Thermal Fragmentation Research Articles

Interplay between coordination sphere engineering and properties of nickel diketonate-diamine complexes as vapor phase precursors for the growth of NiO thin films.

NiO-based films and nanostructured materials have received increasing attention for a variety of technological applications. Among the possible strategies for their fabrication, atomic layer deposition (ALD) and chemical vapor deposition (CVD), featuring manifold advantages of technological interest, represent appealing molecule-to-material routes for which a rational precursor design is a critical step. In this context, the present study is focused on the coordination sphere engineering of three heteroleptic Ni(II) β-diketonate-diamine adducts of general formula [NiL2TMEDA] [L = 1,1,1-trifluoro-2,4-pentanedionate (tfa), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionate (fod) or 2,2,6,6-tetramethyl-3,5-heptanedionate (thd), and TMEDA = N,N,N',N'-tetramethylethylenediamine]. Controlled variations in the diketonate structure are pursued to investigate the influence of steric hindrance and fluorination degree on the chemico-physical characteristics of the compounds. A multi-technique investigation supported by density functional calculations highlights that all complexes are air-insensitive and monomeric and that their thermal properties and fragmentation patterns are directly dependent on functional groups in the diketonate ligands. Preliminary thermal CVD experiments demonstrate the precursors' suitability for the obtainment of NiO films endowed with flat and homogeneous surfaces, paving the way to future implementation for CVD end-uses.

Fabrication of novel Fe (III), Co (II), Hg (II), and Pd (II) complexes based on water‐soluble ligand (NaH2PH): structural characterization, cyclic voltammetric, powder X‐ray diffraction, zeta potential, and biological studies

Sodium4‐hydroxy‐3‐([2‐picolinoylhydrazineylidene]methyl)benzenesulfonate (NaH2PH) was synthesized as a novel water‐soluble ligand, by the condensation of picolinohydrazide with sodium 3‐formyl‐4‐hydroxybenzenesulfonate. The (NaH2PH) ligand and its isolated Co (II), Fe (III), Hg (II), and Pd (II) complexes were analyzed by elemental analysis and characterized by spectroscopic (Fourier transform infrared spectroscopy, UV–visible, powder XRD, 1H NMR,13C NMR, MS) and magnetic measurements. By comparing IR spectra of both ligand and the metal complexes, one can assume that the (NaH2PH) ligand behaves as a bi‐negative tetradentate (ONNO) in [Co (NaPH)(H2O)2].3H2O, and a mono‐negative tridentate (ONO) in [Fe (NaPH)Cl2(H2O)] complex, whereas in [Hg2(NaPH)Cl2(H2O)] complex, (NaH2PH) coordinates as a bi‐negative pentadentate (ONNNO) ligand via deprotonated OH group of phenolic ring (C=N)Py and (C=N*) coordinated to one of Hg (II) ion and the oxygen atom of enolic group and (C=N)az group with the another Hg (II) ion. Moreover, (NaH2PH) acts as bi‐negative tridentate (ONO) ligand in [Pd (NaPH)(H2O)].2H2O complex. The geometries of complexes were suggested based on the UV–visible spectra, magnetic measurements and confirmed by applying discrete Fourier transform (DFT) optimization studies. The thermal fragmentation of both [Pd (NaPH)(H2O)].2H2O and [Co (NaPH)(H2O)2].3H2O complexes was performed, and the kinetic and thermodynamic parameters were computed using the Coats–Redfern and Horowitz–Metzger methods. The redox behavior of divalent ions of cobalt and mercury were discussed by the cyclic voltammetry technique in the presence and absence of (NaH2PH) ligand. Biological potencies of the ligand and its metal complexes were evaluated as antioxidants (ABTS and DPPH), anticancer, DNA, and antimicrobial (Staphylococcus aureus and Bacillus subtilis as Gram (+) bacteria, Escherichia coli and Pseudomonas aeruginosa as Gram (−) bacteria, and Candida albicans as fungi).

