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https://www.readbyqxmd.com/read/28211709/pt-symmetric-real-dirac-fermions-and-semimetals
#1
Y X Zhao, Y Lu
Recently, Weyl fermions have attracted increasing interest in condensed matter physics due to their rich phenomenology originated from their nontrivial monopole charges. Here, we present a theory of real Dirac points that can be understood as real monopoles in momentum space, serving as a real generalization of Weyl fermions with the reality being endowed by the PT symmetry. The real counterparts of topological features of Weyl semimetals, such as Nielsen-Ninomiya no-go theorem, 2D subtopological insulators, and Fermi arcs, are studied in the PT symmetric Dirac semimetals and the underlying reality-dependent topological structures are discussed...
February 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28191927/foldectures-3d-molecular-architectures-from-self-assembly-of-peptide-foldamers
#2
Sung Hyun Yoo, Hee-Seung Lee
The wide range of fascinating supramolecular architectures found in nature, from DNA double helices to giant protein shells, inspires researchers to mimic the diverse shapes and functions of natural systems. Thus, a variety of artificial molecular platforms have been developed by assembling DNA-, peptide-, and protein-based building blocks for medicinal and biological applications. There has also been a significant interest in the research of non-natural oligomers (i.e., foldamers) that fold into well-defined secondary structures analogous to those found in proteins, because the assemblies of foldamers are expected not only to form biomimetic supramolecular architectures that resemble those of nature but also to display unique functions and unprecedented topologies at the same time due to their different folding propensities from those of natural building blocks...
February 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28185393/kibble-zurek-scaling-during-defect-formation-in-a-nematic-liquid-crystal
#3
Ingo Dierking, Nicholas Fowler
Symmetry breaking phase transitions are often accompanied by the formation of topological defects, like in cosmological theories of the early universe, superfluids, liquid crystals or solid state systems. This scenario is described by the Kibble-Zurek mechanism, which predicts respective scaling laws for the defect density ρ. One such scaling law suggests a relation ρ~tQ-1/2 with tQ the change of rate of a control parameter. In contrast to the scaling of the defect density during annihilation with ρ~t-1, which is governed by the attraction of defects of the same strength but opposite sign, the defect formation process, which depends on the rate of change of a physical quantity initiating the transition, is only very scarcely investigated...
February 10, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28185330/smectic-layer-origami-via-preprogrammed-photoalignment
#4
Ling-Ling Ma, Ming-Jie Tang, Wei Hu, Ze-Qun Cui, Shi-Jun Ge, Peng Chen, Lu-Jian Chen, Hao Qian, Li-Feng Chi, Yan-Qing Lu
Hierarchical architecture is of vital importance in soft materials. Focal conic domains (FCDs) of smectic liquid crystals, characterized by an ordered lamellar structure, attract intensive attention. Simultaneously tailoring the geometry and clustering characteristics of FCDs remains a challenge. Here, the 3D smectic layer origami via a 2D preprogrammed photoalignment film is accomplished. Full control of hierarchical superstructures is demonstrated, including the domain size, shape, and orientation, and the lattice symmetry of fragmented toric FCDs...
February 10, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28182489/do-capuchin-monkeys-sapajus-apella-prefer-symmetrical-face-shapes
#5
Annika Paukner, Lauren J Wooddell, Carmen E Lefevre, Eric Lonsdorf, Elizabeth Lonsdorf
In humans, facial symmetry has been linked to an individual's genetic quality, and facial symmetry has a small yet significant effect on ratings of facial attractiveness. The same evolutionary processes underlying these phenomena may also convey a selective advantage to symmetrical individuals of other primate species, yet to date, few studies have examined sensitivity to facial symmetry in nonhuman primates. Here we presented images of symmetrical and asymmetrical human and monkey faces to tufted capuchin monkeys (Sapajus apella) and hypothesized that capuchins would visually prefer symmetrical faces of opposite-sex conspecifics...
February 2017: Journal of Comparative Psychology
https://www.readbyqxmd.com/read/28157123/a-three-dimensional-zn-ii-coordination-polymer-constructed-from-1-1-biphenyl-2-2-4-4-tetracarboxylate-and-1-4-bis-1h-imidazol-1-yl-benzene-ligands-exhibiting-photoluminescence
#6
Feng Su, Liping Lu, Chengyong Zhou, Xiaoxia Wang, Long Sun, Chun Han
Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H4bpta) with C2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(μ5-1,1'-biphenyl-2,2',4,4'-tetracarboxylato)bis[μ2-1,4-bis(1H-imidazol-1-yl)benzene]dizinc(II)], [Zn2(C16H6O8)(C12H10N4)]n, was synthesized solvothermally and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy...
