发布时间：
编译 | 未玖
Nature , 14 April 2022, VOL 604, ISSUE 7905
《自然》 2022年4月14日，第604卷，7905期
天文学 Astronomy
A dusty compact object bridging galaxies and quasars at cosmic dawn
在宇宙黎明时分，星系由尘埃致密体过渡到类星体
作者：S. Fujimoto, G. B. Brammer, D. Watson, G. E. Magdis, V. Kokorev, T. R. Greve, et al.
链接：
摘要：
自从发现发光类星体在宇宙大爆炸后仅存在7亿年以来，了解超大质量黑洞在早期宇宙中如何形成和生长已成为一个重大难题。
理论模拟显示了一种进化序列，尘埃红移的类星体从严重尘埃遮蔽的星暴星系中出现，然后通过释放气体和尘埃过渡到无遮蔽的发光类星体。尽管最后一个阶段的红移已被确定为，但由于它们在光学和近红外波长上的微弱性，目前尚未发现具有类似红移的过渡类星体。
研究组报道了一个紫外致密天体GNz7q的观测结果，它与一个红移为 、尘埃掩蔽的星暴有关。
在该时期，宿主星系的尘埃辐射比任何其他已知物体都要明亮，在480秒差距的中心半径范围内，每年形成1600个太阳质量的恒星。在深部、高分辨率成像和无狭缝光谱中，可识别出一个远紫外的红点源。
GNz7q在X射线中非常微弱，这表明在尘埃星暴核心出现了一个独特的紫外致密恒星形成区或一个康普顿厚、超过爱丁顿极限的黑洞吸积盘。在后一种情况下，观测到的性质与宇宙学模拟的预测一致，并表明GNz7q是晚期无遮蔽发光类星体的祖先。
Abstract：
Understanding how super-massive black holes form and grow in the early Universe has become a major challenge since it was discovered that luminous quasars existed only 700 million years after the Big Bang. Simulations indicate an evolutionary sequence of dust-reddened quasars emerging from heavily dust-obscured starbursts that then transition to unobscured luminous quasars by expelling gas and dust. Although the last phase has been identified out to a redshift of , a transitioning quasar has not been found at similar redshifts owing to their faintness at optical and near-infrared wavelengths. Here we report observations of an ultraviolet compact object, GNz7q, associated with a dust-enshrouded starburst at a redshift of . The host galaxy is more luminous in dust emission than any other known object at this epoch, forming 1,600 solar masses of stars per year within a central radius of 480 parsec. A red point source in the far-ultraviolet is identified in deep, high-resolution imaging and slitless spectroscopy. GNz7q is extremely faint in X-rays, which indicates the emergence of a uniquely ultraviolet compact star-forming region or a Compton-thick super-Eddington black-hole accretion disk at the dusty starburst core. In the latter case, the observed properties are consistent with predictions from cosmological simulations and suggest that GNz7q is an antecedent to unobscured luminous quasars at later epochs.
物理学 Physics
Intelligent infrared sensing enabled by tunable moiré quantum geometry
可调谐莫尔量子几何实现智能红外传感
作者：Chao Ma, Shaofan Yuan, Patrick Cheung, Kenji Watanabe, Takashi Taniguchi, Fan Zhang, et al.
链接：
摘要：
众所周知，固体中布洛赫波函数的量子几何性质，即贝里曲率和量子度量，显著影响着电子的基态和激发态行为。
体光伏效应（BPVE）是一种依赖于激发光偏振的非线性现象，在很大程度上取决于光学跃迁中的量子几何特性。红外BPVE尚未在石墨烯或莫尔体系等新兴平台中观察到，尽管这些平台已报道过与量子几何有关的激发强关联现象。
研究组报道了在扭曲双双层石墨烯（TDBG）中观察到5 µm和 µm处可调谐中红外BPVE，由莫尔诱导的强对称性破缺和量子几何贡献产生。光响应在很大程度上取决于激发光的偏振态，且可通过外部电场进行高度调谐。
这种量子几何特性的广泛可调性使研究组能够使用卷积神经网络同时实现全斯托克斯偏振测量和波长检测，仅使用一个亚波长足迹仅为3 3 µm2的TDBG器件 。
该研究工作不仅揭示了莫尔工程量子几何在可调谐非线性光-物质相互作用中的独特作用，还以极其紧凑的芯片方式为未来智能传感技术开辟了新途径。
Abstract：
Quantum geometric properties of Bloch wave functions in solids, that is, Berry curvature and the quantum metric, are known to significantly influence the ground- and excited-state behaviour of electrons. The bulk photovoltaic effect (BPVE), a nonlinear phenomenon depending on the polarization of excitation light, is largely governed by the quantum geometric properties in optical transitions. Infrared BPVE has yet to be observed in graphene or moiré systems, although exciting strongly correlated phenomena related to quantum geometry have been reported in this emergent platform. Here we report the observation of tunable mid-infrared BPVE at 5 µm and µm in twisted double bilayer graphene (TDBG), arising from the moiré-induced strong symmetry breaking and quantum geometric contribution. The photoresponse depends substantially on the polarization state of the excitation light and is highly tunable by external electric fields. This wide tunability in quantum geometric properties enables us to use a convolutional neural network to achieve full-Stokes polarimetry together with wavelength detection simultaneously, using only one single TDBG device with a subwavelength footprint of merely 3 3 µm2. Our work not only reveals the unique role of moiré engineered quantum geometry in tunable nonlinear light–matter interactions but also identifies a pathway for future intelligent sensing technologies in an extremely compact, on-chip manner.
材料科学 Materials Science
Uniting tensile ductility with ultrahigh strength via composition undulation
通过成分起伏同时实现拉伸塑性与超高强度
作者：Heng Li, Hongxiang Zong, Suzhi Li, Shenbao Jin, Yan Chen, Matthew J. Cabral, et al.
链接：
摘要：
具有纳米晶粒的金属有接近2 GPa的超高强度。然而，这种极端的晶界强化导致几乎所有拉伸塑性的丧失，即使当金属具有面心立方结构（所有晶体结构中塑性最强的结构）时亦如此。
研究组证明了纳米晶镍-钴固溶体虽仍是面心立方单相，但其拉伸强度约为 GPa，塑性断裂伸长率约为16 %。
这种不寻常的拉伸强度和塑性的结合是通过高浓度固溶体中的成分起伏实现的。这种起伏使得层错能和晶格应变在1-10纳米的尺度范围内发生空间变化，从而显著影响了位错运动。
尽管纳米晶粒内部空间非常有限，但位错运动变得缓慢，促进了它们的交互作用、联锁和增殖。因此，流动应力增加，同时位错储存增加，从而提升了应变硬化能力，提高了塑性。
同时，沿位错线的分段脱捕需要较小的激活体积，因此应变速率敏感性增加，这也稳定了拉伸流动。因此，抗位错传播的起伏结构提供了一种强化机制，可在高流动应力下保持拉伸塑性。
Abstract：
Metals with nanocrystalline grains have ultrahigh strengths approaching two gigapascals. However, such extreme grain-boundary strengthening results in the loss of almost all tensile ductility, even when the metal has a face-centred-cubic structure—the most ductile of all crystal structures. Here we demonstrate that nanocrystalline nickel–cobalt solid solutions, although still a face-centred-cubic single phase, show tensile strengths of about gigapascals with a respectable ductility of about 16 per cent elongation to failure. This unusual combination of tensile strength and ductility is achieved by compositional undulation in a highly concentrated solid solution. The undulation renders the stacking fault energy and the lattice strains spatially varying over length scales in the range of one to ten nanometres, such that the motion of dislocations is thus significantly affected. The motion of dislocations becomes sluggish, promoting their interaction, interlocking and accumulation, despite the severely limited space inside the nanocrystalline grains. As a result, the flow stress is increased, and the dislocation storage is promoted at the same time, which increases the strain hardening and hence the ductility. Meanwhile, the segment detrapping along the dislocation line entails a small activation volume and hence an increased strain-rate sensitivity, which also stabilizes the tensile flow. As such, an undulating landscape resisting dislocation propagation provides a strengthening mechanism that preserves tensile ductility at high flow stresses.
