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Understanding the effects of mixed anthropogenic pollutants on the photooxidation of volatile organic compounds (VOCs) is essential for unraveling the formation pathways of secondary organic aerosols (SOA). Yet, it remains a highly challenging experimental target owing to the complexities in the precise measurement of molecular compositions of products and number/mass concentrations of particles as a function of pollutant concentration in the ambient atmosphere. Here, a series of well-defined chamber experiments were performed to explore the effects of NO x and NH 3 on the SOA formation from photooxidation of the most abundant monoterpene, α -pinene. The results indicate that the suppression effect of NO and NO 2 on the α -pinene photooxidation shows monotonous and parabolic trends, respectively. The presence of NH 3 enhances particle number concentrations during the α -pinene + NO x photooxidation by participating in reactions with organic acids. New compounds, including organic peroxides, esters, organic nitrates, and peroxyacyl nitrates, are observed at molecular weight (MW) = 166, 173, 217, 231, 280, 282, 304, and 410 through threshold photoionization making use of a recently constructed vacuum ultraviolet free electron laser in positive ion mode. The molecular structures and formation paths of these species are speculated, which advance the category of VOC oxidation products. Our study provides significant understanding of the influence of NO x and NH 3 on the VOC photooxidation, which can be utilized to establish predictive SOA formation networks and to improve atmospheric models. [Display omitted] • This study investigates the atmospheric components affected by the anthropogenic-biogenic interactions. • The suppression effect of NO and NO 2 on the α -pinene photooxidation shows monotonous and parabolic trends, respectively. • NH 3 enhances the number concentrations of SOA from the α -pinene + NO x photooxidation by reacting with organic acids. • A series of newly-observed compounds advance understanding of atmospheric components. [ABSTRACT FROM AUTHOR]

Colorimetric gel labels (referred to as AKAX) were fabricated to monitor the freshness of fresh-cut papaya in real time using agarose (AR) and konjac glucomannan (KGM) composite gels containing alizarin (AL) and Substance X (X). The AKAX colorimetric gel label produced an ordered color variation from purple to pink-purple to orange-yellow, following the CO 2 concentration in the package, to reflect the fresh-cut fruit freshness. Experimental characterization of the gel label structure revealed that AR, KGM, AL, and X were compatible, while the gel label texture, water-holding capacity, rheology, and thermal stability were improved with the addition of KGM. AKAX colorimetric gel labels maintained excellent color stability and CO 2 sensitivity during storage at 4 °C. The fresh-cut papaya approached spoilage as the color varied from purple to pink-purple, and an orange-yellow color indicated that the fresh-cut papaya had spoiled. Therefore, the developed AKAX colorimetric gel labels serve as effective tools for monitoring the spoilage of fresh-cut papaya. [Display omitted] • Colorimetric gel labels were prepared using neutral agarose and konjac glucomannan. • Gel-labeled colorimetric dye, alizarin, responded to different CO 2 concentrations. • Substance X inhibited color variation and promoted the gel label color sensitivity. [ABSTRACT FROM AUTHOR]

Under the fouling conditions in stationary coal combustion systems, the sticking/rebound behavior of solid incident particles is a key issue in determining the ash deposition rate. From a dynamic point of view, the bulk fly ash, which dominants the deposited mass, successively interacts with the clean tube, the inner fine deposited layer and the bulk deposited layer during ash deposition. In this paper, we experimentally investigate the time-resolved evolution of ash fouling in a 25 kW coal combustor. The deposited mass flux rapidly reaches a stable state that fluctuates around a mean value of ∼3 g/(m2·s) for two kind of probe materials. The rapid initial stage only allows the formation of 1–2 layers of bulk deposited ash, revealing the dominant role of bulk deposit in capturing large incident particles. Inspired by the observation, we apply a 3D adhesive discrete element model (DEM) to fully describe the many-body evolving process subject to the incident events of a 30-µm particle. The simulation agrees well with the experiments when using a higher particle surface energy of 200 mJ/m2. The rapidly growing feature of ash sticking probability with increasing the bulk deposit layers can be reproduced in this case, and an empirical formula is proposed. It is also validated that, at the deposit growth stage, the newly-deposited particles stay just where they impact. The effectiveness of the DEM tool shall benefit a fully-validated sticking/rebound model under the fouling condition that is convenient for CFD use. [ABSTRACT FROM AUTHOR]

