吸附特性曲线测量装置的研制

气相缓蚀吸附特性曲线测量装置结构简单,使用方便。利用它可简便地测定待研究金属在气相缓蚀剂和不同气氛共存条件下表面电位的变化以及其他特特性曲线,它对气相缓蚀剂的研究和教学工作都具有一定的实际意义。     

Variation of bioactive furocoumarins and flavonoids in different varieties of grapefruits and pummelo

Grapefruit juice has been shown to increase the oral bioavailability of many therapeutic drugs. Certain citrus bioactive compounds such as furocoumarins and flavonoids have potent inhibitory effects on cytochrome P450 3A4 (CYP 3A4) enzyme and P-glycoprotein. The levels of these bioactive compounds in the grapefruit juice may affect the magnitude and mechanism of grapefruit juice-induced drug interaction. The levels of three furocoumarins such as dihydroxybergamottin (DHB), paradisin A and bergamottin and flavonoids have been separated and quantified using high-performance liquid chromatography (HPLC) in seven varieties of grapefruits and its parent pummelo. Considerable differences were observed in the levels of these bioactive compounds in different grapefruit varieties. Ray Red showed the lowest (0.492 ± 0.027 DHB μg/ml, 0.059 ± 0.001 μg/ml paradisin A and 0.344 ± 0.030 μg/ml bergamottin) levels of all three furocoumarins and Duncan contain the highest amount of DHB (2.587 ± 0.432 μg/ml) and bergamottin (1.004 ± 0.068 μg/ml), where as Star Ruby contain the highest levels of paradisin A. Pummelo contain the highest levels of naringin (4.587 ± 0.061 mg/ml), while Rio Red showed the lowest level (1.986 ± 0.145 mg/ml) of naringin.     

YZ-1酸化缓蚀剂的合成及其性能

以甲醛、丙酮和乙二胺为原料，经过Mannieh反应合成了曼尼希碱酸化缓蚀剂YZ-1。通过正交实验得出最佳合成条件为：反应温度70℃，反应时间4h，酮醛胺摩尔比为2：2：1，HCl加量1．0％。用静态失重法在不同温度、不同加量以及不同酸液类型及酸液浓度下，对其缓蚀性能进行了综合评价。结果表明，缓蚀剂YZ-1在盐酸、氢氟酸和土酸中均有良好的缓蚀效果，其耐温性高达150℃，是一种很好的高温酸化缓蚀剂。     

Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete

Emulsifiable oils are often used in posttensioned construction to reduce friction losses and provide temporary corrosion protection for tendons prior to grouting. This paper addresses the effects of two emulsifiable oils and three duct types on bond and friction losses. Bond test results indicate that corrugated galvanized steel ducts provide better anchorage than corrugated HDPE ducts. Rigid steel pipes performed poorly because of failure at the duct-concrete or grout-duct interface. Bond test results also indicate that the ultimate strength of posttensioned specimens with oiled tendons is similar to or better than the ultimate strength of specimens with unoiled tendons. However, specimens with oiled tendons experienced greater slip at a given load than specimens with unoiled tendons. Friction test results indicate that current recommended design values for the coefficient of friction for steel pipes and galvanized ducts are accurate. However, the measured coefficient for HDPE ducts is significantly less than the AASHTO-recommended value. Friction tests also indicate that lubrication of the tendon reduces the friction coefficient by 15% in rigid steel pipes and HDPE ducts if stressing occurs while the oil is fresh.     

The effect of adatoms on the corrosion rate of copper

On the premises that corrosion is a surface process and adatoms modify the electronic states of the surface, the influence of Zn, Sn, S, I, F, Ta, Sb, Ti, Bi and Cr adatoms on the corrosion rate of copper was investigated. Adatoms were adsorbed at open-circuit from a solution containing 1.0×10⁻² mol l⁻¹ of the ions of the adatom element. The coverage of the adatoms at the surface was calculated by integration of the area under one of the peaks on the voltammogram of the copper electrode before and after dosing the electrode with the adatom. A significant difference in adsorbability of the adatoms at copper surface was observed. This difference was inter alia attributed to atomic size, crystallographic and kinetic effects. The surface properties were characterized by cyclic voltammetry, and for selected systems by SEM and electron microprobe. Corrosion of the surface in presence and in absence of the adatoms was followed by weight-loss method while surface oxidation, ‘surface corrosion’ was investigated by cyclic voltammetry and by electrochemical polarization techniques. The results showed that the nonmetals (F, S and I) markedly enhanced the rate of corrosion; Cr, Ta, Sb, Bi, Ti, Sn slightly enhanced the rate of corrosion of copper. Zinc, however, was the only element which decreased the rate of corrosion.     

