低温氧化作用对中国黄土记录剩磁的影响

系统地研究了黄土/古土壤样品在加热中磁性矿物及其粒径的变化. 实验结果表明, 在100~200℃之间, 因样品中有机质燃烧而产生的还原环境可以提高样品所含磁铁矿的纯度, 并影响样品的岩石磁学性质, 主要表现在: (1) 样品的矫顽力(Hc)和剩磁矫顽力(Hcr)显著减小; (2) 多畴(MD)磁性矿物的含量增多, 而超顺磁(SP)磁性矿物的含量降低; (3) 天然剩磁热退磁有异常显示; (4) 上述变化随成土作用增强而减弱. 进一步的研究表明, 这一还原过程可有效地消除黄土中MD磁铁矿由天然低温氧化作用(LTO)而携带的次生化学剩磁.     

Suspension culture ofNigella sativa

Summary In suspension culture 91% free cells ofNigella sativa was obtained inWhite's medium supplemented with casein hydrolysate, inositol and adenine. Ploidy distribution pattern was similar in cell clumps of different sizes and free cells. Chromosomal irregularities were more in free cells. A number of globular embryoid were formed when casein hydrolysate, inositol and adenine were added in the medium after subsequent omission of auxin and coconut milk.     

Viral adenosine triphosphatase.

The catalytic and immunological properties of an adenosine triphosphatase from different types of virus have been studied. The avian myeloblastosis virus has been found to be specialized in holding this enzyme in a highly active state as compared to other virus with respect to their host cell enzyme. Catalytically myeloblastosis virus and Rous virus ATPase behave alike, while that of the Reo virus is significantly different.     

Artificial neural network approach to assess selective flocculation on hematite and kaolinite

Because of the current depletion of high grade reserves, beneficiation of low grade ore, tailings produced and tailings stored in tailing ponds is needed to fulfill the market demand. Selective flocculation is one alternative process that could be used for the beneficiation of ultra-fine material. This process has not been extensively used commercially because of its complex dependency on process parameters. In this paper, a selective flocculation process, using synthetic mixtures of hematite and kaolinite in different ratios, was attempted, and the adsorption mechanism was investigated by Fourier transform infrared (FTIR) spectroscopy. A three-layer artificial neural network (ANN) model (4-4-3) was used to predict the separation performance of the process in terms of grade, Fe recovery, and separation efficiency. The model values were in good agreement with experimental values.     

Complex haplotypes, copy number polymorphisms and coding variation in two recently divergent mouse strains

Inbred mouse strains provide the foundation for mouse genetics. By selecting for phenotypic features of interest, inbreeding drives genomic evolution and eliminates individual variation, while fixing certain sets of alleles that are responsible for the trait characteristics of the strain. Mouse strains 129Sv (129S5) and C57BL/6J, two of the most widely used inbred lines, diverged from common ancestors within the last century, yet very little is known about the genomic differences between them. By comparative genomic hybridization and sequence analysis of 129S5 short insert libraries, we identified substantial structural variation, a complex fine-scale haplotype pattern with a continuous distribution of diversity blocks, and extensive nucleotide variation, including nonsynonymous coding SNPs and stop codons. Collectively, these genomic changes denote the level and direction of allele fixation that has occurred during inbreeding and provide a basis for defining what makes these mouse strains unique.     

DNA sequence and analysis of human chromosome 9

Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection.     

The hormone resistin links obesity to diabetes

Diabetes mellitus is a chronic disease that leads to complications including heart disease, stroke, kidney failure, blindness and nerve damage. Type 2 diabetes, characterized by target-tissue resistance to insulin, is epidemic in industrialized societies and is strongly associated with obesity; however, the mechanism by which increased adiposity causes insulin resistance is unclear. Here we show that adipocytes secrete a unique signalling molecule, which we have named resistin (for resistance to insulin). Circulating resistin levels are decreased by the anti-diabetic drug rosiglitazone, and increased in diet-induced and genetic forms of obesity. Administration of anti-resistin antibody improves blood sugar and insulin action in mice with diet-induced obesity. Moreover, treatment of normal mice with recombinant resistin impairs glucose tolerance and insulin action. Insulin-stimulated glucose uptake by adipocytes is enhanced by neutralization of resistin and is reduced by resistin treatment. Resistin is thus a hormone that potentially links obesity to diabetes.