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欧洲研究发现英国林地储存的碳几乎是之前估计的两倍 快报文章
资源环境快报,2023年第1期
作者:  裴惠娟
Microsoft Word(17Kb)  |  收藏  |  浏览/下载:576/0  |  提交时间:2023/01/16
Temperate Forest  Biomass Carbon  Laser Scanning  
澳大利亚研究人员开发出新的勘探技术 快报文章
地球科学快报,2022年第09期
作者:  张树良
Microsoft Word(13Kb)  |  收藏  |  浏览/下载:639/0  |  提交时间:2022/05/10
exploration technology  seismic sensing  laser measurement  Western Australian  
小型卫星PIXL-1将世界上最小的激光终端送入轨道 快报文章
地球科学快报,2021年第3期
作者:  刘文浩
Microsoft Word(15Kb)  |  收藏  |  浏览/下载:433/0  |  提交时间:2021/02/09
compact satellite, PIXL-1, laser terminal, OSIRIS4  
Revealing enigmatic mucus structures in the deep sea using DeepPIV 期刊论文
NATURE, 2020, 583 (7814) : 78-+
作者:  Nguyen, Ngoc Uyen Nhi;  Canseco, Diana C.;  Xiao, Feng;  Nakada, Yuji;  Li, Shujuan;  Lam, Nicholas T.;  Muralidhar, Shalini A.;  Savla, Jainy J.;  Hill, Joseph A.;  Le, Victor;  Zidan, Kareem A.;  El-Feky, Hamed W.;  Wang, Zhaoning;  Ahmed, Mahmoud Salama;  Hubbi, Maimon E.;  Menendez-Montes, Ivan
收藏  |  浏览/下载:48/0  |  提交时间:2020/06/09

Advanced deep-sea imaging tools yield insights into the structure and function of mucus filtration houses built by midwater giant larvaceans.


Many animals build complex structures to aid in their survival, but very few are built exclusively from materials that animals create (1,2). In the midwaters of the ocean, mucoid structures are readily secreted by numerous animals, and serve many vital functions(3,4). However, little is known about these mucoid structures owing to the challenges of observing them in the deep sea. Among these mucoid forms, the '  houses'  of larvaceans are marvels of nature(5), and in the ocean twilight zone giant larvaceans secrete and build mucus filtering structures that can reach diameters of more than 1 m(6). Here we describe in situ laser-imaging technology(7) that reconstructs three-dimensional models of mucus forms. The models provide high-resolution views of giant larvacean houses and elucidate the role that house structure has in food capture and predator avoidance. Now that tools exist to study mucus structures found throughout the ocean, we can shed light on some of nature'  s most complex forms.


  
Synthesis and properties of free-standing monolayer amorphous carbon 期刊论文
NATURE, 2020, 577 (7789) : 199-+
作者:  Toh, Chee-Tat;  Zhang, Hongji;  Lin, Junhao;  Mayorov, Alexander S.;  Wang, Yun-Peng;  Orofeo, Carlo M.;  Ferry, Darim Badur;  Andersen, Henrik;  Kakenov, Nurbek;  Guo, Zenglong;  Abidi, Irfan Haider;  Sims, Hunter;  Suenaga, Kazu;  Pantelides, Sokrates T.;  Ozyilmaz, Barbaros
收藏  |  浏览/下载:21/0  |  提交时间:2020/07/03

Bulk amorphous materials have been studied extensively and are widely used, yet their atomic arrangement remains an open issue. Although they are generally believed to be Zachariasen continuous random networks(1), recent experimental evidence favours the competing crystallite model in the case of amorphous silicon(2-4). In two-dimensional materials, however, the corresponding questions remain unanswered. Here we report the synthesis, by laser-assisted chemical vapour deposition(5), of centimetre-scale, free-standing, continuous and stable monolayer amorphous carbon, topologically distinct from disordered graphene. Unlike in bulk materials, the structure of monolayer amorphous carbon can be determined by atomic-resolution imaging. Extensive characterization by Raman and X-ray spectroscopy and transmission electron microscopy reveals the complete absence of long-range periodicity and a threefold-coordinated structure with a wide distribution of bond lengths, bond angles, and five-, six-, seven- and eight-member rings. The ring distribution is not a Zachariasen continuous random network, but resembles the competing (nano)crystallite model(6). We construct a corresponding model that enables density-functional-theory calculations of the properties of monolayer amorphous carbon, in accordance with observations. Direct measurements confirm that it is insulating, with resistivity values similar to those of boron nitride grown by chemical vapour deposition. Free-standing monolayer amorphous carbon is surprisingly stable and deforms to a high breaking strength, without crack propagation from the point of fracture. The excellent physical properties of this stable, free-standing monolayer amorphous carbon could prove useful for permeation and diffusion barriers in applications such as magnetic recording devices and flexible electronics.


