Assessing the Impact of Differential Measurement Error on Estimates of Fine Particle Mortality
摘要:
In air pollution epidemiology, error in measurements of correlated pollutants has been advanced as a reason to distrust regressions that find statistically significant weak associations. Much of the related debate in the literature and elswhere has been qualitative. To promote quantitative evaluation of such errors, this paper develops an air pollution time-series model based on correlations among unit-normal variables. Assuming there are no other sources of bias present, the model shows the expected amount of relative bias in the regression coefficients df a bivariate regression of coarse and fine particulate matter measurements on daily mortality. The model only requires information on instrumental error and spatial variability, along with the observed regression coefficients and information on the true fine-course correlation. Analytical results show that if one pollutant is truly more harmful than the other, then it must be measured more precisely than the other in order not to bias the ratio of the fine and course regression coefficients. Utilizing published data, a case study of the Harvard Six-Cities study illustrates use of the model and emphasizes the need for data on spatial variability across the study area. Current epidemiology time-series regressions can use this model to address the general concern of correlated pollutants with differing measurement errors.
A Well-Defined (POCOP)Rh Catalyst for the Coupling of Aryl Halides with Thiols
作者:Samuel D. Timpa、Christopher J. Pell、Oleg V. Ozerov
DOI:10.1021/ja505576g
日期:2014.10.22
been shown to favor aryl thiolate reductive elimination at elevated temperatures and in some cases at room temperature, compared with the analogous diarylamido/bis(phosphine) (PNP)Rh pincer system. Concerted reductive elimination has been studied with 6a directly and in the presence of aryl bromide and aryl chloride traps. This investigation demonstrates a clear rate dependence on aryl chloride concentration
Ni nanoparticles on RGO as reusable heterogeneous catalyst: effect of Ni particle size and intermediate composite structures in C–S cross-coupling reaction
The present work demonstrates the C-S cross-coupling reaction between aryl halides and thiols using nickel nanoparticles (Ni NPs) supported on reduced graphene oxide (Ni/RGO) as a heterogeneouscatalyst. It is observed that the uniformly dispersed Ni NPs supported on RGO could exhibit excellent catalytic activity in C-S cross-coupling reactions and the catalytic application is generalized with diverse
We report here an efficient, mild and biomolecule-compatible method for constructing C–S bonds.
我们在这里报告了一种高效、温和且生物分子兼容的构建C-S键的方法。
Copper-Catalyzed Sulfenylation of Boronic Acids with Sulfonyl Hydrazides
作者:Ting-Ting Wang、Fu-Lai Yang、Shi-Kai Tian
DOI:10.1002/adsc.201400995
日期:2015.3.23
bonds has been developed using sulfonyl hydrazides as sulfenyl sources. A range of sulfonyl hydrazides underwent tetrakis(acetonitrile)copper(I) tetrafluoroborate [Cu(CH3CN)4BF4]/2,2′‐bipyridine‐catalyzed sulfenylation with boronic acids under air to give structurally diverse thioethers in moderate to good yields. Preliminary mechanistic studies show that sulfonyl hydrazides are subjected to decomposition
Efficient CS Cross-Coupling of Thiols with Aryl Iodides Catalyzed by Cu(OAc)<sub>2</sub>·H<sub>2</sub>O and 2,2′-Biimidazole
作者:Chenglong Zong、Jianli Liu、Shengyan Chen、Runsheng Zeng、Jianping Zou
DOI:10.1002/cjoc.201300830
日期:2014.3
The classical Ullmann CS crosscoupling reaction of aryl iodides with aromatic/alkyl thiols under catalysis of 15 mol% Cu(OAc)2·H2O and 15 mol% 2,2′‐biimidazole works at 80°C in DMSO for 3 h to provide a variety of aryl sulfides in good to excellent yields.