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J I Flege, J-O Krisponeit, J Höcker, M Hoppe, Y Niu, A Zakharov, A Schaefer, J Falta, E E Krasovskii
The complex structure and morphology of ultrathin praseodymia films deposited on a ruthenium(0001) single crystal substrate by reactive molecular beam epitaxy is analyzed by intensity-voltage low-energy electron microscopy in combination with theoretical calculations within an ab initio scattering theory. A rich coexistence of various nanoscale crystalline surface structures is identified for the as-grown samples, notably comprising two distinct oxygen-terminated hexagonal Pr2O3(0001) surface phases as well as a cubic Pr2O3(111) and a fluorite PrO2(111) surface component...
May 10, 2017: Ultramicroscopy
Albert Dunnink, Thom R G Stams, Alexandre Bossu, Veronique M F Meijborg, Jet D M Beekman, Sofieke C Wijers, Jacques M T De Bakker, Marc A Vos
Aims: The chronic complete atrioventricular block (CAVB) dog is highly sensitive for drug-induced torsade de pointes (TdP) arrhythmias. Focal mechanisms have been suggested as trigger for TdP onset; however, its exact mechanism remains unclear. In this study, detailed mapping of the ventricles was performed to assess intraventricular heterogeneity of repolarization in relation to the initiation of TdP. Methods and results: In 8 CAVB animals, 56 needles, each containing 4 electrodes, were inserted in the ventricles...
May 1, 2017: Europace: European Pacing, Arrhythmias, and Cardiac Electrophysiology
Natalie Pasberg, Daniel den Engelsen, George R Fern, Paul G Harris, Terry G Ireland, Jack Silver
Herein we describe the synthesis and luminescence of nanosized (Lu1-y-xGdx)2O2S:Tby and (Lu1-y-xGdx)2O3:Tby phosphors with y = 0.1 mol% Tb(3+) and y = 2 mol% Tb(3+) and x ranging between 0 and 1. The concentration of Gd(3+) (x) was varied in steps of 0.1 (molar ratio Gd(3+)). The samples at 0.1 < x < 0.7 contained a mixture of (Lu1-xGdx)2O3:Tb(3+) and (Lu1-xGdx)2O2S:Tb(3+), while the samples at x = 0 contained only Lu2O3:Tb(3+). At 0.1 < x < 0.7 Lu2O2S:Tb(3+) and Gd2O2S:Tb(3+) did not form a solid solution, but rather crystallised into two slightly different hexagonal structures...
May 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Justin K Scheer, Thomas Hamelin, Leon Chang, Brian Lemkuil, Bob S Carter, Clark C Chen
BACKGROUND: Real-time magnetic resonance imaging (MRI) visualization during stereotactic needle biopsies affords several valuable benefits to the neurosurgeon, including the opportunity to visually confirm the biopsy site at the time of surgery. Until now, reported experiences with this technique have been limited to the setting of intraoperative MRI or dedicated procedural MRI suites with modified ventilation systems. OBJECTIVE: To describe our experience with 11 consecutive patients who underwent real-time MRI-guided biopsy performed using SmartFrame® stereotaxis (MRI Interventions, Irvine, California) in the setting of a conventional diagnostic MRI suite...
June 1, 2017: Operative Neurosurgery (Hagerstown, Md.)
B J Demaske, A Chernatynskiy, S R Phillpot
The self-diffusion behavior of vanadium subcarbide (V2C) is investigated using density functional theory calculations, owing to its potential application as a diffusion barrier in nuclear applications. Three ordered V2C structures, two of which correspond to experimentally observed phases, are characterized in terms of their equilibrium structural, electronic and elastic properties. Our model for self-diffusion in V2C considers diffusion of carbon and vanadium to occur separately on each sublattice. Two sets of self-diffusion coefficients are calculated for each structure: one for vacancy-mediated diffusion of vanadium and the other for interstitial diffusion of carbon...
June 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Sergey V Ovsyannikov, Elena Bykova, Anna Pakhomova, Denis P Kozlenko, Maxim Bykov, Sergey E Kichanov, Natalia V Morozova, Igor V Korobeinikov, Fabrice Wilhelm, Andrei Rogalev, Alexander A Tsirlin, Alexander V Kurnosov, Yury G Zainulin, Nadezda I Kadyrova, Alexander P Tyutyunnik, Leonid Dubrovinsky
We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo3V4O12 double perovskite with the high-spin (HS) Co(2+) ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co(2+) ions in the direction perpendicular to the oxygen planes...
