Stereochemistry and Stereoelectronics of Azines. 13. Conformational Effects on the Quadrupolarity of Azines. An Ab Initio Quantum-Mechanical Study of a Lateral Synthon

The quadrupole moment of formaldazine, H₂C=N-N=CH₂, has been studied for the trans structure (Ð(C-N-N-C) = = 180) and a series of gauche structures ( > 120). Restricted Hartree-Fock theory, second-order Møller-Plesset theory, and quadratic CI theory have been used in conjunction with the basis sets 6-31G^*, 6-31G**, 6-311G** and 6-311++G**. Formaldazine is a quadrupolar molecule with primitive quadrupole moment tensor components of Q _xx = -22.4, Q _yy = -20.4 and Q _zz = -25.6 DÅ at the theoretical level QCISD/6-311++G**. The examination of the theoretical level dependency shows that the reliable computation of a quadrupole moment requires the use of a flexible basis set. A large part of the component Q _zz = -25.6 DÅ is due to the -system and compares, on a per electron basis, with the Q _zz value of benzene. Conformational changes of the azines in the range 120° < < 180 have but a minute effect on the energy and are associated with only minor electronic relaxation. These conformational changes alter the quadrupole moment tensor components less than Q _xx = +0.4, Q _yy = +1.6 and Q _zz = -1.0 DÅ at QCISD/6-311++G**//QCISD/6-31G*. The direction of these changes is explained by consideration of the rotation of the CN--systems and a small reduction of the CN bond polarity in the gauche structures. The Q _zz component of formaldazine is representative of the quadrupole moment tensor component along the direction of the C ₂ axis of the azine bridge as such. Hence, the results of this study suggest that azines can engage in strong quadrupole-quadrupole interactions and can be employed as lateral synthons in crystal engineering. Electronic Supplementary Material available.     

苜蓿属3种不同花色基因型的染色体核型分析

基于形态学的显著差异,对紫花苜蓿(Medicago sativa L.)、黄花苜蓿(Medicago falcata L.)和白花苜蓿(Alfalfa with Cream flower)进行染色体核型分析,结果表明,3种类型的苜蓿材料在染色体核型方面有显著差别,白花苜蓿和黄花苜蓿都是随体染色体,其中,黄花苜蓿有2条为端部着丝点染色体,其核型公式分别为:紫花苜蓿2n=4x=24m+8sm、黄花苜蓿2n=4x=24m+6sm+2T(SAT)、白花苜蓿2n=4x=24m+8sm(SAT)。紫花苜蓿与白花苜蓿的染色体具有89%的相似性,只是在紫花苜蓿7号染色体和白花苜蓿15号染色体存在随体有无的区别;黄花苜蓿染色体具有独特性,显著区别于紫花苜蓿和白花苜蓿,但从其19号染色体来看,参与了紫花苜蓿或白花苜蓿的构建;白花苜蓿15号随体染色体与黄花苜蓿25号随体染色体和紫花苜蓿7号染色体有高度的相似性,但也存在随体有无的区别。     