Perovskite–organic tandem solar cells with indium oxide interconnect
钙钛矿-氧化铟互连有机串联太阳能电池
作者：K. O. Brinkmann, T. Becker, F. Zimmermann, C. Kreusel, T. Gahlmann, M. Theisen, et al.
链接：
摘要：
多结太阳能电池可以克服单结器件的基本效率限制。金属卤化物钙钛矿型太阳能电池的带隙可调性使其在多结结构中具有吸引力。硅和铜铟硒化镓（CIGS）以及全钙钛矿串联电池的组合已有报道。与此同时，窄间隙非富勒烯受体为有机太阳能电池带来了快速提升的效率。
有机和钙钛矿半导体是一种很有吸引力的组合，具有相似的加工技术。目前，钙钛矿-有机串联电池的效率低于标准，并且受到宽间隙钙钛矿电池的低开路电压（Voc）和子电池之间互连引入损耗的限制。
研究组展示了钙钛矿-有机串联电池的效率为（认证为），Voc高达 伏特。优化的电荷提取层使钙钛矿子电池具有高Voc和填充因子的出色组合。
该串联电池的有机子电池在近红外下提供了高外部量子效率，与对非富勒烯电池有限光稳定性的典型担忧相反，如果激子主要在非富勒烯受体上产生，则表现出出色的操作稳定性。子电池由一层超薄（约纳米）类金属氧化铟层连接，具有前所未有的低光/电损耗。
这项工作为钙钛矿-有机串联电池竖了一座里程碑，它优于最好的p–i–n钙钛矿单结，并与钙钛矿-CIGS和所有钙钛矿多结相媲美。
Abstract：
Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. The bandgap tunability of metal halide perovskite solar cells renders them attractive for multijunction architectures. Combinations with silicon and copper indium gallium selenide (CIGS), as well as all-perovskite tandem cells, have been reported. Meanwhile, narrow-gap non-fullerene acceptors have unlocked skyrocketing efficiencies for organic solar cells. Organic and perovskite semiconductors are an attractive combination, sharing similar processing technologies. Currently, perovskite–organic tandems show subpar efficiencies and are limited by the low open-circuit voltage (Voc) of wide-gap perovskite cells and losses introduced by the interconnect between the subcells. Here we demonstrate perovskite–organic tandem cells with an efficiency of per cent (certified per cent) and a high Voc of volts. Optimized charge extraction layers afford perovskite subcells with an outstanding combination of high Voc and fill factor. The organic subcells provide a high external quantum efficiency in the near-infrared and, in contrast to paradigmatic concerns about limited photostability of non-fullerene cells, show an outstanding operational stability if excitons are predominantly generated on the non-fullerene acceptor, which is the case in our tandems. The subcells are connected by an ultrathin (approximately nanometres) metal-like indium oxide layer with unprecedented low optical/electrical losses. This work sets a milestone for perovskite–organic tandems, which outperform the best p–i–n perovskite single junctions and are on a par with perovskite–CIGS and all-perovskite multijunctions.
机械工程 Mechanical Engineering
Thermophotovoltaic efficiency of 40%
科学家实现40%的热光伏效率
作者：Alina LaPotin, Kevin L. Schulte, Myles A. Steiner, Kyle Buznitsky, Colin C. Kelsall, Daniel J. Friedman, et al.
链接：
摘要：
热光伏（TPV）主要通过光伏效应将红外波长的光转换为电能，可使用比目前普遍存在于电力生产中的涡轮机更高温度的热源进行能量存储和转换。
自从在2000 下使用集成背表面反射器和钨发射极首次展示29%的高效TPV以来，TPV的制造和性能得到了改善。然而，尽管预测TPV的效率可能超过50%，但在温度低于1300 下，实际效率仍仅为32%。
研究组报道了效率超过40%的TPV电池的制造和测量，并通过实验证明了高带隙串联TPV电池的效率。TPV电池是由带隙在 eV的III–V材料组成的双结器件，针对1900-2400 的发射极温度进行了优化。
电池利用带边光谱滤波的概念来获得高效率，使用高反射背表面反射器来拒绝不可用的子带隙辐射返回发射极。在功率密度为 W cm –2 ，发射极温度为2400 的条件下， eV器件的最大效率为（ 1）%。在功率密度为 W cm–2，发射极温度为2127 的条件下， eV器件的最大效率为（ 1）%。
这些电池可以集成到一个TPV系统中，用于热能电网存储，以实现可调度的可再生能源。这为热能电网存储创造了一条途径，以达到足够高的效率和足够低的成本，从而实现电网脱碳。
Abstract：
Thermophotovoltaics (TPVs) convert predominantly infrared wavelength light to electricity via the photovoltaic effect, and can enable approaches to energy storage and conversion that use higher temperature heat sources than the turbines that are ubiquitous in electricity production today. Since the first demonstration of 29% efficient TPVs using an integrated back surface reflector and a tungsten emitter at 2,000 C, TPV fabrication and performance have improved. However, despite predictions that TPV efficiencies can exceed 50%, the demonstrated efficiencies are still only as high as 32%, albeit at much lower temperatures below 1,300 C. Here we report the fabrication and measurement of TPV cells with efficiencies of more than 40% and experimentally demonstrate the efficiency of high-bandgap tandem TPV cells. The TPV cells are two-junction devices comprising III–V materials with bandgaps between and eV that are optimized for emitter temperatures of 1,900–2,400 C. The cells exploit the concept of band-edge spectral filtering to obtain high efficiency, using highly reflective back surface reflectors to reject unusable sub-bandgap radiation back to the emitter. A eV device reached a maximum efficiency of ( 1)% operating at a power density of W cm–2 and an emitter temperature of 2,400 C. A eV device reached a maximum efficiency of ( 1)% operating at a power density of W cm –2 and an emitter temperature of 2,127 C. These cells can be integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy. This creates a pathway for thermal energy grid storage to reach sufficiently high efficiency and sufficiently low cost to enable decarbonization of the electricity grid.
地球科学 Earth Science
Realization of Paris Agreement pledges may limit warming just below 2
实现《巴黎协定》的承诺有望将全球变暖控制在2 以下
作者：Malte Meinshausen, Jared Lewis, Christophe McGlade, Johannes Gütschow, Zebedee Nicholls, Rebecca Burdon, et al.
