In order to synthesize an improved adsorbent for heavy metal ions,we studied the condensation reaction of chitosan with salicylaldehyde in ethanol to form a Schiff base.The effect irradiating the reaction using an ult...In order to synthesize an improved adsorbent for heavy metal ions,we studied the condensation reaction of chitosan with salicylaldehyde in ethanol to form a Schiff base.The effect irradiating the reaction using an ultrasonic liquid processor was contrasted with conventional methods.The IR spectra of condensed chitosan prepared by the two methods showed that their molecular structures were identical.The reaction conditions,including solvents,ultrasonic power density and irradiation time,pH,and reactant ratio,were optimized by orthogonal design.A shorter reaction time and a higher product yield were obtained using ultrasonic-assisted synthesis compared with the traditional method.A condensation degree of 89.63% was achieved using the optimized conditions:i.e.ultrasonic irradiation at 180 W for 60 min;95% ethanol as the solvent,pH 4.0,and salicylaldehyde:chitosan ratio of 6:1.展开更多
Spread-F is a manifestation of ionospheric irregularities and generally takes place at nighttime. However, it can also be ob- served seldom at daytime, It is recognized that acoustic gravity waves （AGWs） play an imp...Spread-F is a manifestation of ionospheric irregularities and generally takes place at nighttime. However, it can also be ob- served seldom at daytime, It is recognized that acoustic gravity waves （AGWs） play an important role in triggering plasma instability which results in spread-F in the ionosphere. The typhoon is a main source of the AGWs. In this paper, two cases of ionospheric daytime spread-F in the period of typhoon were analyzed. One case was on July 29, 1988 and the other was on August 01, 1989. The results showed the following： 1） There were some wave-like disturbances appearing in the HF Doppler records firstly, consequently the Doppler echo traces became scattered, which indicated that the ionospheric spread-F was triggered; 2） the blurred echo traces in the both two cases appeared in the morning （08：30-11：30 Beijing time） and lasted for more than two hours; 3） with the blurred echoes gradually weakening, the traveling ionospheric disturbances （TIDs） still ex- isted and became clearer; 4） the frequency shifts in the two of the radio wave in the ionosphere moved downwards. spread-F during the typhoon period in Asian region. cases were both positive, implying the effective reflecting surface These results provide good observational evidence for daytime展开更多
基金Supported by Doctoral Discipline Special Foundation,Education Ministry of China (No.20050561014)the National High Technology Research and Development Program of China (863 Program) (No.2007AA100405)
文摘In order to synthesize an improved adsorbent for heavy metal ions,we studied the condensation reaction of chitosan with salicylaldehyde in ethanol to form a Schiff base.The effect irradiating the reaction using an ultrasonic liquid processor was contrasted with conventional methods.The IR spectra of condensed chitosan prepared by the two methods showed that their molecular structures were identical.The reaction conditions,including solvents,ultrasonic power density and irradiation time,pH,and reactant ratio,were optimized by orthogonal design.A shorter reaction time and a higher product yield were obtained using ultrasonic-assisted synthesis compared with the traditional method.A condensation degree of 89.63% was achieved using the optimized conditions:i.e.ultrasonic irradiation at 180 W for 60 min;95% ethanol as the solvent,pH 4.0,and salicylaldehyde:chitosan ratio of 6:1.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40974091, 41174135 and 40921063)the Specialized Research Fund for State Key Laboratories
文摘Spread-F is a manifestation of ionospheric irregularities and generally takes place at nighttime. However, it can also be ob- served seldom at daytime, It is recognized that acoustic gravity waves （AGWs） play an important role in triggering plasma instability which results in spread-F in the ionosphere. The typhoon is a main source of the AGWs. In this paper, two cases of ionospheric daytime spread-F in the period of typhoon were analyzed. One case was on July 29, 1988 and the other was on August 01, 1989. The results showed the following： 1） There were some wave-like disturbances appearing in the HF Doppler records firstly, consequently the Doppler echo traces became scattered, which indicated that the ionospheric spread-F was triggered; 2） the blurred echo traces in the both two cases appeared in the morning （08：30-11：30 Beijing time） and lasted for more than two hours; 3） with the blurred echoes gradually weakening, the traveling ionospheric disturbances （TIDs） still ex- isted and became clearer; 4） the frequency shifts in the two of the radio wave in the ionosphere moved downwards. spread-F during the typhoon period in Asian region. cases were both positive, implying the effective reflecting surface These results provide good observational evidence for daytime
