Interstellar Clouds Research Articles

Proton and Electron Irradiations of CH4:H2O Mixed Ices

The organic chemistry occurring in interstellar environments may lead to the production of complex molecules that are relevant to the emergence of life. Therefore, in order to understand the origins of life itself, it is necessary to probe the chemistry of carbon-bearing molecules under conditions that simulate interstellar space. Several of these regions, such as dense molecular cores, are exposed to ionizing radiation in the form of galactic cosmic rays, which may act as an important driver of molecular destruction and synthesis. In this paper, we report the results of a comparative and systematic study of the irradiation of CH4:H2O ice mixtures by 1 MeV protons and 2 keV electrons at 20 K. We demonstrate that our irradiations result in the formation of a number of new products, including both simple and complex daughter molecules such as C2H6, C3H8, C2H2, CH3OH, CO, CO2, and probably also H2CO. A comparison of the different irradiation regimes has also revealed that proton irradiation resulted in a greater abundance of radiolytic daughter molecules compared to electron irradiation, despite a lower radiation dose having been administered. These results are important in the context of the radiation astrochemistry occurring within the molecular cores of dense interstellar clouds, as well as on outer Solar System objects.

Tracing of magnetic fields with gradients: subsonic turbulence

ABSTRACT The recent development of the velocity gradient technique shows the capability of the technique for tracing magnetic field morphology in diffuse interstellar gas and molecular clouds. In this paper, we perform a systematic numerical study of the performance of the velocity and synchrotron gradient for a wide range of magnetization in the subsonic environment. Addressing the studies of magnetic fields in atomic hydrogen, we also study the formation of velocity caustics in spectroscopic channel maps in the presence of thermal broadening. We show that the velocity caustics can be recovered when applied to the cold neutral medium and the gradient technique (GT) can reliably trace magnetic fields there. Finally, we discuss the changes in the anisotropy of observed structure functions when we apply to the analysis the procedures developed within the framework of GT studies.

Exposure to World Trade Center Dust Exacerbates Cognitive Impairment and Evokes a Central and Peripheral Pro-Inflammatory Transcriptional Profile in an Animal Model of Alzheimer's Disease.

The terrorist attacks on September 11, 2001, on the World Trade Center (WTC) led to intense fires and a massive dense cloud of toxic gases and suspended pulverized debris. In the subsequent years, following the attack and cleanup efforts, a cluster of chronic health conditions emerged among First Responders (FR) who were at Ground Zero for prolonged periods and were repeatedly exposed to high levels of WTC particulate matter (WTCPM). Among those are neurological complications which may increase the risk for the development of Alzheimer's disease (AD) later in life. We hypothesize that WTCPM dust exposure affects the immune cross-talking between the periphery and central nervous systems that may induce brain permeability ultimately promoting AD-type phenotype. 5XFAD and wild-type mice were intranasally administered with WTCPM dust collected at Ground Zero within 72 h after the attacks. Y-maze assay and novel object recognition behavioral tests were performed for working memory deficits and learning and recognition memory, respectively. Transcriptomic analysis in the blood and hippocampus was performed and confirmed by RT qPCR. Mice exposed to WTCPM dust exhibited a significant impairment in spatial and recognition short and long-term memory. Furthermore, the transcriptomic analysis in the hippocampal formation and blood revealed significant changes in genes related to immune-inflammatory responses, and blood-brain barrier disruption. These studies suggest a putative peripheral-brain immune inflammatory cross-talking that may potentiate cognitive decline, identifying for the first time key steps which may be therapeutically targetable in future studies in WTC FR.

Oscillations in gas-grain astrochemical kinetics

ABSTRACT We have studied gas-grain chemical models of interstellar clouds to search for non-linear dynamical evolution. A prescription is given for producing oscillatory solutions when a bistable solution exists in the gas-phase chemistry and we demonstrate the existence of limit cycle and relaxation oscillation solutions. As the autocatalytic chemical processes underlying these solutions are common to all models of interstellar chemistry, the occurrence of these solutions should be widespread. We briefly discuss the implications for interpreting molecular cloud composition with time-dependent models and some future directions for this approach.

