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topological phases

Mahesh S Deshmukh, Atul Chaudhary, Pavel N Zolotarev, Ramamoorthy Boomishankar
A novel three-dimensional coordination network 1 in a new 4,5,6-connected topology (4,5,6T115) built from linear Cu(II)4Cl3(H2O)2 clusters and tetrahedral tetrakis(3-pyridyl)vinylsilane ligands is reported. Utilizing a similar tetrahedral ligand, tetrakis(3-pyridyl)ethylsilane, a different framework 2 having Cu(II)2Cl(H2O)2 clusters is obtained in tcs topology. The activated sample of 1 shows an excellent and reversible uptake of I2 in solid as well as in solution phases owing to the presence of uncoordinated chloride ions and electron rich vinylic groups in it...
September 21, 2017: Inorganic Chemistry
A A Zibrov, C Kometter, H Zhou, E M Spanton, T Taniguchi, K Watanabe, M P Zaletel, A F Young
Non-Abelian anyons are a type of quasiparticle with the potential to encode quantum information in topological qubits protected from decoherence. Experimental systems that are predicted to harbour non-Abelian anyons include p-wave superfluids, superconducting systems with strong spin-orbit coupling, and paired states of interacting composite fermions that emerge at even denominators in the fractional quantum Hall (FQH) regime. Although even-denominator FQH states have been observed in several two-dimensional systems, small energy gaps and limited tunability have stymied definitive experimental probes of their non-Abelian nature...
September 20, 2017: Nature
Solomon Owerre, Joachim Nsofini
Quantum information storage using charge-neutral quasiparticles are expected to play a crucial role in the future of quantum computers. In this regard, magnons or collective spin-wave excitations in solid-state materials are promising candidates in the future of quantum computing. Here, we study the quantum squeezing of Dirac and topological magnons in a bosonic honeycomb optical lattice with spin-orbit interaction by utilizing the mapping to quantum spin-$1/2$ XYZ Heisenberg model on the honeycomb lattice with discrete Z$_2$ symmetry and a Dzyaloshinskii-Moriya interaction...
September 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Rose D Bharath, Rajanikant Panda, Venkateswara Reddy Reddam, M V Bhaskar, Suril Gohel, Sujas Bhardwaj, Arvind Prajapati, Pramod Kumar Pal
Background and Purpose: Repetitive transcranial magnetic stimulation (rTMS) induces widespread changes in brain connectivity. As the network topology differences induced by a single session of rTMS are less known we undertook this study to ascertain whether the network alterations had a small-world morphology using multi-modal graph theory analysis of simultaneous EEG-fMRI. Method: Simultaneous EEG-fMRI was acquired in duplicate before (R1) and after (R2) a single session of rTMS in 14 patients with Writer's Cramp (WC)...
2017: Frontiers in Human Neuroscience
Simin Nie, Gang Xu, Fritz B Prinz, Shou-Cheng Zhang
Recognized as elementary particles in the standard model, Weyl fermions in condensed matter have received growing attention. However, most of the previously reported Weyl semimetals exhibit rather complicated electronic structures that, in turn, may have raised questions regarding the underlying physics. Here, we report promising topological phases that can be realized in specific honeycomb lattices, including ideal Weyl semimetal structures, 3D strong topological insulators, and nodal-line semimetal configurations...
September 19, 2017: Proceedings of the National Academy of Sciences of the United States of America
Shikha Gupta, Nikita Basant
Designing of advanced oxidation process (AOP) requires knowledge of the aqueous phase hydroxyl radical ((●)OH) reactions rate constants (k OH), which are strictly dependent upon the pH and temperature of the medium. In this study, pH- and temperature-dependent quantitative structure-property relationship (QSPR) models based on the decision tree boost (DTB) approach were developed for the prediction of k OH of diverse organic contaminants following the OECD guidelines. Experimental datasets (n = 958) pertaining to the k OH values of aqueous phase reactions at different pH (n = 470; 1...
September 16, 2017: Environmental Science and Pollution Research International
A Moussawi, N Derzsy, X Lin, B K Szymanski, G Korniss
Cascading failures are a critical vulnerability of complex information or infrastructure networks. Here we investigate the properties of load-based cascading failures in real and synthetic spatially-embedded network structures, and propose mitigation strategies to reduce the severity of damages caused by such failures. We introduce a stochastic method for optimal heterogeneous distribution of resources (node capacities) subject to a fixed total cost. Additionally, we design and compare the performance of networks with N-stable and (N-1)-stable network-capacity allocations by triggering cascades using various real-world node-attack and node-failure scenarios...