May 18, 2017: Inorganic Chemistry
Jie Liu, Xiayue Fan, Xiaorui Liu, Zhishuang Song, Yida Deng, Xiaopeng Han, Wenbin Hu, Cheng Zhong
A new approach has been developed for in situ preparing cubic-shaped Pt particles with (100) preferential orientation on the surface of the conductive support by using a quick, one-step and clean electrochemical method with periodic square-wave potential. The whole electrochemical deposition process is very quick (only 6 min is required to produce cubic Pt particles), without the use of particular capping agents. The shape and the surface structure of deposited Pt particles can be controlled by the lower and upper potential limits of the square-wave potential...
May 18, 2017: ACS Applied Materials & Interfaces
Jiaxin Shao, Peng Hu
BACKGROUND: Assessment of lung function is vital for the diagnosis of a variety of pathological conditions. Research has been proposed to study pulmonary mechanics and kinematics using two-dimensional (2D) magnetic resonance imaging (MRI). This allows estimation of regional lung tissue mechanics but is limited to 2D information. An approach based on three-dimensional (3D) contrast-enhanced MR angiogram of pulmonary blood vessels and a non-rigid image registration technique is proposed for quantification of lung regional deformations, which can potentially be used for assessment of pulmonary parenchymal mechanics and regional ventilation for disease diagnosis without ionizing radiation...
April 2017: Quantitative Imaging in Medicine and Surgery
Thomas Friedrich Fässler, Antti J Karttunen, Laura-Alice Jantke
The large interest in novel Si allotropes has led to an intense investigation of tetrahedral framework structures during the last years. Recently, a guide to deriving sp3-Si allotropes from atom slabs of the diamond structure enabled a systematic deduction of several low-density modifications. Some of the Si networks were recognized as experimentally known frameworks - so-called chemi-inspired structures. We herein present nine novel Si by modifying three-atom thick slabs of the cubic diamond structure after their smooth distortion by applying the same construction kit...
May 17, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Emilia Olsson, Xavier Aparicio-Anglès, Nora H de Leeuw
The substitutional doping of Ca(2+), Sr(2+), and Ba(2+) on the Sm-site in the cubic perovskite SmCoO3 is reported to improve both electronic and ionic conductivities for applications as solid oxide fuel cell (SOFC) cathodes. Hence, in this study we have used density functional theory (DFT) calculations to investigate dopant configurations at two different dopant concentrations: 25 and 50%. To preserve the electroneutrality of the system, we have studied two different charge compensation mechanisms: the creation of oxygen vacancies, and electronic holes...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Xue Wang, Jiayu Chen, Jianxin Zeng, Qiuxiang Wang, Zejun Li, Ruixuan Qin, Changzheng Wu, Zhaoxiong Xie, Lansun Zheng
We report a photochemical synthesis of Pd/CeO2 catalysts with atomically dispersed Pd. Compared to atomically dispersed Pd/CeO2 with a cubic CeO2 support (Pd/CeO2-CP), atomically dispersed Pd/CeO2 with a truncated octahedral CeO2 support (Pd/CeO2-TOP) exhibited higher activity and selectivity, owing to the synergy between Pd atoms and the (111) surface of CeO2. When compared to Pd/CeO2 with Pd clusters and nanoparticles via chemical reduction, Pd/CeO2-TOP showed excellent activity with an enhancement factor of 324 in CO oxidation, as well as an activity enhancement by a factor of 344 in selective oxidation of benzyl alcohol...
May 17, 2017: Nanoscale
Sung Jun Lim, André Schleife, Andrew M Smith
Optical, electronic and structural properties of nanocrystals fundamentally derive from crystal phase. This is especially important for polymorphic II-VI, III-V and I-III-VI2 semiconductor materials such as cadmium selenide, which exist as two stable phases, cubic and hexagonal, each with distinct properties. However, standard crystallographic characterization through diffraction yields ambiguous phase signatures when nanocrystals are small or polytypic. Moreover, diffraction methods are low-throughput, incompatible with solution samples and require large sample quantities...