Faraday rotation measure variations of repeating fast radio burst sources

ABSTRACT Recently, some fast radio burst (FRB) repeaters were reported to exhibit complex, diverse variations of Faraday rotation measures (RMs), which implies that they are surrounded by an inhomogeneous, dynamically evolving, magnetized environment. We systematically investigate some possible astrophysical processes that may cause RM variations of an FRB repeater. The processes include (1) a supernova remnant (SNR) with a fluctuating medium; (2) a binary system with stellar winds from a massive/giant star companion or stellar flares from a low-mass star companion; (3) a pair plasma medium from a neutron star (including pulsar winds, pulsar wind nebulae, and magnetar flares); (4) outflows from a massive black hole. For the SNR scenario, a large relative RM variation within a few years requires that the SNR is young with a thin and local anisotropic shell, or the size of dense gas clouds in interstellar/circumstellar medium around the SNR is extremely small. If the RM variation is caused by the companion medium in a binary system, it is more likely from the stellar winds of a massive/giant star companion. The RM variation contributed by stellar flares from a low-mass star is disfavored, because this scenario predicts an extremely large relative RM variation during a short period of time. The scenarios invoking a pair plasma from a neutron star can be ruled out due to their extremely low RM contributions. Outflows from a massive black hole could provide a large RM variation if the FRB source is in the vicinity of the black hole.

Chemical Gas Telemetry System Based on Multispectral Infrared Imaging.

Environmental monitoring, public safety, safe production, and other areas all benefit greatly from the use of gas detection technologies. The infrared image of a gas could be used to determine its type from a long distance in gas detection. The infrared image can show the spatial distribution of the gas cloud and the background, allowing for long-distance and non-contact detection during safety production and hazardous chemical accident rescue. In this study, a gas detection system based on multispectral infrared imaging is devised, which can detect a variety of gases and determine the types of gas by separating the infrared radiation. It is made up of an imaging optical system, an uncooled focal plane detector, a filter controller, and a data gathering and processing system. The resolution of the infrared image is 640 × 512 and the working band of the system is 6.5~15 μm. The system can detect traces of pollutants in ambient air or gas clouds at higher concentrations. Ammonia, sulfur hexafluoride, methane, sulfur dioxide, and dimethyl methyl phosphonate were all successfully detected in real time. Ammonia clouds could be detected at a distance of 1124.5 m.

Molecular gas cloud properties atz≃ 1 revealed by the superb angular resolution achieved with ALMA and gravitational lensing

ABSTRACTCurrent observations favour that the massive ultraviolet-bright clumps with a median stellar mass of $\sim 10^7\, {\rm M}_{\odot }$, ubiquitously observed in z ∼ 1–3 galaxies, are star-forming regions formed in situ in galaxies. It has been proposed that they result from gas fragmentation due to gravitational instability of gas-rich, turbulent, and high-redshift discs. We bring support to this scenario by reporting the new discovery of giant molecular clouds (GMCs) in the strongly lensed, clumpy, main-sequence galaxy, A521-sys1, at z = 1.043. Its CO(4–3) emission was mapped with the Atacama Large Millimetre/submillimetre Array (ALMA) at an angular resolution of 0.19 × 0.16 arcsec2, reading down to 30 pc, thanks to gravitational lensing. We identified 14 GMCs, most being virialized, with $10^{5.9}-10^{7.9}\, {\rm M}_{\odot }$ masses and a median $800\, {\rm M}_{\odot }~\mathrm{pc}^{-2}$ molecular gas mass surface density, that are, respectively, 100 and 10 times higher than for nearby GMCs. They are also characterized by 10 times higher supersonic turbulence with a median Mach number of 60. They end up to fall above the Larson scaling relations, similarly to the GMCs in another clumpy z ≃ 1 galaxy, the Cosmic Snake, although differences between the two sets of high-redshift GMCs exist. Altogether they support that GMCs form with properties that adjust to the ambient interstellar medium conditions prevalent in the host galaxy whatever its redshift. The detected A521-sys1 GMCs are massive enough to be the parent gas clouds of stellar clumps, with a relatively high star formation efficiency per free-fall time of ∼11 per cent.

