X射线像增强器及其应用

综述了X射线像增强器的结构、工作原理和性能，简要介绍了它的可能的应用

纸行天下:清朝夹江地区的手工造纸业与地方政治

四川省夹江县的手工造纸“始于隋唐,降至明清,称为极盛“,曾远销东三省、华北及一些东南亚国家。夹江纸的流动,背后实际上是纸产区内的不同人群在纸张贸易圈中的横向流动和在帝国政治空间结构中的纵向流动。与只关注集镇场景及其等级关系的多数研究不同,本文试图以纸的流动为切入点,通过对“物“(纸)的流动的表象的透视,来讨论隐藏于“物“(纸)的资源争夺背后的国家权力的地方化意义,从而对区域社会变迁之多重因素交互作用的过程,进行地域化的理解和做出历史性的解释

Diet composition of Difflugia tuberspinifera( testate amoeba) based on a clone library technique

瘤棘砂壳虫是东亚特有的原生动物,广泛分布于长江与珠江中下游以及福建地区的湖泊和水库,作为水生态系统的捕食者,在维持水生态系统的结构与功能方面发挥着重要作用。利用18S rrnA基因PCr扩增和克隆文库测序等分子生物学技术方法,从基因水平研究瘤棘砂壳虫的食物组成。结果表明:所获得的46条序列在97%相似度水平含有11类OTuS(OPErATIOnAl TAXOnOMIC unITS,操作分类单元),其中包括轮虫6个,桡足类5个,说明瘤棘砂壳虫的捕食类群以轮虫和桡足类为主,同时也证明单细胞生物可以直接以多细胞的后生动物为食。此外,通过克隆文库测序技术分析原生动物的食物组成比例,不仅是一种方便、高效、快速,重复性高的方法,同时也为分析原生动物的生态功能提供了一种新的视角。Difflugia is a morphologically diverse genus of the free-living shelled amoeboid protozoa that are important components of freshwater ecosystems and play crucial roles in nutrient cycles and energy flow through food webs.Difflugia tuberspinifera is an endemic species of East Asia and is widely distributed in freshwater lakes and reservoirs in China.Clearly,this species plays a critical role in maintaining the structure and function of freshwater ecosystems.However,little is known about its diet composition and predatory behavior at both species and gene levels.This testate amoeba( D.tuberspinifera) was first found in the Wujiang River,Guizhou Province,China.Subsequently,more detailed studies on its morphology and biometry have been done on natural populations from Yangtze River and Pearl River valleys,and Fujian reservoirs.Recently,Han et al.illustrated that D.tuberspinifera is an active and agile hunting carnivore that can capture swimming prey including micro-particulates,rotifers,and other metazoans.In previous studies,however,the specimen identifications were done by microscopic examination,which requires a broad and deep taxonomic knowledge and is verylaborious,time-consuming,and somewhat variable because of insufficient taxonomic resolution.In order to facilitate the identification of diet composition in D.tuberspinifera,an inexpensive,efficient,rapid and easy-to handle gene clone library has been developed for diet detection and analysis.The plankton samples were collected from the Hubian Reservoir in Xiamen city in September of 2010.Individual cells were isolated using a glass capillary under an inverted microscope and washed 3—5 times with distilled water before DNA extraction and PCR amplification.The 18 S rRNA gene was amplified by the universal eukaryotic primers,and the purified PCR products were ligated into the p GEM-T vector and transformed into Escherichia coli DH5α-competent cells.In total,46 plasmids containing target gene fragments were successfully identified and sequenced.Each sequence was compared with sequences available in the Gen Bank database using BLAST,and the closest relatives were identified for diet or food composition analysis.Finally,11 OTUs( operational taxonomic units) were identified at 97% sequence similarity level,and they belonged to either Rotifera( 52%) or Copepoda( 48%).Our results,combined with existing data,suggested that:1) the diet composition of Difflugia tuberspinifera is composed of both rotifera and copepoda species;2) unicellular protozoa are not only the food of metazoa,but they can also prey on multicellular micro-metazoa;3) molecular methods are universally applicable,and the SSU rRNA( small subunit ribosomal RNA) gene clone library is an efficient,rapid,and repeatable approach to study the diet composition of protozoa.国家自然科学基金项目(31172114;30800097); 福建省杰出青年科学基金项目(2012J06009

Bacterial community and its relation to environmental variables in a subtropical stratified reservoir for drinking water supply in autumn

