Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and ...Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and a modified constant-sum (MCS) method. Methods were then compared for reported bulk elemental composition of the rocks. The MCS method was based on the sum of eight major elements, which is spatially more stable than one single major ele-ment as used in the IS method, and is quite constant among different rock samples. Calibrations were performed with standard reference materials NIST SRM 610, 612, 614, and 616. Little difference was found between using a single standard and a set of standards, because of the good linearity shown by the reference materials. Comparison of the two calibration methods shows that the MCS method produced better and more stable results than the IS method for heterogeneous samples. With the MCS method, approximately 94% to 95% of the total measurements are within the range of ±100% relative deviation, compared with 82% to 86% with the IS method. The IS method resulted insubstantial overestimations for some rock samples (e.g., 648% for Basalt BCR-2 using NIST SRM 610 as the calibration standard), while the largest deviation with the MCS method was 216% for U in Eagle Ford shale #80 sample. For Quartz latite QLO-1, a relative homogeneous sample, the IS method generated slightly better results than the MCS method. Regardless of method, spatially heterogeneous distribution of elements in the intact rock at the scale of the laser spot is considered to be the main reason for the large relative deviations seen in our work compared to published results.展开更多
Yu et al. (2012) considered a certain dependent right censorship model. We show that this model is equivalent to the independent right censorship model, extending a result with continuity restriction in Williams and L...Yu et al. (2012) considered a certain dependent right censorship model. We show that this model is equivalent to the independent right censorship model, extending a result with continuity restriction in Williams and Lagakos (1977). Then the asymptotic normality of the product limit estimator under the dependent right censorship model follows from the existing results in the literature under the independent right censorship model, and thus partially solves an open problem in the literature.展开更多
身体活动与健康领域部分数据属于成分数据,在研究成分数据对健康的影响时,若忽视成分数据“定和限制”的本质,则会对研究结果产生较大影响。成分数据分析则克服了这一问题,并已应用于多个研究领域。研究梳理了成分数据分析的发展路程与...身体活动与健康领域部分数据属于成分数据,在研究成分数据对健康的影响时,若忽视成分数据“定和限制”的本质,则会对研究结果产生较大影响。成分数据分析则克服了这一问题,并已应用于多个研究领域。研究梳理了成分数据分析的发展路程与方法学,并结合身体活动行为数据的特性探讨了传统相关研究的局限性,综述了使用成分数据分析的活动行为的相关研究。结果显示:1)组合行为产生的健康效应大于单一行为;2)传统的孤立研究的结果存在矛盾性,表明综合分析活动行为与健康结局关联性的必要性;3)成分数据分析的身体活动行为的相关研究基本支持了中高强度身体活动(moderate to vigorous-intensity physical activity,MVPA)的健康效益,但指出MVPA水平的保持则更有意义,此外,还强调了在追求MVPA增加的情况下,剩余时间的合理分配对健康促进的重要意义;4)未来身体活动与健康领域的研究可着重于行为组合模式与健康结局之间的效应及实证性的追踪调查。展开更多
文摘Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and a modified constant-sum (MCS) method. Methods were then compared for reported bulk elemental composition of the rocks. The MCS method was based on the sum of eight major elements, which is spatially more stable than one single major ele-ment as used in the IS method, and is quite constant among different rock samples. Calibrations were performed with standard reference materials NIST SRM 610, 612, 614, and 616. Little difference was found between using a single standard and a set of standards, because of the good linearity shown by the reference materials. Comparison of the two calibration methods shows that the MCS method produced better and more stable results than the IS method for heterogeneous samples. With the MCS method, approximately 94% to 95% of the total measurements are within the range of ±100% relative deviation, compared with 82% to 86% with the IS method. The IS method resulted insubstantial overestimations for some rock samples (e.g., 648% for Basalt BCR-2 using NIST SRM 610 as the calibration standard), while the largest deviation with the MCS method was 216% for U in Eagle Ford shale #80 sample. For Quartz latite QLO-1, a relative homogeneous sample, the IS method generated slightly better results than the MCS method. Regardless of method, spatially heterogeneous distribution of elements in the intact rock at the scale of the laser spot is considered to be the main reason for the large relative deviations seen in our work compared to published results.
文摘Yu et al. (2012) considered a certain dependent right censorship model. We show that this model is equivalent to the independent right censorship model, extending a result with continuity restriction in Williams and Lagakos (1977). Then the asymptotic normality of the product limit estimator under the dependent right censorship model follows from the existing results in the literature under the independent right censorship model, and thus partially solves an open problem in the literature.
文摘身体活动与健康领域部分数据属于成分数据,在研究成分数据对健康的影响时,若忽视成分数据“定和限制”的本质,则会对研究结果产生较大影响。成分数据分析则克服了这一问题,并已应用于多个研究领域。研究梳理了成分数据分析的发展路程与方法学,并结合身体活动行为数据的特性探讨了传统相关研究的局限性,综述了使用成分数据分析的活动行为的相关研究。结果显示:1)组合行为产生的健康效应大于单一行为;2)传统的孤立研究的结果存在矛盾性,表明综合分析活动行为与健康结局关联性的必要性;3)成分数据分析的身体活动行为的相关研究基本支持了中高强度身体活动(moderate to vigorous-intensity physical activity,MVPA)的健康效益,但指出MVPA水平的保持则更有意义,此外,还强调了在追求MVPA增加的情况下,剩余时间的合理分配对健康促进的重要意义;4)未来身体活动与健康领域的研究可着重于行为组合模式与健康结局之间的效应及实证性的追踪调查。
