碳离子辐射引起Hela细胞线粒体DNA 4977 bp的缺失

背景:线粒体DNA4977bp缺失的累积对衰老的多细胞动物来说是一个显著的特征,同时也与各种肿瘤细胞的转移和凋亡有关。目前的研究已证明辐射可特异性地诱导此缺失的产生,有望将其作为新的DNA水平的辐射损伤生物剂量标记。目的:用聚合酶链反应方法检测碳离子辐射引起的Hela细胞线粒体DNA4977bp突变缺失,并观察碳离子辐射剂量及辐射时间与线粒体DNA4977bp缺失的相关性。设计、时间及地点:细胞DNA水平的对照实验,于2008-10/11在甘肃省兰州市近代物理研究所完成。材料:人宫颈癌细胞Hela细胞株。方法:Hela细胞经2～8Gy的碳离子辐射后,于2～24h各个时间点分别提取包含线粒体DNA的全基因组DNA,并用聚合酶链反应法扩增线粒体DNA4977bp缺失的特异片段,通过限制反应模板浓度和聚合酶链反应循环数的方法进行定性分析。主要观察指标:碳离子辐射剂量及辐射时间对线粒体DNA4977bp缺失的影响。结果:经2Gy辐照处理的Hela细胞在2,4,8,24h4个时间点的检测中均无聚合酶链反应阳性产物,8Gy辐照处理的Hela细胞在12,16,24h3个时间点可检测到线粒体DNA4977bp缺失,且随时间延长而累积。辐照后12hHela细胞在8Gy辐照处理后可检测到线粒体DNA4977bp缺失,辐照后16和24hHela细胞在6,8Gy辐照处理后可检测到线粒体DNA4977bp缺失。结论:碳离子辐射引起的Hela细胞线粒体DNA4977bp缺失存在剂量相关性,且其累计程度可能与辐射时间有关。

Micro Insert: A Prototype Full-Ring PET Device for Improving the Image Resolution of a Small-Animal PET Scanner

A full-ring PET insert device should be able to enhance the image resolution of existing small-animal PET scanners. Methods: The device consists of 18 high-resolution PET detectors in a cylindric enclosure. Each detector contains a cerium-doped lutetium oxyorthosilicate array (12 x 12 crystals, 0.72 x 1.51 x 3.75 mm each) coupled to a position-sensitive photomultiplier tube via an optical fiber bundle made of 8 x 16 square multiclad fibers. Signals from the insert detectors are connected to the scanner through the electronics of the disabled first ring of detectors, which permits coincidence detection between the 2 systems. Energy resolution of a detector was measured using a Ge-68 point source, and a calibrated 68Ge point source stepped across the axial field of view (FOV) provided the sensitivity profile of the system. A Na-22 point source imaged at different offsets from the center characterized the in-plane resolution of the insert system. Imaging was then performed with a Derenzo phantom filled with 19.5 MBq of F-18-fluoride and imaged for 2 h; a 24.3-g mouse injected with 129.5 MBq of F-18-fluoride and imaged in 5 bed positions at 3.5 h after injection; and a 22.8-g mouse injected with 14.3 MBq of F-18-FDG and imaged for 2 h with electrocardiogram gating. Results: The energy resolution of a typical detector module at 511 keV is 19.0% +/- 3.1 %. The peak sensitivity of the system is approximately 2.67%. The image resolution of the system ranges from 1.0- to 1.8-mm full width at half maximum near the center of the FOV, depending on the type of coincidence events used for image reconstruction. Derenzo phantom and mouse bone images showed significant improvement in transaxial image resolution using the insert device. Mouse heart images demonstrated the gated imaging capability of the device. Conclusion: We have built a prototype full-ring insert device for a small-animal PET scanner to provide higher-resolution PET images within a reduced imaging FOV. Development of additional correction techniques are needed to achieve quantitative imaging with such an insert.

长白山典型林区森林资源利用适宜性分析

天然林保护不是简单的禁伐 .东北林区作为天然林保护的限伐林区 ,目前仍有一定数量的成过熟林采伐任务 ,如何科学合理地选择伐区非常重要 .鉴于传统森林资源采伐利用操作中存在顾此失彼的问题 ,现代科学的森林资源经营理论认为 ,森林资源利用要坚持可持续利用原则 ,并且要更多考虑森林资源的生态效益 .遥感 (RS)数据及地理信息系统 (GIS)技术 ,通过提供空间选择技术支撑 ,可以准确定位符合采伐标准的森林资源地理位置 ,并确定其面积、森林类型等信息 ,从而促进森林资源的科学合理利用 .本文综合考虑各方面要素 ,以长白山典型林区露水河林业局为例 ,以最大程度发挥森林生态系统的生态功能为原则 ,进行了森林资源利用状况评价 ,对研究区森林资源未来利用的空间选择以及采伐利用方式进行了探讨 ,以期为将来制订科学的森林经营策略提供依据 .