水库在我国东南沿海地区是重要的饮用水水源地,对地区经济发展和社会稳定起到重要作用。选择亚热带地区典型的热分层水库——福建莆田东圳水库,于2011年秋季稳定分层期,以水体温度的垂直变化特征为依据进行分层采样。应用PCrdggE和克隆测序的方法研究浮游细菌群落的垂直分布特征,利用多元统计分析揭示细菌群落与热分层水体理化指标之间的关系。结果显示:溶解氧、电导率、叶绿素A、总氮、氨氮及硝氮在上下层水体中的分布有显著差异,下层缺氧区细菌的SHAnnOnWIEnEr指数和dggE条带数明显高于上层好氧区,表明东圳水库热分层水体中存在明显的物理、化学及生物分层现象。测序结果表明β-变形菌可能是东圳水库中占优势的细菌类群,统计结果提示溶解氧是显著影响细菌群落组成的环境因子。热分层水体的物理化学分层与水体细菌群落结构密切相关,提示水库生态学研究应对水体热分层给予重视。Fujian reservoirs in southeast China are important water resources for economic and social sustainable development,although few have been studied previously.Dongzhen Reservoir,a typical subtropical stratified reservoir in Fujian,was chosen for investigation of bacterial distribution,composition and diversity in autumn 2011.As the only built large reservoir in Putian City,it plays an important role in irrigation,flood control,hydroelectric power,and water supply.Dongzhen Reservoir shows an obvious phenomenon of water thermal stratification during summer and autumn,thus creates a unique gradient of environmental variables along the water column.We investigated the bacterial community and its relation to environmental variables in this study for a better understanding of vertical distribution of bacterial community and theprimary environmental drivers in a stratified reservoir.Five water samples were collected from five different depths according to the vertical changes of temperature.Both PCR-DGGE and sequencing were used to investigate the bacterial community and diversity.Moreover,physical and chemical parameters were measured according to the national standard methods.Multivariate statistical techniques were used to examine the relationship between bacterial community and environmental variables.Principal component analysis( PCA) clearly showed that water temperature,dissolved oxygen( DO),chlorophyll a( Chl a),total nitrogen( TN),ammonia nitrogen( NH4-N),nitrite / nitrate nitrogen( NOx-N) and electric conductivity of the upper aerobic zone were differed from those of the deeper anoxic zone.Both the number of DGGE bands and the Shannon-Wiener index of the deeper anoxic zone were higher than those of the upper aerobic zone.Further,two groups were distinguished by the cluster analysis of bacterial communities based on the Bray-Curtis similarity.Thus,Dongzhen Reservoir presented an obviously physical,chemical,and biological stratified phenomenon.Seven bands that common to all sampling depths were extracted and sequenced,and among which four were identified as Betaproteobacteria,indicating that Betaproteobacteria were the most dominant taxa in Dongzhen Reservoir in autumn.Bacterial community composition and diversity differed greatly among different sampling depths,and these differences were closely related to the physical and chemical stratification of the water body.Redundancy analysis( RDA) demonstrated DO was the significant environmental variable that shaping the bacterial community and diversity( P < 0.01).Therefore,we should pay more attention to DO and thermal stratification of reservoirs for sustainable reservoir management.国家重大科学研究计划(2012CB956103); 中国科学院知识创新工程方向项目(KZCX2-YW-QN401); 国家自然科学基金面上项目(31172114); 福建省杰出青年科学基金项目(2012J06009

INFLUENCE OF SURFACE ROUGHNESS ORIENTATIONS ON FRICTION COEFFICIENT OF WHEEL/RAIL SPECIMEN IN OIL LUBRICATION

黏着力是列车安全与平稳运行的关键因素之一.最大黏着力与摩擦力有关,摩擦力的减小会导致黏着力的降低.表面粗糙度及其取向是影响摩擦系数的重要因素,然而,有关表面粗糙度取向对于混合润滑状态下摩擦系数的影响的研究结论似乎是矛盾的.用激光离散改性技术将车轮试样表面制备成具有菱形、纵纹、横纹3种典型的形貌,并且与不作激光离散改性处理的车轮试样作对比,用基于确定性模型的统一雷诺方程数值分析法和小比例尺度的轮轨试样摩擦学实验,得到的结论是:在油润滑状态下,激光表面形貌大幅提高摩擦系数,其中菱形对应的摩擦系数最大,纵纹与横纹的摩擦系数相差不大,摩擦系数的大小主要取决于由表面粗糙度取向决定的接触区内粗糙峰接触压力与总压力之比,侧流效应也是影响摩擦系数的重要因素,它主要取决于接触区内表面粗糙度的取向

Research of the TV Drama in the Miao Community in Leishan County,Guizhou Province

本文是关于贵州省雷山县一部由当地苗族自编、自导、自演的苗语电视剧的调研报告。这样一部由苗族自己组织拍摄,采用苗语对白,反映现代苗族社会生活变迁的电视剧,是影视市场上的一件新事物,本文将之称为"苗语电视剧现象"。它反映了民族地区民间力量在适应社会文化发展方面具有的能动性,对于以母语为生活用语的民族聚居地区如何发展文化产业,如何丰富少数民族日常文化生活,以及如何进行文化市场开发与管理等问题,都提出了新的思路。In Leishan county of Guizhou,local Miao people write,direct and play a TV play about their own life.It is a new thing in the movie and TV market.The author calls it the phenomenon of the Miao language TV plays.It is reflection of the Initiative of the popular power adaptating with the social cultural development.And it is a new idea for promoting cultural industry,enriching cultural life,and developing and manages culture market in the ethnic region where the ethnic language is used in daily life

