138,335 research outputs found
Retrospective study of more than 9000 feline cutaneous tumours in the UK: 2006–2013
The aim of the study was to utilise a large database available from a UK-based, commercial veterinary diagnostic laboratory to ascertain the prevalence of different forms of cutaneous neoplasia within the feline population, and to detect any breed, sex or age predilections for the more common tumours
Nuclear radiation analysis
A study program of radiation shielding against the deleterious effects of nuclear radiation on man and equipment is reported. The methods used to analyze the radiation environment from bremsstrahlung photons are discussed along with the methods employed by transport code users. The theory and numerical methods used to solve transport of neutrons and gammas are described, and the neutron and cosmic fluxes that would be present on the gamma-ray telescope were analyzed
Activities of \gamma-ray emitting isotopes in rainwater from Greater Sudbury, Canada following the Fukushima incident
We report the activity measured in rainwater samples collected in the Greater
Sudbury area of eastern Canada on 3, 16, 20, and 26 April 2011. The samples
were gamma-ray counted in a germanium detector and the isotopes 131I and 137Cs,
produced by the fission of 235U, and 134Cs, produced by neutron capture on
133Cs, were observed at elevated levels compared to a reference sample of
ice-water. These elevated activities are ascribed to the accident at the
Fukushima Dai-ichi nuclear reactor complex in Japan that followed the 11 March
earthquake and tsunami. The activity levels observed at no time presented
health concerns.Comment: 4 pages, 8 figure
On the use of a sunward-libration-point orbiting spacecraft as an IMF monitor for magnetospheric studies
Magnetospheric studies often require knowledge of the orientation of the IMF. In order to test the accuracy of using magnetometer data from a spacecraft orbiting the sunward libration point for this purpose, the angle between the IMF at ISEE 3, when it was positioned around the libration point, and at ISEE 1, orbiting Earth, has been calculated for a data set of two-hour periods covering four months. For each period, a ten-minute average of ISEE 1 data is compared with ten-minute averages of ISEE 3 data at successively lagged intervals. At the lag time equal to the time required for the solar wind to convect from ISEE 3 to ISEE 1, the median angle between the IMF orientation at the two spacecraft is 20 deg, and 80% of the cases have angles less than 38 deg. The results for the angles projected on the y-z plane are essentially the same
2dF QSO Redshift Survey
With approximately 6000 QSO redshifts,the 2dF QSO redshift survey is already
the biggest complete QSO survey. The aim for the survey is to have 25000 QSO
redshifts, providing an order of magnitude increase in QSO clustering
statistics. We first describe the observational parameters of the 2dF QSO
survey. We then describe several highlights of the survey so far, including new
estimates of the QSO luminosity function and its evolution. We also review the
current status of QSO clustering analyses from the 2dF data. Finally, we
discuss how the complete QSO survey will be able to constrain the value of
Omega_o by measuring the evolution of QSO clustering, place limits on the
cosmological constant via a direct geometrical test and determine the form of
the fluctuation power-spectrum out to the approximately 1000 Mpc scales only
previously probed by COBE.Comment: 6 pages; to be published in Clustering at High Redshift, Marseille,
June 1999, eds. A. Mazure, O. LeFevre, V. Lebru
Observed Consequences of Presupernova Instability in Very Massive Stars
This chapter concentrates on the deaths of very massive stars, the events
leading up to their deaths, and how mass loss affects the resulting death. The
previous three chapters emphasized the theory of wind mass loss, eruptions, and
core collapse physics, but here we emphasize mainly the observational
properties of the resulting death throes. Mass loss through winds, eruptions,
and interacting binaries largely determines the wide variety of different types
of supernovae that are observed, as well as the circumstellar environments into
which the supernova blast waves expand. Connecting these observed properties of
the explosions to the initial masses of their progenitor stars is, however, an
enduring challenge and is especially difficult for very massive stars.
Superluminous supernovae, pair instability supernovae, gamma ray bursts, and
"failed" supernovae are all end fates that have been proposed for very massive
stars, but the range of initial masses or other conditions leading to each of
these (if they actually occur) are still very certain. Extrapolating to infer
the role of very massive stars in the early universe is essentially
unencumbered by observational constraints and still quite dicey.Comment: 39 pages, 5 figures, to appear as chapter in the book "Very Massive
Stars in the Local Universe", ed. J. Vin
MAGMO: Coherent magnetic fields in the star forming regions of the Carina-Sagittarius spiral arm tangent
We present the pilot results of the `MAGMO' project, targeted observations of
ground-state hydroxyl masers towards sites of 6.7-GHz methanol maser emission
in the Carina-Sagittarius spiral arm tangent, Galactic longitudes 280 degrees
to 295 degrees. The `MAGMO' project aims to determine if Galactic magnetic
fields can be traced with Zeeman splitting of masers associated with star
formation. Pilot observations of 23 sites of methanol maser emission were made,
with the detection of ground-state hydroxyl masers towards 11 of these and six
additional offset sites. Of these 17 sites, nine are new detections of sites of
1665-MHz maser emission, three of them accompanied by 1667-MHz emission. More
than 70% of the maser features have significant circular polarization, whilst
only ~10% have significant linear polarization (although some features with up
to 100% linear polarization are found). We find 11 Zeeman pairs across six
sites of high-mass star formation with implied magnetic field strengths between
-1.5 mG and +3.8 mG and a median field strength of +1.6 mG. Our measurements of
Zeeman splitting imply that a coherent field orientation is experienced by the
maser sites across a distance of 5.3+/-2.0 kpc within the Carina-Sagittarius
spiral arm tangent.Comment: 19 pages, 13 figures, accepted for publication in MNRA
A faint galaxy redshift survey to B=24
Using the multislit LDSS-2 spectrograph on the {\it William Herschel
Telescope} we have completed a redshift survey in the magnitude range which has produced 73 redshifts representing a 73\% complete sample
uniformly-selected from four deep fields at high Galactic latitude. The survey
extends out to and includes the highest redshift galaxy () yet
discovered in a field sample. The median redshift, \zmed=0.46, and form of
the redshift distribution constitute compelling evidence against simple
luminosity evolution as an explanation of the large excess of faint galaxies
(2--4 no-evolution) seen in this magnitude range. Rather we
identify the excess population as blue objects with and \,
luminosities similar to local galaxies indicating a dramatic decrease in
the density of such objects over the last Hubble time, confirming the trends
found in brighter redshift surveys. We also find a marked absence of {\it very}
low redshift galaxies (0.1) at faint limits, severely constraining any
significant steepening of the local field galaxy luminosity function at low
luminosities.Comment: uuencoded compressed postscript. The preprint are also available at
URL http://www.ast.cam.ac.uk/preprint/PrePrint.htm
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