High Angular Resolution and Extrasolar Planets Beyond Basic Instrumental Performances

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高中时文阅读：神舟十八号航天员模拟太空应急演练(解析版)

高中英语外刊时文阅读训练神舟十八号航天员模拟太空应急演练Ⅰ.外刊原文阅读Ⅱ.阅读理解专项针对性练习Ш.新课标高频词汇提取及训练Ⅳ.参考译文赏析【原文·外刊阅读】Shenzhou-18 crew conducts emergency drill simulating space debris impact on Tiangong（文章来源：Global Times）After China's Shenzhou-18 crew smoothly delivered their first spacewalk in early July, the three taikonauts recently conducted a series of examination and maintenance works onthe Tiangong space station, as well as a full-system emergency drill incase of internal pressure loss in the space station due to potential spacedebris impact, China Central Television (CCTV) reported Sunday.In coordination with ground control teams, the crew carried out anemergency response exercise, which began with a simulated spacestation pressure loss alarm, where taikonauts checked the alarm status,made judgments and located the leak positions. Meanwhile, the groundteam cooperated seamlessly with the crew to seal the leak in orbit, successfully completing the drill, according to CCTV.Before the drill started, the Shenzhou-18 crew completed equipment confirmation tests, item preparation, manual study and other preparatory tasks, the CCTV report said.Generally speaking, space debris impact can be divided into two scenarios. One is very small particle-like debris that would only cause minor damage which could potentially threaten some external equipment; the other isthe impact of larger debris with sizes of about five millimeters or centimeter-level, which could potentially penetrate the hull, which could even cause severe breaches in the structure, Wang Ya'nan, chief editor ofBeijing-based Aerospace Knowledge magazine, told the Global Times on Sunday.Overall, Tiangong being hit by space debris is a possibility, but unlikely. However, as the Chinese space station now reaches a relatively large scale with its basic construction completed, it must take precautions, Wang said.In the event of such a scenario, China's top priority is ensuring the safety of its taikonauts.Therefore, emergency drills will first need taikonauts to assess the extent of the damage to the space station's compartments, utilizing data from sensors to identify areas with potential leak, Wang noted.If the damage is minor, they can ensure the safety of other compartments by closing off depressurized sections. And in urgent scenarios, the taikonauts will have to conduct an emergency evacuation, including moving to safe compartments or to the docked manned spacecraft for temporary shielding, or even making an emergency return, Wang said.Space observers told the Global Times that they are fully confident that China can handle such scenarios."The space station is like a balloon, with pressure inside high but the external environment is close to a vacuum. However, unlike a balloon, the structure of space station is very sturdy. During the construction stage, Chinese researchers have fully taken into consideration the event of external impacts," Wang said.Additionally, China is not passively defending against these threats. Through international data sharing, as well as ground-to-space observations, we are closely monitoring the trajectories of large debris, allowing us to predict their movements in advance. If they approach the space station, the station can adjust its orbit to avoid a collision, Wang noted.The Global Times learned from Lin Xiqiang, spokesperson of the China Manned Space Agency, in April prior to the launch of Shenzhou-18, that the prevention and damage repair of space debris impact will be a key task during their stay."With human space activities rapidly increasing in recent years, the problem of space debris has become more prominent," Lin said. He noted that they had previously discovered that some of the solar panel cables on Tiangong were damaged by space debris impacts, leading to a partial loss of power supply.Building on the existing space debris protection mechanism at the station, the Shenzhou-18 crew will installdebris protection reinforcement devices on external pipelines, cables and key equipment during their extravehicular activities. They will also conduct external inspections as needed to further ensure the safety of the space station.Apart from the emergency drill, the Shenzhou-18 crew has also recently conducted a study on emotion recognition and evaluation in orbit, using testing software to fill out questionnaires on "mood status," complete color preference tests and emotional image tests.Based on the results, ground researchers will explore the changing patterns of the emotional states of the taikonauts during manned spaceflight missions and study the effects of medium to long-term flights.【原创·阅读理解】1.What did the Shenzhou-18 crew do after their first spacewalk in early July?A. Conducted a series of examination and maintenance works on the Tiangong space station.B. Held a press conference with international space agencies.C. Completed a space debris impact study.D. Launched a new satellite into orbit.【答案】A【解析】根据文章内容，神舟18号航天员在7月初完成首次太空行走后，进行了对天宫空间站的一系列检查和维护工作。

开普勒温度

开普勒温度什么是开普勒温度？开普勒温度是一种用于描述行星轨道上温度分布的物理量。

它得名于德国天文学家约翰内斯·开普勒（Johannes Kepler），他在17世纪提出了行星运动的三大定律之一，即开普勒第三定律。

开普勒温度是通过比较行星的接收到的辐射能量和其发出的热辐射能量来定义的。

根据热力学原理，一个物体在热平衡状态下，它所吸收的辐射能量应该等于其发出的热辐射能量。

因此，可以通过计算一个行星所吸收和发出的辐射能量来确定其表面温度。

开普勒温度的计算公式开普勒温度可以使用如下公式进行计算：其中： - Tk表示开普勒温度； - T表示恒星的表面温度； - R表示恒星的半径；- D表示恒星的距离； - a表示行星与其母星之间的平均距离。

