The bioassay was directed to the fractionation of the methanol extract of the rhizomes of Zingiber officinale Roscoe leading to the isolation of a new antioxidant cyclic diarylheptanoid. The structure of the new compo...The bioassay was directed to the fractionation of the methanol extract of the rhizomes of Zingiber officinale Roscoe leading to the isolation of a new antioxidant cyclic diarylheptanoid. The structure of the new compound was established as 1, 5-epoxy-3-hydroxy-1-(3,4-dihydroxy-5-methoxy-phenyl)-7-(3,4-dihydroxyphenyl) heptane (1) on the basis of MS, 1D and 2D-NMR experiments.展开更多
The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental resu...The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental results. The products populations depend strongly on the temperature. The quantity of ethylene increases quickly as the temperature goes up. The conversion of n-heptane and the mole fraction of primary products from reactive molecular dynamic and chemical kinetic modeling are compared with each other. We also investigated the pre-exponential factor and activation energy for thermal decomposition of n-heptane by kinetic analysis from the reactive force field simulations, which were extracted to be 1.78×10^14 s^-1 and 47.32 kcal/mol respectively.展开更多
In this paper, we investigate HUA’s Theorem for short intervals under GRH. Let E k(x)=#{{n≤x;2|n,k is odd, n≠p 1+p k 2}∪{n≤x;2|n,2|k,(p-1)|k, n1(modp),n≠p 1+p k 2}}. Assume GRH. For any k≥2, any A】0 ...In this paper, we investigate HUA’s Theorem for short intervals under GRH. Let E k(x)=#{{n≤x;2|n,k is odd, n≠p 1+p k 2}∪{n≤x;2|n,2|k,(p-1)|k, n1(modp),n≠p 1+p k 2}}. Assume GRH. For any k≥2, any A】0 and any 0【ε【14,E k(x+H)-E k(x)≤H(log x) -Aholds for x 12-14k+ε≤H≤x, here the implies constant depends at most on A and ε.展开更多
n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dyn...n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dynamics simulations. Temperature effects on the n-heptane pyrolysis and related products distributions have been detailedly analyzed. The simulation results indicate that the temperature effect is characterized in stages. High tern- perature can accelerate the decomposition of n-heptane, but the influence becomes small after it reaches a certain level. According to the different reaction behaviors, pyrolysis of n-heptane could be divided into three stages. The variation trends of the mass fraction evolu- tion of ethylene （C2H4）, C3, and C4 calculated from reactive molecular dynamics simulations are in good agreement with the previous experimental results. The apparent activation en- ergy extracted from the first-order kinetic analysis is 53.96 kcal/mol and a pre-exponential factor is 55.34×10^13 s-1, which is reasonably consistent with the experimental results.展开更多
AIM:To determine the prevalences of TTV and HGV infections among blood donors and patients with chronic liver disease in Korea,to investigate the association of TTV and HGV infections with blood transfusion,and to ass...AIM:To determine the prevalences of TTV and HGV infections among blood donors and patients with chronic liver disease in Korea,to investigate the association of TTV and HGV infections with blood transfusion,and to assess the correlation between TTV and HGV viremia and hepatic damage. METHODS:A total of 391 serum samples were examined in this study.Samples were obtained from healthy blood donors(n=110),hepatitis B surface antigen(HBsAg)-positive donors(n=112),anti-hepatitis C virus(anti-HCV)-positive donors(n=69),patients with type B chronic liver disease (n=81),and patients with type C chronic liver disease(n=19). Trv DNA was detected using the hemi-nested PCR.HGV RNA was tested using RT-PCR.A history of blood transfusion and serum levels of alanine aminotransferase(ALT)and aspartate aminotransferase(AST)were also determined. RESULTS:TTV DNA was detected in 8.2%of healthy blood donors,16.1%of HBsAg-positive donors,20.3%of anti- HCV-positive donors,21.0%of patients with type B chronic liver disease,and 21.1%of patients with type C chronic liver disease.HGV RNA was detected in 1.8%of healthy blood donors,1.8%of HBsAg-positive donors,17.4%of anti-HCV-positive donors,13.6%of patients with type B chronic liver disease,and 10.5%of patients with type C chronic liver disease.The prevalence of TTV and HGV infections in HBV- or HCV-positive donors and patients was significantly higher than in healthy blood donors(P<0.05), except for the detection rate of HGV in HBsAg-positive donors which was the same as for healthy donors.There was a history of transfusion in 66.7%of TTV DNA-positive patients and 76.9%of HGV RNA-positive patients(P<0.05).No significant increase in serum ALT and AST was detected in the TTV or HGV-positive donors and patients. CONCLUSION:TTV and HGV infections are more frequently found in donors and patients infected with HBV or HCV than in healthy blood donors.However,there is no significant association between TTV or HGV infections and liver injury.展开更多
Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible d...Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,temperature-programmed reduction of H2,temperature-programmed desorption of NH3,infrared spectroscopy of adsorbed pyridine,H2 chemisorption,nitrogen adsorption-desorption,scanning electron microscopy and thermogravimetric analysis were performed.Kinetics of n-C7 isomerization were investigated under various hydrogen and n-C7 pressures,and the effects of reaction conditions on catalytic performance were studied.The results showed that bi-and trimetallic catalysts exhibit better performance than monometallic catalysts for this reaction.For example,a maximum i-C7 selectivity（ 〉74%） and multibranched isomer selectivity（40%） were observed for Pt-Sn/HZSM5-HMS at 200 ℃.展开更多
Light hydrocarbons （LHs） are one of the main petroleum fractions in crude oils, and carry much infor- mation regarding the genetic origin and alteration of crude oils. But secondary alterations--especially biodegrad...Light hydrocarbons （LHs） are one of the main petroleum fractions in crude oils, and carry much infor- mation regarding the genetic origin and alteration of crude oils. But secondary alterations--especially biodegrada- tion--have a significant effect on the composition of LHs in crude oils. Because most of the LHs affected in oils underwent only slight biodegradation （rank 1 on the biodegradation scale）, the variation of LHs can be used to describe more the refined features of biodegradation. Here, 23 crude oils from the Dawanqi Oilfield in the Tarim Basin, NW China, eleven of which have been biodegraded to different extents, were analyzed in order to investigate the effect of slight to minor biodegradation on C6--C7 LHs. The study results showed that biodegradation resulted in the prior depletion of straight-chained alkanes, followed by branched alkanes. In slight and minor biodegraded oils, such biodegradation scale could not sufficiently affect C6- C7 cycloalkanes. For branched C6--C7 alkanes, generally, monomethylalkanes are biodegraded earlier than dimethylalkanes and trimethylalkanes, which indicates that branched alkanes are more resistant to biodegradation, with the increase of substituted methyl groups on parent rings. The degree of alkylation is one of the primary controlling factors on the biodegradation of C6-Cv LHs. There is a particular case： although 2,2,3-trimethylbutane has a rela- tive higher alkylation degree, 2,2-dimethylpentane is more resistant to biodegradation than 2,2,3-trimethylbutane. 2,2- Dimethylpentane is the most resistant to biodegradation in branched C6-C7 alkanes. Furthermore, the 2-methylpen- tane/3-methylpentane and 2-methylhexane/3-methylhexane ratios decreased steadily with increasing biodegradation, which implies that isomers of bilateral methyl groups are more prone to bacterial attack relative to mid-chain iso- mers. The position of the alkyls on the carbon skeleton is also one of the critical factors controlling the rate of biodegradation. With increasing biodegradation, Mango＇s LH parameters K1 values decrease and K2 values increase, the values of n-heptane and isoheptane decrease, and the indices of methylcyclohexane and cyclohexane increase. LH parameters should be applied cautiously for the biodegraded oils. Because biodegraded samples belong to slight or minor biodegraded oils, the values of n-heptane and isoheptane from Dawanqi Oilfield can better reflect and determine the ＂Biodegraded＂ zone. When the heptane value is 0-21 and the isoheptane value is 0-2.6, the crude oil in Dawanqi Oilfield is defined as the ＂Biodegraded＂ zone展开更多
