《自然》（20200924出版）一周論文導讀​

編譯｜馮維維

nature, 24 September 2020, Volume 585 Issue 7826

《自然》2020年9月24日，第585卷，7826期

仿生物理Bionic physics

Third-order nanocircuit elements for neuromorphic engineering

用於神經形態工程的三階納米電路元件

▲ 作者：Suhas Kumar, R. Stanley Williams & Ziwen Wang

▲ 連結：https://www.nature.com/articles/s41586-020-2735-5

▲ 摘要

目前，仿生或神經形態人工智慧的硬體方法，依賴於複雜的電晶體電路模擬生物功能。

利用實驗和模型，作者展示了多個電物理過程（包括莫特躍遷動力學）如何形成納米級三階電路元件。

作者演示了由三階元素組成的簡單無電晶體網絡，可執行布爾運算，並為計算上的硬圖劃分問題找到模擬解決方案。這項研究為非常緊湊和密集的功能性神經形態計算原語和高效能的神經科學模型驗證鋪平了道路。

▲ Abstract

Current hardware approaches to biomimetic or neuromorphic artificial intelligence rely on elaborate transistor circuits to simulate biological functions. Using both experiments and modelling, here we show how multiple electrophysical processes—including Mott transition dynamics—form a nanoscale third-order circuit element. We demonstrate simple transistorless networks of third-order elements that perform Boolean operations and find analogue solutions to a computationally hard graph-partitioning problem. This work paves a way towards very compact and densely functional neuromorphic computing primitives, and energy-efficient validation of neuroscientific models.

材料物理Material physics

Colloidal diamond

膠體鑽石

▲ 作者：Mingxin He, Johnathon P. Gales, Étienne Ducrot, Zhe Gong, Gi-Ra Yi, Stefano Sacanna & David J. Pine

▲ 連結：https://www.nature.com/articles/s41586-020-2718-6

▲ 摘要

立方金剛石晶體結構中的自組裝膠體粒子有可能用於製造光子帶隙材料。

作者研究表明，通過使用部分壓縮的四面體簇和可伸縮的黏塊，膠體立方金剛石可使用補片-補片黏合，結合空間連鎖機制，選擇所需的交錯鍵方向自組裝。

光子帶結構計算表明，所得到的晶格具有良好的光學特性，包括寬而完整的光子帶隙。在自組裝立方金剛石結構中的膠體顆粒受到高度約束和機械穩定性，這讓乾燥懸浮液和保持金剛石結構成為可能。

作者表示，這些結構適合於形成具有立方金剛石對稱的高介電對比度光子晶體的模板。

▲ Abstract

Self-assembling colloidal particles in the cubic diamond crystal structure could potentially be used to make materials with a photonic bandgap. Here we show that by using partially compressed tetrahedral clusters with retracted sticky patches, colloidal cubic diamond can be self-assembled using patch–patch adhesion in combination with a steric interlock mechanism that selects the required staggered bond orientation. Photonic bandstructure calculations reveal that the resulting lattices have promising optical properties, including a wide and complete photonic bandgap. The colloidal particles in the self-assembled cubic diamond structure are highly constrained and mechanically stable, which makes it possible to dry the suspension and retain the diamond structure. This makes these structures suitable templates for forming high-dielectric-contrast photonic crystals with cubic diamond symmetry.

氣候學Climatology

The hysteresis of the Antarctic Ice Sheet

南極冰蓋的遲滯現象

▲ 作者：Julius Garbe, Torsten Albrecht, Anders Levermann, Jonathan F. Donges & Ricarda Winkelmann

▲ 連結：https://www.nature.com/articles/s41586-020-2727-5

▲ 摘要

地球上一半以上的淡水資源被南極冰蓋所控制，因此，南極冰蓋是在未來變暖條件下全球海平面上升的最大潛在來源。作者研究表明，南極冰蓋顯示了大量的溫度閾值，超過這些溫度閾值，冰的損失將不可逆轉。

作者利用平行冰原模型發現，與古數據一致的是，在全球變暖水平比工業化前水平高出約2℃的情況下，由於海洋冰原的不穩定性，南極洲西部將面臨長期的局部崩塌。

如果氣溫比工業化前升高6℃~9℃，就會導致現有70%以上的冰量減少。如果氣溫比工業化前的水平上升10℃以上，南極洲將成為近乎無冰之所。

每一種閾值都會引起遲滯現象：即使氣溫逆轉到目前的水平，當前觀察到的冰蓋結構也不會恢復。作者表示，如果不能滿足《巴黎協定》，南極洲對海平面的長期貢獻將顯著增加，並超過所有其他來源。

▲ Abstract

More than half of Earth’s freshwater resources are held by the Antarctic Ice Sheet, which thus represents by far the largest potential source for global sea-level rise under future warming conditions. Here we show that the Antarctic Ice Sheet exhibits a multitude of temperature thresholds beyond which ice loss is irreversible. Consistent with palaeodata we find, using the Parallel Ice Sheet Model, that at global warming levels around 2 degrees Celsius above pre-industrial levels, West Antarctica is committed to long-term partial collapse owing to the marine ice-sheet instability. Between 6 and 9 degrees of warming above pre-industrial levels, the loss of more than 70 per cent of the present-day ice volume is triggered. At more than 10 degrees of warming above pre-industrial levels, Antarctica is committed to become virtually ice-free. Each of these thresholds gives rise to hysteresis behaviour: that is, the currently observed ice-sheet configuration is not regained even if temperatures are reversed to present-day levels. In particular, the West Antarctic Ice Sheet does not regrow to its modern extent until temperatures are at least one degree Celsius lower than pre-industrial levels. Our results show that if the Paris Agreement is not met, Antarctica’s long-term sea-level contribution will dramatically increase and exceed that of all other sources.