ATOMS: ALMA three-millimeter observations of massive star-forming regions – XII: Fragmentation and multiscale gas kinematics in protoclusters G12.42+0.50 and G19.88−0.53

ABSTRACT We present new continuum and molecular line data from the ALMA Three-millimeter Observations of Massive Star-forming regions (ATOMS) survey for the two protoclusters, G12.42+0.50 and G19.88−0.53. The 3 mm continuum maps reveal seven cores in each of the two globally contracting protoclusters. These cores satisfy the radius–mass relation and the surface mass density criteria for high-mass star formation. Similar to their natal clumps, the virial analysis of the cores suggests that they are undergoing gravitational collapse ($\rm \alpha _{vir} \lt \lt 2$). The clump to core scale fragmentation is investigated and the derived core masses and separations are found to be consistent with thermal Jeans fragmentation. We detect large-scale filamentary structures with velocity gradients and multiple outflows in both regions. Dendrogram analysis of the H13CO+ map identifies several branch and leaf structures with sizes ∼ 0.1 and 0.03 pc, respectively. The supersonic gas motion displayed by the branch structures is in agreement with the Larson power law indicating that the gas kinematics at this spatial scale is driven by turbulence. The transition to transonic/subsonic gas motion is seen to occur at spatial scales of ∼0.1 pc indicating the dissipation of turbulence. In agreement with this, the leaf structures reveal gas motions that deviate from the slope of Larson’s law. From the large-scale converging filaments to the collapsing cores, the gas dynamics in G12.42+0.50 and G19.88−0.53 show scale-dependent dominance of turbulence and gravity and the combination of these two driving mechanisms needs to be invoked to explain massive star formation in the protoclusters.

Comprehensive theoretical study of the correlation between the energetic and thermal stabilities for the entire set of 1812 C60 isomers

The thermal stability of fullerenes plays a fundamental role in their synthesis and in their thermodynamic and kinetic properties. Here, we perform extensive molecular dynamics (MD) simulations using an accurate machine-learning-based Gaussian Approximation Potential (GAP-20) force field to investigate the energetic and thermal properties of the entire set of 1812 C60 isomers. Our MD simulations predict a comprehensive and quantitative correlation between the relative isomerization energy distribution of the C60 isomers and their thermal fragmentation temperatures. We find that the 1812 C60 isomers span over an energetic range of over 400 kcal mol−1, where the majority of isomers (∼85%) lie in the range between 90 and 210 kcal mol−1 above the most stable C60-Ih buckminsterfullerene. Notably, the MD simulations show a clear statistical correlation between the relative energies of the C60 isomers and their fragmentation temperature. The maximum fragmentation temperature is 4800 K for the C60-Ih isomer and 3700 K for the energetically least stable isomer, where nearly 80% of isomers lie in a temperature window of 4000–4500 K. In addition, an Arrhenius-based approach is used to map the timescale gap between simulation and experiment and establish a connection between the MD simulations and fragmentation temperatures.

Thermal fragmentation and pulverization behavior of lignite during the vibration drying process and its grey relational analysis of multi-factors

Lignite particles are easy to break into smaller particles in the process of thermal drying, which affect the heat and mass transfer inside the particles. Therefore, it is important to study the fragmentation behavior of lignite for optimizing the drying process. In this article, two concepts of degree of fragmentation (F′) and pulverization ratio (R p ) were put forward to describe the overall fragmentation property of lignite after vibration drying. The results showed that the higher the drying temperature, the more favorable it was for the product particles to fragment. The impact of particle size and feeding amount on F′ and R p was relatively small, but it was still not negligible. There was a critical vibration frequency during vibration drying. Once the vibration frequency exceeded critical value, the fragmentation of particles would be greatly promoted. The grey correlation model of lignite was established to quantitatively analyze the influence of five factors on the fragmentation and pulverization of products in the process of multi-factor coupling drying. Following the grey correlation model, five factors, such as the drying time, vibration frequency, drying temperature, feed particle size and feeding amount were ranked according to their influence on F′ and R p .

