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《自然》(20190124出版)一周論文導讀


科學網翻譯|宗華N,J,VI《自然》年月日第期卷地質學GSNA安...

- 2019年1月25日17時58分
- 科學文摘 / 科學網

科學網

翻譯 | 宗華

Nature, 24 January 2019, Volume 565 Issue 7740

《自然》2019年1月24日第7740期565卷


地質學Geology

Southward propagation of Nazca subduction along the Andes

安第斯山脈沿線納斯卡俯衝的向南擴展

▲ 連結:

▲ 摘要:

安第斯山脈邊緣是長期持續俯衝的板塊構造模式。但自中生代晚期(過去1億年左右)以來其地質情況一直未處於穩定狀態。


這裡,利用層析數據,我們重現了俯衝納斯卡板塊的板塊構造幾何學。這使得我們重建中生代以來的安第斯板塊構造。

我們的模型顯示,現在的納斯卡俯衝階段開始於白堊紀晚期(約8000萬年前)的安第斯山脈北部(南緯5°),然後向南擴展,在新生代早期(約5500萬年前)抵達安第斯山脈南部(南緯40°)。

▲ Abstract

The Andean margin is the plate-tectonic paradigm for long-lived, continuous subduction, yet its geology since the late Mesozoic era (the past 100 million years or so) has been far from steady

state. Here, using tomographic data, we recreate the plate-tectonic geometry of the subducted Nazca slab, which enables us to reconstruct Andean plate tectonics since the late Mesozoic. Our model

suggests that the current phase of Nazca subduction began at the northern Andes (5° S) during the late Cretaceous period (around 80 million years ago) and propagated southwards, reaching the southern

Andes (40° S) by the early Cenozoic era (around 55 million year ago).

天文學Astronomy

A recurrent nova super-remnant in the Andromeda galaxy

仙女座星系中反覆出現的新星超高密度殘骸

▲ 作者:M. J. Darnley, R. Hounsell, T. J. O』Brien, M. Henze, P. Rodríguez-Gil, et al

▲ 摘要:

白矮星上面的氫吸積引發了經典的新星爆發。

同時,接近白矮星(1.4個太陽質量)質量上限,來自伴星的氫快速吸積(每年約為太陽質量的10−7)帶來了時間跨度為幾年到幾十年的頻繁爆發。這種雙星系統被稱為再發新星。

這裡,我們報告稱,重複出現最頻繁的新星——仙女座星系中每年都會爆發的M31N 2008-12a,的確由此類超高密度殘骸環繞。據估測,其大小至少有134×90秒差距。

▲ Abstract

The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption. Close to the upper mass limit of a white dwarf (1.4 solar masses), rapid accretion of hydrogen (about 10−7

solar masses per year) from a stellar companion leads to frequent eruptions on timescales of years to decades. Such binary systems are known as recurrent novae. Here we report that the most

frequently recurring nova, M31N 2008-12a in the Andromeda galaxy (Messier 31 or NGC 224), which erupts annually, is indeed surrounded by such a super-remnant with a projected size of at least 134 by

90 parsecs.

物理學Physics

Unveiling the double-well energy landscape in a ferroelectric layer

揭示鐵電層中雙阱能量圖景

▲ 作者:Michael Hoffmann, Franz P. G. Fengler, Melanie Herzig, et al

▲ 連結:

▲ 摘要:

近1個世紀前被發現的鐵電材料的性質帶來了廣泛的應用,比如數字信息存儲、熱電能量轉換和神經形態計算。

最近,研究證實,鐵電體可擁有負電容,從而可能使傳統電子產品的能量效率超越基本限制。

這裡,我們報告了鐵電體Hf0.5Zr0.52薄層中內在雙阱能量圖景的電學測量結果。

為做到這一點,我們將鐵電體融合進帶有第二介電層的異質結構電容器,以防止轉換期間極化電荷的立即屏蔽。這些結果表明,負電容源自雙阱圖景中的能量障礙。

▲ Abstract

The properties of ferroelectric materials, which were discovered almost a century ago, have led to a huge range of applications, such as digital information storage, pyroelectric energy conversion

and neuromorphic computing. Recently, it was shown that ferroelectrics can have negative capacitance6, which could improve the energy efficiency of conventional electronics beyond fundamental limits.

Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric Hf0.5Zr0.5. To achieve this, we integrated the

ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has

its origin in the energy barrier in a double-well landscape.

Spatially resolved steady-state negative capacitance

空間解析度的穩定態負電容

▲ 作者:Ajay K. Yadav, Kayla X. Nguyen, Zijian Hong, et al

▲ 連結:

▲ 摘要:

負電容是一種新發現的鐵電材料狀態。其通過利用一個通常無法接近的熱力學空間區域,有希望應用於電子產品。

這裡,我們展示了對鐵電—介電異質結構中穩定態負電容的直接測量結果。

我們利用電子顯微鏡並輔以SrTiO超晶格中相場和基於第一原理方法的模擬結果,在原子解析度水平上直接確定了鐵電材料中負電容狀態被穩定下來的局部區域。

▲ Abstract

Negative capacitance is a newly discovered state of ferroelectric materials that holds promise for electronics applications by exploiting a region of thermodynamic space that is normally not

accessible. Here we demonstrate a direct measurement of steady-state negative capacitance in a ferroelectric–dielectric heterostructure. We use electron microscopy complemented by phase-field and

first-principles-based simulations in SrTiOsuperlattices to directly determine, with atomic resolution, the local regions in the ferroelectric material where a state of negative capacitance is

stabilized.

