HL-2A装置密度极限附近边缘剪切流和极向剩余胁强的实验研究

报道了HL-2A装置密度极限附近边缘剪切流和极向剩余胁强的最新实验研究结果。研究发现,等离子体密度向Greenwald密度靠近时,等离子体响应由绝热响应向流体动力学响应转变,导致湍流雷诺胁强中的非扩散项——剩余胁强降低,其径向梯度表征的等离子体自发旋转力矩显著降低。边缘极向流的湍性驱动降低进一步导致边缘E×B极向流剪切强度减弱。这些实验结果证明了湍流剩余胁强的降低是导致托卡马克密度极限附近边缘极向剪切层崩塌的关键因素。

HL-1M托卡马克边缘参数和雷诺胁强的径向分布

利用多组马赫 /朗缪尔探针测量了HL 1M装置刮离层和边缘静电雷诺胁强、等离子体极向旋转、径向和极向电场的径向分布。在低杂波电流驱动、超声分子束注入、多发弹丸注入和中性束注入实验中 ,给出了雷诺胁强和极向流的关系。结果表明 ,由于雷诺胁强的径向变化 。

HL-2A等离子体边缘极向剩余胁强的研究

首次报导了托卡马克等离子体边缘与湍流相关的极向剩余胁强剖面的测量结果。采用外中平面往复式静电探针阵列对HL-2A托卡马克边缘的极向湍流动量输运进行研究。在没有外部动量注入的欧姆放电下,剩余胁强为有限值、且其空间剖面在等离子体边缘具有明显的径向梯度,表明托卡马克等离子体边缘存在极向动量源。由动量源产生的动量主要以扩散形式向与剩余胁强相反的方向传播,最终的结果是等离子体边缘存在有限的雷诺胁强。在最后闭合磁面以内0.5~2cm区域,剩余胁强的梯度提供自发旋转的力矩,由该力矩引起的动量产生与由速度梯度引起的动量扩散共同导致了雷诺胁强出现负梯度,造成动量沉积,从而驱动极向平衡流。

对称性自发破缺所诱发的种子平行雷诺胁强

根据第二类气球模理论,在托卡马克中诸如不稳定漂移波类的环形局部模将在径向呈现源于环形性的对称性自发破缺。以流体离子温度梯度模模型方程为例,解出在准环坐标系中由对称性自发破缺产生的二维局部模本征模式。在略去边带效应后,它成为具有径向位移修正的平板模式。由位移修正离子温度梯度模式导出了种子平行雷诺胁强,而它在传统的(无位移修正的)平板模式下被证明为零。

低温胁迫下草坪草Perennial ryegras(cv,Taya)和Meadow bluegrass(cv.Compact)各抗性生理指标的变化

以草坪草多年生黑麦草Ｐｅｒｅｎｎｉａｌｒｙｅｇｒａｓｓ（Ｔａｙａ）和草地早熟禾Ｍｅａｄｏｗｂｌｕｅｇｒａｓｓ（Ｃｏｍｐａｃｔ）为材料，通过测定在三种低温胁迫强度和不同的胁迫时间下植物体活性氧清除剂超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）的活性、脯氨酸含量、类胡萝卜素含量和相对电导度等抗性生理指标的变化，以确定其胁变程度，研究两种草坪草抗低温胁迫的形式、途径和大小及其抗性机制问题。结果表明：①草地早熟禾Ｃｏｍｐａｃｔ抗低温胁迫的能力较多年生黑麦草的Ｔａｙａ强。②５℃低温胁迫下两种草坪草的ＳＯＤ、ＣＡＴ活性、类胡萝卜素含量均先升后降，呈现单峰型曲线变化，在三种活性氧清除剂的活性或含量上升时，脯氨酸含量、叶绿素含量和相对电导度没有明显的变化，在三种活性氧清除剂活性或含量下降时，叶绿素含量下降，脯氨酸含量和相对电导度上升。而在０℃与－６℃低温胁迫下ＳＯＤ、ＣＡＴ活性、类胡萝卜素含量随胁迫时间的延长，迅速下降，随后叶绿素含量下降，脯氨酸含量、相对电导度上升。③从５℃到０℃到－６℃，随胁强的增大，一定胁迫时间内各抗性生理指标变化幅度，即胁变程度，随之增大。

HL-1M装置高气压分子束注入下边缘等离子体结构

在HL 1M装置的高气压分子束流注入加料实验中,利用提高注入口气源的气压来提高超声分子束流的速度和增加入射的粒子密度,从而改变了边缘电场、等离子体旋转速度和边缘静电雷诺胁强。利用马赫 郎缪尔探针组测量了HL 1M装置刮离层的边缘雷诺胁强、等离子体极向旋转、径向和极向电场的变化。实验结果表明:随着分子束流速度和粒子密度的增加,延伸了分子束流的注入深度,提高了注入速度和效率。

Effect of processing way and aging treatment on properties and microstructures of 7B04 aluminum alloy

The influence of forging and aging treatment on mechanical properties and microstructure of large size prestretched thick plate of 7B04 aluminium alloy was investigated through tensile test, corrosion test, transmission electronic microcopy(TEM) and energy dispersive spectrum(EDS) analysis. The results show that the properties of plate performed extra forging (FSR technology) are much higher than those of plate without forging (CSR technology). T7451 temper is preferred to resisting corrosion than T651 temper due to a wide PFZ and discontinuous grain boundary precipitates.

