Biblioteca Digital

Through long-range transport of dust, the North-African desert supplies essential minerals to the Amazon rain forest. Since North African dust reaches South America mostly during the Northern Hemisphere winter, the dust sources active during winter are the main contributors to the forest. Given that the Bod,l, depression area in southwestern Chad is the main winter dust source, a close link is expected between the Bod,l, emission patterns and volumes and the mineral supply flux to the Amazon. Until now, the particular link between the Bod,l, and the Amazon forest was based on sparse satellite measurements and modeling studies. In this study, we combine a detailed analysis of space-borne and ground data with reanalysis model data and surface measurements taken in the central Amazon during the Amazonian Aerosol Characterization Experiment (AMAZE-08) in order to explore the validity and the nature of the proposed link between the Bod,l, depression and the Amazon forest. This case study follows the dust events of 11-16 and 18-27 February 2008, from the emission in the Bod,l, over West Africa (most likely with contribution from other dust sources in the region) the crossing of the Atlantic Ocean, to the observed effects above the Amazon canopy about 10 days after the emission. The dust was lifted by surface winds stronger than 14 m s(-1)...

O pó de forno elétrico a arco (FEA) é gerado durante a fusão de sucata ferrosa nos fornos elétricos a arco e coletado predominantemente através de filtros de mangas. Esta substância é listada como resíduo sólido perigoso de fonte específica, K061, conforme a Norma ABNT NBR 10004:2004. As maiores empresas siderúrgicas semi-integradas do mundo têm adotado para o tratamento de pó de FEA, fundamentalmente três rotas: a recuperação de zinco e chumbo, através de dois processos complementares, um piro-metalúrgico, o Wäelz kiln e outro hidro-metalúrgico, o processo de dupla lixiviação Óxido de Wäelz; a inertização através da blendagem com a cal, aditivos e água, de forma a alcançar o pH da mistura >11, o que garante que metais pesados como o chumbo, cádmio e o zinco, presentes no pó de forno elétrico, não possam se tornar solúveis, evitando consequentemente, a sua lixiviação e a disposição em aterros industriais de resíduos sólidos perigosos. Sob a perspectiva da sustentabilidade, deve ser considerada a rota da recuperação de zinco e chumbo, que para ser viável necessita reunir a geração de pó de FEA de varias plantas, o que para um país com dimensões continentais pode ser um fator de insucesso. Esse trabalho trata da reciclagem do pó de FEA através do processo de sinterização de um compósito constituído de pó de FEA aglomerado com coque...

A kinetic formulation developed to analyze wave propagation in dusty plasmas, which takes into account the variation of the charge of the dust particles due to inelastic collisions with electrons and ions, is utilized to study the propagation and damping of electrostatic waves with wave number exactly parallel to the external magnetic field and Maxwellian distributions for the electrons and ions in the equilibrium. It is shown that, due to the presence of the dust, the damping of Langmuir waves in the region of large wavelengths is increased as compared to conventional Landau damping. Langmuir waves in the occurrence of collisional charging of dust particles also feature weak damping for small wavelengths, which vanishes if the effect of collisional charging of the dust particles is neglected in the dispersion relation. It is also shown that the damping of ion-acoustic waves is modified by the presence of the dust, and that some damping effect due to the dust particles remains even if the effect of collisional charging of dust particles is neglected in the dispersion relation.

This paper compares reddening values E(B-V) derived from the stellar content of 103 old open clusters and 147 globular clusters of the Milky Way with those derived from DIRBE/IRAS 100 μm dust emission in the same directions. Star clusters at |b| > 20º show comparable reddening values between the two methods, in agreement with the fact that most of them are located beyond the disk dust layer. For very low galactic latitude lines of sight, differences occur in the sense that DIRBE/IRAS reddening values can be substantially larger, suggesting effects due to the depth distribution of the dust. The differences appear to arise from dust in the background of the clusters consistent with a dust layer where important extinction occurs up to distances from the Plane of ≈ 300 pc. For 3% of the sample a significant background dust contribution might be explained by higher dust clouds. We find evidence that the MilkyWay dust lane and higher dust clouds are similar to those of several edge-on spiral galaxies recently studied in detail by means of CCD imaging.