Prediction model for the evolution of hydrogen concentration under leakage in hydrogen refueling station using deep neural networks

The widespread risks of leakages in the hydrogen industry chain require a method that can quickly predict the consequences of accidents, especially in the hydrogen refueling station (HRS). This paper presents a surrogate model based on physics-informed neural network (PINN) that can predict the distribution of hydrogen concentration after a leakage. The proposed Physics-informed Convolutional Long Short-Term Memory Network (PI-ConvLSTM) model improves the concentration prediction results at the gas cloud boundary by adding a physical constraint term to the loss function of the ConvLSTM model. The concentration distributions after hydrogen leakage at HRS simulated by FLACS are used as the training samples, and the concentration data are converted into grayscale maps for training. The hydrogen concentration prediction method with the proposed surrogate model as the core achieves fast prediction of the gas cloud concentration distribution with acceptable accuracy. It is observed that the method can greatly reduce the prediction time of the consequences of hydrogen leak accidents with the surrogate model already trained. It can provide real-time risk warning and consequence prediction for hydrogen refueling station leakage accidents.

On the Galactic Halos Rotation by Planck Data

As galactic halos are not directly visible, there are many ambiguities regarding their composition and rotational velocity. Though most of the dark matter is non-baryonic, some fraction is, and it can be used to trace the halo rotation. Asymmetries in the CMB towards M31 had been seen in the Planck data and ascribed to the rotational Doppler shift of the M31 halo. Subsequently, the same methods were used in the direction of five other galaxies belonging to the Local Group, namely M33, M81, M82, NGC 5128, and NGC 4594. It had been proved that there could be stable clouds of gas and dust in thermal equilibrium with the CMB at 2.7 K, which had been called “virial clouds”. In this paper, adopting this scenerio, an attempt is made to constrain the fraction of dust grains and gas molecules in the clouds.

Determination of the lifting height of dust particles after a mass explosion in an iron ore open pit

Open pit mining is accompanied by emissions of fine dust and hazardous gases into the atmosphere. This is related to the operation of open pit transport, drilling and blasting operations. The release of harmful components into the quarry space and the increase in their concentrations has a negative impact on the health of working personnel and leads to pollution of the environment. In doing so, the nature of fine dust and gases pollution depends on the mining technology and meteorological factors. The problem of reduced effectiveness of dust suppression methods after mass explosions in open pits is relate to insufficient research into the formation of dust and gas cloud. Additional theoretical and experimental research into the dust dynamics of blasting operations is therefore need. The article discusses the stages of formation of the dust and gas cloud after a mass explosion in an iron ore open pit. The results of experimental studies of the evolution of the dust and gas cloud at different points in time after the detonation of borehole charges are presented. Relations for determination of density and dynamic viscosity of gases, gas mixture and gas-dust aerosol are given. A formula for determining the time and height of ascent of spherical dust particles at the dynamic stage of dust and gas cloud formation is obtain. In this case, the assumption is madid that there is no mutual influence of the dynamic and thermal factors after detonation of the charges. The elevation of dust particles due to temperature differences during the heat stage of dust and gas cloud formation is determined. Based on the analysis of the calculation results, the duration of the dynamic stage of cloud formation is determined. It is established that, following the release of solid and gaseous detonation products into the atmosphere, a height distribution of dust particles is observed as a function of their diameter. That said during, the dynamic stage of dust and gas cloud formation, the height of dust particle lift is directly proportional to their diameter, while during the heat stage the inverse relationship is observe. That at the beginning of the thermal stage the deposition of coarse dust particles takes place are established. In this process, fine dust particles rise to a maximum height and are then carried outside the open pit by the airflow.

