Aerosol proteins, as core biological components of bioaerosols, are garnering increasing attention due to their environmental significance, including their roles in atmospheric processes and ...associated health risks. However, observational data on the proteins are very limited, leaving their distribution and variation in the atmosphere poorly understood. To investigate the long-distance transport of proteins with Asian dust in the Northern Hemisphere middle latitude westerlies to remote downwind areas, we quantified the soluble proteins in aerosol particles, referred to as aerosol soluble proteins (ASPs), collected in the coastal city of Kumamoto, Japan, during the spring of 2023, when three dust events occurred. The concentration of ASPs ranged from 0.22 to 1.68 μg m−3, with an average concentration of 0.73 ± 0.36 μg m−3 under dust conditions and 0.31 ± 0.05 μg m−3 under non-dust conditions. During the dust periods, the largest concentration of ASPs (1.68 μg m−3) coincided with the peak concentration of suspended particulate matter, and the concentration strongly correlated with the mass concentration of particles larger than 2.5 μm, indicating a close dependence of ASPs on dust particles. Primary estimations indicated a dry deposition flux of ASPs at approximately 1.10 ± 0.87 mg m−2 d−1 under the dust conditions. These results prove that Asian dust efficiently transports proteins, facilitating their dispersion in the atmosphere.
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•Concentration of aerosol soluble proteins increased by ~135 % in dust periods.•ASPs concentration positively correlated with particles larger than 2.5 μm.•Asian dust carried substantial proteins to remote downwind areas.
GEMS (glass with embedded metal and sulfides) are the dominant carrier of amorphous silicates in anhydrous interplanetary dust particles (IDPs) and one of the most suitable materials to study early ...solar system processes. Amorphous silicates in 105 GEMS from eight IDPs were analyzed regarding texture and chemical composition to reassess GEMS formation theories and genetic relationships to amorphous silicate material in meteorites. Petrography of bulk IDPs was investigated to understand GEMS’ relationships to other IDP components. Furthermore, carbon and nitrogen isotopic compositions were measured. Nearly all GEMS are aggregates of several subgrains with variable amount of nanophase inclusions and different Mg- and Si-contents, while single GEMS are rare. The subgrains within aggregates are typically surrounded by one or more carbon rims with high density. The chemical compositions of GEMS amorphous silicates are subsolar for all major element/Si ratios but exhibit wide heterogeneity. This is not influenced by silicon oil from the capturing process of IDPs as assumed before, as a penetration of the silicon oil is excluded by high resolution EELS (electron energy loss spectroscopy) areal density maps of silicon. Furthermore, low Fe-content in GEMS amorphous silicates shows that these are not altered by aqueous activity on the parent body as it is the case for amorphous silicate material in primitive meteorites. The subsolar element/Si ratios and the wide chemical heterogeneity point to a non-equilibrium fractional condensation origin either in the early solar nebula or in a circumstellar environment and are not in agreement with homogenization via sputtering in the ISM. The close association with carbon around GEMS subgrains and as double-rims around GEMS aggregates argue for a multi-step aggregation after formation of the smallest GEMS subgrains in the ISM or the early solar nebula. Carbon acting as matrix material connecting GEMS and other IDP components has lower areal density as seen from carbon EELS areal density maps and isotopic anomalies varying at the nanometer scale, pointing to different origins and processing of materials to varying extent or at changing temperatures.
To balance GEMS’ subsolar element/Si ratios, a supersolar component in IDPs was assumed to account for the overall chondritic composition of bulk IDPs. Nevertheless, our bulk IDP analyses revealed subsolar, but variable, element/Si ratios for complete particles as well, depending on type and amount of mineral phases in each particle. Pyroxenes in the investigated particles can occur as elongated euhedral crystals, but are overall rare. The dominant crystalline fraction in the investigated IDP samples are equilibrated aggregates (EAs) that show the same chemical compositions as GEMS, indicating that the EAs are recrystallized GEMS grains and formed after GEMS formation as secondary phases.
