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Hisham A Abdel-Aal
Squamate reptiles (around 10,000 species of snakes and lizards) comprise a myriad of distinct terrestrial vertebrates. The diversity within this biological group offers a great opportunity for customized bio-inspired solutions that address a variety of current technological problems especially within the realm of surface engineering and tribology. One subgroup within squamata is of interest in that context, namely the legless reptiles (mainly snakes and few lizards). The promise of that group lies within their functional adaptation as manifested in optimized surface designs and locomotion that is distinguished by economy of effort even when functioning within hostile tribological environments...
November 8, 2017: Journal of the Mechanical Behavior of Biomedical Materials
Yu Bi, Ming-Fang Zhang, Jing Xue, Ran Dong, Yun-Peng Du, Xiu-Hai Zhang
The genus Fritillaria comprises approximately 130 perennial herbaceous species. In the Pharmacopoeia of the People's Republic of China, the bulbs of 11 Fritillaria species are used in Chinese herbal medicines. However, the traditional methods of morphological classification cannot accurately identify closely related species of Fritillaria. Previous studies have attempted to identify these species with universal molecular markers, but insufficient phylogenetic signal was available. In this study, the complete chloroplast genomes of eight Fritillaria species were compared...
January 19, 2018: Scientific Reports
Aniruddha Sahasrabuddhe, Yang Hsia, Florian Busch, William Sheffler, Neil P King, David Baker, Vicki H Wysocki
Computational protein design provides the tools to expand the diversity of protein complexes beyond those found in nature. Understanding the rules that drive proteins to interact with each other enables the design of protein-protein interactions to generate specific protein assemblies. In this work, we designed protein-protein interfaces between dimers and trimers to generate dodecameric protein assemblies with dihedral point group symmetry. We subsequently analyzed the designed protein complexes by native MS...
January 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
Cristhian Iza-Paredes, Ahmad Mohamad Mezher, Mónica Aguilar Igartua, Jordi Forné
Road safety applications envisaged for Vehicular Ad Hoc Networks (VANETs) depend largely on the dissemination of warning messages to deliver information to concerned vehicles. The intended applications, as well as some inherent VANET characteristics, make data dissemination an essential service and a challenging task in this kind of networks. This work lays out a decentralized stochastic solution for the data dissemination problem through two game-theoretical mechanisms. Given the non-stationarity induced by a highly dynamic topology, diverse network densities, and intermittent connectivity, a solution for the formulated game requires an adaptive procedure able to exploit the environment changes...
January 19, 2018: Sensors
Jing-Yuan Chen, Jun Ho Son, Chao Wang, S Raghu
The idea of statistical transmutation plays a crucial role in descriptions of the fractional quantum Hall effect. However, a recently conjectured duality between a critical boson and a massless two-component Dirac fermion extends this notion to gapless systems. This duality sheds light on highly nontrivial problems such as the half-filled Landau level, the superconductor-insulator transition, and surface states of strongly coupled topological insulators. Although this boson-fermion duality has undergone many consistency checks, it has remained unproven...
January 5, 2018: Physical Review Letters
Oscar Viyuela, Liang Fu, Miguel Angel Martin-Delgado
We study the phase diagram and edge states of a two-dimensional p-wave superconductor with long-range hopping and pairing amplitudes. New topological phases and quasiparticles different from the usual short-range model are obtained. When both hopping and pairing terms decay with the same exponent, one of the topological chiral phases with propagating Majorana edge states gets significantly enhanced by long-range couplings. On the other hand, when the long-range pairing amplitude decays more slowly than the hopping, we discover new topological phases where propagating Majorana fermions at each edge pair nonlocally and become gapped even in the thermodynamic limit...
January 5, 2018: Physical Review Letters
Timo Schumann, Luca Galletti, David A Kealhofer, Honggyu Kim, Manik Goyal, Susanne Stemmer
The magnetotransport properties of epitaxial films of Cd_{3}As_{2}, a paradigm three-dimensional Dirac semimetal, are investigated. We show that an energy gap opens in the bulk electronic states of sufficiently thin films and, at low temperatures, carriers residing in surface states dominate the electrical transport. The carriers in these states are sufficiently mobile to give rise to a quantized Hall effect. The sharp quantization demonstrates surface transport that is virtually free of parasitic bulk conduction and paves the way for novel quantum transport studies in this class of topological materials...
