Dust Mass Research Articles

Streaming Torque with Turbulent Diffusion

Abstract Fast type I migration of (proto)planets poses a challenging problem for the core accretion formation scenario. We found that the dust-induced “Streaming Torque” (ST) may slow down or even reverse the planet migration in Q. Hou & C. Yu. But in realistic protoplanetary disks, dust diffusion induced by gas turbulence may have important influences on ST. We perform linear analysis to investigate the effects of dust diffusion on ST. The dependence of ST on dust diffusion may provide better constraints on the turbulence strength and the stopping time τ. We derive the dispersion relation for all the wave modes in the two-fluid system. The dust diffusion will smooth the short-wavelength structure of the the quasi-drift mode and split it into two predominant D-drift modes with opposite directions. The outgoing D-drift mode will contribute to a negative torque on planets, particularly when τ ∼ 0.1, which slightly shifts the zero-torque turning point. We explore how ST depends on the regimes of aerodynamic drag, dust mass fraction, and disk scale height. We compare the radial wavenumbers of D-drift modes under different formulations of dust diffusion and find qualitative agreement. In all cases, τ at the zero-torque turning point, which determines the direction of planetary migration, consistently remains on the order of ∼0.1, corresponding to large pebble-sized dust grains. This suggests that rapid dust coagulation can inhibit the inward migration of planets, implying that weak gas turbulence may enhance the survival of protoplanets.

A synthesis of luminescence and 14C dated dust mass accumulation rates for loess‐palaeosol sequences from the Middle Danube Basin

The Middle Danube (Carpathian) Basin is considered to encompass some of the thickest and most complete records of aeolian dust deposition in Europe, covering the last two glacial–interglacial cycles. In this study, independent, published chronologies based on absolute dating methods were compiled for 34 loess‐palaeosol sequences and modelled using Bayesian statistics. Mass accumulation rates (MARs) calculated from the Bayesian age models range from 50 to 1922 g m−2 a−1 with a mean value of 317±35 g m−2 a−1. The glacial–interglacial changes of the MAR estimates only partially agree with the accepted dust deposition model, where high accumulation rates are observed during the cold glacial stages, while low values are typical for the warmer interglacial periods. There is a rapid increase of MAR values during Marine Isotope Stage (MIS) 2, with the highest deposition in most cases observed ~25–18 ka. During MIS 3, the dust deposition was 1.8 times higher than during MIS 4. Regionally, the MARs appear to be highest in the northern part of the Middle Danube Basin, showing decreasing values towards the south. However, due to a variety of factors such as low dating resolution, age distribution, and biases in the dating method, it is debatable whether these results are representative estimates of atmospheric dust activity in the Middle Danube Basin during MIS 5–MIS 1.

ALMA detections of circumstellar disks in the giant H ii region M17. Probing the intermediate- to high-mass pre-main-sequence population

Our current understanding is that intermediate- to high-mass stars form in a way similar to low-mass stars, through disk accretion. The expected shorter formation timescales, higher accretion rates, and increasingly strong radiation fields compared to their lower-mass counterparts may lead to significantly different physical conditions that play a role in disk formation, evolution, and the possibility of (sub)stellar companion formation therein. We searched for the mm counterparts of four intermediate- to high-mass ($4-10$ young stellar objects (YSOs) in the giant H ii region M17 at a distance of 1.7 kpc. These objects expose their photospheric spectrum such that their location on the pre-main-sequence (PMS) is well established. They have a circumstellar disk that is likely remnant of the formation process. With ALMA we detected, for the first time, these four YSOs in M17, in Band 6 and 7, as well as four other serendipitous objects. In addition to the flux measurements, the source size and spectral index provide important constraints on the physical mechanism(s) producing the observed emission. We applied different models to estimate the dust and gas mass contained in the disks. All our detections are spatially unresolved, constraining the source size to $<120$,au, and have a spectral index in the range $0.5-2.7$. The derived (upper limits on) the disk dust masses are on the order of a few M_⊕, and estimations of the upper limits on the gas mass vary between 10^-5 and 10^-3 Our modeling suggests that the inner disks of the target YSOs are dust depleted. In two objects (B331 and B268) free-free emission indicates the presence of ionized material around the star. The four serendipitous detections are likely low-mass YSOs. We compared the derived disk masses of our M17 targets to those obtained for YSOs in low-mass star-forming regions (SFRs) and Herbig stars, as a function of stellar mass, age, luminosity, and outer disk radius. The M17 sample, though small, is both the most massive and the youngest sample, yet has the lowest mean disk mass. The studied intermediate- to high-mass PMS stars are surrounded by low-mass compact disks that likely no longer offer a significant contribution to either the final stellar mass or the formation of a planetary system. Along with the four serendipitous discoveries, our findings show the capability of ALMA to probe disks in relatively distant high-mass SFRs, and offer tentative evidence of the influence of the massive star formation environment on disk formation, lifetime, and evolution.

