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Margarita G Ilyina, Edward M Khamitov, Rail N Galiakhmetov, Ildar A Mustafin, Akhat G Mustafin
In the present work, a 0.4nm nickel cluster has been theoretically studied. Its equilibrium structural parameters have been calculated by the DFT method based on the PBEH1PBE hybrid functional and split-valence basis set Lanl2DZ including effective core potentials. We have systematically considered diverse spin states of this cluster and find out its ground state. The relative stability of these states depends on the HOMO-LUMO gap. The interaction of the Ni6 with 4-propylheptane С10Н22 has been studied to simulate the process of catalytic cracking of hydrocarbons...
January 3, 2017: Journal of Molecular Graphics & Modelling
Jiajia Ye, Zhihong Wang, Qin Hao, Binbin Liu, Caixia Xu
Fe3O4 octahedra embedded in conductive nanoporous copper (NPC) network are straightforwardly fabricated by means of alloy refining followed by facile electroless dealloying in mild condition. During selectively dissolving the Al from FeCuAl alloy, the residual Cu atoms assemble to form sponge-like nanostructure, meanwhile the Fe atoms undergo spontaneous oxidation and aggregation to grow into Fe3O4 octahedra travelled through NPC network. Owing to the combination of conductive NPC network, Fe3O4 octahedra exhibit dramatically enhanced lithium storage performances with excellent reversible capacity, enhanced rate performance, as well outstanding cyclability compared with pure Fe3O4 octahedra...
January 11, 2017: Journal of Colloid and Interface Science
Alessandro Molle, Joshua Goldberger, Michel Houssa, Yong Xu, Shou-Cheng Zhang, Deji Akinwande
Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with their ligand-functionalized derivatives referred to as Xanes, are comprised of group IVA atoms arranged in a honeycomb lattice - similar to graphene but with varying degrees of buckling. Their electronic structure ranges from trivial insulators, to semiconductors with tunable gaps, to semi-metallic, depending on the substrate, chemical functionalization and strain...
January 16, 2017: Nature Materials
Ruggero Cortini, Xiaolin Cheng, Jeremy C Smith
Electrostatic interactions between DNA molecules have been extensively studied experimentally and theoretically, but several aspects (e.g. its role in determining the pitch of the cholesteric DNA phase) still remain unclear. Here, we performed large-scale all-atom molecular dynamics simulations in explicit water and 150 mM sodium chloride, to reconstruct the potential of mean force (PMF) of two DNA oligomers 24 base pairs long as a function of their interaxial angle and intermolecular distance. We find that the potential of mean force is dominated by total DNA charge, and not by the helical geometry of its charged groups...
January 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Bret C Hess, Erik K Swenson
This systematic study of transition metal (TM) substitution for H on graphane TM x H1-x C, (TM  =  Sc, Ti, V, Cr, Mn) combines ab initio calculations and cluster expansion to explore a huge variety of structures in more than 20 supercells over the full concentration range from x  =  0 to 1. We find energetically favorable structures at each concentration in supercells not studied before. At low x the lowest-energy structures contain lines and bands of TM atoms. For the larger atoms (Sc, Ti, V) the ordering becomes complex at higher concentrations, and their increased interaction in graphene causes H atoms to detach from the graphene to positions above the TMs...
January 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Matthias Massarczyk, Till Rudack, Jürgen Schlitter, Jens Kuhne, Carsten Kötting, Klaus Gerwert
Integration of experimental and computational approaches to investigate chemical reactions in proteins has proven to be very successful. Experimentally, time-resolved FTIR difference-spectroscopy monitors chemical reactions at atomic detail. To decode detailed structural information encoded in IR spectra, QM/MM calculations are performed. Here, we present a novel method which we call Local Mode Analysis (LMA) for calculating IR spectra and assigning spectral IR bands on the basis of movements of nuclei and partial charges from just a single QM/MM trajectory...
January 16, 2017: Journal of Physical Chemistry. B
Zheng-Zhe Lin
Ferromagnetism in half-metallic two-dimensional (2D) materials can lead to unique spintronics applications. In this paper, we report first-principle calculations that predict 2D single-layer C12Mn2 as a ferromagnetic half metal, and 2D single-layer C12Cr2 as an antiferromagnetic semiconductor. A systematic study is carried out to demonstrate the reliability of our research. We employ a bottom-up method to investigate the structural and magnetic stability of single, two and more Cr or Mn atoms on graphyne at room temperature...
