《科學》（20201009出版）一周論文導讀

編譯 | 李言

Science, 9 October 2020, Vol 370, Issue 6513

《科學》2020年10月9日，第370卷，6513期

材料科學Materials Science

The heterogeneity of persistent slip band nucleation and evolution in metals at the micrometer scale

金屬中持續滑移帶在微米尺度上的成核和演化的非均勻性

▲ 作者：Steven Lavenstein, Yejun Gu, Dylan Madisetti, Jaafar A. El-Awady

▲ 連結：

https://science.sciencemag.org/content/370/6513/eabb2690

▲ 摘要

金屬疲勞損傷表現為不可逆位錯運動，隨後裂紋產生並擴展。從無裂紋到裂紋金屬的過渡表徵仍然是金屬疲勞中最具挑戰性的問題之一。持續滑移帶（PSBs）在循環加載過程中在金屬中形成，是這種轉變最重要的方面之一。

通過原位微疲勞實驗，我們研究了PSB的形成和演化機理，發現PSBs普遍存在於微米級。位錯在這個尺度上的累積速率比在大樣品中要小，這延遲了PSB的成核。

我們的結果表明，需要細化金屬PSB和裂紋起始模型，以解釋漸進和非均勻演化。這些發現也將微米尺度的變形機制與大體量的疲勞失效聯繫起來。

▲ Abstract

Fatigue damage in metals manifests itself as irreversible dislocation motion followed by crack initiation and propagation. Characterizing the transition from a crack-free to a cracked metal remains one of the most challenging problems in fatigue. Persistent slip bands (PSBs) form in metals during cyclic loading and are one of the most important aspects of this transition. We used in situ microfatigue experiments to investigate PSB formation and evolution mechanisms, and we discovered that PSBs are prevalent at the micrometer scale. Dislocation accumulation rates at this scale are smaller than those in bulk samples, which delays PSB nucleation. Our results suggest the need to refine PSB and crack-initiation models in metals to account for gradual and heterogeneous evolution. These findings also connect micrometer-scale deformation mechanisms with fatigue failure at the bulk scale in metals.

Black phosphorus composites with engineered interfaces for high-rate high-capacity lithium storage

可用於高速率大容量鋰存儲的黑磷複合材料

▲ 作者：Hongchang Jin, Sen Xin, Chenghao Chuang, Wangda Li, Haiyun Wang, Jian Zhu et al.

▲ 連結：

https://science.sciencemag.org/content/370/6513/192

▲ 摘要

全電動汽車對能在幾分鐘內充電、並能支持跑350英裡的高速率鋰離子電池有極高的需求。高充電率通常會導致在容量和循環穩定性方面的犧牲。

我們報告了黑磷（BP）作為活性陽極用於高速率、高容量鋰存儲器。與石墨碳共價鍵的形成抑制了層狀BP粒子的邊緣重構，保證了快速鋰離子進入的開放邊緣；用電解膨脹聚苯胺包覆共價鍵合的BP-石墨粒子，生成穩定的固態電解質間相，並抑制導電不良的氟化物和碳酸鹽的持續生長，以確保鋰離子的高效輸運。

合成的複合陽極展示了一個能力、速率和循環持久性的出色組合。

▲ Abstract

High-rate lithium (Li) ion batteries that can be charged in minutes and store enough energy for a 350-mile driving range are highly desired for all-electric vehicles. A high charging rate usually leads to sacrifices in capacity and cycling stability. We report use of black phosphorus (BP) as the active anode for high-rate, high-capacity Li storage. The formation of covalent bonds with graphitic carbon restrains edge reconstruction in layered BP particles to ensure open edges for fast Li+ entry; the coating of the covalently bonded BP-graphite particles with electrolyte-swollen polyaniline yields a stable solid–electrolyte interphase and inhibits the continuous growth of poorly conducting Li fluorides and carbonates to ensure efficient Li+ transport. The resultant composite anode demonstrates an excellent combination of capacity, rate, and cycling endurance.

生態學Ecology

Increased extinction in the emergence of novel ecological communities

隨著新生態群落的出現，物種滅絕的現象增多

▲ 作者：John M. Pandolfi, Timothy L. Staples, Wolfgang Kiessling

▲ 連結：

https://science.sciencemag.org/content/370/6513/220

▲ 摘要

環境變化正在把生態組合轉化為新的形態，產生新的群落。我們發展出了一種穩定的方法來檢測新群落，檢查出現的新模式，並量化在新舊群落之間的過渡中原物種數量流動的可能性。

利用全球新生代海洋浮遊生物群落數據集，我們發現在向新群落過渡期間，局部滅絕、起源和遷移的概率是原群落變化的2到4倍。

對於10萬年間的海洋浮遊生物群落來說，新的群落對進一步的滅絕和實質性的群落變化很敏感。

▲ Abstract

Environmental change is transforming ecological assemblages into new configurations, resulting in novel communities. We developed a robust methodology to detect novel communities, examine patterns of emergence, and quantify probabilities of local demographic turnover in transitions to and from novel communities. Using a global dataset of Cenozoic marine plankton communities, we found that the probability of local extinction, origination, and emigration during transitions to a novel community increased two to four times that of background community changes. Although rare, novel communities were five times more likely than chance to shift into another novel state. For marine plankton communities at a 100,000-year time grain, novel communities were sensitive to further extinctions and substantial community change.