Investigation of the effects of anthropogenic pollutants on the mass concentrations, particle number concentrations, and chemical compositions of secondary organic aerosol (SOA) formation is essential in understanding the photooxidation mechanism of volatile organic compounds but has been proven to be a very challenging experimental target because of their complex processes. Here, the effects of NO and SO 2 on SOA formation from isoprene photooxidation were studied by a number of laboratory studies. The results indicate the accumulated O 3 upon the NO conversion triggers the main oxidation reaction, by which the oxidants (i.e., OH and SO 4 −) are derived. The SOA mass concentrations and particle number concentrations are enhanced by NO under low NO concentrations but suppressed by NO under high NO concentrations, which are consistent with previous studies (Kroll et al., 2005 , 2006). This could be rationalized that the large amount of accumulated O 3 inhibit the multi-step isoprene oxidation and a large number of less oxidized products (m/z < 130) absorb or condense on the surface of existing particles, which decelerate the SOA nucleation and growth. The presence of SO 2 accelerates the conversion of NO and the accumulation of O 3 , which promotes the main oxidation reaction of isoprene. New compounds are observed at m/z = 134, 137, 150, 152, and 179 measured by threshold photoionization (positive ion mode) with a tunable vacuum ultraviolet free electron laser and are found to be mainly formed from the isoprene oxidization by O 3 and OH. The present findings provide both macroscopic and microscopic information to advance understanding of atmospheric components affected by the anthropogenic-biogenic interactions in the neighborhood of emission origins. [Display omitted] • The study investigates the atmospheric components affected by the anthropogenic-biogenic interactions. • The accumulated O 3 upon the NO conversion triggers the isoprene oxidation. • The presence of SO 2 accelerates the conversion of NO and the accumulation of O 3 , which promotes the main oxidation reaction of isoprene. • Newly-observed compounds measured by threshold photoionization advance understanding of atmospheric components. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to reveal the mechanisms governing the impaction and sticking dynamics of fly ash particles in pulverized coal combustion. The modeling work is of relevance to experiments in a 25 kW self-sustained down-fired furnace, which provides a sequence of real deposit shapes as varied boundary conditions for CFD simulations. Although the formed ash deposit has a comparable length scale with the probe, it has little effect on the global impaction efficiency of newly-coming particles. However, as the deposit builds up, incident particles impact the deposit and probe at generally larger impact angles and smaller normal velocities despite the almost invariant global impaction efficiency. It results in an enhanced local sticking probability in the center region of the probe, but a decreased one in the lateral regions. The incident kinetic energy of newly sticking particles to the deposit exhibits a converse correlation with their impact angle. The relationship of the averaged local sticking probability as a function of the azimuthal angle of probe is illustrated. Finally, the effect of Reynolds number on global particle impaction efficiency is examined. A universal formula is proposed, which is of importance to bridge lab-scale experiments and practical applications. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the correlations between coal/char fragmentation and fly ash formation during pulverized coal combustion are investigated. We observed an explosion-like fragmentation of Zhundong coal in the early devolatilization stage by means of high-speed photography in the Hencken flat-flame burner. While high ash-fusion (HAF) bituminous and coal-derived char samples only undergo gentle perimeter fragmentation in the char burning stage. Simultaneously, combustion experiments of two kinds of coals were conducted in a 25 kW down-fired combustor. The particle size distributions (PSDs) of both fine particulates (PM 1-10) and bulk fly ash (PM 10+) were measured by Electrical Low Pressure Impactor (ELPI) and Malvern Mastersizer 2000, respectively. The results show that the mass PSD of residual fly ash (PM 1+) from Zhundong coal exhibits a bi-modal shape with two peaks located at 14 µm and 102 µm, whereas that from HAF coal only possesses a single peak at 74 µm. A hybrid model accounting for multiple-route ash formation processes is developed to predict the PSD of fly ash during coal combustion. By incorporating coal/char fragmentation sub-models, the simulation can quantitatively reproduce the measured PM 1+ PSDs for different kinds of coals. The sensitivity analysis further reveals that the bi-modal mass distribution of PM 1+ intrinsically results from the coal fragmentation during devolatilization. [ABSTRACT FROM AUTHOR]

