In this paper, both systolic and diastolic cardiac functions were cvaluatcd in 54 lead exposed and 24 non-exposed workers by Doppler cchocardiography. With regard to systolic cardiac function, the results suggested th...In this paper, both systolic and diastolic cardiac functions were cvaluatcd in 54 lead exposed and 24 non-exposed workers by Doppler cchocardiography. With regard to systolic cardiac function, the results suggested that cardiac systolic function increased in exposed groups as a compensatory response for the effecl of lead on myocardium. To study left ventriculaf diastolic function, 2.5 MHz pulsed Doppler analyses of transmitral flow velocity were performed from apical four-chamber view. The results showed that timerelated parameters were comparable among all groups, but blood flow velocity through the mitral valve and Doppler area fractions changed significantly in lead-exposed groups as cvidenced by increased value A, decreased value E and E/A ratio. The decrease of diastolic cardiac function was more significant in lead intoxication group. It was also observed in this study that the activity in serum of thc MB isoenzyme of creatine phosphokinase (CPK-MB), one of the indices of myocardial damage, was significantly highcr in exposed group than that in control (P (0.05), and a positive correlation was found between CPK-MB activity and Pb-B. It denoted that the inereasing of lead burden leads to more release of CPK-MB from the myocardial cells and suggested the existence of slight myocardial damage, which, conceivably, might cause harm to diastolic cardiac function展开更多
The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaT...The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.展开更多
文摘In this paper, both systolic and diastolic cardiac functions were cvaluatcd in 54 lead exposed and 24 non-exposed workers by Doppler cchocardiography. With regard to systolic cardiac function, the results suggested that cardiac systolic function increased in exposed groups as a compensatory response for the effecl of lead on myocardium. To study left ventriculaf diastolic function, 2.5 MHz pulsed Doppler analyses of transmitral flow velocity were performed from apical four-chamber view. The results showed that timerelated parameters were comparable among all groups, but blood flow velocity through the mitral valve and Doppler area fractions changed significantly in lead-exposed groups as cvidenced by increased value A, decreased value E and E/A ratio. The decrease of diastolic cardiac function was more significant in lead intoxication group. It was also observed in this study that the activity in serum of thc MB isoenzyme of creatine phosphokinase (CPK-MB), one of the indices of myocardial damage, was significantly highcr in exposed group than that in control (P (0.05), and a positive correlation was found between CPK-MB activity and Pb-B. It denoted that the inereasing of lead burden leads to more release of CPK-MB from the myocardial cells and suggested the existence of slight myocardial damage, which, conceivably, might cause harm to diastolic cardiac function
基金Supported by the Thailand Research Fund under Grant No TRG5880097
文摘The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.
