We study spatial correlation of donor charges in HgSe:Fe,Ga using a few simple quantities (mean electrostatic energy of various donor sites, fluctuations of the electrostatic potential).The study uses Monte Carlo simulation techniques.We are able to indicate general trends in the behavior of the correlation when proportion of correlating (Fe3+) and noncorrelating (Ga) charged centers in the sample is changed.
This project differentiates between communication that praises one's political in-group ( in-group praise), attacks the opposition ( out-group derogation), or focuses on policy details ( evidence based), testing their effects on network and attitude polarization. We begin with an agent-based model, which shows that congenial evidence-based exchanges polarize the network and the inclusion of identity-driven communications leads to greater polarization. Once out-group derogation reaches a certain threshold, the network of agents splits into two groups, yet the polarizing effects of in-group praise are yet stronger and emerge more rapidly (i.e., a lower threshold of in-group praise is needed to polarize the network). Using an experimental design on a sample of American partisans, we offer a partial validation of the model. In-group praise and out-group derogation polarize attitudes more than balanced evidence-based news, but not more than congenial evidence-based news. Identity-driven news also has no effects on affective polarization. This multidisciplinary evidence shows that the nature of political content matters.
Optically detected spin resonance was used to measure the effective g-value of electrons at the conduction band minimum in type-I quantum wells. The experiments showed that the spin resonance is induced by electric dipole transitions, and hence is not limited by the short carrier lifetime that renders magnetic dipole transitions impossible. The spin splittings obtained are strongly anisotropic and dependent on quantum well thickness. A calculation without adjustable parameters, using a three-band Kane model, agrees with the experimental data. The bulk effective g-value of used in this calculation was measured on a thick sample.
The composition dependence of the in-plane conduction band effective mass in strained 15-nm-thick lattice-mismatched Ga1−xInxAs/InP single quantum wells was determined by conventional cyclotron and optically detected cyclotron resonance techniques. Our results are in agreement with a self-consistent calculation taking into account effects due to nonparabolicity, confinement, strain, and finite two-dimensional carrier densities.
A variety of magnetotransport measurements have been performed on InSb-CdTe heterojunctions containing high mobility ( approximately 20000 cm2 V-1 s-1) two-dimensional electron gases (2DEGS) with low area carrier densities (Ns approximately 1.8-4.2*1011 cm-2). The experimental data have been compared with self-consistent calculations of the energy levels carried out using the 'three-band' model of narrow-gap semiconductors. The 2DEGS in the samples exhibit well resolved quantum Hall plateaux and Shubnikov-de Haas oscillations at temperatures below 5 K; using these data and the persistent photoconductivity (PPC) effect, the subband occupancies have been evaluated as functions of Ns. Parallel-field magnetoresistance measurements show that only two subbands are occupied, even at the highest carrier densities, and indicate the importance of intersubband scattering. The self-consistent calculations predict the number of occupied subbands correctly, and are in agreement with the experimental subband occupancies when the effects of a small amount of interdiffusion are taken into account. The low-field magnetoresistance of the heterojunctions is at first positive and then negative; this is characteristic of weak localization in the presence of spin-orbit scattering.
Based on an agent based model of opinion changes, described in detail in a recent paper (\arXiv:1507.00126), we attempt to predict, three months in advance, the range of possible results of the Polish parliamentary elections, scheduled for October 25, 2015. The model reproduces semi-quantitatively the poll results for the three parties which dominated the recent presidential elections and allows estimation of some variations of the electoral propaganda campaigns by the parties.
The work investigates the influence of leader on opinion formation in artificial networked societies. The strength of the social influence is assumed to be dictated by distance from one agent to another, as well as individual strengths of the agents. The leader is assumed to have much greater resources, which allows him to tune the way he influences the other agents. We study various strategies of using these resources to optimize the conditions needed to "convince" the whole society to leader's opinion. The flexibility of the model allows it to be used in studies of political, social and marketing activities and opinion formation.
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