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topological phases

Van-Tien Bui, Le Thi Thuy, Joon Sig Choi, Ho-Suk Choi
Three-dimensional (3D) culture dish patterned with a microwell structure demonstrates a great application potential in biotechnology. This study reports on the easy fabrication of an ordered customizable honeycomb microwell array on the surface of polymer substrates including the commercial Petri dish to create a biological platform for cell culture. The fabrication method is based on a very simple solvent dip-coating technique and the methanol accumulation-induced phase separation in which a binary mixture of chloroform and methanol is used to induce a ternary solution and to guarantee the formation of the ordered pore array on the substrate...
November 10, 2017: Journal of Colloid and Interface Science
Guixin Li, Lin Wu, King Fai Li, Shumei Chen, Christian Schlickriede, Zhengji Xu, Siya Huang, Wen-Di Li, Yan Jun Liu, Edwin Yue-Bun Pun, Thomas Zentgraf, Kok Wai Cheah, Yu Luo, Shuang Zhang
The spin and orbital angular momentum (SAM and OAM) of light is providing a new gateway towards high capacity and robust optical communications. While the generation of light with angular momentum is well studied in linear optics, its further integration into nonlinear optical devices will open new avenues for increasing the capacity of optical communications through additional information channels at new frequencies. However, it has been challenging to manipulate the both SAM and OAM of nonlinear signals in harmonic generation processes with conventional nonlinear materials...
November 16, 2017: Nano Letters
Jaime Gómez-Ramírez, Shelagh Freedman, Diego Mateos, José Luis Pérez Velázquez, Taufik Valiante
This paper addresses a fundamental question, are eyes closed and eyes open resting states equivalent baseline conditions, or do they have consistently different electrophysiological signatures? We compare the functional connectivity patterns in an eyes closed resting state with an eyes open resting state to investigate the alpha desynchronization hypothesis. The change in functional connectivity from eyes closed to eyes open, is here, for the first time, studied with intracranial recordings. We perform network connectivity analysis in iEEG and we find that phase-based connectivity is sensitive to the transition from eyes closed to eyes open only in interhemispheral and frontal electrodes...
November 15, 2017: Scientific Reports
Sheng-Shi Li, Wei-Xiao Ji, Shu-Jun Hu, Chang-Wen Zhang, Shi-Shen Yan
Knowledge about chemical functionalization is of fundamental importance to design novel two-dimensional topological insulators. Despite theoretical predictions of quantum spin Hall effect (QSH) insulator via chemical functionalization, it is quite challenging to obtain a high-quality sample, in which the toxicity is also an important factor that cannot be ignored. Herein, using first-principles calculations, we predict an intrinsic QSH effect in amidogen-functionalized Bi/Sb(111) films (SbNH2 and BiNH2), characterized by nontrivial Z2 invariant and helical edge states...
November 15, 2017: ACS Applied Materials & Interfaces
Jan-Philipp Hanke, Frank Freimuth, Chengwang Niu, Stefan Blügel, Yuriy Mokrousov
Reliable and energy-efficient magnetization switching by electrically induced spin-orbit torques is of crucial technological relevance for spintronic devices implementing memory and logic functionality. Here we predict that the strength of spin-orbit torques and the Dzyaloshinskii-Moriya interaction in topologically nontrivial magnetic insulators can exceed by far that of conventional metals. In analogy to the quantum anomalous Hall effect, we explain this extraordinary response in the absence of longitudinal currents as hallmark of monopoles in the electronic structure of systems that are interpreted most naturally within the framework of mixed Weyl semimetals...
November 14, 2017: Nature Communications
Pau Guillamat, Jérôme Hardoüin, Berta M Prat, Jordi Ignés, Francesc Sagues
We present an experimental study of a kinesin/tubulin active nematic formed at different oil interfaces. By tuning the interfacial rheology of the contacting oil, we have been able to condition and control the seemingly chaotic motion that characterizes the self-sustained active flows in our preparations. The active nematic is inherently unstable and spontaneously develops defects from an initial homogeneous state. We show that the steady state and, in particular, the density and dynamics of the defects strongly depends on the rheology of the contacting oil...