基于30个形态性状的中国杏属（Armeniaca Scop.）植物分类学研究

基于与叶和果实相关的30个形态性状(包括20个定性性状和10个定量性状)对中国杏属( Armeniaca Scop.)11种3变种进行了UPGMA聚类分析和主成分分析;在主成分分析基础上,构建了中国杏属植物的OTU散点图;并且,结合降水量分布图绘制了中国杏属植物分布图。聚类分析结果显示：供试杏属植物被分成2支。若包含毛叶梅( A. mume var. goethartiana Koehne),则毛叶梅、梅( A. mume Sieb.)、洪平杏( A. hongpingensis C. L. Li)以及政和杏( A. zhengheensis J. Y. Zhang et M. N. Lu)聚为一支,其余8种2变种聚为另一支;若不包含毛叶梅,梅则被划分在后一个分支中。主成分分析结果显示：前3个主成分的累计贡献率仅60.3180%,说明中国杏属植物的形态性状具有较大的遗传变异;在前3个主成分中,树高、叶片下表面被毛情况、叶长/叶柄长比值、叶长/叶宽比值、果核形状、叶宽、果核宽、叶柄长、果柄长和叶缘锯齿形状的绝对权重值均在0.7以上,表明这10个性状在中国杏属植物的分类学研究中具有重要作用。 OTU散点图显示：中国杏属植物在二维散点图上的分类结果与其聚类结果基本一致,并且,其聚类结果中的各分支在三维散点图上也能够明显区分,说明可以采用前3个主成分中绝对权重值较高的性状对中国杏属植物进行分类。分布图显示：杏属植物遍布中国各省(区),且主要集中分布在400和800 mm等降水量线之间的区域。结合上述研究结果及他人的研究成果,支持“将藏杏﹝A. holosericea ( Batal.) Kost.〕作为杏( A. vulgaris Lam.)的1个变种”以及“将政和杏作为梅的1个变种”的分类处理,并支持“将洪平杏作为独立种”的分类处理。此外,建议将仙居杏( A. xianjuxing J. Y. Zhang et X. Z. Wu)和华仁杏( A. cathayana D. L. Fu et al)作为杏属的栽培种。     

Relocated interglacial lacustrine sediments from an esker at Snickarekullen, S.W. Sweden

Lumps of diatom-rich, laminated sediments were discovered redeposited and interbedded in a Late Weichselian delta sequence in a small glaciofluvial esker at Snickarekullen, south-western Sweden. Radiocarbon dating of the sediments gave an infinite age (45 000 B.P.). The composition and sediment structure of the lumps were studied in epoxy-impregnated thin sections using SEM and EDS. Quantitative and qualitative diatom analyses of the sediments were carried out, as well as pollen and macrofossils analyses. The biostratigraphy is compared with that from Holsteinian interglacial sites in surrounding countries, the evidence for which is briefly reviewed. It is concluded that the sediments were deposited in the central part of a lake probably during different parts of the Holsteinian interglacial. The water body changed from a rather shallow lake with a high pH to a considerably deeper, oligotrophic lake with neutral to slightly acidic water during the sedimentation period. The local and regional vegetation developed from an open pine-birch forest into a much more closed vegetation of pine, spruce, larch, alder and hornbeam.     

Clustered arg genes on a BamHI segment of the Escherichia coli chromosome.

BamHI cleavage of DNAs from transducing phages gamma darg13 (ppc, argECBH, bfe), gamma darg14 (ppc, argECBH) and gamma darg23 (argECBH) yields three purely gamma DNA segments (and, in one case, a fourth), as well as several Excherichia coli-DNA-containing segments. The length (in kilobases, kb) of the segments, determined by electron microscopy and ararose gel electrophoresis is 4.2, 7.5, 8.4, 6.2, 6.9, and 6.4 kb for gamma darg13; 13.0, 7.5, 4.7, 6.2, 6.9, and 6.4 kb for gamma darg 14: and 5.3, 11.0, 4.7, 6.2, 6.9, and 6.4 kb for gamma darg23. Ordering of the segments (in relation to the gamma genetic map and with the direction from left to right corresponding to the clockwise orientation of the E. coli genetic map and to each of the numerical sequences given) reveals, on 26 kb of bacterial DNA, two cleavage sites defining the 7.5-kb segment obtainable from the DNA of either gamam darg13 or gamma darg14. These and analogous findings with argEC and argCB deletion-bearing strains, together with results from heteroduplex experiments, locate argE, argC, argB, and presumably argH on the 7.5-kb segment.     

湿地生态旅游研究进展

湿地富有生物多样性和文化多样性,具有较高的旅游价值、环境教育功能及社区参与功能,湿地生态旅游体现了旅游经济与湿地保护的可持续协调发展,目前已引起国内外政府和学者的普遍关注. 本文对国内外相关研究理论和实践进行了总结,对湿地生态旅游的研究意义、进程、内容、方法和结果等进行了综述,并对湿地生态旅游研究进行了展望,以期推动湿地生态旅游研究的发展,为湿地及相关旅游区的资源开发、环境保护和科学管理提供参考.     