A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-...A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-ray diffraction （XRD）,BET,temperature-programmed desorption of ammonia （NH3-TPD）,temperature-programmed reduction of hydrogen （H2-TPR） and H2-chemisorption techniques,and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor.The reaction temperature,time on stream,space velocity,and the ratio of H2/n-heptane are changed to get the optimal conditions.The Ce（III） and La（III）-exchanged Hβ-zeolites exhibit higher selectivity for isomerized products than the neat Hβ-zeolite.Moreover,the Ce（III）-exchanged catalysts give higher conversions of n-heptane,whereas the La（III）-exchanged ones do not show any improvement in con-version.Under optimal conditions,the catalyst with 0.4% （by mass） Pt and 0.5% （by mass） Ce loading presents very high selectivity of isomerized products of 95.1% coupled with high n-heptane conversion of 68.7%.Effects of the ion-exchange of Ce（III） and La（III） on the catalytic performance are discussed in relation with the physico-chemical properties of catalysts.展开更多
A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface ...A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface of ZnO and Cu(Ⅱ)activated ZnO.The results showed that Cu(Ⅱ)facilitated the xanthate adsorption process on the surface,and led to the formation of cuprous xanthate(CuX),dixanthogen(X_(2))and xanthate aggregates.The adsorption of xanthate on the surface of ZnO and Cu(Ⅱ)activated ZnO was found to both follow the pseudo-first-order kinetic model.When the NaOH solution was used as a desorption agent,the adsorbed xanthate can largely be removed due to the competition between OH^(−)and HX−.However,for Cu(Ⅱ)activated ZnO,the peak intensities at 1197 and 1082 cm^(−1) had no obvious weakening,and the absorption intensities at 1261 and 1026 cm^(−1) increased in the first 5 min,indicating an ion-exchange reaction between OH^(−)and surface zinc bonded xanthate HX−and the reorganization of adsorbed xanthate.展开更多
文摘The bioassay was directed to the fractionation of the methanol extract of the rhizomes of Zingiber officinale Roscoe leading to the isolation of a new antioxidant cyclic diarylheptanoid. The structure of the new compound was established as 1, 5-epoxy-3-hydroxy-1-(3,4-dihydroxy-5-methoxy-phenyl)-7-(3,4-dihydroxyphenyl) heptane (1) on the basis of MS, 1D and 2D-NMR experiments.
基金This work was supported by the National Natural Science Foundation of China （No.21103117）.
文摘The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental results. The products populations depend strongly on the temperature. The quantity of ethylene increases quickly as the temperature goes up. The conversion of n-heptane and the mole fraction of primary products from reactive molecular dynamic and chemical kinetic modeling are compared with each other. We also investigated the pre-exponential factor and activation energy for thermal decomposition of n-heptane by kinetic analysis from the reactive force field simulations, which were extracted to be 1.78×10^14 s^-1 and 47.32 kcal/mol respectively.
文摘In this paper, we investigate HUA’s Theorem for short intervals under GRH. Let E k(x)=#{{n≤x;2|n,k is odd, n≠p 1+p k 2}∪{n≤x;2|n,2|k,(p-1)|k, n1(modp),n≠p 1+p k 2}}. Assume GRH. For any k≥2, any A】0 and any 0【ε【14,E k(x+H)-E k(x)≤H(log x) -Aholds for x 12-14k+ε≤H≤x, here the implies constant depends at most on A and ε.
基金This work was supported by the National Natural Science Foundation of China （No.20273066）.
文摘n-Heptane is the most important straight chain paramn in the fossil-fuel industry. In this work, pyrolysis behavior of n-heptane at high temperature is investigated by a se- ties of ReaxFF based reactive molecular dynamics simulations. Temperature effects on the n-heptane pyrolysis and related products distributions have been detailedly analyzed. The simulation results indicate that the temperature effect is characterized in stages. High tern- perature can accelerate the decomposition of n-heptane, but the influence becomes small after it reaches a certain level. According to the different reaction behaviors, pyrolysis of n-heptane could be divided into three stages. The variation trends of the mass fraction evolu- tion of ethylene （C2H4）, C3, and C4 calculated from reactive molecular dynamics simulations are in good agreement with the previous experimental results. The apparent activation en- ergy extracted from the first-order kinetic analysis is 53.96 kcal/mol and a pre-exponential factor is 55.34×10^13 s-1, which is reasonably consistent with the experimental results.