生態學Ecology

▲ 作者:Julia K. Green, Sonia I. Seneviratne, Alexis M. Berg, et al

▲ 連結:

▲ 摘要:

儘管陸地生物圈吸收了約25%的人類排放二氧化碳,但陸地碳吸收速率仍存在高度的不確定性,並且導致氣候預測的不確定性。

這裡,我們利用一系列試驗中來自4個地球系統模型的數據輸出,分析了陸地凈生物群生產力對土壤濕度變化的響應,並且發現土壤濕度變化和趨勢在整個21世紀誘發大量二氧化碳通量。

作為光合作用和凈生態系統交換對土壤水分可利用度的響應以及溫度上升和陸氣相互作用引發的蒸氣壓差的結果,次季節和年際間土壤濕度變化產生了二氧化碳。

▲ Abstract

Although the terrestrial biosphere absorbs about 25 per cent of anthropogenic carbon dioxide (2) emissions, the rate of land carbon uptake remains highly uncertain, leading to

uncertainties in climate projections. Here we use the data output from four Earth system models from a series of experiments to analyse the responses of terrestrial net biome productivity to

soil-moisture changes, and find that soil-moisture variability and trends induce large CO2 fluxes throughout the twenty-first century. Subseasonal and interannual soil-moisture variability

generate CO2 as a result of the nonlinear response of photosynthesis and net ecosystem exchange to soil-water availability and of the increased temperature and vapour pressure deficit

caused by land–atmosphere interactions.

光學Optics

Computational periscopy with an ordinary digital camera

帶有普通數位相機的計算潛望鏡

▲ 連結:

▲ 摘要:

計算從不同方向抵達的光線數量使擴散反射面得以在潛望鏡中扮演鏡子角色,即在障礙附近進行非視距成像。

由於潛望鏡技術迄今依賴於同飛行時間成正比的光傳播距離,因此它大多數利用昂貴且專業化的超快光學系統進行。

這裡,我們引入一種二維計算潛望鏡技術。其僅要求普通數位相機捕捉的單幅照片。

我們的技術復原了不透明物體的位置以及物體背後的景象,而無須得到控制或者隨時間變化的照明。此時,物體和景象均在相機的視線之外。

▲ Abstract

Computing the amounts of light arriving from different directions enables a diffusely reflecting surface to play the part of a mirror in a periscope—that is, perform non-line-of-sight imaging

around an obstruction. Because computational periscopy has so far depended on light-travel distances being proportional to the times of flight, it has mostly been performed with expensive,

specialized ultrafast optical systems. Here we introduce a two-dimensional computational periscopy technique that requires only a single photograph captured with an ordinary digital camera. Our

technique recovers the position of an opaque object and the scene behind (but not completely obscured by) the object, when both the object and scene are outside the line of sight of the camera,

without requiring controlled or time-varying illumination.

生物學Biology

High levels of auxin signalling define the stem-cell organizer of the vascular cambium

高濃度生長素信號定義維管形成層的幹細胞「組織者」

▲ 連結:


▲ 摘要:

作為一種木質組織,木材源自維管形成層的細胞擴散。木質部和韌皮部分別在形成層裡面和外面產生。

植物的形態發生通常由「組織者」細胞協調。這種細胞指揮相鄰幹細胞經歷編程細胞的分裂和分化。

維管形成層幹細胞的位置以及「組織者」概念能否應用於形成層目前仍然未知。

這裡,利用對擬南芥的譜系追蹤和分子遺傳學研究,我們證實,擁有木質部身份的細胞指揮鄰近維管形成層細胞分裂並且作為幹細胞發揮作用。因此,這些木質部身份的細胞構成了「組織者」。

▲ Abstract

Wood, a type of xylem tissue, originates from cell proliferation of the vascular cambium. Xylem is produced inside, and phloem outside, of the cambium. Morphogenesis in plants is typically

coordinated by organizer cells that direct the adjacent stem cells to undergo programmed cell division and differentiation. The location of the vascular cambium stem cells and whether the organizer

concept applies to the cambium are currently unknown. Here, using lineage-tracing and molecular genetic studies in the roots of Arabidopsis thaliana, we show that cells with a xylem identity direct

adjacent vascular cambial cells to divide and function as stem cells. Thus, these xylem-identity cells constitute an organizer.

Molecular control of macroscopic forces drives formation of the vertebrate hindgut

宏觀力量的分子控制驅動脊椎動物後腸形成

▲ 作者:Nandan L. Nerurkar, ChangHee Lee, L. Mahadevan & Clifford J. Tabin

▲ 連結:

▲ 摘要:

胚胎腸道管是一種可發育成呼吸道和腸胃道的圓柱結構。這裡,我們研究了雞胚中腸道管形態形成早期背後宏觀力量的分子控制。

我們發現,後腸由通過固定尾部腸門(CIP)的集體細胞運動形成,而非由CIP本身的運動形成。

同時,結合體內成像、生物物理學分析以及利用分子和胚胎學方法的數學建模,我們辨別出驅動形成後腸的內胚層中細胞運動的收縮力梯度。

這種力梯度反過來是為了響應成纖維細胞生長因子信號的形態生長梯度而建立的。

▲ Abstract

The embryonic gut tube is a cylindrical structure from which the respiratory and gastrointestinal tracts develop. Here we investigate the molecular control of macroscopic forces underlying early

morphogenesis of the gut tube in the chick embryo. We find that the hindgut is formed by collective cell movements through a stationary caudal intestinal portal (CIP), rather than by movement of the

CIP itself. Further, combining in vivo imaging, biophysics and mathematical modelling with molecular and embryological approaches, we identify a contractile force gradient that drives cell movements

in the hindgut-forming endoderm. The force gradient, in turn, is established in response to a morphogenic gradient of fibroblast growth factor signalling.

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