The young massive stellar cluster associated to RCW121

We report NIR broad and narrow band photometric observations in the direction of the IRAS17149-3916 source that reveal the presence of a young cluster of massive stars embedded in an HII region coincident with RCW121. These observations, together with published radio data, MSX and Spitzer images were used to determine some of the physical parameters of the region. We found 96 cluster member candidates in an area of about 1.5 x 2.0 square arcmin, 30% of them showing excess emission in the NIR. IRS 1, the strongest source in the cluster with an estimated spectral type of O5V-O6V ZAMS based on the color-magnitude diagram, is probably the main ionizing source of the HII region detected at radio wavelengths. Using the integrated Brgamma and the 5 GHz flux densities, we derived a mean visual extinction AV=5.49 magnitudes. From the observed size of the Brgamma extended emission, we calculated the emission measure E and the electron density ne, characteristic of compact HII regions.Comment: 18 pages, 8 figures, accepted for publication on AJ (February/2006

Energy Density-Flux Correlations in an Unusual Quantum State and in the Vacuum

In this paper we consider the question of the degree to which negative and positive energy are intertwined. We examine in more detail a previously studied quantum state of the massless minimally coupled scalar field, which we call a ``Helfer state''. This is a state in which the energy density can be made arbitrarily negative over an arbitrarily large region of space, but only at one instant in time. In the Helfer state, the negative energy density is accompanied by rapidly time-varying energy fluxes. It is the latter feature which allows the quantum inequalities, bounds which restrict the magnitude and duration of negative energy, to hold for this class of states. An observer who initially passes through the negative energy region will quickly encounter fluxes of positive energy which subsequently enter the region. We examine in detail the correlation between the energy density and flux in the Helfer state in terms of their expectation values. We then study the correlation function between energy density and flux in the Minkowski vacuum state, for a massless minimally coupled scalar field in both two and four dimensions. In this latter analysis we examine correlation functions rather than expectation values. Remarkably, we see qualitatively similar behavior to that in the Helfer state. More specifically, an initial negative energy vacuum fluctuation in some region of space is correlated with a subsequent flux fluctuation of positive energy into the region. We speculate that the mechanism which ensures that the quantum inequalities hold in the Helfer state, as well as in other quantum states associated with negative energy, is, at least in some sense, already ``encoded'' in the fluctuations of the vacuum.Comment: 21 pages, 7 figures; published version with typos corrected and one added referenc

Complementary optical-potential analysis of alpha-particle elastic scattering and induced reactions at low energies

A previously derived semi-microscopic analysis based on the Double Folding Model, for alpha-particle elastic scattering on A~100 nuclei at energies below 32 MeV, is extended to medium mass A ~ 50-120 nuclei and energies from ~13 to 50 MeV. The energy-dependent phenomenological imaginary part for this semi-microscopic optical model potential was obtained including the dispersive correction to the microscopic real potential, and used within a concurrent phenomenological analysis of the same data basis. A regional parameter set for low-energy alpha-particles entirely based on elastic-scattering data analysis was also obtained for nuclei within the above-mentioned mass and energy ranges. Then, an ultimate assessment of (alpha,gamma), (alpha,n) and (alpha,p) reaction cross sections concerned target nuclei from 45Sc to 118Sn and incident energies below ~12 MeV. The former diffuseness of the real part of optical potential as well as the surface imaginary-potential depth have been found responsible for the actual difficulties in the description of these data, and modified in order to obtain an optical potential which describe equally well both the low energy elastic-scattering and induced-reaction data of alpha-particles.Comment: 46 pages, 16 figures. n_TOF Collaboration Annual Meeting, Bari, Italy, 28-30 November 2007 (http://www.cern.ch/ntof/Documents/bari_nov07/bari_slides.php); revised version accepted for publication in ADND

Plantas ornamentais em quintais urbanos de Rio Branco, Brasil.

