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Attraction symmetry

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
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...
January 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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
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, both cases being technologically relevant...
December 22, 2016: ACS Nano
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...
December 20, 2016: Accounts of Chemical Research
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
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
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
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
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
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
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
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
Mukesh Kumar Singh, Gopalan Rajaraman
Ab initio calculations performed on a series of lanthanide encapsulated fullerenes reveal {DyOSc}@C82 to be one of the best host-guest pairs to offer a barrier height exceeding 1400 cm(-1). The high-symmetry environment preserved inside the cage quenches the QTM effects up to third-excited states leading to very larger barrier heights and this opens up a new possibility of obtaining attractive SMMs based on lanthanide based endohedral metallo-fullerenes (EMFs).
November 17, 2016: Chemical Communications: Chem Comm
Chuanyi Lu, Daomu Zhao
An analytical expression for the elements of the cross-spectral density matrix of electromagnetic multi-Gaussian Schell-model beams with astigmatic aberration propagating through the turbulent ocean is derived. We investigate the statistical characteristics of the beams on propagation in great detail. It is found that, due to astigmatism, the circular symmetry of such beams suffers a certain degree of damage in the near field. In addition, astigmatism also destroys the attractive far-field flat profiles in free space...
October 10, 2016: Applied Optics
Xiaobo Li, Fangfang Cui, Qingliang Feng, Gang Wang, Xiaosa Xu, Juanxia Wu, Nannan Mao, Xing Liang, Zhongyue Zhang, Jin Zhang, Hua Xu
As an anisotropic 2D layered material, rhenium disulfide (ReS2) has attracted much attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, the low lattice symmetry and interlayer decoupling of ReS2 make asymmetric growth and out-of-plane growth occur quite easily; therefore, thick flake, dendritic and flower-like structures of ReS2 have mostly been obtained previously. Here, we report on an approach based on space-confined epitaxial growth for the controlled synthesis of ReS2 films...
December 7, 2016: Nanoscale
Seema Pande, Wei Huang, Nan Shao, Lei-Ming Wang, Navneet Khetrapal, Wai-Ning Mei, Tian Jian, Lai-Sheng Wang, Xiao Cheng Zeng
Gold nanoclusters have attracted great attention in the past decade due to their remarkable size-dependent electronic, optical, and catalytic properties. However, the structures of large gold clusters are still not well-known because of the challenges in global structural searches. Here we report a joint photoelectron spectroscopy (PES) and theoretical study of the structural evolution of negatively charged core-shell gold nanoclusters (Aun(-)) for n = 42-50. Photoelectron spectra of size-selected Aun(-) clusters are well resolved with distinct spectral features, suggesting a dominating structural type...
November 22, 2016: ACS Nano
Balaram Pradhan, V M Vaisakh, Geetha G Nair, D S Shankar Rao, S Krishna Prasad, Achalkumar Ammathnadu Sudhakar
Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole-based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole-based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin-film states...
October 28, 2016: Chemistry: a European Journal
Nelly Bonifaci, Zhiling Li, Jussi Eloranta, Steven L Fiedler
The interaction potentials of the He2(*) excimer, in the a(3)Σu, b(3)Πg, c(3)Σg, and d(3)Σu electronic states with a ground state helium atom are presented. The symmetry of the interaction potentials closely follows the excimer Rydberg electron density with pronounced short-range minima appearing along the nodal planes of the Rydberg orbital. In such cases, a combination of the electrostatic short-range attraction combined with Pauli repulsion leads to the appearance of unusual long-range maxima in the potentials...
November 17, 2016: Journal of Physical Chemistry. A
Christina Bagwill, Christa Anderson, Elizabeth Sullivan, Varun Manohara, Prithvi Murthy, Charles C Kirkpatrick, Apryll Stalcup, Michael Lewis
A computational study aimed at accurately predicting the strength of the anion-π binding of substituted benzenes is presented. The anion-π binding energies (Ebind) of 37 substituted benzenes and the parent benzene, with chloride or bromide were investigated at the MP2(full)/6-311++G** level of theory. In addition, energy decomposition analysis was performed on 27 selected chloride-arene complexes via symmetry adapted perturbation theory (SAPT), using the SAPT2+ approach. Initial efforts aimed to correlate the anion-π Ebind values with the sum of the Hammett constants σp (Σσp) or σm (Σσm), as done by others...
November 23, 2016: Journal of Physical Chemistry. A
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