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Hydroxyl groups are one of the key factors for the development of coal spontaneous combustion. Although the reaction mechanism has been studied by many scholars, the effects of their positions in the molecule on the reaction characteristics have not been considered. In this paper, Ph−CH2−CH3 was selected as the basic unit to construct small coal molecule models with one hydroxyl at different positions. The microscopic parameters of each model were calculated by density functional theory (DFT), and the elementary reaction pathways and thermodynamic parameters of hydroxyl groups were explored. It was found that the hydrogen of OH is the active site of nucleophilic reaction, the Cα H bond of α-phenethyl alcohol and the O H bonds of the other molecules are most vulnerable to oxygen. All the models can generate H2O in the process of oxidation, other products of alcoholic hydroxyl groups are highly active oxygen-containing free radicals, while that of phenolic hydroxyl groups are quinones or ketones. The results of intrinsic reaction coordinate (IRC) indicated that hydrogen captured by oxygen is endothermic, while the ·OH free radical capturing hydrogen is exothermic. The activation energy of oxygen capturing hydrogen is 98–182 kJ/mol, which shows that the reaction can occur in the middle stage of coal spontaneous combustion (70–120 ℃), and the reaction rate gradually accelerate with the increase of temperature. In the same conditions, the order of the oxidation reaction rates is 2-ethyl phenol > 3-ethyl phenol > 4-ethyl phenol > α-phenethyl alcohol > β-phenethyl alcohol, which is the same as the order of reaction activities but opposite to that of activation energies. The research is helpful to strengthen the judgment of coal spontaneous combustion risk and the development of flame retardant.

Dissimilar joint between low alloy steel 16Mn and 304L austenitic stainless steel was welded in the air and under water with two different flux-cored wires: commercially obtained ER308 filler and specially developed nickel-based tubular wire. For microstructure comparison, dissimilar welded joints in the air and under water were acquired at the same welding procedures. The effect of water environment on microstructure, alloying elements distribution and microhardness profiles of dissimilar welded joints was discussed. The results show that typeⅡ boundary existed between austenitic weld metal and ferritic base metal in underwater welds similar to that in the air welds. The underwater Ni-based welds had a lower dendritic spacing than air welds. The amount of delta-ferrite present in underwater welds with ER308 filler was more than that in air welds because of the higher cooling rate in water environment. Major alloying elements were non-uniformly distributed along the austenitic weld metal/16Mn interface. Macroscopic composition gradients did not tend to form in air welds because of high heat input. Maximum microhardness value of 470 HV in wet welded joints was found in coarse-grained heat affected zone instead of transition zone. The transition zone at 16Mn side of underwater austenitic stainless steel welded joints exhibited high microhardness of 330 HV, which was strongly diluted by ferritic base metal.

A new multi-location soot sampling method is used to enhance the knowledge about the structural evolution of in-flame particles in a light-duty optical diesel engine. Through thermophoresis-based particle sampling performed at multiple in-bowl locations, the soot structures are shown for both early formation stage and later stage from the same combustion event. Three different jet-spacing angles of 45°, 90° and 180° were studied to analyse how different levels of jet–jet interaction impact the soot particle morphology and internal structure. One selected jet–jet interaction condition was further analysed to show differences in soot structures between the up-swirl side and down-swirl side of the wall jets. From transmission electron microscopes (TEM) images of the sampled soot particles and their statistical size analysis, it was found soot particles initially formed within 45∘ separated jet–jet interaction region have un-solidified premature aggregates due to limited carbonisation in the locally fuel-rich mixtures. When these soot particles travelled on the down-swirl side of the jets, they became solidified and carbonised while the oxidation was evident from the smaller soot primary particle and longer carbon-layer fringe and lower tortuosity. The higher mixing on the up-swirl side of the jets further enhanced the soot oxidation, resulting in even smaller soot primary particle, fragmentation of large soot aggregates, and even longer and less curved carbon-layer fringes. Regarding jet–jet interaction, the 180° jet spacing angle created no jet–jet interaction condition on the soot sampler locations. For smaller jet-spacing angles, the increase in jet–jet interaction promoted the soot formation as evidenced by larger and more complex soot aggregates formed due to more active soot aggregation and agglomeration. The soot oxidation became limited at higher jet–jet interaction conditions, which led to more amorphous soot internal structures.

