In the present work, the exchangeable acidity of a red soilcolloid and a latosol colloid at different pH during reacting withfour neutral salts was measured. The results show that theexchangeable acidity increased wit...In the present work, the exchangeable acidity of a red soilcolloid and a latosol colloid at different pH during reacting withfour neutral salts was measured. The results show that theexchangeable acidity increased with increasing amounts of the neutralsalts added, and the relation between them was almost linear. Whenthe amount of the neutral salt added was lower than a certain value,the slop of the line was high, and the slop turned low when theamount exceeded that value, so there was a turning point in eachline. The addition amounts of the neutral salts for the turningpoints were affected by the cation species of the neutral salts, butpH had less effect on them. After the turning points occurred, theexchangeable acidity of the red soil colloid still graduallyincreased with the addition amounts of the neutral salts, but that ofthe latosol colloid did not increase any more.展开更多
The paper aimed to investigate the growth of seedlings of three species of Cassia （C tora, C. sophera and C occidentalis） at different concentrations of salinity （NaC1） and pH treatments. All the species showed th...The paper aimed to investigate the growth of seedlings of three species of Cassia （C tora, C. sophera and C occidentalis） at different concentrations of salinity （NaC1） and pH treatments. All the species showed the highest seedling length under control condition, and with the increase of salinity, C occidentalis showed the highest sensitivity. The seedling length of C tora at 0.05 M NaCI significantly （P = 0.05） decreased to 5.71 cm, and further increase of salinity to 0.1 M, the seedling length was decreased to less than the value of 0.05 M NaC1 treatment and one-third （2.15 cm） of that of control （6.92 cm）. Seeds of all the species failed to germinate at 0.5 M NaC1. Scarified seeds of C. sophera and C occidentalis increased seedling length. The highest seedling length was in C. sophera, followed by C. tora and C. occidentalis. All the species showed significant decrease （P 〈 0.05） of fresh weight with the increase of salinity; scarification of seeds in C. occidentalis and C. sophera showed higher fresh weight than those of without scarification. Experiments at different pH levels did not show any significant （P = 0.05） change in seedling length, except C. sophera, while at acidic pH, both seedling length and dry weight were significantly （P 〈 0.05） decreased.展开更多
New liquid-liquid equilibrium data for polyethylene glycol （PEG） 3000 ＋ CHO2K ＋ H20 systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal cu...New liquid-liquid equilibrium data for polyethylene glycol （PEG） 3000 ＋ CHO2K ＋ H20 systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal curve to be displaced downward and the two-phase region to expand. Accordingly, the binodal curve was adjusted to the Pirdashti equation and the tie-line compositions were correlated using the Othmer-Tobias, Bancroft and Hand equations. The study measured the refractive index and densities of several homogeneous binary and ternary solutions. The solutions were used for calibration within a range of 0% to 30% of the mass of the PEG and potassium formate. The density and refractive index data show a linear variation with the mass fraction of the polymer and the salt. The effect of pH on the binodal, tie-line lengths （TLL） and slope of the tie-line （STL） in the systems was exam- ined. It was found that an increase in pH increased the TLL and decreased the STL It was observed that the density of the aqueous two-phase system was influenced by the TLL The difference in density between phases （△p） increased as the TLL and pH increased. It was found that the TLL and Ap showed a linear relationship. The effective excluded volume （EEV） of the PEG was obtained and it was found that EEV also increased as the pH increased.展开更多
The acidity characteristics of acid sulphate soils of Kuttanad, Kerala, were studied in detail by collecting surface, profile and subsurface soil samples from 20 locations of six soil series viz., Ambalapuzha, Purakka...The acidity characteristics of acid sulphate soils of Kuttanad, Kerala, were studied in detail by collecting surface, profile and subsurface soil samples from 20 locations of six soil series viz., Ambalapuzha, Purakkad, Thotapally, Thuravur, Kallara and - Thakazhi that belonged to acid sulphate soils. The soils were extremely acidic showing a range of pH （H：O） varying from 2.5 to 5.2. Lowest pH was recorded by Thakazhi series and the highest by Thotapally. The potential acidity of soils ranged from 14.71 cmol.kg-1 to 110.5 cmol-kg1 with Thakazhi series showing the highest value. The contribution of hydrolytic acidity to potential acidity ranged from 70.2% to 97.2%. In all soil series, exchangeable A13＋ was greater than exchangeable H~. A significant correlation was observed among pH （KCI）, pH （H20） and pH （CaCI2） in all series.展开更多
