Journal articles on the topic 'Dust growth'
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Saani, Chinwe I., Joshua Kayode, Benson O. Ademiluyi, and M. Yoserizal Saragih. "Effect of Growth Media on Plumule Emergence and Early Seedling Growth of Monodora myristica." Budapest International Research in Exact Sciences (BirEx) Journal 2, no. 4 (October 9, 2020): 436–42. http://dx.doi.org/10.33258/birex.v2i4.1257.
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The study investigated the emergence and early seedling development of Monodora myristica in six different growth media viz: mixture of river sand/top soil, river sand/saw dust, top soil/saw dust, saw dust only, top soil only and river sand only. Results obtained recorded highest percentage germination (63%) in seeds sown in saw dust only. Early seedling growth was observed for four months. The results of this study showed that seedlings sown in mixture of top soil/saw dust recorded highest mean plant height (16.83cm), stem girth ( 2.50mm), and leaf area (46.18cm2) at the end of the experimental time. Seedlings on top soil only had the highest number of leaves (3.89). River sand had the least seedling performance in all the growth parameters examined; plant height (13.27cm), stem collar girth (1.99mm), leaf length (8.61cm), leaf width (4.77cm) and leaf area (30.83cm2). The study established that the % emergence of Monodora myristica seedlings was best in saw dust medium while mixture of top soil/saw dusts is recommended for enhancing early seedling growth of this plant in the nursery.
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Ishibashi, W. "Supercritical dusty BH growth in the early Universe." Monthly Notices of the Royal Astronomical Society 505, no. 4 (June 18, 2021): 5846–52. http://dx.doi.org/10.1093/mnras/stab1728.
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ABSTRACT Supermassive black holes (with ${M_{\rm BH} \sim 10^9\, \mathrm{M}_{\odot }}$) are observed in the first Gyr of the Universe, and their host galaxies are found to contain unexpectedly large amounts of dust and metals. In light of the two empirical facts, we explore the possibility of supercritical accretion and early black hole growth occurring in dusty environments. We generalize the concept of photon trapping to the case of dusty gas and analyse the physical conditions leading to ‘dust photon trapping’. Considering the parameter space dependence, we obtain that the dust photon trapping regime can be more easily realized for larger black hole masses, higher ambient gas densities, and lower gas temperatures. The trapping of photons within the accretion flow implies obscured active galactic nuclei, while it may allow a rapid black hole mass build-up at early times. We discuss the potential role of such dust photon trapping in the supercritical growth of massive black holes in the early Universe.
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AL-HAIDARY, Hanaa Khudhaier Mohammed Ali, and A. F. Abed AL-KHADER. "EVALUATION OF GROWTH AND SEED YIELD OF TWO CULTIVARS OF FLAX." MINAR International Journal of Applied Sciences and Technology 03, no. 04 (December 1, 2021): 17–22. http://dx.doi.org/10.47832/2717-8234.4-3.3.
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In this research, we have conducted an experimental study of the dusty plasma to the Aluminum oxide (Al2O3) dust material with a grain radius of (0.2) µm to (0.6) µm. In the experiment, we use air in the vacuum chamber system under different low pressure (0.1-0.8) Torr. The results have showed that the existence of dust particles in air plasma is equal to the Paschen minimum which is (0.4) Torr with Al2O3 dusty and without dust. The effect of Al2O3 dust particles on the plasma characteristics like floating potential (Vf), plasma potential (Vp), electron saturation current (Ies), temperature of the electron (Te), density of electron (ne) and density of ion (ni) of the DC system that can be calculated in the glow-discharge region. Parameter measurements are taken by four cylindrical probes which are diagnosed at a distance of (40) mm from the cathode diameter, the Paschen minimum at a pressure of (0.4) Torr. The plasma potential and the probe's floating voltage become more negative when dust is immersed in the plasma region. The features of these parameters show that the current discharge decreases while the discharge voltage increases when the aluminum oxide dust particles that are incorporated. And vice versa was in the absence of dust. Electron density increases in the existence of dust particles which causes the electron temperature to decrease.
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Kaur, Daljeet, Suresh C. Sharma, R. S. Pandey, and Ruby Gupta. "Weibel instability oscillation in a dusty plasma with counter-streaming electrons." Laser and Particle Beams 38, no. 1 (January 17, 2020): 8–13. http://dx.doi.org/10.1017/s0263034619000776.
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AbstractWe investigate the Weibel instability (WI) in a dusty plasma which is driven to oscillation by the addition of dust grains in the plasma. Our analysis predicts the existence of three modes in a dusty plasma. There is a high-frequency electromagnetic mode, whose frequency increases with an increase in the relative number density of dust grains and which approaches instability due to the presence of dust grains. The second mode is a damping mode which exists due to dust charge fluctuations in plasma. The third mode is the oscillating WI mode. The dispersion relation and the growth rate of various modes in the dusty plasma are derived using the first-order perturbation theory. The effect of dust grain parameters on frequency and growth rate is also studied and reported.
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Triani, Dian P., Manodeep Sinha, Darren J. Croton, Camilla Pacifici, and Eli Dwek. "The origin of dust in galaxies across cosmic time." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 14, 2020): 2490–505. http://dx.doi.org/10.1093/mnras/staa446.
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ABSTRACT We study the dust evolution in galaxies by implementing a detailed dust prescription in the SAGE semi-analytical model (SAM) for galaxy formation. The new model, called Dusty SAGE, follows the condensation of dust in the ejecta of Type II supernovae and asymptotic giant branch stars, grain growth in the dense molecular clouds, destruction by supernovae shocks, and the removal of dust from the interstellar medium (ISM) by star formation, reheating, inflows, and outflows. Our model successfully reproduces the observed dust mass function at redshift z = 0 and the observed scaling relations for dust across a wide range of redshifts. We find that the dust mass content in the present Universe is mainly produced via grain growth in the ISM. By contrast, in the early Universe, the primary production mechanism for dust is the condensation in stellar ejecta. The shift of the significant production channel for dust characterizes the scaling relations of dust-to-gas (DTG) and dust-to-metal (DTM) ratios. In galaxies where the grain growth dominates, we find positive correlations for DTG and DTM ratios with both metallicity and stellar mass. On the other hand, in galaxies where dust is produced primarily via condensation, we find negative or no correlation for DTM and DTG ratios with either metallicity or stellar mass. In agreement with observation showing that the circumgalactic medium contains more dust than the ISM, our model also shows the same trend for z < 4. Our SAM is publicly available at https://github.com/dptriani/dusty-sage.
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Scott, Erin. "Dust records mountain growth." Nature Reviews Earth & Environment 2, no. 2 (January 20, 2021): 89. http://dx.doi.org/10.1038/s43017-021-00141-3.
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Martínez-González, Sergio, Richard Wünsch, Guillermo Tenorio-Tagle, Sergiy Silich, Dorottya Szécsi, and Jan Palouš. "Dust Grain Growth and Dusty Supernovae in Low-metallicity Molecular Clouds." Astrophysical Journal 934, no. 1 (July 1, 2022): 51. http://dx.doi.org/10.3847/1538-4357/ac77fe.
