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Natalia Berseneva, Hannu-Pekka Komsa, Ville Vierimaa, Torbjörn Björkman, Zheyong Fan, Ari Harju, Milica Todorović, Arkady Krasheninnikov, Risto M Nieminen
Development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open a possibility to create stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0001), but the stabilization mechanism is still unknown...
July 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Olga Sichevych, Yurii Prots, Yuki Utsumi, Lev Akselrud, Marcus Schmidt, Ulrich Burkhardt, Mauro Coduri, Walter Schnelle, Matej Bobnar, Yu-Ting Wang, Yu-Han Wu, Ku-Ding Tsuei, Liu Hao Tjeng, Yuri Grin
The title compound was synthesized by a reaction of the elemental educts in a corundum crucible at 1200 °C under an Ar atmosphere. The excess of Ga used in the initial mixture served as a flux for the subsequent crystal growth at 600 °C. The crystal structure of Yb4Ga24Pt9 was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group C2/m, Pearson symbol mS74, a = 7.4809(1) Å, b = 12.9546(2) Å, c = 13.2479(2) Å, β = 100.879(1)°, V = 1260.82(6) Å(3), RF = 0...
July 18, 2017: Inorganic Chemistry
Bárbara Emanoele Costa Oliveira, Jaime Aparecido Cury, Antônio Pedro Ricomini Filho
This study was conducted to evaluate if extracellular polysaccharides (EPS) are used by Streptococcus mutans (Sm) biofilm during night starvation, contributing to enamel demineralization increasing occurred during daily sugar exposure. Sm biofilms were formed during 5 days on bovine enamel slabs of known surface hardness (SH). The biofilms were exposed to sucrose 10% or glucose + fructose 10.5% (carbohydrates that differ on EPS formation), 8x/day but were maintained in starvation during the night. Biofilm samples were harvested during two moments, on the end of the 4th day and in the morning of the 5th day, conditions of sugar abundance and starvation, respectively...
2017: PloS One
Clélia Martin, Robert David Barker, Erik B Watkins, Frederic Dubreuil, Emily D Cranston, Laurent Heux, Bruno Jean
Cellulose nanocrystals (CNCs) are promising bio-sourced building blocks for the production of high performance materials. In the last ten years, CNCs have been used in conjunction with polymers for the design of multilayered thin films via the layer-by-layer assembly technique. Herein, polymer chains have been replaced with positively charged inorganic gibbsite nanoplatelets (GN) to form hybrid "nanoparticle-only" composite films. A combination of atomic force microscopy and neutron reflectivity experiments was exploited to investigate the growth and structure of the films...
July 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Na Li, Shibin Wang, Yuhan Sun, Shenggang Li
First principles calculations using both molecular cluster and periodic slab models were performed to reveal the mechanism for the formation of dimethoxymethane (DMM) from methanol over V2O5/TiO2-based catalysts. Two different pathways were found, and the formation of DMM was predicted to be initiated by methanol chemisorption followed by a dehydration reaction with hemiacetal catalyzed by acidic sites. For unpromoted V2O5/TiO2 catalysts, we predicted the energy barrier for the rate determining step (RDS) to follow the order formaldehyde (FA) > methyl formate (MF) > DMM, consistent with the experimental observation for the preferential formation of DMM at a relatively low temperature and that of MF at a relatively high temperature...
July 17, 2017: Physical Chemistry Chemical Physics: PCCP
A Embriaco, E V Bellinzona, A Fontana, A Rotondi
We consider the evaluation of lateral spread distributions of charged particle beams at therapeutic energies, due to an absorber in the form of a homogeneous slab or of a stack. We show that the Molière theory has the same degree of flexibility as the Fermi-Eyges, but is much more accurate and does not present particular computing difficulties with the energy loss formula we have employed. It is also shown that the non-Gaussian shape of the projected one dimensional (1D) distributions is not a complication for passing from the projected to the spatial two-dimensional (2D) distribution, if one assumes circular symmetry...
