Genome-wide distribution of histone H3 acetylation in all- trans retinoic acid induced neuronal differentiation of SH-SY5Y cells

With chromatin immunoprecipitation (ChIP) and promoter DNA microarray analyses (ChIP-on-chip), we analyzed the variations of acetylation on histone H3 in all-trans retinoic acid (RA) induced neuronal cell differentiation. Neuroblastoma SH-SY5Y cells were treated with RA for 24 h and the acetylation on histone H3 in the promoter region of the genes was detected. Results showed that, after treatment, the level of acetylation on histone H3 elevated in 597 genes in the genome, and reduced in the other 647 genes compared with those of the control. In summary, we have successfully adopted a high throughput technique to detect and analyze variations of acetylation of histone H3 in human genome at the early phage of RA induced neuronal differentiation of the SH-SY5Y cells. Supported by National Natural Science Foundation of China (Grant Nos. 90408007 and 30721063) and National Key Basic Research and Development Program of China (Grant No. 2004CB518605)     

On the measurement of slip length for liquid flow over super-hydrophobic surface

To design a surface with large slip or larger drag reduction is a pop issue in the fields of liquid transporting and body swimming. In this context, it is a crucial problem to measure the slip length for these surfaces. Here we propose a novel method by using rheometer for this objective. This method is implemented by designing the distribution of the super-hydrophobic area on the sample. Using this method, a slip length of 40 μm for 70 wt% glycerin flow over a super-hydrophobic surface with stripe structure （the period, width and height of ridges are 150 μm, 40 μm and 65 μm, respectively） is measured. The result shows that the slip length measured using this method is in good agreement with former results measured by other methods. This method is fit for measuring the slip length of super-hydrophobic surface whose structure ranges from microto nano-scale.     

Record of environmental change by α-cellulose δ13C of sphagnum peat at Shennongjia, 4000―1000 aBP

The Dajiuhu Basin at Shennongjia, located within typical East Asian Monsoon region, preserves a sub-alpine sphagnum peat deposition in its central area. The topmost 120 cm of the peat covers the last 4000 years according to AMS ^14C dating of pollen concentration. Carbon isotope of a-cellulose, extracted from sphagnum peat, provides a quantitative reconstruction of atmospheric relative humidity, based on transfer functions of C3 plants carbon isotopic fractionation equation and the bryophyte photosynthesis CO2 absorption rate equation. δ^13C, TOC and C/N variations reveal that the Dajiuhu area has experienced a long-term tendency to dry during 4000-1000 aBP, with a major transition happening around 3000 aBP. Four relative dry events are identified at 3400-3200, 3000-2600, 2200-2000 and 1600-1400 aBP, respectively, corresponding to those climate events documented in many global records. Three periodicities, 664 a, 302 a and 277 a enclosed in the atmospheric humidity of Dajiuhu are correlated to the cycles of solar activities. The weakening of East Asia summer monsoon during this period registered in the Dajiuhu peat is consistent with the synchronous weakening of Indian Monsoon. This trend may be attributed to gradual decrease of Northern Hemispheric summer solar insolation and the consequently southward migration of Intertropical Convergent Zone （ITCZ）.     

Design and realization of threshold secret sharing scheme with random weights

A new threshold secret sharing scheme is constructed by introducing the concept of share vector, in which the number of shareholders can be adjusted by randomly changing the weights of them. This kind of scheme overcomes the limitation of the static weighted secret sharing schemes that cannot change the weights in the process of carrying out and the deficiency of low efficiency of the ordinary dynamic weighted sharing schemes for its resending process. Thus, this scheme is more suitable to the case that the number of shareholders needs to be changed randomly during the scheme is carrying out.     

用EGSnrc程序包对单能电子实验过程影响因素的研究

本文运用蒙特卡罗程序EGSinpRZ和EGSnrcMP模拟了不同能量的单能电子入射过程中与AL吸收物质的作用,得到了该过程产生的并且进入了灵敏区的轫致辐射光子和散射电子平均能量以及他们在相应情况下的百分比,结合两种计算方法(全峰面积法TPA和半峰面积法SPA)讨论了轫致辐射和散射对测量结果的影响;研究了实验所用放射源与其包装材料产生的轫致辐射光子对测量的影响;同时用EGSnrcMP程序模拟了吸收曲线,并与实验吸收曲线相比较,讨论了环境本底对计数的影响.     

