Cancellation of atmospheric turbulence effects in entangled two-photon beams

Turbulent airflow in the atmosphere and the resulting random fluctuations in its refractive index have long been known as a major cause of image deterioration in astronomical imaging and figures among the obstacles for reliable optical communication when information is encoded in the spatial profile of a laser beam. Here we show that using correlation imaging and a suitably prepared source of photon pairs, the most severe of the disturbances inflicted on the beam by turbulence can be cancelled out. Other than a two-photon light source, only linear passive optical elements are needed and, as opposed to adaptive optics techniques, our scheme does not rely on active wavefront correction.Comment: 5 pages, 3 figure

Avaliação de genótipos de girassol no Planalto Médio do Rio Grande do Sul na safra 2010/2011.

bitstream/item/62564/1/2011boletimdepesquisaonline80.pd

An artificial aquatic polyp that wirelessly attracts, grasps, and releases objects

The development of light-responsive materials has captured scientific attention and advanced the development of wirelessly driven terrestrial soft robots. Marine organisms trigger inspiration to expand the paradigm of untethered soft robotics into aqueous environments. However, this expansion toward aquatic soft robots is hampered by the slow response of most light-driven polymers to low light intensities and by the lack of controlled multishape deformations. Herein, we present a surface-anchored artificial aquatic coral polyp composed of a magnetically driven stem and a light-driven gripper. Through magnetically driven motion, the polyp induces stirring and attracts suspended targets. The light-responsive gripper is sensitive to low light intensities and has programmable states and rapid and highly controlled actuation, allowing the polyp to capture or release targets on demand. The artificial polyp demonstrates that assemblies of stimuli-responsive materials in water utilizing coordinated motion can perform tasks not possible for single-component devices. [Abstract copyright: Copyright © 2020 the Author(s). Published by PNAS.

Using discrete Ricci curvatures to infer COVID-19 epidemic network fragility and systemic risk

The damage of the novel Coronavirus disease (COVID-19) is reaching unprecedented scales. There are numerous classical epidemiology models trying to quantify epidemiology metrics. Usually, to forecast epidemics, classical approaches need parameter estimations, such as the contagion rate or the basic reproduction number. Here, we propose a data-driven, parameter-free, geometric approach to access the emergence of a pandemic state by studying the Forman-Ricci and Ollivier- Ricci network curvatures. Discrete Ollivier-Ricci curvature has been used successfully to forecast risk in nancial networks and we suggest that those results can provide analogous results for COVID-19 epidemic time-series. We rst compute both curvatures in a toy-model of epidemic time-series with delays, which allows us to create epidemic networks. We also compared our results to classical network metrics. By doing so, we are able to verify that the Ollivier-Ricci and Forman-Ricci curvatures can be a parameter-free estimate for identifying a pandemic state in the simulated epidemic. On this basis, we then compute both Forman-Ricci and Ollivier-Ricci curvatures for real epidemic networks built from COVID-19 epidemic time-series available at the World Health Organization (WHO). This approach allow us to detect early warning signs of the emergence of the pandemic. The advantage of our method lies in providing an early geometrical data marker for the pandemic state, regardless of parameter estimation and stochastic modelling. This work opens the possibility of using discrete geometry to study epidemic networks. Keywords: COVID-19, SARS2, Forman-Ricci Curvature, Ollivier-Ricci curvature, Epidemiology, Topologi- cal Data Analysi

Charge and spin distributions in GaMnAs/GaAs Ferromagnetic Multilayers

A self-consistent electronic structure calculation based on the Luttinger-Kohn model is performed on GaMnAs/GaAs multilayers. The Diluted Magnetic Semiconductor layers are assumed to be metallic and ferromagnetic. The high Mn concentration (considered as 5% in our calculation) makes it possible to assume the density of magnetic moments as a continuous distribution, when treating the magnetic interaction between holes and the localized moment on the Mn(++) sites. Our calculation shows the distribution of heavy holes and light holes in the structure. A strong spin-polarization is observed, and the charge is concentrated mostly on the GaMnAs layers, due to heavy and light holes with their total angular momentum aligned anti-parallel to the average magnetization. The charge and spin distributions are analyzed in terms of their dependence on the number of multilayers, the widths of the GaMnAs and GaAs layers, and the width of lateral GaAs layers at the borders of the structure.Comment: 12 pages,7 figure

