Plasmon dispersion and Landau damping in the nonlinear quantum regime.

We study the dispersion properties of electron plasma waves, or plasmons, which can be excited in quantum plasmas in the nonlinear regime. In order to describe nonlinear electron response to finite amplitude plasmons, we apply the Volkov approach to nonrelativistic electrons. For that purpose, we use the Schrödinger equation and describe the electron population of a quantum plasma as a mixture of quantum states. Within the kinetic framework that we are able to derive from the Volkov solutions, we discuss the role of the wave amplitude on the nonlinear plasma response. Finally, we focus on the quantum properties of nonlinear Landau damping and study the contributions of multiplasmon absorption and emission processes.

Bose-Einstein condensation of photons in microcavity plasmas.

Bose-Einstein condensation of a finite number of photons propagating inside a plasma-filled microcavity is investigated. The nonzero chemical potential is provided by the electrons, which induces a finite photon mass and allows condensation to occur. We derive an equation that models the evolution of the photon-mode occupancies, with Compton scattering taken into account as the mechanism of thermalization. The kinetic evolution of the photon spectrum is solved numerically, and we find evidence of condensation down to nanosecond timescales for typical microplasma conditions, n_{e}∼10^{14}-10^{15}cm^{-3}. The critical temperature scales almost linearly with the number of photons, and we find high condensate fractions at microcavity-plasma temperatures, for experimentally achievable cavity lengths (100-500µm) and photon numbers (10^{10}-10^{12}).

Controlled beat-wave Brillouin scattering in the ionosphere.

Stimulated Brillouin scattering experiments in the ionospheric plasma using a single electromagnetic pump wave have previously been observed to generate an electromagnetic sideband wave, emitted by the plasma, together with an ion- acoustic wave. Here we report results of a controlled, pump and probe beat-wave driven Brillouin scattering experiment, in which an ion-acoustic wave generated by the beating of electromagnetic pump and probe waves, results in electromagnetic sideband waves that are recorded on the ground. The experiment used the EISCAT facility in northern Norway, which has several high power electromagnetic wave transmitters and receivers in the radio frequency range. An electromagnetic pump consisting of large amplitude radio waves with ordinary (O) or extraordinary (X) mode polarization was injected into the overhead ionosphere, along with a less powerful probe wave, and radio sideband emissions observed on the ground clearly show stimulated Brillouin emissions at frequencies agreeing with, and changing with, the pump and probe frequencies. The experiment was simulated using a numerical full-scale model which clearly supports the interpretation of the experimental results. Such controlled beat-wave experiments demonstrate a way of remotely investigating the ionospheric plasma parameters.

Photon bubble turbulence in cold atom gases.

Turbulent radiation flow is commonplace in systems with strong, incoherent, light-matter interactions. In astrophysical contexts, photon bubble turbulence is considered a key mechanism behind enhanced radiation transport, and its importance has been widely asserted for a variety of high energy objects such as accretion disks and massive stars. Here, we show that analogous conditions to those of dense astrophysical objects can be obtained in large clouds of cold atoms, prepared in a laser-cooling experiment, driven close to a sharp electronic resonance. By accessing the spatially-resolved atom density, we are able to identify a photon bubble instability and the resulting regime of photon bubble turbulence. We also develop a theoretical model describing the coupled dynamics of both photon and atom gases, which accurately describes the statistical properties of the turbulent regime. This study thus opens the possibility of simulating radiation-dominated astrophysical systems in cold atom experiments.

Proposal of an iELISA for Mycoplasma bovis diagnosis in dairy cattle and associated risk factors / [Proposta de um iELISA para diagnóstico de Mycoplasma bovis em bovinos leiteiros e fatores de risco associados]

Mycoplasma bovis is a highly contagious agent associated with several pathologies in cattle. The detection of reactive antibodies to M. bovis by Indirect Enzyme-Linked Immunosorbent Assay (iELISA) identifies if there was an exposure to the microorganism. The current study aimed to optimize an iELISA from M. bovis total cell antigen, applying it to bovine serum samples, and to evaluate risk factors. Serum samples were obtained from 400 cows from 17 herds from Southeast Brazil. In the optimization of iELISA, the following was established: 2 µg/mL of antigen, sera dilution 1:300, and conjugate dilution 1:15000. The frequency was 62.3% (249/400) of reactive animals and 100% (17/17) of reactive herds. Risk factors were: herds with more than 100 animals (OR= 3.1; CI= 95%); Holstein breed (OR= 72.5; CI= 95%); cows (OR= 29.7; CI= 95%); intensive breeding system (OR= 3.3; CI= 95%); associated small ruminant production (OR= 4.4; CI= 95%); milk production above 500L (OR= 2.9; CI= 95%); no quarantine (OR= 1.5; CI= 95%); mechanical milking (OR= 5.5; CI= 95%) and cases of mastitis (OR= 5.5; CI= 95%). The proposed iELISA was able to detect antibodies reactive to M. bovis in bovine serum. Knowledge of these risk factors can assist in the implementation of prophylactic measures.(AU)

