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Liquid flow and control without solid walls 期刊论文
NATURE, 2020, 581 (7806) : 58-+
作者:  Hellmuth, Susanne;  Stemmann, Olaf
收藏  |  浏览/下载:52/0  |  提交时间:2020/07/03

Wall-free liquid channels surrounded by an immiscible magnetic liquid can be used to create liquid circuitry or to transport human blood without damaging the blood cells by moving permanent magnets.


When miniaturizing fluidic circuitry, the solid walls of the fluid channels become increasingly important(1) because they limit the flow rates achievable for a given pressure drop, and they are prone to fouling(2). Approaches for reducing the wall interactions include hydrophobic coatings(3), liquid-infused porous surfaces(4-6), nanoparticle surfactant jamming(7), changes to surface electronic structure(8), electrowetting(9,10), surface tension pinning(11,12) and use of atomically flat channels(13). A better solution may be to avoid the solid walls altogether. Droplet microfluidics and sheath flow achieve this but require continuous flow of the central liquid and the surrounding liquid(1,14). Here we demonstrate an approach in which aqueous liquid channels are surrounded by an immiscible magnetic liquid, both of which are stabilized by a quadrupolar magnetic field. This creates self-healing, non-clogging, anti-fouling and near-frictionless liquid-in-liquid fluidic channels. Manipulation of the field provides flow control, such as valving, splitting, merging and pumping. The latter is achieved by moving permanent magnets that have no physical contact with the liquid channel. We show that this magnetostaltic pumping method can be used to transport whole human blood with very little damage due to shear forces. Haemolysis (rupture of blood cells) is reduced by an order of magnitude compared with traditional peristaltic pumping, in which blood is mechanically squeezed through a plastic tube. Our liquid-in-liquid approach provides new ways to transport delicate liquids, particularly when scaling channels down to the micrometre scale, with no need for high pressures, and could also be used for microfluidic circuitry.


  
Observation of the Kondo screening cloud 期刊论文
NATURE, 2020, 579 (7798) : 210-+
作者:  Shahnawaz, Mohammad;  Mukherjee, Abhisek;  Pritzkow, Sandra;  Mendez, Nicolas;  Rabadia, Prakruti;  Liu, Xiangan;  Hu, Bo;  Schmeichel, Ann;  Singer, Wolfgang;  Wu, Gang;  Tsai, Ah-Lim;  Shirani, Hamid;  Nilsson, K. Peter R.;  Low, Phillip A.;  Soto, Claudio
收藏  |  浏览/下载:22/0  |  提交时间:2020/07/03

When a magnetic impurity exists in a metal, conduction electrons form a spin cloud that screens the impurity spin. This basic phenomenon is called the Kondo effect(1,2). Unlike electric-charge screening, the spin-screening cloud(3-6) occurs quantum coherently, forming spin-singlet entanglement with the impurity. Although the spins interact locally around the impurity, the Kondo cloud can theoretically spread out over several micrometres. The cloud has not so far been detected, and so its physical existence-a fundamental aspect of the Kondo effect-remains controversial(7,8). Here we present experimental evidence of a Kondo cloud extending over a length of micrometres, comparable to the theoretical length xi(K). In our device, a Kondo impurity is formed in a quantum dot(2,9-11), coupling on one side to a quasi-one-dimensional channel(12) that houses a Fabry-Perot interferometer of various gate-defined lengths L exceeding one micrometre. When we sweep a voltage on the interferometer end gate-separated by L from the quantum dot-to induce Fabry-Perot oscillations in conductance we observe oscillations in the measured Kondo temperature T-K, which is a signature of the Kondo cloud at distance L. When L is less than xi(K) the T-K oscillation amplitude becomes larger as L becomes smaller, obeying a scaling function of a single parameter L/xi(K), whereas when L is greater than xi(K) the oscillation is much weaker. Our results reveal that xi(K) is the only length parameter associated with the Kondo effect, and that the cloud lies mostly within a length of xi(K). Our experimental method offers a way of detecting the spatial distribution of exotic non-Fermi liquids formed by multiple magnetic impurities or multiple screening channels(13-16) and of studying spin-correlated systems.


  
Multiscale Data Fusion for Surface Soil Moisture Estimation: A Spatial Hierarchical Approach 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (12) : 10443-10465
作者:  Kathuria, Dhruva;  Mohanty, Binayak P.;  Katzfuss, Matthias
收藏  |  浏览/下载:16/0  |  提交时间:2020/02/16
soil moisture remote sensing  scaling  multi-instrument data fusion  spatial hierarchical model  uncertainty  physical controls  
A Nomograph to Incorporate Geophysical Heterogeneity in Soil Moisture Downscaling 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (1) : 34-54
作者:  Gaur, Nandita;  Mohanty, Binayak P.
收藏  |  浏览/下载:20/0  |  提交时间:2019/04/09
remote sensing  soil moisture  dominant physical controls  scaling nomograph  
Accessing vulnerability of land-cover types to climate change using physical scaling downscaling model 期刊论文
INTERNATIONAL JOURNAL OF CLIMATOLOGY, 2017, 37 (6)
作者:  Gaur, Abhishek;  Simonovic, Slobodan P.
收藏  |  浏览/下载:9/0  |  提交时间:2019/04/09
land cover  physical scaling  forest cover  climate change  Saskatchewan