《科學》（20190628出版）一周論文導讀

翻譯 | 宗華

Science, 28 JUNE 2019, VOL 364, ISSUE 6447

《科學》2019年6月28日，第6447期364卷

生物學Biology

Obesity remodels activity and transcriptional state of a lateral hypothalamic brake on feeding

肥胖重塑外側下丘腦抑制進食的活動和轉錄狀態

作者：Mark A. Rossi, Marcus L. Basiri, Jenna A. McHenry ,et al

鏈接：

https://science.sciencemag.org/content/364/6447/1271

摘要：

目前的肥胖症流行是一個重要的全球性健康問題。儘管人們一致認為大腦調節能量平衡，但控制肥胖的神經適應機制尚不清楚。

採用高通量單細胞RNA測序和體內縱向雙光子鈣成像相結合的方法，我們研究了小鼠肥胖模型中下丘腦外側區（LHA）的功能變化。LHA是協調進食的高度保守大腦區域。

研究發現，肥胖影響LHA谷氨酸能神經元的轉錄譜，表現出神經元活動改變的變化。隨後，研究人員追蹤了整個肥胖過程中單個LHA谷氨酸能神經元的編碼特性，發現它們的獎賞反應大大減弱。這些數據表明了飲食如何擾亂內源性飲食抑制系統的功能，以促進暴飲暴食和肥胖。

Abstract

The current obesity epidemic is a major worldwide health concern. Despite the consensus that the brain regulates energy homeostasis, the neural adaptations governing obesity are unknown. Using a combination of high-throughput single-cell RNA sequencing and longitudinal in vivo two-photon calcium imaging, we surveyed functional alterations of the lateral hypothalamic area (LHA)—a highly conserved brain region that orchestrates feeding—in a mouse model of obesity. The transcriptional profile of LHA glutamatergic neurons was affected by obesity, exhibiting changes indicative of altered neuronal activity. Encoding properties of individual LHA glutamatergic neurons were then tracked throughout obesity, revealing greatly attenuated reward responses. These data demonstrate how diet disrupts the function of an endogenous feeding suppression system to promote overeating and obesity.

Color and orientation are jointly coded and spatially organized in primate primary visual cortex

顏色和方向在靈長類初級視覺皮層中被共同編碼和空間組織

作者：Anupam K. Garg, Peichao Li, Mohammad S. Rashid, et al

鏈接：

https://science.sciencemag.org/content/364/6447/1275

摘要：

以往的研究支持教科書上的這樣一種模型，即形狀和顏色是由靈長類初級視覺皮層（V1）的不同神經元提取的。然而，對這個模型的嚴格測試需要比以前更大的刺激空間採樣。

我們利用穩定的GCaMP6f表達和雙光子鈣成像，探測了一個非常大的空間和彩色的視覺刺激空間，並以單細胞解析度繪製了數千個神經元的功能微結構。在V1神經元中，相較於非彩色刺激，有相當比例的神經元對等發光體顏色有強烈的偏好，並且具有方向選擇性。

這表明，V1神經元的方向與顏色是由重疊的迴路相互處理的。單個神經元可以精確無誤地編碼顏色和方向。進一步的分析揭示了顏色調節、方向選擇性和細胞色素氧化酶組織學之間的系統空間關係。

Abstract

Previous studies support the textbook model that shape and color are extracted by distinct neurons in primate primary visual cortex (V1). However, rigorous testing of this model requires sampling a larger stimulus space than previously possible. We used stable GCaMP6f expression and two-photon calcium imaging to probe a very large spatial and chromatic visual stimulus space and map functional microarchitecture of thousands of neurons with single-cell resolution. Notable proportions of V1 neurons strongly preferred equiluminant color over achromatic stimuli and were also orientation selective, indicating that orientation and color in V1 are mutually processed by overlapping circuits. Single neurons could precisely and unambiguously code for both color and orientation. Further analyses revealed systematic spatial relationships between color tuning, orientation selectivity, and cytochrome oxidase histology.

流體力學Fluid Mechanics

Giant vortex clusters in a two-dimensional quantum fluid

二維量子流體中的巨渦團

作者：Guillaume Gauthier, Matthew T. Reeves, Xiaoquan Yu, et al

鏈接：

https://science.sciencemag.org/content/364/6447/1264

摘要：

通過瞬態攪拌給系統增加能量通常會導致更多的混亂。相反，在二維有界流體中，點狀渦被預測在一定能量以上重新排列，形成持續的渦團。

在這項研究中，我們在一個平面超流體中實驗實現了這些渦簇：一個被限制在橢圓幾何中的87Rb玻色—愛因斯坦凝聚體。我們證明，這些團簇持續了很長一段時間，使超流體系統保持在遠離總體平衡的高能狀態。

我們的實驗探索了渦旋物質在負絕對溫度下的狀態，並與拓撲缺陷、二維湍流、氦膜、非線性光學材料、費米子超流體和夸克膠子等離子體等系統的動力學有關。

Abstract

Adding energy to a system through transient stirring usually leads to more disorder. In contrast, point-like vortices in a bounded two-dimensional fluid are predicted to reorder above a certain energy, forming persistent vortex clusters. In this study, we experimentally realize these vortex clusters in a planar superfluid: a 87Rb Bose-Einstein condensate confined to an elliptical geometry. We demonstrate that the clusters persist for long time periods, maintaining the superfluid system in a high-energy state far from global equilibrium. Our experiments explore a regime of vortex matter at negative absolute temperatures and have relevance for the dynamics of topological defects, two-dimensional turbulence, and systems such as helium films, nonlinear optical materials, fermion superfluids, and quark-gluon plasmas.

