物理学Physics

▲ 作者：Wouter Vlemmings, Theo Khouri, Behzad Bojnordi Arbab, Elvire De Beck & Matthias Maercker

▲ 链接：

https://www.nature.com/articles/s41586-024-07836-9

▲ 摘要：

在恒星演化的许多阶段，能量的对流传输都很重要，这在太阳或巨大的演化恒星中已经得到了很好的研究。在大质量红超巨星的表面也发现了对流的特征。同样，对于低质量演化的恒星，也发现了对流的迹象，但对流的时间尺度和大小仍然没有得到很好的限制。

模型表明，对流运动对于产生强风至关重要，强风使恒星核合成的产物返回到星际介质中。研究者报告了一系列重建的干涉测量图像的表面演变的巨星R剑鱼座。这些图像揭示了一个具有突出的小尺度特征的星盘，它提供了恒星表面对流的结构和运动。

他们发现恒星盘上特征的主导结构尺寸为0.72±0.05天文单位。他们测量到地表运动的速度在- 18和+20 km s - 1之间变化，这意味着对流的时间尺度大约是一个月。这表明低质量和高质量演化恒星的对流特性之间可能存在差异。

▲ Abstract：

The transport of energy through convection is important during many stages of stellar evolution, and is best studied in our Sun or giant evolved stars. Features that are attributed to convection are found on the surface of massive red supergiant stars. Also for lower-mass evolved stars, indications of convection are found, but convective timescales and sizes remain poorly constrained. Models indicate that convective motions are crucial to produce strong winds that return the products of stellar nucleosynthesis into the interstellar medium. Here we report a series of reconstructed interferometric images of the surface of the evolved giant star R?Doradus. The images reveal a stellar disk with prominent small-scale features that provide the structure and motions of convection on the stellar surface. We find that the dominant structure size of the features on the stellar disk is 0.72?±?0.05 astronomical units. We measure the velocity of the surface motions to vary between ?18 and +20?km?s?1, which means that the convective timescale is approximately one month. This indicates a possible difference between the convection properties of low-mass and high-mass evolved stars.

▲ 作者：Stefano Carniani, Kevin Hainline, Francesco D’Eugenio, Daniel J. Eisenstein, Peter Jakobsen, Joris Witstok, Benjamin D. Johnson, Jacopo Chevallard, Roberto Maiolino, Jakob M. Helton, Chris Willott, Brant Robertson, Stacey Alberts, Santiago Arribas, William M. Baker, Rachana Bhatawdekar, Kristan Boyett, Andrew J. Bunker, Alex J. Cameron, Phillip A. Cargile, Stéphane Charlot, Mirko Curti, Emma Curtis-Lake, Eiichi Egami, Christopher N. A. Willmer Show authors

▲ 链接：

https://www.nature.com/articles/s41586-024-07860-9

▲ 摘要：

詹姆斯·韦布太空望远镜首次观测的红移为z≈13的星系，彻底改变了人们对宇宙的理解。此外，“黎明”号探测器发现的许多发光星系（z >10）表明，星系发展迅速，与许多标准模型存在明显的张力。然而，这些星系大多缺乏光谱确认，因此它们的距离和性质是不确定的。

研究者展示了韦布先进深河外巡天—近红外光谱仪对两个发光星系在和z = 13.90±0.17处的光谱确认。光谱显示紫外连续带明显的莱曼α断裂，但没有探测到发射线。

这一发现证明，在宇宙大爆炸后3亿年，发光星系就已经存在了，而且比在韦布之前预期的要普遍得多。这两个星系中最遥远的那个出乎意料地明亮，其空间分辨半径为260秒差距。再考虑到第二个星系非常陡峭的紫外线斜率，研究者认为，这两个星系都是由恒星连续辐射主导的，这表明早期宇宙中发光星系的过剩不能完全用黑洞的吸积来解释。星系形成模型需要解决在宇宙历史的早期存在如此巨大和明亮的星系的问题。

