坚吃不懈1208
编译 | 未玖
Nature ,6 May 2021,VOL 593,ISSUE 7857
《自然》 2021年5月6日，第593卷，7857期
天文学 Astronomy
Jets from MRC 0600-399 bent by magnetic fields in the cluster Abell 3376
Abell 3376星系团磁场使MRC 0600-399射流弯曲
作者：James O. Chibueze, Haruka Sakemi, Takumi Ohmura, Mami Machida, Hiroki Akamatsu, Takuya Akahori, et al.
链接：
摘要
众所周知，星系团内部有磁场，但磁场的性质至今仍未明确。在冷稠密等离子体进入热环境等离子体形成的密度接触不连续处可以观察到星系团内部磁场，该不连续处存在于合并星系团Abell3376（红移）中第二亮星系MRC 0600-399附近。
东西方向拉长的X射线发射显示出一个彗星状的结构，达到百万秒差距规模。先前的射电观测发现MRC 0600-399的弯曲喷流，与子星团朝着相同的方向移动，对抗冲压。
研究组报道了MRC 0600-399的射电观测结果，其分辨率和灵敏度分别是先前结果的倍和11倍。与典型射流相比，MRC 0600-399在接触不连续处呈现90度弯曲，准直射流从弯曲点延伸超过100千秒差距。
研究组观察到弥漫的、拉长的发射，将其称之为“双镰刀”结构。光谱指数在弯曲点的下游趋于平缓，表明宇宙射线重新加速。高分辨率数值模拟表明，沿不连续面的有序磁场对射流方向的变化有重要影响。双镰刀射流的形态与模拟结果一致。
该研究结果有助于了解磁场对星系团成员星系和内部介质演化的影响。
Abstract
Galaxy clusters are known to harbour magnetic fields, the nature of which remains unresolved. Intra-cluster magnetic fields can be observed at the density contact discontinuity formed by cool and dense plasma running into hot ambient plasma, and the discontinuity exists near the second-brightest galaxy, MRC 0600-399, in the merging galaxy cluster Abell 3376 (redshift ). Elongated X-ray emission in the east–west direction shows a comet-like structure that reaches the megaparsec scale. Previous radio observations detected the bent jets from MRC 0600-399, moving in same direction as the sub-cluster, against ram pressure. Here we report radio observations of MRC 0600-399 that have and 11 times higher resolution and sensitivity, respectively, than the previous results. In contrast to typical jets, MRC 0600-399 shows a 90-degree bend at the contact discontinuity, and the collimated jets extend over 100 kiloparsecs from the point of the bend. We see diffuse, elongated emission that we name ‘double-scythe’ structures. The spectral index flattens downstream of the bend point, indicating cosmic-ray reacceleration. High-resolution numerical simulations reveal that the ordered magnetic field along the discontinuity has an important role in the change of jet direction. The morphology of the double-scythe jets is consistent with the simulations. Our results provide insights into the effect of magnetic fields on the evolution of the member galaxies and intra-cluster medium of galaxy clusters.
物理学 Physics
Leading hadronic contribution to the muon magnetic moment from lattice QCD
晶格QCD谬子磁矩的领头阶强子贡献
作者：Sz. Borsanyi, Z. Fodor, J. N. Guenther, C. Hoelbling, S. D. Katz, L. Lellouch, et al.
链接：
摘要
粒子物理学的标准模型描述了绝大多数涉及基本粒子的实验和观测。任何偏离它的预测都将是新基础物理学的标志。一个长期存在的偏差与谬子的反常磁矩有关，谬子是一种测量粒子周围磁场的方法。
标准模型预测与紧密分布在个标准差附近的测量结果不一致。当前理论误差和测量误差是可比的；然而，正在进行和计划中的实验旨在将测量误差减少四分之一。理论上，主要误差来源是领头阶强子真空极化（LO-HVP）的贡献。
对于即将进行的测量，必须用独立方法来评估这一贡献的预测，并减少其不确定性。到目前为止，最精确的、与模型无关的测定依赖于色散技术，并结合了电子-正电子湮没为强子的横截面测量。
为了消除对这些实验的依赖，研究组使用从头计算量子色动力学（QCD）和量子电动力学模拟来计算LO-HVP的贡献。
研究组达到了足够的精度来区分谬子反常磁矩的测量和色散方法的预测。该研究结果比用色散关系得到的结果更符合实验测量值。此外，这项工作中使用和开发的方法有望实现精度更高、更强大的计算机。
Abstract
The standard model of particle physics describes the vast majority of experiments and observations involving elementary particles. Any deviation from its predictions would be a sign of new, fundamental physics. One long-standing discrepancy concerns the anomalous magnetic moment of the muon, a measure of the magnetic field surrounding that particle. Standard-model predictions exhibit disagreement with measurements that is tightly scattered around standard deviations. Today, theoretical and measurement errors are comparable; however, ongoing and planned experiments aim to reduce the measurement error by a factor of four. Theoretically, the dominant source of error is the leading-order hadronic vacuum polarization (LO-HVP) contribution. For the upcoming measurements, it is essential to evaluate the prediction for this contribution with independent methods and to reduce its uncertainties. The most precise, model-independent determinations so far rely on dispersive techniques, combined with measurements of the cross-section of electron–positron annihilation into hadrons. To eliminate our reliance on these experiments, here we use ab initio quantum chromodynamics (QCD) and quantum electrodynamics simulations to compute the LO-HVP contribution. We reach sufficient precision to discriminate between the measurement of the anomalous magnetic moment of the muon and the predictions of dispersive methods. Our result favours the experimentally measured value over those obtained using the dispersion relation. Moreover, the methods used and developed in this work will enable further increased precision as more powerful computers become available.