September 15, 2017: Scientific Reports
Piotr Konieczny, Robert Pełka, Dominik Czernia, Robert Podgajny
Conventional (MCE) and rotating (RMCE) magnetocaloric effects have been explored in the two-dimensional (2D) coordination polymer {(tetren)H5)0.8Cu(II)4[W(V)(CN)8]4·7.2H2O}n (WCu-t; tetren = tetraethylenepentamine). The unusual magnetostructural properties were exploited, including the bilayered Prussian Blue like coordination skeleton and the XY easy-plane magnetic anisotropy based on the in-plane correlation between W(V) and Cu(II) spins of (1)/2, underlying the Berezinskii-Kosterlitz-Thouless (BKT) topological phase transition to the long-range-ordered state at TC = 33 K...
September 15, 2017: Inorganic Chemistry
Jun Chen, Peng Yu, John Stenger, Moïra Hocevar, Diana Car, Sébastien R Plissard, Erik P A M Bakkers, Tudor D Stanescu, Sergey M Frolov
Topological superconductivity is an exotic state of matter characterized by spinless p-wave Cooper pairing of electrons and by Majorana zero modes at the edges. The first signature of topological superconductivity is a robust zero-bias peak in tunneling conductance. We perform tunneling experiments on semiconductor nanowires (InSb) coupled to superconductors (NbTiN) and establish the zero-bias peak phase in the space of gate voltage and external magnetic field. Our findings are consistent with calculations for a finite-length topological nanowire and provide means for Majorana manipulation as required for braiding and topological quantum bits...
September 2017: Science Advances
Alexandra de Sitter, Martijn D Steenwijk, Aurélie Ruet, Adriaan Versteeg, Yahou Liu, Ronald A van Schijndel, Petra J W Pouwels, Iris D Kilsdonk, Keith S Cover, Bob W van Dijk, Stefan Ropele, Maria A Rocca, Marios Yiannakas, Mike P Wattjes, Soheil Damangir, Giovanni B Frisoni, Jaume Sastre-Garriga, Alex Rovira, Christian Enzinger, Massimo Filippi, Jette Frederiksen, Olga Ciccarelli, Ludwig Kappos, Frederik Barkhof, Hugo Vrenken
BACKGROUND AND PURPOSE: In vivoidentification of white matter lesions plays a key-role in evaluation of patients with multiple sclerosis (MS). Automated lesion segmentation methods have been developed to substitute manual outlining, but evidence of their performance in multi-center investigations is lacking. In this work, five research-domain automated segmentation methods were evaluated using a multi-center MS dataset. METHODS: 70 MS patients (median EDSS of 2...
September 9, 2017: NeuroImage
Yunwei Zhang, Weikang Wu, Yanchao Wang, Shengyuan A Yang, Yanming Ma
High pressure is able to modify profoundly the chemical bonding and generate new phase structures of materials with chemical and physical properties not accessible at ambient conditions. We here report an unprecedented phenomenon on the pressure-induced formation of semiconducting electrides via compression of layered alkaline-earth subnitrides Ca2N, Sr2N and Ba2N that are conducting electrides with loosely confined electrons in the interlayer voids at ambient pressure. Our extensive first-principles swarm structure searches identified the high-pressure semiconducting electride phases of a tetragonal I-42d structure for Ca2N and a monoclinic Cc structure shared by Sr2N and Ba2N, both of which contain atomic-size cavities with paring electrons distributed in...
September 12, 2017: Journal of the American Chemical Society
Stavros I Dimitriadis, Marios Antonakakis, Panagiotis Simos, Jack M Fletcher, Andrew C Papanicolaou
In the present study a novel data-driven topological filtering technique is introduced to derive the backbone of functional brain networks relying on orthogonal minimal spanning trees (OMST). The method aims to identify the essential functional connections to ensure optimal information flow via the objective criterion of global efficiency minus the cost of surviving connections. The OMST technique was applied to multichannel, resting-state neuromagnetic recordings from four groups of participants: healthy adults (n=50), adults who have suffered mild traumatic brain injury (n=30), typically developing children (n=27), and reading-disabled children (n=25)...
