Topological Line Defects around Graphene Nanopores for DNA Sequencing

Topological line defects in graphene represent an ideal way to produce highly controlled structures with reduced dimensionality that can be used in electronic devices. In this work we propose using extended line defects in graphene to improve nucleobase selectivity in nanopore-based DNA sequencing devices. We use a combination of QM/MM and non-equilibrium Green's functions methods to investigate the conductance modulation, fully accounting for solvent effects. By sampling over a large number of different orientations generated from molecular dynamics simulations, we theoretically demonstrate that distinguishing between the four nucleobases using line defects in a graphene-based electronic device appears possible. The changes in conductance are associated with transport across specific molecular states near the Fermi level and their coupling to the pore. Through the application of a specifically tuned gate voltage, such a device would be able to discriminate the four types of nucleobases more reliably than that of graphene sensors without topological line defects.Comment: 6 figures and 6 page

Composição físico-química de vinhos Riesling Itálico da Serra Gaúcha.

O Riesling Itálico é um dos cultivares Vitis vinifera brancos mais importantes da Serra Gaúcha, RS. Nessa região, ele adquiriu notoriedade a partir da década de 1970, quando foi incentivada sua utilização para elaboração de vinhos brancos varietais e como vinho base para espumante. Por isso, o objetivo deste trabalho foi avaliar a composição físico-química desses vinhos visando à formação de um banco de dados, à determinação de sua identidade varietal e à caracterização regional. Foram analisados 65 vinhos, safras 2002 a 2004, elaborados por 28 vinícolas. As determinações clássicas foram efetuadas por métodos físico-químicos; os compostos voláteis, por cromatogra$a gasosa; e os elementos minerais, exceção ao P, por espectrofotometria de absorção atômica. Os resultados mostram que os vinhos Riesling Itálico enquadraram-se nos limites estabelecidos pela legislação brasileira. Foram observados valores baixos de extrato seco, extrato seco reduzido, prolina, densidade ótica a 420 nm, acidez volátil, aldeído acético e acetato de etila; médios de álcool, pH, soma dos alcoóis superiores e Mg; e elevados, da relação álcool em peso/extrato seco reduzido e dos minerais K, Ca e P

Measuring a Light Neutralino Mass at the ILC: Testing the MSSM Neutralino Cold Dark Matter Model

The LEP experiments give a lower bound on the neutralino mass of about 46 GeV which, however, relies on a supersymmetric grand unification relation. Dropping this assumption, the experimental lower bound on the neutralino mass vanishes completely. Recent analyses suggest, however, that in the minimal supersymmetric standard model (MSSM), a light neutralino dark matter candidate has a lower bound on its mass of about 7 GeV. In light of this, we investigate the mass sensitivity at the ILC for very light neutralinos. We study slepton pair production, followed by the decay of the sleptons to a lepton and the lightest neutralino. We find that the mass measurement accuracy for a few-GeV neutralino is around 2 GeV, or even less if the relevant slepton is sufficiently light. We thus conclude that the ILC can help verify or falsify the MSSM neutralino cold dark matter model even for very light neutralinos.Comment: 7 pages, 1 figure; references adde

Do current WIMP direct measurements constrain light relic neutralinos?

New upper bounds on direct detection rates have recently been presented by a number of experimental collaborations working on searches for WIMPs. In this paper we analyze how the constraints on relic neutralinos which can be derived from these results is affected by the uncertainties in the distribution function of WIMPs in the halo. Various different categories of velocity distribution functions are considered, and the ensuing implications for supersymmetric configurations derived. We conservatively conclude that current experimental data do not constrain neutralinos of small mass (below 50 GeV).Comment: 9 pages, 7 figures, typeset with ReVTeX4. The paper may also be found at http://www.to.infn.it/~fornengo/papers/constraints05.ps.gz or through http://www.astroparticle.to.infn.it/index.htm