time-of-flight secondary ion mass spectrometry (ToF-SIMS)(fig.S11F)(19)and found higher Cl content in CH 3NH 3PbI 3(Cl)films than in CH 3NH 3PbI 3films without Cl.This technique probes the top 2nm of the film.
Although perovskite solar cells have better ra-diative efficiencies than many other types,such as dye-sensitized,organic,or even cadmium tel-luride solar cells,they still suffer from greater non-radiative losses than inorganic materials such as gallium arsenide and are only at present approach-ing the radiative efficiencies of copper indium gallium selenide (CIGS)(31).Our results identify a subpopulation of dark grains and grain bound-aries as specific targets for perovskite growth and passivation studies,and show that local fluores-cence lifetime imaging provides a route by which changes in film processing can be evaluated to assess their influence on carrier recombination in films.By removing these nonradiative path-ways to obtain uniform brightness with high emissivity across all grains,it is likely that we will see the performance of perovskite devices approach the thermodynamic limits for solar cells and other light-emitting devices.
REFERENCES AND NOTES
1.T.C.Sum,N.Mathews,Energ.Environ.Sci.7,2518–2534(2014).
2.M.A.Green,A.Ho-Baillie,H.J.Snaith,Nat.Photonics 8,
506–514(2014).
3.J.Burschka et al .,Nature 499,316–319(2013).
4.G.E.Eperon,V.M.Burlakov,P.Docampo,A.Goriely,
H.J.Snaith,Adv.Funct.Mater.24,151–157(2014).5.G.Xing et al .,Nat.Mater.13,476–480(2014).
6.G.E.Eperon et al .,Energ.Environ.Sci.7,982–988(2014).
7.J.H.Noh,S.H.Im,J.H.Heo,T.N.Mandal,S.I.Seok,Nano
Lett.13,1764–1769(2013).
8.National Center for Photovoltaics at the National Renewable
Energy Laboratory,Research cell efficiency records,https://www.wendangku.net/doc/6d8379449.html,/ncpv/(accessed 11April 2015).9.S.D.Stranks et al .,Science 342,341–344(2013).10.H.Zhou et al .,Science 345,542–546(2014).
https://www.wendangku.net/doc/6d8379449.html,ler,E.Yablonovitch,S.R.Kurtz,IEEE J.Photovolt.
2,303–311(2012).
12.N.K.Noel et al .,ACS Nano 8,9815–9821(2014).13.J.You et al .,ACS Nano 8,1674–1680(2014).
14.P.W.Liang et al .,Adv.Mater.26,3748–3754(2014).15.S.D.Stranks et al .,Phys.Rev.Appl.2,034007(2014).16.F.Deschler et al .,J.Phys.Chem.Lett.5,1421–1426(2014).17. C.Wehrenfennig,M.Liu,H.J.Snaith,M.B.Johnston,
L.M.Herz,Energ.Environ.Sci.7,2269–2275(2014).18.J.S.Manser,P.V.Kamat,Nat.Photonics 8,737–743
(2014).
19.See the supplementary materials on Science Online.20.G.Xing et al .,Science 342,344–347(2013).
21.Y.Yamada,T.Nakamura,M.Endo,A.Wakamiya,Y.Kanemitsu,
J.Am.Chem.Soc.136,11610–11613(2014).22.M.Saba et al .,https://www.wendangku.net/doc/6d8379449.html,mun.5,5049(2014).23.A.Abate et al .,Nano Lett.14,3247–3254(2014).24.S.Watanabe et al .,Nat.Methods 8,80–84(2011).25.E.Edri et al .,Nano Lett.14,1000–1004(2014).26.W.J.Yin,T.Shi,Y.Yan,Adv.Mater.26,4653–4658
(2014).
27.M.M.Lee,J.Teuscher,T.Miyasaka,T.N.Murakami,
H.J.Snaith,Science 338,643–647(2012).
28.P.Gao,M.Gr?tzel,M.K.Nazeeruddin,Energ.Environ.Sci.
7,2448–2463(2014).
29.K.Munechika et al .,Nano Lett.11,2725–2730(2011).30.X.Wen et al .,J.Phys.Chem.Lett.5,3849–3853(2014)https://www.wendangku.net/doc/6d8379449.html,ingstedt et al .,Sci.Rep.4,6071(2014).
32.S.De Wolf et al .,J.Phys.Chem.Lett.5,1035–1039
(2014).
33.C.H.Seager,Annu.Rev.Mater.Sci.15,271–302(1985).34.J.S.Yun et al .,J.Phys.Chem.Lett.6,875–880(2015).35.Q.Dong et al .,Science 347,967–970(2015).36.W.Nie et al .,Science 347,522–525(2015).37.D.Shi et al .,Science 347,519–522(2015).
38.M.Gr?tzel,Nat.Mater.13,838–842(2014).
39.G.Grancini et al .,J.Phys.Chem.Lett.5,3836–3842
(2014).
40.Y.Tidhar et al .,J.Am.Chem.Soc.136,13249–13256
(2014).
41.S.T.Williams et al .,ACS Nano 8,10640–10654(2014).
ACKNOWLEDGMENTS
This material is based in part on work supported by the State of Washington through the University of Washington Clean Energy Institute.D.W.D.acknowledges support from an NSF Graduate Research Fellowship (DGE-1256082).S.M.V.acknowledges support from a National Defense Science and Engineering Graduate Fellowship.The research leading to these results has received funding from the European Union Seventh Framework Program (FP7/2007-2013)under Grant Agreement No.604032of the MESO project.G.E.E.is supported by the Engineering and Physical Sciences Research Council and Oxford Photovoltaics through a
in Science and Engineering.The authors gratefully acknowledge funding from the National Institute for Biomedical Imaging and Bioengineering (NIH grant EB-002027)supporting the National ESCA and Surface Analysis Center for Biomedical Problems and ToF-SIMS instrumentation.D.W.D.thanks I.Braly,S.Braswell,D.Moerman,and https://www.wendangku.net/doc/6d8379449.html,ler for valuable assistance.S.M.V.gratefully acknowledges D.Graham for assistance with ToF-SIMS.Additional data,including materials,methods,and key controls,are available online as supplementary materials (19).
SUPPLEMENTARY MATERIALS
https://www.wendangku.net/doc/6d8379449.html,/content/348/6235/683/suppl/DC1Materials and Methods Supplementary Text Figs.S1to S11
19December 2014;accepted 14April 2015natural gas,has the highest H-to-C ratio of all hydrocarbons;therefore,it is more environmentally friendly in terms of CO 2emissions than oil or coal-derived fuels.
However,30to 60%of natural gas reserves are classified as “stranded ”because shipping gas is not economical,and the costs of liquefaction or building a pipeline are usually prohibitively high (1–5).The problem of natural gas utilization is ex-acerbated by burning and venting of the associated gas produced in the course of crude oil production at remote locations.Conversion of methane into shippable liquids can solve these problems but remains scientifically challenging (1–3,6–8).
direct methane conversion into liquid aromatic hydrocarbons in a single step (dehydroaromati-zation with the main reaction 6CH 4→C 6H 6+9H 2)using catalysts with Mo nanostructures supported on shape-selective zeolites (2,8–16).This technology offers two advantages over other methane activation chemistries:Complete oxida-tion,as well as explosive combustion,is not possi-ble because of the absence of O 2or other oxidizing reagents,and processing can be performed at remote locations because no reagents are needed.The biggest issues in commercialization are rapid catalyst deactivation and comparatively low single-pass conversion levels of ~10%(2,8,13–16).De-velopment of improved catalysts has been hindered by a lack of molecular-level understanding of the identity of the zeolite-supported Mo nanostruc-tures and their structural transformations.
We studied Mo nanostructures supported on ZSM-5zeolites by combining quantum chemical calculations using density functional theory (DFT)with multiple spectroscopic techniques,includ-ing in situ ultraviolet-visible diffuse reflectance
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1
Department of Chemical Engineering and Materials Science,Stevens Institute of Technology,Hoboken,NJ 07030,USA.2
Operando Molecular Spectroscopy and Catalysis Laboratory,Department of Chemical Engineering,Lehigh University,Bethlehem,PA 18015,USA.3Department of Chemical Engineering,National Chung Hsing University,Taichung,Taiwan,Republic of China.
*Corresponding author.E-mail:iew0@https://www.wendangku.net/doc/6d8379449.html, (I.E.W.);simon.podkolzin@https://www.wendangku.net/doc/6d8379449.html, (S.G.P.)