链接：
摘要：
在《格拉斯哥气候公约》签署前的过去五年中，154个缔约方在其国家自主贡献中提交了新的或更新的2030年减缓目标，76个缔约方提出了长期承诺。对2021联合国气候变化大会（COP26）之前承诺的量化表明，将升温控制在2 以下的可能性低于50 %。
研究组证明，如果所有有条件和无条件的承诺都得到充分和及时的执行，全球变暖可以控制在2 以下。根据政府间气候变化专门委员会（IPCC）第六次评估报告中第一工作组对地球系统不确定性进行的概率表征，在全面执行的情况下，峰值升温可被限制在 之间。
研究组回顾性地预测了21世纪的气候变暖，以显示2015-2021年雄心勃勃的总体目标水平如何变化。研究结果依赖于对2030年或2050年之后的限时目标外推、IPCC 特别报告（）情景数据库的特征和承诺的全面实施情况。
对这些因素更悲观的假设将导致更高的升温预测。另一个独立的排放模型框架预测，全球升温峰值为 ，这支持了该研究发现，即各国兑现承诺可能会将全球变暖限制在略低于2 的范围内。
若不仅要将升温控制在“略低于”，还要控制在“远低于”2 或 ，则迫切需要制定政策和采取行动，以在本世纪中叶实现全球C O2 净零排放。
Abstract：
Over the last five years prior to the Glasgow Climate Pact, 154 Parties have submitted new or updated 2030 mitigation goals in their nationally determined contributions and 76 have put forward longer-term pledges. Quantifications of the pledges before the 2021 United Nations Climate Change Conference (COP26) suggested a less than 50 per cent chance of keeping warming below 2 degrees Celsius. Here we show that warming can be kept just below 2 degrees Celsius if all conditional and unconditional pledges are implemented in full and on time. Peak warming could be limited to – degrees Celsius in the full implementation case—building on a probabilistic characterization of Earth system uncertainties in line with the Working Group I contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). We retrospectively project twenty-first-century warming to show how the aggregate level of ambition changed from 2015 to 2021. Our results rely on the extrapolation of time-limited targets beyond 2030 or 2050, characteristics of the IPCC C Special Report () scenario database and the full implementation of pledges. More pessimistic assumptions on these factors would lead to higher temperature projections. A second, independent emissions modelling framework projected peak warming of degrees Celsius, supporting the finding that realized pledges could limit warming to just below 2 degrees Celsius. Limiting warming not only to ‘just below’ but to ‘well below’ 2 degrees Celsius or degrees Celsius urgently requires policies and actions to bring about steep emission reductions this decade, aligned with mid-century global net-zero C O2 emissions
编译 | 未玖
Nature , 20 January 2022, VOL 601, ISSUE 7893
《自然》 2022年1月20日，第601卷，7893期
天文学 Astronomy
Star formation near the Sun is driven by expansion of the Local Bubble
局部气泡的扩张驱动太阳附近恒星形成
作者：Catherine Zucker, Alyssa A. Goodman, João Alves, Shmuel Bialy, Michael Foley, Joshua S. Speagle, et al.
链接：
摘要
几十年来，我们已知道太阳位于一个局部气泡内，即一个由低密度、高温等离子体构成的空腔，周围环绕着一层寒冷的中性气体和尘埃。然而，由于局部星际介质的低分辨率模型，这个外壳的精确形状和范围、形成的动力和时间尺度以及它与附近恒星形成的关联仍不确定。
研究组利用新的空间和动力学约束，对太阳200 pc范围内致密气体和年轻恒星的三维位置、形状和运动进行了分析。他们发现，太阳附近几乎所有的恒星形成复合体都位于局部气泡的表面，它们的年轻恒星主要垂直于气泡表面向外扩张。
对这些年轻恒星轨迹的追踪支持了这样一种说法，即局部气泡起源于大约1400万年前发生在气泡中心附近的恒星诞生和死亡（超新星）的爆发。超新星产生的局部气泡膨胀将周围的星际介质卷起，形成一个扩张的外壳，该外壳现已碎裂并坍缩成附近最明显的分子云，从而为超新星驱动恒星形成理论提供了强有力的观测支持。
Abstract
For decades we have known that the Sun lies within the Local Bubble, a cavity of low-density, high-temperature plasma surrounded by a shell of cold, neutral gas and dust. However, the precise shape and extent of this shell, the impetus and timescale for its formation, and its relationship to nearby star formation have remained uncertain, largely due to low-resolution models of the local interstellar medium. Here we report an analysis of the three-dimensional positions, shapes and motions of dense gas and young stars within 200 pc of the Sun, using new spatial and dynamical constraints. We find that nearly all of the star-forming complexes in the solar vicinity lie on the surface of the Local Bubble and that their young stars show outward expansion mainly perpendicular to the bubble’s surface. Tracebacks of these young stars’ motions support a picture in which the origin of the Local Bubble was a burst of stellar birth and then death (supernovae) taking place near the bubble’s centre beginning approximately 14 Myr ago. The expansion of the Local Bubble created by the supernovae swept up the ambient interstellar medium into an extended shell that has now fragmented and collapsed into the most prominent nearby molecular clouds, in turn providing robust observational support for the theory of supernova-driven star formation.
Black-hole-triggered star formation in the dwarf galaxy Henize 2-10
矮星系Henize 2-10中黑洞触发恒星形成
作者：Zachary Schutte & Amy E. Reines
链接：
摘要
在一些有活动星系核的矮星系中，人们已观察到黑洞驱动的外流，它们可能在加热和喷出气体（从而抑制恒星形成）方面发挥作用，就像它们在较大的星系中所做的那样。黑洞外流能在多大程度上触发矮星系中的恒星形成尚不清楚，因为这一领域的工作以前主要集中在大质量星系上，观测证据很少。
Henize 2-10是一个矮星暴星系，此前有报道称其中心有一个大质量黑洞，但由于某些观测证据与超新星残骸一致，这种解释一直存在争议。在大约9 Mpc距离处有一个机会可了解中心区域，并确定是否有证据表明黑洞流出影响恒星形成。
研究组报道了Henize 2-10的光学观测结果，其线性分辨率为几秒差距。他们发现了一条约150 pc长的电离丝状物，将黑洞区域与一个最新恒星形成区域连接起来。光谱学揭示了一种类似正弦波的位置-速度结构，通过一个简单的进动双极流出进行描述。研究组得出结论，黑洞流出触发了恒星的形成。
Abstract
Black-hole-driven outflows have been observed in some dwarf galaxies with active galactic nuclei, and probably play a role in heating and expelling gas (thereby suppressing star formation), as they do in larger galaxies. The extent to which black-hole outflows can trigger star formation in dwarf galaxies is unclear, because work in this area has previously focused on massive galaxies and the observational evidence is scarce. Henize 2-10 is a dwarf starburst galaxy previously reported to have a central massive black hole, although that interpretation has been disputed because some aspects of the observational evidence are also consistent with a supernova remnant. At a distance of approximately 9 Mpc, it presents an opportunity to resolve the central region and to determine if there is evidence for a black-hole outflow influencing star formation. Here we report optical observations of Henize 2-10 with a linear resolution of a few parsecs. We find an approximately 150-pc-long ionized filament connecting the region of the black hole with a site of recent star formation. Spectroscopy reveals a sinusoid-like position–velocity structure that is well described by a simple precessing bipolar outflow. We conclude that this black-hole outflow triggered the star formation.
