应用GPS与GIS技术进行暗针叶林生态系统样地分析

高海拔地区原始林调查一直难度较大 .采用GPS与GIS技术结合 ,不但便于设置与恢复样地 ,而且还能够比较精确地展现样地空间特征及其中乔木的空间分布格局 .将快速静态定位与局部皮尺检测相结合 ,除个别点偏差较大外 ,定位相对比较精确 ,RMS平均为 2 .84 ,平均三维系统误差分别为 :△B =1 .2m ,△L =1 .2m ,△H =4 .3m ,均方差分别是± 0 .6 ,± 1 .1 ,± 2 1 .1 ,能够满足于森林经营与管理的需要 .GIS分析表明 ,暗针叶林生态系统主林冠层的郁闭度不能完全刻画出树冠对降雨的再分配作用 .该方法充分展示了“2S”技术在小尺度森林生态系统管理中的应用潜力 ,尤其是在海拔较高 ,不便于进行航空、航天测量和常规测量的地区     

Lewis X-Carrying Neoglycolipids Evoke Selective Apoptosis in Neural Stem Cells

Neurochemical Research - N-glycans carrying the Lewis X trisaccharide [Galβ1-4 (Fucα1-3) GlcNAc] are expressed by neural stem cells (NSCs) exclusively before differentiation, and they...     

Electrochemically Modifying the Electronic Structure of IrO2 Nanoparticles for Overall Electrochemical Water Splitting with Extensive Adaptability

Designing the electrocatalysts that are stable and active for extensively adaptable water splitting is highly desirable for developing hydrogen based energy. IrO₂ is a promising and widely used catalyst for the oxygen evolution reaction in commercial applications, but is rarely used for the hydrogen evolution reaction (HER), due to the high Gibbs free energy for hydrogen adsorption (ΔG_H*). Herein, an approach to modify the electronic structure of IrO₂ via cyclic voltammetry is proposed. In this process, Ir(+4) is partially reduced and trace Pt is simultaneously deposited on IrO₂, which greatly lowers the ΔG_H* and thus accelerates the reaction kinetics. The as‐prepared Pt–IrO₂/CC with low noble metal loading (36.6 µg cm^?2_(Ir+Pt)) exhibits excellent HER activity with overpotentials of 5, 22, and 26 mV at 10 mA cm^?2 in 0.5 m H₂SO₄, 1 m KOH, and 1 m phosphate buffer solution, respectively, making it possible to organize an all‐IrO₂ based water electrolyzer. The Pt–IrO₂/CC||IrO₂/CC couple exhibits a promising activity and stability in pH‐universal conditions as well as natural seawater for H₂ production. Density function theory calculations reveal that the optimized electronic structure of IrO₂ balances the ΔG_H*, resulting in a much enhanced HER performance.     

Effects of Heat Stress during Seed Filling Stage on <i>Brassica napus</i> Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise, the threat of heat stress to rapeseed production is becoming more obvious. Exploring the response characteristics of two important biological pathways, oil accumulation and photosynthesis, to heat stress during B. napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed. The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B. napus germplasms with different oil content and environmental sensitivity, including 6 rapeseed varieties which exhibited environment-sensitive/insensitive and with high, medium or low oil content, were tested by whole plant heat stress or the in vitro silique culture system. Both assay exhibited similar trend on oil content of the rapeseed germplasms. The heat effect on the chlorophyll fluorescence kinetic parameters F_v/F_m, ETR and Y(II) were also consistent. Heat stress significantly decreased oil content, although there was abundant genetic variation on heat tolerance among the genotypes. Correlation analysis showed that the decrease rate of F_v/F_m of silique heat-stressed B. napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed (R = 0.9214, P-value < 0.01). Overall, the results indicated that heat stress inhibited oil accumulation and photosynthesis in B. napus developing seed. The decrease rate of chlorophyll fluorescence parameter F_v/F_m of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification. Further, two heat insensitive rapeseed varieties with high oil content were identified.