Highly potent germination inhibitors in aqueous eluate of fruits of Bishop's weed (Ammi majus L.) and avoidance of autoinhibition

The aqueous eluate from fruits ofAmmi majus (Bishop's weed, Umbelliferae) remarkably inhibited germination of adjacent seeds ofAnastatica hierochuntica, lettuce, or tomato but had no effect on intact fruits ofAmmi. Similar inhibition was found in dark or in light, except that seeds ofA. hierochuntica were significantly more inhibited in the dark than in the light. Xanthotoxin was isolated, identified, and found to account for about a sixth of the inhibitory activity of the eluate. After fruits ofAmmi were submerged in a large volume of water for 4 days, the fruits still exuded enough inhibitors to prevent germination ofA. hierochuntica, lettuce, or tomato. Data support also the proposal that the phytotoxins are compartmentalized between the inner and the outer fruit envelopes. The inner layer excludes inhibitors from the embryo and autotoxicity is thus avoided, whereas the outer one ensures a gradual liberation of the phytotoxic compounds. This, as well as the high reactivity of the eluate, the high densities ofAmmi fruits in nature, and their relatively limited annual germination, suggest chemical inhibition of neighboring plant species other thanAmmi. Hence, in addition to their chemical protection against predators of either lower or higher organisms, furanocoumarins in fruits ofAmmi majus may contribute to its success as a weed.     

两类昆虫生长调节剂作用机制的比较

两种昆虫生长调节剂——几丁质合成抑制剂和非舀类蜕皮激素类似物虽然都是作用于蜕皮过程，但有着截然不同的作用机制，本文对这两种杀虫剂作用机制的研究进展进行了总结和比较。     

A new class of corrosion inhibitors for waterborne coatings: 4-methyl-γ-oxo-benzene-butanoic acid complexes

Amine and transition metal based complexes with 4-methyl-γ-oxo-benzene-butanoic acid represent a new class of corrosion inhibitors specifically designed for long-term corrosion protection in waterborne coatings. Today, corrosion protection in waterborne technology is typically achieved using traditional anticorrosive pigments initially developed for use in solventborne coatings. Regulations concerning heavy metals and limitations regarding the compatibility and performance of such materials in waterborne coatings have created a need for novel approaches. Mechanistic aspects are discussed for the 4-methyl-γ-oxo-benzene-butanoic complexes based on electrochemical solution experiments (electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV)) and investigations performed on coated substrates. Exposure results underline the high efficiency of such complexes for both long-term corrosion protection and weld seam rust control in waterborne coatings.     

含杂环甲胺基的氰基丙烯酸酯类光合作用抑制剂的合成和活性研究进展

氰基丙烯酸酯是一类PSII电子传递抑制剂,笔者发现在抑制剂分子疏水性基团苯环被吡啶替代能大大提高其抑制活性,对此先导结构进一步优化,设计合成以下系列新化合物:含2-氯(或烷氧基)-5-吡啶甲胺基的氰基丙烯酸酯、含2-氟-5-吡啶甲胺基的氰基丙烯酸酯、含2-氯-5-噻唑甲胺基的氰基丙烯酸酯、氮在吡啶环不同位置的吡啶甲胺基氰基丙烯酸酯、含烷硫基取代的吡啶甲胺基的氰基丙烯酸酯、含二茂铁甲胺基的氰基丙烯酸酯。生测结果表明:这些含杂环甲胺基的氰基丙烯酸酯类化合物对油菜等十字花科类杂草表现出很好的除草活性,且茎叶处理优于土壤处理。     

气相防锈技术在热力设备防腐蚀中的应用

归纳总结了近年来气相缓蚀剂的研究开发情况,介绍和探讨了气相防锈技术的特点及其在热力设备防腐蚀中的应用,包括气相缓蚀剂的气化装置设计、应用工艺、监测方法等,指出了气相防锈技术的发展趋势.     