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Abstract We present 3D hydrodynamical models of the evolution of superbubbles powered by stellar winds and supernovae from young coeval massive star clusters within low-metallicity (Z = 0.02 Z ⊙), clumpy molecular clouds. We explore the initial stages of the superbubble evolution, including the occurrence of pair-instability and core-collapse supernovae. Our aim is to study the occurrence of dust grain growth within orbiting dusty clumps, and in the superbubble’s swept-up supershell. We also aim to address the survival of dust grains produced by sequential supernovae. The model accounts for the star cluster gravitational potential and self-gravity of the parent cloud. It also considers radiative cooling (including that induced by dust) and a state-of-the-art population synthesis model for the coeval cluster. As shown before, a superbubble embedded into a clumpy medium becomes highly distorted, expanding mostly due to the hot gas streaming through low-density channels. Our results indicate that in the case of massive (∼107 M ⊙) molecular clouds, hosting a super star cluster (∼5.6 × 105 M ⊙), grain growth increments the dust mass at a rate ∼4.8 × 10−5 M ⊙ yr−1 during the first 2.5 Myr of the superbubble’s evolution, while the net contribution of pair-instability and core-collapse supernovae to the superbubble’s dust budget is ∼1200 M ⊙ (M SC/5.6 × 105 M ⊙), where M SC is the stellar mass of the starburst. Therefore, dust grain growth and dust injection by supernovae lead to the creation of, without invoking a top-heavy initial mass function, massive amounts of dust within low-metallicity star-forming molecular clouds, in accordance with the large dust mass present in galaxies soon after the onset of cosmic reionization.
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Crespe, Elisabeth, Jean-Francois Gonzalez, Guillaume Laibe, Sarah T. Maddison, and Laure Fouchet. "Influence of growth on dust settling and migration in protoplanetary discs." Proceedings of the International Astronomical Union 6, S276 (October 2010): 405–6. http://dx.doi.org/10.1017/s1743921311020540.
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AbstractTo form meter-sized pre-planetesimals in protoplanetary discs, dust aggregates have to decouple from the gas at a distance far enough from the central star so they are not accreted. Dust grains are affected by gas drag, which results in a vertical settling towards the mid-plane, followed by radial migration. To have a better understanding of the influence of growth on the dust dynamics, we use a simple grain growth model to determine the dust distribution in observed discs. We implement a constant growth rate into a gas+dust hydrodynamics SPH code and vary the growh rate to study the resulting effect on dust distribution. The growth rate allows us to determine the relative importance between friction and growth.We show that depending on the growth rate, a range of dust distribution can result. For large enough growth rates, grains can decouple from the gas before being accreted onto the central star, thus contributing as planetary building rocks.
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Sharma, Jyotsna, Ajay Gahlot, Suresh C. Sharma, and V. K. Jain. "Effect of dust charge fluctuations on upper hybrid wave instabilities in magnetized dusty plasma." International Journal of Modern Physics: Conference Series 32 (January 2014): 1460350. http://dx.doi.org/10.1142/s2010194514603500.
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The decay instability of an upper hybrid electrostatic wave into an upper hybrid sideband wave and lower hybrid wave is studied in magnetized dusty plasma. A local theory of this process has been developed. The growth rate and mode frequencies of the unstable wave were evaluated based on existing dusty plasma parameters and it is found that the unstable mode frequency and growth rate increases with δ (ion-to-electron density ratio) in the presence and absence of dust charge fluctuations in addition to dust dynamics.
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Pignatale, F. C., J.-F. Gonzalez, Bernard Bourdon, and Caroline Fitoussi. "Size and density sorting of dust grains in SPH simulations of protoplanetary discs – II. Fragmentation." Monthly Notices of the Royal Astronomical Society 490, no. 3 (October 14, 2019): 4428–46. http://dx.doi.org/10.1093/mnras/stz2883.
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ABSTRACT Grain growth and fragmentation are important processes in building up large dust aggregates in protoplanetary discs. Using a 3D two-phase (gas–dust) sph code, we investigate the combined effects of growth and fragmentation of a multiphase dust with different fragmentation thresholds in a time-evolving disc. We find that our fiducial disc, initially in a fragmentation regime, moves towards a pure-growth regime in a few thousands years. Time-scales change as a function of the disc and dust properties. When fragmentation is efficient, it produces, in different zones of the disc, Fe/Si and rock/ice ratios different from those predicted when only pure growth is considered. Chemical fractionation and the depletion/enrichment in iron observed in some chondrites can be linked to the size–density sorting and fragmentation properties of precursor dusty grains. We suggest that aggregation of chondritic components could have occurred where/when fragmentation was not efficient if their aerodynamical sorting has to be preserved. Chondritic components would allow aerodynamical sorting in a fragmentation regime only if they have similar fragmentation properties. We find that, in the inner disc, and for the same interval of time, fragmenting dust can grow larger when compared to the size of grains predicted by pure growth. This counter-intuitive behaviour is due to the large amount of dust that piles up in a fragmenting zone followed by the rapid growth that occurs when this zone transitions to a pure growth regime. As an important consequence, dust can overcome the radial-drift barrier within a few thousands years.
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Williams, Jeremiah. "Spatial Evolution of the Dust-Acoustic Wave." Plasma Science, IEEE Transactions on 41, no. 4 (April 2013): 788–93. http://dx.doi.org/10.1109/tps.2012.2231083.
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Over the past twenty years, the dust-acoustic wave (DAW) has been a subject of intense study. In this paper, high-speed video imaging is employed to measure the evolution of wavefronts of a propagating DAW as it propagates through a weakly coupled dusty plasma system in an argon dc glow discharge plasma. In particular, measurements of the growth, saturation, and, then, damping of the wave mode as the wave propagates through the cloud are reported. It is observed that the wave amplitude initially exhibits rapid growth while the wavefront compresses. After this initial growth, the width of the wavefront remains relatively constant, while the amplitude of the wavefront evolves like the background dust medium. In some cases, it is also observed that the wave amplitude can decay more quickly than the background dust medium.
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Donevski, D., A. Lapi, K. Małek, D. Liu, C. Gómez-Guijarro, R. Davé, K. Kraljic, et al. "In pursuit of giants." Astronomy & Astrophysics 644 (December 2020): A144. http://dx.doi.org/10.1051/0004-6361/202038405.
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The dust-to-stellar mass ratio (Mdust/M⋆) is a crucial, albeit poorly constrained, parameter for improving our understanding of the complex physical processes involved in the production of dust, metals, and stars in galaxy evolution. In this work, we explore trends of Mdust/M⋆ with different physical parameters and using observations of 300 massive dusty star-forming galaxies detected with ALMA up to z ≈ 5. Additionally, we interpret our findings with different models of dusty galaxy formation. We find that Mdust/M⋆ evolves with redshift, stellar mass, specific star formation rates, and integrated dust size, but that evolution is different for main-sequence galaxies than it is for starburst galaxies. In both galaxy populations, Mdust/M⋆ increases until z ∼ 2, followed by a roughly flat trend towards higher redshifts, suggesting efficient dust growth in the distant universe. We confirm that the inverse relation between Mdust/M⋆ and M⋆ holds up to z ≈ 5 and can be interpreted as an evolutionary transition from early to late starburst phases. We demonstrate that the Mdust/M⋆ in starbursts reflects the increase in molecular gas fraction with redshift and attains the highest values for sources with the most compact dusty star formation. State-of-the-art cosmological simulations that include self-consistent dust growth have the capacity to broadly reproduce the evolution of Mdust/M⋆ in main-sequence galaxies, but underestimating it in starbursts. The latter is found to be linked to lower gas-phase metallicities and longer dust-growth timescales relative to observations. The results of phenomenological models based on the main-sequence and starburst dichotomy as well as analytical models that include recipes for rapid metal enrichment are consistent with our observations. Therefore, our results strongly suggest that high Mdust/M⋆ is due to rapid dust grain growth in the metal-enriched interstellar medium. This work highlights the multi-fold benefits of using Mdust/M⋆ as a diagnostic tool for: (1) disentangling main-sequence and starburst galaxies up to z ∼ 5; (2) probing the evolutionary phase of massive objects; and (3) refining the treatment of the dust life cycle in simulations.
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Ishibashi, W. "AGN radiative feedback in the early growth of massive black holes." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 12, 2019): 5225–30. http://dx.doi.org/10.1093/mnras/stz2543.
