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Meng Li, Jing Zhang, Lijun Wang, Baoshan Wang, Christine V Putnis
Potential pathways for inhibiting crystal growth are either via disrupting local microenvironments surrounding crystal-solution interfaces or physically blocking solute molecule attachment. However, the actual mode of inhibition may be more complicated due to the characteristic time scale for the inhibitor adsorption and relaxation to a well-bound state at crystal surfaces. Here we demonstrate the role of citrate (CA) and hydroxycitrate (HCA) in brushite (DCPD, CaHPO4·2H2O) crystallization over a broad range of both inhibitor concentrations and supersaturations by in situ atomic force microscopy (AFM)...
January 18, 2018: Journal of Physical Chemistry. B
Xiaokun Yang, Shawn P Coleman, Jerry Lasalvia, William A Goddard, Qi An
The roles of grain boundaries (GB) in mechanical properties have been examined extensively for metals and alloys; however, for covalent solids their roles in deformation response to applied stress are much less established. We consider here the unusual ceramic, boron carbide (B4C), which is very hard and lightweight but exhibits brittle impact behavior. We used quantum mechanics (QM) simulations to determine the mechanical response in the atomistic structures at GBs under pure shear and also with biaxial shear deformation that mimics indentation stress conditions...
January 18, 2018: ACS Applied Materials & Interfaces
Irina Y Zhuravleva, Nataliya R Nichay, Yuriy Y Kulyabin, Tatyana P Timchenko, Alexander A Korobeinikov, Yuliya F Polienko, Svetlana S Shatskaya, Elena V Kuznetsova, Alexey V Voitov, Alexander V Bogachev-Prokophiev, Alexander M Karaskov
OBJECTIVES: The development of calcification-resistant bioprosthetic materials is a very important challenge for paediatric surgery. The subcutaneous implantation in rats is the well-known first-stage model for this kind of research. Using this model, we aimed to compare calcification of the porcine aortic wall and bovine pericardium and jugular vein wall cross-linked with glutaraldehyde (GA) and ethylene glycol diglycidyl ether (DE). We also determined the efficacy of DE-preserved tissue modification with 2-(2-carboxyethylamino)ethylidene-1,1-bisphosphonic acid (CEABA)...
January 15, 2018: Interactive Cardiovascular and Thoracic Surgery
Takefumi Yamashita
Because antibodies have become an important therapeutic tool, rational antibody design is a challenging issue involving various science and technology fields. From the computational aspect, many types of design-assist methods have been developed, but their accuracy is not fully satisfactory. Because of recent advancements in computational power, molecular dynamics (MD) simulation has become a helpful tool to trace the motion of proteins and to characterize their properties. Thus, MD simulation has been applied to various systems involving antigen-antibody complexes and has been shown to provide accurate insight into antigen-antibody interactions and dynamics at an atomic resolution...
January 15, 2018: International Immunology
Juan M Martinez-Andrade, Miguel Avalos-Borja, Alfredo R Vilchis-Nestor, Luis O Sanchez-Vargas, Ernestina Castro-Longoria
The chelating and antimicrobial capacity of a novel modification of 17% EDTA with silver nanoparticles (AgNPs) (EDTA-AgNPs) was evaluated in-vitro for root canal treatment (RCT). The EDTA-AgNPs solution was characterized by UV-Vis spectroscopy, ζ-potential and high-resolution transmission electron microscopy (HRTEM). Antimicrobial capacity was evaluated against Candida albicans and Staphylococcus aureus in planktonic and biofilm cells by broth macrodilution (24 h) and XTT assays, (1, 10 and 30 min) respectively...
2018: PloS One
Hum N Bandari, Xinyou Ma, Amit Kumar Paul, Philip Smith, William Louis Hase
In this work a Particle Swarm Optimization (PSO) algorithm was used to fit an analytic potential energy function to I-(H2O) intermolecular potential energy curves calculated with DFT/B97-1 theory. The analytic function is a sum of two-body terms, each written as a generalized sum of Buckingham and Lennard-Jones terms with only six parameters. Two models were used to describe the two-body terms between I- and H2O: a 3-site model H2O; and a 4-site model including a ghost atom. The fits are compared with those obtained with a genetic/non-linear least-squares algorithm...
January 18, 2018: Journal of Chemical Theory and Computation
Robert M Parrish, Keiran C Thompson, Todd J Martínez
Symmetry-adapted perturbation theory (SAPT) is a valuable method for analyzing intermolecular interactions. The functional group SAPT partition (F-SAPT) has been introduced to provide additional insight into the origins of noncovalent interactions. Until now, SAPT analysis has been too costly for large ligand-protein complexes where it could provide key insights for chemical modifications that might improve ligand binding. In this paper, we present a large-scale implementation of F-SAPT which is especially efficient when one of the interacting monomers is significantly larger than the other, as is usually the case for drug-protein interactions...