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o n M a y 9, 2015
w w w .s c i e n c e m a g .o r g D o w n l o a d e d f r o m
spectroscopy (UV-vis DRS),in situ infrared (IR)spectroscopy,and operando Raman spectroscopy at elevated reaction temperatures with simulta-neous online mass spectrometry of reaction pro-ducts.We determined the identity and anchoring sites of the initial Mo oxide nanostructures and established structure-activity relationships.The catalytic activity can be fully restored by regener-ating initial Mo oxide nanostructures with a gas-phase O 2treatment.Furthermore,the activity can even be enhanced by controlling the distri-bution of Mo oxide nanostructures by adjusting conditions of such an O 2regeneration treatment.Molybdenum nanostructures supported on ze-olites were initially present in an oxide form after Mo deposition and an oxygen treatment at ele-vated temperatures (our samples were calcined at 773K)(17).The number of MoO x units in an average individual nanostructure was evaluated using the edge energy (E g )of the in situ UV-vis DRS spectra.The E g values for the following well-defined Mo oxide reference compounds are pre-sented in Fig.1A:(i)MoO 6-coordinated Mo 7-Mo 12clusters,(ii)linear chains of alternating MoO 4and MoO 6units,(iii)infinite layered sheets of MoO 5units,(iv)Mo 2O 7dimer as MoO 3-O-MoO 3,(v)iso-lated MoO 4and MoO 6monomers,and (vi)aque-ous molybdate anions as a function of the solution pH (18).The E g values in Fig.1A exhibit a linear correlation with the number of bridging Mo-O-Mo covalent bonds around the central Mo cation and,correspondingly,with the number of MoO x units
in a nanostructure.The E g value for a representa-tive catalyst sample with 2weight percent (wt %)Mo supported on a ZSM-5(Si/Al =15)zeolite,which is the most common zeolite evaluated for methane dehydroaromatization,was 4.8eV,which falls in the range of isolated MoO x nanostructures with a single Mo atom.
The nature of the Mo oxide nanostructures was further examined with in situ Raman spectros-copy by varying the concentration of Mo from 0.7to 3.3wt %on a ZSM-5zeolite support with a constant Si/Al ratio of 15(Fig.1B)and by varying the Si/Al ratio from 15to 140at a constant Mo concentration
of 1.3wt %(Fig.1C).The spectrum for 1.3wt %Mo on ZSM-5with Si/Al =15is shown in both sets in Fig.1,B and C,and a similar spectrum is shown in operando Raman measure-ments with methane flow in fig.S1(17).The ab-sence of sharp Raman bands from crystalline MoO 3nanoparticles (NPs)at 996,815,and 666cm ?1(19)or crystalline Al 2(MoO 4)3at ~1004and 1045cm ?1(18,20)indicates,in agreement with the UV-vis results in Fig.1A,that Mo oxide was completely dispersed;any amorphous Mo oxide species would crystallize at the elevated pretreatment temper-ature of 773K.Some spectra exhibited weak shoulder features at 950cm ?1from Mo oxide species in zeolite framework vacancy defects and at 1026cm ?1from Mo oxide species on extra-framework alumina NPs (17).
For the ZSM-5(Si/Al =15)zeolite in Fig.1B,a single Raman band at 993cm ?1was observed in
the Mo-O stretching region for all Mo concen-trations.However,at higher Si/Al ratios in Fig.1C,a new band at 975cm ?1was observed,and an ad-ditional band appeared at 984cm ?1at the highest Si/Al =140(Fig.1C).These three bands cannot be attributed to a single Mo oxide nanostructure because their relative intensities change with the Si/Al ratio.To determine the identity and anchor-ing sites of these Mo oxide structures in the ZSM-5zeolite framework,various monomeric Mo oxide species were evaluated with DFT calculations,and the calculated normal vibrational modes were compared with the experimental Raman spectra.
After calcination at 773K,Mo was present in its highest oxidation state of +6,as evidenced by the absence of d-d transitions for reduced Mo in the in situ UV-vis spectra.Our DFT calculations show that neutral MoO 3species on framework Si sites are unstable and that framework Al sites are required for anchoring (17).This result is in agree-ment with changes in the in situ IR spectra for surface OH groups as a function of the Mo load-ing in fig.S2(17)that showed preferential elim-ination of Br?nsted acid sites (H +on [AlO 4]–)after Mo deposition.On a site with two adjacent framework Al atoms,the stoichiometry of the Mo oxide species should be Mo(=O)22+as dioxo species to counterbalance the 2–charge of 2[AlO 4]–and maintain Mo in the +6oxidation state.The size of isolated Mo dioxo species serves as a geometric restriction,which determines the acceptable range of separation distances between the two anchor-ing framework Al-atom sites.Because ZSM-5is a Si-rich zeolite,Lowenstein ’s rule prohibits one Al atom to be the first neighbor of another Al atom in the framework as Al-O-Al.An arrangement of Al-O-Si-O-Al with two Al atoms as second neigh-bors was not found experimentally,based on 27Al nuclear magnetic resonance (NMR)and addi-tional characterization for ZSM-5samples with Si/Al >8(21,22).Finally,an arrangement of Al-O-(Si-O)2-Al with two Al atoms as third neigh-bors must be the only possible double Al-atom anchoring sites for Mo dioxo species.Our DFT results confirm that two Al atoms as fourth neigh-bors in Al-O-(Si-O)3-Al can serve only as two in-dividual single anchoring sites (17).
Although the exact distribution of Al atoms among different framework sites in ZSM-5zeo-lites is currently not well understood,it can be varied by adjusting the zeolite synthesis proce-dure.For example,the number of Al atoms as double anchoring sites in the arrangement Al-O-(Si-O)2-Al can be varied from 4to 46%for ZSM-5samples with Si/Al =~20,based on characteri-zation with hydrated Co cations (22).The frac-tion of Al atoms as double anchoring sites typically decreases,but not proportionally,with the increasing Si/Al ratio for the same synthesis procedure (22).Our evaluation of Al-O-(Si-O)2-Al arrangements in ZSM-5shows that these sites can serve as double Al-atom anchoring sites if they are located in the same channel,but not in the same plane.Additional classification of double Al-atom anchoring sites is provided in fig.S4(17).A representative Mo(=O)22+dioxo structure on
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Fig.1.Spectroscopic measurements.(A )Electronic edge values based on in situ UV-vis spectra of reference Mo oxide compounds exhibit a linear correlation with the number of bridging Mo-O-Mo covalent bonds around the central Mo cation.The value of 4.8eV for 2wt %Mo/ZSM-5(Si/Al =15)corresponds to Mo oxide species with a single Mo atom.(B and C )In situ Raman spectra of Mo/ZSM-5catalysts under oxygen flow at 773K as a function of (B)Mo loading for constant Si/Al =15and (C)Si/Al ratio for constant 1.3wt %Mo loading with band assignments to Mo oxide species based on DFT calculations.a.u.,arbitrary units.
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an anchoring site with a pair of Al atoms in T8and T12framework positions is shown in Fig.2.In this nanostructure,the Mo atom is bridge-bonded to two framework Al atoms through two neighboring framework oxygen atoms and ter-minated with two additional oxygen atoms.The normal vibrational modes obtained with DFT calculations for these terminal oxygen atoms in Mo(=O)22+are summarized in Table 1.The sym-metric stretch (n s )is calculated to be at 992cm ?1.The calculated geometries and normal vibration-al modes for the Mo(=O)22+nanostructure on other double Al-atom anchoring sites with two bridging framework O atoms are similar (table S2and fig.S6)(17).On a site with a single framework Al atom,the stoichiometry of Mo oxide species should be Mo(=O)2(OH)+to counterbalance the 1–charge of [AlO 4]–and maintain Mo in the +6oxidation state.The vibrational mode for the sym-metric stretch of the terminal oxygen atoms in these Mo species is predicted to be at 975cm ?1,based on evaluation of geometries and vibra-tional modes of the Mo(=O)2(OH)+nanostructure anchored on single Al-atom sites in T8(Table 1)and other ZSM-5framework positions (table S1and fig.S5)(17).
Raman spectroscopy gives rise to strong bands of symmetric stretches (n s )and weaker bands of asymmetric stretches (n as ),with the latter some-times being undetectable.In our previous studies of MoO 3/SiO 2(19,20),n as for Mo(=O)2was not observed for Mo loadings below 4wt %.Therefore,only n s is expected to be observed for lower Mo loadings.A comparison of the dominant Raman bands at 975and 993cm ?1in Fig.1with the calculated symmetric stretch values (n s )in Table 1(975and 992cm ?1)allowed us to assign these bands to two distinct isolated Mo dioxo species anchored on,respectively,single and double Al-atom framework sites.
