Analysis of Variance of the Composition of a Migmatite

To determine the variation of composition in a Front Range migmatite, an analysis of variance (nested design) was run on field measurements. The regional variation is too small to be considered significant, but the areal variation (between outcrops) is large enough to warrant comparison with some other measurable variable such as country rock composition.     

新疆委陵菜属植物区系成分分析

本文对新疆境内已记载的３４种委陵莱属（Ｐｏｔｅｎｉｔｉｌｌａ　Ｌ．）植物进行了区系成分分析，其中包括：（１）世界分布型；（２）北温带分布型，（３）环北极高山分布型；（４）欧亚北极高山分布型；（５）旧世界温带分布型；（６）温带亚洲分布型；（７）高加索－伊朗－天山分布型；（８）东地中海分布型；（９）西伯利亚－天山分布型；（１０）亚洲中部分布型；（１１）天山－伊朗分布型；（１２）沿喜马拉雅（包括天山）分布型；（１３）阿尔泰－天山分布型；（１４）天山山地分布型；（１５）中国西北部特有种。统计结果表明：旧世界温带分布型的种类最多，有６种，占总数的１７．６％。温带亚洲分布型和沿喜马拉雅分布型次之，均为４种，各占总数的１１．８％。关键词     

Entwined and parallel bundled orbits as alternative models for narrow planetary ringlets

Particle orbits can be bundled in two different ways to produce narrow, Uranus-type ringlets. The usual assumption is that they are packed in a parallel manner in a structure that is essentially only two-dimensional, but it is then difficult to explain the large numbers of particles per unit area of the ring plane that are inferred from the observations. The alternative of a bundle of entwined orbits produces a three-dimensional structure of potentially large projected areal density. A start has been made in identifying possible mechanisms for stabilizing these structures, but much remains to be done, particularly for the less-studied model of entwined orbits. The two models might be discriminated observationally by differences in the motion of the line of intersection of the orbital and equatorial planes, and by the predicted radial reversal (entwined) or nonreversal (parallel) of features in occultation signatures taken at certain longitudes.     

北京喇叭沟门林区维管植物区系分析

喇叭沟门林区是北京市植物种类最丰富的地区之一 ,现有维管植物 6 5 5种、1 3变种及变型 ,隶属于 1 0 2科、36 7属 ,其植物区系在北京地区具有一定的重要性及特殊性 .科、属分析表明该区与北京维管植物分类群结构基本一致 ,维管植物有半数集中于一些世界性大科之中 .以草本植物占优势的植物生活型反映了本区由暖温带向温带过渡的气候特征 .属的分布区类型表明了该区系的温带性质 ,并反映了该区系形成过程中与热带区系的历史渊源以及与东亚区系之间较紧密的联系     

Observation of covalent intermediates in an enzyme mechanism at atomic resolution

In classical enzymology, intermediates and transition states in a catalytic mechanism are usually inferred from a series of biochemical experiments. Here, we derive an enzyme mechanism from true atomic-resolution x-ray structures of reaction intermediates. Two ultra-high resolution structures of wild-type and mutant d-2-deoxyribose-5-phosphate (DRP) aldolase complexes with DRP at 1.05 and 1.10 angstroms unambiguously identify the postulated covalent carbinolamine and Schiff base intermediates in the aldolase mechanism. In combination with site-directed mutagenesis and (1)H nuclear magnetic resonance, we can now propose how the heretofore elusive C-2 proton abstraction step and the overall stereochemical course are accomplished. A proton relay system appears to activate a conserved active-site water that functions as the critical mediator for proton transfer.     

A molecular switch and proton wire synchronize the active sites in thiamine enzymes

Thiamine diphosphate (ThDP) is used as a cofactor in many key metabolic enzymes. We present evidence that the ThDPs in the two active sites of the E1 (EC 1.2.4.1) component of the pyruvate dehydrogenase complex communicate over a distance of 20 angstroms by reversibly shuttling a proton through an acidic tunnel in the protein. This "proton wire" permits the co-factors to serve reciprocally as general acid/base in catalysis and to switch the conformation of crucial active-site peptide loops. This synchronizes the progression of chemical events and can account for the oligomeric organization, conformational asymmetry, and "ping-pong" kinetic properties of E1 and other thiamine-dependent enzymes.     

