Estrutura e distribuição espacial de andirobeiras (Carapa spp.) em floresta de várzea do Estuário Amazônico.

O objetivo geral deste trabalho foi avaliar se a densidade de ocorrência de andirobeiras é dependente da distância do rio Amazonas, analisando sua distribuição espacial e a estrutura diamétrica da população em um trecho de floreta de várzea no Estado do Amapá. Esse trabalho faz parte do projeto Florestam (Ecologia e manejo florestal para uso múltiplo de várzeas do estuário amazônico) e foi desenvolvido em uma área de proteção ambiental (APA) de 136,59 ha, localizada no Distrito da Fazendinha, município de Macapá - AP (00°03’04,24”S e 51º07’42,72”W). Foram lançados 3 transectos perpendiculares à margem do rio Amazonas, distanciados entre si a cada 500 m, para orientar no direcionamento e localização das árvores

A Quantum Approach to Classical Statistical Mechanics

We present a new approach to study the thermodynamic properties of $d$-dimensional classical systems by reducing the problem to the computation of ground state properties of a $d$-dimensional quantum model. This classical-to-quantum mapping allows us to deal with standard optimization methods, such as simulated and quantum annealing, on an equal basis. Consequently, we extend the quantum annealing method to simulate classical systems at finite temperatures. Using the adiabatic theorem of quantum mechanics, we derive the rates to assure convergence to the optimal thermodynamic state. For simulated and quantum annealing, we obtain the asymptotic rates of $T(t) \approx (p N) /(k_B \log t)$ and $\gamma(t) \approx (Nt)^{-\bar{c}/N}$, for the temperature and magnetic field, respectively. Other annealing strategies, as well as their potential speed-up, are also discussed.Comment: 4 pages, no figure

Carbon stock in areas of pasture and native vegetation.

One of the factors that may indicate the quality of soil is the organic matter (SOM), directly linked to structural, biological and chemical soil characteristics, in addition it is stock for carbon (C) and nitrogen (N). For grazing areas, stocks of C and N vary when compared to natural vegetation inventories. Factors such as the type of management adopted, climatic condition and renewal of plants can contribute to stocks become smaller over land use. Thus, the objective of this study was to evaluate the initial and final C stocks in pasture under two types of grazing and native vegetation

Tunable Emergent Heterostructures in a Prototypical Correlated Metal

At the interface between two distinct materials desirable properties, such as superconductivity, can be greatly enhanced, or entirely new functionalities may emerge. Similar to in artificially engineered heterostructures, clean functional interfaces alternatively exist in electronically textured bulk materials. Electronic textures emerge spontaneously due to competing atomic-scale interactions, the control of which, would enable a top-down approach for designing tunable intrinsic heterostructures. This is particularly attractive for correlated electron materials, where spontaneous heterostructures strongly affect the interplay between charge and spin degrees of freedom. Here we report high-resolution neutron spectroscopy on the prototypical strongly-correlated metal CeRhIn5, revealing competition between magnetic frustration and easy-axis anisotropy -- a well-established mechanism for generating spontaneous superstructures. Because the observed easy-axis anisotropy is field-induced and anomalously large, it can be controlled efficiently with small magnetic fields. The resulting field-controlled magnetic superstructure is closely tied to the formation of superconducting and electronic nematic textures in CeRhIn5, suggesting that in-situ tunable heterostructures can be realized in correlated electron materials

Comparison of S=0 and S=1/2 Impurities in Haldane Chain Compound, Y2BaNiO5Y_{2}BaNiO_{5}

