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We study the integral Galactic extinction and reddening based on the galaxy catalog of the South Galactic Cap u-band Sky Survey (SCUSS), where u-band galaxy number counts and u - r color distribution are used to derive the Galactic extinction and reddening respectively. We compare these independent statistical measurements with the reddening map of Schlegel et al. (SFD) and find that both the extinction and reddening from the number counts and color distribution are in good agreement with the SFD results at low extinction regions (E(B - V)(SFD) < 0.12 mag). However, for high extinction regions (E(B - V)(SFD) > 0.12 mag), the SFD map overestimates the Galactic reddening systematically, which can be approximated by a linear relation Delta E(B - V)= 0.43[ E(B - V)(SFD) - 0.12]. By combining the results from galaxy number counts and color distribution, we find that the shape of the Galactic extinction curve is in good agreement with the standard R-V = 3.1 extinction law of O'Donnell.

Debris discs are typically revealed through the presence of excess emission at infrared wavelengths. Most discs exhibit excess at mid- and far-infrared wavelengths, analogous to the solar system's Asteroid and Edgeworth-Kuiper belts. Recently, stars with strong (similar to 1%) excess at near-infrared wavelengths were identified through interferometric measurements. Using the HIgh Precision Polarimetric Instrument, we examined a sub-sample of these hot dust stars (and appropriate controls) at parts-per-million sensitivity in SDSS g' (green) and r' (red) filters for evidence of scattered light. No detection of strongly polarized emission from the hot dust stars is seen. We, therefore, rule out scattered light from a normal debris disk as the origin of this emission. A wavelength-dependent contribution from multiple dust components for hot dust stars is inferred from the dispersion (the difference in polarization angle in red and green) of southern stars. Contributions of 17 ppm (green) and 30 ppm (red) are calculated, with strict 3-sigma upper limits of 76 and 68 ppm, respectively. This suggests weak hot dust excesses consistent with thermal emission, although we cannot rule out contrived scenarios, e.g., dust in a spherical shell or face-on discs. We also report on the nature of the local interstellar medium (ISM), obtained as a byproduct of the control measurements. Highlights include the first measurements of the polarimetric color of the local ISM and the discovery of a southern sky region with a polarization per distance thrice the previous maximum. The data suggest that lambda(max), the wavelength of maximum polarization, is bluer than typical.

The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high angular resolution and high-contrast infrared imaging (1.5-13 mu m). In this paper, we focus on the mid-infrared (8-13 mu m) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in 2015 March. With an interferometric baseline of 14.4 m, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exo-Earth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in 2015 February a calibrated null accuracy of 0.05% over a 3 hr long observing sequence on the bright nearby A3V star beta Leo. This is equivalent to an exozodiacal disk density of 15-30. zodi for a Sun-like star located at 10 pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.

A purpose-built cylindrical resuspension chamber (V=0.437 m3 , S=0.35 m2 , S/V=8.38) was used for the dispersion of samples of soil and various kinds of dust. The samples were studied from the point of view of the number and mass distribution of aerosol particles which could affect the concentration of atmospheric aerosol. The samples were taken from lignite, power plant flue ash and from overburden soil in the North Bohemian surface mine Nastup. The individual samples were pneumatically dispersed inside the chamber under defined temperature-humidity conditions (20řC and relative humidity (RH) 50 %). An APS (Aerodynamic Particle Sizer) processing provided us with average size distributions of particle mass and number. Lignite and flue ash probably have the greatest potential impact on the concentration of atmospheric aerosol in the studied locality. The amount of the resuspended mass of the samples varied between 0.001 % (overburden soil) and 0.32 % (mine road). The lignite and flue ash samples were then analyzed by gravimetric methods using the HI (Harvard Impactor) and the SCI (Sioutas Cascade Impactor). The flue ash contained higher amounts of fine particles than the lignite. Subsequent chemical analysis by electron microscope of the filters with deposits of power plant flue ash showed that the PM2.5...

ABSTRACT Looking up at the sky, we would never guess that our atmosphere contains between one and three billion tons of dust and other particles at any given time.1 Wind assists in keeping this dust airborne, but gravity wins most of the time, forcing the dust particles earthward, proving the old adage: “what goes up, must come down.” Precipitant dust levels in the Western Cape do not follow the same pattern as the precipitant dust levels in the summer rainfall areas of South Africa. Due to the very dry summer conditions in the Western Cape, the precipitant dust levels can be very high, especially if sources of fugitive dust are ignored. An environmental consulting company positioned precipitant dust monitoring units at strategic locations, taking process and open dust sources into account. Both wet and dry depositions have been reported on in this report as one figure. Seasonal changes in, and long-term trends of, the amount of precipitant dust were documented and statistically analysed to determine if the precipitantdust levels were above the South African legislated action levels. The particle size analysis performed on the precipitant dust indicated that the dust was predominantly less than 100_μm and that about 22 percent of the particles by volume were under 15_μm. No significant decline in the precipitant dust levels around the calcining industry was noted. Recommendations are that they increase the dust control measures on site, especially near to the DHF sampling location. There was a significant decrease in the precipitant dust levels to the north and south of the smelting industry from October 2001 to April 2005, p-value 0.005 and 0.048. The recommendations for the smelting industry are that they continue to eliminate fugitive dust sources and that they continue to maintain a high awareness of dust control.

