Dust Absorption Research Articles

An Experimental Study on Wetting of Coal Dust by Surfactant Solution

Surfactants can improve the wetting performance of the dust‐reduction spraying water, thus improving the dust‐reduction effect by spray. In this study, the performance of surfactant solution in wetting coal dust was investigated through experiments. In addition, the effects of surfactant type, mass fraction, metamorphic degree of coal, particle size, and additives were investigated. According to the results of surface tension experiments, the surface tension of the solution decreased with the increase of the concentration of surfactant. However, after reaching CMC, the surface tension did not have significantly decrease. SDBS and OP‐10 had higher efficiency in decreasing the surface tension than the other two types of surfactants. The addition of sodium sulfate additives can further reduce the surface tension of the surfactant solution by a limited range. The coal dust wetting experiment showed that with the increase in the concentration of the surfactant, the contact angle of the droplets on the coal dust tablet was continuously reduced, and the wettability of the solution was continuously improved. The wettability of the OP‐10 solution was optimal. At the same concentration, the minimum contact angle can be obtained in the OP‐10 solution. As the contact angle of the coal dust increased, the growth rate in the coal dust reverse osmosis moisture absorption of the surfactant solution relative to the pure water increased. After the addition of sodium sulfate, the reverse osmosis moisture absorption of coal dust increased to varying degrees. In addition, as the concentration of additives increased, the moisture absorption of coal dust increased.

PENENTUAN HASIL EVALUASI PEMILIHAN SPESIES POHON DALAM PENGENDALIAN POLUSI UDARA PABRIK SEMEN BERDASARKAN KARAKTERISTIK MORFOLOGI.

Abstrak Pesatnya dalam pengembangan pembangunan di negara Indonesia, khususnya bidang industri dan teknologi, tidak terlepas dari masalah pencemaran udara terutama pada lingkungan yaitu gas polutan dan debu. Pencemaran udara perlu dilakukan pengendalian ramah lingkungan dengan peningkatan jumlah vegetasi atau penghijauan dengan menanam spesies tanaman yang memiliki kemampuan tumbuh sertadapat menyerap gas polutan maupun menjerap partikel debu dalam kondisi lingkungan yang tercemar. Penelitian menggunakan analisis deskriptif dengan menilai elemen pohon secara makroskopis untuk memilih jenis pohon yang sesuai dan dapat direkomendasikan sebagai penyerap polutan gas dan penjerap debu berdasarkan skoring kesesuaian pohon. Hasil penelitian menunjukkan bahwa dari 7 (tujuh) spesies pohon dominan yang diidentifikasi, terdapat 3 (tiga) spesies pohon dominan yang sangat sesuai, 3 (tiga) spesies pohon dominan yang sesuai, dan hanya 1 (satu) spesies pohon dominan yang kurang sesuai untuk gas polutan udara. Sedangkan untuk evaluasi mengenai fungsi penjerapan partikel debu menunjukkan bahwa seluruh spesies pohon dominan yang diteliti memiliki kriteria sesuai dalam menjerap debu dengan perolehan nilai evaluasi 65%-75%.

PENENTUAN HASIL EVALUASI PEMILIHAN SPESIES POHON DALAM PENGENDALIAN POLUSI UDARA PABRIK SEMEN BERDASARKAN KARAKTERISTIK MORFOLOGI

The rapid development of the country in Indonesia, especially in the fields of industry and technology, is inseparable from the problem of air pollution, especially in the environment, namely pollutant gas and dust. Air pollution needs to be environmentallyfriendly by increasing the amount of vegetation or reforestation by planting tree species that have the ability to grow and absorb pollutant gases and absorb dust particles in polluted environmental conditions. The study uses descriptive analysis by assessing tree elements macroscopically to select the appropriate tree species and can be recommended as an absorber of gas pollutants and dust absorbers based on tree suitability scoring. The results showed that of 7 (seven) dominant tree species identified, there were 3 (three) dominant tree species that were very suitable, 3 (three) dominant tree species were suitable, and only 1 (one) dominant tree species were not suitable for air pollutant gas. Whereas the evaluation of the function of dust particle absorptionshows that all dominant tree species studied have the appropriate criteria in absorbing dust with the acquisition of 65% -75% evaluation value.
 Keywords: Dust, Pollutant, Tree.

