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Multiwavelength study of nearly face-on low surface brightness disk galaxies

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Research in Astronomy and Astrophysics 2010年第12期10卷 1223-1241页

作者： Dong Gao Yan-Chun Liang Shun-Fang Liu Guo-Hu Zhong Xiao-Yan Chen Yan-Bin Yang Francois Hammer Guo-Chao Yang Li-Cai Deng Jing-Yao Hu National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China ycliang @ nao. cas. cn dgao @ nao. cas. cn Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China GEPI Observatoire de Paris-Meudon 92195 Meudon France Department of Physics Hebei Normal University Shijiazhuang 050016 China

We study the ages of a large sample （1802） of nearly face-on disk low surface brightness galaxies （LSBGs） using the evolutionary population synthesis （EPS） model PEGASE with an exponentially decreasing star formation rate to fit their mul- tiwavelength spectral energy distributions （SEDs） from far-ultraviolet （FUV） to nearinfrared （NIR）. The derived ages of LSBGs are 1-5 Gyr for most of the sample no matter if constant or varying dust extinction is adopted, which are similar to most of the previous studies on smaller samples. This means that these LSBGs formed the majority of their stars quite recently. However, a small part of the sample （~2%-3%） has larger ages of 5-8 Gyr, meaning their major star forming process may have occurred earlier. At the same time, a large sample （5886） of high surface brightness galaxies （HSBGs） are selected and studied using the same method for comparisons. The de- rived ages are 1-5 Gyr for most of the sample （97%） as well. These results probably mean that these LSBGs have not much different star formation histories from their HSBGs counterparts. However, we should notice that the HSBGs are generally about 0.2 Gyr younger, which could mean that the HSBGs may have undergone more recent star forming activities than the LSBGs.

关键词： galaxies: evolution -- galaxies: formation -- galaxies: photometry --galaxies: spiral -- galaxies: statistics -- ultraviolet: galaxies

Manipulating Crystal Growth and Secondary Phase PbI_(2)to Enable Efficient and Stable Perovskite Solar Cells with Natural Additives

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Nano-Micro Letters 2024年第9期16卷 432-448页

作者： Yirong Wang Yaohui Cheng Chunchun Yin Jinming Zhang Jingxuan You Jizheng Wang Jinfeng Wang Jun Zhang Institute of Chemistry Chinese Academy of Sciences(CAS)Beijing 100190People’s Republic of China University of Chinese Academy of Sciences Beijing 100049People’s Republic of China Nanjing University Nanjing 210023People’s Republic of China Wuhan Textile University Wuhan 430200People’s Republic of China

In perovskite solar cells(PSCs),the inherent defects of perovskite film and the random distribution of excess lead iodide(PbI_(2))prevent the improvement of efficiency and ***,natural cellulose is used as the raw material to design a series of cellulose derivatives for perovskite crystallization *** cationic cellulose derivative C-Im-cn with cyano-imidazolium(Im-cn)cation and chloride anion prominently promotes the crystallization process,grain growth,and directional orientation of ***,excess PbI_(2)is transferred to the surface of perovskite grains or formed plate-like crystallites in local *** effects result in suppressing defect formation,decreasing grain boundaries,enhancing carrier extraction,inhibiting non-radiative recombination,and dramatically prolonging carrier ***,the PSCs exhibit a high power conversion efficiency of 24.71%.Moreover,C-Im-cn has multiple interaction sites and polymer skeleton,so the unencapsulated PSCs maintain above 91.3%of their initial efficiencies after 3000 h of continuous operation in a conventional air atmosphere and have good stability under high humidity *** utilization of biopolymers with excellent structure-designability to manage the perovskite opens a state-of-the-art avenue for manufacturing and improving PSCs.

