Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as ...Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.展开更多
Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device perform...Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.展开更多
Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucle...Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucleosides,free amino acids and water-soluble low molecular weight peptides were determined using Qingyuan partridge yellow-feathered broilers as material during 0-4℃ post-mortem aging in 48 h.The results showed that the pH value fell to the limit pH 5.64(4 h)in chicken breast and 6.21(3 h)in thigh.Regardless of chicken breast or thigh,ATP dropped rapidly within 3 h.It was found that the K-value in chicken thigh was the lowest at 2 h indicating the freshness was the best.Considering the equivalent umami concentration(EUC),the value at 3 h and 4 h was relatively high,but the corresponding electronic tongue umami value was not high,which further showed that the water-soluble low molecular taste peptide played an important role on the post-mortem aging process.Combined with cluster analysis and partial least squares discriminant analysis(PLS-DA),it was preliminarily inferred that the optimal time for chilled chicken during 0-4℃ post-mortem aging was 2 h,which could provide a theoretical basis for the further processing of fresh chicken.展开更多
This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the pe...This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.展开更多
We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a p...We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.展开更多
Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of d...Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of diffuse repigmentation on the whole vitiligo surface remains still unknown. In addition to the presence of remaining melanocytes, it is conceivable that dermal melanocyte precursor cells contribute to induce diffuse repigmentation after treatment. Therefore, we investigated here whether dermal and follicular melanocyte precursor cells were reduced or not in vitiligo lesions. We performed an immunostaining for Nestin and p75NGFR as dermal melanocyte precursor cells and MITF/Fzd4 as follicular melanocyte precursor cells and compared the positive cells number between lesions and non-lesions (n = 11). Although MITF<sup>+</sup>/Fzd4<sup>+</sup> cells in the hair follicle were significantly decreased in number in the lesions, Nestin<sup>+</sup> and p75NGFR<sup>+</sup> cells were not. This result indicates that dermal precursor cells could be retained in the vitiligo lesions but be disturbed to differentiate into matured melanocytes.展开更多
[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide...[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide references for the improvement of artificial cultivated A. lancea quality. [Method] Three precursors were added into the MS rooting medium for A. lancea tissue culture plantlets and the volatile oil was extracted by ultrasonication after cultured for several days. The content of atractylon, atractylol, β-eucalyptol and atractydin in the volatile oil were determined by using gas chromatography method. [Result] The addition of xylose, isoprene and tetrahydrofuran impacted the growth indicators, yield of volatile oil and relative percentage content of the four constituents of A. lancea tissue culture plantlets. In the 6 g/L xylose optimized medium, the atractylon and β-eucalyptol content reached up to 4.23% and 56.34%, respectively, 1.41% and 1.66% higher than the control; although the addition of isoprene into medium raised the atractylon content, the accumulation of total volatile oil was inhibited that it decreased by 23.67%, 31.06% and 7.10% to the control; for the tetrahydrofuran optimized medium, the content of atractylon, atractylol and atractydin all increased, and the total volatile oil content increased by 49.97% to the control when the concentration of tetrahydrofuran was 0.07 g/L. [Conclusion] The addition of xylose and tetrahydrofuran promoted the accumulation of principal constituents of the volatile oil, whereas the addition of isoprene inhibited the accumulation.展开更多
Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduct...Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduction(SCR)of NO by NH3across a low reaction temperature window of50–350°C.In this study,the catalysts were characterized using N2adsorption/desorption,X‐ray diffraction,X‐ray fluorescence,H2temperature‐programmed reduction,NH3temperature‐programmed desorption and X‐ray photoelectron spectroscopy.As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2in addition to the presence of low levels of crystalline Mn3O4,which resulted in poor catalytic performance.However,the manganese nitrate precursor formed crystalline MnO2as the major phase in addition to a minor presence of unconverted Mn‐nitrate.Furthermore,manganese acetate resulted principally in a mixture of amorphous Mn2O3and MnO2,and crystalline Mn3O4.From all the catalysts screened,the test performance data showed Mn/beta‐Ac to exhibit the highest NO conversion(97.5%)at240°C,which remained>90%across a temperature window of220–350°C.The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx(Mn2O3and MnO2)species that act as the active phase in the NH3‐SCR process.Furthermore,together with a suitable amount of weakly acidic centers,higher concentration of surface manganese and a greater presence of surface labile oxygen groups,SCR performance was collectively enhanced at low temperature.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.展开更多
