what setting at their institution, and their opinions on the value of a pre-clerkship procedural curriculum. Results: From the 17 school's surveyed, 12 schools responded, with 8 schools responding “yes” that they had a clerkship procedural curriculum. For a pre-clerkship procedural curriculum, only 4 schools responded “yes”. The 5 of the top 10 procedurals skills identified that medical students should know upon graduation, in order, are: IV Access, Airway Management/Ventilator Management, Local anesthesia/field block, Casting, Spontaneous Vaginal Delivery. On a Likert scale, clinician-educators strongly supported a pre-clerkship procedural curriculum (median = 4.00/5.00, mode = 5.00/5.00), and they believed it would decrease anxiety (median = 4.00/5.00), increase confidence (median = 4.00/5.00), and increase technical ability (median = 3.00/5.00) in incoming clerks. Conclusion: Across Canada, the state of undergraduate medical education procedural skills education is inconsistent. With the identification of the Top 10 procedural skills medical students should know upon graduation, the learning objectives of a formal curriculum can be developed. With overwhelming support from physician-educators, a formal pre-clerkship procedural curriculum is poised to redefine the landscape of procedural care for a whole new generation of physicians.
The Commensal Real-time Australian Square Kilometre Array Pathfinder Fast Transients survey is the first extensive astronomical survey using phased array feeds. Since January 2017, it has been searching for fast radio bursts in fly’s eye mode. Here, we present a calculation of the sensitivity and total exposure of the survey that detected the first 20 of these bursts, using the pulsars B1641-45 and B0833-45 as calibrators. The beamshape, antenna-dependent system noise, and the effects of radio-frequency interference and fluctuations during commissioning are quantified. Effective survey exposures and sensitivities are calculated as a function of the source counts distribution. Statistical ‘stat’ and systematics ‘sys’ effects are treated separately. The implied fast radio burst rate is significantly lower than the 37 sky−1 day−1 calculated using nominal exposures and sensitivities for this same sample by Shannon et al. (2018). At the Euclidean (best-fit) power-law index of −1.5 (−2.2), the rate is
(sys) ± 3.6 (stat) sky−1 day−1 (
(sys) ± 2.8 (stat) sky−1 day−1) above a threshold of 56.6 ± 6.6(sys) Jy ms (40.4 ± 1.2(sys) Jy ms). This strongly suggests that these calculations be performed for other FRB-hunting experiments, allowing meaningful comparisons to be made between them.
be a semisimple Lie group with associated symmetric space
, and let
be a cocompact arithmetic group. Let
be a lattice inside a
-module arising from a rational finite-dimensional complex representation of
. Bergeron and Venkatesh recently gave a precise conjecture about the growth of the order of the torsion subgroup
ranges over a tower of congruence subgroups of
. In particular, they conjectured that the ratio
should tend to a nonzero limit if and only if
is a group of deficiency
. Furthermore, they gave a precise expression for the limit. In this paper, we investigate computationally the cohomology of several (non-cocompact) arithmetic groups, including
for various rings of integers, and observe its growth as a function of level. In all cases where our dataset is sufficiently large, we observe excellent agreement with the same limit as in the predictions of Bergeron–Venkatesh. Our data also prompts us to make two new conjectures on the growth of torsion not covered by the Bergeron–Venkatesh conjecture.
Six snow-pit records recovered from Siple Dome, West Antarctica, during 1994 are used to study seasonal variations in chemical (major ion and H202), isotopic (deuterium) and physical stratigraphic properties during the 1988-94 period. Comparison of δD measurements and satellite-derived brightness temperature for the Siple Dome area suggests that most seasonal SD maxima occur within ±4 weeks of each 1 January. Several other chemical species (H2O2, non-sea-salt (nss) SO42-, methanesulfonic acid and NO3-) show coeval peaks with SD, together providing an accurate method for identifying summer accumulation. Sea-salt-derived species generally peak during winter/spring, but episodic input is noted throughout some years. No reliable seasonal signal is identified in species with continental sources (nssCa2+ nss Mg2+), NH4+ or nssCl-. Visible strata such as large depth-hoar layers (>5 cm) are associated with summer accumulation and its metamorphosis, but smaller hoar layers and crusts are more difficult to interpret. A multi-parameter approach is found to provide the most accurate dating of these snow-pit records, and is used to determine annual layer thicknesses at each site Significant spatial accumulation variability exists on an annual basis, but mean accumulation in the sampled 10 km2 grid for the 1988-94 period is fairly uniform.