关键词： Perovskite Solar cells Defect passivation Biomass additives Crystal orientation

Heteroatom Structural Engineering Enables Ethenylene-Bridged Bisisoindigo-Based Copolymers to Exhibit Unique n-Type Transistor Performance

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CCS Chemistry 2024年第2期6卷 473-486页

作者： Yuchai Pan Weifeng Zhang Yankai Zhou Xuyang Wei Hao Luo Jinbei Wei Liping Wang Gui Yu Beijing National Laboratory for Molecular Sciences CAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190 School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049 School of Material Science and Engineering University of Science and Technology BeijingBeijing 100083

Herein,we report three novel electron-deficient aromatics,ethenylene-bridged bisisoindigos 3,3′-((3E,3′E)-((E)-ethene-1,2-diyl)bis(1-(4-decyltetradecyl)-2-oxoind-oline-6-yl-3-ylidene))bis(1-(4-decyltetradecyl)-1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one)(NCcn),3,3′-((3E,3′E)-((E)-ethene-1,2-diyl)bis(1-(4-decyltetradecyl)-7-fluoro-2-oxoindoline-6-yl-3-ylidene))bis(1-(4-decyltetradecyl)-1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one)(NFFN),and(3E,3″E)-6,6″-((E)-ethene-1,2-diyl)bis(1,1′-bis(4-decyltetradecyl)-[3,3′-bipyrrolo[2,3-b]pyridinylidene]-2,2′(1H,1′H)-dione)(NNNN),and their derived donor–acceptor(D–A)copolymers,namely poly[3,3′-((3E,3′E)-((E)-ethene-1,2-diyl)bis(1-(4-decyltetradecyl)-2-oxoindoline-6-yl-3-ylidene))bis(1-(4-decyltetradecyl)-1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one-6-yl)]-alt-[5,6-difluoro-4,7-di[(thiophen-2-yl)-5-yl)]benzo[c][1,2,5]thiadiazole](PNCcn-FBT),poly[3,3′-((3E,3′E)-((E)-ethene-1,2-diyl)bis(1-(4-decyltetradecyl)-7-fluoro-2-oxoindoline-6-yl-3-ylidene))bis(1-(4-decyltetradecyl)-1,3-dihydro-2H-pyrrolo[2,3-b]pyridin-2-one-6-yl)]-alt-[5,6-difluoro-4,7-di[(thiophen-2-yl)-5-yl)]benzo[c][1,2,5]thiadiazole](PNFFNFBT),and poly[(3E,3″E)-6′,6‴-((E)-ethene-1,2-diyl)bis(1,1′-bis(4-decyltetradecyl)-[3,3′-bipyrrolo[2,3-b]pyridinylidene]-2,2′(1H,1′H)-dione-6-yl)]-alt-[5,6-difluoro-4,7-di[(thiophen-2-yl)-5-yl)]benzo[c][1,2,5]thiadiazole](PNNNN-FBT),in which 5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole(FBT)acts as the electron-donating *** ethenylene-bridging unit reduces the steric hindrance of the three *** of heteroatoms,such as fluorine and sp2-nitrogen atoms,endows them with multiple CH···F,CH···N,and N···S intramolecular hydrogen bonds/nonbinding interactions,resulting in increasing backbone planarity from NCcn,NFFN,to NNNN,and thus from PNCcn-FBT,PNFFN-FBT,to *** found that all copolymers formed an improved molecular packing in the 1-chloronaphthalene(cn)-processed thin film compared with the 1,2-d

关键词： D-A copolymers bisisoindigos heteroatom structural engineering n-type field-effect transistors electron mobilities

Scintillation Dynamic Spectra and Transverse Velocities ofSeven Pulsars

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Chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 421-432页

作者： NaWang Xin－JiWu 等 UrumqiAstronomicalObservatory NAO－CASUrumqi830011 DepartmentofAstronomy PekingUniversityBeijing1008

Using a pulsar timing system developed at Urumqi Astronomical Observatory's 25-m telescope, we observed scintillation dynamic spectra for seven pulsars at the relatively high frequency of 1540 MHz over a wide frequency band of 320 MHz. Averaging observations at different epochs, we obtain time scales and decorrelation bandwidths for diffractive scintillation and show that these imply a power-law index for the electron density fluctuation close to 4.0. Assuming this value and that the scattering disk is approximately midway between the pulsar and the earth, we compute transverse velocities for the seven pulsars. These values are generally in good agreement with the proper motion velocities.