Planetary nebulae of the Large Magellanic Cloud II. The connection with the progenitors' properties

The study of planetary nebulae (PNe) offers the opportunity to evaluate the efficiency of the dust production mechanism during the very late asymptotic giant branch (AGB) phases, which allows us to assess the role played by AGB stars as dust manufacturers. We studied the relationship between the properties of PNe, particularly the gas and dust content, and the mass and metallicity of the progenitor stars to understand how dust production works in the late AGB phases and to shed new light on the physical processes the stars and the material in their surroundings are subject to in the period between the departure from the AGB and the start of the PN phase. We considered a sample of nine PNe in the Large Magellanic Cloud, seven of which are characterised by the presence of carbonaceous dust and the remaining two the presence of silicates. For these stars, we estimated the masses and the metallicity of their progenitor stars. We combined results from stellar evolution and dust formation modelling with results from analyses of the spectral energy distribution to determine the relation between the dust and gas mass of the PNe considered and the mass and metallicity of the progenitors. The physical properties of carbon-rich PNe are influenced by the mass of the progenitor star. Specifically, the dust-to-gas ratio in the nebula increases from $5 $ to $6 $ as the progenitor star's mass increases from approximately rm 0.9 M_ ⊙ to rm 2 M_ ⊙ . This change is partly influenced by the effective temperature of the PNe, and it occurs because higher-mass carbon stars are more efficient at producing dust. Consequently, as the progenitor's mass increases, the gas mass of the PN decreases since the larger amounts of dust lead to greater effects from radiation pressure, which pushes the gas outwards. No meaningful conclusions can be drawn from the study of the PNe with silicate-type dust, because the subsample comprises two PNe only, one of which is almost dust-free.

Dust deposition characteristics on photovoltaic arrays investigated through wind tunnel experiments

Optimizing the installation parameters of photovoltaic panels in a photovoltaic array to reduce dust accumulation, thereby enhancing their power generation, is a crucial research topic in the construction of solar power stations in desert regions. Utilizing a series of wind tunnel experiments on a photovoltaic array comprising four equally sized panels, this study assessed how variations in tilt angle, mounting height, spacing, and incoming flow direction influence both the accumulation mass of dust and the particle size distribution in a photovoltaic array. The results indicate that the dust accumulation on the first panel exponential growth with increasing tilt angle, incoming flow angles, and height, while subsequent panels displayed a trend of initial increase followed by a decrease, with a maximum increasing ratio achieved at specific installation configurations, the difference of dust mass on each panel can even be several times. Notably, when the spacing between panels exceeds twice the panel height, the mutual influence on dust deposition becomes negligible, providing a quantifiable threshold for optimal panel spacing. Additionally, significant differences exist in the particle size characteristics of dust in the panel of the array, influenced by the installation parameters of panels and the direction of the incoming flow. This research not only enhances the understanding of dust accumulation in solar energy systems but also offers practical recommendations for optimizing installation strategies, thereby improving the economic viability of solar power stations, particularly in desert regions.

