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Yu C, Viola G, Zhang D, Stroscio Z, Hu Z, Eskilla VR, Grasso S, Wilson RM, Zhou K, Bonini N, Fortes AD, Abrahams I, Yan H. Structural Evolution in BiNbO 4. Inorg Chem 2021; 60:8507-8518. [PMID: 34060816 DOI: 10.1021/acs.inorgchem.1c00149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The sequence of transitions between different phases of BiNbO4 has been thoroughly investigated and clarified using thermal analysis, high-resolution neutron diffraction, and Raman spectroscopy. The theoretical optical phonon modes of the α-phase have been calculated. Based on thermoanalytical data supported by density functional theory (DFT) calculations, the β-phase is proposed to be metastable, while the α- and γ-phases are stable below and above 1040 °C, respectively. Accurate positional parameters for oxygen positions in the three main polymorphs (α, β, and γ) are presented and the structural relationships between these polymorphs are discussed. Even though no significant changes, only relaxation phenomena, are observed in the dielectric behavior of α-BiNbO4 below 1000 °C, evidence of two further subtle transitions at ∼350 and 600 °C is presented through careful analysis of structural parameters from variable temperature neutron diffraction measurements. Such phase variations are also evident in the phonon modes in Raman spectra and supported by changes in the thermoanalytical data. These subtle transitions may correspond to the previously proposed antiferroelectric to ferroelectric and ferroelectric to paraelectric phase transitions, respectively.
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Affiliation(s)
- Chuying Yu
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.,College of Materials Science and Engineering, Hunan University, Changsha, 410082, China
| | - Giuseppe Viola
- Institute for Materials Discovery, University College London (UCL), London WC1E 7JE, United Kingdom
| | - Dou Zhang
- State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, People's Republic of China
| | - Zaira Stroscio
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Zimeng Hu
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | | | - Salvatore Grasso
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.,Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong, Chengdu 610031, Peoples Republic of China
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Kechao Zhou
- State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, People's Republic of China
| | - Nicola Bonini
- Department of Physics, King's College London, Strand, London WC2R 2LS, United Kingdom
| | - A Dominic Fortes
- ISIS Neutron and Muon Spallation Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Isaac Abrahams
- Materials Research Institute, School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Haixue Yan
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
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Hopple AM, Wilson RM, Kolton M, Zalman CA, Chanton JP, Kostka J, Hanson PJ, Keller JK, Bridgham SD. Massive peatland carbon banks vulnerable to rising temperatures. Nat Commun 2020; 11:2373. [PMID: 32398638 PMCID: PMC7217827 DOI: 10.1038/s41467-020-16311-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 04/17/2020] [Indexed: 11/10/2022] Open
Abstract
Peatlands contain one-third of the world's soil carbon (C). If destabilized, decomposition of this vast C bank could accelerate climate warming; however, the likelihood of this outcome remains unknown. Here, we examine peatland C stability through five years of whole-ecosystem warming and two years of elevated atmospheric carbon dioxide concentrations (eCO2). Warming exponentially increased methane (CH4) emissions and enhanced CH4 production rates throughout the entire soil profile; although surface CH4 production rates remain much greater than those at depth. Additionally, older deeper C sources played a larger role in decomposition following prolonged warming. Most troubling, decreases in CO2:CH4 ratios in gas production, porewater concentrations, and emissions, indicate that the peatland is becoming more methanogenic with warming. We observed limited evidence of eCO2 effects. Our results suggest that ecosystem responses are largely driven by surface peat, but that the vast C bank at depth in peatlands is responsive to prolonged warming.
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Affiliation(s)
- A M Hopple
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR, 97403, USA. .,Schmid College of Science and Technology, Chapman University, Orange, CA, 92866, USA. .,Pacific Northwest National Laboratory, Richland, WA, 99354, USA.
| | - R M Wilson
- Earth, Ocean, and Atmospheric Sciences, Florida State University, Tallahassee, FL, 32306, USA
| | - M Kolton
- School of Biological Sciences and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - C A Zalman
- Schmid College of Science and Technology, Chapman University, Orange, CA, 92866, USA
| | - J P Chanton
- Earth, Ocean, and Atmospheric Sciences, Florida State University, Tallahassee, FL, 32306, USA
| | - J Kostka
- School of Biological Sciences and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - P J Hanson
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - J K Keller
- Schmid College of Science and Technology, Chapman University, Orange, CA, 92866, USA
| | - S D Bridgham
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR, 97403, USA
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3
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Tan L, Misquitta AJ, Sapelkin A, Fang L, Wilson RM, Keeble DS, Zhang B, Zhu T, Riehle FS, Han S, Yu K, Dove MT. X-ray total scattering study of magic-size clusters and quantum dots of cadmium sulphide. Nanoscale 2019; 11:21900-21908. [PMID: 31701975 DOI: 10.1039/c9nr06355b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Four types of magic-size CdS clusters and three different CdS quantum dots have been studied using the technique of X-ray total scattering and pair distribution function analysis. We found that the CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of random stacking of layers. However, the results for the magic-size clusters are significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer-range atomic structure clearly does not reflect the layer structures found in the bulk and the quantum dots. We compare the effect of two ligands, phenylacetic acid and oleic acid, showing that in one case the ligand has little effect on the atomic structure of the magic-size nanocluster, and in another it has a significant effect.
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Affiliation(s)
- Lei Tan
- School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.
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Karatutlu A, Boi FS, Wilson RM, Ersoy O, Ortac B, Sapelkin A. A Bean-Like Formation of Germanium Nanoparticles Inside CNTs by the Subsequent Operation of Colloidal Synthesis and Catalytic Chemical Vapor Deposition Methods. Crystal Research and Technology 2018. [DOI: 10.1002/crat.201800123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ali Karatutlu
- Institute of Materials Science and Nanotechnology and UNAM-National Nanotechnology Research Center; Bilkent University; Ankara 06800 Turkey
| | - Filippo S. Boi
- College of Physical Science and Technology; Sichuan University; Chengdu 610064 P. R. China
| | - Rory M. Wilson
- School of Engineering and Material Science; Queen Mary University of London; London E1 4NS UK
| | - Osman Ersoy
- Centre for Condensed Matter and Materials Physics; School of Physics and Astronomy; Queen Mary University of London; London E1 4NS UK
| | - Bulend Ortac
- Institute of Materials Science and Nanotechnology and UNAM-National Nanotechnology Research Center; Bilkent University; Ankara 06800 Turkey
| | - Andrei Sapelkin
- Centre for Condensed Matter and Materials Physics; School of Physics and Astronomy; Queen Mary University of London; London E1 4NS UK
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Uwalaka CO, Karpukhina N, Cao X, Bissasu S, Wilson RM, Cattell MJ. Effect of sandblasting, etching and resin bonding on the flexural strength/bonding of novel glass-ceramics. Dent Mater 2018; 34:1566-1577. [PMID: 30072165 DOI: 10.1016/j.dental.2018.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/03/2018] [Accepted: 07/03/2018] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To process novel leucite glass-ceramics and test the effects of surface treatment and resin bonding on the biaxial flexural strength (BFS) and shear bond strength (SBS). METHODS Alumino-silicate glasses were ball-milled, and heat treated to form leucite glass-ceramics (LG-C, OLG-C), then sintered into ingots. Ingots were heat extruded into a refractory mould to form disc specimens (1.3×14mm diameter). IPS e.max® was used as a commercial comparison. Glass-ceramic test groups were sandblasted (Groups. 1, 4, 6), sandblasted, etched and adhesively bonded (Groups. 2, 5, 7) or lapped, etched and adhesively bonded (Groups. 3, 8). Specimens were adhesively bonded with Monobond S, followed by the application of Variolink II® cement and light curing. BFS testing was at 1mm/min and SBS testing at 0.5mm/min. Samples were characterised using XRD, SEM and profilometry. RESULTS XRD confirmed tetragonal leucite in LG-C/OLG-C and lithium disilicate/lithium orthophosphate in IPS e.max®. Mean BFS (MPa (SD)) were: Gp1 LG-C; 193.1 (13.9), Gp2 LG-C; 217.7 (23.0), Gp3 LG-C; 273.6 (26.7), Gp4 OLG-C; 255.9 (31); Gp5 OLG-C; 288.6 (37.4), Gp6 IPS e.max®; 258.6 (20.7), Gp7 IPS e.max®; 322.3 (23.4) and Gp8 IPS e.max®; 416.4 (52.6). The Median SBS (MPa) were Gp1 LG-C; 14.2, Gp2 LG-C (10s etch); 10.6 and Gp3 IPS e.max®; 10.8. Mean surface roughness was 5-5.1μm (IPS e.max®) and 2.6μm (LG-C). SIGNIFICANCE Novel leucite glass-ceramics with reduced flaw size and fine microstructures produced enhanced BFS and SBS by resin bonding. These properties may be useful for the fabrication of minimally invasive aesthetic and fracture resistant restorations.