This study shows how ethanol addition impacts in-flame and exhaust soot in spark-ignition direct injection (SIDI) engines through direct and simultaneous sampling of particles from the flames and exhaust stream. The thermophoresis-based soot sampling and transmission electron microscope (TEM) imaging was performed for various ethanol blending ratios ranging from 0 to 60%. A quantitative analysis is performed in the images obtained from a standard TEM by yielding the in-flame and exhaust soot number counts, projection area, as well as morphological parameters such as soot primary particle diameter, aggregate radius of gyration, and fractal dimension. In addition, the internal structures and reactivity status of in-flame and exhaust soot particles are unveiled using a high-resolution TEM with carbon fringe length, tortuosity and fringe-to-fringe separation extracted from processed carbon layer fringe images. The results show that both the number counts and projection areas of exhaust soot are much lower than those of the in-flame soot at any fixed ethanol blending ratios. The exhaust soot is smaller in size for both the primary particles and aggregates with more compact aggregate structures, longer and straighter fringe, and lower fringe separation, all indicating significant soot oxidation occurred inside the cylinder before the particles exit through the exhaust. With increasing ethanol blending ratio, almost linear reduction in number counts and projection area is found for both the in-flame and exhaust soot particles, while both soot aggregates and primary particles become smaller with more stretched aggregate structures and shorter, more curved, and narrower gap fringe structures, indicating soot particles with higher reactivity. The significantly lower soot emissions achieved with higher ethanol blending ratio is found to be due primarily to the suppression of soot formation within the flame as evidenced by higher reduction rate of number counts, projection area, and primary particle and aggregate sizes for the in-flame soot than that of the exhaust soot.

The composition and carbon nanostructure of soot are important parameters influencing health and climate effects, and the efficacy of soot mitigation technologies. We used laser-vaporization, electron-ionization aerosol mass spectrometry (or SP-AMS) to systematically investigate relationships between aerosol mass spectra, carbon nanostructure (HRTEM), and composition (thermal-optical carbon analysis) for soot with varying physicochemical properties. SP-AMS refractory black carbon concentrations (based on clusters) were correlated to elemental carbon (r = 0.98, p −8) and equivalent black carbon (aethalometer) concentrations. The SP-AMS large carbon (C+≥6, midcarbons and fullerene carbons) fraction was inversely correlated to fringe length (r = −0.97, p = 0.028) and linearly correlated to the fraction of refractory organic carbon that partially pyrolize during heating (r = 0.89, p −4). This refractory organic carbon material was incompletely detected with conventional aerosol mass spectrometry (flash vaporization at 600 °C). This suggests that (SP-AMS) refractory carbon cluster analysis provides insight to chemical bonding and nanostructures in refractory carbon materials, lowcarbons (C+≥5) indicate mature soot and large carbons indicate refractory organic carbon and amorphous nanostructures related to C5-components. These results have implications for assessments of soot particle mixing state and brown carbon absorption in the atmosphere and enable novel, on-line analysis of engineered carbon nanomaterials and soot characteristics relevant for climate and health.

This study shows how soot particles inside the cylinder of the engine are reduced due to high pressure fuel injection used in a light-duty single-cylinder optical diesel engine fuelled with methyl decanoate, a selected surrogate fuel for the diagnostics. For various injection pressures, planar laser induced incandescence (PLII) imaging and planar laser-induced fluorescence of hydroxyl (OH-PLIF) imaging were performed to understand the temporal and spatial development of soot and high-temperature flames. In addition, a thermophoresis-based particle sampling technique was used to obtain transmission electron microscope (TEM) images of soot aggregates and primary particles for detailed morphology analysis. The OH-PLIF images suggest that an increase in the injection pressure leads to wider distribution of high-temperature flames likely due to better mixing. The enhanced high-temperature reaction can promote soot formation evidenced by both a faster increase of LII signals and larger soot aggregates on the TEM images. However, the increased OH radicals at higher injection pressure accelerates the soot oxidation as shown in a higher decreasing rate of LII signals as well as dramatic reduction of the sampled soot aggregates at later crank angles. The analysis of nanoscale carbon layer fringe structures also shows a consistent trend that, at higher injection pressure, the soot particles are more oxidized to form more graphitic carbon layer structures. Therefore, it is concluded that the in-cylinder soot reduction at higher injection pressure conditions is due to enhanced soot oxidation despite increased soot formation.

