克氏针茅群落地上/地下生物量分配及其对水热因子响应研究

碳循环研究已经成为目前生态学中的研究热点之一。草地生态系统在全球碳循环中占有重要地位，而且大部分草地处于对全球变化敏感的区域，也是研究生态系统对全球变化响应的关键地区。我国草地面积十分辽阔，占我国陆地面积的40%以上，具有极其重要的生态地位和作用。 在碳蓄积研究中，对地上碳库的估计比较容易，而对地下碳库的估计却由于方法上的局限造成估计的精度不高。因此，研究陆地生态系统中植物群落的地上/地下生物量分配模式，尤其是地下生物量的分配，对于全球碳蓄积的 研究具有重要意义。植物生长与环境因子密切相关，植物的生物量分配与环境因子也必然存在一定的相关关系，了 解植物的生物量分配与环境因子之间的关系，并建立相关模式，不但有利于减少生物量调查的工作量，而且能使碳蓄积量估计的精度大大提高。 (1) 本文通过对锡林郭勒草原上的克氏针茅植物群落进行了为期两年的地上和地下生物量观测，初步得到了克氏针茅群落地上/地下生物量分配规律： 2004年地上生物量表现为逐渐增加的趋势，6、7、8月地上生物量较低，9月显著增加，为8月的4.8倍。2005年地上生物量表现出明显的单峰曲线，8月达到峰值，为150.48 g•m-2。2004年地下生物量6月到7月明显增长，7月、8、9月逐渐减少。2005年地下生物量出现两次增加和两次减小的过程。地下生物量在不同层次的分配数量及所占比例存在差异。0~10cm分配的地下生物量最多，所占比例最大，往下各层基本表现出逐层递减的趋势。其中，0~30cm地下生物量占0~80cm总地下生物量的70％。 地下生物量与地上生物量的比值即为根冠比，根冠比也具有明显的季节变化。2004年从6月到9月根冠比表现为逐渐减小的趋势，最小根冠比值出现在9月，为9.22。2005年为明显的反抛物线形状，最小值出现在8月，为19.93。 (2) 分析克氏针茅群落地上生物量、地下生物量、根冠比三者关系的结果表明：克氏针茅草原群落地上生物量和根冠比的相关关系较为明显，而地下生物量与根冠比的相关关系较差。地上生物量与地下生物量的相关关系较好，呈正相关关系。地上生物量对根冠比变化的贡献较大，而地下生物量对根冠比变化的贡献较小。 （3）在观测生物量的同时，用小气候自动观测系统记录了同时期的降水和气温资料，通过分析克氏针茅群落地上、地下生物量及根冠比与降水、气温的关系，得出以下结论： 2004年和2005年地上生物量均与上月降水量有显著相关关系，而两年的地下生物量与降水量的相关关系较差。两年的根冠比变化与上月降水量也具有较好的相关关系。2004年地下生物量与上月平均气温的相关关系较好。2005年地下生物量与月平均气温的相关关系较差。2004和2005年地上生物量与月平均气温有很好的线性关系，但两年的相关关系正好相反。两年的根冠比与月平均气温的相关关系也表现的恰恰相反。 (4) 最后，分析了温室控制试验羊草种群的生物量分配对水热因子响应的阈值。得出以下结论： 土壤相对含水量范围为6065%、温度为26℃时的地上、地下干重都最大，表明这是羊草地上、地上部分生长最适宜的温度和土壤水分。土壤为相对含水量2530%、温度为20℃时根冠比值最大。 温度、土壤水分以及二者的交互作用对羊草根冠比的影响均达到极显著水平。但根冠比对不同温度和土壤水分的敏感度不同。根冠比在一定的温度范围和土壤相对含水量范围内发生敏感变化。

Phenotype and Function of Monocyte-Derived Dendritic Cells from Chinese Rhesus Macaques

Dendritic cells (DCs) play a pivotal role in linking the innate immunity and acquired immunity in responses to pathogen. Non-human primates such as Chinese Rhesus Macaque (CRM) are the favorable models for preclinical study of potential therapeutic drugs,