This study uses the WRF-Chem model combined with the empirical kinetic modeling method(EKMA curve)to study the compound pollution event in Beijing that happened in 13−23 May 2017.Sensitivity tests are conducted to ana...This study uses the WRF-Chem model combined with the empirical kinetic modeling method(EKMA curve)to study the compound pollution event in Beijing that happened in 13−23 May 2017.Sensitivity tests are conducted to analyze ozone sensitivity to its precursors,and to develop emission reduction measures.The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze.When VOCs and NOx were reduced by the same proportion,the effect of O_(3)reduction at peak time was more obvious,and the effect during daytime was more significant than at night.The degree of change in ozone was peak time>daytime average.When reducing or increasing the ratio of precursors by 25%at the same time,the effect of reducing 25%VOCs on the average ozone concentration reduction was most significant.The degree of change in ozone decreased with increasing altitude,the location of the ozone maximum change shifted westward,and its range narrowed.As the altitude increases,the VOCs-limited zone decreases,VOCs sensitivity decreases,NOx sensitivity increases.The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited.Upon examining the EKMA curve,we have found that suburban and urban are sensitive to VOCs.The sensitivity tests indicate that when VOCs in suburban are reduced about 60%,the O_(3)-1h concentration could reach the standard,and when VOCs of the urban decreased by about 50%,the O_(3)-1h concentration could reach the standard.Thus,these findings could provide references for the control of compound air pollution in Beijing.展开更多
Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning e...Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.展开更多
Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the n...Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.展开更多
The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate p...The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate precursors in H_2S/H_2 stream at different temperatures were studied by X-ray photoelectron spectroscopy(XPS) and high-resolution transmission electron microscopy(HRTEM). The organic molybdate precursors lead to MoS_2 catalysts with higher sulfidation degree and smaller active phases to demonstrate higher catalytic activity during hydrodesulfurizaiton(HDS) of 4,6-DMDBT.展开更多
This paper reports the chemical synthesis of tungsten carbide/cobalt (WC/Co) nanocomposite powders via a unique chemical processing technique, involving the using of all water soluble solution of W-, Co- and C-precurs...This paper reports the chemical synthesis of tungsten carbide/cobalt (WC/Co) nanocomposite powders via a unique chemical processing technique, involving the using of all water soluble solution of W-, Co- and C-precursors. In the actual synthesis, large quantities of commercial-scale WC-Co nanocomposite powders are made by an unique combination of converting a molecularly mixed W-, Co-, and C-containing solutions into a complex inorganic polymeric powder precursor, conversion of the inorganic polymeric precursor powder into a W-Co-C-O containing powder intermediates using a belt furnace with temperature at about 500°C - 600°C in an inert atmosphere, followed by carburization in a rotary furnace at temperature less than 1000°C in nitrogen. Liquid phase sintering technique is used to consolidate the WC/Co nanocomposite powder into sintered bulk parts. The sintered parts have excellent hardness in excess of 93 HRA, with WC grains in the order of 200 - 300 nm, while Co phase is uniformly distributed on the grain boundaries of the WC nanoparticles. We also report the presence of cobalt Co precipitates inside tungsten carbide WC nanograins in the composites of the consolidated bulk parts. EDS is used to identify the presence of these precipitates and micro-micro-diffraction technique is employed to determine the nature of these precipitates.展开更多