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Affiliation(s)
- Chinwe O Uwalaka
- Centre for Oral Bioengineering, Bart's and the London, School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel, E1 2AD, UK
| | - Natalia Karpukhina
- Centre for Oral Bioengineering, Bart's and the London, School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel, E1 2AD, UK
| | - Xu Cao
- Centre for Oral Bioengineering, Bart's and the London, School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel, E1 2AD, UK
| | - Sami Bissasu
- Centre for Oral Bioengineering, Bart's and the London, School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel, E1 2AD, UK
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London, London, Mile End Road, E1 4NS, UK
| | - Michael J Cattell
- Centre for Oral Bioengineering, Bart's and the London, School of Medicine and Dentistry, Queen Mary University of London, Turner Street, Whitechapel, E1 2AD, UK.
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6
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Yu C, Viola G, Zhang D, Zhou K, Koval V, Mahajan A, Wilson RM, Tarakina NV, Abrahams I, Yan H. Phase evolution and electrical behaviour of samarium-substituted bismuth ferrite ceramics. Ann Ital Chir 2018. [DOI: 10.1016/j.jeurceramsoc.2017.12.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Baillie D, Wilson RM, Blakie PB. Collective Excitations of Self-Bound Droplets of a Dipolar Quantum Fluid. Phys Rev Lett 2017; 119:255302. [PMID: 29303342 DOI: 10.1103/physrevlett.119.255302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Indexed: 06/07/2023]
Abstract
We calculate the collective excitations of a dipolar Bose-Einstein condensate in the regime where it self-binds into droplets stabilized by quantum fluctuations. We show that the filament-shaped droplets act as a quasi-one-dimensional waveguide along which low-angular-momentum phonons propagate. The evaporation (unbinding) threshold occurring as the atom number N is reduced to the critical value N_{c} is associated with a monopolelike excitation going soft as ε_{0}∼(N-N_{c})^{1/4}. Considering the system in the presence of a trapping potential, we quantify the crossover from a trap-bound condensate to a self-bound droplet.
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Affiliation(s)
- D Baillie
- Department of Physics, Centre for Quantum Science, and Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin 9016, New Zealand
| | - R M Wilson
- Department of Physics, United States Naval Academy, Annapolis, Maryland 21402, USA
| | - P B Blakie
- Department of Physics, Centre for Quantum Science, and Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin 9016, New Zealand
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8
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Chen X, Chen X, Brauer DS, Wilson RM, Law RV, Hill RG, Karpukhina N. Sodium Is Not Essential for High Bioactivity of Glasses. Int J Appl Glass Sci 2017; 8:428-437. [PMID: 29271977 PMCID: PMC5736107 DOI: 10.1111/ijag.12323] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
This study aims to demonstrate that excellent bioactivity of glass can be achieved without the presence of an alkali metal component in glass composition. In vitro bioactivity of two sodium-free glasses based on the quaternary system SiO2-P2O5-CaO-CaF2 with 0 and 4.5 mol% CaF2 content was investigated and compared with the sodium containing glasses with equivalent amount of CaF2. The formation of apatite after immersion in Tris buffer was followed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 31P and 19F solid state MAS-NMR. The dissolution study was completed by ion release measurements in Tris buffer. The results show that sodium free bioactive glasses formed apatite at 3 hours of immersion in Tris buffer, which is as fast as the corresponding sodium containing composition. This signifies that sodium is not an essential component in bioactive glasses and it is possible to make equally degradable bioactive glasses with or without sodium. The results presented here also emphasize the central role of the glass compositions design which is based on understanding of structural role of components and/or predicting the network connectivity of glasses.
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Affiliation(s)
- Xiaojing Chen
- Dental Physical Sciences, Institute of Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Xiaohui Chen
- Division of Dentistry, School of Medical Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Delia S Brauer
- Otto-Schott-Institut, Friedrich-Schiller-Universität, Fraunhoferstr. 6, Jena 07743, Germany
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Robert V Law
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom
| | - Robert G Hill
- Dental Physical Sciences, Institute of Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Natalia Karpukhina
- Dental Physical Sciences, Institute of Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
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Kanwal N, Brauer DS, Earl J, Wilson RM, Karpukhina N, Hill RG. In-vitro apatite formation capacity of a bioactive glass - containing toothpaste. J Dent 2017; 68:51-58. [PMID: 29097120 DOI: 10.1016/j.jdent.2017.10.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 10/14/2017] [Accepted: 10/28/2017] [Indexed: 10/18/2022] Open
Abstract
OBJECTIVES The in-vitro dissolution of bioactive glass-based toothpastes and their capacity to form apatite-like phases in buffer solutions have been investigated. MATERIALS AND METHODS The commercial toothpaste samples were tested on immersion in artificial saliva, Earle's salt solution and Tris buffer for duration from 10min to four days. The powder samples collected at the end of the immersion were studied using solid-state 31P and 19F nuclear magnetic resonance spectroscopy (NMR), X-ray powder diffraction and Fourier transform infrared (FTIR) spectroscopy. The fluoride concentration in the solution remained after the immersion was measured. RESULTS In artificial saliva and in presence of sodium monofluorophosphate (MFP), the bioactive glass and bioactive glass-based toothpastes formed fluoridated apatite-like phases in under 10min. A small amount of apatite-like phase was detected by 31P NMR in the toothpaste with MFP but no bioactive glass. The toothpaste with bioactive glass but no fluoride formed an apatite-like phase as rapidly as the paste containing bioactive glass and fluoride. By contrast, apatite-like phase formation was much slower in Earle's salt solution than artificial saliva and slower than Tris buffer. CONCLUSIONS The results of this lab-based study showed that the toothpaste with MFP and bioactive glass formed a fluoridated apatite in artificial saliva and in Tris buffer, as did the mixture of bioactive glass and MFP. CLINICAL SIGNIFICANCE The presence of fluoride in bioactive glass-containing toothpastes can potentially lead to the formation of a fluoridated apatite, which may result in improved clinical effectiveness and durability. However, this should be further tested intra-orally.
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Affiliation(s)
- Nasima Kanwal
- School of Chemical and Biological Sciences, Queen Mary University of London, London, UK
| | - Delia S Brauer
- Otto-Schott-Institut, Friedrich-Schiller-Universität, Jena, Germany
| | - Jonathan Earl
- GlaxoSmithKline Consumer Healthcare, Weybridge, Surrey, KT13 0DE, UK
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London, London, UK
| | - Natalia Karpukhina
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
| | - Robert G Hill
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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Foss-Feig M, Niroula P, Young JT, Hafezi M, Gorshkov AV, Wilson RM, Maghrebi MF. Emergent equilibrium in many-body optical bistability. Phys Rev A (Coll Park) 2017; 95:10.1103/PhysRevA.95.043826. [PMID: 31093586 PMCID: PMC6513354 DOI: 10.1103/physreva.95.043826] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Many-body systems constructed of quantum-optical building blocks can now be realized in experimental platforms ranging from exciton-polariton fluids to ultracold Rydberg gases, establishing a fascinating interface between traditional many-body physics and the driven-dissipative, nonequilibrium setting of cavity QED. At this interface, the standard techniques and intuitions of both fields are called into question, obscuring issues as fundamental as the role of fluctuations, dimensionality, and symmetry on the nature of collective behavior and phase transitions. Here, we study the driven-dissipative Bose-Hubbard model, a minimal description of numerous atomic, optical, and solid-state systems in which particle loss is countered by coherent driving. Despite being a lattice version of optical bistability, a foundational and patently nonequilibrium model of cavity QED, the steady state possesses an emergent equilibrium description in terms of a classical Ising model. We establish this picture by making new connections between traditional techniques from many-body physics (functional integrals) and quantum optics (the system-size expansion). To lowest order in a controlled expansion-organized around the experimentally relevant limit of weak interactions-the full quantum dynamics reduces to nonequilibrium Langevin equations, which support a phase transition described by model A of the Hohenberg-Halperin classification. Numerical simulations of the Langevin equations corroborate this picture, revealing that canonical behavior associated with the Ising model manifests readily in simple experimental observables.
