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https://www.readbyqxmd.com/read/28735497/conceptual-dft-analysis-of-the-regioselectivity-of-1-3-dipolar-cycloadditions-nitrones-as-a-case-of-study
#1
Ramón Alain Miranda-Quintana, Marco Martínez González, David Hernández-Castillo, Luis A Montero-Cabrera, Paul W Ayers, Christophe Morell
The regioselectivity of the 1,3-dipolar cycloaddition of a model nitrone with a set of dipolarophiles, presenting diverse electronic effects, is analyzed using conceptual density functional theory (DFT) methods. We deviate from standard approaches based on frontier molecular orbitals and formulations of the local hard/soft acid/base principle and use instead the dual descriptor. A detailed analysis is carried out to determine the influence of the way to calculate the dual descriptor, the computational procedure, basis set and choice of method to condensate the values of this descriptor...
August 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28735171/encoding-of-coordination-complexes-with-xml
#2
P Vinoth, P Sankar
An in-silico system to encode structure, bonding and properties of coordination complexes is developed. The encoding is achieved through a semantic XML markup frame. Composition of the coordination complexes is captured in terms of central atom and ligands. Structural information of central atom is detailed in terms of electron status of valence electron orbitals. The ligands are encoded with specific reference to the electron environment of ligand centre atoms. Behaviour of ligands to form low or high spin complexes is accomplished by assigning a Ligand Centre Value to every ligand based on the electronic environment of ligand centre atom...
July 13, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28734704/massive-pneumomediastinum-following-orbital-fracture
#3
Gianfranco Cervellin, Carlotta Bellini, Sara Tarasconi, Paolo Bresciani, Giuseppe Lippi
No abstract text is available yet for this article.
July 17, 2017: American Journal of Emergency Medicine
https://www.readbyqxmd.com/read/28734645/computational-study-of-the-competitive-binding-of-valproic-acid-glucuronide-and-carbapenem-antibiotics-to-acylpeptide-hydrolase
#4
Takeshi Ishikawa, Hiroki Otaki, Satoshi Mizuta, Masami Kuriyama, Osamu Onomura, Norihide Higuchi, Mihoko N Nakashima, Mikiro Nakashima, Kaname Ohyama
The efficacy of the antiepileptic drug VPA is decreased by co-administered carbapenems (CBPMs). The mechanism of CBPM selective inhibition of acylpeptide hydrolase (APEH) hydrolysis of VPA-glucuronide (VPA-G) to VPA is unclear due to the lack of APEH structural information. Here we performed homology modeling of the three-dimensional structure of APEH and subsequent docking simulations with a modeled structure to understand this mechanism. Docking simulations indicated that four groups of binding structures were involved in the binding of VPA-G, panipenem, and meropenem to APEH, but only one or two binding structures were involved in the binding of meropenem with an open β-lactam ring structure and other antibiotics involving ampicillin...
April 30, 2017: Drug Metabolism and Pharmacokinetics
https://www.readbyqxmd.com/read/28734309/universal-two-dimensional-characteristics-in-perovskite-type-oxyhydrides-atio2h-a-li-na-k-rb-cs
#5
Nobuya Sato, Ryosuke Akashi, Shinji Tsuneyuki
A series of unsynthesized perovskite-type oxyhydrides ATiO2H (A = Li, Na, K, Rb, Cs) are investigated by the density functional calculations. These oxyhydrides are stable in the sense of the formation energies for some possible synthesis reactions. They are crystallized into quite similar crystal structures with the long c-axis, and the corner-sharing TiO4H2 octahedra of the ideal perovskite-type structure are deformed into the 5-fold coordinated titanium atoms with the OH plane and the apical oxygen atoms...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734302/analytical-derivatives-of-the-individual-state-energies-in-ensemble-density-functional-theory-method-i-general-formalism
#6
Michael Filatov, Fang Liu, Todd J Martínez
The state-averaged (SA) spin restricted ensemble referenced Kohn-Sham (REKS) method and its state interaction (SI) extension, SI-SA-REKS, enable one to describe correctly the shape of the ground and excited potential energy surfaces of molecules undergoing bond breaking/bond formation reactions including features such as conical intersections crucial for theoretical modeling of non-adiabatic reactions. Until recently, application of the SA-REKS and SI-SA-REKS methods to modeling the dynamics of such reactions was obstructed due to the lack of the analytical energy derivatives...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734300/potential-energy-surfaces-of-quintet-and-singlet-o4
#7
Yuliya Paukku, Ke R Yang, Zoltan Varga, Guoliang Song, Jason D Bender, Donald G Truhlar