Rashba valleys and quantum Hall states in few-layer black arsenic
薄层黑砷中的拉什巴谷和量子霍尔态
作者：Feng Sheng, Chenqiang Hua, Man Cheng, Jie Hu, Xikang Sun, Qian Tao, et al.
链接：
摘要
在非中心对称的二维电子系统中，自旋-轨道耦合（SOC）与库仑相互作用、能带拓扑和外部调制力动态相互作用时，可能会出现令人兴奋的现象。
研究组报道了中心对称的薄层黑砷中SOC和斯塔克效应之间的协同效应，表现为粒子-空穴不对称的拉什巴谷形成和由静电门可逆控制的新奇量子霍尔态。
这些不寻常的发现源于黑砷的皱褶方形晶格，其中重4p轨道形成了一个以 pz 对称的布里渊区为中心的Γ谷，并在X点的时间反转不变动量附近与 px 起源双重简并D谷共存。
当垂直电场破坏结构反转对称性时，强拉什巴SOC被 px 带激活，产生时间反转对称的自旋谷“味”的 D 谷，而Γ谷的拉什巴劈裂受到 pz 对称性的约束。有趣的是，巨大的斯塔克效应显示了相同的 px 轨道选择性，共同移动 D 拉什巴谷的能带最大值，使其超过Γ拉什巴顶部。
这种协调效应使研究组能够实现二维空穴气体的门-可调拉什巴谷操控，其特点是由于形成了依赖于“味”的朗道能级谱，量子霍尔态发生了非常规的偶-奇跃迁。对于二维电子气体，Γ拉什巴谷的量子化特征是从平凡的抛物型腔到螺旋狄拉克费米子的能带拓扑结构中的特殊密度依赖跃迁。
Abstract
Exciting phenomena may emerge in non-centrosymmetric two-dimensional electronic systems when spin–orbit coupling (SOC) interplays dynamically with Coulomb interactions, band topology and external modulating forces. Here we report synergetic effects between SOC and the Stark effect in centrosymmetric few-layer black arsenic, which manifest as particle–hole asymmetric Rashba valley formation and exotic quantum Hall states that are reversibly controlled by electrostatic gating. The unusual findings are rooted in the puckering square lattice of black arsenic, in which heavy 4p orbitals form a Brillouin zone-centred Γ valley with pz symmetry, coexisting with doubly degenerate D valleys of px origin near the time-reversal-invariant momenta of the X points. When a perpendicular electric field breaks the structure inversion symmetry, strong Rashba SOC is activated for the px bands, which produces spin–valley-flavoured D valleys paired by time-reversal symmetry, whereas Rashba splitting of the Γ valley is constrained by the pz symmetry. Intriguingly, the giant Stark effect shows the same px-orbital selectiveness, collectively shifting the valence band maximum of the D Rashba valleys to exceed the Γ Rashba top. Such an orchestrating effect allows us to realize gate-tunable Rashba valley manipulations for two-dimensional hole gases, hallmarked by unconventional even-to-odd transitions in quantum Hall states due to the formation of a flavour-dependent Landau level spectrum. For two-dimensional electron gases, the quantization of the Γ Rashba valley is characterized by peculiar density-dependent transitions in the band topology from trivial parabolic pockets to helical Dirac fermions.
气候学 Climatology
Projected land ice contributions to twenty-first-century sea level rise
陆地冰对21世纪海平面上升的贡献预测
作者：Tamsin L. Edwards, Sophie Nowicki, Ben Marzeion, Regine Hock, Heiko Goelzer, Hélène Seroussi, et al.
