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31.
In this paper, porous WO3 films were prepared by anodic oxidation of metallic tungsten (W) films deposited on alumina substrates. The structural and morphological properties of the porous WO3 films were investigated using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). A large number of cracks appeared on the surface of films after anodization, which makes the films porous. The porous WO3 sensors achieved their maximum response values to NO2 at a low operating temperature of 150 °C. The porous WO3 sensors showed high response values, great stability and fast response-recovery characteristics to different concentration of NO2 gas due to the high specific surface area and special structural and morphological properties. 相似文献
32.
Yuxiang Zhao Yanren Zhu Guolan Ma Qi Wei Shaoxiong Yang Xiaoyu Zeng Hongbin Zhang Jingbo Chen 《Chemical science》2021,12(27):9452
A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (−)-zephyranthine. The concise route includes a catalytic Michael/Michael cascade for the asymmetric synthesis of a penta-substituted cyclohexane with three contiguous stereogenic centers, a remarkable 8-step one-pot operation to easily assemble the zephyranthine tetracyclic skeleton, the regioselective construction of a double bond in the C ring and an asymmetric dihydroxylation. This synthesis is also flexible and paves a potential path to a variety of cyclohexylamine-fused tricyclic or polycyclic alkaloids.A reasonable synthesis design by strategically integrating functional group manipulation into the ring system construction resulted in a short, enantioselective, gram-scale total synthesis of (−)-zephyranthine. 相似文献
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Computational Insights into the Charge Relaying Properties of β‐Turn Peptides in Protein Charge Transfers 下载免费PDF全文
Ru Zhang Dr. Jinxiang Liu Dr. Hongfang Yang Shoushan Wang Meng Zhang Prof. Dr. Yuxiang Bu 《Chemphyschem》2015,16(2):436-446
Density functional theory calculations suggest that β‐turn peptide segments can act as a novel dual‐relay elements to facilitate long‐range charge hopping transport in proteins, with the N terminus relaying electron hopping transfer and the C terminus relaying hole hopping migration. The electron‐ or hole‐binding ability of such a β‐turn is subject to the conformations of oligopeptides and lengths of its linking strands. On the one hand, strand extension at the C‐terminal end of a β‐turn considerably enhances the electron‐binding of the β‐turn N terminus, due to its unique electropositivity in the macro‐dipole, but does not enhance hole‐forming of the β‐turn C terminus because of competition from other sites within the β‐strand. On the other hand, strand extension at the N terminal end of the β‐turn greatly enhances hole‐binding of the β‐turn C terminus, due to its distinct electronegativity in the macro‐dipole, but does not considerably enhance electron‐binding ability of the N terminus because of the shared responsibility of other sites in the β‐strand. Thus, in the β‐hairpin structures, electron‐ or hole‐binding abilities of both termini of the β‐turn motif degenerate compared with those of the two hook structures, due to the decreased macro‐dipole polarity caused by the extending the two terminal strands. In general, the high polarity of a macro‐dipole always plays a principal role in determining charge‐relay properties through modifying the components and energies of the highest occupied and lowest unoccupied molecular orbitals of the β‐turn motif, whereas local dipoles with low polarity only play a cooperative assisting role. Further exploration is needed to identify other factors that influence relay properties in these protein motifs. 相似文献
35.
目的评估胰岛素联合沙格列汀治疗2型糖尿病的有效性和安全性。方法回顾性对照研究50例2型糖尿病患者胰岛素加用沙格列汀或阿卡波糖治疗(48±8)周后血糖水平和血糖波动等指标的变化。结果治疗(48±8)周后,两组血糖、Hb A1c、MAGE均明显下降(P均≤0.001),其中沙格列汀组MAGE的降幅明显大于阿卡波糖组(P=0.024),胃肠道不良反应发生率显著低于阿卡波糖组。结论沙格列汀联合胰岛素具有更强的控制血糖波动的疗效,胃肠道不良反应发生率更低。 相似文献
36.
Tao Li Kaijin Hu Libo Cheng Yin Ding Yuxiang Ding Jinling Shao Liang Kong 《Applied Mathematical Modelling》2011
This study aimed to evaluate continuous and simultaneous variations of dental implant diameter and length, and to identify their relatively optimal ranges in the posterior mandible under biomechanical consideration. A 3D finite element model of a posterior mandibular segment with dental implant was created. Implant diameter ranged from 3.0 to 5.0 mm, and implant length ranged from 6.0 to 16.0 mm. The results showed that under axial load, the maximum Von Mises stresses in cortical and cancellous bones decreased by 76.53% and 72.93% respectively, with the increasing of implant diameter and length; and under buccolingual load, by 83.97% and 84.93%, respectively. Under both loads, the maximum displacements of implant-abutment complex decreased by 58.09% and 75.53%, respectively. The results indicate that in the posterior mandible, implant diameter plays more significant roles than length in reducing cortical bone stress and enhancing implant stability under both loads. Meanwhile, implant length is more effective than diameter in reducing cancellous bone stress under both loads. Moreover, biomechanically, implant diameter exceeding 4.0 mm and implant length exceeding 12.0 mm is a relatively optimal combination for a screwed implant in the posterior mandible with poor bone quality. 相似文献
37.
Qilin Liu Yuxiang Li Hongjun Gao 《Journal of Mathematical Analysis and Applications》2006,320(2):771-778
In this short paper, we investigate blow-up rate of solutions of reaction–diffusion equations with localized reactions. We prove that the solutions have a global blow-up and the rate of blow-up is uniform in all compact subsets of the domain. 相似文献
38.
Liu Shenggang Chen Jiayu Yu Shanfu Zou Wenlu Duan Yuxiang Zhang Fuxin Lin Chongen 《International Journal of Infrared and Millimeter Waves》1987,8(8):885-900
Theoretical and experimental study of Diffraction Radiation Oscillator (DRO) is reported in this paper, it is the first work done in P. R. China. The sphere-cylindrical open cavity used in the DRO has been analysed, the method for testing the field profile and the cold measurement of the open cavity have been worked out. The experimental device was manufactured in our lab. and the theoretical analysis and experimental study of the device have been carried out. The main experimental results are: from 2000 V to 4000 V, the tube operates in the 60–87 GHz band, and the maximum output power is about 800 mW. 相似文献
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贵金属元素电化学分析研究(Ⅷ)——痕量铂的阳极溶出伏安法测定 总被引:1,自引:0,他引:1
用伏安法或石墨电极阳极氧化伏安法测定痕量铂虽有报道,但其灵敏度均不够高。Ghulkina等发现在HCl介质中含Sn(Ⅳ)或Sn(Ⅱ),以Pt-Sn共沉淀在碳糊电极上,使铂的测定限达5×10-9g/L。本文用0.3mol/LH_2SO_4-Hg(Ⅱ)-3.0×10~(14)mol/L KMnO_4体系测Pt,其检测限为0.5μg/L。探讨了利用黄原酸钠纤维素酯(CCX)分离除去试液中Au~(3+)Pd~(2+)等干扰元素。本法已用于实际样品分析,结果较好。 相似文献