January 5, 2018: Physical Review Letters
Tiantian Zhang, Zhida Song, A Alexandradinata, Hongming Weng, Chen Fang, Ling Lu, Zhong Fang
We employed ab initio calculations to identify a class of crystalline materials of MSi (M=Fe, Co, Mn, Re, Ru) having double-Weyl points in both their acoustic and optical phonon spectra. They exhibit novel topological points termed "spin-1 Weyl point" at the Brillouin zone center and "charge-2 Dirac point" at the zone corner. The corresponding gapless surface phonon dispersions are two helicoidal sheets whose isofrequency contours form a single noncontractible loop in the surface Brillouin zone. In addition, the global structure of the surface bands can be analytically expressed as double-periodic Weierstrass elliptic functions...
January 5, 2018: Physical Review Letters
Zhoushen Huang, W Zhu, Daniel P Arovas, Jian-Xin Zhu, Alexander V Balatsky
We show that the topological index of a wave function, computed in the space of twisted boundary phases, is preserved under Hilbert space truncation, provided the truncated state remains normalizable. If truncation affects the boundary condition of the resulting state, the invariant index may acquire a different physical interpretation. If the index is symmetry protected, the truncation should preserve the protecting symmetry. We discuss implications of this invariance using paradigmatic integer and fractional Chern insulators, Z_{2} topological insulators, and spin-1 Affleck-Kennedy-Lieb-Tasaki and Heisenberg chains, as well as its relation with the notion of bulk entanglement...
January 5, 2018: Physical Review Letters
M Sundermann, H Yavaş, K Chen, D J Kim, Z Fisk, D Kasinathan, M W Haverkort, P Thalmeier, A Severing, L H Tjeng
We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5}  J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far...
January 5, 2018: Physical Review Letters
Shijiang Luo, Min Song, Xin Li, Yue Zhang, Jeongmin Hong, Xiaofei Yang, Xuecheng Zou, Nuo Xu, Long You
Magnetic skyrmion, a nano-sized spin texture with topological property, has become an area of significant interest due to the scientific insight that it can provide and also its potential impact on applications such as ultra low-energy and ultra high-density logic gates. In the quest for the reconfiguration of single logic device and the implementation of the complete logic functions, a novel reconfigurable skyrmion logic (RSL) is proposed and verified by micromagnetic simulations. Logic functions including AND, OR, NOT, NAND, NOR, XOR, and XNOR are implemented in the ferromagnetic (FM) nanotrack by virtue of various effects including spin orbit torque, skyrmion Hall effect, skyrmion-edge repulsions, and skyrmion-skyrmion collision...
January 19, 2018: Nano Letters
Patrick D Ellis Fisher, Qi Shen, Bernice Akpinar, Luke K Davis, Kenny Kwok Hin Chung, David Baddeley, Andela Saric, Thomas J Melia, Bart W Hoogenboom, Chenxiang Lin, C Patrick Lusk
Nuclear pore complexes (NPCs) form gateways that control molecular exchange between the nucleus and the cytoplasm. They impose a diffusion barrier to macromolecules and enable the selective transport of nuclear transport receptors with bound cargo. The underlying mechanisms that establish these permeability properties remain to be fully elucidated, but require unstructured nuclear pore proteins rich in Phe-Gly (FG)-repeat domains of different types, such as FxFG and GLFG. While physical modeling and in vitro approaches have provided a framework for explaining how the FG network contributes to the barrier and transport properties of the NPC, it remains unknown whether the number and/or the spatial positioning of different FG-domains along a cylindrical, ~40 nm diameter transport channel contributes to their collective properties and function...
January 19, 2018: ACS Nano
S L Zuo, Y Zhang, L C Peng, X Zhao, R Li, H Li, J F Xiong, M He, T Y Zhao, J R Sun, F X Hu, B G Shen
The evolution of topological magnetic domains microscopically correlates the dynamic behavior of memory units in spintronic application. Nanometric bubbles with variation of spin configurations have been directly observed in a centrosymmetric hexagonal magnet (Mn0.5Ni0.5)65(Ga1-yYy)35 (y = 0.01) using Lorentz transmission electron microscopy. Magnetic bubbles instead of biskyrmions are generated due to the enhancement of quality factor Q caused by the substitution of rare-earth element Y. Furthermore, the bubble density and diversified spin configurations are systematically manipulated via combining the electric current with perpendicular magnetic fields...