February 1, 2017: Acta Crystallographica. Section C, Structural Chemistry
https://www.readbyqxmd.com/read/28155897/predictors-of-facial-attractiveness-and-health-in-humans
#7
Yong Zhi Foo, Leigh W Simmons, Gillian Rhodes
Facial attractiveness has been suggested to provide signals of biological quality, particularly health, in humans. The attractive traits that have been implicated as signals of biological quality include sexual dimorphism, symmetry, averageness, adiposity, and carotenoid-based skin colour. In this study, we first provide a comprehensive examination of the traits that predict attractiveness. In men, attractiveness was predicted positively by masculinity, symmetry, averageness, and negatively by adiposity. In women, attractiveness was predicted positively by femininity and negatively by adiposity...
February 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28097726/role-of-the-edge-properties-in-hydrogen-evolution-reaction-on-mos2
#8
Petr Lazar, Michal Otyepka
Molybdenum disulfide, in particular its edges, has attracted considerable attention as possible substitute of platinum catalysts for hydrogen evolution reaction. Complex nature of the reaction complicates its detailed experimental investigations, which are mostly indirect and sample dependent. Therefore, we employed density functional theory calculations to study how the properties of MoS2 Mo-edge influence the thermodynamics of hydrogen adsorption onto the edge. We discuss the effect of the computational model (one-dimensional nanostripe), border symmetry imposed by its length, sulfur saturation of the edge, and dimensionality of the material...
January 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28081013/magneto-photoluminescence-measurements-of-tungsten-disulphide-monolayers
#9
Jan Kuhnert, Arash Rahimi-Iman, Wolfram Heimbrodt
Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K', respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVD-grown tungsten disulphide (WS2) monolayers at temperatures of 2 K...
March 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28077290/hidden-symmetries-of-dna-molecule
#10
Alexander A Tulub, Vassily E Stefanov
Despite the fact that DNA molecule is studied up and down, we know very little about the role of DNA triplets in coding amino acids and stop-codons. The paper aims to fill this gap through attracting spintronic ideas and carrying out QM/MM computations on a full-turn DNA fragment. The computations reveal two hidden symmetries: the spin splitting (the Rashba effect), confined within each triplet, and the quantum "phase" link between the triplet nature (in total, 64 triplets) and the corresponding amino acid and three stop-codons...
January 8, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/28005333/spin-orbit-coupling-induced-gap-in-graphene-on-pt-111-with-intercalated-pb-monolayer
#11
Ilya I Klimovskikh, Mikhail M Otrokov, Vladimir Yu Voroshnin, Daria Sostina, Luca Petaccia, Giovanni Di Santo, Sangeeta Thakur, Evgueni V Chulkov, Alexander M Shikin
Graphene is one of the most promising materials for nanoelectronics owing to its unique Dirac cone-like dispersion of the electronic state and high mobility of the charge carriers. However, to facilitate the implementation of the graphene-based devices, an essential change of its electronic structure, a creation of the band gap should controllably be done. Brought about by two fundamentally different mechanisms, a sublattice symmetry breaking or an induced strong spin-orbit interaction, the band gap appearance can drive graphene into a narrow-gap semiconductor or a 2D topological insulator phase, respectively, with both cases being technologically relevant...
January 6, 2017: ACS Nano
https://www.readbyqxmd.com/read/27993004/toward-the-rational-design-of-novel-noncentrosymmetric-materials-factors-influencing-the-framework-structures
#12
Kang Min Ok
Solid-state materials with extended structures have revealed many interesting structure-related characteristics. Among many, materials crystallizing in noncentrosymmetric (NCS) space groups have attracted massive attention attributable to a variety of superb functional properties such as ferroelectricity, pyroelectricity, piezoelectricity, and nonlinear optical (NLO) properties. In fact, the characteristics are pivotal to many industrial applications such as laser systems, optical communications, photolithography, energy harvesting, detectors, and memories...
20, 2016: Accounts of Chemical Research
https://www.readbyqxmd.com/read/27966798/chiral-superstructure-mesophases-of-achiral-bent-shaped-molecules-hierarchical-chirality-amplification-and-physical-properties
#13
Khoa V Le, Hideo Takezoe, Fumito Araoka
Chiral mesophases in achiral bent-shaped molecules have attracted particular attention since their discovery in the middle 1990s, not only because of their homochirality and polarity, but also due to their unique physical/physicochemical properties. Here, the most intriguing results in the studies of such symmetry-broken states, mainly helical-nanofilament (HNF) and dark-conglomerate (DC) phases, are reviewed. Firstly, basic information on the typical appearance and optical activity in these phases is introduced...
December 14, 2016: Advanced Materials
https://www.readbyqxmd.com/read/27966756/karyotype-asymmetry-in-cynodon-rich-poaceae-accessions
#14
R B Chiavegatto, C M P Paula, F Souza Sobrinho, F R G Benites, V H Techio
Cynodon is a genus of plants with forage potential that has attracted the interest of breeders. These species have high morphological variability in a large number of varieties and cytotypes, hampering identification. This study aimed to determine the karyotype asymmetry index among accessions of Cynodon to discriminate between them. Karyotype symmetry was based on three estimates, which were compared. The basic number for the genus is x = 9. The results of the chromosome count and DNA quantification, respectively, were as follows: two diploid accessions (2n = 2x = 18 and 1...