July 17, 2017: Physics in Medicine and Biology
I Torres-Xirau, I Olaciregui-Ruiz, R A Rozendaal, P González, B J Mijnheer, J-J Sonke, U A van der Heide, A Mans
In external beam radiotherapy, electronic portal imaging devices (EPIDs) are frequently used for pre-treatment and for in vivo dose verification. Currently, various MR-guided radiotherapy systems are being developed and clinically implemented. Independent dosimetric verification is highly desirable. For this purpose we adapted our EPID-based dose verification system for use with the MR-Linac combination developed by Elekta in cooperation with UMC Utrecht and Philips. In this study we extended our back-projection method to cope with the presence of an extra attenuating medium between the patient and the EPID...
July 17, 2017: Physics in Medicine and Biology
Abbas Rezaian, Hassan Ali Nedaie, Nooshin Banaee
A radiation treatment delivery technique, intensity modulated radiation therapy (IMRT), has found widespread use in the treatment of cancers. One of IMRT implementing methods is IMRT compensator based, which the modulation are done by high Z materials. When photons with energies higher than 8MV interact with high Z material in path, Photoneutrons are produced. In this study, the effect of compensator on photoneutron production was investigated. The Monte Carlo code MCNPX was used to calculate the neutron dose equivalent as a function of the depth in phantom with and without compensator...
June 27, 2017: Applied Radiation and Isotopes
Zin Lin, Marko Lončar, Alejandro W Rodriguez
We exploit recently developed topology-optimization techniques to design complex, wavelength-scale resonators for enhancing various nonlinear χ<sup>(2)</sup> and χ<sup>(3)</sup> frequency conversion processes. In particular, we demonstrate aperiodic, multi-track ring resonators and two-dimensional slab microcavities exhibiting long lifetimes Q≳10<sup>4</sup>, small modal volumes V≳(λ/2n)<sup>3</sup>, and among the largest nonlinear overlaps (a generalization of phase matching in large-etalon waveguides) possible, paving the way for efficient, compact, and wide-bandwdith integrated nonlinear devices...
July 15, 2017: Optics Letters
Om Prakash Gurjar, Radha Kishan Paliwal, Surendra Prasad Mishra
The aim is to study the density, isodose depths, and doses at different points in slab-pinewood-slab (SPS) phantom, solid phantom SP34 (made up of polystyrene), and chest level of actual patient for developing heterogeneous chest phantom mimicking thoracic region of human body. A 6 MV photon beam of field size of 10 cm × 10 cm was directed perpendicular to the surface of computed tomography (CT) images of chest level of patient, SPS phantom, and SP34 phantom. Dose was calculated using anisotropic analytical algorithm...
April 2017: Journal of Medical Physics
Sandeep Nigam, Chiranjib Majumder
While alumina-supported platinum particles are versatile for several oxidation reactions, their viability as ORR catalysts has not been explored to date. Therefore, to assess the prospects of alumina-supported platinum nanoclusters in ORRs, a systematic DFT study has been carried out to explore the oxidation behavior of a Ptn@Al2O3 (n = 1-7, 10) cluster. The results are compared with the oxidation behavior of the corresponding gas phase platinum cluster and that of an extended Pt(111) slab. Both supported and unsupported clusters activate adsorbed oxygen molecules and energetically favor dissociative chemisorption of oxygen, leading to stable oxide formation with Pt-O-Pt linkages...
July 13, 2017: Physical Chemistry Chemical Physics: PCCP
Tim Hilgenfeld, Marcel Prager, Alexander Heil, Franz Sebastian Schwindling, Mathias Nittka, David Grodzki, Peter Rammelsberg, Martin Bendszus, Sabine Heiland
OBJECTIVES: Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time. METHODS: Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence...
July 11, 2017: European Radiology
Meisam Farzalipour Tabriz, Bálint Aradi, Thomas Frauenheim, Peter Deak
Defect calculations, using density functional theory in a local or semi-local approximation, in transition metal oxides are severely handicapped by the electron self-interaction error. The underestimation of the band gap may cause incorrect occupation of defect states and wrong formation energies, and the underestimated localization of the states disfavors the formation of small polarons. These problems can be avoided by using higher level approximations (GW or a correctly chosen hybrid functional), but those methods are computationally too expensive to be used for calculating surface defects in a periodic slab model...