文摘AIM:To determine the prevalences of TTV and HGV infections among blood donors and patients with chronic liver disease in Korea,to investigate the association of TTV and HGV infections with blood transfusion,and to assess the correlation between TTV and HGV viremia and hepatic damage. METHODS:A total of 391 serum samples were examined in this study.Samples were obtained from healthy blood donors(n=110),hepatitis B surface antigen(HBsAg)-positive donors(n=112),anti-hepatitis C virus(anti-HCV)-positive donors(n=69),patients with type B chronic liver disease (n=81),and patients with type C chronic liver disease(n=19). Trv DNA was detected using the hemi-nested PCR.HGV RNA was tested using RT-PCR.A history of blood transfusion and serum levels of alanine aminotransferase(ALT)and aspartate aminotransferase(AST)were also determined. RESULTS:TTV DNA was detected in 8.2%of healthy blood donors,16.1%of HBsAg-positive donors,20.3%of anti- HCV-positive donors,21.0%of patients with type B chronic liver disease,and 21.1%of patients with type C chronic liver disease.HGV RNA was detected in 1.8%of healthy blood donors,1.8%of HBsAg-positive donors,17.4%of anti-HCV-positive donors,13.6%of patients with type B chronic liver disease,and 10.5%of patients with type C chronic liver disease.The prevalence of TTV and HGV infections in HBV- or HCV-positive donors and patients was significantly higher than in healthy blood donors(P<0.05), except for the detection rate of HGV in HBsAg-positive donors which was the same as for healthy donors.There was a history of transfusion in 66.7%of TTV DNA-positive patients and 76.9%of HGV RNA-positive patients(P<0.05).No significant increase in serum ALT and AST was detected in the TTV or HGV-positive donors and patients. CONCLUSION:TTV and HGV infections are more frequently found in donors and patients infected with HBV or HCV than in healthy blood donors.However,there is no significant association between TTV or HGV infections and liver injury.
文摘Pt-（Sn,Re）/HZSM5-HMS catalysts were evaluated for n-heptane isomerization at 200–350 ℃.To characterize the catalyst,X-ray diffraction,X-ray fluorescene,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,temperature-programmed reduction of H2,temperature-programmed desorption of NH3,infrared spectroscopy of adsorbed pyridine,H2 chemisorption,nitrogen adsorption-desorption,scanning electron microscopy and thermogravimetric analysis were performed.Kinetics of n-C7 isomerization were investigated under various hydrogen and n-C7 pressures,and the effects of reaction conditions on catalytic performance were studied.The results showed that bi-and trimetallic catalysts exhibit better performance than monometallic catalysts for this reaction.For example,a maximum i-C7 selectivity（ 〉74%） and multibranched isomer selectivity（40%） were observed for Pt-Sn/HZSM5-HMS at 200 ℃.
