We synthesize composite systems of multi-wall carbon nanotubes(MWCNTs)/SiO_(2) by using the sol−gel method.The dielectric properties of the systems with different-concentration MWCNTs are studied.In our MWCNTs/SiO_(2)...We synthesize composite systems of multi-wall carbon nanotubes(MWCNTs)/SiO_(2) by using the sol−gel method.The dielectric properties of the systems with different-concentration MWCNTs are studied.In our MWCNTs/SiO_(2) inorganic systems,the twin−percolation phenomenon exists when the concentrations of MWCNTs are 5–10%and 15–20%.The permittivity and conductivity have jumping changes.The twin−percolation phenomenon is attributed to the special transfer mechanism of MWCNTs in the system,determined by hopping and migrating electrons.Variations of dielectric properties and conductance of the MWCNTs/SiO_(2) systems are conformed to the percolation theory.The special percolation phenomenon and electric properties of MWCNTs/SiO_(2) can help us comprehend the conductivity mechanism of the MWCNTs/SiO2 systems effectively,and promote the development of a high performance function composite system.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.50872159,50972014 and 51072024.
文摘We synthesize composite systems of multi-wall carbon nanotubes(MWCNTs)/SiO_(2) by using the sol−gel method.The dielectric properties of the systems with different-concentration MWCNTs are studied.In our MWCNTs/SiO_(2) inorganic systems,the twin−percolation phenomenon exists when the concentrations of MWCNTs are 5–10%and 15–20%.The permittivity and conductivity have jumping changes.The twin−percolation phenomenon is attributed to the special transfer mechanism of MWCNTs in the system,determined by hopping and migrating electrons.Variations of dielectric properties and conductance of the MWCNTs/SiO_(2) systems are conformed to the percolation theory.The special percolation phenomenon and electric properties of MWCNTs/SiO_(2) can help us comprehend the conductivity mechanism of the MWCNTs/SiO2 systems effectively,and promote the development of a high performance function composite system.
文摘目的评价经食管心房调搏转复心房扑动(简称房扑)的临床疗效。方法对124例单中心房扑患者,采用经食管心房分级递增或连续递增刺激进行终止。调搏频率为快于房扑频率的10%,经食管起搏心房15~30 s;若未成功转复,可将调搏频率加到扑动频率的120%~130%开始逐级递增或连续递增,最高起搏频率不超过500次/分。观察房扑转复率及不良反应。结果 124例房扑患者中转为窦性心律69例,成功率55.6%。典型房扑(97例,成功率63.9%)和左心房正常(74例,成功率78.4%)的房扑,成功率高于非典型房扑(27例,成功率25.9%)和左房大(50例,成功率36.0%)的房扑。有与无明确心脏病或心脏手术史的房扑患者转复率无差异[55.4%(51/92) vs 56.3%(18/32),P<0.05]。结论食管心房调搏转复房扑有较好的临床疗效,尤其是典型房扑和左心房正常的房扑。