We present global ground-state potential energy surfaces for the quintet and singlet spin states of the O4 system that are suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in electronically adiabatic, spin-conserving O2-O2 collisions. The surfaces are based on MS-CASPT2/maug-cc-pVTZ electronic structure calculations with scaled external correlation. The active space has 16 electrons in 12 orbitals. The calculations cover nine kinds of geometrical arrangements corresponding to dissociative diatom-diatom collisions of O2, geometries corresponding to O3-O, geometries identified by running trajectories, and geometries along linear synchronous transit paths...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734299/state-of-the-art-ab-initio-potential-energy-curve-for-the-xenon-atom-pair-and-related-spectroscopic-and-thermophysical-properties
#8
Robert Hellmann, Benjamin Jäger, Eckard Bich
A new ab initio interatomic potential energy curve for two ground-state xenon atoms is presented. It is based on supermolecular calculations at the coupled-cluster level with single, double, and perturbative triple excitations [CCSD(T)] employing basis sets up to sextuple-zeta quality, which were developed as part of this work. In addition, corrections were determined for higher coupled-cluster levels up to CCSDTQ as well as for scalar and spin-orbit relativistic effects at the CCSD(T) level. A physically motivated analytical function was fitted to the calculated interaction energies and used to compute the vibrational spectrum of the dimer, the second virial coefficient, and the dilute gas transport properties...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734298/excited-state-absorption-spectra-of-dissolved-and-aggregated-distyrylbenzene-a-td-dft-state-and-vibronic-analysis
#9
Eliezer Fernando Oliveira, Junqing Shi, Francisco Carlos Lavarda, Larry Lüer, Begoña Milián-Medina, Johannes Gierschner
A time-dependent density functional theory study is performed to reveal the excited state absorption (ESA) features of distyrylbenzene (DSB), a prototype π-conjugated organic oligomer. Starting with a didactic insight to ESA based on simple molecular orbital and configuration considerations, the performance of various density functional theory functionals is tested to reveal the full vibronic ESA features of DSB at short and long probe delay times.
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734276/embedding-for-bulk-systems-using-localized-atomic-orbitals
#10
F Libisch, M Marsman, J Burgdörfer, G Kresse
We extend projection-based embedding techniques to bulk systems to treat point defects in semiconductors and insulators. To avoid non-additive kinetic energy contributions, we construct the density partition using orthogonal subsets of orbitals. We have implemented our approach in the popular Vienna ab initio simulation package software package. We demonstrate its power for defect structures in silicon and polaron formation in titania, two challenging cases for conventional Kohn-Sham density functional theory...
July 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28734206/theoretical-investigation-of-the-conformational-space-of-baicalin
#11
Juan J Martínez Medina, Evelina G Ferrer, Patricia A M Williams, Nora B Okulik
Flavonoids are a large group of polyphenolic compounds ubiquitously present in plants. They are important components of human diet. They are recognized as potential drug candidates to be used in the treatment and prevention of a lot of pathological disorders, due to their protective effects. Baicalin (7-glucuronic acid 5, 6-dihydroxyflavone) is one of the main single active constituents isolated from the dried roots of Scutellaria baicalensis Georgi. The great interest on this flavonoid is due to its various pharmacological properties, such as antioxidant, antimicrobial, anti-inflammatory, anticancer and so on, and its high accumulation in the roots of S...
July 11, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28733974/impact-of-diabetes-mellitus-on-procedural-and-one-year-clinical-outcomes-following-treatment-of-severely-calcified-coronary-lesions-with-the-orbital-atherectomy-system-a-subanalysis-of-the-orbit-ii-study
#12
Michael S Lee, Brad J Martinsen, Arthur C Lee, Ann N Behrens, Richard A Shlofmitz, Christopher Y Kim, Jeffrey W Chambers
OBJECTIVES: The goal of the study was to investigate the safety and efficacy of the coronary orbital atherectomy system to treat severe coronary artery calcification (CAC) prior to stent placement in diabetic and non-diabetic patients. BACKGROUND: The ORBIT II study reported the safety and efficacy of orbital atherectomy treatment in 443 patients with severe CAC. Percutaneous coronary intervention in diabetic patients is associated with an increased risk of major adverse cardiac events (MACE) compared with non-diabetics...
July 22, 2017: Catheterization and Cardiovascular Interventions
https://www.readbyqxmd.com/read/28733918/feasibility-of-optimized-ultralow-dose-pulsed-fluoroscopy-for-upper-gastrointestinal-tract-examinations-a-phantom-study-with-clinical-correlation
#13
Jakob Weiss, Andreas Pomschar, Carsten Rist, Klement Neumaier, Minglun Li, Wilhelm Flatz, Kolja Thierfelder, Mike Notohamiprodjo
PURPOSE: To establish an optimized ultralow-dose digital pulsed fluoroscopy (FP) protocol for upper gastrointestinal tract examinations and to investigate the radiation dose and image quality. MATERIALS AND METHODS: An Alderson-Rando-Phantom with 60 thermoluminescent dosimeters was used for dose measurements to systematically evaluate the dose-area product (DAP) and organ doses of the optimized FP protocol with the following acquisition parameters: 86.7 kV; 77 mA; 0...
