An HPLC-DAD-ELSD method was developed and validated for the simultaneous quantitation of seven active components（liquiritin, baicalin, wogonoside, baicalein, wogonin, ginsenosides Re and ginsenosides Rb1） in n-butan...An HPLC-DAD-ELSD method was developed and validated for the simultaneous quantitation of seven active components（liquiritin, baicalin, wogonoside, baicalein, wogonin, ginsenosides Re and ginsenosides Rb1） in n-butanol effective fraction of Xiao Chai Hu Tang. A Diamonsil C18（2） column（4.6 mm × 250 mm, 5 μm） was used as the stationary phase and the mobile phase was consisted of acetonitrile and aqueous phosphate acid（0.05%, v/v）. Gradient elution was carried out at the flow rate of 1 m L/min. The detection wavelength was set at 276 nm and an evaporative light scattering detector was also used. Good linearity for all the seven active components was observed. The established method is simple, fast, reliable, and suitable for the quality control of n-butanol effective fraction of Xiao Chai Hu Tang.展开更多
An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently ...An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently from the even mass number isotopes. This mass-indepen- dent isotope fractionation driving force, which originates from the difference in the ground-state electronic energies caused by differences in nuclear size and shape, is cur- rently denoted as the nuclear field shift effect （NFSE）. It is found that the NFSE can drive isotope fractionation of some heavy elements （e.g., Hg, T1, U） to an astonishing degree, far more than the magnitude caused by the con- ventional mass-dependent effect （MDE）. For light ele- ments, the MDE is the dominant factor in isotope fractionation, while the NFSE is neglectable. Furthermore, the MDE and the NFSE both decrease as temperatures increase, though at different rates. The MDE decreases rapidly with a factor of 1/T2, while the NFSE decreases slowly with a factor of 1/T. As a result, even at high temperatures, the NFSE is still significant for many heavy element isotope systems. In this review paper, we begin with an introduction of the basic concept of the NSFE, including its history and recent progress, and follow with the potential implications of the inclusion of the NFSE into the kinetic isotope fractionation effect （KIE） and heavy isotope geochronology.展开更多
Delayed neutron loss is an important parameter in the safety analysis of molten salt reactors. In this study,to obtain the effective delayed neutron fraction under flow condition, a delayed neutron precursor transport...Delayed neutron loss is an important parameter in the safety analysis of molten salt reactors. In this study,to obtain the effective delayed neutron fraction under flow condition, a delayed neutron precursor transport was implemented in the Monte Carlo code MCNP. The moltensalt reactor experiment(MSRE) model was used to analyze the reliability of this method. The obtained flow losses of reactivity for 235 U and 233 U fuels in the MSRE are223 pcm and 100.8 pcm, respectively, which are in good agreement with the experimental values(212 pcm and100.5 pcm, respectively). Then, six groups of effective delayed neutron fractions in a small molten salt reactor were calculated under different mass flow rates. The flow loss of reactivity at full power operation is approximately105.6 pcm, which is significantly lower than that of the MSRE due to the longer residence time inside the active core. The sensitivity of the reactivity loss to other factors,such as the residence time inside or outside the core and flow distribution, was evaluated as well. As a conclusion,the sensitivity of the reactivity loss to the residence time inside the core is greater than to other parameters.展开更多
Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional the...Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64<Ca/(Ca+Mg)<2/16.As a consequence,the 10^3lna between forsterite and other minerals also strongly depend on the Ca content in forsterite.Combining previous studies with our results,the heavier Ca isotopes enrichment sequence in minerals is:forsterite[orthopyroxene[clinopyroxene[calcite & diopside[dolomite[aragonite.Olivineand pyroxenes are enriched in heavier Ca isotope compared to carbonates.The 10^3lna between forsterite with a Ca/(Ca+Mg)of 1/64 and clinopyroxene(Ca/Mg=1/1,i.e.,diopside)is up to^0.64%at 1200 K.The large 103lnaFodiopsiderelative to the current analytical precision for Ca isotope measurements suggests that the dependence of10^3 lnaFo-diopsideon temperature can be used as a thermometer,similar to the one based on the 103lna of 44 Ca/40 Ca between orthopyroxene and diopside.These two Ca isotope thermometers both have a precision approximate to that of elemental thermometers and provide independent constraints on temperature.展开更多