链接：
摘要
陆地冰对全球平均海平面上升的贡献尚未通过最新一组 社会 经济情景的冰盖和冰川模型预测，也未通过由各种计算机模型所产生的不确定性进行的协调 探索 预测。最近的两个国际项目使用多种模型进行了大量预测，但主要使用上一代情景和气候模型，无法充分 探索 已知的不确定性。
研究组使用冰盖和冰川模型的统计模拟来估计新情景下这些预测的概率分布。他们发现，与目前的排放承诺相比，将全球升温限制在 以内，陆地冰融化造成的21世纪海平面上升将减少一半。到2100年，平均海平面当量（SLE）从25 cm降至13 cm，冰川占海平面贡献的一半。
由于在气候变暖过程中冰损失增加和降雪积累的竞争过程存在不确定性，预测的南极贡献并未对排放情景作出明确反应。然而，在风险规避（悲观）的假设下，南极冰损失可能高出5倍，在当前政策和承诺下，陆地冰对SLE的贡献中位数增加到42 cm，即使在 升温的情况下，第95个百分位的预测值也超过半米。
这几乎不可能缓解未来沿海洪水的威胁。考虑到这一大范围（13 cm至42cm SLE），在气候政策和南极应对措施进一步受到限制之前，21世纪海平面上升的适应规划必须考虑到陆地冰贡献的三个不确定性因素。
Abstract
The land ice contribution to global mean sea level rise has not yet been predicted using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models, but primarily used previous-generation scenarios and climate models, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained.
The Paris Climate Agreement and future sea-level rise from Antarctica
巴黎气候协定和未来南极洲海平面上升
作者：Robert M. DeConto, David Pollard, Richard B. Alley, Isabella Velicogna, Edward Gasson, Natalya Gomez, et al.
链接：
摘要
《巴黎协定》旨在将21世纪全球平均升温控制在比工业化前水平高2 以内，并进一步努力控制在 以内。由于海洋热膨胀和陆地冰损失的综合作用，未来几十年的温室气体排放量将对全球平均海平面（GMSL）造成一个世纪甚至更长时间的影响。
南极冰原（AIS）是地球上最大的陆地冰库，其冰损失正在加剧。AIS的广大区域位于海平面以下，容易受到动态不稳定性的影响，这种不稳定性能够产生非常迅速的冰盖消退。然而，实施《巴黎协定》温控目标以减缓或阻止这些不稳定发生的可能性，尚未通过基于物理学的模型进行直接测试。
研究组使用一个经过观测校准的冰盖-冰架模型来证明，当全球升温被限制在2 以内时，整个21世纪南极冰层的流失速度将与今天类似。然而，与现行政策更为一致的情景（允许升温3 ）将在2060年左右使南极冰层融化的速度突然加快，到2100年将导致GMSL每年上升约厘米，比今天快一个数量级。
更多化石燃料密集使用会导致更大的加速。虽然有基岩和海平面反馈机制，以及地球工程二氧化碳减排，但因支撑冰架的变薄和消失而引发的冰盖消退将持续好几个世纪。这些结果表明，如果超出《巴黎协定》的目标，南极洲海平面将有可能迅速而不可阻挡地上升。
Abstract
The Paris Agreement aims to limit global mean warming in the twenty-first century to less than 2 degrees Celsius above preindustrial levels, and to promote further efforts to limit warming to degrees Celsius. The amount of greenhouse gas emissions in coming decades will be consequential for global mean sea level (GMSL) on century and longer timescales through a combination of ocean thermal expansion and loss of land ice. The Antarctic Ice Sheet (AIS) is Earth’s largest land ice reservoir, and its ice loss is accelerating. Extensive regions of the AIS are grounded below sea level and susceptible to dynamical instabilities that are capable of producing very rapid retreat. Yet the potential for the implementation of the Paris Agreement temperature targets to slow or stop the onset of these instabilities has not been directly tested with physics-based models. Here we use an observationally calibrated ice sheet–shelf model to show that with global warming limited to 2 degrees Celsius or less, Antarctic ice loss will continue at a pace similar to today’s throughout the twenty-first century. However, scenarios more consistent with current policies (allowing 3 degrees Celsius of warming) give an abrupt jump in the pace of Antarctic ice loss after around 2060, contributing about centimetres GMSL rise per year by 2100—an order of magnitude faster than today. More fossil-fuel-intensive scenarios result in even greater acceleration. Ice-sheet retreat initiated by the thinning and loss of buttressing ice shelves continues for centuries, regardless of bedrock and sea-level feedback mechanisms or geoengineered carbon dioxide reduction. These results demonstrate the possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded.
考古学 Archaeology
Earliest known human burial in Africa
非洲最早的人类墓葬
作者：María Martinón-Torres, Francesco d’Errico, Elena Santos, Ana Álvaro Gallo, Noel Amano, William Archer, et al.