This study shows how the structure of soot particles within the flame changes due to the relative direction of the swirl flow in a small-bore diesel engine in which significant flame–wall interactions cause about half of the flame travelling against the swirl flow while the other half penetrating in the same direction. The thermophoresis-based particle sampling method was used to collect soot from three different in-flame locations including the flame–wall impingement point near the jet axis and the two 60° off-axis locations on the up-swirl and down-swirl side of the wall-interacting jet. The sampled soot particle images were obtained using transmission electron microscopes and the image post-processing was conducted for statistical analysis of size distribution of soot primary particles and aggregates, fractal dimension, and sub-nanoscale parameters such as the carbon layer fringe length, tortuosity, and spacing. The results show that the jet-wall impingement region is dominated by many small immature particles with amorphous internal structure, which is very different to large, fractal-like soot aggregates sampled from 60° downstream location on the down-swirl side. This structure variation suggests that the small immature particles underwent surface growth, coagulation and aggregation as they travelled along the piston-bowl wall. During this soot growth, the particle internal structure exhibits the transformation from amorphous carbon segments to a typical core–shell structure. Compared to those on the down-swirl side, the soot particles sampled on the up-swirl side show much lower number counts and more compact aggregates composed of highly concentrated primary particles. This soot aggregate structure, together with much narrower carbon layer gap, indicates higher level of soot oxidation on the up-swirl side of the jet.

Graphical abstract, Highlights • More pyrazines were generated in high-intensity ultrasound-Maillard reaction (HIU-MR). • Pyrazines generation pathways were elucidated by Carbohydrate module labeling method. • [M]+ proportion in pyrazines with long-length side chains was lower than thermal MR. • Aldol-type condensation as a high-pressure favored reaction was promoted by HIU. • Cleavage of glucose contributed to the promoted synthesis of pyrazines in HIU-MR., This study evaluated how the generation of pyrazines was promoted by high-intensity ultrasound (HIU) in a Maillard reaction (MR) model system of glucose-glycine. Carbohydrate module labeling (CAMOLA) technique was adopted using D-glucose-13C6 to elucidate the carbon skeleton of both intermediate and final MR products (MRPs). In the D-glucose-13C6-glycine HIU-MR model system, the concentration of 11 types of pyrazines was significantly higher than their counterparts in the thermal MR. Results of CAMOLA analysis showed that a significantly lower proportion of [M]+ in pyrazines with long-length side chains was observed when compared with the pyrazines generated in thermal MR. This phenomenon may suggest the aldol-type condensation was promoted by the HIU, which is a conversion from pyrazines with short-length side chains to those with long-length side chains involving carbonyl compounds. Furthermore, the analysis of isotopomers distribution in 2,3-dimethyl-quinoxaline as the o-phenylenediamine-derivatized 2,3-butanedione indicated that the increased proportion of [M + 4]+ in 2,3-dimethyl-quinoxaline (15.74% ± 0.11%) was attributed to a cleavage of D-glucose-13C6 promoted by the HIU. The above-mentioned findings elucidate that the aldol-type condensation and cleavage of D-glucose contribute to the promoted synthesis of pyrazines. The HIU would generate an extremely high temperature and pressure environment that is favored by the aldol-type condensation as a high-pressure favored reaction. The HIU, therefore, can be further developed as a promising technique to promote flavor generation through the MR.

