吉林省中北部农田土壤有机氯农药的残留特征

通过对吉林省长春、 德惠、 扶余、 公主岭和永吉区域内典型农田土壤进行网格法布点采样, 分析土壤中有机氯农药的残留及在农田土壤中的分布状况, 并探讨有机氯农药残留物的组成及其分布和来源. 结果表明: 研究区域内六六六类（HCHs）和滴滴涕类（DDTs）农药残留检出率较高, 总有机氯农药（OCPs）的残留范围为1.45~83.88 ng/g, HCHs的总质量比为1.17～27.83 ng/g, DDTs农药的总质量比为1.45～81.75 ng/g; OCPs总体分布为长春>公主岭>永吉>德惠>扶余. OCPs的总量与总有机碳（TOC）呈显著的正相关关系; 长春、 德惠、 公主岭和永吉土壤中α-HCH/γ-HCH的平均值为0.37, 即大部分采样点可能有大量林丹（γ-HCH）输入; 除公主岭外, 各采样点的P,P′ DDT/（P,P′-DDD+P,P′-DDE）平均值都小于1, 即土壤中的DDTs类物质主要来自历史残留物, 公主岭部分点位可能受到工业DDTs的影响; 长春区域污染明显高于其他区域; 六六六类以γ-HCH为主要污染物, 滴滴涕类以P,P′-DDT为主要污染物.     

S8联合小分子化合物Z18的抗肿瘤效应研究

 为了探讨S8联合小分子化合物Z18的抗肿瘤效应,本研究通过联合用药方式处理HeLa细胞后,采用台盼蓝染色和流式细胞仪对细胞死亡率和死亡方式进行检测。电镜实验证实Z18诱导细胞自噬,并利用Western Blotting检测联合用药后LC3-II的变化和使用转染了GFP-LC3或mRFP-EGFP-LC3的HeLa细胞检测联合用药对细胞自噬和自噬流的影响。最后通过ATG5 siRNA和CQ抑制自噬和自噬流,观察联合用药对细胞的自噬和死亡的变化,进一步研究S8对Z18的抗肿瘤作用的影响。结果显示,S8联合用药后,细胞死亡率显著升高(P<0.05),死亡方式主要以坏死为主。S8明显地促进了Z18对HeLa细胞的毒性,其促进作用具有剂量依赖性。但联合用药并未降低Z18引起的自噬空泡集聚,LC3-II蛋白表达也未发生变化。抑制自噬后,并未影响联合用药促进细胞死亡的结果。因此,Z18在联合使用S8的情况下,细胞自噬水平没有发生明显变化,而细胞死亡比例明显升高,自噬并不影响联合用药诱导的细胞死亡。S8可能通过调节细胞坏死的其他途径进而促进细胞对Z18的敏感性,并进一步使细胞发生坏死。     

基于SIP的多媒体业务穿越网络地址转换/防火墙研究与设计

研究了IETF关于NGN网络中会话业务穿透NAT技术的各种草案,结合网络的实际情况,对目前SIP业务开展可以使用的几种NAT穿越技术和方案进行了比较,提出了一种结合SIP协议扩展和MIDCOM协议构架的方法,解决了由于传统NAT/FW设备不支持SIP协议,而造成的私网内SIP终端同Internet上的SIP终端之间业务无法互通问题.通过用SIP信令建立的语音会话仿真表明,该方法具有可行性和有效性.     

全随机跳频脉冲信号设计与处理

对于高频雷达系统,通常很难找到一段连续可用的“寂静”频带,为了获得大的距离分辨带宽,可以离散地利用多段可用频带。然而,信号频谱的离散性会造成较高的距离旁瓣。所研究的全随机跳频脉冲信号,通过控制不同频率脉冲出现的概率可以获得较低的距离旁瓣。研究了全随机跳频脉冲信号自相关函数的统计特性,并给出了可用频带连续及非连续两种情况下的信号设计方法。     