大气CO_2和O_3浓度升高对银杏构件生长的影响

采用开顶箱模拟试验,探讨了大气CO2和O3浓度升高对银杏构件生长的影响。结果表明:高浓度O3抑制银杏主枝和侧枝生长(P<0.01);高浓度CO2对银杏粗生长影响不显著(P>0.05),但在高浓度O3和CO2、O3复合气体条件,银杏粗生长受到严重抑制(P<0.01);高浓度CO2可促进银杏叶片面积和干物质的增加,并能提高叶片含水量和抗干旱能力,但在高浓度CO2、O3复合气体条件下,叶片面积增加不显著(P>0.05),而干物质增加极显著(P<0.01);O3对银杏叶片构件生长有明显抑制作用,叶面积大小和干物质量明显低于对照株(P<0.05)。

第94届美国生态学会年会在新墨西哥州阿尔伯克基召开

<正>美国生态学会(ESA)第94届年会于2009年8月2日到7日在新墨西哥州阿尔伯克基(Albuquerque)的国际会议中心举行,3000多人参加此次会议。会议主题是"Ecological Knowledge and a Global Sustainable Society"。8月2日下午5时,美

近300年来中国森林的变迁

以清代以来史料为依据,在现代清查统计资料和前人研究成果的基础上,通过对森林变迁大体趋势及主要过程的客观把握,重新校订了1949年和1700年前人的估算数据,回溯估算了1750～1900年中国各省区每50年森林面积与森林覆被率值,并与现代森林清查资料衔接,分析1700～1998年近300年来中国森林变迁的时空特征。结果表明:近300年来中国现境内共减少森林面积约0.95×108ha,森林覆被率减少9.2个百分点,变化曲线呈先抑后仰;以1960s为界,此前呈加速递减态势,260年间减少森林面积达1.66×10

湖北省近500年区域干湿序列重建及其比较分析

在历史旱涝记载资料可靠性检验的基础上,重建了湖北省3个区域近500年来的干湿气候变化序列,并比较分析了各区域干湿气候变化的趋势特征、准周期性及跃变现象。结果表明:在3个区域中,鄂东区1570~1770、1890~1950年两个时段偏湿,1470~1520、1790~1830年则偏干;鄂北区偏湿时期主要在1470~1530、1710~1750、1850~1910年三个时段,1470~1530、1770~1830年则偏干;鄂西南区有1550~1610、1650~1710、1830~1890、1930~1990

Polyimides derived from 3,3 '-bis(N-aminophthalimide)

A novel diamine, 3,3'-bis(N-aminophthalimide) (BAPI), was prepared from 3,3'-bis(N-phenylphthalimide). Its structure was determined via IR, H-1 NMR, N-15 NMR, elemental analysis, and single-crystal X-ray diffraction analysis. A series of homo- and copolyimides were synthesized by a conventional one-step method in p-chlorophenol. The characteristic IR absorption bands of hydrazine-based imide groups were near 1780, 1750, 1350, 1100, and 730 cm(-1). The polymers showed good solubility in polar aprotic solvents and phenols at room temperature. The temperatures of 5% weight loss (T-5%) of the polyimides ranged from 495 to 530 degrees C in air. DMTA analyses indicated that the glass-transition temperatures (Tgs) of the polyimides were in the range 371-432 degrees C. These polymers had cutoff wavelengths between 350 and 400 nm. The polyimide films of 6FDA/BAPI and 4,4'-HQPDA/BAPI were colorless; other films were pale yellow or yellow.

Chlorohydrin water swellable rubber compatibilized by an amphiphilic craft copolymer. I. Synthesis and characterization of compatibilizer PVA-g-PBA

The graft copolymerization of butyl acrylate onto poly(vinyl alcohol) with eerie ammonium nitrate as redox initiator in a aqueous medium has been investigated. The formation of graft copolymer was confirmed by means of IR, scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD). The percentage of mononer conversion and percentage of grafting varied with concentrations of initiator, nitric acid, monomer, macromolecular backbone (X-n = 1750, M = 80 000), reaction temperature and reaction time. Some inorganic salts and organic solvents have a great influence upon grafting. The reaction mechanism has been explored, and rate equations for the reaction are established. (C) 2000 John Wiley & Sons, Inc.

Cure processing modeling and cure cycle simulation of epoxy-terminated poly(phenylene ether ketone) .3. Determination of the time of pressure application

The curing temperature, pressure, and curing time have significant influence on finished thermosetting composite products. The time of pressure application is one of the most important processing parameters in the manufacture of a thermosetting composite. The determination of the time of pressure application relies on analysis of the viscosity variation of the polymer, associated with curing temperature and curing time. To determine it, the influence of the time of pressure application on the physical properties of epoxy-terminated poly(phenylene ether ketone) (E-PEK)-based continuous carbon fiber composite was studied. It was found that a stepwise temperature cure cycle is more suitable for manufacture of this composite. There are two viscosity valleys, in the case of the E-PEK system, associated with temperature during a stepwise cure cycle. The analysis on the effects of reinforcement fraction and defect content on the composite sheet quality indicates that the width-adjustable second viscosity valley provides a suitable pressing window. The viscosity, ranging from 400 to 1200 Pa . s at the second viscosity valley, is the optimal viscosity range for applying pressure to ensure appropriate resin flow during curing process, which enables one to get a finished composite with optimal fiber volume fraction and low void content. (C) 1997 John Wiley & Sons, Inc.