November 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Sami A Malek, Francesco Avanzi, Keoma Brun-Laguna, Tessa Maurer, Carlos A Oroza, Peter C Hartsough, Thomas Watteyne, Steven D Glaser
Monitoring the snow pack is crucial for many stakeholders, whether for hydro-power optimization, water management or flood control. Traditional forecasting relies on regression methods, which often results in snow melt runoff predictions of low accuracy in non-average years. Existing ground-based real-time measurement systems do not cover enough physiographic variability and are mostly installed at low elevations. We present the hardware and software design of a state-of-the-art distributed Wireless Sensor Network (WSN)-based autonomous measurement system with real-time remote data transmission that gathers data of snow depth, air temperature, air relative humidity, soil moisture, soil temperature, and solar radiation in physiographically representative locations...
November 9, 2017: Sensors
Yavuz Caydamli, Erol Yildirim, Jialong Shen, Xiaomeng Fang, Melissa A Pasquinelli, Richard J Spontak, Alan E Tonelli
Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants reveal the existence of different macroscopic morphologies and surface topologies...
November 8, 2017: Soft Matter
Kun Zhang
Mesoporous nanospheres are highly regarded for their applications in nanomedicine, optical devices, batteries, nanofiltration and heterogeneous catalysis. In the latter field, the dendritic morphology favoring molecular diffusion is a very important morphology known for silica but not yet for carbon. A one-pot, easy and scalable co-sol-gel route using the triphasic resol-surfactant-silica system is shown to yield the topologies of the title by inner radial phase speciation control on a mass-transfer limited process depending on the relative polycondensation rates of the resol polymer and silica phases...
November 6, 2017: Chemistry: a European Journal
Li-Li Li, Sheng-Lin Qiao, Wei-Jiao Liu, Yang Ma, Dong Wan, Jie Pan, Hao Wang
Topological structures of bio-architectonics and bio-interfaces play major roles in maintaining the normal functions of organs, tissues, extracellular matrix, and cells. In-depth understanding of natural self-assembly mechanisms and mimicking functional structures provide us opportunities to artificially control the natural assemblies and their biofunctions. Here, we report an intracellular enzyme-catalyzed polymerization approach for efficient synthesis of polypeptides and in situ construction of topology-controlled nanostructures...
November 2, 2017: Nature Communications
Vincent Jacquemet
The complexity of cardiac fibrillation dynamics can be assessed by analyzing the distribution of phase singularities (PSs) observed using mapping systems. Interelectrode distance, however, limits the accuracy of PS detection. To investigate in a theoretical framework the PS false negative and false positive rates in relation to the characteristics of the mapping system and fibrillation dynamics, we propose a statistical model of phase maps with controllable number and locations of PSs. In this model, phase maps are generated from randomly distributed PSs with physiologically-plausible directions of rotation...
October 2017: Chaos
Luis A Aguirre, Leonardo L Portes, Christophe Letellier
Observability is the property that enables recovering the state of a dynamical system from a reduced number of measured variables. In high-dimensional systems, it is therefore important to make sure that the variable recorded to perform the analysis conveys good observability of the system dynamics. The observability of a network of neuron models depends nontrivially on the observability of the node dynamics and on the topology of the network. The aim of this paper is twofold. First, to perform a study of observability using four well-known neuron models by computing three different observability coefficients...
October 2017: Chaos
Beiwen Li, Song Zhang
Scientific research of a stabilized flapping flight process (e.g. hovering) has been of great interest to a variety of fields including biology, aerodynamics, and bio-inspired robotics. Different from the current passive photogrammetry based methods, the digital fringe projection (DFP) technique has the capability of performing dense superfast (e.g. kHz) 3D topological reconstructions with the projection of defocused binary patterns, yet it is still a challenge to measure a flapping flight process with the presence of rapid flapping wings...