This study tests novel methods for automatically identifying annual layers in a shallow Antarctic ice core (WDC05Q) using images that were collected with an optical scanner at the US National Ice Core Laboratory. A new method of optimized variance maximization (OVM) modeled the density-related changes in annual layer thickness directly from image variance. This was done by using multi-objective complex (MOCOM) parameter optimization to drive a low-pass filtering scheme. The OVM-derived changes in annual layer thickness corresponded well with the results of an independent glaciochemical interpretation of the core. Individual annual cycles in image brightness were then identified by using OVM results to apply a depth-varying low-pass filter and fitting a second-order polynomial to a locally detrended neighborhood. The resulting map of annual cycles agreed to within 1% of the overall annual count of the glaciochemical interpretation. Agreement on the presence of specific annual layer features was 96%. It was also shown that the MOCOM parameter optimization could calibrate the image-based results to match directly the date of a specific volcanic marker.
We have determined accumulation histories by identifying annual-layer horizons in records obtained by three independent methods: (1) glaciochemical analysis on a core, (2) density profiling in the borehole from which the core was taken, using the neutron-probe (NP) technique, and (3) borehole optical stratigraphy (BOS), again in the same borehole. We also used three different techniques for determining density to convert annual-layer thickness to accumulation: (1) gravimetric measurements on core samples, (2) measurement of density using NP and (3) a simple empirical model based on regional climatology. The result is nine different accumulation time series, three of which are completely independent. The chemical-analysis- and NP-derived accumulation time series are correlated, and the ∼70 year means are in agreement. The BOS-derived accumulation ∼70 year mean is slightly lower, probably due to a combination of the empirical density model’s underestimate of the density profile and the misidentification of sub-annual events in the shallow part of the borehole as annual horizons.
The WAIS (West Antarctic Ice Sheet) Divide deep ice core was recently completed to a total depth of 3405 m, ending 50 m above the bed. Investigation of the visual stratigraphy and grain characteristics indicates that the ice column at the drilling location is undisturbed by any large-scale overturning or discontinuity. The climate record developed from this core is therefore likely to be continuous and robust. Measured grain-growth rates, recrystallization characteristics, and grain-size response at climate transitions fit within current understanding. Significant impurity control on grain size is indicated from correlation analysis between impurity loading and grain size. Bubble-number densities and bubble sizes and shapes are presented through the full extent of the bubbly ice. Where bubble elongation is observed, the direction of elongation is preferentially parallel to the trace of the basal (0001) plane. Preferred crystallographic orientation of grains is present in the shallowest samples measured, and increases with depth, progressing to a vertical-girdle pattern that tightens to a vertical single-maximum fabric. This single-maximum fabric switches into multiple maxima as the grain size increases rapidly in the deepest, warmest ice. A strong dependence of the fabric on the impurity-mediated grain size is apparent in the deepest samples.
