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Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging
A dual-contrast agent has been developed for combined ultrasound and photoacoustic imaging. This agent uses vaporization for ultrasound contrast enhancement and photoacoustic signal generation, providing significantly higher signals than thermal expansion, the most commonly used photoacoustic mechanism.
- Katheryne Wilson
- , Kimberly Homan
- & Stanislav Emelianov
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Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas
Tokamak plasmas suffer from magnetohydrodynamic instabilities, driven by gradients in current density or pressure, but techniques to control them are power-hungry and reduce reactor efficiency. Here, an efficient method to control such instabilities using asymmetric ion populations is demonstrated at JET.
- J.P. Graves
- , I.T. Chapman
- & M. Jucker
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Mechanism of supercooled droplet freezing on surfaces
The mechanism through which ice forms on surfaces is of broad technological relevance. This study examines the manner in which ice forms on so-called 'icephobic' surfaces, and demonstrates that simple changes in the environmental conditions can render the icephobicity ineffective.
- Stefan Jung
- , Manish K. Tiwari
- & Dimos Poulikakos
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| Open AccessPhotoswitchable gel assembly based on molecular recognition
Self-assembly through molecular recognition events is used in the production of functionalized materials. This study shows that macroscopic gel assembly can be regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules.
- Hiroyasu Yamaguchi
- , Yuichiro Kobayashi
- & Akira Harada
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| Open AccessViolation of a Leggett–Garg inequality with ideal non-invasive measurements
Quantum mechanics predicts that objects can simultaneously exist in a superposition of two states. Kneeet al.propose and demonstrate experimentally a protocol which fully confirms this prediction, by testing the so-called Leggett–Garg inequality in a non-invasive manner.
- George C. Knee
- , Stephanie Simmons
- & Simon C. Benjamin
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| Open AccessMeasurement of finite-frequency current statistics in a single-electron transistor
Fluctuations of the electrical current in nanoscale devices reveal important details of the physical processes occurring inside them. Using a quantum point contact placed in its vicinity, Ubbelohde et al. measure the electrical fluctuations in a single-electron transistor, and determine the dynamical features of the transport.
- Niels Ubbelohde
- , Christian Fricke
- & Rolf J. Haug
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| Open AccessApproaching the ideal elastic limit of metallic glasses
The elastic limit represents the maximum stress and strain a material can withstand and is well characterized in many crystalline solids, yet remains elusive for metallic glasses. Here, this limit is investigated in submicron metallic glass structures and is found to be twice as high as that of bulk samples.
- Lin Tian
- , Yong-Qiang Cheng
- & Evan Ma
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Metal-adeninate vertices for the construction of an exceptionally porous metal-organic framework
Metal‐organic framework (MOFs) with metal‐carboxylate cluster vertices and long, branched organic linkers are highly porous. Anet al. develop an alternative route to MOFs in which metal‐biomolecule clusters are used as vertices to construct a mesoporous MOF.
- Jihyun An
- , Omar K. Farha
- & Nathaniel L. Rosi
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| Open AccessExtraordinary carrier multiplication gated by a picosecond electric field pulse
Studying carrier multiplication in materials is important to understand their transport properties and interaction with light. Hiroriet al. show that intense terahertz pulses can generate electron-hole pairs in GaAs quantum wells that then emit infrared light, contrary to the effect with a DC field.
- H. Hirori
- , K. Shinokita
- & K. Tanaka
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Revealing the role of defects in ferroelectric switching with atomic resolution
Ferroelectric materials are characterized by a spontaneous polarization, which in practical applications is manipulated by an electric field. This study examines how defects affect the switching with atomic resolution, by usingin situaberration-corrected transmission electron microscopy.
