We show how networks modify the diffusion curve by affecting its symmetry. We demonstrate that a network's degree distribution has a significant impact on the contagion properties of the subsequent adoption process, and we propose a method for uncovering the degree distribution of the adopter network underlying the dissemination process, based exclusively on limited early-stage penetration data. In this paper we propose and empirically validate a unified network-based growth model that links network structure and penetration patterns. Specifically, using external sources of information, we confirm that each network degree distribution identified by the model matches the actual social network that is underlying the dissemination process. We also show empirically that the same method can be used to forecast adoption using an estimation of the degree distribution and the diffusion parameters at an early stage (15%) of the penetration process. We confirm that these forecasts are significantly superior to those of three benchmark models of diffusion. Our empirical analysis indicates that under heavily right-skewed degree distribution conditions (such as scale-free networks), the majority of adopters (in some cases, up to 75%) join the process after the sales peak. This strong asymmetry is a result of the unique interaction between the dissemination process and the degree distribution of its underlying network. ©2012 INFORMS.

Recognizing the interesting effects associated with deep centers in II-VI semiconductors, we reveal the recombination centers map in In-doped CdTe thin films by introducing a systematic and comprehensive phototransport spectroscopy method. The method is more reliable than previous phototransport methods as it is based on a stringent self-consistency of the temperature dependencies of four phototransport properties with a given model. This limits the number of scenarios and narrows the parameter space that can account for the experimental data. We suggest that the deep centers that can account for the data in the studied CdTe system lie both above and below the Fermi level, and that their special distribution can account for some of the "exotic" or "puzzling" phenomena observed in n -type CdTe. However, the main purpose of this work is to use the analysis of the In-doped CdTe system as a vehicle for a quantitative comprehensive test of the qualitative physical-analytic ideas of Rose that have guided numerous studies of phototransport in semiconductors. Introducing here the concept of the "center of gravity" of the density of states distribution further extends these basic ideas. © 2010 The American Physical Society.

The stochastic spatially extended generalized Lotka-Volterra approach introduced in Economics: The Open-Access, Open-Assessment E-Journal (2009), http://www.economics-ejournal.org/economics/discussionpapers/2009-6, Applications of Simulation to Social Sciences, 2000, pp. 301-322 and The European Physical Journal B 62(4) (2008), 505-513, is extended to the study of interactions between economic sectors, countries and blocks. The theory predicts robustly in a very wide range of conditions systematic regularities in the growth rates evolution of various sub-systems. The J-curve phenomenon which was studied in Economics: The Open-Access, Open-Assessment E-Journal (2009), http://www.economics-ejournal.org/economics/discussionpapers/2009-6, is revisited and more empirical support is given to the theory. In particular to the connection between the economic minimum and the crossover of the new emergent leading sector with the old decaying one. We describe the 'Growth Alignment Effect' (GAE), it's theoretical basis and demonstrate it empirically for numerous cases in the inter-national and intra-national economies. The GAE is the concept that in steady state the growth rates of the GDP per capita of the various system components align. We differentiate the GAE predictions from the usual convergence or divergence conceptual framework. Further investigations of GAE and subsidiaries are suggested and possible uses are proposed. Due to it's simple and robust nature, the method can be used as a tool for economic decisions and policy making. © 2009 - IOS Press and the authors. All rights reserved.

We study the distinct effects of dark matter and dark energy on the future evolution of nearby large scale structures using constrained N-body simulations. We contrast a model of cold dark matter and a cosmological constant ($Łambda$CDM) with an open CDM (OCDM) model with the same matter density $Ømega$ m = 0.3 and the same Hubble constant h = 0.7. Already by the time the scale factor has increased by a factor of 6 (29 Gyr from now in $Łambda$CDM; 78 Gyr from now in OCDM) the comoving position of the Local Group is frozen. Well before that epoch the two most massive members of the Local Group, the Milky Way and Andromeda, will merge. However, as the expansion rates of the scale factor in the two models are different, the Local Group will be receding in physical coordinates from Virgo exponentially in a $Łambda$CDM model and at a roughly constant velocity in an OCDM model. More generally, in comoving coordinates the future large scale structure will look like a sharpened image of the present structure: the skeleton of the cosmic web will remain the same, but clusters will be more 'isolated' and the filaments will become thinner. This implies that the long-term fate of large scale structure as seen in comoving coordinates is determined primarily by the matter density. We conclude that although the $Łambda$CDM model is accelerating at present due to its dark energy component while the OCDM model is non-accelerating, their large scale structures in the future will look very similar in comoving coordinates. © IOP Publishing Ltd.

We report clear crystallite size dependencies of the transport and phototransport properties in solid-state ensembles of semiconductor quantum dots. By finding a Meyer-Neldel-like behavior for the former and by comparing the experimental results with computer simulations for the latter, we show that the above dependencies are associated with the quantum confined induced variation of the band gap in the individual dots. These findings go beyond the available knowledge of interparticle conduction mechanisms by providing a basis for the corresponding physical statistics of such quantum dot ensembles. © 2007 The American Physical Society.

We report a more detailed understanding of the thermal-quenching and sensitization processes in tetrahedrally bonded amorphous semiconductors. In particular we reveal in detail the effect of light soaking, in hydrogenated amorphous silicon (a-Si:H), on the shift of the recombination transition, from the dangling bonds to the valence band-tail states as the temperature is lowered. Our experimental observations and model simulations are shown to account for various results in the literature, explaining in detail how the charge neutrality condition determines the recombination process in a-Si:H. This, in turn, demonstrates for the first time that it is possible to deduce the three valence states of the dangling bonds only on the basis of the recombination processes implied by the phototransport observations.

We use the formalism of "maximum principle of Shannon's entropy" to derive the general power law distribution function, using what seems to be a reasonable physical assumption, namely, the demand of a constant mean "internal order" (Boltzmann entropy) of a complex, self-interacting, self-organized system. Since the Shannon entropy is equivalent to the Boltzmann's entropy under equilibrium, non-interacting conditions, we interpret this result as the complex system making use of its intra-interactions and its non-equilibrium in order to keep the equilibrium Boltzmann's entropy constant on the average, thus enabling it an advantage at surviving over less ordered systems, i.e., hinting towards an "Evolution of Structure". We then demonstrate the formalism using a toy model to explain the power laws observed in Cities' populations and show how Zipf's law comes out as a natural special point of the model. We also suggest further directions of theory. © 2003 Elsevier B.V. All rights reserved.

We have been able to determine the density of states map in the band gap of a semiconductor by the measurement of the phototransport properties of its majority and minority carriers. In particular we found that the carrier recombination in single-phase hydrogenated microcrystalline silicon ($μ$c-Si:H) is significantly different from the one in hydrogenated amorphous silicon (a-Si:H) and that it is controlled only by its two band tails. Th e comparison of the observed temperature dependence of the phototransport properties of this material with model simulations further suggests that, while the conduction-band tail has an exponential distribution of states, the valence-band-tail states have a Gaussian-like distribution. This, in turn, meets the challenge of the determination of the analytical shape of the density of states distribution from experimental data. Our experimental procedure implies then that this distribution is associated with the route through which the transport and phototransport take place and thus we conclude that both the recombination and transport in undoped single-phase $μ$c-Si:H take place in the disordered layer that wraps the crystallites. We further conclude that, from the transport and phototransport points of view, the single-phase $μ$c-Si:H is, in general, different from both polycrystalline silicon and a-Si:H. The polycrystalline-silicon-like behavior, when found, appears to be an asymptotic case in which the crystallites are large enough, while the a-Si:H behavior prevails only when there is a significant content of its phase within the system.