2,927 research outputs found
Lorentz symmetry breaking effects on relativistic EPR correlations
Lorentz symmetry breaking effects on relativistic EPR
(Einstein-Podolsky-Rosen) correlations are discussed. From the modified Maxwell
theory coupled to gravity, we establish a possible scenario of the Lorentz
symmetry violation and write an effective metric for the Minkowski spacetime.
Then, we obtain the Wigner rotation angle via the Fermi-Walker transport of
spinors and consider the WKB ((Wentzel-Kramers-Brillouin) approximation in
order to study the influence of Lorentz symmetry breaking effects on the
relativistic EPR correlations.Comment: Accepted for publication in The European Physical Journal C. arXiv
admin note: substantial text overlap with arXiv:1504.07432, arXiv:1504.07262,
arXiv:1412.5080, arXiv:1506.0056
Collaboration networks from a large CV database: dynamics, topology and bonus impact
Understanding the dynamics of research production and collaboration may
reveal better strategies for scientific careers, academic institutions and
funding agencies. Here we propose the use of a large and multidisciplinar
database of scientific curricula in Brazil, namely, the Lattes Platform, to
study patterns of scientific production and collaboration. In this database,
detailed information about publications and researchers are made available by
themselves so that coauthorship is unambiguous and individuals can be evaluated
by scientific productivity, geographical location and field of expertise. Our
results show that the collaboration network is growing exponentially for the
last three decades, with a distribution of number of collaborators per
researcher that approaches a power-law as the network gets older. Moreover,
both the distributions of number of collaborators and production per researcher
obey power-law behaviors, regardless of the geographical location or field,
suggesting that the same universal mechanism might be responsible for network
growth and productivity.We also show that the collaboration network under
investigation displays a typical assortative mixing behavior, where teeming
researchers (i.e., with high degree) tend to collaborate with others alike.
Finally, our analysis reveals that the distinctive collaboration profile of
researchers awarded with governmental scholarships suggests a strong bonus
impact on their productivity.Comment: 8 pages, 8 figure
Gravitational Geometric Phase in the Presence of Torsion
We investigate the relativistic and non-relativistic quantum dynamics of a
neutral spin-1/2 particle submitted an external electromagnetic field in the
presence of a cosmic dislocation. We analyze the explicit contribution of the
torsion in the geometric phase acquired in the dynamic of this neutral
spinorial particle. We discuss the influence of the torsion in the relativistic
geometric phase. Using the Foldy-Wouthuysen approximation, the non-relativistic
quantum dynamics are studied and the influence of the torsion in the
Aharonov-Casher and He-McKellar-Wilkens effects are discussed.Comment: 14 pages, no figur
Self-Forces on Electric and Magnetic Linear Sources in the Space-Time of a Cosmic String
In this paper we calculate the magnetic and electric self-forces, induced by
the conical structure of a cosmic string space-time, on a long straight wire
which presents either a constant current or a linear charge density. We also
show how these self-forces are related by a Lorentz tranformation and, in this
way, explain what two different inertial observers detect in their respective
frames.Comment: 10 pages, LaTeX, to be published in Phys. Rev. D
Electronic properties of curved graphene sheets
A model is proposed to study the electronic structure of slightly curved
graphene sheets with an arbitrary number of pentagon-heptagon pairs and
Stone-Wales defects based on a cosmological analogy. The disorder induced by
curvature produces characteristic patterns in the local density of states that
can be observed in scanning tunnel and transmission electron microscopy.Comment: Corrected versio
Estudo dos postos de trabalho de inspecção de defeitos da indĂșstria tĂȘxtil