苦参和苦豆子的过氧化物酶同工酶谱分析和比较

采用聚丙烯酰胺凝胶电泳技术分析和比较了5个不同产地的苦参和1种苦豆子的过氧化物酶同工酶活性。结果表明：不同产地苦参品种和苦豆子的过氧化物酶同工酶谱迁移率在0.14～0.28之间,共6条酶谱带。聚类分析表明,苦参和苦豆子的亲缘关系较远,而不同产地的苦参种质也存在一定的差异,可分为3类：甘肃成县栽培的苦参与甘肃岷县栽培的苦参为一类,河南卢氏野生苦参单独为一类,河北承德野生苦参和甘肃成县野生苦参为一类。     

长柄马兰（菊科）的形态补充描述及细胞学研究

结合模式产地采集的长柄马兰（Aster longipetiolatus C.C.Chang）标本以及查阅相关文献资料,发现已有的形态描述不充分且缺乏细胞学方面的报道。本研究对长柄马兰的形态特征进行补充描述和核型分析,为探讨其分类地位提供资料。结果包括：①发现并补充长柄马兰新的形态特征：花序托凸起、总苞片3~4层、舌状花具有退化雄蕊、舌片具柔毛、瘦果5肋。②细胞学结果表明,长柄马兰的染色体数目为2n=18,核型公式为2n= 18=16m+2sm,核型属于1A。     

International study on Artemia. LIV. Morphological study of Artemia with emphasis to Old World strains. II. Parthenogenetic populations

Eleven morphometric and one meristic character in 15 parthenogeneticArtemia populations have been studied by using discriminant andcluster analysis as well as scanning electron microscopy.Discriminant analysis revealed five main groups of morphologicalpatterns: (i) the coastal Chinese populations together with apopulation from Kazakhstan, (ii) the inland Chinese salt lakepopulations, (iii) the Greek populations, (iv) one African populationfrom Namibia and (v) a Chinese population from Xuyu (Jiangsuprovince). Cluster analysis was not always in agreement withdiscriminant analysis and these results are discussed.     

玉龙雪山白水1号冰川退缩迹地的植被演替

运用空间代替时间,野外调查和因子分析的方法,研究了自小冰期最盛时以来的玉龙雪山白水1号冰川裸地的植被演替各个阶段的植物群落组成及其数量特征,演替过程中植被类型的变化及其解释,小冰期冰碛垄年龄的估测这3个主要内容.累计调查的55个样方中共出现91种植物,已鉴定出63个种,分属于28个科,46个属,双子叶植物居多,包括乔木、灌木和草本3种生活型的植物.通过统计分析各个演替阶段植物群落的数量特征,揭示出各个阶段植物群落的组成及其替代规律,即:在白水1号冰川末端近250a的退缩迹地上经历了裸地-草本-灌木-乔木的发展阶段.从生态位理论方面来看,这是由于不同物种的生态位及适应性都是不同的,所以构成了不同演替阶段的各自迥异的植物群落,优势种往往是那些生态位比较宽、适应性较强,能在多个演替阶段出现的物种.演替就是朝着生态位不断分化,能够最大限度利用资源的方向发展,其中物种的替代过程实质上就是在生态位不断的分化与接近,激烈的种内与种间竞争的过程中进行着的.基于此通过综合分析海螺沟与玉龙雪山的地理区位特征,气候状况,植被演替过程以及玉龙雪山地区相关的树轮方面的资料,来尝试着估测白水1号冰川小冰期终碛垄的年龄大约在170-250a之间.     

基于能值及系统动力学的中新天津生态城可持续发展模式情景分析

可持续发展动态评价是确保我国第一个国际合作建设的中新天津生态城项目成功的关键基础之一.在对中新天津生态城自然经济状况、功能结构和规划建设指标体系等分析基础上,将能值分析和系统动力学方法相结合,基于功能流视角将生态城系统划分为能物流、货币流及人口流子系统,构建了中新天津生态城可持续发展的能值评价指标体系及系统动力学模型,设计了惯性情景、科技情景、经济情景、环保情景及协调发展情景等5种生态城发展情景,并对各情景下的可持续发展状况进行了仿真和动态评价分析.结果表明：在经济与环境协调发展情景下,中新天津生态城的GDP、能值积累量、货币积累量均呈稳步增长趋势,能值废弃率、废弃物能值比、环境负载率等较小,能值可持续指标(ESI)和生态效率指数(UEI)均处于较低水平,但比其他几种方案更具活力,是中新天津生态城的最佳发展模式.     