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ABSTRACT Growing observational evidence confirms the existence of massive black holes ($M_{\rm BH} \sim 10^9 \, \mathrm{M}_{\odot }$), accreting at rates close to the Eddington limit, at very high redshifts ($z \gtrsim 6\!-\!7$) in the early Universe. Recent observations indicate that the host galaxies of the first quasars are chemically evolved systems, containing unexpectedly large amounts of dust. Such a combination of high luminosities and large dust content should form favourable physical conditions for radiative dusty feedback. We explore the impact of the active galactic nucleus (AGN) feedback, driven by radiation pressure on dust, on the early growth of massive black holes. Assuming Eddington-limited exponential black hole growth, we find that the dynamics and energetics of the radiation pressure-driven outflows also follow exponential trends at late times. We obtain modest outflow energetics (with momentum flux $\dot{p} \lesssim L/c$ and kinetic power $\dot{E}_{\rm k} \lesssim 10^{-3} L$), comparable with available observations of quasar-driven outflows at very high redshifts, but significantly lower than typically observed in local quasars and predicted by wind energy-driven models. AGN radiative dusty feedback may thus play an important role in powering galactic outflows in the first quasars in the early Universe.
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Triani, Dian P., Manodeep Sinha, Darren J. Croton, Eli Dwek, and Camilla Pacifici. "Exploring the relation between dust mass and galaxy properties using Dusty SAGE." Monthly Notices of the Royal Astronomical Society 503, no. 1 (March 5, 2021): 1005–16. http://dx.doi.org/10.1093/mnras/stab558.
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ABSTRACT We explore the relation between dust and several fundamental properties of simulated galaxies using the Dusty SAGE semi-analytic model. In addition to tracing the standard galaxy properties, Dusty SAGE also tracks cold dust mass in the interstellar medium (ISM), hot dust mass in the halo, and dust mass ejected by feedback activity. Based on their ISM dust content, we divide our galaxies into two categories: ISM dust-poor and ISM dust-rich. We split the ISM dust-poor group into two subgroups: halo dust-rich and dust-poor (the latter contains galaxies that lack dust in both the ISM and halo). Halo dust-rich galaxies have high outflow rates of heated gas and dust and are more massive. We divide ISM dust-rich galaxies based on their specific star formation rate (sSFR) into star-forming and quenched subgroups. At redshift z = 0, we find that ISM dust-rich galaxies have a relatively high sSFR, low bulge-to-total (BTT) mass ratio, and high gas metallicity. The high sSFR of ISM dust-rich galaxies allows them to produce dust in the stellar ejecta. Their metal-rich ISM enables dust growth via grain accretion. The opposite is seen in the ISM dust-poor group. Furthermore, ISM dust-rich galaxies are typically late-types, while ISM dust-poor galaxies resemble the early-type population, and we show how their ISM content evolves from being dust-rich to dust-poor. Finally, we investigate dust production from z = 3 to z = 0 and find that all groups evolve similarly, except for the quenched ISM dust-rich group.
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Vericel, Arnaud, Jean-François Gonzalez, Daniel J. Price, Guillaume Laibe, and Christophe Pinte. "Dust growth, fragmentation, and self-induced dust traps in phantom." Monthly Notices of the Royal Astronomical Society 507, no. 2 (August 11, 2021): 2318–38. http://dx.doi.org/10.1093/mnras/stab2263.
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ABSTRACT We present the implementation of a dust growth and fragmentation module in the public smoothed particle hydrodynamics (SPH) code phantom. This module is made available for public use with this paper. The coagulation model considers locally monodisperse dust size distributions around single values that are carried by the SPH particles. Along with the presentation of the model, implementation, and tests, we showcase growth and fragmentation in a few typical circumstellar disc simulations and revisit previous results. The module is also interfaced with the radiative transfer code mcfost, which facilitates the comparison between simulations and ALMA observations by generating synthetic maps. Circumstellar disc simulations with growth and fragmentation reproduce the ‘self-induced dust trap’ mechanism first proposed in 2017, which supports its existence. Synthetic images of discs featuring this mechanism suggest it would be detectable by ALMA as a bright axisymmetric ring at several tens of au from the star. With this paper, our aim is to provide a public tool to be able to study and explore dust growth in a variety of applications related to planet formation.
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SHUKLA, P. K., and M. ROSENBERG. "Drift wave instability in a radially bounded dusty magnetoplasma with parallel ion velocity shear." Journal of Plasma Physics 79, no. 1 (July 17, 2012): 33–35. http://dx.doi.org/10.1017/s0022377812000633.
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AbstractProperties of the coupled dust ion-acoustic drift wave instability in a radially bounded dusty magnetoplasma with an equilibrium sheared parallel ion (SPI) flow are investigated. By using the two-fluid model for the electrons and ions, a wave equation for the low-frequency coupled dust ion-acoustic drift waves in a bounded plasma with stationary charged dust grains is derived. The wave equation admits a linear dispersion relation, which exhibits that the radial boundary affects the growth rate of the coupled ion-acoustic drift wave instability which is excited by the SPI flow. The results should be relevant to dusty magnetoplasma experiments with an SPI flow.
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GUERRA, R., J. T. MENDONÇA, and P. K. SHUKLA. "Stimulated Raman, Brillouin and dust–Brillouin scattering in dusty plasmas." Journal of Plasma Physics 59, no. 2 (February 1998): 343–65. http://dx.doi.org/10.1017/s002237789700620x.
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Stimulated scatterings of large-amplitude electromagnetic waves by Langmuir, dust–ion-acoustic and dust-acoustic waves in unmagnetized dusty plasmas are investigated by employing the standard methods of nonlinear three-wave interactions and by incorporating the effects of grain-charge fluctuations, collisions of electrons and ions with dust grains, the plasma drag on a dust grain (for the case of the dust-acoustic wave) and the dependence of the average dust charge on the dusty plasma parameters. Distinction is made between the charging collisions, when electrons and ions are accumulated onto the grain surface; and Coulomb collisions, when electrons and ions are simply deflected from the grain surface. We investigate the regimes for which Coulomb collisions can be treated under the small-angle-deflection approximation. If the intergrain average spacing is equal to or smaller than the Debye length, the collision frequencies of plasma species with dust grains can be much larger than any collision frequency of the plasma species amongst themselves. In the case of Brillouin stimulated scattering, other important contributions to damping come from Landau and dust-charge fluctuation damping. In the case of dust–Brillouin stimulated scattering, the most important contribution to damping comes from dust-charge fluctuation (if the intergrain average spacing is equal to or smaller than the Debye length) and plasma drag on the dust particles (if the intergrain average spacing is larger than the Debye length). We derive the instability thresholds as a function of the density of the dust grains. Because of the inclusion of the new effects, in both Raman and Brillouin scatterings it is found that the instability threshold powers are drastically increased relative to the dust-free case. In the case of dust–Brillouin scattering, a minimum for the threshold power is found in the transition region between ‘dusty’ and ‘dust-in’ plasma. Growth rates near thresholds are also discussed.
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Lee, Y. H., K. Chen, and P. J. Adams. "Development of a global model of mineral dust aerosol microphysics." Atmospheric Chemistry and Physics 9, no. 7 (April 3, 2009): 2441–58. http://dx.doi.org/10.5194/acp-9-2441-2009.