An XPS study of tarnishing of a gold mask from a pre-Columbian culture

The tarnishing originated on a hammered gold mask was analysed. Red tarnishing was observed after three years of storage in an indoor environment in the Gold Museum of Banco de la República, Bogotá, Colombia. Silver sulphide (Ag₂S) and silver sulphate (Ag₂SO₄) compounds were identified as the origin of the tarnishing phenomenon, which is attributed to environmental contamination. Atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS) techniques were used.     

States and transport of hydrogen in the corrosion process of an AZ91 magnesium alloy in aqueous solution

Mott–Schottky measurement and secondary ion mass spectroscopy (SIMS) were used to investigate the states and transport of hydrogen during the corrosion behavior of an AZ91 magnesium alloy in 0.1 M sodium sulfate solution. The results showed that when samples were immersed or charged in solution, hydrogen atoms diffused into the film and reacted with vacancy to cause the increases of the carrier concentration (excess electron or hole carrier) and diffusion rate of hydrogen. Some hydrogen atoms diffused to interior of matrix and enriched in β phase while others resorted in the corrosive film. With the increase of immersion or charging time, magnesium hydride would be brittle fractured when the inner stress caused by hydrogen pressure and expansion stress of formation of magnesium hydride was above the fracture strength, which provided the direct experimental evidence of the hydrogen embrittlement (HE) mechanism of magnesium and its alloys. After immersion in solution, the transfer of excess electrons to the interfaces of corrosion film and solution would destroy the charge equilibrium in the film and stimulate the adsorption of , which resulted in the initiation of localized corrosion; after cathodic charging and then immersion, the enrichment of hydrogen atoms at interior of corrosion film would combine into hydrogen gas to form high pressure and result in the rupture of corrosion film, and localized corrosion initiated and developed at surface. Therefore, localized corrosion nucleated earlier on the charged samples than on the uncharged samples. Hydrogen invasion accelerated the corrosion of matrix.     

Effect of Exogenous Auxin Treatment on Cell Wall Polymers of Strawberry Fruit

The role of auxin in the fruit-ripening process during the early developmental stages of commercial strawberry fruits (Fragaria x ananassa) has been previously described, with auxin production occurring in achenes and moving to the receptacle. Additionally, fruit softening is a consequence of the depolymerization and solubilization of cell wall components produced by the action of a group of proteins and enzymes. The aim of this study was to compare the effect of exogenous auxin treatment on the physiological properties of the cell wall-associated polysaccharide contents of strawberry fruits. We combined thermogravimetric (TG) analysis with analyses of the mRNA abundance, enzymatic activity, and physiological characteristics related to the cell wall. The samples did not show a change in fruit firmness at 48 h post-treatment; by contrast, we showed changes in the cell wall stability based on TG and differential thermogravimetric (DTG) analysis curves. Less degradation of the cell wall polymers was observed after auxin treatment at 48 h post-treatment. The results of our study indicate that auxin treatment delays the cell wall disassembly process in strawberries.     

Corrosion of reinforcing steel in neutral and acid solutions simulating the electrolytic environments in the micropores of concrete in the propagation period

Steel embedded in concrete passivates due to the alkaline nature of the concrete pore solution. Reinforcement corrosion develops when the alkalinity is neutralized. Corrosion, in turn, induces acidification of the surrounding pore solution. In the present paper, corrosion rate of corrugated steel bars is studied and measured at different pH values in solutions simulating chloride environments. The media considered consists of saturated calcium hydroxide solutions containing Na and K⁺, neutralized with ferrous chloride. This latter substance is the soluble compound produced during the corrosion of steel after chloride attack. Hydrochloric acid solutions of different pHs were prepared in order to compare the steel corrosion rates in these solutions with those observed in ferrous chloride solutions of the same pH. A comparison of polarization resistance measurements (R_p) with gravimetrically weight loss determined is presented. Tafel slopes results are also included. Additionally, a comparison is made between measurements of AC impedance with those of the R_p method. The results indicate that the corrosion rate in the studied media follows the general trend found in other media of similar pH values: corrosion increases in acidic solutions, remains rather stable for pH range 3-11 and decreases significantly in highly alkaline solutions.     

An experimental comparison of three wire beam electrode based methods for determining corrosion rates and patterns

Laboratory experiments have been carried out to examine the advantages and limitations of three wire beam electrode (WBE) based techniques, including the noise resistance R_n-WBE method, the overpotential-galvanic current method, and the galvanic current method, in determining corrosion rates and patterns. These techniques have been applied simultaneously to several selected corrosion systems of different characteristics. It has been found that the R_n-WBE method has advantages over other WBE based methods when applying to WBE surfaces under uniform corrosion. However, the R_n-WBE method has been found to be unsuitable for low noise level corrosion systems. It has also been found that both R_n-WBE and overpotential-galvanic current methods are similarly applicable to WBE surfaces under nonuniform corrosion. However, the galvanic current method has been found to be suitable only for WBE surfaces under highly localised corrosion. Some related issues regarding R_n calculation such as trend removal and its effects on corrosion mapping have also been discussed.