Studies on the specificity of acetylaminoacyl-peptide hydrolase.

In a continuing attempt to explore the types of specificity determinants that may affect protein-protein (peptide) interactions, a number of short (2-5 residues) acetylated peptides have been compared as substrates for the enzyme acetylaminoacyl-peptide hydrolase (EC 3.4.19.1). The reference substrate was Ac-AAAA, and most of the other substrates were derived from this basic structure by single amino acid substitutions. The Km and kcat for the different substrates were determined by standard steady-state kinetics, and the corresponding delta delta GT++ value derived from kcat/Km was used for the comparison, setting delta detal GT++ for Ac-AAAA equal to 0. The best substrates were found to be those containing negative charges (Asp > Glu) or aromatic residues in positions 1', 2', or 3' (delta delta GT++ values of 2-5 kJ); the negative charge provided by the C-terminus of the substrate also appears to be important, since the amide and O-Me ester derivatives caused a change in delta delta GT++ values of -7 to -8 kJ from the reference peptide. The stimulating effect of the negative charges is consistent with the inhibitory effect of positive charges in similar peptides (Krishna RG, Wold F, 1992, Protein Sci 1:582-589), and the proposed active site model incorporates subsites for both charge-charge and hydrophobic interactions. In assessing all the data, it is clear that the properties of the individual substrates reflect the total make-up of each peptide and not only the effect of a single residue in a given position.(ABSTRACT TRUNCATED AT 250 WORDS)     

生态系统的环分析方法

生态系统的环分析方法郭中伟，李典谟（中国科学院动物研究所，北京１０００８０）ＬｏｏｐＡｎａｌｙｓｉｓｉｎＥｃｏｓｙｓｔｅｍＳｔｕｄｙ．￥ＧｕｏＺｈｏｎｇｗｅｉ；ＬｉＤｉａｎｍｏ（ＩｎｓｔｉｔｕｔｅｏｆＺｏｏｌｏｇｙ，，ＡｃａｄｅｍｉａＳｉｎｉｃａ，Ｂ...     

International study on Artemia. LIII. Morphological study of Artemia with emphasis to Old World strains. I. Bisexual populations

A detailed morphological and allometrical study was performed withadult males and females of eleven bisexual populations of brineshrimp Artemia. Multivariate procedures, discriminant andcluster analysis, allowed to separate and group together populationswhich exhibit great genetic similarities. The eleven populationsstudied form four distinct groups: the A. franciscana group,the A. tunisiana group, the A. urmiana group and abroader group which includes Eastern Old World populations. Scanningelectron microscopy revealed differences in the male genital organsof an A. tunisiana population by lacking a medial protuberancein the base of the penes while the pattern of the ectodermal ridgesof the brood pouch of A. urmiana markedly differed from theother populations studied.     

Phytochemical and chemotaxonomic study of Pulsatilla cernua (Thunb.) Bercht. ex J. Presl

Twenty-two compounds were isolated from the 70% EtOH–H₂O extract of Pulsatilla cernua (Thunb.) Bercht. ex J. Presl roots, and their structures were determined based on ¹H NMR, ¹³C NMR and MS spectroscopic data, including (+)-pinoresinol (1), matairesinol (2), 4-ethoxycinnamic acid (3), p-hydroxy ethyl cinnamate (4), 3-(4′-methoxyphenyl)-2(E)-propenoic acid (5), methyl 4-hydroxycinnamate (6), radicol (7), cryptomeridiol (8), fraxinellone (9), diolmycin B2 (10), hederagonic acid (11), hederagenin (12), oleanolic acid (13), 3-O-α-L-arabinopyranosyl-oleanolic acid (14), hederagenin 3-O-α-L-arabinopyranoside (15), 3-O-[α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] oleanolic acid (16), hederasaponin B (17), kizutasaponin K₁₂ (18), patrinia saponin H3 (19), hederacholichiside F (20), cernuoside A (21) and cernuoside B (22). Eight compounds (3–10) were isolated and identified from the genus Pulsatilla for the first time.     