It has been primarily confirmed that before the occurrence of a middle or major earthquake, anomalies in the residuals of universal time and latitude measurements obtained by astrometric observations may appear. We in...It has been primarily confirmed that before the occurrence of a middle or major earthquake, anomalies in the residuals of universal time and latitude measurements obtained by astrometric observations may appear. We investigate the relation between the residual anomalies and the three key factors of an earthquake. To build a network of observational sites so as to obtain data of residuals of universal time and latitude from multi-instruments would be of certain significance for determining three key factors of an earthquake, especially for positioning epicenter. The data from multi-instruments would also be valuable for studies of the variation of the vertical. It is proposed to manufacture potable and high-accuracy astrometric instruments and to build observational network to obtain anomalies of universal time and latitude in the regions with high earthquake uprising possibilities.展开更多
The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were ...The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species in the solutions were confirmed by laser Raman spectroscopy(LRS). The UV-Vis spectra results indicated that the solutions containing both phosphoric acid and citric acid could change the existing form of nickel species. Five corresponding Ni Mo/Al_2O_3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulfided and characterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of(Ni)Mo S2 slabs and the promoting effect of Ni species. The catalyst prepared mainly with [P2Mo5O23]^(6-)-like species used as precursors exhibited worse dispersion of(Ni)Mo S2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]^(4-)-like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species showed better hydrodesulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.展开更多
In this paper, we find the optimal precursors which can cause double-gyre regime transitions based on conditional nonlinear optimal perturbation (CNOP) method with Regional Ocean Modeling System (ROMS). Firstly, we si...In this paper, we find the optimal precursors which can cause double-gyre regime transitions based on conditional nonlinear optimal perturbation (CNOP) method with Regional Ocean Modeling System (ROMS). Firstly, we simulate the multiple-equilibria regimes of double-gyre circulation under different viscosity coefficient and obtain the bifurcation diagram, then choose two equilibrium states (called jet-up state and jet-down state) as reference states respectively, propose Principal Component Analysis-based Simulated Annealing (PCASA) algorithm to solve CNOP-type initial perturbations which can induce double-gyre regime transitions between jet-up state and jet-down state. PCASA algorithm is an adjoint-free method which searches optimal solution randomly in the whole solution space. In addition, we investigate CNOP-type initial perturbations how to evolve with time. The results show:(1) the CNOP-type perturbations present a two-cell structure, and gradually evolves into a three-cell structure at predictive time;(2) by superimposing CNOP-type perturbations on the jet-up state and integrating ROMS, double-gyre circulation transfers from jet-up state to jet-down state, and vice versa, and random initial perturbations don't cause the transitions, which means CNOP-type perturbations are the optimal precursors of double-gyre regime transitions;(3) by analyzing the transition process of double-gyre regime transitions, we find that CNOP-type initial perturbations obtain energy from the background state through both barotropic and baroclinic instabilities, and barotropic instability contributes more significantly to the fast-growth of the perturbations. The optimal precursors and the dynamic mechanism of double-gyre regime transitions revealed in this paper have an important significance to enhance the predictability of double-gyre circulation.展开更多
CO2-TPD was demonstrated an effective way to investigate the phase formation during pyrolysis for the preparation of composite oxides using metal-organic molecules as precursors.Based on the CO2-TPD results, it was f...CO2-TPD was demonstrated an effective way to investigate the phase formation during pyrolysis for the preparation of composite oxides using metal-organic molecules as precursors.Based on the CO2-TPD results, it was found that calcination condition had deep effect on the carbonate formation and the minimum firing temperature to acquire pure phase composite oxide.An optimized calcination schedule was then developed.展开更多
Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on st...Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on structure and performance of iron molybdate catalyst prepared by mechanochemical route, three typical and cheap iron precursors have been used in preparation of iron molybdate catalyst. Many characterization methods have been employed to obtain the physical and chemical properties of iron molybdate catalyst. Results indicate that iron precursors have the significant impact on the phase composition, crystal morphology and catalytic performance in the conversion of methanol to formaldehyde. It is hard to regulate the phase composition by changing Mo/Fe mole ratios for Fe2(SO4)3 as iron precursor. In addition, as for Fe2(SO4)3, the formaldehyde yield is lower than that from iron molybdate catalyst prepared with Fe(NO3)3·9H2O due to the reduction in Fe2(MoO4)3 phase as active phase. Based on mechanochemical and coprecipitation method, the solvent water could be a key factor for the formation of MoO3 and Fe2(MoO4) for FeCl3·6H2O and Fe2(SO4)3 as precursors. Iron molybdate catalyst prepared with Fe(NO3)3·9H2O by mechanochemical route, shows the best methanol conversion and formaldehyde yield in this reaction.展开更多
