BACKGROUND Inflammatory bowel disease(IBD)is a common chronic intestinal inflammatory disease.High oxidative stress is a treatment target for IBD.Cerium oxide(CeO2)nanomaterials as nanozymes with antioxidant activity ...BACKGROUND Inflammatory bowel disease(IBD)is a common chronic intestinal inflammatory disease.High oxidative stress is a treatment target for IBD.Cerium oxide(CeO2)nanomaterials as nanozymes with antioxidant activity are potential drugs for the treatment of colitis.AIM To synthesize hollow cerium(H-CeO2)nanoparticles by one-step method and to validate the therapeutic efficacy of H-CeO2 in IBD.METHODS H-CeO2 was synthesized by one-step method and examined its characterization and nanoenzymatic activity.Subsequently,we constructed dextran sulfate so-dium(DSS)-induced colitis in mice to observe the effects of H-CeO2 on colonic inflammation.The effects of H-CeO2 on colon inflammation and reactive oxygen species(ROS)levels in IBD mice were detected by hematoxylin and eosin staining and dichlorofluorescein diacetate staining,respectively.Finally,the biological sa-fety of H-CeO2 on mice was evaluated by hematoxylin and eosin staining,blood routine,and blood biochemistry.RESULTS H-CeO2 nanoparticles prepared by the one-step method were uniform,monodi-sperse and hollow.H-CeO2 had a good ability to scavenge ROS,∙OH and∙OOH.H-CeO2 reduced DSS-induced decreases in body weight and colon length,colonic epithelial damage,inflammatory infiltration,and ROS accumulation.H-CeO2 administration reduced the disease activity index of DSS-induced animals from about 8 to 5.H-CeO2 had no significant effect on body weight,total platelet count,hemoglobin,white blood cell,and red blood cell counts in healthy mice.No significant damage to major organs was observed in healthy mice following H-CeO2 administration.CONCLUSION The one-step synthesis of H-CeO2 nanomaterials had good antioxidant activity,biosafety,and inhibited deve-lopment of DSS-induced IBD in mice by scavenging ROS.展开更多
At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standar...At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standard.Thus,establishing an objective identification method is greatly important.In this study,an objective synoptic analysis technique for TRP(OSAT_TRP)is proposed to identify TRP using daily precipitation datasets,historical tropical cyclone(TC)track data,and the ERA5 reanalysis data.This method includes three steps:first,independent rain belts are separated,and those that might relate to TCs'remote effects are distinguished according to their distance from the TCs.Second,the strong water vapor transport belt from the TC is identified using integrated horizontal water vapor transport(IVT).Third,TRP is distinguished by connecting the first two steps.The TRP obtained through this method can satisfy three criteria,as follows:1)the precipitation occurs outside the circulation of TCs,2)the precipitation is affected by TCs,and 3)a gap exists between the TRP and TC rain belt.Case diagnosis analysis,compared with subjective TRP results and backward trajectory analyses using HYSPLIT,indicates that OSAT_TRP can distinguish TRP even when multiple TCs in the Northwest Pacific are involved.Then,we applied the OSAT_TRP to select typical TRPs and obtained the synoptic-scale environments of the TRP through composite analysis.展开更多
Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to pre...Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.展开更多
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu...Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.展开更多
Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structu...Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.展开更多
CeO 2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO 2 has cubic crystalline str...CeO 2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO 2 has cubic crystalline structure of space group O 5 H-F M3M, when calcination temperature is in the range of 250～800 ℃. TEM images reveal that CeO 2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO 2 relative density show that the relative density of CeO 2 nanocrystalline powders increases with increasing CeO 2 particle size.展开更多
A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that ...A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared （FTIR） spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.展开更多
Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 p...Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.展开更多
Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980...Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.展开更多
The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, tens...The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, tensile test, and differential scanning calorimetry. The results revealed that the recrystallized grains of the alloy after the solution treatment with hot air became smaller and more uniform, compared with solution treatment with electrical resistance. The texture of the alloy after two solution treatment methods was different. More rotated cube components were formed through solution treatment with electrical resistance, which was better for improving the drawability of the alloy. The strength of the alloy under the solution treatment with hot air was higher before stamping, because of the small uniform grains and many clusters in the matrix. The alloy solution treated with hot air also possessed good bake hardenability, because the transformation occurred on more clusters in the matrix.展开更多
Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectrosc...Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+.展开更多
Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To im...Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To improve the humidity resistance of the water soluble core and optimize the process parameters applied in manufacturing of the water soluble core,a precipitation method and a two-level-three-full factorial central composite design were used,respectively.The properties of the cores treated by the precipitation method were compared with that without any treatment.Through a systematical study by means of both an environmental scanning electron microscope(ESEM) and an energy dispersive X-ray(EDX) analyzer,the results indicate that the hygroscopicity can be reduced by 20% and the obtained optimal process conditions for three critical control factors affecting the hygroscopicity are 0.2 g·mL-1 calcium chloride concentration,4% water concentration and 0 min ignition time.The porous surface coated by calcium chloride and the high humidity resistance products generated in the precipitation reaction between calcium chloride and potassium carbonate may contribute to the lower hygroscopicity.展开更多
In this study,a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR)suitable over the Tibetan Plateau(TP)was proposed by analyzing Global Precipitation Measurement(GPM)DPR Level-2 dat...In this study,a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR)suitable over the Tibetan Plateau(TP)was proposed by analyzing Global Precipitation Measurement(GPM)DPR Level-2 data in summer from 2014 to 2020.It was found that the DPR rain type classification algorithm(simply called DPR algorithm)has mis-identification problems in two aspects in summer TP.In the new algorithm of rain type classification in summer TP,four rain types are classified by using new thresholds,such as the maximum reflectivity factor,the difference between the maximum reflectivity factor and the background maximum reflectivity factor,and the echo top height.In the threshold of the maximum reflectivity factors,30 d BZ and 18 d BZ are both thresholds to separate strong convective precipitation,weak convective precipitation and weak precipitation.The results illustrate obvious differences of radar reflectivity factor and vertical velocity among the three rain types in summer TP,such as the reflectivity factor of most strong convective precipitation distributes from 15 d BZ to near 35 d BZ from 4 km to 13 km,and increases almost linearly with the decrease in height.For most weak convective precipitation,the reflectivity factor distributes from 15 d BZ to 28 d BZ with the height from 4 km to 9 km.For weak precipitation,the reflectivity factor mainly distributes in range of 15–25 d BZ with height within 4–10 km.It is also shows that weak precipitation is the dominant rain type in summer TP,accounting for 40%–80%,followed by weak convective precipitation(25%–40%),and strong convective precipitation has the least proportion(less than 30%).展开更多
ZnO particles doped with 0 mol%-5 mol% Cd dopant were successfully synthesized by a precipitation method.The as-synthesized products were characterized by thermogravimetric analysis(TGA),differential scanning calorime...ZnO particles doped with 0 mol%-5 mol% Cd dopant were successfully synthesized by a precipitation method.The as-synthesized products were characterized by thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),X-ray diffraction(XRD),photoluminescence(PL) spectroscopy,Raman spectroscopy,scanning electron microscopy(SEM) coupled with an energydispersive X-ray(EDX) spectroscopy and transmission electron microscopy(TEM).The precursors showed weight loss at 35-700℃ caused by phase transformation and evaporation processes.The as-synthesized products were specified as hexagonal wurtzite ZnO.The crystallite size of ZnO samples doped with 0 mol%-5 mol% Cd gradually increased with the increase in Cd content.The photocatalytic activities of 0 mol%-5 mol% Cd-doped ZnO samples were evaluated through photodecolorization of methylene blue(MB) under ultraviolet(UV) radiation.In this research,ZnO doped with 3 mol% Cd shows the best photocatalytic activity in degrading of MB molecules as much as 89% within 240 min.展开更多
The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcinatio...The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcination temperature, on the surface area were studied respectively. The Y_2O_3 sample with specific surface area of more than 60 m^2·g^(-1) and L.O.I less than 1% was prepared in the suitable precipitation condition and calcinations temperature when the ammonia used as precipitant. The SEM shows that the Y_2O_3 prepared with large surface area is the aggregation of about 50 nm particles.展开更多
In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness tempera...In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness temperature data,corresponding "precipitation field dictionary" and "channel brightness temperature dictionary" are formed.The retrieval of precipitation field based on brightness temperature data is studied through the classification rule of k-nearest neighbor domain (KNN) and regularization constraint.Firstly,the corresponding "dictionary" is constructed according to the training sample database of the matched GPM precipitation data and H8 brightness temperature data.Secondly,according to the fact that precipitation characteristics in small organizations in different storm environments are often repeated,KNN is used to identify the spectral brightness temperature signal of "precipitation" and "non-precipitation" based on "the dictionary".Finally,the precipitation field retrieval is carried out in the precipitation signal "subspace" based on the regular term constraint method.In the process of retrieval,the contribution rate of brightness temperature retrieval of different channels was determined by Bayesian model averaging (BMA) model.The preliminary experimental results based on the "quantitative" evaluation indexes show that the precipitation of H8 retrieval has a good correlation with the GPM truth value,with a small error and similar structure.展开更多
Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic ...Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic reaction was applied under light intensity equal to 1.45 × 10-7 Einstein mol-1 to investigate the kinetics and thermodynamic parameters for photo-decolorization of reactive black 5 dye in collide solution of bare and Cr-doped ZnS. The mean crystal size and particle size for bare ZnS are more than those values for prepared Cr loaded ZnS.展开更多
The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase struc...The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2（P2O7）：Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0：0.4：0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2（P2O7）：Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.展开更多
YAG：Ce3＋ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG：Ce3＋ phosphor was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and photolumine...YAG：Ce3＋ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG：Ce3＋ phosphor was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and photoluminescent emission spectra.By using acetic acid as solvent,YAG：Ce3＋ powder with small particle size（≤2 μm） was obtained at a relatively lower sintering temperature of 1400 oC.With the content of acetic acid increasing,small particles dissolved and disappeared,but larger particles grew up and changed its shape from spherical to partially rectangular.Meanwhile,the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method.It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment,and therefore,a better homogeneity of activators of Ce3＋.展开更多
Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studi...Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI（OH）3 sols are produced by using 0.1 mol/L Al（NO3）3·9H2O and 0.16 mol/L （NH4）2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%（volume fraction） surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity.展开更多
文摘BACKGROUND Inflammatory bowel disease(IBD)is a common chronic intestinal inflammatory disease.High oxidative stress is a treatment target for IBD.Cerium oxide(CeO2)nanomaterials as nanozymes with antioxidant activity are potential drugs for the treatment of colitis.AIM To synthesize hollow cerium(H-CeO2)nanoparticles by one-step method and to validate the therapeutic efficacy of H-CeO2 in IBD.METHODS H-CeO2 was synthesized by one-step method and examined its characterization and nanoenzymatic activity.Subsequently,we constructed dextran sulfate so-dium(DSS)-induced colitis in mice to observe the effects of H-CeO2 on colonic inflammation.The effects of H-CeO2 on colon inflammation and reactive oxygen species(ROS)levels in IBD mice were detected by hematoxylin and eosin staining and dichlorofluorescein diacetate staining,respectively.Finally,the biological sa-fety of H-CeO2 on mice was evaluated by hematoxylin and eosin staining,blood routine,and blood biochemistry.RESULTS H-CeO2 nanoparticles prepared by the one-step method were uniform,monodi-sperse and hollow.H-CeO2 had a good ability to scavenge ROS,∙OH and∙OOH.H-CeO2 reduced DSS-induced decreases in body weight and colon length,colonic epithelial damage,inflammatory infiltration,and ROS accumulation.H-CeO2 administration reduced the disease activity index of DSS-induced animals from about 8 to 5.H-CeO2 had no significant effect on body weight,total platelet count,hemoglobin,white blood cell,and red blood cell counts in healthy mice.No significant damage to major organs was observed in healthy mice following H-CeO2 administration.CONCLUSION The one-step synthesis of H-CeO2 nanomaterials had good antioxidant activity,biosafety,and inhibited deve-lopment of DSS-induced IBD in mice by scavenging ROS.
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_1136)the National Natural Scientific Foundation of China(No.42275037)+2 种基金the Basic Research Fund of CAMS(No.2023Z016)the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(No.SCSF202202)supported by the Jiangsu Collaborative Innovation Center for Climate Change。
文摘At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standard.Thus,establishing an objective identification method is greatly important.In this study,an objective synoptic analysis technique for TRP(OSAT_TRP)is proposed to identify TRP using daily precipitation datasets,historical tropical cyclone(TC)track data,and the ERA5 reanalysis data.This method includes three steps:first,independent rain belts are separated,and those that might relate to TCs'remote effects are distinguished according to their distance from the TCs.Second,the strong water vapor transport belt from the TC is identified using integrated horizontal water vapor transport(IVT).Third,TRP is distinguished by connecting the first two steps.The TRP obtained through this method can satisfy three criteria,as follows:1)the precipitation occurs outside the circulation of TCs,2)the precipitation is affected by TCs,and 3)a gap exists between the TRP and TC rain belt.Case diagnosis analysis,compared with subjective TRP results and backward trajectory analyses using HYSPLIT,indicates that OSAT_TRP can distinguish TRP even when multiple TCs in the Northwest Pacific are involved.Then,we applied the OSAT_TRP to select typical TRPs and obtained the synoptic-scale environments of the TRP through composite analysis.