After injection, for which a short fuel injection follows the main injection, is proved to be effective in reducing soot emissions in diesel engines. The present study aims to better understand this in-cylinder soot reduction mechanism of after injection with a particular emphasis on its efficacy in a small-bore diesel engine in which more significant flame-wall interactions could cause different behaviour compared with extensively studied heavy-duty diesel engines in the literature. With the main injection only case as a baseline, two after-injection cases of close-coupled and long-dwell timings have been investigated in a single-cylinder common-rail optical engine. Various optical/laser-based imaging diagnostics have been performed including line-of-sight integrated chemiluminescence imaging of OH*, planar laser-induced florescence of hydroxyl (OH-PLIF), planar laser-induced incandescence of soot (PLII) and transmission electron microscope (TEM) imaging of thermophoretically sampled in-flame soot particles to visualise the spatial and temporal evolution of high temperature reaction and soot as well as particle structure. The results indicate that both after-injection strategies introduce a secondary heat release that leads to additional bulk gas temperature rise and thereby promoting the late-cycle soot oxidation. However, the efficacy is found to be dependent upon the after-injection timing. The OH-PLIF and PLII images show that the close-coupled after-injection induces additional high-temperature reaction and soot formation due to high ambient gas temperature. The new reaction occurs near the jet–wall impingement point, which is well separated from the main combustion zone as the main fuel jet travelled along the bowl wall due to significant jet–wall interactions. Although the main and after-injection soot are decoupled, soot morphology analysis based on TEM images suggests that the close-coupled after-injection does enhance the oxidation of main combustion-generated soot particles through the breakdown of large soot aggregates at elevated temperatures and with increased OH radicals. In comparison, both OH-PLIF and PLII images show no visual evidences of decoupled after-injection combustion for the long-dwell case due to insufficient temperature as the additional reaction occurs later in the expansion stroke. However, the increased OH radicals and breakdown of soot aggregates in the main combustion region are evident in OH-PLIF and TEM images. Overall, the close-coupled after-injection adds more soot but induces a higher degree of oxidation for the main combustion-generated soot particles. By contrast, the promotion of soot oxidation is less significant for the long-dwell after-injection but it produces no extra soot.

Less is known about controls of sedimentary structures in groundwater As distributions in sedimentary aquifers, and quantitative description of relationship between sedimentary environment and high As groundwater (according to WHO, As > 10 μg/L) is a challenging issue. Three hundred and eighty-two hydrogeological borehole loggings (well depths of 50–300 m) were collected and four hundred and ninety nine groundwater samples were taken to investigate controls of paleochannels on groundwater arsenic distribution in shallow aquifers of alluvial plain in the Hetao Basin. Results showed that the swing zone, formed by bursting, diversion and swing of ancient Yellow River course since the Late Pleistocene, has an obviously corresponding relationship with spatial variability of groundwater As in the Hetao Basin. “Swing Intensity Index” ( S ), which is firstly defined as the sum of clay-sand ratio ( R ) and the number of clay layers ( N ), can be used as the sedimentary facies symbol to establish the new recognition method for hosting high As groundwater. There is a positive correlation between the swing intensity index ( S ) of paleochannels and groundwater As concentrations. The swing zones of paleochannels with high S values represent hydrogeochemical characteristics of the strong reducing environment, serious evaporation, strong cation exchange, and the low infiltration recharge of surface water, which lead to enrichment of groundwater As in the shallow aquifers.

This study reports the effect of fuel aromatic content on soot particle development inside the cylinder of an optically accessible engine. A custom-made set of fuels of 4%, 14% and 24% aromatic content was carefully studied under pilot-main injection conditions. Time-resolved imaging of cool frame, OH* chemiluminescence signals and soot luminosity were performed to visualise the overall reaction development. Planar laser induced fluorescence imaging of HCHO and incandescence imaging of soot were also performed to obtain detailed understanding of reactions and soot distributions. Soot is analysed at a particle level. Using the thermophoresis-based particle sampling method, soot aggregates were collected from multiple in-bowl locations. The subsequent transmission electron microscope (TEM) imaging of the collected soot particles enables structural analysis of soot particles as well as sub-nano-scale carbon layers. The results showed that the aromatic content has little impact on reactions and flame development among the tested fuels. However, the soot formation starts to occur earlier, and its growth rate is much higher for a higher aromatic fuel. As a result, both the peak soot and remaining soot is measured higher for a higher aromatic fuel. The carbon-layer fringe analysis shows more mature, graphitised structures with higher aromatics at both formation-dominant and oxidation-dominant stages. The most noticeable trend is observed from larger soot aggregates for a higher aromatic fuel while the overall shapes are similar.