In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing...In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing time , and so on . The best conditions in this research are : the concentration of Na2SiO3 and organic matters are 4. 50% and 26.4% respectively, pH = 3.3 , T = 65℃ , ageing time is 30min , dried at 150 ℃ , the size of SiC precursors is about 2.0μm .展开更多
Advanced glycation end products(AGEs)might pose health risks,and processing and storage could accelerate the generation of AGEs in meat.However,limited few reports indicated the changes of AGEs contents in meat during...Advanced glycation end products(AGEs)might pose health risks,and processing and storage could accelerate the generation of AGEs in meat.However,limited few reports indicated the changes of AGEs contents in meat during storage.In this study,the aim is to investigate the oxidation and precursors and their roles in the formation of N^(ε)-carboxymethyl-lysine(CML)in raw and cooked chicken meat after post-mortem ageing and storage.As post-mortem ageing and storage time increased,the CML content in cooked chicken breast significantly increased from 1.81 mg/kg to 2.00 mg/kg during 0-6 h,and then decreased from 2.00 mg/kg to 1.80 mg/kg during 6 h-1 day,finally increased again during 1-7 days,while the CML contents of raw and cooked leg significantly and continuously increased from 1.78 mg/kg to 2.08 mg/kg.Furthermore,CML was extremely positively correlated with fat oxidation(R^(2)=0.793,P<0.01),protein oxidation(R^(2)=0.917,P<0.01)and glyoxal(R^(2)=0.678,P<0.05),and was negatively correlated with lysine(R^(2)=0.536,P<0.05).No significant correlation was observed between the Schiff base and CML.展开更多
基金supported by the National Natural Science Foundation of China(52325001,52170009,and 52091542)the National Key Research and Development Program of China(2021YFC3200700)+3 种基金the Program of Shanghai Academic Research Leader,China(21XD1424000)the International Cooperation Project of Shanghai Science and Technology Commission(20230714100)the Key-Area Research and Development Program of Guangdong Province(2020B1111350001)Tongji University Youth 100 Program.
文摘Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.
基金financial support from the National Natural Science Foundation of China(grant nos.52172198,51902117,and 91733301)。
文摘Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.
基金supported by China Agriculture Research System of MOF and MARA (CARS-41)Wens Fifth Five R&D Major Project (WENS-2020-1-ZDZX-007)
文摘Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucleosides,free amino acids and water-soluble low molecular weight peptides were determined using Qingyuan partridge yellow-feathered broilers as material during 0-4℃ post-mortem aging in 48 h.The results showed that the pH value fell to the limit pH 5.64(4 h)in chicken breast and 6.21(3 h)in thigh.Regardless of chicken breast or thigh,ATP dropped rapidly within 3 h.It was found that the K-value in chicken thigh was the lowest at 2 h indicating the freshness was the best.Considering the equivalent umami concentration(EUC),the value at 3 h and 4 h was relatively high,but the corresponding electronic tongue umami value was not high,which further showed that the water-soluble low molecular taste peptide played an important role on the post-mortem aging process.Combined with cluster analysis and partial least squares discriminant analysis(PLS-DA),it was preliminarily inferred that the optimal time for chilled chicken during 0-4℃ post-mortem aging was 2 h,which could provide a theoretical basis for the further processing of fresh chicken.
基金supported by the National Natural Science Foundation of China (42030202)。
文摘This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.
文摘We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.
文摘Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of diffuse repigmentation on the whole vitiligo surface remains still unknown. In addition to the presence of remaining melanocytes, it is conceivable that dermal melanocyte precursor cells contribute to induce diffuse repigmentation after treatment. Therefore, we investigated here whether dermal and follicular melanocyte precursor cells were reduced or not in vitiligo lesions. We performed an immunostaining for Nestin and p75NGFR as dermal melanocyte precursor cells and MITF/Fzd4 as follicular melanocyte precursor cells and compared the positive cells number between lesions and non-lesions (n = 11). Although MITF<sup>+</sup>/Fzd4<sup>+</sup> cells in the hair follicle were significantly decreased in number in the lesions, Nestin<sup>+</sup> and p75NGFR<sup>+</sup> cells were not. This result indicates that dermal precursor cells could be retained in the vitiligo lesions but be disturbed to differentiate into matured melanocytes.