链接：
摘要
人类殡葬习俗的起源和演变是人们感兴趣和喜欢争论的话题。中石器时代（MSA）的人类墓葬在非洲很罕见，在东非也不为人知。
研究组在肯尼亚热带高地海岸的Panga ya Saidi（PYS）洞穴遗址MSA层中发现了一具距今万年前的岁幼儿的部分骨骼。最新挖掘揭示了这个坑的特征，里面有一个蜷曲的幼儿。
对坑中内容物和包裹考古层的地球化学、粒度和微观形态的分析表明，该坑是人为挖掘的。埋藏学证据，如骨骼部分的严密连接或良好的解剖关系以及腐烂的组织学证据，均支持新鲜尸体的就地分解。
在分解过程中，不稳定的关节几乎没有移位，这表明其埋葬在一个填满的空间（墓地）中，至此，人们在PYS发现了非洲已知最古老的人类墓葬。
部分骨骼的形态评估与智人分类一致，尽管在牙齿中保留了一些原始特征，但越来越多的证据表明，在我们物种出现的过程中，现代特征的非渐进组装。PYS墓葬揭示了MSA人群如何与死者互动。
Abstract
The origin and evolution of hominin mortuary practices are topics of intense interest and debate. Human burials dated to the Middle Stone Age (MSA) are exceedingly rare in Africa and unknown in East Africa. Here we describe the partial skeleton of a roughly to child dating to thousand years ago, which was recovered in the MSA layers of Panga ya Saidi (PYS), a cave site in the tropical upland coast of Kenya. Recent excavations have revealed a pit feature containing a child in a flexed position. Geochemical, granulometric and micromorphological analyses of the burial pit content and encasing archaeological layers indicate that the pit was deliberately excavated. Taphonomical evidence, such as the strict articulation or good anatomical association of the skeletal elements and histological evidence of putrefaction, support the in-place decomposition of the fresh body. The presence of little or no displacement of the unstable joints during decomposition points to an interment in a filled space (grave earth), making the PYS finding the oldest known human burial in Africa. The morphological assessment of the partial skeleton is consistent with its assignment to Homo sapiens, although the preservation of some primitive features in the dentition supports increasing evidence for non-gradual assembly of modern traits during the emergence of our species. The PYS burial sheds light on how MSA populations interacted with the dead.
小宝151205
随着我国旅游行业的快速发展,越来越多的外国友人到我国旅游,所以在我国旅游可持续发展进程当中英语导游十分重要。下面是我精选的关于英文 导游词 范文 五篇，仅供参考，希望能帮助到大家!
英文导游词篇一：云南
Welcome to Yunnan, Welcome to Tengchong! It’s my honor to be your guide. Today we are going to visit the volcanoes and hot springs in Tengchong, which are the most famous here.
As we will get there in a few minutes, first allow me to give you a brief intoduction of Tengchong. Tengchong is located in the southwest of China and occupies an area of 5800 square kilometers. There are 23 nationalities here, such as 汉、傣、回、白 nationalities and so on. When we mentioned Tengchong, three things will come into mind, which are: the volcanoes and hot springs having 10,000 years, the border city having 1,000 years and the fair of jade having 100 years.
Later we will get to the volcanoes and the hot spring, so now I can tell you something about the latter two ones. They all can reflect the long history Tengchong has. Tengchong is a city on boarder. And because of its location, it has been an important place for military reasons. And that’s a part of its history. It’s also regarded as the county of manners, and it is the hometown of so many famous people. And another part of its history is that Tengchong is one trade center of jade between China and Burma. So don’t forget to get a round to the jade fair. I think you will feel interested.
OK, everyone, here is the Library of the Volcanoes. Now let’s have a look at .The volcanoes in Tengchong are famous in China, and it’s one of the four groups of volcanoes in China. The strong extravasations are the cause of the landform of Tengchong. There is a lieder in Tengchong saying that:” Such a place Tengchong, nine in ten mountains have no peaks.” It’s very vivid, from that you can see so many volcanoes are in Tengchong. There are 97 volcanoes in Tengchong now with high value of tourism and scientific research.
英文导游词篇二：重庆
Evening Scenes of Chongqing
The Red Star Pavilion in the Pipasha Park, the Kansheng Pavilion in the Eling Park, and a place called Yikeshu on the Nanshan Mountain are vintage points for observing the nocturnal scenes of the mountain city of Chongqing. At night the entire city is inundated in an ocean of lights, which form a colorful three-dimensional painting, with waves of the Yangtze and Jialing rivers glistening against the moonlit, star spangled sky.
Sites of the Provisional Capital
Chongqing figured importantly in modem Chinese history. During the War of Resistance against Japan, it was the "provisional capital" of China under the Kuomintang rule from November 1937 to October 1945. Vestiges of that period are still there in and around the city. These include the Red Crag Village and 50 Zengjiayan, as well as Chiang Kai-shek's mansion, Guiyuan Garden, Linyuan Garden, and the mansion of . Kong, the embassies of various countries to China, as well as former residences of important politicians, generals and cultural figures.
Martyrs' Mausoleum at Mount Gele
The former headquarters, radio station and prison of the Bureau of Investigation and Statistics of the Military Council (a colossal secret service of the Kuomintang) at the foot of the Gele Mountain in Shapingba District have become the mausoleum for those who died a martyr's death there in China's dark days. In the dying years of World War 11, it was the site of the "Sino0US Institute for Cooperation in Special Technology".
