Colloidal synthesis and phase transformation of all-inorganic bismuth halide perovskite nanoplates

Lead-free bismuth-based halide perovskites and their analogues have attracted research interest for their high stability and optoelectronic properties.However,the morphology-controlled synthesis of bismuth-based perovskite nanocrystals has been rarely demonstrated.Herein,we report the colloidal synthesis of zero-dimensional(0D)Cs3BiCl6 nanosheets(NSs),Cs3Bi2Cl9 NSs/nanoplates(NPs)and Cs4MnBi2Cl12 NPs through a hot-injection method.We demonstrate that the Cs3BiCl6 NSs,as an initial product of Cs3Bi2Cl9 and Cs4MnBi2Cl12 NPs,can transform into Cs3Bi2Cl9 NSs or Cs4MnBi2Cl12 NPs via Cl-induced metal ion insertion reactions under the templating effect of Cs3BiCl6.This growth mechanism is also applicable for the synthesis of Cs4CdBi2Cl12 nanoplates.Furthermore,the alloying of Cd2+into Cs4MnBi2Cl12 lattice could weaken the strong coupling effect between Mn and Mn,which leads to a prolonged photoluminescence lifetime and an enhanced photoluminescence quantum yield(PLQY).As a proof of concept,the alloyed Cs4MnxCd1–xBi2Cl12 NPs are used as a scintillator,which show a lowest detection limit of 134.5 nGy/s.The X-ray imaging results display a high spatial resolution of over 20 line pairs per millimeter(lp/mm).These results provide new insights in the synthesis of anisotropic bismuth-based perovskite nanocrystals and their applications in radiation detection.

Application of neural network to model rainfall pattern of Ethiopia

In this paper,we have constructed Artificial Neural Network models which could capture rainfall pattern of Ethiopia.The data was collected from 147 stations across Ethiopia.Seven homogenized rainfall stations have been created based on both local and global patterns of datasets.Back-of-Word algorithm was used for extracting patterns of the datasets.K-means algorithm was used for clustering purpose.Each of the data of homogenized regions was interpolated using a spatial average.Two time series models,ARMA and Facebook’s Prophet,have been fitted for each of spatial averages as baseline models.Both have been shown to perform weak for generalization purpose as spatially averaged datasets lose their strong seasonal pattern.On the other hand,the proposed Long Short Term Memory(LSTM)was found to be the best fitted model in comparison to the baseline models.The hyperparameters of the LSTM have been tuned to get optimal parameters.Besides,the RMSE of the baseline model was used as a benchmark for tuning the LSTM used.

Convergence rate of principal component analysis with local-linear smoother for functional data under a unified weighing scheme

The unified weighing scheme for the local-linear smoother in analysing functional data can deal with data that are dense,sparse or of neither type.In this paper,we focus on the convergence rate of functional principal component analysis using this method.Almost sure asymptotic consistency and rates of convergence for the estimators of eigenvalues and eigenfunctions have been established.We also provide the convergence rate of the variance estimation of the measurement error.Based on the results,the number of observations within each curve can be of any rate relative to the sample size,which is consistent with the earlier conclusions about the asymptotic properties of the mean and covariance estimators.

From the water sources of the Tibetan Plateau to the ocean:State of nutrients in the Changjiang linked to land use changes and climate variability

Anthropogenic activity is an important driver of changes in the chemistry of nutrients(N,P,and Si)over watersheds at the sub-continental scale(e.g.,106km~2)and can markedly modify their seaward fluxes to the global ocean.In the present study,we reviewed the current status of nutrient chemistry in Changjiang(Yangtze River)based on data collected through 11 expeditions along a river course spanning 4,500 km and 15–20 major tributaries during 1997–2016 as well as monthly monitoring at the river mouth since 1980.The data were analyzed together with published results in the literature to synthesize the recent developments and current state of nutrients in the Changjiang.Previously published results from the Qinghai-Tibetan Plateau head waters were included to realize the systematics of nutrients for the whole drainage basin.Here,we showed that tributaries of the upper reaches of watersheds collectively determine the regime with high concentration and skewed species ratio of nutrients in the Changjiang mainstream,producing profound effects over a water course of 2,000–2,500 km further downstream and until the river mouth.Moreover,using data across the Three Gorges Reservoir(TGR)during 2003–2016,we evaluated the trapping and/or amplifying effects of the Three Gorges Dam(TGD)on nutrient chemistry.Tide-influenced river delta contributed an additional 20%dissolved inorganic phosphorus and 5–10%dissolved inorganic nitrogen and dissolved silicates to the seaward flux,dramatically affecting the stoichiometry of nutrients at the river mouth.Next,based on compiled data on supply and export,legacy nutrients were evaluated.Both nitrogen and phosphorus are in the accumulation phase over the watersheds,and the legacy nutrient fluxes are much higher than the annual riverine seaward fluxes.Finally,we demonstrated that the seaward fluxes of anthropogenic nutrients from the Changjiang exceed those from other top 10 largest rivers on this planet,which can be attributed to land use changes in the China over the last three to four decades.