May 17, 2017: Nature Communications
Peter Mellor, Nicola Willson, Nadene Claydon, Erik I Paling, Belinda Parker, Nicole Wylie, Paul Mackey, Harry Houridis
A sedimentation scanner was used to measure daily sediment height at 10 sites associated with a 14 million cubic metre dredging project in Port Hedland harbour, Western Australia between July 2011 and May 2012. Data were collected from seven potential impact sites, where up to 35 mm of additional sedimentation was predicted via modelling to result from dredging and at three reference sites, where background variation was monitored. A variety of mangrove habitat health indices from each site (including leaf area and health, pneumatophore and faunal burrow density) were collected before, during and after dredging...
May 17, 2017: Environmental Technology
Paula Kayser, Sean Injac, Brendan J Kennedy, Thomas Vogt, Maxim Avdeev, Helen E Maynard-Casely, Zhaoming Zhang
The crystal and magnetic structures of double perovskites of the type Ba2-xSrxYOsO6 were studied by synchrotron X-ray and neutron powder diffraction methods, bulk magnetic susceptibility measurements, and X-ray absorption spectroscopy. The structures were refined using combined neutron and synchrotron data sets based on an ordered array of corner-sharing YO6 and OsO6 octahedra, with the Ba/Sr cations being completely disordered. The structure evolves from cubic to monoclinic Fm3̅m (x ≈ 0.6) → I4/m (x ≈ 1...
May 17, 2017: Inorganic Chemistry
R Viswanath, H S Bhojya Naik, G Arun Kumar, I K Suresh Gowda, S Yallappa
Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn(2+) ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)-visible light and photoluminescence (PL) studies...
May 16, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
Charlotte A L Dixon, Jason A McNulty, Steven Huband, Pamela A Thomas, Philip Lightfoot
The perovskite Li0.2Na0.8NbO3 is shown, by powder neutron diffraction, to display a unique sequence of phase transitions at elevated temperature. The ambient temperature polar phase (rhombohedral, space group R3c) transforms via a first-order transition to a polar tetragonal phase (space group P42mc) in the region 150-300°C; these two phases correspond to Glazer tilt systems a(-)a(-)a(-) and a(+)a(+)c(-), respectively. At 500°C a ferroelectric-paraelectric transition takes place from P42mc to P42/nmc, retaining the a(+)a(+)c(-) tilt...
May 1, 2017: IUCrJ
Owais Ahmed Waseem, Ho Jin Ryu
The WxTaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys...
May 16, 2017: Scientific Reports
Rupak Thapa, Chintan Bhagat, Pragya Shrestha, Suvash Awal, Pravin Dudhagara
BACKGROUND: Silver nanoparticles (AgNPs) are believed to be emerging tool against various infectious diseases including multi-drug resistant (MDR) bacteria. In the present study, in vitro synthesis of AgNPs was optimized using 1:50 ratio of macerozyme (25 μg/μl) and 1 mM AgNO3 incubated at 80 °C for 8 h. AgNPs were characterized by UV-Visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD)...
May 16, 2017: Annals of Clinical Microbiology and Antimicrobials
Rasha H Zedan, Dina El-Fayoumi, Ahmed Awadein
PURPOSE: To investigate the onset and rate of progression of high anisometropia in myopic children younger than 13 years. METHODS: A retrospective study was performed on children with anisometropia younger than 13 years with myopia of more than 4.00 diopters (D) in the more ametropic eye and a difference in spherical equivalent refraction of 4.00 D between both eyes. All children had a complete ophthalmologic examination, including measurement of visual acuity and cycloplegic refraction every 3 to 6 months for at least 5 years...
May 15, 2017: Journal of Pediatric Ophthalmology and Strabismus
Karan Jakhar, Ashesh Chattopadhyay, Atul Thakur, Rishi Raj
Prediction and analysis of the shapes of liquid-vapor interface of droplets under the influence of external forces is critical for various applications. In this regard, a geometric model which can capture the macroscopic shape of the liquid-vapor interface in tandem with the subtleties near the contact line, particularly in the regime where the droplet shape deviates significantly from the idealized spherical cap geometry, is desirable. Such deviations may occur when external forces such as gravity or centrifugal dominate over the surface tension force...
May 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
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