基于Geant4-DNA工具包的单能电子微剂量学模拟研究

应用Geant4－DNA工具包分析和评估了不同物理过程影响因素对低能电子在液态水中的影响,为建立放射治疗与辐射防护所关心的微剂量学基本数据库提供理论支撑。在最新版本的Geant4中,Geant4-DNA工具包中共有7个物理模型可模拟电子在液态水中的输运。根据不同模型的特点,本文选择其中5个适用的模型来模拟单能入射电子(0.1～20 keV)在液态水中的输运过程;比较各模型记录的径迹结构具体信息,包括相互作用过程总次数、电离和激发次数及相应沉积能量占比等;分析Geant4-DNA选项模型、抽样位点小球半径及相互作用过程等因素对线能均值的影响。模拟结果显示:“option0”与“option2” 之间、“option4”与“option5”之间的模拟结果基本吻合;由于各个模型相互作用截面的不同,“option2”、“option4”和“option6”的径迹信息及线能均值均存在差异;模型对线能均值的影响随着抽样位点小球半径的增大而减小。本工作通过设置不同输运控制条件较全面地比较了Geant4-DNA工具包中的不同选项模型,对用户根据需要选择合适的模型模拟单能电子有帮助和指导作用,为完善电子在液态水中的微剂量学数据库并用于评估电离辐射在微观尺度的生物学效应提供依据。     

不同品种烤烟各部位烟叶成熟过程中非挥发性有机酸含量的变化

为探明不同品种烤烟各部位烟叶成熟过程中多元有机酸和高级脂肪酸含量变化的差异,以红大、云烟87、K326、中烟100为材料进行了研究。结果表明,中烟100中非挥发性有机酸含量较低,而红大、云烟87和K326较高,下部叶非挥性有机酸含量显著高于中部叶和上部叶。烟叶中多元有机酸含量随成熟增加而逐渐减少,上部叶、中部叶的高级脂肪酸含量则随成熟度增加表现出先减后增再减的趋势,而下部叶则表现为随成熟度增加而逐渐下降的趋势。     

南、北芡实提取物的抗氧化活性比较及其GC-MS分析

用80%乙醇、95%甲醇、正丁醇、乙酸乙酯、氯仿、石油醚等溶剂分别提取南、北芡实中抗氧化活性物质,比较了不同提取物对体外清除DPPH.、羟自由基(.OH)及超氧自由基(O2.-)的效果,并利用GC-MS对南、北芡实抗氧化提取物中主要成分进行了分析。试验结果表明:不同溶剂的芡实提取物都具有抗氧化作用,但能力存在差异。南芡95%甲醇提取物清除DPPH.能力最佳,而北芡正丁醇提取物清除能力最佳。二者80%乙醇和95%甲醇提取物均具有较好的清除DPPH.、羟自由基(.OH)、超氧阴离子自由基(O2.-)能力。GC-MS分析结果表明,南、北芡实抗氧化提取物的主要成分和含量不同,但均含有甾醇类和生育酚类化合物;另外还有多种含不饱和键的酰胺类、酯类等物质。南芡95%甲醇、80%乙醇和石油醚提取物中生育酚类化合物和绝大部分甾醇含量高于北芡;北芡正丁醇和乙酸乙酯提取物中生育酚含量高于南芡。     

Oxygen depletion properties of glucose-grafted polyethylene resins filled with sodium ascorbate/modified iron compounds

Oxygen scavenging plastic can react with oxygen that was trapped in the packaging materials or permeated into the packages, and then, extend the shelf life of food contained in packages. Sodium ascorbate (SA) and modified iron (MFe) compounds were chosen as the main components of oxygen scavengers to prepare the oxygen scavenging LDPE plastics. However, the widely used hydrophobic LDPE packaging material will slow down the oxygen depletion rate of these oxygen scavenger compounds. So glucose was used to modify the hydrophobic property of LDPE to improve the oxygen depletion properties of LDPE oxygen scavenging plastic. The oxygen depletion efficiency of L₉₅[SA_x(MFe)_y]₅ series samples improved initially as the weight ratios of SA/MFe increase, and reached the best as the weight ratios of SA/MFe approach 7/3. After modifying LDPE with glucoses, the oxygen depletion efficiency of each ML₉₅[SA_x(MFe)_y]₅ specimen improved even better than that of the corresponding L₉₅[SA_x(MFe)_y]₅ specimen with the same loading of oxygen scavenger compound, wherein the oxygen depletion efficiency of ML₉₅[SA_x(MFe)_y]₅ series specimens reached the best as the weight ratios of SA/MFe approach 1/9. In consistent with the oxygen depletion properties found in the previous section, the peroxide values of modeled food samples tested in the airtight flask with L₉₅[SA_x(MFe)_y]₅ and ML₉₅[SA_x(MFe)_y]₅ series samples reduce consistently as their oxygen depletion properties improve. In order to understand the interesting oxygen depletion properties of L₉₅[SA_x(MFe)_y]₅ and ML₉₅[SA_x(MFe)_y]₅ series samples, Fourier transform infrared spectroscopy, scanning electron microscope and energy dispersive X-rays analysis of these samples were performed.     