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Affiliation(s)
- M Foss-Feig
- United States Army Research Laboratory, Adelphi, Maryland 20783, USA
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
- Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, Maryland 20742, USA
| | - P Niroula
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - J T Young
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
| | - M Hafezi
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
- Department of Electrical and Computer Engineering and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA
| | - A V Gorshkov
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
- Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, Maryland 20742, USA
| | - R M Wilson
- Department of Physics, United States Naval Academy, Annapolis, Maryland 21402, USA
| | - M F Maghrebi
- Joint Quantum Institute, NIST and University of Maryland, College Park, Maryland 20742, USA
- Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, Maryland 20742, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
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11
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Theocharopoulos AL, Bushby AJ, P'ng KM, Wilson RM, Tanner KE, Cattell MJ. Interfacial modulus mapping of layered dental ceramics using nanoindentation. J Adv Prosthodont 2016; 8:479-488. [PMID: 28018566 PMCID: PMC5179487 DOI: 10.4047/jap.2016.8.6.479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 10/01/2016] [Accepted: 11/02/2016] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The aim of this study was to test the modulus of elasticity (E) across the interfaces of yttria stabilized zirconia (YTZP) / veneer multilayers using nanoindentation. MATERIALS AND METHODS YTZP core material (KaVo-Everest, Germany) specimens were either coated with a liner (IPS e.max ZirLiner, Ivoclar-Vivadent) (Type-1) or left as-sintered (Type-2) and subsequently veneered with a pressable glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). A 5 µm (nominal tip diameter) spherical indenter was used with a UMIS CSIRO 2000 (ASI, Canberra, Australia) nanoindenter system to test E across the exposed and polished interfaces of both specimen types. The multiple point load – partial unload method was used for E determination. All materials used were characterized using Scanning Electron Microscopy (SEM) and X – ray powder diffraction (XRD). E mappings of the areas tested were produced from the nanoindentation data. RESULTS A significantly (P<.05) lower E value between Type-1 and Type-2 specimens at a distance of 40 µm in the veneer material was associated with the liner. XRD and SEM characterization of the zirconia sample showed a fine grained bulk tetragonal phase. IPS e-max ZirPress and IPS e-max ZirLiner materials were characterized as amorphous. CONCLUSION The liner between the YTZP core and the heat pressed veneer may act as a weak link in this dental multilayer due to its significantly (P<.05) lower E. The present study has shown nanoindentation using spherical indentation and the multiple point load - partial unload method to be reliable predictors of E and useful evaluation tools for layered dental ceramic interfaces.
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Affiliation(s)
- Antonios L Theocharopoulos
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, Mile End, London, UK.; Cork University Dental School and Hospital, Wilton, Cork, Ireland
| | - Andrew J Bushby
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, Mile End, London, UK
| | - Ken My P'ng
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, Mile End, London, UK
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, Mile End, London, UK
| | - K Elizabeth Tanner
- Department of Civil and Mechanical Engineering, University of Glasgow, Glasgow, UK
| | - Michael J Cattell
- Barts & The London School of Dentistry, Centre for Adult Oral Health, Stepney Way, Whitechapel, London, UK
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12
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Kent NW, Blunn G, Karpukhina N, Davis G, de Godoy RF, Wilson RM, Coathup M, Onwordi L, Quak WY, Hill R. In vitro
and in vivo
study of commercial calcium phosphate cement HydroSet™. J Biomed Mater Res B Appl Biomater 2016; 106:21-30. [DOI: 10.1002/jbm.b.33809] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 10/13/2016] [Accepted: 10/16/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Niall W. Kent
- Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London E1 4NS UK
- Centre for Nature Inspired Engineering; University College London, Torrington Place; London WC1E 7JE UK
- Warwick Medical School; University of Warwick; Coventry CV4 7AL UK
| | - Gordon Blunn
- John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital; Stanmore UK
| | - Natalia Karpukhina
- Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London E1 4NS UK
| | - Graham Davis
- Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London E1 4NS UK
| | - Roberta Ferro de Godoy
- John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital; Stanmore UK
| | - Rory M. Wilson
- School of Engineering and Materials Science; Queen Mary University of London; London E1 4NS UK
| | - Melanie Coathup
- John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital; Stanmore UK
| | - Lyris Onwordi
- John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital; Stanmore UK
| | - Wen Yu Quak
- John Scales Centre for Biomedical Engineering; Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital; Stanmore UK
| | - Robert Hill
- Dental Physical Sciences, Institute of Dentistry, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London E1 4NS UK
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13
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Luo D, Shahid S, Wilson RM, Cattell MJ, Sukhorukov GB. Novel Formulation of Chlorhexidine Spheres and Sustained Release with Multilayered Encapsulation. ACS Appl Mater Interfaces 2016; 8:12652-12660. [PMID: 27176115 DOI: 10.1021/acsami.6b02997] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This work demonstrates the synthesis of new chlorhexidine polymorphs with controlled morphology and symmetry, which were used as a template for layer-by-layer (LbL) encapsulation. LbL self-assembly of oppositely charged polyelectrolytes onto the drug surface was used in the current work, as an efficient method to produce a carrier with high drug content, improved drug solubility and sustained release. Coprecipitation of the chlorhexidine polymorphs was performed using chlorhexidine diacetate and calcium chloride solutions. Porous interconnected chlorhexidine spheres were produced by tuning the concentration of calcium chloride. The size of these drug colloids could be further controlled from 5.6 μm to over 20 μm (diameter) by adjusting the coprecipitation temperature. The chlorhexidine content in the spheres was determined to be as high as 90%. These particles were further stabilized by depositing 3.5 bilayers of poly(allylamine hydrochloride) (PAH) and polystyrenesulfonate (PSS) on the surface. In vitro release kinetics of chlorhexidine capsules showed that the multilayer shells could prolong the release, which was further demonstrated by characterizing the remaining chlorhexidine capsules with SEM and confocal microscopy. The new chlorhexidine polymorph and LbL coating has created novel chlorhexidine formulations. Further modification to the chlorhexidine polymorph structure is possible to achieve both sustained and stimuli responsive release, which will enhance its clinical performance in medicine and dentistry.
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Affiliation(s)
- Dong Luo
- School of Engineering and Materials Science, Queen Mary University of London , London E1 4NS, United Kingdom
| | - Saroash Shahid
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London , London E1 2AD, United Kingdom
| | - Rory M Wilson
- School of Engineering and Materials Science, Queen Mary University of London , London E1 4NS, United Kingdom
| | - Michael J Cattell
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London , London E1 2AD, United Kingdom
| | - Gleb B Sukhorukov
- School of Engineering and Materials Science, Queen Mary University of London , London E1 4NS, United Kingdom
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14
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Al Mansour F, Karpukhina N, Grasso S, Wilson RM, Reece MJ, Cattell MJ. The effect of spark plasma sintering on lithium disilicate glass-ceramics. Dent Mater 2015. [DOI: 10.1016/j.dental.2015.07.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Chen S, Briscoe J, Shi Y, Chen K, Wilson RM, Dunn S, Binions R. A simple, low-cost CVD route to high-quality CH3NH3PbI3perovskite thin films. CrystEngComm 2015. [DOI: 10.1039/c5ce01496d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Boi FS, Wilson RM, Mountjoy G, Ibrar M, Baxendale M. Boundary layer chemical vapour synthesis of self-organised ferromagnetically filled radial-carbon-nanotube structures. Faraday Discuss 2014; 173:67-77. [PMID: 25466445 DOI: 10.1039/c4fd00071d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Boundary layer chemical vapour synthesis is a new technique that exploits random fluctuations in the viscous boundary layer between a laminar flow of pyrolysed metallocene vapour and a rough substrate to yield ferromagnetically filled radial-carbon-nanotube structures departing from a core agglomeration of spherical nanocrystals individually encapsulated by graphitic shells. The fluctuations create the thermodynamic conditions for the formation of the central agglomeration in the vapour which subsequently defines the spherically symmetric diffusion gradient that initiates the radial growth. The radial growth is driven by the supply of vapour feedstock by local diffusion gradients created by endothermic graphitic-carbon formation at the vapour-facing tips of the individual nanotubes and is halted by contact with the isothermal substrate. The radial structures are the dominant product and the reaction conditions are self-sustaining. Ferrocene pyrolysis yields three common components in the nanowire encapsulated by multiwall carbon nanotubes, Fe3C, α-Fe, and γ-Fe. Magnetic tuning in this system can be achieved through the magnetocrystalline and shape anisotropies of the encapsulated nanowire. Here we demonstrate proof that alloying of the encapsulated nanowire is an additional approach to tuning of the magnetic properties of these structures by synthesis of radial-carbon-nanotube structures with γ-FeNi encapsulated nanowires.