A study about some physicochemical parameters of Egbe reservoir was carried out from September 2005 to December 2006. The parameters include mean temperature, pH, conductivity, alkalinity, TSS, TDS, DO and BOD which h...A study about some physicochemical parameters of Egbe reservoir was carried out from September 2005 to December 2006. The parameters include mean temperature, pH, conductivity, alkalinity, TSS, TDS, DO and BOD which have values of 28.7±0.9 ℃ ; 8.3±0.3; 831±172.5 μS/cm; 165.4±18.3 mg/L; 0.06±0.1 mg/L; 0.4±0.6 mg/L; 7.8±2.4 mg/L and 5.2±1.6mg/L, respectively. Temperature and pH were measured in the field using mercury-in-glass thermometer calibrated in degrees Celsius and pH meter, respectively. TSS and TDS were measured by grayimetric methods, while alkalinity was measured titrimetrically and DO and BOD were measured by Winkler＇s method. For the nutrients, nitrate was measured color±metrically, phosphate by Stannous Chloride method and sulphate by turbidimetric method. Mean concentration of nitrate, phosphate, and sulphate were 15.6±8.6 rag/L; 42.5±19.4 mg/L and 72.3±14.7 mg/L respectively. Nowadays, eutrophication of natural waters is one of the most significant causes of deterioration of water quality, and nitrates and phosphates are probably the key nutrients in controlling the growth of aquatic plants. Though the mean concentration of nitrates and phosphates in the reservoir water were within the acceptable limit, yet their concentrations in some locations of reservoir were high enough to encourage the growth of aquatic macrophytes which would increase productivities. Hence, it is necessary to check their further increase, and periodic monitoring and preventive measures must be adopted to save the reservoir from eutrophication.展开更多
In this study, we apply both palrwise AMBER03 force field and the recently developed polarized force field to study the folding process of EK peptide under various ion strength and pH conditions. The polarized force f...In this study, we apply both palrwise AMBER03 force field and the recently developed polarized force field to study the folding process of EK peptide under various ion strength and pH conditions. The polarized force field is based on our newly proposed adaptive hydrogen bond-specific charge （AHBC） scheme. These two force fields differ only by the atomic charges. Solvent effect is described with generalized Born models （IGB5 in AMBER 10 package）. The result shows that although when applying AMBER03 charge, the helical structure is preferred, its dependence on salt concentration and pH is qualitatively wrong. While using AHBC the peptide finds its native structure within 10 ns, and then fluctuates around this folded state. Under high salt concentration or extreme pH conditions the calculated helical structure probability drops, which is in qualitative agreement with the experiment. Analysis of the atomic charges and the interaction between the donor-acceptor pair in main hydrogen bonds shows that the helical structure is stabilized when polarization effect is counted. It again shows that polarization effect is a very important improvement over traditional force field and is essential for protein folding. We also prove that the salt bridge interaction between 4-residue apart GLU and LYS residues is not critical to the stability of helical structure of EK peptide, but is merely an auxiliary factor, also in agreement with the experiment.展开更多
In order to utilize the wasted saline-sodic soils under shallow groundwater condition, a 3-year field study was carried in a field cropped with Lycium barbarum L. and irrigated by drip irrigation with saline groundwat...In order to utilize the wasted saline-sodic soils under shallow groundwater condition, a 3-year field study was carried in a field cropped with Lycium barbarum L. and irrigated by drip irrigation with saline groundwater under the water table depth of 30-40 cm in the northern Yinchuan Plain, China. Effects of cropping duration （one, two, and three years） on soil salinity, soil solution composition, and pH in three adjacent plots were investigated in 2008. Results showed that a high irrigation frequency maintained high soil water potential and subsequently facilitated infiltration and downward movement of water and salt in the crop root zone. Salt accumulated on the edges of the ridges, and soil saturated-paste electrical conductivity （ECe） was higher in the edge. Concentrations of Na^＋, Ca^2＋, Mg^2＋, Cl^-, and SO24^- in the soil increased with the soil depth as did the ECe, while HCO3 and pH had a relative uniform distribution in soil profile. As planting year increased, the ECe and soil salts in the field had a decreasing tendency, while in the root zone they decreased immediately after irrigation and then remained relatively stable in the following growing seasons. HCO3 and pH had little change with the planting year. Results suggested that the application of drip irrigation with saline water could ameliorate saline-sodic soil and provide a relatively feasible soil environment for saline-sodic soils with shallow groundwater.展开更多
基金Project (Nos. 49971046 and 49831005) supported by the National Natural Science Foundation of China.