  
Field-resolved infrared spectroscopy of biological systems 期刊论文
NATURE, 2020, 577 (7788) : 52-+
作者:  Pupeza, Ioachim;  Huber, Marinus;  Trubetskov, Michael;  Schweinberger, Wolfgang;  Hussain, Syed A.;  Hofer, Christina;  Fritsch, Kilian;  Poetzlberger, Markus;  Vamos, Lenard;  Fill, Ernst;  Amotchkina, Tatiana;  Kepesidis, Kosmas V.;  Apolonski, Alexander;  Karpowicz, Nicholas;  Pervak, Vladimir;  Pronin, Oleg;  Fleischmann, Frank;  Azzeer, Abdallah;  Zigman, Mihaela;  Krausz, Ferenc
收藏  |  浏览/下载:30/0  |  提交时间:2020/07/03

The proper functioning of living systems and physiological phenotypes depends on molecular composition. Yet simultaneous quantitative detection of a wide variety of molecules remains a challenge(1-8). Here we show how broadband optical coherence opens up opportunities for fingerprinting complex molecular ensembles in their natural environment. Vibrationally excited molecules emit a coherent electric field following few-cycle infrared laser excitation(9-12), and this field is specific to the sample'  s molecular composition. Employing electro-optic sampling(10,12-15), we directly measure this global molecular fingerprint down to field strengths 10(7) times weaker than that of the excitation. This enables transillumination of intact living systems with thicknesses of the order of 0.1 millimetres, permitting broadband infrared spectroscopic probing of human cells and plant leaves. In a proof-of-concept analysis of human blood serum, temporal isolation of the infrared electric-field fingerprint from its excitation along with its sampling with attosecond timing precision results in detection sensitivity of submicrograms per millilitre of blood serum and a detectable dynamic range of molecular concentration exceeding 10(5). This technique promises improved molecular sensitivity and molecular coverage for probing complex, real-world biological and medical settings.


  
Potential circadian effects on translational failure for neuroprotection 期刊论文
NATURE, 2020
作者:  Sakai, Akito;  Minami, Susumu;  Koretsune, Takashi;  Chen, Taishi;  Higo, Tomoya;  Wang, Yangming;  Nomoto, Takuya;  Hirayama, Motoaki;  Miwa, Shinji;  Nishio-Hamane, Daisuke;  Ishii, Fumiyuki;  Arita, Ryotaro;  Nakatsuji, Satoru
收藏  |  浏览/下载:28/0  |  提交时间:2020/07/03

Neuroprotectant strategies that have worked in rodent models of stroke have failed to provide protection in clinical trials. Here we show that the opposite circadian cycles in nocturnal rodents versus diurnal humans(1,2) may contribute to this failure in translation. We tested three independent neuroprotective approaches-normobaric hyperoxia, the free radical scavenger alpha-phenyl-butyl-tert-nitrone (alpha PBN), and the N-methyl-d-aspartic acid (NMDA) antagonist MK801-in mouse and rat models of focal cerebral ischaemia. All three treatments reduced infarction in day-time (inactive phase) rodent models of stroke, but not in night-time (active phase) rodent models of stroke, which match the phase (active, day-time) during which most strokes occur in clinical trials. Laser-speckle imaging showed that the penumbra of cerebral ischaemia was narrower in the active-phase mouse model than in the inactive-phase model. The smaller penumbra was associated with a lower density of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive dying cells and reduced infarct growth from 12 to 72 h. When we induced circadian-like cycles in primary mouse neurons, deprivation of oxygen and glucose triggered a smaller release of glutamate and reactive oxygen species, as well as lower activation of apoptotic and necroptotic mediators, in '  active-phase'  than in '  inactive-phase'  rodent neurons. alpha PBN and MK801 reduced neuronal death only in '  inactive-phase'  neurons. These findings suggest that the influence of circadian rhythm on neuroprotection must be considered for translational studies in stroke and central nervous system diseases.


Studies in rats and mice at different times of day suggest that the failure of neuroprotective strategies for stroke in translational studies might be related to the difference in circadian cycles between humans and rodents.