开普勒温度的意义和应用开普勒温度是研究行星大气层特性和适居性的重要指标。

它可以帮助科学家判断一个行星是否有可能存在液态水，从而提供了寻找外地球类行星的线索。

开普勒温度还可以用于比较不同行星之间的温度差异。

通过计算不同行星的开普勒温度，我们可以了解它们所处环境的热力学特性，并进一步推测其大气成分、气候条件等信息。

此外，开普勒温度还有助于研究恒星和行星系统中潜在存在生命的可能性。

如果一个行星位于其母恒星适居带内，并且具有适当范围内的开普勒温度，那么它有可能拥有液态水和其他生命所需的条件。

开普勒温度与适居性适居性是指一个天体能否提供适合地球生命存在和发展的环境条件。

开普勒温度是评估行星适居性的重要因素之一。

根据开普勒温度的计算公式，我们可以推断以下几点： - 如果一个行星的开普勒温度过高，超过了液态水的临界点，那么该行星上很可能不存在液态水，从而不适合生命存在。

- 如果一个行星的开普勒温度过低，低于液态水的临界点，那么该行星上也不适合生命存在。

- 只有当一个行星的开普勒温度在适当范围内（通常在0℃到100℃之间），才有可能存在液态水和类地球生命。

因此，通过计算行星的开普勒温度，我们可以初步判断其是否具备适居性。

SrVO3 Hubbard band 和氧空位

PHYSICAL REVIEW B94,241110(R)(2016)Hubbard band versus oxygen vacancy states in the correlated electron metal SrVO3S.Backes,1T.C.R¨o del,2,3F.Fortuna,2E.Frantzeskakis,2P.Le F`e vre,3F.Bertran,3M.Kobayashi,4R.Yukawa,4 T.Mitsuhashi,4M.Kitamura,4K.Horiba,4H.Kumigashira,4R.Saint-Martin,5A.Fouchet,6B.Berini,6Y.Dumont,6A.J.Kim,1F.Lechermann,7,8H.O.Jeschke,1M.J.Rozenberg,9R.Valent´ı,1,*and A.F.Santander-Syro2,†1Institut f¨u r Theoretische Physik,Goethe-Universit¨a t Frankfurt,Max-von-Laue-Strasse1,60438Frankfurt am Main,Germany 2CSNSM,Univ.Paris-Sud,CNRS/IN2P3,Universit´e Paris-Saclay,91405Orsay Cedex,France3Synchrotron SOLEIL,L’Orme des Merisiers,Saint-Aubin-BP48,91192Gif-sur-Yvette,France 4Photon Factory,Institute of Materials Structure Science,High Energy Accelerator Research Organization(KEK),1-1Oho,Tsukuba305-0801,Japan5SP2M-ICMMO-UMR-CNRS8182Universit´e Paris-Sud,Universit´e Paris-Saclay,91405Orsay Cedex,France 6GEMaC,Universit´e de Versailles St.Quentin en Y.-CNRS,Universit´e Paris-Saclay,Versailles,France7Institut f¨u r Theoretische Physik,Universit¨a t Hamburg,Jungiusstrasse9,20355Hamburg,Germany8Institut f¨u r Keramische Hochleistungswerkstoffe,TU Hamburg-Harburg,D-21073Hamburg,Germany 9Laboratoire de Physique des Solides,CNRS,Univ.Paris-Sud,Universit´e Paris-Saclay,91405Orsay Cedex,France(Received22February2016;published19December2016)We study the effect of oxygen vacancies on the electronic structure of the model strongly correlatedmetal SrVO3.By means of angle-resolved photoemission spectroscopy(ARPES)synchrotron experiments,we investigate the systematic effect of the UV dose on the measured spectra.We observe the onset of a spuriousdose-dependent prominent peak at an energy range where the lower Hubbard band has been previously reportedin this compound,raising questions on its previous interpretation.By a careful analysis of the dose-dependenteffects we succeed in disentangling the contributions coming from the oxygen vacancy states and from the lowerHubbard band.We obtain the ARPES spectrum in the limit of a negligible concentration of vacancies,wherea clear signal of a lower Hubbard band remains.We support our study by means of state-of-the-art ab initiocalculations that include correlation effects and the presence of oxygen vacancies.Our results underscore therelevance of potential spurious states affecting ARPES experiments in correlated metals,which are associatedwith the ubiquitous oxygen vacancies as extensively reported in the context of a two-dimensional electron gas atthe surface of insulating d0transition metal oxides.DOI:10.1103/PhysRevB.94.241110Introduction.A major challenge of modern physics is to understand the fascinating phenomena in strongly correlated transition metal oxides(TMOs),which emerge in the neighbor-hood of the Mott insulator state.Some preeminent examples that have gathered interest for almost30years are high temperature superconductivity,colossal magnetoresistance, heavy fermion physics,and,of course,the Mott metal-insulator transition itself[1].Signiﬁcant theoretical progress was made with the introduction of dynamical meanﬁeld theory (DMFT)and its combination with ab initio density functional methods[local density approximation(LDA)+DMFT],which allows treatment of the interactions promoting itinerancy and localization of electrons on equal footing[2–4].Among the most emblematic achievements of DMFT is the prediction of a Hubbard satellite,which separates from the conduction band of a metal.This satellite results from the partial localization of conduction electrons due to their mutual Coulomb repulsion. Early DMFT studies also showed that it is the precursor of the localized electronic states of a Mott insulator[5].Since then,these predictions promoted a large number of studies using photoemission spectroscopy,which is a technique to directly probe the presence of Hubbard bands.In this context, the TMO system SrVO3has emerged as the drosophila model system to test the predictions of strongly correlated electron *valenti@itp.uni-frankfurt.de†andres.santander@csnsm.in2p3.fr theories.In fact,SrVO3is arguably the simplest correlated metal.It is a simple cubic perovskite,with nominally one electron per V site,which occupies a threefold degenerate t2g conduction band.While the presence of a satellite in the photoemission spectra of Ni metal was already well known,in the context of correlated TMOs,the Hubbard band was originally reported in a systematic investigation of Ca1−x Sr x VO3[6],which was followed by many subsequent studies,including angle-resolved photoemission spectroscopy (ARPES)[7–9]and comparisons with theoretical predictions (see,for instance,Refs.