Exciton optical absorption in asymmetric ZnO/ZnMgO double quantum wells with mixed phases

The optical absorption of exciton interstate transition in Zn1-xlMgxlO/ZnO/Zn1-xcMgxcO/ZnO/Zn1-xrMgxrO asymmetric double quantum wells(ADQWs)with mixed phases of zinc-blende and wurtzite in Zn1-xMgxO for 0.37<x<0.62 is discussed.The mixed phases are taken into account by our weight model of fitting.The states of excitons are obtained by a finite difference method and a variational procedure in consideration of built-in electric fields(BEFs)and the Hartree potential.The optical absorption coefficients(OACs)of exciton interstate transition are obtained by the density matrix method.The results show that Hartree potential bends the conduction and valence bands,whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and holes.Furthermore,the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement effects.There are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively,and the OACs merge together under some special conditions.The computed result of exciton interband emission energy agrees well with a previous experiment.Our conclusions are helpful for further relative theoretical studies,experiments,and design of devices consisting of these quantum well structures.

Development of heart failure risk prediction models based on a multi-marker approach using random forest algorithms

Background:The early identification of heart failure(HF)risk may favorably affect outcomes,and the combination of multiple biomarkers may provide a more comprehensive and valuable means for improving the risk of stratification.This study was conducted to assess the importance of individual cardiac biomarkers creatine kinase MB isoenzyme(CK-MB),B-type natriuretic peptide(BNP),galectin-3(Gal-3)and soluble suppression of tumorigenicity-2(sST2)for HF diagnosis,and the predictive performance of the combination of these four biomarkers was analyzed using random forest algorithms.Methods:A total of 193 participants(80 patients with HF and 113 age-and gender-matched healthy controls)were included from June 2017 to December 2017.The correlation and regression analysis were conducted between cardiac biomarkers and echocardiographic parameters.The accuracy and importance of these predictor variables were assessed using random forest algorithms.Results:Patients with HF exhibited significantly higher levels of CK-MB,BNP,Gal-3,and sST2.BNP exhibited a good independent predictive capacity for HF(AUC 0.956).However,CK-MB,sST2,and Gal-3 exhibited a modest diagnostic performance for HF,with an AUC of 0.709,0.711,and 0.777,respectively.BNP was the most important variable,with a remarkably higher mean decrease accuracy and Gini.Furthermore,there was a general increase in predictive performance using the multi-marker model,and the sensitivity,specificity was 91.5%and 96.7%,respectively.Conclusion:The random forest algorithm provides a robust method to assess the accuracy and importance of predictor variables.The combination of CK-MB,BNP,Gal-3,and sST2 achieves improvement in prediction accuracy for HF.

Isolation and Functional Characterisation of the Genes Encoding Δ~8-Sphingolipid Desaturase from Brassica rapa

8-Sphingolipid desaturase is the key enzyme that catalyses desaturation at the C8 position of the long-chain base of sphingolipids in higher plants. There have been no previous studies on the genes encoding AS-sphingolipid desaturases in Brassica rapa. In this study, four genes encoding AS-sphingolipid desaturases from B. rapa were isolated and characterised. Phylogenetic analyses indicated that these genes could be divided into two groups： BrD8A, BrD8C and BrD8D in group I, and BrD8B in group II. The two groups of genes diverged before the separation of Arabidopsis and Brassica. Though the four genes shared a high sequence similarity, and their coding desaturases all located in endoplasmic reticulum, they exhibited distinct expression patterns. Heterologous expression in Saccharomyces cerevisiae revealed that BrD8A/B/C/D were functionally diverse AS-sphingolipid desaturases that catalyse different ratios of the two products 8（Z）- and 8（E）-C18-phytosphingenine. The aluminium tolerance of transgenic yeasts expressing BrD8A/B/C/D was enhanced compared with that of control cells. Expression of BrD8A in Arabidopsis changed the ratio of 8（Z）：8（E）-C 18-phytosphingenine in transgenic plants. The information reported here provides new insights into the biochemical functional diversity and evolutionary relationship of AS-sphingolipid desaturase in plants and lays a foundation for further investigation of the mechanism of 8（Z）- and 8（E）-C18- phytosphingenine biosynthesis.

Hydrogen trapping and electrochemical corrosion behavior of V–N microalloyed X80 pipeline steels consisting of acicular ferrite and polygonal ferrite

Hydrogen trapping behavior of V–N microalloyed X80 pipeline steels was studied by means of hydrogen permeation and hydrogen induced cracking(HIC)tests.In addition,the electrochemical performance of the steels in 3.5 wt.%NaCl solution was investigated.Results indicated that the microstructure of experimental steels mainly consisted of acicular ferrite and polygonal ferrite(PF).When the fraction of PF was 9.1%and 30.4%,hydrogen effective diffusion coefficient was 1.624×10^(−6) and 3.121×10^(−6) cm^(2)/s,respectively.The pipeline steels were not susceptible to HIC.Numerous potential hydrogen traps distributed in homogeneous dispersion were conducive to high HIC resistance.With increasing the fraction of PF from 9.1%to 30.4%,the corrosion current density increased from 5.39×10^(−6) to 9.49×10^(−6) A cm^(−2),the corrosion potential decreased from−0.48 to−0.57 V,and the charge transfer resistance decreased from 2301 to 2068Ωcm^(2),respectively.Increased fraction of PF was disadvantageous for corrosion resistance because of galvanic corrosion.