基金Supported by the National Natural Science Foundation of China(31070443)the National Science Foundation of China for Talent Training in Basic Research(J1103507)+1 种基金The Priority Academic Program Development of Jiangsu Higher Education Institutions,Innovation Promotion Project of Nanjing Municipal Science and Technology Commissions(201105058)the Practice and Innovation Training Program for the Students of Nanjing Normal University~~
文摘[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide references for the improvement of artificial cultivated A. lancea quality. [Method] Three precursors were added into the MS rooting medium for A. lancea tissue culture plantlets and the volatile oil was extracted by ultrasonication after cultured for several days. The content of atractylon, atractylol, β-eucalyptol and atractydin in the volatile oil were determined by using gas chromatography method. [Result] The addition of xylose, isoprene and tetrahydrofuran impacted the growth indicators, yield of volatile oil and relative percentage content of the four constituents of A. lancea tissue culture plantlets. In the 6 g/L xylose optimized medium, the atractylon and β-eucalyptol content reached up to 4.23% and 56.34%, respectively, 1.41% and 1.66% higher than the control; although the addition of isoprene into medium raised the atractylon content, the accumulation of total volatile oil was inhibited that it decreased by 23.67%, 31.06% and 7.10% to the control; for the tetrahydrofuran optimized medium, the content of atractylon, atractylol and atractydin all increased, and the total volatile oil content increased by 49.97% to the control when the concentration of tetrahydrofuran was 0.07 g/L. [Conclusion] The addition of xylose and tetrahydrofuran promoted the accumulation of principal constituents of the volatile oil, whereas the addition of isoprene inhibited the accumulation.
基金supported by the National Science and Technology Program of China(CDGC01-KT16)~~
文摘Two series of Mn/beta and Mn/ZSM‐5catalysts were prepared to study the influence of how different Mn precursors,introduced to the respective parent zeolites by wet impregnation,affected the selective catalytic reduction(SCR)of NO by NH3across a low reaction temperature window of50–350°C.In this study,the catalysts were characterized using N2adsorption/desorption,X‐ray diffraction,X‐ray fluorescence,H2temperature‐programmed reduction,NH3temperature‐programmed desorption and X‐ray photoelectron spectroscopy.As the manganese chloride precursor only partially decomposed this primarily resulted in the formation of MnCl2in addition to the presence of low levels of crystalline Mn3O4,which resulted in poor catalytic performance.However,the manganese nitrate precursor formed crystalline MnO2as the major phase in addition to a minor presence of unconverted Mn‐nitrate.Furthermore,manganese acetate resulted principally in a mixture of amorphous Mn2O3and MnO2,and crystalline Mn3O4.From all the catalysts screened,the test performance data showed Mn/beta‐Ac to exhibit the highest NO conversion(97.5%)at240°C,which remained>90%across a temperature window of220–350°C.The excellent catalytic performance was ascribed to the enrichment of highly dispersed MnOx(Mn2O3and MnO2)species that act as the active phase in the NH3‐SCR process.Furthermore,together with a suitable amount of weakly acidic centers,higher concentration of surface manganese and a greater presence of surface labile oxygen groups,SCR performance was collectively enhanced at low temperature.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.
基金This study is funded by Air Pollution Special Project of the Ministry of Science and Technology(Grant No.2017YFCOZ10006)the National Natural Science Foundation of China(Grant No.41975173)。
文摘This study uses the WRF-Chem model combined with the empirical kinetic modeling method(EKMA curve)to study the compound pollution event in Beijing that happened in 13−23 May 2017.Sensitivity tests are conducted to analyze ozone sensitivity to its precursors,and to develop emission reduction measures.The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze.When VOCs and NOx were reduced by the same proportion,the effect of O_(3)reduction at peak time was more obvious,and the effect during daytime was more significant than at night.The degree of change in ozone was peak time>daytime average.When reducing or increasing the ratio of precursors by 25%at the same time,the effect of reducing 25%VOCs on the average ozone concentration reduction was most significant.The degree of change in ozone decreased with increasing altitude,the location of the ozone maximum change shifted westward,and its range narrowed.As the altitude increases,the VOCs-limited zone decreases,VOCs sensitivity decreases,NOx sensitivity increases.The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited.Upon examining the EKMA curve,we have found that suburban and urban are sensitive to VOCs.The sensitivity tests indicate that when VOCs in suburban are reduced about 60%,the O_(3)-1h concentration could reach the standard,and when VOCs of the urban decreased by about 50%,the O_(3)-1h concentration could reach the standard.Thus,these findings could provide references for the control of compound air pollution in Beijing.
