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David R Glowacki, W J Rodgers, Robin Shannon, Struan H Robertson, Jeremy N Harvey
The extent to which vibrational energy transfer dynamics can impact reaction outcomes beyond the gas phase remains an active research question. Molecular dynamics (MD) simulations are the method of choice for investigating such questions; however, they can be extremely expensive, and therefore it is worth developing cheaper models that are capable of furnishing reasonable results. This paper has two primary aims. First, we investigate the competition between energy relaxation and reaction at 'hotspots' that form on the surface of diamond during the chemical vapour deposition process...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Song Liu, Adri C T van Duin, Diana M van Duin, Bin Liu, James H Edgar
Atomistic-scale insights into the growth of a continuous, atomically thin hexagonal boron nitride (hBN) lattice from elemental boron and nitrogen on Ni substrates were obtained from multi-scale modeling combining density functional theory (DFT) and reactive molecular dynamics (rMD). The quantum mechanical calculations focused on the adsorption and reaction energetics for the hBN building-block species, i.e., atomic B, N, BxNy (x, y = 1-2), on Ni(111) and Ni(211), and the diffusion pathways of elemental B and N on these slab model surfaces and in the sublayer...
March 20, 2017: ACS Nano
Ana Lourenco, David Shipley, Nigel Wellock, Russell Thomas, Hugo Bouchard, Andrzej Kacperek, Francesco Fracchiolla, Stefano Lorentini, Marco Schwarz, Niall MacDougall, Gary Royle, Hugo Palmans
The aim of this work was to evaluate the water-equivalence of new trial plastics designed specifically for light-ion beam dosimetry as well as commercially available plastics in clinical proton beams. The water-equivalence of materials was tested by computing a plastic-to-water conversion factor, <i>H</i><sub><i>pl</i>,w</sub>. Trial materials were characterized experimentally in 60 MeV and 226 MeV un-modulated proton beams and the results were compared with Monte Carlo simulations using the FLUKA code...
March 20, 2017: Physics in Medicine and Biology
Akihito Uji, Siva Balasubramanian, Jianqin Lei, Elmira Baghdasaryan, Mayss Al-Sheikh, SriniVas R Sadda
PURPOSE: To investigate the impact of multiple en face image averaging on quantitative measurements of the retinal microvasculature using optical coherence tomography angiography (OCTA). DESIGN: Prospective, observational, cross-sectional case series. PARTICIPANTS: Twenty-one healthy individuals with normal eyes. METHODS: Macular OCTA images were acquired from all participants using the Zeiss Cirrus 5000 with Angioplex OCTA software (Carl Zeiss Meditec, Dublin, CA)...
March 16, 2017: Ophthalmology
Pawel Strak, Konrad Sakowski, Pawel Kempisty, Stanislaw Krukowski
A new scenario for the thermalization process of adsorbates at solid surfaces is proposed. The scenario is based on the existence of an electric dipole layer in which the electron wavefunctions extend over the positive ions, creating a strong local electric field which drags the electrons into the solid interior and repels the positive ions. During adsorption the electrons tunnel into the solid interior, conveying the excess energy. The positive ions are retarded by the field, losing the excess kinetic energy, and are located smoothly into the adsorption sites...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
Kasra A Rezaei, Qinqin Zhang, Chieh-Li Chen, Jennifer Chao, Ruikang K Wang
PURPOSE: To image vascular features of retinitis pigmentosa (RP) using optical coherence tomography angiography (OCTA). METHODS: Patients with RP were imaged by spectral domain optical coherence tomography based angiography (OCTA). The optical microangiography (OMAG) algorithm was applied to scanned datasets to generate 3D OCTA retinal angiograms, i.e., OMAG angiograms. Motion tracking was used to minimize artifacts due to eye movement, and large field of view OMAG angiograms were achieved through a montage scanning protocol...
March 17, 2017: Graefe's Archive for Clinical and Experimental Ophthalmology
S Rudinsky, A S Sanz, R Gauvin
The numerical analysis of the diffraction features rendered by transmission electron microscopy typically relies either on classical approximations (Monte Carlo simulations) or quantum paraxial tomography (the multislice method and any of its variants). Although numerically advantageous (relatively simple implementations and low computational costs), they involve important approximations and thus their range of applicability is limited. To overcome such limitations, an alternative, more general approach is proposed, based on an optimal combination of wave-packet propagation with the on-the-fly computation of associated Bohmian trajectories...
