Off-axis retrieval of orbital angular momentum of light stored in cold atoms

We report on the storage of orbital angu- lar momentum (OAM) of light of a Laguerre-Gaussian mode in an ensemble of cold cesium atoms and its re- trieval along an axis different from the incident light beam. We employed a time-delayed four-wave mixing configuration to demonstrate that at small angle (2o), after storage, the retrieved beam carries the same OAM as the one encoded in the input beam. A calculation based on mode decomposition of the retrieved beam over the Laguerre-Gaussian basis is in agreement with the experimental observations done at small angle values. However, the calculation shows that the OAM retrieving would get lost at larger angles, reducing the fidelity of such storing-retrieving process. In addition, we have also observed that by applying an external magnetic field to the atomic ensemble the retrieved OAM presents Larmor oscillations, demonstrating the possibility of its manipulation and off-axis retrieval.Comment: 9 pages, 4 figure

Viscous Cosmology

We discuss the possibility to implement a viscous cosmological model, attributing to the dark matter component a behaviour described by bulk viscosity. Since bulk viscosity implies negative pressure, this rises the possibility to unify the dark sector. At the same time, the presence of dissipative effects may alleviate the so called small scale problems in the $\Lambda$CDM model. While the unified viscous description for the dark sector does not lead to consistent results, the non-linear behaviour indeed improves the situation with respect to the standard cosmological model.Comment: Latex file, 7 pages, 6 figures. To appear in the proceedings of the XIIth International Conference on Gravitation, Astrophysics and Cosmology, June 28-July 5, 2015, PFUR, Moscow, Russi

Inovação no desenvolvimento de embalagens para frutas e vegetais in natura

A maioria das pessoas não se dá conta que as embalagens para hortifruticolas acondicionam seres vivos. Estas embalagens possuem significados e usos tão específicos que mereceriam estar catalogadas numa categoria particular e não na categoria genérica de embalagens para alimentos. Os seres vivos que acondicionam pertencem a diversos tipos, espécies e categorias, e possuem qualidades essenciais e características organolépticas, sensoriais únicas. Por isto, as embalagens para hortofruticolas, e o seu processo de desenvolvimento, devem que respeitar o caráter único de cada produto. O desrespeito a este caráter único tem contribuído fortemente para que as embalagens reduzam o tempo de vida útil das frutas, legumes e verduras e aumentem as perdas pós-colheita. As embalagens não devem ser genéricas. Contudo, esta não tem sido a visão dos projetistas e dos produtores industriais das embalagens para hortifruticolas. A Divisão de Desenho Industrial do Instituto Nacional de Tecnologia criou um processo – e método – inovador de design para o projeto de embalagens para frutas, legumes e verduras, que respeita as singularidades de cada tipo de produto. Apresentamos este processo e método neste artigo. Submetemos a avaliações - sob o ponto de vista de redução das perdas -, estas novas embalagens em comparação com todas as outras existentes no Brasil. Escolhemos as embalagens para caquis (Diospyros kaki) para demonstrar estas avaliações porque no Brasil perde-se, nos processos de pós-colheita, cerca de 80 % de todo o caqui plantado.ABSTRACT: Most people do not realize that the packaging for horticultural contained living beings. These packages have specific meanings and uses that deserve to be cataloged in a particular category and not in the general category of food packaging. Living beings contained therein belong to various types, species and categories, and have unique essential qualities, organolep_c properties and sensory characteristics. Therefore, the packaging for horticultural, and its development process, must respect the unique character of each product. Failure to comply with this unique character have contributed strongly to the packaging reduce the useful life of fruits and vegetables and increase post-harvest losses. Packaging must not be generic. However, this has not been the vision of designers and industrial producers of packaging for horticultural. We present this process and method in this paper. We submit to assessments these new packages compared with all other existing in Brazil, from the point of view reducing losses. We chose the packaging for persimmons (Diospyros kaki) to demonstrate these assessments because in Brazil in the post-harvest processes about 80% of all planted persimmon are lost.info:eu-repo/semantics/publishedVersio