Mapping carbon accumulation potential from global natural forest regrowth

測繪全球天然森林再生的碳積累潛力

▲ 作者：Susan C. Cook-Patton, Sara M. Leavitt, Bronson W. Griscom, etc.

▲ 連結：https://www.nature.com/articles/s41586-020-2686-x

▲ 摘要

為遏制全球變暖，必須大力減少溫室氣體排放，並捕獲大氣中多餘的二氧化碳。

作者彙編了13112個碳積累的地理測量值，他們將野外測量數據與66個環境協變量層相結合，創建了一份全球1公裡解析度地圖，其中包含了自然再生森林頭30年的潛在地表碳積累速率。

地圖顯示了全球範圍內超過100倍的碳累積率變化，並表明政府間氣候變化專門委員會（IPCC）的違約率可能平均低估了32%的地表碳累積率，而且沒有捕捉到生態區內8倍的變化。

作者得出的結論是，天然林再生最大減緩氣候變化的潛力比以前報告的低11%，這是由於對潛在新森林的位置使用了過高的比率。

▲ Abstract

To constrain global warming, we must strongly curtail greenhouse gas emissions and capture excess atmospheric carbon dioxide. To assess why and where rates differ, here we compile 13,112 georeferenced measurements of carbon accumulation. We combine the field measurements with 66 environmental covariate layers to create a global, one-kilometre-resolution map of potential aboveground carbon accumulation rates for the first 30 years of natural forest regrowth. This map shows over 100-fold variation in rates across the globe, and indicates that default rates from the Intergovernmental Panel on Climate Change (IPCC) may underestimate aboveground carbon accumulation rates by 32 per cent on average and do not capture eight-fold variation within ecozones. Conversely, we conclude that maximum climate mitigation potential from natural forest regrowth is 11 per cent lower than previously reported owing to the use of overly high rates for the location of potential new forest.

生態學Ecology

Bending the curve of terrestrial biodiversity needs an integrated strategy

改變陸地生物多樣性曲線需遵循綜合策略

▲ 作者：David Leclère, Michael Obersteiner, Lucy Young, etc.

▲ 連結：https://www.nature.com/articles/s41586-020-2705-y

▲ 摘要

需要加大努力，防止陸地生物多樣性及其所提供的生態系統服務進一步遭受損失。

作者使用土地使用和生物多樣性綜合模型來評估人類是否以及如何逆轉，由棲息地轉換造成的陸地生物多樣性下降，這是對生物多樣性的一個主要威脅。

研究表明，立即採取行動，既符合更廣泛的可持續發展議程，又具有前所未有的雄心和協調，可以為日益增長的人口提供糧食，同時扭轉由棲息地轉換引起的全球陸地生物多樣性趨勢。

作者表示，雄心勃勃的保護努力和糧食系統轉型是2020年後有效的生物多樣性戰略的核心。

▲ Abstract

Increased efforts are required to prevent further losses to terrestrial biodiversity and the ecosystem services that it provides. Here we use an ensemble of land-use and biodiversity models to assess whether—and how—humanity can reverse the declines in terrestrial biodiversity caused by habitat conversion, which is a major threat to biodiversity5. We show that immediate efforts, consistent with the broader sustainability agenda but of unprecedented ambition and coordination, could enable the provision of food for the growing human population while reversing the global terrestrial biodiversity trends caused by habitat conversion. Our results show that ambitious conservation efforts and food system transformation are central to an effective post-2020 biodiversity strategy.

生物地理學Biogeography

Metabolic trait diversity shapes marine biogeography

代謝性狀多樣性塑造了海洋生物地理學

▲ 作者：Curtis Deutsch, Justin L. Penn & Brad Seibel

▲ 連結：https://www.nature.com/articles/s41586-020-2721-y

▲ 摘要

氣候和生理塑造生物地理學，但物種的範圍限制很少歸因於生物的數量特徵。

作者評估了物種的地理範圍邊界，是否符合海洋動物生物多樣性的全球橫截面需氧能量獲取的生態生理極限。

他們觀察到代謝率和供氧效率之間的密切關係，以及這些特性的溫度敏感性之間的密切關係，表明海洋動物對低氧（缺氧）的耐受性有很強的選擇。

由此產生的海洋動物生理容忍度的寬度預測了各種地理環境的變化——從熱帶到高緯度，從淺水到深水——這比僅根據溫度或氧氣建立的模型更符合物種分布。

▲ Abstract

Climate and physiology shape biogeography, yet the range limits of species can rarely be ascribed to the quantitative traits of organisms. Here we evaluate whether the geographical range boundaries of species coincide with ecophysiological limits to acquisition of aerobic energy for a global cross-section of the biodiversity of marine animals. We observe a tight correlation between the metabolic rate and the efficacy of oxygen supply, and between the temperature sensitivities of these traits, which suggests that marine animals are under strong selection for the tolerance of low O2 (hypoxia). The breadth of the resulting physiological tolerances of marine animals predicts a variety of geographical niches—from the tropics to high latitudes and from shallow to deep water—which better align with species distributions than do models based on either temperature or oxygen alone.