作者:冯维维 来源:科学网微信公众号 发布时间:2023/7/2 21:26:18
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《科学》(20230630)一周论文导读

 

编译 | 冯维维

Science, 30 Jun 2023, Volume 380, Issue 6652

《科学》6月30日,第380卷,6652期

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物理学Physics

Observation of high-energy neutrinos from the Galactic plane

从银道面观测高能中微子

▲ 作者:ICECUBE COLLABORATIONAuthors Info & Affiliations

▲ 链接:

https://www.science.org/doi/10.1126/science.adc9818

▲ 摘要:

高能宇宙射线,即不断撞击地球大气层的原子核,其起源尚不清楚。由于星际磁场的偏转,银河系内产生的宇宙射线从随机方向到达地球。然而,宇宙射线在其源附近和传播过程中与物质相互作用,产生高能中微子。

研究者使用机器学习技术搜索中微子发射,该技术应用于冰立方中微子天文台10年的数据。通过将漫射发射模型与背景假设进行比较,我们确定了银河面中微子发射的显著性水平为4.5σ。这个信号与来自银河系的中微子漫射一致,但也可能来自一群未解析的点源。

▲ Abstract:

The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth’s atmosphere, is unknown. Because of deflection by interstellar magnetic fields, cosmic rays produced within the Milky Way arrive at Earth from random directions. However, cosmic rays interact with matter near their sources and during propagation, which produces high-energy neutrinos. We searched for neutrino emission using machine learning techniques applied to 10 years of data from the IceCube Neutrino Observatory. By comparing diffuse emission models to a background-only hypothesis, we identified neutrino emission from the Galactic plane at the 4.5σ level of significance. The signal is consistent with diffuse emission of neutrinos from the Milky Way but could also arise from a population of unresolved point sources.

A tera–electron volt afterglow from a narrow jet in an extremely bright gamma-ray burst

一次超亮伽马射线爆发

▲ 作者:LHAASO COLLABORATIONAuthors Info & Affiliations

▲ 链接:

https://www.science.org/doi/10.1126/science.adg9328

▲ 摘要:

长伽马射线暴(GRBs)是由大质量恒星爆炸产生的,会产生一股接近光速的物质射流。LHAASO合作项目观测到了极其明亮的GRB 221009A的高能(太电子伏特)伽马射线。

GRB偶然发生在探测器的大视场内,因此相关数据涵盖了快速上升、峰值喷射和逐渐变暗的余辉。对观测结果的建模显示,喷流的开口角度小于1度,这几乎完全指向地球,解释了这次GRB不寻常的亮度。

▲ Abstract:

Long gamma-ray bursts (GRBs) are produced by the explosion of a high-mass star, which produces a jet of material moving close to the speed of light. The LHAASO Collaboration observed the extremely bright GRB 221009A in very-high-energy (tera–electron volt) gamma rays. The GRB serendipitously occurred within the large field of view of their detector, so these data cover the rapid rise, peak emission, and gradually dimming afterglow. Modeling of the observations showed that the jet had an opening angle of less than one degree, which must have been pointed almost exactly toward Earth, explaining the unusual brightness of this GRB.

Improving metrology with quantum scrambling

用量子置乱改进计量

▲ 作者:ZEYANG LI(李泽阳), SIMONE COLOMBO, CHI SHU, GUSTAVO VELEZ, SAúL PILATOWSKY-CAMEO, ROMAN, SOONWON CHOI, MIKHAIL LUKIN, EDWIN PEDROZO-PE?AFIEL, AND VLADAN VULETI?

▲ 链接:

https://www.science.org/doi/10.1126/science.adg9500

▲ 摘要:

量子置乱描述了信息在量子系统中传播到许多自由度,使得信息不再是局部可访问的,而是分布在整个系统中。这可以解释量子系统如何成为经典,并且获得了有限的温度,或者落入黑洞的物质的信息如何似乎被抹去。

作者研究了相空间中多粒子系统在双稳点附近的指数置乱,并将其用于纠缠增强计量。利用时间反转协议观测到计量增益和超时序相关器同时呈指数增长,从实验上验证了量子计量与量子信息置乱之间的关系。研究结果表明,能够以指数级速度产生纠缠的快速置乱动力学对实际计量有用,导致超出标准量子极限的6.8(4)分贝增益。

▲ Abstract:

Quantum scrambling describes the spreading of information into many degrees of freedom in quantum systems, such that the information is no longer accessible locally but becomes distributed throughout the system. This idea can explain how quantum systems become classical and acquire a finite temperature, or how in black holes the information about the matter falling in is seemingly erased. We probe the exponential scrambling of a multiparticle system near a bistable point in phase space and utilize it for entanglement-enhanced metrology. A time-reversal protocol is used to observe a simultaneous exponential growth of both the metrological gain and the out-of-time-order correlator, thereby experimentally verifying the relation between quantum metrology and quantum information scrambling. Our results show that rapid scrambling dynamics capable of exponentially fast entanglement generation are useful for practical metrology, resulting in a 6.8(4)-decibel gain beyond the standard quantum limit.