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Abstract. A mineral dust module is developed and implemented into the global aerosol microphysics model, GISS-TOMAS. The model is evaluated against long-term measurements of dust surface mass concentrations and deposition fluxes. Predicted mass concentrations and deposition fluxes are in error on average by a factor of 3 and 5, respectively. The comparison shows that the model performs better near the dust source regions but underestimates surface concentrations and deposition fluxes in more remote regions. Including only sites with measured dust concentrations of at least 0.5 μg m−3, the model prediction agrees with observations to within a factor of 2. It was hypothesized that the lifetime of dust, 2.6 days in our base case, is too short and causes the underestimation in remote areas. However, a sensitivity simulation with smaller dust particles and increased lifetime, 3.7 days, does not significantly improve the comparison. These results suggest that the underestimation of mineral dust in remote areas may result from local factors/sources not well described by the global dust source function used here or the GCM meteorology. The effect of dust aerosols on CCN(0.2%) concentrations is negligible in most regions of the globe; however, CCN(0.2%) concentrations change decrease by 10–20% in dusty regions the impact of dust on CCN(0.2%) concentrations in dusty regions is very sensitive to the assumed size distribution of emissions. If emissions are predominantly in the coarse mode, CCN(0.2%) decreases in dusty regions up to 10–20% because dust competes for condensable H2SO4, reducing the condensational growth of ultrafine mode particles to CCN sizes. With significant fine mode emissions, however, CCN(0.2%) doubles in Saharan source regions because the direct emission of dust particles outweighs any microphysical feedbacks. The impact of dust on CCN concentrations active at various water supersaturations is also investigated. Below 0.1%, CCN concentrations increase significantly in dusty regions due to the presence of coarse dust particles. Above 0.2%, CCN concentrations show a similar behavior as CCN(0.2%).
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Kumar, Amit, Ruby Gupta, and Jyotsna Sharma. "Effect of dust grains on the parametric coupling of a lower hybrid wave driven ion cyclotron wave in a tokamak plasma." AIP Advances 12, no. 3 (March 1, 2022): 035026. http://dx.doi.org/10.1063/5.0085062.
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In this article, the effect of dust charge fluctuations on the parametric upconversion of a lower hybrid wave into an ion cyclotron wave and a side band wave in a two-ion species tokamak plasma is studied. When the oscillatory velocity of plasma electrons is a few percent of the sound velocity, the lower hybrid wave becomes unstable and decays into two modes: an ion cyclotron wave mode and a low frequency lower hybrid side band wave. Furthermore, a ponderomotive force by a lower hybrid pump and a side band wave is exerted on the existing electrons, which drives the ion cyclotron decay mode. The presence of negatively charged dust grains and their shape, size, radius, and density influence the instability. The growth rate of instability is calculated by considering typical existing D–T (Deuterium–Tritium) dusty plasma parameters, and it is observed that the growth rate increases with the relative density of dust grains, number density of dust grains, oscillatory velocity of electrons, and amplitude of pump waves. However, the normalized growth rate increases with the unstable wave frequency, and it also increases as we increase the ratio of deuterium to tritium density. Here, the growth rate decreases with the increase in the size of dust grains and electron cyclotron frequency. The theoretical results summarized in the present study are able to efficiently elaborate the complexity produced in plasma properties in a tokamak due to the dust–plasma interactions, which are briefly discussed here.
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Vorobyov, Eduard I., and Vardan G. Elbakyan. "Gravitoviscous protoplanetary disks with a dust component." Astronomy & Astrophysics 631 (October 11, 2019): A1. http://dx.doi.org/10.1051/0004-6361/201936132.
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Aims. Spatial distribution and growth of dust in a clumpy protoplanetary disk subject to vigorous gravitational instability and fragmentation is studied numerically with sub-au resolution using the FEOSAD code. Methods. Hydrodynamics equations describing the evolution of self-gravitating and viscous protoplanetary disks in the thin-disk limit were modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust with a variable maximum radius. The conversion of small to grown dust, dust growth, friction of dust with gas, and dust self-gravity were also considered. Results. We found that the disk appearance is notably time-variable with spiral arms, dusty rings, and clumps, constantly forming, evolving, and decaying. As a consequence, the total dust-to-gas mass ratio is highly non-homogeneous throughout the disk extent, showing order-of-magnitude local deviations from the canonical 1:100 value. Gravitationally bound clumps formed through gravitational fragmentation have a velocity pattern that deviates notably from the Keplerian rotation. Small dust is efficiently converted into grown dust in the clump interiors, reaching a maximum radius of several decimeters. Concurrently, grown dust drifts towards the clump center forming a massive compact central condensation (70–100 M⊕). We argue that protoplanets may form in the interiors of inward-migrating clumps before they disperse through the action of tidal torques. We foresee the formation of protoplanets at orbital distances of several tens of au with initial masses of gas and dust in the protoplanetary seed in the (0.25–1.6) MJup and (1.0–5.5) M⊕ limits, respectively. The final masses of gas and dust in the protoplanets may however be much higher due to accretion from surrounding massive metal-rich disks/envelopes. Conclusions. Dusty rings formed through tidal dispersal of inward-migrating clumps may have a connection to ring-like structures found in youngest and massive protoplanetary disks. Numerical disk models with a dust component that can follow the evolution of gravitationally bound clumps through their collapse phase to the formation of protoplanets are needed to make firm conclusions on the characteristics of planets forming through gravitational fragmentation.
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Kukfisz, Bożena, and Robert Piec. "The Fire and Explosion Hazard of Coloured Powders Used during the Holi Festival." International Journal of Environmental Research and Public Health 18, no. 21 (October 21, 2021): 11090. http://dx.doi.org/10.3390/ijerph182111090.
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During the world-famous Holi festival, people throw and smear each other with a colored powder (Holi color, Holi powder, Gulal powder). Until now, adverse health and environmental effects (skin and eye irritation, air pollution, and respiratory problems) have been described in the available literature. However, the literature lacks data on the flammable and explosive properties of these powders during mass events, despite the fact that burns, fires, and explosions during the Holi festival have taken place many times. The aim of the article is to present the fire and explosion parameters of three currently used Holi dust and cornflour dust types as reference dust. The minimum ignition temperature of the dust layer and dust cloud, the maximum explosion pressure and its maximum rate of growth over time, the lower explosion limit, the limit of oxygen concentration, and the minimum ignition energy were determined. Tests confirmed that the currently available Holi powders should be classified as flammable dusts and low-explosive dusts. The likelihood of a fire or explosion during mass incidents involving a Holi dust-air mixture is high.
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Churg, A., B. Gilks, and J. Dai. "Induction of fibrogenic mediators by fine and ultrafine titanium dioxide in rat tracheal explants." American Journal of Physiology-Lung Cellular and Molecular Physiology 277, no. 5 (November 1, 1999): L975—L982. http://dx.doi.org/10.1152/ajplung.1999.277.5.l975.
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Respirable ambient particles [particulate matter <10 μm (PM10)] are associated with both acute and chronic adverse health effects including chronic airflow obstruction. PM10 can induce expression of inflammatory and fibrogenic mediators, but there is controversy about the types and/or sizes of particles involved and, in particular, whether ultrafine particles are the major toxic agents. To examine whether particle size affects mediator generation, we exposed rat tracheal explants, an inflammatory cell-free model of the airway wall, to various concentrations up to 500 μg/cm2 of fine (0.12 μm) or ultrafine (0.021 μm) titanium dioxide (anatase), maintained the explants in an organ culture in air for 1–7 days, and used RT-PCR to examine the expression of fibrogenic mediators and procollagen. No increase in gene expression was seen at 1 or 3 days, but at 5 days, ultrafine dust induced a small increase in procollagen. At 7 days, fine titanium dioxide produced significantly greater increases for platelet-derived growth factor (PDGF)-B, transforming growth factor-α, and transforming growth factor-β compared with those by ultrafine dust; both dusts produced similar increases for PDGF-A; and ultrafine dust produced increases in procollagen expression, whereas fine dust had no effect. Expression levels were dose related. Both dusts produced a similar decrease in expression of PDGF receptor-α and a similar increase in PDGF receptor-β. These observations suggest that ultrafine particles are intrinsically able to induce procollagen expression even in the absence of inflammatory cells; that chronic exposure to PM10 may result in chronic airflow obstruction, in part because of ultrafine particle-mediated increases in airway wall fibrosis; and that chemically identical dusts of differing size can produce quite different patterns of gene expression in the airway wall. Differential upregulation of PDGF receptors does not appear to explain dust-induced fibrosis in this model.
