植物导水模型初探

目前世界上对于植物长距离水分运输的微观机理假说存在争论。据此本文初步讨论了植物的导水模型。从流体力学角度讨论了水分在植物体内的运动状态,得出导管中的水分流动是在层流的状态下进行,且必须考虑粘性的作用;通过分析流体的层流运动,建立了导管中一维的流体模型,并简化导管以连续的梯形圆柱排列;分析受力,列出N-S方程,并求解出了一维导管模型的半径与压力梯度和各节管长的关系表达式。研究结果表明,模型中每一节导管的水受力都是平衡的,且各节之间相互独立。     

(HAlNH)n(n=2～3)环状化合物的结构特征

用自洽场理论 (HF)和密度泛函理论 (DFT)的B3LYP方法 ,在 6 31G 的水平上对化合物(HAlNH) 2 和 (HAlNH) 3 的几何结构进行优化 ,并分别与环丁二烯C4 H4 和苯分子C6H6的结构和成键方式进行比较。以B3LYP STO 3G方法讨论其分子轨道波函数 (Ψ)。结果表明 :C4 H4 和 (HAlNH) 2 均为D2h对称 ,前者为长方形结构 ,形成两个孤立的π键 ;而后者为菱形结构 ,形成一个π44键。C6H6和 (HAlNH) 3分子点群分别为D6h和D3h,并均形成一个π66键。成键原子对分子轨道的贡献不同 ,其中C原子是完全等价的 ,而Al和N原子各不相同 ,N原子比Al的贡献要大得多     

Wave propagation in saturated ground using the volume fractions

The purpose of this paper is to study the dynamic behavior of soft ground including a porous layer by considering the porosity change. In order to take the porosity change into account, the concept of the volume fraction, which has been proposed in continuum mechanics, is introduced. The constitutive equations presented by Bowen are applied to the analysis of the porous media. According to Bowen's theory, the porosity is considered as a variable called the volume fraction and has its own constitutive equation. The constitutive equation of the volume fraction has thermoelastic equation coefficients and is determined by the strains of the solid and the fluid. This means that the compressibilities of the solid and the fluid are considered. When the special condition is assumed, Bowen's theory can contain Biots's theory, which has been applied in earthquake engineering. The wave propagation in the ground including a porous layer, modeled by Bowen's theory, is studied and compared with that of Biot's theory. One-dimensional attenuation and surface amplitude are calculated. The effect of the volume fraction is discussed with respect to the compressibilities of the solid and the fluid.     

Site-specifically Hydrolytic Cleavage of Oxidized Insulin B Chain With Cu(II) Ion

Selectively chemical cleavage of peptides and proteins is one of the most important reactions in both chemical and biochemical processes. Over the past decade, the interaction of palladium(II) complexes with methionine, cysteine and histidine-containing peptides and proteins and the hydrolytic cleavage of the corresponding amide bond by Pd(II) complexes have been extensively studied1-13. However, reports concerning the directly selective hydrolysis of peptides and proteins with other simple …     

Two new secoiridoid glucosides from Syringa velutina Kom

Chemical investigation of Syringa velutina Kom. led to the isolation of two new secoiridoid glucosides. Their structures were identified as 6'-0-(6, 7-dihyrofoliamenthoyl)-8-epi-kingisidic acid (syrveoside A, 1) and 6'-O-menthiafoloyl-8-epi-kingisidic acid (syrveoside B, 2) on the basis of chemical and physicochemical evidence.     

The Reaction Of Metal Trialkyls With Benzo[H]Quinolin-10-ol

IntroductionThechemistryoforganoaluminum,organogalliumandorganoindiumcomplexeshasattractedmuchat'tentionduenotonlytotheirinterestingstructuralandchemicalpropertiesbutalsotheirapplicationinsemiconductormaterialsl-5.InthecourseofourstudiesonexploringvolatileMOCVDprecursorsthathavethepropertiesoflowertoxicityandhigherstability,wehaverecentlyreportedonthesynthesisandcharacterizationofintermolecularadducts'-',novelbondingmodecomplexes",',andthecomplexesinwhichN/Omixed-donorcrownethersasligands'l'…     

Four Triterpene Oligoglycosides from the seeds of Aesculus Chinensis

TheseedsofAesculuschinensisBge.(Hippocastanaceae)havebeenusedasfolkmedicineforthetreatmentofdistensionandpaininchestandabdomenl.Untilnow,thereisnoreportonitschemicalconstituents.Thispaperdescribesstructureelucidationoftwonewcompounds,escinsIVa3andIVb4onthebasisofspectroscopicmethodsandcomparisonwithescinsla1andfo22.Amongthem,EscinlaIwasstudiedbyX-raydistractionanalysis.Compound3,whitepowder,showediRbandsduetocarboxylanda,p-unsaturatedesterat1740,1713and1640cm-'andstrongabsorptionbandsat34…     

MALDI-TOF-MS analysis of small molecules using modified mesoporous material SBA-15 as assisted matrix

Mesoporous silica, SBA-15 was successfully functionalized with quinoline moiety, and was applied as a matrix in the MALDI-TOF-MS analysis of small molecules. The modified SBA-15 material [SBA-15-8-(3-(triethoxysilyl)propoxy) quinoline, SBA-15-8QSi] was obtained by using calcined SBA-15 and 8-hydroxy quinoline. The structure of the functionalized mesoporous material was systemically characterized by TEM, the N₂ adsorption-desorption isotherm technique and FT-IR spectra. Compared with DHB and SBA-15, SBA-15-8QSi demonstrated several advantages in the analysis of small molecules with MALDI-TOF-MS, such as less background interference ions, high homogeneity, and better reproducibility. Based on these results, the various analytical parameters were optimized. The ideal operating conditions were (1) methanol used as the dissolving solvent; (2) sample first dropping method; (3) a ratio between the analyte and the matrix of 3.5:10. Under these optimization conditions, a low detection limit (8 pmol for L-Arginine-HCl) and high reproducibility (≤29%) were obtained. This technique was successfully applied to the analysis of various types of small molecules, such as saccharides, amino acids, metabolites, and natural honey.