1,149 research outputs found
Conditional strategies and the evolution of cooperation in spatial public goods games
The fact that individuals will most likely behave differently in different
situations begets the introduction of conditional strategies. Inspired by this,
we study the evolution of cooperation in the spatial public goods game, where
besides unconditional cooperators and defectors, also different types of
conditional cooperators compete for space. Conditional cooperators will
contribute to the public good only if other players within the group are likely
to cooperate as well, but will withhold their contribution otherwise. Depending
on the number of other cooperators that are required to elicit cooperation of a
conditional cooperator, the latter can be classified in as many types as there
are players within each group. We find that the most cautious cooperators, such
that require all other players within a group to be conditional cooperators,
are the undisputed victors of the evolutionary process, even at very low
synergy factors. We show that the remarkable promotion of cooperation is due
primarily to the spontaneous emergence of quarantining of defectors, which
become surrounded by conditional cooperators and are forced into isolated
convex "bubbles" from where they are unable to exploit the public good. This
phenomenon can be observed only in structured populations, thus adding to the
relevance of pattern formation for the successful evolution of cooperation.Comment: 7 two-column pages, 7 figures; accepted for publication in Physical
Review
Note and Comment
The Law School; Pleading Estoppel; Libels on Person and on Property; The Conflict Between a Patentee\u27s Right to Monopoly and a State Anti-Monopoly Statut
Dynamical charge and spin density wave scattering in cuprate superconductor
We show that a variety of spectral features in high-T_c cuprates can be
understood from the coupling of charge carriers to some kind of dynamical order
which we exemplify in terms of fluctuating charge and spin density waves. Two
theoretical models are investigated which capture different aspects of such
dynamical scattering. The first approach leaves the ground state in the
disordered phase but couples the electrons to bosonic degrees of freedom,
corresponding to the quasi singular scattering associated with the closeness to
an ordered phase. The second, more phenomological approach starts from the
construction of a frequency dependent order parameter which vanishes for small
energies. Both theories capture scanning tunneling microscopy and angle-resoved
photoemission experiments which suggest the protection of quasiparticles close
to the Fermi energy but the manifestation of long-range order at higher
frequencies.Comment: 27 pages, 13 figures, to appear in New J. Phy
A Two-Player Game of Life
We present a new extension of Conway's game of life for two players, which we
call p2life. P2life allows one of two types of token, black or white, to
inhabit a cell, and adds competitive elements into the birth and survival rules
of the original game. We solve the mean-field equation for p2life and determine
by simulation that the asymptotic density of p2life approaches 0.0362.Comment: 7 pages, 3 figure
Altered expression of the DNA repair protein, N-methylpurine-DNA glycosylase (MPG), in breast cancer
AbstractWe examined expression of N-methylpurine-DNA glycosylase (MPG), a DNA repair enzyme that removes N-alkylpurine damage, in normal, malignant, and immortalized breast epithelial cells, and breast cancer cell lines (MDA-MB-231, MCF7, T47D). Northern analysis showed increased expression in cancer versus normal breast epithelial cells (2–24-fold). Southern blots revealed no gene amplification or polymorphisms. Immunofluorescence, immunohistochemistry, and Western blot analysis demonstrated increased MPG protein expression in the tumor cells that correlated with elevated glycosylase activity. Since MPG overexpression has been shown to be paradoxically associated with increased susceptibility to DNA damage, up-regulation of this gene may suggest a functional role in breast carcinogenesis
Note and Comment
Civil Liability for False Testimony; Review by the Courts of the Decisions of the Land Department; Right of One Partner to Sue His Co-Partners in Conversion; Does a Tax Deed, Void on it Face, Give Color of Title; Interference With Employment by Trade Union
A Fluid Dynamics Calculation of Sputtering from a Cylindrical Thermal Spike
The sputtering yield, Y, from a cylindrical thermal spike is calculated using
a two dimensional fluid dynamics model which includes the transport of energy,
momentum and mass. The results show that the high pressure built-up within the
spike causes the hot core to perform a rapid expansion both laterally and
upwards. This expansion appears to play a significant role in the sputtering
process. It is responsible for the ejection of mass from the surface and causes
fast cooling of the cascade. The competition between these effects accounts for
the nearly linear dependence of with the deposited energy per unit depth
that was observed in recent Molecular Dynamics simulations. Based on this we
describe the conditions for attaining a linear yield at high excitation
densities and give a simple model for this yield.Comment: 10 pages, 9 pages (including 9 figures), submitted to PR
Renormalization Group Analysis of a Noisy Kuramoto-Sivashinsky Equation
We have analyzed the Kuramoto-Sivashinsky equation with a stochastic noise
term through a dynamic renormalization group calculation. For a system in which
the lattice spacing is smaller than the typical wavelength of the linear
instability occurring in the system, the large-distance and long-time behavior
of this equation is the same as for the Kardar-Parisi-Zhang equation in one and
two spatial dimensions. For the case the agreement is only qualitative.
On the other hand, when coarse-graining on larger scales the asymptotic flow
depends on the initial values of the parameters.Comment: 8 pages, 5 figures, revte
Coulomb Explosion and Thermal Spikes
A fast ion penetrating a solid creates a track of excitations. This can
produce displacements seen as an etched track, a process initially used to
detect energetic particles but now used to alter materials. From the seminal
papers by Fleischer et al. [Phys. Rev. 156, 353 (1967)] to the present [C.
Trautmann, S. Klaumunzer and H. Trinkaus, Phys. Rev. Lett. 85, 3648 (2000)],
`Coulomb explosion' and thermal spike models are treated as conflicting models
for describing ion track effects. Here molecular dynamics simulations of
electronic-sputtering, a surface manifestation of ion track formation, show
that `Coulomb explosion' produces a `heat' spike so that these are early and
late aspects of the same process. Therefore, differences in scaling are due to
the use of incomplete spike models.Comment: Submitted to PRL. 4 pages, 3 figures. For related movies see:
http://dirac.ms.virginia.edu/~emb3t/coulomb/coulomb.html PACS added in new
versio
Current Noise in ac-Driven Nanoscale Conductors
The theory for current fluctuations in ac-driven transport through nanoscale
systems is put forward. By use of a generalized, non-Hermitian Floquet theory
we derive novel explicit expressions for the time-averaged current and the
zero-frequency component of the power spectrum of current fluctuations. A
distinct suppression of both the zero-frequency noise and the dc-current occurs
for suitably tailored ac-fields. The relative level of transport noise, being
characterized by a Fano factor, can selectively be manipulated by ac-sources;
in particular, it exhibits both characteristic maxima and minima near current
suppression.Comment: 4 pages, 2 figure
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