Weak discontinuities in one-dimensional compressible nonideal gas dynamics

This article concerns the study of various parameter effects on the propagation of weak discontinuities by using the method of characteristics. Analytical solutions of the quasi-linear system of hyperbolic partial differential equations (PDEs) are obtained and examined the evolutionary behavior of shock in the characteristic plane. The general behavior of solutions to the Bernoulli equation, which determines the evolution of weak discontinuity in a nonlinear system, is studied in detail. Also, we discuss the formation and distortion of compressive and expansive discontinuities under the van der Waals parameter effect and small particles for planar and cylindrical symmetric flow. The comparison between planar flow and cylindrical symmetric flow is studied under the influence of nonidealness and mass fraction of dust particles. It is found that the compressive waves become shock after a certain lapse of time. The medium considered here is the mixture of van der Waals gas with small dust particles.

Properties of Bonding Sealants in the Sealing of Cement-Based Materials

This paper describes the issue of sealing cement-based materials. These materials can also include concrete elements or cement fiber boards. For the purposes of this work, a cement fiber material is selected, namely glass. This material has good effects in terms of small dust particles on the surface, which damage the bonding sealant and the substrate. Focus on its suitability for sealing cement-based substrates. The method for determining the properties of the sealant and the properties of the stylistic joint between the sealant and the base material is the tensile test. For the purpose of this test, one representative of neutral silicones, one representative of acetate silicones and one representative for acrylic sealants shall be selected. From the results of the tensile test, it is clear that with a suitable choice of the combination of bonding sealant and primer, it is possible to seal such a problematic substrate with good results.

Opportunities for interstellar dust detection by the Interstellar Probe

<p>Interstellar Probe is an ambitious mission concept, to reach interstellar space (up to 1000 AU). Its launch date is between 2030 and 2042 and its goals cover different fields of science from planetary science, heliophysics (heliosphere), to astronomy. One main goal is to significantly expand our knowledge about our heliosphere, the interstellar medium, and how both interact with each other. Among many other instruments, the space probe is planned to carry a dust mass spectrometer that will be able to capture dust particles and measure their composition. This will be especially useful for measuring the interstellar dust of the local interstellar medium that continuously streams through the solar system and has been directly detected for the first time with the Ulysses spacecraft in the 1990s. The mass distributions from such in situ dust detections in the solar system so far have shown a significant discrepancy compared to the results from astronomical observations. We performed a series of simulations of the interstellar dust trajectories and distribution inside the solar system and use them to predict the ability of the Interstellar Probe to measure interstellar dust particles and how this ability is affected by different spacecraft trajectories and dust detector setups. We also discuss how the filtering of small dust particles at the boundary regions of the heliosphere affects our predictions and indicate how in situ dust measurements can be used to constrain the filtering process. In general, most of the dust particles can be measured if the spacecraft moves towards the nose of the heliosphere. However, we also find a significant correlation between the presence of small dust particles (<0.3 microns) in the inner solar system and the phase of the solar cycle which is caused by the filtering effect of the solar magnetic field via the Lorentz force. Inside the heliosphere, the interstellar Probe may be able to detect and analyze up to 1 interstellar dust particle per day for particle sizes >0.1 micron and many more of the smaller particles, depending on the state of the solar magnetic field and the dust filtering at the boundary of the heliosphere. Outside the heliosphere, the absence of dust filtering should increase the detection rate of small particles (<0.1 microns) to more than 10 per day.</p>

Observational signatures of eccentric Jupiters inside gas cavities in protoplanetary discs

Predicting how a young planet shapes the gas and dust emission of its parent disc is key to constraining the presence of unseen planets in protoplanetary disc observations. We investigate the case of a 2 Jupiter mass planet that becomes eccentric after migrating into a low-density gas cavity in its parent disc. Two-dimensional hydrodynamical simulations are performed and post-processed by three-dimensional radiative transfer calculations. In our disc model, the planet eccentricity reaches ∼0.25, which induces strong asymmetries in the gas density inside the cavity. These asymmetries are enhanced by photodissociation and form large-scale asymmetries in 12CO J=3→2 integrated intensity maps. They are shown to be detectable for an angular resolution and a noise level similar to those achieved in ALMA observations. Furthermore, the planet eccentricity renders the gas inside the cavity eccentric, which manifests as a narrowing, stretching and twisting of iso-velocity contours in velocity maps of 12CO J=3→2. The planet eccentricity does not, however, give rise to detectable signatures in 13CO and C18O J=3→2 inside the cavity because of low column densities. Outside the cavity, the gas maintains near-circular orbits, and the vertically extended optically thick CO emission displays a four-lobed pattern in integrated intensity maps for disc inclinations $\gtrsim$ 30○. The lack of large and small dust inside the cavity in our model further implies that synthetic images of the continuum emission in the sub-millimetre, and of polarized scattered light in the near-infrared, do not show significant differences when the planet is eccentric or still circular inside the cavity.