Introduction: Paramedics in our region do not perform 15-lead ECGs. As a result, patients experiencing a Right Ventricular Infarct (RVI) may receive nitroglycerin (NTG). In many cases, paramedics do not administer NTG to those with inferior STEMI out of concern that there may be an associated RVI. The purpose of this study is to determine if there is a difference in prehospital adverse events (AEs) associated with NTG administration in patients with unrecognized RVIs compared to those with an inferior STEMI and no RVI. Methods: Ambulance Call Records (ACR) of patients with prehospital STEMI between Jan 1, 2012 and Dec 31, 2015 were analyzed for the incidence of NTG administration. AEs were defined as HR<60 bpm, systolic BP <100 mmHg or drop of 1/3, GCS decrease of >2, syncope, arrest or death. Hospital records were reviewed to determine patients diagnosed with an inferior STEMI without RVI and those with a concurrent or primary RVI as diagnosed on angiography, ECG or discharge diagnosis. Results: Of the 334 ACRs that were filtered and manually reviewed, 144 were excluded (not STEMI, inter-facility transports, duplicate ACR) resulting in 189 patients that had a prehospital STEMI. The mean (SD) age was 66.9 (13.5) years and 70.6% were male. Of 189 STEMI patients, 82 (42.9%) received NTG. Nineteen (41.3%) of these patients were subsequently diagnosed with RVI and 27 (58.7%) had inferior STEMI without RVI. For patients receiving NTG, AEs occurred in 11 (57.9%) within the RVI group, and 10 (37.0%) within the inferior STEMI group (Δ 20.9%, 95% CI -7.8% to 45.4%, p=0.2). Cardiac arrest or death did not occur in either group. A total of 107 did not receive NTG and of these, 93 (86.9%) did not meet conditions or had contraindications for NTG use (22 RVI, 42 inferior STEMI). Three patients had a cardiac arrest and one died while in EMS care, none of which received NTG or had RVIs. Conclusion: Results of this study suggest no difference in the rate of AEs between patients with inferior STEMI and STEMI with RVI when NTG is administered in the prehospital setting. In our EMS system, the conditions and contraindications of NTG administration may be protective against AEs in RVIs, so the potential benefit of a prehospital 15-lead ECG may be limited.
We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope.
From June 15 to 28, 1991 the Compton Gamma-Ray Observatory (CGRO) observed the radio-loud quasar 3C 273. All four CGRO instruments detected radiation from this quasar in their relevant energy range (from 20 keV to 5 GeV). Simultaneous and quasi-simultaneous observations (spanning the time period May 27 – July 25, 1991) by instruments sensitive at other wavelengths have also been obtained. The data from all these observations spanning the frequency range from ∼ 109 Hz to ∼ 1026 Hz were collected and analysed. The resulting energy-density spectrum is shown in the figure below. It shows two maxima, one in the UV, another one at low-energy γ-rays which have nearly the same strength (the corresponding luminosities per decade of frequency for H0 = 60(km/s)/Mpc are 3.2·1046 erg/s and 2.7·1046 erg/s, respectively). A break of the spectrum at low-energy γ-rays is evident. From a detailed analysis a break energy of (2±1.5) MeV could be derived corresponding to a frequency of (4.8±3.6)·1020 Hz. The observed spectral break between X- and γ-rays is ∼ 0.8, much higher than the value of 0.5 predicted by some models. A more detailed paper on this topic is in preparation (Lichti et al.).
We present the results of an HI aperture synthesis mosaic of the Large Magellanic Cloud (LMC), made by combining data from 1344 separate pointing centers using the Australia Telescope Compact Array (ATCA). The resolution of the mosaiced image is 1′ (15 pc, using a distance to the LMC of 50 kpc).
The recently completed HI mosaic survey of the Large Magellanic Cloud (Kim et al. 1997) reveals complex structure in the interstellar medium, including filaments, arcs, holes and shells. We have catalogued giant and supergiant HI shells and searched for correlations with Hα emission, using a new image taken with a camera lens mounted on the 16-inch telescope at Siding Spring Observatory.
Direct solar flare neutrons are a valuable diagnostic of high-energy ion acceleration in these events, and COMPTEL improves over all previous cosmic neutron detectors in its capacity for neutron energy measurement. Previous studies of COMPTEL neutron data have worked with an incomplete model of the instrumental response, applying energy-by-energy detection efficiencies. Here we employ statistical regularisation techniques with the full (Monte Carlo simulation derived) response matrix to produce improved estimates of neutron numbers and energy distribution. These techniques are applied to data from the well-observed 15 June 1991 flare. Our improved treatment of the instrumental response results in a reduction of 73% in total neutron numbers, compared with previously deduced values. Implications for the picture of primary ion acceleration in this flare are briefly discussed.