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Affiliation(s)
- Filippo S Boi
- School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
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17
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Chen X, Chen X, Brauer DS, Wilson RM, Hill RG, Karpukhina N. Bioactivity of Sodium Free Fluoride Containing Glasses and Glass-Ceramics. Materials (Basel) 2014; 7:5470-5487. [PMID: 28788139 PMCID: PMC5456181 DOI: 10.3390/ma7085470] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/16/2014] [Accepted: 07/18/2014] [Indexed: 01/28/2023]
Abstract
The bioactivity of a series of fluoride-containing sodium-free calcium and strontium phosphosilicate glasses has been tested in vitro. Glasses with high fluoride content were partially crystallised to apatite and other fluoride-containing phases. The bioactivity study was carried out in Tris and SBF buffers, and apatite formation was monitored by XRD, FTIR and solid state NMR. Ion release in solutions has been measured using ICP-OES and fluoride-ion selective electrode. The results show that glasses with low amounts of fluoride that were initially amorphous degraded rapidly in Tris buffer and formed apatite as early as 3 h after immersion. The apatite was identified as fluorapatite by 19F MAS-NMR after 6 h of immersion. Glass degradation and apatite formation was significantly slower in SBF solution compared to Tris. On immersion of the partially crystallised glasses, the fraction of apatite increased at 3 h compared to the amount of apatite prior to the treatment. Thus, partial crystallisation of the glasses has not affected bioactivity significantly. Fast dissolution of the amorphous phase was also indicated. There was no difference in kinetics between Tris and SBF studies when the glass was partially crystallised to apatite before immersion. Two different mechanisms of apatite formation for amorphous or partially crystallised glasses are discussed.
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Affiliation(s)
- Xiaojing Chen
- Dental Physical Science, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
| | - Xiaohui Chen
- Dental Physical Science, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
| | - Delia S Brauer
- Otto-Schott-Institut, Friedrich-Schiller-Universität, Fraunhoferstr. 6, Jena 07743, Germany.
| | - Rory M Wilson
- School of Engineering and Materials Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
| | - Robert G Hill
- Dental Physical Science, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
| | - Natalia Karpukhina
- Dental Physical Science, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
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18
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Boi FS, Mountjoy G, Luklinska Z, Spillane L, Karlsson LS, Wilson RM, Corrias A, Baxendale M. The origin of long-period lattice spacings observed in iron-carbide nanowires encapsulated by multiwall carbon nanotubes. Microsc Microanal 2013; 19:1298-1302. [PMID: 23816334 DOI: 10.1017/s1431927613001918] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Structures comprising single-crystal, iron-carbon-based nanowires encapsulated by multiwall carbon nanotubes self-organize on inert substrates exposed to the products of ferrocene pyrolysis at high temperature. The most commonly observed encapsulated phases are Fe₃C, α-Fe, and γ-Fe. The observation of anomalously long-period lattice spacings in these nanowires has caused confusion since reflections from lattice spacings of ≥ 0.4 nm are kinematically forbidden for Fe₃C, most of the rarely observed, less stable carbides, α-Fe, and g-Fe. Through high-resolution electron microscopy, selective area electron diffraction, and electron energy loss spectroscopy we demonstrate that the observed long-period lattice spacings of 0.49, 0.66, and 0.44 nm correspond to reflections from the (100), (010), and (001) planes of orthorhombic Fe₃C (space group Pnma). Observation of these forbidden reflections results from dynamic scattering of the incident beam as first observed in bulk Fe₃C crystals.With small amounts of beam tilt these reflections can have significant intensities for crystals containing glide planes such as Fe₃C with space groups Pnma or Pbmn.
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Affiliation(s)
- Filippo S Boi
- School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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Nuccio L, Willis M, Schulz L, Fratini S, Messina F, D'Amico M, Pratt FL, Lord JS, McKenzie I, Loth M, Purushothaman B, Anthony J, Heeney M, Wilson RM, Hernández I, Cannas M, Sedlak K, Kreouzis T, Gillin WP, Bernhard C, Drew AJ. Importance of spin-orbit interaction for the electron spin relaxation in organic semiconductors. Phys Rev Lett 2013; 110:216602. [PMID: 23745907 DOI: 10.1103/physrevlett.110.216602] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Indexed: 05/05/2023]
Abstract
Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of the fundamental physics behind electron spin relaxation in organic semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but the role of the spin-orbit interaction remains elusive. Here, we report muon spin spectroscopy and time-resolved photoluminescence measurements on two series of molecular semiconductors in which the strength of the spin-orbit interaction has been systematically modified with a targeted chemical substitution of different atoms at a particular molecular site. We find that the spin-orbit interaction is a significant source of electron spin relaxation in these materials.
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Affiliation(s)
- L Nuccio
- Queen Mary University of London, School of Physics and Astronomy, Mile End Road, London E1 4NS, United Kingdom.
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20
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Shah FA, Brauer DS, Wilson RM, Hill RG, Hing KA. Influence of cell culture medium composition onin vitrodissolution behavior of a fluoride-containing bioactive glass. J Biomed Mater Res A 2013; 102:647-54. [DOI: 10.1002/jbm.a.34724] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/07/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Furqan A. Shah
- School of Engineering and Materials Science; Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
- Department of Biomaterials; Sahlgrenska Academy at University of Gothenburg; Box 412 SE-405 30 Göteborg Sweden
| | - Delia S. Brauer
- Dental Physical Sciences; Barts and the London School of Medicine and Dentistry, Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
- Otto-Schott-Institut; Friedrich-Schiller-Universität; Fraunhoferstr. 6 07743 Jena Germany
| | - Rory M. Wilson
- School of Engineering and Materials Science; Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
| | - Robert G. Hill
- Dental Physical Sciences; Barts and the London School of Medicine and Dentistry, Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
| | - Karin A. Hing
- School of Engineering and Materials Science; Queen Mary University of London; Mile End Road London E1 4NS United Kingdom
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21
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Wilson RM, Michel P, Olsen S, Gibberd RW, Vincent C, El-Assady R, Rasslan O, Qsous S, Macharia WM, Sahel A, Whittaker S, Abdo-Ali M, Letaief M, Ahmed NA, Abdellatif A, Larizgoitia I. Patient safety in developing countries: retrospective estimation of scale and nature of harm to patients in hospital. BMJ 2012; 344:e832. [PMID: 22416061 DOI: 10.1136/bmj.e832] [Citation(s) in RCA: 180] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To assess the frequency and nature of adverse events to patients in selected hospitals in developing or transitional economies. DESIGN Retrospective medical record review of hospital admissions during 2005 in eight countries. SETTING Ministries of Health of Egypt, Jordan, Kenya, Morocco, Tunisia, Sudan, South Africa and Yemen; the World Health Organisation (WHO) Eastern Mediterranean and African Regions (EMRO and AFRO), and WHO Patient Safety. PARTICIPANTS Convenience sample of 26 hospitals from which 15,548 patient records were randomly sampled. MAIN OUTCOME MEASURES Two stage screening. Initial screening based on 18 explicit criteria. Records that screened positive were then reviewed by a senior physician for determination of adverse event, its preventability, and the resulting disability. RESULTS Of the 15,548 records reviewed, 8.2% showed at least one adverse event, with a range of 2.5% to 18.4% per country. Of these events, 83% were judged to be preventable, while about 30% were associated with death of the patient. About 34% adverse events were from therapeutic errors in relatively non-complex clinical situations. Inadequate training and supervision of clinical staff or the failure to follow policies or protocols contributed to most events. CONCLUSIONS Unsafe patient care represents a serious and considerable danger to patients in the hospitals that were studied, and hence should be a high priority public health problem. Many other developing and transitional economies will probably share similar rates of harm and similar contributory factors. The convenience sampling of hospitals might limit the interpretation of results, but the identified adverse event rates show an estimate that should stimulate and facilitate the urgent institution of appropriate remedial action and also to trigger more research. Prevention of these adverse events will be complex and involves improving basic clinical processes and does not simply depend on the provision of more resources.
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Affiliation(s)
- R M Wilson
- New York City Health and Hospital Corporation, 125 Worth Street, New York, NY 10013, USA.
