胡杨分布的新发现

胡杨,属杨柳科杨属树种,学名Populus euphratica Oliver,又称为异叶杨、胡桐、梧桐等。胡杨在我国分布于新疆、青海、甘肃、内蒙古、宁夏等省区,在新疆分布最广,尤其是南疆塔里木河流域。《中国植物志》、《新疆植物检索表》,新疆农垦局编的《胡杨》等著作中都指出,胡杨分布于我国北纬37°-47°之间的广大地区,但据新疆地理所1985年-1986年两年野外考察和     

Properties of plasma radiation during discharges with improved confinement on HL-2A Tokamak

In the recent experiment on the HL-2A tokamak, two types of improved confinement regimes have been achieved in different configurations. One is the improved confinement regime in limiter configuration during electron cyclotron resonant heating (ECRH), characterized by a sharp decrease in H_α emission accompanied by an increase in the total radiation of plasma, the line averaged electron density and the stored energy of plasma. The other is high confinement regime (H-mode) in divertor configuration during a combination of ECRH and Neutral beam injection (NBI) heating, characterized with edge localized modes (ELMs) besides the features mentioned above. The ELMs are found to be localized on the plasma edge (r/a ≥ 0.8), causing average losses of particles and stored energy in the ranges of about 1--3% and 3--5% respectively during a single ELM event. So far, the ELMs observed in the HL-2A are type III ELMs with low amplitude and high repetition frequency in a range from 200 Hz to 350 Hz. An investigation of the radiated power density profiles shows that radiative cooling effect plays a significant role in the transition back to the L-mode and the triggering of ELM events.     

铁白云石矿物学特征及原生次生成因机制

长期以来,铁白云石的命名划分标准混乱,一直被当成高温及次生的产物.综述了国内外铁白云石的研究进展,详细探讨了铁白云石的矿物学特征,特别在其成因中加入了微生物因素,运用地质微生物学探讨原生铁白云石的成因机制.研究认为:（1）铁白云石命名划分依据应遵照国际矿物学会的原则,以铁是否替代白云石晶格中半数镁的位置为标准,分为白云石和铁白云石;（2）详述铁白云石矿物学及其晶体特征;（3）铁白云石成因分为原生沉淀及次生两种,微生物介导形成原生白云石的过程中,有助于铁进入到白云石晶格中,增加晶格中铁的含量.