Morphology,Nanostructure,and Oxidation Reactivity of Particulate Matter Emitted by Diesel Blending with Various Aromatics

This study aims to analyze the influence of the polycyclic aromatic hydrocarbon(PAH)content in diesel on the physical and chemical properties of diesel soot particles.Four diesel fuels with different PAH content were tested on a 11.6 L direct-injection diesel engine.The raw particulate matter(PM)before the after-treatment devices was collected using the thermophoresis sampling system and the filter sampling system.A transmission electron microscope and Raman spectrometer are used to analyze the physical properties of the soot particles,including morphology,primary particle size distribution,and graphitization degree.A Fourier transform infrared spectrometer and thermogravimetric analyzer are used to characterize the surface chemical composition and oxidation reactivity of soot particles,respectively.The results show that as the PAH content in the fuel decreases,the size of the primary soot particles decreases from 29.58 to 26.70 nm.The graphitization degree of soot particles first increases and then decreases,and the relative content of the aliphatic hydrocarbon functional groups of soot particles first decreases and then increases.The T_(10),T_(50),and T_(90) of soot from high-PAH fuel are 505.3,589.3,and 623.5℃,while those from low-PAH fuel are 480.1,557.5,and 599.2℃,respectively.This indicates that exhaust PM generated by the low-PAH fuel has poor oxidation reactivity.However,as the PAH content in fuel is further decreased,the excessively high cetane number may cause uneven mixing and incomplete combustion,leading to enhanced oxidation reactivity.

Experimental investigation into the oxidation reactivity,morphology and graphitization of soot particles from diesel/n-octanol mixtures

Aiming to investigate the impacts of n-octanol addition on the oxidation reactivity,morphology and graphitization of diesel exhaust particles,soot samples were collected from a four-cylinder turbocharged diesel engine fueled with D100(neat diesel fuel),DO15(85%diesel and 15%n-octanol,V/V)and DO30(70%diesel and 30%n-octanol,V/V).All tests were conducted at two engine speeds of 1370 and 2150 r/min under a fixed torque of 125 N·m.The soot properties were characterized by thermogravimetric analyzer(TGA),transmission electron microscopy(TEM)and Raman spectroscopy(RS).The higher volatile organic fraction content,lower soot oxidation temperatures and lower activation energy from TGA results indicated that both the increasing n-octanol concentration and engine speed enhanced the soot oxidation reactivity.Additionally,quantitative analysis of TEM images showed that the soot derived from DO30 had the smallest primary particle diameters and fractal dimension,followed by those of soot produced by DO15 and D100.The RS results demonstrated that the n-octanol addition and higher engine speed led to a larger D1-FWHM(D1-full width at half maximum),A_(D1)/A_(T)(area ratio of D1 band and the total spectral)and A_(D3)/A_(T)(area ratio of D3 band and the total spectral)as well as a smaller L_(a)(crystallite width),revealing a lower degree of graphitization.Furthermore,the correlations between characterization parameters of soot properties and reactivity were nonlinear.

Comparative Study on Soot Reduction, Soot Nanostructure and Oxidation Reactivity of n-heptane/DMC and Isooctane/DMC Inverse Diffusion Flames

Dimethyl carbonate(DMC)is an environmentally oxygenated compound which can be used efficiently for soot reduction.This paper compared the soot reduction,soot nanostructure and oxidation reactivity from inverse diffusion flames(IDFs)of the hydrocarbon fuels,namely n-heptane and isooctane doped with DMC.Effects of DMC additions on soot reduction were discussed.DMC addition is more effective for the soot reduction of n-heptane/DMC IDF than isooctane/DMC IDF.The morphology and nanostructures of soot particles were investigated by Transmission Electron Microscopy(TEM)and High Resolution TEM(HRTEM),and the soot graphitization and oxidation reactivity were analyzed by X-ray Diflfraction(XRD)and Thermogravimetric Analyzer(TGA),respectively.The results of HRTEM images showed that many larger aggregates were observed for the structures of soot particles from IDFs with DMC additions.The soot particles exhibited more liquid-like material,more amorphous,higher disorganized layers,and less graphitic than that of IDFs without DMC additions.With increasing of DMC blending rate,soot particles changed younger to have shorter fringe length,higher tortuosity,and greater fringe separation.Based on the XRD and TGA results,the degree of the soot graphitization level decreased;the soot mass lost significantly faster,and the soot become more reactive.