Male Allocare in Rhinopithecus bieti at Xiaochangdu, Tibet: Is It Related to Energetic Stress?

Male allocare among nonhuman primates has frequently been investigated from the perspective of the caretaker. Here we examined whether male allocare relates to environmental factors or the females＇ energetic stress. We researched the possible differences of allocare between sexes in free-ranging black-and-white snub-nosed monkeys （Rhinopithecus bieti） in Tibet. A combination of stepwise least squares regression analysis was used to identify the influence of ecological factors （temperature, rainfall, etc.） and infant age that best account for seasonal variation of allocare. The results indicate, except for the functions of infant age, however, that male allocare is a negative function of temperature and female allocare is a positive function of temperature. Specifically, we tested the energetic stress hypothesis, which predicts that the energetic burden of females in a severe environment favour an increased rate of male allocare during the seasons of high energetic stress. We analyzed the allocare difference between high energetic stress season （Mar - Apr）, when temperature was low, food availability was scarce, and infants were young, and low energetic stress season （Jun - Aug）, based on data obtained during June 2003 - June 2004. Our results supported the energetic stress hypothesis because male allocare in high energetic stress season was higher than that of in low energetic stress season and female allocate was reverse. Therefore, we propose it is the energetic stress on female that make male allocare possible. Male take these interests for other aims and meet some functional hypothesis, which are addressed from the perspective of the male.

PSⅡ Photochemistry and Xanthophyll Cycle in Two Superhigh-yield Rice Hybrids, Liangyoupeijiu and Hua-an 3 During Photoinhibition and Subsequent Restoration

PSⅡ photochemistry and xanthophyll cycle during photoinhibition (exposed to strong light of 2 000 μmol photons·m -2 ·s -1 ) and the subsequent restoration were compared between two superhigh_yield rice hybrids (Liangyoupeijiu and Hua_an 3, the newly developed rice hybrids from two parental lines) and the traditional rice hybrid Shanyou 63 developed from three parental lines. The results showed that the maximal efficiency of PSⅡ photochemistry ( Fv/Fm ), the efficiency of excitation energy capture by open PSⅡ centers ( Fv′/Fm′ ), and the yield of PSⅡ electron transport ( Φ PSⅡ ) of the three rice hybrids decreased during photoinhibition. However, a greater decrease in Fv/Fm , Fv′/Fm′ , and Φ PSⅡ was observed in Shanyou 63 than in Liangyoupeijiu and Hua_an 3. At the same time, the components of xanthophyll cycle, antherxanthin (A) and zeathanxin (Z) increased rapidly while violaxanthin (V) decreased considerably. Both the rate of accumulation and the amount of A and Z in the two superhigh_yield rice hybrids were higher than that in Shanyou 63. The de_epoxidation state (DES) of xanthophyll cycle increased rapidly with the fast accumulation of A and Z, and reached the maximal level after first 30 min during photoinhibition. Of the three hybrids, the increasing rate of DES in Liangyoupeijiu and Hua_an 3 was higher than that in Shanyou 63. After photoinhibition treatment, the plant materials were transferred to a dim light (70 μmol photons·m -2 ·s -1 ) for restoration. During restoration, both chlorophyll fluorescence parameters and xanthophyll cycle relaxed gradually, but the rate and level of restoration in the two superhigh_yield rice hybrids were higher than those in Shanyou 63. Our results suggest that Liangyoupeijiu and Hua_an 3 had higher resistance to photoinhibition and higher capacity of non_radiative energy dissipation associated with xanthophyll cycle, as well as higher rate of restoration after photoinhibition, than Shanyou 63 when subjected to strong light.

A size-gradient hypothesis for alpine treeline ecotones

Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.

Drought may be beneficial to the competitive advantage of Amaranthus spinosus

Drought can affect the growth and soil enzyme activities of invasive alien plants(IAPs).It is imperative to evaluate the competitive advantage of IAPs compared with that of the native species and the activities of soil enzymes under drought.This study aimed to evaluate the competitive advantage of the IAP Amaranthus spinosus that originated from tropical America compared with the native Chinese species A.tricolor and the activities of soil enzymes under drought.A competitive co-culture of A.spinosus and A.tricolor was established using a planting basin experiment.The two species were treated with different levels of drought,i.e.(i)the control;(ii)a light level of drought and(iii)a heavy level of drought.The functional traits,osmotic adjustment and the activities of antioxidant enzymes of the two species,as well as soil pH and electrical conductivity,contents of soil microbial biomass carbon and the activities of soil enzymes were determined.The relative competition intensity and relative dominance of A.spinosus were greater than those of A.tricolor under drought.Drought may provide an advantage to the competitive advantage of A.spinosus.Soil water-soluble salt content and sucrose hydrolytic power of A.spinosus were greater than those of A.tricolor under drought.The ability of A.spinosus to grow in soil with higher levels of water-soluble salt contents and sucrose hydrolytic power under drought may aid in its acquisition and utilization of nutrients.