物理学 Physics
Topological triple phase transition in non-Hermitian Floquet quasicrystals
非厄米-弗洛凯准晶体的拓扑三重相变
作者：Sebastian Weidemann, Mark Kremer, Stefano Longhi & Alexander Szameit
链接：
摘要
相变连接着物质的不同状态，通常伴随着对称性的自发破坏。一个重要的相变类型是迁移率转变，其中著名的安德森局域化增加随机性会导致金属-绝缘体跃迁。凝聚态物理学中拓扑学的引入导致了拓扑相变和拓扑绝缘体材料的发现。
非厄米系统对称性的相变描述了向平均守恒能量和新拓扑相的转变。体电导率、拓扑学和非厄米对称破缺似乎源于不同的物理学，因此可能以分离的现象出现。然而，在非厄米准晶体中，这种转变可通过形成一个三重相变而相互关联。
研究组报道了一个三重相变的实验观察，其中改变单个参数的同时会引起局域化（金属-绝缘体）、拓扑和奇偶-时间对称破缺（能量）相变。物理学表现为时间驱动（弗洛凯）耗散准晶体。
研究组通过耦合光纤环路中的光子量子行走来实现他们的想法，并强调了非厄米准晶体合成物质中拓扑、对称破缺和迁移率相变的相互关联。该研究结果有望应用于相变器件，在其中可预测和控制体-边输运以及与环境的能量或粒子交换。
Abstract
Phase transitions connect different states of matter and are often concomitant with the spontaneous breaking of symmetries. An important category of phase transitions is mobility transitions, among which is the well known Anderson localization, where increasing the randomness induces a metal–insulator transition. The introduction of topology in condensed-matter physics lead to the discovery of topological phase transitions and materials as topological insulators. Phase transitions in the symmetry of non-Hermitian systems describe the transition to on-average conserved energy and new topological phases. Bulk conductivity, topology and non-Hermitian symmetry breaking seemingly emerge from different physics and, thus, may appear as separable phenomena. However, in non-Hermitian quasicrystals, such transitions can be mutually interlinked by forming a triple phase transition. Here we report the experimental observation of a triple phase transition, where changing a single parameter simultaneously gives rise to a localization (metal–insulator), a topological and parity–time symmetry-breaking (energy) phase transition. The physics is manifested in a temporally driven (Floquet) dissipative quasicrystal. We implement our ideas via photonic quantum walks in coupled optical fibre loops. Our study highlights the intertwinement of topology, symmetry breaking and mobility phase transitions in non-Hermitian quasicrystalline synthetic matter. Our results may be applied in phase-change devices, in which the bulk and edge transport and the energy or particle exchange with the environment can be predicted and controlled.
Quantum logic with spin qubits crossing the surface code threshold
超越表面码阈值的自旋比特量子逻辑
作者：Xiao Xue, Maximilian Russ, Nodar Samkharadze, Brennan Undseth, Amir Sammak, Giordano Scappucci, et al.
链接：
摘要
量子比特的高保真控制对于量子算法的可靠执行和实现容错（纠正错误的速度快于错误发生的速度）至关重要。容错的核心要求用错误阈值表示。然而实际阈值取决于许多细节，一个常见目标是约1%误差阈值的表面码。
两比特门保真度超过99%一直是半导体自旋量子比特的主要目标。由于可以利用先进的半导体技术，这些量子比特有望扩展。
研究组报道了一种基于自旋的硅量子处理器，其单比特门和两比特门保真度都高于，通过门集断层扫描进行验证。当包含相邻量子比特的串扰和空转误差时，平均单比特门保真度仍保持在99%以上。
通过这个高保真门集，研究组使用变分量子本征求解器算法完成了计算分子基态能量的艰巨任务。半导体量子比特超越了两比特门保真度99%的阈值，身处高噪声的中等规模量子器件时代，在容错和可能的应用方面已争取到一席之地。
Abstract
High-fidelity control of quantum bits is paramount for the reliable execution of quantum algorithms and for achieving fault tolerance—the ability to correct errors faster than they occur. The central requirement for fault tolerance is expressed in terms of an error threshold. Whereas the actual threshold depends on many details, a common target is the approximately 1% error threshold of the well-known surface code. Reaching two-qubit gate fidelities above 99% has been a long-standing major goal for semiconductor spin qubits. These qubits are promising for scaling, as they can leverage advanced semiconductor technology. Here we report a spin-based quantum processor in silicon with single-qubit and two-qubit gate fidelities, all of which are above , extracted from gate-set tomography. The average single-qubit gate fidelities remain above 99% when including crosstalk and idling errors on the neighbouring qubit. Using this high-fidelity gate set, we execute the demanding task of calculating molecular ground-state energies using a variational quantum eigensolver algorithm. Having surpassed the 99% barrier for the two-qubit gate fidelity, semiconductor qubits are well positioned on the path to fault tolerance and to possible applications in the era of noisy intermediate-scale quantum devices.
Fast universal quantum gate above the fault-tolerance threshold in silicon
硅中超越容错阈值的快速通用量子门
作者：Akito Noiri, Kenta Takeda, Takashi Nakajima, Takashi Kobayashi, Amir Sammak, Giordano Scappucci, et al.
链接：
摘要
能够解决难题的容错量子计算机依赖于量子纠错。表面码是最有前途的纠错码之一，它要求通用门保真度超过99%的纠错阈值。
在众多量子位平台中，只有超导电路、捕获离子和金刚石中的氮空位中心能满足这一要求。硅中的电子自旋量子位因其纳米制造能力而颇有潜力应用于大规模量子计算机，但由于运行缓慢，两比特门保真度被限制在98%。
研究组通过使用微磁感应梯度场和可调谐双量子位耦合的快速电子控制，在硅自旋量子位中实现了的两比特门保真度和的单比特门保真度。他们确定了量子位的旋转速度和耦合强度，稳健地实现了高保真门。
使用该通用门集，研究组成功实现了Deutsch-Jozsa和Grover搜索算法。研究结果表明，通用门保真度超越了容错阈值，并有望实现可扩展硅量子计算机。
Abstract
Fault-tolerant quantum computers that can solve hard problems rely on quantum error correction. One of the most promising error correction codes is the surface code, which requires universal gate fidelities exceeding an error correction threshold of 99 per cent. Among the many qubit platforms, only superconducting circuits, trapped ions and nitrogen-vacancy centres in diamond have delivered this requirement. Electron spin qubits in silicon are particularly promising for a large-scale quantum computer owing to their nanofabrication capability, but the two-qubit gate fidelity has been limited to 98 per cent owing to the slow operation. Here we demonstrate a two-qubit gate fidelity of per cent, along with single-qubit gate fidelities of per cent, in silicon spin qubits by fast electrical control using a micromagnet-induced gradient field and a tunable two-qubit coupling. We identify the qubit rotation speed and coupling strength where we robustly achieve high-fidelity gates. We realize Deutsch–Jozsa and Grover search algorithms with high success rates using our universal gate set. Our results demonstrate universal gate fidelity beyond the fault-tolerance threshold and may enable scalable silicon quantum computers.
