《科学》（20190628出版）一周论文导读

翻译 | 宗华

Science, 28 JUNE 2019, VOL 364, ISSUE 6447

《科学》2019年6月28日，第6447期364卷

生物学Biology

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

肥胖重塑外侧下丘脑抑制进食的活动和转录状态

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

▲ 链接：

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

▲ 摘要：

目前的肥胖症流行是一个重要的全球性健康问题。尽管人们一致认为大脑调节能量平衡，但控制肥胖的神经适应机制尚不清楚。

采用高通量单细胞RNA测序和体内纵向双光子钙成像相结合的方法，我们研究了小鼠肥胖模型中下丘脑外侧区（LHA）的功能变化。LHA是协调进食的高度保守大脑区域。

研究发现，肥胖影响LHA谷氨酸能神经元的转录谱，表现出神经元活动改变的变化。随后，研究人员追踪了整个肥胖过程中单个LHA谷氨酸能神经元的编码特性，发现它们的奖赏反应大大减弱。这些数据表明了饮食如何扰乱内源性饮食抑制系统的功能，以促进暴饮暴食和肥胖。

▲ 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

颜色和方向在灵长类初级视觉皮层中被共同编码和空间组织

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

▲ 链接：

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

▲ 摘要：

以往的研究支持教科书上的这样一种模型，即形状和颜色是由灵长类初级视觉皮层（V1）的不同神经元提取的。然而，对这个模型的严格测试需要比以前更大的刺激空间采样。

我们利用稳定的GCaMP6f表达和双光子钙成像，探测了一个非常大的空间和彩色的视觉刺激空间，并以单细胞分辨率绘制了数千个神经元的功能微结构。在V1神经元中，相较于非彩色刺激，有相当比例的神经元对等发光体颜色有强烈的偏好，并且具有方向选择性。

这表明，V1神经元的方向与颜色是由重叠的回路相互处理的。单个神经元可以精确无误地编码颜色和方向。进一步的分析揭示了颜色调节、方向选择性和细胞色素氧化酶组织学之间的系统空间关系。

▲ 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.

流体力学Fluid Mechanics

Giant vortex clusters in a two-dimensional quantum fluid

二维量子流体中的巨涡团

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

▲ 链接：

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

▲ 摘要：

通过瞬态搅拌给系统增加能量通常会导致更多的混乱。相反，在二维有界流体中，点状涡被预测在一定能量以上重新排列，形成持续的涡团。

在这项研究中，我们在一个平面超流体中实验实现了这些涡簇：一个被限制在椭圆几何中的87Rb玻色—爱因斯坦凝聚体。我们证明，这些团簇持续了很长一段时间，使超流体系统保持在远离总体平衡的高能状态。

我们的实验探索了涡旋物质在负绝对温度下的状态，并与拓扑缺陷、二维湍流、氦膜、非线性光学材料、费米子超流体和夸克胶子等离子体等系统的动力学有关。

▲ 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

二维超流体中由湍流引起的大尺度流动的演化

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

▲ 链接：

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

▲ 摘要：

非平衡相互作用系统可演化出大尺度结构和秩序。在二维紊流中，看上去随机的流体旋涡运动可以演化为持续的大尺度旋涡。为解释这种行为，Lars Onsager提出了一种基于量子化旋涡的统计水动力模型。

这里，我们报告了对Onsager模型的实验验证。我们拖动栅格势垒穿过扁超流体玻色—爱因斯坦凝聚体，以产生非平衡涡旋分布。

我们观察到由涡旋蒸发加热驱动的逆能量级联的迹象，导致以负绝对温度为特征的稳态结构。我们的研究结果为定量研究远离平衡的相互作用量子系统的涌现结构开辟了一条道路。

▲ 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/物理学Materials/Physics

Impact-resistant nacre-like transparent materials

耐冲击的珍珠状透明材料

▲ 作者：Z. Yin, F. Hannard, F. Barthelat

▲ 链接：

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

▲ 摘要：

玻璃具有优异的光学性能、硬度和耐久性，但固有的脆性和较差的抗冲击性限制了其应用。层压和回火可改善冲击响应，但不能抑制脆性。

我们提出了一种生物启发的夹层玻璃。它复制了软体动物贝壳珍珠层的三维“砖瓦加水泥”布局，具有周期性的三维结构和透明热塑性弹性体构成的夹层。这种材料复制了“平板滑动机制”。这是天然珍珠层韧性的关键，但在合成珍珠层中基本上没有。

滑块产生了大面积的非线性变形，显著提高韧性。这种珍珠状玻璃在保持高强度和刚度的同时，比夹层玻璃和钢化玻璃具有两到三倍的抗冲击性。

▲ 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

对拓扑保护边缘信道中马约拉纳零模的观测

▲ 作者：Berthold Jäck, Yonglong Xie, Jian Li, et al

▲ 链接：

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

▲ 摘要：

在螺旋边缘模式（如拓扑绝缘子模式）下的超导近邻配对，被预测为实现马约拉纳零模（MZMs）提供了一个独特的平台。

我们利用扫描隧道显微镜测量法，探测了近邻诱导的超导性和磁性对生长在超导铌衬底上并装饰有磁性铁团簇的铋（111）薄膜螺旋铰链态的影响。与模型计算结果一致，我们的测量结果显示，在超导螺旋边缘通道和铁团簇之间的界面出现了一个局域的MZM，并且沿边缘有一个强磁化分量。

我们的实验还解决了MZM的自旋特征。它将其与超导体中可能在零能量下意外发生的微小间隙态区分开来。

▲ 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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