基金the National Natural Science Foundatlon of China under grant No.50172004,50273002 ,50333070.
文摘Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.
基金supported by the Open Foundation of Key Laboratory of the Ministry of Educationof Nonferrous Metal Alloys and Processes(No.EKL09002)The Ph.D.Fund Project of Lanzhou University of Science and Technology(No.BS01200904)
文摘Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.
基金the financial support by the National Key Basic Research Development Program "973" Project (2012CB224800) of China
文摘The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate precursors in H_2S/H_2 stream at different temperatures were studied by X-ray photoelectron spectroscopy(XPS) and high-resolution transmission electron microscopy(HRTEM). The organic molybdate precursors lead to MoS_2 catalysts with higher sulfidation degree and smaller active phases to demonstrate higher catalytic activity during hydrodesulfurizaiton(HDS) of 4,6-DMDBT.
文摘This paper reports the chemical synthesis of tungsten carbide/cobalt (WC/Co) nanocomposite powders via a unique chemical processing technique, involving the using of all water soluble solution of W-, Co- and C-precursors. In the actual synthesis, large quantities of commercial-scale WC-Co nanocomposite powders are made by an unique combination of converting a molecularly mixed W-, Co-, and C-containing solutions into a complex inorganic polymeric powder precursor, conversion of the inorganic polymeric precursor powder into a W-Co-C-O containing powder intermediates using a belt furnace with temperature at about 500°C - 600°C in an inert atmosphere, followed by carburization in a rotary furnace at temperature less than 1000°C in nitrogen. Liquid phase sintering technique is used to consolidate the WC/Co nanocomposite powder into sintered bulk parts. The sintered parts have excellent hardness in excess of 93 HRA, with WC grains in the order of 200 - 300 nm, while Co phase is uniformly distributed on the grain boundaries of the WC nanoparticles. We also report the presence of cobalt Co precipitates inside tungsten carbide WC nanograins in the composites of the consolidated bulk parts. EDS is used to identify the presence of these precipitates and micro-micro-diffraction technique is employed to determine the nature of these precipitates.
基金State Natural Science Foundation of China (19973011).
文摘It has been primarily confirmed that before the occurrence of a middle or major earthquake, anomalies in the residuals of universal time and latitude measurements obtained by astrometric observations may appear. We investigate the relation between the residual anomalies and the three key factors of an earthquake. To build a network of observational sites so as to obtain data of residuals of universal time and latitude from multi-instruments would be of certain significance for determining three key factors of an earthquake, especially for positioning epicenter. The data from multi-instruments would also be valuable for studies of the variation of the vertical. It is proposed to manufacture potable and high-accuracy astrometric instruments and to build observational network to obtain anomalies of universal time and latitude in the regions with high earthquake uprising possibilities.
基金supported by the National Key Basic Research Program of China(973 Program,2012CB224802)the SINOPEC project(No.114013)
文摘The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species in the solutions were confirmed by laser Raman spectroscopy(LRS). The UV-Vis spectra results indicated that the solutions containing both phosphoric acid and citric acid could change the existing form of nickel species. Five corresponding Ni Mo/Al_2O_3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulfided and characterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of(Ni)Mo S2 slabs and the promoting effect of Ni species. The catalyst prepared mainly with [P2Mo5O23]^(6-)-like species used as precursors exhibited worse dispersion of(Ni)Mo S2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]^(4-)-like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species showed better hydrodesulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.
