κ-卡拉胶热可逆凝胶的非遍历行为研究

采用散射斑纹(speckle)技术,即散射光强涨落法,研究了κ-卡拉胶(KC)热可逆凝胶的非遍历行为.证明了非遍历性的存在,并研究了浓度、温度等条件对该非遍历性的影响.结果表明:该物理凝胶存在非遍历性,并随KC浓度增加,凝胶非遍历性增大;随温度升高,凝胶非遍历性逐渐减小,直至消失.     

Photothermochemical process in ammonium perchlorate crystals: II

The influence of phase transition (PT) on the process of thermal development of a latent image arising after X-ray and uv irradiation of ammonium perchlorate (AP) crystals has been studied. Despite the production of a large number of new dislocations accompanying PT, it essentially does not influence the thermal development: The developed image does not smear at PT, remaining as clear as before it. By comparing mirror-symmetric surfaces of cleavage planes of AP crystals, it has been shown that at doses of X-ray and uv irradiation sufficient for obtaining an image, no production of new dislocations was observed in AP crystals. It is suggested that latent image arises due to formation during irradiation of chlorine oxidic products of radiolysis: ClO₃, ClO₂, and ClO as well as the corresponding ions ClO^?, ClO^?₂, and ClO^?₃, i.e., initiators of AP low-temperature decomposition.     

Construction of a 2,6-difunctionalized 2-methyl-2H-1-benzopyran library by using a solid-phase synthesis protocol

[reaction: see text] A library containing 1200 analogues of 2,6-difunctionalized 2-methyl-2H-1-benzopyran was constructed by using a solid-phase synthesis protocol. Polymer-bound 6-amido-, 6-sulfonamido-, and 6-uredo-functionalized 2-hydroxymethyl-2-methylbenzopyrans 10 were prepared as part of a first-generation diversification step by employing reactions of respective acid halides, sulfonyl chlorides, and isocyanates with the amine precursor 7. Transformations of the resin-bound intermediates 10 by reactions with alkyl and acid halides were then used to produce a diverse series of 2,6-difunctionalized 2-methyl-2H-1-benzopyran analogues 12 and 14.     

Study of Tea Digitized Chromatographic Fingerprint Spectra Using Micellar Electrokinetic Chromatography

IntroductionTeaisthemostwidelyconsumedbeverageinpeople’slife .Theheightenedpopularityofthisbeveragethroughouttheworldinrecentyearsmaybedueinparttotheevidenceofarelationshipbetweenteaconsumptionandpreventionofcertainformsofhumandisease .Themaincomponentsofteaarepolyphenoliccompounds ,commonlyknownascatechins ,whichrepresentagroupofcom poundsbelongingtotheflavonoidfamily .Thesecom poundsarewidelydistributedinthetealeavesandconsti tuteupto 30 %ofthedryleafweight.1Muchinteresthasbeenfocusedoncat…     

Intermolecular Nuclear Relaxations and Molecular Site-Site Pair Correlation Functions in Liquids

Intermolecular nuclear relaxation studies of real liquids and the results of theoretical calculations for model potential functions have provided significant information on the role of molecular interactions in the structure of liquids. The intermolecular proton-proton paircorrelation function (pcf), obtained from the reference interaction site model (RISM) is used as the equilibrium distribution and is used to obtarn an effective force for the calculation of intermolecular proton relaxation rates in liquid benzene, 1,3,5-trideuterobenzene and ethane. For liquid ethane, better agreement with experiment is observed with the pcf obtained from the Monte Carlo simulation than with the RISM result.     

Theoretical and experimental investigation of the effect of proton transfer on the (27)al MAS NMR line shapes of zeolite-adsorbate complexes: an independent measure of solid Acid strength

Assessing the degree of proton transfer from a Br?nsted acid site to one or more adsorbed bases is central to arguments regarding the strength of zeolites and other solid acids. In this regard certain solid-state NMR measurements have been fruitful; for example, some (13)C, (15)N, or (31)P resonances of adsorbed bases are sensitive to protonation, and the (1)H chemical shift of the Br?nsted site itself reflects hydrogen bonding. We modeled theoretically the structures of adsorption complexes of several bases on zeolite HZSM-5, calculated the quadrupole coupling constants (Q(cc)) and asymmetry parameters (eta) for aluminum in these complexes and then in turn simulated the central transitions of their (27)Al MAS NMR spectra. The theoretical line width decreased monotonically with the degree of proton transfer, reflecting structural relaxation around aluminum as the proton was transferred to a base. We verified this experimentally for a series of adsorbed bases by way of single-pulse MAS and triple quantum MQMAS (27)Al NMR. The combined theoretical and experimental approach described here provides a strategy by which (27)Al data can be applied to resolve disputed interpretations of proton transfer based on other evidence.     

A new method for the synthesis of 1,4,5-oxadiazocines and its application in the structure modification of natural products

A new method for the synthesis of eight-membered heterocyclic 1,4,5-oxadiazocines has been described from β-diketone and β,β,β-triketone with an acidic α-hydrogen. The method entails the reaction of a di- or triketone with 2-hydroxyethylhydrazine and an aldehyde in the presence of acetic acid providing respectable yield.     

Differential pulse polarographic determination of salicylaldehyde as its Girard-P derivative

A method for the determination of salicylaldehyde (2 × 10^–6–10^–4 M) by differential-pulse polarography, based on the in situ formation of its Girard-P derivative in aqueous solution at pH 2.5, is proposed. The relative standard deviation was 1.5% (ten determinations of 4 × 10^–5 M level). The applicability of this method was checked in synthetic samples containing salicyl alcohol,o-aminophenol, 2-methylphenol, salicylic acid and 4-aminobenzoic acid.     

表面修饰二氧化锡纳米微晶的制备与表征

制备了硅烷偶联剂KH-570表面修饰的SnO2纳米微晶，通过FT-IR、XPS、TEM和TG-DTA对其结构和表面特性进行表征和研究. FT-IR和XPS分析结果确证了KH-570与SnO2表面是以化学键合或物理吸附方式相结合,粒子表面存在酯基等有机官能团的红外吸收特征；观测到KH-570中Si原子的Si2s和Si2p谱线. TEM分析表明，表面修饰反应增强了SnO2纳米微晶的疏水性和分散性.由XPS和TG的实测数据探讨了纳米粒子具有较低包覆量的可能原因.     

SCF discrete-variational Xα calculations of the NH4Cl Auger spectrum

Formalism for calculations of the singlet and triplet Auger energies within the Xα model is presented. Using this method the KVV Auger spectrum of NH₄Cl is calculated and the theoretical intensities are determined within a one-center approximation. The calculated spectrum reproduces quite well all the main features observed for solid NH₄Cl. A new interpretation of the spectrum is suggested.