January 18, 2018: Journal of Chemical Theory and Computation
David James Coughtrie, Robin Giereth, Daniel Kats, Hans-Joachim Werner, Andreas Köhn
Internally contracted multireference coupled cluster (icMRCC) theory is embedded within multireference perturbation theory (MRPT) to calculate energy differences in large strongly correlated systems. The embedding scheme is based on partitioning the orbital spaces of a complete active space self consistent field (CASSCF) wave function, with the truncated virtual space constructed by transforming selected projected atomic orbitals (PAOs). MRPT is applied to the environment using a subtractive embedding approach, that also allows for multilayer embedding...
January 18, 2018: Journal of Chemical Theory and Computation
Jiri Brabec, Jakub Lang, Masaaki Saitow, Jiri Pittner, Frank Neese, Ondrej Demel
This article reports development of a local variant of Mukherjee's state specific multireference coupled cluster method based on the domain-based pair natural orbital approach (DLPNO-MkCC). The current implementation is restricted to connected single and double excitations and model space with up to biexcited references. The performance of the DLPNO-MkCCSD was tested on calculations of tetramethyleneethane. The results show that above 99.9% of correlation energy was recovered, with respect to the conventional MkCC method...
January 18, 2018: Journal of Chemical Theory and Computation
Jia-Wei Liu, Lei Feng, Haifeng Su, Zhi Wang, Quan-Qin Zhao, Xingpo Wang, Chen-Ho Tung, Di Sun, Lan-Sun Zheng
Although there has been an upsurge of interest in anisotropic assembly of inorganic nanoparticles, atomically precise self-assembly of anisotropic (nonspherical) high-nuclearity metal clusters is extremely rare. Herein, we presented two novel silver nanoclusters, Ag52 (SD/Ag23) and Ag76 (SD/Ag24), which are interiorly templated by five MoO42- and a pair of Mo6O228- anions, respectively, and co-protected by bridging RSH and terminal diphosphine ligands exteriorly. Regiospe-cific distribution diphosphine ligands on the surface and the arrangement of multiple molybdate templates within the nanoclusters synergetically tailor their shapes to anisotropic oblate spheroid and elongated rod, respectively, as opposed to isotropic nanospheres...
January 18, 2018: Journal of the American Chemical Society
Julian Horn, Anna Widera, Sebastian Litters, Elisabeth Kaifer, Hans-Jörg Himmel
Diborane(4) compounds are versatile reagents in synthetic chemistry. Generally, diboranes(4) with sp2-hybridized boron atoms react as electrophiles. By contrast, the chemistry of nucleophilic diborane(4) compounds with two sp3-hybridized boron atoms is very much underdeveloped. In this work, we systematically vary the substituents of electron-rich diborane(4) compounds with bridging guanidinate substituents. In this way, five new diboranes are synthesized and fully characterized. Using quantum chemical computations, we show that the electronic properties and reactivity of these compounds can be rationally varied by the choice of substituents...
January 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Zhichao Wang, Tao Li, Yunrui Duan, Weikang Wu, Zhenyang Zhao, Yao Liu, Hui Li
We investigated the unusual layering transition (LT) in quasi-2D liquid silicon dioxide (SiO2) confined in a nanoslit. Our results indicate that the slit size and pressure induce the abnormal LT in liquid SiO2, accompanied by a rapid change in the density, diffusion coefficient, pair correlation function and average potential energy. The silicon and oxygen atoms are almost completely separated under the extremely strong confinement effect, which is the characteristic feature of the LT. The negative slope of the LT lines in the phase diagram at different pressures suggests that a confinement-induced LT occurs at high pressure and a pressure-induced LT occurs at low pressure...
January 18, 2018: Physical Chemistry Chemical Physics: PCCP
Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner
The interaction between KrOF2 or XeOF2 and the 1,2, 1,3, and 1,4 diazines is characterized chiefly by a Kr/XeN aerogen bond, as deduced from ab initio calculations. The most stable dimers take advantage of the σ-hole on the aerogen atom, wherein the two molecules lie in the same plane. The interaction is quite strong, as much as 18 kcal mol-1. A second class of dimer geometry utilizes the π-hole above the aerogen atom in an approximate perpendicular arrangement of the two monomers; these structures are not as strongly bound: 6-8 kcal mol-1...