Impact of microplastics and nanoplastics on liver health:Current understanding and future research directions

With continuous population and economic growth in the 21st century,plastic pollution is a major global issue.However,the health concern of microplastics/nanoplastics(MPs/NPs)decomposed from plastic wastes has drawn public attention only in the recent decade.This article summarizes recent works dedicated to understanding the impact of MPs/NPs on the liver-the largest digestive organ,which is one of the primary routes that MPs/NPs enter human bodies.The interrelated mechanisms including oxidative stress,hepatocyte energy re-distribution,cell death and autophagy,as well as immune responses and inflammation,were also featured.In addition,the disturbance of microbiome and gut-liver axis,and the association with clinical diseases such as metabolic dysfunction-associated fatty liver disease,steatohepatitis,liver fibrosis,and cirrhosis were briefly discussed.Finally,we discussed potential directions in regard to this trending topic,highlighted current challenges in research,and proposed possible solutions.

Reactive oxygen species, nitric oxide and plant cell death associated with caspase-like protease activity during somatic embryogenesis in Fraxinus mandshurica

Programmed cell death occurs in browning explants of Fraxinus mandshurica during somatic embryogenesis, but the underlying mechanism is unclear. In this study, single cotyledons of zygotic embryos of F. mandshurica were used as explants. Mitochondrial structure and function, caspase-3-like protease activity, hydrogen peroxide metabolism, and nitric oxide accumulation induced by high concentrations of sucrose and plant growth regulators were studied. The results show that plant growth regulators induced somatic embryogenesis and also promoted explant browning. High sucrose concentrations had similar effects. High concentrations of sucrose and plant growth regulators led to the accumulation of hydrogen peroxide and nitric oxide which induced changes in mitochondrial structure and function such as modifications in mitochondrial morphology, increased membrane permeability, decreased membrane potential, and the release of cytochrome c into the cytoplasm. An increase in caspase-3-like protease activity triggered programmed cell death in some browning explant cells. During somatic embryogenesis there were increased activities of superoxide dismutase, peroxidase, and catalase, which are associated with hydrogen peroxide metabolism and jointly maintain reactive oxygen species levels. Intracellular nitric oxide synthase and nitrate reductase activities were not significantly correlated with nitric oxide content. Instead, intracellular nitric oxide may be derived from non-enzymatic reactions. Our results indicate that hydrogen peroxide and nitric oxide may function as signals, playing key roles in somatic embryogenesis and programmed cell death of explant cells of F. mandshurica. The interaction between nitric oxide and reactive oxygen species determines the occurrence of programmed cell death in explant cells;somatic embryogenesis and programmed cell death are positively regulated by hydrogen peroxide. However, the regulation of nitric oxide is complex.

Carbon-based single-atom catalysts in advanced oxidation reactions for water remediation:From materials to reaction pathways

Single-atom catalysts(SACs)have been widely recognized as state-of-the-art catalysts in environment remediation because of their exceptional performance,100%metal atomic utilization,almost no secondary pollution,and robust structures.Most recently,the activation of persulfate with carbon-based SACs in advanced oxidation processes(AOPs)raises tremendous interest in the degradation of emerging contaminants in wastewater,owning to its efficient and versatile reactive oxidant species(ROS)generation.However,the comprehensive and critical review unraveling the underlying relationship between structures of carbon-based SACs and the corresponding generated ROS is still rare.Herein,we systematically summarize the fundamental understandings and intrinsic mechanisms between single metal atom active sites and produced ROS during AOPs.The types of emerging contaminants are firstly elaborated,presenting the prior pollutants that need to be degraded.Then,the preparation and characterization methods of carbon-based SACs are overviewed.The underlying material structure–ROS type relationship in persulfate-based AOPs is discussed in depth to expound the catalytic mechanisms.Finally,we briefly conclude the current development of carbon-based SACs in AOPs and propose the prospects for rational design and synthesis of carbon-based SACs with on-demand catalytic performances in AOPs in future research.