КОМПЛЕКСНАЯ ОЦЕНКА ЗАПЫЛЕННОСТИ ПРИЗЕМНОГО СЛОЯ АТМОСФЕРЫ В ГРАНИЦАХ ГОРНОГО ОТВОДА УГОЛЬНОГО РАЗРЕЗА

The article describes the results of gravimetric and electrical methods for analyzing the dust content of the atmosphere of a coal mine before and after a mass explosion. The relevance of this study is due to the need to uncover the mechanisms of influence of the meteorological parameters of the region, as well as the microclimate of the coal mine on the formation and further spread of the dust and gas cloud within the boundaries of the section and beyond. The influence of climatic conditions and microclimate of the section on the trajectory of the dust and gas cloud propagation within the quarry was determined by determining the mass gain of samplers located in a certain sector, as well as by conducting a priori and a posteriori estimates of the dust content of the surface layer of the atmosphere. The results of the study can be used to establish new empirical patterns describing the influence of meteorological parameters on the trajectory of a dust and gas cloud in the atmosphere, as well as to develop new empirical patterns describing the influence of meteorological parameters on the trajectory of dust and gas cloud propagation in the atmosphere, as well as for the development of new methods of cloud monitoring and control.

Разработка параметрической модели определения газового состава воздушной среды (аммиак, сероводород, углекислый газ) животноводческого помещения

Indoor climate parameters influence the productivity of animals and their physiological condition. Exceeding permissible concentrations of gases leads to animal diseases, loss of productivity, and the mortality of young cattle. Therefore, it is reasonable to predict the concentration of gas composition in the livestock houses. To determine and distribute harmful gases (ammonia, hydrogen sulphide, and carbon dioxide) in the livestock house, the authors performed the 3D modeling of a fragment of the farm in the SolidWorks 2020 software package. Parametric models of gas movement under different conditions were created and optimal measurement points of gas concentration in the livestock house were determined. The simulations made it possible to determine the direction of air flows and detect accumulations and clouds of gases. The maximum concentration of carbon dioxide was detected at 0.9m (an air speed of 0 m/sec) and at 1.3m (a speed of 0.75 m/sec). The highest concentration of hydrogen sulphide was found in the area bordering the ridge space (an air speed of 0 m/s) and at the level of 2.25 m (a speed of 2 m/s). The highest concentration of ammonia was observed under the roof and in the area under the ridge (an air speed of 2 m/s). It is recommended to install hydrogen sulphide and ammonia sensors under the ridge, while carbon dioxide, hydrogen sulphide and ammonia sensors – in the stall, carbon dioxide and hydrogen sulphide sensors – near the feed table. Concentrations should be measured at heights of 500, 1500, and 3000 mm. When the concentration of emitted gas increases and other conditions are equal, the concentration of gas in the cloud increases, but the structure of the cloud changes insignificantly. Parameter interrogation sensors should be installed in enclosed ventilated boxes in the same manner as in weather stations.

Laboratory Simulation of the Positron–Dust Interaction and its Implication for Interstellar Dark Clouds

We report the first laboratory experiment dealing with the interaction of a cosmic dust simulant with positrons emitted from a 22Na radioisotope. Measurements of a charge of micrometer SiO2 dust grains with an accuracy of one elementary charge e revealed +1 e steps due to positron annihilation inside the grain. The observed average rate of these charging events agrees well with prediction of a model based on the continuous slowing down approximation of energetic of positrons inside the grain. Less frequent charge steps larger than +1 e were attributed to emission of secondary electrons during positron slowing down. The determined coefficient of secondary electron emission is approximately inversely proportional to the grain radius. The experimental results led us to the formulation of a possible scenario of interstellar dark clouds charging.

Theoretical study on macroscopic thermodynamic properties of NO<sup>+</sup> ion system

