Wavelength-Resolved UV Photoelectric Charging Dynamics of Nanoparticles: Comparison of Spheres and Aggregates

The objective of this work is to understand the charging dynamics of metal nanoparticles under wavelength-selected UV irradiation, with a particular focus on the effect of particle structure on the quantum yield. We employed an ion mobility analysis technique to measure the size-resolved single charging efficiency of structure-controlled silver nanoparticles (spheres vs. aggregates) in the mobility diameter (D _m) range of 10 ～ 100 nm. We found that the measured particle charging efficiency follows D ² _m dependence for both spherical and aggregate particles. Based on the measured charging efficiency and calculated particle photon absorption cross section, we are also able to determine the mobility size dependence of photoelectric quantum yield for both spheres and aggregates. The quantum yield of spheres is a constant for larger particles (50 nm or larger) but significantly enhanced as particle size decreases. The quantum yield of aggregates is shown to be particle structure dependent and does not behave as a simple summation of individual primary particles. The aggregate particles have higher quantum yield compared with spheres of the same mobility size but is offset by the lower photon absorption cross section, and thus overall charging efficiency of aggregates is lower than spheres of the same mobility size.

© 2013 American Association for Aerosol Research     

Stir‐frying treatments affect the phenolics profiles and cellular antioxidant activity of Adinandra nitida tea (Shiyacha) in daily tea model

Adinandra nitida tea (Shiyacha) is a well‐known resource of functional foods with many healthful features. Effect of stir frying on phenolics, aromatic compounds, cellular antioxidant and antiproliferative activities in A. nitida tea was investigated. Stir‐fried samples depicted a significant increase in total water‐soluble solid, phenolics and flavonoids contents, respectively. In stir‐fried treated samples, main compounds were higher than in corresponding untreated samples. Similar trend was observed in aromatic compounds. Hydrophilic peroxyl radical scavenging capacity and oxygen radical absorbance capacity were enhanced immensely in the treated samples. Furthermore, cellular antioxidant activities of treated samples were higher than those of untreated samples. Stir‐fried samples exhibited higher antiproliferative activity on HepG2 cells, whereas an lack in untreated samples. These findings suggest that stir frying could be an effective technique to improve A. nitida tea quality, and support that A. nitida tea could act as a potential functional food against intracellular oxidative stress and inhibitor of liver cancer.     

An alternative to traditional iron-ore sinter phase classification

An alternative to the traditional quantification of iron ore sinter mineralogy is presented through the use of QEMSCAN instrumentation. The classification of minerals by QEMSCAN is based on chemical composition whilst the traditional classification of iron ore sinter mineralogy, through point counting, is based on morphology. The classification of iron ore sinter minerals through XRD is based on crystal structure. Advantages of the QEMSCAN technique include the ability to distinguish magnesio ferrites from calcio magnetites and the fact that calcium ferrite and silico-ferrite of calcium and aluminium (SFCA) distinction is not dependant on the sectioning of the sample mount.     

Fractal-based algorithmic design of Chinese ice-ray lattices

Chinese ice-ray lattices are perhaps one of the earliest and controlled designs of asymmetric and complex patterns applied as a traditional motif in windows.Suc...     

Delta-ferrite recovery structures in low-carbon steels

The development of delta-ferrite recovery substructures in low-carbon steels has been observed in-situ utilizing laser scanning confocal microscopy (LSCM). Well-developed sub-boundaries with interfacial energies much smaller than that of delta-ferrite grain boundaries formed following transformation from austenite to delta-ferrite on heating. It is proposed that transformation stresses associated with the austenite to delta-ferrite phase transformation generate dislocations that subsequently recover into sub-boundaries by a process of polygonization. Experimental evidence in support of this proposal was found in a ferritic stainless steel. Thermal cycling through the high-temperature delta-ferrite/austenite/delta-ferrite phase transformation leads to the development of a well-defined recovery substructure, which, in turn, modifies the low-temperature austenite decomposition product from Widmanstätten to polygonal ferrite, with a commensurate change in hardness.     

振兴我国天然气工业研究报告之一——振兴天然气工业必须走社会主义商品经济的道路

我国天然气工业的发展与国民经济的需要不相适应,虽然可以提出许多原因,而根本原因是没有真正承认天然气工业也是社会主义商品经济的一个产业部门,没有给予天然气企业以真正的商品生产者、经营者的地位。振兴天然气工业,必须走商品经济的道路。     

A structure model and growth mechanism for novel carbon nanotubes

The growth of carbon nanotubes from catalytic thermal decomposition of acetylene on fine iron particles has been studied. Electron microscopic images of the carbon nanotubes as formed and after annealing treatment are presented. Besides the ordinary carbon nanotubes which have been reported (S. Iijima, Nature, 354 (1991) 56), we have found, at first time, two other new kinds of carbon nanotubes: one is straight or curved nanotube with many irregular multi-layered diaphragms in the hollow core, in particular, the fringes of the wall of the tubes are not parallel to the axis of the tube; another one has many regular diaphragms (bamboo-like) which keep almost constant distance with each other. A model that postulates two steps growth of nanotubes from catalyst particles is proposed to explain the microstructure of the novel carbon nanotubes.     

采用辅助谐振网络实现零电压开关的移相控制全桥变换器

移相控制全桥变换器能够实现开关管的零电压开关,但滞后桥臂难度很大。本文提出了电流增强原理,在此基础上,提出了一种新颖的移相控制全桥变换器,它是在传统的全桥变换器中加入了一个辅助谐振网络,来帮助实现滞后桥臂开关管的零电压开关。在文中,对这种变换器的工作原理作了分析,仿真与实验结果验证了该变换器的可行性。     

(S)-(+)-γ-苄氧基甲基-γ-丁内酯的合成研究

以Ｌ 谷氨酸为原料,首先在－５～０℃条件下重氮化,随后常温内酯化,然后在对甲苯磺酸催化下于苯中回流进行酯化,用硼氢化钠在常温下还原,最后用氧化银作为碱发生常温威廉逊（Ｗｉｌｉａｍｓｏｎ）醚化反应,以３２３％的总产率合成了标题化合物。