July 22, 2017: La Radiologia Medica
https://www.readbyqxmd.com/read/28733664/charge-injection-carriers-recombination-and-homo-energy-level-relationship-in-perovskite-solar-cells
#14
Jesús Jiménez-López, Werther Cambarau, Lydia Cabau, Emilio Palomares
We present a comparative study between a series of well-known semiconductor polymers, used in efficient organic solar cells as hole transport materials (HTM), and the state-of-the art material used as hole transport material in perovskite solar cells: the spiro-OMeTAD. The observed differences in solar cell efficiencies are studied in depth using advanced photoinduced spectroscopic techniques under working illumination conditions. We have observed that there is no correlation between the highest occupied molecular orbital (HOMO) energy levels of the organic semiconductors and the measured open-circuit voltage (VOC)...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28733663/electronic-structure-of-srsn2as2-near-the-topological-critical-point
#15
L-Y Rong, J-Z Ma, S-M Nie, Z-P Lin, Z-L Li, B-B Fu, L-Y Kong, X-Z Zhang, Y-B Huang, H-M Weng, T Qian, H Ding, R-Z Tai
Topological materials with exotic quantum properties are promising candidates for quantum spin electronics. Different classes of topological materials, including Weyl semimetal, topological superconductor, topological insulator and Axion insulator, etc., can be connected to each other via quantum phase transition. For example, it is believed that a trivial band insulator can be twisted into topological phase by increasing spin-orbital coupling or changing the parameters of crystal lattice. With the results of LDA calculation and measurement by angle-resolved photoemission spectroscopy (ARPES), we demonstrate in this work that the electronic structure of SrSn2As2 single crystal has the texture of band inversion near the critical point...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28733661/helical-phase-structure-of-radiation-from-an-electron-in-circular-motion
#16
M Katoh, M Fujimoto, N S Mirian, T Konomi, Y Taira, T Kaneyasu, M Hosaka, N Yamamoto, A Mochihashi, Y Takashima, K Kuroda, A Miyamoto, K Miyamoto, S Sasaki
We theoretically show that a single free electron in circular motion radiates an electromagnetic wave possessing helical phase structure, which is closely related to orbital angular momentum carried by it. We experimentally demonstrate it by interference and double-slit diffraction experiments on radiation from relativistic electrons in spiral motion. Our results indicate that photons carrying orbital angular momentum should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in cosmic space...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28733634/unconventional-band-inversion-and-intrinsic-quantum-spin-hall-effect-in-functionalized-group-v-binary-films
#17
Sheng-Shi Li, Wei-Xiao Ji, Ping Li, Shu-Jun Hu, Tie Zhou, Chang-Wen Zhang, Shi-Shen Yan
Adequately understanding band inversion mechanism, one of the significant representations of topological phase, has substantial implications for design and regulation of topological insulators (TIs). Here, by identifying an unconventional band inversion, we propose an intrinsic quantum spin Hall (QSH) effect in iodinated group-V binary (ABI2) monolayers with a bulk gap as large as 0.409 eV, guaranteeing its viable application at room temperature. The nontrivial topological characters, which can be established by explicit demonstration of Z2 invariant and gapless helical edge states, are derived from the band inversion of antibonding states of p x,y orbitals at the K point...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28733624/scenarios-of-polaron-involved-molecular-adsorption-on-reduced-tio2-110-surfaces
#18
Yunjun Cao, Min Yu, Shandong Qi, Shiming Huang, Tingting Wang, Mingchun Xu, Shujun Hu, Shishen Yan
The polaron introduced by the oxygen vacancy (Vo) dominates many surface adsorption processes and chemical reactions on reduced oxide surfaces. Based on IR spectra and DFT calculations of NO and CO adsorption, we gave two scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces. For NO adsorption, the subsurface polaron electron transfers to a Ti:3d-NO:2p hybrid orbital mainly on NO, leading to the large redshifts of vibration frequencies of NO. For CO adsorption, the polaron only transfers to a Ti:3d state of the surface Ti5c cation underneath CO, and thus only a weak shift of vibration frequency of CO was observed...
July 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28733046/isolated-orbital-metastasis-as-an-initial-presentation-of-a-breast-cancer
#19
Ismael Mora-Guzmán, Rocío Maqueda González, Beatriz Doblado Cardellach, Ana Rodríguez Sánchez
No abstract text is available yet for this article.
July 18, 2017: Cirugía Española
https://www.readbyqxmd.com/read/28732167/quantum-transport-and-subband-structure-of-modulation-doped-gaas-alas-core-superlattice-nanowires
#20
Dominik Irber, Jakob Seidl, Damon James Carrad, Jonathan Becker, Nari Jeon, Bernhard Loitsch, Julia Winnerl, Sonja Matich, Markus Döblinger, Yang Tang, Stefanie Morkötter, Gerhard Abstreiter, Jonathan J Finley, M Grayson, Lincoln Lauhon, Gregor Koblmueller
Modulation-doped III-V semiconductor nanowire (NW) heterostructures have recently emerged as promising candidates to host high-mobility electron channels for future high-frequency, low-energy transistor technologies. The one-dimensional geometry of NWs also makes them attractive for studying quantum confinement effects. Here, we report correlated investigations into the discrete electronic sub-band structure of confined electrons in the channel of Si delta-doped GaAs/AlAs core-superlattice NW heterostructures and the associated signatures in low-temperature transport...
July 21, 2017: Nano Letters
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