Evolution of large-scale flow from turbulence in a two-dimensional superfluid

二維超流體中由湍流引起的大尺度流動的演化

作者：Shaun P. Johnstone, Andrew J. Groszek, Philip T. Starkey, et al

鏈接：

https://science.sciencemag.org/content/364/6447/1267

摘要：

非平衡相互作用系統可演化出大尺度結構和秩序。在二維紊流中，看上去隨機的流體旋渦運動可以演化為持續的大尺度旋渦。為解釋這種行為，Lars Onsager提出了一種基於量子化旋渦的統計水動力模型。

這裡，我們報告了對Onsager模型的實驗驗證。我們拖動柵格勢壘穿過扁超流體玻色—愛因斯坦凝聚體，以產生非平衡渦旋分布。

我們觀察到由渦旋蒸發加熱驅動的逆能量級聯的跡象，導致以負絕對溫度為特徵的穩態結構。我們的研究結果為定量研究遠離平衡的相互作用量子系統的湧現結構開闢了一條道路。

Abstract

Nonequilibrium interacting systems can evolve to exhibit large-scale structure and order. In two-dimensional turbulent flow, the seemingly random swirling motion of a fluid can evolve toward persistent large-scale vortices. To explain such behavior, Lars Onsager proposed a statistical hydrodynamic model based on quantized vortices. Here, we report on the experimental confirmation of Onsager』s model. We dragged a grid barrier through an oblate superfluid Bose–Einstein condensate to generate nonequilibrium distributions of vortices. We observed signatures of an inverse energy cascade driven by the evaporative heating of vortices, leading to steady-state configurations characterized by negative absolute temperatures. Our results open a pathway for quantitative studies of emergent structures in interacting quantum systems driven far from equilibrium.

材料/物理學Materials/Physics

Impact-resistant nacre-like transparent materials

耐衝擊的珍珠狀透明材料

作者：Z. Yin, F. Hannard, F. Barthelat

鏈接：

https://science.sciencemag.org/content/364/6447/1260

摘要：

玻璃具有優異的光學性能、硬度和耐久性，但固有的脆性和較差的抗衝擊性限制了其應用。層壓和回火可改善衝擊響應，但不能抑制脆性。

我們提出了一種生物啟發的夾層玻璃。它複製了軟體動物貝殼珍珠層的三維「磚瓦加水泥」布局，具有周期性的三維結構和透明熱塑性彈性體構成的夾層。這種材料複製了「平板滑動機制」。這是天然珍珠層韌性的關鍵，但在合成珍珠層中基本上沒有。

滑塊產生了大面積的非線性變形，顯著提高韌性。這種珍珠狀玻璃在保持高強度和剛度的同時，比夾層玻璃和鋼化玻璃具有兩到三倍的抗衝擊性。

Abstract

Glass has outstanding optical properties, hardness, and durability, but its applications are limited by its inherent brittleness and poor impact resistance. Lamination and tempering can improve impact response but do not suppress brittleness. We propose a bioinspired laminated glass that duplicates the three-dimensional 「brick-and-mortar」 arrangement of nacre from mollusk shells, with periodic three-dimensional architectures and interlayers made of a transparent thermoplastic elastomer. This material reproduces the 「tablet sliding mechanism,」 which is key to the toughness of natural nacre but has been largely absent in synthetic nacres. Tablet sliding generates nonlinear deformations over large volumes and significantly improves toughness. This nacre-like glass is also two to three times more impact resistant than laminated glass and tempered glass while maintaining high strength and stiffness.

Observation of a Majorana zero mode in a topologically protected edge channel

對拓撲保護邊緣信道中馬約拉納零模的觀測

作者：Berthold J?ck, Yonglong Xie, Jian Li, et al

鏈接：

https://science.sciencemag.org/content/364/6447/1255

摘要：

在螺旋邊緣模式（如拓撲絕緣子模式）下的超導近鄰配對，被預測為實現馬約拉納零模（MZMs）提供了一個獨特的平台。

我們利用掃描隧道顯微鏡測量法，探測了近鄰誘導的超導性和磁性對生長在超導鈮襯底上並裝飾有磁性鐵團簇的鉍（111）薄膜螺旋鉸鏈態的影響。與模型計算結果一致，我們的測量結果顯示，在超導螺旋邊緣通道和鐵團簇之間的界面出現了一個局域的MZM，並且沿邊緣有一個強磁化分量。

我們的實驗還解決了MZM的自旋特徵。它將其與超導體中可能在零能量下意外發生的微小間隙態區分開來。

Abstract

Superconducting proximity pairing in helical edge modes, such as those of topological insulators, is predicted to provide a unique platform for realizing Majorana zero modes (MZMs). We used scanning tunneling microscopy measurements to probe the influence of proximity-induced superconductivity and magnetism on the helical hinge states of bismuth(111) films grown on a superconducting niobium substrate and decorated with magnetic iron clusters. Consistent with model calculations, our measurements revealed the emergence of a localized MZM at the interface between the superconducting helical edge channel and the iron clusters, with a strong magnetization component along the edge. Our experiments also resolve the MZM』s spin signature, which distinguishes it from trivial in-gap states that may accidentally occur at zero energy in a superconductor.

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