REsolved ALMA and SMA Observations of Nearby Stars (REASONS)

Context. Planetesimal belts are ubiquitous around nearby stars, and their spatial properties hold crucial information for planetesimal and planet formation models. Aims. We present resolved dust observations of 74 planetary systems as part of the REsolved ALMA and SMA Observations of Nearby Stars (REASONS) survey and archival reanalysis. Methods. We uniformly modelled interferometric visibilities for the entire sample to obtain the basic spatial properties of each belt, and combined these with constraints from multi-wavelength photometry. Results. We report key findings from a first exploration of this legacy dataset: (1) Belt dust masses are depleted over time in a radially dependent way, with dust being depleted faster in smaller belts, as predicted by collisional evolution. (2) Most belts are broad discs rather than narrow rings, with much broader fractional widths than rings in protoplanetary discs. We link broad belts to either unresolved substructure or broad planetesimal discs produced if protoplanetary rings migrate. (3) The vertical aspect ratios (h = H/R) of 24 belts indicate orbital inclinations of ~1–20º, implying relative particle velocities of ~0.1–4 km/s, and no clear evolution of heights with system age. This could be explained by early stirring within the belt by large bodies (with sizes of at least ~140 km to the size of the Moon), by inheritance of inclinations from the protoplanetary disc stage, or by a diversity in evolutionary pathways and gravitational stirring mechanisms. We release the REASONS legacy multidimensional sample of millimetre-resolved belts to the community as a valuable tool for follow-up multi-wavelength observations and population modelling studies.

КРЕМНИЙЛІ ҚОРЫТПАЛАР ӨНДІРІСІ ШАҢДАРЫНЫҢ ЖОҒАРЫ ТЕМПЕРАТУРА ӘСЕРІ КЕЗІНДЕГІ МАССА ЖОҒАЛЫМЫН ЗЕРТТЕУ

The article presents technological solutions for the formation and utilization of microsilicon dust formed in the filters of gas purification plants for the production of siliceous alloys. The paper provides convincing arguments for the separation of dispersed dust and mass losses and shows ways to recycle man-made waste from ferroalloy production. The scope of application of dust accumulating in a pile and stored in big bag bags is not fully provided. One of the solutions to the environmental problem can be the work carried out in the article. The results of laboratory studies show the results of primary studies on the extraction of silicon carbide from microsilicon dust. A research work on the loss of dust mass was carried out in the Tamman high-temperature furnace, and specific causes of mass loss were identified. A sufficient amount of silicon dioxide in the dust can be a source of silicon to produce silicon carbide, which makes it possible to obtain a product using a low-carbon reducing agent. The use of neftekox as a reducing agent corresponds to the trend of obtaining silicon carbide using traditional technology. The article provides prerequisites for the production of silicon carbide using silica instead of quartz sand. Due to solid and gas-phase synthesis, mass loss indicators are considered an important physico-chemical characteristic of charge materials.

There is no disk mass budget problem of planet formation

The inferred dust masses from Class II protoplanetary disk observations are lower than or equal to the masses of the observed exoplanet systems. This poses the question of how planets form if their natal environments do not contain enough mass. This hypothesis has entered the literature as the ``mass budget problem'' of planet formation. We utilized numerical simulations of planet formation via pebble and gas accretion, including migration, in a viscously evolving protoplanetary disk, while tracing the time evolution of the dust mass. As expected, we found that the presence of a giant planet in the disk can influence the evolution of the disk itself and prevent rapid dust mass loss by trapping the dust outside its orbit. Early formation is crucial for giant planet formation, as we found in our previous work; therefore, our findings strengthen the hypothesis that planet formation has already occurred or is ongoing in Class II disks. More importantly, we find that the optically thin dust mass significantly underestimates the total dust mass in the presence of a dust-trapping deep gap. We also show that the beam convolution smears out the feature from a deep gap, especially if the planet forms in the inner disk. Such hidden dust mass, along with early planet formation, could be the answer to the hypothetical mass budget problem.

Transiting Jupiters around M Dwarfs Have Similar Masses to FGK Warm Jupiters

Abstract This paper presents a comparative analysis of the bulk properties (mass and radius) of transiting giant planets (≳8R ⊕) orbiting FGKM stars. Our findings suggest that the average mass of M-dwarf Jupiters is lower than that of their solar-type counterparts, primarily due to the scarcity of super-Jupiters (≳2 M J) around M dwarfs. However, when super-Jupiters are excluded from the analysis, we observe a striking similarity in the average masses of M-dwarf and FGK warm-Jupiters. We propose that these trends can be explained by a minimum disk dust mass threshold required for Jovian formation through core accretion, which is likely to be satisfied more often around higher-mass stars. This simplistic explanation suggests that the disk mass has more of an influence on giant planet formation than other factors, such as the host star mass, formation location, metallicity, radiation environment, etc., and also accounts for the lower occurrence of giant planets around M-dwarf stars. Additionally, we explore the possibility of an abrupt transition in the ratio of super-Jupiters to Jupiters around F-type stars at the Kraft break, which could be a product of vsini-related detection biases, but requires additional data from an unbiased sample with published nondetections to confirm. Overall, our results provide valuable insights into the formation and evolution of giant exoplanets across a diverse range of stellar environments.