基金supports from the National Key R&D Program of China(Grant No.2023YFB4203301)National Natural Science Foundation of China(Grant No.52238008)Postdoctoral Fellowship Program of CPSF(Grant No.GZC20241516).
文摘Microbially induced calcite precipitation(MICP)and Enzyme induced calcite precipitation(EICP)techniques were implemented to reinforce the large-scale calcareous sand in this study.Then a coupled numerical model to predict the biochemical reactions and hydraulic characteristics of MICP and EICP reactions was proposed and verified by physical experiments.Results showed that:This model could describe the variations of bacteria,calcium,calcite,permeability over time reasonably.It is necessary to consider the influence of the calculation domain scale when simulating the convection-diffusionreaction in the multi-process of MICP and EICP reactions.The numerical and experimental values of calcite content are 0.841 g/cm^(3) and 0.861 g/cm^(3) for MICP-reinforced sand,0.263 g/cm^(3) and 0.227 g/cm^(3) for EICP-reinforced sand after 192 h of reaction.The reaction rate k_(rea) is an important parameter to control the calcite content.Accordingly,the permeability coefficient of MICP and EICP reinforced calcareous sand decreases by 32%and 18%.Due to the influence of substance transportation and calcite precipitation,the calcite shows a trend of decreasing firstly and then increasing with the enhancing of the initial permeability coefficient in biochemical reactions.The optimal injecting ratio q11:q12 in this study is 100:300 mL/min.The process for the application of MICP and EICP coupled numerical model is also recommended,which provides reference for engineering projects in ground improvement.
文摘Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.
文摘Nanometer TiO 2 powders were obtained from TiOSO 4 and studied by XRD, TEM and BET. The result indicated that pH and heat treatment temperature have great effects on their grain size and crystal phase structure. Annealed at 500 ℃, nanometer TiO 2 with a specific surface area of 101.39 m 2 ·g -1 and a grain size about 10 nm were obtained(pH=5); and with a specific surface area of 95.48 m 2 ·g -1 and a grain size about 30 nm were obtained(pH=10). The research indicated that crystal phase transformation of rutile at 750 ℃made great promotion in grain size growth.
文摘CeO 2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO 2 has cubic crystalline structure of space group O 5 H-F M3M, when calcination temperature is in the range of 250～800 ℃. TEM images reveal that CeO 2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO 2 relative density show that the relative density of CeO 2 nanocrystalline powders increases with increasing CeO 2 particle size.
文摘A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared （FTIR） spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.
基金Project supported by the International Cooperation of Science and Technology Ministry PRC (2005DFBA028)the National Natural Science Foundation of China (59925412)
文摘Using cetyltrimethylammonium bromide （CTAB） as the template agent, cerium nitrate as the cerium resource, yttrium nitrate as the yttrium resource, and ammonium carbonate as the precipitating agent, mesoporous CeO2 powders doped with different yttrium contents were successfully synthesized using a chemical precipitation method, under an alkalescent condition. Properties of the obtained samples were characterized and analyzed with X-ray diffraction （XRD）, energy dispersive analysis of X-rays （EDAX）, transmission electron microscopy （TEM）, infrared （IR） absorbance, and the BET method. For the prepared samples with 20% （molar ratio） Y-doped content, a BET specific surface area of 106. 6 m^2 · g^- 1, with an average pore size of3~27 nm were obtained. XRD patterns showed that the doped samples were with a cubic fluorite structure. TEM micrographs revealed that the doped samples showed a spherical morphology with a diameter ranging from 20 to 30 nm and a round pore shape. IR results indicated that the Ce-O-Ce vibration intensity decreased as the Y-doped content increased. N2 adsorption-desorption isotherms showed that the samples possessed typical mesopore characteristics. The average pore size of the samples decreased alter mesoporous CeO2 was doped with yttrium, and the average pore size decreased largely as the Y-doped content increased.