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22
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Chen X, Chadwick TC, Wilson RM, Hill RG, Cattell MJ. Crystallization and flexural strength optimization of fine-grained leucite glass-ceramics for dentistry. Dent Mater 2011; 27:1153-61. [DOI: 10.1016/j.dental.2011.08.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/29/2011] [Accepted: 08/19/2011] [Indexed: 11/30/2022]
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23
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24
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25
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Baklar MA, Koch F, Kumar A, Domingo EB, Campoy-Quiles M, Feldman K, Yu L, Wobkenberg P, Ball J, Wilson RM, McCulloch I, Kreouzis T, Heeney M, Anthopoulos T, Smith P, Stingelin N. Solid-state processing of organic semiconductors. Adv Mater 2010; 22:3942-3947. [PMID: 20845373 DOI: 10.1002/adma.200904448] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Affiliation(s)
- Mohammed A Baklar
- Department of Materials, Imperial College London, London SW7 2AZ, UK
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26
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Groves PJ, Wilson RM, Dieppe PA, Shellis RP. Synthesis of triclinic calcium pyrophosphate crystals. J Mater Sci Mater Med 2007; 18:1355-60. [PMID: 17277979 DOI: 10.1007/s10856-007-0129-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Accepted: 03/08/2006] [Indexed: 05/13/2023]
Abstract
This paper presents a method for preparing crystals of triclinic calcium pyrophosphate (t-CPPD). A calcium pyrophosphate intermediate is first prepared by reaction of potassium pyrophosphate and calcium chloride. Samples of the intermediate are dissolved in hydrochloric acid and urea added. Upon heating to 95-100 degrees C, hydrolysis of the urea causes the pH to rise and t-CPPD crystallises out. Purity of the product was ascertained by chemical and physical analysis. Where large crystals are required an unstirred system is used, while smaller crystals are produced by stirring the reaction mixture.
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Affiliation(s)
- P J Groves
- Division of Restorative Dentistry, University of Bristol Dental School, Lower Maudlin Street, Bristol BS1 2LY, UK
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27
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Kulak AN, Iddon P, Li Y, Armes SP, Cölfen H, Paris O, Wilson RM, Meldrum FC. Continuous structural evolution of calcium carbonate particles: a unifying model of copolymer-mediated crystallization. J Am Chem Soc 2007; 129:3729-36. [PMID: 17335283 DOI: 10.1021/ja067422e] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two double-hydrophilic block copolymers, each comprising a nonionic block and an anionic block comprising pendent aromatic sulfonate groups, were used as additives to modify the crystallization of CaCO3. Marked morphological changes in the CaCO3 particles were observed depending on the reaction conditions used. A poly(ethylene oxide)-b-poly(sodium 4-styrenesulfonate) diblock copolymer was particularly versatile in effecting a morphological change in calcite particles, and a continuous structural transition in the product particles from polycrystalline to mesocrystal to single crystal was observed with variation in the calcium concentration. The existence of this structural sequence provides unique insight into the mechanism of polymer-mediated crystallization. We propose that it reflects continuity in the crystallization mechanism itself, spanning the limits from nonoriented aggregation of nanoparticles to classical ion-by-ion growth. The various pathways to polycrystalline, mesocrystal, and single-crystal particles, which had previously been considered to be distinct, therefore all form part of a unifying crystallization framework based on the aggregation of precursor subunits.
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Affiliation(s)
- Alex N Kulak
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
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28
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Shellis RP, Wilson RM. Apparent solubility distributions of hydroxyapatite and enamel apatite. J Colloid Interface Sci 2006; 278:325-32. [PMID: 15450451 DOI: 10.1016/j.jcis.2004.06.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Accepted: 06/01/2004] [Indexed: 10/26/2022]
Abstract
Samples of human dental enamel and hydroxyapatite were equilibrated at 5 mg/40 ml for 9 days at 37 degrees C with acetate buffers adjusted to a range of saturations with respect to hydroxyapatite. Sigmoidal apparent solubility distributions, in which the fraction dissolved was plotted against--log(ion activity product for hydroxyapatite) (pIHA), were constructed. About 10% of the hydroxyapatite and 14% of the enamel was very soluble, dissolving even at pIHA 55. The apparent solubility distributions for both solids were invariant with pH (4.5, 5.0, 5.5), within experimental error, showing that solubility was controlled by a phase with the stoichiometry of hydroxyapatite, probably in the form of a surface layer or complex on the crystals, in agreement with other studies on carbonate-apatites and bone mineral. The pIHA at 50% dissolution was employed as an average value. The pIHA (50%) values for pooled data (58.76 for enamel and 60.17 for hydroxyapatite) were lower than the respective pIHA previously measured by conventional equilibration techniques. However, the average pIHA measured for enamel was higher than that obtained by the same technique in another study, possibly because of differences in specimen preparation and equilibration time. The possible implications of the findings for understanding the process of dental caries are discussed.
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Affiliation(s)
- R P Shellis
- Department of Oral and Dental Science, University of Bristol, Bristol, UK.
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29
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Wilson RM, Dowker SEP, Elliott JC. Rietveld refinements and spectroscopic structural studies of a Na-free carbonate apatite made by hydrolysis of monetite. Biomaterials 2006; 27:4682-92. [PMID: 16750850 DOI: 10.1016/j.biomaterials.2006.04.033] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2006] [Accepted: 04/26/2006] [Indexed: 11/24/2022]
Abstract
Seven nominally identical samples of Na-free carbonate apatite (CO(3)Ap) were prepared by reaction of CaHPO(4) with ammonium carbonate solution at 70 degrees C over 3 days. They were studied by chemical analysis, Rietveld analysis of powder X-ray diffraction (XRD) data, Ca/P ratio determinations (quantitative phase analysis of CaO, Ca(OH)(2) and hydroxyapatite formed after heating to 900 degrees C from Rietveld analysis of XRD data), He pycknometry, (1)H, (13)C and (31)P MAS NMR spectrometry and Fourier transform infrared and Raman spectroscopy. Spectroscopy showed the apatite products were B-type CO(3)Aps (CO(3)(2-) replacing PO(4)(3-)) and XRD that one sample contained 1.6 wt% calcite with a trace in another. Mean results of the six essentially calcite-free samples were: a=9.405(5)A, c=6.896(2)A; 11.2 wt% CO(3); unit cell contents, Ca(8.241)(PO(4))(4.344)(CO(3))(1.656)(OH)(0.139) x 2.29H(2)O; mole Ca/P ratio from chemical analyses, 1.897(22) and from powder XRD phase analysis of samples decarbonated at 900 degrees C, 1.892(25). Density determinations indicated that the 2.29mol of H(2)O were in the unit cell. Rietveld refinements were undertaken without and with explicit modelling of the CO(3)(2-) ion. The latter used constraints to maintain the CO(3)(2-) ion in its known geometry and the total of PO(4)(3-) and CO(3)(2-) ions per unit cell at six. Without the CO(3)(2-) ion in the model, PO(4) volume, P-O bond lengths and P occupancy were apparently reduced, consistent with CO(3)(2-) replacing PO(4)(3-) ions. With the CO(3)(2-) ion modelled, the reductions were less and the CO(3)(2-) ion occupied the "sloping" face of the replaced PO(4)(3-) ion in two-fold disorder about the mirror plane. The angle between the normal to the plane of the ion and the c-axis was 34 degrees , close to 35.3 degrees , the equivalent angle for the PO(4)(3-) ion. When modelled, the CO(3)(2-) ion occupancy was 1.81 ions per unit cell, in reasonable agreement with unit cell contents determined chemically (1.66). The OH(-) ion occupancy was elevated (2.33 ions per unit cell versus 0.14 inferred from the charge balance), which we ascribe to H(2)O molecules occupying sites in c-axis channels. The Ca/P ratio from occupancies (2.31) was also elevated over that determined chemically (1.90). We attribute this to loss of Ca from Ca sites increasing the apparent anisotropic displacement parameters of remaining Ca atoms, leading to an apparently increased occupancy.
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Affiliation(s)
- Rory M Wilson
- Queen Mary College, University of London, Dental Biophysics, Francis Bancroft Building, Mile End Road, London E1 4NS, UK.