The identification of the isolated Mo oxide structures provided insight as to how they were affected by the main catalyst formulation param-eters:the Mo loading and Si/Al ratio.At a low Si/Al =15,Mo oxide species preferentially anchored on sites with two Al atoms (band at 993cm ?1in Fig.1B).Even at the highest Mo loading of 3.3wt %,the Al/Mo atomic ratio is 2.8,which allowed all Mo atoms to be anchored on double Al-atom sites.However,when the Si/Al ratio increased,the number of Al atoms per unit volume of the zeolite decreased,and the number of sites with two Al atoms should have decreased more rapidly than the overall number of Al atoms.As a result,at higher Si/Al ratios of 25and 40in Fig.1C,the dominant band was at 975cm ?1,arising from Mo(=O)2OH species anchored on sites with one Al atom.The identification of single and double Al-atom anchoring sites is in agreement with previous findings that each Mo atom displaces one H +from framework [AlO 4]–sites in ZSM-5with Si/Al =40and two H +in ZSM-5with Si/Al =15(23).At the highest Si/Al =140shown in Fig.1C,when the corresponding Al/Mo ratio fell below unity to 0.8,there were not even enough single Al-atom sites for stabilizing all Mo atoms.For this catalyst formulation,Mo oxide species were forced
to be stabilized,not in the zeolite pores but on the least preferable Si sites on the external surface of the zeolite.A new band at 984cm ?1for Si/Al =140in Fig.1C is consistent with our previous Raman spectra for Mo oxide species supported on amor-phous SiO 2(19,20).Our DFT calculations con-firmed that Mo dioxo species did not stabilize in zeolite pores in the absence of Al sites and that the structure of isolated Mo(=O)2dioxo species as (Si-O-)2Mo(=O)2on the external surface of the zeolite (Fig.1;full details in fig.S8and table S4)(17)is similar to that on SiO 2.These findings are also supported by the in situ IR spectra of the surface OH region for ZSM-5(Si/Al =15)as a function of the Mo loading in fig.S2(17).The intensity of the peak at 3608cm ?1for OH groups on framework Al sites (24)decreased through re-placement by Mo oxide species at low Mo load-ings,followed by a decrease in the intensity of the peak at 3745cm ?1for OH groups on the external surface Si sites (24)at higher Mo loadings.The isolated Mo oxide structures preferentially anchored on double Al-atom framework sites,then single Al-atom framework sites,and finally Si sites on the external surface of the zeolite.The isolated Mo oxide nanostructures anchored on these three types of zeolite sites are shown schematically in Fig.1and with 3D animation in movie S1.
Dynamic changes of Mo nanostructures under reaction and regeneration conditions were eval-uated by simultaneously collecting operando Raman spectroscopy and online mass spectrom-etry measurements,first with CH 4flow at 953to 1053K (fig.S1)(17)and then under regeneration
conditions with gas-phase O 2flow at 773K (figs.S10and S11)(17).Upon CH 4introduction,CO 2was the only initial carbon-containing product,and the Raman band at 993cm ?1for the isolated Mo oxide structures gradually disappeared.Be-cause CH 4was the only reactant,Mo oxide nano-structures reduced to oxycarbide or carbide species.Several studies with different techniques,such as x-ray absorption fine structure,Mo L III edge x-ray absorption near-edge structure,and 95Mo NMR,provide direct evidence that the reduced Mo phase is a carbide with the stoichiometry of MoC x or MoC x O y and that the initial oxide species ag-glomerate into particles with a size of ~0.6nm (25–28).After the induction period,CO 2forma-tion stopped,the Raman band at 993cm ?1for the initial Mo oxide species was no longer observed (Fig.2B and fig.S1)(17),and the catalyst per-formed CH 4dehydroaromatization with C 6H 6as the main hydrocarbon product.
Our results demonstrate that an O 2treatment can reverse both the carbide formation and the agglomeration of Mo nanostructures.The Raman spectra at 753K for the initial catalyst with iso-lated Mo oxide structures and for the regenerated catalyst after reaction in Fig.2are similar,with a single band at 993cm ?1and a shoulder feature at 950cm ?1.The similarity in the Raman band po-sitions and intensities before reaction and after regeneration indicates that the regeneration con-verts carbided Mo NPs into an oxide phase,redisperses this phase into isolated oxide nano-structures with a single Mo atom,and allows these Mo oxide species to diffuse and then stabilize on substantially the same zeolite anchoring sites as in the initial catalyst before the reaction.
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Fig.2.Operando Raman spectra of 2wt %Mo/ZSM-5(Si/Al =15).Spectra (A )after initial pretreatment with
gas-phase oxygen,(B )during reaction with methane,and (C )after regeneration with gas-phase oxygen are shown.The spectra demonstrate that the initial Mo(=O)22+nanostructures anchored on double Al-atom framework sites (shown schematically on the right and in a zeolite pore below)with a vibrational mode at 993cm ?1are recovered after regeneration.
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Effects of regeneration time with O 2on the iden-tity of Mo nanostructures and on catalytic perform-ance with CH 4after regeneration were evaluated by combining additional Raman spectroscopic measurements with reaction testing.Raman spectra were collected in O 2flow at 773K for two 1.3wt %Mo/ZSM-5(Si/Al =15and 25)catalysts after their deactivation in reaction with CH 4.The evolution of Raman spectra as a function of regeneration time in figs.S10A and S11A (17)shows that isolated Mo oxide nano-structures were regenerated sequentially.Isolated Mo(=O)2species anchored on double Al-atom framework sites were regenerated first,as evi-denced by a single initial Raman band at 993cm ?1.With increased regeneration time,a second Raman band at 975cm ?1caused by Mo(=O)2OH species anchored on single Al-atom sites appeared and grew in intensity.Finally,a third Raman band at 984cm ?1due to Mo(=O)2species anchored on Si sites on the external surface of the zeolite ap-peared and grew in intensity for the catalyst with a lower Al concentration in the zeolite (Si/Al =25instead of 15).These direct spectroscopic observa-tions demonstrate that exposure to gas-phase O 2first regenerates isolated Mo oxide nanostruc-tures anchored on sites with two Al atoms,then forces these species to migrate to sites with one Al atom and,eventually,to Si sites on the external surface of the zeolite.
A comparison of C 6H 6formation rates in CH 4conversion as a function of time on stream for a fresh 1.3wt %Mo/ZSM-5catalyst (Si/Al =25)versus the same catalyst after deactivation in the for 120min (Fig.3A)demonstrates that the cat-alytic performance can be fully restored.The C 6H 6formation rates after regeneration matched those for the fresh catalyst.Additional reaction results for C 6H 6and H 2formation rates for two 1.3wt %Mo/ZSM-5(Si/Al =15and 25)catalysts as a function of regeneration time (figs.S10and S11)(17)show that both the overall activity and selectivity to C 6H 6fully recovered after regener-ation.Thus,rapid catalyst deactivation can be successfully addressed by regeneration with gas-phase O 2,and the catalyst lifetime can be ex-tended by repeated regeneration cycles.
Correlations between the structure of the ini-tial Mo oxide species and catalytic performance can be established by comparing the evolution of the Raman spectra with changes in reaction rates as a function of regeneration time in figs.S10and S11(17).The catalytic activity was restored once Mo oxide nanostructures on double Al-atom framework sites were regenerated (after ~20min).With increased regeneration time,these isolated Mo oxide species migrated from double to single Al-atom zeolite framework sites,and the catalytic performance with CH 4remained unchanged.Fur-thermore,the catalytic performance of a regen-erated catalyst can be optimized and may exceed that of a fresh catalyst if the regeneration treat-ment is stopped before Mo oxide nanostructures are forced to migrate to Si anchoring sites on the external surface of the zeolite.Specifically for the 1.3wt %Mo/ZSM-5(Si/Al =25)catalyst,Mo oxide nanostructures were regenerated and moved from double to single Al-atom zeolite framework sites (fig.S11A)(17).Notably,Mo nanostructures re-mained anchored on zeolite framework Al sites when the regeneration was limited to this dura-tion,and the rates of C 6H 6formation for such regenerated catalyst samples actually exceeded those for the fresh catalyst.The C 6H 6formation rates for a catalyst regenerated for 100min in Fig.3A exceeded those for the same catalyst be-fore deactivation during the initial time on stream period.In contrast,when the regeneration time was extended beyond 100min,Mo oxide nano-structures were forced to migrate from Al frame-work sites to Si anchoring sites on the external surface of the zeolite.This change in the anchor-ing sites caused the catalytic activity to decrease to the level of the fresh catalyst,and the C 6H 6formation rates for the catalyst regenerated for 120min (Fig.3A)matched those for the fresh cat-alyst.With time on stream with CH 4,the catalytic activity declined likely because of migration,growth,and coking of Mo NPs,and the performance for all regenerated catalysts eventually became in-distinguishable.However,in the first 60min of time on stream,the benzene formation rates in Fig.3A and fig.S11C (17)were dependent on the identity of the initial Mo oxide nanostructures.For understanding these initial activity differ-ences,transition-state DFT calculations were used for comparing CH 4activation over catalytic Mo carbide nanostructures anchored on the identi-fied three types of anchoring sites:double and single Al-atom zeolite framework sites and Si sites on the external surface of the zeolite.The calculations compared the first step (breaking SCIENCE https://www.wendangku.net/doc/6d8379449.html,
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Catalytic activity of Mo nanostructures.(A )Benzene formation methane conversion over a 1.3wt %Mo/ZSM-5(Si/Al =25)catalyst.catalytic activity declines with time on stream but is fully restored after of gas-phase oxygen regeneration.Initial activity is enhanced by controlling the distribution of Mo nanostructures:Activity is higher after of regeneration when Mo oxide nanostructures are anchored mostly
on framework Al sites and not forced to migrate to Si sites on the surface of the zeolite.(B to F )Reaction mechanism calculations show the energy barrier for methane activation with the formation of CH species on the surface of the catalyst is lower when a Mo nanostructure anchored on a framework Al site [(B),(E),and (F)]versus on a Si site external surface [(B)to (D)].