JWST Captures a Sudden Stellar Outburst and Inner Disk Wall Destruction

Abstract We analyze JWST/MIRI observations of T Cha, a highly variable (ΔV ∼ 3–5 mag) accreting Sun-like star surrounded by a disk with a large (∼15 au) dust gap. We find that the JWST mid-IR spectrum is significantly different from the Spitzer spectrum obtained 17 yr before—the emission at short wavelengths (5–10 μm) has decreased by ∼2/3 while that at longer wavelengths (15–25 μm) has increased by up to a factor of ∼3. The JWST spectrum is contemporaneous with a fairly constant higher optical emission captured by the All Sky Automated Survey. After analyzing and modeling both spectral energy distributions, we propose that JWST caught the star during an outburst that partly destroyed and significantly reduced the height of the asymmetric inner disk wall responsible for the high optical variability and lower 15–25 μm emission during the Spitzer period. The dust mass lost during this outburst is estimated to be comparable (∼1/5) to the upper limit of the total micron-sized dust mass in the inner disk of T Cha now. Monitoring this system during possible future outbursts and more observations of its quiescent state will reveal if the inner disk can be replenished or will continue to be depleted and vanish.

Cloud-scale elemental abundance variations and the CO-to-dust-mass conversion factor in M31

Abstract From a spectroscopic survey of candidate H ii regions in the Andromeda galaxy (M31) with MMT/Hectospec, we have identified 294 H ii regions using emission line ratios and calculated elemental abundances from strong-line diagnostics (values ranging from sub-solar to super-solar) producing both Oxygen and Nitrogen radial abundance gradients. The Oxygen gradient is relatively flat, while the Nitrogen gradient is significantly steeper, indicating a higher N/O ratio in M31’s inner regions, consistent with recent simulations of galaxy chemical evolution. No strong evidence was found of systematic galaxy-scale trends beyond the radial gradient. After subtracting the radial gradient from abundance values, we find an apparently stochastic and statistically significant scatter of standard deviation 0.06 dex, which exceeds measurement uncertainties. One explanation includes a possible collision with M32 200 - 800 Myrs ago. Using the two-point correlation function of the Oxygen abundance, we find that, similar to other spiral galaxies, M31 is well-mixed on sub-kpc scales but less so on larger (kpc) scales, which could be a result of an exponential decrease in mixing speed with spatial scale, and the aforementioned recent merger. Finally, the MMT spectroscopy is complemented by a dust continuum and CO survey of individual Giant Molecular Clouds, conducted with the Submillimeter Array. By combining the MMT and SMA observations, we obtain a unique direct test of the Oxygen abundance dependence of the α′(12CO) factor which is crucial to convert CO emission to dust mass. Our results suggest that within our sample there is no trend of the α′(12CO) with Oxygen abundance.

Intermediate mass T Tauri disk masses and a comparison to their Herbig disk descendants