An Imprint of the Galactic Magnetic Field in the Diffuse Unpolarized Dust Emission

Abstract It is well known that aligned, aspherical dust grains emit polarized radiation and that the degree of polarization depends on the angle ψ between the interstellar magnetic field and the line of sight (LOS). However, anisotropy of the dust absorption cross sections also modulates the total intensity of the radiation as the viewing geometry changes. We report a detection of this effect in the high Galactic latitude Planck data, finding that the 353 GHz dust intensity per N H i is smaller when the Galactic magnetic field is mostly in the plane of the sky and larger when the field is mostly along the LOS. These variations are of opposite sign and roughly equal magnitude as the changes in polarized intensity per N H i with ψ, as predicted. In principle, the variation in intensity can be used in conjunction with the dust polarization angle to constrain the full 3D orientation of the Galactic magnetic field.

Preparation of robust antistatic waterborne polyurethane coating

In this study, a novle robust antistatic waterborne polyurethane (WBPU)-ZrO2 nanoparticle (NP) coating is specially designed using sol-gel process. For this purpose the effective parameters on resin performance and surface resistivity of the synthesized coating investigated and optimized. The WBPU composite containing 6 wt% ZrO2 NPs, dissipates electrostaic charges with surface resistivity of 9.1 × 109 Ω sq−1 and also improves adhesion strength about 30 % compared with neat resin. Moreover, the homogenous distribution of modified ZrO2 NPs provides a surface roughness of 27.0 nm which can avoid the absorption of dust on the surface. Facile fabrication of robust WBPU–ZrO2 coating with considerable antistatic properity provides a pathway to the development of environmental friendly antistatic surfaces. The improved properties of synthesized WBPU–ZrO2 coating are mainly due to (i) stable adhesion of ZrO2 NPs into WBPU resin after cross-linking with resin matrix, (ii) formation of a rough structure on the coating surface, and (iii) modification of resin performance that provides film hemogenity.

High-resolution radiation transfer modelling of barred galaxies

AbstractDust radiative transfer simulations provide us with the unique opportunity to study the heating mechanisms of dust by the stellar radiation field. From 2D observational images we derive the 3D distributions of stars and dust. Our aim is to analyze the contribution of the different stellar populations to the radiative dust heating processes in the nearby face-on barred galaxies NGC 1365, M 83 and M 95. We wish to decompose the FIR-submm SED and quantify the fraction directly related to star formation. To model the complex geometries mentioned above, we used SKIRT, a state-of-the-art, 3D Monte Carlo radiative transfer code designed to simulate the absorption, scattering and thermal re-emission of dust in a variety of environments. We find that the contribution of the evolved stars (8 Gyr) to the dust heating is non-negligible (∼35%) and can reach as high as 70%. We also find a tight correlation between the heating fraction by the unevolved stars (⩽ 100 Myr) and the specific star formation rate.

Dirt-cheap Gas Scaling Relations: Using Dust Absorption, Metallicity, and Galaxy Size to Predict Gas Masses for Large Samples of Galaxies