Dazu Grottoes
The Dazu Grottoes in the county of the same name is best known for the stone carvings on the Baodingshan and Beishan mountains, which are fine example of grotto sculpture in the late years of Chinese feudalism. The sculptures, done in fastidious chisel work and gracious imagery, are marked by a new sculptural language that eschews religious taboos and espouses true life.
Yangtze River's Three Gorges
Sailong down the Yangtze from Chongqing to Yichang allows visitors to see the spectacular scenery of the Three Gorges along with its splendid cultural heritage and fabled local folklore. The cruise, which combines sightseeing with scientific, artistic and folklore exploration, is a national-caliber tourist program. The 193-km-long Three Gorges, consisting of the majestic Qutangxia, statuesque Wuxia and ferocious Xilingxia gorges, is one of and ferocious Xilongxia gorges, is one of the world's major canyons. Along the way there are such scenic attractions as the Fengdu Mountain. Baidi city, Shibao village, Zhang Fel's Temple, Qu Yuan's Temple, and the Three Gorges Dam.
Lesser Three Gorges
The Daning River is the largest Yangtze tributary, which rises in the southern side of the Daba Mountain and flows for 250km before emptying itself into the Yangtze at the western entrance to the Wuxia Gorge. The Lesser Three Gorges on the Daning River, a 50km-long affair covering the Longmenxia, Bawuxia and Dicuixia gorges in the lower reaches of the river, is billed as one of China's 40 best scenic resorts thanks to its gorgeous mountains, elegant peaks, turbulent rapids, limpid water, exotic rock imagery and serene scenery.
Diaoyu City, Hechuan
Established in 1242, or the 2nd year of the Chunyou reign of the Southern Song, Diaoyu City covers square km up the Diaoyu Mountain on the southern shore of the Jialing River in Hechuan City's Heyang Town. In 1258, the Mongols launched a three-way attack on the Song, and in February the next year Diaoyu City found itself besieged. The Song army mounted a valiant counterattack that last3ed for 36 years, and made world war history by rebuffing a strong enemy with a weak force. This prompted some European historians to laud Diaoyu City as the "Mecca of the East" and "Where God broke his whip". The ruins of the ancient battlefield of Diaoyu City are well kept there.
Jinyun Mountain
Nicknamed "Less Mount Emei", Jinyun Mountain is a national scenic resort 55km from downtown Chongqing.
Furong Cave, Wulung
The Furong (Hibiscus) Cave is located by the Furong River in Wulung County. The main part of the cave is 2,700 metres in length and square metres in area. The Splendid Cave is the most impressive. Housed in it are nearly 30 varieties of stalactites chiseled into every manner of exotic imagery by the cunning labor of nature. Major attractions are Gold Throne Hall, Leifeng Pagoda and Sky-reaching Jade Pillar.
英文导游词篇三：玉龙雪山
Locating between 10004’-10016’east longitude and 2703’-2740’ north latitude, Jade Dragon Snow Mountain (Yulong Mountain) is the southernmost glacier in the Northern Hemisphere. Consisting of 13 peaks, among which Shanzidou is the highest one with an altitude of 5,600 meters (18,360 feet), Jade Dragon Snow Mountain stretches a length of 35 kilometers (22 miles) and a width of 20 kilometers (13 miles). Looking from Lijiang Old Town in the south which is 15 kilometers (nine miles) away, the snow-covered and fog-enlaced mountain resembles a jade dragon lying in the clouds, hence, the name Jade Dragon Snow Mountain.
According to the geologists’ research, for about 400 million years the area around Jade Dragon Snow Mountain was the ocean and it was during the last 600 thousand years that the different landscapes had come into being because of the uprising of the lithosphere. Archaic legend about this mysterious and beautiful snow mountain goes like this: Once upon a time, Jade Dragon Snow Mountain and Haba Snow Mountain were twins. They had lived on panning in Golden Sand River until one day an evil fiend usurped the river. The brothers were very brave and had a fierce fight with the fiend, Haba died in the fight and Jade Dragon drove off the fiend after wearing out 13 swords. For guarding the people and preventing the return of the fiend, Jade Dragon held the 13 swords in hands day and night. As time passed, the brothers had turned into the two snow mountains, and the 13 swords had become the 13 peaks. Jade Dragon Snow Mountain is a holy mountain for the local Naxi people not only because of the legend, but also because long time ago, it was a place for young lovers to sacrifice their young lives in honor of true love and to escape from the arranged marriages and feudal ethics.
