Trisomy represses Apc(Min)-mediated tumours in mouse models of Down's syndrome

Epidemiological studies spanning more than 50 yr reach conflicting conclusions as to whether there is a lower incidence of solid tumours in people with trisomy 21 (Down's syndrome). We used mouse models of Down's syndrome and of cancer in a biological approach to investigate the relationship between trisomy and the incidence of intestinal tumours. Apc(Min)-mediated tumour number was determined in aneuploid mouse models Ts65Dn, Ts1Rhr and Ms1Rhr. Trisomy for orthologues of about half of the genes on chromosome 21 (Hsa21) in Ts65Dn mice or just 33 of these genes in Ts1Rhr mice resulted in a significant reduction in the number of intestinal tumours. In Ms1Rhr, segmental monosomy for the same 33 genes that are triplicated in Ts1Rhr resulted in an increased number of tumours. Further studies demonstrated that the Ets2 gene contributed most of the dosage-sensitive effect on intestinal tumour number. The action of Ets2 as a repressor when it is overexpressed differs from tumour suppression, which requires normal gene function to prevent cellular transformation. Upregulation of Ets2 and, potentially, other genes involved in this kind of protective effect may provide a prophylactic effect in all individuals, regardless of ploidy.     

后方法教学法与英语“四位一体”教学法

后方法教学法是20世纪中后期国外出现的一种全新的外语教学思想,它有别于传统意义上的教学法,是一种开放式的动态教学思想。英语"四位一体"教学法是以知识为基础、以素养为最高目标的英语教学法,是符合我国外语教学国情、教情和学情的本土化的教学方法。     

海洋热带假丝酵母菌株中角鲨烯的分析与鉴定

从红树林白骨壤(Avicennia reacemosa)生长的高潮带土壤中分离得到1株热带假丝酵母(Candidatropicalis),用YPD培养基培养48h,离心收集菌体细胞,用正己烷萃取菌体中的脂溶性成分并用傅里叶红外光谱仪和气相色谱-质谱仪对其进行检测分析.结果表明菌株脂溶性成分傅里叶红外光谱与数据库中角鲨烯...     

纺纱锭子组合系统动特性研究

对纺纱锭子组合系统的动特性进行研究,采用传递矩阵法及导纳法编制了计算程序,分别对锭子在空锭、带筒管但筒管上无纱线、带筒管且带筒管上有满卷纱线三种状态下的第一阶、二阶临界转速和振型进行了分析计算.     

陕西省能源消费碳排放分析及预测

陕西省是西部大开发战略实施的重点省份,近年来国民经济呈现快速增长势头,"十一五"以及"十二五"节能减排任务艰巨.本文采用IPCC2006提出的能源碳排放计算方法,根据近年来陕西省能源消耗、GDP增长以及产业变化的相关数据,分析陕西省碳排放的现状,探讨了能源结构和产业结构变动对碳排放量的影响,通过卡亚公式对2009～2020年能源碳排放量趋势进行了预测.研究表明,陕西省GDP的快速增长导致能源碳排放总量的上升,以煤类能源为主导的能源结构是碳排放强度较高的主要因素,预测显示碳排放总量将在人均GDP达到3.5万元附近出现拐点.针对陕西省能源碳排放的趋势,提出了持续优化能源结构,降低煤类能源比重,促进产业结构升级,加快第三产业发展,发展新能源等多种应对策略.     

“十二五”时期太原产业发展和产业选择刍议

运用SWOT分析法对太原市的产业发展所面临的内部优势和劣势、外部机遇和威胁进行了分析,并提出了加快发展产业战略选择。     

Growth characteristics of directionally solidified Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/YAG/ZrO<Subscript>2</Subscript> ternary hypereutectic <Emphasis Type="Italic">in situ</Emphasis> composites under ultra-high temperature gradient

Oxide eutectic ceramic in situ composites have attracted significant interest in the application of high-temperature structural materials because of their excellent high-temperature strength, oxidation and creep resistance, as well as outstanding microstructural stability. The directionally solidified ternary Al₂O₃/YAG/ZrO₂ hypereutectic in situ composite was successfully prepared by a laser zone remelting method, aiming to investigate the growth characteristic under ultra-high temperature gradient. The microstructures and phase composition of the as-solidified hypereutectic were characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that the composite presents a typical hypereutectic lamellar microstructure consisting of fine Al₂O₃ and YAG phases, and the enriched ZrO₂ phases with smaller sizes are randomly distributed at the Al₂O₃/YAG interface and in Al₂O₃ phases. Laser power and scanning rate strongly affect the sample quality and microstructure characteristic. Additionally, coarse colony microstructures were also observed, and their formation and the effect of temperature gradient on the microstructure were discussed.     

一种有向传感器网络改进粒子群覆盖增强算法

优化传感器网络覆盖对于合理分配网络的空间资源、更好地完成信息感知和采集任务、提高网络的生存能力都具有重要的意义.在分析传感器节点有向感知模型的基础上,提出了一种有向传感器网络改进粒子群覆盖增强算法.该算法针对随机部署有向传感器网络,以网络区域覆盖率为优化目标,采用改进的多步式位置可选择更新粒子群优化算法,通过调整传感器...     

低氮胁迫对粮饲兼用型玉米幼苗生长的影响

选用通辽地区主栽的粮饲兼用型玉米品种郑单958和金山10为试验材料进行无土栽培,研究低氮胁迫对玉米幼苗生物学特性的影响,结果表明:低氮胁迫下,两品种根数、根体积、干重、株高等指标较小,且增长速度远低于高氮处理;随着生育进行,两品种根冠比均随着氮素水平的提高而下降,郑单958玉米幼苗根冠比在0 mmol/L与2 mmol/L、8 mmol/L之间存在显著差异;金山10号根冠比在0.4 mmol/L与8 mmol/L之间存在显著差异,0 mmol/L与8 mmol/L之间存在极显著差异.