eta-production on the proton via electromagnetic and hadronic probes

The reactions pi(-)p -> eta n and gamma p -> eta p are investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region The meson-baryon channels included are pi N, pi Delta, sigma N, and rho N The direct eta-photoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)circle times O(3) symmetry In the models search, the following known nucleon resonances are embodied S-11(1535), S-11(1650), P-11(1440), P-11(1710), P-13(1720), D-13(1520), D-13(1700), D-15(1675), and F-15(1680). Data for the pi(-)p -> eta n reaction from threshold up to a total center-of-mass energy of W approximate to 2 GeV are satisfactorily reproduced For the photoproduction channel: two additional higher mass known resonances, P-13(1900) and F-15(2000), are also considered However, reproducing the data for gamma p -> eta p requires, within our approach, two new nucleon resonances, for which we extract, mass and width

《保护生态学:生物圈和生物存活》简介

<正> 保护生态学从1969年沿用开始,一直作为一个概念和术语,没有发展成为一门有明确研究对象、范畴和方法论的独立学科。直到1993年由George W.Cox编辑,由Wm.C.Brown Publishers出版的《保护生态学:生物圈和生物存活》(Conservation Ecology:Biosphere and Biosurvival)才奠定了保护生态学理论和实践的基础。该书中G.W.Cox将传统生态学与其它相关学科的相关知识结合起来,运用了保护生物学的理论和方法。全书短小精悍,结构明快,共352页分为三大部分。第一部分回顾了生态学的概念,介绍了生态学的发展历史。接着介绍了"绝灭生态学"(The ecology of extinction),作者回顾了过去及近代生物的绝灭率,绝灭物种的生活史足迹等,认为:近代物种绝灭率由于人

持久性有毒物污染底泥修复技术进展

评述了底泥中持久性有毒污染物的危害。在分析持久性有毒污染物污染底泥修复技术现状及面临问题的基础上 ,指出浅水湖泊持久性有毒污染物污染底泥修复的发展方向是植物 -微生物联合修复 ,水库、深水湖泊等持久性有毒物污染底泥修复的发展趋势为物理化学 -生物协同修复 ,修复目标是在环保疏浚、生态清淤的基础上 ,实现持久性有毒污染物污染底泥的无害化和资源化处置

原油萃取汽提水中的酚

渣油催化裂化装置产生的含硫污水经汽提后虽脱除了大部分的硫、氮化合物，但仍含有较高浓度的酚类物质直接排入污水处理厂，其酚负荷约占全厂进水总酚的一半以上，极易造成对生物处理设施的冲击，导致活性污泥恶化，严重影响总排污水综合合格率。因此，在汽提水进入污水厂...

中国东北植被生态学研究中的焦点问题

中国东北植被经过半个多世纪的系统研究 ,但有关植被生态学一些争论性问题尚未统一 .本文仅就作者近年来研究工作涉及到的内容和关注的问题 ,提出一些看法 :1)中国东北植被地带性分布规律可用Kira的温暖指数 (WI)、寒冷指数 (CI)和作者的湿度指数 (HI)进行定量解释 .2 )大兴安岭北部山地 ,在海拔14 0 0m以上存在冻原植被 ,是作者于 196 3年首次发现的我国第三块冻原植被 ,其WI <15℃·月 .3)大小兴安岭植被分界线是我国植被区划中第一级分区界线 ,其位置在爱辉 -果松沟 -嫩江以南附近 ,WI为 4 5℃·月 .4 )大兴安岭植被地带性分异显著 ,南段、中段为典型草原地带和森林草原地带 ,北段为针叶林地带 ,HI值分别为 3 5～ 5 5、5 5～ 7 5、>7 5mm/℃·月 .大兴安岭东麓阔叶林是森林草原带上的森林植被类型 .5 )东北东部山地岳桦林是山地植被垂直带谱重要组成部分之一 ,是山地森林垂直分布林线 ,WI为 2 0～ 15℃·月为地带性植被类型 ,而WI>2 0℃·月为非地带性植被类型 .6 )内蒙古浑善达克沙地云杉林是陆地上非常罕见的森林生态系统类型 ,但这种云杉林究竟是哪一树种组成 ,在中国植物分类上一直是个争论性问题 ,作者通过核型分析和同工酶实验进一步证明是一个新种即沙地云杉Piceamongolica(H .Q .Wu)W .D .

