6,555 research outputs found
Induction probe determines levels of liquid metals
Mutual-inductance probe accurately measures liquid levels in a variety of liquid metals at elevated temperatures. It can be used in pyrochemical processes for the recovery of spent reactor fuel
Calibration of a polarimetric imaging SAR
Calibration of polarimetric imaging Synthetic Aperture Radars (SAR's) using point calibration targets is discussed. The four-port network calibration technique is used to describe the radar error model. The polarimetric ambiguity function of the SAR is then found using a single point target, namely a trihedral corner reflector. Based on this, an estimate for the backscattering coefficient of the terrain is found by a deconvolution process. A radar image taken by the JPL Airborne SAR (AIRSAR) is used for verification of the deconvolution calibration method. The calibrated responses of point targets in the image are compared both with theory and the POLCAL technique. Also, response of a distributed target are compared using the deconvolution and POLCAL techniques
Quantum Films Adsorbed on Graphite: Third and Fourth Helium Layers
Using a path-integral Monte Carlo method for simulating superfluid quantum
films, we investigate helium layers adsorbed on a substrate consisting of
graphite plus two solid helium layers. Our results for the promotion densities
and the dependence of the superfluid density on coverage are in agreement with
experiment. We can also explain certain features of the measured heat capacity
as a function of temperature and coverage.Comment: 13 pages in the Phys. Rev. two-column format, 16 Figure
Radiative corrections to the Higgs boson decay rate in the minimal supersymmetric model
We consider radiative corrections to the decay rate
of the heavy {\it CP}-even Higgs boson of the minimal supersymmetric model to
two bosons. We perform a one loop Feynman diagram calculation in the
on-mass-shell renormalization scheme, and include the third generation of
quarks and squarks. The tree level rate is suppressed by a mixing angle factor
and decreases as for large . The corrected rate overcomes this
suppression and increases with for ~GeV. The corrections can
be very large and depend in detail on the top squark masses and -term, as
well as the supersymmetric Higgs mass parameter .Comment: 22 pages, 9 figures available from authors, UCB-PTH-92/23 and
LBL-3249
Entropy Encoding, Hilbert Space and Karhunen-Loeve Transforms
By introducing Hilbert space and operators, we show how probabilities,
approximations and entropy encoding from signal and image processing allow
precise formulas and quantitative estimates. Our main results yield orthogonal
bases which optimize distinct measures of data encoding.Comment: 25 pages, 1 figur
A deep submillimetre survey of the Galactic Centre
We present first results from a submillimetre continuum survey of the
Galactic Centre `Central Molecular Zone' (CMZ), made with SCUBA on the James
Clerk Maxwell Telescope. SCUBA's scan-map mode has allowed us to make extremely
wide-field maps of thermal dust emission with unprecedented speed and
sensitivity. We also discuss some issues related to the elimination of
artefacts in scan-map data. Our simultaneous 850/450 micron maps have a total
size of approximately 2.8 x 0.5 degrees (400 x 75 pc) elongated along the
galactic plane. They cover the Sgr A region-including Sgr A*, the circumnuclear
disc, and the +20 km/s and +50 km/s clouds; the area around the Pistol; Sgr
B2-the brightest feature on the map; and at their Galactic Western and Eastern
edges the Sgr C and Sgr D regions. There are many striking features such as
filaments and shell-like structures, as well as point sources such as Sgr A*
itself. The total mass in the Central Molecular Zone is greater than that
revealed in previous optically-thin molecular line maps by a factor of ~3, and
new details are revealed on scales down to 0.33 pc across this 400 pc wide
region.Comment: 12 pages, 3 figures, (figures now smaller, in paper body), accepted
by ApJ
Size effects in statistical fracture
We review statistical theories and numerical methods employed to consider the
sample size dependence of the failure strength distribution of disordered
materials. We first overview the analytical predictions of extreme value
statistics and fiber bundle models and discuss their limitations. Next, we
review energetic and geometric approaches to fracture size effects for
specimens with a flaw. Finally, we overview the numerical simulations of
lattice models and compare with theoretical models.Comment: review article 19 pages, 5 figure
Mode resolved travel time statistics for elastic rays in three-dimensional billiards
We consider the ray limit of propagating ultrasound waves in
three-dimensional bodies made from an homogeneous, isotropic, elastic material.