A two-step-cascade membrane separation by ultrafiltration was performed on caprine milk prepared under different temperature conditions to eliminate beta-lactoglobulin (β-Lg) from the whey fraction. Effects of temper...A two-step-cascade membrane separation by ultrafiltration was performed on caprine milk prepared under different temperature conditions to eliminate beta-lactoglobulin (β-Lg) from the whey fraction. Effects of temperature treatment and membrane pore size on the elimination of β-Lg and retention of alpha-lactalbumin (α-La) were examined to determine the optimum permeate fraction for production of infant formula analogues from caprine milk. The frozen raw caprine milk, with and without prior pasteurization, showed the best membrane separation performance. The permeates obtained from the 800/30kDa membrane combination showed the optimal results. The infant formula analog produced using the casein and 800/30kDa-permeate fractions of the treated caprine milk had the closest similarity to human milk with respect to the total protein content (1.3g 100g-1), beta-lactoglobulin content (1% - 2%), and casein- α-lactalbumin ratio (0.6 - 0.7). Membrane performance during ultrafiltration of caprine milk was affected by temperature treatment of the milk prior to membrane separation.展开更多
Objective To investigate the effect of adipose stromal vascular fraction cells(SVFs)on the survival rate of fat ransplantation.Methods 0.5mL autologous fat tissue was mixed with: ① DiI-labeled autologous SVFs (Group ...Objective To investigate the effect of adipose stromal vascular fraction cells(SVFs)on the survival rate of fat ransplantation.Methods 0.5mL autologous fat tissue was mixed with: ① DiI-labeled autologous SVFs (Group A);②展开更多
Results on the existence of piecewise continuous solutions for two classes of initial value problems of impulsive singular fractional differential equations are obtained.
Objective: To investigate the weight losing, antihyperlipidemic and cardioprotective effects of the alkaloid fraction of Hunteria umbellata(H. umbellata) seed.Methods: Adult female Wistar rats(weight range: 120-150 g)...Objective: To investigate the weight losing, antihyperlipidemic and cardioprotective effects of the alkaloid fraction of Hunteria umbellata(H. umbellata) seed.Methods: Adult female Wistar rats(weight range: 120-150 g) were randomly divided into 4 and 5 treatment groups in the normal and triton-induced hyperlipidemic models, respectively. and were daily treated for 14 d before they were humanely sacrificed under inhaled diethyl ether anesthesia. About 5 mL of whole blood was obtained by cardiac puncture from each treated rat, from which serum for lipids assay was subsequently separated. Tissue samples of livers of treated rats were harvested and processed for histopathological analysis.Results: Repeated daily oral treatments of normal rats with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata resulted in significant(P<0.05 and P<0.001) and dose-dependent weight loss, and decreases in the serum triglyceride, total cholesterol and low density lipoprotein cholesterol, while significantly(P<0.001) increased the serum levels of high density lipoprotein cholesterol fraction. Similarly, oral pre-treatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata for 14 d before induction of hyperlipidemia with triton WR-1339 significantly(P<0.01, P<0.001) and dose-dependently attenuated increases in the average body weights, serum levels of triglyceride, total cholesterol and low density lipoprotein cholesterol while also significantly(P<0.01, P<0.001) and dose-dependently attenuated significant(P<0.001) decrease in the serum high-density lipoproteincholesterol levels when compared to the untreated control values. However, the results obtained for 50 mg/kg of alkaloid fraction of H. umbellata in both normal and triton WR-1339-induced hyperlipidemic rats were comparable to that recorded for 20 mg/kg of simvastatin. Similarly, oral pretreatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata significantly improved the histological lesions of fatty hepatic degeneration induced by triton WR-1339 treatment.Conclusions: Overall, results of this study showed that repeated oral treatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata elicited weight losing, antihyperlipidemic and cardioprotective effects in triton WR-1339 induced hyperlipidemic rats that were mediated via de novo cholesterol biosynthesis inhibition.展开更多