关键词： pulsars: general ISM: general

Bonding Interaction of Adjacent Pt and Ag Single-Atom Pairs on Carbon Nitride Efficiently Promotes Photocatalytic H_(2)Production

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CCS Chemistry 2024年第6期6卷 1523-1534页

作者： Guanchao Wang Chaofan Zhang Wantong Zhao Baojun Wang Yuefeng Liu Ting Zhang Wenguang Cui Riguang Zhang Zhongkui Zhao State Key Laboratory of Fine Chemicals Department of Catalysis Chemistry and EngineeringSchool of Chemical EngineeringDalian University of TechnologyDalian 116024 State Key Laboratory of Clean and Efficient Coal Utilization College of Chemical Engineering and TechnologyTaiyuan University of TechnologyTaiyuan 030024 Dalian National Laboratory for Clean Energy Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023 cas.Key Laboratory of Bio-Based Materials Qingdao Institute of Bioenergy and Bioprocess TechnologyChinese Academy of SciencesQingdao 266101 College of Chemical Engineering Shijiazhuang UniversityShijiazhuang 050035

Dual-atom catalysts(DACs)represent an exciting advance in the field of heterogeneous *** not only retain the beneficial characteristics of single-atom catalysts(SACs),but they also harness the synergistic effects that arise from the proximity of neighboring single-metal ***,the fabrication of heteronuclear dual-atom metals positioned adjacently for use in photocatalysis remains a significant ***,we report the atomically dispersed adjacent Pt-Ag dual-atom pairs on carbon nitride(Pt1Ag1-a/cn)by a facile hydrogen-bonding assembly strategy via pyrolysis of the hydrogen-bonding supramolecule containing melamine-Ag and cyanuric acid-Pt complexes on carbon nitride(cn),through which the light absorption depressed by deposited carbonaceous materials during the preparation of dual-atom metals via a traditional method like the pyrolysis of the metal-organic *** to the synergism achieved by the bonding interaction of adjacent Pt and Ag single-atom pairs,the developed Pt1Ag1-a/cn with 0.21%Pt loading shows a high turnover frequency(TOF)of 1115 h^(−1)with a H_(2)evolution rate(HER)of 12,000μmol g^(−1)h^(−1)for photocatalytic water splitting under simulated solar light irradiation(325 h^(−1)of TOF with 3480μmol g^(−1)h^(−1)of HER under visible light irradiation).This strategy outperforms the previously reported SACs on cn-based *** functional theory(DFT)calculations demonstrate that the adjacent Ag atom acts as a coordination atom to effectively regulate the electronic structure of the Pt atom and thus brings the d-band center of Pt close to the Fermi energy level,which is beneficial for the H_(2)*** work presents a facile and general strategy for designing diverse adjacent diatomic cocatalysts in photocatalysis without depressing light absorption by the deposited carbon during the DAC preparation via previously reported methods.

关键词： dual-atom metal catalysts synergistic effect graphitic carbon nitride hydrogen evolution photocatalysis

Metal organic polymers with dual catalytic sites for oxygen reduction and oxygen evolution reactions

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Carbon Energy 2023年第5期5卷 127-137页

作者： Sijia Liu Minghao Liu Xuewen Li Shuai Yang Qiyang Miao Qing Xu Gaofeng Zeng cas.Key Laboratory of Low-Carbon Conversion Science and Engineering Shanghai Advanced Research Institute(SARI)Chinese Academy of Sciences(CAS)ShanghaiChina School of Physical Science and Technology ShanghaiTech UniversityShanghaiChina School of Chemical Engineering University of Chinese Academy of SciencesBeijingChina