微量琼脂—凝胶免疫双扩散技术在猪气喘病诊断上的应用

在1981年实验研究的基础上,1982年我们应用自制的猪肺炎霉形体浓缩提纯抗原及自制家兔抗猪肺炎霉形体血清,在忻县的解村农场,忻县曹村大队猪场,长子县种猪场,长子同贺大队猪场及长子食品公司的猪场,进行猪气喘病的免疫双扩散技术诊断试验,同时应用X射线透视及对流免疫电泳技术作对比,检查了各种类型的猪206头,共检出阳性反应猪146头,占被检总数206头的70.87％,其中X射线透视阳性猪81头,占检出阳性猪146头的55.5％;免疫双扩散检出阳性猪131头,占检出阳性猪数的89.7％;对流电泳检出阳性猪115头,占检出阳性猪数的78.8％。在血清学检查的同时挑出8头不同类型阳性反应猪进行了剖检及微生物学检查,均为阳性。不同诊断技术表明:琼扩的检出率最高,X射线透视检出率最低,对流电泳不及琼扩,差异显著,由此认为琼脂——凝胶免疫双扩散技术由于操作简便,特异性高,检出率较高,适用于猪气喘猪的诊断及猪的大批检疫。     

镜泊湖熔岩台地种子植物区系调查分析

经野外调查,已知镜泊湖熔岩台地有野生种子植物81科270属493种,其中裸子植物1科1属1种,被子植物80科269属492种。本区地理成分比较复杂,属、种分别具有13个和22个分布区类型,均以温带成分占绝对优势：温带分布属188属,占总属数的84．68％;温带分布种394种,占总种数83．83％。     

Magnetic flux transport on the sun

Although most of the magnetic flux observed on the sun originates in the low-latitude sunspot belts, this flux is gradually dispersed over a much wider range of latitudes by supergranular convective motions and meridional circulation. Numerical simulations show how these transport processes interact over the 11-year sunspot cycle to produce a strong "topknot" polar field, whose existence near sunspot minimum is suggested by the observed strength of the interplanetary magnetic field and by the observed areal extent of polar coronal holes. The required rates of diffusion and flow are consistent with the decay rates of active regions and with the rotational properties of the large-scale solar magnetic field.     

Protein hydration in aqueous solution

High-resolution proton nuclear magnetic resonance studies of protein hydration in aqueous solution show that there are two qualitatively different types of hydration sites. A well-defined, small number of water molecules in the interior of the protein are in identical locations in the crystal structure and in solution, and their residence times are in the range from about 10(-2) to 10(-8) second. Hydration of the protein surface in solution is by water molecules with residence times in the subnanosecond range, even when they are located in hydration sites that contain well-ordered water in the x-ray structures of protein single crystals.     

Quantifying Associations among Dimensions of Ears and Their Form Factors in Maize(Zea Mays)Using Dimensional Analysis

Ear morphological traits such as volume and shape are important features of maize and the quantitative associations among them can help understand kernel yield determination. 150 mature ears each of 4 maize cultivars were collected from field experiments, and ear length(L), diameter(D), area(S) and volume(V) were recorded for individual ears, kernel weight per ear also recorded for a portion of the examined ears. Following principles of dimensional analysis, 8 theoretical equations of 3 sets,which relate ear higher dimensions to its length and diameter, were developed and parameterized and validated with the field observations. The 3 optimized equations showed that the shape of ears in maize can be featured with 3 dimensionless form factors, namely diameter-to-length ratio(c=D/L), areal form factor(b=S/L/D), and volumetric form factor(a=V/L/D/D). Statistically,all of them were significantly different among cultivars, and a's values varied from 0.582 to 0.612, and b's 0.839-0.868, and c's 0.242-0.308. Volumetric form factor and areal form factor could estimate precisely ear volume and area respectively, but diameter-to-length ratio was not suitable to estimate ear diameter by its length. Ear volume explained almost all variation of ear kernel weight and product L*D*D did the same substantially. Dimensional analysis proved to be promising in understanding relationship among morphological traits of ears in maize. Its application in crop researches should improve our knowledge of the physical properties of crop plants.     

Does ammonia hydrogen bond?

Spectroscopic characterizations of the stereochemistry of complexes of ammonia (NH(3)) have strongly confirmed some long-held ideas about the weak interactions of NH(3) while casting doubt on others. As expected, NH(3) is observed to be a nearly universal proton acceptor, accepting hydrogen bonds from even some of the weakest proton donors. Surprisingly, no evidence has been found to support the view that NH(3) acts as a proton donor through hydrogen bonding. A critical evaluation of the work that has been done to gather such evidence, as well as of earlier work involving condensed-phase observations, suggests that NH(3) might well be best described as a powerful hydrogen-bond acceptor with little propensity to donate hydrogen bonds.     