The effect of strengthening thermal fragmentation by rotary kiln on sulfur distribution of fragmentation char with low-rank coal

Thermal fragmentation of low-rank coal was generally viewed as a negative effect. Actually, the thermal fragmentation had a positive effect on the pyrolysis desulfurization of low-rank coals, and it is expected to be a new way to realize the desulfurization of large-size char. A fixed bed pyrolysis device and rotary kiln pyrolysis device were used to investigate the effect of pure thermal action and thermo-mechanical action on the sulfur distribution in thermal fragmentation char of lignite and sub-bituminous coal at 300–900 °C. The intervention mechanism of thermo-mechanical strengthen thermal fragmentation on low-rank coal with different coalification degrees was obtained. For lignite, the non-sulfur components were more fragmented than the high-sulfur components due to thermo-mechanical action at the low-temperature stage. Fragmentation of high sulfur components dominated thermal fragmentation at the high-temperature stage. For sub-bituminous coal, conjoined structures and plastic layer hindered the fragmentation of sulfur-containing components by pure thermal action. The thermo-mechanical action under rotary kiln pyrolysis was helpful for the fragmentation of the conjoined structure and the separation of the char and plastic layer, thereby reducing the Fe-S minerals and organic sulfur content of the large-size char. The difference in organic sulfur caused by thermo-mechanical action is mainly due to the fragmentation of sulfone components.

Correlation between the energetic and thermal properties of C40 fullerene isomers: An accurate machine-learning force field study

The isomerisation energies and thermal stabilities of the entire set of C 40 fullerene isomers are investigated using molecular dynamics simulations with the recently developed machine-learning-based Gaussian Approximation Potential (GAP-20) force field. Our simulations predict high statistical correlation between the relative isomerisation energy distribution of all C 40 isomers and their thermal fragmentation temperatures. The most energetically and thermally stable isomer is the symmetric C 40 - D 2 isomer and its fragmentation temperature is 3875 ± 25 K. In contrast, the least stable isomer is the D 5d nanorod-shaped isomer which is 146.8 kcal mol −1 higher in energy and decomposes at 2975 ± 25 K, i.e., around 900 K below the most stable isomer. In addition, we show that most isomers lie in the range between 20 and 60 kcal mol −1 above the most stable isomer, and nearly 60% of isomers decompose in the temperature range of 3425–3675 K. These computational results provide valuable insights into the synthesis of C 40 fullerenes at high-temperatures. • Using the accurate machine-learning (GAP-20) carbon potential • Systematic study of the energetic and thermal properties of C40 fullerenes • We consider the entire set of C40 fullerene isomers. • We find a distinct correlation between the energetic and thermal stabilities.

Effects of thermal string fragmentation in inelastic pp collisions at the CERN Super Proton Synchrotron with beam momenta from 20 to 158 GeV/ c

The proton stopping behavior in proton-proton ($\mathit{pp}$) collisions at beam momentum of 20, 31, 40, 80, 158 GeV/$c$ suggests that more physics mechanisms are at play than traditionally assumed in Monte Carlo event generators. It is shown that the thermal string fragmentation model of pythia 8.303 is able to provide a good description of the observables in inelastic $\mathit{pp}$ collisions such as the rapidity and transverse momentum spectra of protons, charged pions, and charged kaons at the whole CERN SPS energies.

