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Semih Cetindag, Bishnu Tiwari, Dongyan Zhang, Yoke Khin Yap, Sangil Kim, Jerry W Shan
The alignment of hexagonal boron-nitride nanotubes (BNNTs) in aqueous KCl solutions under spatially uniform electric fields was examined experimentally, using direct optical visualization to probe the orientation dynamics of individual BNNTs for different electric-field frequencies. Different from most previously studied nanowires and nanotubes, BNNTs are wide-bandgap materials which are essentially insulating at room temperature. We analyze the electro-orientation of BNNTs in the general context of polarizable cylindrical particles in liquid suspensions, whose behavior can fall into different regimes, including alignment due to Maxwell-Wagner induced dipoles at high frequencies, and alignment due to fluid motion of the electrical double layer around the particles at lower frequencies...
May 29, 2017: Journal of Colloid and Interface Science
Shreya Vardhan, Giuseppe De Tomasi, Markus Heyl, Eric J Heller, Frank Pollmann
We study the effects of local perturbations on the dynamics of disordered fermionic systems in order to characterize time irreversibility. We focus on three different systems: the noninteracting Anderson and Aubry-André-Harper (AAH) models and the interacting spinless disordered t-V chain. First, we consider the effect on the full many-body wave functions by measuring the Loschmidt echo (LE). We show that in the extended or ergodic phase the LE decays exponentially fast with time, while in the localized phase the decay is algebraic...
July 7, 2017: Physical Review Letters
Minoru Kawamura, Ryutaro Yoshimi, Atsushi Tsukazaki, Kei S Takahashi, Masashi Kawasaki, Yoshinori Tokura
The instability of the quantum anomalous Hall (QAH) effect has been studied as a function of the electric current and temperature in ferromagnetic topological insulator thin films. We find that a characteristic current for the breakdown of the QAH effect is roughly proportional to the Hall-bar width, indicating that the Hall electric field is relevant to the breakdown. We also find that electron transport is dominated by variable range hopping (VRH) at low temperatures. Combining the current and temperature dependences of the conductivity in the VRH regime, the localization length of the QAH state is evaluated to be about 5  μm...
July 7, 2017: Physical Review Letters
Bruno Mera, Chrysoula Vlachou, Nikola Paunković, Vítor R Vieira
We study the behavior of the Uhlmann connection in systems of fermions undergoing phase transitions. In particular, we analyze some of the paradigmatic cases of topological insulators and superconductors in one dimension, as well as the BCS theory of superconductivity in three dimensions. We show that the Uhlmann connection signals phase transitions in which the eigenbasis of the state of the system changes. Moreover, using the established fidelity approach and the study of the edge states, we show the absence of thermally driven phase transitions in the case of topological insulators and superconductors...
July 7, 2017: Physical Review Letters
Michael J Klein, Gabriel M Veith, Arumugam Manthiram
Lithium sulfide (Li2S) is under intense study because it is the insulating discharge product of ultra-high energy density lithium-sulfur (Li-S) batteries and a candidate cathode material for lithium metal-free Li-S cells. In this work, we report the fabrication of an apparatus for sputter deposition of Li2S films ranging in thickness from a few nanometers to several microns at rates over 2 nm min-1. High-temperature annealing of the films is shown to produce crystalline films of high chemical purity Li2S for the first time...
July 21, 2017: Journal of the American Chemical Society
Tobias Meier, Rémy Pawlak, Shigeki Kawai, Yan Geng, Xunshan Liu, Silvio Decurtins, Prokop Hapala, Alexis Baratoff, Shi-Xia Liu, Pavel Jelinek, Ernst Meyer, Thilo Glatzel
Electron donor-acceptor molecules are of outstanding interest in molecular electronics and organic solar cells for their intramolecular charge transfer controlled via electrical or optical excitation. The preservation of their electronic character in the ground state upon adsorption on a surface is cardinal for their implementation in such single-molecule devices. Here, we investigate by atomic force microscopy and scanning tunneling microscopy a prototypical system consisting of a π-conjugated tetrathiafulvalene-fused dipyridophenazine molecule adsorbed on thin NaCl films on Cu(111)...
July 21, 2017: ACS Nano
Anthony Knap, Nicholas R Turner, Gopal Bera, D Abigail Renegar, Tamara Frank, Jose Sericano, Bernhard M Riegl
There are few studies that have evaluated hydrocarbon toxicity to vertically migrating deep-sea micronekton. Crustaceans were collected alive using a 9 m(2) Tucker trawl with a thermally insulated cod end and returned to the laboratory in 10 °C seawater. Toxicity of the polycyclic aromatic hydrocarbon 1-methylnapthalene to Americamysis bahia, Janicella spinacauda, Systellaspis debilis, Sergestes sp., Sergia sp., and a euphausid sp. was assessed in a constant exposure toxicity test utilizing a novel passive dosing toxicity testing protocol...