An HST/STIS View of Protoplanetary Disks in Upper Scorpius: Observations of Three Young M-Stars

We present observations of three protoplanetary disks in visible scattered light around M-type stars in the Upper Scorpius OB association using the STIS instrument on the Hubble Space Telescope. The disks around stars 2MASS J16090075–1908526, 2MASS J16142029–1906481 and 2MASS J16123916–1859284 have all been previously detected with ALMA, and 2MASS J16123916–1859284 has never previously been imaged at scattered light wavelengths. We process our images using Reference Differential Imaging, comparing and contrasting three reduction techniques – classical subtraction, Karhunen-Loéve Image Projection and Non-Negative Matrix Factorisation, selecting the classical method as the most reliable of the three for our observations. Of the three disks, two are tentatively detected (2MASS J16142029–1906481 and 2MASS J16123916–1859284), with the third going undetected. Our two detections are shown to be consistent when varying the reference star or reduction method used, and both detections exhibit structure out to projected distances of ≳ 200 au. Structures at these distances from the host star have never been previously detected at any wavelength for either disk, illustrating the utility of visible-wavelength observations in probing the distribution of small dust grains at large angular separations.

Multipotent Stromal Cell Extracellular Vesicle Distribution in Distant Organs after Introduction into a Bone Tissue Defect of a Limb

When administered intravenously, extracellular vesicles derived from multipotent stromal cells (MSC EVs) immediately pass through the lungs along with the blood and regularly spread to all organs. When administered intraperitoneally, they are absorbed either into the blood or into the lymph and are quickly disseminated throughout the body. The possibility of generalized spread of MSC EVs to distant organs in case of local intratissular administration remains unexplored. However, it is impossible to exclude MSC EV influence on tissues distant from the injection site due to the active or passive migration of these injected nanoparticles through the vessels. The research is based on findings obtained when studying the samples of lungs, heart, spleen, and liver of outbred rabbits of both sexes weighing 3–4 kg at various times after the injection of EVs derived from MSCs of bone marrow origin and labeled by PKH26 into an artificially created defect of the proximal condyle of the tibia. MSC EVs were isolated by serial ultracentrifugation and characterized by transmission electron microscopy and flow cytometry. After the introduction of MSC EVs into the damaged proximal condyle of the tibia of rabbits, these MSC EVs can be found most frequently in the lungs, myocardium, liver, and spleen. MSC EVs enter all of these organs with the blood flow. The lungs contained the maximum number of labeled MSC EVs; moreover, they were often associated with detritus and were located in the lumen of the alveoli. In the capillary network of various organs except the myocardium, MSC EVs are adsorbed by paravasal phagocytes; in some cases, specifically labeled small dust-like objects can be detected throughout the entire experiment—up to ten days of observation. Therefore, we can conclude that the entire body, including distant organs, is effected both by antigenic detritus, which appeared in the bloodstream after extensive surgery, and MSC EVs introduced from the outside.

Organic matter and water from asteroid Itokawa

Understanding the true nature of extra-terrestrial water and organic matter that were present at the birth of our solar system, and their subsequent evolution, necessitates the study of pristine astromaterials. In this study, we have studied both the water and organic contents from a dust particle recovered from the surface of near-Earth asteroid 25143 Itokawa by the Hayabusa mission, which was the first mission that brought pristine asteroidal materials to Earth’s astromaterial collection. The organic matter is presented as both nanocrystalline graphite and disordered polyaromatic carbon with high D/H and 15N/14N ratios (δD = + 4868 ± 2288‰; δ15N = + 344 ± 20‰) signifying an explicit extra-terrestrial origin. The contrasting organic feature (graphitic and disordered) substantiates the rubble-pile asteroid model of Itokawa, and offers support for material mixing in the asteroid belt that occurred in scales from small dust infall to catastrophic impacts of large asteroidal parent bodies. Our analysis of Itokawa water indicates that the asteroid has incorporated D-poor water ice at the abundance on par with inner solar system bodies. The asteroid was metamorphosed and dehydrated on the formerly large asteroid, and was subsequently evolved via late-stage hydration, modified by D-enriched exogenous organics and water derived from a carbonaceous parent body.

ALMA detection of the dusty object silhouetted against the S0 galaxy NGC 3269 in the Antlia cluster

Context. An intriguing silhouette of a small dust patch can be seen against the disk of the S0 galaxy NGC 3269 in the Antlia cluster in optical images. The images do not provide any clue as to whether the patch is a local Jupiter mass-scale cloudlet or a large extragalactic dust complex. Aims. We aim to resolve the nature of this object: is it a small Galactic cloudlet or an extragalactic dust complex? Methods. ALMA and APEX spectroscopy and Gemini GMOS long-slit spectroscopy were used to measure the velocity of the patch and the NGC 3269 disk radial velocity curve. Results. A weak 16 ± 2.5 km s−1 wide 12CO(2 − 1) TMB 19 ± 2.5. mK line in a 2.″2 by 2.″12 beam associated with the object was detected with ALMA. The observed heliocentric velocity, Vr, hel = 3878 ± 5.0 km s−1, immediately establishes the extragalactic nature of the object. The patch velocity is consistent with the velocity of the nucleus of NGC 3269, but not with the radial velocity of the NGC 3269 disk of the galaxy at its position. The ∼4″ angular size of the patch corresponds to a linear size of ∼1 kpc at the galaxy’s Hubble distance of 50.7 Mpc. The mass estimated from the 12CO(2 − 1) emission is ∼1.4 × 106(d/50.7 Mpc)2 M⊙, while the attenuation derived from the optical spectrum implies a dust mass of ∼2.6 × 104(d/50.7 Mpc)2 M⊙. The derived attenuation ratio A′B/(A′B − A′R) of 1.6 ± 0.11 is substantially lower than the corresponding value for the mean Milky Way extinction curve for point sources (2.3). Conclusions. We established the extragalactic nature of the patch, but its origin remains elusive. One possibility is that the dust patch is left over from the removal of interstellar matter in NGC 3269 through the interaction with its neighbour, NGC 3268.