Herbig disks are prime sites for the formation of massive exoplanets and looking into the precursors of these disks can offer clues for determining planet formation timescales. The precursors of Herbig stars, called intermediate-mass T Tauri (IMTT) stars, have spectral types later than F, but stellar masses between 1.5 and 5 $M_ These stars will eventually become Herbig stars of spectral types A and B. The aim of this work is to obtain the dust and gas masses and radii of all IMTT disks with ALMA archival data. The obtained disk masses are then compared to Herbig disks and T Tauri disks and the obtained disks sizes to those of Herbig disks. ALMA Band 6 and 7 archival data were obtained for 34 IMTT disks with continuum observations, 32 of which have at least ^12CO ^13CO or C^18O observations, but with most of them at quite shallow integrations. The disk integrated flux together with a stellar luminosity-scaled disk temperature were used to obtain a total disk dust mass by assuming optically thin emission. Using thermochemical Dust And LInes (DALI) models drawn from previous works, we also obtained gas masses of 10 out of 35 of the IMTT disks based on the CO isotopologues. From the disk masses and sizes, we obtained the cumulative distributions. The IMTT disks in this study have the same dust mass and radius distributions as Herbig disks. The dust mass of the IMTT disks is higher compared to that of the T Tauri disks, as also found for the Herbig disks. No differences in dust mass were found for group I versus group II disks, in contrast to Herbig disks. The disks for which a gas mass could be determined display a similarly high-mass as to the Herbig disks. Comparing the disk dust and gas mass distributions to the mass distribution of exoplanets shows that there also is not enough dust mass in disks around intermediate-mass stars to form massive exoplanets. On the other hand, there is more than enough gas to form the atmospheres of exoplanets. We conclude that the sampled IMTT disk population is almost indistinguishable compared to Herbig disks, as their disk masses are the same, even though the former objects are younger. Based on this study, we conclude that planet formation is already well underway in these objects and, thus, planet formation is expected to start early on in the lifetime of Herbig disks. Combined with our findings on group I and group II disks, we conclude that most disks around intermediate-mass pre-main sequence stars converge quickly to small disks, unless they are prevented from doing so by a nearby massive exoplanet.

Nanosilicates and molecular silicate dust species: properties and observational prospects

Silicate dust is found in a wide range of astrophysical environments. Nucleation and growth of silicate dust grains in circumstellar environments likely involves species with diameters ranging from <1 nm (molecular silicates) to a few nanometers (nanosilicates). When fully formed silicate grains with sizes ∼0.1 μm enter the interstellar medium, supernovae shockwaves cause collision-induced shattering which is predicted to redistribute a significant proportion of the silicate dust mass into a huge number of nanosilicates. This presumed population has thus far not been unambiguously confirmed by observation but is one of the main candidates for causing the anomalous microwave emission. By virtue of their extreme small size, nanosilicates and molecular silicates could exhibit significantly different properties to larger silicate grains, which could be of astrochemical and astrophysical importance. Herein, we briefly review the properties of these ultrasmall silicate dust species with a focus on insights arising from bottom-up atomistic computational modelling. Finally, we highlight how such modelling also has the unique potential to predict observationally verifiable spectral features of nanosilicates that may be detectable using the James Webb Space Telescope.

A spectrophotometric analysis and dust properties of classical nova V5584 Sgr

ABSTRACT In this work, optical observations of the nova V5584 Sgr are presented. These observations cover different phases including pre-maximum, early decline, and nebular. The spectra are dominated by hydrogen Balmer, Fe ii, and O i lines with P-Cygni profiles in the early phase, which are subsequently observed in complete emission. The presence of numerous Fe ii lines and low ejecta velocity aligns with the Fe ii type nova classification. From optical and NIR colours, it is clear that this nova manifests dust formation in the ejecta. The dust temperature and mass were estimated from a spectral energy distribution (SED) fit to the JHK band magnitudes and the Wide field Infrared Survey Explorer data. Light-curve analysis shows t$_2$ and t$_3$ values of $\sim$ 26 and $\sim$ 48 d, classifying the nova as moderately fast. The physical and chemical properties during early decline and later phases were evaluated using the photoionization code CLOUDY. The best-fitting model parameters from two epochs of multiwavelength spectra are compatible with a hot white dwarf source with a roughly constant luminosity of $\sim$(2.08 $\pm$ 0.10) $\times$ 10$^{36}$ erg s$^{-1}$. We find an ejected mass of $\sim$(1.59 $\pm$ 0.04) $\times$ 10$^{-4}$ M$_{\odot }$. Abundance analysis indicates that the ejecta is significantly enriched relative to solar values, with O/H = 30.2, C/H = 10.8, He/H = 1.8, Mg/H = 1.68, Na/H = 1.55, and N/H = 45.5 in the early decline phase, and O/H = 4.5, Ne/H = 1.5, and N/H = 24.5 in the nebular phase.