July 21, 2017: Environmental Toxicology and Chemistry
A-S Pawlik, T Kämpfe, A Haußmann, T Woike, U Treske, M Knupfer, B Büchner, E Soergel, R Streubel, A Koitzsch, L M Eng
Conducting domain walls (CDWs) in ferroelectric materials are promising candidates for applications in a manifold of nanoscale, optoelectronic devices. Characterization of their microscopic properties, however, remains challenging due to their small dimension and highly insulating environment. Here, we inspect individual CDWs in single-crystalline LiNbO3 by the combination of photoemission electron microscopy (PEEM) and second harmonic generation (SHG) microscopy. While SHG unveils the overall domain wall inclination angle α, PEEM is sensitive to local conductance variations, both at and away from the domain wall...
July 21, 2017: Nanoscale
Shunfeng Wang, Junyong Wang, Weijie Zhao, Francesco Giustiniano, Leiqiang Chu, Ivan Verzhbitskiy, Justin Zhou Yong, Goki Eda
We report on efficient carrier-to-exciton conversion and planer electroluminescence from tunnel diodes based on a metal-insulator-semiconductor van der Waals heterostack consisting of few-layer graphene (FLG), hexagonal boron nitride (hBN), and monolayer tungsten disulfide (WS2). These devices exhibit excitonic electroluminescence with extremely low threshold current density of a few pA∙μm-2, which is several orders of magnitude lower compared to the previously reported values for the best planar EL devices...
July 21, 2017: Nano Letters
Haoming Fang, Yunhong Zhao, Yafei Zhang, Yanjuan Ren, Shulin Bai
In order to meet the increasing demands for effective heat management of electronic devices, graphene based polymeric composite is considered to be one of the candidate materials due to the ultrahigh thermal conductivity of graphene. However, poor graphene dispersion, low quality of exfoliated graphene and strong phonon scattering at graphene/matrix interface restrict the heat dissipation ability of graphene filled composites. Here, a facile and versatile approach to bond graphene foam (GF) with polydimethylsiloxane (PDMS) is proposed and the corresponding composite with considerable improvement of thermal conductivity and insulativity is fabricated...
July 21, 2017: ACS Applied Materials & Interfaces
Qing Lin He, Lei Pan, Alexander L Stern, Edward C Burks, Xiaoyu Che, Gen Yin, Jing Wang, Biao Lian, Quan Zhou, Eun Sang Choi, Koichi Murata, Xufeng Kou, Zhijie Chen, Tianxiao Nie, Qiming Shao, Yabin Fan, Shou-Cheng Zhang, Kai Liu, Jing Xia, Kang L Wang
Majorana fermion is a hypothetical particle that is its own antiparticle. We report transport measurements that suggest the existence of one-dimensional chiral Majorana fermion modes in the hybrid system of a quantum anomalous Hall insulator thin film coupled with a superconductor. As the external magnetic field is swept, half-integer quantized conductance plateaus are observed at the locations of magnetization reversals, giving a distinct signature of the Majorana fermion modes. This transport signature is reproducible over many magnetic field sweeps and appears at different temperatures...
July 21, 2017: Science
Saipriya Tewari, Anil Agarwal, Sujeet K Gautam, Rajashree Madabushi
Our intent is to report a case of intercostal neuralgia occuring as a complication of splanchnic radiofreqency ablation (RFA), due to a breach in the integrity of the insulating sheath of the RFA needle.A 48-year-old man presented to our pain clinic with upper abdominal pain due to chronic pancreatitis, recalcitrant to medical management. We decided to perform bilateral splanchnic nerve RFA in this patient. After confirmation of bilateral correct needle placement under fluoroscopic guidance and sensorimotor testing, RFA was performed on the right side uneventfully...
July 2017: Pain Physician
Barry Bradlyn, L Elcoro, Jennifer Cano, M G Vergniory, Zhijun Wang, C Felser, M I Aroyo, B Andrei Bernevig
Since the discovery of topological insulators and semimetals, there has been much research into predicting and experimentally discovering distinct classes of these materials, in which the topology of electronic states leads to robust surface states and electromagnetic responses. This apparent success, however, masks a fundamental shortcoming: topological insulators represent only a few hundred of the 200,000 stoichiometric compounds in material databases. However, it is unclear whether this low number is indicative of the esoteric nature of topological insulators or of a fundamental problem with the current approaches to finding them...
July 19, 2017: Nature
Siming Ren, Mingjun Cui, Jibin Pu, Qunji Xue, Liping Wang
Boron nitride (BN) monolayer (1L) with high impermeability and resistivity seems to hold promise as a long-term corrosion barrier for Cu at ambient condition, which is supported by recent researches. Here we perform a complete study of the alternating temperature tests (the sample is exposed in air for 30 days and subsequently heated at 200 ℃ for 2 h) and electrochemical measurements on 1L and multilayers BN coated Cu foils. Results imply that the BN coated Cu foils are less oxidized than uncoated Cu foil after alternating temperature tests, regardless of the layers of BN...
