沉默信息调节因子2相关酶1在骨关节炎中的作用机制

探讨沉默信息调节因子2相关酶1(SIRT 1)在骨关节炎中潜在的调控机制,为今后研发骨关节炎靶向药物提供理论依据。SIRT 1是一种依赖于烟酰胺腺嘌呤二核苷酸蛋白质脱乙酰酶,通过调控核转录因子-κB、叉头盒O家族成员蛋白、过氧化物酶体增殖物激活受体γ共激活剂1α、SRY-Box转录因子9、矮小相关转录因子2去乙酰化及相关通路蛋白,缓解骨关节炎软骨细胞中的炎症反应、线粒体功能障碍、细胞外基质降解和细胞凋亡及衰老,有助于预防骨关节炎的软骨损伤并促进软骨组织的修复。

Reduction of Efficiency Droop and Modification of Polarization Fields of InGaN-Based Green Light-Emitting Diodes via Mg-Doping in the Barriers

We demonstrate that the Mg-doping in barriers can partially screen the polarization fields of InGaN-based green light-emitting diodes.The photocurrent spectra show that the Mg-doping samples have smaller polarization fields and the blue shift of the peak with increasing current is observed.The reduction of polarization fields can be attributed to the screening of the impurity holes generated by the Mg atoms in the barriers.The efficiency droop is sensitive to the Mg-doping concentration in barriers,while the sample with Mg concentration of 5×10^(19) cm^(-3) exhibits the lowest efficiency degradation of 12.4%at a high injection current.

Dielectric layer-dependent surface plasmon effect of metallic nanoparticles on silicon substrate

The electromagnetic interaction between Ag nanoparticles on the top of the Si substrate and the incident light has been studied by numerical simulations. It is found that the presence of dielectric layers with different thicknesses leads to the varied resonance wavelength and scattering cross section and consequently the shifted photocurrent response for all wavelengths. These different behaviours are determined by whether the dielectric layer is beyond the domain where the elcetric field of metallic plasmons takes effect, combined with the effect of geometrical optics. It is revealed that for particles of a certain size, an appropriate dielectric thickness is desirable to achieve the best absorption. For a certain thickness of spacer, an appropriate granular size is also desirable. These observations have substantial applications for the optimization of surface plasmon enhanced silicon solar cells.

Effect of Hydrogen and Nitrogen Carrier Gas Ratio on the Structural and Optical Properties of AlInGaN Alloy

Undoped AlInGaN epilayers on GaN templates with different hydrogen(H_(2))and nitrogen(N_(2))carrier gas ratios(1:8,2:8,and 3:8 as samples 1,2 and 3,respectively)were grown.When the flow ratio of H_(2) and N_(2) rises from 1:8 to 3:8,an indium composition decrease from 3%to 1.2%is observed while the aluminum content stays constant at any flow ratio.Due to the quantum-dot-like effect,photoluminescence intensity is enhanced in the sample with the low carrier gas flow ratio of H_(2)/N_(2).However,the potential well caused by indium uneven distribution is nonuniform,which is more severe in the sample with carrier gas flow ratio 1:8.The process of carrier transfer from shallow to deep potential wells would be more difficult to accomplish,resulting in the reduction of the photoluminescence intensity.This is found to be consistent with the carriers'lifetime with the help of time-resolved photoluminescence.

基于高光谱的水稻叶片氮含量估计的深度森林模型研究

高光谱遥感已经成为快速诊断作物水氮状态的一种有效手段。然而,传统的回归方法和机器学习往往难以挖掘高光谱的全部信息,深度神经网络又通常需要大量的训练数据,因此本研究试图探索在少量数据条件下构建深度学习模型并实现叶片氮含量的精准估计。通过在湖北省监利县开展了连续2年不同氮素胁迫水平的水稻试验,测量了作物全生育期内的216组冠层光谱和叶片氮含量。基于一阶导数光谱,本文构建了一种新的深度学习模型(深度森林DF)来进行叶片氮含量的反演,并与2种经典机器学习模型(随机森林RF和支持向量机SVM)和一种深度神经网络模型(多层感知器MLP)进行比较。结果表明,在基于少量高光谱数据的情况下,DF对水稻叶片氮含量的估算精度要高于MLP,其中预测精度最高的模型为全波段光谱反演的DF模型(R^(2)=0.919,RMSE=0.327)。在2种经典机器学习模型中,RF的估计效果优于SVM,但2种模型结果都不够稳定。研究表明,深度森林可以提升高光谱反演叶片氮含量的精度和稳定性,并且可以通过多粒度扫描相对减轻过拟合程度。该研究结果可为少量数据条件下快速监测作物叶片氮含量提供参考。

载流子复合机制对InGaN多量子阱蓝光LED调制带宽的影响

通过设计InGaN多量子阱LED有源区的不同结构,研究了载流子复合机制对LED调制速度的影响。结果显示,由于窄量子阱LED的载流子空间波函数重叠几率更高,且电子泄露效应更显著,所以复合速率更快,调制带宽更高。In组分为1%的InGaN量子垒LED可提高辐射复合的权重,使得调制带宽高于GaN量子垒LED;In组分为5%时,电子泄露和俄歇复合占据主导地位,且由于这两种复合机制复合速率很快,所以调制带宽显著提高。