Comparing dark-and photo-Fenton-like degradation of emerging pollutant over photo-switchable Bi2WO6/CuFe2O4: Investigation on dominant reactive oxidation species

The extensive use of tetracycline hydrochloride(TCH)poses a threat to human health and the aquatic environment.Here,magnetic p-n Bi2WO6/CuFe2O4 catalyst was fabricated to efficiently remove TCH.The obtained Bi2WO6/CuFe2O4 exhibited 92.1%TCH degradation efficiency and 50.7%and 35.1%mineralization performance for TCH and raw secondary effluent from a wastewater treatment plant in a photo-Fenton-like system,respectively.The remarkable performance was attributed to the fact that photogenerated electrons accelerated the Fe(III)/Fe(II)and Cu(II)/Cu(I)conversion for the Fenton-like reaction between Fe(II)/Cu(I)and H2O2,thereby generating abundant·OH for pollutant oxidation.Various environmental factors including H2O2 concentration,initial pH,catalyst dosage,TCH concentration and inorganic ions were explored.The reactive oxidation species(ROS)quenching results and electron spin resonance(ESR)spectra confirmed that·O2-and·OH were responsible for the dark and photo-Fenton-like systems,respectively.The degradation mechanisms and pathways of TCH were proposed,and the toxicity of products was evaluated.This work contributes a highly efficient and environmentally friendly catalyst and provides a clear mechanistic explanation for the removal of antibiotic pollutants in environmental remediation.

BaTiO_(3)@Au nanoheterostructure suppresses triple-negative breast cancer by persistently disrupting mitochondrial energy metabolism

Abnormal metabolism has become a potential target for highly malignant and invasive triple-negative breast cancer(TNBC)due to its relatively low response to traditional therapeutics.The existing metabolic interventions demonstrated unsatisfactory therapeutic outcomes and potential systemic toxicity,resulting from the metabolic instability and limited targeting ability of inhibitors as well as complex tumor microenvironment.To address these limitations,here we developed a robust pyroelectric BaTiO_(3)@Au core–shell nanostructure(BTO@Au)to selectively and persistently block energy generation of tumor cells.Stimulated by near-infrared(NIR)laser,the Au shell could generate heat to activate the BaTiO_(3)core to produce reactive oxygen species(ROS)regardless of the constrained microenvironment,thus prominently inhibits mitochondrial oxidative phosphorylation(OXPHOS)and reduces ATP production to induce TNBC cell apoptosis.The therapeutic effects have been well demonstrated in vitro and in vivo,paving a new way for the development of metabolic interventions.

Revisiting the contribution of Fe^(Ⅳ)O^(2+)in Fe(Ⅱ)/peroxydisulfate system

Recent studies have proposed that the high-valent iron species(such as Fe^(Ⅳ)O^(2+))rather than sulfate radical(SO_(4)^(·-))and hydroxyl radical(·OH)are the main reactive oxidant species(ROS)in Fe(Ⅱ)/peroxydisulfate(PDS)system with the methyl phenyl sulfoxide(PMSO)as the Fe^(Ⅳ)O^(2+)probe.However,many operational factors may interfere with the accuracy of this method,so the contribution of Fe^(Ⅳ)O^(2+)calculated by this method is controversial.In this study,the possible effect of Fe(Ⅱ)concentration,pollutant type,reducing agent,or coexisted anions on Fe^(Ⅳ)O^(2+)production and its corresponding contribution to the removal of target pollutants in the Fe(Ⅱ)/PDS system were investigated in detail,and the intrinsic mechanisms involved were also explored.This study shows that ROS generation is a complex process in the Fe(Ⅱ)/PDS system,and multiple combinatorial approaches are urgently required to deeply explore the contribution of ROS to the elimination of target contaminants.