A magnetic assembly approach to chiral superstructures

手性上部结构的磁组装方法

▲ 作者:ZHIWEI LI, QINGSONG FAN, ZUYANG YE, CHAOLUMEN WU, ZHONGXIANG WANG, AND YADONG YIN

▲ 链接:

https://www.science.org/doi/10.1126/science.adg2657

▲ 摘要:

胶体组装成手性超结构通常是通过模板或光刻图案化方法完成的,只适用于具有特定成分和形态的材料,尺寸范围很窄。在这项研究中,手性超结构可以通过磁性组装任何化学成分的材料,在从分子到纳米和微观结构的所有尺度上迅速形成。

研究证明了四极场手性是由空间中一致的场旋转引起的永磁体产生的。将手性场应用于磁性纳米颗粒产生远程手性超结构,该超结构由样品的磁场强度和磁体的方向控制。将手性转移到任何非手性分子是通过将客体分子(如金属、聚合物、氧化物、半导体、染料和荧光团)加入磁性纳米结构中来实现的。

▲ Abstract:

Colloidal assembly into chiral superstructures is usually accomplished with templating or lithographic patterning methods that are only applicable to materials with specific compositions and morphologies over narrow size ranges. Here, chiral superstructures can be rapidly formed by magnetically assembling materials of any chemical compositions at all scales, from molecules to nano- and microstructures. We show that a quadrupole field chirality is generated by permanent magnets caused by consistent field rotation in space. Applying the chiral field to magnetic nanoparticles produces long-range chiral superstructures controlled by field strength at the samples and orientation of the magnets. Transferring the chirality to any achiral molecules is enabled by incorporating guest molecules such as metals, polymers, oxides, semiconductors, dyes, and fluorophores into the magnetic nanostructures.

地质学Geology

Gullies on Mars could have formed by melting of water ice during periods of high obliquity

火星沟壑或是高倾角时期水冰融化形成的

▲ 作者:J. L. DICKSON , A. M. PALUMBO, J. W. HEAD, L. KERBER, C. I. FASSETT, AND M. A. KRESLAVSKY

▲ 链接:

https://www.science.org/doi/10.1126/science.abk2464

▲ 摘要:

火星上的沟壑类似于地球上的水渠,但它们大多位于高海拔,在目前的气候条件下,不可能存在液态水。有人认为,仅二氧化碳冰的升华就可能形成火星上的沟壑。

研究者使用一般环流模型表明,当火星的旋转轴倾斜达到35度时,海拔最高的火星沟壑与经历水的三相点以上压力的地形边界重合。这些情况在过去几百万年里反复发生,最近一次发生在63万年前。如果这些地方存在地表水冰,那么当温度上升到273开尔文以上时,水冰就会融化。研究者提出了一种由水冰融化和二氧化碳冰升华驱动的双沟形成情景。

▲ Abstract:

Gullies on Mars resemble water-carved channels on Earth, but they are mostly at elevations where liquid water is not expected under current climate conditions. It has been suggested that sublimation of carbon dioxide ice alone could have formed Martian gullies. We used a general circulation model to show that the highest-elevation Martian gullies coincide with the boundary of terrain that experienced pressures above the triple point of water when Mars’ rotational axis tilt reached 35°. Those conditions have occurred repeatedly over the past several million years, most recently ~630,000 years ago. Surface water ice, if present at these locations, could have melted when temperatures rose >273 kelvin. We propose a dual gully formation scenario that is driven by melting of water ice followed by carbon dioxide ice sublimation.

Agricultural expansion raises groundwater and increases flooding in the South American plains

农业扩张导致地下水抬升和南美平原洪水增加

▲ 作者:JAVIER HOUSPANOSSIAN, RAUL GIMéNEZ, JUAN I. WHITWORTH-HULS, MARCELO D. NOSETTO, WLODEK TYCH, PETER M. ATKINSON, MARIANA C. RUFINO, AND ESTEBAN G. JOBBáGY

▲ 链接:

https://www.science.org/doi/10.1126/science.add5462

▲ 摘要:

农业对水文的区域影响主要与灌溉有关。研究者展示了雨养农业如何留下大规模的印记。过去四十年,南美平原上农业扩张的范围和速度为雨养农业对水文学的影响提供了一个前所未有的案例。

遥感分析表明,由于一年生作物取代了原生植被和牧场,洪水的覆盖范围逐渐增加了一倍,增加了它们对降水的敏感性。地下水从深层(12米至6米)转移到浅层(4米至0米)状态,减少了下降水平。田间研究和模拟表明,土壤根系深度和土壤蒸散量的下降是造成这种水文变化的原因。

这些发现表明,在次大陆和年代际尺度上,与雨养农业扩张有关的洪水风险不断升级。

▲ Abstract:

Regional effects of farming on hydrology are associated mostly with irrigation. In this work, we show how rainfed agriculture can also leave large-scale imprints. The extent and speed of farming expansion across the South American plains over the past four decades provide an unprecedented case of the effects of rainfed farming on hydrology. Remote sensing analysis shows that as annual crops replaced native vegetation and pastures, floods gradually doubled their coverage, increasing their sensitivity to precipitation. Groundwater shifted from deep (12 to 6 meters) to shallow (4 to 0 meters) states, reducing drawdown levels. Field studies and simulations suggest that declining rooting depths and evapotranspiration in croplands are the causes of this hydrological transformation. These findings show the escalating flooding risks associated with rainfed agriculture expansion at subcontinental and decadal scales.

 
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