- Peng Gao
- , Christopher T. Nelson
- & Xiaoqing Pan
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Inverse barocaloric effect in the giant magnetocaloric La–Fe–Si–Co compound
When materials change temperature as a result of the application of pressure or a change in the magnetization, they are said to display a barocaloric or magnetocaloric effect, respectively. This study reports a substantial barocaloric effect in the giant magnetocaloric material LaFe11.33Co0.47Si1.2.
- Lluís Mañosa
- , David González-Alonso
- & Subham Majumdar
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Interface engineering of quantum Hall effects in digital transition metal oxide heterostructures
Topological insulators are a class of materials with an unusual band structure that makes them metallic at the surface and insulating in the bulk. Okamoto and co-workers use electronic structure calculations to predict a new family of possible topological insulators based on transition-metal oxides.
- Di Xiao
- , Wenguang Zhu
- & Satoshi Okamoto
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| Open AccessStable prenucleation mineral clusters are liquid-like ionic polymers
Prenucleation clusters have been observed during the early stages of calcium carbonate formation, contrary to classical models. Here, computer simulations indicate that the clusters are composed of an ionic polymer with alternating calcium and carbonate ions, and a dynamic topology of chains, branches and rings.
- Raffaella Demichelis
- , Paolo Raiteri
- & Denis Gebauer
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Low-power nano-optical vortex trapping via plasmonic diabolo nanoantennas
Optical vortex traps are appealing for handling delicate particles, but conventional techniques are challenging with objects smaller than the diffraction limit of light. By exploiting plasmonic resonances in gold diabolo nanoantennas, Kanget al. demonstrate low-power vortex trapping of nano-scale objects.
- Ju-Hyung Kang
- , Kipom Kim
- & Hong-Gyu Park
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| Open AccessTandem synthesis of alternating polyesters from renewable resources
Biomass-derived monomers are a renewable resource for the production of polymers. Robertet al. develop an auto-tandem catalytic transformation for the synthesis of aliphatic polyesters—'activated' monomers are prepared from dicarboxylic acids, which can be copolymerized with epoxides.
- Carine Robert
- , Frédéric de Montigny
- & Christophe M. Thomas
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Rebalancing of internally generated carriers for mid-infrared interband cascade lasers with very low power consumption
Mid-infrared semiconductor lasers suffer from a high threshold power density, but interband cascade lasers may offer a more efficient alternative. Here, theory and experiments on such emitters demonstrate remarkably low thresholds and power consumption compared to state-of-the-art quantum cascade lasers.
- I. Vurgaftman
- , W.W. Bewley
- & J.R. Meyer
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Photon diffusion near the point-of-entry in anisotropically scattering turbid media
Optical imaging and spectroscopy rely on understanding how light enters and propagates through turbid media, yet its behaviour near the point-of-entry has remained elusive. Now Vitkinet al. report an analytical solution to this problem and demonstrate its agreement with simulations and experiments.
- Edward Vitkin
- , Vladimir Turzhitsky
- & Lev T. Perelman
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Band structure engineering in (Bi1−xSbx)2Te3 ternary topological insulators
The unique band structure of topological insulators gives rise to insulating bulk and unusual metallic surface properties. By tuning the content of Sb in the ternary compound (Bi1–xSbx)2Te3, Wang and collaborators show it is possible to control the precise features of the band structure in a continuous fashion.
- Jinsong Zhang
- , Cui-Zu Chang
- & Yayu Wang
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A complex multi-notch astronomical filter to suppress the bright infrared sky
The night sky viewed from Earth is very bright at infrared wavelengths due to atmospheric emission, making land-based astronomy difficult in this spectral region. Here, a photonic filter is demonstrated to suppress this unwanted light, opening new paths to infrared astronomy with current and future telescopes.
- J. Bland-Hawthorn
- , S.C. Ellis
- & C. Trinh
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Spin waves and magnetic exchange interactions in insulating Rb0.89Fe1.58Se2
Unlike the other iron-based superconductors, the parent compounds of the alkaline iron selenide superconductors are insulators. Dai and colleagues examine the spin-wave excitations in these materials and uncover evidence for a common magnetic origin for all iron-based superconductors.