September 11, 2017: Brain Connectivity
Chao Chen, Fanxing Kong, Xiaohu Wei, San H Thang
In this study, a series of functional peptide-based RAFT agents were designed and synthesized by the solid-phase supported peptide synthesis method. These novel RAFT agents have enabled chemists to make well-defined peptide-polymer conjugates with complicated topological structures. Additionally, our results have shown an unexpected reaction that takes place during these syntheses, and the conversion of a nitrile group to a carboxamide group has been evidently elucidated and unambiguously confirmed.
September 11, 2017: Chemical Communications: Chem Comm
Ruey-Song Huang, Ching-Fu Chen, Martin I Sereno
The macaque monkey ventral intraparietal area (VIP) contains neurons with aligned visual-tactile receptive fields anchored to the face and upper body. Our previous fMRI studies using standard head coils found a human parietal face area (VIP + complex; putative macaque VIP homologue) containing superimposed topological maps of the face and near-face visual space. Here, we construct high signal-to-noise surface coils and used phase-encoded air puffs and looming stimuli to map topological organization of the parietal face area at higher resolution...
September 6, 2017: NeuroImage
Warren Fon, Matthew H Matheny, Jarvis Li, Lev Krayzman, Michael C Cross, Raissa M D'Souza, James P Crutchfield, Michael L Roukes
Control of the global parameters of complex networks has been explored experimentally in a variety of contexts. Yet, the more difficult prospect of realizing arbitrary network architectures, especially analog physical networks that provide dynamical control of individual nodes and edges, has remained elusive. Given the vast hierarchy of time scales involved, it also proves challenging to measure a complex network's full internal dynamics. These span from the fastest nodal dynamics to very slow epochs over which emergent global phenomena, including network synchronization and the manifestation of exotic steady states, eventually emerge...
September 21, 2017: Nano Letters
Qingyun Yu, Ze Tao, Juntao Song, Y C Tao, Jun Wang
The narrow quantum spin Hall (QSH) insulator is characterized by interedge coupling, which could feature exotic transport phenomena, and thus serves as the key element for topological superconducting electronic devices. Herein, we theoretically explore possible Josephson π states in a QSH insulator strip touching on two s-wave superconductors in the presence of the interedge coupling. It is shown that the interedge coupling could give rise to a 0 - π transition modulated by the gate voltage, originating from an additional π phase difference caused by the interedge backscattering...
September 6, 2017: Scientific Reports
Xiao Li, José A Martínez-González, Juan P Hernández-Ortiz, Abelardo Ramírez-Hernández, Ye Zhou, Monirosadat Sadati, Rui Zhang, Paul F Nealey, Juan J de Pablo
Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed...
September 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Zhenwei Yao
Understanding geometric frustration of ordered phases in two-dimensional condensed matter on curved surfaces is closely related to a host of scientific problems in condensed matter physics and materials science. Here, we show how two-dimensional Lennard-Jones crystal clusters confined on a sphere resolve geometric frustration and form pentagonal vacancy structures. These vacancies, originating from the combination of curvature and physical interaction, are found to be topological defects and they can be further classified into dislocational and disclinational types...
September 4, 2017: Soft Matter
Liang Gong, Zhenghua Hou, Zan Wang, Cancan He, Yingying Yin, Yonggui Yuan, Haisan Zhang, Luxian Lv, Hongxing Zhang, Chunming Xie, Zhijun Zhang
BACKGROUND: Graph theoretical analyses have identified disrupted functional topological organization across the brain in patients with major depressive disorder (MDD). However, the relationship between brain topology and short-term treatment responses in patients with MDD remains unknown. METHODS: Sixty-eight patients with MDD and 63 cognitively normal (CN) subjects were recruited at baseline and underwent resting-state functional magnetic resonance imaging scans...
August 31, 2017: Journal of Affective Disorders
Debsankha Manik, Marc Timme, Dirk Witthaut
We study multistability in phase locked states in networks of phase oscillators under both Kuramoto dynamics and swing equation dynamics-a popular model for studying coarse-scale dynamics of an electrical AC power grid. We first establish the existence of geometrically frustrated states in such systems-where although a steady state flow pattern exists, no fixed point exists in the dynamical variables of phases due to geometrical constraints. We then describe the stable fixed points of the system with phase differences along each edge not exceeding π/2 in terms of cycle flows-constant flows along each simple cycle-as opposed to phase angles or flows...
August 2017: Chaos
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