地球科学 Earth Science
Historical glacier change on Svalbard predicts doubling of mass loss by 2100
2100年斯瓦尔巴群岛的冰川质量损失将翻倍
作者：Emily C. Geyman, Ward J. J. van Pelt, Adam C. Maloof, Harald Faste Aas & Jack Kohler
链接：
摘要
冰川和冰盖的融化约占目前海平面上升的三分之一，超过了体积更大的格陵兰岛或南极冰原所造成的损失。北极斯瓦尔巴群岛的空间气候梯度比下个世纪预测的现世气候变化要大，它是一个自然实验室，用于限制冰川的气候敏感性并预测其对未来变暖的反应。
研究组将 历史 冰川和现代冰川的观测联系起来，预测21世纪冰川变薄的速度将是1936-2010年的两倍多。利用1936和1938年的 历史 航拍图像存档，他们通过运动结构摄影测量法重建了斯瓦尔巴群岛上1594条冰川的三维几何形状。
研究组将这些重建数据与现代冰川海拔数据进行比较，得出了70多年时间跨度内质量平衡的空间模式，使人们能够通过年际和年代际变化的噪声，来量化诸如温度和降水等变量如何控制冰川的损失。
研究组发现融化速率对温度有很强的依赖性，即平均夏季温度每升高1 ，面积归一化质量平衡每年减少 m的水当量。最后，研究组设计了一个时空替代方案，将他们的 历史 冰川观测与气候预测相结合，并对斯瓦尔巴群岛的21世纪冰川变化做出一级预测。
Abstract
The melting of glaciers and ice caps accounts for about one-third of current sea-level rise, exceeding the mass loss from the more voluminous Greenland or Antarctic Ice Sheets. The Arctic archipelago of Svalbard, which hosts spatial climate gradients that are larger than the expected temporal climate shifts over the next century, is a natural laboratory to constrain the climate sensitivity of glaciers and predict their response to future warming. Here we link historical and modern glacier observations to predict that twenty-first century glacier thinning rates will more than double those from 1936 to 2010. Making use of an archive of historical aerial imagery from 1936 and 1938, we use structure-from-motion photogrammetry to reconstruct the three-dimensional geometry of 1,594 glaciers across Svalbard. We compare these reconstructions to modern ice elevation data to derive the spatial pattern of mass balance over a more than 70-year timespan, enabling us to see through the noise of annual and decadal variability to quantify how variables such as temperature and precipitation control ice loss. We find a robust temperature dependence of melt rates, whereby a 1 C rise in mean summer temperature corresponds to a decrease in area-normalized mass balance of m yr 1 of water equivalent. Finally, we design a space-for-time substitution to combine our historical glacier observations with climate projections and make first-order predictions of twenty-first century glacier change across Svalbard.
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sci-hub专门免费下载外文文献，但网站经常换域名，有时不稳定，新域名也有卡顿打不开现象，而且没有收录新文献，目前2022年文献基本下不到。
学术文献下载器（)，把海量中外文献数据库资源整合一起，涵盖上面提到的文献数据库，文献资源庞大涉及全科，包括谷歌学术和sci-hub下载不了的文献。适合学校资源不够的高校生或者是单位没有数据库资源的科研人员查阅下载文献资料。
小木虫论坛-SCI期刊点评专栏：拥有来自国内各大院校、科研院所的博硕士研究生和企业研发人员对期刊的专业点评，覆盖了8000+ SCI期刊杂志的专业点评信息，为国内外学术科研人员论文投稿、期刊选择等提供了专业的建议。小木虫论坛秉承“为中国学术科研免费提供动力”宗旨，已成为千万硕博 ...浏览6707 回答81 Epigenetics经验分享：with editor一个月了，好慢呐，有战友投过这个期刊 么，版面费多少？ 2 0 2021-07-01 ms8933482113232354 影响因子: 经验分享：EPIGENETICS-US的2020年度#影响因子#为 168 0 2021-02-18 ms6032332839474392 …浏览6707 回答81 科技大数据知识发现平台平台围绕大数据与文献情报智能服务，提供知识发现丰富化和多维度化：提供多维度分面展示，快速发现知识；利用STKOS语义支持相关搜索词分析与规范；提供对专利的关联发现，辅助了解当前关注方向的专利产出，辅助寻求科研合作关系；提供对期刊的关联发现，对期刊按领域、研究方向、期刊的 ...浏览6707 回答81 Editorial:BrainInsulinResistanceinNeurodevelopmental首页 资讯 期刊 导师 问答 求职 发Paper 文献直达 高级搜索 期刊列表 论文助手 搜索 当前位置： X-MOL 学术 › Front. Neurosci. › 论文详情 Editorial: Brain Insulin Resistance in …如何快速使用endnote首先推荐你一个网站，xmol。. 为了搜索你的领域，首先要了解两个方法，第一doi，第二，关键词。. 后者你需要科学上网 。. 你看到了一篇文献，你可以在文献里找到doi或者是以文章期刊名，页码等的引用格式。. 复制doi或者引用格式到xmol，一搜就会直达文章 ...科研过程中，如何订阅本领域重要的期刊，使其整期推送新的 ...2019-7-30如何评价化学咨询平台x-mol？ - 知乎2016-4-11你写论文时发现了哪些非常神的网站？ - 知乎2016-2-27查看更多结果如何快速查询JACS文献XMOL化学 2015-08-11 2698人看过 JACS可以说是每个化学人梦寐以求的能发一篇论文的地方，可以说是化学类杂志的龙头。化学人经常需要查询JACS的文献。如何在谷歌学术不能用、ACS访问太慢、百度太渣的情况下，快速查询到JACS的文献呢？AnalyticalandBioanalyticalChemistry期刊最新论文,化学Analytical and Bioanalytical Chemistry期刊最新论文，,顶级期刊最新论文图文内容，出版社网站每日同步更新，点击标题直达论文原文，自定义关注的期刊，覆盖PubMed的论文库，快速方便精准的找到您想要的 …iomedicalMicrodevices期刊最新论文,化学/材料,Biomedical Microdevices期刊最新论文，,顶级期刊最新论文图文内容，出版社网站每日同步更新，点击标题直达论文原文，自定义关注的期刊，覆盖PubMed的论文库，快速方便精准的找到您想要的论文中国实用外科杂志中国实用外科杂志Chinese Journal of Practical Surgery. 核心期刊 JST Pж (AJ) CSCD 统计源期刊. 基本信息. 曾用刊名： 实用外科杂志. 主办单位： 中国医师协会;中国实用医学杂志社. 出版周期： 月刊. ISSN： 1005-2208. CN： …化学SCI期刊目录导航SCI期刊搜索 - 最新影响因子查询 中科院分区源于2019年12月17日《2019年中国科学院文献情报中心期刊分区表》“基础版”，仅供参考! 仪器仪表 光谱学 全科医学与补充医学 分析化学 化学综合 声学 学科教育 工程：化工 工程：土木 应用化学 数学跨学科应用 无机 ...小木虫论坛-SCI期刊点评专栏：拥有来自国内各大院校、科研院所的博硕士研究生和企业研发人员对期刊的专业点评，覆盖了8000+ SCI期刊杂志的专业点评信息，为国内外学术科研人员论文投稿、期刊选择等提供了专业的建议。小木虫论坛秉承“为中国学术科研免费提供动力”宗旨，已成为千万硕博 ...Epigenetics经验分享：with editor一个月了，好慢呐，有战友投过这个期刊 么，版面费多少？ 2 0 2021-07-01 ms8933482113232354 影响因子: 经验分享：EPIGENETICS-US的2020年度#影响因子#为 168 0 2021-02-18 ms6032332839474392 …科技大数据知识发现平台平台围绕大数据与文献情报智能服务，提供知识发现丰富化和多维度化：提供多维度分面展示，快速发现知识；利用STKOS语义支持相关搜索词分析与规范；提供对专利的关联发现，辅助了解当前关注方向的专利产出，辅助寻求科研合作关系；提供对期刊的关联发现，对期刊按领域、研究方向、期刊的 ...Editorial:BrainInsulinResistanceinNeurodevelopmental首页 资讯 期刊 导师 问答 求职 发Paper 文献直达 高级搜索 期刊列表 论文助手 搜索 当前位置： X-MOL 学术 › Front. Neurosci. › 论文详情 Editorial: Brain Insulin Resistance in …如何快速使用endnote首先推荐你一个网站，xmol。. 