基金the Foundation for the University by Educational Department of Liaoning (05L337)Key Laboratory of Rare Earth Chemistry and Physics, Chinese Academy of Sciences
文摘Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.
基金Project(2016YFB0300605)supported by the National Key Research and Development Program of ChinaProject(51234002)supported by the National Natural Science Foundation of China+1 种基金Project(L2013113)supported by the Liaoning Province Science and Technology,ChinaProject(N140703002)supported by the Fundamental Research Funds for the Central Universities,China
文摘The effects of different solution methods on microstructure, mechanical properties and precipitation behavior of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, tensile test, and differential scanning calorimetry. The results revealed that the recrystallized grains of the alloy after the solution treatment with hot air became smaller and more uniform, compared with solution treatment with electrical resistance. The texture of the alloy after two solution treatment methods was different. More rotated cube components were formed through solution treatment with electrical resistance, which was better for improving the drawability of the alloy. The strength of the alloy under the solution treatment with hot air was higher before stamping, because of the small uniform grains and many clusters in the matrix. The alloy solution treated with hot air also possessed good bake hardenability, because the transformation occurred on more clusters in the matrix.
基金financially supported by the Science and Technology Research Project of Department of Education of Liaoning Province,China(No.L2011063)
文摘Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+.
文摘Water soluble core has been widely used in manufacturing complex metal components with hollow configurations or internal channels;however,the soluble core can absorb water easily from the air at room temperature.To improve the humidity resistance of the water soluble core and optimize the process parameters applied in manufacturing of the water soluble core,a precipitation method and a two-level-three-full factorial central composite design were used,respectively.The properties of the cores treated by the precipitation method were compared with that without any treatment.Through a systematical study by means of both an environmental scanning electron microscope(ESEM) and an energy dispersive X-ray(EDX) analyzer,the results indicate that the hygroscopicity can be reduced by 20% and the obtained optimal process conditions for three critical control factors affecting the hygroscopicity are 0.2 g·mL-1 calcium chloride concentration,4% water concentration and 0 min ignition time.The porous surface coated by calcium chloride and the high humidity resistance products generated in the precipitation reaction between calcium chloride and potassium carbonate may contribute to the lower hygroscopicity.
基金funded by the National Natural Science Foundation of China project(Grant Nos.42275140,42230612,91837310,92037000)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0104)。
文摘In this study,a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR)suitable over the Tibetan Plateau(TP)was proposed by analyzing Global Precipitation Measurement(GPM)DPR Level-2 data in summer from 2014 to 2020.It was found that the DPR rain type classification algorithm(simply called DPR algorithm)has mis-identification problems in two aspects in summer TP.In the new algorithm of rain type classification in summer TP,four rain types are classified by using new thresholds,such as the maximum reflectivity factor,the difference between the maximum reflectivity factor and the background maximum reflectivity factor,and the echo top height.In the threshold of the maximum reflectivity factors,30 d BZ and 18 d BZ are both thresholds to separate strong convective precipitation,weak convective precipitation and weak precipitation.The results illustrate obvious differences of radar reflectivity factor and vertical velocity among the three rain types in summer TP,such as the reflectivity factor of most strong convective precipitation distributes from 15 d BZ to near 35 d BZ from 4 km to 13 km,and increases almost linearly with the decrease in height.For most weak convective precipitation,the reflectivity factor distributes from 15 d BZ to 28 d BZ with the height from 4 km to 9 km.For weak precipitation,the reflectivity factor mainly distributes in range of 15–25 d BZ with height within 4–10 km.It is also shows that weak precipitation is the dominant rain type in summer TP,accounting for 40%–80%,followed by weak convective precipitation(25%–40%),and strong convective precipitation has the least proportion(less than 30%).
基金financially supported by the Chiang Mai University Research Fundthe administration of Materials Science Research Center,Faculty of Science,Chiang Mai University,Thailand。
文摘ZnO particles doped with 0 mol%-5 mol% Cd dopant were successfully synthesized by a precipitation method.The as-synthesized products were characterized by thermogravimetric analysis(TGA),differential scanning calorimetry(DSC),X-ray diffraction(XRD),photoluminescence(PL) spectroscopy,Raman spectroscopy,scanning electron microscopy(SEM) coupled with an energydispersive X-ray(EDX) spectroscopy and transmission electron microscopy(TEM).The precursors showed weight loss at 35-700℃ caused by phase transformation and evaporation processes.The as-synthesized products were specified as hexagonal wurtzite ZnO.The crystallite size of ZnO samples doped with 0 mol%-5 mol% Cd gradually increased with the increase in Cd content.The photocatalytic activities of 0 mol%-5 mol% Cd-doped ZnO samples were evaluated through photodecolorization of methylene blue(MB) under ultraviolet(UV) radiation.In this research,ZnO doped with 3 mol% Cd shows the best photocatalytic activity in degrading of MB molecules as much as 89% within 240 min.