[10–20],among others).One of the most salient features in SrVO3is the observation of a broad peak at an energy of about−1.5eV in angle integrated photoemission spectra(upper black curve in Fig.1), which is interpreted as a Hubbard satellite linked to the V t2g electrons.This feature is also seen in a large range of 3d1materials[21,22].The ratio of spectral strength between the quasiparticle(QP)state and the incoherent satellite in SrVO3is an important indicator of the magnitude of electron correlations[1,2].However,photoemission experiments using different photon energies or light brilliance have reported very dissimilar values for such a ratio[11],making the quantitative benchmarking of realistic ab initio theories for correlated electron systems difﬁcult[6,11,18,23,24].Moreover,as shown in Fig.1,a broad peak at about the same energy is also observed in several d0TMO cubic perovskites,such as SrTiO3, KTaO3,or anatase TiO2.Nevertheless,in all these cases the feature has been clearly linked to the presence of oxygenS.BACKES et al.PHYSICAL REVIEW B94,241110(R)(2016)FIG.1.Integrated UV photoemission spectra for various per-ovskite oxides,showing a quasiparticle peak at E F and an in-gap state at energies between1and1.5eV.For SrVO3(upper black curve),a correlated-electron metal,the QP peak corresponds to the bulk conduction band,and as will be shown further,the in-gap state is a superposition of the lower Hubbard band and localized electronic states associated with oxygen vacancies.For the other d0 oxides,such as KTaO3(blue curve),anatase TiO2(green curve), or SrTiO3(red curve),the QP peak and in-gap state correspond respectively to a conﬁned quasi-2D electron gas at the sample surface and to localized states,all formed by oxygen vacancies.The crystal orientation(normal to the samples’surface)is indicated in all cases. defects[25–32].Interestingly,recent ab initio calculations show that the spectral weight at−1.3eV in SrTiO3most likely is not of Ti t2g orbital character,but should be understood as an in-gap defect state with Ti e g character[33–36].Thus,we are confronted with the fact that at about1.5eV below the Fermi level(E F),weﬁnd the lower Hubbard bands of d1systems as well as the in-gap states of oxygen-deﬁcient d0systems.In view of these observations one may unavoidably wonder(and worry),despite the great success of DMFT methods,whether the putative Hubbard satellite of SrVO3might also originate from oxygen vacancy states.Moreover,one should also worry about the possibility of these extrinsic states affecting the features of the conduction band dispersion.In the present Rapid Communication we resolve these issues in a thorough manner.We present a systematic photoemission study of SrVO3,to demonstrate dramatic consequences in the spectra due to the creation of oxygen ing ARPES,we directly show that the UV or x-rays used for measurements can produce a large enhancement, of almost an order of magnitude,of the peak at−1.5eV, similar to the effect observed in d0oxide insulators[25–28,37].Despite these signiﬁcant effects on the energy states around the Mott-Hubbard band,we are able to determine the bulk SrVO3photoemission spectrum in the limit of a negligible concentration of vacancies,where a clear signal of the dispersive correlated Hubbard band remains.We support the interpretation of the experimental data by means of state-of-the-art LDA+DMFT calculations on SrVO3with oxygen vacancies.Consistent with our experimental data,the calculations show that oxygen vacancies produce states(of e g symmetry)at energies near the Hubbard satellite.While our study provides deﬁnite evidence of a correlated Hubbard band in SrVO3as predicted by DMFT,it also underlines the signiﬁcant effects due to oxygen vacancies,which may also affect photoemission data in other TMOs.Methods.The bulk-like relaxed,crystalline(001)oriented SrVO3thinﬁlms were grown by pulsed laser deposition (PLD)either at the GEMaC laboratory,then measured at the CASSIOPEE beamline of Synchrotron SOLEIL,or in a PLD chamber directly connected to the ARPES setup at beamline2A of KEK-Photon Factory(KEK-PF)[9,38,39]. To clean the surfaces in UHV prior to ARPES experiments at SOLEIL,the SrVO3thinﬁlms were annealed at550◦C for t=5–20min at pressures lower than2×10−8Torr.At KEK-PF,the PLD growth was performed under a pressure below10−7Torr,to obtain UHV-clean surfaces,using a Sr2V2O7target,which has excess oxygen with respect to SrVO3,thus minimizing the formation of vacancies during the growth.In all cases,the surface quality was conﬁrmed right before ARPES measurements by low-energy electron diffraction(LEED).The thinﬁlms measured at KEK-PF showed a c(4×4)surface reconstruction,which does not affect the analysis and conclusions of this work.For the ARPES measurements we used linearly polarized photons in the energy range30–110eV and hemispherical electron analyzers with vertical slits at SOLEIL and horizontal slits at KEK-PF.The angular and energy resolutions were0.25◦and 15meV.The mean diameter of the incident photon beam was smaller than100μm.The UV light brilliance,measured using calibrated photodiodes,was≈5×109photons s−1μm−2at SOLEIL,and about100times smaller at KEK-PF.The samples were cooled down to T=20K before measuring.Unless speciﬁed otherwise,all data were taken at that temperature. The results were reproduced on more thanﬁve samples.All through this Rapid Communication,directions and planes are deﬁned in the cubic unit cell of SrVO3.We denote [hkl]the crystallographic directions in real space, hkl the corresponding directions in reciprocal space,and(hkl)the planes orthogonal to those directions.The indices h,k,and l of hkl correspond to the reciprocal lattice vectors of the cubic unit cell of SrVO3.The Supplemental Material[40]presents further details about the sample growth and measurements.Experimental results.Figure2(a)shows the integrated photoemission spectra of SrVO3as a function of the UV dose, measured at CASSIOPEE SOLEIL under the same conditions of light brilliance of any standard ARPES experiment at a third-generation synchrotron.The measurements were done by continuously irradiating the sample with hν=33eV photons while recording the spectra as a function of irradiation time, with an accumulation time of about2min per spectrum.The blue and black curves show spectra for the lowest and highest measured doses,obtained respectively after∼2min and∼2h of irradiation.These data clearly demonstrate that the very UV or x-rays used for photoemission experiments can produce radical changes in the measured spectra of SrVO3.Note in fact that a similar effect has been observed for VO2[41].In particular,from Fig.2(a)we observe that the amplitude ofHUBBARD BAND VERSUS OXYGEN V ACANCY STATES IN THE...PHYSICAL REVIEW B94,241110(R)(2016)FIG.2.