化學Chemistry

Electro-inductive effect: Electrodes as functional groups with tunable electronic properties

電感應效應：電極作為具有可調電子特性的官能團

▲ 作者：Joon Heo, Hojin Ahn, Joonghee Won, Jin Gyeong Son, Hyun Kyong Shon et al.

▲ 連結：

https://science.sciencemag.org/content/370/6513/214

▲ 摘要

我們將攜帶硫醇的分子固定在金電極上，代替官能團施加不同的誘導效應。通過施加不同的電壓，固定化分子的性質可以得到調整。

通過對開路電位施加-0.25伏的溫和負電壓，苯甲酸酯的鹼催化皂化反應被完全抑制。此外，當芳基滷化物襯底固定在金電極上時，施加電壓可以改變鈴木-宮浦交叉偶聯反應的速率。

最後，兩級羧酸醯胺化表明，在加入碳二醯亞胺偶聯試劑和引入胺之間的施加電壓的切換有利於羧酸醯胺化。

▲ Abstract

In place of functional groups that impose different inductive effects, we immobilize molecules carrying thiol groups on a gold electrode. By applying different voltages, the properties of the immobilized molecules can be tuned. The base-catalyzed saponification of benzoic esters is fully inhibited by applying a mildly negative voltage of –0.25 volt versus open circuit potential. Furthermore, the rate of a Suzuki-Miyaura cross-coupling reaction can be changed by applying a voltage when the arylhalide substrate is immobilized on a gold electrode. Finally, a two-step carboxylic acid amidation is shown to benefit from a switch in applied voltage between addition of a carbodiimide coupling reagent and introduction of the amine.

Cryo-EM with sub–1 Å specimen movement

冷凍電鏡中小於1埃的標本移動

▲ 作者：Katerina Naydenova, Peipei Jia, Christopher J. Russo

▲ 連結：

https://science.sciencemag.org/content/370/6513/223

▲ 摘要

冷凍電鏡（cryo-EM）中的大多數信息丟失是由於在成像過程中粒子的運動造成的，我們對這一點仍然知之甚少。

我們的研究表明，這種運動是由懸浮冰的屈曲和隨後的變形引起的，其閾值直接取決於由支撐箔片設置的凍結水層的形狀。我們設計了一個樣本支撐，以消除屈曲和減少電子束引起的粒子運動到小於1埃。

該設計允許精確箔跟蹤成像期間與高速探測器，從而減少對低溫級精度和穩定性的要求。它包括最大密度的孔，這增加了在自動冷凍電鏡中的產出量而不降低數據質量。無運動成像允許在零電子曝光時的樣本外推到三維地圖，並且在輻射損傷發生之前。

▲ Abstract

Most information loss in cryogenic electron microscopy (cryo-EM) stems from particle movement during imaging, which remains poorly understood. We show that this movement is caused by buckling and subsequent deformation of the suspended ice, with a threshold that depends directly on the shape of the frozen water layer set by the support foil. We describe a specimen support design that eliminates buckling and reduces electron beam–induced particle movement to less than 1 angstrom. The design allows precise foil tracking during imaging with high-speed detectors, thereby lessening demands on cryostage precision and stability. It includes a maximal density of holes, which increases throughput in automated cryo-EM without degrading data quality. Movement-free imaging allows extrapolation to a three-dimensional map of the specimen at zero electron exposure, before the onset of radiation damage.

量子物理Quantum Physics

Spacetime from bits

量子引力中的時空問題

▲ 作者：Mark Van Raamsdonk

▲ 連結：

https://science.sciencemag.org/content/370/6513/198

▲ 摘要

在量子引力的反德西特/共形場論中，一些量子引力理論中的時空幾何和引力物理狀態被編碼在一個普通的非引力系統的量子狀態中。

在此，我展示了這個非引力系統可以被一個放置在高度糾纏態中、任意大的非相互作用系統（「bits」）所取代。這種構造表明了時空幾何產生於量子引力的基本自由度之間的糾纏，而消除這種糾纏就等同於時空的瓦解。

這種設置也揭示了編碼空間時間的糾纏態可以用某種張量網絡進行表示，在這種張量網絡中，單個張量與少量位元的狀態相關。

▲ Abstract

In the anti–de Sitter/conformal field theory approach to quantum gravity, the spacetime geometry and gravitational physics of states in some quantum theory of gravity are encoded in the quantum states of an ordinary nongravitational system. Here, I demonstrate that this nongravitational system can be replaced with an arbitrarily large collection of noninteracting systems (「bits」) placed in a highly entangled state. This construction makes manifest the idea that spacetime geometry emerges from entanglement between the fundamental degrees of freedom of quantum gravity and that removing this entanglement is tantamount to disintegrating spacetime. This setup also reveals that the entangled states encoding spacetimes may be well represented by a certain type of tensor network in which the individual tensors are associated with states of small numbers of bits.