Radiation- and Photo-Induced Oxidation Pathways of Methionine in Model Peptide Backbone under Anoxic Conditions

Within the reactive oxygen species (ROS) generated by cellular metabolisms, hydroxyl radicals (HO^•) play an important role, being the most aggressive towards biomolecules. The reactions of HO^• with methionine residues (Met) in peptides and proteins have been intensively studied, but some fundamental aspects remain unsolved. In the present study we examined the biomimetic model made of Ac-Met-OMe, as the simplest model peptide backbone, and of HO^• generated by ionizing radiation in aqueous solutions under anoxic conditions. We performed the identification and quantification of transient species by pulse radiolysis and of final products by LC-MS and high-resolution MS/MS after γ-radiolysis. By parallel photochemical experiments, using 3-carboxybenzophenone (CB) triplet with the model peptide, we compared the outcomes in terms of short-lived intermediates and stable product identification. The result is a detailed mechanistic scheme of Met oxidation by HO^•, and by CB triplets allowed for assigning transient species to the pathways of products formation.     

非径向管板焊接接头的超声检测

对AP1000压水堆核电站安全壳贯穿件的非径向管板焊接接头结构特点进行了介绍,并分析其超声检测工艺的重点和难点。通过建立统一的缺陷定位坐标系并结合被检构件的几何特点进行综合分析,推导得出了h值(缺陷回波最高点距套管外壁的距离)的计算方法。为超声检测对这类焊接接头缺陷的准确识别和定位提供了行之有效的方法,为解决这类焊接接头的超声检测技术受限区提供了行之有效的措施。     

AAOA-MBR工艺在工程中的应用分析

通过对AAOA-MBR工艺在实际工程中的应用,分析该工艺处理城市污水的节能减排效能。实践表明AAOA-MBR工艺具有很强的抗冲击负荷能力,在进水质水量大幅度波动、且碳源匮乏的情况下,仍能取得良好的处理效果。实际工程运行四年来,厂区出水各项指标均稳定优于城镇污水处理厂污染物排放标准(GB 18918-2002)中的一级A标准,其中COD、BOD₅、SS、NH₃^-N去除率分别达到可分别达到90.14%、98.25%、95.58%和98.2%;通过对运行期间污水处理量与耗电量相关关系进行回归分析可知,当处理水量达到设计规模时,其吨水耗电量预测为0.31kWh/m³。同时,基于对污水处理系统的沿程水质检测,优化进水水量分配和内循环回流比并进行产水泵联动改造,可进一步提高系统节能减排效果。     

超声强化过氧化氢-维生素C体系糖汁脱色的研究

研究超声强化过氧化氢-维生素C复合脱色剂体系对糖汁脱色的规律,考察了超声功率、复合脱色剂用量、超声温度和时间对糖汁脱色率的影响。试验结果表明:超声空化强化过氧化氢-维生素C对糖汁具有良好的脱色效果,当处理糖汁量为100 mL,超声功率为260 W,过氧化氢与维生素C的用量均为1.6 mL,空化温度为70℃,超声时间为6 min时,脱色率达到53.4%。通过正交试验分析,得到各个因素对糖汁脱色率影响的主次关系为:超声功率>复合脱色剂用量>超声时间>空化温度。     

Sustainable progress into batchwise coloration of polyurethane nanofibers by using ultrasonic energy

Abstract

In this decade, aesthetic potentials of electrospun polymeric nanofibers for advanced apparels have been studied. For the first time, we studied the sustainable aspects in the batchwise dyeing process of electrospun polymeric nanofibers in terms of conserving thermal energy and reducing the wastewater pollution. The nanofibrous mats were prepared using polyurethane (PU) polymer followed by dyeing with disperse dyes by conventional (CN) dyeing method as well as ultrasonic (US)-assisted dyeing method. Potential of savings in thermal energy (1000?kcal), dwell time (40?min) and quantity of disperse dyes (1.5% on the mass of nanofibers) were realized during the US-assisted dyeing method in comparison with the CN dyeing method. Further, total dissolved solids (TDS) and chemical oxygen demand (COD) contents of dyeing effluents demonstrated considerable ecological merits of the US dyeing method in terms of 30% reduction in TDS and 46% reduction in COD contents in comparison with the CN dyeing method. Excellent color strength (K/S) (reached 10) of dyed PU nanofibrous mats were achieved by US-assisted dyeing method in comparison with the K/S (reached 6) with CN dyeing method. Attenuated total reflectance-Fourier transform infra-red (FTIR) spectroscopy, UV–Vis spectrophotometer and Scanning electron microscopy (SEM) analysis were also applied during the study for characterization.     