January 16, 2017: Physical Chemistry Chemical Physics: PCCP
Mostafa Ahmadi, Sandie Pioge, Charles-Andre Fustin, Jean-Francois Gohy, Evelyne van Ruymbeke
Synthesis of combs with well-entangled backbones and long branches with high densities has always been a challenge. Steric hindrance frequently leads to coupling of chains and structural imperfections that cannot be easily distinguished by traditional characterization methods. Research studies have therefore tried to use a combination of different methods to obtain more information on the actual microstructures. In this work, a grafting-from approach is used to synthesize poly(n-butyl acrylate) combs using atom transfer radical polymerization (ATRP) in three steps including the synthesis of a backbone, cleavage of protecting groups and growth of side branches...
January 16, 2017: Soft Matter
R H Aguilera-Del-Toro, F Aguilera-Granja, L C Balbás, A Vega
We report a comprehensive theoretical study of the structural and electronic properties of neutral and charged nickel oxide clusters, NinOm(0/±) (n = 3-8 and m = 1-10), in the context of recent experiments of photodissociation and Ion Mobility Mass Spectrometry. By means of density functional theory calculations in the generalized gradient approximation for exchange and correlation, we determined the putative ground states as well as the low-energy structural- and spin-isomers which were then used to explore the favorable fragmentation channels of the nickel oxide cationic clusters, and the resulting most abundant products, in good qualitative agreement with photodissociation measurements...
January 16, 2017: Physical Chemistry Chemical Physics: PCCP
Andre Neumann, Jessica Lindlau, Léo Colombier, Manuel Nutz, Sina Najmaei, Jun Lou, Aditya D Mohite, Hisato Yamaguchi, Alexander Högele
Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional optoelectronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides...
January 16, 2017: Nature Nanotechnology
Sut Kam Ho, Dario Machado Garcia
A two-pulse laser-excited atomic fluorescence (LEAF) technique at 193 nm wavelength was applied to the analysis of indium tin oxide (ITO) layer on polyethylene terephthalate (PET) film. Fluorescence emissions from analytes were induced from plumes generated by first laser pulse. Using this approach, non-selective LEAF can be accomplished for simultaneous multi-element analysis and it overcomes the handicap of strict requirement for laser excitation wavelength. In this study, experimental conditions including laser fluences, times for gating and time delay between pulses were optimized to reveal high sensitivity with minimal sample destruction and penetration...
January 1, 2017: Applied Spectroscopy
Nerea Mascaraque, Mathieu Bauchy, Morten M Smedskjaer
Glasses gradually dissolve and corrode when they are exposed to aqueous solutions and for many applications it is necessary to understand and predict the kinetics of the glass dissolution. Despite the recent progress in understanding the impact of chemical composition on the dissolution rate, a detailed understanding of the structural and topological origin of chemical durability in solutions of different pH is still largely lacking. Such knowledge would enable the tailoring of glass dissolution kinetics as a function of chemical composition...
January 16, 2017: Journal of Physical Chemistry. B
Jürgen Heck, Alejandra Escribano, Torben Steenbock, Carmen Herrmann, Conrad Stork
Attaching an organometallic unit to a dithienylethene (DTE) molecular switch can allow to vary its switching and spectroscopic properties, and to create switchable magnetic properties. In this work, two different dithienylethene molecular switches were used as a bridge between two cobalt sandwich units. The only difference between the switching cores was in the size of the cycloalkene ring connecting both thiophene rings. The complexes present different oxidation states for the cobalt atoms, which were demonstrated to determine the switching reaction...
January 16, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Daniel A Gonçalves, Ana C Soncin, George L Donati, Mirian C Dos Santos
Tungsten coil atomic emission spectrometry (WCAES) is used to determine trace levels of Mn (403.1 nm) and Cr (425.5 nm) in cow placenta. All samples were collected in Ilha Solteira, SP, Brazil. The instrumental setup is based on a tungsten filament extracted from 150 W, 15 V microscope light bulbs, a solid state power supply, fused silica lens, crossed Czerny-Turner spectrograph, and a thermoelectrically cooled charge-coupled device detector. The limits of detection (LOD) and quantification (LOQ) for Cr are 2 and 8 μg L(-1), and 20 and 60 μg L(-1) for Mn, respectively...