A poeira gerada no processo de fabricação de materiais cerâmicos pode ser um agente de risco à saúde dos trabalhadores, em especial quando em sua composição houver a presença de polimorfos da sílica nas formas cristalinas do ?-quartzo e da cristobalita. A exposição ocupacional à poeira respirável desses polimorfos pode ocasionar o aparecimento da silicose e de outras doenças associadas. Na indústria de revestimentos cerâmicos as informações sobre as características da poeira gerada nos seus processos e sobre a prevalência da silicose no setor são insuficientes para definir a magnitude do risco da exposição ocupacional à sílica. Este estudo de campo busca identificar parâmetros físicos e a concentração em sílica cristalina do material particulado suspenso no ar em indústrias de revestimentos cerâmicos para pisos e paredes. Foram selecionadas nove indústrias no município de Santa Gertrudes, no estado de São Paulo, com processo de fabricação por via seca, onde a matéria-prima principal é a argila vermelha proveniente da Formação Corumbataí. O estudo realizou-se por meio da observação sistemática das etapas do processo industrial, da coleta e análise de amostras da poeira presente nos ambientes de trabalho e da análise mineralógica da massa cerâmica manufaturada. As amostras de poeira foram analisadas por ravimetria e por difratometria de raios-X (DRX). Foi determinada a presença na poeira de partículas com tamanho na fração respirável (< 10 µm)...

In this article we describe the assessment and control of lead dust exposure in the Treatment of Lead-exposed Children (TLC) Trial, a clinical trial of the effects of oral chelation on developmental end points in urban children with moderately elevated blood lead levels. To reduce potential lead exposure from settled dust or deteriorated paint during the drug treatment phase of the trial, the homes of 765 (98%) of the randomized children (both active and placebo drug treatment groups) were professionally cleaned. Lead dust measurements were made in a sample of 213 homes before and after cleaning. Geometric mean dust lead loadings before cleaning were 43, 29, 308, and 707 micro g/ft2 in the kitchen floor, playroom floor, playroom windowsill, and playroom window well samples respectively. Following cleaning, floor dust lead loadings were reduced on average 32% for paired floor samples (p < 0.0001), 66% for windowsills (p < 0.0001), and 93% for window wells (p < 0.0001). Cleaning was most effective for 146 homes with precleaning dust lead levels above the recommended clearance levels, with average reductions of 44%, 74%, and 93% for floors (p < 0.0001), windowsills (p < 0.0001), and window wells (p < 0.0001), respectively. Despite these substantial reductions in dust lead loadings...

We present results studying the distribution and properties of the diffuse dust in the Milky Way Galaxy using large optical surveys—specifically, the Sloan Digital Sky Survey (SDSS) and the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1). This work has resulted in accurate measurements of dust reddening in regions of low extinction over large regions of sky. We present maps of reddening from dust covering the footprint of the SDSS, which covers one quarter of the sky. We present preliminary maps of dust covering the Pan-STARRS1 footprint, which covers three-quarters of the sky, including most of the plane of our Galaxy. We use these maps of dust to decisively exclude some simple parameterizations of dust extinction (Cardelli et al., 1989) in favor of others (Fitzpatrick, 1999). We show that the extinction predicted by the widely-used far-infrared dust map of Schlegel et al. (1998) is overestimated by 18%, and recalibrate that map using our extinction measurements. We further map variation in the properties of the dust, as indicated by variation in the amount of extinction relative to the amout of far-infrared dust extinction, and by variation in the ratio of dust extinction at different frequencies. We confirm these results by measuring reddening using two independent techniques and data sets...