The Resolved Behavior of Dust Mass, Polycyclic Aromatic Hydrocarbon Fraction, and Radiation Field in ∼800 Nearby Galaxies

We present resolved 3.6–250 μm dust spectral energy distribution (SED) fitting for ∼800 nearby galaxies. We measure the distribution of radiation field intensities heating the dust, the dust mass surface density (Σd), and the fraction of dust in the form of polycyclic aromatic hydrocarbons (PAHs; q PAH). We find that the average interstellar radiation field ( U¯ ) is correlated both with stellar mass surface density (Σ⋆) and star formation rate surface density (ΣSFR), while more intense radiation fields are only correlated with ΣSFR. We show that q PAH is a steeply decreasing function of ΣSFR, likely reflecting PAH destruction in H ii regions. Galaxy-integrated q PAH is strongly, negatively correlated with specific star formation rate (sSFR) and offset from the star-forming “main sequence” (ΔMS), suggesting that both metallicity and star formation intensity play a role in setting the global q PAH. We also find a nearly constant M d/M * ratio for galaxies on the main sequence, with a lower ratio for more quiescent galaxies, likely due to their lower gas fractions. From these results, we construct prescriptions to estimate the radiation field distribution in both integrated and resolved galaxies. We test these prescriptions by comparing our predicted U¯ to results of SED fitting for stacked “main-sequence” galaxies at 0 < z < 4 from M. Béthermin et al. and find sSFR is an accurate predictor of U¯ even at these high redshifts. Finally, we describe the public delivery of matched-resolution Wide-field Infrared Survey Explorer and Herschel maps along with the resolved dust SED-fitting results through the Infrared Science Archive.

New Zealand Southern Alps Blanketed by Red Australian Dust During 2019/2020 Severe Bushfire and Dust Event

AbstractEpisodic deposition of light absorbing impurities on glaciers reduces albedo and exacerbates snow melt. In 2019/2020 a devastating Australian bushfire and desert dust event combined with favorable meteorological conditions transported an unprecedented mass of impurities across the Tasman Sea turning the Southern Alps of Aotearoa New Zealand red. Here we use time lapse cameras, airmass back trajectories, snow impurity geochemistry, and remote sensing to quantify the timing, provenance, and mass deposition of the event. Deposited in late November 2019, the impurities were dominated by mineral dust with a distinct southeastern Australian geochemical fingerprint. The event deposited ∼4,500 ± 500 tons of red dust to Southern Alps permanent snow and ice with a mean dust mass concentration of 6.5 ± 0.7 g m−2. A southeast Australian desert dust storm generated by the same type of meteorological conditions as the 2020 New Year bushfires was the main driver of the glacier discoloration.

The effect of radiation pressure on the dispersal of photoevaporating discs

Abstract Observed IR excesses indicate that protoplanetary discs evolve slowly for the majority of their lifetime before losing their near- and mid-IR excesses on short timescales. Photoevaporation models can explain this ‘two-timescale’ nature of disc evolution through the removal of inner regions of discs after a few million years. However, they also predict the existence of a population of non-accreting discs with large cavities. Such discs are scarce within the observed population, suggesting the models are incomplete. We explore whether radiation-pressure-driven outflows are able to remove enough dust to fit observations. We simulate these outflows using cuDisc, including dust dynamics, growth/fragmentation, radiative transfer and a parameterisation of internal photoevaporation. We find that, in most cases, dust mass-loss rates are around 5-10 times too small to meet observational constraints. Particles are launched from the disc inner rim, however grains larger than around a micron do not escape in the outflow, meaning mass-loss rates are too low for the initial dust masses at gap-opening. Only systems that have smooth photoevaporation profiles with gas mass-loss rates &amp;gt;∼5 × 10−9 M⊙ yr−1 and disc dust masses &amp;lt;∼1 M⊕at the time of gap opening can meet observational constraints; in the current models these manifest as EUV winds driven by atypically large high-energy photon fluxes. We also find that the height of the disc’s photosphere is controlled by small grains in the outflow as opposed to shadowing from a hot inner rim; the effect of this can be seen in synthetic scattered light observations.

Applying Finite Mixture Models to Quantify Respirable Dust Mass in Coal and Metal-Nonmetal Mines Using Fourier Transform Infrared Spectroscopy.