During 1990 we surveyed the southern sky using a multi-beam receiver at frequencies of 4850 and 843 MHz. The half-power beamwidths were 4 and 25 arcmin respectively. The finished surveys cover the declination range between +10 and −90 degrees declination, essentially complete in right ascension, an area of 7.30 steradians. Preliminary analysis of the 4850 MHz data indicates that we will achieve a five sigma flux density limit of about 30 mJy. We estimate that we will find between 80 000 and 90 000 new sources above this limit. This is a revised version of the paper presented at the Regional Meeting by the first four authors; the surveys now have been completed.
This paper describes the first results from a 20 deg2 mosaic of the Small Magellanic Cloud (SMC) in the λ21-cm line of neutral hydrogen. The mosaic consists of 320 separate pointings with the 375-m array of the Australia Telescope Compact Array. The angular resolution is 1′· 5 (26 pc, for a distance of 60 kpc) and the velocity resolution is l·6kms−1. The images reveal a structure of remarkable complexity, with much of the spatial power contained in high-brightness temperature compact knots and filaments. Numerous wind-blown ‘bubbles’ and ‘supershells’ are evident in the data, both inside and outside the stellar confines of the SMC. Some high-density H I regions are seen to correlate with Hα regions, indicating sites of current star formation. However, many high-column-density H I regions are devoid of optical emission and may represent regions of future star formation. These regions may be under-abundant in diffuse molecular gas due to the high radiation field and low metallicity of the SMC.
We present the result of an HI aperture synthesis mosaic of the Large Magellanic cloud (LMC), made recently with the Australia Telescope Compact Array (ATCA). The resolution of the mosaiced images is l′.0 (15 pc, using a distance to the LMC of 50 kpc). In contrast to its appearance at other wavelengths, the LMC is remarkably symmetrical in HI on the largest scales, with the bulk of the HI residing in a disk of diameter 8.°4 (7.3 kpc). Outer spiral structure is clearly seen, though the features appear to be due to differential rotation, therefore transient in nature. On small to medium scales, the combined action of numerous shells and supershells dominate the structures and motions of the HI gas in the LMC. A good correlation is seen between supershells previously identified in Hα (e.g. Meaburn 1980) and HI structures. We compare the results with a new wide-field Hα image.
We discuss the stellar halos of massive elliptical galaxies, as revealed by our ambitious integral-field spectroscopic survey MASSIVE. We show that metallicity drops smoothly as a function of radius out to ~ 2.5 Re, while the [α/Fe] abundance ratios stay flat. The stars in the outskirts likely formed rapidly (to explain the high ratio of alpha to Fe) but in a relatively shallow potential (to explain the low metallicities). This is consistent with expectations for a two-phase growth of massive galaxies, in which the second phase involves accretion of small satellites. We also show some preliminary study of the gas content of these most MASSIVE galaxies.
Chorion type may significantly influence the prenatal environment of twins. This study explored the associations between chorion type and gestational age, birth weight, birth length, and the timing of emergence of the first primary tooth in two populations of twins, Australian and Dutch. Additionally, we investigated the relationship between chorion type and birth weight discordance (BWD) in order to determine whether a significant relationship existed between discordance in birth weight and discordance in the timing of emergence of the first primary tooth. The two study samples consisted of 409 Australian twin pairs and 301 Dutch twin pairs, all of European ancestry. Data were collected through a combination of questionnaires and recording charts administered to the parents and through linkage with biological databases. In the Australian sample, monozygotic monochorionic (MZMC) twins experienced the shortest mean gestation time (35 weeks), the lowest mean birth length (46 cm) and the lowest mean birth weight (2.3 kg) compared with other twin groups. For the same variables in the Dutch sample, these trends with MZMC twinning were not observed. Chorion type did not significantly affect the mean timing of emergence of the first primary tooth in either sample. Monochorionicity was found to be significantly associated with BWD in both samples, but there was a significant association between BWD in MZMC twin pairs and timing of emergence of the first primary tooth only in the Australian sample. Results from this study support previous findings that the timing of emergence of the first primary tooth is influenced strongly by genetic factors and is well protected from environmental disturbances.