Aims. The Pipe Nebula is characterized by a low star-formation rate and is therefore an ideal environment to explore how initial conditions, including core characteristics, affect star-formation efficiencies. Methods. In a continued study of the molecular core population of the Pipe Nebula, we present a molecular-line survey of 52 cores. Previous research has shown a variety of different chemical evolutionary stages among the cores. Using the Mopra Radio Telescope, we observed the ground rotational transitions of HCO+, H13CO+, HCN, H13CN, HNC, and N2H+. These data are complemented with near-infrared extinction maps to constrain the column densities, effective dust temperatures derived from Herschel data, and NH3-based gas kinetic temperatures. Results. The target cores are located across the nebula, span visual extinctions between 5 and 67 mag, and effective dust temperatures (averaged along the lines of sight) between 13 and 19 K. The extinction-normalized integrated line intensities, a proxy for the abundance in constant excitation conditions of optically thin lines, vary within an order of magnitude for a given molecule. The effective dust temperatures and gas kinetic temperatures are correlated, but the effective dust temperatures are consistently higher than the gas kinetic temperatures. Combining the molecular line and temperature data...

Thesis (Ph. D.)--University of Rochester. Dept. of Physics and Astronomy, 2009.; I present an analysis of mid-infrared spectra of T Tauri stars observed largely as part of the Spitzer IRS Disks Guaranteed Time Observing program, focusing on the composition of the solid-state dust in the upper layers of the protoplanetary disks surrounding these stars. First, I quickly summarize our understanding of the early evolution of our Solar System, with special regard to studies of primitive Solar System dust, and I review studies of Young Stellar Objects. I describe how the data are reduced via spectral extraction methods designed to yield high quality spectra. Next, I provide some background on radiative transfer models of protoplanetary disks to justify the use of simplified dust emission models to measure the dust composition of the upper layers of these disks. I apply these models to five protoplanetary disk spectra that each show evidence for a high abundance of silica dust, in order to identify the polymorphs, or crystalline forms, of silica most likely giving rise to the distinctive features in the spectra, and I discuss the implications for processing of dust in protoplanetary disks. This is followed by a discussion on finding the optimal dust grain opacities to use in modeling protoplanetary disks and some limitations of the simple dust emission models I use. Finally...

In surface mineral workings, dust is potentially generated from a range of activities like site preparation, stockpiling, loading, transportation and mineral processing operations. Aggregate quarries are one of the largest extractive industrial sectors in UK. This project investigates the propensity of a limestone ore to generate dust due to handling and comminution processes. The dustiness of a limestone ore is assessed using the Warren Spring Laboratory rotating drum (HSE-WSL). The effect of the operating parameters of the WSL rotating drum to the dustiness of limestone is evaluated prior to testing. Preliminary testing on the effect of the operational parameters to the dustiness values showed that the consistency of the end results is closely related to them, thus they need to be carefully controlled. Also, control testing took place to identify the maximum dustiness value per operational parameter, so as to define an optimum set for the limestone sample. This testing procedure is compared with the HSL proposed testing procedure and their differences are quantified. The use of the optimum experimental protocol (OPT-TP) determined by preliminary testing yielded much higher dustiness values even though the initial mass of test material is less than the sample mass used in the HSL testing procedure (HSL-TP). A variety of different fractions is tested and the dustiness indices of the total dust and the health related fractions are determined. Different limestone fractions were found to exhibit different dustiness levels...

Context. High-resolution data from Spitzer, Herschel, and Planck allow us to probe the entire spectral energy distribution (SED) of morphologically separated components of the dust emission from nearby galaxies and allow a more detailed comparison between data and models.; Aims. We wish to establish the physical origin of dust heating and emission based on radiation transfer models, that self-consistently connect the emission components from diffuse dust and the dust in massive star forming regions.; Methods. NGC 4214 is a nearby dwarf galaxy with a large set of ancillary data, ranging from the ultraviolet (UV) to radio, including maps from Spitzer and Herschel and detections from Planck. We mapped this galaxy with MAMBO at 1.2???mm at the IRAM 30???m telescope. We extracted separate dust emission components for the HII regions (plus their associated PDRs on pc scales) and for the diffuse dust (on kpc scales). We analysed the full UV to FIR/submm SED of the galaxy using a radiation transfer model that self-consistently treats the dust emission from diffuse and star forming (SF) complexes components, considering the illumination of diffuse dust both by the distributed stellar populations and by escaping light from the HII regions. While maintaining consistency within the framework of this model...