Tripartite Graph Clustering for Dynamic Sentiment Analysis on Social Media

The growing popularity of social media (e.g, Twitter) allows users to easily share information with each other and influence others by expressing their own sentiments on various subjects. In this work, we propose an unsupervised \emph{tri-clustering} framework, which analyzes both user-level and tweet-level sentiments through co-clustering of a tripartite graph. A compelling feature of the proposed framework is that the quality of sentiment clustering of tweets, users, and features can be mutually improved by joint clustering. We further investigate the evolution of user-level sentiments and latent feature vectors in an online framework and devise an efficient online algorithm to sequentially update the clustering of tweets, users and features with newly arrived data. The online framework not only provides better quality of both dynamic user-level and tweet-level sentiment analysis, but also improves the computational and storage efficiency. We verified the effectiveness and efficiency of the proposed approaches on the November 2012 California ballot Twitter data.Comment: A short version is in Proceeding of the 2014 ACM SIGMOD International Conference on Management of dat

Evidence of surface transport and weak anti-localization in single crystal of Bi2Te2Se topological insulator

Topological insulators are known to their metallic surface states, a result of strong-spin-orbital coupling, that show unique surface transport phenomenon. But these surface transports are buried in presence of metallic bulk conduction. We synthesized very high quality Bi$_2$Te$_2$Se single crystals by modified Bridgman method, that possess high bulk resistivity of $>$20~$\Omega$cm below 20~K, whereas the bulk is mostly inactive and surface transport dominates. Temperature dependence resistivity follows the activation law like a gap semiconductor in temperature range 20-300~K. We designed a special measurement geometry, which aims to extract the surface transport from the bulk. This special geometry is applied to measure the resistance and found that Bi$_2$Te$_2$Se single crystal exhibits a cross over from bulk to surface conduction at 20~K. Simultaneously, the material also shows strong evidence of weak anti-localization in magneto-transport due to the protection against scattering by conducting surface states. This novel simple geometry is an easy route to find the evidence of surface transport in topological insulators, which are the promising materials for future spintronic applications.Comment: 6 Pages, 4 Figure

Charge reversal of colloidal particles

A theory is presented for the effective charge of colloidal particles in suspensions containing multivalent counterions. It is shown that if colloids are sufficiently strongly charged, the number of condensed multivalent counterion can exceed the bare colloidal charge leading to charge reversal. Charge renormalization in suspensions with multivalent counterions depends on a subtle interplay between the solvation energies of the multivalent counterions in the bulk and near the colloidal surface. We find that the effective charge is {\it not} a monotonically decreasing function of the multivalent salt concentration. Furthermore, contrary to the previous theories, it is found that except at very low concentrations, monovalent salt hinders the charge reversal. This conclusion is in agreement with the recent experiments and simulations

Deficiências minerais em pastagens do Estado do Rio de Janeiro.

bitstream/item/65349/1/CTAA-DOCUMENTOS-8-DEFICIENCIAS-MINERAIS-EM-PASTAGENS-DO-ESTADO-DO-RIO-DE-JANEIRO-FL-02171.pd

Experimental analysis of lateral impact on planar brittle material

The fragmentation of alumina and glass plates due to lateral impact is studied. A few hundred plates have been fragmented at different impact velocities and the produced fragments are analyzed. The method employed in this work allows one to investigate some geometrical properties of the fragments, besides the traditional size distribution usually studied in former experiments. We found that, although both materials exhibit qualitative similar fragment size distribution function, their geometrical properties appear to be quite different. A schematic model for two-dimensional fragmentation is also presented and its predictions are compared to our experimental results. The comparison suggests that the analysis of the fragments' geometrical properties constitutes a more stringent test of the theoretical models' assumptions than the size distribution