5,711 research outputs found
Imperfect Imitation Can Enhance Cooperation
The promotion of cooperation on spatial lattices is an important issue in
evolutionary game theory. This effect clearly depends on the update rule: it
diminishes with stochastic imitative rules whereas it increases with
unconditional imitation. To study the transition between both regimes, we
propose a new evolutionary rule, which stochastically combines unconditional
imitation with another imitative rule. We find that, surprinsingly, in many
social dilemmas this rule yields higher cooperative levels than any of the two
original ones. This nontrivial effect occurs because the basic rules induce a
separation of timescales in the microscopic processes at cluster interfaces.
The result is robust in the space of 2x2 symmetric games, on regular lattices
and on scale-free networks.Comment: 4 pages, 4 figure
Unitary chiral dynamics in decays into and the role of the scalar mesons
We make a theoretical study of the \J decays into ,
, and using the techniques of
the chiral unitary approach stressing the important role of the scalar
resonances dynamically generated through the final state interaction of the two
pseudoscalar mesons. We also discuss the importance of new mechanisms with
intermediate exchange of vector and axial-vector mesons and the role played by
the OZI rule in the \J\phi\pi\pi vertex, quantifying its effects. The results
nicely reproduce the experimental data for the invariant mass distributions in
all the channels considered.Comment: Prepared for the 10th International Symposium on Meson-Nucleon
Physics and the Structure of the Nucleo
How and when can one identify hadronic molecules in the baryon spectrum
A method to identify hadronic molecules in the particle spectrum is reviewed
and the conditions for its applicability discussed. Special emphasis is put on
the discussion of molecule candidates in the baryon spectrum.Comment: Talk presentent at NSTAR 2007, 5 - 8 September 2007, Bonn, German
Second--order equation of state with the Skyrme interaction. Cutoff and dimensional regularization with the inclusion of rearrangement terms
We evaluate the second--order (beyond--mean--field) contribution to the
equation of state of nuclear matter with the effective Skyrme force and use
cutoff and dimensional regularizations to treat the ultraviolet divergence
produced by the zero--range character of this interaction. An adjustment of the
force parameters is then performed in both cases to remove any double counting
generated by the explicit computation of beyond--mean--field corrections with
the Skyrme force. In addition, we include at second order the rearrangement
terms associated to the density--dependent part of the Skyrme force and discuss
their effect. Sets of parameters are proposed to define new effective forces
which are specially designed for second--order calculations in nuclear matter.Comment: 29 figures, 9 table
Spin injection from EuS/Co multilayers into GaAs detected by polarized electroluminescence
We report on the successful spin injection from EuS/Co multilayers into (100) GaAs at low temperatures. The spin injection was verified by means of polarized electroluminescence (EL) emitted from AlGaAs/GaAs-based spin-light-emitting diodes in zero external magnetic field. Spin-polarized electrons were injected from prototype EuS/Co spin injector multilayers. The use of semiconducting and ferromagnetic EuS circumvents the impedance mismatch. The EL was measured in side emission with and without an external magnetic field. A circular polarization of 5% at 8 K and 0 T was observed. In view of the rather rough interface between the GaAs substrate and first EuS layer, improvement of the interface quality is expected to considerably enhance the injected electron spin polarization
Calorimetric Study Of Intercalation Of N-alkyldiamines Into α-titanium Hydrogenphosphate
A series of n-alkyldiamines of general formula H2N(CH2)nNH2 (n = 2-9) has been intercalated into the crystalline lamellar compound α-Ti(HPO4)2·H2O (TiP) from aqueous solution. The amount intercalated was followed batchwise at 298 ± 1 K and the variation of the original interlayer distance for TiP (756 pm) was followed by X-ray powder diffraction. Linear correlations with good fits were obtained for the interlamellar distance (d) or for the number of moles intercalated (nint) as a function of the number of carbon atoms in the aliphatic chain (nc): d =(883.14 ± 12.76) + (108.51 ± 2.20)nc and nint =(5.79 ± 0.12) - (0.28 ± 0.02)nc. The exothermic enthalpies for the intercalation are related to the monomolecular layer arrangement with a longitudinal axis inclined by 58° to the inorganic sheets. The enthalpies for the overall reaction 2O3P-OH(c) + H2N(CH2)nNH2(c, l) = O3P - O-+H3N(CH2)nNH3+-O - PO3(c); ΔintH, determined by reaction-solution calorimetry at 298.15 ± 0.02 K are correlated with the number of carbons in the aliphatic chain or the interlamellar distance, by the equations Δint H= -(56.16 ± 0.67)-(2.06 ± 0.12)nC and ΔintH = -(39.41 ± 1.41)-(1.80 × 10-2 ± 0.10 × 10-2)d. The enthalpic value for nc = 0 gave -56.17 ± 0.67 kJ mol-1 which corresponds to the intercalation of two moles of ammonium cation.61219631966Alberti, G., Galli, P.C., Costantino, U., Torracca, E., (1967) J. Inorg. Nucl. Chem., 29, p. 571Clearfield, A., (1982) Inorganic Ion Exchange Materials, , CRC Press, Boca Raton, FLSuárez, M., Garcia, J.R., Rodriguez, J., (1984) J. Phys. Chem., 88, p. 159Alberti, G., Casciola, M., Costantino, U., (1985) J. Colloid Interface Sci., 107, p. 25
Human behavior in Prisoner's Dilemma experiments suppresses network reciprocity
During the last few years, much research has been devoted to strategic
interactions on complex networks. In this context, the Prisoner's Dilemma has
become a paradigmatic model, and it has been established that imitative
evolutionary dynamics lead to very different outcomes depending on the details
of the network. We here report that when one takes into account the real
behavior of people observed in the experiments, both at the mean-field level
and on utterly different networks the observed level of cooperation is the
same. We thus show that when human subjects interact in an heterogeneous mix
including cooperators, defectors and moody conditional cooperators, the
structure of the population does not promote or inhibit cooperation with
respect to a well mixed population.Comment: 5 Pages including 4 figures. Submitted for publicatio
GRAMMATICAL COMPETENCE LEVEL AND GRAMMAR LEARNING STRATEGY OF PRE-SERVICE TEACHERS
This study attempted to determine the grammar learning strategy and grammatical competence level of the 2nd year and 3rd year pre-service teachers. Additionally, this study aimed to investigate the relationship between their grammar learning strategy usage and grammatical competence level. To this end, the study employed the descriptive-correlational research method. Data were collected through a questionnaire facilitated in Google Forms. The study's results revealed that, first, the pre-service teachers have highly used the Grammar Learning Strategies in general and when categorized as Cognitive, Meta-cognitive, and Socio-affective; although all GLS categories were highly used, the one with the highest mean was the Cognitive GLS while the least was the Socio-affective GLS. Second, respondents were found to have a fair level of grammatical competence in general as well as when specified to Subject-Verb Agreement, Pronoun-Antecedent Agreement, Parts of Speech, and Adjective-Adverb Agreement. Lastly, it was found in this present study that there is a highly significant relationship between grammar learning strategy usage and grammatical competence level but it is a weak positive correlation at 0.20. This outcome is conducive to better understand the pre-service teachers' GLS usage, to maximize the other GLS which were not highly used, and to supply some references for enhancing one’s grammatical competence level. Article visualizations
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