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

双功能有机物修饰电极的修饰层结构对催化细胞色素C的电极反应的影响

用光谱电化学法研究了双功能有机物健那绿的电化学性质。在铂电极上,健那绿发生四步单电子传递过程。在健那绿修饰电极上细胞色素C的直接、非均相电子传递反应是准可逆氧化还原反应,电极反应速率常数K_s=4.17×10~(-4)cm/s。电极表面的修饰方法不同对细胞色素C的电极反应有很大影响。

Larval metamorphosis and morphological characteristic analysis of triploid shrimp Fenneropenaeus chinensis (Osbeck, 1765)

Both MI and MII triploids were successfully produced by heat shock in Chinese shrimp Fenneropenaeus chinensis. The inducing conditions for MI and MII triploids were optimized. The highest inducing rate obtained for MI triploids reached more than 90%, and that for MII triploids reached nearly 100% at the nauplius stage as evaluated using flow cytometry. Comparisons of survival rates at larval stages between triploids and diploids or diploids experiencing treatment and diploids without treatment were performed. At larval stage from nauplii to postlarvae, heat shocks lowered survival at larval stages even if the ploidy was not changed. Ploidy did not affect shrimp larvae survival, and no significant difference was found in the survival of shrimp larvae between MI and MII triploids. Highly significant differences were observed in the morphology of triploids and diploids, and no apparent difference was found in the morphology of MI and MII triploids at the grow-out stages. Discriminating formulae for triploid and diploid shrimp at grow-out stage were developed and could be used to distinguish triploids from diploids based on morphological parameters. MI and MII triploids of shrimp have the potential to be used in aquaculture.

Isolation and characterization of microsatellite loci from mangrove red snapper Lutjanus argentimaculatus

Lutjanus argentimaculatus, also called mangrove red snapper, is a commercially important fish in East Asia. A proper understanding of population structure is primarily linked with the management of genetic resources in exploiting marine fisheries. Herein, seven microsatellite loci, which showed high polymorphism (observed heterozygosity per locus ranging from 0.3571 to 0.7857 and expected heterozygosity per locus ranging from 0.6236 to 0.8821), were isolated and characterized from L. argentimaculatus. Cross-species amplifications also indicate that primers designed for these loci may be useful for further studies about other closely phylogenetic species of the family Lutjanidae.

高寒草甸土壤有机碳储量及其垂直分布特征

青藏高原是全球变化的敏感区．高寒草甸草原是青藏高原上最主要的放牧利用草地资源之一．选择青藏高原东北隅海北站内具有代表性的高寒草甸土壤进行高分辨率采样．测定土壤根系和有机碳含量．研究得出．青藏高原高寒草甸土壤贮存有巨大的根系生物量（23544．60kgha^-1～27947kgha^-1）和土壤有机碳（21．52GtC）：自然土壤表层（0-10cm）储存了整个剖面土壤有机碳总量的30％左右。比较发现．高寒草甸土壤的有机碳平均贮存量（23．17×10^4kgCha^-1）（0-60cm）较相应深度的热带森林土壤、灌丛土壤和草地土壤的有机碳贮存量高约1～5倍多。在全球碳预算研究中．青藏高原高寒草甸土壤有机碳库不可忽视。随着全球变暖．表层土壤有机碳分解释放的CO2将增加。为了减少高寒草甸生态系统的碳排放。应加强高寒草甸土壤地表覆被的保护．合理种植深根系植物。这对减缓全球大气CO2浓度升高的速率以及可持续开发高寒草甸的生态服务功能都具有重要意义。