1,171 research outputs found
Should It Be Illicit to Solicit ? A Legal Analysis of Policy Options to Regulate Solicitation of Organs for Transplant
Should It Be Illicit to Solicit ? A Legal Analysis of Policy Options to Regulate Solicitation of Organs for Transplant
Recently, there have been several well-publicized cases in which a patient in need of a transplant has solicited an organ through the use of commercial advertising and organized media campaigns. When deceased organs are directed to an individual as a result of solicitation rather than allocated through the national system, equity and medical utility are sacrificed. For this reason, regulation of deceased organ solicitation may be desirable. However, because solicitation of organs is likely to be considered constitutionally protected charitable speech, there are significant legal issues to consider. This article analyzes the legality of four possible policy options to resolve the ethical dilemma raised by solicitation of deceased organs for transplant
Experimental growth law for bubbles in a "wet" 3D liquid foam
We used X-ray tomography to characterize the geometry of all bubbles in a
liquid foam of average liquid fraction and to follow their
evolution, measuring the normalized growth rate
for 7000 bubbles. While
does not depend only on the number of faces of a bubble, its average over
faced bubbles scales as for large s at all times. We
discuss the dispersion of and the influence of on
.Comment: 10 pages, submitted to PR
Viscous instabilities in flowing foams: A Cellular Potts Model approach
The Cellular Potts Model (CPM) succesfully simulates drainage and shear in
foams. Here we use the CPM to investigate instabilities due to the flow of a
single large bubble in a dry, monodisperse two-dimensional flowing foam. As in
experiments in a Hele-Shaw cell, above a threshold velocity the large bubble
moves faster than the mean flow. Our simulations reproduce analytical and
experimental predictions for the velocity threshold and the relative velocity
of the large bubble, demonstrating the utility of the CPM in foam rheology
studies.Comment: 10 pages, 3 figures. Replaced with revised version accepted for
publication in JSTA
Cluster Persistence: a Discriminating Probe of Soap Froth Dynamics
The persistent decay of bubble clusters in coarsening two-dimensional soap
froths is measured experimentally as a function of cluster volume fraction.
Dramatically stronger decay is observed in comparison to soap froth models and
to measurements and calculations of persistence in other systems. The fraction
of individual bubbles that contain any persistent area also decays, implying
significant bubble motion and suggesting that T1 processes play an important
role in froth persistence.Comment: 5 pages, revtex, 4 eps figures. To appear in Europhys. Let
Bubble kinetics in a steady-state column of aqueous foam
We measure the liquid content, the bubble speeds, and the distribution of
bubble sizes, in a vertical column of aqueous foam maintained in steady-state
by continuous bubbling of gas into a surfactant solution. Nearly round bubbles
accumulate at the solution/foam interface, and subsequently rise with constant
speed. Upon moving up the column, they become larger due to gas diffusion and
more polyhedral due to drainage. The size distribution is monodisperse near the
bottom and polydisperse near the top, but there is an unexpected range of
intermediate heights where it is bidisperse with small bubbles decorating the
junctions between larger bubbles. We explain the evolution in both bidisperse
and polydisperse regimes, using Laplace pressure differences and taking the
liquid fraction profile as a given.Comment: 7 pages, 3 figure
The bar PANDA focussing-lightguide disc DIRC
bar PANDA will be a fixed target experiment internal to the HESR antiproton storage ring at the future FAIR complex. The ANDA detector requires excellent particle-identification capabilities in order to achieve its scientific potential. Cherenkov counters employing the DIRC principle were chosen as PID detectors for the Target Spectrometer. The proposed Focussing-Lightguide Disc DIRC will cover the forward part of the Target Spectrometer acceptance in the angular range between 5° and 22°. Its design includes a novel approach to mitigate dispersion effects in the solid radiator of a DIRC counter using optical elements. The dispersion correction will enable the Focussing-Lightguide Disc DIRC to provide pion-kaon identification for momenta well above 3.5 GeV/c
EvryFlare II: Rotation Periods of the Cool Flare Stars in TESS Across Half the Southern Sky
We measure rotation periods and sinusoidal amplitudes in Evryscope light
curves for 122 two-minute K5-M4 TESS targets selected for strong flaring. The
Evryscope array of telescopes has observed all bright nearby stars in the
South, producing two-minute cadence light curves since 2016. Long-term,
high-cadence observations of rotating flare stars probe the complex
relationship between stellar rotation, starspots, and superflares. We detect
periods from 0.3487 to 104 d, and observe amplitudes from 0.008 to 0.216 g'
mag. We find the Evryscope amplitudes are larger than those in TESS with the
effect correlated to stellar mass (p-value=0.01). We compute the Rossby number
(Ro), and find our sample selected for flaring has twice as many intermediate
rotators (0.040.44) rotators; this may
be astrophysical or a result of period-detection sensitivity. We discover 30
fast, 59 intermediate, and 33 slow rotators. We measure a median starspot
coverage of 13% of the stellar hemisphere and constrain the minimum magnetic
field strength consistent with our flare energies and spot coverage to be 500
G, with later-type stars exhibiting lower values than earlier-types. We observe
a possible change in superflare rates at intermediate periods. However, we do
not conclusively confirm the increased activity of intermediate rotators seen
in previous studies. We split all rotators at Ro~0.2 into Prot10
d bins to confirm short-period rotators exhibit higher superflare rates, larger
flare energies, and higher starspot coverage than do long-period rotators, at
p-values of 3.2 X 10^-5, 1.0 X 10^-5, and 0.01, respectively.Comment: 16 pages, 8 figures, 3 tables. Ancillary machine-readable files
included. Accepted for publication in ApJ (proofs submitted). Includes
significant new material, including starspot color that depends on stellar
mass, more rotation periods, potential changes in activity during spin-down,
and examples of binary rotator
Variables in the Southern Polar Region Evryscope 2016 Dataset
The regions around the celestial poles offer the ability to find and
characterize long-term variables from ground-based observatories. We used
multi-year Evryscope data to search for high-amplitude (~5% or greater)
variable objects among 160,000 bright stars (Mv < 14.5) near the South
Celestial Pole. We developed a machine learning based spectral classifier to
identify eclipse and transit candidates with M-dwarf or K-dwarf host stars -
and potential low-mass secondary stars or gas giant planets. The large
amplitude transit signals from low-mass companions of smaller dwarf host stars
lessens the photometric precision and systematics removal requirements
necessary for detection, and increases the discoveries from long-term
observations with modest light curve precision. The Evryscope is a robotic
telescope array that observes the Southern sky continuously at 2-minute
cadence, searching for stellar variability, transients, transits around exotic
stars and other observationally challenging astrophysical variables. In this
study, covering all stars 9 < Mv < 14.5, in declinations -75 to -90 deg, we
recover 346 known variables and discover 303 new variables, including 168
eclipsing binaries. We characterize the discoveries and provide the amplitudes,
periods, and variability type. A 1.7 Jupiter radius planet candidate with a
late K-dwarf primary was found and the transit signal was verified with the
PROMPT telescope network. Further followup revealed this object to be a likely
grazing eclipsing binary system with nearly identical primary and secondary K5
stars. Radial velocity measurements from the Goodman Spectrograph on the 4.1
meter SOAR telescope of the likely-lowest-mass targets reveal that six of the
eclipsing binary discoveries are low-mass (.06 - .37 solar mass) secondaries
with K-dwarf primaries, strong candidates for precision mass-radius
measurements.Comment: 32 pages, 17 figures, accepted to PAS
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