文摘In the present work, the exchangeable acidity of a red soilcolloid and a latosol colloid at different pH during reacting withfour neutral salts was measured. The results show that theexchangeable acidity increased with increasing amounts of the neutralsalts added, and the relation between them was almost linear. Whenthe amount of the neutral salt added was lower than a certain value,the slop of the line was high, and the slop turned low when theamount exceeded that value, so there was a turning point in eachline. The addition amounts of the neutral salts for the turningpoints were affected by the cation species of the neutral salts, butpH had less effect on them. After the turning points occurred, theexchangeable acidity of the red soil colloid still graduallyincreased with the addition amounts of the neutral salts, but that ofthe latosol colloid did not increase any more.
文摘The paper aimed to investigate the growth of seedlings of three species of Cassia （C tora, C. sophera and C occidentalis） at different concentrations of salinity （NaC1） and pH treatments. All the species showed the highest seedling length under control condition, and with the increase of salinity, C occidentalis showed the highest sensitivity. The seedling length of C tora at 0.05 M NaCI significantly （P = 0.05） decreased to 5.71 cm, and further increase of salinity to 0.1 M, the seedling length was decreased to less than the value of 0.05 M NaC1 treatment and one-third （2.15 cm） of that of control （6.92 cm）. Seeds of all the species failed to germinate at 0.5 M NaC1. Scarified seeds of C. sophera and C occidentalis increased seedling length. The highest seedling length was in C. sophera, followed by C. tora and C. occidentalis. All the species showed significant decrease （P 〈 0.05） of fresh weight with the increase of salinity; scarification of seeds in C. occidentalis and C. sophera showed higher fresh weight than those of without scarification. Experiments at different pH levels did not show any significant （P = 0.05） change in seedling length, except C. sophera, while at acidic pH, both seedling length and dry weight were significantly （P 〈 0.05） decreased.
文摘New liquid-liquid equilibrium data for polyethylene glycol （PEG） 3000 ＋ CHO2K ＋ H20 systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal curve to be displaced downward and the two-phase region to expand. Accordingly, the binodal curve was adjusted to the Pirdashti equation and the tie-line compositions were correlated using the Othmer-Tobias, Bancroft and Hand equations. The study measured the refractive index and densities of several homogeneous binary and ternary solutions. The solutions were used for calibration within a range of 0% to 30% of the mass of the PEG and potassium formate. The density and refractive index data show a linear variation with the mass fraction of the polymer and the salt. The effect of pH on the binodal, tie-line lengths （TLL） and slope of the tie-line （STL） in the systems was exam- ined. It was found that an increase in pH increased the TLL and decreased the STL It was observed that the density of the aqueous two-phase system was influenced by the TLL The difference in density between phases （△p） increased as the TLL and pH increased. It was found that the TLL and Ap showed a linear relationship. The effective excluded volume （EEV） of the PEG was obtained and it was found that EEV also increased as the pH increased.
文摘The acidity characteristics of acid sulphate soils of Kuttanad, Kerala, were studied in detail by collecting surface, profile and subsurface soil samples from 20 locations of six soil series viz., Ambalapuzha, Purakkad, Thotapally, Thuravur, Kallara and - Thakazhi that belonged to acid sulphate soils. The soils were extremely acidic showing a range of pH （H：O） varying from 2.5 to 5.2. Lowest pH was recorded by Thakazhi series and the highest by Thotapally. The potential acidity of soils ranged from 14.71 cmol.kg-1 to 110.5 cmol-kg1 with Thakazhi series showing the highest value. The contribution of hydrolytic acidity to potential acidity ranged from 70.2% to 97.2%. In all soil series, exchangeable A13＋ was greater than exchangeable H~. A significant correlation was observed among pH （KCI）, pH （H20） and pH （CaCI2） in all series.