Improved shape evolution of copper interconnects prepared by jet-stream etching

In the preparation of copper interconnects in the conductor pattern of a printed circuit board (PCB), wet etching processes are commonly adopted for creating patterns of high-density interconnects. Currently available techniques of immersion and spray etching could lead to poorly shaped wires due to complex flow fields or the disturbing puddling effect. A modified technique of arrayed jet-stream etching was developed in this work, aiming at producing well-defined copper interconnects on a PCB in a significantly shorter time. The results were appealing in that copper interconnects of 35/140 μm (thickness/width) exhibiting etching factors of greater than 6 were obtained in 20 s, much better than the conventional ones with etching factors of 3 to 5 and etching times of at least 2 min. In addition, uniformly etched copper interconnects with less than 20 μm undercuts were observed on one etching line. One additional point to note is that no banking agents or inhibitors as commonly seen in conventional etching techniques were needed in this new processing method.     

Melting behavior of poly(trimethylene terephthalate)

In this study, the melting behavior of isothermally crystallized polytri‐ methylene terephthalate (PTT) was investigated. Multiple melting behaviors in DSC heating trace were found because two populations of lamellar stacks were formed during primary crystallization and the recrystallization at heating process, respectively. This fact could be also confirmed from the result of optical microscopy observation. The Hoffman–Weeks equation was applied to obtain equilibrium melting temperature (T). The T value of PTT is about 525 K, which is 10 K higher than that reported. Combining the enthalpy of fusion from the DSC result and the degree of crystallinity from WAXD result, the value of the equilibrium‐melting enthalpy ΔH was deduced to be approximately 28.8 kJ mol^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2426–2433, 2002     

Effect of dispersion method and process variables on the properties of supercritical CO2 foamed polystyrene/graphite nanocomposite foam

In this study, polystyrene/nanographite nanocomposite foams were made by different compounding methods, such as direct compounding, pulverized sonication compounding, and in situ polymerization, to understand the effect of the process variables on the morphology of the nanocomposites and their foam. The foam was made by batch foaming using CO₂ as the blowing agent. Various foaming pressures and temperatures were studied. The results indicated that the cell size decreased and the cell morphology was improved with the advanced dispersion of the nanoparticles. Among the three methods, the in situ polymerization method provided the best dispersion and the resulting nanocomposite foam had the finest cell size and the highest cell density. In addition, adding nanoparticles as a nucleating agent can make foams of similar cell size and cell density at a much lower foaming pressure. This result can be explained by the classical nucleation theory. This discovery could open up a newroute to produce microcellular foams at a low foaming pressure. POLYM. ENG. SCI., 53:2061–2072, 2013. © 2013 Society of Plastics Engineers     

J-104石油管道固定片胶的研制

主要介绍以乙烯-丙烯酸乙酯共聚物为主体材料,适当加入增粘剂、填料和其它助剂,制成的一种新型胶粘剂。研究了它们的配比与性能的关系。并采用了辐射交联的技术方法,使这种胶粘剂对聚乙烯粘接性能更好。     

Physical study of room‐temperature‐cured epoxy/thermally reduced graphene oxides with various contents of oxygen‐containing groups

In this study, the effects of different oxygen‐containing group contents in thermally reduced graphene oxides (TRGs) for enhancing the physical properties of epoxy nancomposites was examined. The epoxy/TRG nanocomposites (ETNs) were prepared by a room temperature curing method in the presence of TRGs containing different oxygen‐containing groups and were then characterized by Fourier transform infrared spectroscopy. TRG contents with higher oxygen‐containing group contents (ca 33%) were found to show better dispersion capability in the epoxy matrix than TRGs with lower oxygen‐containing group contents (ca 11%) based on morphological observations by transmission electron microscopy. The better dispersion capability of TRGs with higher oxygen‐containing group contents in ETN membranes was found to lead to significantly enhanced mechanical strength, thermal stability and thermal conductivity based on measurements of dynamic mechanical analysis, tensile tests, thermogravimetric analysis and by the transient plane source technique. © 2014 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry     

Effect of annealing on poly(urethane‐siloxane) copolymers

The N‐substituted polyaniline (PANi) was synthesized by incorporation of bromine‐terminated polystyrene (PS‐Br) onto the emeraldine form of polyaniline. End brominated polystyrene was synthesized by atom transfer radical polymerization (ATRP) technique and then deprotonated polyaniline was reacted with PS‐Br to prepare PS‐grafted PANi (PS‐g‐PANi) copolymer through N‐grafting reaction. The degree of N‐grafting can be controlled by adjusting the molar feed ratio of PS‐Br to the number of repeat units of PANi. The microstructure and compositions of the PS‐g‐PANi copolymers with different degrees of N‐substitution were characterized by FT‐IR, elemental analysis, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The cyclicvoltammetry shows that the electroactivity of N‐substituted PANi is strongly dependent on the degree of N‐grafting. The solubility of PS‐g‐PANi copolymers in common organic solvents such as tetrahydrofuran and chloroform was improved by increasing the degree of N‐grafting, and also the samples are partially soluble in xylene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007