法定计量单位在磁化率测定实验中的应用

阐明了法定计量单位在磁化率测定中的应用，文中以具体实验数据分别采用传统的电磁单位和法定计量单位表示出实验中所涉及的各物理量的数值和单位，并加以计算。还对实验中容易混淆的概念予以澄清．     

Pectinoacetals A-C: novel sterol hemiacetals from the gorgonianCtenocella pectinata

Three polyhydroxylated sterol hemiacetals, pectinoacetals A-C (1–3) have been isolated as their acetyl derivatives (4–6) from the acetic anhydride treated organic extract of the Indo-Pacific gorgonianCtenocella pectinata. These natural products were found to undergo very rapid epimerization at the C-18 chiral center and thus exist only as an equilibrium mixture of two diastereomers. The structure assignments are based on spectral studies and chemical modifications of the natural products.     

氰桥配合物[Ni(Ⅱ)Ln]_2[Fe(Ⅱ)(CN)_6]的光谱研究

亚铁氰化钾水溶液和[NiLn]~(2+)(L=H_2dmg和tetren分别表示丁二酮肟和四乙烯五胺)溶液反应得到比较稳定的红棕色晶体。经元素分析、UV-Vis光谱和红外光谱的测试,证明它们是氰桥配合物[Ni(Ⅱ)Ln-NC-Fe(Ⅱ)(CN)_4-CN-Ni(Ⅱ)Ln]。     

S—I—Ni开路循环水分解制氢的反应条件及动力学研究

本文对闭路循环ＮＩＳ法进行了改进，提出了改进的Ｓ—Ｉ—Ｎｉ三段开路循环水分解制氢的新方法。对循环中的主要反应进行了较系统的反应条件及动力学实验研究，获得了此反应的适宜反应条件及动力学方程，为进一步开发此循环打下了基础。     

Evidence from mosaic analysis of the masculinizing gene her-1 for cell interactions in C. elegans sex determination.

Sex in Caenorhabditis elegans is determined by a regulatory cascade of seven interacting autosomal genes controlled by three X-linked genes in response to the X chromosome-to-autosome (X/A) ratio. XX animals (high X/A) develop as self-fertile hermaphrodites, and XO animals (low X/A) develop as males. The activity of the first gene in the sex-determining cascade, her-1, is required for male sexual development. XO her-1 loss-of-function mutants develop as self-fertile hermaphrodites, whereas XX her-1 gain-of-function mutants develop as masculinized intersexes. By genetic mosaic analysis using a fused free duplication linking her-1 to a cell-autonomous marker gene, we show here that her-1 expression in a sexually dimorphic cell is neither necessary nor sufficient for that cell to adopt a male fate. Our results suggest that her-1 is expressed in many, possibly all, cells and that its gene product can function non-autonomously through cell interactions to determine male sexual development.     

14C measurement of forest soils in Dinghushan Biosphere Reserve

Organic carbon in forest soils of Qingyunsi and Wukesong profiles can be divided into fast and slow components. Δ 14C values of these profiles decrease with increasing of depth. The Δ 14C values in 30-40 cm depth interval of Wukesong profile are decreasing sharply until a very low value, showing that a strong geological environment change occurred about 1 560 years ago. The 14C apparent ages of Wukesong profile show that the coniferous and broad-leaf mixed forests around Wukesong profile have been developing since 425 a BP, which is consistent with historical documents. The penetrating depths of "bomb 14C" in Qingyunsi and Wukesong profiles are 10 and 20 cm, respectively.     

Sequence and analysis of chromosome 2 of the plant Arabidopsis thaliana

Arabidopsis thaliana (Arabidopsis) is unique among plant model organisms in having a small genome (130-140 Mb), excellent physical and genetic maps, and little repetitive DNA. Here we report the sequence of chromosome 2 from the Columbia ecotype in two gap-free assemblies (contigs) of 3.6 and 16 megabases (Mb). The latter represents the longest published stretch of uninterrupted DNA sequence assembled from any organism to date. Chromosome 2 represents 15% of the genome and encodes 4,037 genes, 49% of which have no predicted function. Roughly 250 tandem gene duplications were found in addition to large-scale duplications of about 0.5 and 4.5 Mb between chromosomes 2 and 1 and between chromosomes 2 and 4, respectively. Sequencing of nearly 2 Mb within the genetically defined centromere revealed a low density of recognizable genes, and a high density and diverse range of vestigial and presumably inactive mobile elements. More unexpected is what appears to be a recent insertion of a continuous stretch of 75% of the mitochondrial genome into chromosome 2.     

A structural change in the kinesin motor protein that drives motility

Kinesin motors power many motile processes by converting ATP energy into unidirectional motion along microtubules. The force-generating and enzymatic properties of conventional kinesin have been extensively studied; however, the structural basis of movement is unknown. Here we have detected and visualized a large conformational change of an approximately 15-amino-acid region (the neck linker) in kinesin using electron paramagnetic resonance, fluorescence resonance energy transfer, pre-steady state kinetics and cryo-electron microscopy. This region becomes immobilized and extended towards the microtubule 'plus' end when kinesin binds microtubules and ATP, and reverts to a more mobile conformation when gamma-phosphate is released after nucleotide hydrolysis. This conformational change explains both the direction of kinesin motion and processive movement by the kinesin dimer.