红外菲涅尔透镜的注射超声辅助成型优化

为了提升聚合物红外菲涅尔透镜的光学性能,以其表面微沟槽的成型质量为目标,提出了一种高效的注射超声辅助成型方法,并对工艺参数进行了综合质量优化。首先分析了超声振动对聚合物的加热和加压效应,设计了一套一模两腔的对比试验模具;接着以红外菲涅尔透镜的调制传递函数MTF和齿形平均高度h为优化质量目标,设计了四步骤的多目标优化流程,通过试验设计、基于BP神经网络的质量目标与注射工艺参数关系建模、基于NSGA-Ⅱ的多目标优化和试验验证进行工艺参数的综合优化。实验结果表明:该多目标优化流程具有很高的精度,MTF和h的平均预测误差MPE分别为4.16%和3.32%;注射超声辅助成型的菲涅尔透镜微沟槽具有更高的复制质量,其齿沟槽平均高度h增加了15.6%,且h值的波动量随着h值的增大而增大,MTF值受齿高h均匀性的影响大于齿高h对其的影响。     

The thermodynamic characteristics of a Stirling/pulse tube hybrid cryocooler

A Stirling/pulse tube hybrid cryocooler (SPC), comprised of a Stirling cryocooler as the first stage and a pulse tube cryocooler as the second stage, features the ability of shifting cooling capacity between stages by adjusting the movement of the displacer in the first stage. Such an ability allows an SPC to accommodate itself to time-varying heat loads at different temperatures, which makes it a competitive candidate in space applications. However, due to the gas coupling, there exists a significant mutual effect between stages which endows an SPC with special thermodynamic characteristics and has a significant effect on the SPC’s capability of shifting cooling capacity between stages. With the phasor analysis and the thermodynamic analysis, this paper establishes an idealized model of an SPC. The model is then used to study the effect of the second stage on the first stage and reveal the condition that an SPC is able to shift cooling capacity between stages. Also, the model is compared with a Sage numerical model and the two models are consistent on the overall trend. Though it is unable to reflect reality precisely, the idealized model can interpret the mechanism and highlight some of the essential nature of an SPC, which will eventually benefit the appropriate design of an SPC.     

基于数值微分核脉冲信号数字处理方法

核反应堆核测量系统测量探测器输出的核脉冲信号，该信号后沿拖尾很长，在计数率较高时容易产生信号堆积和基线漂移等问题，导致源区计数率测量上限仅能达到105 Hz左右。文中基于数值微分方法，采用数字处理技术，在时域上分析了核脉冲信号经过前置放大、信号成形、低通滤波和脉冲甄别后的输出，并利用探测器实测信号进行了仿真。仿真结果表明，基于数值微分的数字处理方法可以实现相邻0.4 μs脉冲信号的识别和测量，将源区测量计数率上限提升到2×106 Hz以上。      

Relations between asphaltene content,viscosity reduction rate of heavy oil and ultrasonic parameters

Ultrasonic treatment could decrease the viscosity of heavy oil and previous study on had focused on one heavy oil sample and involved less on the influence of asphaltene content. This study examined the effect of asphaltene content on viscosity reduction rate by ultrasonication. A comparison on samples with various asphaltene content and vibration parameter was made. The results showed that the optimal vibration frequency might decrease as the asphaltene content increased, whereas the optimal vibration intensity and the optimal treatment time were suggested to be enlarged. A semi-quantitative correlation was matched, which helped for numerical simulation about ultrasonic treatment.