<sec>NO<sup>+</sup> is one of the most important ions in the atmospheric ionosphere and ionospheric phenomena such as auroras, and is one of the most stable diatomic cations existing in interstellar clouds. It is crucial to understand the thermodynamic properties of NO<sup>+</sup> ion for exploring the composition of interstellar gas. To obtain macroscopic thermodynamic properties of diatomic molecules and ions, a practical theoretical method is to determine the partition function associated with a potential model. This approach can be used to calculate various thermodynamic properties of the system based on the microscopic information.</sec><sec>In this work, the improved Hulbert-Hirschfelder (IHH) based potential energy model is used to simulate the potential energy curve of NO<sup>+</sup> in the ground electronic state. Then, the rovibrational energy levels for the ground electronic state of the NO<sup>+</sup> are obtained by numerically solving the radial Schrödinger equation through using the LEVEL program for the IHH potential function. Finally, the total partition function and the thermodynamic properties such as the molar heat capacity, entropy, enthalpy and reduced molar Gibbs free energy of NO<sup>+</sup> in a temperature range of 100–6000 K are calculated in the frame of the quantum statistical ensemble theory. The comparison indicates that the potential energy curve calculated based on IHH potential energy function is in better agreement with the experimental data. The root mean square error of IHH potential and experimental Rydberg-Klein-Rees (RKR) potential is 96.9 cm<sup>–1</sup>, the root mean square error of Hulbert-Hirschfelder (HH) potential is 112.7 cm<sup>–1</sup>, and the root mean square error of MRCI/aug-cc-pV6Z potential is 133 cm<sup>–1</sup>. And the macroscopic thermodynamic properties of NO<sup>+</sup> predicted by IHH are closer to the experimental values, which shows that the IHH potential model is also applicable to the ion system.</sec><sec>A feasible method is presented to obtain the thermodynamic properties of gaseous diatomic ions based on microscopic information by constructing reliable analytical potential energy function associated with quantum statistical ensemble theory.</sec>

The vibronic state dependent predissociation of H2S: determination of all fragmentation processes.

Photochemistry plays a significant role in shaping the chemical reaction network in the solar nebula and interstellar clouds. However, even in a simple triatomic molecule photodissociation, determination of all fragmentation processes is yet to be achieved. In this work, we present a comprehensive study of the photochemistry of H2S, derived from cutting-edge translational spectroscopy measurements of the H, S(1D) and S(1S) atom products formed by photolysis at wavelengths across the range 155-120 nm. The results provide detailed insights into the energy disposal in the SH(X), SH(A) and H2 co-fragments, and the atomisation routes leading to two H atoms along with S(3P) and S(1D) atoms. Theoretical calculations allow the dynamics of all fragmentation processes, especially the bimodal internal energy distributions in the diatomic products, to be rationalised in terms of non-adiabatic transitions between potential energy surfaces of both 1A' and 1A'' symmetry. The comprehensive picture of the wavelength-dependent (or vibronic state-dependent) photofragmentation behaviour of H2S will serve as a text-book example illustrating the importance of non-Born-Oppenheimer effects in molecular photochemistry, and the findings should be incorporated in future astrochemical modelling.

ВЛИЯНИЕ ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ УГОЛЬНОГО РАЗРЕЗА И МЕТЕОРОЛОГИЧЕСКИХ УСЛОВИЙ НА СКОРОСТЬ КОНВЕКТИВНЫХ ПОТОКОВ ВОЗДУХА, ТРАЕКТОРИЮ И ДАЛЬНОСТЬ РАСПРОСТРАНЕНИЯ ПЫЛЕГАЗОВОГО ОБЛАКА В АТМОСФЕРЕ

The article describes the results of studying the parameters of the convective state of the atmosphere of a coal mine, shows their effect on the speed of ascending air flows, and also provides information on the impact of regional meteorological conditions on the trajectory and range of propagation of a dust and gas cloud formed as a result of a mass explosion at a coal mine. The results of the study can be used to uncover the mechanisms of formation of a dust and gas cloud, to make adjustments to existing methods for calculating cloud parameters, such as the height of elevation above the surface of the exploding block, the range and speed of its propagation, as well as to develop new methods for monitoring and controlling the cloud.

Dynamics of dust particles with virions in gas cloud

The relevance is due to the lack of study and development of models of the movement of virions under the action of gravitational and dissipative components in the Earth's atmosphere. The article presents the results of modeling the movement of virions in space under the action of a different combination of components of the force vector. Virion motion models are presented. Virion motion models characterize the dependence of virion velocity on coordinate and time. The influence of the components of the force vector on the character of movement of the virion was investigated.

