Alternate islands of multiple isochronous chains in wave-particle interactions

We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous island chains varies as a function of the wave parameters. We observe that in all the resonances, the number of chains is related to the amplitude of the various resonant terms. We determine analytically the position of the periodic points and the number of island chains as a function of the wave number and wave period. Such information is very important when one is concerned with regular particle acceleration, since it is necessary to adjust the initial conditions of the particle to obtain the maximum acceleration.Comment: Submitte

Characterization of the Intra-Unit-Cell magnetic order in Bi2Sr2CaCu2O8+d

As in YBa2Cu3O6+x and HgBa2CuO8+d, the pseudo-gap state in Bi2Sr2CaCu2O8+d is characterized by the existence of an intra-unit-cell magnetic order revealed by polarized neutron scattering technique. We report here a supplementary set of polarized neutron scattering measurements for which the direction of the magnetic moment is determined and the magnetic intensity is calibrated in absolute units. The new data allow a close comparison between bilayer systems YBa2Cu3O6+x and Bi2Sr2CaCu2O8+d and rise important questions concerning the range of the magnetic correlations and the role of disorder around optimal doping.Comment: 12 pages, 8 figures, submitted to physical review

From “boat to plate”: creating value through sustainable fish supply chain visibility

Environmental concerns about the scarcity of marine resources are critical driving forces for firms aiming to prepare their supply chains for sustainability. Building on previous work, this paper highlights the mplementation of good practices geared towards sustainable operations in the seafood department, which were pursued in an exploratory retailer case. Outcomes of the adopted environmentally and socially acceptable fish retailing strategies, ranged from traceability, to self-certification and eco-labelling. The consequences for business were, as follows: stronger collaboration and trust across the chain of custody, improvement of sponsors’ image and of consumers’ loyalty and, progress in the Greenpeace retailers’ evaluation ranking.info:eu-repo/semantics/publishedVersio

Nanometric pitch in modulated structures of twist-bend nematic liquid crystals

The extended Frank elastic energy density is used to investigate the existence of a stable periodically modulate structure that appears as a ground state exhibiting a twist-bend molecular arrangement. For an unbounded sample, we show that the twist-bend nematic phase $N_{TB}$ is characterized by a heliconical structure with a pitch in the nano-metric range, in agreement with experimental results. For a sample of finite thickness, we show that the wave vector of the stable periodic structure depends not only on the elastic parameters but also on the anchoring energy, easy axis direction, and the thickness of the sample.Comment: 11 page

Tetragonal tungsten bronze compounds: relaxor vs mixed ferroelectric - dipole glass behavior

We demonstrate that recent experimental data (E. Castel et al J.Phys. Cond. Mat. {\bf 21} (2009), 452201) on tungsten bronze compound (TBC) Ba$_2$Pr$_x$Nd$_{1-x}$FeNb$_4$O$_{15}$ can be well explained in our model predicting a crossover from ferroelectric ($x=0$) to orientational (dipole) glass ($x=1$), rather then relaxor, behavior. We show, that since a "classical" perovskite relaxor like Pb(Mn$_{1/3}$ Nb$_{2/3}$)O$_3$ is never a ferroelectric, the presence of ferroelectric hysteresis loops in TBC shows that this substance actually transits from ferroelectric to orientational glass phase with $x$ growth. To describe the above crossover theoretically, we use the simple replica-symmetric solution for disordered Ising model.Comment: 5 two-column pages, 4 figure

Calagem melhora a disponibilidade de cálcio no solo e a produtividade de Ilex paraguariensis St. Hil.