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zeolite (Fig.3,B to D).The CH 4initially approaches an exposed Mo atom,an atom that is not directly bonded to the zeolite.In the transition state (Fig.3,C and E),CH 4forms a Mo-CH 3-H-C cycle in which the C atom of CH 4binds to the exposed Mo atom and,simultaneously,one of the H atoms of CH 4binds to a C atom in the carbide.Thus,a Mo-C pair of atoms in the Mo carbide nanostructure serves as a single catalytic active site.This dual Mo-C site activates CH 4in a scissoring motion that produces a CH 3group bonded to Mo and an H atom bonded to C of the carbide (Fig.3,D and F).Although the mechanism of CH 4activation is similar,differences in geometries and electronic properties of Mo carbide nanostructures anchored on Al and Si sites lead to differences in their catalytic properties.The CH 4activation energy over the Mo carbide anchored on the double Al-atom site of 112kJ/mol in Fig.3E is lower than 140kJ/mol for the Si site in Fig.3C.The transition state for the single Al-atom anchoring site is analogous to that for the double Al-atom site in Fig.3E,with a comparable activation energy of 117kJ/mol (table S6)(17).The CH 4reaction is therefore predicted to be dominated by the activity of Mo nanostructures anchored on framework Al sites.This computa-tional result is consistent with known experimen-tal observations that the catalytic activity of Mo nanostructures depends strongly on the Si/Al ratio of the supporting zeolite and declines sub-stantially when Al framework sites are lost through dealumination (2,8,13–15,30).
The obtained information on the identity of Mo structures,their regeneration,and their in-fluence on catalytic activity opens new oppor-tunities for rational design of improved catalyst formulations and for optimizing reaction condi-tions for direct conversion of natural gas into liquid transportation fuels and valuable feed-stocks for the chemical industry.It is important to control the distribution of Mo oxide species and limit their anchoring to framework Al sites because initial Mo oxide nanostructures anchored on Al sites of the zeolite framework are converting into carbided Mo NPs with higher catalytic ac-tivity than those produced by initial Mo oxide species anchored on Si sites.The number and distribution of single and double Al-atom anchor-ing sites can be optimized by adjusting a zeolite synthesis procedure.The number of Si anchoring sites on the external surface of the zeolite can be reduced,or these Si sites can be eliminated com-pletely by adjusting the Mo deposition pro-cedure.Furthermore,the catalytic performance of Mo species and their periodic regeneration can be optimized by adjusting catalyst formula-tions (for example,with promoter metals)and changing the temperatures of the reaction and regeneration,flow rates,and other reaction conditions.
REFERENCES AND NOTES
1. E.McFarland,Science 338,340–342(2012).
2.J.H.Lunsford,Catal.Today 63,165–174(2000).
3.S.G.Podkolzin,E.E.Stangland,M.E.Jones,
E.Peringer,J.A.Lercher,J.Am.Chem.Soc.129,2569–2576(2007).
4.R.Khalilpour,I.A.Karimi,Energy 40,317–328(2012).
5.International Energy Agency,“Golden rules for a golden age of
gas -World Energy Outlook special report on unconventional gas,”(International Energy Agency,Paris,France,2012);https://www.wendangku.net/doc/6d8379449.html,/goldenrules/.
https://www.wendangku.net/doc/6d8379449.html,binger,J.E.Bercaw,Nature 417,507–514
(2002).
7.X.Guo et al .,Science 344,616–619(2014).8. A.Holmen,Catal.Today 142,2–8(2009).9.L.Wang et al .,Catal.Lett.21,35–41(1993).
10.L.Y.Chen,L.W.Lin,Z.S.Xu,X.S.Li,T.Zhang,J.Catal.
157,190–200(1995).
11. F.Solymosi,A.Erd?helyi,A.Sz?ke,Catal.Lett.32,43–53
(1995).
12.J.Z.Zhang,M.A.Long,R.F.Howe,Catal.Today 44,293–300
(1998).
13.Y.Xu,X.Bao,L.Lin,J.Catal.216,386–395(2003).
14.Z.R.Ismagilov,E.V.Matus,L.T.Tsikoza,Energy Environ.Sci 1,
526–541(2008).
15.T.V.Choudhary,E.Aksoylu,D.W.Goodman,Catal.Rev.Sci.
Eng.45,151–203(2003).
16.J.J.Spivey,G.Hutchings,Chem.Soc.Rev.43,792–803
(2014).
17.Supplementary materials are available on Science Online.18.H.Tian,C.A.Roberts,I.E.Wachs,J.Phys.Chem.C 114,
14110–14120(2010).
19.E.L.Lee,I.E.Wachs,J.Phys.Chem.C 111,14410–14425
(2007).
20.E.L.Lee,I.E.Wachs,J.Phys.Chem.C 112,20418–20428
(2008).
21.S.Sklenak et al .,Phys.Chem.Chem.Phys.11,1237–1247
(2009).
22.J.D ěde ?ek,Z.Sobalík,B.Wichterlová,Catal.Rev.Sci.Eng.54,
135–223(2012).
23.J.-P.Tessonnier et al .,J.Phys.Chem.B 110,10390–10395
(2006).
24.P.Hoffmann,J.A.Lobo,Microporous Mesoporous Mater.106,
122–128(2007).
26.H.Aritani,H.Shibasaki,H.Orihara,A.Nakahira,J.Environ.Sci.
(China)21,736–740(2009).
27.S.Liu,L.Wang,R.Ohnishi,M.Ichikawa,J.Catal.181,175–188
(1999).
28.H.Zheng et al .,J.Am.Chem.Soc.130,3722–3723
(2008).
29.J.Gao et al .,J.Phys.Chem.C 118,4670–4679
(2014).
30.J.P.Tessonnier,B.Louis,S.Rigolet,M.J.Ledoux,
C.Pham-Huu,Appl.Catal.A 336,79–88(2008).
ACKNOWLEDGMENTS
The work in S.G.P.’s group at Stevens Institute of Technology was supported by the NSF under grant CBET-1133987.The work in I.E.W.’s group at Lehigh University was supported by the NSF under grant CBET-1134012.The Materials Studio software was used under a collaborative research license from BIOVIA Corp.in San Diego,California.Author contributions:J.G.and Y.Z.obtained the
