2,028 research outputs found
Evolutionary game dynamics of controlled and automatic decision-making
We integrate dual-process theories of human cognition with evolutionary game
theory to study the evolution of automatic and controlled decision-making
processes. We introduce a model where agents who make decisions using either
automatic or controlled processing compete with each other for survival. Agents
using automatic processing act quickly and so are more likely to acquire
resources, but agents using controlled processing are better planners and so
make more effective use of the resources they have. Using the replicator
equation, we characterize the conditions under which automatic or controlled
agents dominate, when coexistence is possible, and when bistability occurs. We
then extend the replicator equation to consider feedback between the state of
the population and the environment. Under conditions where having a greater
proportion of controlled agents either enriches the environment or enhances the
competitive advantage of automatic agents, we find that limit cycles can occur,
leading to persistent oscillations in the population dynamics. Critically,
however, these limit cycles only emerge when feedback occurs on a sufficiently
long time scale. Our results shed light on the connection between evolution and
human cognition, and demonstrate necessary conditions for the rise and fall of
rationality.Comment: 9 pages, 7 figure
Three-portal technique for anterior cruciate ligament reconstruction: Use of a central medial portal
Standard endoscopic reconstruction of the anterior cruciate ligament (ACL) is performed with the use of 2 arthroscopic portals. The surgical error most commonly associated with ACL reconstruction is improper positioning of the tunnel. Errors in femoral tunnel position may be related to poor visualization of the lateral wall. When anatomic double-bundle ACL reconstruction is performed, proper visualization of the lateral wall is essential to ensure correct placement of both tunnels. We propose the use of a central portal, in addition to more standard anterolateral and anteromedial portals, to enhance visualization of the lateral wall. In addition, the arthroscope can be moved interchangeably throughout the portals during the procedure for improved viewing during specific steps. An accessory anteromedial portal placed inferiorly and medially allows placement of the femoral tunnels while providing a high central anteromedial portal for best visualization of the lateral wall. As a result, no notchplasty is required, and a more anatomic reconstruction can be performed
GW method with the self-consistent Sternheimer equation
We propose a novel approach to quasiparticle GW calculations which does not
require the computation of unoccupied electronic states. In our approach the
screened Coulomb interaction is evaluated by solving self-consistent
linear-response Sternheimer equations, and the noninteracting Green's function
is evaluated by solving inhomogeneous linear systems. The frequency-dependence
of the screened Coulomb interaction is explicitly taken into account. In order
to avoid the singularities of the screened Coulomb interaction the calculations
are performed along the imaginary axis, and the results are analytically
continued to the real axis through Pade' approximants. As a proof of concept we
implemented the proposed methodology within the empirical pseudopotential
formalism and we validated our implementation using silicon as a test case. We
examine the advantages and limitations of our method and describe promising
future directions.Comment: 18 pages, 6 figure
Doping effects on the electronic and structural properties of CoO2: An LSDA+U study
A systematic LSDA+U study of doping effects on the electronic and structural
properties of single layer CoO2 is presented. Undoped CoO2 is a charge transfer
insulator within LSDA+U and a metal with a high density of states (DOS) at the
Fermi level within LSDA. (CoO2), on the other hand, is a band
insulator with a gap of 2.2 eV. Systems with fractional doping are metals if no
charge orderings are present. Due to the strong interaction between the doped
electron and other correlated Co d electrons, the calculated electronic
structure of (CoO2) depends sensitively on the doping level x. Zone
center optical phonon energies are calculated under the frozen phonon
approximation and are in good agreement with measured values. Softening of the
phonon at doping x ~0.25 seems to indicate a strong electron-phonon
coupling in this system. Possible intemediate spin states of Co ions, Na
ordering, as well as magnetic and charge orderings in this system are also
discussed.Comment: 11 pages, 12 figure
Reply to "Comment on `First-principles calculation of the superconducting transition in MgB2 within the anisotropic Eliashberg formalism'"
The recent preprint by Mazin et al. [cond-mat/0212417] contains many
inappropriate evaluations and/or criticisms on our published work [Phys. Rev. B
66, 020513 (2002) and Nature 418, 758 (2002)]. The preprint
[cond-mat/0212417v1] was submitted to Physical Review B as a comment on one of
our papers [Phys. Rev. B 66, 020513 (2002)]. In the reviewing process, Mazin et
al. have withdrawn many of the statements contained in cond-mat/0212417v1,
however two claims remain in their revised manuscript [cond-mat/0212417v3]: (1)
the calculated variations of the superconducting energy gap within the sigma-
or the pi-bands are not observable in real samples due to scatterings, and (2)
the Coulomb repulsion mu(k,k') is negligibly small between sigma- and pi-states
and thus should be approximated by a diagonal 2 x 2 matrix in the sigma and pi
channels. Here, we point out that the former does not affect the validity of
our theoretical work which is for the clean limit, and that the latter is not
correct
Chinese scientists and US leadership in the life sciences
To the Editor — We, the undersigned,
are leaders in US academic and industrial
biomedical research and drug development.
We are concerned that recent actions by
government agencies and universities with
respect to Chinese scientists in the United
States could threaten US leadership in
biomedical science
Evolution of Lyman Alpha Galaxies: Stellar Populations at z ~ 0.3
We present the results of a stellar population analysis of 30 Lyman alpha
emitting galaxies (LAEs) at z ~ 0.3, previously discovered with the Galaxy
Evolution Explorer (GALEX). With a few exceptions, we can accurately fit model
spectral energy distributions to these objects, representing the first time
this has been done for a large sample of LAEs at z < 3, a gap of ~ 8 Gyr in the
history of the Universe. From the 26/30 LAEs which we can fit, we find an age
and stellar mass range of 200 Myr - 10 Gyr and 10^9 - 10^11 Msol, respectively.
These objects thus appear to be significantly older and more massive than LAEs
at high-redshift. We also find that these LAEs show a mild trend towards higher
metallicity than those at high redshift, as well as a tighter range of dust
attenuation and interstellar medium geometry. These results suggest that
low-redshift LAEs have evolved significantly from those at high redshift.Comment: Accepted for publication in the Astrophysical Journal. Replaced with
accepted version. Eight pages, four figures, in emulateapj forma
- …