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis of MAFLD

The pathogenesis of metabolic-associated fatty liver disease(MAFLD)is complex and thought to be dependent on multiple parallel hits on a background of genetic susceptibility.The evidence suggests that MAFLD progression is a dynamic two-way process relating to repetitive bouts of metabolic stress and inflammation interspersed with endogenous anti-inflammatory reparative responses.In MAFLD,excessive hepatic lipid accumulation causes the production of lipotoxins that induce mitochondrial dysfunction,endoplasmic reticular stress,and over production of reactive oxygen species(ROS).Models of MAFLD show marked disruption of mitochondrial function and reduced oxidative capacitance with impact on cellular processes including mitophagy,oxidative phosphorylation,and mitochondrial biogenesis.In excess,ROS modify insulin and innate immune signaling and alter the expression and activity of essential enzymes involved in lipid homeostasis.ROS can also cause direct damage to intracellular structures causing hepatocyte injury and death.In select cases,the use of anti-oxidants and ROS scavengers have been shown to diminish the proapoptopic effects of fatty acids.Given this link,endogenous anti-oxidant pathways have been a target of interest,with Nrf2 activation showing a reduction in oxidative stress and inflammation in models of MAFLD.Thyroid hormone receptorβ(THRβ)agonists and nuclear peroxisome proliferationactivated receptor(PPAR)family have also gained interest in reducing hepatic lipotoxicity and restoring hepatic function in models of MAFLD.Unfortunately,the true interplay between the clinical and molecular components of MAFLD progression remain only partly understood.Most recently,multiomics-based strategies are being adopted for hypothesis-free analysis of the molecular changes in MAFLD.Transcriptome profiling maps the unique genotype-phenotype associations in MAFLD and with various single-cell tran scriptome-based projects underway,there is hope of novel physiological insights to MAFLD progression and uncover therapeutic targets.

Exposure to perfluorooctane sulfonate reduced cell viability and insulin release capacity of β cells

Per-and polyfluoroalkyl substances(PFAS)are found to have multiple adverse outcomes on human health.Recently,epidemiological and toxicological studies showed that exposure to PFAS had adverse impacts on pancreas and showed association with insulin abnormalities.To explore how PFAS may contribute to diabetes,we studied impacts of perfluorooctane sul-fonate(PFOS)on cell viability and insulin release capacity of pancreatic β cells by using in vivo and in vitro methods.We found that 28-day administration with PFOS(10 mg/(kg body weight·day))caused reductions of pancreas weight and islet size in male mice.PFOS admin-istration also led to lower serum insulin level both in fasting state and after glucose infusion among male mice.For cell-based in vitro bioassay,we used mouse β-TC-6 cancer cells and found 48-hr exposure to PFOS decreased the cell viability at 50 μmol/L.By measuring insulin content in supernatant,48-hr pretreatment of PFOS(100 μmol/L)decreased the insulin re-lease capacity of β-TC-6 cells after glucose stimulation.Although these concentrations were higher than the environmental concentration of PFOS,it might be reasonable for high con-centration of PFOS to exert observable toxic effects in mice considering mice had a faster removal efficiency of PFOS than human.PFOS exposure(50 μmol/L)to β-TC-6 cells induced intracellular accumulation of reactive oxidative specie(ROS).Excessive ROS induced the re-active toxicity of cells,which eventually invoke apoptosis and necrosis.Results in this study provide evidence for the possible causal link of exposure to PFOS and diabetes risk.

A comparative study to evaluate the effect of limited access dressing on diabetic ulcers

Aim:Emerging evidence favors the important role of antioxidants,matrix metalloproteinases(MMPs),and nitric oxide(NO)in the healing of diabetic wounds.There is a lack of substantial evidence regarding the effects of negative pressure on antioxidants,MMPs and NO in chronic wounds associated with diabetes.Methods:A total of 55 type 2 diabetic patients with leg ulcers were divided into 2 groups:a limited access dressing(LAD)group(n=27)and a conventional dressing group(n=28).Levels of hydroxyproline,total protein,MMP-2 and MMP-9,NO and antioxidants including reduced glutathione(GSH)and the oxidative biomarker malondialdehyde(MDA)were measured in the granulation tissue at days 0 and 10.Changes in levels between the LAD and conventional groups were determined by the Student’s t-test.Results:After 10 days of treatment,the LAD vs.conventional dressing group showed increase in the levels of hydroxyproline(mean±standard deviation=55.2±25.1 vs.29.2±1,P<0.05),total protein(12.8±6.5 vs.8.34±3.2,P<0.05),NO(1.13±0.52 vs.0.66±0.43,P<0.05),GSH(7.0±2.4 vs.6.6±2.2,P<0.05)and decrease in MMP-2(0.47±0.33 vs.0.62±0.30,P<0.05),MMP-9(0.32±0.20 vs.0.53±0.39,P<0.05)and MDA(6.8±2.3 vs.10.4±3.4,P<0.05).Conclusion:When compared to conventional dressings,LAD induces biochemical changes by significantly increasing the levels of hydroxyproline,total protein,NO and antioxidants levels,and significantly reducing MMPs(MMP-2 and MMP-9)and an oxidative biomarker in diabetic wounds.These biochemical changes are thought to favor diabetic wound healing.