编译 | 未玖

Nature, 5 December 2024, Volume 636, Issue 8041

《自然》2024年12月5日，第636卷，8041期

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天文学Astronomy

In situ spheroid formation in distant submillimetre-bright galaxies

遥远亚毫米亮星系中的原位核球形成

▲ 作者：Qing-Hua Tan, Emanuele Daddi, Benjamin Magnelli, Camila A. Correa, Frédéric Bournaud, Sylvia Adscheid, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08201-6

▲摘要：当今宇宙中的大多数恒星都位于核球中，核球是螺旋星系和椭圆星系的聚集，其形成仍是一个未解之谜。长久以来，人们一直怀疑高红移的红外/亚毫米亮星系与核球形成有关。然而到目前为止，由于关注核球恒星发射时严重的尘埃遮蔽，或囿于观察亚毫米波长时的方法和有限信噪比，这种关联一直很难得到证明。

研究组证明了核球由遥远宇宙中高亮度的星暴星系核心内的恒星形成直接产生。这是由ALMA亚毫米表面亮度分布得出的。该分布与指数盘的亮度分布和倾斜的高轴比分布有很大偏差。这些星系中的大多数都是完全三轴的，而不是扁平的圆盘：其三轴中最短轴和最长轴的比率平均为一半，并且随着空间紧凑度的增加而增加。

该观测结果得到了模型的支持，揭示了一个通过星暴原位形成核球的宇宙学相关途径，这可能由作用于非共面气体吸积流供给的星系相互作用（和合并）优先触发。

▲ Abstract：Most stars in today’s Universe reside within spheroids, which are bulges of spiral galaxies and elliptical galaxies. Their formation is still an unsolved problem. Infrared/submillimetre-bright galaxies at high redshifts have long been suspected to be related to spheroid formation. Proving this connection has been hampered so far by heavy dust obscuration when focusing on their stellar emission or by methodologies and limited signal-to-noise ratios when looking at submillimetre wavelengths. Here we show that spheroids are directly generated by star formation within the cores of highly luminous starburst galaxies in the distant Universe. This follows from the ALMA submillimetre surface brightness profiles, which deviate substantially from those of exponential disks, and from the skewed-high axis-ratio distribution. Most of these galaxies are fully triaxial rather than flat disks: the ratio of the shortest to the longest of their three axes is half, on average, and increases with spatial compactness. These observations, supported by simulations, reveal a cosmologically relevant pathway for in situ spheroid formation through starbursts that is probably preferentially triggered by interactions (and mergers) acting on galaxies fed by non-coplanar gas accretion streams.

物理学Physics

Observation of Hilbert space fragmentation and fractonic excitations in 2D

二维希尔伯特空间碎片和分形激发的观测

▲ 作者：Daniel Adler, David Wei, Melissa Will, Kritsana Srakaew, Suchita Agrawal, Pascal Weckesser, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08188-0

▲摘要：脱离平衡状态的孤立量子系统的弛豫行为是多体物理学中最有趣的问题之一。非平衡态的量子系统通常通过扰乱局部信息和建立纠缠熵而弛豫到热平衡态。然而，哈密顿量中的动力学约束可能导致这一基本范式的崩溃。因为基础希尔伯特空间分裂成动态解耦的子扇区，其中热化被强烈抑制。

研究组通过实验观测了二维倾斜玻色-哈伯德模型中的希尔伯特空间碎片。利用量子气体显微镜，他们设计了各种各样的初始状态，并发现了希尔伯特空间碎片的丰富表现形式，包括体态、界面和缺陷，即二维、一维和零维物体。具体而言，具有相同粒子数和能量的均匀初始态在弛豫动力学上有显著差异。

在整体、非热化的棋盘式状态上插入受控缺陷，研究组观察到高度各向异性的亚维动力学，这是其分形性质的直接标志。局域态和热化态之间的界面依次表现出依据其取向的动力学。该研究结果标志着超越一维的希尔伯特空间碎片的观测，以及伴随的分形直接观察，为深入研究约束系统中的微观输运现象奠定了基础。

▲ Abstract：The relaxation behaviour of isolated quantum systems taken out of equilibrium is among the most intriguing questions in many-body physics. Quantum systems out of equilibrium typically relax to thermal equilibrium states by scrambling local information and building up entanglement entropy. However, kinetic constraints in the Hamiltonian can lead to a breakdown of this fundamental paradigm owing to a fragmentation of the underlying Hilbert space into dynamically decoupled subsectors in which thermalization can be strongly suppressed. Here we experimentally observe Hilbert space fragmentation in a two-dimensional tilted Bose–Hubbard model. Using quantum gas microscopy, we engineer a wide variety of initial states and find a rich set of manifestations of Hilbert space fragmentation involving bulk states, interfaces and defects, that is, two-, one- and zero-dimensional objects. Specifically, uniform initial states with equal particle number and energy differ strikingly in their relaxation dynamics. Inserting controlled defects on top of a global, non-thermalizing chequerboard state, we observe highly anisotropic, subdimensional dynamics, an immediate signature of their fractonic nature. An interface between localized and thermalizing states in turn shows dynamics depending on its orientation. Our results mark the observation of Hilbert space fragmentation beyond one dimension, as well as the concomitant direct observation of fractons, and pave the way for in-depth studies of microscopic transport phenomena in constrained systems.

