Ground-state of graphene in the presence of random charged impurities

We calculate the carrier density dependent ground state properties of graphene in the presence of random charged impurities in the substrate taking into account disorder and interaction effects non-perturbatively on an equal footing in a self-consistent theoretical formalism. We provide detailed quantitative results on the dependence of the disorder-induced spatially inhomogeneous two-dimensional carrier density distribution on the external gate bias, the impurity density, and the impurity location. We find that the interplay between disorder and interaction is strong, particularly at lower impurity densities. We show that for the currently available typical graphene samples, inhomogeneity dominates graphene physics at low ($\lesssim 10^{12}$ cm$^{-2}$) carrier density with the density fluctuations becoming larger than the average density.Comment: Final version, accepted for publication in Phys. Rev. Let

Effective use of product quality information in meat processing

This paper presents a case study on use of advanced product quality information in meat processing. To serve segmented customer demand meat processors consider use of innovative sensor technology to sort meat products to customer orders. To assess the use of this sensor technology a discrete-event simulation model is built. Various scenarios were defined for processing strategy (buffered or non-buffered), the number of end product groups to sort to and the availability of product quality information. The performance of these scenarios is measured w.r.t. order compliance, labor consumption and throughput-time. Our results reveal that the current processing and product sorting strategy is in-effective for sorting to a large number of end product groups. Furthermore, the current availability of product quality information is insufficient to ensure high levels of order compliance for advanced product quality products

Individual Attitudes Towards Others, Misanthropy Analysis in a Cross-Country Perspective

In general, misanthropy has been analyzed taking into account residents of one country and just comparing results. Instead of doing that, we employ 2004 International Social Survey Program and analyze its determinants in a cross-country model taking into account both individual characteristics and country effects. Our model shows, as expected, that misanthropy could be explained by some sociodemographic and economic individual characteristics. For instance, being a woman, having a university degree, being married lowers misanthropy while being young; having a low income, having no political preferences, being self-employed makes people more misanthropic. Moreover, in order to capture fix effects, we included (dummies) variables per country of residence and almost all of them result significant in determining misanthropy. This last result indicates that not only individual characteristics matters but also some factors regarding context also play a significant role. Finally, we show that there is a strong relationship among our misanthropy ranking of countries and two corruption perception rankings.misanthropy, trust, cross-country research, individual attitudes

The perception of corruption in a cross-country perspective: Why are some individuals more perceptive than others?

The concept of corruption varies widely depending on societies and people. We expect that context influences on corruption perception. Previous studies shed light on the incidence of individual characteristics on the perceived level of corruption and show the effect of country of residence. In order to extend this previous research, the aim of this paper is to analyze how context, culture and/ or history shape corruption perception considering specific country characteristics. The data source is the module on Citizenship of the 2004 International Social Survey Program (ISSP). Taking into account some subsamples (considering country characteristics such us: size, European Union membership, etc.), we estimate ordered probit models. We find that the incidence of country of residence remains even when we consider countries with some characteristic in common.corruption, microeconomic behavior, comparative research, public opinion, ISSP

Signatures of Klein tunneling in disordered graphene p-n-p junctions

We present a method for obtaining quantum transport properties in graphene that uniquely combines three crucial features: microscopic treatment of charge disorder, fully quantum mechanical analysis of transport, and the ability to model experimentally relevant system sizes. As a pertinent application we study the disorder dependence of Klein tunneling dominated transport in p-n-p junctions. Both the resistance and the Fano factor show broad resonance peaks due to the presence of quasi bound states. This feature is washed out by the disorder when the mean free path becomes of the order of the distance between the two p-n interfaces.Comment: 4 pages, 4 figure

Coherent phenomena in semiconductors

A review of coherent phenomena in photoexcited semiconductors is presented. In particular, two classes of phenomena are considered: On the one hand the role played by optically-induced phase coherence in the ultrafast spectroscopy of semiconductors; On the other hand the Coulomb-induced effects on the coherent optical response of low-dimensional structures. All the phenomena discussed in the paper are analyzed in terms of a theoretical framework based on the density-matrix formalism. Due to its generality, this quantum-kinetic approach allows a realistic description of coherent as well as incoherent, i.e. phase-breaking, processes, thus providing quantitative information on the coupled ---coherent vs. incoherent--- carrier dynamics in photoexcited semiconductors. The primary goal of the paper is to discuss the concept of quantum-mechanical phase coherence as well as its relevance and implications on semiconductor physics and technology. In particular, we will discuss the dominant role played by optically induced phase coherence on the process of carrier photogeneration and relaxation in bulk systems. We will then review typical field-induced coherent phenomena in semiconductor superlattices such as Bloch oscillations and Wannier-Stark localization. Finally, we will discuss the dominant role played by Coulomb correlation on the linear and non-linear optical spectra of realistic quantum-wire structures.Comment: Topical review in Semiconductor Science and Technology (in press) (Some of the figures are not available in electronic form