470 research outputs found
Mortality and immortality : the Nobel Prize as an experiment into the effect of status upon longevity
It has been known for centuries that the rich and famous have longer lives than the poor and ordinary. Causality, however, remains trenchantly debated. The ideal experiment
would be one in which extra status could somehow be dropped upon a sub-sample of individuals while those in a control group of comparable individuals received none. This
paper attempts to formulate a test in that spirit. It collects 19th-century birth data on science Nobel Prize winners. Correcting for potential biases, we estimate that winning the Prize, compared to merely being nominated, is associated with between 1 and 2 years of extra longevity
Single-layer metal-on-metal islands driven by strong time-dependent forces
Non-linear transport properties of single-layer metal-on-metal islands driven
with strong static and time-dependent forces are studied. We apply a
semi-empirical lattice model and use master equation and kinetic Monte Carlo
simulation methods to compute observables such as the velocity and the
diffusion coefficient. Two types of time-dependent driving are considered: a
pulsed rotated field and an alternating field with a zero net force
(electrophoretic ratchet). Small islands up to 12 atoms were studied in detail
with the master equation method and larger ones with simulations. Results are
presented mainly for a parametrization of Cu on Cu(001) surface, which has been
the main system of interest in several previous studies. The main results are
that the pulsed field can increase the current in both diagonal and axis
direction when compared to static field, and there exists a current inversion
in the electrophoretic ratchet. Both of these phenomena are a consequence of
the coupling of the internal dynamics of the island with its transport. In
addition to the previously discovered "magic size" effect for islands in
equilibrium, a strong odd-even effect was found for islands driven far out of
equilibrium. Master equation computations revealed non-monotonous behavior for
the leading relaxation constant and effective Arrhenius parameters. Using cycle
optimization methods, typical island transport mechanisms are identified for
small islands.Comment: 39 pages, 20 figures, to appear in Phys. Rev. E [corrected typo of
the x-axis label in Fig. 6
Counting Lattice Animals in High Dimensions
We present an implementation of Redelemeier's algorithm for the enumeration
of lattice animals in high dimensional lattices. The implementation is lean and
fast enough to allow us to extend the existing tables of animal counts,
perimeter polynomials and series expansion coefficients in -dimensional
hypercubic lattices for . From the data we compute formulas
for perimeter polynomials for lattice animals of size in arbitrary
dimension . When amended by combinatorial arguments, the new data suffices
to yield explicit formulas for the number of lattice animals of size
and arbitrary . We also use the enumeration data to compute numerical
estimates for growth rates and exponents in high dimensions that agree very
well with Monte Carlo simulations and recent predictions from field theory.Comment: 18 pages, 7 figures, 6 tables; journal versio
Hypermatrix factors for string and membrane junctions
The adjoint representations of the Lie algebras of the classical groups
SU(n), SO(n), and Sp(n) are, respectively, tensor, antisymmetric, and symmetric
products of two vector spaces, and hence are matrix representations. We
consider the analogous products of three vector spaces and study when they
appear as summands in Lie algebra decompositions. The Z3-grading of the
exceptional Lie algebras provide such summands and provides representations of
classical groups on hypermatrices. The main natural application is a formal
study of three-junctions of strings and membranes. Generalizations are also
considered.Comment: 25 pages, 4 figures, presentation improved, minor correction
Variation in Prices Charged to Patients for Specialty Intraocular Lenses Inserted during Universally Covered Cataract Surgery
Patients often pay for specialty intraocular lenses (IOLs) for cataract surgery covered by universal insurance. This practice creates the potential for inequitable pricing where the medical service provider is also the retailer. We measured the variation in prices between cataract surgeons for the same IOL and associated testing.We telephoned every cataract surgeon in Ontario, Canada, and asked their price for the most common type of specialty IOL as a prospective patient. We measured the total prices quoted and variation between providers.We contacted 404 ophthalmologists. There were 256 that performed cataract surgery but 127 offered the most commonly employed specialty IOL and would provide a price to patients over the telephone. We obtained prices from all 127 ophthalmologists. Prices for the same lens and associated testing varied substantially between ophthalmologists from 2790 (median 528-$915). There was variation in all components of the total out-of-pocket price, including the price for the IOL itself, charges for uninsured eye measurements, and non-specific supplemental fees.Although cataract surgery is covered by public health insurance, some ophthalmologists charge much more than others for the same specialty IOL and associated testing. Greater access to price information and better regulatory control could help ensure patients receive fair value for out-of-pocket health expenses
Simulations of lattice animals and trees
The scaling behaviour of randomly branched polymers in a good solvent is
studied in two to nine dimensions, using as microscopic models lattice animals
and lattice trees on simple hypercubic lattices. As a stochastic sampling
method we use a biased sequential sampling algorithm with re-sampling, similar
to the pruned-enriched Rosenbluth method (PERM) used extensively for linear
polymers. Essentially we start simulating percolation clusters (either site or
bond), re-weigh them according to the animal (tree) ensemble, and prune or
branch the further growth according to a heuristic fitness function. In
contrast to previous applications of PERM, this fitness function is {\it not}
the weight with which the actual configuration would contribute to the
partition sum, but is closely related to it. We obtain high statistics of
animals with up to several thousand sites in all dimension 2 <= d <= 9. In
addition to the partition sum (number of different animals) we estimate
gyration radii and numbers of perimeter sites. In all dimensions we verify the
Parisi-Sourlas prediction, and we verify all exactly known critical exponents
in dimensions 2, 3, 4, and >= 8. In addition, we present the hitherto most
precise estimates for growth constants in d >= 3. For clusters with one site
attached to an attractive surface, we verify the superuniversality of the
cross-over exponent at the adsorption transition predicted by Janssen and
Lyssy. Finally, we discuss the collapse of animals and trees, arguing that our
present version of the algorithm is also efficient for some of the models
studied in this context, but showing that it is {\it not} very efficient for
the `classical' model for collapsing animals.Comment: 17 pages RevTeX, 29 figures include
Road Trauma in Teenage Male Youth with Childhood Disruptive Behavior Disorders: A Population Based Analysis
Donald Redelmeier and colleagues conducted a population-based case-control study of 16-19-year-old males hospitalized for road trauma or appendicitis and showed that disruptive behavior disorders explained a significant amount of road trauma in this group
What Economics of Shortage and The Socialist System have to say to the (Hungarian) readers today
Methods for specifying the target difference in a randomised controlled trial : the Difference ELicitation in TriAls (DELTA) systematic review
Peer reviewedPublisher PD
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