Mycoplasma bovis é um agente altamente contagioso relacionado a várias patologias em bovinos. A detecção de anticorpos reativos a M. bovis por Ensaio de Imunoadsorção Enzimática Indireto (iELISA) identifica se houve exposição ao microrganismo. O presente estudo teve como objetivo otimizar um iELISA de antígeno celular total de M. bovis, aplicando-o a amostras de soro bovino, bem como avaliar fatores de risco. Amostras de soro foram obtidas de 400 vacas de 17 rebanhos da Região Sudeste do Brasil. Na otimização do iELISA foram obtidos: 2µg/mL de antígeno, diluição dos soros 1:300 e do conjugado 1:15000. A frequência de animais reativos foi de 62,3% (249/400) e de 100% (17/17) para os rebanhos. Os fatores de risco foram: rebanhos com mais de 100 animais (OR= 3,1; IC= 95%); raça Holandesa (OR= 72,5;IC= 95%); vacas (OR= 29,7;IC= 95%); sistema intensivo (OR= 3,3; C= 95%); produção de pequenos ruminantes (OR= 4,4;IC=95%); produção de leite acima de 500L (OR= 2,9;IC= 95%); sem quarentena (OR= 1,5;IC= 95%); ordenha mecânica (OR= 5,5;IC= 95%) e casos de mastite (OR= 5,5;IC= 95%). O iELISA proposto foi capaz de detectar anticorpos reativos a M. bovis no soro bovino. O conhecimento desses fatores de risco pode auxiliar na implementação de medidas profiláticas.(AU)

Low coherence-induced resonance in double-layer structures having parity-time symmetry.

We derive simple formulas for the transmittance T and reflectance R of Gaussian-Schell beams incident upon any stratified dielectric structure by using second-order classical coherence theory in the space-frequency picture. The formalism is applied to a particular structure consisting of a double layer, with balanced gain and loss, satisfying parity-time symmetry conditions. It is shown that sources with a low degree of spatial coherence, on the order of the wavelength, can induce large resonant peaks in the transmitted and reflected amplitudes. The resonance peaks vanish as the spatial coherence increases.

Evaluation and application of a new scintillator-based heat-resistant back-scattered electron detector during heat treatment in the scanning electron microscope.

A new high-temperature detector dedicated to the collection of backscattered electrons is used in combination with heating stages up to 1050°C, in high-vacuum and low-vacuum modes in order to evaluate its possibilities through signal-to-noise ration measurements and different applications. Four examples of material transformations occurring at high temperature are herein reported: grain growth during annealing of a rolled platinum foil, recrystallisation of a multiphased alloy, oxidation of a Ni-based alloy and complex phase transformations occurring during the annealing of an Al-Si coated boron steel. The detector could be potentially adapted to any type of SEM and it offers good opportunities to perform high-temperature experiments in various atmospheres.

Catechin-based Dentin Pretreatment and the Clinical Performance of a Universal Adhesive: A Two-year Randomized Clinical Trial.

CLINICAL RELEVANCE: At 24 months, the dentin pretreatment with epigallocatechin-3-gallate did not impair the clinical performance of the adhesive Single Bond Universal regardless of the bonding strategy used. SUMMARY: Purpose: To evaluate the two-year effect of dentin pretreatment with epigallocatechin-3-gallate (EGCG) on the clinical performance of restorations of noncarious cervical lesions (NCCLs) with Single Bond Universal, applied in two different modes (self-etch and etch-and-rinse).Methods and Materials: In this randomized clinical trial, 33 volunteers were selected, and 156 NCCLs were assigned to four groups: ER, etch-and-rinse; ER-EGCG, 0.1% EGCG dentin pretreatment + etch-and-rinse; SE, self-etch; and SE-EGCG, 0.1% EGCG dentin pretreatment + self-etch. The NCCLs were restored with a nanofilled resin composite and evaluated at baseline and at six, 12, 18, and 24 months using FDI criteria for retention, marginal staining, marginal adaptation, caries, and postoperative sensitivity. Two evaluators were blinded to the treatments performed, and impressions were taken for resin replicas to allow indirect observations. Statistical analyses were performed with Kruskal-Wallis and McNemar tests with a significance level of 5%.Results: Six restorations (one from ER, two from SE, one from ER-EGCG, and two from SEEGCG) were lost at 24 months with no significant differences (p>0.05). The retention rates were 97.0% (ER and ER-EGCG), 94.1% (SE), and 94.2% (SE-EGCG). For marginal adaptation, a significant difference was detected between the baseline and 24 months for the SE group (p=0.0313). There were no statistical differences among all other evaluated criteria at 24 months, neither for each group at baseline nor for 24-month comparisons (p>0.05).Conclusions: The pretreatment with EGCG provided no benefit in the clinical performance of the adhesive regardless of the bonding strategy used. In addition, it adds an additional required step to the restorative procedure.

