典型微量金属元素对铜绿微囊藻生长影响的研究

针对Cu、Fe、Zn的不同离子浓度对铜绿微囊藻生长的影响进行研究,以期为水体富营养化防治的进一步开展提供理论支持。试验采用BG11培养基,分别测定了3种微量金属在不同浓度下铜绿微囊藻细胞密度和细胞叶绿素a含量变化。结果表明:当Cu、Fe、Zn浓度分别为0.001、3~12、0.05 mg/L时,铜绿微囊藻生长最佳,且在最佳浓度范围内铜绿微囊藻对Cu、Fe、Zn的利用率与其生长状况呈明显的相关性。Cu、Fe、Zn在不同浓度范围对藻类光合作用的促进或抑制是影响其生长的主要因素。因此,控制水体蓝藻暴发时,除了调节氮磷以外,通过微量金属元素浓度的调节也可作为一条有效抑制蓝藻暴发的途径。     

单水滴附载的Lamb波宽频Chirp激励成像研究

为研究水滴附载效应对Lamb波传播特性的影响,基于Lamb波与不连续介质相互作用的远场散射原理,采用稀疏传感器阵列对单水滴附载的远场散射信号进行试验监测,研究宽频Chirp激励方法和窄带响应的滤波提取算法,优化选取对表面水滴敏感的Lamb波模态和成像中心频率、调制周期数,最终实现对不同体积水滴的椭圆算法定位成像.结果表明:水滴附载对Lamb波A0模态的传播特性影响显著,即使微小的单水滴附载亦会对监测信号产生较大影响.椭圆算法可实现单水滴附载的定位成像,成像质量除受水滴体积大小影响外,成像颜色带宽的设置亦与成像质量息息相关.     

Effects of high hydrostatic pressure treatments on haemagglutination activity and structural conformations of phytohemagglutinin from red kidney bean (Phaseolus vulgaris)

Red kidney beans were subjected to high hydrostatic pressure (HHP) treatment (50, 150, 250, 350, 450 MPa) and phytohaemagglutinin (PHA) was then extracted by affinity chromatography. It appeared that HHP treatment could increase crude extract yield and decrease its haemagglutination activity. For purified samples, PHA yield was not affected at pressures <450 MPa while the haemagglutination activity was noticeably reduced at 450 MPa. The structural changes were investigated using electrophoresis, size exclusion chromatography (SEC), Fourier transform infrared (FTIR) and differencial scanning calorimetry (DSC). Electrophoresis and SEC profiles revealed a new high molecular weight polymer after 450 MPa treatment. At pressures <450 MPa, FTIR showed an increase in β-sheet structure and a decrease in α-helix. At 450 MPa, the bands at 1688 cm^?1, representing aggregate strands and random coils, increased. The conclusions are that pressures <450 MPa can cause PHA unfolding and induce PHA aggregation at 450 MPa.     

Ambient mercury sources in Rochester, NY: results from Principle Components Analysis (PCA) of Mercury Monitoring Network Data

Continuous atmospheric measurements of speciated mercury (Hg) (elemental mercury (Hg?), reactive gaseous mercury (RGM), and particulate mercury (Hgp)) were made in Rochester, NY from Dec 2007 to May 2009. Continuous measurements of ozone (O?), sulfur dioxide (SO?), carbonmonoxide (CO), particulate matter (PM?.?), and meteorological data were also available. A principle components analysis (PCA) of 3886 observations of 13 variables for the period identified six major factors. Melting snow was observed to be a source of Hg?in winters. Positive correlations between RGM and O? in the spring and summer may be indicative of Hg? oxidation. RGM concentrations increased simultaneously with SO? suggesting the influence of coal fired power plants (CFPP). The ?fth factor (F5) containing O? (high negative loading), CO (positive loading), Hg? and Hg(p) (positive), and/or RGM (negative) was identified as a mobile source which was usually observed during morning rush hours (6:00-9:00 a.m.). The concentrations of the three mercury species from the direction of the CFPP were significantly reduced following the shutdown of this source.     

单茂金属化合物催化烯烃聚合

综述了单茂金属化合物催化烯烃聚合的机理及研究进展，指出IVB族元素钛、锆、铪的单茂金属化合物催化烯烃及α－烯烃的均聚和共聚的活性很好，并通过改变配体结构及聚合条件可得到立构规整性的聚合物，桥联的单茂金属化合物催化乙烯，丙烯聚合的活性相当高，可得到高间规度的聚丙烯和支化的超低密度聚乙烯，但催化苯乙烯的活性很低，VB族元素钒，铌、钽的单茂金属化合物作为烯烃催化剂可得到分子量分布相当窄（1．05）的聚烯烃，另外，单茂铬化合物在很低的Al/Cr(45-100)下具有相当高的催化活性，单茂镍化合物由于其亲氧性小，可催化极性单体（如甲基丙烯酸甲酯等）聚合。     