文摘A study about some physicochemical parameters of Egbe reservoir was carried out from September 2005 to December 2006. The parameters include mean temperature, pH, conductivity, alkalinity, TSS, TDS, DO and BOD which have values of 28.7±0.9 ℃ ; 8.3±0.3; 831±172.5 μS/cm; 165.4±18.3 mg/L; 0.06±0.1 mg/L; 0.4±0.6 mg/L; 7.8±2.4 mg/L and 5.2±1.6mg/L, respectively. Temperature and pH were measured in the field using mercury-in-glass thermometer calibrated in degrees Celsius and pH meter, respectively. TSS and TDS were measured by grayimetric methods, while alkalinity was measured titrimetrically and DO and BOD were measured by Winkler＇s method. For the nutrients, nitrate was measured color±metrically, phosphate by Stannous Chloride method and sulphate by turbidimetric method. Mean concentration of nitrate, phosphate, and sulphate were 15.6±8.6 rag/L; 42.5±19.4 mg/L and 72.3±14.7 mg/L respectively. Nowadays, eutrophication of natural waters is one of the most significant causes of deterioration of water quality, and nitrates and phosphates are probably the key nutrients in controlling the growth of aquatic plants. Though the mean concentration of nitrates and phosphates in the reservoir water were within the acceptable limit, yet their concentrations in some locations of reservoir were high enough to encourage the growth of aquatic macrophytes which would increase productivities. Hence, it is necessary to check their further increase, and periodic monitoring and preventive measures must be adopted to save the reservoir from eutrophication.
基金supported by the National Natural Science Foundation of China (20803034)the Shanghai Rising-Star Program+2 种基金supported by the Nanyang Technological University Start-up (M58110043)support from the National Natural Science Foundation of China (20933002)Shanghai Pujiang Program (09PJ1404000)
文摘In this study, we apply both palrwise AMBER03 force field and the recently developed polarized force field to study the folding process of EK peptide under various ion strength and pH conditions. The polarized force field is based on our newly proposed adaptive hydrogen bond-specific charge （AHBC） scheme. These two force fields differ only by the atomic charges. Solvent effect is described with generalized Born models （IGB5 in AMBER 10 package）. The result shows that although when applying AMBER03 charge, the helical structure is preferred, its dependence on salt concentration and pH is qualitatively wrong. While using AHBC the peptide finds its native structure within 10 ns, and then fluctuates around this folded state. Under high salt concentration or extreme pH conditions the calculated helical structure probability drops, which is in qualitative agreement with the experiment. Analysis of the atomic charges and the interaction between the donor-acceptor pair in main hydrogen bonds shows that the helical structure is stabilized when polarization effect is counted. It again shows that polarization effect is a very important improvement over traditional force field and is essential for protein folding. We also prove that the salt bridge interaction between 4-residue apart GLU and LYS residues is not critical to the stability of helical structure of EK peptide, but is merely an auxiliary factor, also in agreement with the experiment.
基金Supported by the Chinese Academy of Sciences Action Plan for the Development of Western China (No. KZCX2-XB2-13)the Chinese Academy of Sciences Knowledge Innovation Program (No. KSCX2-YW-N-003)the 100 Talents Program of Chinese Academy of Sciences
文摘In order to utilize the wasted saline-sodic soils under shallow groundwater condition, a 3-year field study was carried in a field cropped with Lycium barbarum L. and irrigated by drip irrigation with saline groundwater under the water table depth of 30-40 cm in the northern Yinchuan Plain, China. Effects of cropping duration （one, two, and three years） on soil salinity, soil solution composition, and pH in three adjacent plots were investigated in 2008. Results showed that a high irrigation frequency maintained high soil water potential and subsequently facilitated infiltration and downward movement of water and salt in the crop root zone. Salt accumulated on the edges of the ridges, and soil saturated-paste electrical conductivity （ECe） was higher in the edge. Concentrations of Na^＋, Ca^2＋, Mg^2＋, Cl^-, and SO24^- in the soil increased with the soil depth as did the ECe, while HCO3 and pH had a relative uniform distribution in soil profile. As planting year increased, the ECe and soil salts in the field had a decreasing tendency, while in the root zone they decreased immediately after irrigation and then remained relatively stable in the following growing seasons. HCO3 and pH had little change with the planting year. Results suggested that the application of drip irrigation with saline water could ameliorate saline-sodic soil and provide a relatively feasible soil environment for saline-sodic soils with shallow groundwater.