As plantas ornamentais são importantes na cultura e no bem estar dos moradores das cidades na Amazônia. Este trabalho teve como objetivo caracterizar as espécies vegetais de uso ornamental em quintais urbanos de Rio Branco, Acre, e a relação com aspectos sociais. Foram realizadas entrevistas semiestruturadas, abrangendo 132 quintais urbanos, entre 2009 e 2011. Os bairros selecionados para este estudo foram Aeroporto Velho, Placas e Conjunto Novo Horizonte, situados na periferia do município. Foram catalogadas 140 espécies ornamentais, pertencentes a 49 famílias botânicas, com destaque para Euphorbiaceae (7%), Arecaceae (6,4%) e Araceae (5%). Entre as espécies ornamentais registradas, 57,5% são exóticas, 16% apresentam uso medicinal e 44% são herbáceas. A análise de regressão dos dados entre a diversidade de espécies, a área e os parâmetros sociais dos entrevistados não mostrou significância. O cultivo de plantas ornamentais em quintais urbanos de Rio Branco auxilia na ambiência da residência e melhoria da paisagem, gera bem estar aos moradores pelo espaço de lazer e contribui para a conservação de recursos genéticos

Competição de gramíneas forrageiras em relação a ervas invasoras de pastagens em Porto Velho-RO.

O presente trabalho teve por finalidade testar métodos de controle e gramíneas mais competitivas com as ervas invasoras, visando minimizar os custos de seu controle em sistemas integrados.bitstream/item/56193/1/COT1602-0001.pd

Improving light harvesting in polymer photodetector devices through nanoindented metal mask films

To enhance light harvesting in organic photovoltaic devices, we propose the incorporation of a metal (aluminum) mask film in the system’s usual layout. We fabricate devices in a sandwich geometry, where the mask (nanoindented with a periodic array of holes of sizes d and spacing s) is added between the transparent electrode and the active layer formed by a blend of the semiconducting polymer P3HT and substituted fullerene. Its function is to promote trapping of the incident light into the device’s cavity (the region corresponding to the active layer). For d, we set a value that allows light diffraction through the holes in the relevant absorption range of the polymer. To optimize the mask structure, we consider a very simple model to determine the s leading to trapped fields that are relatively intense and homogeneous within the device. From measurements of the action spectra, we show that, indeed, such architecture can considerably improve the resulting photocurrent efficiencies—one order of magnitude in the best situation studied.

Agrobiodiversidade dos quintais urbanos de Rio Branco, AC.

O objetivo deste estudo foi relatar a ocorrência de espécies vegetais cultivadas nos quintais urbanos de Rio Branco, AC. Foram diagnosticados aspectos socioecnômicos das familias e um levantamento das espécies vegetais cultivadas em 100 quintais situados na cidade de Rio Branco, AC no final do segundo semestre de 2011 e inicio do primeiro semestre de 2012. O trabalho foi realizado em alguns bairros da cidade de Rio Branco, especificamente na baixada do Sul, região composta por 15 bairoos conhecidos por abrigar migrantes da zona rural, com uso de questionário aplicado em entrevista presencial contendo perguntas semi-estruturadas ao responsável pelo quintal, através de uma técnica chamada "bola de neve" ("Snow ball') (Bailey, 1994), que é usada para uma seleção intencional de informantes. As espécies vegetais foram identificadas no campo e através de comparação na literatura especializada e classificadas botanicamente e quanto ao seu uso pelos moradores

Grazer control of the fine-scale distribution of phytoplankton in warm-core Gulf Stream rings

We measured in situ rates of primary production, zooplankton grazing and the fine-scale distribution of zooplankton abundance, along with continuous observations of salinity, temperature and fluorescence in vertical profiles of two warm-core Gulf Stream rings and a station in the northern Sargasso Sea. A subsurface chlorophyll maximum was located within the pycnocline at all nineteen of the pump stations. In the majority of pump profiles, subsurface chlorophyll maxima coincided with maxima in particulate organic carbon and ATP. However, neither zooplankton biomass or numerical abundance were related to chlorophyll concentrations. Maxima in zooplankton biomass and grazing generally occurred at depths of highest primary production. Zooplankton grazing and biomass were more closely coupled to phytoplankton production per unit chlorophyll (P-chl) rather than production per unit volume (absolute production). Our results suggest that after the seasonal thermocline is established, phytoplankton removal by zooplankton is greatest in the upper water column where P-chl is higher. This phytoplankton removal by zooplankton limits the amount of absolute primary production in the upper water column and results in a subsurface maximum of absolute production at depths where grazing pressure is reduced. In contrast, the subsurface chlorophyll maximum, likely formed from both production at depth and sinking, does not appear to be a site of enhanced zooplankton grazing activity