1,201 research outputs found
Book Review: Urban Structure Matters
No full textJTLU, vol. 2, no. 1, (2009) pp. 81-83.The author reviews the book Urban Structure Matters by Petter Naess (Routledge, 2006).Chen, Xueming. (2009). Book Review: Urban Structure Matters. Retrieved from the University Digital Conservancy, 10.5198/jtlu.v2i1.107
Paleoproterozoic crustal growth in the North China Craton: evidence from the Luliang Complex
No full textAbstract not availableM. Santosh, Qiong-Yan Yang, Xueming Teng, Li Tan
Reconfiguration of the proteasome during chaperone-mediated assembly
No full textThe proteasomal ATPase ring, comprising Rpt1-Rpt6, associates with the heptameric α ring of the proteasome core particle (CP) in the mature proteasome, with the Rpt C-terminal tails inserting into pockets of the α ring[superscript 1-4]. Rpt ring assembly is mediated by four chaperones, each binding a distinct Rpt subunit[superscript 5-10]. We report that the base subassembly of the proteasome, which includes the Rpt ring, forms a high affinity complex with the CP. This complex is subject to active dissociation by the chaperones Hsm3, Nas6, and Rpn14. Chaperone-mediated dissociation was abrogated by a nonhydrolyzable ATP analog, indicating that chaperone action is coupled to nucleotide hydrolysis by the Rpt ring. Unexpectedly, synthetic Rpt tail peptides bound α pockets with poor specificity, except for Rpt6, which uniquely bound the α2/α3 pocket. Although the Rpt6 tail is not visualized within an α pocket in mature proteasomes[superscript 2-4], it inserts into the α2/α3 pocket in the base-CP complex and is important for complex formation. Thus, the Rpt-CP interface is reconfigured when the lid complex joins the nascent proteasome to form the mature holoenzyme
Solvation structure around the Li+ ion in succinonitrile-lithium salt plastic crystalline electrolytes
No full textHerein, we discuss the study of solvation dynamics of lithium-succinonitrile (SN) plastic crystalline electrolytes by ultrafast vibrational spectroscopy. The infrared absorption spectra indicated that the CN stretch of the Li+ bound and unbound succinonitrile molecules in a same solution have distinct vibrational frequencies (2276 cm(-1) vs. 2253 cm(-1)). The frequency difference allowed us to measure the rotation decay times of solvent molecules bound and unbound to Li+ ion. The Li+ coordination number of the Li+-SN complex was found to be 2 in the plastic crystal phase (22 degrees C) and 2.5-3 in the liquid phase (80 degrees C), which is independent of the concentration (from 0.05 mol kg(-1) to 2 mol kg(-1)). The solvation structures along with DFT calculations of the Li+-SN complex have been discussed. In addition, the dissociation percentage of lithium salt was also determined. In 0.5 mol kg(-1) LiBF4-SN solutions at 80 degrees C, 60% +/- 10% of the salt dissociates into Li+, which is bound by 2 or 3 solvent molecules. In the 0.5 mol kg(-1) LiClO4-SN solutions at 80 degrees C, the salt dissociation ratio can be up to 90% +/- 10%.National Natural Science Foundation of China [21373213, 2013CB834604]; Chinese Academy of Sciences; Ministry of Science and TechnologySCI(E)[email protected]
Design of grating based narrow band reflector on SOI waveguide
No full textA grating-based narrowband wavelength selective reflector on silicon on insulator waveguide is proposed here. The 500 nm thick silicon waveguide is used in the reflector design. The design consists of dual-etch layers for different grating sets separated by the center cavity. The dutycycle, grating-period, and side etching depth are optimized for achieving high reflection and narrow bandwidth. The proposed reflector shows a reflection of 96 % with a full-width halfmaximum bandwidth of 1.5 nm at 1550 nm wavelengths.