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30
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Dowker SEP, Elliott JC, Davis GR, Wilson RM, Cloetens P. Three-dimensional study of human dental fissure enamel by synchrotron X-ray microtomography. Eur J Oral Sci 2006; 114 Suppl 1:353-9; discussion 375-6, 382-3. [PMID: 16674712 DOI: 10.1111/j.1600-0722.2006.00315.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The three-dimensional morphology of human tooth fissures and the quantification of mineral distribution in fissure enamel are pertinent to the development and diagnosis of caries. Synchrotron X-ray microtomography was used to measure linear attenuation coefficients (at 25 keV) at high spatial resolution with a volume-imaging element (cubic voxel) of 4.9x4.9x4.9 microm3 in a block from a human premolar that included part of a stained fissure. From the linear attenuation coefficient, the mineral concentration, expressed as gHAp cm-3 (where HAp is stoichiometric hydroxyapatite), was calculated. The mean mineral concentration in bulk enamel was 2.84 gHAp cm-3. Well-defined regions (1.5-2.6 gHAp cm-3), extending up to approximately 130 microm from the base of some narrower lengths of the fissure and up to approximately 50 microm deep from the fissure surface, were attributed to hypomineralization. Other regions of low mineral concentration, some (1.4-2.3 gHAp cm-3) lying within the expected course of the fissure base and some (2.2-2.7 gHAp cm-3) deep to the pit, were also considered to be of developmental origin. However, a diffuse distribution of low mineral concentrations (2.2-2.7 gHAp cm-3) in the pit walls was attributed primarily to demineralization from caries. The fissure contained heterogeneous material (<or=0.5 gHAp cm-3) exhibiting partial mineralization.
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Affiliation(s)
- Stephanie E P Dowker
- Institute of Dentistry, Barts and The London, Queen Mary's School of Medicine and Dentistry, London, UK.
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31
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Wilson RM, Elliott JC, Dowker SEP, Rodriguez-Lorenzo LM. Rietveld refinements and spectroscopic studies of the structure of Ca-deficient apatite. Biomaterials 2005; 26:1317-27. [PMID: 15475062 DOI: 10.1016/j.biomaterials.2004.04.038] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Accepted: 04/23/2004] [Indexed: 11/25/2022]
Abstract
Nine samples of Ca-deficient apatite (Ca-def Ap) were prepared from suspensions of CaHPO4 (monetite) at 90 degrees C by raising the pH from approximately 4 through release of NH3 produced by the hydrolysis of urea. Products were dried at 100 degrees C for 24h and studied by chemical analyses, X-ray powder diffraction (XRPD) (and Rietveld analysis of this data), Ca/P ratio determination (quantitative phase analysis of samples after heating to 900 degrees C from Rietveld analysis of XRPD data), scanning electron microscopy, He pycknometry, 1H and 31P MAS NMR spectrometry and Fourier transform infrared and Raman spectroscopy. All samples contained apatite, but three also contained monetite. Infrared and Raman spectroscopy confirmed the presence of HPO4(2-) and absence of carbonate ions in the six monetite-free samples. Mean results for the six samples were: a = 9.4320(40), c = 6.8751(31) A; unit cell formula from chemical analysis neglecting protonation of phosphate ion, Ca(9.303(50))(PO4)6(OH)(0.606(99)).1.97(12)H2O; theoretical density 3.10 g cm(-3); experimental density (mean for three samples) 3.15 g cm(-3); and Ca/P mole ratio from chemical analysis and phase analysis after heating to 900 degrees C, 1.550(8) and 1.550(2), respectively. An earlier assignment of a line at 6 ppm in the 1H NMR spectrum of similar samples to HPO4(2-) ions could not be confirmed; hence no information about the HPO4(2-) ion content could be derived, in disagreement with the previous NMR study. A shoulder at approximately 0.9 ppm relative to 85 wt% H3PO4 in the 31P NMR spectrum was assigned to HPO4(2-) ions. Occupancies from the Rietveld structure refinements indicated preferential loss of Ca from Ca2 sites compared with Ca1, but the loss was substantially smaller than expected from chemical analyses. It is suggested that imperfect modelling of the structure in the refinement, particularly disorder associated with the Ca2 site, resulted in errors in Ca2 occupancies. The P-O bonds were slightly shorter than those in stoichiometric hydroxyapatite, rather than longer as might be expected from protonation of phosphate tetrahedra. However, consideration of known acid phosphate structures indicated that it was unlikely that the increase in P-O lengths would be sufficient to be detected. The observed decrease was tentatively assigned to the presence of Ca2+ ion vacancies.
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Affiliation(s)
- Rory M Wilson
- Dental Biophysics, Medical Sciences Building, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
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Dowker SEP, Elliott JC, Davis GR, Wilson RM, Cloetens P. Synchrotron X-Ray Microtomographic Investigation of Mineral Concentrations at Micrometre Scale in Sound and Carious Enamel. Caries Res 2004; 38:514-22. [PMID: 15528905 DOI: 10.1159/000080580] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2003] [Accepted: 01/08/2004] [Indexed: 11/19/2022] Open
Abstract
Synchrotron X-ray microtomography (XMT) was used to measure the linear attenuation coefficient (LAC) for 1.9-microm sidelength voxels within approximal brown spot lesions and sound human enamel. XMT demonstrated three-dimensional features, notably sheets with approximately 30 microm periodicity having low LAC, identified as regions of demineralization corresponding to Retzius lines. Quantitative three-dimensional measurements of mineral concentration, derived from LAC with assumption of a single model composition, were consistent with previous measurements of sound and carious enamel from microradiographic projections. The uncertainty in measurements of mineral concentration and mineral fraction volume was investigated by modelling enamel with a range of composition and component densities. This analysis showed that, although mineral concentration can be determined from LAC with an error of <0.2 g cm(-3), the variation in pore fraction volume within caries lesions cannot be reliably determined from X-ray attenuation measurements alone.
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Affiliation(s)
- S E P Dowker
- Institute of Dentistry, Barts and The London, Queen Mary's School of Medicine and Dentistry, London, UK.
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Abstract
X-ray and time of flight neutron diffraction data, FTIR and MAS-NMR spectra, and ICP-AES and carbonate analyses have been collected from a sodium-containing carbonate apatite (CO(3) content 12.5(7)wt%). A structural model based on Holly Springs hydroxyapatite without CO(3)(2-) ions showed an apparent reduction in the PO(4) tetrahedral volume which is ascribed to CO(3)(2-) replacing PO(4)(3-) ions in the lattice. Four structural models from the literature with the CO(3)(2-) ion explicitly modelled were fitted to the neutron diffraction data by the Rietveld method. The best fit was obtained with the CO(3)(2-) ion in disorder between the mirror symmetry related faces of a vacant PO(4)(3-) site and with the normal to the plane of the CO(3)(2-) ion at approximately 30 degrees to the c-axis. This angle is consistent with results from previous polarised IR measurements on single crystals of francolite (a fluorocarbonate apatite) and human dental enamel. Further refinement of the model revealed a hitherto unknown atom site close to the unit cell origin, (possibly a water molecule). The refined hexagonal unit cell parameters from the neutron diffraction data were a=9.3446(3)A and c=6.9199(4)A.
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Affiliation(s)
- Rory M Wilson
- Dental Biophysics, Medical Sciences Building, Queen Mary, University of London, Mile End Road, London, UK E1 4NS.
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Affiliation(s)
- R M Wilson
- QaRNS, Royal North Shore Hospital, Sydney, New South Wales, Australia.
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Driscoll CO, Dowker SEP, Anderson P, Wilson RM, Gulabivala K. Effects of sodium hypochlorite solution on root dentine composition. J Mater Sci Mater Med 2002; 13:219-223. [PMID: 15348646 DOI: 10.1023/a:1013894432622] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Sodium hypochlorite (NaOCl) solution,<or=5% w/v available chlorine (abbreviated subsequently to %), is widely used as an irrigant in root canal treatment of teeth, so its effects on dentine are of clinical importance. The effects of approximately 0.5%, 3% and 5% NaOCl solution on the composition of root dentine were studied at ambient temperature. For dentine powder treated for 30 min, depletion of the organic phase was confirmed by infrared spectroscopy. Apatite lattice parameters showed no significant change, but NaCl was also detected by X-ray powder diffraction. The low solubility of apatite mineral in the NaOCl solutions was demonstrated by the constant weight of bulk enamel specimens immersed for seven days. The stability of the mineral phase was confirmed by scanning microradiography (SMR), an X-ray attenuation method employing photon counting. Repeated SMR measurements of the local mineral content of bulk samples of root dentine and a synthetic hydroxyapatite aggregate during exposure to pumped NaOCl solutions for 100 h showed no mineral loss. As predicted from apatite chemistry, reaction of NaOCl with the mineral phase can be excluded as a primary factor in changes in mechanical properties of treated dentine. Effects of retention of NaCl on endodontic sealants requires further investigation.