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LIU, SAN QIU, and HUI BIN QIU. "Dust acoustic instability with non-extensive distribution." Journal of Plasma Physics 79, no. 1 (August 20, 2012): 105–11. http://dx.doi.org/10.1017/s0022377812000761.
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AbstractThe instability of dust acoustic waves driven by electrons and ions with different drift velocities in dusty non-extensive plasma is investigated based on the kinetic theory. The non-extensivity parameters of non-extensive distribution for three plasma components are different from each other. The instability growth rate is shown to be dependent on the non-extensivity parameters as well as on the ion--electron number density ratio. In the extensive limit (q=1), the result in Maxwellian distribution plasma is recovered. The instability growth rate is found to decrease as the population of suprathermal electrons and dust grains increases, but it enhances when the number of suprathermal ions increases and electron density decreases.
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Heinrich, J. R., S. H. Kim, J. K. Meyer, and R. L. Merlino. "Experimental quiescent drifting dusty plasmas and temporal dust acoustic wave growth." Physics of Plasmas 18, no. 11 (November 2011): 113706. http://dx.doi.org/10.1063/1.3660546.
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Graziani, L., R. Schneider, M. Ginolfi, L. K. Hunt, U. Maio, M. Glatzle, and B. Ciardi. "The assembly of dusty galaxies at z ≥ 4: statistical properties." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 24, 2020): 1071–88. http://dx.doi.org/10.1093/mnras/staa796.
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ABSTRACT The recent discovery of high-redshift dusty galaxies implies a rapid dust enrichment of their interstellar medium (ISM). To interpret these observations, we run a cosmological simulation in a 30 h−1 cMpc/size volume down to z ≈ 4. We use the hydrodynamical code dustygadget, which accounts for the production of dust by stellar populations and its evolution in the ISM. We find that the cosmic dust density parameter (Ωd) is mainly driven by stellar dust at z ≳ 10, so that mass- and metallicity-dependent yields are required to assess the dust content in the first galaxies. At z ≲ 9, the growth of grains in the ISM of evolved systems [log(M⋆/M⊙) > 8.5] significantly increases their dust mass, in agreement with observations in the redshift range 4 ≲ z < 8. Our simulation shows that the variety of high-redshift galaxies observed with the Atacama Large Millimeter Array can naturally be accounted for by modelling the grain growth time-scale as a function of the physical conditions in the gas cold phase. In addition, the trends of dust-to-metal and dust-to-gas (${\cal D}$) ratios are compatible with the available data. A qualitative investigation of the inhomogeneous dust distribution in a representative massive halo at z ≈ 4 shows that dust is found from the central galaxy up to the closest satellites along polluted filaments with $\rm log({\cal D}) \le -2.4$, but sharply declines at distances d ≳ 30 kpc along many lines of sight, where $\rm log({\cal D}) \lesssim -4.0$.
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Stark, C. R., H. E. Potts, and D. A. Diver. "Elliptical dust growth in astrophysical plasmas." Astronomy & Astrophysics 457, no. 2 (September 12, 2006): 365–70. http://dx.doi.org/10.1051/0004-6361:20064922.
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Wada, Koji, Hidekazu Tanaka, Toru Suyama, Hiroshi Kimura, and Tetsuo Yamamoto. "COLLISIONAL GROWTH CONDITIONS FOR DUST AGGREGATES." Astrophysical Journal 702, no. 2 (August 21, 2009): 1490–501. http://dx.doi.org/10.1088/0004-637x/702/2/1490.
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Alinejad, H., and M. Mahdavi. "Existence and stability of modulated dust-acoustic wave packets in the presence of nonthermal ions." Canadian Journal of Physics 93, no. 3 (March 2015): 271–77. http://dx.doi.org/10.1139/cjp-2014-0007.
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The effects of dust temperature and energetic (nonthermal) ions are incorporated in the study of modulated instability of dust-acoustic (DA) waves in a dusty plasma containing warm adiabatic dust grains, isothermal electrons and hot ions obeying a nonthermal distribution. Based on the multiple space and time scales perturbation, a nonlinear Schrödinger equation is derived with a solution showing a new relationship between the modulated DA wave packets and ion nonthermality. It is shown that as the population of fast ions increases, the transition from stable dark envelope solitons to unstable ones shifts to the smaller wavelength regions. The instability growth rate reduces owing to the presence of nonthermal ions. It is also found that the effects of dust temperature and electron concentration modify the criteria for the modulational instability of DA waves. The results could be useful for understanding the properties of modulated wave packets and their evolution in space and laboratory dusty plasmas, such as those in and around the Earth’s foreshock.
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Pierens, Arnaud. "On the non-axisymmetric fragmentation of rings generated by the secular gravitational instability." Monthly Notices of the Royal Astronomical Society 504, no. 3 (January 23, 2021): 4522–32. http://dx.doi.org/10.1093/mnras/stab183.
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ABSTRACT Ringed structures have been observed in a variety of protoplanetary discs. Among the processes that might be able to generate such features, the Secular Gravitational Instability (SGI) is a possible candidate. It has also been proposed that the SGI might lead to the formation of planetesimals during the non-linear phase of the instability. In this context, we employ two-fluid hydrodynamical simulations with self-gravity to study the non-axisymmetric, non-linear evolution of ringed perturbations that grow under the action of the SGI. We find that the non-linear evolution outcome of the SGI depends mainly on the initial linear growth rate. For SGI growth rates smaller than typically σ ${\lesssim}$ 10−4–10−5 Ω, dissipation resulting from dust feedback introduces a m = 1 spiral wave in the gas, even for Toomre gas stability parameters Qg > 2 for which non-axisymmetric instabilities appear in a purely gaseous disc. This one-armed spiral subsequently traps dust particles until a dust-to-gas ratio ϵ ∼ 1 is achieved. For higher linear growth rates, the dust ring is found to undergo gravitational collapse until the bump in the surface density profile becomes strong enough to trigger the formation of dusty vortices through the Rossby Wave Instability (RWI). Enhancements in dust density resulting from this process are found to scale with the linear growth rate, and can be such that the dust density is higher than the Roche density, leading to the formation of bound clumps. Fragmentation of axisymmetric rings produced by the SGI might therefore appear as a possible process for the formation of planetesimals.
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Dell’Agli, Flavia. "Modelling dust production in AGB stars." Proceedings of the International Astronomical Union 12, S323 (October 2016): 165–68. http://dx.doi.org/10.1017/s1743921317000953.
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AbstractAsymptotic giant branch (AGB) stars are among the most important gas and dust polluters of the Universe. The latest AGB evolutionary models take into account dust production in the circumstellar envelope of these stars, starting from a detailed computation of the main physical processes and chemical surface variations occurring in this evolutionary phase. Following the formation and growth of dust particles, they provide the unique possibility of interpreting the AGB population observed in resolved galaxies. The first application was for the Spitzer observations of dusty AGBs in the Magellanic Clouds, characterising carbon-rich and oxygen-rich stars in terms of initial mass, epoch of star formation, evolutionary time on the AGB and dust contribution. The same set of models are able to interpret the CNO surface abundances observed for the PNe of the same galaxies.
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Nathan, Terrence R., Dustin F. P. Grogan, and Shu-Hua Chen. "Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves." Geosciences 9, no. 9 (September 5, 2019): 388. http://dx.doi.org/10.3390/geosciences9090388.
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An analytical analysis is combined with numerical modeling simulations in order to expose the physical and dynamical processes that control the zonal-mean transport of Saharan mineral dust aerosols during the incipient growth phase of African easterly waves. The analytical analysis provides the theoretical basis for understanding and predicting how the waves and background flow combine to affect the zonal-mean eddy transports of dust. The analytically derived transport equations―which are valid for any wave field, irrespective of its spatial or temporal scale―predict that the eddy transports of dust are largest where the maximum in the background dust gradients coincide with a critical surface, i.e., where the Doppler-shifted frequency of the wave field vanishes. Linear simulations of the eddy dust transports are conducted using a mechanistic version of the Weather Research and Forecasting (WRF) model coupled to an interactive dust model. The simulations show that the eddy dust transports are directed down the background dust gradients and that the meridional transports of dust dominate over the vertical transports. The numerical simulations confirm the theoretical predictions. The predictions are used to explain recent statistical analyses of reanalysis data for dust-coupled African easterly waves.