The EM algorithm has been used for inference of the mixture cure models. However, the complete-data and incomplete-data specifications have never been postulated appropriately in literature. The goal of this paper is to fill in this gap by deriving proper specifications.

The present study unveils the soot formation processes occurring inside the piston-bowl of a small-bore diesel engine by conducting the thermophoresis-based soot sampling experiments at various locations along the flame development path. Based on planar laser-induced incandescenece (PLII) and planar laser-induced florescence of hydroxyl (OH-PLIF) imaging performed in the same optical engine previously, it was understood that the sooting flame impinges on and then flows along the bowl wall, suggesting a soot growth and persistence near the fuel-rich wall region. In the present study, a soot sampling probe is placed in five different locations including the flame–wall impingement point and four further downstream regions: two 60° and two 120° from the jet axis with two different distances from the bowl wall in each angle. Methyl decanoate is selected as a surrogate fuel due to its low-sooting propensity and thus reduced laser attenuation in the reference PLII images; however, the fuel produces high enough number of soot particles for the in-flame sampling and their statistical analysis. The transmission electron microscope (TEM) images of the sampled soot particle aggregates and their statistical analysis of sizes and fractal dimensions as well as nanoscale internal pattern of the soot primary particles show that precursor-like, small soot particles with amorphous internal carbon layer structures form in the flame–wall impingement region, which grow in size and become large soot aggregates as travelling along the bowl wall. The detailed analysis clearly indicates that the soot precursors underwent the surface growth, aggregation and coagulation to produce large, long-stretched soot aggregates during which the amorphous soot carbon layers transformed into a typical core–shell structure. At further downstream locations, the continued surface growth increases the size of soot primary particles in the core region of the soot aggregates while the oxidation of the soot primary particles located in the outer region tends to reduce the aggregate size, resulting in more compact structures. In the outer region of the flame, the intensive soot oxidation induced by the hydroxyl attack further reduces the size of large soot aggregates and at the same time, eliminates the small soot aggregates. Throughout these soot formation/oxidation processes, the soot carbon layer gaps continue to decrease, indicating more mature soot primary particles.

Conventional food fermentation is time-consuming, and maturation of fermented foods normally requires a huge space for long-term storage. Ultrasound is a technology that emerged in the food industry to improve the efficacy of food fermentation and presents great potentials in maturation of fermented foods to produce fermented foods with high quality. Proliferation of microorganisms was observed along with promoted enzyme activities and metabolic performance when treated by a short-term ultrasonication (

The development of multi-target-directed ligands (MTDLs) may improve complex central nervous system diseases such as Alzheimer's disease (AD). Here, a series of 7-O-1, 2, 3-triazole hesperetin derivatives was evaluated for their inhibition of cholinesterase, anti-neuroinflammatory, and neuroprotective activity. Among the hesperetin derivatives, compound a8 (7-O-((1-(3-chlorobenzyl)-1H-1,2,3-triazol-4-yl)methyl)hesperetin) possessed excellent anti-butyrylcholinesterase activity (IC50 = 3.08 ± 0.29 μM) and exhibited good anti-neuroinflammatory activity (IC50 = 2.91 ± 0.47 μM) against NO production through remarkably blocking the NF-κB signaling pathway and inhibiting the phosphorylation of P65. In addition, a8 showed a remarkable neuroprotective effect and lacked neurotoxicity up to 50 μM concentration. Furthermore, possessing significant self-mediated Aβ1-42 aggregation inhibitory activity, chelated biometals and reduced ROS production were found in compound a8. In the bi-directional transport assay, a8 exhibited a blood–brain barrier penetrating ability. In this study, the Morris water maze task showed that compound a8 significantly improved the learning and memory impairment of the scopolamine-induced AD mice model. Results highlighted the potential of compound a8 to be a potential MTDL for the development of anti-AD agents.

