The organization and control of an evolving interdependent population

Starting with Darwin, biologists have asked how populations evolve from a low fitness state that is evolutionarily stable to a high fitness state that is not. Specifically of interest is the emergence of cooperation and multicellularity where the fitness of individuals often appears in conflict with that of the population. Theories of social evolution and evolutionary game theory have produced a number of fruitful results employing two-state two-body frameworks. In this study, we depart from this tradition and instead consider a multi-player, multi-state evolutionary game, in which the fitness of an agent is determined by its relationship to an arbitrary number of other agents. We show that populations organize themselves in one of four distinct phases of interdependence depending on one parameter, selection strength. Some of these phases involve the formation of specialized large-scale structures. We then describe how the evolution of independence can be manipulated through various external perturbations.     

掺硫硒化镓晶体在太赫兹波段的光学特性

利用太赫兹时域光谱技术测量了掺硫硒化镓(GaSe1-xSx)晶体在太赫兹波段的光学参数,包括折射系数、吸收系数等.使用自由空间电光取样法获得了太赫兹电磁波的脉冲波形.对不同硫掺杂量的硒化镓晶体进行了研究,在硫的掺杂量为0,0.01,0.14,0.26,0.37时,在0.2-2.0THz测得了GaSe1.S.的折射系数、...     

Energy and environment : Nordic energy scenarios for 2010 and 2030

The concept of a sustainable energy sector has received wide attention since the publication of the Brundtland Report in 1987. This paper analyses the possibilities of establishing by 2010 and 2030 an energy system in the Nordic countries which prevents the critical loads of NO_x and SO₂ respectively on the most vulnerable Nordic ecological systems being exceeded. In addition, the present concentration of CO₂ in the atmosphere should not be significantly exceeded within a time horizon to around 2050. Different scenarios have been investigated in order to analyse the scope for attaining such a sustainable energy development within the limits of existing technologies and known potentials of renewable energy sources. Data on the technologies are available in a special catalogue.     

Dielectric and piezoelectric properties of PbFe1/2Nb1/2O3-PbTiO3 ceramics from the morphotropic phase boundary compositional range

Dielectric, X-ray, and piezoelectric studies of highly-resistive Li-doped (1-x)PbFe(1/2)Nb(1/2)O(3)-(x)PbTiO(3) (PFN-xPT) ceramics from the 0 ≤ x ≤ 0.2 range fabricated by solid-state synthesis and usual sintering have been carried out. Distinct anomalies of dielectric and piezoelectric parameters, corresponding to the transition between rhombohedral (monoclinic) and tetragonal ferroelectric phases, have been observed in pure PFN and PFN-xPT compositions with PbTiO(3) content up to 8 mol.%. The x,T-phase diagram of the PFN-xPT solid solution system has been constructed using these data.     

Redox doping behaviour of poly(3,4-ethylenedithiothiophene) - The counterion effect

Poly(3,4-ethylenedithiothiophene) - PEDTT, an alkylene sulphur derivative of PEDOT, presents itself as an interesting polymer with a number of disparate redox and chromic properties compared to its close analogue - PEDOT. In this study we present the results of an investigation into the electrochemical doping process of PEDTT, using four different electrolyte solutions, differing in anion content of the chosen salt. The results show that the anion identity plays a key role in the redox reactions accompanying these processes in what could be interpreted as anion ionochromism. In situ UV-Vis spectroelectrochemical experiments reveal an intriguing double electrochromic transition of PEDTT films during their oxidative doping, going from golden-yellow through green to pomegranate - a quality not so common within the family of electroactive conjugated polymers. The evolution of each UV-Vis spectrum over a potential range indicates that different redox states of the polymer are responsible for the chromatic changes. In the reduction half-cycle, the dedoping process of PEDTT appears to follow a path dissimilar to the p-doping one, featuring only one, direct electrochromic transition of the film’s colour, bypassing the green state, and a distinct two-step bleaching process of doping-induced charge carrier bands. The observed electrochemical and spectral phenomena have been accredited to the specific redox behaviour of doping-induced radical cation and cationic defect states interacting with the dithioalkylene sulphur atom.