Evaluating the Application of Rock Breakage without Explosives in Underground Construction—A Critical Review of Chemical Demolition Agents

The method of drilling and blasting with explosives is widely used in rock fragmentation applications in underground construction projects, such as tunnels and caverns. However, the use of explosives is associated with rigorous safety and environmental constraints, since blasting creates toxic fumes, ground vibrations, and dust. Because of these constraints, there has been a growing interest in transitioning away from explosives-based rock fragmentation. The use of explosives-free methods could lead to continuous operation by eliminating the need for idle time with additional ventilation required to exhaust the blast fumes. This paper first presents a critical review of various methods that have been developed so far for rock fragmentation without explosives. Such methods include thermal fragmentation, plasma blasting, controlled foam injection, radial-axial splitter, and supercritical carbon dioxide. Thermal fragmentation, as the name implies, uses high heat to spall high-grade ore. However, it requires high heat energy, which requires additional ventilation as compared to normal conditions to cool the work area. Plasma blasting uses a high temperature and pressure plasma to fracture rock in a safe manner. While this method may be environmentally friendly, its usage may significantly slow tunnel development due to the need to haul one or more large energy capacitor banks into and out of the work area repeatedly. Controlled foam injection is another chemical method, whereby foam is the medium for fracturing. Although claimed to be environmentally friendly, it may still pose safety risks such as air blast or flyrock due to its dynamic nature. A radial-axial splitter (RASP) is an instrument specially designed to fracture a borehole in the rock face but only at the pace of one hole at a time. Supercritical carbon dioxide is used with the equipment designed to provide a high-pressure jet stream to fracture rock, and replaces water in these instruments. The method of soundless chemical demolition agents (SCDA) is evaluated in more detail and its merits over others are highlighted, making it a potentially viable alternative to blasting with explosives in underground excavation applications. Future work involves the optimization of SCDA for implementation in underground mines. The discussion compares the key features and limitations, and future work needs are underlined.

Galactic H ii region IRAS 17149 − 3916 – a multiwavelength study

ABSTRACT This paper presents a multiwavelength investigation of the Galactic H ii region IRAS 17149 − 3916. Using the Giant Meterwave Radio Telescope, India, first low-frequency radio continuum observations at 610 and 1280 MHz for this region are presented. The ionized gas emission displays an interesting cometary morphology, which is likely powered by the early-type source, E4 (IRS-1). The origin of the cometary morphology is discussed under the framework of the widely accepted bow shock, champagne flow, and clumpy cloud mechanisms. The mid- and far-infrared data from Spitzer-GLIMPSE and Herschel-Hi-GAL reveal a complex network of pillars, clumps, bubble, filaments, and arcs suggesting the profound influence of massive stars on the surrounding medium. Triggered star formation at the tip of an observed pillar structure is reported. High-resolution ALMA continuum data show a string of cores detected within the identified clumps. The core masses are well explained by thermal Jeans fragmentation and support the hierarchical fragmentation scenario. Four ‘super-Jeans’ cores are identified which, at the resolution of the present data set, are suitable candidates to form high-mass stars.

Thermal decomposition of heptafluoropropylene-oxide-dimer acid (GenX)

Incineration appears as a viable strategy in the disposal of the notorious perfluoroalkyl substances (PFASs) in a process that typically leads to fluorine mineralization. Central in the design of such operation is to comprehend the underlying chemical mechanisms that dictate thermal fragmentation of PFASs into smaller perfluorinated cuts and HF. Among notable short-chain PFASs entities is the heptafluoropropylene-oxide-dimer acid (HFPO-DA, C5F11C(O)OH), commercially known as GenX synthesized as a possible replacement of other PFASs compounds. However, reaction pathways that underpin the degradation of GenX at temperatures relevant to its decomposition in incinerators (i.e., cement kilns), remain unknown. Herein, we map out all plausible initial reactions that govern the thermal decomposition of GenX. Simultaneous elimination of HF and CO2 appears as the kinetically most favored channel with an accessible activation enthalpy of ∼62.0 kcal/mol. Fission of the ether linkage in the 1,1,1,2,2,3,3-heptafluoro-3-[(1-fluoroethenyl)oxy] propane molecule (that forms after HF/CO2 elimination) affords a wide array of CnFm cuts, most notably CF2 at elevated temperatures. Constructed kinetic model plots temperature-dependent profiles of important species. It is predicted that GenX to commence decomposition around 700 K at a residence time of 2.0 s, a value that is generally applied in incinerators. Findings from the study call to further investigate interactions between the predicted major fluorine carriers (HF and CF2) and other constituents encountered in relevant incineration mediums, most notably, calcium hydroxides and polymeric materials.