Coal spontaneous combustion has always been a global catastrophe, which threatens valuable coal resources, human safety and health, and the environment. The key to preventing coal spontaneous combustion is early monitoring at the low-temperature oxidation stage of coal. The terahertz dielectric property measurement system and machine learning algorithms were used to test the feasibility of a non-contact real-time fast discrimination of oxidized coal from its unoxidized counterparts. Logistic regression analysis (LRA), Support vector machines (SVM), and random forest (RF) models were applied to classify coals based on oxidation degree. The results proved that differences of dielectric properties at terahertz band between unoxidized and oxidized coals did exist. The best classification result with an accuracy of 87.50% in the prediction set was achieved using the SVM method based on Gaussian kernel function combined with low-frequency (75-110 GHz) terahertz spectrum of the imaginary part of dielectric constant. The results prove that terahertz dielectric constant spectrum, combined with machine learning algorithms, would be a promising technique to monitor coal spontaneous combustion with high efficiency.

Three custom-made jet fuels with cetane numbers 30, 40 and 51 are investigated in an optically accessible small-bore compression-ignition engine. The low-temperature and high-temperature reactions are visualised using planar laser-induced fluorescence imaging of formaldehyde (HCHO-PLIF) and hydroxyl radicals (OH-PLIF) and is complemented with high-speed, line-of-sight integrated signal imaging of cool-flame and OH* chemiluminescence. For soot measurements, planar laser-induced incandescence (soot-PLII) imaging is performed. The cool-flame chemiluminescence and HCHO-PLIF images show that the low-temperature reaction develops quicker and covers a larger area in the combustion chamber for higher cetane number fuels. Also, the OH* chemiluminescence and OH-PLIF images indicate the transition from low-temperature reaction to high-temperature reaction occurs faster in both spatial distribution/concentration and temporal evolution, indicating the predominant effect of higher fuel reactivity despite lower charge premixing. The results obtained for single injection conditions are extended to pilot-main injection conditions in an attempt to further reduce the charge premixing to the level that its impact becomes measurable. Indeed, the significantly reduced charge premixing condition induces lower HCHO-PLIF and OH-PLIF for CN50 than those of CN40 while the soot-PLII is most intense. The CN30 exhibits the lowest soot-PLII than the other two fuels due to the enhanced charge premixing but the OH-PLIF signals are weaker due to the lower fuel reactivity. This study successfully identifies the important trade-off characteristics between fuel reactivity and charge premixing among the tested fuels and given injection conditions, CN40 shows the most optimised performance with the strong high-temperature reaction and low remaining in-cylinder soot.

Oxygenated biodiesel presents lower sooting propensity than conventional diesel, providing a good opportunity to resolve the high particulate emissions issue. This study reports soot morphology details of methyl decanoate, a selected surrogate fuel for the larger fatty acid methyl esters in biodiesel. The size distribution of soot primary particles and aggregates as well as the fractal dimension of the aggregates are discussed in comparison to those of a conventional diesel fuel. In addition, nanoscale soot parameters such as carbon fringe length, tortuosity, and fringe-to-fringe separation distance are analysed to clarify the internal structure variations depending on the fuel type. Of particular interest are the structures of soot particles within the flame in a running diesel engine. Compared with numerous previous studies reporting exhaust soot particle structures of biodiesel, the present study provides additional and complementary information about soot particles under high formation and oxidation processes during the main combustion event. Thermophoresis-based soot particles collection was conducted in a small-bore optical diesel engine using a sampling probe placed within the combustion chamber for the direct exposure of a transmission electron microscope (TEM) grid to sooting flames. The TEM images were post-processed for statistical analysis of the aforementioned morphology and nanostructure parameters. The results show that methyl decanoate generates smaller soot primary particles and aggregates with lower fractal dimension, which could be explained either by the earlier stage of soot formation or more oxidised soot status. From the fringe separation results showing a smaller gap for methyl decanoate, it is concluded that the sampled in-flame soot particles were more oxidised likely due to the presence of oxidisers in fuel.

