流动注射电位滴定研究：氟化物沉淀滴定测锂

设计制作了一种简便的梯度混合室,并考察了其性能,试验结果证实了此混合室的合理性和有效性.用此混合室建立了流动注射电位滴定测锂的新方法,载流为1×10~(-5)～1×10~(-4)mol·L~(-1)的F~乙醇-水(9 1)溶液,流速4.2ml·min~(-1),混合室体积400μl,进样体积120μl,分析速度60样·h~(-1),检出范围取决于载流中滴定剂的浓度,方法用于卤水中锂的测定,结果令人满意.     

Hydroxy peroxy nitrites and nitrates from OH initiated reactions of isoprene

The reaction of hydroxy peroxy radicals (RO(2)) with NO represents one of the most crucial tropospheric processes, leading to terrestrial ozone formation or NO(x)() removal and chain termination. We investigate the formation of hydroxy peroxy nitrites (ROONO) and nitrates (RONO(2)) from the OH-isoprene reactions using DFT and ab initio theories and variational RRKM/master equation (vRRKM/ME) formalism. The binding energies of ROONO from NO addition to RO(2) are determined to be in the range of 20-22 kcal mol(-)(1), and the bond dissociation energies of ROONO to form an alkoxy radical (RO) and NO(2) range from 6 to 9 kcal mol(-)(1). Isomerization of ROONO to RONO(2) is exothermic by 22-28 kcal mol(-)(1). The entrance and exit channels of the RO(2)-NO reaction are found to be barrierless, and the rate constants to form ROONO are calculated to be 3 x 10(-)(12) to 2 x 10(-)(11) cm(3) molecule(-)(1) s(-)(1) using the canonical variational transition state theory. The vRRKM/ME analysis reveals negligible stabilization of excited ROONO and provides an assessment of ROONO isomerization to RONO(2).     

Study of the concentration and separation of cadmium with microcrystalline phenolphthalein modified by crystal violet

A new method for cadmium separation and concentration with microcrystalline phenolphthalein modified by crystal violet (CV) was developed in the paper. In the presence of potassium iodide (KI) and CV, cadmium are quantitatively absorbed on microcrystalline phenolphthalein in the pH range 1.0-6.0 as the forms of water-insoluble ion-associated complexes (CdI₃⁻)·(CV⁺) and (CdI₄²⁻)·(CV⁺)₂. Effect of different parameters such as phenolphthalein amount, stirring time, the concentration of CV and KI, various salts and metal ions was studied in detail. During the present study, a significant enhancement of the extraction of cadmium was observed. Cd(II) can be completely separated from Zn(II), Fe(II), Co(II), Ni(II), Mn(II), Cr(III) and Al(III) in this microcrystalline system and well concentrated without the interference of these metal ions at high level. The possible reactive mechanism of cadmium concentration has been discussed. Analytical results obtained by this new method were very gratifying.     

ATRP grafting of styrene from benzyl chloride functionalized polysiloxanes: An AFM and TGA study of the Cu(0)/bpy catalyst

Various combinations of Cu(0), CuCl, 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) were used as catalysts for the grafting polymerizations of styrene from polysiloxane macroinitiators functionalized with benzyl chloride. While Cu(0)/bpy alone promotes the grafting, narrower polydispersities were obtained in the presence of CuCl. Analysis of the Cu(0) surface before and after polymerization by a combination of AFM, TGA and FTIR investigations reveals the formation of bpy or phen films on Cu(0). In the presence of CuCl, the ligand film appears decorated with CuCl particles which increase in size with increasing the CuCl concentration. The initial layer occurs most likely as a result of complexation between the ligands and the Cu(0) surface and acts as a support for the rest of the film. These observations are consistent with the film formation on Cu(0) from related nitrogen donors and indicate that the reactivity of the Cu surface may depend not only on its prior treatment but also on the deposition of ligands from the reaction mixture.     

ON A CLASS OF METHOD FOR SOLVING PROBLEMS WITH RANDOM BOUNDARY NOTCHES AND/OR CRACKS(Ⅱ) COMPUTATIONS FOR BOUNDARY NOTCHES

This work is a continuation of the discussion of [1], On a class of method for solving problems with random boundary notches and/or cracks, (I) by C. Ouyang (Appl. Math. & Mech., vol. 1, No. 2, 1980). Here computations for boundary notches are made by using the theory and formulas presented in [1]. In the computation modification is also made for the boundary conditions in parametric plane in [1]. Numerical results for examples show that within ranges of parameter considered in the paper, for example L, the present method in quite workable in practical computations.     

