Stokes-operator-squeezed continuous-variable polarization states

We investigate nonclassical Stokes-operator variances in continuous-wave polarization-squeezed laser light generated from one and two optical parametric amplifiers. A general expression of how Stokes-operator variances decompose into two-mode quadrature operator variances is given. Stokes parameter variance spectra for four different polarization-squeezed states have been measured and compared with a coherent state. Our measurement results are visualized by three-dimensional Stokes-operator noise volumes mapped on the quantum Poincare sphere. We quantitatively compare the channel capacity of the different continuous-variable polarization states for communication protocols. It is shown that squeezed polarization states provide 33% higher channel capacities than the optimum coherent beam protocol.

Experimental investigation of criteria for continuous variable entanglement

We generate a pair of entangled beams from the interference of two amplitude squeezed beams. The entanglement is quantified in terms of EPR paradox and inseparability criteria, with both results clearly beating the standard quantum limit. We experimentally analyze the effect of decoherence on each criterion and demonstrate qualitative differences. We also characterize the number of required and excess photons present in the entangled beams and provide contour plots of the efficacy of quantum information protocols in terms of these variables.

Experimental investigation of continuous-variable quantum teleportation

We report the experimental demonstration of quantum teleportation of the quadrature amplitudes of a light field. Our experiment was stably locked for long periods, and was analyzed in terms of fidelity F and with signal transfer T-q=T++T- and noise correlation V-q=Vinparallel to out+Vinparallel to out-. We observed an optimum fidelity of 0.64+/-0.02, T-q=1.06+/-0.02, and V-q=0.96+/-0.10. We discuss the significance of both T-q>1 and V-q

Continuous variable polarization entanglement, experiment and analysis

We generate and characterize continuous variable polarization entanglement between two optical beams. We first produce quadrature entanglement, and by performing local operations we transform it into a polarization basis. We extend two entanglement criteria, the inseparability criteria proposed by Duan et al (2000 Phys. Rev. Lett. 84 2722) and the Einstein–Podolsky–Rosen (EPR) paradox criteria proposed by Reid and Drummond (1988 Phys. Rev. Lett. 60 2731), to Stokes operators; and use them to characterize the entanglement. Our results for the EPR paradox criteria are visualized in terms of uncertainty balls on the Poincaré sphere. We demonstrate theoretically that using two quadrature entangled pairs it is possible to entangle three orthogonal Stokes operators between a pair of beams, although with a bound √3 times more stringent than for the quadrature entanglement.

Identification and characterization of pptA: a gene involved in the phase-variable expression of phosphorylcholine on pili of Neisseria meningitidis

Pili of pathogenic Neisseria are major virulence factors associated with adhesion, cytotoxicity, twitching motility, autoaggregation, and DNA transformation. Pili are modified posttranslationally by the addition of phosphorylcholine. However, no genes involved in either the biosynthesis or the transfer of phosphorylcholine in Neisseria meningitidis have been identified. In this study, we identified five candidate open reading frames (ORFs) potentially involved in the biosynthesis or transfer of phosphorylcholine to pilin in N. meningitidis. Insertional mutants were constructed for each ORF in N. meningitidis strain C311#3 to determine their effect on phosphorylcholine expression. The effect of the mutant ORFs on the modification by phosphorylcholine was analyzed by Western analysis with phosphorylcholine-specific monoclonal antibody TEPC-15. Analysis of the mutants showed that ORF NMB0415, now defined as pptA (pilin phosphorylcholine transferase A), is involved in the addition of phosphorylcholine to pilin in N. meningitidis. Additionally, the phase variation (high frequency on-off switching of expression) of phosphorylcholine on pilin is due to changes in a homopolymeric guanosine tract in pptA.

An analysis of helium primordial nucleosynthesis with a variable cosmological coupling

The synthesis of helium in the early Universe depends on many input parameters, including the value of the gravitational coupling during the period when the nucleosynthesis takes place. We compute the primordial abundance of helium as function of the gravitational coupling, using a semi-analytical method, in order to track the influence of G in the primordial nucleosynthesis. To be specific, we construct a cosmological model with varying G, using the Brans-Dicke theory. The greater the value of G at nucleosynthesis period, the greater the predicted abundance of helium. Using the observational data for the abundance of primordial helium, constraints for the time variation of G are established.