基金financially supported by the National Natural Science Foundation of China (Grant No.41272158 and 41172136)
文摘Light hydrocarbons （LHs） are one of the main petroleum fractions in crude oils, and carry much infor- mation regarding the genetic origin and alteration of crude oils. But secondary alterations--especially biodegrada- tion--have a significant effect on the composition of LHs in crude oils. Because most of the LHs affected in oils underwent only slight biodegradation （rank 1 on the biodegradation scale）, the variation of LHs can be used to describe more the refined features of biodegradation. Here, 23 crude oils from the Dawanqi Oilfield in the Tarim Basin, NW China, eleven of which have been biodegraded to different extents, were analyzed in order to investigate the effect of slight to minor biodegradation on C6--C7 LHs. The study results showed that biodegradation resulted in the prior depletion of straight-chained alkanes, followed by branched alkanes. In slight and minor biodegraded oils, such biodegradation scale could not sufficiently affect C6- C7 cycloalkanes. For branched C6--C7 alkanes, generally, monomethylalkanes are biodegraded earlier than dimethylalkanes and trimethylalkanes, which indicates that branched alkanes are more resistant to biodegradation, with the increase of substituted methyl groups on parent rings. The degree of alkylation is one of the primary controlling factors on the biodegradation of C6-Cv LHs. There is a particular case： although 2,2,3-trimethylbutane has a rela- tive higher alkylation degree, 2,2-dimethylpentane is more resistant to biodegradation than 2,2,3-trimethylbutane. 2,2- Dimethylpentane is the most resistant to biodegradation in branched C6-C7 alkanes. Furthermore, the 2-methylpen- tane/3-methylpentane and 2-methylhexane/3-methylhexane ratios decreased steadily with increasing biodegradation, which implies that isomers of bilateral methyl groups are more prone to bacterial attack relative to mid-chain iso- mers. The position of the alkyls on the carbon skeleton is also one of the critical factors controlling the rate of biodegradation. With increasing biodegradation, Mango＇s LH parameters K1 values decrease and K2 values increase, the values of n-heptane and isoheptane decrease, and the indices of methylcyclohexane and cyclohexane increase. LH parameters should be applied cautiously for the biodegraded oils. Because biodegraded samples belong to slight or minor biodegraded oils, the values of n-heptane and isoheptane from Dawanqi Oilfield can better reflect and determine the ＂Biodegraded＂ zone. When the heptane value is 0-21 and the isoheptane value is 0-2.6, the crude oil in Dawanqi Oilfield is defined as the ＂Biodegraded＂ zone
基金Supported by the Jiangsu Provincial Key Natural Science Foundation for Universities（06KJA53012） the National Natural Science Foundation of China（20476046 20976084）
文摘A series of Pt catalysts supported on the Hβ-zeolite that is ion-exchanged with the rare earth metal ions of Ce（III） and La（III）,are prepared by impregnation,characterized by inductively coupled plasma （ICP）,X-ray diffraction （XRD）,BET,temperature-programmed desorption of ammonia （NH3-TPD）,temperature-programmed reduction of hydrogen （H2-TPR） and H2-chemisorption techniques,and evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor.The reaction temperature,time on stream,space velocity,and the ratio of H2/n-heptane are changed to get the optimal conditions.The Ce（III） and La（III）-exchanged Hβ-zeolites exhibit higher selectivity for isomerized products than the neat Hβ-zeolite.Moreover,the Ce（III）-exchanged catalysts give higher conversions of n-heptane,whereas the La（III）-exchanged ones do not show any improvement in con-version.Under optimal conditions,the catalyst with 0.4% （by mass） Pt and 0.5% （by mass） Ce loading presents very high selectivity of isomerized products of 95.1% coupled with high n-heptane conversion of 68.7%.Effects of the ion-exchange of Ce（III） and La（III） on the catalytic performance are discussed in relation with the physico-chemical properties of catalysts.
基金supported by the National Natural Science Foundation of China (Nos.51274104,50874052)the National Basic Research Program of China (No.2011CB933700)。
文摘A continuous online in situ attenuated total reflection Fourier-transform infrared(ATR-FTIR)spectroscopic technique was used to investigate the adsorption and desorption kinetics of heptyl xanthate(KHX)on the surface of ZnO and Cu(Ⅱ)activated ZnO.The results showed that Cu(Ⅱ)facilitated the xanthate adsorption process on the surface,and led to the formation of cuprous xanthate(CuX),dixanthogen(X_(2))and xanthate aggregates.The adsorption of xanthate on the surface of ZnO and Cu(Ⅱ)activated ZnO was found to both follow the pseudo-first-order kinetic model.When the NaOH solution was used as a desorption agent,the adsorbed xanthate can largely be removed due to the competition between OH^(−)and HX−.However,for Cu(Ⅱ)activated ZnO,the peak intensities at 1197 and 1082 cm^(−1) had no obvious weakening,and the absorption intensities at 1261 and 1026 cm^(−1) increased in the first 5 min,indicating an ion-exchange reaction between OH^(−)and surface zinc bonded xanthate HX−and the reorganization of adsorbed xanthate.
