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https://www.readbyqxmd.com/read/28633132/radon-emanation-from-fresh-altered-and-disturbed-granitic-rock-characterized-by-14-c-pmma-impregnation-and-autoradiography
#1
Karl-Heinz Hellmuth, Marja Siitari-Kauppi, Hannu Arvela, Antero Lindberg, Lionel Fonteneau, Paul Sardini
Radon emanation from intact samples of fresh ("BG"), altered ("Fract") and disturbed ("EDZ") Finnish granitic rock from Kuru (Finland) and its dependence on humidity and rock structural factors was studied. The pore network of the rock was characterized by microscopy and impregnation with (14)C-PMMA (polymethylmethacrylate) resin and autoradiography. The radon emanation factor was increasing linearly with the relative humidity. (14)C-PMMA autoradiography of the altered zones and the EDZ indicated significant, mineral-specific increase of porosity and porosity gradients towards the fracture surfaces (Fract) and microcracks within the EDZ...
June 13, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28633093/fracture-resistance-of-ceramic-and-polymer-based-occlusal-veneer-restorations
#2
Majed Al-Akhali, Mohamed Sad Chaar, Adham Elsayed, Abdulaziz Samran, Matthias Kern
OBJECTIVES: The purpose of this in vitro study was to evaluate the influence of thermodynamic loading on the durability and fracture resistance behavior of occlusal veneers fabricated from different biomedical dental CAD/CAM materials. METHODS: The occlusal surfaces of 64 extracted premolars were prepared in the enamel layer and restored with occlusal veneers with a fissure/cusp thickness of 0.5/0.8mm made from four different dental CAD/CAM materials: group LD lithium disilicate (e...
June 13, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28632501/evaluation-of-automatic-dose-rate-control-for-flat-panel-imaging-using-a-spatial-frequency-domain-figure-of-merit
#3
Michiel Dehairs, Hilde Bosmans, Walter Desmet, Nicholas W Marshall
Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC technique. Phantom thickness covered a water equivalent thickness range of 2...
June 20, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28625665/color-stability-of-glass-fiber-reinforced-polypropylene-for-non-metal-clasp-dentures
#4
Manamu Nagakura, Yasuhiro Tanimoto, Norihiro Nishiyama
PURPOSE: The purpose of this study was to investigate the color stability of a glass-fiber-reinforced thermoplastic (GFRTP), for use in non-metal clasp dentures (NMCDs). METHODS: GFRTPs composed of E-glass fibers and polypropylene with 2 mass% of pigments were fabricated using injection molding. According to our previous study on the optimum fiber content for GFRTPs, we prepared GFRTPs with fiber contents of 0, 10, and 20 mass% (GF0, GF10, and GF20). Commercially available NMCD and PMMA materials were used as controls...
June 15, 2017: Journal of Prosthodontic Research
https://www.readbyqxmd.com/read/28623701/transition-temperature-of-poly-methyl-methacrylate-determined-by-time-of-flight-secondary-ion-mass-spectrometry-and-contact-angle-measurements
#5
Yi Fu, Yiu-Ting R Lau, Lu-Tao Weng, Kai-Mo Ng, Chi-Ming Chan
The surface chain conformations of poly(methyl methacrylate) (PMMA) at different temperatures were extensively studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Similar to our previous experimental studies on polystyrene (PS) and poly(2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), a transition temperature (TT) could be identified through the principal component analysis (PCA) of the ToF-SIMS spectra obtained from the PMMA samples annealed at different temperatures. Interestingly, our results show that the TT depended on molecular weight and was about 50-60˚C below the bulk glass transition temperature (Tg) and therefore could possibly be related to the surface glass transition temperature (Tg(S))...
June 1, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28620229/novel-bioactive-glass-based-injectable-bone-cement-with-improved-osteoinductivity-and-its-in-vivo-evaluation
#6
Tengjiao Zhu, Huihui Ren, Ailing Li, Bingchuan Liu, Caiyun Cui, Yanmei Dong, Yun Tian, Dong Qiu
Recently, more and more attention has been paid to the development of a new generation of injectable bone cements that are bioactive, biodegradable and are able to have appropriate mechanical properties for treatment of vertebral compression fractures (VCFs). In this study, a novel PSC/CS composite cement with high content of PSC (a phytic acid-derived bioactive glass) was prepared and evaluated in both vitro and vivo. The PSC/CS cement showed excellent injectability, good resistance to disintegration, radiopacity and suitable mechanical properties...
June 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28617583/tof-sims-depth-profiling-of-ps-b-pmma-block-copolymers-using-arn-c60-and-cs-sputtering-ions
#7
T Terlier, G Zappalà, C Marie, D Leonard, J-P Barnes, A Licciardello
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a high performance tool for molecular depth profiling of polymer films, in particular when they are structured in microphases. However, a major issue is the degradation of polymer materials under ion irradiation in reactions such as cross-linking, chain breaking, or reorganization processes of polymers which have been demonstrated for materials such as polystyrene (PS) and poly(methyl methacrylate) (PMMA). This work aims at comparing ToF-SIMS molecular depth profiling of structured polymers (polystyrene (PS)-b-polymethyl methacrylate (PMMA) block copolymers (BCP)) using either ultralow energy cesium or the more recently introduced C60(++) (under NO dosing and with sample cooling) and argon cluster ion beams (using Ar1500(+) ions at 5 keV)...