Estudo da resistência não drenada de solo de baixa consistência por meio de ensaios de campo e laboratório

A variabilidade natural dos solos torna complexo o conhecimento de suas propriedades na elaboração de projetos geotécnicos, sendo a determinação da resistência ao cisalhamento não drenada um parâmetro importante nas análises de estabilidade de solos moles. Os ensaios de laboratório de cone e palheta, não convencionais, os ensaios de campo de palheta e piezocone e os ensaios de compressão simples e triaxial não adensado e não drenado foram utilizados para mensurar a resistência não drenada de uma camada de argila marinha mole localizada na planície costeira central brasileira. Os ensaios de laboratório foram realizados em amostras indeformadas coletadas com amostradores de pistão estacionário em vertical próxima à realização dos ensaios de campo. O sítio foi investigado preliminarmente por sondagens de simples reconhecimento, sendo apresentado o perfil estratigráfico por meio de modelagem computacional. Foram também realizados ensaios para caracterização física (análise granulométrica, teor de umidade, limites de liquidez e plasticidade, densidade real dos grãos) e mineralógica (difração de raios X), e ensaios de adensamento para obtenção do histórico de tensões e classificação de qualidade das amostras indeformadas. Os valores de resistência não drenada obtidos pelos ensaios de laboratório foram comparados ao perfil contínuo de resistência determinado empiricamente pelo ensaio de piezocone, com fator de cone Nkt calibrado pelo ensaio de palheta de campo, apresentando boa concordância, com a variabilidade natural do solo influenciando de forma preponderante a qualidade das amostras na variação entre os resultados. Os valores de resistência obtidos pelos ensaios de laboratório de cone e palheta foram comparados entre si, apresentando boa compatibilidade. Ambos, quando comparados ao ensaio de palheta de campo, não apresentaram boa concordância. Os resultados de resistência obtidos pelos ensaios de compressão simples e triaxial apresentaram boa compatibilidade com os resultados do ensaio de laboratório de cone, o que não ocorreu com os resultados do ensaio de laboratório de palheta. Na comparação entre a resistência normalizada pela tensão de sobreadensamento obtida pelos diversos métodos e algumas correlações empíricas da literatura internacional, foi observado para as amostras de solo com índice de plasticidade superior a 60% boa concordância com as correlações de Mesri (1975) e Jamiolkowski et al (1985). Os ensaios não convencionais apresentaram boa confiabilidade, que aliado a simplicidade e agilidade de execução, justificam a difusão destes na prática da investigação geotécnica brasileira como método alternativo para complementar e dar suporte às estimativas de resistência não drenada de solos moles.

Alguns teoremas limites para sequências de variáveis aleatórias

O Teorema Central do Limite e a Lei dos Grandes Números estão entre os mais importantes resultados da teoria da probabilidade. O primeiro deles busca condições sob as quais [fórmula] converge em distribuição para a distribuição normal com parâmetros 0 e 1, quando n tende ao infinito, onde Sn é a soma de n variáveis aleatórias independentes. Ao mesmo tempo, o segundo estabelece condições para que [fórmula] convirja a zero, ou equivalentemente, para que [fórmula] convirja para a esperança das variáveis aleatórias, caso elas sejam identicamente distribuídas. Em ambos os casos as sequências abordadas são do tipo [fórmula], onde [fórmula] e [fórmula] são constantes reais. Caracterizar os possíveis limites de tais sequências é um dos objetivos dessa dissertação, já que elas não convergem exclusivamente para uma variável aleatória degenerada ou com distribuição normal como na Lei dos Grandes Números e no Teorema Central do Limite, respectivamente. Assim, somos levados naturalmente ao estudo das distribuições infinitamente divisíveis e estáveis, e os respectivos teoremas limites, e este vem a ser o objetivo principal desta dissertação. Para as demonstrações dos teoremas utiliza-se como estratégia principal a aplicação do método de Lyapunov, o qual consiste na análise da convergência da sequência de funções características correspondentes às variáveis aleatórias. Nesse sentido, faremos também uma abordagem detalhada de tais funções neste trabalho.

Considerations about the recommendations of the Commission on the Limits of the Continental Shelf on the Amazon fan

In 2004, Brazil submitted to the Commission on the Limits of the Continental Shelf (CLCS) a Submission for the outer limit of the Brazilian continental shelf for its extension beyond the limits of 200 nautical miles. In 2007, the CLCS presented its recommendations, however it did not recommend four areas proposed by Brazil, the Amazon Fan among them. The objective of this study is to present the main legal and technical aspects of the controversy about the Amazon Fan, in order to evaluate some alternatives for a future submission, new or revised.

