2,670 research outputs found
Information seeking in the Humanities: physicality and digitality
This paper presents a brief overview of a research project
that is examining the information seeking practices of
humanities scholars. The results of this project are being
used to develop digital resources to better support these
work activities. Initial findings from a recent set of
interviews is offered, revealing the importance of physical
artefacts in the humanities scholars’ research processes and
the limitations of digital resources. Finally, further work
that is soon to be undertaken is summarised, and it is hoped
that after participation in this workshop these ideas will be
refined
Monitoring RXTE Observations of Markarian 348: the origin of the column density variations
We analyze 37 RXTE observations of the type 2 Seyfert galaxy Mrk348 obtained
during a period of 14 months. We confirm the spectral variability previous
reported by Smith et al., in the sense that thecolumn density decreases by a
factor of ~3 as the count rate increases. Column density variations could
possibly originate either due to the random drift of clouds within the
absorption screen, or due to photoionization processes. Our modeling of the
observed variations implies that the first scenario is more likely. These
clouds should lie in a distance of >2 light years from the source, having a
diameter of a few light days and a density of >10^7 cm^(-3), hence probably
residing outside the Broad Line Region.Comment: 6 pages, 3 figures, to appear in MNRA
The falling chain of Hopkins, Tait, Steele and Cayley
A uniform, flexible and frictionless chain falling link by link from a heap
by the edge of a table falls with an acceleration if the motion is
nonconservative, but if the motion is conservative, being the
acceleration due to gravity. Unable to construct such a falling chain, we use
instead higher-dimensional versions of it. A home camcorder is used to measure
the fall of a three-dimensional version called an -slider. After
frictional effects are corrected for, its vertical falling acceleration is
found to be . This result agrees with the theoretical
value of for an ideal energy-conserving -slider.Comment: 17 pages, 5 figure
Cavity optoelectromechanical regenerative amplification
Cavity optoelectromechanical regenerative amplification is demonstrated. An
optical cavity enhances mechanical transduction, allowing sensitive measurement
even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was
linewidth narrowed to 6.6\pm1.4 mHz, 30 times smaller than previously achieved
with radiation pressure driving in such a system. These results may have
applications in areas such as ultrasensitive optomechanical mass spectroscopy
Variable X-ray Absorption in the Seyfert 2 Galaxy Mrk 348
We present RXTE monitoring observations of the Seyfert 2 galaxy Mrk 348
spanning a 6 month period. The time-averaged spectrum in the 3-20 keV band
shows many features characteristic of a Compton-thin Seyfert 2 galaxy, namely a
hard underlying power-law continuum (photon index = 1.8) with heavy soft X-ray
absorption (N_h ~ 10^23 cm^-2) plus measureable iron line emission (equivalent
width ~ 100 eV) and, at high energy, evidence for a reflection component (R <
1). During the first half of the monitoring period the X-ray continuum flux
from Mrk 348 remained relatively steady. However this was followed by a
significant brightening of the source (by roughly a factor of 4) with the
fastest change corresponding to a doubling of its X-ray flux on a timescale of
about 20 days. The flux increase was accompanied by a marked softening of X-ray
spectrum most likely attributable to a factor 3 decline in the intrinsic
line-of-sight column density. In contrast the iron line and the reflection
components showed no evidence of variability. These observations suggest a
scenario in which the central X-ray source is surrounded by a patchy
distribution of absorbing material located within about a light-week of the
nucleus of Mrk 348. The random movement of individual clouds within the
absorbing screen, across our line of sight, produces substantial temporal
variations in the measured column density on timescales of weeks to months and
gives rise to the observed X-ray spectral variability. However, as viewed from
the nucleus the global coverage and typical thickness of the cloud layer
remains relatively constant.Comment: 19 pages, 3 figures Accepted for publication in the Astrophysical
Journa
Polarization Squeezing of Continuous Variable Stokes Parameters
We report the first direct experimental characterization of continuous
variable quantum Stokes parameters. We generate a continuous wave light beam
with more than 3 dB of simultaneous squeezing in three of the four Stokes
parameters. The polarization squeezed beam is produced by mixing two quadrature
squeezed beams on a polarizing beam splitter. Depending on the squeezed
quadrature of these two beams the quantum uncertainty volume on the
Poincar\'{e} sphere became a `cigar' or `pancake'-like ellipsoid.Comment: 4 pages, 5 figure
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