2,482 research outputs found
Ovarian and cervical cancer awareness: development of two validated measurement tools.
The aim of the study was to develop and validate measures of awareness of symptoms and risk factors for ovarian and cervical cancer (Ovarian and Cervical Cancer Awareness Measures)
Magnetotransport with two occupied subbands in a Si(100) inversion layer
We have studied an electron transport in inversion layers of high-mobility
Si(100) samples. At high electron concentrations and temperatures below 4.2 K,
two series of Shubnikov-de Haas oscillations have been observed. The
temperature damping of the second series oscillations indicates that the second
occupied subband belongs to the first energy level of the fourfold-degenerate
ladder . Samples with two occupied subbans exhibit a strong anomalous
negative magnetoresitance, reaching of a zero field value
at 12 T. The resistance decrease is more pronounced for lower
temperatures and higher electron concentrations. We explain this behaviour by
an increase of the second subband mobility due to the freezing-out of the
scattering of electrons. Based on the measured periods of SdH
oscillations, we conclude that the electrons are distributed inhomogeneously
beneath the sample gate.Comment: 4 pages. RevTex text and 4 PostScript figures in a single
tar-compressed file produced by 'uufiles
Cyclotron effective mass of 2D electron layer at GaAs/AlGaAs heterojunction subject to in-plane magnetic fields
We have found that Fermi contours of a two-dimensional electron gas at
\rmGaAs/Al_xGa_{1-x}As interface deviate from a standard circular shape under
the combined influence of an approximately triangular confining potential and
the strong in-plane magnetic field. The distortion of a Fermi contour manifests
itself through an increase of the electron effective cyclotron mass which has
been measured by the cyclotron resonance in the far-infrared transmission
spectra and by the thermal damping of Shubnikov-de Haas oscillations in tilted
magnetic fields with an in-plane component up to 5 T. The observed increase of
the cyclotron effective mass reaches almost 5 \% of its zero field value which
is in good agreement with results of a self-consistent calculation.Comment: 4 pages, Revtex, figures can be obtained on request from
[email protected]; to appear in Phys. Rev. B (in press). No changes, the
corrupted submission replace
Spectroscopy of High-Redshift Supernovae from the ESSENCE Project: The First Four Years
We present the results of spectroscopic observations from the ESSENCE
high-redshift supernova (SN) survey during its first four years of operation.
This sample includes spectra of all SNe Ia whose light curves were presented by
Miknaitis et al. (2007) and used in the cosmological analyses of Davis et al.
(2007) and Wood-Vasey et al. (2007). The sample represents 273 hours of
spectroscopic observations with 6.5 - 10-m-class telescopes of objects detected
and selected for spectroscopy by the ESSENCE team. We present 174 spectra of
156 objects. Combining this sample with that of Matheson et al. (2005), we have
a total sample of 329 spectra of 274 objects. From this, we are able to
spectroscopically classify 118 Type Ia SNe. As the survey has matured, the
efficiency of classifying SNe Ia has remained constant while we have observed
both higher-redshift SNe Ia and SNe Ia farther from maximum brightness.
Examining the subsample of SNe Ia with host-galaxy redshifts shows that
redshifts derived from only the SN Ia spectra are consistent with redshifts
found from host-galaxy spectra. Moreover, the phases derived from only the SN
Ia spectra are consistent with those derived from light-curve fits. By
comparing our spectra to local templates, we find that the rate of objects
similar to the overluminous SN 1991T and the underluminous SN 1991bg in our
sample are consistent with that of the local sample. We do note, however, that
we detect no object spectroscopically or photometrically similar to SN 1991bg.