预应力混凝土多T梁桥的极限承载力

针对预应力混凝土多T梁桥,基于实体退化壳单元,研究了多T梁桥极限承载力的计算方法.利用Owen屈服准则、Hinton压碎准则和双折线模型考虑了混凝土和钢筋的材料非线性效应,有效地模拟了预应力混凝土多T梁桥的开裂、屈服和失效全过程.引入实体退化壳单元理论,描述了预应力混凝土多T梁桥,其中普通钢筋和预应力钢筋采用分层单元模拟,并根据所采用的非线性理论编制了相应的非线性计算程序.结合预应力混凝土多T梁桥实桥破坏性试验资料比较可知,理论计算结果与试验数据吻合良好,研究表明用实体退化壳单元模拟预应力混凝土多T梁桥是可行的,相应的极限承载力计算方法和计算程序是正确的.     

火灾下混凝土空心板的温度场

为了研究火灾下混凝土空心板温度场分布,基于流固耦合传热理论,采用流体动力学软件FLUENT,建立空心板混凝土和封闭空洞内空气耦合模型并进行计算.通过典型算例,对相同外形尺寸下混凝土实心板和空心板温度场的分布进行了比较;对空洞内空气的自然对流和内壁面间辐射换热进行了分析;同时考虑了内壁面取绝热边界条件的可行性.分析结果表明:延火1 h内,空心板与实心板温度场分布相近,随后差异明显;空洞通过内部空气自然对流与壁面间辐射换热对空心板温度场分布产生影响,并随延火时间增长而愈加明显;内壁面取绝热边界条件会高估空心板空洞附近的温度.空气一混凝土耦合传热系统模型可以解决常规单独计算混凝土空心板传热无法确定其空洞内边界条件的问题.     

贵州省遵义地区表层土壤中多环芳烃分布特征

调查研究了151个取至贵州省遵义地区12个市(县)的土壤中的多环芳烃(PAHs)的背景含量及与各市(县)总污染物排放量的关系.遵义地区各县(市)表层土壤中PAHs含量介于0.8～251 μg/kg,从单个化合物的检出情况来看,主要以二环、三环和四环PAHs检出率较高,其中四环以苯并(a)蒽,苯并(b)蒽及屈为主,检出率分别为41.7%,38.1%和34.4%.三环PAHs中以菲与蒽的检出率较高分别为37.1%和30.5%,具有两个环化合物以芴与苊为主,检出率分别为41.1%和27.8%.遵义地区各县(市)表层土壤PAHs检出特征虽大体相同,但其含量却有较大差异,其中遵义县∑PAHs的含量最最高,平均为74.5μg/kg,最低为绥阳县为13.74μg/kg,各采样点平均16种PAHs含量从低到高依次为:绥阳县、湄潭县、桐梓县、仁怀、务川县、余庆县、凤冈县、正安县、习水县、赤水县、道真县和遵义县.各县∑PAHs含量的差异与该县市空气与废水排放总量呈显著正相关,相关系数r为0.971,表明贵州土壤中的PAHs主要来自于能源物质的燃烧和PAHs全球范围内的自然迁移,但土壤处于较低污染状态.     

天堂鸟翼凤蝶平板模型绕流特性实验研究

蝴蝶的扑翼飞行因其相对翼展较大、扑翼频率低等特点引起广泛关注, 尤其是具有越 洋迁徙特性的蝴蝶更是备受瞩目. 本文以天堂鸟翼凤蝶这种长距离迁徙蝴蝶作为研究对象, 设计了简化模型, 应用氢气泡流动显示的方法研究该蝴蝶翼面绕流结构, 包括前缘涡、翼尖涡、翼身相交处的分离泡和马蹄形尾迹等流动结构, 并进一步讨论了各绕流结构随迎角的变化规律. 特别是在本实验条件下观测到的倒八字形前缘涡结构, 是一种新的流动现象.     

一种高速14/16双模相位开关预分频器

分析了无线通信领域频率综合器的关键模块高速预分频器(prescaler)的设计方法,并根据电路要求设计了一个适用于WLAN 802.11a/b/g标准的14/16双模相位开关预分频器.该电路采用SMIC 0.18μm CMOS工艺实现,总芯片面积470μm×420μm.测试结果表明在1.8 V电源电压下它的正常分频范围高达1.46~6 GHz.当输入频率为6 GHz时,电路在14和16两种分频模式下相位噪声分别为-117.70 dBc/Hz@10 kHz和-118.36 dBc/Hz@10 kHz.