Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

IEECAS SKLLQG

利用贺兰山北部树轮资料重建过去270年以来6-8月平均干燥指数

IEECAS SKLLQG

陕西咸阳人工林地土壤干层研究

IEECAS SKLLQG

束流调制器物理机制与电子学设计

兰州重离子回旋加速器装置H IRFL在某种工作模式下,需要对束流在时间上进行调制,以避免束流对输运线造成损伤;并在加速器引出的束流能量较高且流强很大时,采用束流调制器可使调束在较低的流强下进行,而不必改变加速器的参数。调制器由加装在束运管道上的两个平行电极与相应的电子学电路组成。为满足调制脉冲前后沿的时间要求,电子学设计着重考虑展宽电压放大器频带低品质因数电路设计。

大兴安岭呼中林区火烧迹地粗木质残体特征

对大兴安岭呼中林区不同年份火烧迹地的粗木质残体特征进行了研究.结果表明:呼中林区火烧迹地粗木质残体贮量在24.87～180.98m3.hm-2,其中倒木和枯立木分别为6.03～93.91m3.hm-2和15.29～138.37m3.hm-2,且不同年份火烧迹地之间差异显著;倒木、枯立木所占比例分别为24.26%～86.00%和14.01%～75.4%,且不同年份火烧迹地之间差异显著;倒木和枯立木的优势径级分别为2.50～20cm和1.50～15m,优势长度分别为2.50～15cm和5～20m;随着火烧迹地的恢复,粗木质残体贮量的动态变化不明显.粗木质残体特征与火前林分条件和火烧强度密切相关.

Magnetic microsphere and its use in biochemical separation and analysis

Magnetic microsphere comprises a magnetically responsive metal or metal oxide core surrounded by a polymer shell with active groups. Nowadays, methods of directly coating polymer, monomer polymerazation, impregnation, extrusion and biological synthesis are generally used to prepare magnetic particles. This kind of superparamagnetic microspheres can be attached to chemical, biochemical and biological substances by their active groups, then applying a magnetic field to separate from the media. Preparation and utilization of magnetic microspheres in immunoassay, nucleic acid hybrization assay, gene sequencing, cell isolation, enzyme immoblization, receptor isolation and other Gelds are reviewed with 44 references in this paper. Also, the further development is outlooked.

磁微球及其在生化分离分析中的应用

磁微球是以金属或金属氧化物为核,外面包被带有活性基团物质的一种新型生物分离材料.目前制备磁微球的方法有包埋法、聚合法、浸渍法、挤压法和生物合成法等.这种微球通过其活性基团与化学、生化和生物物质连接后,利用其顺磁性外加一定磁场可实现与介质分离.本文全面地介绍了磁微球的制备,详尽评述了其在免疫分析、核酸杂交分析、基因测序、细胞分离、酶的固定、受体分离等各个领域的应用.

Studies on the PTC/NTC effect of carbon black filled low density polyethylene composites

The positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of carbon black (CB) filled low density polyethylene (LDPE) composites was studied using electrical resistivity spectra, DSC, tensile mechanical analysis (TMA) and small-angle X-ray scattering (SAXS) techniques. The three LDPEs used have a similar crystallinity and different melting index (MI). The experimental results indicate that the CB has no significant effect on the crystallinity and the long spacing of crystalline domains of LDPE. Based upon the TMA and dynamic elastic modulus spectra, it can be concluded that the PTC effect is related to the thermal expansion of the polymer matrix, and the NTC effect is caused by a decrease of the elastic modulus of the polymer at high temperatures. The NTC effect can be reduced by enhancing either the elastic modulus or the interaction between carbon black and matrix. (C) 1997 Elsevier Science Ltd.

新拓扑指数A_m在有机物气相色谱法中光离子化灵敏度的分析中的应用

本文把Am拓扑指数与分子连接性指数首次用于有机化合物气相色谱分析的光离子化灵敏度的结构-性能相关性研究中，在与相应体系的光离子化灵敏度进行相关分析时发现，Am指数、分子连接性指数均能较好地反映化合物的结构特征，将二者组合，得到了更为满意的构效关系的数学模型。

稀土与L-谷氨酰胺配合物的电子能谱研究

合成了通式为LnL_3Cl_3·2H_2O(Ln=Eu,Tb,Ho,Tm;L=L-谷氨酰胺)的固体配合物。用XPS辅以元素分析、热分析及IR光谱研究了配合物的组成及性质。观察到配合物中O_(1a)、Ln_(3d)、Ln_(4d)和Cl_(2p)结合能的变化,并发现Eu配合物Eu_(3d)谱峰的伴峰结构,讨论了伴峰产生的机理。

Analysis of tandem repeats in the genome of Chinese shrimp Fenneropenaeus chinensis

Through random sequencing, we found a total of 884000 base-pairs (bp) of random genomic sequences in the genome of Chinese shrimp (Fenneropenaeus chinensis). Using bio-soft Tandem Repeat Finder (TRF) software, 2159 tandem repeats were found, in which there were 1714 microsatellites and 445 minisatellites, accounting for 79.4% and 20.6% of repeat sequences, respectively. The cumulative length of repeat sequences was found to be 116685 bp, accounting for 13.2% of the total DNA sequence; the cumulative length of microsatellites occupied 9.78% of the total DNA sequence, and that of minisatellites occupied 3.42%. In decreasing order, the 20 most abundant repeat sequence classes were as follows: AT (557), AC (471), AG (274), AAT (92), A (56), AAG (28), ATC (27), ATAG (27), AGG (18), ACT (15), C (11), AAC (11), ACAT (11), CAGA (10), AGAA (9), AGGG (7), CAAA (7), CGCA (6), ATAA (6), AGAGAA (6). Dinucleotide repeats, not only in the aspect of the number, but also in cumulative length, were the preponderant repeat type. There were few classes and low copy numbers of repeat units of the pentanucleotide repeat type, which included only three classes: AGAGA, GAGGC and AAAGA. The classes and copy numbers of heptanucleotide, eleven-nucleotide and thirteen-nucleotide primer-number-composed repeats were distinctly less than that of repeat types beside them.