(a)Photoemission spectra of SrVO3as a function of UV dose,measured at Synchrotron SOLEIL(hν=33eV).The energy distribution curves(EDCs)were extracted from raw ARPES data around the 002point integrated along the k= 010 direction.(b)Corresponding momentum distribution curves(MDCs)integrated over50meV below E F.Peaks in the MDCs indicate the Fermi momenta.(c),(d)Same as(a),(b)for SrTiO3(hν=47eV).Theﬁlling of a2DEG upon UV irradiation is evidenced by the formation of QP peaks in the EDCs and MDCs at E F[inset of(c)and(d),respectively].All data were taken at20K.the in-gap state at−1.5eV,and,more signiﬁcantly,the ratio of in-gap to quasiparticle(QP)amplitudes,strongly increase with increasing UV dose,going from about1:3in a pristine sample to more than2:1in a heavily irradiated sample. Importantly,note that the QP peak position remains basically dose independent,implying that the carriers created by the UV or x irradiation do not signiﬁcantly dope the conduction band,and form dominantly localized states.This is conﬁrmed in Fig.2(b),which shows that the Fermi momenta of the QP band,given by the peak positions in the momentum distribution curves(MDCs)at E F,are also dose independent. Additional data presented in the Supplemental Material further demonstrate that our measurements yield the expected3D bulk Fermi surface of SrVO3.Thus,the observed increase in intensity of the in-gap state upon UV irradiation cannot be ascribed to a change inﬁlling of the conduction band,which could have affected the electron correlations.Instead,this unambiguously shows the light-assisted formation of localized defect states at essentially the same energy as that of the expected intrinsic lower Hubbard band—which should then resemble the in-gap peak observed at the lowest UV doses.In fact,as mentioned previously,it is well established that strong doses of UV or x-rays create a large concentration of oxygen vacancies in several d0perovskites[25–32,42]. As illustrated in Figs.2(c)and2(d)for the case of SrTiO3, the progressive doping of the surface region with oxygen vacancies,due to synchrotron UV irradiation,has two effects: the formation of a very intense in-gap state at about−1.3eV, and,in contrast to SrVO3,the simultaneous creation of a sharp QP peak at E F corresponding to a conﬁned quasi-2D electron gas(2DEG)at the samples’surface.The effective mass of such2DEG,precisely determined by ARPES,matches the mass expected from density functional theory calcula-tions[25,26,43,44].Thus,as in SrVO3,the increase in intensityof the in-gap state observed in SrTiO3upon UV or x irradiationcannot be due to an onset or increase of electron correlations,and should be ascribed to an extrinsic effect.We therefore conclude that,in SrVO3,exposure to syn-chrotron UV or x-rays creates oxygen vacancies,which are inturn responsible for the extrinsic increase in intensity of thein-gap state evidenced by our measurements.This effect canseriously obscure the determination of the spectral function ofthis model system,thus hampering the advancement of validtheories for correlated electron systems.Theﬁndings described above imply that the correct ex-perimental determination of the vacancy-free photoemissionspectrum of SrVO3should(i)use samples that from thebeginning have the lowest possible concentration of oxygenvacancies,and(ii)use doses of UV or x-ray light low enoughto avoid light-induced changes in the measured spectra.Tothis end,we measured SrVO3thinﬁlms grown directly insitu at beamline2A of KEK-PF.As mentioned before,the growth protocol of such thinﬁlms minimizes the formationof vacancies,while the UV light brilliance at KEK-PF is ∼100times smaller than the one in Figs.2(a)and2(b)from measurements at SOLEIL.We checked(see the SupplementalMaterial)that under these conditions the spectra did notchange with time,even after several hours of measurements.The resulting energy-momentum ARPES map,and its secondderivative,are presented in Figs.3(a)and3(b).One clearlyobserves the dispersing QP band along with an also dispersivein-gap state of weaker intensity,corresponding to the intrinsiclower Hubbard band,as reported in previous works[7].Theintrinsic spectral function of SrVO3will then be given by such aphotoemission spectrum,which approaches the vacancy-freelimit,modulo dipole-transition matrix elements,inherent toS.BACKES et al.PHYSICAL REVIEW B94,241110(R)(2016)FIG.3.(a)Energy-momentum ARPES intensity map measured at KEK-PF with a low UV dose on a SrVO3sample prepared in situ,using a well-established protocol to minimize the formation of oxygen vacancies(see the main text and Supplemental Material).Note that due to the choice of light polarization,the heavy bands along(100)are not observed and only the contribution of the light d xy band is detected.The data were acquired at hν=88eV around ¯103.(b)Second derivative(negative values)of the map in(a).The use of second derivatives allows a better visualization of the dispersion of both the quasiparticle and Mott-Hubbard bands on the same color plot.The dispersionless feature at E F is a spurious effect of such a second derivative on the Fermi-Dirac cutoff.