We observed a long-range transport event of mineral dust from North Africa to South Europe during the Saharan Mineral Dust Experiment (SAMUM) 2006. Geometrical and optical properties of that dust plume were determined with Sun photometer of the Aerosol Robotic Network (AERONET) and Raman lidar near the North African source region, and with Sun photometers of AERONET and lidars of the European Aerosol Research Lidar Network (EARLINET) in the far field in Europe. Extinction-to-backscatter ratios of the dust plume over Morocco and Southern Europe do not differ. ??ngstr??om exponents increase with distance from Morocco. We simulated the transport, and geometrical and optical properties of the dust plume with a dust transport model. The model results and the experimental data show similar times regarding the appearance of the dust plume over each EARLINET site. Dust optical depth from the model agrees in most cases to particle optical depth measured with the Sun photometers. The vertical distribution of the mineral dust could be satisfactorily reproduced, if we use as benchmark the extinction profiles measured with lidar. In some cases we find differences. We assume that insufficient vertical resolution of the dust plume in the model calculations is one reason for these deviations.

Dust forecasting has become important to military operations over the past three decades. Rules of thumb have been the primary resource for forecasting dust. In recent years, algorithms for weather models have been created to produce atmospheric dust concentration forecasts and are now coming into use operationally. The question becomes how good are the models and what causes errors in their forecasts? This study examines the accuracy of the U. S. Navy's Coupled Ocean Atmospheric Mesoscale Model dust module during the United Arab Emirates Unified Aerosol Experiment. The study also attempts to determine what causes any error if present. The primary method to verify the model's aerial coverage accuracy is through equitable threat score. Case studies are then conducted to verify the scores and identify sources of any errors identified. Results indicate the model performs well with respect to sourcing dust plumes. Errors in modeled aerial coverage as compared to real world observations appear to be the result of an inability for the model to properly advect suspended dust near the surface layer. Unconfirmed dust plumes in the model seemed to be the result of inaccurate surface characteristics.

Rasmussen et al. (2001) observed that Sb concentrations were enriched in household dust relative to outdoor garden soil samples and suspected the enrichment may be due to anthropogenic internal sources. Antimony trioxide (Sb2O3) is commonly found in various halogen flame-retardants and is a suspected carcinogen (IARC, 1989). North Americans spend a significant proportion of their time indoors, and are frequently exposed to dust. Therefore, characterizing potentially harmful metal(loid)s (i.e. Sb2O3) has become of increasing priority to various governmental agencies. A combination of micro-analytical synchrotron techniques (micro X-ray fluorescence (µXRF), micro X-ray diffraction (µXRD), micro X-ray absorption near-edge spectroscopy (µXANES)) and environmental scanning electron microscopy (ESEM) were used to characterize five archived samples provided by Health Canada. Two samples were in the 90th percentile for Sb content in household dust from a suite of 50 houses studied by Rasmussen et al. (2001). The corresponding garden soils of these houses were also analysed. The fifth sample was a children’s bedroom from a house studied in detail by Walker et al. (2010). Synchrotron microanalysis of Sb presents many challenges, given its high absorption energy (31 KeV)...

This study provides a detailed description of the sources, transport, dispersion, and deposition of two major dust events originating from the high‐altitude subtropical Puna‐Altiplano Plateau (15?26°S; 65?69°W) in South America. A long and severe drought provided the right conditions for the onset of both events in July 2009 and 2010. Dust was transported SE and deposited over the Pampas region and was observed to continue to the Atlantic Ocean. Dust monitoring stations located downwind recorded both events, and samples were characterized through chemical and textural analysis. Through a combination of meteorological data and satellite observations (CALIPSO andMODIS detectors), we estimate the emission flux for the 2010 event. This estimate was used to constrain the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) transport model and simulate the dust event. Both satellite imagery and model results agree in the location and extension of the dust cloud. CALIPSO detected dust between ~6000 and ~8500 m a.s.l., which remained at this height during most of its trajectory. The dust cloud mixed with a strong convective system in the region, and the associated precipitation brought down significant amounts of dust to the ground. Dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12.4?14.1 μm...