December 2, 2016: Genetics and Molecular Research: GMR
https://www.readbyqxmd.com/read/27918303/a-one-dimensional-zinc-ii-coordination-polymer-with-a-three-dimensional-supramolecular-architecture-incorporating-1-1h-benzimidazol-2-yl-methyl-1h-tetrazole-and-adipate
#15
Chun Li Liu, Qiu Ying Huang, Xiang Ru Meng
The synthesis of coordination polymers or metal-organic frameworks (MOFs) has attracted considerable interest owing to the interesting structures and potential applications of these compounds. It is still a challenge to predict the exact structures and compositions of the final products. A new one-dimensional coordination polymer, catena-poly[[[bis{1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole-κN(3)}zinc(II)]-μ-hexane-1,6-dicarboxylato-κ(4)O(1),O(1'):O(6),O(6')] monohydrate], {[Zn(C6H8O4)(C9H8N6)2]·H2O}n, has been synthesized by the reaction of Zn(Ac)2 (Ac is acetate) with 1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole (bimt) and adipic acid (H2adi) at room temperature...
December 1, 2016: Acta Crystallographica. Section C, Structural Chemistry
https://www.readbyqxmd.com/read/27917558/multivariate-sexual-selection-on-male-tegmina-in-wild-populations-of-sagebrush-crickets-cyphoderris-strepitans-orthoptera-haglidae
#16
G D Ower, J Hunt, S K Sakaluk
Although the strength and form of sexual selection on song in male crickets have been studied extensively, few studies have examined selection on the morphological structures that underlie variation in males' song, particularly in wild populations. Geometric morphometric techniques were used to measure sexual selection on the shape, size and symmetry of both top and bottom tegmina in wild populations of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males...
November 7, 2016: Journal of Evolutionary Biology
https://www.readbyqxmd.com/read/27908105/role-of-sharp-avoided-crossings-in-short-hyper-radial-range-in-recombination-of-the-cold-4-he3-system
#17
Bin-Bin Wang, Yong-Chang Han, Shu-Lin Cong
The role of sharp avoided crossings (SACs) in a short hyper-radial range R≤ 50 a.u. in the calculation of recombination for a cold (4)He3 system is investigated in the adiabatic hyperspherical representation by "turning off and on" the relevant nonadiabatic couplings. The influence of SACs on the recombination is related with the channels of the system and with the scattering energy. For J(Π) = 0(+) symmetry, the two-body recombination channel has an attractive potential well, which makes radial wave functions of both two-body recombination channel and three-body continuum channels accessible in the short hyper-radial range where SACs are located...
November 28, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27865023/layered-post-transition-metal-dichalcogenides-x-m-m-x-and-their-properties
#18
Jan Luxa, Yong Wang, Zdenek Sofer, Martin Pumera
A(III) B(VI) chalcogenides are an interesting group of layered semiconductors with several attractive properties, such as tunable band gaps and the formation of solid solutions. Unlike the typically sandwiched structure of transition-metal dichalcogenides, A(III) B(VI) layered chalcogenides with hexagonal symmetry are stacked through the X-M-M-X motif, in which M is gallium and indium, and X is sulfur, selenium, and tellurium. In view of the inadequate study of the electrochemical properties and great interest in layered materials towards energy-related research, herein the inherent electrochemistry of GaS, GaSe, GaTe, and InSe has been studied, as well as the exploration of their potential as hydrogen evolution reaction (HER) electrocatalysts...
December 23, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27864064/an-emerging-class-of-amphiphilic-dendrimers-for-pharmaceutical-and-biomedical-applications-janus-amphiphilic-dendrimers
#19
REVIEW
Dhiraj R Sikwal, Rahul S Kalhapure, Thirumala Govender
In recent years, a new class of dendrimer, known as Janus dendrimers (JDs), has attracted much attention due to their different structures and properties to the conventional symmetric forms. The broken symmetry of JDs offers the opportunity to form complex self-assembled materials, and presents new sets of properties that are presently inconceivable for homogeneous or symmetrical dendrimers. Due to their unique features, JDs have a promising future in pharmaceutical and biomedical fields, as seen from the recent interest in their application in conjugating multiple drugs and targeting moieties, forming supramolecular hydrogels, enabling micellar delivery systems, and preparing nano-vesicles, known as dendrimersomes, for drug encapsulation...
January 15, 2017: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/27858048/supracolloidal-reconfigurable-polyhedra-via-hierarchical-self-assembly
#20
Daniel Morphew, Dwaipayan Chakrabarti
Enclosed three-dimensional structures with hollow interiors have been attractive targets for the self-assembly of building blocks across different length scales. Colloidal self-assembly, in particular, has enormous potential as a bottom-up means of structure fabrication exploiting a priori designed building blocks because of the scope for tuning interparticle interactions. Here we use computer simulation study to demonstrate the self-assembly of designer charge-stabilised colloidal magnetic particles into a series of supracolloidal polyhedra, each displaying a remarkable two-level structural hierarchy...
December 6, 2016: Soft Matter
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