作者:冯维维 来源:科学网微信公众号 发布时间:2023/10/29 21:26:54
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《自然》(20231026出版)一周论文导读

 

编译 | 冯维维

Nature, Volume 622 Issue 7984, 26 October 2023

《自然》第622卷,7984期,2023年10月26日

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天体物理学Astrophysics

Confirmation and refutation of very luminous galaxies in the early Universe

韦布望远镜观测到早期宇宙明亮星系

▲ 作者:Pablo Arrabal Haro, Mark Dickinson, Steven L. Finkelstein, Jeyhan S. Kartaltepe, Callum T. Donnan, Denis Burgarella, Jorge A. Zavala, etc.

▲ 链接:

https://www.nature.com/articles/s41586-023-06521-7

▲ 摘要:

在宇宙历史的最初5亿年里,第一批恒星和星系形成,给宇宙播下了重元素,并最终重新电离了星系间介质。詹姆斯·韦布太空望远镜观测发现了令人惊讶的大量早期恒星形成星系候选者,根据多波段光度法估计,其距离(红移,z)大到z≈16,远超JWST之前的限制。

虽然这样的光度红移通常是稳健的,但它们可能遭受简并和偶尔的灾难性错误。需要光谱测量来验证这些来源,并可靠地量化可以约束星系形成模型和宇宙学的物理特性。

研究者展示了韦布光谱,证实了两个非常明亮的星系的红移为z>11,并证明了另一个候选星系的红移为z≈16,而非此前认为的z = 4.9,它们具有不寻常的星云线发射和尘埃变红的组合,与更遥远天体的颜色类似。

这些结果加强了早期快速形成非常明亮星系的证据,同时也强调了光谱验证的必要性。大量明亮的早期星系或表明当前星系形成模型的缺陷,或与通常认为在后期成立的物理性质(如恒星初始质量函数)的偏差。

▲ Abstract:

During the first 500 million years of cosmic history, the first stars and galaxies formed, seeding the Universe with heavy elements and eventually reionizing the intergalactic medium Observations with the James Webb Space Telescope (JWST) have uncovered a surprisingly high abundance of candidates for early star-forming galaxies, with distances (redshifts, z), estimated from multiband photometry, as large as z ≈ 16, far beyond pre-JWST limits. Although such photometric redshifts are generally robust, they can suffer from degeneracies and occasionally catastrophic errors. Spectroscopic measurements are required to validate these sources and to reliably quantify physical properties that can constrain galaxy formation models and cosmology. Here we present JWST spectroscopy that confirms redshifts for two very luminous galaxies with z > 11, and also demonstrates that another candidate with suggested z ≈ 16 instead has z = 4.9, with an unusual combination of nebular line emission and dust reddening that mimics the colours expected for much more distant objects. These results reinforce evidence for the early, rapid formation of remarkably luminous galaxies while also highlighting the necessity of spectroscopic verification. The large abundance of bright, early galaxies may indicate shortcomings in current galaxy formation models or deviations from physical properties (such as the stellar initial mass function) that are generally believed to hold at later times.

Geophysical evidence for an enriched molten silicate layer above Mars’s core

火核外层存在丰富熔融硅酸盐层

▲ 作者:Henri Samuel, Mélanie Drilleau, Attilio Rivoldini, Zongbo Xu, Quancheng Huang, Rapha?l F. Garcia, Vedran Leki?, Jessica C. E. Irving, James Badro, Philippe H. Lognonné, James A. D. Connolly, Taichi Kawamura, Tamara Gudkova & William B. Banerdt

▲ 链接:

https://www.nature.com/articles/s41586-023-06601-8

▲ 摘要:

在火星上探测到的深反射S波推断出火核的大小为1830±40km,但这需要的轻元素含量与实验岩石学的限制不相容。

一种假设是火星地幔的成分是均匀的,这与最近测量到的沿核心-地幔边界衍射的异常缓慢传播的P波不一致。

另一种假设是,火星的地幔是不均匀的,这是早期岩浆海洋凝固形成一个富含铁和产热元素的基底层的结果。这种富集导致在岩心上方形成熔融硅酸盐层,由部分熔融层覆盖。

研究表明这种结构与所有地球物理数据兼容,特别是(1)深反射和衍射地幔地震相位;(2)地震频率上的弱剪切衰减;(3)火星在火卫一潮汐上的耗散性质。

在这个场景中,火核的大小为1650±20km,意味着其密度为6.5 g cm-3,比以前的估计大5%~8%,并且可以用比以前所需的更少、更少的合金轻元素来解释,其数量与实验和宇宙化学的限制相一致。最后,层状地幔结构需要外部源来产生记录在火星地壳中的磁信号。

▲ Abstract:

The detection of deep reflected S waves on Mars inferred a core size of 1,830 ± 40 km, requiring light-element contents that are incompatible with experimental petrological constraints. This estimate assumes a compositionally homogeneous Martian mantle, at odds with recent measurements of anomalously slow propagating P waves diffracted along the core–mantle boundary. An alternative hypothesis is that Mars’s mantle is heterogeneous as a consequence of an early magma ocean that solidified to form a basal layer enriched in iron and heat-producing elements. Such enrichment results in the formation of a molten silicate layer above the core, overlain by a partially molten layer. Here we show that this structure is compatible with all geophysical data, notably (1) deep reflected and diffracted mantle seismic phases, (2) weak shear attenuation at seismic frequency and (3) Mars’s dissipative nature at Phobos tides. The core size in this scenario is 1,650 ± 20 km, implying a density of 6.5 g cm-3, 5–8% larger than previous seismic estimates, and can be explained by fewer, and less abundant, alloying light elements than previously required, in amounts compatible with experimental and cosmochemical constraints. Finally, the layered mantle structure requires external sources to generate the magnetic signatures recorded in Mars’s crust.