We apply novel survival analysis techniques to investigate the relationship between a number of the properties of galaxies and their atomic (MH i) and molecular () gas mass, with the aim of devising efficient, effective empirical estimators of the cold gas content in galaxies that can be applied to large optical galaxy surveys. We find that dust attenuation, AV, of both the continuum and nebular emission, shows significant partial correlations with , after controlling for the effect of star formation rate (SFR). The partial correlation between AV and MH i, however, is weak. This is expected because in poorly dust-shielded regions molecular hydrogen is dissociated by far-ultraviolet photons. We also find that the stellar half-light radius, R50, shows significant partial correlations with both and MH i. This hints at the importance of environment (e.g., galactocentric distance) on the gas content of galaxies and the interplay between gas and SFR. We fit multiple regression to summarize the median, mean, and the 0.15/0.85 quantile multivariate relationships among , AV, metallicity, and/or R50. A linear combination of AV and metallicity (inferred from stellar mass) or AV and R50, can estimate molecular gas masses within ∼2.5–3 times the observed masses. If SFR is used in addition, can be predicted to within a factor ≲2. In this case, AV and R50 are the two best secondary parameters that improve the primary relation between and SFR. Likewise, MH i can be predicted to within a factor ≲3 using R50 and SFR.

Experiment on pollution control in µ-abrasive jet machining using liquid films

Micro Abrasive Jet Machining (µ-AJM) uses a high-velocity abrasive jet to erode features in target substrates for a variety of applications, including microfluidic device fabrication and micro-electro-mechanical. AJM can result in dusty and pollution environments due to airborne, abrasive particles that eventually settle. In this experiment, the workpiece is kept in liquid medium and experiment is conducted to investigate the effect of liquid film thickness on Material Removal Rate (MRR), Radial Overcut (ROC) and percentage captured particles. The liquid film thickness is varied from 1 mm to 3 mm. From the experiment result, input parameters are optimized for the required output responses. The Microcontroller and sensors are used for maintaining the level of the liquid film inside the chamber for dust absorption.

Dirt-cheap gas scaling relations: Using dust attenuation and galaxy radius to predict gas masses for large samples of AGNs

AbstractWe analyze the molecular and atomic gas data from the GALEX Arecibo SDSS Survey (xGASS) and the extended CO Legacy Database (xCOLD GASS) IRAM survey using novel survival analysis techniques to identify a small number of stellar properties that best correlate with the gas mass. We find that the dust absorption, AV, and the stellar half-light radius, R50, are likely the two best secondary parameters than improve the Kennicutt - Schmidt type relation between the gas mass and the star formation rate, SFR. We fit multiple regression, taking into account gas mass upper limits, to summarize the median, mean, and the 0.15/0.85 quantile multivariate relationships between the gas mass (atomic or molecular hydrogen), SFR, AV and/or R50. In particular, we find that the AV of both the stellar continuum and nebular gas emission shows a significant partial correlation with the molecular hydrogen after controlling for the effect of SFR. The partial correlation between the AV and the atomic gas, however, is weak and their zero-order correlation may be explained by SFR. This is expected since in poorly dust-shielded regions molecular hydrogen is dissociated by the far ultraviolet photons and HI is the dominant phase. Similarly, R50 shows significant partial correlations with both atomic and molecular gas masses. This hints at the importance of environment (e.g., galacto-centric distance) on the gas contents galaxies and on the interplay between gas and star formation rate. We apply the gas scaling relations we found to a large sample of type 2 and type 1 AGNs and infer that the gas mass correlates with AGN luminosity. This correlation is inconsistent with the prediction of AGN feedback models that strong AGNs remove or heat cold gas in their host galaxies.

Interstellar dust along the line of sight of GX 3+1

Context.Studying absorption and scattering of X-ray radiation by interstellar dust grains allows us to access the physical and chemical properties of cosmic grains even in the densest regions of the Galaxy.Aims.We aim at characterising the dust silicate population which presents clear absorption features in the energy band covered by theChandraX-ray Observatory. Through these absorption features, in principle, it is possible to infer the size distribution, composition, and structure of silicate in the interstellar medium. In particular, in this work we investigate magnesium and silicon K-edges.Methods.We built X-ray extinction models for 15 dust candidates using newly acquired synchrotron measurements. These models were adapted for astrophysical analysis and implemented in the SPEXspectral fitting program. We used the models to reproduce the dust absorption features observed in the spectrum of the bright low mass X-ray binary GX 3+1, which is used as a background source.Results.With the simultaneous analysis of the two edges we test two different size distributions of dust: one corresponding to the standard Mathis-Rumpl-Nordsieck model and one considering larger grains (n(a) ∝ai−3.5with 0.005μm <a1< 0.25μm and 0.05μm <a2< 0.5μm, respectively, withathe grain size). These distributions may be representative of the complex Galactic region towards this source. We find that up to 70% of dust is constituted by amorphous olivine. We discuss the crystallinity of the cosmic dust found along this line of sight. Both magnesium and silicon are highly depleted into dust (δZ= 0.89 and 0.94, respectively), while their total abundance does not depart from solar values.

