长白山阔叶红松林冠层光合生产力的模拟研究

森林作为陆地生态系统的主体，在碳的生物地球化学循环中起着关键的作用，因此对森林生态系统生产力的研究具有重要意义。本文以长白山阔叶红松林为研究对象，在2005年7月~9月对其主要优势种红松、紫椴、蒙古栎、水曲柳的生理生态学参数进行了测定，并利用单叶尺度的光合作用-气孔导度-能量平衡耦合模型，以及冠层尺度的多层模型，对单叶尺度以及冠层尺度的光合作用进行了模拟，主要的结论有： （1）长白山阔叶红松林主要优势树种红松、紫椴、蒙古栎、水曲柳的生理生态学参数：光合有效辐射吸收率a、初始量子效率α、光饱和时的最大净光合作用速率Pmax、最大的Rubisco催化反应速率Vcmax、CO2饱和时的最大净光合作用速率Jmax有着明显且不同的季节变化。7、8月水曲柳的α值最大，分别为0.077、0.064，9月紫椴的最大，为0.051。红松的Vcmax值在7、9月为四个树种中最大的，分别为：49.085、43.072μmol•m-2•s-1，8月为水曲柳最大，为66.041μmol•m-2•s-1。 （2）对优势树种单叶尺度的净光合作用速率An和气孔对CO2的导度gsc进行模拟发现：紫椴、蒙古栎、水曲柳的An、gsc的值在7~9月要大于红松，进入植物生长末期的9月则随着生理活性的下降而迅速下降，而红松则表现较为平稳且略有上升。7月蒙古栎的An、gsc的最大值最大分别为15.055μmol•m-2•s-1、0.400 mol•m-2•s-1；8月水曲柳的最大分别为22.944μmol•m-2•s-1、0.567 mol•m-2•s-1；9月紫椴的最大分别为12.045μmol•m-2•s-1、0.249 mol•m-2•s-1。 （3）通过模拟得到：长白山阔叶红松林冠层2005年8月的净光合作用速率An有着明显的日变化特征， 8月林冠的净光合作用速率最大值可以达到44.880μmol•m-2•s-1，该月白天净光合作用速率的总量可以达到23.580 mol•m-2。通过与观测值比较发现模拟结果能够较好地反映冠层光合作用的特征。

Numerical simulation of a bubble rising in shear-thinning fluids

The motion of a single bubble rising freely in quiescent non-Newtonian viscous fluids was investigated experimentally and computationally. The non-Newtonian effects in the flow of viscous inelastic fluids are modeled by the Carreau theological model. An improved level set approach for computing the incompressible two-phase flow with deformable free interface is used. The control volume formulation with the SIMPLEC algorithm incorporated is used to solve the governing equations on a staggered Eulerian grid. The simulation results demonstrate that the algorithm is robust for shear-thinning liquids with large density (rho(1)/rho(g) up to 10(3)) and high viscosity (eta(1)/eta(g) up to 10(4)). The comparison of the experimental measurements of terminal bubble shape and velocity with the computational results is satisfactory. It is shown that the local change in viscosity around a bubble greatly depends on the bubble shape and the zero-shear viscosity of non-Newtonian shear-thinning liquids. The shear-rate distribution and velocity fields are used to elucidate the formation of a region of large viscosity at the rear of a bubble as a result of the rather stagnant flow behind the bubble. The numerical results provide the basis for further investigations, such as the numerical simulation of viscoelastic fluids. (C) 2010 Elsevier B.V. All rights reserved.

东秦岭南洛河上游黄土地层年代的初步研究及其在旧石器考古中的意义

IEECAS SKLLQG

Early effects of carbon-ion irradiation on murine lymphocytes and thymocytes

To estimate the biological risks from space radiation encountered by cosmonauts in outer space, the effects from whole-body exposure to carbon ions or X-rays irradiations at 0, 0.39, 0.55 and 1 Gy at a dose rate of 0.2 Gy/min were investigated in BALB/c mice. The relative thymus and spleen weights were measured at 24 h after exposure, and the cell cycle distribution and percentage of apoptosis of thymocytes and spleen and peripheral blood lymphocytes were determined by flow cytometry. The data showed that exposure to carbon ions delayed cell progression of peripheral blood lymphocytes in S-phase, and delayed thymocytes and spleen lymphocytes in G(0)/G(1)-phase. Apoptosis of thymocytes and peripheral blood lymphocytes induced by carbon ions increased more rapidly with dose than was the case for X-rays. There were some differences between the relative weight loss of the thymus and the spleen with increasing dose of either carbon ions or X-rays. The results obtained provide evidence of dose- and organ-specific differences induced by carbon ions compared to X-rays, with increased apoptosis in peripheral blood lymphocytes and thymocytes, but not spleen lymphocytes. Our data may suggest that further work would be of interest to estimate risk of changes in immune function during particle radiation exposures in space travel. (c) 2007 COSPAR