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991.
Analysis of heating effect on the process of high deposition rate microcrystalline silicon 下载免费PDF全文
A possible heating effect on the process of high deposition rate microcrystalline silicon has been studied.It includes the discharge time-accumulating heating effect,discharge power,inter-electrode distance,and total gas flow rate induced heating effect.It is found that the heating effects mentioned above are in some ways quite similar to and in other ways very different from each other.However,all of them will directly or indirectly cause the increase of the substrate surface temperature during the process of depositing microcrystalline silicon thin films,which will affect the properties of the materials with increasing time.This phenomenon is very serious for the high deposition rate of microcrystalline silicon thin films because of the high input power and the relatively small inter-electrode distance needed.Through analysis of the heating effects occurring in the process of depositing microcrystalline silicon,it is proposed that the discharge power and the heating temperature should be as low as possible,and the total gas flow rate and the inter-electrode distance should be suitable so that device-grade high quality deposition rate microcrystalline silicon thin films can be fabricated. 相似文献
992.
We review some recent progress in our understanding of the lowest-lying spin-1/2 and spin-3/2 baryon magnetic moments (MMs) in terms of Chiral Perturbation Theory (ChPT).In particular,we show that at next-to-leading-order ChPT can describe the MMs of the octet baryons quite well.We also make predictions for the decuplet MMs at the same chiral order.Among them,the MMs of the Δ++ and Δ + are found to agree well with data within the experimental uncertainties. 相似文献
993.
We report a two‐step anodizing approach for the fabrication of large‐scale open‐ended TiO2 nanotube arrays (TNAs) on a conductive Au layer. In this method, a deposited Ti/Au bilayer film is initially anodized under a high potential to form and shape the TNAs. A following low potential is then in situ applied at a suitable time to slowly eliminate the remaining barrier layer at the bottom of the TNAs without further treatment. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
995.
The development of silica‐filling elastomers with high mechanical performance and good processability is still a great challenge. In this study, we fabricated siloxane‐grafted atactic 1,2‐polybutadiene (1,2‐PB) rubber through grafting poly(1,3‐butadiene)‐block‐(dimethylsiloxane) (PB‐b‐PDMS) onto 1,2‐PB molecular chains by coordination polymerization using a molybdenum (Mo)‐based catalyst system. The PB‐b‐PDMS with active double bonds was synthesized by anionic polymerization. Fourier transform infrared analysis (FTIR), elementary analysis, and GPC‐MALLS‐viscometer analyses verified the incorporation of PB‐b‐PDMS and the grafting structure in the resulting polymer. Scanning electron microscope (SEM), bound rubber testing, and dynamic mechanical analysis demonstrated that the graft‐modification with PB‐b‐PDMS improved silica dispersity in the 1,2‐PB matrix because the incorporation of siloxane groups provided stronger interfacial interaction with silica. Meanwhile, the graft‐modified 1,2‐PB exhibited lower Mooney viscosity, higher tensile strength, and lower heat build‐up than unmodified 1,2‐PB. This concept provides novel inspiration for the preparation of advanced rubber with promoted silica compatibility and mechanical performance. 相似文献
996.
The efficiency becomes a key issue in today's natural product total synthesis. While biomimetic synthesis is one of the most elegant strategies to achieve synthetic efficiency and thus to approach the ideal synthesis, most biogenetic pathways are unknown or unconfirmed. In this account, we demonstrate, through the shortest and also the most efficient asymmetric total syntheses of the hexacyclic alkaloid (?)‐chaetominine to date, that on the basis of biogenetic thinking, one can develop quite efficient bio‐inspired total synthesis, which in turn serves to suggest and chemically validate plausible biosynthetic routes for the natural product. The synthetic strategy thus developed is also inspiring for the development of other synthetic methods and efficient total synthesis of other natural products. 相似文献
997.
Chenxiao Cao Peixia Du Xiaomeng Zhu Huijiao Yan Xiangyun Song Heng Zhu Yanling Geng Daijie Wang 《Journal of separation science》2019,42(16):2621-2627
Toddalia asiatica (Linn.) Lam. is a medical plant traditionally used to treat coughs, fevers, and various diseases. Alkaloids are the main active ingredients in Toddalia asiatica (Linn.) Lam., but traditional methods for screening and separation are complex and labor‐intensive. In this work, an efficient strategy was developed to rapidly screen, identify, and separate neuraminidase inhibitors from Toddalia asiatica (Linn.) Lam. Ultrafiltration, high performance liquid chromatography, and time‐of‐flight mass spectrometry were employed for rapid screening and identification of neuraminidase inhibitors. A two‐phase solvent system comprising n‐hexane/ethyl acetate/methanol/water (5:5:3:7, v/v) was then selected for separation by high‐speed counter‐current chromatography. A sample loading of 200 mg and a stepwise flow rate were achieved by increasing the flow rate from 2 to 4 mL/min after 4 h. Three main fluoroquinoline alkaloids (haplopine, skimmianine, and 5‐methoxydictamnine) along with two coumarins were obtained via one‐step separation and their structures were determined by mass spectrometry and nuclear magnetic resonance. In vitro assays revealed skimmianine with half‐maximal inhibitory concentration of 16.2 ± 0.7 µmol/L was selected as the potential highest neuraminidase inhibitor. The results suggest that ultrafiltration high performance liquid chromatography–mass spectrometry combined with high‐speed counter‐current chromatography is efficient for the screening and isolation of neuraminidase inhibitors from complex natural products. 相似文献
998.
Xin Jin Xue Geng Liujun Jia Zeqin Xu Lin Ye Yongquan Gu Ai‐Ying Zhang Zeng‐Guo Feng 《Macromolecular bioscience》2019,19(8)
Aiming to construct small diameter (ID <6 mm) off‐the‐shelf tissue‐engineered vascular grafts, the end‐group heparinizd poly(ε‐caprolactone) (PCL) is synthesized by a three‐step process and then electrospun into an inner layer of double‐layer vascular scaffolds (DLVSs) showing a hierarchical double distribution of nano‐ and microfibers. Afterward, PCL without the end‐group heparinization is electrospun into an outer layer. A steady release of grafted heparin and the existence of a glycocalyx structure give the grafts anticoagulation activity and the conjugation of heparin also improves hydrophilicity and accelerates degradation of the scaffolds. The DLVSs are evaluated in six rabbits via a carotid artery interpositional model for a period of three months. All the grafts are patent until explantation, and meanwhile smooth endothelialization and fine revascularization are observed in the grafts. The composition of the outer layer of scaffolds exhibits a significant effect on the aneurysm dilation after implantation. Only one aneurysm dilation is detected at two months and no calcification is formed in the follow‐up term. How to prevent aneurysms remains a challenging topic. 相似文献
999.
Yangye Geng Zhen Zhu Yingying Wang Yiyun Wang Shuiping Ouyang Ke Zheng Wenbo Ye Yimin Fan Zixin Wang Dejing Pan 《Electrophoresis》2019,40(10):1436-1445
This work presents a microfluidic device, which was patterned with (i) microstructures for hydrodynamic capture of single particles and cells, and (ii) multiplexing microelectrodes for selective release via negative dielectrophoretic (nDEP) forces and electrical impedance measurements of immobilized samples. Computational fluid dynamics (CFD) simulations were performed to investigate the fluidic profiles within the microchannels during the hydrodynamic capture of particles and evaluate the performance of single‐cell immobilization. Results showed uniform distributions of velocities and pressure differences across all eight trapping sites. The hydrodynamic net force and the nDEP force acting on a 6 μm sphere were calculated in a 3D model. Polystyrene beads with difference diameters (6, 8, and 10 μm) and budding yeast cells were employed to verify multiple functions of the microfluidic device, including reliable capture and selective nDEP‐release of particles or cells and sensitive electrical impedance measurements of immobilized samples. The size of immobilized beads and the number of captured yeast cells can be discriminated by analyzing impedance signals at 1 MHz. Results also demonstrated that yeast cells can be immobilized at single‐cell resolution by combining the hydrodynamic capture with impedance measurements and nDEP‐release of unwanted samples. Therefore, the microfluidic device integrated with multiplexing microelectrodes potentially offers a versatile, reliable, and precise platform for single‐cell analysis. 相似文献
1000.
Caizhu Chang Jialin Geng Yuguo Du Qingwei Lv ZhiBing Dong Jun Liu 《Tetrahedron》2019,75(29):3933-3938
Stereoselective total synthesis of aspinolides B, E and J, naturally occurring 10-membered lactones, were accomplished by divergent strategies starting from the commercially available 2,3-O-isopropylidene-d-ribose and methyl d-lactate. The synthesis features rapid access to the both key fragments from chiral pool and the formation of 10-membered ring lactones containing trans double bond employing cross-metathesis reaction (CM) and intramolecular Shiina macrolactonization. 相似文献