▲ Abstract：

The first observations of the James Webb Space Telescope (JWST) have revolutionized our understanding of the Universe by identifying galaxies at redshift z?≈?13 . In addition, the discovery of many luminous galaxies at Cosmic Dawn (z?>?10) has suggested that galaxies developed rapidly, in apparent tension with many standard models. However, most of these galaxies lack spectroscopic confirmation, so their distances and properties are uncertain. Here we present JWST Advanced Deep Extragalactic Survey–Near-Infrared Spectrograph spectroscopic confirmation of two luminous galaxies at  and z?=?13.90?±?0.17. The spectra reveal ultraviolet continua with prominent Lyman-α breaks but no detected emission lines. This discovery proves that luminous galaxies were already in place 300?million years after the Big Bang and are more common than what was expected before JWST. The most distant of the two galaxies is unexpectedly luminous and is spatially resolved with a radius of 260?parsecs. Considering also the very steep ultraviolet slope of the second galaxy, we conclude that both are dominated by stellar continuum emission, showing that the excess of luminous galaxies in the early Universe cannot be entirely explained by accretion onto black holes. Galaxy formation models will need to address the existence of such large and luminous galaxies so early in cosmic history.

▲ 作者：Jr-Chiun Yu, Shaurya Bhave, Lee Reeve, Bo Song & Ulrich Schneider

▲ 链接：

https://www.nature.com/articles/s41586-024-07875-2

▲ 摘要：

无序的存在实质上影响了物理系统的行为。它可以引起慢动力学或玻璃动力学，或完全抑制输运，如在安德森绝缘体中，通常扩展的波函数，如光场或电子布洛赫波变得指数局域化。无序和相互作用的综合效应是丰富的凝聚态物理的核心。

在玻色子系统中，它也可以导致额外的量子态，如玻色玻璃——一种在无序玻色子系统中出现的没有长程相相干的绝缘但可压缩的状态，与众所周知的相互作用玻色子的超流体和莫特绝缘基态不同。研究者报道了在八重对称准晶体光学晶格中使用超冷原子的二维玻色玻璃的实验实现。通过探测系统的相干性，他们观察到玻色玻璃到超流体的转变，并绘制了弱相互作用状态下的相图。

研究进一步证明了在典型的实验时间尺度上不可能绝热穿越玻色玻璃，通过检查恢复相干性的能力，并讨论了与玻色玻璃预期的非遍历性的联系。该观察结果与最近的量子蒙特卡罗预测非常吻合，为实验测试玻色玻璃、多体局域化和玻璃动力学之间的联系铺平了道路。

▲ Abstract：

The presence of disorder substantially influences the behaviour of physical systems. It can give rise to slow or glassy dynamics, or to a complete suppression of transport as in Anderson insulators, where normally extended wavefunctions such as light fields or electronic Bloch waves become exponentially localized. The combined effect of disorder and interactions is central to the richness of condensed-matter physics. In bosonic systems, it can also lead to additional quantum states such as the Bose glass—an insulating but compressible state without long-range phase coherence that emerges in disordered bosonic systems and is distinct from the well-known superfluid and Mott insulating ground states of interacting bosons. Here we report the experimental realization of the two-dimensional Bose glass using ultracold atoms in an eight-fold symmetric quasicrystalline optical lattice. By probing the coherence properties of the system, we observe a Bose-glass-to-superfluid transition and map out the phase diagram in the weakly interacting regime. We furthermore demonstrate that it is not possible to adiabatically traverse the Bose glass on typical experimental timescales by examining the capability to restore coherence and discuss the connection to the expected non-ergodicity of the Bose glass. Our observations are in good agreement with recent quantum Monte Carlo predictions6 and pave the way for experimentally testing the connection between the Bose glass, many-body localization and glassy dynamics more generally.

生物学和古人类学

Biology & Paleoanthropology

▲ 作者：Jianwei Chen, Yangyang Jia, Ying Sun, Kun Liu, Changhao Zhou, Chuan Liu, Denghui Li, Guilin Liu, Chengsong Zhang, Tao Yang, Lei Huang, Yunyun Zhuang, Dazhi Wang, Dayou Xu, Qiaoling Zhong, Yang Guo, Anduo Li, Inge Seim, Ling Jiang, Lushan Wang, Simon Ming Yuen Lee, Yujing Liu, Dantong Wang, Guoqiang Zhang,Guangyi Fan Show authors

▲ 链接：

https://www.nature.com/articles/s41586-024-07891-2

▲ 摘要：

过去二十年，从海洋系统中检索到的微生物基因组数量显著增加。然而，将这种海洋基因组多样性转化为生物技术和生物医学应用仍然具有挑战性。研究者从公开的海洋宏基因组中恢复了43191个细菌和古细菌基因组，包括138个不同门的广泛多样性，重新定义了海洋细菌基因组大小的上限，并揭示了基因编辑CRISPR-Cas系统和抗生素抗性基因之间的复杂权衡。

