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991.
Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification 下载免费PDF全文
Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992,optical parametric chirped pulse amplification(OPCPA)became the most promising method for the amplification of broadband optical pulses.In the meantime,we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers.The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level.Meanwhile,the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field.In this paper,we overview the basic principles,trends in development,and current state of the ultrashort and laser systems based on OPCPA,respectively. 相似文献
992.
A Novel L‐Cysteine Electrochemical Sensor Using Sulfonated Graphene‐poly(3,4‐Ethylenedioxythiophene) Composite Film Decorated with Gold Nanoparticles 下载免费PDF全文
Xiaoqiang Wang Yangping Wen Limin Lu Jingkun Xu Long Zhang Yuanyuan Yao Haohua He 《Electroanalysis》2014,26(3):648-655
By exploiting the electrostatic interaction between positively charged 3,4‐ethylenedioxythiophene cation radicals and negatively charged sulfonated graphene (SG) sheets, we prepared a poly(3,4‐ethylenedioxythiophene)‐sulfonated graphene (SG‐PEDOT) composite film by a one‐step electrochemical process. The composite was further decorated with gold nanoparticles (AuNPs) and employed as an electrode material for the detection of L ‐cysteine (Cys). The SG‐PEDOT composite film is shown to provide a rough surface for the electrodeposition of AuNPs and to improve substrate accessibility and interaction with Cys. Moreover, the AuNPs‐decorated composite exhibits better electrocatalytic performance than that of a SG‐PEDOT composite only. Under optimum experimental conditions, the amperometric current of the sensor is linearly related to the concentration of Cys in the 0.1 to 382 µM range, and the detection limit is 0.02 µM (at S/N=3). The modified electrode displays favorable selectivity, good stability and high reproducibility. The method was successfully applied to the detection of Cys in spiked human urine. 相似文献
993.
Xiaolin Qiu Lixin Lu Zhixiong Zhang Guoyi Tang Guolin Song 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1441-1449
This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n-octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g?1) and crystallization (94.8 J g?1) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/n-octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n-octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential. 相似文献
994.
Shuhua Liu Lu Wang Yuxin Gao Baoying Yu Yun Bai 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1483-1492
The hydration properties of slag sulfate cement (SSC), slag Portland cement (PSC), and ordinary Portland cement (POC) were compared in this study by determining the compressive strength of pastes, the hydration heat of binders within 72 h, the pore structure, the hydration products, and the hydration degree. The results indicated that main hydration products of PSC paste and POC paste are calcium hydroxide and C–S–H gel, while those of SSC paste are ettringite and C–S–H gel from the analyses of XRD, TG–DTA, and SEM. At the early curing age, the compressive strength depends on the clinker content in the cementitious system, while at the late curing age, which is related to the potential reactivity of slag. From hydration heat analysis, the cumulative hydration heat of PSC is lower than that of POC, but higher than that of SSC. Slag can limit chemical reaction and the delayed coagulation of gypsum, which also plays a role in the early hydration. So SSC shows the lowest heat release and slag can’t be simulated without a suitable alkaline solution. Based on MIP analysis, the porosity of POC paste is the smallest while the average pore size is the biggest. At the age of 90 days, the compressive strength of SSC can get higher development because of its relative smaller pore size than that of PSC and POC paste. 相似文献
995.
Lu Tian Arash Tahmasebi Jianglong Yu 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1577-1584
Thermal decomposition of magnesite is investigated by using a TG–MS. Different kinetic methods including Coats–Redfern, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose are used to investigate the thermal decomposition kinetics of magnesite. It was observed that the activation energy values obtained by these methods are similar. The average apparent activation energy is found to be about 203 kJ mol?1. The raw magnesite and its decomposition products obtained at different temperatures are analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The concentration of functional groups, crystal structure and composition, and apparent morphology of decomposition products were studied in detail. The FTIR, XRD, and SEM analyses showed that magnesite was completely decomposed at 973 K to form MgO. 相似文献
996.
Spectroscopic and Computational Study of a Nonheme Iron Nitrosyl Center in a Biosynthetic Model of Nitric Oxide Reductase 下载免费PDF全文
Dr. Saumen Chakraborty Julian Reed Matthew Ross Dr. Mark J. Nilges Igor D. Petrik Dr. Soumya Ghosh Prof. Dr. Sharon Hammes‐Schiffer Prof. Dr. J. Timothy Sage Prof. Dr. Yong Zhang Prof. Dr. Charles E. Schulz Prof. Dr. Yi Lu 《Angewandte Chemie (International ed. in English)》2014,53(9):2417-2421
A major barrier to understanding the mechanism of nitric oxide reductases (NORs) is the lack of a selective probe of NO binding to the nonheme FeB center. By replacing the heme in a biosynthetic model of NORs, which structurally and functionally mimics NORs, with isostructural ZnPP, the electronic structure and functional properties of the FeB nitrosyl complex was probed. This approach allowed observation of the first S=3/2 nonheme {FeNO}7 complex in a protein‐based model system of NOR. Detailed spectroscopic and computational studies show that the electronic state of the {FeNO}7 complex is best described as a high spin ferrous iron (S=2) antiferromagnetically coupled to an NO radical (S= 1/2) [Fe2+‐NO.]. The radical nature of the FeB‐bound NO would facilitate N? N bond formation by radical coupling with the heme‐bound NO. This finding, therefore, supports the proposed trans mechanism of NO reduction by NORs. 相似文献
997.
Shih-I Lu 《Theoretical chemistry accounts》2014,133(2):1-7
A comparison is presented of uncontracted multireference singles and doubles configuration interaction (MRCI) and internally contracted MRCI potential energy surfaces for the reaction ${\text{H}}\left( {^{2} {\text{S}}} \right) + {\text{O}}_{2} \left( {^{3} \sum\nolimits_{g}^{ - } {} } \right) \to {\text{HO}}_{2} \left( {^{2} {\text{A}}^{{\prime \prime }} } \right)$ . It is found that internal contraction leads to significant differences in the reaction kinetics relative to the uncontracted calculations. 相似文献
998.
Visible‐Light‐Induced CS Bond Activation: Facile Access to 1,4‐Diketones from β‐Ketosulfones 下载免费PDF全文
Jun Xuan Zhu‐Jia Feng Prof. Dr. Jia‐Rong Chen Dr. Liang‐Qiu Lu Prof. Dr. Wen‐Jing Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(11):3045-3049
A novel method for the synthesis of 1,4‐diketones from β‐ketosulfones was developed by means of a visible light‐induced C?S bond activation process. Symmetrical and unsymmetrical 1,4‐diketones can be easily prepared in moderate to good yields. 相似文献
999.
Control of Chiral Nanostructures by Self‐Assembly of Designed Amphiphilic Peptides and Silica Biomineralization 下载免费PDF全文
Zhehao Huang Dr. Yuan Yao Dr. Lu Han Prof. Shunai Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):17068-17076
Peptides, the fundamental building units of biological systems, are chiral in molecular scale as well as in spatial conformation. Shells are exquisite examples of well‐defined chiral structures produced by natural biomineralization. However, the fundamental mechanism of chirality expressed in biological organisms remains unclear. Here, we present a system that mimics natural biomineralization and produces enantiopure chiral inorganic materials with controllable helicity. By tuning the hydrophilicity of the amphiphilic peptides, the chiral morphologies and mesostructures can be changed. With decreasing hydrophilicity of the amphiphilic peptides, we observed that the nanostructures changed from twisted nanofibers with a hexagonal mesostructure to twisted nanoribbons with a lamellar mesostructure, and the extent of the helicity decreased. Defining the mechanism of chiral inorganic materials formed from peptides by noncovalent interactions can improve strategies toward the bottom‐up synthesis of nanomaterials as well as in the field of bioengineering. 相似文献
1000.
Highly Enantioselective Catalytic System for Asymmetric Copolymerization of Carbon Dioxide and Cyclohexene Oxide 下载免费PDF全文
Yuan‐Zhao Hua Liu‐Jie Lu Pei‐Jin Huang Dong‐Hui Wei Prof. Ming‐Sheng Tang Prof. Dr. Min‐Can Wang Prof. Dr. Jun‐Biao Chang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12394-12398
A new ligand can be easily prepared, and its intramolecular dinuclear zinc complexes act as a high performance catalyst for the asymmetric alternating copolymerization of cyclohexene oxide and CO2 under very mild conditions (1 atm CO2, room temperature), affording completely alternating polycarbonates with up to 93.8 % enantiomeric excess (ee) and 98 % yield. A high Mn value of 28 600 and a relatively narrow polydispersity (Mw/Mn ratio) of 1.43 were also achieved. 相似文献