(c),(d)Same as(a),(b)after a strong UV irradiation dose,measured at SOLEIL(hν=33eV),typical of modern third-generation synchrotrons.The measurements were done at hν=33eV close to 002.All data were taken at20K.Note that at constant photon energy,ARPES maps out the electronic structure at a spherical surface of three-dimensional (3D)k space,which can be locally approximated to a plane for all our measurements(details in the Supplemental Material).The different choice of photon energies and k-space positions for measurements at KEK-PF[(a)and(b)]and SOLEIL[(c)and(d)]was dictated by the different geometrical conﬁgurations and constraints of the beamlines in both synchrotrons.the photoemission process,which can still modulate the intensity of the QP peak relative to the Hubbard peak.A calculation of such matrix elements requires a full one-step calculation of the photoemission process,which is beyond the scope of this work.By contrast,Figs.3(c)and3(d) show the momentum-resolved electronic structure of a sample, measured at SOLEIL,that was intensively irradiated.There, the peak at−1.5eV becomes broader,more intense,and nondispersive—all characteristic signatures of a high random concentration of oxygen vacancies.Numerical calculations.To rationalize from a microscopic point of view the inﬂuence of oxygen vacancies on the electronic structure of SrVO3,we performed charge self-consistent LDA+DMFT calculations for bulk SrVO3and var-ious relaxed oxygen-deﬁcient SrVO3supercells.The latter are computationally demanding calculations.We shall focus here on the case of a2×2×3supercell with two oxygen vacancies located at opposite apical sites of one vanadium atom,as shown in the inset of Fig.4(b).We use such a vacancy arrangement as it is the prototypical one for d0compounds[43].For our LDA+DMFT calculations we chose values of U= 2.5eV and J=0.6eV for vanadium and included the effects of bandwidth renormalization due to dynamically screened Coulomb interactions by following the prescription suggested in Ref.[45](the LDA+DMFT unrenormalized data are shown in the Supplemental Material).In Figs.4(a)and4(c)we show, respectively,the results of the k-integrated and k-resolved spectral functions for bulk SrVO3without oxygen vacancies. Weﬁnd the expected features of a t2g quasiparticle peak at the Fermi level and a lower Hubbard band at negative energies of the same t2g nature,in agreement with the photoemission spectra in Fig.2(a)and Figs.3(a)and3(b).The light band at E F along k 100 [Fig.4(c)]consists of two degenerate bands of d xy and d xz characters,while the heavy band along the same direction has d yz character.While comparing with the measured k-resolved spectral function[Figs.3(a)and3(b)],HUBBARD BAND VERSUS OXYGEN V ACANCY STATES IN THE...PHYSICAL REVIEW B94,241110(R)(2016)FIG.4.LDA+DMFT results for SrVO3including bandwidth renormalization effects[45].(a)k-integrated spectral function for bulk SrVO3.The V t2g orbitals show a quasiparticle peak at E F and a lower Hubbard band at−1.6eV.(b)Spectral function for the2×2×3supercell of SrVO3with two oxygen vacancies.An additional nondispersive V e g vacancy state originating from the V atom neighboring the oxygen vacancies leads to a sharp peak below the Fermi level at∼−1.0eV.The V t2g orbitals show a quasiparticle peak at E F and a lower Hubbard band at−1.8eV.(c)and(d)show the corresponding spectral functions(multiplied by a Fermi-Dirac function at20K)along the X- -X path.one should bear in mind that along -X(or -Y)the heavy d yz(or d xz)bands are silenced by dipole-transition selection rules in the experiment[25].Inclusion of bandwidth renormalization[45]renders the lower Hubbard band at an energy(−1.6eV)in reasonable agreement with experiment (−1.5eV).We adopted typical values for U and J from the literature.We did not attempt to further optimize the values to get a better quantitative agreement with the experimental data, for two reasons:First is the heavy numerical cost,and second, as we show next in the calculations with oxygen vacancies, the adopted values facilitate the distinct visualization of the contributions from the Hubbard and localized states to the incoherent peak at∼−1.5eV.The removal of oxygen atoms in the system leads to the donation of two electrons per oxygen to its surrounding. Already at the level of density functional theory(DFT)in the local density approximation(LDA)(see the Supplemental Material),weﬁnd that most of the charge coming from the additional electrons is transferred to the3d z2orbitals of the neighboring V atom,developing into a sharp peak of e g symmetry located around−1.0eV,i.e.,at an energy close to the position of the experimentally observed oxygen vacancy states.In analogy to the experimental average over many lattice sites,note that averaging among various supercells with differentoxygen vacancy locations and concentrations(which is beyondthe scope of the present work)would result in a wider in-gape g band,as demonstrated for the case of SrTiO3(see Fig.3ofRef.[34])and for some cases in SrVO3(see the SupplementalMaterial,Fig.S7).By including electronic correlations within(bandwidth renormalized)LDA+DMFT we then see that allthe experimental observations qualitatively emerge.In fact,the conducting t2g orbitals develop a lower Hubbard bandpeaked at energies about−1.8eV[Figs.4(b)and4(d)],similarto the bulk case without oxygen vacancies.Most notably,this lower Hubbard satellite does not increase in amplitudewith the introduction of vacancies,but rather broadens.Inaddition,the oxygen vacancy defect states situated at about −1eV remain qualitatively unchanged by the correlation effects,but experience a broadening with respect to the pureLDA case.This is in agreement with the photoemission data,evidencing that the increase in intensity of the in-gap statein the oxygen-deﬁcient SrVO3is not to be attributed to anincrease in population of the lower Hubbard satellite,butinstead to the manifestation of vacancy states of e g character.Conclusions.In summary,we performed a detailed study of the effects of oxygen vacancies in the spectroscopy of the