Periodic orbits for a class of reversible quadratic vector field on R-3

For a class of reversible quadratic vector fields on R-3 we study the periodic orbits that bifurcate from a heteroclinic loop having two singular points at infinity connected by an invariant straight line in the finite part and another straight line at infinity in the local chart U-2. More specifically, we prove that for all n is an element of N, there exists epsilon(n) > 0 such that the reversible quadratic polynomial differential systemx = a(0) + a(1y) + a(3y)(2) + a(4Y)(2) + epsilon(a(2x)(2) + a(3xz)),y = b(1z) + b(3yz) + epsilon b(2xy),z = c(1y) +c(4az)(2) + epsilon c(2xz)in R-3, with a(0) < 0, b(1)c(1) < 0, a(2) < 0, b(2) < a(2), a(4) > 0, c(2) < a(2) and b(3) is not an element of (c(4), 4c(4)), for epsilon is an element of (0, epsilon(n)) has at least n periodic orbits near the heteroclinic loop. (c) 2007 Elsevier B.V. All rights reserved.

Visual and acoustic communication in the Brazilian torrent frog, Hylodes asper (Anura : Leptodactylidae)

We studied the signaling, territorial, and courtship behaviors of the diurnal frog Hylodes asper. Visual and acoustic communication were used during intraspecific interactions involving males, females. and subadults. Hylodes aspcr has a complex visual communication system, of which foot-flagging is the most distinctive display observed in the repertoire of visual signals. The splash zone produced by the waterfalls and torrents creates a high, nearly constant, humidity near the streams, reducing the risk of desiccation which enables the diurnal activity of H. asper. Although the ambient sound pressure levels (SPL), measured at the calling sites, are similar to the SPL of the advertisement calls, the high-pitched calls of H, asper, are spectrally different from the noise produced by the water current. Thus. The ambient noise produced by the water current may not interfere significantly with the acoustic communication of this species. The noise and the nearly constant and high humidity produced by the torrents and waterfalls, along with the availability of Light, probably favored the evolution of contrasting colors and visual communication in H. asper: Males of H, aspcr excavate underwater chambers that are probably used to shelter the eggs and to prevent the clutch from being drifted downstream.

Local structure and near-infrared emission features of neodymium-based amine functionalized organic/inorganic hybrids

Nd3+-based organic/inorganic hybrids have potential application in the field of integrated optics. Attractive sol-gel derived di-urea and di-urethane cross-linked poly (oxyethylene) (POE)/siloxane hybrids (di-ureasils and di-urethanesils, respectively) doped with neodymium triflate (Nd(CF3SO3)(3)) were examined by Fourier transform mid-infrared (FT-IR), Raman (FT-Raman), Si-29 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and photoluminescence spectroscopies, and small-angle X-ray scattering (SAXS). The goals of this work were to determine which cation coordinating site of the host matrix (ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the photoluminescence properties. The main conclusion derived from this study is that the hydrogen-bonded associations formed throughout the materials play a major role in the hybrids nanostructure and photoluminescence properties.

Visual communication in Brazilian species of anurans from the Atlantic forest

Visual communication is widespread among several anuran families, but seems to be more common than currently thought. We investigated and compared visual communication in six species of an anuran community in the Brazilian Atlantic forest. Four are nocturnal species: Hyalinobatrachium uranoscopum (Centrolenidae), Hyla albomarginata, Hyla sp. (aff. ehrhardti), and Scinax eurydice (Hylidae), and two are diurnal species: Hylodes phyllodes and Hylodes asper ( Leptodactylidae). For H. uranoscopum, H. albomarginata, S. eurydice, and H. phyllodes, this is the first record of visual communication. Observations were made at Nucleo Picinguaba, Parque Estadual da Serra do Mar, in the Municipality of Ubatuba, State of São Paulo, Brazil. Descriptions of behaviour were based on individuals observed in the field, using sequence sampling with continuous tape recording for behavioural observations. Eight new behaviours are described: body wiping, face wiping, jump display, leg kicking, limb lifting, mouth opening, toe flagging, and vocal sac display. of the 42 anuran species known from Nucleo Picinguaba, at least six ( approximately 14%) display visual communication. The evolution of visual signals in these species may be related to the availability of ambient light, the structural complexity of the habitat, and/or the ambient noise. They may also have evolved to aid in the location of the individual, to avoid physical combat, and/or may be a by-product of seismic communication.