Jade Dragon Snow Mountain is a sanctuary for rare animals and wild plants. In fact, one fourth of all plant species in China can be found here and 20 primeval forest communities shelter a big family of 400 types of trees and 30 kinds of animals which are protected by the state. These species live in different temperature levels and create different kinds of views of Jade Dragon Snow Mountain. The 13 peaks, which have the altitudes of at least 4,000 meters, are covered by snow all year round; the mountain is called the "Natural Glacier Museum" for it has all types of glacier. Move down from the mountaintop and you can see rivers and pools, which are formed by the thawed snow water running along the valley and through the forests. The plants and the animals are different according to the altitude, so are the views. Every sight brings you a surprise and every step takes you to a new scene. Each of the meadows on Jade Dragon Snow Mountain has its own special character due to their different landscape and height. For instance, Yunshanping (Spruce Plateau) is grassland with gigantic spruces whilst Ganhaizi (Dry Sea) used to be a highland lake as its name tells, the meadow was formed after the water had dried up. Jade Dragon Snow Mountain now is a famous scenic spot for sightseeing, mountaineering, skiing, exploration, scientific research and taking holiday. Besides, widespread legends and myths of the Naxi ethnic minority and the unclimbed Shanzidou are all important attractive spots for those who come to Jade Dragon Snow Mountain.
英文导游词篇四：丽江壁画
Ten kilometers (six miles) northwest of Lijiang Old Town, there are several ancient villages, including Baisha, Dayan, Shuhe, Yangxi and Xuesong. There, the invaluable Lijiang Mural is stored, preserved and displayed in 15 venerable temples, such as Juexian, Wande, Guiyi temples and Sanbi Garden. Altogether, the mural used to include more than 200 pieces of fresco. However, hundreds of years of historical vicissitudes have left only 55 pieces in good condition. The most famous frescos are known as Baisha Mural of the Dabaoji (Great Treasure) Palace and the Colored Glaze Temple (Liuli Dian) in the town of Baisha.
Most of the temples were built from the early days of the Ming Dynasty (1368-1644) to the early Qing Dynasty (1644-1911), and the Lijiang Mural was created at the same time, over the course of about 300 hundred years. In Lijiang, it was an era of rapid economic development, mutual acculturation of multinational culture, and the growth of religions. Accordingly, Lijiang Mural was an artistic representation of this cooperation, communication and progress. The authors of these mural paintings had come from different nations, including the local Naxi Dongba painters; the Taoist painter Zhang from the Central Plain; an Lama artist Guchang; Han painters Ma Xiaoxian and Li Zeng; and many other artists who were unknown to the public
The originality and figures of the mural paintings reflect the different religious cultures and artistic forms of Buddhism, Lamaism, Daoism and the Naxi Dongba religion, as developed in a Naxi school. Therefore, Lijiang Mural is quite different from other frescos. Each painting includes at least one hundred portraits, but perspective is used very well, and the close, middle and establishing images are clear. The various lifelike portraits are not only Buddhas but also ordinary people such as bureaucrats, criminals, tourists and executioners. Many of the scenes and subject matters are drawn from daily life-people are shown fishing, riding horses, weaving, dancing and casting iron. The painters used different methods of portrayal within the different elements of the fresco, such as flesh, garments, jewelry, weapons and many other components. The style of these true-life frescos is rural and unconstrained; the colors are strong and have intense contrast but are also unified. The Lijiang Mural fully demonstrates the superb artistic skills, outstanding creativity and rich imaginations of these excellent craftsmen. The vivid and exact figures, flowing lines, well-defined colors and powerful effects of the exquisite details make the Lijiang Mural not only the rare treasure of art, but also forceful proof of national solidarity and an important source of information for research on national religions, arts and history.
英文导游词篇五：平遥古城
Ladies and gentlemen, this time we are going to visit the famous Pingyao County. Pingyao County is one of the cultural heritages of the world heritage list. Please keep the floor clean during the tour. If you have any questions, you can ask first came to the first tourist spot: South Street. The composition of Pingyao County is crisscrossed four streets, eight small streets, seventy-two winding streets, and now we come to the South Street of four Avenue. You see, on both sides of the street, old and famous shops are flourishing traditional commercial streets. During the Qing Dynasty, South Street controlled more than fifty percent of the financial institutions in the Street is known as "the first street of Finance in Qing Dynasty", and it is a main street directly connected with East Street. And the East Avenue North and South Street intersection, North Street is to the west central small streets and seventy-two lanes are named in the nearby buildings or marked signs; some are named in the temple temple; some are named in a city in the city; and some streets and lanes have been unable to explore the source of the are many beautiful legends in Pingyao County, such as sleeping aunts and drug wives, and burning Town God's Temple. Please take a good tour of this beautiful ancient city.
猫咪抱抱
编译 | 李言
Science , 07 MAY 2021, VOL 372, ISSUE 6542
《科学》 2021年5月7日，第372卷，6542期
古人类学 Paleoanthropology
Unearthing Neanderthal population history using nuclear and mitochondrial DNA from cave sediments
利用洞穴沉积物中的核和线粒体DNA挖掘尼安德特人的种群 历史
作者：Benjamin Vernot, Elena I. Zavala, Asier Gómez-Olivencia, Zenobia Jacobs, et al.