- Miaoyin Wang
- , Chen Fang
- & Pengcheng Dai
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Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures
Magnetic resonance force microscopy is a scanning probe technique capable of detecting and imaging electron spins. Vinanteet al.bring the operating temperature of this method into the millikelvin temperature regime, revealing spin diffusion phenomena that were hitherto inaccessible.
- A. Vinante
- , G. Wijts
- & T.H. Oosterkamp
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Low-concentration mechanical biosensor based on a photonic crystal nanowire array
Nanomechanical resonators are attractive as ultra-low concentration sensors of biomolecules, as their small scale allows for sensitive mass detection. Here, using a nanowire array as part of a photonic crystal, such a device is presented for light trapping, absorption and low-concentration sensing.
- Yuerui Lu
- , Songming Peng
- & Amit Lal
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| Open AccessObservation of an anomalous decoherence effect in a quantum bath at room temperature
Quantum objects are subject to decoherence effects due to the surrounding environment. This study demonstrates experimentally a counterintuitive example of anomalous decoherence, in which electron spins residing at nitrogen vacancy centres in diamond display longer coherence times under stronger noises.
- Pu Huang
- , Xi Kong
- & Jiangfeng Du
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| Open AccessGraphene chiral liquid crystals and macroscopic assembled fibres
Chiral liquid crystals of two-dimensional colloids have not been extensively investigated. Xu and Gao show that graphene oxide can form chiral liquid crystals, and demonstrate that they can be spun into macroscopic fibres, and that subsequent chemical reduction provides graphene fibres with high conductivity.
- Zhen Xu
- & Chao Gao
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Plasmon resonance enhanced multicolour photodetection by graphene
Among the wide range of potential applications of graphene, photodetection is believed to be among the most promising. By combining graphene with plasmonic nanostructures, Duan and colleagues observe dramatic improvements in the efficiency and spectral sensitivity of graphene-based photodetectors.
- Yuan Liu
- , Rui Cheng
- & Xiangfeng Duan
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| Open AccessGate-tuned normal and superconducting transport at the surface of a topological insulator
Topological insulators are a unique class of materials characterized by exotic metallic states at their surface, while remaining insulated in the bulk. Sacépéet al. show how to manipulate normal and superconducting electronic transport at the surface of the topological insulator Bi2Se3, by tuning a gate-voltage to vary the electronic density.
- Benjamin Sacépé
- , Jeroen B. Oostinga
- & Alberto F. Morpurgo
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Three-dimensional high-resolution quantitative microscopy of extended crystals
X-ray ptychography has been used to extend the field of view in high-resolution quantitative imaging. Godardet al. develop Bragg-mode ptychography to reconstruct, in three dimensions, a crystalline specimen that is too large to be studied as a single object with a coherence-limited X-ray beam.
- P. Godard
- , G. Carbone
- & V. Chamard
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| Open AccessSuppression of the intrinsic stochastic pinning of domain walls in magnetic nanostripes
The propagation of magnetic domain walls in nanowires offers promise as the basis of future memory storage technologies. Muñoz and Prieto show that the random pinning of domain walls to structural defects in the nanowires can be suppressed at low fields, thus improving the reliability of the transmission of the domain walls substantially.
- Manuel Muñoz
- & José L. Prieto
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Towards hybrid superlattices in graphene
The controllable modification of graphene by chemical functionalization can modulate its optical and electronic properties. Sunet al. devise a functionalisation-based method to pattern graphane/graphene superlattices within a single sheet of graphene.
- Zhengzong Sun
- , Cary L. Pint
- & James M. Tour
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Charge density waves in the graphene sheets of the superconductor CaC6
Charge density waves in the structure and electron density of layered materials are closely linked to superconductivity. Using scanning tunnelling techniques, Rahnejatet al. demonstrate the occurrence of such waves in the doped graphene sheets of the superconductor CaC6.