Effects of ring substituents on the protective properties of self-assembled benzenethiols on copper

The self-assembled monolayers (SAMs) of a series of substituted benzenethiol (BT) molecules, X-C₆H₄-SH (where X = meta-NH₂, ortho-NH₂, para-NH₂, para-NHCOCH₃, para-F, para-CH₃ and para-CH(CH₃)₂), have been prepared by adsorption from a solution onto a fresh copper (Cu) surface pretreated by a nitric acid etch. The corrosion inhibition efficiency of the modified Cu surfaces in a sulfuric acid solution was investigated by electrochemical characterization. The protection afforded by the substituted functional groups on BT is strongly influenced by the type and the position of the substituent on the benzene ring. BT molecules without any substituent group on the ring are ineffective corrosion inhibitors, indicating that the chemical configuration is the key factor in determining the efficacy of the SAMs as barriers to electrochemically corrosive ions. It is further proposed that the steric hindrance offered by the substituted group in the SAMs plays a very important role in determining its barrier properties.     

Composite corrosion inhibitors for secondary alkaline zinc anodes

The corrosion inhibition property of PEG600 and In(OH)3 as composite corrosion inhibitors for secondary alkaline zinc electrodes was studied, and the inhibition efficiency was determined as 81.9%. The research focused on the mechanism by the methods of electrochemical impedance spectroscopy, polarization curves and IR spectroscopy. The results indicate that the corrosion inhibition effectiveness is attributed to the joint inhibition of anodic zinc dissolution and cathodic hydrogen evolution. And the anodic process is depressed to a greater extent than the cathodic process. The synergistic mechanism of the composite inhinbitors proves to be the enhancement of adsorption of PEG600 by In(OH)3. Potentiostatic experiment results and SEM images verify the inhibition of dendritic growth by the composite inhibitors.     

The isoxazolidines: the effects of steric factor and hydrophobic chain length on the corrosion inhibition of mild steel in acidic medium

Several new isoxazolidines having varying degree of steric environment and hydrophobic chain length, prepared efficiently using single-step nitrone cycloaddition reactions, are tested for corrosion inhibition of mild steel in 1 M and 5 M HCl at 50-70 °C range by gravimetric and electrochemical methods. All compounds have shown very good corrosion inhibition efficiency (IE%) in acidic solution. Steric crowding around the nitrogen centres and hydrophobic chain lengths as well as increase in temperature (in the presence of the inhibitor in the higher concentration range 100-400 ppm) are found to increase the inhibition efficiency of the isoxazolidines. Thermodynamic parameters (ΔG°_ads, ΔH°_ads, ΔS°_ads) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction in the presence of one of the isoxazolidines were determined. Experimental results agree with the Temkin adsorption isotherm. The inhibition of corrosion in 1 M HCl, influenced by both physi- and chemi-sorption, was found to be under mixed control, but predominantly under cathodic control.     

汽车发动机冷却液中镁合金缓蚀剂的研究

采用XRD、电化学极化曲线、化学浸泡等实验方法，研究了腐蚀性水体系中单种无机盐、复配无机盐缓蚀剂对AZ91D镁合金的缓蚀作用，并用正交优化设计确定了Na2MoO4+Na2SiO3+KMnO4复配无机盐缓蚀剂的优化配方；研究了水-乙二醇（1：1）防冻液基础液体系中缓蚀剂对AZ91D镁合金的缓蚀作用.结果表明，在腐蚀性水中KMnO4、Na3PO4、Na2MoO4和NaF对AZ91D镁合金有一定的缓蚀作用，Na2B4O7不具有缓蚀作用，有可能加速其腐蚀；复配Na3PO4+KMnO4及Na2MoO4+Na2SiO3+KMnO4对AZ91D镁合金腐蚀有缓蚀作用，而Na3PO4+Na2B4O7会加速其腐蚀.在水-乙二醇体系中，Na2S对AZ91D镁合金腐蚀有较好的缓蚀作用；确定了2种适用于水-乙二醇中的有机-无机复合缓蚀剂配方，缓蚀效率分别为98.1％和94.3％.