Cotton leaf curl virus (CLCuV) belongs to the subgroup III of geminiviruses with single strand DNA genome. Study demonstrated that the bidirectional promoter of CLCuV had activity in Agrobacterium tumefaciens (Smith e...Cotton leaf curl virus (CLCuV) belongs to the subgroup III of geminiviruses with single strand DNA genome. Study demonstrated that the bidirectional promoter of CLCuV had activity in Agrobacterium tumefaciens (Smith et Townsend) Conn. This is the first report for the activity of the bidirectional promoter of geminivirus in A. tumefaciens. Results showed that the activity of the complementary sense promoter was stronger than that of virion sense promoter, and was detected 2-fold higher than that of CaMV 35S promoter in A. tumefaciens. Moreover, the promoter 5' deletion analysis indicated that the mean GUS activity driven by a 287 nucleotides complementary sense promoter fragment (from-287 to the translation initiation site) is 4 times higher than that driven by the whole complementary sense promoter in A. tumefaciens. This result suggested that there might exist negative regulatory elements in this deleted fragment. The function of other cis-elements included in CLCuV complementary sense promoter was also discussed in this paper.展开更多
The dissolution of nickel and cobalt from Caldag lateritic nickel ore using the combination of sulphuric and ascorbic acids was investigated. The use of other organic acids, namely citric, maleic and stearic acids, as...The dissolution of nickel and cobalt from Caldag lateritic nickel ore using the combination of sulphuric and ascorbic acids was investigated. The use of other organic acids, namely citric, maleic and stearic acids, as synergistic reagents was studied for comparison. The results revealed that the use of ascorbic and citric acids markedly improved the dissolution of cobalt compared to the other two organic acids that only showed slight synergistic effect on the leaching rate. In terms of nickel dissolution, ascorbic acid is the most effective synergist, followed by citric, maleic and stearic acids in descending order. Under the most optimized conditions found in this study, i.e., using 1 mol/L of sulphuric acid with the presence of 4 g/L of ascorbic acid at 80 ℃and solid-to-liquid ratio of 1/10, more than 99% and 98% leaching rates of cobalt and nickel, respectively, can be achieved within 4 h of leaching. In addition, the leaching performance is relatively insensitive to the change of ascorbic acid concentration from 2 to 4 g/L which is highly desirable from operational perspective.展开更多
Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore it...Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.展开更多
Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change o...Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary's law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy's law.展开更多
The soil-water characteristic curve (SWCC) is the primary partially saturated soil information as its behavior and properties can be derived from it. Although there have been many studies of unsaturated soils and the ...The soil-water characteristic curve (SWCC) is the primary partially saturated soil information as its behavior and properties can be derived from it. Although there have been many studies of unsaturated soils and the SWCC, there is still no combined constitutive model that can simulate soil characteristics accurately. In cases when hydraulic hysteresis is dominant (e.g. under cyclic loading) it is particularly important to use the SWCC. In the past decades, several mathematical expressions have been proposed to model the curve. There are various influences on the SWCC as a source of information, so the curves obtained from conventional tests often cannot be directly applied; and the mathematical expressions from one scenario cannot be used to simulate another situation. The effects of void ratio, initial water content, stress state and high suction were studied in this work revealing that water content and stress state are more important than the other effects; but that the influences tend to decrease when suction increases. The van Genuchten model was modified to simulate better the changes in the degree of saturation at low values of suction. Predictions were compared with experimental results to determine the simulation capability of the model.展开更多
Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free t...Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free troposphere are made using surface Micro-Pulse Lidar (MPL) measurements. The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E), which is near the major dust source regions of the Taklimakan and Gobi deserts. The vertical distribution of the MPL backscattering suggested that nondust aerosols floated from ground level to an altitude of approximately 9 km around the source regions. Early morning hours are characterized by a shallow aerosol layer of a few hundred meters thick. As the day progresses, strong convective eddies transport the aero- sols vertically to more than 1500 m.展开更多
文摘Cotton leaf curl virus (CLCuV) belongs to the subgroup III of geminiviruses with single strand DNA genome. Study demonstrated that the bidirectional promoter of CLCuV had activity in Agrobacterium tumefaciens (Smith et Townsend) Conn. This is the first report for the activity of the bidirectional promoter of geminivirus in A. tumefaciens. Results showed that the activity of the complementary sense promoter was stronger than that of virion sense promoter, and was detected 2-fold higher than that of CaMV 35S promoter in A. tumefaciens. Moreover, the promoter 5' deletion analysis indicated that the mean GUS activity driven by a 287 nucleotides complementary sense promoter fragment (from-287 to the translation initiation site) is 4 times higher than that driven by the whole complementary sense promoter in A. tumefaciens. This result suggested that there might exist negative regulatory elements in this deleted fragment. The function of other cis-elements included in CLCuV complementary sense promoter was also discussed in this paper.