为了搜索你的领域，首先要了解两个方法，第一doi，第二，关键词。. 后者你需要科学上网 。. 你看到了一篇文献，你可以在文献里找到doi或者是以文章期刊名，页码等的引用格式。. 复制doi或者引用格式到xmol，一搜就会直达文章 ...科研过程中，如何订阅本领域重要的期刊，使其整期推送新的 ...2019-7-30如何评价化学咨询平台x-mol？ - 知乎2016-4-11你写论文时发现了哪些非常神的网站？ -如何快速查询JACS文献XMOL化学 2015-08-11 2698人看过 JACS可以说是每个化学人梦寐以求的能发一篇论文的地方，可以说是化学类杂志的龙头。化学人经常需要查询JACS的文献。如何在谷歌学术不能用、ACS访问太慢、百度太渣的情况下，快速查询到JACS的文献呢？AnalyticalandBioanalyticalChemistry期刊最新论文,化学Analytical and Bioanalytical Chemistry期刊最新论文，,顶级期刊最新论文图文内容，出版社网站每日同步更新，点击标题直达论文原文，自定义关注的期刊，覆盖PubMed的论文库，快速方便精准的找到您想要的 …BiomedicalMicrodevices期刊最新论文,化学/材料,Biomedical Microdevices期刊最新论文，,顶级期刊最新论文图文内容，出版社网站每日同步更新，点击标题直达论文原文，自定义关注的期刊，覆盖PubMed的论文库，快速方便精准的找到您想要的论文
第一种：web of sciencesci收录的期刊，可以在web of science网站上查询到。当查看某一本sci的期刊号时，就可以登录web of science，按照提示，完成该本sci期刊的检索，在相关信息介绍中，就可以找到sci期刊号。
第二种：中国知网中国知网是非常大的数据库，收录了很多期刊。我们可以登录中国知网，检索要查询的sci期刊，只要该本sci期刊收录，就可以找到该本期刊的介绍，查看到对应的期刊号。
第三种：sci期刊分区名单sci期刊名单每年都会更新一次，每次更新都会公布最新的期刊分区名单。这份名单中，包括每本sci期刊的介绍，自然也可以查看到对应的期刊号。
一区sci期刊有哪些如下：
一区sci期刊有Nature和Science，一区sci期刊还有Cell Metabolism 、Cancer Cell、Science Advances、Cell Reports、Nature Microbiology、Nature Biotechnology、Autophagy、Journal of Hepatology、Hepatology、Circulation等刊物，这些刊物在本专业中都是顶尖刊物，发表难度也是可想而知的。
国内也有很多优秀刊物被检索收录，这部分刊物也是国内作者发表sci论文选择刊物时首先会关注并选择的，包括Cell Research、Mol Cell、Cell Discovery、Fungal Diversity、Molecular Plant、Protein & Cell、Cellular & Molecular Immunology、Bone Research等等。
一区二区是sci期刊特有的期刊分类标准，sci将其检索的期刊按照影响因子高低分为四个区，也就是一区二区三区四区，四个区中对应不同的刊物，四个区中一区影响因子最高，四区最低，所以一区二区论文对应的就是发表在一区期刊和二区期刊的论文。
中文sci期刊如下：化学学报、物理学报、高等学校化学学报、岩石学报、植物分类学报、物理化学学报、高分子学报、分析化学、地球物理学报、无机化学学报、有机化学、无机材料学报、生物化学与生物物理进展、化学进展、稀有金属材料与工程、光谱学与光谱分析、新型碳材料、金属学报、红外与毫米波学报。
SCI全称是ScienceCitationIndex，是美国科学信息研究院（InstituteforScientificInformation，简称ISI）出版的一部世界著名的期刊文献检索工具，其出版形式包括印刷版期刊和光盘版及联机数据库，还发行了互联网上Web版数据库。SCI收录全世界出版的数、理、化、农、林、医、生命科学、天文、地理、环境、材料、工程技术等自然科学各学科的核心期刊约3500种。
sci经过50多年的发展，现在已经发展成为当代世界非常重要的大型数据库，并且已经列入国际六大著名检索系统之一。这是一部非常重要的检索工具书，同时也是科学研究成果评价的一项重要依据。
被SCI收录的中国期刊，整体数量还是比较少的，但是依然是一个缓慢的上升趋势。想查找这个还是比较容易的，大家直接进入知网就可以查询到。先点击期刊导航，然后点击数据库刊源导航，再点击SCI科学引文索引。所有被收录的中国期刊就能在这里查到了。
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李霞.顾幸勇.刘琪 查看详情 [期刊论文] -中国陶瓷2004(03) 高朋召 三维碳纤维预制体/陶瓷基复合材料的制备及性能研究 2004 廖树帜.张邦维 查看详情 [期刊论文] -稀有金属材料与工程1998(05) 郑燕青.施尔畏.李汶军 查看详情 [期刊论文] -中国科学2001(04) 葛荣德.刘志宏 查看详情 1995 Voleeanov E 查看详情 2007(2-3) Blumm J 查看详情 2005(09) 更多...相似文献(10条)期刊论文 Sol-gel法制备ZrO2/钙铝硅系微晶玻璃复合材料的研究 - 中国陶瓷2005,41(1) 期刊论文 Sol-Gel法制备Al2O3-SiO2-TiO2-ZrO2复合陶瓷膜的研究 - 中国陶瓷2003,39(6) 外文期刊 Synthesis of ZrO2-SiO2 mesocomposite with high ZrO2 content via a novel sol-gel method 2005,84(1/3) 外文期刊 Optical properties of sol-gel derived ZrO2-TiO2 composite films 2007,515(20/21) 期刊论文 溶胶-凝胶法制备定向排列的纳米结构二氧化锆薄膜 - 清华大学学报(自然科学版)2001,41(4_5) 外文期刊 Influence of La2O3 and ZrO2 as promoters on surface and catalytic properties of CuO/MgO system prepared by sol-gel method 2006,299(0) 外文期刊 Photocatalytic degradation of 2,4-dichlorophenoxiacetic acid and 2,4,6-trichlorophenol with ZrO2 and Mn/ZrO2 sol-gel materials 2006,37(3) 期刊论文 Sol-Gel法制备ZrO2粉的析晶机制 - 稀有金属材料与工程2005,34(z1) 外文会议 Preparation of ZrO2/nano-TiO2 composite powder by sol-gel method 2007 外文期刊 Phase evolution of sol-gel CaO-ZrO2 using sulfuric acid as hydrolysis catalyst 2006,37(3
在国内外学术期刊发表的主要论文如下：1. Nd-Fe-B (B≤50at.%)三元系相图的研究，《中国科学》A辑，, , 1985, . Phase Diagrams of Nd-Fe-B Ternary System, <
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论文中医药的网络推广(英文版本)。。 文件密码 RAR文件密码为：
Any survey of tax sources should begin with the nation’s fairest and most productive soure of revenue, the individual income tax. 任何税收来源的调查都应开始于国家最公正、生产性最强的国民收入来源--个人所得税. All advanced industrial countries levy a dircct tax on individual incomes, but nowhere is this tax as important as in the United States. In recent years,about 40 percent of federal cash receipts has been collected from this source. 所有先进的工业国家都对个人所得直接征税，但没有哪个国家在征此税时像美国一样重要。近年来,约40%的联邦现金收入都来源于此. The individual income tax is uniquely suited for raising revenue in a democratic country where the distribution of income, and therefore of ability to pay,is unequal. Theoreticians may disagree about the meaningfulness of the term “ability to pay,” but the close association between a man’s income and taxpaying ability is commonly accepted. There is also general acceptance of the idea of progression in income taxation. 个人所得税是非常适合民主国家增加国民收入的,在民主国家里收入分配和支付能力是不平等的. 理论家可能不赞成"支付能力"的长远意义,但个人收入和纳税能力间的密切关系却是普遍接受的. 