Artículo de publicación ISI; Low-metallicity galaxies exhibit different properties of the interstellar medium (ISM) compared to nearby spiral galaxies. Obtaining a resolved inventory of the various gas and dust components of massive star-forming regions and diffuse ISM is necessary to understand how those differences are driven. We present a study of the infrared/submillimetre (submm) emission of the massive star-forming complex N158–N159–N160 located in the Large Magellanic Cloud (LMC). Combining observations from the Spitzer Space Telescope (3.6–70 μm), the Herschel Space Observatory (100–500 μm) and Large APEX Bolometer Camera (LABOCA) (on Atacama Pathfinder EXperiment, 870 μm) allows us to work at the best angular resolution available now for an extragalactic source (a few parsec for the LMC).We observe a remarkably good correlation between the Herschel Spectral and Photometric Imaging Receiver (SPIRE) and LABOCA emission and resolve the low surface brightnesses emission.We use the Spitzer and Herschel data to perform a resolved spectral energy distribution (SED) modelling of the complex. Using modified blackbodies, we derive an average ‘effective’ emissivity index of the cold dust component βc of 1.47 across the complex. If βc is fixed to 1.5...

Artículo de publicación ISI; The HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) of the Magellanic Clouds will use dust emission to investigate the life cycle of matter in both the Large and Small Magellanic Clouds (LMC and SMC). Using the Herschel Space Observatory’s PACS and SPIRE photometry cameras, we imaged a 2◦ × 8◦ strip through the LMC, at a position angle of ∼22.5◦ as part of the science demonstration phase of the Herschel mission. We present the data in all 5 Herschel bands: PACS 100 and 160 μm and SPIRE 250, 350 and 500 μm. We present two dust models that both adequately fit the spectral energy distribution for the entire strip and both reveal that the SPIRE 500 μm emission is in excess of the models by ∼6 to 17%. The SPIRE emission follows the distribution of the dust mass, which is derived from the model. The PAH-to-dust mass ( fPAH) image of the strip reveals a possible enhancement in the LMC bar in agreement with previous work. We compare the gas mass distribution derived from the HI 21 cm and CO J = 1−0 line emission maps to the dust mass map from the models and derive gas-to-dust mass ratios (GDRs). The dust model, which uses the standard graphite and silicate optical properties for Galactic dust...

Contribution presented at the 39th Annual Meeting of the Division for Planetary Sciences of the American Astronomical Association (DPS 2007), October 7-12, 2007 Orlando, Florida.; When Deep Impact fired its projectile into the nucleus of comet 9P/Tempel 1, a cloud made of dust and icy grains was ejected from the impact crater. The dust was subsequently accelerated by gas drag. About a week after the impact event, the dust cloud has dispersed due to its expansion and the force exerted by solar radiation pressure. The light curve of the dust cloud contains information about its formation and evolution: the time scale of the production of impact created material can be derived from the time scale of the brightness increase. The velocity distribution of the cloud is indicative of acceleration processes in the inner coma of the comet. Finally, the abundance of large dust particles created by the impact can be estimated from the brightness of the cloud several days after the impact when small particles have been pushed away by radiation pressure.; Here we analyze data obtained by the Narrow Angle Camera (NAC) of OSIRIS onboard the ESA spacecraft Rosetta to derive the velocity distribution of the dust cloud from an inversion of its light curve. OSIRIS observed comet Tempel 1 near-continuously for more than two weeks around the impact. A model of the expansion of the ejecta is compared to the light curve seen by the NAC. We derive a broad velocity distribution of the dust particles...

An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI), Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa) is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs), trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde) and the Caribbean (USVI and Trinidad & Tobago). Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean...