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高红移Lyman Break星系 被引量:1
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作者 束成钢 姜佩芳 《天文学进展》 CSCD 北大核心 2002年第2期190-199,共10页
总结了到目前为止用所谓 Lyman Break方法(亦称为UV drop 方法)观测得到的高红移(z≈3)Lyman break星系的观测特征,包括光度函数、半光度半径分布、空间密度及成团性、恒星速度弥散、超星风及大尺度气体团块运动和金属丰度等。还对其目... 总结了到目前为止用所谓 Lyman Break方法(亦称为UV drop 方法)观测得到的高红移(z≈3)Lyman break星系的观测特征,包括光度函数、半光度半径分布、空间密度及成团性、恒星速度弥散、超星风及大尺度气体团块运动和金属丰度等。还对其目前的理论工作做了综合介绍,对当前两种主要模型进行了评述并提出了作者的个人观点。 展开更多
关键词 LymanBreak星系 星系形成 高红移亮星系 光度函度 空间密度 恒星 超星风 成团性
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大尺度天区上的类星体观测(英文)
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作者 何香涛 《北京师范大学学报(自然科学版)》 CAS CSCD 1992年第1期61-66,共6页
评述了目前巡天观测技术的进展情况.讨论了类星体的成团性和红移极限,以及室女座星系团区内的最新观测结果.
关键词 类星体 成团性 红移极限
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红移z≈1极红天体的研究进展
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作者 方官文 汪敏 +2 位作者 马仲阳 陈洋 孔旭 《天文学进展》 CSCD 北大核心 2015年第1期44-58,共15页
极红天体(EROs)是指利用光学和近红外两个波段的色指数(如I-K>4 mag)挑选出来的一类星系。研究表明极红天体可分为两类:一类是被大量尘埃红化的高红移恒星形成星系,主要是较年轻的旋涡或不规则星系,有恒星正在形成,称为DGs;另一类是... 极红天体(EROs)是指利用光学和近红外两个波段的色指数(如I-K>4 mag)挑选出来的一类星系。研究表明极红天体可分为两类:一类是被大量尘埃红化的高红移恒星形成星系,主要是较年轻的旋涡或不规则星系,有恒星正在形成,称为DGs;另一类是由年老星族(≥1 Ga)主导的高红移椭圆星系,基本上没有或仅有弱的恒星形成,简称为OGs。极红天体中这两种不同类型的星系,很可能是近邻大质量星系的前身星系,只是分别代表着不同的形成历史。介绍了不同类型极红天体的各种物理性质的研究进展,如形态和结构、光谱特征、成团性、红移分布和星系计数等,以及阐述了该领域未来的研究方向。 展开更多
关键词 高红移星系 星系形态 星系光谱 星系成团性
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红移z≈2极亮红外星系的研究进展
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作者 方官文 林泽森 孔旭 《天文学进展》 CSCD 北大核心 2017年第1期16-34,共19页
极亮红外星系(ULIRGs)是指红外(IR,8~1000μm)光度L_(IR)>10^(12)L_⊙的一类星系。研究表明,红移z≈2处极亮红外星系是大质量(M_*>10^(11)M_⊙)、富尘埃和强恒星形成(大于100 M_⊙·a^(-1))的特殊星系。极亮红外星系可分成活... 极亮红外星系(ULIRGs)是指红外(IR,8~1000μm)光度L_(IR)>10^(12)L_⊙的一类星系。研究表明,红移z≈2处极亮红外星系是大质量(M_*>10^(11)M_⊙)、富尘埃和强恒星形成(大于100 M_⊙·a^(-1))的特殊星系。极亮红外星系可分成活动星系核起主导作用的源和恒星形成占主导的星系。恒星形成主导的源,中红外光谱有明显的多环芳香烃辐射;而活动星系核主导的星系,光谱呈现出幂律形式并有很强的硅线吸收。极亮红外星系的静止光学波段形态存在多样化,既有并合结构特征,又有椭圆形态。这类星系很可能是近邻大质量宁静星系的前身星系。介绍了红移z=2附近极亮红外星系的各种物理性质的研究进展,如形态和结构、光谱特征、成团性、尘埃分布和形成机制等,以及阐述了该领域未来的研究方向。 展开更多
关键词 高红移星系 星系观测 星系形态 星系光谱 星系成团性
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Synthesis of a novel organic nonlinear optical chromophore and the Testing for μ_gβ Value 被引量:1
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作者 HAN Li-kun JIANG Ya-dong LI Wei CAI Yuan 《Optoelectronics Letters》 EI 2007年第1期50-53,共4页
A novel second-order nonlinear optical chromophore (DCDHF-2-V) was synthesized from 3-Hydroxy-3-methyl-2-butanae, propanedinitrile and 4-diethylaminobenzaldehyde by aldol condensation reaction. Molecular structural ... A novel second-order nonlinear optical chromophore (DCDHF-2-V) was synthesized from 3-Hydroxy-3-methyl-2-butanae, propanedinitrile and 4-diethylaminobenzaldehyde by aldol condensation reaction. Molecular structural characterization was investigated by elemental analysis, FTIR, and 1H-NMR spectra. The melting point obtained from DSC thermogram was almost 251 ℃, and the compound shows a thermal stability up to 270 ℃. Second-order NLO properties of the chromophore were measured by solvatochromic method. From the quantum-mechanical two-level model, it can be obtained that the μgβ value of DCDHF-2-V is 6520×10^-48esu atthe wavelength of 1064 nm. 展开更多
关键词 有机非线光学发色团 合成 μgβ值 测试 热稳定
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Formation and Water Stability of Aggregates in Red Soils as Affected by Organic Matter 被引量:39
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作者 ZHANG MINGKUI HE ZHENLI +1 位作者 CHEN GUOCHAO HUANG CHANGYONGI andM. J. WILSON ̄2( ̄1DePartment of Land Use and Applied Chemistry, Zhejiang Agricultural University, Hangzhou 31O029(China))( ̄2Soils and Soil Microbiology Division, Macaulay Land Use Research Inst 《Pedosphere》 SCIE CAS CSCD 1996年第1期39-45,共7页
The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studi... The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studied. The results showed that the water stability of soil aggregates declined with increasing size, especially for the low organic matter soils. Organic matter plays a key role in the formation of water-stable soil aggregates. The larger the soil aggregate size, the greater the impact of organic matter on the water stability of soil aggregates. Removal of organic matter markedly disintegrated the large water-stable aggregates (> 2.0 mm) and increased the small ones (< 0.25-0.smm) to some extent, whereas removal of free iron(aluminium) oxides considerably destroyed aggregates of all sizes, especially the < 0.25-0.5 mm classes. The contents of organic matter in water-stable aggregates increased with aggregate sizes. It is concluded from this study that small water-stable aggregates (< 0.25-0.5 mm) were chiefly cemented by Fe and Al oxides whilst the large ones (> 2.0 mm) were mainly glued up by organic matter. Both free oxides and organic matter contribute to the formation and water stability of aggregates in red soils. 展开更多
关键词 AGGREGATE free oxides organic matter red soil water stability
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Small-sized cuprous oxide species on silica boost acrolein formation via selective oxidation of propylene 被引量:2
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作者 Ling-Ling Guo Jing Yu +6 位作者 Wei-Wei Wang Jia-Xu Liu Hong-Chen Guo Chao Ma Chun-Jiang Jia Jun-Xiang Chen Rui Si 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 2021年第2期320-333,共14页
Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for the... Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation.Nevertheless,the elucidation of the structure-performance relationships for these systems remains a scientific challenge.In this work,copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity(up to 25.5%conversion and 66.8%selectivity)in the propylene-selective oxidation of acrolein at 300℃.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide(CuO)clusters into cuprous oxide(Cu2O)clusters.With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy(DB-FTIR),the allyl intermediate(CH2=CHCH2*)was clearly observed,along with the as-formed Cu2O species.The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process,and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene. 展开更多
关键词 Propylene selective oxidation Cuprous oxide cluster Acrolein formation Active species In situ characterization
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Post-synthesis modification of porous organic polymers with amine: a task-specific microenvironment for CO2 capture 被引量:2
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作者 Yankai Li Li Yang +2 位作者 Xiang Zhu Jun Hu Honglai Liu 《International Journal of Coal Science & Technology》 EI 2017年第1期50-59,共10页
A porous organic polymer named FC-POP was facilely synthesized with extraordinary porosity and excellent stability. Further covalent incorporation of various amines including single amine group, multi-amine groups of ... A porous organic polymer named FC-POP was facilely synthesized with extraordinary porosity and excellent stability. Further covalent incorporation of various amines including single amine group, multi-amine groups of diethylenediamine (DETA), and poly-amine groups of polyethylenimine (PEI) to the network gave rise to task-specific modification of the microenvironments to make them more suitable for CO2 capture. As a result, significant boost of CO2 adsorption capacity of 4.5 mmol/g (for FC-POP-CH2DETA, 273 K, 1 bar) and the CO2/N2 selectivity of 736.1 (for FC- POP-CH2PEI) were observed after the post-synthesis amine modifications. Furthermore, these materials can be regener- ated in elevated temperature under vacuum without apparent loss of CO2 adsorption capacity. 展开更多
关键词 Porous organic polymers Friedel-Crafts alkylation Post-synthesis Amine modification CO2 capture
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酶法改性对玉米粉中蛋白结构变化的研究 被引量:3
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作者 孙步云 林子木 +3 位作者 杨强 郑爽 李新华 祁冰 《现代食品科技》 EI CAS 北大核心 2016年第11期235-240,161,共7页
本文采用SDS-PAGE凝胶电泳比较了3种酶改性玉米粉及未处理玉米粉中醇溶蛋白和谷蛋白亚基组成的差异,并对谷蛋白亚基分子量进行了分析;采用傅里叶红外光谱(FT-IR)研究了酶改性过程中谷蛋白二级结构的变化。结果表明:酶法改性对玉米谷蛋... 本文采用SDS-PAGE凝胶电泳比较了3种酶改性玉米粉及未处理玉米粉中醇溶蛋白和谷蛋白亚基组成的差异,并对谷蛋白亚基分子量进行了分析;采用傅里叶红外光谱(FT-IR)研究了酶改性过程中谷蛋白二级结构的变化。结果表明:酶法改性对玉米谷蛋白的结构产生了较大影响,而对醇溶蛋白的影响较小;α-淀粉酶与碱性蛋白酶复合处理会产生协同效应,促进玉米谷蛋白的水解,产生大量低分子量亚基;单一酶改性会使玉米谷蛋白结构变得无序,经复合酶处理后,α-螺旋比例最高,结构趋于稳定。以上结果说明,酶法改性过程中,谷蛋白结构的变化可能是玉米粉面团成团性改良的一个重要因素。本研究揭示了玉米粉酶法改性工艺的部分作用机理,为玉米面粉面团改性研究及产品研发提供了科学依据。 展开更多
关键词 玉米面粉 蛋白质 结构 成团性
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Syntheses of Two Chiral Clusters [η~5-C_5H_4C(NR)CH_3]- RuNiM(CO)_5(μ_3-S) (R =NH-C_6H_3-2,4-(NO_2)_2,M=Mo,3;M=W,4) and the Single-crystal Structure of Cluster 3
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作者 边治国 陈玉岗 +1 位作者 殷元骐 李庆山 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2003年第3期301-304,共4页
The new chiral clusters [h5-C5H4C(NR)CH3]RuNiM(CO)5(m3-S) (R = NH-C6H3-2,4- (NO2)2, M = Mo, 3; M = W, 4) were synthesized and the structure of cluster 3 was determined by single-crystal X-ray analysis. Crystal data: C... The new chiral clusters [h5-C5H4C(NR)CH3]RuNiM(CO)5(m3-S) (R = NH-C6H3-2,4- (NO2)2, M = Mo, 3; M = W, 4) were synthesized and the structure of cluster 3 was determined by single-crystal X-ray analysis. Crystal data: C23H16O9N4MoNiRuS, Mr = 780.18, orthorhombic, space group Pbca with the following crystallographic parameters: a = 13.207(4), b = 16.036(5), c = 25.513(8) , Z = 8, V = 5403(3) 3, Dc = 1.918 g/cm3, m = 1.834 mm-1 and F(000) = 3072. The final R = 0.0512 and wR = 0.1132 for 2525 reflections with I > 2.00s(I). 展开更多
关键词 synthesis CHIRAL CLUSTER crystal structure
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Synthesis and Properties of Novel Surface Active Maleic Monomer Containing Phosphate Group
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作者 Mykola Borzenkov Yuri Galadjun +1 位作者 Natalia Mitina Orest Hevus 《Journal of Chemistry and Chemical Engineering》 2014年第5期493-500,共8页
A novel surface active monomer (surfmer) containing poly(ethylene glycol) chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP (N-vinylpyrrolidone) and with ... A novel surface active monomer (surfmer) containing poly(ethylene glycol) chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP (N-vinylpyrrolidone) and with NVP and VEP (5-tert-butylperoxy-5-methyl-2-hexene-3-yne monomer) led to formation of corresponding surface-active copolymers. The capability of application of resulted copolymers as surface active macroinitiators of emulsion polymerization of styrene and as components of polymeric scaffolds was investigated. 展开更多
关键词 Surface active monomers surface tension surface active polymers emulsion polymerization polymeric scaffolds.
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In-situ green synthesis of highly active GSH-capped Pt–Au–Ag-hybrid nanoclusters 被引量:2
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作者 CHEN DongHua GAO ShengPing +2 位作者 UR REHMAN Fawad JIANG Hui WANG XueMei 《Science China Chemistry》 SCIE EI CAS 2014年第11期1532-1537,共6页
Recently much attention has been paid to the application of metal hybrid nanoparticles in industrial catalytic fields because of their super-efficient catalytic activity and attractive properties. We explored a novel ... Recently much attention has been paid to the application of metal hybrid nanoparticles in industrial catalytic fields because of their super-efficient catalytic activity and attractive properties. We explored a novel strategy to prepare GSH-capped Pt–Au–Ag-hybrid nanoclusters through the synergistic effect between ascorbic acid(VC) and glutathione(GSH) with chloroplatinic acid, chloroauric acid, and silver nitrate as precursors. The potential utilization of as-prepared GSH-capped Pt–Au–Aghybrid nanoclusters for catalytic applications has been evaluated through the reduction of 4-nitrophenol(4-NP) with NaBH4; we obtained the kinetic data by monitoring with UV-Vis spectroscopy. Our results illustrate that GSH-capped Pt–Au– Ag-hybrid nanoclusters could facilitate the process of reduction of 4-NP in a way that is unprecedented. This approach may offer a novel, non-cytotoxicity, efficient catalyst for industry. 展开更多
关键词 Pt–Au–Ag-hybrid ascorbic acid glutathione 4-NITROPHENOL catalyst
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Synthesis of β-alkynyl α-amino acids via palladium-catalyzed alkynylation of unactivated C(sp^3)-H bonds 被引量:2
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作者 Bo Wang Gang He Gong Chen 《Science China Chemistry》 SCIE EI CAS CSCD 2015年第8期1345-1348,共4页
β-Di-substituted α-amino acids(AAs) contain adjacent carbon stereogenic centers and pose considerable synthetic challenge. Complementary to the conventional synthesis strategies based on the transformation of existi... β-Di-substituted α-amino acids(AAs) contain adjacent carbon stereogenic centers and pose considerable synthetic challenge. Complementary to the conventional synthesis strategies based on the transformation of existing functional groups, we envisioned these molecules could be quickly accessed via selective functionalization of sp3 hybridized C-H bonds on the side chains of common α-AA precursors. We report a readily applicable method to prepare β-alkynyl α-amino acids via Pd-catalyzed diastereoselective C(sp3)-H alkynylation of common α-amino acids precursors with acetylene bromide. 展开更多
关键词 α-amino acids C-H functionalization PALLADIUM
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