DYNAMIC PROCESS OF VALENCE CHANGE OF EUROPIUM ION IN EUROPIUM DIFLUORIDE AT HIGH-TEMPERATURE

The dynamic process of the ionic valence changing from Eu~(2+) to Eu~(3+) in EuF_2 at high temperature has been investigated by ESCA, high,temperature X-ray diffraction, high temperature spectrum, high temperature magnetic Isusceptibility and Mssbauer spectrum. It has been shown that the formed Eu~(3+) exists in different compounds when EuF_2 is heated to high temperature in different atmospheres. In air, Eu~(3+) exists in the form of hexagonal EuOF, in nitrogen, in the form of orthogonal EuF_3 and non-hexa...

The effects of random surface waves on the steady Ekman current solutions

The response of near-surface current profiles to wind and random surface waves are studied based on the approach of Jenkins [1989. The use of a wave prediction model for driving a near surface current model. Dtsch. Hydrogr. Z. 42,134-149] and Tang et al. [2007. Observation and modeling of surface currents on the Grand Banks: a study of the wave effects on surface currents. J. Geophys. Res. 112, C10025, doi:10.1029/2006JC004028]. Analytic steady solutions are presented for wave-modified Ekman equations resulting from Stokes drift, wind input and wave dissipation for a depth-independent constant eddy viscosity coefficient and one that varies linearly with depth. The parameters involved in the solutions can be determined by the two-dimensional wavenumber spectrum of ocean waves, wind speed, the Coriolis parameter and the densities of air and water, and the solutions reduce to those of Lewis and Belcher [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans. 37, 313-351] when only the effects of Stokes drift are included. As illustrative examples, for a fully developed wind-generated sea with different wind speeds, wave-modified current profiles are calculated and compared with the classical Ekman theory and Lewis and Belcher's [2004. Time-dependent, coupled, Ekman boundary layer solutions incorporating Stokes drift. Dyn. Atmos. Oceans 37, 313-351] modification by using the Donelan and Pierson [1987. Radar scattering and equilibrium ranges in wind-generated waves with application to scatterometry. J. Geophys. Res. 92, 4971-5029] wavenumber spectrum, the WAM wave model formulation for wind input energy to waves, and wave energy dissipation converted to currents. Illustrative examples for a fully developed sea and the comparisons between observations and the theoretical predictions demonstrate that the effects of the random surface waves on the classical Ekman current are important, as they change qualitatively the nature of the Ekman layer. But the effects of the wind input and wave dissipation on surface current are small, relative to the impact of the Stokes drift. (C) 2008 Elsevier Ltd. All rights reserved.

A modified HPLC method for analysis of PSP toxins in algae and shellfish from China

Improvements to an established HPLC method are introduced. The modified method is more efficient for separation and detection of the toxins responsible for paralytic shellfish poisoning (PSP). The PSP toxin content of two strains of Alexandrium tamarense and approximately forty shellfish samples collected from different locations in China have been analyzed with this HPLC method. Only one shellfish sample, collected from Lianyungang, China, contained PSP toxins.

青海岩黄芪属(Hedysarum)一新变型

发表黄芪属一新变型

土壤水分胁迫对不同耐旱性春小麦品种叶片色素含量的影响

研究选用耐旱性强的“定西24”和“高原671”与耐旱性弱的“高原448”和“青春533”春小麦品种，在盆栽条件下比较了不同耐旱性品种在拔节后经不同程度水分胁迫后叶片的多种生理参数；叶片相对含水量、净光合速率、叶绿素a、叶绿素b、叶绿素总量和类胡萝卜素含量。结果表明：在土壤相对含水量75％、55％、40％和30％这4个等级上，这些生理指标均随土壤相对含水量的降低而下降，耐旱性强的品种降低慢，且降低幅度小。在水分胁迫下，4个品种叶片的叶绿素a、叶绿素b和叶绿素总量下降，证明此时光合器生理功能遭到破坏；在轻度水分胁迫下，耐旱性强的品种定西24和高原671叶片的类胡萝卜素含量上升；在严重水分胁迫下，4个品种的叶片类胡萝卜素含量明显下降，可能此时自由基积累超过了抗氧化剂的清除能力，从而使细胞受到损伤。根据本研究结果，可以将轻度水分胁迫下叶片类胡萝卜素含量升高作为春小麦品种耐旱性的选择指标之一。