级数所得税的观点也被普遍接受. The individual income tax has still another attractive feature. Income alone does not differentiate a man’s ability to pay—his family responsibilities are also important. A single person may be able to along on an income of $3000 a year, but a married man with two children would have great diffculty making ends meet. The individual income tax takes such differences into account through the personal exemptions and deductions, which are subtracted before arriving at the income subject to tax. 个人所得税还有另一个吸引人的特点. 收入不足以区分一个人的支付能力—他的家庭责任也是很重要的. 单身男士也许每年收入达3000美元, 但带着两个孩子的已婚男人要想收支相抵却很困难. 个人所得税通过个人豁免和扣除将这种差异解决了, 个人免税额在应纳税收之前就扣除了. The revenue potential of the individual income tax has been recognized only recently. For almost thirty years after its adoption in 1913, the tax applied mainly to a small group of high income people. Exemptions were high by current standards and few incomes were large enough rates. In the national effort to raise needed revenue during World War Ⅱ, exemptions were drastically were increased in 1946 and 1948,but have remained low by prewar standards. Tax rates were also raised in wartime, and have remained much higher than in earlier years. At the same time, personal incomes have continued to increase with the growth of the economy (and with the inflation that occurred during and after World WarⅡ and the Korean War). The combination of lower exemptions, higher rates, and higher incomes increased the yield of the individual income tax manyfold. In1939, tax liabilities were about $1 billion; in 1966, they are in excess of $50 billion. 个人所得税的收入潜力最近才得到公认. 在1913年实施后的30年里，个人所得税主要应用于一小部分高收入人士. 在现行标准下豁免是很高的，低收入者占很大的比率. 二战期间,国家努力增加收入，豁免急剧减少。1946年和1948年有所提高，但从战前的水准看，仍然很低。税率在战时也有人提出,但比起早些年仍高多了. 在此同时, 个人收入随经济增长继续增加,(也与其间和二战后的通货膨胀和朝鲜战争的因素) . 较低的豁免,高利率,高收入的结合成倍地增加了个人所得税. 1939年，纳税义务约为10亿美元; 但1966年,超过了500亿美元. This tremendous expansion could not have been possible without ready compliance with income tax laws and effective many countries where compliance is poor and administration is weak, there is great reluctance to rely heavily on the income tax. In this country, the record of compliance is good—although it can still be improved—and practical methods have been developed for administering a mass income tax (at a cost of only about 1/2 of 1 percent of tax collected). In the late 1930’s many people—even high-placed officials of the Internal Revenue Service—doubted that an income tax covering almost everyone could be administered effectively. Although some problems remain, in an advanced country the administrative feasibility of an individual income tax of almost universal coverage is no longer questioned. 没有所得税法律的遵守和有效的管理，这个巨大的扩张是不可能的。许多国家法律意识差，管理松散,过于依赖所得税就很困难. 在这个国家, 守法记录还好--虽然它仍可以得到改善--实用方法已制定用来管理大量所得税(按成本仅约为1%的税收额的1 / 2 ) . 在20世纪30年代后期，很多人甚至美国国内税局的高级官员都认为关系每个人的所得税应得到有效管理. 尽管一些问题依然存在, 在一个先进的国家个人所得税的几乎全面普及在行政上的可行性已不存在质疑. There are good economic reasons for using the income tax as a major source of revenue. The automatie flexibility of the income tax promotes economic stability and the progressive rates help prevent excessive concentration of economic power and control. Some believe that the income tax is also needed to moderate the growth of private savings of high income people, which is likely to hold down private demand for goods and believe that a high income tax impairs work and investment incentives and , therefore, reduces the nation’s economic growth. These are difficult questions which will be discussed later. Nonetheless, it is correct to say that the modern individual income tax. If carefully designed and well administered, is a powerful and essential economic instrument for a modern indusrtial econmy. 使用所得税作为财政收入主要来源有很好的经济原因. 该所得税的自动灵活性能促进经济稳定，累进税率有助于防止经济权力和控制过分集中. 有人认为所得税也需缓和高收入人群的私人储蓄增长, 这很可能压抑商品的服务的私人需求。有人认为高所得税降低工作和投资动力,因此,减少了国家的经济增长. 这些都是日后讨论的难题. 但是,现代的个人所得税是正确的. 如果经过精心设计和良好管理,是现代工业化经济的有力而必要的经济手段。 Structure of the Federal Income Tax 联邦所得税结构 The basic structure of the federal income tax is simple. The taxpayer adds up all his taxable sources of income, subtracts certain allowable deductions and exemptions for himself, his wife, children, and other dcpendents,and then applies the tax rates to the difference. But this procedure has many pitfalls for the taxpayer, and difficult questions of tax policy arise at almost every stage. Consequently, it is important to understand the main features of the income tax structure. 联邦所得税的基本结构是很简单的. 纳税人增添了他的一切应纳税收入,减去某些自己的、妻子的、孩子的和其他相关人的允许扣除和豁免权,然后适用税率差额. 但这种程序对纳税人也有很多陷阱,税收政策的难题几乎出现在每一阶段. 因此,了解所得税结构的主要特征是重要的. Adjusted Gross Income and Taxable Income调整过的总收入和应纳税收入 The two major concepts of income that appear on the tax return are: adjusted gross income and taxable income. 