Metal-organic frameworks and covalent organic frameworks have been widely employed in electrochemical catalysis owing to their designable skeletons,controllable porosities,and well-defined catalytic ***,the poor chemical stability and low electron conductivity limited their activity,and single-functional sites in these frameworks hindered them to show multifunctional roles in catalytic ***,we have constructed novel metal organic polymers(Co-HAT-cn and Ni-HAT-cn)with dual catalytic centers(metal-N_(4) and metal-N_(2))to catalyze oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).By using different metal centers,the catalytic activity and selectivity were *** them,Co-HAT-cn catalyzed the ORR in a 4e^(-)pathway,with a half-wave potential of 0.8 V versus RHE,while the Ni-HAT-cn catalyze ORR in a 2e^(-)pathway with H_(2)O_(2) selectivity over 90%.Moreover,the Co-HAT-cn delivered an overpotential of 350 mV at 10 mA cm^(-2) with a corresponding Tafel slope of 24 mV dec^(-1) for OER in a 1.0 M KOH aqueous *** experimental results revealed that the activities toward ORR were due to the M-N_(4) sites in the frameworks,and both M-N_(4) and M-N_(2) sites contributed to the *** work gives us a new platform to construct bifunctional catalysts.

关键词： covalent organic frameworks metal organic polymers oxygen evolution reaction oxygen reduction reaction single atom catalysts

Driving factors behind multiple populations

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Science China(Physics,Mechanics & Astronomy) 2024年第5期67卷 172-181页

作者： Ruoyun Huang Baitian Tang Chengyuan Li Doug Geisler Mario Mateo Ying-Yi Song Holger Baumgardt Julio A.Carballo-Bello Yue Wang Jundan Nie Bruno Dias JoséG.Fernández-Trincado School of Physics and Astronomy Sun Yat-sen UniversityZhuhai 519082China CSST Science Center for the Guangdong-Hong Kong-Macao Greater Bay Area Zhuhai 519082China Departamento de Astronomía Universidad de ConcepcionConcepcionChile Instituto de Investigación Multidisciplinario en Ciencia y Tecnología Universidad de La SerenaLa SerenaChile Departamento de Astronomía Facultad de CienciasUniversidad de La SerenaChile Department of Astronomy University of MichiganAnn Arbor 48109USA David A.Dunlap Department of Astronomy&Astrophysics University of TorontoToronto ON M5S 3H4Canada Dunlap Institute for Astronomy&Astrophysics University of TorontoToronto ON M5S 3H4Canada School of Mathematics and Physics The University of QueenslandSt.Lucia QLD 4072Australia Instituto de Alta Investigación Universidad de TarapacáAricaChile cas.Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Instituto de Astrofísica Departamento de Ciencias FísicasFacultad de Ciencias ExactasUniversidad Andres BelloSantiagoChile Instituto de Astronomía Universidad Católica del NorteAntofagastaChile

Star clusters were historically considered simple stellar populations,with all stars sharing the same age and initial chemical ***,the presence of chemical anomalies in globular clusters(GCs),called multiple stellar populations(MPs),has challenged star formation theories in dense *** studies show that mass,metallicity,and age are likely controlling parameters for the manifestation of *** the limit between clusters with/without MPs in physical parameter space is crucial to reveal the driving mechanism behind their *** this study,we look for MP signals in Whiting 1,which is traditionally considered a young *** the Magellan telescope,we obtained low-resolution spectra withinλλ=3850-5500?for eight giants of Whiting *** measured the C and N abundances from the cn and CH spectral indices.C and N abundances have variations comparable with their measurement errors(~0.1 dex),suggesting that MPs are absent from Whiting *** these findings with literature studies,we propose a limit in the metallicity *** compactness index parameter space,which relatively clearly separates star clusters with/without MPs(GCs/open clusters).This limit is physically *** a larger scale,the galactic environment determines cluster compactness and metallicity,leading to metal-rich,diffuse,old clusters formed ex *** proposed limit also impacts our understanding of the formation of the Sagittarius dwarf galaxy:star clusters formed after the first starburst(age≤8-10 Gyr).These clusters are simple stellar populations because the enriched galactic environment is no longer suitable for MP formation.