March 14, 2017: Journal of Chemical Physics
Carlos Molero, Raúl Rodríguez-Berral, Francisco Mesa, Francisco Medina
Microstructured metallic devices have been extensively studied because of their interesting properties for controlling the transmission, reflection, and absorption of electromagnetic waves. A very simple implementation is an array of infinitely long parallel metal strips printed on a dielectric substrate. In the past few years, several analytical models have been reported based on the use of equivalent circuits with distributed and lumped components to account for the electrical performance of these structures...
February 2017: Physical Review. E
Indra Yohannes, Heru Prasetio, Karoline Kallis, Christoph Bert
We report an investigation on the accuracy of dose calculation based on the cone-beam computed tomography (CBCT) images of the nonbowtie filter kV imaging system of the Vero linear accelerator. Different sets of materials and tube voltages were employed to generate the Hounsfield unit lookup tables (HLUTs) for both CBCT and fan-beam CT (FBCT) systems. The HLUTs were then implemented for the dose calculation in a treatment planning system (TPS). Dosimetric evaluation was carried out on an in-house-developed cube phantom that consists of water-equivalent slabs and inhomogeneity inserts...
July 2016: Journal of Applied Clinical Medical Physics
Kwang Hyun Song, Karen Chin Snyder, Jinkoo Kim, Haisen Li, Wen Ning, Robert Rusnac, Paul Jackson, James Gordon, Salim M Siddiqui, Indrin J Chetty
2.5 MV electronic portal imaging, available on Varian TrueBeam machines, was characterized using various phantoms in this study. Its low-contrast detectability, spatial resolution, and contrast-to-noise ratio (CNR) were compared with those of conventional 6 MV and kV planar imaging. Scatter effect in large patient body was simulated by adding solid water slabs along the beam path. The 2.5 MV imaging mode was also evaluated using clinically acquired images from 24 patients for the sites of brain, head and neck, lung, and abdomen...
July 2016: Journal of Applied Clinical Medical Physics
Wayne D Gray
Why games? How could anyone consider action games an experimental paradigm for Cognitive Science? In 1973, as one of three strategies he proposed for advancing Cognitive Science, Allen Newell exhorted us to "accept a single complex task and do all of it." More specifically, he told us that rather than taking an "experimental psychology as usual approach," we should "focus on a series of experimental and theoretical studies around a single complex task" so as to demonstrate that our theories of human cognition were powerful enough to explain "a genuine slab of human behavior" with the studies fitting into a detailed theoretical picture...
March 13, 2017: Topics in Cognitive Science
Dapeng Zhao, Moeto Fujisawa, Genti Toyokuni
On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i...
March 15, 2017: Scientific Reports
Daniel G Zhang, Vladimir Feygelman, Eduardo G Moros, Kujtim Latifi, Sarah Hoffe, Jessica Frakes, Geoffrey G Zhang
Flattening filter-free (FFF) beams produce higher dose rates. Combined with compensator-based intensity modulated radiotherapy (IMRT) techniques, the dose delivery for each beam can be much shorter compared to the flattened beam MLC-based or flattened beam compensator-based IMRT. This 'snap shot' IMRT delivery is beneficial to patients for tumor motion management. Due to softer energy, superficial doses in FFF beam treatment are usually higher than those from flattened beams. Due to no flattening filter, thus less photon scattering, peripheral doses are usually lower in FFF beam treatment...
January 2017: Journal of Applied Clinical Medical Physics
Fabian Lambert, Alireza Akbari, Peter Thalmeier, Ilya Eremin
Quasiparticle interference (QPI) imaging of Bogoliubov excitations in quasi-two-dimensional unconventional superconductors has become a powerful technique for measuring the superconducting gap and its symmetry. Here, we present the extension of this method to three-dimensional superconductors and analyze the expected QPI spectrum for the two-component heavy-fermion superconductor UPt_{3} whose gap structure is still controversial. Starting from a 3D electronic structure and the three proposed chiral gap models E_{1g,u} or E_{2u}, we perform a slab calculation that simultaneously gives extended bulk states and topologically protected in-gap dispersionless surface states...