三种嵩草群落中若干植物种的生态位宽度与重叠分析

本文利用Ｌｅｖｉｎｓ和Ｐｉａｎｋａ公式，在多维生态因子梯度上测定了海北地区高寒草甸三种嵩草（Ｋｏｂｒｅｓｉａ）群落中若干植物种的生态位宽度和生态位重叠。结果表明：三种嵩草群落中优势种群的生态位宽度都较大，其中小嵩草（Ｋ．ｐｙｇｍａｅａ）在土壤水势、光照强度和坡向等三维因子上的生态位宽度分别是０．９１８、０．８９６和０．９１０；矮嵩草（Ｋ．ｈｕｍｉｌｉｓ）和藏嵩草（Ｋ．ｔｉｂｅｔｌｃａ）在土壤水势维上的生态位宽度分别是０．８７５和０．８６６；植物种如具有较大的生态位，则种间的生态位重叠亦较高；植物种对间若有相似的生物学一生态学特征, 生态位重叠有降低的趋势小篙草和矮篙草在三维上的重叠值分别是0.671、0.719和0.686某些杂类草与优质牧草之间存有较大的重叠, 这主要与长期过度放牧、优良牧草受到抑制以及生境退化有关。

Morphological and reproductive response of Caragana microphylla to different stocking rates

Understanding the effect on host plants of defending against herbivores is important in grazing ecology and grassland management. In this study, the morphological and reproductive responses of Caragana microphylla Lam. to grazing sheep were investigated using a 15-year grazing experiment with six stocking rates in the Inner Mongolia steppe of China. Plant height, rachis length, leaflet size, and number of pods decreased significantly, whereas spine density and length increased significantly with increased stocking rate. Significant negative correlations were observed between production of vegetative and reproductive organs and defensive organs, indicating that it is costly for C. microphylla to defend against herbivores and that morphological miniaturization and a tradeoff between production and defense were main responses of C. microphylla to herbivores. (c) 2006 Elsevier Ltd. All rights reserved.

Seasonal regulations of energetics, serum concentrations of leptin, and uncoupling protein 1 content of brown adipose tissue in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau

Survival of small mammals in winter requires proper adjustments in physiology, behavior and morphology. The present study was designed to examine the changes in serum leptin concentration and the molecular basis of thermogenesis in seasonally acclimatized root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau. In January root voles had lower body mass and body fat mass coupled with higher nonshivering thermogenesis (NST) capacity. Consistently, cytochrome c oxidase activity and mitochondrial uncoupling protein-1 (UCP1) protein contents in brown adipose tissues were higher in January as compared to that in July. Circulating level of serum leptin was significantly lower in winter and higher in July. Correlation analysis showed that serum leptin levels were positively related with body mass and body fat mass while negatively correlated with UCP1 protein contents. Together, these data provided further evidence for our previous findings that root voles from the Qinghai-Tibetan plateau mainly depend on higher NST coupled with lower body mass to enhance winter survival. Further, fat deposition was significantly mobilized in cold winter and leptin was potentially involved in the regulation of body mass and thermogenesis in root voles. Serum leptin might act as a starvation signal in winter and satiety signal in summer.

基于岩溶生态系统特性的水土流失敏感性评价

在岩溶地区大范围内进行土壤侵蚀风险评价需要寻求新的简单有效的方法,建立适合岩溶地区特点的评估模型,才能避免水土流失治理规划的失误。考虑岩溶地区碳酸盐岩成土速率低、存在石漠化等特点,选取土壤允许流失量和退化岩溶生态系统的基岩裸露率,结合年平均降水、坡度、植被指数,在生成各单因素评价图的基础上,在Arcview中完成单因素图的叠加分析,得到贵州省岩溶地区水土流失敏感性综合评价图,并将其划分为不敏感、轻度敏感、中度敏感和强度敏感四级。在此基础上,探讨了贵州省水土流失敏感性的空间分异规律,提出水土流失预防治理的优先区。