Anomalous metamagnetic-like transition in a FeRh/Fe3Pt interface occurring at T approximate to 120 K in the field-cooled-cooling curves for low magnetic fields

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The use of shallow seismic reflection technique in near surface exploration of urban sites: An evaluation in the city of SãO Paulo, Brazil

In order to evaluate the use of shallow seismic technique to delineate geological and geotechnical features up to 40 meters depth in noisy urban areas covered with asphalt pavement, five survey lines were conducted in the metropolitan area of São Paulo City. The data were acquired using a 24-bit, 24-channel seismograph, 30 and 100 Hz geophones and a sledgehammer-plate system as seismic source. Seismic reflection data were recorded using a CMP (common mid point) acquisition method. The processing routine consisted of: prestack band-pass filtering (90-250 Hz); automatic gain control (AGC); muting (digital zeroin) of dead/noisy traces, ground roll, air-wave and refracted-wave; CMP sorting; velocity analyses; normal move-out corrections; residual static corrections; f-k filtering; CMP stacking. The near surface is geologically characterized by unconsolidated fill materials and Quaternary sediments with organic material overlying Tertiary sediments with the water table 2 to 5 m below the surface. The basement is composed of granite and gneiss. Reflections were observed from 40 milliseconds to 65 ms two-way traveltime and were related to the silt clay layer and fine sand layer contact of the Tertiary sediments and to the weathered basement. The CMP seismic-reflection technique has been shown to be useful for mapping the sedimentary layers and the bedrock of the São Paulo sedimentary basin for the purposes of shallow investigations related to engineering problems. In spite of the strong cultural noise observed in these urban areas and problems with planting geophones we verified that, with the proper equipment, field parameters and particularly great care in data collection and processing, we can overcome the adverse field conditions and to image reflections from layers as shallow as 20 meters.

Observation of long-range, near-side angular correlations in pPb collisions at the LHC

Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, η, and full azimuth, φ, as a function of charged particle multiplicity and particle transverse momentum, pT. In high-multiplicity events, a long-range (2<|δη|<4), near-side (δφ≈0) structure emerges in the two-particle δη-δφ correlation functions. This is the first observation of such correlations in proton-nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at s=7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of pT=1-1.5 GeV/c and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions. © 2012 CERN.

The perception of brazilian researchers concerning the factors that influence the citation of their articles: A study in the field of sustainability

With growing institutional pressure from the Brazilian government to increase the impact of research that it funds, Brazilian researchers are increasingly interested in discovering factors that affect the citation of their articles. The aim of the present article was to assess the perceptions of Brazilian sustainability researchers to identify factors that influence the impacts of their research. A survey was conducted with researchers in the field of sustainability and 89 questionnaires were completed. All of those researchers have articles or research projects in the field of sustainability (mixing environmental, social and/or economical) recorded in the Scielo or Lattes Curriculum Brazilian databases. Results suggest four factors that may explain the impact of article citations: (1) prestige of the author and the research network; (2) prestige of the means of publication and indexing; (3) accessibility and quality characteristics of the article; and (4) international nature of communication and scope of the study. Surprisingly, such factors were not statistically significant in explaining the citations of the participating researchers. These results show the need to consider other factors that can explain the impact of research, discovering the missing links. © 2013 Elsevier Inc.

Observation of a new boson with mass near 125 GeV in pp collisions at √=7 and 8 TeV

A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb-1 at √=7 TeV, and up to 5.3 fb-1 at √ s=8 TeV. The results for five Higgs boson decay modes γγ, ZZ, WW, ττ, and bb, which show a combined local significance of 5 standard deviations near 125 GeV, are reviewed. A fit to the invariant mass of the two high resolution channels, γγ and ZZ → 4ℓ, gives a mass estimate of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The measurements are interpreted in the context of the standard model Lagrangian for the scalar Higgs field interacting with fermions and vector bosons. The measured values of the corresponding couplings are compared to the standard model predictions. The hypothesis of custodial symmetry is tested through the measurement of the ratio of the couplings to the W and Z bosons. All the results are consistent, within their uncertainties, with the expectations for a standard model Higgs boson. [Figure not available: see fulltext.] © 2013 CERN for the benefit of the CMS collaboration.