computational and reaction-testing results and discussed the overall results;J.-M.J.and Y.T.obtained the experimental spectroscopic data and discussed the overall results;I.E.W.conceived and supervised the spectroscopic experiments and interpreted the results;and S.G.P.conceived and supervised the calculations and reaction testing,interpreted the results,and prepared the initial manuscript.
SUPPLEMENTARY MATERIALS
https://www.wendangku.net/doc/6d8379449.html,/content/348/6235/686/suppl/DC1Materials and Methods Figs.S1to S12Tables S1to S6References Movie S1
16January 2015;accepted 26March 2015Published online 9April 2015;system II (PSII)of plants,algae,and cyano-bacteria facilitates splitting of water into O 2,protons,and electrons (1–4).Crystallo-graphic structures (5–8)reveal that the core of the OEC consists of a Mn 3CaO 4cubane motif and a “dangler ”Mn linked via two bridging ox-ides,forming a distinct asymmetric Mn 4Ca-cluster (Fig.1A).This cluster is coordinated to four water
groups of the amino acid residues of the PSII polypeptides (Fig.1C).The structure of the OEC as well as the oxidation states of the four manga-nese ions undergo changes during the water-oxidation reaction cycle,or S-state cycle (4,9,10).Spectroscopic results and computational chem-istry have provided insight in reaction interme-diates and mechanisms (4,9–16).The lability of
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is a Science 2015 by the American Association for the Advancement of Science; all rights reserved. The title Copyright American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the Science o n M a y 9, 2015
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1876-6102 ? 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://www.wendangku.net/doc/6d8379449.html,/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL doi: 10.1016/j.egypro.2015.11.340 E nergy Procedia 78 ( 2015 )2657 – 2662 ScienceDirect 6th International Building Physics Conference, IBPC 2015 Changing to energy efficient light sources – An analysis of the energy balance of buildings Johan Nordén*, Henrik Karlsson, Caroline Markusson, Svein Ruud, Mikael Lindgren, Patrik Ollas SP Technical Research Institute of Sweden, Ideon Science Park, SE-223 63, Lund, Sweden Abstract New light sources such as LED lamps have the potential to reduce the electricity for lighting significantly. However, by reducing the electricity for lighting, the building heating demand is increased. The effects on the building energy balance of changing to more efficient light sources has been investigated by dynamic thermal modelling of typical Swedish single-family and multi-family residential houses. The results show savings on an average of 3.5 kWh/m 2 and 0.62 €/m 2 for single-family houses, and 3.4 kWh/m 2 and 0.61 €/m 2 for apartments in multi-family houses annually when changing from incandescent and halogen lamps to LED lamps. ? 2015 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL. Keywords: energy balance; lighting; energy efficiency; internal l oads 1. Introduction The European target to halve the energy use in the built environment by 2050 will require all new buildings to be constructed as nearly zero-energy buildings or passive houses. The significantly lower heating demand of such buildings increases the emphasis on heat generated by devices, persons, lighting etc. in the energy balance calculations. For buildings with nearly zero- energy standards, even modest energy supply from internal loads can result in overheating. The heat will partly be stored in the building structure, partly heat the indoor air, and partly be ventilated. Since the storage of energy depends on the penetration depth and dampening of the heat wave, the distribution of heat and the dynamics with the indoor environment becomes more complex. A deeper understanding on how surface temperatures and the air temperature are influenced by the energy from lighting as well as from devices is therefore required in order to improve the design and control of new buildings. In the study presented here, we have analysed the effects on the energy use and cost when changing from incandescent and halogen lamps to LED lamps, lamps which today have an equal or better performance than CFL lamps. This has been simulated for typical building types of Sweden with different heating distribution systems, insulation thicknesses, lighting scenarios etc. The buildings are representative of the Swedish housing stock from 1970 up to now; both for single-family houses and multi- family houses. A living room was simulated with two lighting scenarios, one case with a pendent luminaire and spotlights recessed into the ceiling, and one with a pendent luminaire and surface mounted luminaires in the ceiling. The luminaires used were one pendent luminaire with an opal diffuser, one surface mounted luminaire, and one recessed spotlight. All are typical luminaires used in Swedish households. The light sources used were incandescent, HV halogen, and LED lamps. * Corresponding author. Tel.: +46-10-516 5000. E-mail address: johan.norden@sp.se Available online at https://www.wendangku.net/doc/6d8379449.html, ? 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://www.wendangku.net/doc/6d8379449.html,/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the CENTRO CONGRESSI INTERNAZIONALE SRL