In this paper, we introduce the fractional generalized Langevin equation (FGLE) in quantum systems with memory effect. For a particular form of memory kernel that characterizes the quantum system, we obtain the analyt...In this paper, we introduce the fractional generalized Langevin equation (FGLE) in quantum systems with memory effect. For a particular form of memory kernel that characterizes the quantum system, we obtain the analytical solution of the FGLE in terms of the two-parameter Mittag-Leffler function. Based on this solution, we study the time evolution of this system including the qubit excited-state energy, polarization and von Neumann entropy. Memory effect of this system is observed directly through the trapping states of these dynamics.展开更多
Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especiall...Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.展开更多
Objective:To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice.Methods:Parasiteamia was induced unto mice by intraperitoneal injection of 1.25×10&...Objective:To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice.Methods:Parasiteamia was induced unto mice by intraperitoneal injection of 1.25×10<sup>5</sup> Trypanosoma in normal saline.Five days when a high level of parasiteamia was established treatment commenced until ten days.The mice were treated with 10,20 and 40 mg/kg bt.of the extract and 5 and 10 mg/kg bt.of the fraction（F<sub>2</sub>）,respectively for 5 days.Diminazene acelurate at the dose of 3.5 mg/kg bt.for two days was used as the reference drug.The level of parasitaemia and packed cell volume（PCV） of the animals estimated. Results:At doses of 10,20 and 40 mg/kg the crude extract showed a sharp reduction in the level of parasitaemia in mice compared with the untreated group.The mice treated with F,at doses of 5 and 10 mg/kg showed a sharp reduction in the level of parasitamia to zero in day 9,and a gradual recovery from the 12th day of treatment.This effect is comparable to that of the mice treated with 7 mg/kg of standard drug diminazene aceturate.The PCV of the treated showed a gradual decrease with time,but not as much as the untreated group.Phytochemical screening revealed the presence of glycosides,alkaloids,carbohydrates,tannins and proteins in the Abrus precatorius powder while F<sub>2</sub> was rich in alkaloids.Conclusions:This study shows that both the extract and the fractions of Abrus precatorius seeds exhibited a promising trypanocidal property.Alkaloids may be responsible for the observed activity.展开更多
The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model,...The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), 6D = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of 6 and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the 6 and d, and vice versa. However, 6 and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Uriimqi is simulated. The simulated stable isotopic ratio vs temperature and the SD vs δ18O curves are very consistent with the actual regressions and MWL at Uriimqi, respectively.展开更多
基金Foundation for Young Scholars of Shanxi Province,China(Grant No.2011021007-2)
文摘An HPLC-DAD-ELSD method was developed and validated for the simultaneous quantitation of seven active components（liquiritin, baicalin, wogonoside, baicalein, wogonin, ginsenosides Re and ginsenosides Rb1） in n-butanol effective fraction of Xiao Chai Hu Tang. A Diamonsil C18（2） column（4.6 mm × 250 mm, 5 μm） was used as the stationary phase and the mobile phase was consisted of acetonitrile and aqueous phosphate acid（0.05%, v/v）. Gradient elution was carried out at the flow rate of 1 m L/min. The detection wavelength was set at 276 nm and an evaporative light scattering detector was also used. Good linearity for all the seven active components was observed. The established method is simple, fast, reliable, and suitable for the quality control of n-butanol effective fraction of Xiao Chai Hu Tang.