archetypal strongly correlated electron system SrVO3.We found that oxygen vacancy states,which are created by UV or x-ray irradiation,occur at energies close to the Hubbard satellite.This dramatically affects the measured line shape of the Mott-Hubbard band and the ratio of intensities between the quasiparticle and the Mott-Hubbard peaks.By means of a systematic study under a controlled irradiation dose, using samples directly grown in situ,we were able to obtain the photoemission spectrum of the bulk SrVO3system in the limit of a negligible concentration of oxygen vacancies. Our experimental interpretation is supported by LDA+DMFT calculations,which provided further insight into the likely nature of the oxygen vacancy states.Acknowledgments.We thank Silke Biermann,Ralph Claessen,Marc Gabay,and Michael Sing for discussions. This work was supported by public grants from the French National Research Agency(ANR),project LACUNES No. ANR-13-BS04-0006-01,and the“Laboratoire d’Excellence Physique Atomes Lumi`e re Mati`e re”(LabEx PALM project ELECTROX)overseen by the ANR as part of the“Investisse-ments d’Avenir”program(reference:ANR-10-LABX-0039). S.B.,A.J.K.,F.L.,H.O.J.,and R.V.gratefully acknowledge the Deutsche Forschungsgemeinschaft forﬁnancial support through Grant FOR1346.T.C.R.acknowledges funding from the RTRA–Triangle de la Physique(project PEGASOS).A.F.S.-S.is thankful for support from the Institut Universitairede France.S.B.and T.C.R.contributed equally to this work.[1]M.Imada,A.Fujimori,and Y.Tokura,Metal-insulator transi-tions,Rev.Mod.Phys.70,1039(1998).[2]A.Georges,G.Kotliar,W.Krauth,and M.J.Rozenberg,Dynamical meanﬁeld theory of strongly correlated electronsS.BACKES et al.PHYSICAL REVIEW B94,241110(R)(2016)and the limit of inﬁnite dimensions,Rev.Mod.Phys.68,13 (1996).[3]G.Kotliar and D.V ollhardt,Strongly correlated materials:Insights from dynamical mean-ﬁeld theory,Phys.Today57(3), 53(2004).[4]G.Kotliar,S.Y.Savrasov,K.Haule,V.S.Oudovenko,O.Parcollet,and C.A.Marianetti,Electronic structure calculations with dynamical mean-ﬁeld theory,Rev.Mod.Phys.78,865 (2006).[5]X.Y.Zhang,M.J.Rozenberg,and G.Kotliar,Mott Transitionin the d=∞Hubbard Model at Zero Temperature,Phys.Rev.Lett.70,1666(1993).[6]I.H.Inoue,I.Hase,Y.Aiura,A.Fujimori,Y.Haruyama,T.Maruyama,and Y.Nishihara,Systematic Development of the Spectral Function in the3d1Mott-Hubbard System Ca1−x Sr x VO3,Phys.Rev.Lett.74,2539(1995).[7]M.Takizawa,M.Minohara,H.Kumigashira,D.Toyota,M.Oshima,H.Wadati,T.Yoshida,A.Fujimori,M.Lippmaa,M.Kawasaki,H.Koinuma,G.Sordi,and M.Rozenberg,Coherent and incoherent d band dispersions in SrVO3,Phys.Rev.B80, 235104(2009).[8]T.Yoshida,M.Hashimoto,T.Takizawa,A.Fujimori,M.Kubota,K.Ono,and H.Eisaki,Mass renormalization in the bandwidth-controlled Mott-Hubbard systems SrVO3and CaVO3studied by angle-resolved photoemission spectroscopy,Phys.Rev.B 82,085119(2010).[9]S.Aizaki,T.Yoshida,K.Yoshimatsu,M.Takizawa,M.Minohara,S.Ideta,A.Fujimori,K.Gupta,P.Mahadevan,K.Horiba,H.Kumigashira,and M.Oshima,Self-Energy on the Low-to High-Energy Electronic Structure of Correlated Metal SrVO3,Phys.Rev.Lett.109,056401(2012).[10]M.J.Rozenberg,I.Inoue,H.Makino,F.Iga,and Y.Nishihara,Low Frequency Spectroscopy of the Correlated Metallic System Ca1−x Sr x VO3,Phys.Rev.Lett.76,4781(1996).[11]A.Sekiyama,H.Fujiwara,S.Imada,S.Suga,H.Eisaki,S.I.Uchida,K.Takegahara,H.Harima,Y.Saitoh,I. A.Nekrasov,G.Keller,D.E.Kondakov,A.V.Kozhevnikov,Th.Pruschke,K.Held,D.V ollhardt,and V.I.Anisimov,Mutual Experimental and Theoretical Validation of Bulk Photoemis-sion Spectra of Sr1−x Ca x VO3,Phys.Rev.Lett.93,156402 (2004).[12]E.Pavarini,S.Biermann,A.Poteryaev,A.I.Lichtenstein,A.Georges,and O.K.Andersen,Mott Transition and Suppression of Orbital Fluctuations in Orthorhombic3d1Perovskites,Phys.Rev.Lett.92,176403(2004).[13]B.Amadon,F.Lechermann,A.Georges,F.Jollet,T.O.Wehling,and A.I.Lichtenstein,Plane-wave based electronic structure calculations for correlated materials using dynamical mean-ﬁeld theory and projected local orbitals,Phys.Rev.B77,205112 (2008).[14]M.Aichhorn,L.Pourovskii,V.Vildosola,M.Ferrero,O.Parcollet,T.Miyake,A.Georges,and S.Biermann,Dynamical mean-ﬁeld theory within an augmented plane-wave framework: Assessing electronic correlations in the iron pnictide LaFeAsO, Phys.Rev.B80,085101(2009).[15]M.Karolak,T.O.Wehling, F.Lechermann,and A.I.Lichtenstein,General DFT++method implemented with pro-jector augmented waves:Electronic structure of SrVO3and the Mott transition in Ca2−x Sr x RuO4,J.Phys.:Condens.Matter23, 085601(2011).[16]H.Lee,K.Foyevtsova,J.Ferber,M.Aichhorn,H.O.Jeschke,and R.Valent´ı,Dynamical cluster approximation within an aug-mented plane wave framework:Spectral properties of SrVO3, Phys.Rev.B85,165103(2012).[17]J.M.Tomczak,M.Casula,T.Miyake, F.Aryasetiawan,and S.Biermann,Combined GW and dynamical mean-ﬁeld theory:Dynamical screening effects in transition metal oxides, Europhys.Lett.100,67001(2012).[18]C.Taranto,M.Kaltak,N.Parragh,G.Sangiovanni,G.Kresse,A.Toschi,and K.Held,Comparing quasiparticle GW+DMFTand LDA+DMFT for the test bed material SrVO3,Phys.Rev.B 88,165119(2013).[19]J.M.Tomczak,M.Casula,T.Miyake,and S.Biermann,Asymmetry in band widening and quasiparticle lifetimes in SrVO3:Competition between screened exchange and local correlations from combined GW and dynamical mean-ﬁeld theory GW+DMFT,Phys.Rev.B90,165138(2014).[20]A.van Roekeghem and S.Biermann,Screened exchangedynamical meanﬁeld theory and its relation to density functional theory:SrVO3and SrTiO3,Europhys.Lett.108,57003(2014).[21]A.Fujimori,I.Hase,H.Namatame,Y.Fujishima,Y.Tokura,H.Eisaki,S.Uchida,K.Takegahara,and F.M.F.de Groot,Evolution of the Spectral Function in Mott-Hubbard Systems with d1Conﬁguration,Phys.Rev.Lett.69,1796(1992). 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高三英语科学前沿展望练习题40题(答案解析)

