編譯 | 馮維維
Science, 30 Jun 2023, Volume 380, Issue 6652
【資料圖】
《科學》6月30日，第380卷，6652期
物理學Physics
Observation of high-energy neutrinos from the Galactic plane
從銀道面觀測高能中微子
▲ 作者：ICECUBE COLLABORATIONAuthors Info & Affiliations
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adc9818
▲ 摘要：
高能宇宙射線，即不斷撞擊地球大氣層的原子核，其起源尚不清楚。由于星際磁場的偏轉(zhuǎn)，銀河系內(nèi)產(chǎn)生的宇宙射線從隨機方向到達地球。然而，宇宙射線在其源附近和傳播過程中與物質(zhì)相互作用，產(chǎn)生高能中微子。
研究者使用機器學習技術(shù)搜索中微子發(fā)射，該技術(shù)應(yīng)用于冰立方中微子天文臺10年的數(shù)據(jù)。通過將漫射發(fā)射模型與背景假設(shè)進行比較，我們確定了銀河面中微子發(fā)射的顯著性水平為4.5σ。這個信號與來自銀河系的中微子漫射一致，但也可能來自一群未解析的點源。
▲ 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
一次超亮伽馬射線爆發(fā)
▲ 作者：LHAASO COLLABORATIONAuthors Info & Affiliations
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adg9328
▲ 摘要：
長伽馬射線暴（GRBs）是由大質(zhì)量恒星爆炸產(chǎn)生的，會產(chǎn)生一股接近光速的物質(zhì)射流。LHAASO合作項目觀測到了極其明亮的GRB 221009A的高能（太電子伏特）伽馬射線。
GRB偶然發(fā)生在探測器的大視場內(nèi)，因此相關(guān)數(shù)據(jù)涵蓋了快速上升、峰值噴射和逐漸變暗的余輝。對觀測結(jié)果的建模顯示，噴流的開口角度小于1度，這幾乎完全指向地球，解釋了這次GRB不尋常的亮度。
▲ 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
用量子置亂改進計量
▲ 作者：ZEYANG LI(李澤陽), SIMONE COLOMBO, CHI SHU, GUSTAVO VELEZ, SAúL PILATOWSKY-CAMEO, ROMAN, SOONWON CHOI, MIKHAIL LUKIN, EDWIN PEDROZO-PE?AFIEL, AND VLADAN VULETI?
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adg9500
▲ 摘要：
量子置亂描述了信息在量子系統(tǒng)中傳播到許多自由度，使得信息不再是局部可訪問的，而是分布在整個系統(tǒng)中。這可以解釋量子系統(tǒng)如何成為經(jīng)典，并且獲得了有限的溫度，或者落入黑洞的物質(zhì)的信息如何似乎被抹去。
作者研究了相空間中多粒子系統(tǒng)在雙穩(wěn)點附近的指數(shù)置亂，并將其用于糾纏增強計量。利用時間反轉(zhuǎn)協(xié)議觀測到計量增益和超時序相關(guān)器同時呈指數(shù)增長，從實驗上驗證了量子計量與量子信息置亂之間的關(guān)系。研究結(jié)果表明，能夠以指數(shù)級速度產(chǎn)生糾纏的快速置亂動力學對實際計量有用，導致超出標準量子極限的6.8（4）分貝增益。
▲ 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
手性上部結(jié)構(gòu)的磁組裝方法
▲ 作者：ZHIWEI LI, QINGSONG FAN, ZUYANG YE, CHAOLUMEN WU, ZHONGXIANG WANG, AND YADONG YIN
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adg2657
▲ 摘要：
膠體組裝成手性超結(jié)構(gòu)通常是通過模板或光刻圖案化方法完成的，只適用于具有特定成分和形態(tài)的材料，尺寸范圍很窄。在這項研究中，手性超結(jié)構(gòu)可以通過磁性組裝任何化學成分的材料，在從分子到納米和微觀結(jié)構(gòu)的所有尺度上迅速形成。
研究證明了四極場手性是由空間中一致的場旋轉(zhuǎn)引起的永磁體產(chǎn)生的。將手性場應(yīng)用于磁性納米顆粒產(chǎn)生遠程手性超結(jié)構(gòu)，該超結(jié)構(gòu)由樣品的磁場強度和磁體的方向控制。將手性轉(zhuǎn)移到任何非手性分子是通過將客體分子（如金屬、聚合物、氧化物、半導體、染料和熒光團）加入磁性納米結(jié)構(gòu)中來實現(xiàn)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.
地質(zhì)學Geology
Gullies on Mars could have formed by melting of water ice during periods of high obliquity
火星溝壑或是高傾角時期水冰融化形成的
▲ 作者：J. L. DICKSON , A. M. PALUMBO, J. W. HEAD, L. KERBER, C. I. FASSETT, AND M. A. KRESLAVSKY
▲ 鏈接：
https://www.science.org/doi/10.1126/science.abk2464
▲ 摘要：
火星上的溝壑類似于地球上的水渠，但它們大多位于高海拔，在目前的氣候條件下，不可能存在液態(tài)水。有人認為，僅二氧化碳冰的升華就可能形成火星上的溝壑。
研究者使用一般環(huán)流模型表明，當火星的旋轉(zhuǎn)軸傾斜達到35度時，海拔最高的火星溝壑與經(jīng)歷水的三相點以上壓力的地形邊界重合。這些情況在過去幾百萬年里反復發(fā)生，最近一次發(fā)生在63萬年前。如果這些地方存在地表水冰，那么當溫度上升到273開爾文以上時，水冰就會融化。研究者提出了一種由水冰融化和二氧化碳冰升華驅(qū)動的雙溝形成情景。
▲ 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
農(nóng)業(yè)擴張導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
▲ 鏈接：
https://www.science.org/doi/10.1126/science.add5462
▲ 摘要：
農(nóng)業(yè)對水文的區(qū)域影響主要與灌溉有關(guān)。研究者展示了雨養(yǎng)農(nóng)業(yè)如何留下大規(guī)模的印記。過去四十年，南美平原上農(nóng)業(yè)擴張的范圍和速度為雨養(yǎng)農(nóng)業(yè)對水文學的影響提供了一個前所未有的案例。
遙感分析表明，由于一年生作物取代了原生植被和牧場，洪水的覆蓋范圍逐漸增加了一倍，增加了它們對降水的敏感性。地下水從深層（12米至6米）轉(zhuǎn)移到淺層（4米至0米）狀態(tài)，減少了下降水平。田間研究和模擬表明，土壤根系深度和土壤蒸散量的下降是造成這種水文變化的原因。
這些發(fā)現(xiàn)表明，在次大陸和年代際尺度上，與雨養(yǎng)農(nóng)業(yè)擴張有關(guān)的洪水風險不斷升級。
▲ 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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