Pretende-se com esta comunicaçaÌo apresentar o trabalho desenvolvido no aÌmbito da campanha TeÌxtil do IDICT, onde se realizou um estudo dos postos de trabalho de inspecçaÌo de defeitos da Industria TeÌxtil. O trabalho centrou-se particularmente nos aspectos ErgonoÌmicos dos postos de trabalho: âMetedeira de Fiosâ, âRevistadeiraâ e âInspecçaÌo Finalâ. Cada um dos postos de trabalho foi caracterizado em funçaÌo dos seguintes aspectos: caracteriÌsticas gerais; postura e trabalho muscular; percepçaÌo, vigilaÌncia e destreza; ambiente fiÌsico e organizaçaÌo do trabalho. O modelo de actuaçaÌo usado consistiu na realizaçaÌo de uma seÌrie de questoÌes, cuja resposta conduziu aÌ elaboraçaÌo de um preÌ-diagnoÌstico dos postos de trabalho de inspecçaÌo. Este preÌ-diagnoÌstico constitui, por sua vez, a base para a proposta de um conjunto de recomendaçoÌes e sugestoÌes ao niÌvel da iluminaçaÌo, ruiÌdo, aspectos ergonoÌmicos do assento e medidas administrativas
Sistema automåtico para inspecção visual de defeitos em tecidos
Pretende-se com esta comunicaçaÌo apresentar o trabalho desenvolvido no aÌmbito da Campanha TeÌxtil do IDICT, onde se aplicaram algoritmos de processamento de imagem aÌ inspecçaÌo de defeitos em tecidos. Devido aÌ complexidade do problema em estudo foi necessaÌrio construir um sistema de iluminaçaÌo estruturada para garantir luminosidade constante no tecido a inspeccionar. Um sistema de captura e processamento de imagens a cores foi desenvolvido, para o sistema operativo Windows 98, tendo por base a placa de aquisiçaÌo Matrox Meteor II e o software Microsoft Visual C++. ApoÌs a conversaÌo de imagens a cores em niÌveis de cinzento foram desenvolvidos algoritmos de binarizaçaÌo, baseados em anaÌlise estatiÌstica e morfologia matemaÌtica. Os algoritmos desenvolvidos abrangem os seguintes defeitos em tecidos: falta de fio, fio grosso, fio duplo, borboto, mancha e noÌdoa. Para cada tecido a inspecionar eÌ necessaÌrio um periÌodo de treino do sistema de forma a identificar os paraÌmetros estatiÌsticos que o caracterizam, meÌdia e desvio padraÌo dos niÌveis de cinzento. O sistema inspecciona de forma automaÌtica os defeitos descritos em tecidos penteados de uma soÌ cor, tendo sido obtidos resultados bastante satisfatoÌrios para o nuÌmero de tecidos disponibilisados pelas empresas da regiaÌo
Peritoneal and hepatic hydatid disease causing major bile duct destruction
Echinococcosis is endemic in Mediterranean regions and is found primarily in the liver. Biliary fistula is a common complication, but major biliary duct involvement is very rare, and occurs in 0.47% of patients with hepatic hydatid disease. Cyst rupture causing secondary peritoneal hydatidosis is a rare but serious complication. We report the case of a 27-year-old man with multiple peritoneal and hepatic hydatid cysts. The patient came to our attention with cholestatic jaundice. Imaging exams showed numerous peritoneal cysts and massive hydatid disease of the liver, which involved the hepatic confluence, with destruction of the right hepatic duct and fistula formation to the left hepatic duct. The patient was treated with pre-operative albendazole therapy and radical surgery, which consisted of resection of all peritoneal cysts and extended right hepatectomy with biliary reconstruction. No recurrence was seen on CT investigations on the 12th month following surgery. Radical surgical approach remains the treatment of choice
TRADE LIBERALIZATION, THE EXCHANGE RATE AND JOB AND WORKER FLOWS IN BRAZIL
Over the 1990's Brazil experienced a massive trade liberalization and wide variation in the real exchange rate. At the same time, employment growth was small and in manufacturing there was a significant reduction in total manufacturing. The main goal of this article is to idntify the effects of the exchange rate and trade liberalization on job and worker flows in Brazil. Using a novel sector exchange rate measure, our results suggest that a depreciation of the exchange rate affects net employment growth by increasing job creation and hires, with no effect on job reallocation. Tariffs have no effect on job or worker flows, while import penetration decrease job growth by increasing job destruction. The results suggest that the echange rate have a very important role on job and worker flows, even after controlling for openess and sector specificities.
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