Pattern formation and coexistence domains for a nonlocal population dynamics

In this communication we propose a most general equation to study pattern formation for one-species population and their limit domains in systems of length L. To accomplish this we include non-locality in the growth and competition terms where the integral kernels are now depend on characteristic length parameters alpha and beta. Therefore, we derived a parameter space (alpha,beta) where it is possible to analyze a coexistence curve alpha*=alpha*(\beta) which delimits domains for the existence (or not) of pattern formation in population dynamics systems. We show that this curve has an analogy with coexistence curve in classical thermodynamics and critical phenomena physics. We have successfully compared this model with experimental data for diffusion of Escherichia coli populations

Atividade ovicida e repelente de pó de citronela sobre o caruncho do feijão-caupi.

O caruncho Callosobruchus maculatus (Fabr.) é considerado a principal praga de grãos e sementes armazenados de feijão-caupi, por causar danos diretos e indiretos, que podem levar às perdas quantitativas e qualitativas, inviabilizando a comercialização ou o consumo. Para o controle dessa praga, tem-se utilizado os inseticidas sintéticos, que ao longo dos anos, tem causado muitos problemas à saúde humana e ao meio ambiente. Os inseticidas botânicos têm se tornado uma alternativa promissora no controle de pragas de grãos armazenados. O objetivo deste trabalho foi avaliar a atividade ovicida e repelente do pó vegetal de citronela, Cymbopogon nardus, sobre C. maculatus

Distribuição do sistema radicular de espécies vegetais cultivadas na entrelinha de mangueiras.

Propondo práticas culturais para o manejo de solo desenvolveu-se um estudo com coquetéis vegetais, semeados na entrelinha da mangueira com o objetivo de verificar a capacidade que diferentes espécies vegetais têm de adicionar massa seca, bem como avaliar o desenvolvimento do sistema radicular e a influência sobre a resistência a penetração

Cultivation of Perennial Herbaceous legumes in weed management in coffee plantation on the Cerrado.

The aim of this study was to evaluate the cultivation of perennial herbaceous legumes on weed control and yield of the coffee crop in the Cerrado. The experimental design was a randomized complete block with four replications. The 10 treatments tested in factorial 4 × 2 + 2, were four legumes: forage peanut (Arachis pintoi), hybrid Java (Macrotyloma axillare), perennial soybean (Neonotonia wightii) and wild ground nut (Calopogonium mucunoides); two forms in the interrows of coffee plants with two and three rows of legumes spaced by 0.50 m and 0.25 m, respectively; and two additional treatments consisted of hand weeding with hoe and chemical control with glyphosate. The hybrid Java and wild ground nut in the first year and the hybrid Java and perennial soybean in the second year, all followed by forage peanut, promoted lower density and biomass of the weeds. The wild ground nut in the first year and forage peanut in the second year showed higher soil cover. The hybrid Java had its highest biomass production in two years, and wild ground nut being higher in the first year. The cultivation of perennial herbaceous legumes promoted weed control without interfering in the productivity of the coffee crop

Identificação de fontes de resistência de arroz ao gorgulho-aquático Oryzophagus oryzae por meio de seleção recorrente de plantas.

Oryzophagus oryzae (Costa Lima) (Coleoptera: Curculionidae) é o inseto mais prejudicial à cultura do arroz irrigado por submersão no Sul do Brasil. O inseto adulto (gorgulho-aquático) alimenta-se das folhas de arroz. O corte das raízes pelas larvas (bicheira-da-raiz), porém, é que resulta em perdas de produtividade, que oscilam de 10 a 18%. Apesar de algumas práticas do manejo da cultura do arroz contribuírem para que a população larval não atinja o nível de dano econômico, este efeito tem sido mínimo, induzindo, nas duas últimas décadas, ao uso crescente do controle químico. Neste contexto, considerando as vantagens que cultivares resistentes a O. oryzae podem proporcionar quanto à redução de perdas de produtividade e da aplicação de inseticidas, o uso dessas é visto como promissor para o aumento da rentabilidade e da segurança ambiental