湿地松×洪都拉斯加勒比松及亲本DNA胞嘧啶甲基化的初步研究

以湿地松×洪都拉斯加勒比松（Pinus elliottii×P.caribaea var.hondurensis）及亲本为实验材料,采用甲基化敏感扩增多态性技术对其基因组中CCGG位点的甲基化相对水平及遗传变异模式进行了初步分析。结果表明,杂种及亲本CCGG总甲基化相对水平介于77.74%~81.75%,CG甲基化相对水平略低于CNG甲基化水平,CG/CNG甲基化相对水平高于亲本。杂种遗传自亲本的CG与CNG甲基化位点数之比接近1：1,遗传自母本的甲基化位点数与遗传自父本的CCGG甲基化位点数比例为1：1;杂种产生的全新甲基化与完全去甲基化位点数之比接近7：1,初步推测大量甲基化变异促进了杂合体的生长发育。     

森林生态系统生物能流的瞬态分析

森林生态系统生物能流的瞬态分析欧阳兵（中国科学院大气物理所大气数值模拟国家重点实验室,北京１０００８０）Ｔｒａｎｓｉｅｎｔ－ＳｔａｔｅＡｎａｌｙｓｉｓｏｎＢｉｏｔｉｃＥｎｅｒｇｙＦｌｏｗｉｎＦｏｒｅｓｔＥｃｏｓｙｓｔｅｍ．￥ＯｕｙａｎｇＢｉｎｇ（ＬＡ...     

Limnology of 46 lakes and ponds on Banks Island, N.W.T., Canadian Arctic Archipelago

The goal of this study was to describe and quantify the physical and chemical limnological properties of 46 lakes and ponds on Banks Island, to explore the effects of ecoclimatic differences on the water chemistry of these study sites, and to establish baseline conditions for this previously unexplored limnological region, which could then be used in subsequent long-term environmental monitoring programs. A key finding was that the study sites on Banks Island represented a large nutrient concentration gradient from ultra-oligotrophic to hypereutrophic waters. In general, the study sites were relatively nutrient rich by Arctic standards (i.e. mean total nitrogen (TN_mean)=504.2μg/l and mean total phosphorus (TPU_mean)=18.0μg/l); concentrations that are amongst the highest of any previous limnological survey from similar latitudes. Dissolved organic carbon (DOC) concentrations were also some of the highest reported to date amongst all other Canadian Arctic island limnological surveys. These values reflect the milder climate, concentrated animal life and lushness of Banks Island, as compared to other Canadian Arctic Archipelago islands. Principal components analysis (PCA) separated sites along a conductivity/ionic and elevation gradient on Axis 1 (λ₁=0.343), and a metal (Fe, Zn, Al) and alkalinity-related (DIC, pH) gradient on the second axis (λ₂=0.187). Canonical variate analysis (CVA) was used to explore the classification of the study sites into Low Arctic, Mid Arctic or High Arctic designations based on their limnological characteristics.     

The effects of dissolved heavy metals on attached diatoms in the Uintah Basin of Utah,U.S.A.

The relationships of diatom species to dissolved heavy metals in the streams of the Uintah Basin of Utah were studied through four seasons of 1977–1978. Niche center gradient analysis, cluster analysis and correlation analysis were performed.Achnanthes minutissima, Cyclotella meneghiniana, Cymbella minuta, Gomphonema parvulum, Navicula secreta var.apiculata, Nitzschia frustulum, Nitzschia frustulum var.perminuta, Nitzschia frustulum var.perpusilla, Nitzschia palea, andSynedra ulna appear to be indicator species of high or low heavy metal concentrations. Several other species also showed meaningful relationships to high or low heavy metal concentrations.Dept. of Physics and Astronomy, Brigham Young UniversityDept. of Physics and Astronomy, Brigham Young University