怎样在《Science》杂志上发表文章 佚名 一、《Science》杂志概况 美国的《Science》杂志为国际上著名的自然科学综合类学术期刊,在世界学术界享有盛誉,反映其被引文量的影响因子始终高居《SCI》收录的5700种科学期刊的前十位。据2001年最新统计,《Science》杂志年发表论文数901篇,被引用次数282431,影响因子为23.329,排名所有科学期刊的第8位。由于其独特的学术地位,国内许多科研院所为鼓励学术人员在该刊发表文章,都制定了优厚的奖励措施。 《Science》杂志创刊于1880年,目前在全球拥有16.5万个订户,超过《N ature》杂志三倍。《Science》杂志具有新闻杂志和学术期刊的双重特点,每周除向世界各地发布有关科学技术和科技政策的重要新闻外,还发表全球科技研究最显著突破的研究论文和报告。 《Science》杂志发表的论文涉及所有科学学科,特别是物理学、生命科学、化学、材料科学和医学中最重要的、最激动人心的研究进展。据统计,发表的论文中60%有关生命科学,40%是属于物理科学领域的(见附录1)。每年《Scien ce》杂志还出版大约15期专辑,展示某一专门领域的最新成果,例如生物技术、寄生虫学、纳米技术、计算机技术等。除高水平的论文外,每期专辑还发表有关科技职业的专题文章和以不同国家、地区为对象的专栏。 除了为发表全世界最好的科学论文和报道全球最好的科学新闻而努力外,《S cience》杂志还有三个特别重要的目标: ?将《Science》杂志和科学带入更多的发展中国家的科学工作者的家中和实验室里; ?帮助世界各地青年科技工作者更多地了解今后十年最重要的科技发展趋势、最新的科学仪器和技术以及科技职业的选择; ?用电子手段传播科技信息,进一步提高信息质量,并且通过与发展中国家和发达国家的团体合作利用计算机互联网传送杂志,降低发行成本。 1995年,《Science》杂志与时俱进,实现了上网,即科学在线《Science Online》,提供《Science》杂志全文、摘要和检索服务。特别要注意的是:网络版是印刷版的补充,而不是替代。网络版上许多内容是免费的,如今日科学(S cience Now)报道每日科学新闻;科学后浪(Science Next Wave)给未来科学家提供职业信息;科学事业(Science Careers)提供就职机会、会议和研究活
【原创】回答美国《科学》杂志提出的125个重大科学前沿问题(2) 文/简浩 据2018年01月12日07:44新浪科技载,北京时间1月12日消息,据国外媒体报道,目前,《科学》杂志提出125个重大问题,其中涉及到宇宙形成、地球演化、生命兴起和人类生理谜团等。以下分别回答125个其中的10个科学前沿问题: 30、是什么给类星体提供动力?答: 宇宙高速自转运动的中心,会不断积累热能,久而久之,形成宇宙大爆炸,本质就是“超能核聚变”。聚变出新一轮的质子、中子、电子、离子等轻物质,又会形成一轮又一轮的年轻的“类星体”,在宇宙空间自转运动的螺旋辐射动能推动下,仍然继续向外圆螺旋扩张。 所有星系的前半生,都曾经是“极端天体”中的“类星体”,银河系也不例外。 类星体看似星系,又不完全像是普通星系,看似恒星,又不完全像是普通恒星,所以被称作“类星体”。 新形成的类星体距宇宙中心最近,公转度最快,物质分子就会产生剧烈震荡,因此,类星体就像滚雪球一样,“公转特快、自转特慢、占空特小、密度特大、热能特大、亮度特大”,释放的能量却是普通星系的数千倍以上,亮度是正常星系的千倍以上。 类星体边公转、边螺旋、边扩张、边膨胀,前一轮扩张到外圆轨道的类星体公转运动开始减速,类星体内的空间开始伸展、密度变小、能量变小、亮度变小、占空变大,后来逐渐演变为正常星系。 宇宙中所有星系(包括类星体)的公转速度和自转速度,都有一个共同而普遍的规律,也是宇宙的基本规律:距离宇宙中心(重力源)越近的星体,位能会越小,自转速度则越慢,而动能会越大,公转速度则越快。反之,距离宇宙中心(重力源)越远的星体,位能会越大,自转速度则越快,而动能会越小,公转速度则越慢。 这就是类星体为什么会高速公转运动,能给类星体自身带来巨大动能的原因。 31、黑洞的本质是什么?答: 黑洞里面是中子或夸克。黑洞是实体天体,不是虚拟物质。所有星系中心都有黑洞存在,黑洞是“统领星系”的实体“极端天体”。 黑洞的特征:“质量特大、引力特大、磁场超强、密度超大、能量超大、热能超大、自转太快、体积太小”,就是光线也逃不脱黑洞的引力。 黑洞的运行机制:“边高速自转、边疯狂吞噬、边高温高压、边高能聚变,边增加自重、边超能喷射”。黑洞吞噬的天体物质,只有少数与黑洞是同类的物质被黑洞吸收,大多数非同类物质不能被黑洞吸收,都要从黑洞的两极喷射出去。因此,黑洞能使自身星系的总体质量逐渐增加,能使恒星、行星等天体物质也逐渐增加。 黑洞的本质:进行天体物质的“循环回炉”、“脱胎换骨”、“物质洗牌”,黑洞的本质就是一座强大的“高能核聚变工厂”。喷射散发的质子、中子、电子、离子,大多数又形成了新恒星,银河系外围边缘的年轻恒星就是这样的来历。 黑洞喷射的高能粒子:基本都是新生恒星的“原料”氢元素物质,而产生的重元素物质微乎其微,只能形成极少量的星际尘埃。 被黑洞吞噬的已经衰老的天体物质,经过黑洞“秘密”的聚变“深加工”,喷射出来的高能粒子,从此获得“重新做人”的机会,焕然一新,成为年轻的新粒子、新质子。 黑洞带着星系的公转运动,由于公转速度高,一般最低速度也有600km/s,这样一来,黑洞就会像“弯道超车”一样,黑洞就会发生倾斜。 黑洞倾斜的规律:距离宇宙中心越近的星系,黑洞倾斜度则越小,反之,距离宇宙中心越远的星系,黑洞的倾斜度则越大。
世界顶级的管理学部分期刊目录 Rank 1: Administrative Science Quarterly (ASQ) 管理科学季刊 Rank 2: Academy of Management Review (AMR) 中国科学院管理评论Rank 3: Academy of Management Journal (AMJ) 管理学会期刊 Rank 4: Journal of Applied Psychology (JAP) 应用心理学杂志 Rank 5: Strategic Management Journal (SMJ) 战略管理杂志 Rank 6: Personnel Psychology (Perpsych) 人事心理学 Rank 7: Organizational Behavior and Human Decision Processes (OBHDP)组织行为与人类决策过程 Rank 8: Management Science (MS) 管理科学 Rank 9: Journal of Vocational Behavior (JVB) 中国职业行为 Rank 10:Journal of Management (JOM) 管理学报 Rank 11:Industrial and Labor Relations Review (I&LRR) 工业和劳动关系回顾 Rank 12:Journal of Occupational and Organizational Psychology (JOOP) 职业与组织心理学 Rank 13:Journal of Human Resources (JHR) 人力资源杂志 Rank 14:Journal of Organizational Behavior (JOB) 中国组织行为 Rank 15:Journal of Management Studies (JMS) 管理研究杂志 Rank 16:Decision Sciences (DS) 决策科学 Rank 17:Journal of International Business Studies (JIBS) 中国国际商务研究Rank 18:Human Relations (HR) 人际关系 Rank 19:Industrial Relations (IR) 劳资关系 Rank 20:Harvard Business Review (HBR) 哈佛商业评论 Rank 21:California Management Review (CMR) 加州管理评论 Rank 22:Solan Management Review (SMJ) 索兰管理评论 Rank 23:Journal of Business Venturing (JBR) 创业杂志
◎=◎“电气科学与工程”学科领域的国内外著名刊物◎=◎: ◆国际著名刊物: 1、IEEE TRANSACTIONS ON ENERGY CONVERSION 美国(各种能量转换理论,装置及控制领域等) 2、IEEE TRANSACTIONS ON POWER SYSTEMS 美国(电力系统领域) 3、IEEE TRANSACTIONS ON POWER ELECTRONICS 美国(电力电子器件,电路与系统等) 4、IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 美国(电解质与绝缘,高电压领域) 5、IEEE TRANSACTIONS ON MAGNETICS 美国(信息电磁场与波,强电的电机电磁装置与控制领域) 6、IEEE TRANSACTIONS ON POWER DELIVERY 美国(电力发配电等,电力系统领域) ◆相关的几大牛刊: 1、PROCEEDINGS OF THE IEEE 美国(含盖电气,计算机科学等领域, “电气与电子领域综合类”) 2、IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS 美国(含盖面宽,电气,控制系统,工业电子等, 属于“电气、电子应用综合类”) 3、IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS 美国(工业应用电子科学与技术, 检测与转换等) 4、IEEE TRANSACTIONS ON PLASMA SCIENCE 美国(等离子体科学,偏理科) ◆国内权威刊物: 1*.《中国电机工程学报》,领域:电气工程、能源动力工程等。 2*.《电工技术学报》,领域:电工技术领域。 3*.《电力系统自动化》,领域:电气工程学科的电力系统自动化领域。 4.《电机与控制学报》,领域:电气工程学科的电机、电力电子、电气传动。 5.《电网技术》,领域:电气工程学科的电力系统及其自动化。 6.《继电器》,领域:电气工程学科的电力系统及其自动化。 7.《电力自动化设备》,领域:电气工程学科的电力系统及其自动化装备。