水氮数据联合驱动的冬小麦数据同化研究

水氮状态的准确估计对于作物生长模拟和产量估计十分重要。数据同化可以集成观测和模型,从而实现更加准确的模拟。然而,传统的数据同化系统大多关注叶面积指数(LAI)、土壤含水量(SM),对于氮素状态估计的研究相对较少,缺乏水氮数据联合驱动的数据同化研究。采用集合卡尔曼滤波(EnKF)方法对SWAPWOFOST模型构建冬小麦生长的数据同化系统,通过引入叶片氮累积量(LNA)的观测,同时更新SM、LAI、LNA和作物产量等关键状态变量后进行作物生长模拟。结果表明,只加入LAI和SM可以很好更新模型的土壤水分剖面和LAI,但是对于LNA和产量的模拟效果不佳;加入LNA观测后,有效提高了作物LAI、LNA和产量的模拟精度。同时更新模型状态和参数(SSPE)比只更新状态(USO)的模拟效果更好,尤其是在土壤含水量的估计中。无论是水分还是氮素状态模拟出现偏差的情况,都很难准确估计最终的作物产量,而水氮数据联合驱动的结果最优。此外,研究中的数据同化系统在不同观测误差和观测频率下都具有良好的稳健性。该研究有助于深入理解冬小麦生长与水氮状态的关系,对实际应用中的作物生长模拟和产量估计具有一定指导意义。

施氮水平对冬小麦收获品质影响的模拟研究

冬小麦产量及蛋白质的准确估计具有重要意义。基于作物模型对作物生长和氮素吸收等关键生理过程的模拟,可以实现对产量、蛋白质产量及含量的评估。但现有作物模型对储存器官利用氮的能力(库过程)进行了简化,鲜有模型考虑多种因素对该过程的影响。研究采用单籽粒氮积累模型与SWAP相结合的方法,考虑温度、水分、氮素水平、基因型多因素对库过程的影响,构建了SWAP-pro模型。与原模型的对比结果表明,SWAP对冬小麦氮胁迫情况估计不准确,产量模拟精度不高,且明显低估冬小麦蛋白质产量;SWAP-pro能对叶面积指数、叶片氮、生物量等指标进行较好的模拟,具有一定的稳健性。模型能更准确稳定地模拟冬小麦氮胁迫情况,产量的模拟精度优于SWAP,且对蛋白质产量的模拟精度更高。该研究有助于深入理解氮循环与冬小麦收获品质形成的关系,对于产量和蛋白质估计具有一定指导意义。

Computational Investigation of InxGa1-xN/InN Quantum-Dot Intermediate-Band Solar Cell

An Inx Ga1_xN/lnN quantum-dot intermediate-band solar cell is calculated by means of solving the Schrodinger equation according to the Kronig-Penney model. Based on particular assumptions, the power conversion efficiency is worked out. The results reveal that the InxGa1- xN/InN quantum-dot intermediate-band solar cell manifests much larger power conversion efficiency than that of p-n junction solar cells, and the power conversion efficiency strongly depends on the size of the quantum dot and the interdot distance.

Cathodoluminescence of Yellow and Blue Luminescence in Undoped Semi-insulating GaN and n-GaN

Yellow and blue luminescence in undoped GaN layers with different resistivities are studied by cathodoluminescence.Intense yellow and blue luminescence bands are observed in semi-insulating GaN,while in n-GaN the yellow luminescence and blue luminescence bands are very weak.The stronger yellow and blue luminescences in semi-insulating GaN are correlated to the higher edge-type dislocation density.The scanning cathodoluminescence image reveals strong defect-related luminescence at the grain boundaries where the dislocations accumulate.It is found that the relative intensity of the blue luminescence band to the yellow luminescence band increases with the cathodoluminescence beam energies and is larger in n-GaN with a lower density of edge-type dislocations.An approximately 3.35eV shoulder next to the near-band-edge peak is observed in n-GaN but not in semi-insulating GaN.A redshift of the near-band-edge peak with cathodoluminescence beam energy is observed in both samples and is explained by internal absorption.

探讨多模态影像学对脾脏炎性肌纤维母细胞瘤的诊断价值

目的为了提高脾脏炎性肌纤维母细胞瘤的诊断水平,探讨多模态影像学的价值。方法回顾分析本院1例成人脾炎性肌纤维母细胞瘤(inflammatory pseudotumor of spleen,SIMT)患者的影像资料,包括彩色超声、CT平扫及增强、MRI平扫,并复习文献。结果脾脏内数枚肿块,以低回声为主,回声不均,边界尚清,形态规整,内见少许血流信号。CT平扫为等密度,其内见小片状低密度区;增强后呈轻度至中度不均匀强化。MRI表现:T1WI上低或等信号,T2WI序列及T2WI抑脂序列为等及高信号,病灶周围见完整包膜,DWI图为等及高信号,信号不均匀。病理学及免疫组化结果为SIMT;EB病毒(+)。结论SIMT临床表现缺乏特异性,最终需病理学确诊。多模态影像学检查对脾炎性肌纤维母细胞瘤有很高的诊断和鉴别诊断价值。

Effects of etching conditions on surface morphology of periodic inverted trapezoidal patterned Si(100) substrate

In this paper,the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide(TMAH) solution with isopropyl alcohol(IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A series of experiments are performed by changing TMAH concentration,IPA concentration,etching temperature and etching time. The structure of inverted trapezoidal patterns and roughness of the bottom surface are characterized by scanning electron microscopy(SEM) and atomic force microscopy(AFM). The results show that with TMAH concentration increases,the roughness of bottom surface will decrease. The addition of IPA into TMAH solution improves the morphology of the bottom surface significantly. Low temperature is beneficial to get a smooth bottom surface. Furthermore,etching time can change the bottom surface roughness. A model is proposed to explain the etching processes. The hillock area ratio of the bottom surface has the same tendency as the etching area ratio. Finally,smooth silicon inverted trapezoidal patterns are obtained for epitaxial growth of Ga N-based light emitting diode(LED) devices.