The variations in soot particle morphology due to jet-to-jet variations and jet–jet interactions have been investigated in a single-cylinder, optically accessible light-duty diesel engine by conducting thermophoretic particle sampling and subsequent transmission electron microscope (TEM) imaging of both in-flame and exhaust soot particles. To this end, the soot sampling experiments were conducted for three different jet configurations including two single-jets (Jet A and Jet B) and a double-jet (Jet AB however, the high jet–jet interaction at fixed injection duration conditions causes the increased number of soot particles compared with the single-jet cases, suggesting higher soot formation in the jet–jet interaction region. Both the soot aggregate and primary particle sizes of the double-jet with the fixed injection duration are lower than those of the single-jets, implying that the soot particles in the jet–jet interaction region are in the earlier stage of soot formation. The same trend is observed in the exhaust samples, albeit the differences are much less. It is likely due to the progression in soot formation/oxidation occurring inside the cylinder of the engine before the particles exit through the exhaust. Compared to marked variations in the soot particle sizes, the fractal dimension is largely unchanged due either to jet-to-jet variations or jet–jet interactions in both in-flame and exhaust soot particles.

This study presents planar laser-induced fluorescence of fuel and hydroxyl (fuel- and OH-PLIF) and incandescence of soot (soot-PLII) together with morphology and nanostructure information of soot particles sampled via thermophoresis to clarify the in-cylinder soot processes under the influence of jet to jet interactions. The experiments were carried out in a single-cylinder, small-bore optical diesel engine fuelled by a low-sooting methyl decanoate fuel for diagnostic purposes. Two different nozzle configurations of one hole and two holes were used to simulate isolated single-jet and double-jet conditions, respectively. Results show that fuel-rich mixture formed in the jet–jet interaction region causes the faster initial growth of soot that persists for a longer period of time, compared to the soot formed in the wall-impingement region of the single jet. These soot particles impacted by the jet–jet interaction have larger aggregates composed of larger primaries, and the nanoscale internal structures show higher carbon fringe-to-fringe separations, both of which indicate higher particle reactivity and the formation stage of soot.

To study the occurrence of biofouling phenomenon on heat exchanger surfaces, a new biofouling thermal resistance model for heat exchanger surface was developed. Considering the effect of microbial activity on fouling resistance, a growth term of surface biofilm was introduced into the Kern–Seaton model. The microbial growth dynamics was described by using a modified Gompertz model. The occurrence of fouling process due to iron bacteria in a tube and an alternating elliptical axis tube were considered as examples to validate the fouling model. The results showed that the relative error between the calculated data obtained from new microbial fouling resistance model and experimental data was less than 10%, in addition to the induction phase.

A series of 7-O-amide hesperetin derivatives were subjected to multi-target biological evaluation of anti-Alzheimer's disease. Most of the compounds showed good in vitro inhibitory activity against cholinesterase, of which compound 7c (7-O-(4-(morpholinoethyl)-acetamide) hesperetin) was the most effective anti-eqBuChE derivative (IC50 = 0.28 ± 0.05 μM) and exerted neuroprotective effects. Further biological evaluation found that compounds 4d, 4e and 7c showed strong antioxidant, anti-Aβ self-aggregation and anti-neuroinflammatory activities. Compound 7c could inhibit the expression of iNOS and COX-2 proteins and prevent LPS-induced inflammatory response in BV2 cells. In addition, compound 7c could chelate biometal ions such as Cu2+ and Zn2+. In the vivo study, the MWM test confirmed that compound 7c could improve the cognitive impairment caused by scopolamine. In summary, the above studies have shown that the optimized compound 7c has great development potential as MTDL for the treatment of AD.