基金funding support from the973 Program(2014CB440904)Chinese NSF projects(41225012,41490635,41530210)
文摘An anomalous isotope effect exists in many heavy element isotope systems （e.g., Sr, Gd, Zn, U）. This effect used to be called the ＂odd--even isotope effect＂ because the odd mass number isotopes behave differently from the even mass number isotopes. This mass-indepen- dent isotope fractionation driving force, which originates from the difference in the ground-state electronic energies caused by differences in nuclear size and shape, is cur- rently denoted as the nuclear field shift effect （NFSE）. It is found that the NFSE can drive isotope fractionation of some heavy elements （e.g., Hg, T1, U） to an astonishing degree, far more than the magnitude caused by the con- ventional mass-dependent effect （MDE）. For light ele- ments, the MDE is the dominant factor in isotope fractionation, while the NFSE is neglectable. Furthermore, the MDE and the NFSE both decrease as temperatures increase, though at different rates. The MDE decreases rapidly with a factor of 1/T2, while the NFSE decreases slowly with a factor of 1/T. As a result, even at high temperatures, the NFSE is still significant for many heavy element isotope systems. In this review paper, we begin with an introduction of the basic concept of the NSFE, including its history and recent progress, and follow with the potential implications of the inclusion of the NFSE into the kinetic isotope fractionation effect （KIE） and heavy isotope geochronology.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of the Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘Delayed neutron loss is an important parameter in the safety analysis of molten salt reactors. In this study,to obtain the effective delayed neutron fraction under flow condition, a delayed neutron precursor transport was implemented in the Monte Carlo code MCNP. The moltensalt reactor experiment(MSRE) model was used to analyze the reliability of this method. The obtained flow losses of reactivity for 235 U and 233 U fuels in the MSRE are223 pcm and 100.8 pcm, respectively, which are in good agreement with the experimental values(212 pcm and100.5 pcm, respectively). Then, six groups of effective delayed neutron fractions in a small molten salt reactor were calculated under different mass flow rates. The flow loss of reactivity at full power operation is approximately105.6 pcm, which is significantly lower than that of the MSRE due to the longer residence time inside the active core. The sensitivity of the reactivity loss to other factors,such as the residence time inside or outside the core and flow distribution, was evaluated as well. As a conclusion,the sensitivity of the reactivity loss to the residence time inside the core is greater than to other parameters.
基金financially supported by the Natural Science Foundation of China (Nos. 41721002, 41473011)Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund
文摘Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64<Ca/(Ca+Mg)<2/16.As a consequence,the 10^3lna between forsterite and other minerals also strongly depend on the Ca content in forsterite.Combining previous studies with our results,the heavier Ca isotopes enrichment sequence in minerals is:forsterite[orthopyroxene[clinopyroxene[calcite & diopside[dolomite[aragonite.Olivineand pyroxenes are enriched in heavier Ca isotope compared to carbonates.The 10^3lna between forsterite with a Ca/(Ca+Mg)of 1/64 and clinopyroxene(Ca/Mg=1/1,i.e.,diopside)is up to^0.64%at 1200 K.The large 103lnaFodiopsiderelative to the current analytical precision for Ca isotope measurements suggests that the dependence of10^3 lnaFo-diopsideon temperature can be used as a thermometer,similar to the one based on the 103lna of 44 Ca/40 Ca between orthopyroxene and diopside.These two Ca isotope thermometers both have a precision approximate to that of elemental thermometers and provide independent constraints on temperature.
文摘A two-step-cascade membrane separation by ultrafiltration was performed on caprine milk prepared under different temperature conditions to eliminate beta-lactoglobulin (β-Lg) from the whey fraction. Effects of temperature treatment and membrane pore size on the elimination of β-Lg and retention of alpha-lactalbumin (α-La) were examined to determine the optimum permeate fraction for production of infant formula analogues from caprine milk. The frozen raw caprine milk, with and without prior pasteurization, showed the best membrane separation performance. The permeates obtained from the 800/30kDa membrane combination showed the optimal results. The infant formula analog produced using the casein and 800/30kDa-permeate fractions of the treated caprine milk had the closest similarity to human milk with respect to the total protein content (1.3g 100g-1), beta-lactoglobulin content (1% - 2%), and casein- α-lactalbumin ratio (0.6 - 0.7). Membrane performance during ultrafiltration of caprine milk was affected by temperature treatment of the milk prior to membrane separation.
文摘Objective To investigate the effect of adipose stromal vascular fraction cells(SVFs)on the survival rate of fat ransplantation.Methods 0.5mL autologous fat tissue was mixed with: ① DiI-labeled autologous SVFs (Group A);②
基金Supported by the Natural Science Foundation of Guangdong Province (S2011010001900)the Guangdong Higher Education Foundation for High-Level Talents
文摘Results on the existence of piecewise continuous solutions for two classes of initial value problems of impulsive singular fractional differential equations are obtained.