Inversion method of target gas cloud transmittance based on atmospheric profile synthesis background

The sky infrared background radiation varies greatly with spatial distribution and time. When scanning Fourier transform infrared remote sensing imaging system scans the target gas cloud with the sky as the background, the background radiation corresponding to each scanned pixel is different, and the background does not have a constant baseline. It is extremely difficult to obtain the background spectrum of each pixel in real time, which affects the inversion accuracy of the target gas cloud transmittance. An inversion method of target gas cloud transmittance based on atmospheric profile synthesis background is proposed in this work. The temperature, humidity, pressure, and ozone profiles of the measured locations and the atmospheric model are used to generate the sky infrared background in order to solve the problem, i.e. the difficulty in measuring the clean sky infrared background spectrum in the chemical industry park. This paper proposes that there is a continuous derivable relationship between the sky infrared background spectrum and the cosine of zenith angle at each wavenumber, so a small amount of sky infrared background spectrum with a zenith angle gradient can quickly generate a sky infrared background spectrum at any elevation angle. The proposed method is verified by the moderate resolution atmospheric radiative transfer model (MODTRAN) software simulation and the remote sensing imaging experiment of SF<sub>6</sub> gas. The proposed method can quickly generate the sky infrared background spectrum corresponding to any angle within a gradient elevation angle and accurately invert the target gas cloud transmittance at each pixel. The results show that the distribution trend of the column concentration of the SF<sub>6</sub> gas cloud is consistent with the actual distribution, and the correlation is 0.99979.

Atomic oxygen abundance toward Sagittarius B2

A substantial fraction of oxygen in diffuse clouds is unaccounted for by observations and is postulated to be in an unknown refractory form, referred to as unidentified depleted oxygen (UDO), which, depending on the local gas density, may contribute up to 50% of the total oxygen content. Previous Infrared Space Observatory (ISO) observations suggest that a significant fraction of oxygen in even denser, translucent clouds may be in atomic form. We have analyzed velocity-resolved archival SOFIA observations of the 63 μm fine-structure [O I] transition toward the high-mass star-forming region Sgr B2(M) in the Central Molecular Zone. The foreground spiral-arm clouds as well as the extended Sgr B2 envelope between the Sun and the background dust continuum source produce multiple [O I] absorption components, spectrally separated in velocity space. The gas-phase atomic oxygen column density in foreground clouds toward Sgr B2 is well correlated with the total hydrogen column density, with an average atomic oxygen abundance of (2.51 ± 0.69) × 10−4 with respect to hydrogen nuclei. This value is in good agreement with the earlier ISO measurements on the same line of sight, and is about 35% lower than the total interstellar medium oxygen abundance in the low-density warm gas, as measured in the UV. We find no evidence that a significant fraction of the oxygen on the line of sight toward Sagittarius B2 is in the form of UDO.

Thermal behavior of astrophysical amorphous molecular ices.

Ice is a major component of astrophysical environments - from interstellar molecular clouds through protoplanetary disks to evolved solar systems. Ice and complex organic matter coexist in these environments as well, and it is thought primordial ice brought the molecules of life to Earth four billion years ago, which could have kickstarted the origin of life on Earth. To understand the journey of ice and organics from their origins to becoming a part of evolved planetary systems, it is important to complement high spatial and spectral resolution telescopes such as JWST with laboratory experimental studies that provide deeper insight into the processes that occur in these astrophysical environments. Our laboratory studies are aimed at providing this knowledge. In this article we present simultaneous mass spectrometric and infrared spectroscopic investigation on how molecular ice mixtures behave at different temperatures and how this information is critical to interpret observational data from protoplanetary disks as well as comets. We find that amorphous to crystalline water ice transformation is the most critical phenomenon that differentiates between outgassing of trapped volatiles such as CO2vs. outgassing of pure molecular ice domains of the same in a mixed molecular ice. Crystalline water ice is found to trap only a small fraction of other volatiles (<5%), indicating ice grain composition in astrophysical and planetary environments must be different depending on whether the ice is in amorphous phase or transformed into crystalline phase, even if the crystalline ice undergoes radiation-induced amorphization subsequently. Crystallization of water ice is a key differentiator for many ices in astronomical environments as well as in our Solar System.