- K.C. Rahnejat
- , C.A. Howard
- & M. Ellerby
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| Open AccessIntegrated photonic quantum gates for polarization qubits
As quantum information processing continues to develop apace, the need for integrated photonic devices becomes ever greater for both fundamental measurements and technological applications. To this end, Crespiet al.demonstrate a high-fidelity photonic controlled-NOT gate on a glass chip.
- Andrea Crespi
- , Roberta Ramponi
- & Paolo Mataloni
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Concurrent transition of ferroelectric and magnetic ordering near room temperature
Magnetoelectric materials combine ferroelectric and magnetic properties through a coupling of the spin and lattice degrees of freedom. Here, magnetoelectric bismuth ferrite is found to simultaneously undergo both a magnetic and a ferroelectric transition at the same temperature.
- Kyung-Tae Ko
- , Min Hwa Jung
- & Chan-Ho Yang
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High pressure partially ionic phase of water ice
Dissociation of ice into an ionic solid is rare due to the high energy cost of proton transfer. In this study, structure search simulation is used to predict the formation of a partially ionic phase in ice at low temperature and high pressure, which consists of coupled alternate layers of hydroxide and hydronium.
- Yanchao Wang
- , Hanyu Liu
- & Yanming Ma
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| Open AccessExperimental loss-tolerant quantum coin flipping
When two spatially separated parties flip a coin, it is impossible to choose between two alternatives in an unbiased manner. This study presents a quantum coin-flipping protocol that overcomes this problem and ensures a dishonest party cannot bias the outcome completely.
- Guido Berlín
- , Gilles Brassard
- & Wolfgang Tittel
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| Open AccessA new regime for mechanical annealing and strong sample-size strengthening in body centred cubic molybdenum
Mechanical annealing is a process through which the dislocation density in submicrometre metal crystals can be removed purely by applying a mechanical stress. This study shows that mechanical annealing occurs in body centred cubic molybdenum, and not only in face centred crystals as previously thought.
- Ling Huang
- , Qing-Jie Li
- & Evan Ma
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| Open AccessCoupling artificial molecular spin states by photon-assisted tunnelling
Tunnelling transitions triggered by microwave irradiation between coupled quantum dots have generally been assumed to be spin-conserving. This study shows that this condition is violated in the presence of spin–orbit coupling, thus opening new possibilities for manipulating a two–spin qubit system by microwave irradiation.
- L.R. Schreiber
- , F.R. Braakman
- & L.M.K. Vandersypen
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Experimental generation of an eight-photon Greenberger–Horne–Zeilinger state
Generation of multipartite entanglement between quantum states is crucial for developing quantum computation systems, although it has proven harder to achieve for photons than ions. Here, an eight-photon entangled state based on four independent photon pairs is observed, beating the previous record of six.
- Yun-Feng Huang
- , Bi-Heng Liu
- & Guang-Can Guo
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| Open AccessHigh-density magnetoresistive random access memory operating at ultralow voltage at room temperature
Magnetoresistive random access memory offers significant promise as a next-generation memory technology. Nan and colleagues present a design concept for a device that simultaneously possesses ultrahigh storage capacity, ultralow power dissipation, and high-speed operation at room temperature.
- Jia-Mian Hu
- , Zheng Li
- & Ce-Wen Nan
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Copper hexacyanoferrate battery electrodes with long cycle life and high power
Batteries that operate at high power and cycling efficiencies could facilitate the development of large-scale energy storage systems. Wessellset al.report a metal–organic framework electrode that operates in an inexpensive aqueous electrolyte with excellent capacity retention over a very large number of cycles.
- Colin D. Wessells
- , Robert A. Huggins
- & Yi Cui
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| Open AccessElectric field-induced chemical locomotion of conducting objects
External electric fields have been used to control the motion of small objects through electrostatic repulsion. Here, electric fields are used to polarize conducting objects, triggering their movement by spatially separated electrochemical reactions leading to directionally controlled bubble evolution.