Pathway complexity in supramolecular polymerization

Self-assembly provides an attractive route to functional organic materials, with properties and hence performance depending sensitively on the organization of the molecular building blocks. Molecular organization is a direct consequence of the pathways involved in the supramolecular assembly process, which is more amenable to detailed study when using one-dimensional systems. In the case of protein fibrils, formation and growth have been attributed to complex aggregation pathways that go beyond traditional concepts of homogeneous and secondary nucleation events. The self-assembly of synthetic supramolecular polymers has also been studied and even modulated, but our quantitative understanding of the processes involved remains limited. Here we report time-resolved observations of the formation of supramolecular polymers from π-conjugated oligomers. Our kinetic experiments show the presence of a kinetically favoured metastable assembly that forms quickly but then transforms into the thermodynamically favoured form. Quantitative insight into the kinetic experiments was obtained from kinetic model calculations, which revealed two parallel and competing pathways leading to assemblies with opposite helicity. These insights prompt us to use a chiral tartaric acid as an auxiliary to change the thermodynamic preference of the assembly process. We find that we can force aggregation completely down the kinetically favoured pathway so that, on removal of the auxiliary, we obtain only metastable assemblies.     

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected 'mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior.     

大熊猫肠道抗生素耐药菌质粒的研究

对分离自四川省卧龙保护区大熊猫肠道的6株大肠杆菌的抗生素抗性与质粒的关系进行了研究,结果显示：6株大肠杆菌中都存在不同大小的质粒DNA;采用SDS高温法处理每株大肠杆菌后,有2类质粒在琼脂糖凝胶上的条带数减少,菌株的抗生素抗性水平也有所降低,有2株菌的某些抗生素抗性完全消失;将分离自6株大肠杆菌的质粒转化大肠杆菌JM109,获得1个氨苄青霉素抗性转化子.这些结果表明,大熊猫肠道中的大肠杆菌的抗生素抗性与它们含有的质粒有关.     

In vivo enhancer analysis of human conserved non-coding sequences

Identifying the sequences that direct the spatial and temporal expression of genes and defining their function in vivo remains a significant challenge in the annotation of vertebrate genomes. One major obstacle is the lack of experimentally validated training sets. In this study, we made use of extreme evolutionary sequence conservation as a filter to identify putative gene regulatory elements, and characterized the in vivo enhancer activity of a large group of non-coding elements in the human genome that are conserved in human-pufferfish, Takifugu (Fugu) rubripes, or ultraconserved in human-mouse-rat. We tested 167 of these extremely conserved sequences in a transgenic mouse enhancer assay. Here we report that 45% of these sequences functioned reproducibly as tissue-specific enhancers of gene expression at embryonic day 11.5. While directing expression in a broad range of anatomical structures in the embryo, the majority of the 75 enhancers directed expression to various regions of the developing nervous system. We identified sequence signatures enriched in a subset of these elements that targeted forebrain expression, and used these features to rank all approximately 3,100 non-coding elements in the human genome that are conserved between human and Fugu. The testing of the top predictions in transgenic mice resulted in a threefold enrichment for sequences with forebrain enhancer activity. These data dramatically expand the catalogue of human gene enhancers that have been characterized in vivo, and illustrate the utility of such training sets for a variety of biological applications, including decoding the regulatory vocabulary of the human genome.     

Supercurrent reversal in quantum dots

When two superconductors are electrically connected by a weak link--such as a tunnel barrier--a zero-resistance supercurrent can flow. This supercurrent is carried by Cooper pairs of electrons with a combined charge of twice the elementary charge, e. The 2e charge quantum is clearly visible in the height of voltage steps in Josephson junctions under microwave irradiation, and in the magnetic flux periodicity of h/2e (where h is Planck's constant) in superconducting quantum interference devices. Here we study supercurrents through a quantum dot created in a semiconductor nanowire by local electrostatic gating. Owing to strong Coulomb interaction, electrons only tunnel one-by-one through the discrete energy levels of the quantum dot. This nevertheless can yield a supercurrent when subsequent tunnel events are coherent. These quantum coherent tunnelling processes can result in either a positive or a negative supercurrent, that is, in a normal or a pi-junction, respectively. We demonstrate that the supercurrent reverses sign by adding a single electron spin to the quantum dot. When excited states of the quantum dot are involved in transport, the supercurrent sign also depends on the character of the orbital wavefunctions.