华南贵东杂岩体单颗粒锆石激光探针ICPMS U-Pb定年及其成岩意义

系统的单颗粒锆石激光探针ICPMS U-Pb同位素定年表明, 贵东杂岩体是印支期~燕山期多次岩浆侵入形成的复式杂岩体, 其中鲁溪岩体(239 ± 5 Ma)、下庄岩体(235.8 ± 7.6 Ma)是印支期花岗岩; 隘子岩体(160.1 ± 6.1 Ma)、司前岩体(151 ± 11 Ma)是燕山期花岗岩. 下庄岩体中1275~2137 Ma残留锆石的发现, 表明贵东花岗岩杂岩体的物质来源与华南元古宙陆壳基底有关. 详细的单颗粒锆石激光探针ICPMS U-Pb同位素定年为研究该杂岩体的形成演化与构造作用、成矿作用的关系提供了重要的依据.     

基于知识神经网络的运载火箭弹道选择

在火箭发射中,往往有多组来自不同设备的测量弹道,进行可靠的火箭弹道选择是飞行状态监视和安控判断的前提.考虑到火箭飞行过程和测量环境的复杂性,提出了一种基于知识神经网络的运载火箭弹道选择方法.把火箭飞行弹道的先验知识和弹道样本的学习训练相结合,先利用数据的连续性排除跳变弹道,然后计算弹道间的差异,最后采用一个神经网络判断各条弹道的可靠性,并结合测量设备精度进行选优.实验和仿真表明了这种方法的可靠性和有效性.     

Unscheduled CDK1 activity in G1 phase of the cell cycle triggers apoptosis in X-irradiated lymphocytic leukemia cells

Cyclin-dependent kinase 1 (CDK1) is a major component of the cell cycle progression engine. Recently, several investigations provided evidence demonstrating that unscheduled CDK1 activation may also be involved in apoptosis in cancerous cells. In this article, we demonstrate that X-ray irradiation induced G1 arrest in MOLT-4 lymphocytic leukemia cells, the arrest being accompanied by reduction in the activity of CDK2, but increased CDK1 activity and cell apoptosis in the G1 phase. Interestingly, this increase in CDK1 and apoptosis by ionizing radiation was prevented by pretreatment with the CDK1 inhibitor, roscovitine, suggesting that CDK1 kinase activity is required for radiation-induced apoptotic cell death in this model system. Furthermore, cyclin B1 and CDK1 were detected co-localizing and associating in G1 phase MOLT-4 cells, with the cellular lysates from these cells revealing a genotoxic stress-induced increase in CDK1 phosphorylation (Thr-161) and dephosphorylation (Tyr-15), as analyzed by postsorting immunoprecipitation and immunoblotting. Finally, X-irradiation was found to increase Bcl-2 phosphorylation in G1 phase cells. Taken together, these novel findings suggest that CDK1 is activated by unscheduled accumulation of cyclin B1 in G1 phase cells exposed to X-ray, and that CDK1 activation, at the wrong time and in the wrong phase, may directly or indirectly trigger a Bcl-2-dependent signaling pathway leading to apoptotic cell death in MOLT-4 cells. Received 30 March 2006; received after revision 23 June 2006; accepted 24 August 2006 J. Wu and Y. Feng contributed equally to this work.     

Selective antiproliferative effects of thymidine

A substance with antiproliferative bioactivity in an aqueous extract ofCordyline terminalis was purified and identified by mass spectrometry to be the natural nucleoside, thymidine. 10^–5M Thymidine inhibited EL4 cell replication and decreased cell viability after 12–24 h. The effect was highly specific for this nucleoside. Treated cell cultures showed a significant increase in S phase cells and a corresponding decrease in G₁ phase cells. Nitrobenzylthioinosine (which prevented facilitated entry of thymidine) protected cells from the antiproliferative action of thymidine. A human breast cancer cell line (MCF7) was also growth-inhibited by 10^–5M thymidine but a murine lymphoma cell line (K36) was not. Thus, submillimolar thymidine has effects on cell proliferation which are selective both with respect to specificity for the compound and for different tumour cell lines.     