出现在纳税申报单上的两大收益好象是:调整过的总收入和应纳税收入. Adjusted gross income is the closest approach in tax law to what all economist might call “total income.” But it departs from an economic definition of income in some important respects. It represents the total income from all taxable sources, less certain expenses incurred in earning that income. In general, only money income is treated as taxable, but many items are excluded. Such exclusions include one-half of realized capital gains on assets held six months or more, interest on state and local government bonds,all transfer payments(for example,social security benefits and unemployment compensation), fringe benefits received by employees from their employers(the most important of these are contributions to pension plans), and income on savings through life insurance. The emphasis on money income automatically excludes unrealized capital gains and such imputed income as the rental value of owner-occupied homes. 在税法上调整的总收入是所有经济学家称之为"总收入"的最接近说法。 但是,在某些重要方面，它背离了收入的经济学定义. 它表示所有应纳税来源的总收入，较少的赚取收入中的确定开支. 一般说来,只有货币收入被视为应税的,但很多项目都被排除在外. 这种排除包括二分之一的持有六个月或以上的已实现资本收益，国家和当地政府公债的利息,所有的转移支付(例如,社会保障福利和失业补偿) , 雇员从其雇主那得到的附加福利(贡献中最重要的是为养老金计划) , 和加入了人寿保险的储蓄收入. 对货币收入的强调自动排除了未实现资本收益和这种像所有者租税价的推算收入. Adjusted gross income is used on the tax return in two ways. First, it is the income concept built into the simplified tax table, which is used for determining tax on more than 25 million returns. Second,it provedes the basis for placing limits on some of the personal deductions which are subrtacted in computing taxable income. 调整后的总收入用于纳税申报单有两种方式. 第一,它是收入概念建成的简易税表, 用于决定税收突破2500万美元的回报. 第二,它提供了限制某些个人扣除的基础，个人扣除在计算应纳税收入时已经减去了. Taxable income is computed by making two sets of deductions from adjusted gross income. The rirst are personal expenditures which are allowed as deductions by law—charitable contributions, interest paid,state-local income, general sales, property and gasoline taxes, medical and dental expenses above 3 percent of adjusted gross income, and casualty and theft losses above $100 for each lieu of these deductions, the taxpayer may use the standard deduction of 10 percent of adjusted gross income(with a minimum of $200 plus $100 for each exemption,and a maximum of $1000 for single persons and married persons filing joint returns and $500 for married couples filing separate returns). 应税收入是从调整过的总收入中制作两套扣除法计算而来的. 剩下的是法律允许扣除的个人支出--慈善捐款,所付利息,国有地方收入,一般销售 财产和汽油税, 高于调整后总收入3%的医疗及牙科服务费用, 伤亡和每次损失100美元以上的偷盗损失。代替上述扣减， 纳税人可使用10%调整后的总收入的标准扣除额 (最低200美元,加上每项豁免100美元,单身和夫妻联合备案的已婚人士每人最高1000美元，并返回500美元为已婚备案夫妻分开报税) . When the present standard deduction was first adopted in 1944, it was used by over 80 percent of the persons filing incomes have risen and deductible expenditures have increased,the percentage using the standard deduction has declined. In 1963, the standard deduction was still being used on million returns, or 56 percent of the million filed(Appendix Table C-6). But the amount of the standard deduction was small compared to home ownership, state-local taxes,and use of consumer credit, as well as the normal increase in expenditures that occurs as incomes rise. Total deductions reported on all 1963 returns amounted to $ billion; of this amount, $ billion were itemized deductions and $ billion were standard deduction. 现行标准扣除额首次在1944年应用时， 它被用于个人存档返还的80%以上.随着收入的增加和可扣除支出增加, 用于标准扣除额的比率也有所下降. 1963年标准扣除额仍被用于3580万的回报, 或6390万存档56% (附录表C 6 ) . 但征收的标准扣除额是比较小的，与国有、地方税,消费品信贷的使用, 以及随收入增加而不断增加的正常开支相比.1963年报告的总扣除额回到了592亿美元; 这一数额中, 有461亿美元详细说明了扣除项目,131亿美元为标准扣除额.
海洋生物来源药物先导化合物的研究进展【摘要】海洋生物中活性物质丰富，本篇文章对国内外近3年来从海洋生物中分离提取到的萜类化合物以及糖苷类化合物进行了归纳，并对其研究趋势进行了展望。这些新发现的萜类化合物广泛分布于海藻、珊瑚、海绵以及一些海洋真菌等海洋生物中，主要以单萜、倍半萜、二萜、三萜结构型式存在；而糖苷类化合物在海藻、海绵、海参、海星等海洋生物中发现大部分以糖苷脂、甾体糖苷、萜类糖苷型式存在。【关键词】海洋生物萜类化合物糖苷类生物活性【Abstract】.【Keywords】Marineorganism;terpenoid;glycoside;bioactivity海洋是生命之源，由于海洋环境的特殊性，具有高压、低营养、低温（特别是深海）、无光照以及局部高温、高盐等生命极限环境，海洋生物适应了海洋独特的生活环境，必然造就了海洋生物具有独特的代谢途径和遗传背景，必定也会有新的、在许多陆地生物中未曾发现过的新结构类型和特殊生物活性的化合物。萜类物质是一类天然的烃类物质，其分子中具有异戊二烯(C5H8)的基本单位。故凡由异戊二烯衍生的化合物，其分子式符合(C5H8)n通式的均称萜类化合物(terpenoids)或异戊二烯类化合物（isopenoids）。但有些情况下，在分子合成过程中由于正碳离子引起的甲基迁移或碳架重排以及烷基化、降解等原因，分子的某一片断会不完全遵照异戊二烯规律产生出一些变形碳架，它们仍属于萜类化合物。海洋生物中萜类化合物主要以单萜、倍半萜、二萜、二倍半萜为主，三萜和四萜种类和数量都较少，且大部分以糖苷形式存在。萜类化合物是海洋生物活性物质的重要组成部分，广泛分布于海藻、珊瑚、海绵、软体动物等海洋生物中，具有细胞毒性、抗肿瘤活性、杀菌止痛等活性作用。糖苷的分类有多种方法，按照在生物体内是原生的还是次生的可将其分为原生糖苷和次生糖苷（从原生糖苷中脱掉一个以上的苷称为次生苷或次级苷）；按照糖苷中含有的单糖基的个数可将糖苷分为单糖苷、双糖苷、三糖苷等；按照糖苷的某些特殊化学性质或生理活性可将糖苷分为皂苷、强心苷等；按照苷元化学结构类型可分为黄酮糖苷、蒽醌糖苷、生物碱糖苷、三萜糖苷等，海洋类的糖苷大部分是按照此特点分类的，主要包括鞘脂类糖苷、甾体糖苷、萜类糖苷和大环内酯糖苷等，在很多海洋生物如海藻、珊瑚、海参、海绵等中均发现有糖苷类化合物存在。已有的研究表明海洋糖苷类成分大都具有抗肿瘤、抗病毒、抗炎、抗菌、增强免疫力等生物活性。抗白血病和艾氏癌药物阿糖胞苷Ara-C(D-arabinosylcytosine)1、抗病毒药物的Ara-A2以及Ara-C的N4-C16-19饱和脂肪酰基化衍生物3是海洋糖苷类药物成功开发的典范〔1〕。本篇文章对国内外自2005年来从海洋生物中分离提取到的萜类化合物以及糖苷类化合物进行了总结。1萜类化合物单萜2005年等人〔2〕对从红藻Plo