Inhibition of the activity of mushroom tyrosinase by alkylbenzoic acids

The inhibition kinetics of alkylbenzoic acids on the diphenolase activity of mushroom tyrosinase have been investigated. The results show that the alkylbenzoic acids assayed can lead to reversible inhibition of the enzyme; furthermore, o-toluic acid and m-toluic acid are mixed-type inhibitors and p-alkylbenzoic acids are uncompetitive inhibitors. The inhibition constants have been determined. For these p-alkylbenzoic acids, the inhibition strength follows the order: p-toluic acid < p-ethylbenzoic acid < p-propylbenzoic acid < p-isopropylbenzoic acid < p-tert-butylbenzoic acid < p-butylbenzoic acid < p-pentylbenzoic acid < p-hexylbenzoic acid < p-heptylbenzoic acid < p-octylbenzoic acid, indicating that the hydrophobic p-alkyl group played an important role in the inhibition of the enzyme. The inhibitory effects were potentiated with increasing lengths of the hydrocarbon chains. The inhibitory effects of o-toluic acid and p-isopropylbenzoic acid on the monophenolase activity have also been studied. The results show that both o-toluic acid and p-isopropylbenzoic acid can lengthen the lag time and decrease the steady-state activity of the enzyme.     

Crystallization Behaviors of amino-terminated polyurethane (ATPU)-grafted polypropylene

Summary A melt-grafting approach was employed to prepare a novel functional polypropylene(FPP)—amino-terminated polyurethane grafted polypropylene (PP-g-ATPU). The crystallization behaviors of PP and PP/FPP blends were characterized using differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and polarized optical microscopy (POM). The effects of FPP composition on crystallization behavior, crystal transformation, and morphology of PP/FPP crystalline were investigated. The results showed that at a low dosage (<2.0 wt%) ATPU acted as a heterogeneous nucleation agent during the crystallization of PP/FPP blends. However, when the content of ATPU reached 2.0 wt% or higher, ATPU deteriorated the crystallization of PP or PP/FPP blends. The crystallite size decreased and the number of crystallites increased as the ATPU content increased. The Avrami analysis was adopted to describe the isothermal crystallization process. The difference in the exponent n between PP and PP/FPP suggested that the isothermal crystallization kinetics of PP/FPP blends followed a three-dimensional growth via heterogeneous nucleation. In terms of the half-time of the crystallization, t_1/2, the crystallization rate of functional PP blends was faster than that of PP homopolymer at a given crystallization temperature.     

Frequency encoding of resonant mass sensors for chemical vapor detection

Chemical vapors can be detected by a resonant mass sensor array with selective absorption coatings implementing a frequency encoding method. The sensor array consists of sensor elements with different frequencies for their identifications in the frequency response obtained with a pulse Fourier transform detection scheme. Zero-loading resonance frequencies are chosen so that frequency shift due to absorption is bounded within a predefined region so that there is no overlap of peaks and all peaks can be assigned to the correct elements at any operation conditions. Mechanical oscillations of all or selected numbers of the sensor elements are excited by application of an excitation signal. Free oscillation decay signals from all or selectively excited sensor elements are detected and digitized. The free oscillation decay signal is subjected to a spectral analysis routine converting into a frequency spectrum, in which frequency shifts due to absorption of chemical vapors can be obtained. The implementation of the frequency encoding method with pulse Fourier transform detection to resonant mass sensors allows simultaneous multisensor detection, fast data acquisition speed, high signal-to-noise ratio by coaddition of raw data, flexible excitation, reduced complexity of electronic hardware, application of advanced data/spectral analysis algorithms, and realization of many other advantages by the introduction of the pulse Fourier transform method. A practical chemical vapor sensing system is demonstrated experimentally by use of nine frequency-encoded and polymer-coated sensors.     

回火温度对16Col4Ni10Cr2Mo钢断裂韧度和抗应力腐蚀性能的影响

研究了回火温度对１６Ｃｏｌ４Ｎｉｌ０Ｃｒ２Ｍｏ钢断裂韧度Ｋ_（ＩＣ）和抗应力腐蚀性能Ｋ_（ＩＳＣＣ）的影响。发现５１０℃以下回火Ｋ_（ＩＣ）和冲击值ａ_ｋ的变化一致，都表现出回火马氏体脆性，但在回火脆性区内Ｋ_（ＩＣ）不降低。在二次硬化峰之前Ｋ_（ＩＳＣＣ）值很低，这是二次硬化钢不能在硬化峰之前回火使用的重要原因。     

气侵检测仪的研制与应用

基于气体侵入井眼后按气液两相流型分布的原理，利用声波可以早期检测到气侵。文章对气侵进行了深入研究，研制了声波气侵检测仪，做到了生产过程中早期气侵检测，以避免井喷的发生，并及时发现油气层。     

新生儿经皮黄疸检测仪的校准

针对经皮黄疸检测仪在使用过程中测量结果无法溯源的问题,通过分析经皮黄疸检测仪的检测原理,研究其测量结果与血清法测胆红素的相关性,提出可尝试采用标准溶液法、标准板法和胆红素浓度模拟法对经皮黄疸检测仪进行校准,并探讨了校准方法的可行性。     

淬火加热温度对超细晶Q&P钢组织性能的影响

研究了淬火加热温度对超细晶Q&P钢微观组织、元素分布、残留奥氏体体积分数和力学性能的影响。结果表明,当淬火加热温度升高时,铁素体含量逐渐减少,马氏体含量升高,残留奥氏体含量呈现先增加后减少的趋势,高淬火加热温度下C元素的扩散速率加快,残留奥氏体的机械稳定性更好。软相铁素体的存在为试验钢提供了良好的韧性。当淬火加热温度为820 ℃时,Q&P钢的综合力学性能最好,抗拉强度为863 MPa,伸长率为26.1%,强塑积为22.5 GPa·%。     

Dielectric properties and current–voltage nonlinear behavior of Ca1−xSrxCu3Ti4O12 ceramics

The effects of Sr doping on the dielectric properties and current–voltage nonlinear behavior of CCTO were investigated. By combining the observations of dielectric properties, current–voltage nonlinearity and impedance spectroscopy, we have found that Sr doping has influenced the electrical properties by adjusting the impedance characteristics of the grain and grain boundary. Among the Sr-CCTO specimens in this work, as Sr doping concentration is 10%, the specimen (Sr-CCTO-2) has the highest permittivity and lowest nonlinear coefficient.     

赤泥的特殊工程性能及其利用之研究

原赤泥强度低，工程上已很少应用。现研究表明，它含有１８种胶结力极强的化合物，针对该特点，提出用析水、脱水和加ＣａＯ的改造对策，增强了赤泥的强度，工程性能得到显著的改善。用赤泥筑坝，坝高可增加２～３倍，还可用于地基补强、做强防渗层以及铺筑路面等。