Although systematic effects could reduce the high-redshift rate we expect based
on the low-redshift surveys, it is possible that SN 1991bg-like SNe Ia are less
prevalent at high redshift.Comment: 21 pages, 17 figures, accepted to A
Strongly Variable z=1.48 FeII and MgII Absorption in the Spectra of z=4.05 GRB 060206
We report on the discovery of strongly variable FeII and MgII absorption
lines seen at z=1.48 in the spectra of the z=4.05 GRB 060206 obtained between
4.13 to 7.63 hours (observer frame) after the burst. In particular, the FeII
line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA to 0.28+-0.21 AA,
only to increase to 0.96+-0.21 AA in a later date spectrum. The MgII doublet
shows even more complicated evolution: the weaker line of the doublet drops
from 2.05+-0.25 AA to 0.92+-0.32 AA, but then more than doubles to 2.47+-0.41
AA in later data. The ratio of the EWs for the MgII doublet is also variable,
being closer to 1:1 (saturated regime) when the lines are stronger and becoming
closer to 2:1 (unsaturated regime) when the lines are weaker, consistent with
expectations based on atomic physics. We have investigated and rejected the
possibility of any instrumental or atmospheric effects causing the observed
strong variations. Our discovery of clearly variable intervening FeII and MgII
lines lends very strong support to their scenario, in which the characteristic
size of intervening patches of MgII ``clouds'' is comparable to the GRB beam
size, i.e, about 10^16 cm. We discuss various implications of this discovery,
including the nature of the MgII absorbers, the physics of GRBs, and
measurements of chemical abundances from GRB and quasar absorption lines.Comment: 14 pages, 3 figures, 1 table; ApJ Letters, accepte
Reducing drug related deaths : a pre-implementation assessment of knowledge,barriers and enablers for naloxone distribution through general practice
Peer reviewedPublisher PD
Low Carbon Abundance in Type Ia Supernovae
We investigate the quantity and composition of unburned material in the outer
layers of three normal Type Ia supernovae (SNe Ia): 2000dn, 2002cr and 20 04bw.
Pristine matter from a white dwarf progenitor is expected to be a mixture of
oxygen and carbon in approximately equal abundance. Using near-infrared (NIR,
0.7-2.5 microns) spectra, we find that oxygen is abundant while carbon is
severely depleted with low upper limits in the outer third of the ejected mass.
Strong features from the OI line at rest wavelength = 0.7773 microns are
observed through a wide range of expansion velocities approx. 9,000 - 18,000
km/s. This large velocity domain corresponds to a physical region of the
supernova with a large radial depth. We show that the ionization of C and O
will be substantially the same in this region. CI lines in the NIR are expected
to be 7-50 times stronger than those from OI but there is only marginal
evidence of CI in the spectra and none of CII. We deduce that for these three
normal SNe Ia, oxygen is more abundant than carbon by factors of 100 - 1,000.
MgII is also detected in a velocity range similar to that of OI. The presence
of O and Mg combined with the absence of C indicates that for these SNe Ia,
nuclear burning has reached all but the extreme outer layers; any unburned
material must have expansion velocities greater than 18,000 km/s. This result
favors deflagration to detonation transition (DD) models over pure deflagration
models for SNe Ia.Comment: accepted for publication in Ap
Exploring the Structure of Distant Galaxies with Adaptive Optics on the Keck-II Telescope
We report on the first observation of cosmologically distant field galaxies
with an high order Adaptive Optics (AO) system on an 8-10 meter class
telescope. Two galaxies were observed at 1.6 microns at an angular resolution
as high as 50 milliarcsec using the AO system on the Keck-II telescope. Radial
profiles of both objects are consistent with those of local spiral galaxies and
are decomposed into a classic exponential disk and a central bulge. A
star-forming cluster or companion galaxy as well as a compact core are detected
in one of the galaxies at a redshift of 0.37+/-0.05. We discuss possible
explanations for the core including a small bulge, a nuclear starburst, or an
active nucleus. The same galaxy shows a peak disk surface brightness that is
brighter than local disks of comparable size. These observations demonstrate
the power of AO to reveal details of the morphology of distant faint galaxies
and to explore galaxy evolution.Comment: 5 pages, Latex, 3 figures. Accepted for publication in P.A.S.
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