1,865 research outputs found
The Obligation to Participate in Biomedical Research
The current prevailing view is that participation in biomedical research is
above and beyond the call of duty. While some commentators have offered
reasons against this, we propose a novel public goods argument for an obligation
to participate in biomedical research. Biomedical knowledge is a public
good, available to any individual even if that individual does not contribute
to it. Participation in research is a critical way to support an important
public good. Consequently, all have a duty to participate. The current social
norm is that individuals participate only if they have a good reason to do so.
The public goods argument implies that individuals should participate unless
they have a good reason not to. Such a shift would be of great aid to the
progress of biomedical research, eventually making society significantly
healthier and longer lived
Structural properties of silicon dioxide thin films densified by medium-energy particles
Classical molecular-dynamics simulations have been carried out to investigate
densification mechanisms in silicon dioxide thin films deposited on an
amorphous silica surface, according to a simplified ion-beam assisted
deposition (IBAD) scenario. We compare the structures resulting from the
deposition of near-thermal (1 eV) SiO particles to those obtained with
increasing fraction of 30 eV SiO particles. Our results show that there
is an energy interval - between 12 and 15 eV per condensing SiO unit on
average - for which the growth leads to a dense, low-stress amorphous
structure, in satisfactory agreement with the results of low-energy ion-beam
experiments. We also find that the crossover between low- and high-density
films is associated with a tensile to compressive stress transition, and a
simultaneous healing of structural defects of the {\em a-}SiO network,
namely three- and four-fold rings. It is observed, finally, that densification
proceeds through significant changes at intermediate length scales (4--10 \AA),
leaving essentially unchanged the ``building blocks'' of the network, viz. the
Si(O) tetrahedra. This latter result is in qualitative agreement
with the mechanism proposed to explain the irreversible densification of
amorphous silica recovered from high pressures ( 15--20 GPa).Comment: 12 pages including 10 postscript figures; submitted to Phys. Rev. B;
related publications can be found on web site
http://www.centrcn.umontreal.ca/~lewi
Are Proxima and Alpha Centauri Gravitationally Bound?
Using the most recent kinematic and radial velocity data in the literature,
we calculate the binding energy of Proxima Centauri relative to the center of
mass of the Alpha Centauri system. When we adopt the centroids of the observed
data, we find that the three stars constitute a bound system, albeit with a
semi-major axis that is on order the same size as Alpha Centauri AB's Hill
radius in the galactic potential. We carry out a Monte Carlo simulation under
the assumption that the errors in the observed quantities are uncorrelated. In
this simulation, 44% of the trial systems are bound, and systems on the 1-3
sigma tail of the radial velocity distribution can have Proxima currently
located near the apastron position of its orbit. Our analysis shows that a
further, very significant improvement in the characterization of the system can
be gained by obtaining a more accurate measurement of the radial velocity of
Proxima Centauri.Comment: 10 pages total, 4 pages of text, 1 page of references, 3 figures, and
2 tables This article will be published in The Astronomical Journa
Seeing motion and apparent motion
In apparent motion experiments, participants are presented with what is in fact a succession of two brief stationary stimuli at two different locations, but they report an impression of movement. Philosophers have recently debated whether apparent motion provides evidence in favour of a particular account of the nature of temporal experience. I argue that the existing discussion in this area is premised on a mistaken view of the phenomenology of apparent motion and, as a result, the space of possible philosophical positions has not yet been fully explored. In particular, I argue that the existence of apparent motion is compatible with an account of the nature of temporal experience that involves a version of direct realism. In doing so, I also argue against two other claims often made about apparent motion, viz. that apparent motion is the psychological phenomenon that underlies motion experience in the cinema, and that apparent motion is subjectively indistinguishable from real motion
Principles for allocation of scarce medical interventions
Allocation of very scarce medical interventions such as organs and vaccines is a persistent ethical challenge. We evaluate eight simple allocation principles that can be classiïŹed into four categories: treating people equally, favouring the worst-oïŹ, maximising total beneïŹts, and promoting and rewarding social usefulness. No single principle is suïŹcient to incorporate all morally relevant considerations and therefore individual principles must be combined into multiprinciple allocation systems. We evaluate three systems: the United Network for Organ Sharing points systems, quality-adjusted life-years, and disability-adjusted life-years. We recommend an alternative systemâthe complete lives systemâwhich prioritises younger people who have not yet lived a complete life, and also incorporates prognosis, save the most lives, lottery, and instrumental value principle
G 112-29 (=NLTT 18149), a Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity and Common Age
We have made a search for common proper motion (CPM) companions to the wide
binaries in the solar vicinity. We found that the binary GJ 282AB has a very
distant CPM companion (NLTT 18149) at a separation s=1.09 \arcdeg. Improved
spectral types and radial velocities are obtained, and ages determined for the
three components. The Hipparcos trigonometric parallaxes and the new radial
velocities and ages turn out to be very similar for the three stars, and
provide strong evidence that they form a physical system. At a projected
separation of 55733AU from GJ 282AB, NLTT 18149 ranks among the widest physical
companions known.Comment: 13 pages, 3 figures, submmited to Ap
Standing by our principles: Meaningful guidance, moral foundations, and multi-principle methodology in medical scarcity
Background
Several quantitative surveys have been conducted internationally to gather empirical information about physiciansâ general attitudes towards health care rationing. Are physicians ready to accept and implement rationing, or are they rather reluctant? Do they prefer implicit bedside rationing that allows the physicianâpatient relationship broad leeway in individual decisions? Or do physicians prefer strategies that apply explicit criteria and rules? Objectives
To analyse the range of survey findings on rationing. To discuss differences in response patterns. To provide recommendations for the enhancement of transparency and systematic conduct in reviewing survey literature. Methods
A systematic search was performed for all English and non-English language references using CINAHL, EMBASE, and MEDLINE. Three blinded experts independently evaluated title and abstract of each reference. Survey items were extracted that match with: (i) willingness to ration health care or (ii) preferences for different rationing strategies. Results
16 studies were eventually included in the systematic review. Percentages of respondents willing to accept rationing ranged from 94% to 9%. Conclusions
The conflicting findings among studies illustrate important ambivalence in physicians that has several implications for health policy. Moreover, this review highlights the importance to interpret survey findings in context of the results of all previous relevant studies
A Spitzer IRAC Imaging Survey for T Dwarf Companions Around M, L, and T Dwarfs: Observations, Results, and Monte Carlo Population Analyses
We report observational techniques, results, and Monte Carlo population
analyses from a Spitzer Infrared Array Camera imaging survey for substellar
companions to 117 nearby M, L, and T dwarf systems (median distance of 10 pc,
mass range of 0.6 to \sim0.05 M\odot). The two-epoch survey achieves typical
detection sensitivities to substellar companions of [4.5 {\mu}m] \leq 17.2 mag
for angular separations between about 7" and 165". Based on common proper
motion analysis, we find no evidence for new substellar companions. Using Monte
Carlo orbital simulations (assuming random inclination, random eccentricity,
and random longitude of pericenter), we conclude that the observational
sensitivities translate to an ability to detect 600-1100K brown dwarf
companions at semimajor axes greater than ~35 AU, and to detect 500-600K
companions at semimajor axes greater than ~60 AU. The simulations also estimate
a 600-1100K T dwarf companion fraction of < 3.4% for 35-1200 AU separations,
and < 12.4% for the 500-600K companions, for 60-1000 AU separations.Comment: 35 pages, 6 figure
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