Synthesis of novel C-2 substituted pyrimidine nucleoside analogs

A series of 2-(2-oxoalkylidene)-4(1H)-pyrimidinone nucleoside analogs were synthesized by the addition of the lithium enolates of methylketones to 2,5′- and 2,2′-anhydrouridines and to 2,5′-anhydrothymidines. Alternatively, 2-thiouridine was alkylated with bromomethyl ketones to yield 2-(2-oxoalkyl)thio-4(1H)-pyrimidinone ribofuranosides in good yields. These intermediates were subsequently transformed into the title compounds via an Eschenmoser sulfur extrusion reaction. The 2-(2-oxoalkylidene)-4-(1H)-pyrimidinone nucleoside analogs exhibit enol proton signals in their ¹H nmr spectra indicative of hydrogen bonding between N-3 and keto oxygen. These structures offer functional groups with potential for Watson-Crick hydrogen bonding.     

Direct Electrochemistry of Hemoglobin Immobilized in Sodium Alginate Film on the Ionic Liquid [BMIM]PF6 Modified Carbon Paste Electrode

In recent years the direct electron transfer of redox protein on electrode surface has attracted great attentions1. Different kind of modified electrode and various supporting films for immobilization of proteins had been proposed. But most of them are ba…     

Strategies to enhance the enzymatic hydrolysis of pretreated softwood with high residual lignin content

Pretreatment of Douglas-fir by steam explosion produces a substrate containing approx 43% lignin. Two strategies were investigated for reducing the effect of this residual lignin on enzymatic hydrolysis of cellulose: mild alkali extraction and protein addition. Extraction with cold 1% NaOH reduced the lignin content by only approx 7%, but cellulose to glucose conversion was enhanced by about 30%. Before alkali extraction, addition of exogenous protein resulted in a significant improvement in cellulose hydrolysis, but this protein effect was substantially diminished after alkali treatment. Lignin appears to reduce cellulose hydrolysis by two distinct mechanisms: by forming a physical barrier that prevents enzyme access and by non-productively binding cellulolytic enzymes. Cold alkali appears to selectively remove a fraction of lignin from steam-exploded Douglas-fir with high affinity for protein. Corresponding data for mixed softwood pretreated by organosolv extraction indicates that the relative importance of the two mechanisms by which residual lignin affects hydrolysis is different according to the pre- and post-treatment method used.     

Synthesis of 2′-deoxyguanosine containing a N2-polyamine

The synthesis of benzylated N²-(4,7,10,13-tetraazatridec-1-yl)-2′-deoxyguanosines 4 was accomplished by a key nucleophilic reaction of the novel unsymmetrical polyamine 2 , with 3′,5′-O-(tetraisopropyldisiloxane-1,3-diyl)-2-chloro-2′-deoxyinosine ( 1 ).     

Synthesis of imidazo[4,5-d]pyridazine nucleosides related to inosine

Several imidazo[4,5-d]pyridazine nucleosides which are structurally similar to inosine were synthesized. Anhydrous stannic chloride-catalyzed condensation of persilylated imidazo[4,5-d]-pyridazin-4(5H)one (1) and imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 16 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 3 ) provided (after sodium methoxide deblocking) 6-β-D-ribo furanosylimidazo[4,5-d]pyridazin-4(5H)one (5) and 3,6-di-(β-D-ribofuranosyI)imidazo[4,5-d]pyridazin-4-one ( 7 ); and 1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 19 ) and 1,5 or 6-di-(β-D-ribofuranosyl)imidazo[4,5-d ]pyridazine-4,7(5H or 6H)dione ( 21 ), respeeitvely. 4,7-Diehloro-1-β-D-ribofuranosylimidazo[4,5-d]pyridazine ( 12 ) and dimethyl 1-β-D-ribofuranosylimidazole-4,5-dicarboxylate ( 26 ), both prepared from stannic chloride-catalyzed ribosylations of the corresponding heterocycles, were converted in several steps to 3-β-D-ribo-furanosy limidazo[4,5-d]pyridazin-4(5H)one ( 14 ) and nucleosidc 19 , respectively. Acid-catalyzed isopropylidenation of mesomeric betaine 7 or nuclcoside 14 provided 3-(2,3-isopropylidene-β-D-ribofuranosyl)imidazo[4,5-d]pyrizin-4(5H)one ( 31 ). 1-β-D-Ribofuranosylimidazo[4,5-d]-pyridazine ( 29 ) was obtained in several steps from nueleoside 12 . The structure of the nucleosides was established by the use of carbon-13 and proton nmr.