The problem of self-heating of combustible dusts accumulated on hot surfaces has caused several fires and dust explosions. The current test standards (ASTM E 2021, EN50281-2-1) used to ensure safe environment for a given dust, define a safe temperature of the flat hot surface for certain dust layer thickness. Since in these standards, measurement of temperature is taken along the centerline, they mainly represent a simplified scenario of one-dimensional heat transfer. A need to investigate behavior of spontaneous ignition in dust deposits in complex geometries forms the motivation of this work. The effect of hot surface geometry is experimentally studied by devising wedge-shaped configurations having angles of 60o and 90o. Results show that ignition always occurred around the top region in the case of 60o wedge, and in the top and middle regions in the case of 90o wedge. These trends are explained by investigating three parameters affecting the ignition behavior, namely, the heat transfer from the hot plate to the dust, the rate of heat transfer between different regions within the dust and the minimum volume of dust required to produce sufficient heat release. A mathematical method has been proposed to predict the ignition behavior of dust deposit subjected to any boundary conditions arising due to geometrical confinement. Further, numerical simulations have been carried out to simulate the conjugate heat transfer in the interface of dust surface and air. Both analyses, mathematical and numerical, compare well with the experimental data. Furthermore, in the standard test method, ASTM E- 2021, a metal ring is used to contain the sample dusts. It is observed from experimental and numerical simulations that the resultant temperature field is not one-dimensional as desired since the corner part ignites first due to heat transfer from both the bottom plate and the metal ring, which is at almost same temperature as that of bottom plate. Theories those describe the thermal ignition in these standard tests, use the assumption that the heat flow is unidirectional. Therefore, a better substitute to the metal ring has been proposed as a ring made out of an insulating material (having low thermal conductivity). This makes the heat transfer to the dust layer phenomenally one-dimensional. Another leg of the experiments have been carried out to investigate the effect of weathering of combustible dusts on their spontaneous ignition process. Two types of weathering methods, heat- and moisture-weathering are used. Sample preparation and weathering quantification methods follow the standard test procedure. Thermogravimetric analysis has been employed to understand the variation in weight loss of fresh, heat-weathered and moisture-weathered samples of coal and organic dusts. Preliminary results show that heat weathering increases the hazard level for organic (wheat) dust. In summary, the current research work mainly involves modification of the standard test method such as ASTM E-2021 to include an insulated ring instead of a metal ring to ensure one-dimensional heat transfer and extending the test method to include wedge-shaped geometries. The spontaneous ignition of combustible dust in the new setups is investigated thoroughly. Furthermore, mathematical and numerical models have been proposed to simulate the experimental tests. Finally, the effect of two types of weathering processes on the characteristics of spontaneous ignition has been studied. In all the cases, results are thoroughly discussed with the explanation of the physics involved.

Airborne dusts can transport radioactive materials in the form of isolated individual radioactively-hot particles containing high concentrations of radioisotopes. These airborne particles may be inhaled or ingested, becoming a source of internal radiation exposure. After the March 11, 2011, nuclear reactor accidents at Fukushima Daiichi, in northern Japan; eighty-five Japanese environmental samples and 234 US and Canadian samples were collected and analyzed by gamma spectrometry, autoradiography, scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDS), and total alpha and beta counts. Social media and volunteer organizations were an important part of the sample collection effort. The combination of autoradiography and SEM/EDS allowed individual radioactively-hot particles to be isolated and analyzed. Detectable levels of 134Cs and 137Cs were found in 62 of 85 Japanese particulate matter samples. The median dust specific activity for Japanese samples was 2.5 Bq g-1 +/- 1.6 Bq g-1, while the mean dust specific activity was 71 Bq g-1 (RSD = 335 %). The mean was skewed high due to five dust samples with sharply higher specific activities. These five samples had specific activities ranging from 167 kBq g-1 to 5.2 PBq kg-1. Only four of 234 US and Canadian environmental samples had detectable levels of both 134Cs and 137Cs. Gross gamma spectroscopy of Japanese samples also detected 131I and 60Co. US and Canadian dust samples showed primarily naturally-occurring nuclides. More than 300 individual hot particles were identified in Japanese samples. The Japanese particles analyzed by SEM/EDS were found to contain cesium, americium, radium, polonium, tellurium, rubidium and other necessarily or potentially radioactive elements. No cesium-containing hot particles were found in the US, however some dust particles were found that contained uranium, thorium and plutonium. These US particles were all related to identified uranium mines or nuclear materials storage and processing sites. Some of the hot particles detected in this study could cause significant radiation exposures to individuals if inhaled. Where hot particles are present in the environment, radiation dose models must include this exposure component to remain accurate.

"This study investigates the interaction of micron- sized coal particles entrained into lean methane €“ air premixed flames. In a typical axisymmetric burner, coal particles are made to naturally entrain into a stream of the premixed reactants using an orifice plate setup. Pittsburgh seam coal dust, with three particle sizes in the range of 0 to 25 µm, 53 to 63 µm, and 75 to 90 µm is used. The effects of different coal dust concentrations (10 €“ 300 g/m3) at three lean equivalence ratios, ϕ (methane-air) of 0.75, 0.80 and 0.85 on the laminar burning velocity are determined experimentally. The laminar burning velocity of the coal dust-methane-air mixture is determined by taking a shadowgraph of the resulting flame and using the cone-angle method. The results show that the addition of coal dust in methane-air premixed flame reduces the laminar burning velocity at particle size of 53 to 63 µm and 75 to 90 µm. However, burning velocity promotion is observed for 0 to 25 µm particles at ϕ = 0.80. Two competing effects are assumed involved in the process. The first is burning velocity promotion effect that the released volatile increases the gaseous mixture equivalence ratio and thus the burning velocity. The second is the heat sink effect of the coal particles to reduce the flame temperature and accordingly the burning velocity. A mathematical model is developed based on such assumption and it can successfully predict the change of laminar burning velocity at various dust concentration. Furthermore, the implication of this study to coal mine safety is discussed."