February 24, 2017: Physical Review Letters
Thayanne Monteiro Ramos-Oliveira, Camila Vieira Silva, Paula Mendes Acatauassu Nunes, Cecília Pedroso Turssi, Peter Rechmann, Patricia Moreira de Freitas
This in situ study aimed to investigate the effect of a tin-containing fluoride solution in preventing enamel erosion. Also, its effects on the partly demineralized zone were assessed for the first time. Thirteen volunteers participated in this 2-phase study, wearing removable intra-oral appliances containing four sterilized bovine enamel slabs, for 8 days, where 2 treatment protocols were tested using samples in replicas (n = 13): CO - no treatment (negative control) and FL - AmF/NaF/SnCl2 solution (500 ppm F-, 800 ppm Sn2+, pH = 4...
March 6, 2017: Brazilian Oral Research
Xiang Gao, Kelin Wang
Episodic tremor and accompanying slow slip, together called ETS, is most often observed in subduction zones of young and warm subducting slabs. ETS should help us to understand the mechanics of subduction megathrusts, but its mechanism is still unclear. It is commonly assumed that ETS represents a transition from seismic to aseismic behaviour of the megathrust with increasing depth, but this assumption is in contradiction with an observed spatial separation between the seismogenic zone and the ETS zone. Here we propose a unifying model for the necessary geological condition of ETS that explains the relationship between the two zones...
March 6, 2017: Nature
Belto Dieudonné, Johann Chable, Monique Body, Christophe Legein, Etienne Durand, Fabrice Mauvy, Sébastien Fourcade, Marc Leblanc, Vincent Maisonneuve, Alain Demourgues
Pure tysonite-type Ce1-xSrxF3-x solid solutions for 0 ≤ x < 0.15 were prepared by a solid-state route at 900 °C. The cell parameters follow Vegard's laws for 0 ≤ x ≤ 0.10 and the solubility limit is identified (0.10 < xlimit < 0.15). For 0 ≤ x ≤ 0.05, the F2-(Ce,Sr) and F3-(Ce,Sr) bond distances into [Ce1-xSrxF]((2-x)+) slabs strongly vary with x. This slab buckling is maximum around x = 0.025 and strongly affects the more mobile F1 fluoride ions located between the slabs. The (19)F MAS NMR spectra show the occurrence of F1-F2,3 exchange at 64 °C...
March 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Kawin Setsompop, Qiuyun Fan, Jason Stockmann, Berkin Bilgic, Susie Huang, Stephen F Cauley, Aapo Nummenmaa, Fuyixue Wang, Yogesh Rathi, Thomas Witzel, Lawrence L Wald
PURPOSE: To develop an efficient acquisition for high-resolution diffusion imaging and allow in vivo whole-brain acquisitions at 600- to 700-μm isotropic resolution. METHODS: We combine blipped-controlled aliasing in parallel imaging simultaneous multislice (SMS) with a novel slab radiofrequency (RF) encoding gSlider (generalized slice-dithered enhanced resolution) to form a signal-to-noise ratio-efficient volumetric simultaneous multislab acquisition. Here, multiple thin slabs are acquired simultaneously with controlled aliasing, and unaliased with parallel imaging...
March 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Sandra Murphy, Paul Dowling, Kay Ohlendieck
The pioneering work by Patrick H. O'Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry1975, 250, 4007-4021). The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O'Farrell method or slightly modified gel electrophoretic techniques...
September 9, 2016: Proteomes
Sabina Merlo, Paolo Poma, Eleonora Crisà, Dino Faralli, Marco Soldo
In this work, we have applied optical low-coherence reflectometry (OLCR), implemented with infra-red light propagating in fiberoptic paths, to perform static and dynamic analyses on piezo-actuated glass micro-membranes. The actuator was fabricated by means of thin-film piezoelectric MEMS technology and was employed for modifying the micro-membrane curvature, in view of its application in micro-optic devices, such as variable focus micro-lenses. We are here showing that OLCR incorporating a near-infrared superluminescent light emitting diode as the read-out source is suitable for measuring various parameters such as the micro-membrane optical path-length, the membrane displacement as a function of the applied voltage (yielding the piezo-actuator hysteresis) as well as the resonance curve of the fundamental vibration mode...
February 25, 2017: Sensors
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