The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. S...The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. Significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.展开更多
The present study aimed to investigate the effectiveness of the use of some antioxidants-<i>α</i>-tocopherol, n-octyl gallate, L-ascorbic acid 6-palmitate and matcha extract (green tea) as inhibitors of g...The present study aimed to investigate the effectiveness of the use of some antioxidants-<i>α</i>-tocopherol, n-octyl gallate, L-ascorbic acid 6-palmitate and matcha extract (green tea) as inhibitors of grape seeds, walnuts and corn germ oils oxidation. The oxidation was studied in a forced regime during 700 h, by the addition of hydrogen peroxide and Cu<sup>2+</sup> ions. The optimal conditions of the accelerated oxidation process in the analysed systems were established. The progress of lipid oxidation was evaluated by measuring the peroxide value (PV) and conjugated dienes and trienes (CD, CT). A series of secondary products of the lipid oxidation were identified: hexanal, octanal and hydroxy-nonadienal. The intensity of the formation of these compounds during oxidation was monitored. The results of this study showed that the oil samples with the addition of antioxidants showed considerably lower oxidation values compared to the control sample. More effective was the action of L-ascorbic acid 6-palmitate and n-octyl gallate, the optimum concentration <span>was 0.1%. An inhibitory effect of the oxidation process was noted for <i>α</i>-</span>tocopherol and matcha extract, the optimal addition concentration was 1%.展开更多
DHA with varying degrees of oxidation was obtained by the Schaal oven acceleration method.Then,the temporal changes in free radicals,volatile compounds,and carbonyl compounds in oxidized DHA was analyzed using HSSPME-...DHA with varying degrees of oxidation was obtained by the Schaal oven acceleration method.Then,the temporal changes in free radicals,volatile compounds,and carbonyl compounds in oxidized DHA was analyzed using HSSPME-GC-MS,the content of which were increased with the oxidation time.RAW264.7 macrophages were used to evaluate the effects of DHA oxidation products on the oxidative stress,gene and protein expression of inflammatory factors at different oxidation times.With the increase of oxidation time,oxidized DHA stimulated cells with significantly higher levels of reactive oxygen species(ROS),nitric oxide(NO)and malondialdehyde(MDA),while superoxide dismutase(SOD)activity was significantly inhibited.It also stimulated a significant increase in the expression of tumor necrosis factor-α(TNF-α),interleukin(IL-1β)and inducible nitric oxide synthase(iNOS),which exacerbated the cellular inflammatory response.Data on DHA oxidation products were analyzed using OPLS-DA.The compound(E,E)-2,4-heptadienal was identified as a potential differential metabolite capable of distinguishing among six oxidation time points.Furthermore,the pro-inflammatory effects of oxidized DHA were accurately predicted using partial least squares regression(PLSR)and support vector regression(SVR)models.This study established a correlation between volatile oxidation products and their potential pro-inflammatory effects,which were readily detectable through high-throughput assays.It thereby provided a rapid and reliable method for assessing the predicted bioactivity of DHA at varying levels of oxidation.展开更多
To shorten the time required for the pickling process and to enhance the quality of ferritic stainless steel plates,the effects of oxidants including hydrogen peroxide（H2O2）,potassium permanganate（KMnO4）,and potas...To shorten the time required for the pickling process and to enhance the quality of ferritic stainless steel plates,the effects of oxidants including hydrogen peroxide（H2O2）,potassium permanganate（KMnO4）,and potassium chlorate（KClO3）on the pickling behavior in HCl-based electrolyte as well as the surface quality of hot-rolled and blasted 430 stainless steel（430-SS）were studied.Experiments were conducted using mass-loss tests,microstructure analyses,potentiodynamic