文摘The dissolution of nickel and cobalt from Caldag lateritic nickel ore using the combination of sulphuric and ascorbic acids was investigated. The use of other organic acids, namely citric, maleic and stearic acids, as synergistic reagents was studied for comparison. The results revealed that the use of ascorbic and citric acids markedly improved the dissolution of cobalt compared to the other two organic acids that only showed slight synergistic effect on the leaching rate. In terms of nickel dissolution, ascorbic acid is the most effective synergist, followed by citric, maleic and stearic acids in descending order. Under the most optimized conditions found in this study, i.e., using 1 mol/L of sulphuric acid with the presence of 4 g/L of ascorbic acid at 80 ℃and solid-to-liquid ratio of 1/10, more than 99% and 98% leaching rates of cobalt and nickel, respectively, can be achieved within 4 h of leaching. In addition, the leaching performance is relatively insensitive to the change of ascorbic acid concentration from 2 to 4 g/L which is highly desirable from operational perspective.
基金Project supported in part by the Deutsche Forschungsgemeinschaft (DFG), Germany (No. RO 1080/8-1) jointly by Max-Planck Gesellschaft and the Chinese Academy of Sciences through a travel grant to the first author.
文摘Ground-penetrating radar (GPR) has been used predominantly for environments with low electrical conductivity like freshwater aquifers, glaciers, or dry sandy soils. The objective of the present study was to explore its application for mapping in subsurface agricultural soils to a depth of several meters. For a loamy sand and a clayey site on the North China Plain, clay inclusions in the sand were detected; the thickness, inclination, and continuity of the confining clay and silt layers was assessed; and a local water table was mapped. Direct sampling (soil coring and profiling) in the top meter and independent measurement of the water table were utilized to confirm the findings. Also, effective estimates of the dielectric number for the site with the dielectric number of moist clayey soils depending strongly on frequency were obtained. Thus, important properties of soils, like the arrangement and type of layers and in particular their continuity and inclination, could be explored with moderate efforts for rather large areas to help find optimal locations for the time-consuming and expensive measurements which would be necessary to detail a model of the subsurface.
基金Projects(50878191,51109092)supported by the National Natural Science Foundation of China
文摘Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary's law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy's law.
基金Project (No. 22833012) supported by the China Scholarship Council
文摘The soil-water characteristic curve (SWCC) is the primary partially saturated soil information as its behavior and properties can be derived from it. Although there have been many studies of unsaturated soils and the SWCC, there is still no combined constitutive model that can simulate soil characteristics accurately. In cases when hydraulic hysteresis is dominant (e.g. under cyclic loading) it is particularly important to use the SWCC. In the past decades, several mathematical expressions have been proposed to model the curve. There are various influences on the SWCC as a source of information, so the curves obtained from conventional tests often cannot be directly applied; and the mathematical expressions from one scenario cannot be used to simulate another situation. The effects of void ratio, initial water content, stress state and high suction were studied in this work revealing that water content and stress state are more important than the other effects; but that the influences tend to decrease when suction increases. The van Genuchten model was modified to simulate better the changes in the degree of saturation at low values of suction. Predictions were compared with experimental results to determine the simulation capability of the model.
基金supported by the National Natural Science Foundation of China under Grant Nos. 40628005 and 40633017
文摘Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free troposphere are made using surface Micro-Pulse Lidar (MPL) measurements. The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E), which is near the major dust source regions of the Taklimakan and Gobi deserts. The vertical distribution of the MPL backscattering suggested that nondust aerosols floated from ground level to an altitude of approximately 9 km around the source regions. Early morning hours are characterized by a shallow aerosol layer of a few hundred meters thick. As the day progresses, strong convective eddies transport the aero- sols vertically to more than 1500 m.