富锂正极材料xLiNbO·（1-x）LiMO（M=Mn,Co;0<x<1）的制备及电化学性能研究

采用高温固相法合成了含铌富锂材料xLiNbO·（1-x）LiMnO（0<x<1）,研究了LiNbO含量对其结构和性能的影响.X射线衍射分析结果表明当x取值在0.25.67之间时可得到纯相固溶体材料,属立方晶系,为Fm-3m空间群.x=0.25和x=0.43的材料具有较好的电化学性能,首次放电容量可达216 mAh·g,但是两者都表现出明显的电压衰退,x=0.43的材料由于含有更多的LiNbO组分,电压衰减的情况得到了抑制.x=0.43材料的非原位XPS和XAFS研究表明,其充电过程分为两个阶段,4.3 V以下的阶段发生的电化学过程是脱出Li同时Mn被氧化到Mn,4.3 V以上的阶段则由O的氧化来提供电荷补偿.通过对x=0.43的样品进行钴掺杂,考察了钴掺杂对0.43LiNbO·0.57LiMnCoO（y=0.25,0.5）结构和性能的影响.研究表明钴掺杂改善了材料电导,降低了电极传荷阻抗,从而提高了材料倍率性能,同时保持了较好的循环稳定性.国家自然科学基金(Nos.21233004,21473148,21428303)；福建省自然科学基金(No.2014J05019)资助~~

Synthesis and Electrochemical Performance of Lithium Rich Cathode Materials xLi(3)NbO(4)center dot(1-x)LiMO2 (M=Mn, Co; 0 < x < 1) for Li-ion Batteries

采用高温固相法合成了含铌富锂材料xLi_3NbO_4·(1-x)LiMnO_2; (0<x<1),研究了Li_3NbO_4含量对其结构和性能的影响.X射线衍射分析结果表明当x取值在0.25~0.67之间时可得到纯相固溶体材料,; 属立方晶系,为空间群.和x=0.43的材料具有较好的电化学性能,首次放电容量可达216; mAh·g~(-1),但是两者都表现出明显的电压衰退,x=0.43的材料由于含有更多的Li_3NbO_4组分,电压衰减的情况得到了抑制.x=0.; 43材料的非原位XPS和XAFS研究表明,其充电过程分为两个阶段,4.3; V以下的阶段发生的电化学过程是脱出Li~+同时Mn~(3+)被氧化到Mn~(4+),4.3; V以上的阶段则由O~(2-)的氧化来提供电荷补偿.通过对x=0.43的样品进行钴掺杂,考察了钴掺杂对0.43Li_3NbO_4·0.57LiMn; _(1-y)Co_yO_2(y=0.25,0.5)结构和性能的影响.研究表明钴掺杂改善了材料电导,降低了电极传荷阻抗,从而提高了材料倍率性能,同; 时保持了较好的循环稳定性.Lithium rich material xLi(3)NbO(4)center dot(1-x) LiMnO2 (0<x<1) was successfully synthesized by solid state method. Stoichiometric amounts of Li2CO3, Mn2O3 and Nb2O5 were mixed by ball milling, and the mixture was calcinated at 900 degrees C for 5 h under Ar atmosphere. X-ray diffraction (XRD) results indicate that the samples with 0.25<x<0.67 can be indexed as a cubic structure with Fm-3m space group. Electrochemical results show that the samples of x=0.25 and 0.43 have better electrochemical performance, both delivering 216 mAh.g(-1) in the initial cycle between 2 V and 4.8 V. Although voltage decay is an intrinsic drawback of lithium excess materials, the sample of x=0.43 decays slower. We speculate that Li3NbO4 helps stabilizing the crystal structure. Ex-situ XPS and XAS studies show that the charging process can be divided into two stages. In the first stage, below 4.3 V, Mn3+ is oxidized to Mn4+, in the second stage, O2- is oxidized. The reversible oxidation of O2- is the origin of the achievement of large reversible capacity. Co3+ doped material 0.43Li(3)NbO(4)center dot 0.57LiMn(1-y)Co(y)O(2) (y=0.25; 0.5) was also synthesized by the same procedure. The structure of the doped material maintains the cubic structure with smaller lattice constant and the variation of lattice constant is in proportion to the amount of Co3+. Galvanostatic charge and discharge tests show that 0.43Li(3)NbO(4)center dot 0.57LiMn(0.75)Co(0.25)O(2) also delivers a large capacity of 215 mAh.g(-1) in the first cycle between 2 V and 4.8 V, but the voltage plateau in the charging process decreased from 4.3 V to 4.1 V, it can be attributed to the weak dissociation energy of Mn-O bond and the overlap of Co3+/4+ 3d and O2- 2p energy band. The electrochemical impedance spectroscopy results show that a moderate amount of Co3+ doped into the material decreases the charge transfer resistance. After doped with Co3+, the rate capability is improved.National Natural Science Foundation of China [21233004, 21473148,; 21428303]; Natural Science Foundation of Fujian Province [2014J05019