链接：
摘要
骨头和牙齿是更新世人类DNA的重要来源，但很少在考古遗址中发现。从洞穴沉积物中可以提取到线粒体DNA（mtDNA），但它们对种群关系的研究价值有限。
因此，我们开发了收集和分析沉积物中核DNA的方法，并将其应用于20万至5万年前的西欧和西伯利亚南部的洞穴沉积物中。
我们在大约10万年前的西班牙北部发现了一个伴随着mtDNA更替的种群更替。我们还确定了尼安德特人在晚更新世早期的两次辐射进化事件。我们的工作为从沉积物中微量的核DNA研究古人类的种群 历史 奠定了基础。
Abstract
Bones and teeth are important sources of Pleistocene hominin DNA, but are rarely recovered at archaeological sites. Mitochondrial DNA (mtDNA) has been retrieved from cave sediments but provides limited value for studying population relationships. We therefore developed methods for the enrichment and analysis of nuclear DNA from sediments and applied them to cave deposits in western Europe and southern Siberia dated to between 200,000 and 50,000 years ago. We detected a population replacement in northern Spain about 100,000 years ago, which was accompanied by a turnover of mtDNA. We also identified two radiation events in Neanderthal history during the early part of the Late Pleistocene. Our work lays the ground for studying the population history of ancient hominins from trace amounts of nuclear DNA in sediments.
古生物学 Paleobiology
Evolution of vision and hearing modalities in theropod dinosaurs
兽脚类恐龙视觉和听觉模式的进化
作者：Jonah N. Choiniere, James M. Neenan, Lars Schmitz, David P. Ford, et al.
链接：
摘要
猫头鹰和夜莺是在夜间活动的猎食者，它们结合了视觉和听觉的改变，以克服在弱光下感官表现的限制。这种感官改变在非鸟类的兽脚类恐龙中未被发现，并且在向鸟类进化的谱系中极少被确认。
我们研究了现存和灭绝的兽脚亚目动物的视觉和听觉的形态功能代理，并证明了感官模式的深度进化分歧。夜行性捕食在非鸟类的阿瓦拉慈龙类早期就进化出来了，表现为极弱的视力和听觉敏感度的增加。
晚白垩纪的沙漠鸟面龙拥有更特殊的听力，可以与今天的仓鸮媲美。早在现代鸟类辐射进化出现之前，这种感觉适应能力的结合就在恐龙身上独立进化，并为恐龙和哺乳动物的融合提供了一个显著的例子。
Abstract
Owls and nightbirds are nocturnal hunters of active prey that combine visual and hearing adaptations to overcome limits on sensory performance in low light. Such sensory innovations are unknown in nonavialan theropod dinosaurs and are poorly characterized on the line that leads to birds. We investigate morphofunctional proxies of vision and hearing in living and extinct theropods and demonstrate deep evolutionary pergences of sensory modalities. Nocturnal predation evolved early in the nonavialan lineage Alvarezsauroidea, signaled by extreme low-light vision and increases in hearing sensitivity. The Late Cretaceous alvarezsauroid Shuvuuia deserti had even further specialized hearing acuity, rivaling that of today’s barn owl. This combination of sensory adaptations evolved independently in dinosaurs long before the modern bird radiation and provides a notable example of convergence between dinosaurs and mammals.
材料科学 Materials Science
Reversible fusion and fission of graphene oxide–based fibers
氧化石墨烯纤维的可逆融合和分裂
作者：Dan Chang, Jingran Liu, Bo Fang, Zhen Xu, et al.
链接：
摘要
刺激反应融合和分裂在生物组织和人工分子组装中被广泛观察到。然而，在重复聚变和分裂的过程中，设计一个结构和性能持久的系统仍然具有挑战性。
我们研究了氧化石墨烯（GO）纤维的可逆融合和分裂，在溶剂的刺激下，许多宏观纤维可以融合成较厚的纤维，也可以分离成原始的单个纤维。
氧化石墨烯纤维壳层由溶剂蒸发和渗透引起的动态几何变形是实现可逆聚变-裂变循环的关键。这一原理被扩展到实现复杂纤维组件和客体化合物的包含或排出之间的灵活转化。
Abstract
Stimuli-responsive fusion and fission are widely observed in both bio-organizations and artificial molecular assemblies. However, the design of a system with structure and property persistence during repeated fusion and fission remains challenging. We show reversible fusion and fission of wet-spun graphene oxide (GO) fibers, in which a number of macroscopic fibers can fuse into a thicker one and can also separate into original inpidual fibers under stimulation of solvents. The dynamic geometrical deformation of GO fiber shells, caused by solvent evaporation and infiltration, is the key to the reversible fusion-fission cycles. This principle is extended to implement flexible transitions between complex fiber assemblies and the inclusion or expulsion of guest compounds.
量子物理 Quantum Physics
Direct observation of deterministic macroscopic entanglement
宏观物体量子纠缠的直接证据
作者：Shlomi Kotler, Gabriel A. Peterson, Ezad Shojaee, Florent Lecocq, et al.