基金Supported by Institute of International Education(IIE ID:15101139)
文摘Objective: To investigate the weight losing, antihyperlipidemic and cardioprotective effects of the alkaloid fraction of Hunteria umbellata(H. umbellata) seed.Methods: Adult female Wistar rats(weight range: 120-150 g) were randomly divided into 4 and 5 treatment groups in the normal and triton-induced hyperlipidemic models, respectively. and were daily treated for 14 d before they were humanely sacrificed under inhaled diethyl ether anesthesia. About 5 mL of whole blood was obtained by cardiac puncture from each treated rat, from which serum for lipids assay was subsequently separated. Tissue samples of livers of treated rats were harvested and processed for histopathological analysis.Results: Repeated daily oral treatments of normal rats with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata resulted in significant(P<0.05 and P<0.001) and dose-dependent weight loss, and decreases in the serum triglyceride, total cholesterol and low density lipoprotein cholesterol, while significantly(P<0.001) increased the serum levels of high density lipoprotein cholesterol fraction. Similarly, oral pre-treatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata for 14 d before induction of hyperlipidemia with triton WR-1339 significantly(P<0.01, P<0.001) and dose-dependently attenuated increases in the average body weights, serum levels of triglyceride, total cholesterol and low density lipoprotein cholesterol while also significantly(P<0.01, P<0.001) and dose-dependently attenuated significant(P<0.001) decrease in the serum high-density lipoproteincholesterol levels when compared to the untreated control values. However, the results obtained for 50 mg/kg of alkaloid fraction of H. umbellata in both normal and triton WR-1339-induced hyperlipidemic rats were comparable to that recorded for 20 mg/kg of simvastatin. Similarly, oral pretreatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata significantly improved the histological lesions of fatty hepatic degeneration induced by triton WR-1339 treatment.Conclusions: Overall, results of this study showed that repeated oral treatments with 25 and 50 mg/kg/day of alkaloid fraction of H. umbellata elicited weight losing, antihyperlipidemic and cardioprotective effects in triton WR-1339 induced hyperlipidemic rats that were mediated via de novo cholesterol biosynthesis inhibition.
文摘In this paper, we introduce the fractional generalized Langevin equation (FGLE) in quantum systems with memory effect. For a particular form of memory kernel that characterizes the quantum system, we obtain the analytical solution of the FGLE in terms of the two-parameter Mittag-Leffler function. Based on this solution, we study the time evolution of this system including the qubit excited-state energy, polarization and von Neumann entropy. Memory effect of this system is observed directly through the trapping states of these dynamics.
基金the funding supports from the strategic priority research program (B) of CAS (XDB18010100)Chinese NSF projects (Nos. 41530210, 41490635)
文摘Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.
文摘Objective:To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice.Methods:Parasiteamia was induced unto mice by intraperitoneal injection of 1.25×10<sup>5</sup> Trypanosoma in normal saline.Five days when a high level of parasiteamia was established treatment commenced until ten days.The mice were treated with 10,20 and 40 mg/kg bt.of the extract and 5 and 10 mg/kg bt.of the fraction（F<sub>2</sub>）,respectively for 5 days.Diminazene acelurate at the dose of 3.5 mg/kg bt.for two days was used as the reference drug.The level of parasitaemia and packed cell volume（PCV） of the animals estimated. Results:At doses of 10,20 and 40 mg/kg the crude extract showed a sharp reduction in the level of parasitaemia in mice compared with the untreated group.The mice treated with F,at doses of 5 and 10 mg/kg showed a sharp reduction in the level of parasitamia to zero in day 9,and a gradual recovery from the 12th day of treatment.This effect is comparable to that of the mice treated with 7 mg/kg of standard drug diminazene aceturate.The PCV of the treated showed a gradual decrease with time,but not as much as the untreated group.Phytochemical screening revealed the presence of glycosides,alkaloids,carbohydrates,tannins and proteins in the Abrus precatorius powder while F<sub>2</sub> was rich in alkaloids.Conclusions:This study shows that both the extract and the fractions of Abrus precatorius seeds exhibited a promising trypanocidal property.Alkaloids may be responsible for the observed activity.
基金This work was supported by the National High Technology Research and Development Program of China (863 Program, Grant No. 2002AA135360), the National Natural Science Foundation of China (Grant No. 40271025), the National Key Research Project (Grant No.
文摘The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), 6D = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of 6 and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the 6 and d, and vice versa. However, 6 and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Uriimqi is simulated. The simulated stable isotopic ratio vs temperature and the SD vs δ18O curves are very consistent with the actual regressions and MWL at Uriimqi, respectively.