Mineral dust is an important component of the climate
system, interacting with radiation, clouds, and biogeochemical systems and
impacting atmospheric circulation, air quality, aviation, and solar ...energy
generation. These impacts are sensitive to dust particle size distribution
(PSD), yet models struggle or even fail to represent coarse (diameter (d)
>2.5 µm) and giant (d>20 µm) dust
particles and the evolution of the PSD with transport. Here we examine three
state-of-the-art airborne observational datasets, all of which measured the
full size range of dust (d=0.1 to >100 µm) at different
stages during transport with consistent instrumentation. We quantify the
presence and evolution of coarse and giant particles and their contribution
to optical properties using airborne observations over the Sahara (from the
Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical
eastern Atlantic (from the AER-D field campaign). Observations show significantly more abundant coarse and giant dust
particles over the Sahara compared to the SAL: effective diameters of up to
20 µm were observed over the Sahara compared to 4 µm in the
SAL. Excluding giant particles over the Sahara results in significant
underestimation of mass concentration (40 %), as well as underestimates of
both shortwave and longwave extinction (18 % and 26 %, respectively, from
scattering calculations), while the effects in the SAL are smaller but
non-negligible. The larger impact on longwave extinction compared to
shortwave implies a bias towards a radiative cooling effect in dust models,
which typically exclude giant particles and underestimate coarse-mode
concentrations. A compilation of the new and published effective diameters against dust age since uplift
time suggests that two regimes of dust transport exist. During the initial
1.5 d, both coarse and giant particles are rapidly deposited. During the
subsequent 1.5 to 10 d, PSD barely changes with transport, and the coarse
mode is retained to a much greater degree than expected from estimates of
gravitational sedimentation alone. The reasons for this are unclear and
warrant further investigation in order to improve dust transport schemes
and the associated radiative effects of coarse and giant particles in
models.
We present initial observations of the interstellar body 2I/(2019 Q4) Borisov taken to determine its nature prior to the perihelion in 2019 December. Images from the Nordic Optical Telescope show a ...prominent, morphologically stable dust coma and tail. The dust cross-section within 15,000 km of the nucleus averages 130 km2 (assuming geometric albedo 0.1) and increases by about 1% per day. If sustained, this rate indicates that the comet has been active for ∼100 days prior to the observations. Cometary activity thus started in 2019 June, at which time C/Borisov was at ∼4.5 au from the Sun, a typical distance for the onset of water ice sublimation in comets. The dust optical colors, B − V = 0.80 0.05, V − R = 0.47 0.03 and R− I = 0.49 0.05, are identical to those of a sample of (solar system) long-period comets. The colors are similar to those of 1I/(2017 U1) 'Oumuamua, indicating a lack of the ultrared matter that is common in the Kuiper Belt, on both interstellar objects. The effective size of the dust particles is estimated as = 100 m, based on the length of the dust tail and the 100 day lifetime. With this size, the ejected dust mass is of order 1.3 × 107 kg and the current dust mass loss rate ∼2 kg s−1. We set an upper limit to the nucleus radius using photometry at rn ≤3.8 km (again for albedo 0.1) and we use a statistical argument to show that the nucleus must be much smaller, likely a few hundred meters in radius.
The light scattered from dust grains in debris disks is typically modeled as compact spheres using the Lorenz-Mie theory or as porous spheres by incorporating an effective medium theory. In this work ...we examine the effect of incorporating a more realistic particle morphology on estimated radiation-pressure blowout sizes. To calculate the scattering and absorption cross-sections of irregularly shaped dust grains, we use the discrete dipole approximation. These cross-sections are necessary to calculate the β-ratio, which determines whether dust grains can remain gravitationally bound to their star. We calculate blowout sizes for a range of stellar spectral types corresponding with stars known to host debris disks. As with compact spheres, more luminous stars blow out larger irregularly shaped dust grains. We also find that dust grain composition influences blowout size such that absorptive grains are more readily removed from the disk. Moreover, the difference between blowout sizes calculated assuming spherical particles versus particle morphologies more representative of real dust particles is compositionally dependent as well, with blowout size estimates diverging further for transparent grains. We find that the blowout sizes calculated have a strong dependence on the particle model used, with differences in the blowout size calculated being as large as an order of magnitude for particles of similar porosities.
Mg alloy waste dust can react with water to produce hydrogen in the production of Mg alloy products, which has the possibility to lead to fires or explosions. Firstly, from the perspective of safety ...management, this paper systematically studies the impact of the difference of hydrogen evolution amount of magnesium based alloy waste dust particles(Mg–Al/Mg–Zn) on the risk of wet dust collector under different environmental conditions, and a two-stage hydrogen evolution model was constructed. Secondly, from a technical point of view, a method of using environmentally-friendly, cost-effective sodium phosphate to inhibit the hydrogen evolution reaction of Mg alloys is also proposed. The morphologies of Mg alloy dust particles before and after reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and chemical dynamics modeling before the related reaction mechanisms were identified. The research outcome of the present study could provide effective technical guidance for preventing hydrogen explosion accidents at Mg alloy fabrication facilities.