木通食植瓢虫幼虫及卵的超微形态与生物学研究

本文着重研究了木通食植瓢虫(Epilachna clematicola Cao et Xiao)卵壳以及幼虫体表超微形态,为其分类提供了依据。通过对其年生活史、发育起点温度、有效积温的研究,建立了不同虫期及全世代的历期预测式;测定结果表明:木通食植瓢虫在昆明地区一年发生2代,与野外实际发生情况比较,基本上是吻合的。     

Evidence for coherent proton tunneling in a hydrogen bond network

We observed coherent proton tunneling in the cyclic network of four hydrogen bonds in calix[4]arene. The tunneling frequency of 35 megahertz was revealed by a peak in the magnetic field dependence of the proton spin-lattice relaxation rate measured with field-cycling nuclear magnetic resonance in the solid state at temperatures below 80 kelvin. The amplitude of the coherent tunneling peak grows with temperature according to a Boltzmann law with energy D/kB = (125 +/- 10) kelvin (where kB is Boltzmann's constant). The tunneling peak can be interpreted in the context of level crossings in the region where the tunneling frequency matches the proton Larmor frequency. The tunneling spectrum reveals fine structure that we attribute to coupling between the hydrogen bonds in the network. The characteristics of the tunneling peak are interpreted in the context of the potential energy surface experienced by the hydrogen atoms in the network.     

Molecular basis of proton motive force generation: structure of formate dehydrogenase-N

The structure of the membrane protein formate dehydrogenase-N (Fdn-N), a major component of Escherichia coli nitrate respiration, has been determined at 1.6 angstroms. The structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 angstroms through the enzyme. The menaquinone reduction site associated with a possible proton pathway was also characterized. This structure provides critical insights into the proton motive force generation by redox loop, a common mechanism among a wide range of respiratory enzymes.     

芝麻不同部位开花结蒴规律及蒴果发育特性研究

为明确芝麻纵向不同部位的开花结蒴规律和蒴果发育特性,以郑芝98N09为研究对象,于芝麻盛花期将其植株纵向划分为下部节位(8节位以下)、中部节位(9～20节位)和上部节位(20节位以上),调查了各部位的开花结蒴特性和蒴果发育情况。结果表明,随着节位的增加,郑芝98N09开花和结蒴数目呈先增加后下降的变化趋势。其中,在第15节位开花数目达最大值,为9.3朵/节;在第12节位结蒴数目达最大值,为4.2个/节位。不同部位结蒴能力比较,中部节位结蒴能力最高,开花结蒴率为45.1%;上部节位次之,为30.1%;下部节位仅为25.0%。中部蒴果的长度、宽度、鲜质量和籽粒的鲜质量、干质量以及果皮干质量均高于下部蒴果和上部蒴果;下、中、上部蒴果平均灌浆速率分别为0.003 5、0.004 4、0.003 0g/(蒴.d),表明在蒴果发育过程中光合物质优先供应中部蒴果。     

从Hackelia californica中分离的两种新生物碱

本文报道了从Hackelia californica中分离和鉴定的两种新的吡略里西啶类生物碱的结构,并与相近结构的latifoline拉替夫林进行了比较。     

Magnetic response of metamaterials at 100 terahertz

An array of single nonmagnetic metallic split rings can be used to implement a magnetic resonance, which arises from an inductor-capacitor circuit (LC) resonance, at 100-terahertz frequency. The excitation of the LC resonance in the normal-incidence geometry used in our experiments occurs through the coupling of the electric field of the incident light to the capacitance. The measured optical spectra of the nanofabricated gold structures come very close to the theoretical expectations. Additional numerical simulations show that our structures exhibit a frequency range with negative permeability for a beam configuration in which the magnetic field couples to the LC resonance. Together with an electric response that has negative permittivity, this can lead to materials with a negative index of refraction.     

Detection and examination of anthrosols by phosphate analysis

Land-use analysis of anthrosols has been performed by a new, two-part method. A rapid qualitative field test assists in locating past settlements and determining their areal and temporal extent, even where artifacts are missing. The field-test results are verified and samples are analyzed further by quantitative soil phosphate fractionation. Laboratory fractionation reveals much more than the simple phosphate test used at present. Like the chemical field test, it uses minute soil samples and may be invaluable where disturbance of the landscape is forbidden. Phosphate fractions reflect the details of man-induced changes in the soil and the timing of their appearance.