Frontal and cingulate gray matter volume reduction in heroin dependence: Optimized voxel-based morphometry

Aims: Repeated exposure to heroin, a typical opiate, causes neuronal adaptation and may result in anatomical changes in specific brain regions, particularly the frontal and limbic cortices. The volume changes of gray matter (GM) of these brain regions, ho

Hydrodynamics in an expanded bed of large size ion-exchange resin, and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 x 7 Styrene-DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (20S to 1030 gm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid-phase dispersion coefficient was found to be of the order 10(-5) m(2) s(-1), which falls into the range 1.0 x 10(-6) to 1.0 X 10(-5) m(2) s(-1) observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations.

Developments in transgenic fish in the people's Republic of China

In the People's Republic of China, genetically modified (GM) fish are being developed primarily to produce desirable alterations to growth rates or feed-conversion efficiency. Up to the present, no transgenic fish have been commercially approved for human consumption. This review introduces advances in the People's Republic of China in transgenic fish studies, biosafety studies of fast-growth GM fish, and the regulation of GM fish.

Role of Bi3+ ions for Er3+ ions efficient 1.54 mu m light emission in Er/Bi codoped SiO2 thin film prepared by sol-gel method

Er/Bi codoped SiO2 thin films were prepared by sol-gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 degrees C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 mu m light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 gm reached maximum at 800 degrees C and decreased dramatically at 1000 degrees C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol-gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er-Bi-Si-O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED

Selective-area MOCVD growth for distributed feedback lasers integrated with vertically tapered self-aligned waveguide

The growth pressure and mask width dependent thickness enhancement factors of selective-area MOCVD. grow th were investigated in this article. A, high enhancement of 5.8 was obtained at 130 mbar with the mask width of 70 mum. Mismatched InGaAsP (-0.5%) at the maskless region which could ensure the material at butt-joint region to be matched to InP was successively grown by controlling the composition and mismatch modulation in the selective-area growth. The upper optical confinement layer and the butt-coupled tapered thickness waveguide were regrown simultaneously in separated confined heterostructure 1.55 gm distributed feedback laser, which not only offered the separated optimization of the active region and the integrated spotsize converter, but also reduced the difficulty of the butt-joint selective regrowth. A narrow beam of 9degrees and 12degrees in the vertical and horizontal directions, a low threshold current of 6.5 mA was fabricated by using this technique. (C) 2003 Elsevier Science B.V. All rights reserved.

Analysis of the interfaces of [NiFe/Mo](30) and [Fe/Mo](30) multilayers

The interface states of [NiFe/Mo](30) and [Fe/Mo](30) multilayers have been investigated by x-ray small angle reflection and diffuse scattering. Significant interface roughness correlation was observed in both ultrathin [NiFe/Mo](30) and [Fe/Mo](30) multilayers. An uncorrelated roughness of about 27-3.1 Angstrom was revealed in the [NiPe/Mo](30) multilayers, which is explained as originating from a transition layer between the NiFe and the Mo layers. By the technique of diffuse scattering, it is clearly indicated that the interfacial roughness of NiFe/Mo is much smaller than that of Fe/Mo although the lattice mismatch is the same in both multilayers.

A widely tunable continuous-time LPF for a direct conversion DBS Tuner

A continuous-time 7th-order Butterworth Gm-C low pass filter (LPF) with on-chip automatic tuning circuit has been implemented for a direct conversion DBS tuner in a 0.35um SiGe BiCMOS technology. The filter's -3dB cutoff frequency f(0) can be tuned from 4MHz to 40MHz. A novel translinear transconductor (Gm) cell is used to implement the widely tunable and high linear filter. The filter has -0.5dB passband gain, 28nV/Hz(1/2) input referred noise, -2dBVrms passband IIP3, 24dBVrms stopband IIP3. The I/Q LPFs with the tuning circuit draw 16mA (with f(0)=20MHz) from 3.3 V supply, and occupy an area of 0.45 mm(2).