Here, the nonlinear convective transport of non-Newtonian fluids embedded with dust particles over a stretched surface is investigated. The silent features of non-Newtonian fluid are considered by ...Casson and Carreau fluid models. The heat transfer mechanism involves the influences of a magnetic dipole, nonlinear radiative heat and non-uniform heat source/sink. The convective condition is also retained at the boundary. The non-linear partial differential equations that model the transport phenomenon was transformed, non-dimensionalized and parameterized. The subsequent boundary value problems were computed numerically for distinct pertinent parameters using Runge–Kutta based shooting techniques. The present results are validated with the existing literature by direct comparison. The heat transfer rate in Casson/Carreau fluid phase is significantly higher than that of dust phase.
•Casson parameter β has opposite effects on velocity and temperature profiles.•The nonlinear convection parameter increases the momentum boundary layer thickness.•The dimensionless temperature increases with rise in thermal radiation.•The skin friction coefficient and the local Nusselt number increases by increasing values of λ.
A Highly Settled Disk around Oph163131 Villenave, M.; Stapelfeldt, K. R.; Duchêne, G. ...
The Astrophysical journal,
05/2022, Letnik:
930, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
High dust density in the midplane of protoplanetary disks is favorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. Vertical ...settling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin and high-density regions. In this work, we aim to study these mechanisms in the highly inclined protoplanetary disk SSTC2D J163131.2-242627 (Oph 163131,
i
∼ 84°). We present new high-angular-resolution continuum and
12
CO ALMA observations of Oph 163131. The gas emission appears significantly more extended in the vertical and radial direction compared to the dust emission, consistent with vertical settling and possibly radial drift. In addition, the new continuum observations reveal two clear rings. The outer ring, located at ∼100 au, is well-resolved in the observations, allowing us to put stringent constraints on the vertical extent of millimeter dust particles. We model the disk using radiative transfer and find that the scale height of millimeter-sized grains is 0.5 au or less at 100 au from the central star. This value is about one order of magnitude smaller than the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of the large grains is occurring in the disk. When adopting a parametric dust settling prescription, we find that the observations are consistent with a turbulent viscosity coefficient of about
α
≲ 10
−5
at 100 au. Finally, we find that the thin dust scale height measured in Oph 163131 is favorable for planetary growth by pebble accretion: a 10
M
E
planet may grow within less than 10 Myr, even in orbits exceeding 50 au.
Understanding planet formation requires one to discern how dust grows in protoplanetary disks. An important parameter to measure in disks is the maximum dust grain size present. This is usually ...estimated through measurements of the dust opacity at different millimeter wavelengths assuming optically thin emission and dust opacity dominated by absorption. However, Atacama Large Millimeter/submillimeter Array (ALMA) observations have shown that these assumptions might not be correct in the case of protoplanetary disks, leading to overestimation of particle sizes and to underestimation of the disk's mass. Here, we present an analysis of high-quality ALMA and Very Large Array images of the HL Tau protoplanetary disk, covering a wide range of wavelengths, from 0.8 mm to 1 cm, and with a physical resolution of ∼7.35 au. We describe a procedure to analyze a set of millimeter images without any assumption about the optical depth of the emission, and including the effects of absorption and scattering in the dust opacity. This procedure allows us to obtain the dust temperature, the dust surface density, and the maximum particle size at each radius. In the HL Tau disk, we found that particles have already grown to a few millimeters in size. We detect differences in the dust properties between dark and bright rings, with dark rings containing low dust density and small dust particles. Different features in the HL Tau disk seem to have different origins. Planet-disk interactions can explain substructure in the external half of the disk, but the internal rings seem to be associated with the presence of snow lines of several molecules.
The concept of a hybrid nanofluid has piqued the interest of numerous researchers due to its potential for increased thermal properties, which results in high transfer rates. Hybrid nanofluids are ...used in heat transport systems such as electronic cooling, and applications in biomedical and pharmaceutical relief. Thus, the present paper inspects the impact of Lorentz forces on the Casson fluid flow of water-based Fe
3
O
4
-MWCNT hybrid nanofluid induced by dust particles from a stretching sheet. The leading PDEs are changed into ODEs by employing similarity variables and then achieving an exact solution for these transformed ODEs. The impacts of distinct physical constraints including fluid interaction particle parameter, Casson parameter, and magnetic parameter on the dust velocity and fluid velocity for normal nanofluid (Fe
3
O
4
/H
2
O) and hybrid nanofluid (Fe
3
O
4
-MWCNT/ H
2
O) are addressed in detail. The present analytic solution shows a strong correlation with earlier published numerical studies in limited cases.
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