Effect of Nano－SiC and Nano－Si Doping on Critical Current Density of MgB2

The discovery of superconductivity in magnesium diboride (MgB2) has opened up a new field in materials science research. It offers a possibility of a new class of high performance superconducting materials for practical applications because of the relatively low cost of fabrication, high critical current densities (Jc)and fields, large coherence length, absence of Weak links, higher Tc (Tc = 39 K) compared with Nb3Sn and Nb-Ti alloys (two or four times that of Nb3Sn and Nb-Ti alloys). However, the weak flux pinning in the magnetic field remains a major challenge. This paper reports the most interesting results on nenomaterial (SiC and Si) doping in magnesium diboride. The high density of nano-scele defects introduced by doping is responsible for the enhanced pinning. The fabrication method, critical current density, microstructures, flux pinning and cost for magnesium diboride bulks, wires and tapes are also discussed. It is believed that high performance SiC doped MgB2 will have a great potential for many practical applications at 5K to 25K up to 5T.     

Synthesis and Fluorescence Spectrum of a Novel Pyrazoline Derivative

1 Results 2-pyrazolines and carbaozole derivatives are well known fluorescent compounds with high quantum yields[1],and have been investigated in many other respects[2,3].In this paper,carbazole radical was introduced to pyrazoline ring on C-5,and a novel derivative,named 1-phenyl-3-biphenyl-5-(N-ethyl carbazole-3-yl)-2-pyrazoline (PBEP) (5) was synthesized: The product PBEP was characterized by IR,1H NMR,and elementary analysis.Yield: 47.2%.M.P 104-106 ℃.1H NMR (CDCl3) δ/10-6: 1.5(3H,—CH3).2.4(2H,—...     

Markov过程在股市分析中的应用

作为基础数学在经济运动规律分析预测方面的应用，将 Ｍ ａｒｋｏｖ 过程理论，应用于股票交易市场，对股价综合指数的涨（跌）幅度，进行状态分类，建立起对市场运行周期、稳态概率、稳定程度、投资利润等的分析预测模型，并利用这一模型对上海证券交易所股价综合的部分历史数据作了相应的分析，得到了较为理想的结果。     

基于GT的过程机械快速设计系统的开发

过程机械的设计直接关系到产品的质量、成本和可靠性。在分析过程机械设计的特点和现状的基础上,运用成组技术构建了一个基于成组技术的过程机械快速设计系统,并且对开发过程中的零件分类方法、GT码的编制、编码检索与相似性判别以及三维设计系统的二次开发等关键技术进行了阐述。快速设计系统的使用可以缩短产品设计周期,使产品快速面市,提高产品的竞争力。     

The genome of the social amoeba Dictyostelium discoideum

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.     

Antitumor effect of β-elemene in non-small-cell lung cancer cells is mediated via induction of cell cycle arrest and apoptotic cell death

-Elemene is a novel anticancer drug, which was extracted from the ginger plant. However, the mechanism of action of -elemene in non-small-cell lung cancer (NSCLC) remains unknown. Here we show that -elemene had differential inhibitory effects on cell growth between NSCLC cell lines and lung fibroblast and bronchial epithelial cell lines. In addition, -elemene was found to arrest NSCLC cells at G2-M phase, the arrest being accompanied by decreases in the levels of cyclin B1 and phospho-Cdc2 (Thr-161) and increases in the levels of p27^kip1 and phospho-Cdc2 (Tyr-15). Moreover, -elemene reduced the expression of Cdc25C, which dephosphorylates/activates Cdc2, but enhanced the expression of the checkpoint kinase, Chk2, which phosphorylates/ inactivates Cdc25C. These findings suggest that the effect of -elemene on G2-M arrest in NSCLC cells is mediated partly by a Chk2-dependent mechanism. We also demonstrate that -elemene triggered apoptosis in NSCLC cells. Our results clearly show that -elemene induced caspase-3, –7 and –9 activities, decreased Bcl-2 expression, caused cytochrome c release and increased the levels of cleaved caspase-9 and poly(ADP-ribose) polymerase in NSCLC cells. These data indicate that the effect of -elemene on lung cancer cell death may be through a mitochondrial release of the cytochrome c-mediated apoptotic pathway.Received 12 January 2005; accepted 5 February 2005     

The nucleotide receptor P2Y13 is a key regulator of hepatic High-Density Lipoprotein (HDL) endocytosis

Cell surface receptors for high-density lipoprotein (HDL) on hepatocytes are major partners in the regulation of cholesterol homeostasis. We recently identified a cell surface ATP synthase as a high-affinity receptor for HDL apolipoprotein A-I (apoA-I) on human hepatocytes. Stimulation of this ectopic ATP synthase by apoA-I triggered a low-affinity-receptor-dependent HDL endocytosis by a mechanism strictly related to the generation of ADP. This suggests that nucleotide G-protein- coupled receptors of the P2Y family are molecular components in this pathway. Only P2Y₁ and P2Y₁₃ are present on the membrane of hepatocytes. Using both a pharmacological approach and small interference RNA, we identified P2Y₁₃ as the main partner in hepatic HDL endocytosis, in cultured cells as well as in situ in perfused mouse livers. We also found a new important action of the antithrombotic agent AR-C69931MX as a strong activator of P2Y₁₃-mediated HDL endocytosis. Received 9 May 2005; received after revision 24 June 2005; accepted 1 September 2005     

Ethanol inhibits insulin expression and actions in the developing brain

Ethanol-induced cerebellar hypoplasia is associated with inhibition of insulin-stimulated survival signaling. The present work explores the mechanisms of impaired insulin signaling in a rat model of fetal alcohol syndrome. Real-time quantitative RT-PCR demonstrated reduced expression of the insulin gene in cerebella of ethanol-exposed pups. Although receptor expression was unaffected, insulin and insulin-like growth factor (IGF-I) receptor tyrosine kinase (RTK) activities were reduced by ethanol exposure, and these abnormalities were associated with increased PTP1b activity. In addition, glucose transporter molecule expression and steady-state levels of ATP were reduced in ethanol-exposed cerebellar tissue. Cultured cerebellar granule neurons from ethanol-exposed pups had reduced expression of genes encoding insulin, IGF-II, and the IGF-I and IGF-II receptors, and impaired insulin- and IGF-I-stimulated glucose uptake and ATP production. The results demonstrate that ethanol inhibits insulin-mediated actions in the developing brain by reducing local insulin production and insulin RTK activation, leading to inhibition of glucose transport and ATP production.Received 30 December 2004; received after revision 1 March 2005; accepted 10 March 2005