We present the effect of Zn (S=0) and Cu (S=1/2) substitution at the Ni site of S=1 Haldane chain compound $Y_{2}BaNiO_{5}$. $^{89}$Y NMR allows us to measure the local magnetic susceptibility at different distances from the defects. The $^{89}$Y NMR spectrum consists of one central peak and several less intense satellite peaks. The shift of the central peak measures the uniform susceptibility, which displays a Haldane gap $Delta$$equiv$100 K and it corresponds to an AF coupling J$equiv$260 K between the near-neighbor Ni spins. Zn or Cu substitution does not affect the Haldane gap. The satellites, which are evenly distributed on the two sides of the central peak, probe the antiferromagnetic staggered magnetization near the substituted site, which decays exponentially. Its extension is found identical for both impurities and corresponds accurately to the correlation length $xi$(T) determined by Monte Carlo (QMC) simulations for the pure compound. In the case of non-magnetic Zn, the temperature dependence of the induced magnetization is consistent with a Curie law with an "effective" spin S=0.4 on each side of Zn, which is well accounted by Quantum Monte Carlo computations of the spinless-defect-induced magnetism. In the case of magnetic Cu, the similarity of the induced magnetism to the Zn case implies a weak coupling of the Cu spin to the nearest- neighbor Ni spins. The slight reductionin the induced polarization with respect to Zn is reproduced by QMC computations by considering an antiferromagnetic coupling of strength J'=0.1-0.2 J between the S=1/2 Cu-spin and nearest-neighbor Ni-spin.Comment: 15 pages, 18 figures, submitted to Physical Review

Improving Many-Objective Evolutionary Algorithms by Means of Edge-Rotated Cones

Given a point in $m$-dimensional objective space, any $\varepsilon$-ball of a point can be partitioned into the incomparable, the dominated and dominating region. The ratio between the size of the incomparable region, and the dominated (and dominating) region decreases proportionally to $1/2^{m-1}$, i.e., the volume of the Pareto dominating orthant as compared to all other volumes. Due to this reason, it gets increasingly unlikely that dominating points can be found by random, isotropic mutations. As a remedy to stagnation of search in many objective optimization, in this paper, we suggest to enhance the Pareto dominance order by involving an obtuse convex dominance cone in the convergence phase of an evolutionary optimization algorithm. We propose edge-rotated cones as generalizations of Pareto dominance cones for which the opening angle can be controlled by a single parameter only. The approach is integrated in several state-of-the-art multi-objective evolutionary algorithms (MOEAs) and tested on benchmark problems with four, five, six and eight objectives. Computational experiments demonstrate the ability of these edge-rotated cones to improve the performance of MOEAs on many-objective optimization problems

Competing orders in a magnetic field: spin and charge order in the cuprate superconductors

We describe two-dimensional quantum spin fluctuations in a superconducting Abrikosov flux lattice induced by a magnetic field applied to a doped Mott insulator. Complete numerical solutions of a self-consistent large N theory provide detailed information on the phase diagram and on the spatial structure of the dynamic spin spectrum. Our results apply to phases with and without long-range spin density wave order and to the magnetic quantum critical point separating these phases. We discuss the relationship of our results to a number of recent neutron scattering measurements on the cuprate superconductors in the presence of an applied field. We compute the pinning of static charge order by the vortex cores in the `spin gap' phase where the spin order remains dynamically fluctuating, and argue that these results apply to recent scanning tunnelling microscopy (STM) measurements. We show that with a single typical set of values for the coupling constants, our model describes the field dependence of the elastic neutron scattering intensities, the absence of satellite Bragg peaks associated with the vortex lattice in existing neutron scattering observations, and the spatial extent of charge order in STM observations. We mention implications of our theory for NMR experiments. We also present a theoretical discussion of more exotic states that can be built out of the spin and charge order parameters, including spin nematics and phases with `exciton fractionalization'.Comment: 36 pages, 33 figures; for a popular introduction, see http://onsager.physics.yale.edu/superflow.html; (v2) Added reference to new work of Chen and Ting; (v3) reorganized presentation for improved clarity, and added new appendix on microscopic origin; (v4) final published version with minor change

The small GTPase Rab29 is a common regulator of immune synapse assembly and ciliogenesis

Acknowledgements We wish to thank Jorge Galán, Gregory Pazour, Derek Toomre, Giuliano Callaini, Joel Rosenbaum, Alessandra Boletta and Francesco Blasi for generously providing reagents and for productive discussions, and Sonia Grassini for technical assistance. The work was carried out with the financial support of Telethon (GGP11021) and AIRC.Peer reviewedPostprin