高三英语科学前沿展望练习题40题(答案解析)1. Scientists in the field of gene editing are exploring new techniques that could potentially _______ genetic diseases.A. preventB. promoteC. produceD. project答案解析：A。

本题考查对基因编辑领域相关词汇的理解以及在语境中的运用。

在基因编辑领域，科学家探索新技术的目的通常是预防基因疾病，“prevent”有“预防”的意思；“promote”表示“促进、提升”，通常用于积极事物的推动，与预防疾病语境不符；“produce”是“生产、产生”，不能与基因疾病搭配表示积极意义；“project”作动词有“计划、投射”等意思，与语境无关。

2. With the development of artificial intelligence, machines are becoming more and more capable of _______ complex tasks that were once exclusive to humans.A. handlingB. hangingC. hankeringD. harming答案解析：A。

本题的关键在于理解人工智能的能力。

在这个语境下，随着人工智能的发展，机器变得更有能力处理复杂任务，“handling”有“处理、应对”的意思；“hanging”是“悬挂”；“hankering”是“渴望”，为不及物动词，不能直接接任务；“harming”是“伤害”，均不符合语境。

3. In space exploration, astronauts often face challenges such as microgravity, which can _______ their physical and mental health.A. affectB. effectC. affordD. after答案解析：A。

life beyond earth 词汇

[P11] yield: 积极支持,热心拥护 [P12]boosterism: 积极支持热心拥护剩余物； [P13]residue: what remains after a part or quantity is taken or used剩余物；剩余物残余新纪元的; 有重大意义的; [P14]epochal: 新纪元的有重大意义的划时代的 [P14]settle for: to accept or allow sth., esp. sth. not entirely desirable.满足于 e.g.. He’ll settle for any kind of work. 持续的, 持久的; [P15]abiding: 持续的持久的不变的 [P15] hydrogen, nitrogen: H,N. 氢，氮逃不掉地; 解不开地; [P15]inextribly: 逃不掉地解不开地解决不了地 [P16]photosynthesis: process by which green plants convert carbon dioxide and water into food using the energy in sunlight 光合作用 [P16]basaltic rock: 玄武岩岩石
yieldБайду номын сангаас
• 生出，出产；产生：the apple tree yields plenty of apples. • ~capacity 生产能力 • 交出，投降：not yield a step. They yield the fortress to the enemy.
Life beyond earth
plausible
• Such talk, however plausible, is actually specious and groundless. 这些话，讲起来好像有道理，实际上是毫无根据、似是而非的空谈。 • He cast about in his mind for some plausible excuse for not turning up at the meeting. 他心里在算盘，想找一个什么说得过去的理由来解释他为什么没有到会。

高一宇宙探索英语阅读理解30题

高一宇宙探索英语阅读理解30题1<背景文章>The solar system is a fascinating place. It consists of the sun, eight planets, moons, asteroids, comets, and other celestial bodies. The sun is at the center of the solar system and is a massive ball of hot gas. It provides light and heat to all the planets.The eight planets in the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each planet has its own unique characteristics. Mercury is the closest planet to the sun and is very hot during the day and very cold at night. Venus is known as the Earth's sister planet because it is similar in size and composition. However, it has a thick atmosphere of carbon dioxide, which makes it very hot.Earth is the only planet known to support life. It has a moderate climate and a large amount of water. Mars is often called the Red Planet because of its reddish color. It has a thin atmosphere and evidence of past water.Jupiter is the largest planet in the solar system. It has a thick atmosphere of hydrogen and helium and many moons. Saturn is known for its beautiful rings. Uranus and Neptune are ice giants and have very cold temperatures.The planets in the solar system are in different positions. They orbit the sun in elliptical paths. The distance between the planets and the sun varies, which affects their temperatures and climates.1. The sun is at the center of the solar system and is a massive ball of ___.A. waterB. gasC. rockD. ice答案：B。

高英选四U6 Space and beyond The Call of the Challenger

3. What do you know about China’s future plans for space exploration?
The Call of
the Challenger
Understanding ideas
Do you know these space exploration “ Firsts”
First landing on the Moon
On 20 July 1969, Guided by a computer that was much less powerful than the ones used by today`s average school students, all three astronauts of the Apollo 11 mission made it safely back to Earth.
Look at the timeline and answer the questions.
1. Which of these spacecraft had a human on board when launched?
2. What are the recent events in China’s space programme? Add them to the timeline.
Space and beyond
Starting out
Watch the video and answer the questions.
1. How was the Sun formed? 2. Where are the Asteroid Belt and the
Kuiper Belt in the solar system? 3. What else do you know about the solar

中考英语太空探索的科学意义单选题40题

中考英语太空探索的科学意义单选题40题1. Scientists have discovered a new planet which might have water. This discovery ______ our understanding of the universe.A. expandsB. extendsC. spreadsD. stretches答案：A。

解析：本题考查动词的辨析。

expand有“扩大，扩展（知识、视野等）”的意思，在这里表示这一发现扩大了我们对宇宙的理解，符合太空探索科学意义中发现新事物对人类认知的扩展，是最恰当的；extend主要表示在长度、时间等方面的延伸；spread表示传播消息、疾病等）；stretch表示拉伸、伸展，这三个选项均不符合题意。

2. The discovery of exoplanets (系外行星) has made ______ possible for us to think about the existence of other forms of life.A. itB. thisC. thatD. one答案：A。

解析：本题考查it作形式宾语的用法。

make it + 形容词/名词+ to do sth.是一个固定结构，这里it指代后面的to think about the existence of other forms of life，其他选项没有这种用法，在太空探索科学意义方面，系外行星的发现使我们思考外星生命存在成为可能，这种语法结构正确表达了这一意义。

3. New research in space shows that some asteroids (小行星) may contain valuable minerals. This ______ future space mining.A. leads toB. results fromC. aims atD. depends on答案：A。