Adaptive optics imaging and spectroscopy of the radio galaxy 3C294

Abstract3C 294 is a powerful FR II type radio galaxy at z = 1.786. Due to its proximity of a bright star, it has been subject to several adaptive optics supported imaging studies. The system shows a clumpy structure indicative of a merging system. There is even tentative evidence that 3C 294 hosts a dual AGN. In order to distinguish between the various scenarios for 3C 294 we performed deep high-resolution adaptive optics imaging and optical spectroscopy of 3C 294 with the Large Binocular Telescope. We resolve the 3C 294 system in three distinct components separated by a few tenths of an arcsecond. One of them is compact, the other two are extended. The nature of the latter is unclear. They could be a single galaxy with an internal dust absorption feature, a galaxy merger, or two galaxies at different redshifts. We can now uniquely associate the radio source of 3c 294 with one of the extended components. Based on our spectroscopy, we determine a slightly different redshift of z = 1.784. We find, however, in addition a single emission line at a wavelength of 6745 AA, which might be identified with Lyα at z = 4.56. It thus appears unlikely that 3C294 hosts a dual AGN; it might rather be a pair of AGNs with very small projected separation.

Resolving the puzzle of type IIP SN 2016X

ABSTRACT The enigmatic type IIP SN 2016X demonstrates the unprecedented asphericity in the nebular Hα line profile, the absence of nebular [O i] emission, and the unusual occultation effect due to the internal dust. The hydrodynamic modelling of the bolometric light curve and expansion velocities suggests that the event is an outcome of the massive star explosion that ejected 28 M$\odot$ with the kinetic energy of 1.7 × 1051 erg and 0.03 M$\odot$ of radioactive 56Ni. We recover the bipolar distribution of 56Ni from the Hα profile via the simulation of the emissivity produced by non-spherical 56Ni ejecta. The conspicuous effect of the dust absorption in the Hα profile rules out the occultation by the dusty sphere or dusty thick disc, but turns out consistent with the thin dusty disc-like structure in the plane perpendicular to the bipolar axis. We speculate that the absence of the nebular [O i] emission might originate from the significant cooling of the oxygen-rich matter mediated by CO and SiO molecules.

X-ray extinction from interstellar dust

Aims. We present a study on the prospects of observing carbon, sulfur, and other lower abundance elements (namely Al, Ca, Ti, and Ni) present in the interstellar medium using future X-ray instruments. We focus in particular on the detection and characterization of interstellar dust along the lines of sight. Methods. We compared the simulated data with different sets of dust aggregates, either obtained from past literature or measured by us using the SOLEIL-LUCIA synchrotron beamline. Extinction by interstellar grains induces modulations of a given photolelectric edge, which can be in principle traced back to the chemistry of the absorbing grains. We simulated data of instruments with characteristics of resolution and sensitivity of the current Athena, XRISM, and Arcus concepts. Results. In the relatively near future, the depletion and abundances of the elements under study will be determined with confidence. In the case of carbon and sulfur, the characterization of the chemistry of the absorbing dust will be also determined, depending on the dominant compound. For aluminum and calcium, despite the large depletion in the interstellar medium and the prominent dust absorption, in many cases the edge feature may not be changing significantly with the change of chemistry in the Al- or Ca-bearing compounds. The exinction signature of large grains may be detected and modeled, allowing a test on different grain size distributions for these elements. The low cosmic abundance of Ti and Ni will not allow us a detailed study of the edge features.

