Trypanosomatids are common and diverse parasites of Drosophila

SUMMARYDrosophila melanogasteris an important model system of immunity and parasite resistance, yet most studies use parasites that do not naturally infect this organism. We have studied trypanosomatids in natural populations to assess the prevalence and diversity of these gut parasites. We collected several species ofDrosophilafrom Europe and surveyed them for trypanosomatids using conserved primers for two genes. We have used the conserved GAPDH sequence to construct a phylogenetic tree and the highly variable spliced leader RNA to assay genetic diversity. All 5 of the species that we examined were infected, and the average prevalence ranged from 1 to 6%. There are several different groups of trypanosomatids, related to other monoxenous Trypanosomatidae. These may represent new trypanosomatid species and were found in different species of EuropeanDrosophilafrom different geographical locations. The detection of a little studied natural pathogen inD. melanogasterand related species provides new opportunities for research into both theDrosophilaimmune response and the evolution of hosts and parasites.</jats:p

Upper bound for the conductivity of nanotube networks

Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. By considering ideal ballistic-like contacts between nanotubes we use the Kubo formalism to calculate the upper bound for the conductivity of such films and show how it depends on the nanotube concentration as well as on their aspect ratio. Highest measured conductivities reported so far are approaching this limiting value, suggesting that further progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied Physics Letter

Resistivity study of the pseudogap phase for (Hg,Re) - 1223 superconductors

The pseudogap phase above the critical temperature of high $T_{c}$ superconductors (HTSC) presents different energy scales and it is currently a matter of intense study. The complexity of the HTSC normal state requires very accurate measurements with the purpose of distinguishing different types of phenomena. Here we have performed systematically studies through electrical resistivity ($\rho$) measurements by several different current densities in order to obtain an optimal current for each sample. This approach allows to determine reliable values of the pseudogap temperature $T^{*}(n)$, the layer coupling temperature between the superconductor layers $T_{LD}(n)$, the fluctuation temperature $T_{scf}(n)$ and the critical temperature $T_{c}(n)$ as function of the doping $n$. The interpretation of these different temperature scales allows to characterize possible scenarios for the (Hg,Re) - 1223 normal state. This method, described in detail here, and used to derive the (Hg,Re)-1223 phase diagram is general and can be applied to any HTSC.Comment: 31 pages, 12 figures, Latex; 25 pages, LaTeX; 11 figures; rewrited section II and III; added 18 reference; rewrited title, added discussion sectio

Bound-to-bound and bound-to-continuum optical transitions in combined quantum dot - superlattice systems

By combining band gap engineering with the self-organized growth of quantum dots, we present a scheme of adjusting the mid-infrared absorption properties to desired energy transitions in quantum dot based photodetectors. Embedding the self organized InAs quantum dots into an AlAs/GaAs superlattice enables us to tune the optical transition energy by changing the superlattice period as well as by changing the growth conditions of the dots. Using a one band envelope function framework we are able, in a fully three dimensional calculation, to predict the photocurrent spectra of these devices as well as their polarization properties. The calculations further predict a strong impact of the dots on the superlattices minibands. The impact of vertical dot alignment or misalignment on the absorption properties of this dot/superlattice structure is investigated. The observed photocurrent spectra of vertically coupled quantum dot stacks show very good agreement with the calculations.In these experiments, vertically coupled quantum dot stacks show the best performance in the desired photodetector application.Comment: 8 pages, 10 figures, submitted to PR

Spherical Scalar Field Halo in Galaxies

We study a spherically symmetric fluctuation of scalar dark matter in the cosmos and show that it could be the dark matter in galaxies, provided that the scalar field has an exponential potential whose overall sign is negative and whose exponent is constrained observationally by the rotation velocities of galaxies. The local space-time of the fluctuation contains a three dimensional space-like hypersurface with surplus of angle.Comment: 5 REVTeX pages, no figures. Contains important suggestions provided by the referee. Final version, to appear in Phys. Rev.

IMPLICAÇÕES DA MADEIRA NA IDENTIDADE E SEGURANÇA DE QUEIJOS ARTESANAIS

A madeira é secularmente utilizada na manufatura dos utensílios empregados na fabricação de alimentos artesanais, como por exemplo, tonéis de fermentação de bebidas alcoólicas, tinas, formas, prateleiras e bancadas para produção de queijos. Essas superfícies apresentam estrutura porosa, o que permite o desenvolvimento de comunidades microbianas conhecidas como biofilmes. Fungos filamentosos, leveduras e bactérias do ácido acético e lático (BAL) presentes nesses biofilmes são responsáveis pelas características peculiares de alimentos como cidras, vinhos, vinagres e de uma gama variada de queijos artesanais, garantindo sabores e odores característicos desses alimentos, assim como sua segurança. Pesquisas recentes demonstraram que a presença de BAL, em biofilmes, diminuiu a adesão de patógenos como Escherichia coli e Staphylococcus aureus, principais indicadores de práticas de fabricação insatisfatórias em ambientes de produção de alimentos. Em 2002 a legislação criada para a fabricação do queijo Minas artesanal, estabeleceu padrões físicoquímicos e microbiológicos para a elaboração desses queijos, e eliminou o uso das formas e bancadas de madeira, como uma medida para cercear a proliferação de patógenos nesses produtos. Essa medida foi preventiva e emergencial, embora ainda hoje questionada pelos produtores tradicionais, conhecedores das práticas utilizadas em países da Europa, onde a madeira tem um papel importante nas características de vários produtos artesanais, especialmente em alguns tipos de queijos com Denominação de Origem Protegida (DOP). Essa revisão tem como objetivo reunir informações relacionadas ao papel da madeira na produção de alimentos, assim como dos biofilmes nela formados e da função dos mesmos nas características e segurança de queijos artesanais