566 research outputs found
Contribution of thermal noise to the line width of Josephson radiation from superconducting point contacts
Contribution of thermal noise to line width of Josephson radiation from superconducting point contact
Research and development of superconducting thin films Final report, 15 Dec. 1965 - 15 Dec. 1966
Superconducting niobium thin film productio
Superconduction thin films
Superconduction thin films, and properties and applications of Josephson effect at radio frequencie
High Mass Triple Systems: The Classical Cepheid Y Car
We have obtained an HST STIS ultraviolet high dispersion Echelle mode
spectrum the binary companion of the double mode classical Cepheid Y Car. The
velocity measured for the hot companion from this spectrum is very different
from reasonable predictions for binary motion, implying that the companion is
itself a short period binary. The measured velocity changed by 7 km/ s during
the 4 days between two segments of the observation confirming this
interpretation. We summarize "binary" Cepheids which are in fact members of
triple system and find at least 44% are triples. The summary of information on
Cepheids with orbits makes it likely that the fraction is under-estimated.Comment: accepted by A
Hubble Space Telescope WFPC-2 Imaging of Cassiopeia A
The young SNR Cassiopeia A was imaged with WFPC-2 through four filters
selected to capture the complete velocity range of the remnant's main shell in
several important emission lines. Primary lines detected were [O III]
4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364,
and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in
all four filters. Considerable detail is observed in the reverse-shocked ejecta
with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright
and faint emission features appear highly clumped. Large differences in [S III]
and [O III] line intensities indicating chemical abundance differences are also
seen, particularly in knots located along the bright northern limb and near the
base of the northeast jet. A line of curved overlapping filament in the
remnant's northwestern rim appears to mark the location of the remnant's
reverse shock front in this region. Finger-like ejecta structures elsewhere
suggest cases where the reverse shock front is encountering the remnant's
clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots
("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with
diffuse edges facing away from the center of expansion. Three color composite
images of the whole remnant and certain sections along with individual filter
enlargements of selected regions of the bright optical shell are presented and
discussed.Comment: 26 pages, 12 figures Accepted to the Astronomical Journa
Vortex Structure Around a Magnetic Dot in Planar Superconductors
The problem of the giant vortex state around a magnetic dot which is embedded
in a superconducting film is investigated. The full non-linear, self-consistent
Ginzburg-Landau equations are solved numerically in order to calculate the free
energy, the order parameter of the host superconductor, the internal magnetic
field due to the supercurrents, the corresponding current density, the
magnetization probed in the vicinity of the dot, and the normal electron
density as a function of the various parameters of the system. We find that, as
we increase the magnetic moment of the dot, higher flux quanta vortex states
become energetically more favorable, as they can better compete with the
external magnetic field via the Meissner effect. In addition to that, they
progressively become closer to each other in energy with direct experimental
consequences, i.e. physical quantities like magnetization may fluctuate when
measured, for example, as a function of a uniform external magnetic field.Comment: text 21 pages (REVTEX), 8 figures available upon reques
Polaris the Cepheid returns: 4.5 years of monitoring from ground and space
We present the analysis of 4.5 years of nearly continuous observations of the
classical Cepheid Polaris, which comprise the most precise data available for
this star. We have made spectroscopic measurements from ground and photometric
measurements from the WIRE star tracker and the SMEI instrument on the Coriolis
satellite. Measurements of the amplitude of the dominant oscillation (P = 4
days), that go back more than a century, show a decrease from 120 mmag to 30
mmag (V magnitude) around the turn of the millennium. It has been speculated
that the reason for the decrease in amplitude is the evolution of Polaris
towards the edge of the instability strip. However, our new data reveal an
increase in the amplitude by about 30% from 2003-2006. It now appears that the
amplitude change is cyclic rather than monotonic, and most likely the result of
a pulsation phenomenon. In addition, previous radial velocity campaigns have
claimed the detection of long-period variation in Polaris (P > 40 days). Our
radial velocity data are more precise than previous datasets, and we find no
evidence for additional variation for periods in the range 3-50 days with an
upper limit of 100 m/s. However, in the WIRE data we find evidence of variation
on time-scales of 2-6 days, which we interpret as being due to granulation.Comment: Accepted by ApJ. 8 pages. Quality of figures 1+3+7 degrade
The radius and effective temperature of the binary Ap star beta CrB from CHARA/FLUOR and VLT/NACO observations
The prospects for using asteroseismology of rapidly oscillating Ap (roAp)
stars are hampered by the large uncertainty in fundamental stellar parameters.