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a rXiv:as tr o-ph/22377v12Fe b22High Angular Resolution and Extrasolar Planets:Beyond Basic Instrumental Performances Jean Schneider CNRS -Paris Observatory,92195Meudon,France –Jean.Schneider@obspm.fr Abstract I review the characteristics of planetary systems accessible to imaging.I show that,beyond the basic angular resolution and dynamics performances of an optical “architecture”,other performances such as photometric precision,spectral range or timing are necessary to access some physical characteristics of the planets.1Introduction The main problem faced by the imaging of planetary systems is to separate the planets from their parent star.This requires two equally important capabilities:a suﬃcent angular resolution to separate the planet from thestar and a method of supression of stellar light to ﬁght the very high star to planet contrast (of the order of 106to 109).But many characteristics of the planetary system require other capabilities and the present paper is intended to point out that the traditional couple “High angular resolution and contrast”is not the ﬁnal response to all the scientiﬁc questions.12Characteristics of planets accessible to imag-ingMass:The most traditional quantity accessible beyond radial velocity mea-surements is the planet mass.The latter is measurable by astrometry.The astrometric precision forbidds to measure mass below a few Eerth masses. Another way to measure planet masses,with a much higher precision and down to fractions of Mars masses is to detect satellites of light planets and to infer the mass from the satellites revolution period and distance to the planet from Kepler laws(Schneider and Riaud2001).Radius R pl:It is can in principle be deduced from the planet thermal ﬂux(F pl)th given by(F pl)th=4πσR2pl×T4pl(1) The planet temperature T pl can be infered from the matching of a planckian function to the observed thermal spectrum(forgetting here complications due to absorption features).Albedo A:It can be measured from the reﬂectedﬂux(F pl)refl given by(F pl)refl(t)=F∗×A× R pldependence completely diﬀerent from(2.3),even in case of circular orbit. The solution is then to measureφ(t)along the orbit.That requires the capability to revisit the target several times(more then10along the orbit).Binary planets:By“binary planet”I mean a planet with a large satellite companion which can eventually be as large as the planet itself.In the Solar System we do not know such binary planets.But since binary astero¨ıds and brown dwarfs haved been discovered these last years,it is not an unreal-istic speculation that binary planets may exists in other planetary systems. They would not constitute just a curiosity,their existence would disturbe the planet mass function deduced from dynamical(radial velocity,astrometric and timing)measurements.How the separate a single from a binary planet?Even if the binary planet cannot be resolved,a straightforward way is to measure the position variations of the binary planet photocenter.Its amplitude(∆x)ph along a binary orbital period(“month”)is given by|F1a1−F2a2|(∆x)ph=(6)(M1+M2)(T41R21+T42R22)For instance,for an Earth with a large moon(half the Earth size),the pho-tocenter amplitude is3.310−3UA(=0.3mas10pc).3Variations of the planet temperature and albedo:Annual:It can be due to the eccentricity of the orbit or to the inclination of the planet rotation axis with respect to the normal to the orbital plane (seasonal variation).For an orbit with an eccentricity e,one simply has ∆T/T=e.In that case,the star to planet distance projected on the sky varies by an amount2ea sinα(=0.1a in case of an eccentricity0.1and α=30o)between two positions of extreme temperature variation.Diurnal:The combination of the existence of surface albedo inhome-geneities(continents and oceans)with the diurnal rotation of the planet causes a periodic variation of its reﬂectedﬂux.The period of this variation gives the duration of the day and its amplitude gives constraints on the sur-face features.For instance,on Earth,the albedo contrast continents/oceans is200to300%,giving rise to a relativeﬂux variation of a few tenths for the whole planet.Random:It is due to planet clouds or dust storms.On Earth,the global cloud coverage varies from30%to50%.For a mean surface albedo of20% and a cloud albedo of80%,the resulting random global albedo variation has an amplitude of10-20%.Some of these eﬀects have been estimated quantitatively in the case of the Earth(Ford,Turner and Seager2001).Nevertheless,it must be remarked that they will be diﬃcult to disentangle from other eﬀects(such as eccentric orbits or binary planets or planetary rings)without additional information on the planet position.It is important to point out that several conditions must be fulﬁlled in order to make these eﬀects measurable:1.The angular resolution must be suﬃcient(a fraction of mas)2.In order to detect both reﬂected light and thermal emission,both visibleand mid infrared spectral domain must be accessible3.The photometric precision must be suﬃcient to detect temperaturevariations(of the order of at most a few percent)4.It must be possible to make separate exposures shorter than a planetrotation period at any time along the orbit.This exludes inertial scannning modes of the celestial sphere.43Conclusion:constraints on future space mis-sion“architectures”Imaging is scientiﬁcally more productive for optical architectures having, in addition to obvious angular resolution(large baseline)and stellar light rejection power•Suﬃcientlyﬂexible pointing capabilities•Suﬃcient photometric precision•Adequate spectral domainArchitectures fulﬁlling these conditions are feasible.For instance the“hy-pertelescope”concept(Labeyrie1996)is now under study in the framework of the Terrestrial Planet Finder project(Ridgway2000).References[1]Des Marais D.,Harwit M.,Jucks K.,Kasting J.,Lunine J.,Lin D.,Seager S.,Schneider J.,Traub W.and Woolf N.,2002,Biosignatures and Plane-tary Properties to be Investigated by the TPF Mission.JPL Publication 01-008[2]Ford E.,Seager S.and Turner E.2001,Characterization of extrasolar terrestrial planets from diurnal photometric variability.Nature,412,885[3]Labeyrie A.,1996,Resolved imaging of extra-solar planets with future 10-100km optical interferometric arrays.Astron.and Astrophys.Suppl., 118,517[4]Ridgway S.et al.2001,Terrestrial Planet Finder:Architectures and Search Strategy.BAAS32,No4.,70.03[5]Schneider J.1999,The study of extrasolar planets:methods of detection,ﬁrst discoveries and future perspectives.C.R.Acad.Sci.Paris,327,Serie II b,621[6]Schneider J.and Riaud P.,2002,submitted5[7]Woolf,N.2001private communication;see also Des Marais et al20026。