polarization curves,and electrochemical impedance spectroscopy measurements.The results showed that the addition of oxidants substantially accelerated the pickling process of 430-SS by enhancing the cathodic reaction rate and reducing the charge transfer resistance.In electrolytes comprising 5-8mass% HCl at a temperature of 40-60 ℃ and at the same concentration within the range from 0to 2mass%,H2O2 was demonstrated to be superior to KMnO4 and KClO3in accelerating the pickling process.The surface quality of 430-SS pickled in the presence of H2O2 was better than those of specimens pickled in the presence of KMnO4 and KClO3 when the removal of the oxide layer,intergranular corrosion,and surface roughness were collectively considered.When 1mass% H2O2 was added,the mass loss rate of 430-SS was increased by 629%and no residual oxide layer or intergranular corrosion was observed on the surface of the steel;in addition,the roughness was only 1.7μm.H2O2 was determined to be a better oxidant than KMnO4 and KClO3 when the pickling process,surface quality,solution recycling,and environment protection were considered as a whole.展开更多
Minthostachys mollis(Benth)Griseb.is a variety of‘peperina’with high pulegone+methone content but with a higher menthone content.The objective was to evaluate the antioxidant activity(AA)of peperina essential oil(PE...Minthostachys mollis(Benth)Griseb.is a variety of‘peperina’with high pulegone+methone content but with a higher menthone content.The objective was to evaluate the antioxidant activity(AA)of peperina essential oil(PEO)lower in pulegone/MENT(menthone+isomenthone)ratio combined with butylated hydroxytoluene(BHT).PEO was performed by gas chromatography with mass spectrometry(GC-MS).The thermal stability of PEO was determined at 60℃ for 28 days and analysed by GC-MS with SPME.Free Radical Scavening Activity(FRSA-DPPH test)and Total Phenol Content(TPC-analysed with Folin-cicolteau reagent)determined indirect AA.Direct AA was performed with accelerated oxidation of sunflower oil for 28 days at 60℃.Concentrations of 0.02,0.01 and 0.005%w/w(1,2 and 3)were used for the antioxidant BHT(B1,B2 and B3),PEO(P1,P2 and P3)and combinations.Chemical indicators(Conjugated Dienes,Peroxide Value and Anisidine Value),complete oxidation(Total Oxidation Value and Integral Oxidation Value)and volatiles(2-heptenal(Z)and 2,4-Decadienal(E,E))were determined.The pulegone/MENT ratio was 0.59 but the combinations B2P2 and B2P1 allow the use of lower concentration of BHT with higher efficiency.The low pulegone/MENT PEO can be combined with BHT to delay oxidation.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.50025412)
文摘The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. Significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.
文摘The present study aimed to investigate the effectiveness of the use of some antioxidants-<i>α</i>-tocopherol, n-octyl gallate, L-ascorbic acid 6-palmitate and matcha extract (green tea) as inhibitors of grape seeds, walnuts and corn germ oils oxidation. The oxidation was studied in a forced regime during 700 h, by the addition of hydrogen peroxide and Cu<sup>2+</sup> ions. The optimal conditions of the accelerated oxidation process in the analysed systems were established. The progress of lipid oxidation was evaluated by measuring the peroxide value (PV) and conjugated dienes and trienes (CD, CT). A series of secondary products of the lipid oxidation were identified: hexanal, octanal and hydroxy-nonadienal. The intensity of the formation of these compounds during oxidation was monitored. The results of this study showed that the oil samples with the addition of antioxidants showed considerably lower oxidation values compared to the control sample. More effective was the action of L-ascorbic acid 6-palmitate and n-octyl gallate, the optimum concentration <span>was 0.1%. An inhibitory effect of the oxidation process was noted for <i>α</i>-</span>tocopherol and matcha extract, the optimal addition concentration was 1%.
基金supported by project by the Natural Science Foundation of Beijing Municipality,China(No.6212002).