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Affiliation(s)
- C O Driscoll
- Eastman Dental Institute for Oral Health Care Sciences, University College London, London WC1X 8LD, UK
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Wilson RM, Donly KJ. Demineralization around orthodontic brackets bonded with resin-modified glass ionomer cement and fluoride-releasing resin composite. Pediatr Dent 2001; 23:255-9. [PMID: 11447960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
PURPOSE Enamel demineralization adjacent to orthodontic brackets is one of the risks associated with orthodontic treatment. Glass ionomer cements have been shown to decrease enamel demineralization adjacent to brackets and bands but do not exhibit bond strengths comparable to resin composites. The purpose of this in vitro study was to compare a fluoride-releasing resin composite versus a resin-modified glass ionomer cement for inhibition of enamel demineralization surrounding orthodontic brackets. METHODS Forty-five teeth were randomly assigned to 3 groups of 15 teeth. Fifteen were bonded with Concise (3M), a non-fluoride-releasing resin composite (control); 15 teeth were bonded with Light Bond (Reliance), a fluoride-releasing resin composite; and 15 teeth were bonded with Fuji Ortho LC (GC Corporation), a resin-modified glass ionomer cement. The teeth were placed in an artificial caries solution to create lesions. Following sectioning of the teeth in a buccolingual direction, polarized light microscopy was utilized to evaluate enamel demineralization adjacent to the orthodontic bracket. The area of the lesion was measured 100 microns from the orthodontic bracket and bonding agent. RESULTS MANOVA (P < .0001) and Duncan's test (P < .05) indicated the resin-modified glass ionomer cement (Fuji Ortho LC) and the fluoride-releasing resin composite (Light Bond) had significantly less adjacent enamel demineralization than the non-fluoride-releasing resin composite control. However, there was no significant difference between the resin-modified glass ionomer cement and the fluoride-releasing resin composite. CONCLUSIONS Based on the results of this in vitro study, it can be concluded that Fuji Ortho LC and Light Bond exhibit significant inhibition of adjacent demineralization compared to the non-fluoride-releasing control.
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Affiliation(s)
- R M Wilson
- Department of Pediatric Dentistry, Dental School, University of Texas Health Science Center at San Antonio, USA
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Abstract
OBJECTIVE To investigate the cause and outcome of high fever in Jamaican children with homozygous sickle cell disease. DESIGN Retrospective review of febrile episodes in a three year period (1 September 1993 to 31 August 1996). SETTING Sickle cell clinic, an outpatient clinic in Kingston run by the Medical Research Council Laboratories (Jamaica). PATIENTS Patients with homozygous sickle cell disease under 17 years of age presenting with an axillary temperature >/= 39.0 degrees C (102.4 degrees F). MAIN OUTCOME MEASURES Diagnosis, death. RESULTS There were 165 events in 144 patients (66 (45.8%) boys) with a median age of 6.1 years. Bacteraemia was found in 10 (6.1%) events (three Streptococcus pneumoniae, two Haemophilus influenzae type b, two Salmonella sp, one Escherichia coli, one Enterobacter sp, and one Acinetobacter sp), and urinary tract infections in four (2.4%). All cultures of cerebrospinal fluid were sterile. Acute chest syndrome occurred in 36 (21.8%) events. A painful crisis was associated with 45 (27.3%) events and was the only pathology identified in 20 events (12.1%). Hospital admission was necessary in 66 cases including all those with bacteraemia and 31 with acute chest syndrome. There were two deaths: a 5 year old boy with septic shock associated with H influenzae septicaemia, and a 3 year old boy with the acute chest syndrome. CONCLUSIONS Painful crisis and acute chest syndrome were the most common complications associated with high fever, but other important associated features included bacteraemia and urinary tract infection. Enteric Gram negative organisms accounted for 50% of positive blood cultures.
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Affiliation(s)
- K J Wierenga
- Sickle Cell Unit, formerly MRC Laboratories (Jamaica), University of the West Indies, Mona, Kingston, Jamaica, West Indies.
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Thomas EJ, Studdert DM, Runciman WB, Webb RK, Sexton EJ, Wilson RM, Gibberd RW, Harrison BT, Brennan TA. A comparison of iatrogenic injury studies in Australia and the USA. I: Context, methods, casemix, population, patient and hospital characteristics. Int J Qual Health Care 2000; 12:371-8. [PMID: 11079216 DOI: 10.1093/intqhc/12.5.371] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVE To better understand the differences between two iatrogenic injury studies of hospitalized patients in 1992 which used ostensibly similar methods and similar sample sizes, but had quite different findings. The Quality in Australian Health Care Study (QAHCS) reported that 16.6% of admissions were associated with adverse events (AE), whereas the Utah, Colorado Study (UTCOS) reported a rate of 2.9%. SETTING Hospitalized patients in Australia and the USA. DESIGN Investigators from both studies compared methods and characteristics and identified differences. QAHCS data were then analysed using UTCOS methods. MAIN OUTCOME MEASURES Differences between the studies and the comparative AE rates when these had been accounted for. RESULTS Both studies used a two-stage chart review process (screening nurse review followed by confirmatory physician review) to detect AEs; five important methodological differences were found: (i) QAHCS nurse reviewers referred records that documented any link to a previous admission, whereas UTCOS imposed age-related time constraints; (ii) QAHCS used a lower confidence threshold for defining medical causation; (iii) QAHCS used two physician reviewers, whereas UTCOS used one; (iv) QAHCS counted all AEs associated with an index admission whereas UTCOS counted only those determining the annual incidence; and (v) QAHCS included some types of events not included in UTCOS. When the QAHCS data were analysed using UTCOS methods, the comparative rates became 10.6% and 3.2%, respectively. CONCLUSIONS Five methodological differences accounted for some of the discrepancy between the two studies. Two explanations for the remaining three-fold disparity are that quality of care was worse in Australia and that medical record content and/or reviewer behaviour was different.
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Affiliation(s)
- E J Thomas
- Department of Medicine, Brigham and Women's Hospital, Boston, MA, USA.
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Wilson RM. Screening for breast and cervical cancer as a common cause for litigation. A false negative result may be one of an irreducible minimum of errors. BMJ 2000; 320:1352-3. [PMID: 10818006 PMCID: PMC1118031 DOI: 10.1136/bmj.320.7246.1352] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Affiliation(s)
- S N Weingart
- Division of General Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.
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Morgan H, Wilson RM, Elliott JC, Dowker SE, Anderson P. Preparation and characterisation of monoclinic hydroxyapatite and its precipitated carbonate apatite intermediate. Biomaterials 2000; 21:617-27. [PMID: 10701462 DOI: 10.1016/s0142-9612(99)00225-2] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Five 100 g batches of a carbonate apatite (the intermediate) were produced by heating an aqueous slurry of CaCO3 and CaHPO4 with an overall Ca/P mole ratio of 5/3 with vigorous stirring. Each intermediate produced by boiling off water was heated in vacuum at 1100 degrees C to remove carbonate, then steamed at 900 degrees C to ensure complete hydroxylation. Comparison of calculated and observed X-ray diffraction patterns showed final products containing 50-100 wt% monoclinic hydroxyapatite (remainder hexagonal). Rietveld refinements in P6(3)/m gave structures similar to several hydroxyapatite standards, including NIST SRM 2910, although there was no evidence from X-ray diffraction that the latter was in the monoclinic form. Refinements from standards and final products were slightly different from published single crystal data for Holly Springs hydroxyapatite. This is attributed to known impurities in mineral hydroxyapatite and indicates that parameters from the Rietveld refinements are closer to the true values for pure hydroxyapatite. Rietveld refinements for intermediates showed small, but significant differences from the final product, the largest being in O1x, O2x and O(H)z. All P-O bond lengths were shorter than in the final product, resulting in a 3.2% lower PO4 tetrahedron volume. The occupancies of P and Ca(2) were reduced. These differences are attributed to partial replacement of PO4(3) by CO3(2-) ions.
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Affiliation(s)
- H Morgan
- Department of Biophysics in relation to Dentistry, Queen Mary & Westfield College, London, UK
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Affiliation(s)
- A B Carle
- Department of Chemistry, University of Cincinnati, OH 45221-0172, USA
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Picone G, Wilson RM. Medicare home health agency utilization, 1984-1994. Inquiry 1999; 36:291-303. [PMID: 10570662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
This study analyzes the determinants of Medicare home health agency (HHA) use in 1984, 1989, and 1994. We estimated a two-part model, modified to adjust for heteroskedasticity, using data from the National Long-Term Care Surveys and the sample members' Medicare claim files. We found an evolving pattern of determinants of Medicare HHA utilization. The rapid increase in use after HHA guideline revisions in 1989 was associated closely with rising importance of limitations in activities of daily living and instrumental activities of daily living as determinants of expected utilization. Our results show little evidence that Medicare home health services substitute for informal home care, though they may reduce the use of skilled nursing facility care.
