Ultafast organic nonlinear optical molecules and the realization of mesoscopic photonic devices

In the twentieth century, revolutionary changes took place in the human society and people’s life-style due to the improvement of the optoelectronic information technology based on the second-order nonlinear optical effects, such as the electro-optic effect, the second harmonic generation (SHG), and so on. Along with the rapid development of light information technology, new principles and methods of nonlinear optics are needed, and the third-order nonlinear optical effects attract great attention. The research progress of nonlinear optics is reviewed in this article. Our research work on the third-order nonlinear optical materials, ultrafast and low-power organic all-optical photonic crystal switching are introduced.     

Age and genesis of the Myanmar jadeite: Constraints from U-Pb ages and Hf isotopes of zircon inclusions

Myanmar jadeite (jadeitite) is well known for its economical value and distinctive tectonic locality within the collisional belt between India and Eurasian plates. However, it is less studied for its genesis and geodynamic implications due to precipitous topography, adverse weather and local military conflicts in the area. By means of combined ICP-MS and LA-MC-ICPMS techniques, we have carried out in-situ trace elements, U-Pb and Lu-Hf isotopes for zircon inclusions in a piece of jadeite gem sample. CL imaging suggests that the zircons are metasomatic in origin, and contain mineral inclusions of jadeite and omphacite. Seventy-five analyses on 16 grains of the zircons yield a U-Pb age of 158 ± 2 Ma. The Myanmar zircons differ from other types in that they have no significant Eu anomalies despite high HREE concentrations. Measured ¹⁷⁶Hf/¹⁷⁷Hf ratios range from 0.282976 to 0.283122, with an average value of 0.283066 ± 7; ε_Hf(t) value of 13.8 ± 0.3 (n=75). These results indicate that the Myanmar jadeite was formed in the Late Jurassic, probably by interaction of fluid released from subducted oceanic slab with mantle wedge. Therefore, its formation has no genetic relationship to the continental collision between Indian and Euroasian plates. Supported by National Natural Science Foundation of China (Grant No. 40673039) and the Science Plan Foundation of Guangdong (Grant No. 2007B031200005)     

Magma flow inferred from magnetic fabrics in Wanning gabbro pluton and diabase dykes, Hainan

Measurements of anisotropy of magnetic susceptibility (AMS) were performed on a gabbro pluton and 7 diabase dykes in the Wanning area, southeast Hainan Island. Rock magnetism showed that pseudo-single domain (PSD) to multidomain (MD) Ti-poor magnetite carries the magnetic fabric in the gabbro pluton whereas MD Ti-poor magnetite carries the magnetic fabric in the diabase dykes. The corrected anisotropy degree (Pj ) in most specimens was found to be less than 1.2 which is indicative of a possible flow-related magnetic fabric. The AMS eigenvectors within each site are generally well grouped. The maximum susceptibility axes (K1 ) of the gabbro pluton are inclined towards the north at low angles (< 30°). K1 axes of the diabase dykes are inclined towards the NNW and SSE with dip angles of ≤ 30°. From this study, it appears that the emplacement mode of the gabbro pluton was characterized by intrusion from the north to the south at a low angle whereas the diabase dykes were emplaced from the NNW to the SSE at low to moderate angles. This was verified by comparison of the rock fabric to the magnetic fabric. All of this evidence leads to the conclusion that the Wanning gabbro pluton and diabase dykes were the products of pulsative intrusion from the same magma chamber in the area far to the north of Wanning, which suggests that basic rocks may exist beneath the Indosin- ian granite in the area to the north of Wanning.     

Trends of the precipitation acidity over China during 1992–2006

The trends of the precipitation acidity from 1992 to 2006 were studied, based on the long-term acid rain observations at 74 sites in China. The results show that there was no remarkable change or extension of acid rain area (i.e., with annual mean of precipitation pH<5.6) during the 15 years. The largest and continuous acid rain area exists in the south of the Yangtze River, while the acid rain areas north of the Yangtze River remain separate. The severe acid rain area (i.e., with annual mean of precipitation pH<4.5) exists mainly in the south of the Yangtze River. The overall precipitation acidity for the 74 stations showed different trends before 1999 and after 2000. In the period 1992–1999, the precipitation acidity at most of the sites remained steady or showed a decreasing trend. After 2000, however, an increasing trend of the precipitation acidity was observed at many sites in North China, Central China, East China, and South China. As a result, the pattern of acid rain area changed during 1992–2006. The precipitation over North China, Central China, and South China became more acidified in the 15 years, with more pronounced trends in North China and the north of Central China. A slight decrease in the precipitation acidity was found in Southwest China, an area characterized as severest acid rain area for about two decades after the early 1980s. Consequently, the center of severe acid rain area in the south of the Yangtze River moved eastwards. The non-hydrogen conductivity (NHC), which is defined as the difference between the measured precipitation conductivity and the H+ conductivity calculated from measured pH, was estimated and treated as a proxy of soluble ions in precipitation. The result shows that the overall trend of the NHC before 1999 was pronounced and positive, while the trend after 2000 was inconspicuous or slightly negative. During 2000–2006, the change rate of pH was positively correlated to that of the NHC at 21 sites, implying that the increasing acidities found at these sites may partly be attributed to the decrease in the concentration of airborne particulate matter in recent years.     

基于流态化技术硅粉直接氮化制备氮化硅粉

提出了一种基于流态化技术,利用硅粉直接氮化制备氮化硅粉的新工艺。在常温下,以氮气为载气,将硅粉快速流化并夹带离开供料装置,硅粉和氮气组成的气-固两相流进入到预热器中,预热后的混合物从底部进入到高温悬浮床的高温区,以稀相气力输送的方式连续穿过高温悬浮床,在高温常压下发生燃烧合成反应,最后在出口经冷却装置冷却后,由收集装置收集,得到氮化产物。借助SEM、XRD、元素分析和FTIR等方法分析了氮化产物的形貌、物相组成、化学成分以及价键结构。实验结果表明：对于平均粒径为2.7μm的硅粉,在反应温度为1653K, 反应时间为2.7min时,硅的转化率为53.4%,氮化产物为非晶氮化硅粉。通过理论预测,如果将反应温度升高至1723K,硅粉氮化7.1min后,其转化率可达99%。本文提出的方法可连续制备优质氮化硅粉,而且比现有的其他制备方法具有更高的生产效率。