Deep late-time observations of the supernova impostors SN 1954J and SN 1961V

ABSTRACT SN 1954J in NGC 2403 and SN 1961V in NGC 1058 were two luminous transients whose definitive classification as either non-terminal eruptions or supernovae remains elusive. A critical question is whether a surviving star can be significantly obscured by dust formed from material ejected during the transient. We use three lines of argument to show that the candidate surviving stars are not significantly optically extinct (τ ≲ 1) by dust formed in the transients. First, we use SED fits to new HST optical and near-IR photometry. Secondly, neither source is becoming brighter as required by absorption from an expanding shell of ejected material. Thirdly, the ejecta masses implied by the Hα luminosities are too low to produce significant dust absorption. The latter two arguments hold independent of the dust properties. The Hα fluxes should also be declining with time as t−3, and this seems not to be observed. As a result, it seems unlikely that recently formed dust can be responsible for the present faintness of the sources compared to their progenitors, although this can be verified with the James Webb Space Telescope. This leaves three possibilities: (1) the survivors were misidentified; (2) they are intrinsically less luminous; (3) SN 1954J and SN 1961V were true supernovae.

PEMILIHAN JENIS POHON MENJERAP DEBU DI MEDIAN JALAN KOTA BANDAR LAMPUNG

Trees species are suitable to be planted in the median of the road must be able to absorb and to reduce air pollution. Determination of leaf samples was carried out using the purposive sampling method. The measurement of dust was carried out using a laboratory experimental method, namely the gravimetric method. The results of the research show that the trees that have the greatest dust absorption ability on tanjung (Mimusops elengi) are 0.00123 gr/cm2 and trees that have the ability to lie falsely with mahogany (Swietenia mahagoni) are 0.00022 gr/cm2. Tanjung tree is a plant that has a high ability to absorb dust, has smooth, shiny leaves, curved leaves and curved upward, and fragrant flowers. Tanjung tree is the most effective tree planted in the median road for dust absorption. Tanjung trees are recommended to be planted in the median road so that dust in the air is reduced.

Silicate features in the circumstellar envelopes of the Class I binary driving source of HH 250

Context. The silicate feature near 10 μm is one of the main tools available to study the mineralogy of circumstellar disks and envelopes, providing information on the thermal processing, growth, location, and circulation of dust grains. Aims. We investigate the silicate feature of the two Class I components of HH 250-IRS, a resolved binary system with a separation of 0″53 driving a Herbig-Haro flow. Each component has its own circumstellar envelope, and the system is surrounded by a circumbinary disk. Methods. We carried out low resolution spectroscopy in the 8–13 μm range using VISIR, the thermal infrared imager and spectrograph at ESO’s Very Large Telescope. Results. The silicate features of both sources are clearly different. The northwest (NW) component has a broad, smooth absorption profile lacking structure. We attribute most of it to foreground interstellar dust absorption, but estimate that additional absorption by amorphous silicates takes place in the circumstellar envelope of the young stellar object. The southeast (SE) component shows the silicate feature in emission, with structure longward of 9.5 μm indicating the presence of crystalline dust in the dominant form of forsterite. The apparent lack of an absorption feature caused by foreground dust is probably due to the filling of the band with emission by amorphous silicates in the envelope of the object. Conclusions. Despite their virtually certain coevality, the differences in the components of the HH 250-IRS binary are most likely due to markedly different circumstellar environments. The NW component displays an unevolved envelope, whereas dust growth and crystallization has taken place in the SE component. The weak or absent signatures of enstatite in the latter are fairly unusual among envelopes with crystalline dust, and we tentatively relate it to a possible wide gap or an inner truncation of the disk already hinted at in previous observations by a drop in the L′-band flux, which might indicate that the SE component could actually be a very close binary. We speculate that the clear differences between the silicate feature spectra of both components of HH 250-IRS may be due either to disk evolution sped up by multiplicity, or by accretion variability leading to episodes of crystal formation. Different inclinations with respect to the line of sight may play a role as well, although it is very unlikely that they are the sole element for the differences between both objects.