Although As concentrations have been investigated in shallow groundwater from the Hetao basin, China, less is known about U and As distributions in deep groundwater, which would help to better understand their origins and fate controls. Two hundred and ninety-nine groundwater samples, 122 sediment samples, and 14 rock samples were taken from the northwest portion of the Hetao basin, and analyzed for geochemical parameters. Results showed contrasting distributions of groundwater U and As, with high U and low As concentrations in the alluvial fans along the basin margins, and low U and high As concentrations downgradient in the flat plain. The probable sources of both As and U in groundwater were ultimately traced to the bedrocks in the local mountains (the Langshan Mountains). Chemical weathering of U-bearing rocks (schist, phyllite, and carbonate veins) released and mobilized U as UO2(CO3)2(2-) and UO2(CO3)3(4-) species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO3(-) were favorable (OSO), resulting in high groundwater U concentrations. Conversely, the recent weathering of As-bearing rocks (schist, phyllite, and sulfides) led to the formation of As-bearing Fe(III) (hydr)oxides in sediments, resulting in low groundwater As concentrations. Arsenic mobilization and U immobilization occurred in suboxic conditions where reduction of Fe(III) oxides was favorable and reducing conditions (SOR). Reduction of As-bearing Fe(III) (hydr)oxides, which were formed during palaeo-weathering and transported and deposited as Quaternary aquifer sediments, was believed to release As into groundwater. Reduction of U(VI) to U(IV) would lead to the formation of uraninite, and therefore remove U from groundwater. We conclude that the contrasting distributions of groundwater As and U present a challenge to ensuring safe drinking water in analogous areas, especially with high background values of U and As.

We develop a fast fiber-based in situ fluorescence system for phytoplankton taxonomy. The fluorescence is excited by high power LEDs with different wavelengths through a customized fiber bundle to the place of interest. Sinusoidal-amplitude-modulation (SAM) techniques are employed. The detection time is shorten to 0.1 s because the fluorescence is excited and demodulated by different wavelengths simultaneously. The fluorescence signal is demodulated by a digital lock-in amplifier. The device is tested in Shenzhen Bay, South China Sea.

This paper reports the difference between the irreversibility and available energy loss of heat transfer process in heat exchanger. Based on the irreversibility analyzing in parallel flow and counter-flow heat exchangers, the driving force equipartition principle is derived. Then by the deduction of putting the principle in counter-flow heat exchanger, the principle application feasibility is discussed further. The results show that the changing trend of irreversibility and available energy loss are different obviously. With NTU variation, the available energy loss is declining gradually until stability while the irreversibility is increased first then reduced sharply. It is clear that process with big irreversibility is not always bad, and the available energy loss per unit heat transfer is more suitable for heat exchange criterion. Further, the heat exchangers or heat transfer process can be optimized by changing the temperature distribution.

This paper investigates how spatial distributions of groundwater arsenic (As) concentration and speciation are related to and are dependent on regional hydraulic gradients in a shallow aquifer containing elevated groundwater As in the Hetao Plain of Northern China. Groundwater samples (n = 165) were collected along three representative transects in the western, central and eastern parts of the Hetao Plain, spanning a wide range of total As concentration (0.36–916.7 μg/l), arsenite concentration (0.2–719.4 μg/l) and hydraulic gradients (0.11–23.31‰). The hydrodynamic conditions of the aquifer generally fall into the following four categories from the north to the south: Piedmont and discharge areas with high hydraulic gradient, runoff areas with weak or strong hydraulic gradient, and areas influenced by recharge from the Yellow River. Along all three transects, high groundwater As usually corresponds to low hydraulic gradients except for the discharge areas. In the runoff area in central Hetao Plain and the recharge area in southern Hetao Plain, the concentration of arsenic is more than 10 μg/l when the hydraulic gradient is less than 0.8‰. An empirical relationship between groundwater As concentration and groundwater hydraulic gradient can be established for the runoff area. The systematic changes in As concentrations and speciation along the groundwater flow path in the shallow groundwater support the notion that low hydraulic gradient of the groundwater is important in promoting As enrichment in groundwater.