October 30, 2017: Optics Express
Bryce S Murray, Samo Kralj, Charles Rosenblatt
Nematic cells patterned with square arrays of strength m = ±1 topological defects were examined as a function of cell thickness (3 < h < 7.5 μm), temperature, and applied voltage. Thicker cells tend to exhibit an escape or partial escape of the nematic director as a means of mitigating the elastic energy cost near the defect cores, whereas thinner cells tend to favor splitting of the integer defects into pairs of half-integer strength defects. On heating the sample into the isotropic phase and cooling back into the nematic, some apparently split defects can reappear as unsplit integer defects, or vice versa...
October 30, 2017: Soft Matter
Tonya D Andreeva, Svetla D Petrova, Kirilka Mladenova, Veselina Moskova-Doumanova, Tanya Topouzova-Hristova, Yulia Petseva, Nikola Mladenov, Konstantin Balashev, Zdravko Lalchev, Jordan A Doumanov
Bestrophinopathies are ocular diseases caused by mutations in the human bestrophin-1 (hBest1) - transmembrane Ca(2+)-activated chloride channel protein, mainly expressed in the retinal pigment epithelium (RPE) cells. hBest1 is also an important transporter for neurotransmitters such as glutamate (Glu) and γ-aminobutyric acid (GABA) in the nervous system. Recently, a new biological role of hBest1, related to its possible involvement in the pathology of brain diseases (Alzheimer's, Parkinson's disease) has been proposed...
October 18, 2017: Colloids and Surfaces. B, Biointerfaces
Pablo Ares, Juan José Palacios, Gonzalo Abellán, Julio Gómez-Herrero, Félix Zamora
Antimonene, defined in sensu stricto as a single layer of antimony atoms, is recently the focus of numerous theoretical works predicting a variety of interesting properties and is quickly attracting the attention of the scientific community. However, what places antimonene in a different category from other 2D crystals is its strong spin-orbit coupling and a drastic evolution of its properties from the monolayer to the few-layer system. The recent isolation of this novel 2D material pushes the interest for antimonene even further...
October 27, 2017: Advanced Materials
Ming Yang, Yong Zheng Luo, Ming Gang Zeng, Lei Shen, Yun Hao Lu, Jun Zhou, Shi Jie Wang, Iam Keong Sou, Yuan Ping Feng
A large bulk band gap and tunable Dirac carriers are desired for practical device applications of topological insulators. However, most known topological insulators are narrow gap materials and the manipulation of their Dirac surface states is limited by residual bulk charge carriers originating from intrinsic defects. In this study, via density functional theory based first-principles calculations, we predict that a layered hexagonal structure of Bi2S3 is stable, and it becomes a topological insulator under a moderate compressive pressure of about 5...
November 8, 2017: Physical Chemistry Chemical Physics: PCCP
Natália Menezes, Giandomenico Palumbo, Cristiane Morais Smith
It has been shown that local four-fermion interactions on the edges of two-dimensional time-reversal-invariant topological insulators give rise to a new non-Fermi-liquid phase, called helical Luttinger liquid (HLL). Here, we provide a first-principle derivation of this HLL based on the gauge-theory approach. We start by considering massless Dirac fermions confined on the one-dimensional boundary of the topological insulator and interacting through a three-dimensional quantum dynamical electromagnetic field...
October 26, 2017: Scientific Reports
D N Basov, R D Averitt, D Hsieh
The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities...
October 25, 2017: Nature Materials
Qi Zhang, Lin Xie, Guangqing Liu, Sergei Prokhorenko, Yousra Nahas, Xiaoqing Pan, Laurent Bellaiche, Alexei Gruverman, Nagarajan Valanoor
Observation of a new type of nanoscale ferroelectric domains, termed as "bubble domains"-laterally confined spheroids of sub-10 nm size with local dipoles self-aligned in a direction opposite to the macroscopic polarization of a surrounding ferroelectric matrix-is reported. The bubble domains appear in ultrathin epitaxial PbZr0.2 Ti0.8 O3 /SrTiO3 /PbZr0.2 Ti0.8 O3 ferroelectric sandwich structures due to the interplay between charge and lattice degrees of freedom. The existence of the bubble domains is revealed by high-resolution piezoresponse force microscopy (PFM), and is corroborated by aberration-corrected atomic-resolution scanning transmission electron microscopy mapping of the polarization displacements...
October 24, 2017: Advanced Materials
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