- Gabriel Loget
- & Alexander Kuhn
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Ultrafast direct modulation of a single-mode photonic crystal nanocavity light-emitting diode
Photonic alternatives to electrical circuits require low energy demand and fast modulation speed, which has proven difficult for on-chip devices. Using quantum dot photonic crystal nanocavities, Vučkovićet al. demonstrate an electrically-switchable light-emitting diode with such capabilities.
- Gary Shambat
- , Bryan Ellis
- & Jelena Vučković
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| Open AccessWide-band quantum interface for visible-to-telecommunication wavelength conversion
Most quantum communication experiments are performed at visible wavelengths, yet practical, long-range schemes need photons in the telecommunications range. Here, down-conversion of a visible photon to the near-infrared is demonstrated, while retaining its entanglement to another visible photon.
- Rikizo Ikuta
- , Yoshiaki Kusaka
- & Nobuyuki Imoto
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| Open AccessPore surface engineering in covalent organic frameworks
Covalent organic frameworks form a porous skeleton with a precise pore size and geometry, but control of the pore surface is challenging. Here, a protocol is introduced for pore surface engineering of covalent organic frameworks, allowing the control of composition and density of organic groups in the pores.
- Atsushi Nagai
- , Zhaoqi Guo
- & Donglin Jiang
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Self-assembly of DNA nanotubes with controllable diameters
DNA nanotubes could be used to transport nano-cargo and incorporated into nano-devices. In this study, rolling circle amplification is used to generate DNA subunits, and their thermodynamic growth results in the formation of nanotubes with a controlled diameter.
- Ofer I. Wilner
- , Ron Orbach
- & Itamar Willner
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Selective dispersion of high purity semiconducting single-walled carbon nanotubes with regioregular poly(3-alkylthiophene)s
Metallic and semiconducting carbon nanotubes generally coexist in 'as-grown' materials. In this study, single-walled nanotubes are sorted using regioregular poly(3-alkylthiophene)s; rational selection of polymers, solvent and temperature allows the selective dispersion of semiconducting carbon nanotubes.
- Hang Woo Lee
- , Yeohoon Yoon
- & Zhenan Bao
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Functionalized arrays of Raman-enhancing nanoparticles for capture and culture-free analysis of bacteria in human blood
Detecting bacteria in clinical samples usually requires culture processes that are time consuming and impede rapid diagnoses. Now, a surface-enhanced Raman spectroscopic method is reported that allows the label- and culture-free detection and analysis of bacteria.
- Ting-Yu Liu
- , Kun-Tong Tsai
- & Yuh-Lin Wang
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A submicron plasmonic dichroic splitter
The miniaturization of optical devices is crucial for their on-chip integration with a variety of technological applications. Here, Liuet al. present an ultracompact beam splitter to control the direction of light through the generation of surface plasmon polaritons.
- John S.Q. Liu
- , Ragip A. Pala
- & Mark L. Brongersma
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Differentially photo-crosslinked polymers enable self-assembling microfluidics
Leaves and tissues contain three-dimensional networks of fluidic channels, but similar artificial self-assembling systems have not yet been produced. Jamalet al. develop methods to produce three-dimensional microfluidic networks with curved geometries from the self-assembly of photopatterned polymers.
- Mustapha Jamal
- , Aasiyeh M. Zarafshar
- & David H. Gracias
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Direct stereoselective α-arylation of unmodified enals using an organocatalytic cross-coupling-like reaction
Cross-coupling reactions are widely used for creating new carbon–carbon bonds in chemical syntheses. Using the cross-coupling concept, Wang and colleagues present an organocatalytic strategy for the direct and stereoselective α-arylation of enals that occurs under mild conditions.
- Xixi Song
- , Aiguo Song
- & Wei Wang