Using a Monte Carlo approach, we simulate the propagation and proliferation of
elastic rays using realistic angle dependent reflection coefficients, taking
into account mode conversion and ray-splitting. For a few simple geometries, we
analyse the long time equilibrium distribution focussing on the energy ratio
between compressional and shear waves. Finally, we study the travel time
statistics, i.e. the distribution of the amount of time a given trajectory
spends as a compressional wave, as compared to the total travel time. These
results are intimately related to recent elastodynamics experiments on Coda
wave interferometry by Lobkis and Weaver [Phys. Rev. E 78, 066212 (2008)].Comment: 11 pages, 10 figures, (minor corrections, improved style
HI study of the warped spiral galaxy NGC5055: a disk/dark matter halo offset?
We present a study of the HI distribution and dynamics of the nearby spiral
galaxy NGC5055 based on observations with the Westerbork Synthesis Radio
Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to
3.5 R_25, and shows a pronounced warp that starts at the end of the bright
optical disk (R_25= 11.6 kpc). This very extended warp has large-scale
symmetry, which along with the rotation period of its outer parts (~1.5 Gyr at
40 kpc), suggests a long-lived phenomenon. The rotation curve rises steeply in
the central parts up to the maximum velocity (v_max ~ 206 km/s). Beyond the
bright stellar disk (R_25), it shows a decline of about 25 km/s and then
remains flat out to the last measured point. The standard analysis with
luminous and dark matter components shows the dynamical importance of the disk.
The best fit to the rotation curve is obtained with a ``maximum disk''. Less
satisfactory fits with lighter disks help to set a firm lower limit of 1.4 to
the mass-to-light ratio in F band of the disk. Such a ``minimum disk''
contributes about 60% of the observed maximum rotational velocity. NGC5055
shows remarkable overall regularity and symmetry. A mild lopsidedness is
noticeable, however, both in the distribution and kinematics of the gas. The
tilted ring analysis of the velocity field led us to adopt different values for
the kinematical centre and for the systemic velocity for the inner and the
outer parts of the system. This has produced a remarkable result: the
kinematical and geometrical asymmetries disappear, both at the same time. These
results point at two different dynamical regimes: an inner region dominated by
the stellar disk and an outer one, dominated by a dark matter halo offset with
respect to the disk.Comment: Accepted for publication in A&A. Minor correction
Developing affordable and accessible pro‐angiogenic wound dressings; incorporation of 2 deoxy D‐ribose (2dDR) into cotton fibres and wax‐coated cotton fibres
The absorption capacity of cotton dressings is a critical factor in their widespread use where they help absorb wound exudate. Cotton wax dressings, in contrast, are used for wounds where care is taken to avoid adhesion of dressings to sensitive wounds such as burn injuries. Accordingly, we explored the loading of 2‐deoxy‐D‐ribose (2dDR), a small sugar, which stimulates angiogenesis and wound healing in normal and diabetic rats, into both types of dressings and measured the release of it over several days. The results showed that approximately 90% of 2dDR was released between 3 and 5 days when loaded into cotton dressings. For wax‐coated cotton dressings, several methods of loading of 2dDR were explored. A strategy similar to the commercial wax coating methodology was found the best protocol which provided a sustained release over 5 days.
Cytotoxicity analysis of 2dDR loaded cotton dressing showed that the dressing stimulated metabolic activity of fibroblasts over 7 days confirming the non‐toxic nature of this sugar‐loaded dressings. The results of the chick chorioallantoic membrane (CAM) assay demonstrated a strong angiogenic response to both 2dDR loaded cotton dressing and to 2dDR loaded cotton wax dressings. Both dressings were found to increase the number of newly formed blood vessels significantly when observed macroscopically and histologically.
We conclude this study offers a simple approach to developing affordable wound dressings as both have the potential to be evaluated as pro‐active dressings to stimulate wound healing in wounds where management of exudate or prevention of adherence to the wounds are clinical requirements
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