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Tominaga, Ryosuke T., Hiroshi Kobayashi, and Shu-ichiro Inutsuka. "Nonlinear Outcome of Coagulation Instability in Protoplanetary Disks. I. First Numerical Study of Accelerated Dust Growth and Dust Concentration at Outer Radii." Astrophysical Journal 937, no. 1 (September 1, 2022): 21. http://dx.doi.org/10.3847/1538-4357/ac82b4.
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Abstract Our previous linear analysis presents a new instability driven by dust coagulation in protoplanetary disks. The coagulation instability has the potential to concentrate dust grains into rings and assist dust coagulation and planetesimal formation. In this series of papers, we perform numerical simulations and investigate the nonlinear outcome of coagulation instability. In this paper (Paper I), we first conduct local simulations to demonstrate the existence of coagulation instability. Linear growth observed in the simulations is in good agreement with the previous linear analysis. We next conduct radially global simulations to demonstrate that coagulation instability develops during the inside-out disk evolution owing to dust growth. To isolate the various effects on dust concentration and growth, we neglect the effects of back-reaction to a gas disk and dust fragmentation in Paper I. This simplified simulation shows that neither back-reaction nor fragmentation is a prerequisite for local dust concentration via the instability. In most runs with weak turbulence, dust concentration via coagulation instability overcomes dust depletion due to radial drift, leading to the formation of multiple dust rings. The nonlinear development of coagulation instability also accelerates dust growth, and the dimensionless stopping time τ s reaches unity even at outer radii (>10 au). Therefore, coagulation instability is one promising process to retain dust grains and to accelerate dust growth beyond the drift barrier.
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Park, KwangHo, Gen Chiaki, and John H. Wise. "Accelerated Growth of Seed Black Holes by Dust in the Early Universe." Astrophysical Journal 936, no. 2 (September 1, 2022): 116. http://dx.doi.org/10.3847/1538-4357/ac886c.
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Abstract We explore the effect of dust on the growth of seed black holes (BHs) in the early universe. Previous 1D radiation-hydrodynamic (RHD) simulations show that increased radiation pressure on dust further suppresses the accretion rate than the case for the chemically pristine gas. Using the Enzo+Moray code, we perform a suite of 3D RHD simulations of accreting BHs in a dusty interstellar medium (ISM). We use the modified Grackle cooling library to consider dust physics in its nonequilibrium chemistry. The BH goes through an early evolutionary phase, where ionizing BH radiation creates an oscillating H ii region as it cycles between accretion and feedback. As the simulations proceed, dense cold gas accumulates outside the ionized region where inflow from the neutral medium meets the outflow driven by radiation pressure. In the late phase, high-density gas streams develop and break the quasi-spherical symmetry of the ionized region, rapidly boosting the accretion rate. The late phase is characterized by the coexistence of strong ionized outflows and fueling high-density gas inflows. The mean accretion rate increases with metallicity reaching a peak at Z ∼ 0.01–0.1 Z ☉, one order of magnitude higher than the one for pristine gas. However, as the metallicity approaches the solar abundance, the mean accretion rate drops as the radiation pressure becomes strong enough to drive out the high-density gas. Our results indicate that a dusty metal-poor ISM can accelerate the growth rate of BHs in the early universe, but can also stun its growth as the ISM is further enriched toward the solar abundance.
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SHUKLA, NITIN, P. K. SHUKLA, C. S. LIU, and G. E. MORFILL. "Generation of magnetic fields in a positive–negative dusty plasma." Journal of Plasma Physics 73, no. 2 (April 2007): 141–44. http://dx.doi.org/10.1017/s0022377806006210.
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Abstract.It is shown that purely growing magnetic fields in a two-component dusty plasma can e generated due to the equilibrium drift of positive and negative dust grains. For this purpose, a linear dispersion relation has been derived by using the hydrodynamic equations for the charged dust fluids, the Maxwell equation and Faraday' law. The dispersion relation admits a purely growing instability, the growth rate of which is proportional to the equilibrium streaming speeds of positive and negative dust grains. A possible physical explanation for the instability is offered. Applications of our investigation to magnetic fields in the thin Martian environments, interplanetary spaces and dense molecular clouds are mentioned.
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DUHA, S. S., M. S. RAHMAN, A. A. MAMUN, and M. G. M. ANOWAR. "Multidimensional instability of dust ion-acoustic solitary waves in a magnetized dusty electronegative plasma." Journal of Plasma Physics 78, no. 3 (February 10, 2012): 279–88. http://dx.doi.org/10.1017/s0022377812000025.
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AbstractBasic features of obliquely propagating dust ion-acoustic (DIA) solitary waves, and their multidimensional instability in a magnetized dusty electronegative plasma (DENP) containing Boltzmann electrons, Boltzmann negative ions, adiabatic mobile positive ions, and negatively charged stationary dust have been theoretically investigated by reductive perturbation method and small-k perturbation expansion technique. The combined effects of ion adiabaticity, external magnetic field (obliqueness), and negatively charged dust, which are found to significantly modify the basic properties (speed, amplitude, width, and instability) of small but finite-amplitude DIA solitary waves, are explicitly examined. It is also found that the instability criterion and the growth rate of unstable perturbation are significantly modified by the external magnetic field, the propagation directions of both the nonlinear waves, and their perturbation modes. The implications of our results in space and laboratory dusty plasmas are briefly discussed.
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Vijayan, Aswin P., Scott J. Clay, Peter A. Thomas, Robert M. Yates, Stephen M. Wilkins, and Bruno M. Henriques. "Detailed dust modelling in the L-Galaxies semi-analytic model of galaxy formation." Monthly Notices of the Royal Astronomical Society 489, no. 3 (July 15, 2019): 4072–89. http://dx.doi.org/10.1093/mnras/stz1948.
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ABSTRACT We implement a detailed dust model into the L-Galaxies semi-analytical model which includes: injection of dust by type II and type Ia supernovae (SNe) and AGB stars; grain growth in molecular clouds; and destruction due to supernova-induced shocks, star formation, and reheating. Our grain growth model follows the dust content in molecular clouds and the inter-cloud medium separately, and allows growth only on pre-existing dust grains. At early times, this can make a significant difference to the dust growth rate. Above z ∼ 8, type II SNe are the primary source of dust, whereas below z ∼ 8, grain growth in molecular clouds dominates, with the total dust content being dominated by the latter below z ∼ 6. However, the detailed history of galaxy formation is important for determining the dust content of any individual galaxy. We introduce a fit to the dust-to-metal (DTM) ratio as a function of metallicity and age, which can be used to deduce the DTM ratio of galaxies at any redshift. At z ≲ 3, we find a fairly flat mean relation between metallicity and the DTM, and a positive correlation between metallicity and the dust-to-gas (DTG) ratio, in good agreement with the shape and normalization of the observed relations. We also match the normalization of the observed stellar mass–dust mass relation over the redshift range of 0–4, and to the dust mass function at z = 0. Our results are important in interpreting observations on the dust content of galaxies across cosmic time, particularly so at high redshift.
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Couëdel, L., M. Mikikian, A. A. Samarian, and L. Boufendi. "Self-excited void instability during dust particle growth in a dusty plasma." Physics of Plasmas 17, no. 8 (August 2010): 083705. http://dx.doi.org/10.1063/1.3479831.
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Kimura, Yuki, Kyoko K. Tanaka, Yuko Inatomi, Frank T. Ferguson, and Joseph A. Nuth. "Inefficient Growth of SiOx Grains: Implications for Circumstellar Outflows." Astrophysical Journal Letters 934, no. 1 (July 1, 2022): L10. http://dx.doi.org/10.3847/2041-8213/ac8002.