Asymptotic behavior of the length of the longest increasing subsequences of random walks.

We numerically estimate the leading asymptotic behavior of the length L_{n} of the longest increasing subsequence of random walks with step increments following Student's t-distribution with parameters in the range 1/2≤ν≤5. We find that the expected value E(L_{n})∼n^{θ}lnn, with θ decreasing from θ(ν=1/2)≈0.70 to θ(ν≥5/2)≈0.50. For random walks with a distribution of step increments of finite variance (ν>2), this confirms previous observation of E(L_{n})∼sqrt[n]lnn to leading order. We note that this asymptotic behavior (including the subleading term) resembles that of the largest part of random integer partitions under the uniform measure and that, curiously, both random variables seem to follow Gumbel statistics. We also provide more refined estimates for the asymptotic behavior of E(L_{n}) for random walks with step increments of finite variance.

Optical Control of the Topology of Laser-Plasma Accelerators.

We propose a twisted plasma accelerator capable of generating relativistic electron vortex beams with helical current profiles. The angular momentum of these vortex bunches is quantized, dominates their transverse motion, and results in spiraling particle trajectories around the twisted wakefield. We focus on a laser wakefield acceleration scenario, driven by a laser beam with a helical spatiotemporal intensity profile, also known as a light spring. We find that these light springs can rotate as they excite the twisted plasma wakefield, providing a new mechanism to control the twisted wakefield phase velocity and enhance energy gain and trapping efficiency beyond planar wakefields.

Density classification performance and ergodicity of the Gacs-Kurdyumov-Levin cellular automaton model IV.

Almost four decades ago, Gacs, Kurdyumov, and Levin introduced three different cellular automata to investigate whether one-dimensional nonequilibrium interacting particle systems are capable of displaying phase transitions, and, as a byproduct, they introduced the density classification problem (the ability to classify arrays of symbols according to their initial density) in the cellular automata literature. Their model II became a well-known model in theoretical computer science and statistical mechanics. The other two models, however, did not receive much attention. Here we characterize the density classification performance of Gacs, Kurdyumov, and Levin's model IV, a four-state cellular automaton with three absorbing states-only two of which are attractive-by numerical simulations. We show that model IV compares well with its sibling model II in the density classification task: the additional states slow down the convergence to the majority state but confer a slight advantage in classification performance. We also show that, unexpectedly, initial states diluted in one of the nonclassifiable states are more easily classified. The performance of model IV under the influence of noise was also investigated, and we found signs of an ergodic-nonergodic phase transition at some small finite positive level of noise, although the evidence is not entirely conclusive. We set an upper bound on the critical point for the transition, if any.

Plasmon excitations with a semi-integer angular momentum.

We provide an explicit model for a spin-1/2 quasi-particle, based on the superposition of plasmon excitations in a quantum plasmas with intrinsic orbital angular momentum. Such quasi-particle solutions can show remarkable similarities with single electrons moving in vacuum: they have spin-1/2, a finite rest mass, and a quantum dispersion. We also show that these quasi-particle solutions satisfy a criterium of energy minimum.

Axion-Plasmon Polaritons in Strongly Magnetized Plasmas.

Axions are hypothetical particles related to the violation of the charge-parity symmetry within the strong sector of the standard model, being one of the most prone candidates for dark matter. Multiple attempts to prove their existence are currently performed in different physical systems. Here, we predict that axions may couple to the electrostatic (Langmuir) modes of a strongly magnetized plasma, and show that a new quasiparticle can be defined, the axion-plasmon polariton. The excitation of axions can be inferred from the pronounced modification of the dispersion relation of the Langmuir waves, a feature that we estimate to be accessible in state-of-the-art plasma-based experiments.

Chemical profiling of two congeneric sea mat corals along the Brazilian coast: adaptive and functional patterns.