January 18, 2018: Physical Chemistry Chemical Physics: PCCP
Akarsh Verma, Avinash Parashar
Aim of this article is to study the effects of functional groups such as hydroxyl, epoxide and carboxyl on the fracture toughness of graphene. These functional groups form the backbone of intrinsic atomic structure of graphene oxide (GO). Molecular dynamics based simulations were performed in conjunction with reactive force field parameters to capture the Mode-I fracture toughness of functionalised graphene. Simulations were performed in stages, to study the effect of these functional groups, individually as well as altogether on the fracture toughness of GO nanosheet...
January 18, 2018: Nanotechnology
Marco Di Giovannantonio, Giorgio Contini
Surface-confined polymerization is a bottom-up strategy to create one- and two-dimensional covalent organic nanostructures with a π-conjugated backbone, which are suitable to be employed in real-life electronic devices, due to their high mechanical resistance and electronic charge transport efficiency. This strategy makes it possible to change the properties of the final nanostructures by a careful choice of the monomer architecture (<i>i.e.</i> of its constituent atoms and their spatial arrangement)...
January 18, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Zenghui Wu, Guoan Tai, Xufeng Wang, Tingsong Hu, Rui Wang, Wanlin Guo
Compared with MoS2 and WS2, the selenide analogues have narrower band gaps and higher electron mobilities, which make them more applicable to real electrical devices. Besides, few-layered metal selenides have higher electrical conductivity, carrier mobility and light absorption than the corresponding monolayers. However, the large-scale and high-quality growth of few-layered metal selenides remains a significant challenge. Here, we develop a facile method to grow large-area and highly-crystalline few-layered MoSe2 by directly selenizing the Mo foil surfaces at 550 oC within 60 min under ambient pressure...
January 18, 2018: Nanotechnology
Laura E Ratcliff, Augustin Degomme, José A Flores-Livas, Stefan Goedecker, Luigi Genovese
Performing high accuracy hybrid functional calculations for condensed matter systems containing a large number of atoms is at present computationally very demanding or even out of reach if high quality basis sets are used. We present a highly optimized multiple GPU implementation of the exact exchange operator which allows one to perform fast hybrid functional density-functional theory calculations with systematic basis sets without additional approximations for up to a thousand atoms...
January 18, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Muhammad Rashad, Hongzhang Zhang, Muhammad Asif, Kai Feng, Xianfeng Li, Huamin Zhang
Potentially safe and economically feasible magnesium batteries (MBs) have attracted tremendous research attention as an alternative to high cost and unsafe lithium ion batteries (LIBs). In current work, for the first time, we report a novel room temperature approach to dope atomic species sodium between the vanadium oxide crystal lattice to obtain NaV3O8.1.69H2O (NVO) nanobelts. Synthesized NVO nanobelts are used as electrode material for MBs. The MBs cells demonstrate stable discharge specific capacity of 110 mA h g-1 at a current density of 10 mA g-1 and a high cyclic stability i...
January 18, 2018: ACS Applied Materials & Interfaces
Le Zhang, Peng Fei Liu, Yu Hang Li, Meng Yang Zu, Xu Li, Zheng Jiang, Yun Wang, Huijun Zhao, Huagui Yang
Boosting the sluggish kinetics of hydrogen evolution reaction in alkaline environments is the key for large application of water-alkali and chlor-alkali electrolysis. Herein, for the first time, we use nitrogen atoms to precisely modulate electrochemical active sites on the surface of nickel oxide with low coordinated oxygen atoms, to achieve enhanced kinetics of alkaline hydrogen evolution. Theoretical and experimental results demonstrate that the surface charge redistribution after modulation simultaneously facilitates the initial water dissociation step, as well as the subsequent recombination of Had from low coordinated oxygen sites and desorption of OH-ad from nickel sites, thus accelerating the overall hydrogen evolution process...
January 18, 2018: ChemSusChem
Chi Zhang, Lei Xie, Yuanqi Ding, Chunxue Yuan, Wei Xu
From the interplay between high-resolution scanning tunneling microscopy imaging/manipulations and density functional theory calculations, we display the hierarchical formation of supramolecular networks by codeposition of 9eG molecules and Fe atoms on Au(111) based on the flexible coordination bonds (the adaptability and versatility in the coordination modes). In the first step, homochiral islands composed of homochiral G4Fe2 motifs are formed; and then in the second step, thermal treatment results in the transformation into the porous networks composed of heterochiral G4Fe2 motifs with the ratio of the components being constant...
January 18, 2018: Physical Chemistry Chemical Physics: PCCP
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