Abstract: The interfacial electronic structure of MoO3− x /graphene has been investigated using photoemission spectroscopy. The experimental data showed that upon deposition of MoO3− x , the Fermi level of graphene shifts downward gradually from its Dirac point due to the p-type doping effect. From the Fermi level shift of −0.28eV, the hole density of graphene was estimated to be 5.44×1012 cm−2. The formation of surface negative dipole due to electron transfer from graphene to the deposited MoO3− x films increased the sample′s work function. The existence of gap states in MoO3− x induced by oxygen vacancies greatly reduced the hole injection barrier at the MoO3− x /graphene interface. [Copyright &y& Elsevier]

Abstract: Nano-sized Sm0.5Sr0.5CoO3−δ (SSC) was fabricated onto the inner face of porous BaCe0.8Sm0.2O2.9 (BCS) backbone by ion impregnation technique to form a composite cathode for solid oxide fuel cells (SOFCs) with BCS, a proton conductor, as electrolyte. The electro-performance of the composite cathodes was investigated as function of fabricating conditions, and the lowest polarization resistance, about 0.21Ωcm2 at 600°C, was achieved with BCS backbone sintered at 1100°C, SSC layer fired at 800°C, and SSC loading of 55wt.%. Impedance spectra of the composite cathodes consisted of two depressed arcs with peak frequency of 1kHz and 30Hz, respectively, which might correspond to the migration of proton and the dissociative adsorption and diffusion of oxygen, respectively. There was an additional arc peaking at 1Hz in the Nyquist plots of a single cell, which should correspond to the anode reactions. With electrolyte about 70μm in thickness, the simulated anode, cathode and bulk resistances of cells were 0.021, 0.055 and 0.68Ωcm2 at 700°C, relatively, and the maximum power density was 307mWcm−2 at 700°C. [Copyright &y& Elsevier]

With the increasing use of low-rank coal, the upgraded semi-char produced through low-temperature pyrolysis of lignite is one of promising alternatives towards the clean and high efficient utilization. The co-firing of these pyrolytic semi-chars with parent coals has received more attention. In this paper, a kind of semi-char, produced from Hulunbuir (HB) lignite under a pyrolysis temperature of 504 °C, was burned in a 25 kW self-sustained pulverized coal combustor. Different mass blending ratios of semi-char (0%, 40%, 60% and 100%) were used. The results indicate that the PM 0.1 yield from pure combustion of HB lignite is ∼1.6 times of that from semi-char. The PM 0.1 yields of the coal/char blends are much less than the linear summation of yields of two blending fuels without considering their interactions. As for coarser PM mode, the reductions still exist for both PM 0.1–1 and PM 1–10 particles. The different PM yields of pure combustion cases are attributed to less volatile mineral species and also less fragmentation degree of semi-chars during combustion. A mechanism is postulated for PM reduction during the combustion of coal blends. PM 0.1 amounts are decreased since the volatilized mineral species is considerably scavenged by the previously formed semi-char surfaces, as partly evidenced from a time scale analysis. The scavenged compounds then serve as “glue” to convert ash particles to larger agglomerates, which may result in the reduction of PM 0.1–10 yields. [ABSTRACT FROM AUTHOR]