国外部分 期刊名(英文)期刊名(中文)影响因子 (部分) 备注 管理科学类包括战略管理SM、运筹研究OR、创新管理IM顶级期刊 ACADEMY OF MANAGEMENT REVIEW管理评论 3.9 ADMINISTRATIVE SCIENCE QUARTERLY管理科学季刊 3.3 STRATEGIC MANAGEMENT JOURNAL战略管理季刊 2.5 ACADEMY OF MANAGEMENT JOURAL管理学术期刊 2.4 JOURNAL OPERTION MANAGEMENT运筹管理期刊 1.795 JOURNAL PRODUCT INNOVATION MANAGEMENT产品创新管理期刊 1.623 MANAGEMENTSCIENCE管理科学 1.468 MATHPROGRAM数学规划 1.29 MATH OPERATION RESEARCH数学运筹研究 1.146 OPERTION RESEARCH运筹研究0.672 EUROPE JOURNAL OPERATION RESEARCH欧洲运筹研究期刊0.605 INTERNATIONAL JOURNAL PRODUCTION RESEARCH 产品研究国际期刊0.557 OPERATION RESEARCH LETTER运筹研究通讯0.449 JOURNAL OPERATION RESEARCH SOCIETY运筹研究世界期刊0.416 PRODUCTION OPERATION MANAGEMENT产品运作管理0.393 ANNUAL OPERATION RESEARCH运筹研究年刊0.331 INTERNATIONAL JOURNAL TECHNOLOGY MANAGEMENT 国际技术管理期刊0.266 金融、会计、商业顶级期刊 JOURNAL OF FINANCE金融学期刊 2.8 JOURNAL OF CONSUMER RESEARCH消费者研究期刊 2.5 JOURNAL OF MARKETING;市场学期刊2 JOURNAL OF FINANCIAL ECONOMICS金融经济学期刊 1.9 JOURNAL OF MARKETING RESEARCH市场学研究期刊 1.7 MARKETING SCIENCE市场期刊 1.4 REVIEW OF FINANCIAL STUDIES;金融研究评论 1.3 JOURNAL OF BUSINESS商业期刊 1.2 JOURNAL OF ACCOUNTING RESEARCH会计期刊 1.1 FINANCE MANAGEMENT金融管理 WORLD BANK ECONOMICS REVIEW世界银行经济评论 JOURNAL OF MONEY CREDIT AND BANKING货币信用与银行期刊JOURNAL OF MONETARY ECONOMICS货币金融期刊 JOURNAL OF FINANCIAL INTERMEDIATION金融中介期刊 JOURNAL OF INTERNATIONAL 国际货币与金融期刊
《Science》 一、《Science》杂志概况 美国的《Science》杂志为国际上著名的自然科学综合类学术期刊,在世界学术界享有盛誉,反映其被引文量的影响因子始终高居《SCI》收录的5700种科学期刊的前十位。据2001年最新统计,《Science》杂志年发表论文数901篇,被引用次数282431,影响因子为23.329,排名所有科学期刊的第8位。由于其独特的学术地位,国内许多科研院所为鼓励学术人员在该刊发表文章,都制定了优厚的奖励措施。 《Science》杂志创刊于1880年,目前在全球拥有16.5万个订户,超过《N ature》杂志三倍。《Science》杂志具有新闻杂志和学术期刊的双重特点,每周除向世界各地发布有关科学技术和科技政策的重要新闻外,还发表全球科技研究最显著突破的研究论文和报告。 《Science》杂志发表的论文涉及所有科学学科,特别是物理学、生命科学、化学、材料科学和医学中最重要的、最激动人心的研究进展。据统计,发表的论文中60%有关生命科学,40%是属于物理科学领域的(见附录1)。每年《Scien ce》杂志还出版大约15期专辑,展示某一专门领域的最新成果,例如生物技术、寄生虫学、纳米技术、计算机技术等。除高水平的论文外,每期专辑还发表有关科技职业的专题文章和以不同国家、地区为对象的专栏。 除了为发表全世界最好的科学论文和报道全球最好的科学新闻而努力外,《S cience》杂志还有三个特别重要的目标: ?将《Science》杂志和科学带入更多的发展中国家的科学工作者的家中和实验室里; ?帮助世界各地青年科技工作者更多地了解今后十年最重要的科技发展趋势、最新的科学仪器和技术以及科技职业的选择; ?用电子手段传播科技信息,进一步提高信息质量,并且通过与发展中国家和发达国家的团体合作利用计算机互联网传送杂志,降低发行成本。 1995年,《Science》杂志与时俱进,实现了上网,即科学在线《Science Online》,提供《Science》杂志全文、摘要和检索服务。特别要注意的是:网络版是印刷版的补充,而不是替代。网络版上许多内容是免费的,如今日科学(S cience Now)报道每日科学新闻;科学后浪(Science Next Wave)给未来科学家提供职业信息;科学事业(Science Careers)提供就职机会、会议和研究活
怎样在《Science》杂志上发表文章 一、《Science》杂志概况 美国的《Science》杂志为国际上著名的自然科学综合类学术期刊,在世界学术界享有盛誉,反映其被引文量的影响因子始终高居《SCI》收录的5700种科学期刊的前十位。据2001年最新统计,《Science》杂志年发表论文数901篇,被引用次数282431,影响因子为23.329,排名所有科学期刊的第8位。由于其独特的学术地位,国内许多科研院所为鼓励学术人员在该刊发表文章,都制定了优厚的奖励措施。 《Science》杂志创刊于1880年,目前在全球拥有16.5万个订户,超过《N ature》杂志三倍。《Science》杂志具有新闻杂志和学术期刊的双重特点,每周除向世界各地发布有关科学技术和科技政策的重要新闻外,还发表全球科技研究最显著突破的研究论文和报告。 《Science》杂志发表的论文涉及所有科学学科,特别是物理学、生命科学、化学、材料科学和医学中最重要的、最激动人心的研究进展。据统计,发表的论文中60%有关生命科学,40%是属于物理科学领域的(见附录1)。每年《Scien ce》杂志还出版大约15期专辑,展示某一专门领域的最新成果,例如生物技术、寄生虫学、纳米技术、计算机技术等。除高水平的论文外,每期专辑还发表有关科技职业的专题文章和以不同国家、地区为对象的专栏。 除了为发表全世界最好的科学论文和报道全球最好的科学新闻而努力外,《S cience》杂志还有三个特别重要的目标: ?将《Science》杂志和科学带入更多的发展中国家的科学工作者的家中和实验室里; ?帮助世界各地青年科技工作者更多地了解今后十年最重要的科技发展趋势、最新的科学仪器和技术以及科技职业的选择; ?用电子手段传播科技信息,进一步提高信息质量,并且通过与发展中国家和发达国家的团体合作利用计算机互联网传送杂志,降低发行成本。 1995年,《Science》杂志与时俱进,实现了上网,即科学在线《Science Online》,提供《Science》杂志全文、摘要和检索服务。特别要注意的是:网络版是印刷版的补充,而不是替代。网络版上许多内容是免费的,如今日科学(S cience Now)报道每日科学新闻;科学后浪(Science Next Wave)给未来科学家提供职业信息;科学事业(Science Careers)提供就职机会、会议和研究活
极具权威性的美国科学杂志《今日心理学》 阅读答案 极具权威性的美国科学杂志《今日心理学》近日刊登了一篇惊人的文章,文章指出,原先人们认为海产品对大脑最有益,多吃海产品可以提高人的智力,但美国科学家最新研究的结果却大大出乎人们的预料。研究发现,森林中的野果比如红莓苔子、黑莓果等对大脑的益处远远超过海产品,排在第一位;占据第二位的是蔬菜,其次才是鱼等海产品。 研究人员发现,红莓苔子之所以排在排在第一位,是因为其中含有大量能与自由氧离子发生相互作用的抗氧化剂。抗氧化剂的存在几乎破坏了对血管和心脏有极大破坏性的胆醇激素。黑莓果里面含有的抗氧化剂要相对少一些,但含有对视力和听力非常有益的成分。大叶子的红甜菜和圆白菜含有一种能把发展成帕金森氏综合症的酶破坏掉的物质。菠菜能够延缓神经系统的衰老,还可以防止认知能力出现问题。相比之下,鱼的作用就小多了,只有鲑鳟鱼、金枪鱼、沙丁鱼和鲱鱼含有能分解有害酶的脂肪酸,此外,这些鱼中还有大量大脑所需要的磷。 俄罗斯医学科学院食品研究的教授波波夫也持这样的观点。他认为,野果不仅对大脑有益,对心脏也有好处。他们的研究发现,许多含有大量维生素C和蔗糖的蔬菜,对大脑的活动也特别有益。 但几乎所有的专家都认为,如果认为只吃了上述食品你就变得聪明了,那就大错特错了。这样的食品结构会引起营
养的失衡,食品应该是多种多样的。 还有一种观点认为巧克力可以提高智力。的确,巧克力中含有一些对大脑有益的物质。研究发现每天吃50克巧克力可以延缓机体的衰老,但这里所指的是黑色的苦巧克力。哪些非常甜的、含有奶制品的巧克力含有大量糖,过多食用这样的巧克力会产生许多不良问题,如糖尿病、肥胖症等。 食品专家指出,在日常饮食中,最重要的是保持一个良好习惯,每餐不能吃得太饱。饱满的午餐会降低大脑的活动能力,出现所谓的“食困”现象,但紧张的工作与低能量的饮食也是不相容的。因此,最合理的方法是多吃一些蔬菜、豆制品和液体,但不是啤酒和浓茶。 科学研究还发现,其实大脑最好的营养成分是葡萄糖,大脑细胞需要大量的葡萄糖。葡萄糖通常存在于谷物、土豆和豆角中,桃子、香蕉和梨中也含有丰富的葡萄糖。 研究人员指出,食品本身并不能提高智力。含有维生素B的食品,比如肉、鱼、花生等,可以帮助促进大脑思维的过程,消除疲劳。早晨吃上一个橙子可以一整天精神饱满。如果你不能利用这些食品恢复体质,还可以用合成维生素补充。但是要想开发智力,最好的方法是不断学习、读好书,与有文化有知识的人交流。 8.下列对美国科学家最新研究的结果表述正确的一项是() A.蔬菜之所以排在鱼等海产品之前,是因为蔬菜比鱼等海产品含有更多的营养。
鲁白 (2002年9月25日在复旦大学上海医学院的讲课录音记录) 下面谈一下投稿的基本过程,特别是与Cell、Nature、Science、PNAS 等影响因子比较高的杂志有关的一些技术性问题,也许可以打破其神秘感。其实这些杂志的主编,编辑们都经常在介绍其政策,评审标准,过程,等等。他们也经常来中国访问。今天我来代替他们介绍一下。一个系列杂志叫Cell、Neuron、Immunity…..等等,原来都是从Cell分出来的。这个杂志的基本特点是它有一个非常强的编委Editorial Board。怎样的人可以当编委呢?他们往往是有名的科学家,而且也愿意并能够非常快地对投稿做出评估。这些科学家也经常被选来做评审reviewer。大家都知道每篇文章送到杂志社后,都要请该领域的2-3专家看,并匿名写出评审意见给作者。你不知道是谁写的,但这些专家会给你提出批评,哪些地方不好,哪些地方需要进一步做实验,怎么样做,这就叫杂志评审。 Cell、Neuron、Immunity等这些杂志的评审不少就是编委做的。因为现在杂志竞争的重要因素是发表要快,而做编委的专家能很快写出评审意见来。还有一个特点,Cell等杂志主编,编辑有非常大的权利,他们甚至可以象追星族那样去追科学家,去参加各种各样的科学会议,当看到你有非常重要的最新成果,他们会去竞争,会问你,你的文章写出来了没有,我保证给你多少时间发表,等等。另一个系列是Nature衍生出来的,这些杂志的特点是没有一个编委,但有一个评审专家库, 也就是说谁来评审,不是乱选的。这些杂志主编,编辑也有相当大的权利。这些是什么人呢?他们一般是读完博士,然后到非常好的实验室做博士后,这些人也许自己没有做出什么特别重大的贡献,没有什么好的文章,但他们欣赏能力特别好,文笔非常好,写得又快。你可不要小看他们,虽然自己没有做出什么伟大的工作来,但他们的思想水平学术水平都相当不错,看得多,写得快,Nature、Science的编辑大同小异,都是这样一批年纪不大的人,很活跃,经常参加各种各样的会议和活动。 Science杂志的编辑权利相对小些,因为他们还有一个编委会editorial board,有相当大的权利。一般过程是,当你的文章送到Science杂志社后,编辑先做一个初审,看一下是不是基本够格,然后他还要把文章的摘要Abstract送到编委会的某一个人那里,认可以后,才可以拿出去评审。两道关卡,大部分文章一下子就这样被砍掉了。 PNAS杂志是美国科学院院刊,文章有好有坏,院士自己投稿就不需要经过评审,叫做contribute。院士原来一年可以五篇,后来减到四篇、三篇,就是院士自己写的文章,只要你投就给你发表,不需要经过评审,相信你是院士,投科学论文应该有责任心的。第二种叫做Communicate,不是院士自己的文章,是你的文章,院士觉得你的文章不错,他来给你通讯,投到PNAS杂志,这文章要评审,但是评审专家由院士自己来选。所以这个也不怎么样。还有一种叫Track C,就象一般杂志,你只要投过去,然后编辑部来给你选一个院士,由他来找评审专家,相对来说,这比较客观些,所以Track C的文章质量就相对好一些。我不是说院士的文章都很差,但院士有特权,可以把在其他杂志发不出去的文章,投到PNAS上去,所以在PNAS上有很多不怎么样的文章。