45钢激光氮合金化涂层的组织性能及工艺优化

利用激光合金化技术在45钢表面制备了氮合金化层,并采用正交试验法优化了合金化工艺参数,采用OM、XRD、显微硬度计和摩擦磨损试验机等手段研究了优化工艺处理后的合金化层的组织及性能。结果表明,随激光功率和扫描速度增大,合金化层硬度呈先增后降的趋势,在1.0 kW和500 mm·min^-1时硬度分别达到最大值782 HV0.3和725 HV0.3,随着搭接率的增加,合金化层硬度逐渐下降,其最优工艺为:激光功率1.0 kW、扫描速度500 mm/min和搭接率30%;经最优工艺处理后的合金化区组织由γ-(Fe,N)、γ-(Fe,C)、针状马氏体、γ′(Fe₄N)、ε(Fe₂N)以及Fe₃C等固溶体和化合物组成,以柱状晶和胞状晶为主,厚度约为120 μm,平均硬度约为816 HV0.3,热影响区组织由少量针状马氏体以及残留奥氏体等组成,厚度约为200 μm,硬度由768 HV0.3到242 HV0.3呈梯度分布;合金化层的摩擦因数约为0.4827,磨损率为8.218×10^-15 m³·N^-1·m^-1。     

Characterization of antioxidant activity and volatile compounds of Maillard reaction products derived from different peptide fractions of peanut hydrolysate

Five peptide fractions isolated from peanut hydrolysate were purified by ultrafiltration and gel filtration chromatography. Their reaction degrees with glucose or lecithin in Maillard reaction were compared. Glucose consumption, oxygen radical absorbance capacity (ORAC) values and volatile compounds composition of peanut hydrolysate (PH) and its peptide fractions after thermal treatment and Maillard reaction were evaluated. Results revealed that the peptide fraction of 1-3 kDa showed the highest antioxidant activity. The peptides with smaller molecular weight showed a higher reaction degree to increase antioxidant activity and to produce more volatile compounds through Maillard reaction. Analysis of molecular weight distribution showed that peptide degradation and cross-linking simultaneously occurred during the Maillard reaction. In addition, lecithin addition to peptide-glucose system caused a significant increase of antioxidant activity possibly due to more nitrogen-containing compounds formed.     

Effect of xylose on the molecular and particle size distribution of peanut hydrolysate in Maillard reaction system

BACKGROUND: The Maillard reaction is a complex series of reactions between reducing sugars and amino groups. Changing any of reaction parameters would alter the reaction pathway. This study investigated the effect of xylose concentration on the molecular and particle size distribution of Maillard reaction products (MRPs) derived from peanut hydrolysate and xylose to discuss their formation mechanism. RESULTS: Molecular weight and particle size distribution analyses indicated that both peptide degradation and peptide cross‐linking occurred during the Maillard reaction. Heat treatment would make the high‐molecular‐weight peptides degrade into low‐molecular‐weight peptides and free amino acids. Maillard reaction increased the molecular weight and particle sizes of products as the xylose concentration increased from 1% to 4%. CONCLUSION: The study shows that both peptide degradation and peptide cross‐linking occurred during the Maillard reaction. The thermal degradation product (TDP) and MRPs had significantly different molecular size distribution, and the particle size distribution of TDPs and MRPs had similar change tendency to that of the molecular size distribution. These would provide an insight into the formation mechanism of MRPs. Copyright © 2011 Society of Chemical Industry     

Emulsifying properties of the transglutaminase-treated crosslinked product between peanut protein and fish (Decapterus maruadsi) protein hydrolysates

BACKGROUND: Defatted peanut meal, a protein‐rich by‐product from the oil extraction industry, is underutilised owing to its inferior functional properties. In this study, transglutaminase (TGase) crosslinking and proteolysis were used to improve the emulsifying properties of peanut protein isolate (PPI) extracted from the meal. PPI and PPI hydrolysate (PPIH) were conjugated separately with fish (Decapterus maruadsi) protein hydrolysate (DPH), catalysed by TGase to obtain improvements in the emulsifying properties. RESULTS: Analyses by electrophoresis and high‐performance liquid chromatography indicated that polymers were formed in all TGase‐treated samples. In emulsions of PPIH, PPI‐DPH and PPIH‐DPH the volume/surface average particle diameter (d₃₂), creaming and instability phenomenon were decreased and the zeta‐potential was increased after TGase treatment, showing improved emulsifying activity and emulsion stability. In the case of PPI, TGase treatment had no effect on the emulsifying activity, but the emulsion stability of TGase‐treated PPI was improved. CONCLUSION: The study showed that TGase crosslinking and proteolysis could improve the emulsifying properties of PPI, while proteolysis followed by TGase crosslinking proved more efficient. The emulsifying properties of the heterologous protein systems of PPI‐DPH and PPIH‐DPH were also improved by TGase treatment. Copyright © 2010 Society of Chemical Industry     

某型自发电电站动力系统匹配研究

动力系统是自发电电站的主要组成部分之一,其合理性将直接影响电站的使用性能及技术指标。介绍了依据电站所需功率对动力传动系统液压泵、马达选型匹配的方法,并对选定元件进行动力系统特性分析,最后通过样机试验验证了结论。