多点源空气污染高斯扩散模式并行方法研究

为提高基于高斯模式的空气污染扩散计算的效率,研究从污染源、研究区域空间分层与栅格划分等3个因子入手,设计单因子、双因子和三因子作用下的多种并行算法,同时采用PC机群对算法进行实现. 针对珠三角区域空气污染并行计算试验结果表明,并行算法能将计算时间减少90%,大大提高了模型计算效率,很大程度上满足了基于高斯模式的空气污染实时计算要求.      

不同包衣剂对棉花种子萌发及幼苗生长的影响

用不同的棉花型包衣剂和玉米型包衣剂处理棉花种子,选择2种温度条件进对其进行培养,测定发芽率、幼苗长度和幼苗重量,研究不同包衣剂对棉花种子萌发及幼苗的影响.试验结果表明,经过包衣剂处理的棉花种子在发芽率和幼苗的生长状况上均优于未处理的种子,对棉花型包衣剂成分进行调整,能有效影响棉花早期的生长.     

Novel Elastomeric Fabrics for the Treatment of Hypertrophic Burn Scars Using Polyhexamethylene Biguanide Antimicrobial Agents

In burn treatments,microorganisms on pressure garments during pressure therapy can prevent rehabilitation by causing functional,hygienic,and aesthetic difficulties. As bacterium is one of the most trouble-causing organisms,they can threaten patients causing infection during the long period of use of these garments.Novel burn pressure garments having durable antimicrobial property were developed using polyhexamethylene biguanide( PHMB)antimicrobial agent procedure on highly elastic nylon 66 /spandex fabrics in powernet,flat warp and weft knitted structures using paddry-cure method. Commercial wireless pressure sensors were used to control pressures at an acceptable medical range. Antimicrobial activity,wash durability,Fourier transform infrared spectroscopy(FTIR) and Scanning electron microscopy(SEM) analyses were conducted for the treated samples. Antimicrobial test results following AATCC 100 Test Method showed 99% reduction of bacteria for the fabric samples treated with PHMB. A small but significant decrease in antimicrobial activity was observed even after50 launderings. These treatments also yield good results to prevent odor,decrease infection by preventing and /or blocking microbial growth according to the antimicrobial mechanism and support reducing of scarring by providing a hygienic environment around the scar.     

A family study of endophenotypes for psychosis within an early intervention programme in Hong Kong: Rationale and preliminary findings

The study of endophenotypes may be a viable strategy to tackle the genetic complexity and phenotypic heterogeneity of psychosis, but this research direction is relatively under-developed in China as compared to Western countries. We have recently initiated one of the first family studies of endophenotypes for psychosis in China. Patients entering an established early psychosis intervention service are recruited into this research project for phenotyping, endophenotyping and genotyping. At the endophenotypic...     

c-Myc regulates mammalian body size by controlling cell number but not cell size.

Overexpression of the proto-oncogene c-myc has been implicated in the genesis of diverse human tumours. c-Myc seems to regulate diverse biological processes, but its role in tumorigenesis and normal physiology remains enigmatic. Here we report the generation of an allelic series of mice in which c-myc expression is incrementally reduced to zero. Fibroblasts from these mice show reduced proliferation and after complete loss of c-Myc function they exit the cell cycle. We show that Myc activity is not needed for cellular growth but does determine the percentage of activated T cells that re-enter the cell cycle. In vivo, reduction of c-Myc levels results in reduced body mass owing to multiorgan hypoplasia, in contrast to Drosophila c-myc mutants, which are smaller as a result of hypotrophy. We find that c-myc substitutes for c-myc in fibroblasts, indicating they have similar biological activities. This suggests there may be fundamental differences in the mechanisms by which mammals and insects control body size. We propose that in mammals c-Myc controls the decision to divide or not to divide and thereby functions as a crucial mediator of signals that determine organ and body size.