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991.
A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated. 相似文献
992.
Qingfeng Liu Jing Ma Liying Tan Yanping Zhou Siyuan Yu 《Journal of Russian Laser Research》2013,34(3):226-229
We study the influence of temperature on the gain of 980 nm pumped erbium-doped fiber amplifier (EDFA) before and after the electron irradiation. Our experimental results indicate that in the irradiation process the EDFA gain at low temperatures is less than that at high temperatures, but after 7 days recovery, the EDFA gain at low temperatures is significantly higher than that at high temperatures. After 200 krad electron irradiation, the EDFA gain is more sensitive to temperature as compared to non-irradiated one. 相似文献
993.
The glass formation in the SiO2-rich region of the ternary oxide system Al2O3–ZrO2–SiO2 with MgO, CaO, and TiO2 as melting aids was analyzed. The crystallization of glasses with different content of TiO2 and phase evolution with the temperature was studied by X-ray diffraction, infrared, laser Raman spectroscopy and transmission electron microscopy. The use of TiO2 favored formation and crystallization of the glasses due to the decrease of the viscosity of melts and acting as a nucleating agent. The crystalline phase of t-ZrO2 was developed at temperatures as low as 880°C whereas in as prepared specimens without TiO2 its presence was not detected. For the specimens with TiO2, t-ZrO2 and mullite were the principal phases at 1000°C. TiO2 addition did not change the crystallization sequence but decreased the formation temperature of the crystalline phases. Most of Ti4+ ions entered into t-ZrO2 and only a small portion in mullite, but the surplus was detected in ZrTiO4. 相似文献
994.
995.
This paper studies the problem of pricing high-dimensional American options. We propose a method based on the state-space partitioning algorithm developed by Jin et al. (2007) and a dimension-reduction approach introduced by Li and Wu (2006). By applying the approach in the present paper, the computational efficiency of pricing high-dimensional American options is significantly improved, compared to the extant approaches in the literature, without sacrificing the estimation precision. Various numerical examples are provided to illustrate the accuracy and efficiency of the proposed method. Pseudcode for an implementation of the proposed approach is also included. 相似文献
996.
Qian Xia Jinglu Tan Shengyang Cheng Yongnian Jiang Ya Guo 《Photochemistry and photobiology》2019,95(6):1495-1503
Following a step excitation, chlorophyll fluorescence (ChlF) from photosystem II (PSII) of a dark‐adapted photosynthetic organism exhibits the well‐known OJIP pattern. The OJIP induction has been widely used in plant science and agriculture engineering. While the J and I phases are related to transitions of photochemical reaction redox states, characteristic fluorescence intensities at the two phases (Fj and Fi) are often treated at fixed time points in routine measurement and thus do not account for variations in plant and experimental conditions, this (1) neglects the differences in the time of appearance of these phases, which is potentially useful information for characterizing plant status and environmental factors, and (2) leads to errors in measured Fj and Fi values in the many publications. In this work, an alternative method for consistent measurement of Fj and Fi was presented. The proposed method measures the curvatures in the OJIP curve and automatically tracks the characteristic transition points under variable sample and experimental conditions. Experiments were carried out to demonstrate the concept and classification capabilities of the method. This research has established a new framework to analyze ChlF and has enhanced the application capability of ChlF. It is expect useful in analysis ChlF from PSII. 相似文献
997.
James Mitchell Naveena Yanamala Yi Lei Tan Eric E. Gardner Kalyan C. Tirupula Fernanda Balem Mordechai Sheves Daniel Nietlispach Judith Klein‐Seetharaman 《Photochemistry and photobiology》2019,95(3):787-802
The chlorophyll‐derivative chlorin e6 (Ce6) identified in the retinas of deep‐sea ocean fish is proposed to play a functional role in red bioluminescence detection. Fluorescence and 1H NMR spectroscopy studies with the bovine dim‐light photoreceptor, rhodopsin, indicate that Ce6 weakly binds to it with μm affinity. Absorbance spectra prove that red light sensitivity enhancement is not brought about by a shift in the absorbance maximum of rhodopsin. 19F NMR experiments with samples where 19F labels are either placed at the cytoplasmic binding site or incorporated as fluorinated retinal indicate that the cytoplasmic domain is highly perturbed by binding, while little to no changes are detected near the retinal. Binding of Ce6 also inhibits G‐protein activation. Chemical shift changes in 1H‐15N NMR spectroscopy of 15N‐Trp labeled bovine rhodopsin reveal that Ce6 binding perturbs the entire structure. These results provide experimental evidence that Ce6 is an allosteric modulator of rhodopsin. 相似文献
998.
Wei Shyang Tan Ting‐Yin Lee Sheng‐Fang Tseng Ying‐Feng Hsu Masanori Ebina Tetsuya Taketsugu Shing‐Jong Huang Jye‐Shane Yang 《中国化学会会志》2019,66(9):1141-1156
Despite the long history of polyaniline chemistry, backbone‐substituted polyanilines are limited. Here, we report the synthesis of pentiptycene‐incorporated polyanilines through acidic aniline oxidative polymerization with three pentiptycene derivatives, TA, DA, and TP, as nucleate additives. The reactivity of TA > DA ? TP, as evidenced by structural and property analysis of the corresponding polyaniline products, demonstrates a radical coupling mechanism and the formation of Dewar π‐complex intermediates for the chain propagation. In addition, the iptycene substituent effect on enhancing the electrochemical stability and charge storage capability of polyaniline are discussed with a clip model, namely, the threading of neighboring polyaniline chains through the U‐ and V‐shaped cavities of pentiptycene restricts lateral motions of the polymer chains and promotes interchain conductivity. Density function theory (DFT) calculations suggest a larger clipping effect for the U versus V cavities. Both the conclusion of a terminal planar p‐phenylenediamine (ppda) group being the key component of an effective nucleate and the concept of interchain clipping for enhanced electrochemical performance should facilitate the design and synthesis of novel polyanilines for electronic applications. 相似文献
999.
Diaportheone A (1), a chromone natural product was previously isolated from the endophytic fungi Diaporthe sp. P 133. Its structure was established by spectroscopic methods, however, its absolute configuration remained undefined. This study dealt on the total synthesis of diaportheone A (1) utilizing the cyclization and in situ thermal syn-elimination of a β-ketosulfoxide. The C-1R absolute configuration of the natural product was established by X-ray crystallography of the synthetic diaportheone A (1) (>99%?ee) and comparison with the optical rotation. 相似文献