Determining Star Formation Thresholds from Observations

Abstract Most gas in giant molecular clouds is relatively low-density and forms star inefficiently, converting only a small fraction of its mass to stars per dynamical time. However, star formation models generally predict the existence of a threshold density above which the process is efficient and most mass collapses to stars on a dynamical timescale. A number of authors have proposed observational techniques to search for a threshold density above which star formation is efficient, but it is unclear which of these techniques, if any, are reliable. In this paper we use detailed simulations of turbulent, magnetised star-forming clouds, including stellar radiation and outflow feedback, to investigate whether it is possible to recover star formation thresholds using current observational techniques. Using mock observations of the simulations at realistic resolutions, we show that plots of projected star formation efficiency per free-fall time εff can detect the presence of a threshold, but that the resolutions typical of current dust emission or absorption surveys are insufficient to determine its value. In contrast, proposed alternative diagnostics based on a change in the slope of the gas surface density versus star formation rate surface density (Kennicutt-Schmidt relation) or on the correlation between young stellar object counts and gas mass as a function of density are ineffective at detecting thresholds even when they are present. The signatures in these diagnostics sometimes taken as indicative of a threshold in observations, which we generally reproduce in our mock observations, do not prove to correspond to real physical features in the 3D gas distribution.

Dust absorption and scattering in the silicon K-edge

Context. The composition and properties of interstellar silicate dust are not well understood. In X-rays, interstellar dust can be studied in detail by making use of the fine structure features in the Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearing dust, such as investigating the crystallinity, abundance, and the chemical composition along a given line of sight. Aims. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds that complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. Methods. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. Results. Most lines of sight can be fit well by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance, and depletion along each of the sightlines. We find a possible gradient of 0.06 ± 0.02 dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.

Simulating the potential of trees to reduce particulate matter pollution in urban areas throughout the year

Particulate matter pollution, especially in an urban environment, is a health risk that affects many people, and the current trend shows that these problems will increase in the near future. To combat this form of air pollution, many different strategies and policies are investigated: from reducing the emission of particulate matter to finding ways of filtering the air. In this study, we explore the idea of using trees in an urban area to reduce particulate matter concentration. Since the absorption of fine dust by trees is a complex problem, influenced by many factors, we use a computer model to simulate the effect of various trees throughout the year to find the optimal candidate. We find that coniferous trees have a significant advantage, since they also absorb during the winter months, where the air quality is worse. We also conclude that a large enough area of a well-suited tree species is a feasible way to increase air quality and in some cases even to reduce the particulate matter pollution to an acceptable level.

GASP – XVI. Does cosmic web enhancement turn on star formation in galaxies?

Galaxy filaments are a peculiar environment, and their impact on the galaxy properties is still controversial. Exploiting the data from the GAs Stripping Phenomena in galaxies with MUSE (GASP), we provide the first characterisation of the spatially resolved properties of galaxies embedded in filaments in the local Universe. The four galaxies we focus on show peculiar ionised gas distributions: Halpha clouds have been observed beyond four times the effective radius. The gas kinematics, metallicity map and the ratios of emission line fluxes confirm that they do belong to the galaxy gas disk, the analysis of their spectra shows that very weak stellar continuum is associated to them. Similarly, the star formation history and luminosity weighted age maps point to a recent formation of such clouds. The clouds are powered by star formation, and are characterised by intermediate values of dust absorption. We hypothesise a scenario in which the observed features are due to "Cosmic Web Enhancement": we are most likely witnessing galaxies passing through or flowing within filaments that assist the gas cooling and increase the extent of the star formation in the densest regions in the circumgalactic gas. Targeted simulations are mandatory to better understand this phenomenon.