Information and communication technology for disaster risk management in the Caribbean: subregional solutions to the challenge of limited human resource capacity

This document was adapted from a paper originally presented to the 8th Annual Caribbean Conference of Comprehensive Disaster Management, held in Montego Bay, Jamaica in December, 2013. It summarizes several activities that ECLAC has undertaken to assess the current state of information and communications technology (ICT) in the field of disaster risk management (DRM) as practiced in the Caribbean. These activities included an in-depth study that encompassed a survey of disaster management organizations in the region, an Expert Group Meeting attended by the heads of several national disaster offices, and a training workshop for professionals working in DRM in the Caribbean. One of the notable conclusions of ECLAC’s investigation on this topic is that the lack of human capacity is the single largest constraint that is faced in the implementation of ICT projects for DRM in the Caribbean. In considering strategies to address the challenge of limited human capacity at a regional level, two separate issues are recognized – the need to increase the ICT capabilities of disaster management professionals, and the need to make ICT specialists available to disaster management organizations to advise and assist in the implementation of technology-focused projects. To that end, two models are proposed to engage with this issue at a regional level. The first entails the establishment of a network of ICT trainers in the Caribbean to help DRM staff develop a strategic understanding of how technology can be used to further their organizational goals. The second is the development of “Centres of Excellence” for ICT in the Caribbean, which would enable the deployment of specialized ICT expertise to national disaster management offices on a project-by-project basis.

A contribuition to the study of channel coding in wireless communication systems

Pós-graduação em Engenharia Elétrica - FEIS

Cellular behavior as a dynamic field for exploring bone bioengineering: A closer look at cell-biomaterial interface

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

FLOW AROUND A SQUARE CYLINDER POSITIONED NEAR A SMOOTH FLAT PLATE

Vortex shedding phenomenon produced by a square cylinder placed close to a smooth flat plate is experimentally studied by means of flow visualization techniques and hot-film anemometry. Qualitative and quantitative information about the flow field has been obtained for Reynolds numbers up to 1,000. Vortex shedding images in several Reynolds number have been captured and the non dimensional vortex shedding frequency has been obtained as a function of the Reynolds number.

Local order and magnetic field effects on the electronic properties of disordered binary alloys in the quantum site percolation limit

Electronic properties of disordered binary alloys are studied via the calculation of the average Density of States (DOS) in two and three dimensions. We propose a new approximate scheme that allows for the inclusion of local order effects in finite geometries and extrapolates the behavior of infinite systems following finite-size scaling ideas. We particularly investigate the limit of the Quantum Site Percolation regime described by a tight-binding Hamiltonian. This limit was chosen to probe the role of short range order (SRO) properties under extreme conditions. The method is numerically highly efficient and asymptotically exact in important limits, predicting the correct DOS structure as a function of the SRO parameters. Magnetic field effects can also be included in our model to study the interplay of local order and the shifted quantum interference driven by the field. The average DOS is highly sensitive to changes in the SRO properties and striking effects are observed when a magnetic field is applied near the segregated regime. The new effects observed are twofold: there is a reduction of the band width and the formation of a gap in the middle of the band, both as a consequence of destructive interference of electronic paths and the loss of coherence for particular values of the magnetic field. The above phenomena are periodic in the magnetic flux. For other limits that imply strong localization, the magnetic field produces minor changes in the structure of the average DOS. © World Scientific Publishing Company.

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

The transport properties of the two-dimensional system in HgTe-based quantum wells containing simultaneously electrons and holes of low densities are examined. The Hall resistance, as a function of perpendicular magnetic field, reveals an unconventional behavior, different from the classical N-shaped dependence typical for bipolar systems with electron-hole asymmetry. The quantum features of magnetotransport are explained by means of numerical calculation of the Landau level spectrum based on the Kane Hamiltonian. The origin of the quantum Hall plateau sigma(xy) = 0 near the charge neutrality point is attributed to special features of Landau quantization in our system.