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Abstract To explain observations of abundant circumstellar dust and high stellar wind velocity, most models simply postulate the efficient nucleation and growth of silicate dust particles. Here, we report measurement of the SiO–(SiOx)n grain sticking coefficient in a microgravity sounding rocket experiment, indicating very inefficient (0.005–0.016) grain formation from the vapor. Application of this measurement to radiative-driven winds in oxygen-rich asymptotic giant branch stars indicates that the initial grain condensate population should consist of very tiny dust particles in very large numbers. Aggregation of this dust population will produce low-dimension fractal aggregates that should couple well to the stellar radiation field and efficiently drive stellar mass loss.
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Zhuravlev, V. V. "Dynamic role of dust in formation of molecular clouds." Monthly Notices of the Royal Astronomical Society 500, no. 2 (November 5, 2020): 2209–26. http://dx.doi.org/10.1093/mnras/staa3424.
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ABSTRACT Dust is the usual minor component of the interstellar medium. Its dynamic role in the contraction of the diffuse gas into molecular clouds is commonly assumed to be negligible because of the small mass fraction, f ≃ 0.01. However, as shown in this study, the collective motion of dust grains with respect to the gas may considerably contribute to the destabilization of the medium on scales λ ≲ λJ, where λJ is the Jeans length-scale. The linear perturbations of the uniform self-gravitating gas at rest are marginally stable at λ ≃ λJ, but as soon as the drift of grains is taken into account, they begin growing at a rate approximately equal to $(f \tau)^{1/3} t^{-1}_{\mathrm{ ff}}$, where τ is the stopping time of grains expressed in units of the free-fall time of the cloud, tff. The physical mechanism responsible for such a weak dependence of the growth rate on f is the resonance of heavy sound waves stopped by the self-gravity of gas with weak gravitational attraction caused by perturbations of the dust fraction. Once there is stationary subsonic bulk drift of the dust, the growing gas–dust perturbations at λ < λJ become waves propagating with the drift velocity projected on to the wavevector. Their growth has a resonant nature as well and the growth rate is substantially larger than that of the recently discovered resonant instability of gas–dust mixture in the absence of self-gravity. The new instabilities can facilitate gravitational contraction of cold interstellar gas into clouds and additionally produce dusty domains of sub-Jeans size at different stages of molecular cloud formation and evolution.
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Ostrovskii, Andrei B., S. Yu Parfenov, A. I. Vasyunin, A. V. Ivlev, and V. A. Sokolova. "Optical properties and dust temperatures in clumpy diffuse medium." Monthly Notices of the Royal Astronomical Society 495, no. 4 (May 28, 2020): 4314–25. http://dx.doi.org/10.1093/mnras/staa1460.
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ABSTRACT In this study, we explore the impact of inhomogeneities in the spatial distribution of interstellar dust on spatial scales of ≤1 au caused by ion shadowing forces on the optical properties of diffuse interstellar medium (ISM) as well as on the dust temperature. We show that recently proposed possibility that interstellar dust grains in the diffuse ISM are grouped in spherical cloudlets (clumps) may significantly affect the observed optical properties of the diffuse ISM in comparison to that calculated under the commonly accepted assumption on the uniform dust/gas mixture if the size of clumps ≳0.1 au. We found that opacity of an arbitrary region of diffuse ISM quickly decreases with growth of dusty clumps. We also studied the dependence of opacity and dust temperature inside the dusty clumps on their size. We show that the clumps larger than 0.1 au are opaque for far-ultraviolet radiation. Dust temperature exhibits a gradient inside a clump, decreasing from the edge to the centre by several degrees for a clump of a size of 0.1 au and larger. We argue that dust temperatures and high opacity within clumps larger than 0.1 au may facilitate somewhat more efficient synthesis of molecules on surfaces of interstellar grains in the diffuse ISM than it was anticipated previously. On the other hand, the presence of clumps with sizes below 0.1 au makes small or negligible influence on the optical properties of the diffuse ISM in comparison to the case with uniform dust/gas mixture.
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Zhu(朱照寰), Zhaohuan, and Chao-Chin Yang(楊朝钦). "Streaming instability with multiple dust species – I. Favourable conditions for the linear growth." Monthly Notices of the Royal Astronomical Society 501, no. 1 (November 21, 2020): 467–82. http://dx.doi.org/10.1093/mnras/staa3628.
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ABSTRACT A recent study suggests that the streaming instability, one of the leading mechanisms for driving the formation of planetesimals, may not be as efficient as previously thought. Under some disc conditions, the growth time-scale of the instability can be longer than the disc lifetime when multiple dust species are considered. To further explore this finding, we use both linear analysis and direct numerical simulations with gas fluid and dust particles to mutually validate and study the unstable modes of the instability in more detail. We extend the previously studied parameter space by one order of magnitude in both the range of the dust-size distribution [Ts, min, Ts, max] and the total solid-to-gas mass ratio ε and introduce a third dimension with the slope q of the size distribution. We find that the fast-growth regime and the slow-growth regime are distinctly separated in the ε–Ts, max space, while this boundary is not appreciably sensitive to q or Ts, min. With a wide range of dust sizes present in the disc (e.g. Ts, min ≲ 10−3), the growth rate in the slow-growth regime decreases as more dust species are considered. With a narrow range of dust sizes (e.g. Ts, max/Ts, min = 5), on the other hand, the growth rate in most of the ε–Ts, max space is converged with increasing dust species, but the fast and the slow growth regimes remain clearly separated. Moreover, it is not necessary that the largest dust species dominate the growth of the unstable modes, and the smaller dust species can affect the growth rate in a complicated way. In any case, we find that the fast-growth regime is bounded by ε ≳ 1 or Ts, max ≳ 1, which may represent the favourable conditions for planetesimal formation.
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Mattsson, Lars. "Galactic dust evolution with rapid dust formation in the interstellar medium due to hypersonic turbulence." Monthly Notices of the Royal Astronomical Society 491, no. 3 (December 2, 2019): 4334–44. http://dx.doi.org/10.1093/mnras/stz3359.
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ABSTRACT Turbulence can significantly accelerate the growth of dust grains by accretion of molecules. For dust dynamically coupled to the gas, the growth rate scales with the square of the Mach number, which means that the growth time-scale can easily be reduced by more than an order of magnitude. The limiting time-scale is therefore rather the rate of molecular cloud formation, which means that dust production in the interstellar medium can rapidly reach the levels needed to explain the dust masses observed at high redshifts. Thus, turbulence may be the solution to the replenishment problem in models of dust evolution in high-redshift galaxies and explain the dust masses seen at $z$ = 7–8. A simple analytic galactic dust-evolution model is presented, where grain growth nicely compensates for the expected higher rate of dust destruction by supernova shocks. This model is simpler, relies on fewer assumptions and seems to yields a better fit to data derived from observations, compared to previous models of the same type.
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Takahashi, Y., M. Higashi, T. Furukawa, and S. Mitsunobu. "Change of iron species and iron solubility in Asian dust during the long-range transport from western China to Japan." Atmospheric Chemistry and Physics Discussions 11, no. 7 (July 8, 2011): 19545–80. http://dx.doi.org/10.5194/acpd-11-19545-2011.
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Abstract. In the North Pacific, transport and deposition of mineral dust from Asia appear to be one of major sources of iron which can regulate growth of phytoplankton in the ocean. In this process, it is essential to identify chemical species of iron contained in Asian dust, because bioavailability of iron in the ocean is strongly influenced by the solubility of iron, which in turn is dependent on iron species in the dust. Here, we report that clay minerals (illite and chlorite) in the dusts near the source (western China) are transformed into ferrihydrite by atmospheric chemical processes during their long-range transport to eastern China and Japan based on the speciation by X-ray absorption fine structure (XAFS) and other methods such as X-ray diffraction and chemical extraction. Moreover, it was found that iron in the dust after the transport becomes more soluble in our leaching experiments conducted for 24 h compared with those for initial dusts possibly due to the formation of ferrihydrite in the atmosphere. Our findings suggested that ferrihydrite secondarily formed during the transport is an important source of soluble iron species, which can be more soluble than clay minerals initially contained in the mineral dust such as illite and chlorite.
