Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ ...Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3＋ so that the crosslinking between HPAM and Cr3＋ can be prevented completely. Due to the decomposi- tion of the bicarbonate （HCO3-） embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3＋ increased accordingly. When the complexation of Cr3＋ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased signif- icantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate （KH2PO4）, the release of CO2 was very slow and the condition was highly con- trolled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3＋ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.展开更多
This paper investigates 218 related party transactions （RPTs） in Israel, an economy characterized by a high percentage of closely-held finns and identifies a non-linear inverted U connection between the value effect...This paper investigates 218 related party transactions （RPTs） in Israel, an economy characterized by a high percentage of closely-held finns and identifies a non-linear inverted U connection between the value effect of RPT and the level of finn ownership concentration. This non-linear connection is similar to the worldwide documented quadratic （inverted U） relation between ownership concentration and a finn＇s Tobin＇s Q. The relation becomes even statistically stronger, when measuring ownership concentration using a strategic power approach, in an attempt to identify the source of this puzzling connection.展开更多
Pectinase was immobilized onto chitosan support itsing glutaraldehyde as a coupling agent to obtain high activity and stability of pectinase.x A maximum residual activity of 55% was obtained with 0.4 mg proteirdg chit...Pectinase was immobilized onto chitosan support itsing glutaraldehyde as a coupling agent to obtain high activity and stability of pectinase.x A maximum residual activity of 55% was obtained with 0.4 mg proteirdg chitosan （w/w）, 5% （v/v） g/utara/dehyde, and 4℃ for the crosslinking reaction. The optimal pH and temperature for pectinase activity changed from 3.0 and 40℃ to 3.5 and 50℃, respectively, after immobilization The immobilized enzyme exhibited higher stability under varying conditions of pH and temperature and better reusability than the free enzyme.展开更多
基金supported by the National Natural Science Foundation of China(No.51273189)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05016)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05046)
文摘Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3＋ so that the crosslinking between HPAM and Cr3＋ can be prevented completely. Due to the decomposi- tion of the bicarbonate （HCO3-） embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3＋ increased accordingly. When the complexation of Cr3＋ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased signif- icantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate （KH2PO4）, the release of CO2 was very slow and the condition was highly con- trolled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3＋ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.
文摘This paper investigates 218 related party transactions （RPTs） in Israel, an economy characterized by a high percentage of closely-held finns and identifies a non-linear inverted U connection between the value effect of RPT and the level of finn ownership concentration. This non-linear connection is similar to the worldwide documented quadratic （inverted U） relation between ownership concentration and a finn＇s Tobin＇s Q. The relation becomes even statistically stronger, when measuring ownership concentration using a strategic power approach, in an attempt to identify the source of this puzzling connection.
文摘Pectinase was immobilized onto chitosan support itsing glutaraldehyde as a coupling agent to obtain high activity and stability of pectinase.x A maximum residual activity of 55% was obtained with 0.4 mg proteirdg chitosan （w/w）, 5% （v/v） g/utara/dehyde, and 4℃ for the crosslinking reaction. The optimal pH and temperature for pectinase activity changed from 3.0 and 40℃ to 3.5 and 50℃, respectively, after immobilization The immobilized enzyme exhibited higher stability under varying conditions of pH and temperature and better reusability than the free enzyme.
