512 research outputs found
Semiconductor resonator solitons above band gap
We show experimentally the existence of bright and dark spatial solitons in
semiconductor resonators for excitation above the band gap energy. These
solitons can be switched on, both spontaneously and with address pulses,
without the thermal delay found for solitons below the band gap which is
unfavorable for applications. The differences between soliton properties above
and below gap energy are discussed.Comment: 4 pages, 7 figure
Coupled Replicator Equations for the Dynamics of Learning in Multiagent Systems
Starting with a group of reinforcement-learning agents we derive coupled
replicator equations that describe the dynamics of collective learning in
multiagent systems. We show that, although agents model their environment in a
self-interested way without sharing knowledge, a game dynamics emerges
naturally through environment-mediated interactions. An application to
rock-scissors-paper game interactions shows that the collective learning
dynamics exhibits a diversity of competitive and cooperative behaviors. These
include quasiperiodicity, stable limit cycles, intermittency, and deterministic
chaos--behaviors that should be expected in heterogeneous multiagent systems
described by the general replicator equations we derive.Comment: 4 pages, 3 figures,
http://www.santafe.edu/projects/CompMech/papers/credlmas.html; updated
references, corrected typos, changed conten
An Evaluation of Body-grip Trap Trigger Configurations for Reducing River Otter Take Incidental to Beaver Trapping
River otter (Lontra canadensis) populations in North America have been the focus of significant restoration efforts. Wildlife management agencies, concerned about the unintentional take of river otters incidental to beaver (Castor canadensis) trapping, may recommend techniques to avoid capturing river otters. River otter avoidance techniques that are ineffective or diminish trap performance for beavers are undesirable. We conducted a field evaluation in 2015 and 2016 in Wisconsin to assess how two trigger configurations (offset and center) on body-grip traps would affect the incidental capture rate of river otters during beaver trapping. We also evaluated effects of each configuration on beaver capture rates, body lengths, and anatomical locations of trap-jaw strikes. We used size 330 body-grip traps equipped with identical triggers and alternated between trigger configurations during beaver damage management activities. We captured 8 river otters with each trap trigger configuration. Trap-jaw strikes on beavers differed between trigger configurations, with offset triggers resulting in more abdomen strikes and center triggers causing more cervical vertebrae strikes. We found that an offset trigger configuration did not reduce incidental take of otters and was less effective for trapping beavers
Fractional Generalization of Gradient Systems
We consider a fractional generalization of gradient systems. We use
differential forms and exterior derivatives of fractional orders. Examples of
fractional gradient systems are considered. We describe the stationary states
of these systems.Comment: 11 pages, LaTe
Random Field and Random Anisotropy Effects in Defect-Free Three-Dimensional XY Models
Monte Carlo simulations have been used to study a vortex-free XY ferromagnet
with a random field or a random anisotropy on simple cubic lattices. In the
random field case, which can be related to a charge-density wave pinned by
random point defects, it is found that long-range order is destroyed even for
weak randomness. In the random anisotropy case, which can be related to a
randomly pinned spin-density wave, the long-range order is not destroyed and
the correlation length is finite. In both cases there are many local minima of
the free energy separated by high entropy barriers. Our results for the random
field case are consistent with the existence of a Bragg glass phase of the type
discussed by Emig, Bogner and Nattermann.Comment: 10 pages, including 2 figures, extensively revise
Diffusion and viscosity in a supercooled polydisperse system
We have carried out extensive molecular dynamics simulations of a supercooled
polydisperse Lennard-Jones liquid with large variations in temperature at a
fixed pressure. The particles in the system are considered to be polydisperse
both in size and mass. The temperature dependence of the dynamical properties
such as the viscosity () and the self-diffusion coefficients () of
different size particles is studied. Both viscosity and diffusion coefficients
show super-Arrhenius temperature dependence and fit well to the well-known
Vogel-Fulcher-Tammann (VFT) equation. Within the temperature range
investigated, the value of the Angell's fragility parameter (D )
classifies the present system into a strongly fragile liquid. The critical
temperature for diffusion () increases with the size of the
particles. The critical temperature for viscosity () is larger than
that for the diffusion and a sizeable deviations appear for the smaller size
particles implying a decoupling of translational diffusion from viscosity in
deeply supercooled liquid. Indeed, the diffusion shows markedly non-Stokesian
behavior at low temperatures where a highly nonlinear dependence on size is
observed. An inspection of the trajectories of the particles shows that at low
temperatures the motions of both the smallest and largest size particles are
discontinuous (jump-type). However, the crossover from continuous Brownian to
large length hopping motion takes place at shorter time scales for the smaller
size particles.Comment: Revtex4, 7 pages, 8 figure
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Participation in medical decision-making across Europe: an international longitudinal multicenter study
Background: The purpose of this paper was to examine national differences in the desire to participate in decision-making of people with severe mental illness in six European countries.
Methods: The data was taken from a European longitudinal observational study (CEDAR; ISRCTN75841675). A sample of 514 patients with severe mental illness from the study centers in Ulm, Germany, London, England, Naples, Italy, Debrecen, Hungary, Aalborg, Denmark and Zurich, Switzerland were assessed as to desire to participate in medical decision-making. Associations between desire for participation in decision-making and center location were analyzed with generalized estimating equations.
Results: We found large cross-national differences in patients’ desire to participate in decision-making, with the center explaining 40% of total variance in the desire for participation (p<0.001). Averaged over time and independent of patient characteristics, London (mean=2.27), Ulm (mean=2.13) and Zurich (mean=2.14) showed significantly higher scores in desire for participation, followed by Aalborg (mean=1.97), where scores were in turn significantly higher than in Debrecen (mean=1.56). The lowest scores were reported in Naples (mean=1.14). Over time, desire for participation in decision-making increased significantly in Zurich (b=0.23) and decreased in Naples (b=-0.14). In all other centers, values remained stable.
Conclusions: This study demonstrates that patients’ desire for participation in decisionmaking varies by location. We suggest that more research attention be focused on identifying specific cultural and social factors in each country to further explain observed differences across Europe
- …