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Variability in the analysis of a single neuroimaging dataset by many teams 期刊论文
NATURE, 2020
作者:  Liu, Jifeng;  Soria, Roberto;  Zheng, Zheng;  Zhang, Haotong;  Lu, Youjun;  Wang, Song;  Yuan, Hailong
收藏  |  浏览/下载:41/0  |  提交时间:2020/07/03

Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses(1). The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset(2-5). Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed.


The results obtained by seventy different teams analysing the same functional magnetic resonance imaging dataset show substantial variation, highlighting the influence of analytical choices and the importance of sharing workflows publicly and performing multiple analyses.


  
Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites 期刊论文
NATURE, 2020, 580 (7803) : 360-+
作者:  van den Brink, Susanne C.;  Alemany, Anna;  van Batenburg, Vincent;  Moris, Naomi;  Blotenburg, Marloes;  Vivie, Judith;  Baillie-Johnson, Peter;  Nichols, Jennifer;  Sonnen, Katharina F.;  Arias, Alfonso;  van Oudenaarden, Alexander
收藏  |  浏览/下载:40/0  |  提交时间:2020/07/03

Halide perovskite materials have promising performance characteristics for low-cost optoelectronic applications. Photovoltaic devices fabricated from perovskite absorbers have reached power conversion efficiencies above 25 per cent in single-junction devices and 28 per cent in tandem devices(1,2). This strong performance (albeit below the practical limits of about 30 per cent and 35 per cent, respectively(3)) is surprising in thin films processed from solution at low-temperature, a method that generally produces abundant crystalline defects(4). Although point defects often induce only shallow electronic states in the perovskite bandgap that do not affect performance(5), perovskite devices still have many states deep within the bandgap that trap charge carriers and cause them to recombine non-radiatively. These deep trap states thus induce local variations in photoluminescence and limit the device performance(6). The origin and distribution of these trap states are unknown, but they have been associated with light-induced halide segregation in mixed-halide perovskite compositions(7) and with local strain(8), both of which make devices less stable(9). Here we use photoemission electron microscopy to image the trap distribution in state-of-the-art halide perovskite films. Instead of a relatively uniform distribution within regions of poor photoluminescence efficiency, we observe discrete, nanoscale trap clusters. By correlating microscopy measurements with scanning electron analytical techniques, we find that these trap clusters appear at the interfaces between crystallographically and compositionally distinct entities. Finally, by generating time-resolved photoemission sequences of the photo-excited carrier trapping process(10,11), we reveal a hole-trapping character with the kinetics limited by diffusion of holes to the local trap clusters. Our approach shows that managing structure and composition on the nanoscale will be essential for optimal performance of halide perovskite devices.


  
A simple dynamic model explains the diversity of island birds worldwide 期刊论文
NATURE, 2020
作者:  Li, Junxue;  Wilson, C. Blake;  Cheng, Ran;  Lohmann, Mark;  Kavand, Marzieh;  Yuan, Wei;  Aldosary, Mohammed;  Agladze, Nikolay;  Wei, Peng;  Sherwin, Mark S.;  Shi, Jing
收藏  |  浏览/下载:28/0  |  提交时间:2020/07/03

Colonization, speciation and extinction are dynamic processes that influence global patterns of species richness(1-6). Island biogeography theory predicts that the contribution of these processes to the accumulation of species diversity depends on the area and isolation of the island(7,8). Notably, there has been no robust global test of this prediction for islands where speciation cannot be ignored(9), because neither the appropriate data nor the analytical tools have been available. Here we address both deficiencies to reveal, for island birds, the empirical shape of the general relationships that determine how colonization, extinction and speciation rates co-vary with the area and isolation of islands. We compiled a global molecular phylogenetic dataset of birds on islands, based on the terrestrial avifaunas of 41 oceanic archipelagos worldwide (including 596 avian taxa), and applied a new analysis method to estimate the sensitivity of island-specific rates of colonization, speciation and extinction to island features (area and isolation). Our model predicts-with high explanatory power-several global relationships. We found a decline in colonization with isolation, a decline in extinction with area and an increase in speciation with area and isolation. Combining the theoretical foundations of island biogeography(7,8) with the temporal information contained in molecular phylogenies(10) proves a powerful approach to reveal the fundamental relationships that govern variation in biodiversity across the planet.


Using a global molecular phylogenetic dataset of birds on islands, the sensitivity of island-specific rates of colonization, speciation and extinction to island features (area and isolation) is estimated.


  
Frame envy in energy policy ideology: A social constructivist framework for wicked energy problems 期刊论文
ENERGY POLICY, 2017, 109
作者:  Valentine, Scott Victor;  Sovacool, Benjamin K.;  Brown, Marilyn A.
收藏  |  浏览/下载:18/0  |  提交时间:2019/04/09
Interpretive frames  Conceptual framework  Analytical approach  Epistemology  Ontology  Social constructivism  
A process-based insight into nonstationarity of the probability distribution of annual runoff 期刊论文
WATER RESOURCES RESEARCH, 2017, 53 (5)
作者:  Jiang, Cong;  Xiong, Lihua;  Guo, Shenglian;  Xia, Jun;  Xu, Chong-Yu
收藏  |  浏览/下载:13/0  |  提交时间:2019/04/09
annual runoff distribution  nonstationarity detection  process-based analytical derivation approach  Fu equation