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PNAS Plus Significance Statements

Intrusion and extrusion of water in hydrophobic nanopores

Antonio Tinti, Alberto Giacomello, Yaroslav Grosu, and Carlo Massimo Casciola

Molecular springs, constituted by nanoporous materials immersed in a nonwetting liquid, are compact, economical, and efficient means of storing energy, owing to their enormous surface area. Surface energy is accumulated during liquid intrusion inside the pores and released by decreasing liquid pressure and thus triggering confined cavitation. State-of-the-art atomistic simulations shed light on the intrusion and extrusion of water in hydrophobic nanopores, revealing conspicuous deviations from macroscopic theories, which include accelerated cavitation, increased intrusion pressure, and reversible intrusion and extrusion processes. Understanding these nanoscale phenomena is the key to a better design of molecular springs as it allows relating the characteristics of the materials to the overall properties of the devices, e.g., their operational pressure and efficiency. (See pp. E10266–E10273.)

Parallel magnetic field suppresses dissipation in superconducting nanostrips

Yong-Lei Wang, Andreas Glatza, Gregory J. Kimmel, Igor S. Aranson, Laxman R. Thoutam, Zhi-Li Xiao, Golibjon R. Berdiyorov, Fran?ois M. Peeters, George W. Crabtree, and Wai-Kwong Kwok

Absolute zero resistance of superconducting materials is difficult to achieve in practice due to the motion of microscopic Abrikosov vortices, especially when external currents are applied. Even a partial resistance reduction via vortex immobilization by microscopic material imperfections is the holy grail of superconductivity research. It is commonly believed that the dissipation increases with applied magnetic field since the number of vortices increases as well. Through the example of molybdenum–germanium superconducting nanostrips, we show that resistive losses due to vortex motion can actually be decreased by applying an increasing applied magnetic field parallel to the current. This surprising recovery of superconductivity is achieved through “vortex crowding”: The increased number of vortices impedes their mutual motion, resulting in straight, untwisted vortices. (See pp. E10274–E10280.)

Closed-loop control of targeted ultrasound drug delivery across the blood–brain/tumor barriers in a rat glioma model

Tao Sun, Yongzhi Zhang, Chanikarn Power, Phillip M. Alexander, Jonathan T. Sutton, Muna Aryal, Natalia Vykhodtseva, Eric L. …

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