基金Supported by the National Natural Science Foundation of China(No.41405097)the Fundamental Research Funds for the Central Universities of China in 2017
文摘In this paper, we find the optimal precursors which can cause double-gyre regime transitions based on conditional nonlinear optimal perturbation (CNOP) method with Regional Ocean Modeling System (ROMS). Firstly, we simulate the multiple-equilibria regimes of double-gyre circulation under different viscosity coefficient and obtain the bifurcation diagram, then choose two equilibrium states (called jet-up state and jet-down state) as reference states respectively, propose Principal Component Analysis-based Simulated Annealing (PCASA) algorithm to solve CNOP-type initial perturbations which can induce double-gyre regime transitions between jet-up state and jet-down state. PCASA algorithm is an adjoint-free method which searches optimal solution randomly in the whole solution space. In addition, we investigate CNOP-type initial perturbations how to evolve with time. The results show:(1) the CNOP-type perturbations present a two-cell structure, and gradually evolves into a three-cell structure at predictive time;(2) by superimposing CNOP-type perturbations on the jet-up state and integrating ROMS, double-gyre circulation transfers from jet-up state to jet-down state, and vice versa, and random initial perturbations don't cause the transitions, which means CNOP-type perturbations are the optimal precursors of double-gyre regime transitions;(3) by analyzing the transition process of double-gyre regime transitions, we find that CNOP-type initial perturbations obtain energy from the background state through both barotropic and baroclinic instabilities, and barotropic instability contributes more significantly to the fast-growth of the perturbations. The optimal precursors and the dynamic mechanism of double-gyre regime transitions revealed in this paper have an important significance to enhance the predictability of double-gyre circulation.
文摘CO2-TPD was demonstrated an effective way to investigate the phase formation during pyrolysis for the preparation of composite oxides using metal-organic molecules as precursors.Based on the CO2-TPD results, it was found that calcination condition had deep effect on the carbonate formation and the minimum firing temperature to acquire pure phase composite oxide.An optimized calcination schedule was then developed.
基金supported by the Chang Jiang Scholars Programme of China, the Key research and development project of Xinjiang Uygur Autonomous Region (2017B02012)the Natural Science Foundation of Xinjiang University (BS62331)the Xinjiang Uygur Autonomous Region 100 Young Doctors Introduction Program。
文摘Mechanochemical synthesis has been applied for many novel material preparations and gained more and more attention due to green and high-efficiency recently. In order to explore the influences of iron precursors on structure and performance of iron molybdate catalyst prepared by mechanochemical route, three typical and cheap iron precursors have been used in preparation of iron molybdate catalyst. Many characterization methods have been employed to obtain the physical and chemical properties of iron molybdate catalyst. Results indicate that iron precursors have the significant impact on the phase composition, crystal morphology and catalytic performance in the conversion of methanol to formaldehyde. It is hard to regulate the phase composition by changing Mo/Fe mole ratios for Fe2(SO4)3 as iron precursor. In addition, as for Fe2(SO4)3, the formaldehyde yield is lower than that from iron molybdate catalyst prepared with Fe(NO3)3·9H2O due to the reduction in Fe2(MoO4)3 phase as active phase. Based on mechanochemical and coprecipitation method, the solvent water could be a key factor for the formation of MoO3 and Fe2(MoO4) for FeCl3·6H2O and Fe2(SO4)3 as precursors. Iron molybdate catalyst prepared with Fe(NO3)3·9H2O by mechanochemical route, shows the best methanol conversion and formaldehyde yield in this reaction.
文摘In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing time , and so on . The best conditions in this research are : the concentration of Na2SiO3 and organic matters are 4. 50% and 26.4% respectively, pH = 3.3 , T = 65℃ , ageing time is 30min , dried at 150 ℃ , the size of SiC precursors is about 2.0μm .
基金supported by China Agriculture Research System(CARS-41-Z06)。
文摘Advanced glycation end products(AGEs)might pose health risks,and processing and storage could accelerate the generation of AGEs in meat.However,limited few reports indicated the changes of AGEs contents in meat during storage.In this study,the aim is to investigate the oxidation and precursors and their roles in the formation of N^(ε)-carboxymethyl-lysine(CML)in raw and cooked chicken meat after post-mortem ageing and storage.As post-mortem ageing and storage time increased,the CML content in cooked chicken breast significantly increased from 1.81 mg/kg to 2.00 mg/kg during 0-6 h,and then decreased from 2.00 mg/kg to 1.80 mg/kg during 6 h-1 day,finally increased again during 1-7 days,while the CML contents of raw and cooked leg significantly and continuously increased from 1.78 mg/kg to 2.08 mg/kg.Furthermore,CML was extremely positively correlated with fat oxidation(R^(2)=0.793,P<0.01),protein oxidation(R^(2)=0.917,P<0.01)and glyoxal(R^(2)=0.678,P<0.05),and was negatively correlated with lysine(R^(2)=0.536,P<0.05).No significant correlation was observed between the Schiff base and CML.