物理学Physics

A superconducting nanowire single-photon camera with 400,000 pixels

40万像素的超导纳米线单光子相机

▲ 作者:B. G. Oripov, D. S. Rampini, J. Allmaras, M. D. Shaw, S. W. Nam, B. Korzh & A. N. McCaughan

▲ 链接:

https://www.nature.com/articles/s41586-023-06550-2

▲ 摘要:

过去50年,超导探测器的广泛应用为探测微弱的电磁信号提供了卓越的灵敏度和速度。这些探测器可以在非常低的温度下工作,产生最小的多余噪音,是测试非局部性质、研究暗物质、绘制早期宇宙以及执行量子计算和通信的理想选择。

然而,尽管它们具有吸引人的特性,但目前还没有大规模的超导相机——即使是最大的演示也从未超过20,000像素。对于超导纳米线单光子探测器(SNSPDs)来说尤其如此。

研究者开发了一款40万像素SNSPD相机,比目前的技术水平提高了400倍。其成像区域不包含辅助电路,架构的可扩展性远远超出了目前的演示,为在广泛的电磁频谱范围内具有接近统一检测效率的大画幅超导相机铺平了道路。

▲ Abstract:

For the past 50 years, superconducting detectors have offered exceptional sensitivity and speed for detecting faint electromagnetic signals in a wide range of applications. These detectors operate at very low temperatures and generate a minimum of excess noise, making them ideal for testing the non-local nature of reality, investigating dark matter, mapping the early universe and performing quantum computation and communication. Despite their appealing properties, however, there are at present no large-scale superconducting cameras—even the largest demonstrations have never exceeded 20,000?pixels15. This is especially true for superconducting nanowire single-photon detectors (SNSPDs). These detectors have been demonstrated with system detection efficiencies of 98.0%, sub-3-ps timing jitter, sensitivity from the ultraviolet21 to the mid-infrared and microhertz dark-count rates3, but have never achieved an array size larger than a kilopixel. Here we report on the development of a 400,000-pixel SNSPD camera, a factor of 400 improvement over the state of the art. The imaging area contains no ancillary circuitry and the architecture is scalable well beyond the present demonstration, paving the way for large-format superconducting cameras with near-unity detection efficiencies across a wide range of the electromagnetic spectrum.

Dipolar quantum solids emerging in a Hubbard quantum simulator

哈伯德量子模拟器出现偶极量子固体

▲ 作者:Lin Su, Alexander Douglas, Michal Szurek, Robin Groth, S. Furkan Ozturk, Aaron Krahn, Anne H. Hébert, Gregory A. Phelps, Sepehr Ebadi, Susannah Dickerson, Francesca Ferlaino, Ognjen Markovi? & Markus Greiner

▲ 链接:

https://www.nature.com/articles/s41586-023-06614-3

▲ 摘要:

在量子力学多体系统中,长程和各向异性相互作用促进了丰富的空间结构,并可能导致量子挫折,从而产生大量复杂的、强相关的量子相。远距离相互作用在自然界中起着重要作用;然而,晶格系统的量子模拟在很大程度上无法实现这种相互作用。

利用极性分子、里德伯原子、光学空腔或磁性原子探索远程相互作用晶格系统的探索正在进行。

研究者利用超冷磁性铒原子,在具有远距离偶极相互作用的强相关晶格系统中实现了新的量子相。当他们将偶极相互作用调整为系统中主要的能量尺度时,观察到从超流体到偶极量子固体的量子相变,研究者使用带手风琴晶格的量子气体显微镜直接检测到这一点。通过偶极子取向控制相互作用的各向异性,可以实现多种条纹有序态。

此外,通过非绝热跃迁,研究者观察到一系列亚稳条纹有序态的出现。研究表明,利用光学晶格中的远程偶极相互作用可以实现新的强相关量子相,为具有远程和各向异性相互作用的广泛晶格模型的量子模拟打开了大门。

▲ Abstract:

In quantum mechanical many-body systems, long-range and anisotropic interactions promote rich spatial structure and can lead to quantum frustration, giving rise to a wealth of complex, strongly correlated quantum phases1. Long-range interactions play an important role in nature; however, quantum simulations of lattice systems have largely not been able to realize such interactions. A wide range of efforts are underway to explore long-range interacting lattice systems using polar molecules, Rydberg atoms, optical cavities or magnetic atoms. Here we realize novel quantum phases in a strongly correlated lattice system with long-range dipolar interactions using ultracold magnetic erbium atoms. As we tune the dipolar interaction to be the dominant energy scale in our system, we observe quantum phase transitions from a superfluid into dipolar quantum solids, which we directly detect using quantum gas microscopy with accordion lattices. Controlling the interaction anisotropy by orienting the dipoles enables us to realize a variety of stripe-ordered states. Furthermore, by transitioning non-adiabatically through the strongly correlated regime, we observe the emergence of a range of metastable stripe-ordered states. This work demonstrates that novel strongly correlated quantum phases can be realized using long-range dipolar interactions in optical lattices, opening the door to quantum simulations of a wide range of lattice models with long-range and anisotropic interactions.

A microfluidic transistor for automatic control of liquids

一种用于液体自动控制的微流控晶体管

▲ 作者:Kaustav A. Gopinathan, Avanish Mishra, Baris R. Mutlu, Jon F. Edd & Mehmet Toner

▲ 链接:

https://www.nature.com/articles/s41586-023-06517-3

▲ 摘要:

微流体技术在分子生物学、合成化学、诊断学和组织工程等领域取得了显著进展。然而,长期以来,该领域一直迫切需要以电子电路的精度、模块化和可扩展性来操纵流体和悬浮物。

研究者利用流体的流动限制现象来开发一种能够比例放大的微流体元件,其流量—压力特性完全类似于电子晶体管的电流-电压特性。他们使用该微流控晶体管直接将基本电子电路转换为流控域,包括放大器,调节器,电平移位器,逻辑门和锁存器。

他们还结合这些构建块来创建更复杂的流体控制器,如计时器和时钟。

最后,研究者展示了一个粒子分配器电路,它可以感知单个悬浮粒子,执行信号处理,并相应地以确定性的方式控制每个粒子的运动,而不需要电子器件。

通过利用大量的电子电路设计,基于微流体晶体管的电路使流体自动控制器能够为芯片上的实验室平台操纵液体和单个悬浮颗粒。

▲ Abstract:

Microfluidics have enabled notable advances in molecular biology, synthetic chemistry, diagnostics and tissue engineering. However, there has long been a critical need in the field to manipulate fluids and suspended matter with the precision, modularity and scalability of electronic circuits. Here we exploit the fluidic phenomenon of flow limitation to develop a microfluidic element capable of proportional amplification with flow–pressure characteristics completely analogous to the current–voltage characteristics of the electronic transistor. We then use this microfluidic transistor to directly translate fundamental electronic circuits into the fluidic domain, including the amplifier, regulator, level shifter, logic gate and latch. We also combine these building blocks to create more complex fluidic controllers, such as timers and clocks. Finally, we demonstrate a particle dispenser circuit that senses single suspended particles, performs signal processing and accordingly controls the movement of each particle in a deterministic fashion without electronics. By leveraging the vast repertoire of electronic circuit design, microfluidic-transistor-based circuits enable fluidic automatic controllers to manipulate liquids and single suspended particles for lab-on-a-chip platforms.

化学Chemistry

Geminal-atom catalysis for cross-coupling

交叉偶联的双原子催化

▲ 作者:Xiao Hai, Yang Zheng, Qi Yu, Na Guo, Shibo Xi, Javier Pérez-Ramírez, Jiong Lu, etc.

▲ 链接:

https://www.nature.com/articles/s41586-023-06529-z

▲ 摘要:

单原子催化剂(SACs)具有明确的活性位点,使其成为有机合成领域的潜在兴趣点。然而,由于空间环境和电子量子态的限制,这些稳定在固体载体上的单核金属物种的结构可能不是催化复杂分子转化的最佳选择。研究者报道了一类非均相双原子催化剂(GACs),它们以特定的配位和空间接近对单原子位点进行配对。

原位表征和量子理论研究表明,这种交叉偶联的动态过程是由两种不同的反应物在双金属位点的吸附引起的,使得均偶联不可行。GACs的这些固有优势使其能够组装具有多个配位位点的杂环,具有空间拥塞的支架和具有高特异性和稳定活性的药物。放大实验和转化为连续流表明广泛适用于精细化学品的制造。

▲ Abstract:

Single-atom catalysts (SACs) have well-defined active sites, making them of potential interest for organic synthesis. However, the architecture of these mononuclear metal species stabilized on solid supports may not be optimal for catalysing complex molecular transformations owing to restricted spatial environment and electronic quantum states. Here we report a class of heterogeneous geminal-atom catalysts (GACs), which pair single-atom sites in specific coordination and spatial proximity. In situ characterization and quantum-theoretical studies show that such a dynamic process for cross-coupling is triggered by the adsorption of two different reactants at geminal metal sites, rendering homo-coupling unfeasible. These intrinsic advantages of GACs enable the assembly of heterocycles with several coordination sites, sterically congested scaffolds and pharmaceuticals with highly specific and stable activity. Scale-up experiments and translation to continuous flow suggest broad applicability for the manufacturing of fine chemicals.

 
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