January 19, 2018: Nanoscale
Cipriano Rangel, Joaquin Espinosa-Garcia
Within the Born-Oppenheimer approximation a full-dimensional analytical potential energy surface, PES-2017, was developed for the gas-phase hydrogen abstraction reaction between the chlorine atom and ethane, which is a nine body system. This surface presents a valence-bond/molecular mechanics functional form dependent on 60 parameters and is fitted to high-level ab initio calculations. This reaction presents little exothermicity, -2.30 kcal mol-1, with a low height barrier, 2.44 kcal mol-1, and intermediate complexes in the entrance and exit channels...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Frigyes Samuel Racz, Peter Mukli, Zoltan Nagy, Andras Eke
Brain function is organized as a network of functional connections between different neuronal populations with connection strengths dynamically changing in time and space. Studies investigating functional connectivity (FC) usually follow a static approach when describing FC by considering the connectivity strengths constant, however a dynamic approach seems more reasonable, as this way the spatio-temporal dynamics of the underlying system can also be captured. Objective: The scale-free, i.e. fractal nature of neural dynamics is an inherent property of the nervous system...
January 19, 2018: Physiological Measurement
Marta Giacomello, Luca Scorrano
Mitofusins are outer membrane proteins essential for mitochondrial fusion. Their accepted topology posits that both N and C termini face the cytoplasm. In this issue, Mattie et al. (2018. J. Cell Biol. demonstrate instead that their C termini reside in the intermembrane space. These findings call for a revision of the current models of mitochondrial fusion.
January 18, 2018: Journal of Cell Biology
S Nandi, S Ahmed, A K Saxena
The virulence of tuberculosis infections resistant to conventional combination drug regimens cries for the design of potent fluoroquinolone compounds to be used as second line antimycobacterial chemotherapeutics. One of the most effective in silico methods is combinatorial design and high throughput screening by a ligand-based pharmacophore prior to experiment. The combinatorial design of a series of 3850 fluoroquinolone and isothiazoloquinolone compounds was then screened virtually by applying a topological descriptor based quantitative structure activity relationship (QSAR) for predicting highly active congeneric quinolone leads against Mycobacterium fortuitum and Mycobacterium smegmatis...
February 2018: SAR and QSAR in Environmental Research
Chihun In, Sangwan Sim, Beom Kim, Hyemin Bae, Hyunseung Jung, Woosun Jang, Myungwoo Son, Jisoo Moon, Maryam Salehi, Seung Young Seo, Aloysius Soon, Moon-Ho Ham, Hojin Lee, Seongshik Oh, Dohun Kim, Moon-Ho Jo, Hyunyong Choi
Understanding the mutual interaction between electronic excitations and lattice vibrations is key for electronic transport and optoelectronic phenomena. Dynamic manipulation of such interaction is elusive as it requires varying the material composition on the atomic level. In turn, recent studies on topological insulators (TIs) have revealed the coexistence of a strong phonon resonance and topologically protected Dirac plasmon, both in the terahertz (THz) frequency range. Here, using these intrinsic characteristics of TIs, we demonstrate a new methodology for controlling electron-phonon interaction by lithographically engineered Dirac surface plasmons in the Bi2Se3 TI...
January 18, 2018: Nano Letters
M Rubinson, N Levit-Binnun, A Peled, J Naim-Feil, D Freche, E Moses
A fundamental issue in the dynamics of complex systems is the resilience of the network in response to targeted attacks. This paper explores the local dynamics of the network attack process by investigating the order of removal of the nodes that have maximal degree, and shows that this dynamic network response can be predicted from the graph's initial connectivity. We demonstrate numerically that the maximal degree M(τ) of the network at time step τ decays exponentially with τ via a topology-dependent exponent...
November 2017: Physical Review. E
Pascal P Klamser, Marc Wiedermann, Jonathan F Donges, Reik V Donner
The adaptive voter model has been widely studied as a conceptual model for opinion formation processes on time-evolving social networks. Past studies on the effect of zealots, i.e., nodes aiming to spread their fixed opinion throughout the system, only considered the voter model on a static network. Here we extend the study of zealotry to the case of an adaptive network topology co-evolving with the state of the nodes and investigate opinion spreading induced by zealots depending on their initial density and connectedness...
November 2017: Physical Review. E
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