极具权威性的美国科学杂志《今日心理学》阅读答案 :巧克力极具权威性的美国科学杂志《今日心理学》近日刊登了一篇惊人的文章,文章指出,原先人们认为海产品对大脑最有益,多吃海产品可以提高人的智力,但美国科学家最新研究的结果却大大出乎人们的预料。研究发现,森林中的野果比如红莓苔子、黑莓果等对大脑的益处远远超过海产品,排在第一位;占据第二位的是蔬菜,其次才是鱼等海产品。 研究人员发现,红莓苔子之所以排在排在第一位,是因为其中含有大量能与自由氧离子发生相互作用的抗氧化剂。抗氧化剂的存在几乎破坏了对血管和心脏有极大破坏性的胆醇激素。黑莓果里面含有的抗氧化剂要相对少一些,但含有对视力和听力非常有益的成分。大叶子的红甜菜和圆白菜含有一种能把发展成帕金森氏综合症的酶破坏掉的物质。菠菜能够延缓神经系统的衰老,还可以防止认知能力出现问题。相比之下,鱼的作用就小多了,只有鲑鳟鱼、金枪鱼、沙丁鱼和鲱鱼含有能分解有害酶的脂肪酸,此外,这些鱼中还有大量大脑所需要的磷。 俄罗斯医学科学院食品研究的教授波波夫也持这样的观点。他认为,野果不仅对大脑有益,对心脏也有好处。他们的研究发现,许多含有大量维生素C和蔗糖的蔬菜,对大脑的活动也特别有益。 但几乎所有的专家都认为,如果认为只吃了上述食品你就变得聪明了,那就大错特错了。这样的食品结构会引起营养的失衡,食品应该是多种多样的。 还有一种观点认为巧克力可以提高智力。的确,巧克力中含有一些对大脑有益的物质。研究发现每天吃50克巧克力可以延缓机体的衰老,但这里所指的是黑色的苦巧克力。哪些非常甜的、含有奶制品的巧克力含有大量糖,过多食用这样的巧克力会产生许多不良问题,如糖尿病、肥胖症等。 食品专家指出,在日常饮食中,最重要的是保持一个良好习惯,每餐不能吃得太饱。饱满的午餐会降低大脑的活动能力,出现所谓的”食困”现象,但紧张的工作与低能量的饮食也是不相容的。因此,最合理的方法是多吃一些蔬菜、豆制品和液体,但不是啤酒和浓茶。 科学研究还发现,其实大脑最好的营养成分是葡萄糖,大脑细胞需要大量的葡萄糖。葡萄糖通常存在于谷物、土豆和豆角中,桃子、香蕉和梨中也含有丰富的葡萄糖。
SCI各领域国际顶尖学术期刊一览 中国科学院科技情报中心将各领域的SCI期刊按影响因子大小分成四个区,其中一区和二区为高影响因子论文,三区为中等影响因子论文,四区为低影响因子论文。其中,一区和二区的一小部分杂志被列为顶尖学术期刊(TopJournal)。 要比较各校在高水平的杂志的论文发表情况,可以根据顶尖杂志的名单和一区二区的杂志名单,查询ISI网站,谁好谁差,一比就知,无需争辩,一目了然。 以下为各领域顶尖学术期刊的详细名单 分区中文分类刊名简称 1 地学ACTAASTRONOM 1 地学ADVGEOPHYS 1 地学AMJSCI 1 地学BAMMETEOROLSOC
1 地学CLIMDYNAM 1 地学JCLIMATE 1 地学JPETROL 1 地学LIMNOLOCEANOGR 1 地学QUATERNARYSCIREV 1 地学REVGEOPHYS 1 地学TELLUSB 2 地学AMMINERAL 2 地学CHEMGEOL 2 地学EARTHPLANETSCLETT 2 地学GEOCHIMCOSMOCHIMAC 2 地学GEOLOGY 2 地学GEOPHYSRESLETT 2 地学JGEOPHYSRES 2 地学JATMOSSCI
2 地学MONWEATHERREV 1 地学天文ANNUREVASTRONASTR 1 地学天文ASTROPHYSJ 1 工程技术ACTAMATER 1 工程技术ADVMATER 1 工程技术AICHEJ 1 工程技术ANNUREVBIOMEDENG 1 工程技术ANNREVMATERRES 1 工程技术APPLSPECTROSC 1 工程技术ARTIFINTELL 1 工程技术ARTIFLIFE 1 工程技术BIOMATERIALS 1 工程技术CHEMVAPORDEPOS 1 工程技术CHEMMATER
怎样在《科学》杂志上发表文章 (这是非正式译文,最近更新是在2001年5月,不一定包括编辑部最新的要求。请以英文原文为准。) 《科学》是一个周刊,是发表最好的原始研究论文、以及综述和分析当前研究和科学政策的同行评议的期刊。我们在美国首都华盛顿和英国剑桥的编辑部欢迎任何领域和任何地方的投稿。争取在《科学》发表文章的竞争很激烈,许多投稿在没有得到进一步的同行评议之前就被退回。我们对在有广泛兴趣的领域中有创新的文章优先。我们对投来的稿件坚定地履行快速评审、快速发表的原则。 下面介绍一下: 署名文章的栏目 稿件的选择 接受稿件的条件 文章的署名 曾经发表的文章 与《科学》联系 稿件的准备 在线的补充数据 投稿 《科学》周刊参考文献格式
署名文章的栏目 报告(Reports)栏目发表新的有广泛意义的重要研究成果。报告长度不超过2500单词或《科学》版面的3页。报告要包括摘要和引言。参考文献应在30条以内。 研究文章(Research Articles)栏目发表反映某一领域的重大突破的文章,文章长度不超过4500单词或5页,包括一个摘要、一个引言、和加有简短的小标题的内容部分。参考文献建议最多不超过40条。技术评论(Technical Comments)讨论《科学》周刊过去6个月内发表的论文,长度不超过500单词。原文章作者将被给与答复评论的机会。评论和答复都要得到评议和必要的编辑。讨论的提要刊登在印刷版,全文刊登在电子版。 《科学》指南(Science's Compass)栏目为广大读者提供由科学家或其他专家撰写的对当前科学问题的评论。除了读者来信,本栏目的文章都是由编辑们约稿的,但有时对未被邀请的稿件也予以考虑。来信(Letters)一般不超过300单词,讨论《科学》上已发表的内容或普遍感兴趣的问题。来信应该直接投到我们的网站(或以电子信形式投来().编辑不通知作者是否收到来信,而且可能对来信加以修改以求明了或满足版面的限制。来信发表时,编辑一般不再征求作者的意见。政策论坛(Policy Forum)(2000单词以下)讨论科学政策,科学与社会短文(Essays on Science and Society)(2000单词)着重于科学与
科学的发展往往出乎我们的意料——美《科学》杂志主编点评本年度 十大科技突破 被列为2011年十大科技突破榜首的是HPTN052的HIV研究项目——早期口服抗逆转录病毒药物(ARVs)预防HIV感染,研究对1700多对异性伴侣中其中一位感染了人类免疫缺陷病毒(HIV)的感染者进行了实验,其中一半感染者服用了这种抗逆转录病毒药物,而另一半人则当他们的免疫系统下降到危险的程度时才给予治疗,结果发现早期治疗者伴侣受感染的比例大为降低,受感染者本身的情况也有所改善。可以相信,ARVs与之前其他效果较好的临床治疗方法相结合,可以一年前不可想象的方式阻止全世界艾滋病疫情的泛滥。“在下一代人中消除艾滋病的远大目标可有望实现,”美国国务卿希拉里·克林顿在上个月对科学家们如此说道。 这并不是说,我们要放弃寻找艾滋病疫苗,ARVs作为一种预防性治疗手段,并无法承诺在一夜之间改变艾滋病疫情蔓延的严峻形势,但它让我们看到了攻克艾滋病的希望,并在2011年十大科技进展中名列榜首。 本年度榜上有名的另外九大科技突破也令人兴奋,大多数科技领域都取得了稳步进展,这也正符合了科技进步的总趋势。目前已有迹象表明,2012年将是一个令人兴奋的科学年,欧洲粒子物理研究所的科学家有可能发现一直以来令人难以捉摸的希格斯玻色子存在的迹象,这是一种解释其他粒子如何获得质量的假想中的基本粒子,它将成为来年科学界重大突破之一,我们期待这一成果的最新报道。但是,未来科学的发展往往总是出乎我们的意料,未来一年必定会给我们带来更多令人眼花缭乱的惊喜。 但是,今年科学界的新闻并非都是喜讯,遗憾的是,我们生活在一个“否定科学”已成为一种时尚的时代,例如在美国,许多政界人物迫于种种压力,不愿意公开支持关于气候变化的科学事实。为了应对这种“否定科学”现象,正如我一直反复强调的那样,科学界需要更重视科学教育,不是简单地将所知道的知识传授给学生,同时还要将科学家推理和解决问题的能力赋予所有的学生,也许有一天,科学教育在提高学生动手能力和探索世界能力方面所取得的显著成果也将成为年度重大科技突破之一。 ——布鲁斯·艾伯茨 相关链接2011年十大科学突破 近期美国《科学》杂志公布了其评选的本年度十大重要科学突破,一项大规模艾滋病临床试验成果被列为本年度最重要的科学突破,其他九项突破涉及行星科学、考古学、生命科学、天文学和化学等。 艾滋病防治获重大进展 令人信服的一些新证据显示,口服抗逆转录病毒药物(ARVs)可有效预防异性伴侣间的艾滋病传染。
S C I各领域国际顶尖学术期刊一览中国科学院科技情报中心将各领域的SCI期刊按影响因子大小分成四个区,其中一区和二区为高影响因子论文,三区为中等影响因子论文,四区为低影响因子论文。其中,一区和二区的一小部分杂志被列为顶尖学术期刊(TopJournal)。以下为生物领域顶尖学术期刊的详细名单 分区?中文分类??刊名简称? 1 生物 AMJHUMGENET 1 生物 ANNUREVBIOCHEM 1 生物 ANNUREVBIOPHBIOM 1 生物 ANNUREVCELLDEVBI 1 生物 ANNUREVGENET 1 生物 ANNUREVMICROBIOL 1 生物 ANNUREVPHYSIOL 1 生物 ANNUREVPLANTPHYS 1 生 物 BBA-REVBIOMEMBRANES 1 生物 BIOESSAYS 1 生物 CELL 1 生物 CURRBIOL 1 生物 CURROPINCELLBIOL 1 生物 CURROPINGENETDEV 1 生物 CURROPINPLANTBIOL 1 生物 CURROPINSTRUCBIOL 1 生物 CYTOKINEGROWTHFR 1 生物 DEVELOPMENT 1 生物 DEVCELL 1 生物 EMBOJ
1 生物 FASEBJ 1 生物 FEMSMICROBIOLREV 1 生物 GENEDEV 1 生物 GENOMERES 1 生物 HUMMOLGENET 1 生物 JCELLBIOL 1 生物 MICROBIOLMOLBIOLR 1 生物 MOLCELLBIOL 1 生物 MOLBIOLCELL 1 生物 MOLCELL 1 生物 NATBIOTECHNOL 1 生物 NATCELLBIOL 1 生物 NATGENET 1 生物 NATREVGENET 1 生物 NATREVMOLCELLBIO 1 生物 NATSTRUCTBIOL 1 生物 PLANTCELL 1 生物 PROGNUCLEICACIDRE 1 生物 TRENDSBIOCHEMSCI 1 生物 TRENDSCELLBIOL 1 生物 TRENDSECOLEVOL 1 生物 TRENDSGENET 1 生物 TRENDSPLANTSCI 2 生物 AMJPHYSIOL-CELLPH 2 生物 APPLENVIRONMICROB 2 生物 BIOCHEMJ 2 生物 BIOCHEMISTRY-US 2 生物 BIOLREPROD 2 生物 BIOPHYSJ 2 生物 DEVBIOL