The Anion Effect on Li+ Ion Coordination Structure in Ethylene Carbonate Solutions
No full textRechargeable lithium ion batteries are an attractive alternative power source for a wide variety of applications. To optimize their performances, a complete description of the solvation properties of the ion in the electrolyte is crucial. A comprehensive understanding at the nanoscale of the solvation structure of lithium ions in nonaqueous carbonate electrolytes is, however, still unclear. We have measured by femtosecond vibrational spectroscopy the orientational correlation time of the CO stretching mode of Li+-bound and Li+ unbound ethylene carbonate molecules, in LiBF4, LiPF6, and LiClO4 ethylene carbonate solutions with different concentrations. Surprisingly, we have found that the coordination number of ethylene carbonate in the first solvation shell of Li+ is only two, in all solutions with concentrations higher than 0.5 M. Density functional theory calculations indicate that the presence of anions in the first coordination shell modifies the generally accepted tetrahedral structure of the complex, allowing only two EC molecules to coordinate to Li+ directly. Our results demonstrate for the first time, to the best of our knowledge, the anion influence on the overall structure of the first solvation shell of the Li+ ion. The formation of such a cation/solvent/anion complex provides a rational explanation for the ionic conductivity drop of lithium/carbonate electrolyte solutions at high concentrations.National Natural Science Foundation of China [21373213]; Chinese Academy of Sciences; Ministry of Science and Technology; NSF [CHE-1503865]; Welch foundation [C-1752]; Packard Fellowship; Sloan Fellowship; PKU; DSM-Energie CEA Program; [ANR-2011 PRGE002-04 ALIBABA]SCI(E)[email protected]; [email protected]; [email protected]; [email protected]
Li-Ion solvation in propylene carbonate electrolytes determined by molecular rotational measurements
No full textLithium-ion batteries are an attractive power source for a wide variety of applications. Expanding the performance limit of current Li-ion batteries requires ion-solvent interaction, which governs the ion transport behavior of electrolytes, to be fully understood. We herein examine the coordination number of the Li+ ion in LiPF6-PC solutions using femtosecond vibrational spectroscopy. Surprisingly, we found that the coordination number of PC in the first solvation shell of Li+ decreases from 4 to 2 as the salt concentration increases. At dilute salt concentrations, the Li(PC)(4)(+) complex with a tetrahedral geometry is dominant, while at high salt concentrations, the presence of anions in the first solvation shell modifies the solvation structure, leading only 2 PC molecules to coordinate to Li+ directly. The variety of the solvation structure provides a rational explanation for the ionic conductivity changing as the salt concentration increases
Effects of Li on microstructure and friction and wear behavior of 7075 aluminum alloy for drill pipe
No full text7075-(0%, 0.5%, 1%, 2%, mass fraction)Li alloy was prepared by hot pressing sintering, and the effects of Li on microstructure and friction and wear behavior of 7075 Al alloy were investigated. The results show that the density of 7075-0.5Li alloy reaches above 99% at sintering pressure of 60 kN. Al alloy consists of α-Al, η and S' phases. With the increase of Li content to 2%, the η phase decreases, δ' and δ phases increase, but α-Al is still the main phase. The hardness and wear rate of Al alloy are 71.25HV and 3.50×10-3 mm3·N-1·m-1, respectively. As the Li content increases, the hardness of Al-Li alloy decreases and the wear rate increases. However, 7075-0.5Li exhibits higher hardness and lower wear rate than those of Al alloy. Both oxidation wear and adhesion wear occurs in 7075-Li alloy. With the increase of Li content, the η phase is reduced, the hardness decreases, the brittleness of Al2O3 is high which has a weak bonding with the matrix, and the dendrite spacing of microstructure widens, resulting in the transition from the abrasive wear to adhesive wear of the alloy, and therefore the wear resistance gradually decreases. Compared with Al alloy, 7075-0.5Li alloy prepared by hot pressing sintering shows a better wear resistance
Lun Dong Han di shi yu hao zu zhi hun yin guan xi ji wai qi shi li zhi xiao chang.
No full text論文(碩士)--香港中文大學,1968.Manuscript.Includes bibliographical references (leaves 300-309).Thesis (M.A.)--Xianggang Zhong wen da xue, 1968.Chapter (一) --- 引言Chapter (二) --- 東漢政權之本質及帝室與族之婚姻關係Chapter (甲) --- 東政權之本質Chapter (乙) --- 帝室與豪族之婚姻關係Chapter (丙) --- 親族之休戚相關Chapter (三) --- 東漢帝室嗣續與外戚勢力二者關聯之考察Chapter (甲) --- 郭陰馬三氏與帝室嗣續Chapter (乙) --- 臨朝諸后與帝室嗣續Chapter （丙） --- 諸帝嗣子之多寡有無Chapter （丁） --- 舊權之尊重Chapter （四） --- 東漢事規臺閣與權移外戚因果關係之論析Chapter （甲） --- 中朝與外朝之別Chapter （乙） --- 尚書權任與外戚擅政之關係Chapter （丙） --- 外戚以大將軍錄上書事Chapter （五） --- 東漢外戚勢力之淌長與京師柄及北官位置之關係Chapter （甲） --- 東漢京兵之重Chapter （乙） --- 外戚之操持兵柄與參決國政Chapter （丙） --- 外戚勢力消長之關鍵Chapter （丁） --- 北軍與北宮建置之形勢Chapter (六) --- 結
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