材料科学Materials Science

Mineralized collagen plywood contributes to bone autograft performance

矿化胶原胶合板助力自体骨移植

▲ 作者：Marc Robin, Elodie Mouloungui, Gabriel Castillo Dali, Yan Wang, Jean-Louis Saffar, Graciela Pavon-Djavid, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08208-z

▲ 摘要：自体骨（AB）是骨移植手术的金标准，尽管其可用性有限且需要额外的手术部位。传统上，用于骨修复的竞争性生物材料主要聚焦模仿骨的矿物质方面，生物活性陶瓷的广泛临床应用证明了这一点。然而，AB也表现出可能会严重影响骨再生的分层有机结构。

研究组在小鼠和绵羊骨缺损模型中使用了一系列无细胞仿生胶原基材料，证明了分层混合微观结构（特别是胶原的扭曲胶合板模式及其与结晶不良的生物磷灰石的结合）有利于骨再生。该研究表明，结构上最仿生的材料具有刺激骨生长的潜力，突出了物理化学特性在支持骨形成中的关键作用，并为具有竞争力的骨移植材料提供了广阔的前景。

▲ Abstract：Autologous bone (AB) is the gold standard for bone-replacement surgeries, despite its limited availability and the need for an extra surgical site. Traditionally, competitive biomaterials for bone repair have focused on mimicking the mineral aspect of bone, as evidenced by the widespread clinical use of bioactive ceramics. However, AB also exhibits hierarchical organic structures that might substantially affect bone regeneration. Here, using a range of cell-free biomimetic-collagen-based materials in murine and ovine bone-defect models, we demonstrate that a hierarchical hybrid microstructure—specifically, the twisted plywood pattern of collagen and its association with poorly crystallized bioapatite—favourably influences bone regeneration. Our study shows that the most structurally biomimetic material has the potential to stimulate bone growth, highlighting the pivotal role of physicochemical properties in supporting bone formation and offering promising prospects as a competitive bone-graft material.

信息科学Information Science

Combining quantum processors with real-time classical communication

将量子处理器与实时经典通信相结合

▲ 作者：Almudena Carrera Vazquez, Caroline Tornow, Diego Ristè, Stefan Woerner, Maika Takita & Daniel J. Egger

▲ 链接：https://www.nature.com/articles/s41586-024-08178-2

▲ 摘要：量子计算机根据量子力学定律来处理信息。目前的量子硬件存在噪声，只能在短时间内存储信息，且仅限于几个量子比特（即量子位），通常以平面连接排列。然而，量子计算的许多应用需要比单个量子处理单元（QPU）更多量子位的硬件所提供平面晶格更多的连通性。学界希望通过使用经典通信连接QPU来解决这些限制，这尚未得到实验证明。

研究组通过实验实现了误差降低的动态电路和电路切割，使用多达142个量子位、跨越两个各有127个量子位且通过经典链路实时连接的QPU，来创建需要周期性连接的量子态。在动态电路中，量子门可在运行时间（量子位相干时间的一小部分）内，通过中间电路测量的结果进行经典控制。

研究组的实时经典链路使其能够根据另一个QPU的测量结果在其中一个QPU上应用量子门。此外，误差降低的控制流增强了量子比特的连通性和硬件的指令集，从而提升了量子计算机的通用性。该工作表明，人们可将多个量子处理器作为一个整体，通过实时经典链路实现误差降低的动态电路。

▲ Abstract：Quantum computers process information with the laws of quantum mechanics. Current quantum hardware is noisy, can only store information for a short time and is limited to a few quantum bits, that is, qubits, typically arranged in a planar connectivity. However, many applications of quantum computing require more connectivity than the planar lattice offered by the hardware on more qubits than is available on a single quantum processing unit (QPU). The community hopes to tackle these limitations by connecting QPUs using classical communication, which has not yet been proven experimentally. Here we experimentally realize error-mitigated dynamic circuits and circuit cutting to create quantum states requiring periodic connectivity using up to 142 qubits spanning two QPUs with 127 qubits each connected in real time with a classical link. In a dynamic circuit, quantum gates can be classically controlled by the outcomes of mid-circuit measurements within run-time, that is, within a fraction of the coherence time of the qubits. Our real-time classical link enables us to apply a quantum gate on one QPU conditioned on the outcome of a measurement on another QPU. Furthermore, the error-mitigated control flow enhances qubit connectivity and the instruction set of the hardware thus increasing the versatility of our quantum computers. Our work demonstrates that we can use several quantum processors as one with error-mitigated dynamic circuits enabled by a real-time classical link.