链接：
摘要
机械系统的量子纠缠是在不同的物体运动时产生的，它们之间的关联程度如此之高，以至于不能够被单独描述。
虽然量子力学可能适用于各种大小的物体，但随着质量的增加，直接观测纠缠变得具有挑战性，需要以极小的误差进行测量和控制。
在这里，使用脉冲电学，我们确定地使质量为70微克的两个机械鼓面纠缠在一起。通过近量子极限测量两个鼓的位置和动量积分，我们进行了量子态断层扫描，从而直接观察纠缠。
这种纠缠的宏观系统将在量子力学的基础测试中发挥作用，使感知超越标准量子极限成为可能，并作为未来量子网络的长期网络节点发挥作用。
Abstract
Quantum entanglement of mechanical systems emerges when distinct objects move with such a high degree of correlation that they can no longer be described separately. Although quantum mechanics presumably applies to objects of all sizes, directly observing entanglement becomes challenging as masses increase, requiring measurement and control with a vanishingly small error. Here, using pulsed electromechanics, we deterministically entangle two mechanical drumheads with masses of 70 picograms. Through nearly quantum-limited measurements of the position and momentum quadratures of both drums, we perform quantum state tomography and thereby directly observe entanglement. Such entangled macroscopic systems are poised to serve in fundamental tests of quantum mechanics, enable sensing beyond the standard quantum limit, and function as long-lived nodes of future quantum networks.
Quantum mechanics–free subsystem with mechanical oscillators
带有机械振荡器的无量子力学子系统
作者：Laure Mercier de Lépinay, Caspar F. Ockeloen-Korppi, Matthew J. Woolley, Mika A. Sillanpää
链接：
摘要
量子力学为连续测量振荡器位置的精度设定了一个极限。我们通过构造一个有效的振荡器，展示了如何测量一个没有测量量子反作用的振荡器。
我们利用两个微机械振荡器实现了这样一个不涉及量子力学的子系统，并显示了两个集体求积的测量结果，同时对它们都避开了8分贝的量子反作用，获得了一个在完全量子极限的2倍以内的总噪声。
这有助于弱力的检测和振荡器非经典运动状态的产生和测量。此外，我们通过测量在可分性界下分贝的段量，直接验证了两个振荡器的量子纠缠。
Abstract
Quantum mechanics sets a limit for the precision of continuous measurement of the position of an oscillator. We show how it is possible to measure an oscillator without quantum back-action of the measurement by constructing one effective oscillator from two physical oscillators. We realize such a quantum mechanics–free subsystem using two micromechanical oscillators, and show the measurements of two collective quadratures while evading the quantum back-action by 8 decibels on both of them, obtaining a total noise within a factor of 2 of the full quantum limit. This facilitates the detection of weak forces and the generation and measurement of nonclassical motional states of the oscillators. Moreover, we directly verify the quantum entanglement of the two oscillators by measuring the Duan quantity decibels below the separability bound.
动物学 Zoology
Extreme altitudes during diurnal flights in a nocturnal songbird migrant
夜间鸣禽候鸟在日间飞行时的极端高度
作者：Sissel Sjöberg, Gintaras Malmiga, Andreas Nord, Arne Andersson, et al.
链接：
摘要
数十亿只夜间迁徙的鸣禽每年都会飞越海洋和沙漠。通过使用多传感器数据记录器，我们发现，大苇莺（Acrocephalus arundinaceus）在穿越地中海和撒哈拉沙漠时，会定期将它们本来只能在夜间飞行的飞行时间延长至白天。
出乎意料的是，当延长飞行时间时，他们在黎明时陡然攀升，从平均海拔2394米上升到日间飞行的极端高度（平均海拔5367米，最高海拔6267米）。
这种以前不为人知的在白天迁徙时使用非常高的飞行高度的行为可能是由环境温度、风、捕食、视野范围和太阳辐射的日变化引起的。我们对这一行为的发现为鸟类飞行限制提供了新的视角，并可能有助于解释夜间迁徙的进化。
Abstract
Billions of nocturnally migrating songbirds fly across oceans and deserts on their annual journeys. Using multisensor data loggers, we show that great reed warblers (Acrocephalus arundinaceus) regularly prolong their otherwise strictly nocturnal flights into daytime when crossing the Mediterranean Sea and the Sahara Desert. Unexpectedly, when prolonging their flights, they climbed steeply at dawn, from a mean of 2394 meters above sea level to reach extreme cruising altitudes (mean 5367 and maximum 6267 meters above sea level) during daytime flights. This previously unknown behavior of using exceedingly high flight altitudes when migrating during daytime could be caused by diel variation in ambient temperature, winds, predation, vision range, and solar radiation. Our finding of this notable behavior provides new perspectives on constraints in bird flight and might help to explain the evolution of nocturnal migration.
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