8,807 research outputs found
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
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
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 BiTeSe single crystals by
modified Bridgman method, that possess high bulk resistivity of
20~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 BiTeSe 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
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 especÃficos 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 caracterÃsticas
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 contribuÃdo 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
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
Charge renormalization and phase separation in colloidal suspensions
We explore the effects of counterion condensation on fluid-fluid phase
separation in charged colloidal suspensions. It is found that formation of
double layers around the colloidal particles stabilizes suspensions against
phase separation. Addition of salt, however, produces an instability which, in
principle, can lead to a fluid-fluid separation. The instability, however, is
so weak that it should be impossible to observe a fully equilibrated
coexistence experimentally.Comment: 7 pages, Europhysics Letters (in press
Spin-phonon coupling in Gd(Co1/2Mn1/2)O3 perovskite
We have investigated the temperature-dependent Raman-active phonons and the
magnetic properties of Gd(Co1/2Mn1/2)O3 perovskite ceramics in the temperature
range from 40 K to 300 K. The samples crystallized in an orthorhombic distorted
simple perovskite, whose symmetry belongs to the Pnma space group. The data
reveals spin-phonon coupling near the ferromagnetic transition occurring at
around 120 K. The correlation of the Raman and magnetization data suggests that
the structural order influences the magnitude of the spin-phonon coupling.Comment: 3 Figures, suplementary materia
The conduciveness of CA-rule graphs
Given two subsets A and B of nodes in a directed graph, the conduciveness of
the graph from A to B is the ratio representing how many of the edges outgoing
from nodes in A are incoming to nodes in B. When the graph's nodes stand for
the possible solutions to certain problems of combinatorial optimization,
choosing its edges appropriately has been shown to lead to conduciveness
properties that provide useful insight into the performance of algorithms to
solve those problems. Here we study the conduciveness of CA-rule graphs, that
is, graphs whose node set is the set of all CA rules given a cell's number of
possible states and neighborhood size. We consider several different edge sets
interconnecting these nodes, both deterministic and random ones, and derive
analytical expressions for the resulting graph's conduciveness toward rules
having a fixed number of non-quiescent entries. We demonstrate that one of the
random edge sets, characterized by allowing nodes to be sparsely interconnected
across any Hamming distance between the corresponding rules, has the potential
of providing reasonable conduciveness toward the desired rules. We conjecture
that this may lie at the bottom of the best strategies known to date for
discovering complex rules to solve specific problems, all of an evolutionary
nature
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