Selective aromatic production from fast pyrolysis of sugarcane bagasse lignin over ZSM-5 catalyst

Organosolv lignin extracted from sugarcane bagasse (BG-lignin) and commercial grade lignin (Comm-OS) were use as starting materials in this study. From our previous work, aromatic furan (2,3-dihydrobenzofurn) was mainly produced from fast pyrolysis of BG-lignin and Comm-OS at 400–600 °C while alkyl phenol and phenol are more favorable at 700 °C. However, more thermal fragmentation was simultaneously redundant which results in low aromatic selectivity. In this work, aromatic production from lignin with molecular sieve ZSM-5 catalysts was studied using Py-GCMS instrument with biomass to catalyst ratio (B:C) of 1:1, 1:5, and 1:10. Aromatic furan and monolignol (H-unit, G-unit, and S-unit) were transform to hydrocarbon species with addition of ZSM-5 catalyst according to elimination of side chain by demethoxylation, dehydroxylation, and dealkylation reactions. Maximum aromatic production was found at B:C of 1:10 for both Comm-OS and BG-lignin of 87.31% and 88.22%, respectively, while aliphatic hydrocarbon was more abundant for BG-lignin of 43.21% (1:5). Moreover, ZSM-5 exhibit instinctive performance on MAHs and PAHs production especially at B:C of 1:5 and 1:10. Nevertheless, polymerization between MAHs results in PAHs also observed for both Comm-OS and BG-lignin. From the result, transformation of aromatic furan could be limited by introduction of molecular sieve ZSM-5 which enhance the oxygen elimination from phenol derivative and favorable for aromatic and BTX production.

The Partitional Behavior of sulfur and minerals in the thermal fragmentation char during pyrolysis of lignite

In the lignite pyrolysis process, the pulverization of char due to thermal fragmentation are not considered a positive phenomenon. However, we found that the thermal fragmentation effect was beneficial to the desulfurization of char. It was investigated that the yield, total sulfur, and different forms of sulfur distribution of thermal fragmentation char (TFC) with different particle sizes at 300–900 °C. Sulfur tended to be concentrated in the pulverization char by thermal fragmentation. Compared with the total sulfur content of raw coal of 1.69%, the lowest sulfur content of char with the same particle size range after pyrolysis and screening treatment reached 0.86%. The enrichment of total sulfur in the low-temperature stage was derived from sulfate and sulfide sulfur as well as in medium and high temperature stage was mainly derived from sulfide and organic sulfur. Further, the mechanism of mineral transformation and sulfur partitional behavior was explored. The minerals composition, apparent morphology, and surface chemical state of TFC were characterized by X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). It was found that Fe-S minerals with coarse-size were concentrated in the pulverization char in the form of active distribution. Organic sulfur was also enriched in pulverization char in medium and high temperature stages.

Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization

Abstract. Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online molecular characterization of chemical reaction products and intermediates, detection of native biomolecules, in vivo metabolomics, and environmental monitoring with negligible thermal and ionization-induced fragmentation for over two decades. However, the EESI extraction mechanism remains uncertain. Prior studies disagree on whether particles between 20 and 400 nm diameter are fully extracted or if the extraction is limited to the surface layer. Here, we examined the analyte extraction mechanism by assessing the influence of particle size and coating thickness on the detection of the molecules therein. We find that particles are extracted fully: organics-coated NH4NO3 particles with a fixed core volume (156 and 226 nm in diameter without coating) showed constant EESI signals for NH4NO3 independent of the shell coating thickness, while the signals of the secondary organic molecules comprising the shell varied proportionally to the shell volume. We also found that the EESI sensitivity exhibited a strong size dependence, with an increase in sensitivity by 1–3 orders of magnitude as particle size decreased from 300 to 30 nm. This dependence varied with the electrospray (ES) droplet size, the particle size and the residence time for coagulation in the EESI inlet, suggesting that the EESI sensitivity was influenced by the coagulation coefficient between particles and ES droplets. Overall, our results indicate that, in the EESI, particles are fully extracted by the ES droplets regardless of the chemical composition, when they are collected by the ES droplets. However, their coalescence is not complete and depends strongly on their size. This size dependence is especially relevant when EESI is used to probe size-varying particles as is the case in aerosol formation and growth studies with size ranges below 100 nm.

Woody encroachment of grasslands: Near-surface thermal implications assessed through the lens of an astronomical event.

Temperature has long been understood as a fundamental condition that influences ecological patterns and processes. Heterogeneity in landscapes that is structured by ultimate (climate) and proximate (vegetation, topography, disturbance events, and land use) forces serve to shape thermal patterns across multiple spatio‐temporal scales. Thermal landscapes of grasslands are likely shifting as woody encroachment fragments these ecosystems and studies quantifying thermal fragmentation in grassland systems resulting from woody encroachment are lacking. We utilized the August 21st, 2017, solar eclipse to mimic a rapid sunrise/sunset event across a landscape characterized as a grassland to experimentally manipulate levels of solar radiation in the system. We then quantified changes in near‐surface temperatures resulting from changes in solar radiation levels during the eclipse. Temperatures were monitored across three grassland pastures in central Oklahoma that were characterized by different densities (low, medium, and high) of Juniperus virginiana to understand the impact of woody encroachment on diurnal temperature patterns and thermal heterogeneity in a grassland's thermal landscape. The largest temperature range across sites that occurred during the eclipse was in the mixed grass vegetation. Similarly, the largest change in thermal heterogeneity occurred in the grassland with the lowest amount of woody encroachment. Thermal heterogeneity was lowest in the highly encroached grassland, which also experienced the lowest overall change in thermal heterogeneity during the eclipse. Time series models suggested that solar radiation was the most influential factor in predicting changes in thermal heterogeneity as opposed to ambient temperature alone. These results suggest that highly encroached grasslands may experience lower diurnal variability of temperatures at the cost of a decrease in the overall thermal heterogeneity of that landscape. It appears that fine‐scale spatio‐temporal thermal variation is largely driven by solar radiation, which can be influenced by vegetation heterogeneity inherent within a landscape.

Thermally induced variations in the nanostructure and reactivity of soot particles emitted from a diesel engine

This work focuses on the thermally induced variation in the nanostructure, size of primary particles and oxidative reactivity of diesel soot and a commercial carbon black in an inert gas environment at temperatures ranging from 600 to 1000 °C. Soot nanostructure and size were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The soot reactivity was evaluated with respect to activation energy (Ea) and characteristic oxidation temperature, including peak temperature (TP) and burnout temperature (Tb), using thermogravimetric analysis (TGA). The mass loss of diesel soot and carbon black rises when increasing the thermal treatment temperature, especially at 1000 °C, and a significant quantity of mass loss can be observed, which is primarily due to thermal fragmentation and the desorption of chemical species on soot surfaces. The HRTEM and XRD results all indicate that the thermally treated soot samples have more ordered nanostructure than the untreated samples. There is a reduction in the size of primary particles as thermal treatment temperature increases. The soot reactivity decreases after thermal treatment, as manifested by the elevation in Ea, TP, and Tb values. Moreover, the oxidation reactivity of soot samples is closely associated with the fringe length, tortuosity, and fringe tortuosity. Compared to carbon black, diesel soot with a more disorder structure has a higher oxidative reactivity.

Characterization of Metal-Bound Benzimidazole Derivatives, Effects on Tumor Cells of Lung Cancer.