  
Constraining Microfractures in Foliated Alpine Fault Rocks With Laser Ultrasonics 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (8)
作者:  Simpson, Jonathan;  Adam, Ludmila;  van Wijk, Kasper;  Charoensawan, Jirapat
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/02
microfractures  rock physics  fault zones  laser ultrasonics  
Observation of Bose-Einstein condensates in an Earth-orbiting research lab 期刊论文
NATURE, 2020, 582 (7811) : 103-+
作者:  Yamamoto, Keisuke;  Venida, Anthony;  Yano, Julian;  Biancur, Douglas E.;  Kakiuchi, Miwako;  Gupta, Suprit;  Sohn, Albert S. W.;  Mukhopadhyay, Subhadip;  Lin, Elaine Y.;  Parker, Seth J.;  Banh, Robert S.;  Paulo, Joao A.;  Wen, Kwun Wah;  Debnath, Jayanta;  Kim, Grace E.;  Mancias, Joseph D.;  Fearon, Douglas T.;  Perera, Rushika M.;  Kimmelman, Alec C.
收藏  |  浏览/下载:46/0  |  提交时间:2020/07/03

Quantum mechanics governs the microscopic world, where low mass and momentum reveal a natural wave-particle duality. Magnifying quantum behaviour to macroscopic scales is a major strength of the technique of cooling and trapping atomic gases, in which low momentum is engineered through extremely low temperatures. Advances in this field have achieved such precise control over atomic systems that gravity, often negligible when considering individual atoms, has emerged as a substantial obstacle. In particular, although weaker trapping fields would allow access to lower temperatures(1,2), gravity empties atom traps that are too weak. Additionally, inertial sensors based on cold atoms could reach better sensitivities if the free-fall time of the atoms after release from the trap could be made longer(3). Planetary orbit, specifically the condition of perpetual free-fall, offers to lift cold-atom studies beyond such terrestrial limitations. Here we report production of rubidium Bose-Einstein condensates (BECs) in an Earth-orbiting research laboratory, the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with free-expansion times extending beyond one second, providing an initial demonstration of the advantages offered by a microgravity environment for cold-atom experiments and verifying the successful operation of this facility. With routine BEC production, continuing operations will support long-term investigations of trap topologies unique to microgravity(4,5), atom-laser sources(6), few-body physics(7,8)and pathfinding techniques for atom-wave interferometry(9-12).


  
Femtosecond-to-millisecond structural changes in a light-driven sodium pump 期刊论文
NATURE, 2020, 583 (7815) : 314-+
作者:  Moore, Luiza;  Leongamornlert, Daniel;  Coorens, Tim H. H.;  Sanders, Mathijs A.;  Ellis, Peter;  Dentro, Stefan C.;  Dawson, Kevin J.;  Butler, Tim;  Rahbari, Raheleh;  Mitchell, Thomas J.;  Maura, Francesco;  Nangalia, Jyoti;  Tarpey, Patrick S.;  Brunner, Simon F.;  Lee-Six, Henry;  Hooks, Yvette;  Moody, Sarah;  Mahbubani, Krishnaa T.;  Jimenez-Linan, Mercedes;  Brosens, Jan J.;  Iacobuzio-Donahue, Christine A.;  Martincorena, Inigo;  Saeb-Parsy, Kourosh;  Campbell, Peter J.;  Stratton, Michael R.
收藏  |  浏览/下载:55/0  |  提交时间:2020/07/03

Light-driven sodium pumps actively transport small cations across cellular membranes(1). These pumps are used by microorganisms to convert light into membrane potential and have become useful optogenetic tools with applications in neuroscience. Although the resting state structures of the prototypical sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) have been solved(2,3), it is unclear how structural alterations overtime allow sodium to be translocated against a concentration gradient. Here, using the Swiss X-ray Free Electron Laser(4), we have collected serial crystallographic data at ten pump-probe delays from femtoseconds to milliseconds. High-resolution structural snapshots throughout the KR2 photocycle show how retinal isomerization is completed on the femtosecond timescale and changes the local structure of the binding pocket in the early nanoseconds. Subsequent rearrangements and deprotonation of the retinal Schiff base open an electrostatic gate in microseconds. Structural and spectroscopic data, in combination with quantum chemical calculations, indicate that a sodium ion bind stransiently close to the retinal within one millisecond. In the last structural intermediate, at 20 milliseconds after activation, we identified a potential second sodium-binding site close to the extracellular exit. These results provide direct molecular insight into the dynamics of active cation transport across biological membranes.