化学Chemistry

Coupling of unactivated alkyl electrophiles using frustrated ion pairs

用受阻离子对偶联非活化烷基亲电试剂

▲ 作者：Sven Roediger, Emilien Le Saux, Philip Boehm & Bill Morandi

▲ 链接：https://www.nature.com/articles/s41586-024-08195-1

▲ 摘要：交叉亲电偶联反应已发展成为快速组装重要有机分子的主要策略。两种易于获得的亲电试剂偶联形成新的C-C键，与需要预先形成活性有机金属物质的传统交叉偶联策略相比具有关键优势。然而，形成几乎所有有机化合物核心的C(sp3)–C(sp3)键对当前策略而言仍颇具挑战，亟需设计创新策略。

研究组报道了一个独特且无过渡金属的平台来形成这种键，而无需激活或稳定偶联对象上的基团。该反应由受阻离子对中不寻常的单电子转移来实现，可偶联含有官能团的片段，这在相关的过渡金属催化过程中颇具挑战性。

此外，这种新机械流形可进一步应用于其他反应的设计，展示了这种反应的广泛潜力。研究组预计该结果将为进一步探索这种反应模式提供一个框架，以解决有机合成中的挑战性难题。

▲ Abstract：Cross-electrophile coupling reactions have evolved into a major strategy for rapidly assembling important organic molecules. Two readily accessible electrophiles are coupled to form new C–C bonds, providing a key advantage over traditional cross-coupling strategies that require the preformation of reactive organometallic species. Yet, the formation of C(sp3)–C(sp3) bonds that form the core of nearly all organic compounds remains highly challenging with current approaches, calling for the design of innovative new strategies. Here we report a distinct, transition-metal-free platform to form such bonds without the need for activating or stabilizing groups on the coupling partners. The reaction is enabled by an unusual single-electron transfer in a frustrated ion pair, and it can couple fragments containing functional groups that would be challenging in related transition-metal-catalysed processes. Moreover, we could further leverage this new mechanistic manifold in the design of other reactions, showing the broad potential of this type of reactivity. We anticipate that our results will provide a framework for further exploration of this reactivity pattern to tackle challenging problems in organic synthesis.

地球科学Earth Science

Isoprene nitrates drive new particle formation in Amazon’s upper troposphere

异戊二烯硝酸盐驱动亚马逊上对流层形成新粒子

▲ 作者：Joachim Curtius, Martin Heinritzi, Lisa J. Beck, Mira L. P?hlker, Nidhi Tripathi, Bianca E. Krumm, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08192-4

▲ 摘要：热带上对流层的新粒子形成（NPF）是全球大气气溶胶的重要来源。众所周知，NPF发生在亚马逊盆地，但成核机制和化学前体尚未确定。

研究组提供了全面的原位飞机测量结果，表明异戊二烯的极低挥发性氧化产物（特别是某些有机硝酸盐）驱动了亚马逊上对流层的NPF。有机硝酸盐源于在雷电产生的氮氧化物存在下，森林排放物中异戊二烯由OH引发的氧化。在日出后约2小时，夜间深对流的外流中开始成核爆发，产生超过每立方厘米50000个颗粒的高气溶胶浓度。

研究组报道了前驱气体和粒子的特征日周期的测量结果。观测结果表明，生物成因的异戊二烯、伴随闪电的热带深对流、氧化光化学和低环境温度之间的相互作用独特地促进了NPF。这些粒子随着时间的推移而增长，经过远距离传输，并通过沉降下降到下对流层，在那里可作为云凝结核（CCN），影响地球的水文循环、辐射收支和气候。

▲ Abstract：New particle formation (NPF) in the tropical upper troposphere is a globally important source of atmospheric aerosols. It is known to occur over the Amazon basin, but the nucleation mechanism and chemical precursors have yet to be identified. Here we present comprehensive in situ aircraft measurements showing that extremely low-volatile oxidation products of isoprene, particularly certain organonitrates, drive NPF in the Amazonian upper troposphere. The organonitrates originate from OH-initiated oxidation of isoprene from forest emissions in the presence of nitrogen oxides from lightning. Nucleation bursts start about 2?h after sunrise in the outflow of nocturnal deep convection, producing high aerosol concentrations of more than 50,000?particles?cm?3. We report measurements of characteristic diurnal cycles of precursor gases and particles. Our observations show that the interplay between biogenic isoprene, deep tropical convection with associated lightning, oxidation photochemistry and the low ambient temperature uniquely promotes NPF. The particles grow over time, undergo long-range transport and descend through subsidence to the lower troposphere, in which they can serve as cloud condensation nuclei (CCN) that influence the Earth’s hydrological cycle, radiation budget and climate.