Respirable dust mass is a prevalent occupational health hazard to the mining workforce. Mineral matrices observed in the mine environment are complex, time varying, and heterogeneous. This poses a challenge to assessing dust exposure using Fourier transform infrared (FT-IR) spectrometry as calibrations for constituent dust species (e.g., crystalline silica) have historically been trained using homogeneous standards or simple mixtures therein. Investigations have considered direct-on-filter analysis, which collects FT-IR spectra directly from sampling filters for calibration, as an alternative. Direct-on-filter analysis using a partial least squares (PLS) method has gained particular interest recently due to the potential to rapidly quantify multiple species from a single filter at the mine site. By design, heterogeneity, and its presumed impact on method accuracy, cannot be addressed in the laboratory when using a direct-on-filter approach motivating the need for more advanced calibration approaches. When heterogeneity is present, mixture of experts (MoE) finite mixture models offer a promising and novel alternative to PLS direct-on-filter analysis as MoE incorporates cluster discovery, regression, and outlier identification into model fitting. Three MoE models of increasing complexity were tasked with determining respirable dust mass in 243 field samples from thirteen active coal, limestone, sandstone, and silver mines. All MoE models, including those using only "expert" spectroscopic predictors or a combination of expert and categorical "gate" variables (e.g., mine type), significantly outperform PLS in terms of accuracy (α = 0.05). Decomposing bias by mine type shows that accuracy generally improves across all types considered when MoE models are not overfitted. The MoE method's effectiveness was linked to its ability to endogenously classify outliers as well as possibly to the use of an additional cluster model for mass predictions. Overall, MoE methods appear as a capable and novel tool to addressing problems of heterogeneity for direct-on-filter quantitative analysis.

Spatiotemporal migration of dust pollution during the tunnel mucking process and development of dust removal trolley based on computational fluid dynamics technology

ABSTRACT During tunnel construction, the protracted mucking phase poses significant occupational health risks, particularly from dust exposure. This study delves into comprehensive numerical simulations to examine the spatiotemporal dynamics of dust particles during the mucking process. A distinct ‘bimodal pattern’ was characterized by higher concentrations in the mucking area (0-30 m) and the inverted arch area (60-110 m), where concentrations exceed 30 mg/m3 under all conditions. To address this issue, a novel dust removal system has been developed. Integrating six dust collectors and one air curtain device, a dust removal trolley is strategically positioned at z = 70 m to locally purify the air. The extracted wind speed of the dust collectors ( V inlet 1 ) and the air curtain’s wind speed ( V inlet 2 ) are optimized based on ventilation conditions and dust dispersion characteristics. This system effectively reduces dust mass concentrations to below 4.8 mg/m3 at six worker locations.

Dust mass in protoplanetary disks with porous dust opacities

Atacama Large Millimeter/submillimeter Array surveys have suggested that protoplanetary disks are not massive enough to form the known exoplanet population, based on the assumption that the millimeter continuum emission is optically thin. In this work, we investigate how the mass determination is influenced when the porosity of dust grains is considered in radiative transfer models. The results show that disks with porous dust opacities yield similar dust temperatures, but systematically lower millimeter fluxes, as compared to disks that incorporate compact dust grains. Moreover, we have recalibrated the relation between dust temperature and stellar luminosity for a wide range of stellar parameters. We also calculated the dust masses of a large sample of disks using the traditionally analytic approach. The median dust mass from our calculation is about six times higher than the literature result, and this is mostly driven by the different opacities of porous and compact grains. A comparison of the cumulative distribution function between disk dust masses and exoplanet masses shows that the median exoplanet mass is about two times lower than the median dust mass when grains are assumed to be porous and there are no exoplanetary systems with masses higher than the most massive disks. Our analysis suggests that adopting porous dust opacities may alleviate the mass budget problem for planet formation. As an example illustrating the combined effects of optical depth and porous dust opacities on the mass estimation, we conducted new IRAM/NIKA-2 observations toward the IRAS 04370+2559 disk and performed a detailed radiative transfer modeling of the spectral energy distribution (SED). The best-fit dust mass is roughly 100 times higher than the value given by a traditionally analytic calculation. Future spatially resolved observations at various wavelengths are required to better constrain the dust mass.