July 20, 2017: ACS Applied Materials & Interfaces
Cui Zhang, Prabesh Dulal, Bethanie J H Stadler, David C Hutchings
The first experimental TE-mode silicon-on-insulator (SOI) isolators using Faraday Rotation are here realized to fill the 'missing link' in source-integrated near infrared photonic circuits. The isolators are simple 1D 2-element waveguides, where garnet claddings and longitudinal magnetic fields produce nonreciprocal mode conversion, the waveguide equivalent of Faraday Rotation (FR). Quasi-phase matched claddings are used to overcome the limitations of birefringence. Current experimental SOI isolators use nonreciprocal phase shift (NRPS) in interferometers or ring resonators, but to date NRPS requires TM-modes, so the TE-modes normally produced by integrated lasers cannot be isolated without many ancillary polarisation controls...
July 19, 2017: Scientific Reports
Manfred R Enstipp, Charles-André Bost, Céline Le Bohec, Caroline Bost, Yvon Le Maho, Henri Weimerskirch, Yves Handrich
Little is known about the early life at sea of marine top predators, like deep-diving king penguins (Aptenodytes patagonicus), although this dispersal phase is probably a critical phase in their life. Apart from finding favourable foraging sites, they have to develop effective prey search patterns as well as physiological capacities that enable them to capture sufficient prey to meet their energetic needs. To investigate the ontogeny of their thermoregulatory responses at sea, we implanted 30 juvenile king penguins and 8 adult breeders with a small data logger that recorded pressure and subcutaneous temperature continuously for up to 2...
July 15, 2017: Journal of Experimental Biology
Benhu Zhou, Benliang Zhou, Yagang Yao, Guanghui Zhou, Ming Hu
We theoretically calculate spin-dependent transmission probability and spin Seebeck coefficient for a zigzagedge graphene nanoribbon (ZGNR) p-n junction with periodically attached stubs under a perpendicular magnetic field and a ferromagnetic insulator. By using the nonequilibrium Green's function (NEGF) method combining with the tight-binding Hamiltonian, it is demonstrated that, the spin-dependent transmission probability and spin Seebeck coefficient for two types of superlattices can be modulated by the potential drop, the magnetization strength, the number of periods of the superlattice, the strength of the perpendicular magnetic field, and the Anderson disorder strength...
July 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Michele Leduc, Joy Richard, Safia Costes, Dany Muller, Annie Varrault, Vincent Compan, Julia Mathieu, Jean-François Tanti, Gilles Pagès, Jacques Pouyssegur, Gyslaine Bertrand, Stéphane Dalle, Magalie A Ravier
AIMS/HYPOTHESIS: Insufficient insulin secretion from pancreatic beta cells, which is associated with a decrease in beta cell mass, is a characteristic of type 2 diabetes. Extracellular signal-related kinase 1 and 2 (ERK1/2) inhibition in beta cells has been reported to affect insulin secretion, gene transcription and survival, although whether ERK1 and ERK2 play distinct roles is unknown. The aim of this study was to assess the individual roles of ERK1 and ERK2 in beta cells using ERK1 (also known as Mapk3)-knockout mice (Erk1 (-/-) mice) and pharmacological approaches...
July 18, 2017: Diabetologia
Zengtao Bao, Jialin Sun, Xiaoqian Zhao, Zengyao Li, Songkui Cui, Qingyang Meng, Ye Zhang, Tong Wang, Yanfeng Jiang
Sensitive and quantitative detection of tumor markers is highly required in the clinic for cancer diagnosis and consequent treatment. A field-effect transistor-based (FET-based) nanobiosensor emerges with characteristics of being label-free, real-time, having high sensitivity, and providing direct electrical readout for detection of biomarkers. In this paper, a top-down approach is proposed and implemented to fulfill a novel silicon nano-ribbon FET, which acts as biomarker sensor for future clinical application...
2017: International Journal of Nanomedicine
B Leedahl, D W Boukhvalov, E Z Kurmaev, A Kukharenko, I S Zhidkov, N V Gavrilov, S O Cholakh, P Huu Le, C Wei Luo, A Moewes
Topological insulators have become one of the most prominent research topics in materials science in recent years. Specifically, Bi2Te3 is one of the most promising for technological applications due to its conductive surface states and insulating bulk properties. Herein, we contrast the bulk and surface structural environments of dopant ions Cr, Mn, Fe, Co, Ni, and Cu in Bi2Te3 thin films in order to further elucidate this compound. Our measurements show the preferred oxidation state and surrounding crystal environment of each 3d-metal atomic species, and how they are incorporated into Bi2Te3...
July 18, 2017: Scientific Reports
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