Four new ligands and four new copper (II) coordination compounds were prepared and characterized by chemical, elemental analysis, cytotoxicity, and FTIR spectroscopy (Fourier transform infrared spectroscopy). The nature of metal–ligand coordination was investigated. The thermal properties of complexes in the solid state were studied using TG-MS techniques (thermogravimetric analysis coupled with mass spectrometry) under dynamic flowing air atmosphere to analyze the principal volatile thermal decomposition and fragmentation products that evolved during thermolysis. The intermediate and final solid thermolysis products were also determined. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay was used to evaluate active metabolic cells as an IC50 (half maximal inhibitory concentration). The relationship between antitumor activity and the position of nitrogen atoms in the organic ligand has been shown.

Fragmentation and kinematics in high-mass star formation

Context. The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research. Aims. We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation. Methods. Employing the NOrthern Extended Millimeter Array and the IRAM 30 m telescope, we observed two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3 mm continuum and spectral line emission at a high angular resolution (~0.8″). Results. We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, these cores follow a mass-size relation of approximately M ∝ r2.0 ± 0.3, corresponding to constant mean column densities. However, with different temperature assumptions, a steeper mass-size relation up to M ∝ r3.0 ± 0.2, which would be more likely to correspond to constant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicating that the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at first sight – multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50 km s−1 pc−1 in ISOSS23053 – the findings can all be explained within the framework of a dynamical cloud collapse scenario. Conclusions. While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows, is nonetheless not as well constrained and would require future investigation.

Vibration drying of lignite based on the thermal fragmentation property and its prediction model

A lignite vibrating mixed-flow screening and drying system was implemented in this study. Vibration is conducive to heat and mass transfer between the hot carrier gas and lignite particles and prompts large particles into small particles based on their thermal fragmentation to improve the drying efficiency. During the vibration drying process, most or all of the large particles were broken into smaller particles, and there was always a clear moisture gradient with respect to the particle size fractions. The particle size–remaining moisture gradient (Ms) was defined to describe the nonuniformity of the dryness among different size particles based on their mass content. Ms increased first and then decreased with drying time, and a high drying rate usually resulted in larger differences in moisture among the products, whereas a lower residual moisture content reduced the differences. The Weibull model was suitable for describing and predicting the vibration drying kinetics of lignites. Based on the results of this study, a vibration drying pilot system will be designed and set up to obtain a new drying system.

Star formation in ‘the Brick’: ALMA reveals an active protocluster in the Galactic centre cloud G0.253+0.016

ABSTRACT G0.253+0.016, aka ‘the Brick’, is one of the most massive (>105 M⊙) and dense (>104 cm−3) molecular clouds in the Milky Way’s Central Molecular Zone. Previous observations have detected tentative signs of active star formation, most notably a water maser that is associated with a dust continuum source. We present ALMA Band 6 observations with an angular resolution of 0.13 arcsec (1000 AU) towards this ‘maser core’ and report unambiguous evidence of active star formation within G0.253+0.016. We detect a population of eighteen continuum sources (median mass ∼2 M⊙), nine of which are driving bi-polar molecular outflows as seen via SiO (5–4) emission. At the location of the water maser, we find evidence for a protostellar binary/multiple with multidirectional outflow emission. Despite the high density of G0.253+0.016, we find no evidence for high-mass protostars in our ALMA field. The observed sources are instead consistent with a cluster of low-to-intermediate-mass protostars. However, the measured outflow properties are consistent with those expected for intermediate-to-high-mass star formation. We conclude that the sources are young and rapidly accreting, and may potentially form intermediate- and high-mass stars in the future. The masses and projected spatial distribution of the cores are generally consistent with thermal fragmentation, suggesting that the large-scale turbulence and strong magnetic field in the cloud do not dominate on these scales, and that star formation on the scale of individual protostars is similar to that in Galactic disc environments.