关键词： stellar galactic galaxy

Defect-rich ultrathin poly-heptazine-imide-framework nanosheets with alkali-ion doping for photocatalytic solar hydrogen and selective benzylamine oxidation

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Nano Research 2022年第10期15卷 8760-8770页

作者： Chaofeng Zhu Xiao Luo Congyan Liu Yang Wang Xihai Chen Yan Wang Qing Hu Xiaojun Wu Bo Liu School of Chemistry and Materials Science University of Science and Technology of ChinaHefei 230026China Synergetic Innovation of Quantum Information&Quantum Technology CAS Key Laboratory of Materials for Energy Conversionand CAS Center for Excellence in NanoscienceSchool of Chemistry and Materials SciencesUniversity of Science and Technology of ChinaHefei 230026China Max Planck Institute of Colloids and Interfaces Am Mühlenberg 114476 PotsdamGermany

Polymeric carbon nitride(cn)as a metal-free photocatalyst holds great promise to produce high-value chemicals and H_(2) fuel utilizing clean solar ***,the wider deployment of pristine cn is critically hampered by the poor charge carrier transport and high ***,we develop a facile salt template-assisted interfacial polymerization strategy that insitu introduces alkali ions(Na+,K+)and nitrogen defects in cn(denoted as v-cn-KNa)to simultaneously promote charge separation and transportation and steer photoexcited holes and electrons to their oxidation and reduction *** photocatalyst exhibits an impressive photocatalytic H_(2) evolution rate of 8641.5μmol·g^(−1)·h^(−1)(33-fold higher than pristine cn)and also works readily in real seawater(10752.0μmol·g^(−1)·h^(−1))with a high apparent quantum efficiency up to 18.5%at 420 *** addition,we further demonstrate that the v-cn-KNa can simultaneously produce H_(2) and N-benzylidenebenzylamine without using any other sacrificial *** situ characterizations and DFT calculations reveal that the alkali ions notably promote charge transport,while the nitrogen defects generate abundant edge active sites,which further contribute to efficient electron excitation to trigger photoredox reactions.

关键词： carbon nitride photocatalysis alkali ion doping hydrogen production amine oxidative coupling

Eutectic high entropy alloy syntactic foam

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Journal of Materials Science & Technology 2023年第18期149卷 177-189页

作者： Jin Meng Yu Qiao Tian-Wei Liu Yuan-Yuan Tan Fu-Hua Cao Yan Chen Hai-Ying Wang Lan-Hong Dai State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of Sciences(CAS)Beijing 100190China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China cas.Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei 230027China

High-strength metallic foams have a wide range of applications in engineering as lightweight structural and energy-absorbing ***,it is challenging to obtain metallic foam with both good energy absorption performance and high ***,we developed a novel metal matrix syntactic foam fabri-cated with AlCoCrFeNi_(2.1) eutectic high entropy alloy and alumina cenospheres that exhibits a remarkable combination of high strength and energy absorption performance under both quasi-static and dynamic *** porous structure of syntactic foam fully exploits the properties of the AlCoCrFeNi_(2.1) alloy matrix with a unique FCC/B2 dual-phase eutectic microstructure and thus yields exceptional *** discovered that this dual-phase microstructure not only provides high strength but also allows the pores to collapse in a progressive and diffusive way,which enables the formation of a high and smooth energy absorption *** is found that the heterogeneity between the two phases in the matrix can provide back stress strengthening,and it also induces multiple micro shear bands and microcracks as additional energy dissipation modes as the deformation *** unique mechanism ensures the strength of microstructures and makes them fracture promptly,which causes the balance of strengthening and softening on the macro *** work opens the avenue for developing advanced high-strength lightweight structural and energy-absorbing materials.

关键词： Eutectic high entropy alloy Foams Metal matrix composites(MMCs) Energy absorption