July 10, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Michele Paulatto, Mireille Laigle, Audrey Galve, Philippe Charvis, Martine Sapin, Gaye Bayrakci, Mikael Evain, Heidrun Kopp
Subducting slabs carry water into the mantle and are a major gateway in the global geochemical water cycle. Fluid transport and release can be constrained with seismological data. Here we use joint active-source/local-earthquake seismic tomography to derive unprecedented constraints on multi-stage fluid release from subducting slow-spread oceanic lithosphere. We image the low P-wave velocity crustal layer on the slab top and show that it disappears beneath 60-100 km depth, marking the depth of dehydration metamorphism and eclogitization...
July 10, 2017: Nature Communications
Pongthep Prajongtat, Songwut Suramitr, Somkiat Nokbin, Koichi Nakajima, Koichiro Mitsuke, Supa Hannongbua
Structural and electronic properties of eight isolated azo dyes (ArNNAr', where Ar and Ar' denote the aryl groups containing benzene and naphthalene skeletons, respectively) were investigated by density functional theory (DFT) based on the B3LYP/6-31G(d,p) and TD-B3LYP/6-311G(d,p) methods The effect of methanol solvent on the structural and electronic properties of the azo dyes was elucidated by employing a polarizable continuum model (PCM). Then, the azo dyes adsorbed onto the anatase TiO2 (101) slab surface through a carboxyl group...
June 11, 2017: Journal of Molecular Graphics & Modelling
Sangjun Lee, Thang Q Tran, Hyungjun Heo, Myunghwan Kim, Sangin Kim
We propose a novel device structure for the perfect absorption of a one-sided lightwavve illumination, which consists of a high-contrast grating (HCG) and an evanescently coupled slab with an absorbing medium (graphene). The operation principle and design process of the proposed structure are analyzed using the coupled mode theory (CMT), which is confirmed by the rigorous coupled wave analysis (RCWA). According to the CMT analysis, in the design of the proposed perfect absorber, the HCG, functioning as a broadband reflector, and the lossy slab structure can be optimized separately...
July 6, 2017: Scientific Reports
Jeetesh Gawande, Siddharth Jain, John A Santoshi
Isolated radial head fractures are rare and comprise about 2% of all fractures around the elbow. Bilateral radial head fractures are even rarer and few cases have been reported. We present a case of bilateral elbow effusion in a 28-year-old male patient. An initial diagnosis of inflammatory arthritis was made but on investigation it turned out to be a case of bilateral radial head fracture. The patient was managed conservatively with 10 days of immobilisation in above elbow slab followed by active elbow range of movement exercises...
May 29, 2017: Chinese Journal of Traumatology, Zhonghua Chuang Shang za Zhi
Mojdeh Dehghan, Jose Estevam Vieira Ozorio, Simon Chanin, Daranee Tantbirojn, Antheunis Versluis, Franklin Garcia-Godoy
Tooth erosion from an acidic insult may be exacerbated by toothbrushing. The purposes of this study were to develop an in vitro methodology to measure enamel loss after brushing immediately following an acidic episode and to investigate the effect of brushing with an anti-erosive toothpaste. The null hypotheses tested were that tooth erosion after brushing with the toothpaste would not be different from brushing with water and that a 1-hour delay before brushing would not reduce tooth erosion. Forty bovine enamel slabs were embedded, polished, and subjected to baseline profilometry...
July 2017: General Dentistry
Yu Izawa, Shumpei Mori, Tatsuya Nishii, Hiroki Matsuzoe, Hiroshi Imada, Hideya Suehiro, Kazuhiko Nakayama, Kensuke Matsumoto, Hidekazu Tanaka, Sei Fujiwara, Koji Fukuzawa, Ken-Ichi Hirata
Preprocedural recognition of the segment of latest mechanical contraction along with the anatomy of the coronary venous system is important for successful and effective cardiac resynchronization therapy. We present a case of ischemic cardiomyopathy who underwent implantation of a cardiac resynchronization therapy device with a defibrillator, which was facilitated by preprocedural computed tomographic images reconstructed to visualize the left ventricular slab and the coronary venous system simultaneously on the cardiac contour...
July 2017: Echocardiography
Masayuki Nishi, Yasuhiro Kuwayama, Jun Tsuchiya, Taku Tsuchiya
Water transported into Earth's interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth's deep interior, implying that surface water may be transported as far as the core-mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system...
July 13, 2017: Nature
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