Metabolomic profiles were explored to understand environmental and taxonomic influences on the metabolism of two congeneric zoanthids, Palythoa caribaeorum and P. variabilis, collected across distinct geographical ranges. Integrated mass spectrometry data suggested the major influence of geographical location on chemical divergence when compared to species differentiation.

Genetic diversity of high performance cultivars of upland and irrigated Brazilian rice.

The objective of this study was to analyze the diversity and discrimination of high-performance Brazilian rice cultivars using microsatellite markers. Twenty-nine rice cultivars belonging to EMBRAPA Arroz e Feijão germplasm bank in Brazil were genotyped by 24 SSR markers to establish their structure and genetic discrimination. It was demonstrated that the analyzed germplasm of rice presents an expressive and significant genetic diversity with low heterogeneity among the cultivars. All 29 cultivars were differentiated genetically, and were organized into two groups related to their upland and irrigated cultivation systems. These groups showed a high genetic differentiation, with greater diversity within the group that includes the cultivars for irrigated system. The genotyping data of these cultivars, with the morphological e phenotypical data, are valuable information to be used by rice breeding programs to develop new improved cultivars.

Approximate probabilistic cellular automata for the dynamics of single-species populations under discrete logisticlike growth with and without weak Allee effects.

We investigate one-dimensional elementary probabilistic cellular automata (PCA) whose dynamics in first-order mean-field approximation yields discrete logisticlike growth models for a single-species unstructured population with nonoverlapping generations. Beginning with a general six-parameter model, we find constraints on the transition probabilities of the PCA that guarantee that the ensuing approximations make sense in terms of population dynamics and classify the valid combinations thereof. Several possible models display a negative cubic term that can be interpreted as a weak Allee factor. We also investigate the conditions under which a one-parameter PCA derived from the more general six-parameter model can generate valid population growth dynamics. Numerical simulations illustrate the behavior of some of the PCA found.

Tonks-Dattner resonances in a quantum plasma bubble.

We establish the spectrum of Tonks-Dattner mode resonances in a quantum plasma bubble and consider the spectral changes associated with plasma quenching and plasma expansion. The quantum corrections associated with the mode spectrum are specified, which can be used as a diagnostic tool to identify the quantum regime. The frequency shifts associated with time-varying plasma bubbles correspond to time refraction and can also be used as a plasma diagnostic. We also study the energy mode coupling, in the presence of a low-frequency perturbation. It will be shown that the mode coupling equations take the form of generalized Bloch equations, where a nonlinear Rabi frequency can also be identified.

Streptococcus agalactiae infection in cancer patients: a five-year study.

Although the highest burden of Streptococcus agalactiae infections has been reported in industrialized countries, studies on the characterization and epidemiology are still limited in developing countries and implementation of control strategies remains undefined. The aim of this retrospective study was to assess the epidemiological, clinical, and microbiological aspects of S. agalactiae infections in cancer patients treated at a Reference Brazilian National Cancer Institute - INCA, Rio de Janeiro, Brazil. We reviewed the clinical and laboratory records of all cancer patients identified as having invasive S. agalactiae disease during 2010-2014. The isolates were identified by biochemical analysis and tested for antimicrobial susceptibility. A total of 263 strains of S. agalactiae were isolated from cancer patients who had been clinically and microbiologically classified as infected. S. agalactiae infections were mostly detected among adults with solid tumors (94 %) and/or patients who have used indwelling medical devices (77.2 %) or submitted to surgical procedures (71.5 %). Mortality rates (in-hospital mortality during 30 days after the identification of S. agalactiae) related to invasive S. agalactiae infections (n = 28; 31.1 %) for the specific category of neoplasic diseases were: gastrointestinal (46 %), head and neck (25 %), lung (11 %), hematologic (11 %), gynecologic (4 %), and genitourinary (3 %). We also found an increase in S. agalactiae resistance to erythromycin and clindamycin and the emergence of penicillin-less susceptible isolates. A remarkable number of cases of invasive infections due to S. agalactiae strains was identified, mostly in adult patients. Our findings reinforce the need for S. agalactiae control measures in Brazil, including cancer patients.

Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering.

Twisted Laguerre-Gaussian lasers, with orbital angular momentum and characterized by doughnut-shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high-gradient positron acceleration. The production of ultra-high-intensity twisted laser pulses could then also have a broad influence on relativistic laser-matter interactions. Here we show theoretically and with ab initio three-dimensional particle-in-cell simulations that stimulated Raman backscattering can generate and amplify twisted lasers to petawatt intensities in plasmas. This work may open new research directions in nonlinear optics and high-energy-density science, compact plasma-based accelerators and light sources.

High Orbital Angular Momentum Harmonic Generation.

We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.