文摘The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcination temperature, on the surface area were studied respectively. The Y_2O_3 sample with specific surface area of more than 60 m^2·g^(-1) and L.O.I less than 1% was prepared in the suitable precipitation condition and calcinations temperature when the ammonia used as precipitant. The SEM shows that the Y_2O_3 prepared with large surface area is the aggregation of about 50 nm particles.
基金Supported by National Natural Science Foundation of China(41805080)Natural Science Foundation of Anhui Province,China(1708085QD89)+1 种基金Key Research and Development Program Projects of Anhui Province,China(201904a07020099)Open Foundation Project Shenyang Institute of Atmospheric Environment,China Meteorological Administration(2016SYIAE14)
文摘In this paper,the application of an algorithm for precipitation retrieval based on Himawari-8 (H8) satellite infrared data is studied.Based on GPM precipitation data and H8 Infrared spectrum channel brightness temperature data,corresponding "precipitation field dictionary" and "channel brightness temperature dictionary" are formed.The retrieval of precipitation field based on brightness temperature data is studied through the classification rule of k-nearest neighbor domain (KNN) and regularization constraint.Firstly,the corresponding "dictionary" is constructed according to the training sample database of the matched GPM precipitation data and H8 brightness temperature data.Secondly,according to the fact that precipitation characteristics in small organizations in different storm environments are often repeated,KNN is used to identify the spectral brightness temperature signal of "precipitation" and "non-precipitation" based on "the dictionary".Finally,the precipitation field retrieval is carried out in the precipitation signal "subspace" based on the regular term constraint method.In the process of retrieval,the contribution rate of brightness temperature retrieval of different channels was determined by Bayesian model averaging (BMA) model.The preliminary experimental results based on the "quantitative" evaluation indexes show that the precipitation of H8 retrieval has a good correlation with the GPM truth value,with a small error and similar structure.
文摘Zinc sulfide photocatalysts doped with chromium (1:1)% were synthesized via precipitation technique. Their characteristics were studied by X-ray diffraction (XRD), AFM and Florescence spectrometer. The photocatalytic reaction was applied under light intensity equal to 1.45 × 10-7 Einstein mol-1 to investigate the kinetics and thermodynamic parameters for photo-decolorization of reactive black 5 dye in collide solution of bare and Cr-doped ZnS. The mean crystal size and particle size for bare ZnS are more than those values for prepared Cr loaded ZnS.
基金financially supported by the National Natural Science Foundation of China(No.21273060)the Program for New Century Excellent Talents in Heilongjiang Provincial University(No.1251-NCET-014)
文摘The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2（P2O7）：Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0：0.4：0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2（P2O7）：Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.
基金Project supported by the Natural Science Foundation of Jiangxi Province (2009GQC0042)Foundation of Jiangxi Educational Committee(GJJ10153)+1 种基金Major Science and Technology Project of Jiangxi Province (2010AZD00100)Foundation of Jiangxi University of Science and Technology (Jxxjzd10007)
文摘YAG：Ce3＋ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG：Ce3＋ phosphor was characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and photoluminescent emission spectra.By using acetic acid as solvent,YAG：Ce3＋ powder with small particle size（≤2 μm） was obtained at a relatively lower sintering temperature of 1400 oC.With the content of acetic acid increasing,small particles dissolved and disappeared,but larger particles grew up and changed its shape from spherical to partially rectangular.Meanwhile,the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method.It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment,and therefore,a better homogeneity of activators of Ce3＋.
文摘Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor AI（OH）3 sols are produced by using 0.1 mol/L Al（NO3）3·9H2O and 0.16 mol/L （NH4）2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024%（volume fraction） surfactant PEG600, and reacting at 40℃, 1000 r/min stirring rate for 15min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80℃ for 8h, final calcined at 800℃ for 1h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH^7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m^2/g in BET specific surface area, 7 - 11 nm in pore diameter, and not lower than 99.93% in purity.
