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991.
Two-channel tunable laser diode based on photonic crystals 总被引:2,自引:0,他引:2
S. Mahnkopf M. Arlt M. Kamp V. Colson Guang-Hua Duan A. Forchel 《Photonics Technology Letters, IEEE》2004,16(2):353-355
We report the development of a tunable laser diode array monolithically integrated with a Y-coupler structure based on photonic crystals. The laser diodes consist of two longitudinally coupled photonic crystal waveguide segments that are separated by a photonic crystal mirror section. Quasicontinuous tuning is achieved in a 30.6-nm window with 100-GHz channel spacing as typically required by wavelength-division-multiplexing applications. The sources can be operated independently allowing the simultaneous transmission of two freely selectable wavelengths. 相似文献
992.
BACKGROUND: Cyclo-oxygenase-1 (COX-1) is believed to produce prostaglandins vital to mucosal defence, whereas cyclo-oxygenase-2 (COX-2) is induced at sites of inflammation. Little is known about the regulation of COX-2 in the stomach, particularly during the period following mucosal injury. In this study, we examined COX-1 and COX-2 expression shortly after administration of NSAIDs or ethanol. METHODS: Fasted rats were given aspirin, salicylate, indomethacin or ethanol (20% or 40%) orally. Three hours later the stomach was excised, the severity of damage scored and samples taken for RT-PCR of COX-1 and COX-2 mRNA and immunohistochemistry. Nitric oxide synthase mRNA (iNOS and eNOS) and activity were also measured. RESULTS: Aspirin, indomethacin and the higher concentration of ethanol produced widespread mucosal damage, whereas salicylate and 20% ethanol caused only superficial epithelial damage. Aspirin caused a significant increase in COX-2 mRNA expression and a marked increase in COX-2 immunoreactivity, particularly in the superficial mucosa. Expression of COX-1 (mRNA and protein) was unaffected by aspirin, as were NOS mRNA expression and enzyme activity. Pre-treatment with prostaglandin E2 prevented the induction of COX-2 by aspirin. Salicylate and indomethacin caused modest increases in COX-2 immunoreactivity but no change in COX-2 mRNA. Neither concentration of ethanol affected COX-2 mRNA or protein expression, suggesting that this was a specific response to the aspirin, rather than to injury. CONCLUSIONS: These results demonstrate a rapid up-regulation of COX-2 expression in response to aspirin, possibly representing a compensatory response to inhibition of gastric prostaglandin synthesis. 相似文献
993.
G.H. Duan P. Gallion 《Photonics Technology Letters, IEEE》1991,3(4):302-304
It is shown that drive current noise could lead to an important increase of linewidth and a Gaussian line shape of tunable multielectrode distributed Bragg reflector (DBR) lasers. As an example, the drive current noise induced linewidth (DCNIL) has been measured to be about 120 MHz using a standard DC source through at 50 Omega resistor to drive the Bragg section of a tested DBR laser. For tunable lasers with an electronic tuning efficiency of more than 1 GHz/mA ultralow noise current sources should be used to ensure a negligible DCNIL.<> 相似文献
994.
995.
The cathodic electrode process of Y~(3+) ions on the Mo electrode in the LiCl-KCl molten salt withYCl_3(3wt%) in the temperature range of 450~530℃ has been investigated using cyclic voltammetry andchronopotentiometry.The convolution technique has been applied to the treatment of cyclic voltammogram.Theresults show that the reduction mechanism of Y~(3+) ion is Y~(3+)+3e=Y,a simple one-step process.The cathodicprocess is very close to a reversible process under lower scanning rates,and is diffusion-controlled.The cathodicproduct is an insoluble product. 相似文献
996.
997.
RTM专用端羟基低粘度不饱和聚酯树脂的合成研究 总被引:1,自引:0,他引:1
本文对端羟基低粘度不饱和聚酯树脂的配方、合成工艺方法进行了研究,通过控制二元醇的摩尔过量百分率,选择合适的封端二元醇得到了一类粘度低、高端羟基的新型不饱和聚酯树脂,并通过IR动态跟踪了该不饱和聚酯树脂双键交联反应和端羟基与TDI之间的两类反应,结果证实了该树脂中两类反应能同时发生.研究结果显示通过该共混方法改性能有效的降低树脂的粘度,且能大幅提高力学性能. 相似文献
998.
J. S. Zhang Z. Q. Sun G. L. Chen X. J. Liu H. Cui X. J. Duan 《Metallurgical and Materials Transactions A》1997,28(5):1261-1269
A metal matrix composite (MMC) of 2014 aluminum alloy reinforced with 15 vol pct SiC particulate was produced by the spray-forming-deposition
process. The as-deposited preform revealed a high density and a homogeneous reinforcement distribution. Reactive products
were not found on interfaces between the reinforcement and the matrix. Compared to the control alloy, the composite showed
accelerated aging after solutionizing at 502 °C, while aging was retarded after solutionizing at 475 °C. Analysis indicated
that the activation energy was almost the same for the aging process after different solutionizing treatments. This suggested
that while the thermal barrier for the aging process was the same, other factors affecting the aging process should be considered.
For example, the effective concentration of the precipitate forming elements possibly decreased after incompletely solutionizing
at 475 °C. After heat treatment, the composite showed a tensile strength similar to the control alloy. The wear resistance
of the composite improved considerably. The aging behavior of the composite was also studied using the nanoindentation technique.
Steep gradient distribution of elastic modulus and hardness around the reinforcement SiC particulate was observed. Theoretical
analysis showed that this could be attributed to the gradient distribution of precipitates, resulting from a gradient distribution
of dislocation density around the SiC particulates caused by residual thermal misfit stresses. 相似文献
999.
1000.
氧与激光辐照对多孔硅光致发光光谱的影响 总被引:1,自引:1,他引:0
毛晋昌 《红外与毫米波学报》1992,11(5):401-405
将化学腐蚀后的多孔硅样品分别置于大气和氧气中,用激光连续辐照其表面.观察到多孔硅的光致发光光谱峰位随辐照时间增加发生蓝移,最后达到稳定,在真空中作同样处理的多孔硅光致发光峰位却没有移动.X射线光电子谱测量结果表明,在大气及氧气中激光辐照的多孔硅层内并未探测到二氧化硅,结合红外吸收光谱实验,认为蓝移的原因可能是氧置换了多孔硅内表面的硅,出现Si-O-Si结构的结果. 相似文献