Peaceful rise and the limits of Chinese exceptionalism

Throughout the last thirty years of opening to the world Beijing has stressed that its rise will be peaceful and that, from a strategic point of view, China is exceptional. There are many challenges facing Beijing's response to the US rebalancing to the Asia-Pacific, but we consider that the ones with greater impact are, in point of fact, of a domestic nature and constitute limits to Chinese exceptionalism.

Use efficiency of variable rate of nitrogen prescribed by optical sensor in corn

ABSTRACT The efficiency of nitrogen fertilizer in corn is usually low, negatively affecting plant nutrition, the economic return, and the environment. In this context, a variable rate of nitrogen, prescribed by crop sensors, has been proposed as an alternative to the uniform rate of nitrogen traditionally used by farmers. This study tested the hypothesis that variable rate of nitrogen, prescribed by optical sensor, increases the nitrogen use efficiency and grain yield as compared to uniform rate of nitrogen. The following treatments were evaluated: 0; 70; 140; and 210 kg ha-1 under uniform rate of nitrogen, and 140 kg ha -1 under variable rate of nitrogen. The nitrogen source was urea applied on the soil surface using a distributor equipped with the crop sensor. In this study, the grain yield ranged from 10.2 to 15.5 Mg ha-1, with linear response to nitrogen rates. The variable rate of nitrogen increased by 11.8 and 32.6% the nitrogen uptake and nitrogen use efficiency, respectively, compared to the uniform rate of nitrogen. However, no significant increase in grain yield was observed, indicating that the major benefit of the variable rate of nitrogen was reducing the risk of environmental impact of fertilizer.

On the Suitability of Suffix Arrays for Lempel-Ziv Data Compression

Lossless compression algorithms of the Lempel-Ziv (LZ) family are widely used nowadays. Regarding time and memory requirements, LZ encoding is much more demanding than decoding. In order to speed up the encoding process, efficient data structures, like suffix trees, have been used. In this paper, we explore the use of suffix arrays to hold the dictionary of the LZ encoder, and propose an algorithm to search over it. We show that the resulting encoder attains roughly the same compression ratios as those based on suffix trees. However, the amount of memory required by the suffix array is fixed, and much lower than the variable amount of memory used by encoders based on suffix trees (which depends on the text to encode). We conclude that suffix arrays, when compared to suffix trees in terms of the trade-off among time, memory, and compression ratio, may be preferable in scenarios (e.g., embedded systems) where memory is at a premium and high speed is not critical.

From here to diversity: globalization and intercultural dialogues

From Here to Diversity: Globalization and Intercultural Dialogues sees interculturalism as movement, transit, travel, the dynamics between cultures. Contemporary intercultural travel is a global journey, a circumnavigation at the speed of light that underwrites all the comings and goings, the departures and arrivals, the transmissions and receptions that are implicit in this title. Hence, From Here to Diversity examines the motivations, characteristics and implications of cultural interactions in their perpetual movement, devoid of spatial or temporal borders, in a dangerous but stimulating indefinition of limits. In the contemporary intercultural dialogue, new voices are making themselves heard, as valuable sources of study: the voices of women; non-occidentals; the non-powerful; forgotten narratives of a past that was as intercultural as the present (after all, what is colonialism other than a perverse form of interculturality?); global entertainment; tourism; oral literature; diaries; mythical narratives; the cinema; ethnography; new teachings, among so many others. Because this project is also intercultural at its source and subject, From Here to Diversity: Globalization and Intercultural Dialogues adds to the coherence of the project by including contributions from the most wide-ranging backgrounds and nationalities, without fear of the alterity that, after all, we propose to study.

A Sensorless PMDC Motor Speed Controller with a Logical Overcurrent Protection

A method to control the speed or the torque of a permanent-magnet direct current motor is presented. The rotor speed and the external torque estimation are simultaneously provided by appropriate observers. The sensorless control scheme is based on current measurement and switching states of power devices. The observer’s performances are dependent on the accurate machine parameters knowledge. Sliding mode control approach was adopted for drive control, providing the suitable switching states to the chopper power devices. Despite the predictable chattering, a convenient first order switching function was considered enough to define the sliding surface and to correspond with the desired control specifications and drive performance. The experimental implementation was supported on a single dsPIC and the controller includes a logic overcurrent protection.

Sustainable Tourism and Agriculture Multifunctionality by PAR: A Variable Selection Approach

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