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This paper introduces a simple framework of counterfactual estimation for causal inference with time‐series cross‐sectional data, in which we estimate the average treatment effect on the treated by directly imputing counterfactual outcomes for treated observations. We discuss several novel estimators under this framework, including the fixed effects counterfactual estimator, interactive fixed effects counterfactual estimator and matrix completion estimator. They provide more reliable causal estimates than conventional two‐way fixed effects models when treatment effects are heterogeneous or unobserved time‐varying confounders exist. Moreover, we propose a new dynamic treatment effects plot, along with several diagnostic tests, to help researchers gauge the validity of the identifying assumptions. We illustrate these methods with two political economy examples and develop an open‐source package, fect, in both R and Stata to facilitate implementation. [ABSTRACT FROM AUTHOR]

Process‐based land surface models are important tools for estimating global wetland methane (CH4) emissions and projecting their behavior across space and time. So far there are no performance assessments of model responses to drivers at multiple time scales. In this study, we apply wavelet analysis to identify the dominant time scales contributing to model uncertainty in the frequency domain. We evaluate seven wetland models at 23 eddy covariance tower sites. Our study first characterizes site‐level patterns of freshwater wetland CH4 fluxes (FCH4) at different time scales. A Monte Carlo approach was developed to incorporate flux observation error to avoid misidentification of the time scales that dominate model error. Our results suggest that (a) significant model‐observation disagreements are mainly at multi‐day time scales (<15 days); (b) most of the models can capture the CH4 variability at monthly and seasonal time scales (>32 days) for the boreal and Arctic tundra wetland sites but have significant bias in variability at seasonal time scales for temperate and tropical/subtropical sites; (c) model errors exhibit increasing power spectrum as time scale increases, indicating that biases at time scales <5 days could contribute to persistent systematic biases on longer time scales; and (d) differences in error pattern are related to model structure (e.g., proxy of CH4 production). Our evaluation suggests the need to accurately replicate FCH4 variability, especially at short time scales, in future wetland CH4 model developments. Plain Language Summary: Land surface models are useful tools to estimate and predict wetland methane (CH4) flux but there is no evaluation of modeled CH4 flux error at different time scales. Here we use a statistical approach and observations from eddy covariance sites to evaluate the performance of seven wetland models for different wetland types. The results suggest models have captured CH4 flux variability at monthly or seasonal time scales for boreal and Arctic tundra wetlands but failed to capture the observed seasonal variability for temperate and tropical/subtropical wetlands. The analysis suggests that improving modeled flux at short time scale is important for future model development. Key Points: Significant model‐observation disagreements were found at multi‐day and weekly time scales (<15 days)Models captured variability at monthly and seasonal time (42–142 days) scales for boreal and Arctic tundra sites but not for temperate and tropical sitesThe model errors show that biases at multi‐day time scales may contribute to persistent systematic biases on longer time scales [ABSTRACT FROM AUTHOR]

Hole transport materials (HTMs) are an integral part of highly efficient perovskite solar cells (PSCs). Although the traditional HTM Spiro-OMeTAD achieves excellent performance, its high cost limits its future large-scale application during commercialization of PSCs. Therefore, it is essential to develop low-cost and efficient alternative HTMs. Herein, we successfully synthesize two novel HTMs DTP-1 and DTP-2 by employing methoxy-substituted terthienyl (DTP) as the core unit and adjusting the electron donors. Research indicates that the introduction of methoxy groups on the core unit enhances its electron donating ability; thus, the capping groups with slightly lower electron donating ability should be adopted to get well-matched energy levels. After optimization, the best-performing power conversion efficiency (PCE) of DTP-1 based PSCs is 21.1%, which is much higher than those of PSCs based on DTP-2 (15.6%) and THP-1 (20.5%). Furthermore, under the conditions of RH 30–45% and room temperature, the DTP-1-based devices maintain 80.5% of the initial PCE after aging for 840 h, which is better than those of DTP-2 (22.0%) and THP-1 (71.5%). [ABSTRACT FROM AUTHOR]

BACKGROUND: Euryale ferox Salisb. is widely grown in China and Southeast Asia as a grain crop and medicinal plant. The composition, morphology, structure, physicochemical properties, thermal properties, and in vitro digestibility of North Euryale ferox seeds starch (NEFS), hybrid Euryale ferox seeds starch (HEFS), and South Euryale ferox seeds starch (SEFS) were studied. RESULT: Of the varieties that were studied, the amylose content of NEFS (23.03%) was the highest. Starch granules of each variety were smooth, sharp, small, and had an average diameter of 2 μm. All three varieties were A‐type crystals with crystallinity ranging from 26.42% to 28.17%. The degree of double helix and the short‐range order ranged from 1.9006 to 2.5324 and 1.4294 to 1.6006, respectively. The high proportion of C1 region in NEFS (17.74%) and HEFS (17.66%) were found. Thermodynamic properties in North Euryale ferox seeds included the highest onset temperature (To) (71.43 °C), peak temperature (Tp) (76.60 °C), conclusion temperature (Tc) (82.77 °C), enthalpy of gelatinization (ΔH) (12.64 J g−1), and peak viscosity (1514 mPa·s). All three varieties maintained a low level of in vitro digestibility, with the highest resistant starch (RS) content (29.57%), the lowest rapidly digestible starch (RDS) content (27.07%), and the slowest hydrolysis kinetic constant (0.0303) in NEFS. CONCLUSION: The results revealed that the low digestibility of NEFS was attributable to compact granules, high crystallinity, high degree of order, and strong thermal stability. These digestive, physicochemical, and thermodynamic properties provide information for the future application of Euryale ferox seed starch in the food industry. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]