Results in the literature for the effective temperature (Teff) often span a
range of 1000 K. Our goal is to reduce systematic errors and improve the Teff
calibration of Ap stars based on new interferometric measurements. We obtained
long-baseline interferometric observations of beta CrB using the CHARA/FLUOR
instrument. To disentangle the flux contributions of the two components of this
binary star, we obtained VLT/NACO adaptive optics images. We determined limb
darkened angular diameters of 0.699+-0.017 mas for beta CrB A (from
interferometry) and 0.415+-0.017 mas for beta CrB B (from surface brightness-
color relations), corresponding to radii of 2.63+-0.09 Rsun (3.4 percent
uncertainty) and 1.56+-0.07 Rsun (4.5 percent). The combined bolometric flux of
the A and B components was determined from satellite UV data, spectrophotometry
in the visible and broadband data in the infrared. The flux from the B
component constitutes 16+-4 percent of the total flux and was determined by
fitting an ATLAS9 model atmosphere to the broad-band NACO J and K magnitudes.
Combining the flux of the A component with its measured angular diameter, we
determine the effective temperature Teff(A) = 7980+-180 K (2.3 percent). Our
new interferometric and imaging data enable a nearly model-independent
determination of the effective temperature of beta CrB A. Including our recent
study of alpha Cir, we now have direct Teff measurements of two of the
brightest roAp stars, providing a strong benchmark for an improved calibration
of the Teff scale for Ap stars. This will support the use of potentially strong
constraints imposed by asteroseismic studies of roAp stars.Comment: 7 pages, accepted by A&
Scoping review of priority setting of research topics for musculoskeletal conditions
Objective Describe research methods used in priority-setting exercises for musculoskeletal conditions and synthesise the priorities identified. Design Scoping review. Setting and population Studies that elicited the research priorities of patients/consumers, clinicians, researchers, policy-makers and/or funders for any musculoskeletal condition were included. Methods and analysis We searched MEDLINE and EMBASE from inception to November 2017 and the James Lind Alliance top 10 priorities, Cochrane Priority Setting Methods Group, and Cochrane Musculoskeletal and Back Groups review priority lists. The reported methods and research topics/questions identified were extracted, and a descriptive synthesis conducted. Results Forty-nine articles fulfilled our inclusion criteria. Methodologies and stakeholders varied widely (26 included a mix of clinicians, consumers and others, 16 included only clinicians, 6 included only consumers or patients and in 1 participants were unclear). Only two (4%) reported any explicit inclusion criteria for priorities. We identified 294 broad research priorities from 37 articles and 246 specific research questions from 17 articles, although only four (24%) of the latter listed questions in an actionable format. Research priorities for osteoarthritis were identified most often (n=7), followed by rheumatoid arthritis (n=4), osteoporosis (n=4) and back pain (n=4). Nearly half of both broad and specific research priorities were focused on treatment interventions (n=116 and 111, respectively), while few were economic (n=8, 2.7% broad and n=1, 0.4% specific), implementation (n=6, 2% broad and n=4, 1.6% specific) or health services and systems research (n=15, 5.1% broad and n=9, 3.7% specific) priorities. Conclusions While many research priority-setting studies in the musculoskeletal field have been performed, methodological limitations and lack of actionable research questions limit their usefulness. Future studies should ensure they conform to good priority-setting practice to ensure that the generated priorities are of maximum value. PROSPERO registration number CRD42017059250
The period and amplitude changes of Polaris (alpha UMi) from 2003 to 2007 measured with SMEI
We present an analysis of 4.5 years of high precision (0.1%) space-based
photometric measurements of the Cepheid variable Polaris, obtained by the broad
band Solar Mass Ejection Imager (SMEI) instrument on board the Coriolis
satellite. The data span from April 2003 to October 2007, with a cadence of 101
minutes and a fill factor of 70%. We have measured the mean peak to peak
amplitude across the whole set of observations to be 25 mmag. There is,
however, a clear trend that the size of the oscillations has been increasing
during the observations, with peak to peak variations less than 22 mmag in
early 2003, increasing to around 28 mmag by October 2007, suggesting that the
peak to peak amplitude is increasing at a rate of 1.39 \pm 0.12 mmag yr^{-1}.
Additionally, we have combined our new measurements with archival measurements
to measure a rate of period change of 4.90 \pm 0.26 s yr^{-1} over the last 50
years. However, there is some suggestion that the period of Polaris has
undergone a recent decline, and combined with the increased amplitude, this
could imply evolution away from an overtone pulsation mode into the fundamental
or a double pulsation mode depending on the precise mass of Polaris.Comment: 6 pages, 7 figures, 2 tables, accepted in MNRA
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