对这些海洋基因组的硅生物勘探导致发现了一种新的CRISPR-Cas9系统，10种抗菌肽和3种降解聚对苯二甲酸乙二醇酯的酶。体外实验证实了其有效性和疗效。这项工作证明，全球规模的测序计划促进了人们对微生物多样性如何在海洋中进化和维持的理解，并证明了如何可持续地利用这些计划来推进生物技术和生物医学。

▲ Abstract：

The past two decades has witnessed a remarkable increase in the number of microbial genomes retrieved from marine systems. However, it has remained challenging to translate this marine genomic diversity into biotechnological and biomedical applications. Here we recovered 43,191 bacterial and archaeal genomes from publicly available marine metagenomes, encompassing a wide range of diversity with 138 distinct phyla, redefining the upper limit of marine bacterial genome size and revealing complex trade-offs between the occurrence of CRISPR–Cas systems and antibiotic resistance genes. In silico bioprospecting of these marine genomes led to the discovery of a novel CRISPR–Cas9 system, ten antimicrobial peptides, and three enzymes that degrade polyethylene terephthalate. In vitro experiments confirmed their effectiveness and efficacy. This work provides evidence that global-scale sequencing initiatives advance our understanding of how microbial diversity has evolved in the oceans and is maintained, and demonstrates how such initiatives can be sustainably exploited to advance biotechnology and biomedicine.

▲ 作者：J. Víctor Moreno-Mayar, Bárbara Sousa da Mota, Tom Higham, Signe Klemm, Moana Gorman Edmunds, Jesper Stenderup, Miren Iraeta-Orbegozo, Véronique Laborde, Evelyne Heyer, Francisco Torres Hochstetter, Martin Friess, Morten E. Allentoft, Hannes Schroeder, Olivier Delaneau & Anna-Sapfo Malaspinas

▲ 链接：

https://www.nature.com/articles/s41586-024-07881-4

▲ 摘要：

拉帕努伊岛（也被称为复活节岛）是世界上最孤立的有人居住的地方之一。它的考古记录吸引了许多人的想象力，其中包括被称为“摩艾”的标志性巨石雕像。对拉帕努伊岛的广泛研究产生了两个突出的争论。

首先，拉帕努伊人的历史被描述为一个资源过度开发的警告故事，最终导致了人口的大规模崩溃——“生态灭绝”理论。其次，在与欧洲人接触之前，跨太平洋航行到美洲的可能性仍然存在争议。

为了解决这些争议，研究者基于15个古老的拉帕努伊人个体重建了拉帕努伊人的基因组历史。他们对这些个体进行了放射性碳测定和全基因组测序，发现这些人来自波利尼西亚人，与现在的拉帕努伊人关系最密切。通过有效的种群规模重建和广泛的种群遗传学模拟，研究者否定了生态灭绝理论提出的17世纪严重种群瓶颈的情景。

此外，古代和现在的拉帕努伊人携带着相似比例的美洲原住民混合物（约10%）。利用贝叶斯方法综合遗传和放射性碳年代，他们估计这一混合事件发生在公元1250~1430年。

▲ Abstract：

Rapa Nui (also known as Easter Island) is one of the most isolated inhabited places in the world. It has captured the imagination of many owing to its archaeological record, which includes iconic megalithic statues called moai. Two prominent contentions have arisen from the extensive study of Rapa Nui. First, the history of the Rapanui has been presented as a warning tale of resource overexploitation that would have culminated in a major population collapse—the ‘ecocide’ theory. Second, the possibility of trans-Pacific voyages to the Americas pre-dating European contact is still debated. Here, to address these questions, we reconstructed the genomic history of the Rapanui on the basis of 15 ancient Rapanui individuals that we radiocarbon dated (1670–1950?CE) and whole-genome sequenced (0.4–25.6×). We find that these individuals are Polynesian in origin and most closely related to present-day Rapanui, a finding that will contribute to repatriation efforts. Through effective population size reconstructions and extensive population genetics simulations, we reject a scenario involving a severe population bottleneck during the 1600s, as proposed by the ecocide theory. Furthermore, the ancient and present-day Rapanui carry similar proportions of Native American admixture (about 10%). Using a Bayesian approach integrating genetic and radiocarbon dates, we estimate that this admixture event occurred about 1250–1430?CE.

人工智能 Artificial intelligence