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Tominaga, Ryosuke T., Hidekazu Tanaka, Hiroshi Kobayashi, and Shu-ichiro Inutsuka. "Nonlinear Outcome of Coagulation Instability in Protoplanetary Disks. II. Dust-ring Formation Mediated by Backreaction and Fragmentation." Astrophysical Journal 940, no. 2 (November 30, 2022): 152. http://dx.doi.org/10.3847/1538-4357/ac97e8.
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Abstract In our previous work (Paper I), we demonstrated that coagulation instability results in dust concentration against depletion due to the radial drift and accelerates dust growth locally. In this work (Paper II), we perform numerical simulations of coagulation instability taking into account effects of backreaction to gas and collisional fragmentation of dust grains. We find that the slowdown of the dust drift due to backreaction regulates dust concentration in the nonlinear growth phase of coagulation instability. The dust-to-gas surface density ratio increases from 10−3 up to ∼10−2. Each resulting dust ring tends to have a mass of ≃0.5 M ⊕ − 1.5 M ⊕ in our disk model. In contrast to Paper I, the dust surface density profile shows a local plateau structure at each dust ring. In spite of the regulation at the nonlinear growth, the efficient dust concentration reduces their collision velocity. As a result, dust grains can grow beyond the fragmentation barrier, and the dimensionless stopping time reaches unity, as in Paper I. The necessary condition for the efficient dust growth is (1) weak turbulence of α < 1 × 10−3 and (2) a large critical velocity for dust fragmentation (>1 m s−1). The efficient dust concentration in outer regions will reduce the inward pebble flux and is expected to decelerate the planet formation via the pebble accretion. We also find that the resulting rings can be unstable to secular gravitational instability (GI). The subsequent secular GI promotes planetesimal formation. We thus expect that a combination of these instabilities is a promising mechanism for dust-ring and planetesimal formation.
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Tominaga, Ryosuke T., Shu-ichiro Inutsuka, and Hiroshi Kobayashi. "Coagulation Instability in Protoplanetary Disks: A Novel Mechanism Connecting Collisional Growth and Hydrodynamical Clumping of Dust Particles." Astrophysical Journal 923, no. 1 (December 1, 2021): 34. http://dx.doi.org/10.3847/1538-4357/ac173a.
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Abstract We present a new instability driven by a combination of coagulation and radial drift of dust particles. We refer to this instability as “coagulation instability” and regard it as a promising mechanism to concentrate dust particles and assist planetesimal formation in the very early stages of disk evolution. Because of dust-density dependence of collisional coagulation efficiency, dust particles efficiently (inefficiently) grow in a region of positive (negative) dust density perturbations, leading to a small radial variation of dust sizes and as a result radial velocity perturbations. The resultant velocity perturbations lead to dust concentration and amplify dust density perturbations. This positive feedback makes a disk unstable. The growth timescale of coagulation instability is a few tens of orbital periods even when dust-to-gas mass ratio is on the order of 10−3. In a protoplanetary disk, radial drift and coagulation of dust particles tend to result in dust depletion. The present instability locally concentrates dust particles even in such a dust-depleted region. The resulting concentration provides preferable sites for dust–gas instabilities to develop, which leads to further concentration. Dust diffusion and aerodynamical feedback tend to stabilize short-wavelength modes, but do not completely suppress the growth of coagulation instability. Therefore, coagulation instability is expected to play an important role in setting up the next stage for other instabilities, such as streaming instability or secular gravitational instability, to further develop toward planetesimal formation.
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Arakawa, Sota, Hidekazu Tanaka, and Eiichiro Kokubo. "Impacts of Viscous Dissipation on Collisional Growth and Fragmentation of Dust Aggregates." Astrophysical Journal 933, no. 2 (July 1, 2022): 144. http://dx.doi.org/10.3847/1538-4357/ac7460.
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Abstract Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is known that the collisional behavior of individual dust particles strongly depends on the strength of viscous dissipation force; however, impacts of viscous dissipation on the collisional behavior of dust aggregates have not been studied in detail, especially for the cases of oblique collisions. Here we investigated the impacts of viscous dissipation on the collisional behavior of dust aggregates. We performed numerical simulations of collisions between two equal-mass dust aggregates with various collision velocities and impact parameters. We also changed the strength of viscous dissipation force systematically. We found that the threshold collision velocity for the fragmentation of dust aggregates barely depends on the strength of viscous dissipation force when we consider oblique collisions. In contrast, the size distribution of fragments changes significantly when the viscous dissipation force is considered. We obtained the empirical fitting formulae for the size distribution of fragments for the case of strong dissipation, which would be useful to study the evolution of size and spatial distributions of dust aggregates in protoplanetary disks.
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Stark, C. R., and D. A. Diver. "Evolution of spheroidal dust in electrically active sub-stellar atmospheres." Astronomy & Astrophysics 644 (December 2020): A131. http://dx.doi.org/10.1051/0004-6361/202037589.
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Context. Understanding the source of sub-stellar polarimetric observations in the optical and near-infrared is key to characterizing sub-stellar objects and developing potential diagnostics for determining properties of their atmospheres. Differential scattering from a population of aligned, non-spherical dust grains is a potential source of polarization that could be used to determine geometric properties of the dust clouds. Aims. This paper addresses the problem of the spheroidal growth of dust grains in electrically activated sub-stellar atmospheres. It presents the novel application of a mechanism whereby non-spherical, elongated dust grains can be grown via plasma deposition as a consequence of the surface electric field effects of charged dust grains. Methods. We numerically solve the differential equations governing the spheroidal growth of charged dust grains via plasma deposition as a result of surface electric field effects in order to determine how the dust eccentricity and the dust particle eccentricity distribution function evolve with time. From these results, we determine the effect of spheroidal dust on the observed linear polarization. Results. Numerical solutions show that e ≈ 0.94 defines a watershed eccentricity, where the eccentricity of grains with an initial eccentricity less than (greater than) this value decreases (increases) and spherical (spheroidal) growth occurs. This produces a characteristic bimodal eccentricity distribution function yielding a fractional change in the observed linear polarization of up to ≈0.1 corresponding to dust grains of maximal eccentricity at wavelengths of ≈1 μm, consistent with the near infrared observational window. Order of magnitude calculations indicate that a population of aligned, spheroidal dust grains can produce degrees of polarization P ≈ 𝒪(10−2 − 1%) consistent with observed polarization signatures. Conclusions. The results presented here are relevant to the growth of non-spherical, irregularly shaped dust grains of general geometry where non-uniform surface electric field effects of charged dust grains are significant. The model described in this paper may also be applicable to polarization from galactic dust and dust growth in magnetically confined plasmas.
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Ricci, L., L. Testi, A. Natta, and K. J. Brooks. "Dust grain growth inρ-Ophiuchi protoplanetary disks." Astronomy and Astrophysics 521 (October 2010): A66. http://dx.doi.org/10.1051/0004-6361/201015039.
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Matthews, Lorin S., and Truell W. Hyde. "Charging and Growth of Fractal Dust Grains." IEEE Transactions on Plasma Science 36, no. 1 (2008): 310–14. http://dx.doi.org/10.1109/tps.2007.913923.
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Korpi, A., A. L. Pasanen, P. Pasanen, and P. Kalliokoski. "Microbial growth and metabolism in house dust." International Biodeterioration & Biodegradation 40, no. 1 (January 1997): 19–27. http://dx.doi.org/10.1016/s0964-8305(97)00032-2.
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