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Affiliation(s)
- G Picone
- Department of Economics, University of South Florida, Tampa 33620, USA
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Abstract
Previousreports indicating that the apparent solubilities of carbonate-apatites are low appear to conflict with findings that carbonate incorporation into the apatite structure tends to reduce stability. Carbonate-apatites were prepared by a precipitation method and by hydrolysis of monetite and brushite. Apparent solubility profiles were determined by measuring dissolution after exposure for 24 h to acetate buffers with known saturations with respect to hydroxyapatite. All preparations showed a range of apparent solubilities, in agreement with previous work. Precipitated samples had higher apparent solubilities than samples prepared by hydrolysis and this was correlated with differences in crystallinity. Further experiments showed that pyrophosphate ion reduced the apparent solubility, but it was concluded that pyrophosphate occurring naturally in synthetic apatites would be insufficient to cause low apparent solubilities. Microscopical observations showed that precipitated carbonate-apatites were composed of small crystals of uniform size, whereas carbonate-apatites prepared by hydrolysis consisted of both small crystals and very large crystals. The low apparent solubilities observed in the latter preparations are attributed to the large crystals. The surface phenomena possibly involved in apparent solubility behavior are discussed. Copyright 1999 Academic Press.
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Affiliation(s)
- RP Shellis
- MRC Dental Group, Dental School, Lower Maudlin Street, Bristol, BS1 2LY, United Kingdom
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Baker RS, Wilson RM, Flowers CW, Lee DA, Wheeler NC. A population-based survey of hospitalized work-related ocular injury: diagnoses, cause of injury, resource utilization, and hospitalization outcome. Ophthalmic Epidemiol 1999; 6:159-69. [PMID: 10487971 DOI: 10.1076/opep.6.3.159.1505] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Occupational injury is a major source of ocular trauma and is often preventable. A statewide population-based survey of severe work-related ocular injury was generated by using the California Hospital discharge database to identify hospitalized ocular injury and workers compensation as principal payor to identify work-relatedness. Information concerning diagnoses, procedures, causes of injury, length of hospital stay, total hospital charges and disposition at hospital discharge were obtained for injuries occurring during the calendar year 1988. A total of 455 admissions for work-related ocular trauma were identified. The most common work-related ocular trauma diagnoses associated with hospitalizations were open globe injury (46%), adnexal wounds (20%), orbital fractures (11%), and traumatic hyphema (11%). The most common causes of work-related ocular trauma were foreign-body or projectile objects (19%), transport vehicles (18%), cutting or piercing objects (17%), and assaults (9%). Approximately 8% reported other than routine disposition at time of hospital discharge, including long-term nursing or rehabilitation services and death. Mean hospital stay when ocular trauma was the principal admitting diagnosis was 3.7 days. Results differed significantly for admissions reporting ocular trauma as the principal admitting diagnosis compared to admissions that did not. Hospitalized work-related ocular trauma is represented by a wide spectrum of injuries with substantial morbidity and economic costs. Projected to the United States population, these data indicate annual hospital charges excluding professional fees of $14.6 million when work-related ocular trauma is the principal admitting diagnosis and $40 million for admissions where ocular trauma is either a principal or secondary diagnosis.
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Affiliation(s)
- R S Baker
- UCLA School of Medicine Charles R. Drew University of Medicine and Science Los Angeles, CA 90059, USA.
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Pfeifer SL, Wilson RM, Gawkrodger DJ. Clearance of acanthosis nigricans associated with the HAIR-AN syndrome after partial pancreatectomy: an 11-year follow-up. Postgrad Med J 1999; 75:421-2. [PMID: 10474728 PMCID: PMC1741275 DOI: 10.1136/pgmj.75.885.421] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
We describe a woman with the syndrome characterised by hyperandrogenism, insulin resistance and acanthosis nigricans (the HAIR-AN syndrome), and an associated insulinoma (islet B-cell tumour), whose signs and symptoms cleared after partial pancreatectomy.
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Abstract
OBJECTIVE To examine the causes of adverse events (AEs) resulting from healthcare to assist in developing strategies to minimise preventable patient injury. DESIGN Descriptions of the 2353 AEs previously reported by the Quality in Australian Health Care Study (QAHCS) were reviewed. A qualitative approach was used to develop categories for human error and for prevention strategies to minimise these errors. These categories were then used to classify the AEs identified in the QAHCS, and the results were analysed with previously reported preventability and outcome data. RESULTS 34.6% of the causes of AEs were categorised as "a complication of, or the failure in, the technical performance of an indicated procedure or operation", 15.8% as "the failure to synthesise, decide and/or act on available information", 11.8% as "the failure to request or arrange an investigation, procedure or consultation", and 10.9% as "a lack of care and attention or failure to attend the patient". AEs in which the cause was cognitive failure were associated with higher preventability scores than those involving technical performance. The main prevention strategies identified were "new, better, or better implemented policies or protocols" (23.7% of strategies), "more or better formal quality monitoring or assurance processes" (21.2%), "better education and training" (19.2%), and "more consultation with other specialists or peers" (10.2%). CONCLUSION The causes of AEs or errors leading to AEs can be characterised, and human error is a prominent cause. Our study emphasises the need for designing safer systems for care which protect the patient from the inevitability of human error. These systems should provide new policies and protocols and technological support to aid the cognitive activities of clinicians.
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Affiliation(s)
- R M Wilson
- Royal North Shore Hospital, Sydney, NSW.
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Wolitski RJ, Rietmeijer CA, Goldbaum GM, Wilson RM. HIV serostatus disclosure among gay and bisexual men in four American cities: general patterns and relation to sexual practices. AIDS Care 1998; 10:599-610. [PMID: 9828956 DOI: 10.1080/09540129848451] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The present study examined patterns of serostatus disclosure among previously untested HIV-seropositive and HIV-seronegative gay and bisexual men recruited from four American cities (n = 701). Six months after learning their HIV serostatus, 97% of study participants had disclosed their test results to at least one other individual. Consistent with earlier studies, test results were most frequently shared with friends and the respondent's primary partner. HIV serostatus was disclosed less frequently to family members, co-workers, and non-primary sex partners. Compared with HIV-seronegative men, HIV-seropositive men were more likely to have disclosed their status to a health care provider and less likely to have shared this information with family members. Of seropositive men, 11% did not disclose their serostatus to their primary partner and 66% did not disclose to a non-primary sex partner. Of HIV-seropositive men with one or more non-primary partners, 16% of those who did not disclose their serostatus reported inconsistent condom use during anal intercourse with these partners. No significant differences in self-reported sexual practices were observed for HIV-seropositive disclosers versus non-disclosers. Compared with HIV-seronegative men who did not disclose, seronegative men who shared information about their serostatus were more likely to have had receptive anal intercourse with their primary partner (p < 0.05) and to have engaged in mutual masturbation (p < 0.005), receptive oral sex (p < 0.005) and insertive anal intercourse (p < 0.05) with non-primary partners. No significant differences were observed between disclosers and non-disclosers with regard to condom use. Implications of the findings for future research and HIV prevention programmes are discussed.
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Affiliation(s)
- R J Wolitski
- Behavioral Intervention Research Branch, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
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Bendinskas KG, Harsch A, Wilson RM, Midden WR. Sequence-specific photomodification of DNA by an oligonucleotide-phenanthrodihydrodioxin conjugate. Bioconjug Chem 1998; 9:555-63. [PMID: 9736489 DOI: 10.1021/bc970209a] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We introduce a new member of a family of photochemically active oligonucleotide conjugates. A Phenanthrodihydrodioxin (PDHD)-based agent was synthesized and covalently linked to a 5'-end of the 9-mer oligonucleotide via a hexamethylene linker. The conjugate hybridized to a complementary 30-nucleotide-long target and efficiently cleaved it in a sequence specific manner. Up to 67% of target was specifically damaged (51% cross-links and 16% direct cleavage). While the photosensitizer alone nonspecifically damaged only Gs in a single-stranded target, its conjugate cross-linked to and damaged also A, T, and C sites in a target in agreement with duplex and triplex formation.
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Affiliation(s)
- K G Bendinskas
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, USA.
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Abstract
We analyze the effect of the uncertainty of the incidence of illness on the demand for medical care and on the accumulation of health capital and wealth over the retirement years. We use a simplified version of a dynamic Grossman household production model to characterize patterns of an individual's precautionary behavior. Elderly individuals respond to uncertainty by smoothing their expected utility over time by making specific patterns of purchases of medical care and consumption. We examine these patterns for individuals with different degrees of risk aversion.
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Affiliation(s)
- G Picone
- College of Business Administration, University of South Florida, Tampa 33620, USA.
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