Avaliou-se a influência da calagem na disponibilidade de Ca2+ no solo, produtividade e teor foliar de Ca e Al em erva-mate. Instalaram-se experimentos em três locais, avaliando-se cinco doses superficiais de calcário dolomítico para atingir 50 % das seguintes saturações por bases: 0, 30, 60, 90 e 120 %. Após 18 meses, avaliou-se: teor de Ca2+ no solo em três profundidades; teor foliar de Ca e Al e produtividade de erva-mate comercial (ECOM). A calagem, não alterou o teor foliar de Ca, mas, reduziu o de Al. A calagem, aumentou o teor de Ca 2+ no solo e, a produtividade de ECOM entre 21 e 27 %. Em solos com baixa disponibilidade natural de Ca 2+, a calagem deve disponibilizá-lo entre 4,0-4,5 cmol c dm-3 na profundidade de 0-5 cm, já em solos com alta disponibilidade de Ca 2+, a calagem deve disponibilizar o nutriente até 6,0 cmolc dm-3 para o cultivo da erva-mate

Adubação potássica e intervalos de colheita influenciam o potássio do solo e a produtividade de cultivos de erva-mate.

O trabalho objetivou avaliar a adubação potássica e intervalos de colheita na disponibilidade de potássio, produtividade e distribuição do conteúdo de potássio na massa colhida da erva-mate. Avaliaram-se doses de 0, 20, 40, 80, 160 e 320 kg ha-1 de K2O para colheitas com intervalos de 12, 18 e 24 meses. Quantificou-se a disponibilidade de potássio em duas profundidades do solo e a produtividade de erva-mate comercial (ECOM) e galho grosso (GG) e distribuição do conteúdo de K nesses componentes. A adubação potássica aumentou a disponibilidade de potássio no solo e aumentou a produtividade da erva-mate. Para cultivos em solos com disponibilidade em nível baixo de potássio, recomenda-se doses próximas a 190, 270 e 320 kg ha-1 de K2O, respectivamente, para colheitas com intervalos de 12, 18 e 24 meses. Na retirada do GG da área, requer adubação de reposição do potássio adicional entre 20 a 30 %

Modular Acquisition and Stimulation System for Timestamp-Driven Neuroscience Experiments

Dedicated systems are fundamental for neuroscience experimental protocols that require timing determinism and synchronous stimuli generation. We developed a data acquisition and stimuli generator system for neuroscience research, optimized for recording timestamps from up to 6 spiking neurons and entirely specified in a high-level Hardware Description Language (HDL). Despite the logic complexity penalty of synthesizing from such a language, it was possible to implement our design in a low-cost small reconfigurable device. Under a modular framework, we explored two different memory arbitration schemes for our system, evaluating both their logic element usage and resilience to input activity bursts. One of them was designed with a decoupled and latency insensitive approach, allowing for easier code reuse, while the other adopted a centralized scheme, constructed specifically for our application. The usage of a high-level HDL allowed straightforward and stepwise code modifications to transform one architecture into the other. The achieved modularity is very useful for rapidly prototyping novel electronic instrumentation systems tailored to scientific research.Comment: Preprint submitted to ARC 2015. Extended: 16 pages, 10 figures. The final publication is available at link.springer.co

Semiclassical Evolution of Dissipative Markovian Systems

A semiclassical approximation for an evolving density operator, driven by a "closed" hamiltonian operator and "open" markovian Lindblad operators, is obtained. The theory is based on the chord function, i.e. the Fourier transform of the Wigner function. It reduces to an exact solution of the Lindblad master equation if the hamiltonian operator is a quadratic function and the Lindblad operators are linear functions of positions and momenta. Initially, the semiclassical formulae for the case of hermitian Lindblad operators are reinterpreted in terms of a (real) double phase space, generated by an appropriate classical double Hamiltonian. An extra "open" term is added to the double Hamiltonian by the non-hermitian part of the Lindblad operators in the general case of dissipative markovian evolution. The particular case of generic hamiltonian operators, but linear dissipative Lindblad operators, is studied in more detail. A Liouville-type equivariance still holds for the corresponding classical evolution in double phase, but the centre subspace, which supports the Wigner function, is compressed, along with expansion of its conjugate subspace, which supports the chord function. Decoherence narrows the relevant region of double phase space to the neighborhood of a caustic for both the Wigner function and the chord function. This difficulty is avoided by a propagator in a mixed representation, so that a further "small-chord" approximation leads to a simple generalization of the quadratic theory for evolving Wigner functions.Comment: 33 pages - accepted to J. Phys.