文摘DHA with varying degrees of oxidation was obtained by the Schaal oven acceleration method.Then,the temporal changes in free radicals,volatile compounds,and carbonyl compounds in oxidized DHA was analyzed using HSSPME-GC-MS,the content of which were increased with the oxidation time.RAW264.7 macrophages were used to evaluate the effects of DHA oxidation products on the oxidative stress,gene and protein expression of inflammatory factors at different oxidation times.With the increase of oxidation time,oxidized DHA stimulated cells with significantly higher levels of reactive oxygen species(ROS),nitric oxide(NO)and malondialdehyde(MDA),while superoxide dismutase(SOD)activity was significantly inhibited.It also stimulated a significant increase in the expression of tumor necrosis factor-α(TNF-α),interleukin(IL-1β)and inducible nitric oxide synthase(iNOS),which exacerbated the cellular inflammatory response.Data on DHA oxidation products were analyzed using OPLS-DA.The compound(E,E)-2,4-heptadienal was identified as a potential differential metabolite capable of distinguishing among six oxidation time points.Furthermore,the pro-inflammatory effects of oxidized DHA were accurately predicted using partial least squares regression(PLSR)and support vector regression(SVR)models.This study established a correlation between volatile oxidation products and their potential pro-inflammatory effects,which were readily detectable through high-throughput assays.It thereby provided a rapid and reliable method for assessing the predicted bioactivity of DHA at varying levels of oxidation.
基金Item Sponsored by Liaoning Province Programs for Science and Technology Development of China(2012221013)
文摘To shorten the time required for the pickling process and to enhance the quality of ferritic stainless steel plates,the effects of oxidants including hydrogen peroxide（H2O2）,potassium permanganate（KMnO4）,and potassium chlorate（KClO3）on the pickling behavior in HCl-based electrolyte as well as the surface quality of hot-rolled and blasted 430 stainless steel（430-SS）were studied.Experiments were conducted using mass-loss tests,microstructure analyses,potentiodynamic polarization curves,and electrochemical impedance spectroscopy measurements.The results showed that the addition of oxidants substantially accelerated the pickling process of 430-SS by enhancing the cathodic reaction rate and reducing the charge transfer resistance.In electrolytes comprising 5-8mass% HCl at a temperature of 40-60 ℃ and at the same concentration within the range from 0to 2mass%,H2O2 was demonstrated to be superior to KMnO4 and KClO3in accelerating the pickling process.The surface quality of 430-SS pickled in the presence of H2O2 was better than those of specimens pickled in the presence of KMnO4 and KClO3 when the removal of the oxide layer,intergranular corrosion,and surface roughness were collectively considered.When 1mass% H2O2 was added,the mass loss rate of 430-SS was increased by 629%and no residual oxide layer or intergranular corrosion was observed on the surface of the steel;in addition,the roughness was only 1.7μm.H2O2 was determined to be a better oxidant than KMnO4 and KClO3 when the pickling process,surface quality,solution recycling,and environment protection were considered as a whole.
文摘Minthostachys mollis(Benth)Griseb.is a variety of‘peperina’with high pulegone+methone content but with a higher menthone content.The objective was to evaluate the antioxidant activity(AA)of peperina essential oil(PEO)lower in pulegone/MENT(menthone+isomenthone)ratio combined with butylated hydroxytoluene(BHT).PEO was performed by gas chromatography with mass spectrometry(GC-MS).The thermal stability of PEO was determined at 60℃ for 28 days and analysed by GC-MS with SPME.Free Radical Scavening Activity(FRSA-DPPH test)and Total Phenol Content(TPC-analysed with Folin-cicolteau reagent)determined indirect AA.Direct AA was performed with accelerated oxidation of sunflower oil for 28 days at 60℃.Concentrations of 0.02,0.01 and 0.005%w/w(1,2 and 3)were used for the antioxidant BHT(B1,B2 and B3),PEO(P1,P2 and P3)and combinations.Chemical indicators(Conjugated Dienes,Peroxide Value and Anisidine Value),complete oxidation(Total Oxidation Value and Integral Oxidation Value)and volatiles(2-heptenal(Z)and 2,4-Decadienal(E,E))were determined.The pulegone/MENT ratio was 0.59 but the combinations B2P2 and B2P1 allow the use of lower concentration of BHT with higher efficiency.The low pulegone/MENT PEO can be combined with BHT to delay oxidation.