January 16, 2017: Biological Trace Element Research
Runze Han, Peng Huang, Yudi Zhao, Zhe Chen, Lifeng Liu, Xiaoyan Liu, Jinfeng Kang
In this paper, resistive random access memory (RRAM)-based crossbar arrays with the cell structure of Pt/[AlO y /HfO x ] m /TiN were fabricated by using atomic layer deposition (ALD) technique. The RRAM devices in the arrays show excellent performances such as good uniformity and high reliability. Based on the fabricated RRAM array, a complete set of basic logic operations including NOR and XNOR were successfully demonstrated.
December 2017: Nanoscale Research Letters
Bang Li, Xin Yan, Xia Zhang, Xiaomin Ren
We report on the self-catalyzed growth of InAs nanowires on InP substrate by metal-organic chemical vapor deposition. At a moderate V/III ratio, tapered nanowires are obtained, suggesting a strong surface diffusion effect. Dense twin faults are observed perpendicular to the nanowire growth direction due to the fluctuation of In atoms in the droplet originating from the surface diffusion effect. At a lower V/III ratio, the nanowires exhibit kinking, which is associated with a high adhesion due to a large sticking coefficient of TMIn...
December 2017: Nanoscale Research Letters
Yongho Kim, Binh Khanh Mai, Sumin Park
High-valent Cu and Fe species, which are generated from dioxygen activation in metalloenzymes, carry out the functionalization of strong C-H bonds. Understanding the atomic details of the catalytic mechanism has long been one of the main objectives of bioinorganic chemistry. Large H/D kinetic isotope effects (KIEs) were observed in the C-H activation by high-valent non-heme Cu or Fe complexes in enzymes and their synthetic models. The H/D KIE depends significantly on the transition state properties, such as structure, energies, frequencies, and shape of the potential energy surface, when the tunneling effect is large...
January 16, 2017: Journal of Biological Inorganic Chemistry: JBIC
Attila Forgács, Rosa Pujales-Paradela, Martín Regueiro-Figueroa, Laura Valencia, David Esteban-Gómez, Mauro Botta, Carlos Platas-Iglesias
We have reported here a series of ligands containing pentadentate 6,6'-(azanediylbis(methylene))dipicolinic acid units that differ in the substituent present at the amine nitrogen atom (acetate: H3DPAAA; phenyl: H2DPAPhA; dodecyl: H2DPAC12A; 4-hexylphenyl: H2DPAC6PhA). The protonation constants of the hexadentate DPAAA(3-) and pentadentate DPAPhA(2-) ligands and the stability constants of their Mn(2+) complexes were determined using pH-potentiometry (25 °C, 0.15 M NaCl). The mono-hydrated [Mn(DPAAA)](-) complex (log KMnL = 13...
January 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Corey J Cochrane, Jordana Blacksberg, Mark A Anders, Patrick M Lenahan
No abstract text is available yet for this article.
January 16, 2017: Scientific Reports
Hongkun He, Khosrow Rahimi, Mingjiang Zhong, Ahmed Mourran, David R Luebke, Hunaid B Nulwala, Martin Möller, Krzysztof Matyjaszewski
Cubosomes are micro- and nanoparticles with a bicontinuous cubic two-phase structure, reported for the self-assembly of low molecular weight surfactants, for example, lipids, but rarely formed by polymers. These objects are characterized by a maximum continuous interface and high interface to volume ratio, which makes them promising candidates for efficient adsorbents and host-guest applications. Here we demonstrate self-assembly to nanoscale cuboidal particles with a bicontinuous cubic structure by amphiphilic poly(ionic liquid) diblock copolymers, poly(acrylic acid)-block-poly(4-vinylbenzyl)-3-butyl imidazolium bis(trifluoromethylsulfonyl)imide, in a mixture of tetrahydrofuran and water under optimized conditions...
January 16, 2017: Nature Communications
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