June 15, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28616140/photochromic-benzo-b-phosphole-oxide-with-excellent-thermal-irreversibility-and-fatigue-resistance-in-the-thin-film-solid-state-via-direct-attachment-of-dithienyl-units-to-the-weakly-aromatic-heterocycle
#8
Nathan Man-Wai Wu, Hok-Lai Wong, Vivian Wing-Wah Yam
A novel photochromic benzo[b]phosphole oxide has been demonstrated to display photochromic properties with excellent fatigue resistance and thermal irreversibility in polymethylmethacrylate (PMMA) thin film under ambient conditions. The remarkable photochromic behaviour can be achieved by rational molecular design, in which the weakly aromatic phosphole oxide is directly incorporated into the photo-responsive dithienylethene units. Photopatterning via photoinduced colouration and decolouration has been performed to demonstrate the repeatable and distinct transformation between the bistable states, making it a promising candidate with photoswitching properties for optoelectronic applications...
February 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28615491/enhanced-osteointegration-of-poly-methylmethacrylate-bone-cements-by-incorporating-strontium-containing-borate-bioactive-glass
#9
Xu Cui, Chengcheng Huang, Meng Zhang, Changshun Ruan, Songlin Peng, Li Li, Wenlong Liu, Ting Wang, Bing Li, Wenhai Huang, Mohamed N Rahaman, William W Lu, Haobo Pan
Although poly(methylmethacrylate) (PMMA) cements are widely used in orthopaedics, they have numerous drawbacks. This study aimed to improve their bioactivity and osseointegration by incorporating strontium-containing borate bioactive glass (SrBG) as the reinforcement phase and bioactive filler of PMMA cement. The prepared SrBG/PMMA composite cements showed significantly decreased polymerization temperature when compared with PMMA and retained properties of appropriate setting time and high mechanical strength...
June 2017: Journal of the Royal Society, Interface
https://www.readbyqxmd.com/read/28614155/the-role-of-the-back-plate-in-angle-anatomy-with-the-boston-type-i-keratoprosthesis
#10
Elise V Taniguchi, Eleftherios I Paschalis, Alja Crnej, Ai Ren, Kathryn A Colby, James Chodosh, Louis R Pasquale, Lucy Q Shen, Claes H Dohlman, Andrea Cruzat
PURPOSE: To quantitatively evaluate the angle anatomy in eyes with the Boston type I keratoprosthesis (B-KPro) differing in the back plate (BP) material and size using anterior segment optical coherence tomography. METHODS: B-KPro eyes with poly(methyl methacrylate) (PMMA) (7.0 and 8.5 mm) and titanium (7.0, 8.5, and 9.5 mm) BPs were imaged with anterior segment optical coherence tomography. The angle opening distance at 500 μm from the scleral spur (AOD500), trabecular iris surface area at 500 μm from the scleral spur (TISA500), and trabecular iris angle at 500 μm from the scleral spur (TIA500) were measured...
June 13, 2017: Cornea
https://www.readbyqxmd.com/read/28613314/directed-ordering-of-phase-separated-domains-and-dewetting-of-thin-polymer-blend-films-on-a-topographically-patterned-substrate
#11
Nandini Bhandaru, Alamgir Karim, Rabibrata Mukherjee
Substrate pattern guided self-organization of ultrathin and confined polymeric films on a topographically patterned substrate is a useful approach for obtaining ordered meso and nano structures over large areas, particularly if the ordering is achieved during film preparation itself, eliminating any post-processing such as thermal or solvent vapor annealing. By casting a dilute solution of two immiscible polymers, polystyrene (PS) and polymethylmethacrylate (PMMA), from a common solvent (toluene) on a topographically patterned substrate with a grating geometry, we show the formation of self-organized meso patterns with various degrees of ordering...
June 14, 2017: Soft Matter
https://www.readbyqxmd.com/read/28613074/blue-to-green-emitting-neutral-ir-iii-complexes-bearing-pentafluorosulfanyl-groups-a-combined-experimental-and-theoretical-study
#12
Amlan K Pal, Adam F Henwood, David B Cordes, Alexandra M Z Slawin, Ifor D W Samuel, Eli Zysman-Colman
A structure-property relationship study of neutral heteroleptic (1 and 2, [Ir(C(∧)N)2(L(∧)X)]) and homoleptic (3 and 4, fac-[Ir(C(∧)N)3]) Ir(III) complexes (where L(∧)X = anionic 2,2,6,6-tetramethylheptane-3,5-dionato-κO(3),κO(6) (thd) and C(∧)N = a cyclometalating ligand bearing a pentafluorosulfanyl (-SF5) electron-withdrawing group (EWG) at the C4 (HL1) and C3 (HL2) positions of the phenyl moiety) is presented. These complexes have been fully structurally characterized, including by single-crystal X-ray diffraction, and their electrochemical and optical properties have also been extensively studied...
June 14, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28609471/finite-element-analysis-of-6-large-pmma-skull-reconstructions-a-multi-criteria-evaluation-approach
#13
Angela Ridwan-Pramana, Petr Marcián, Libor Borák, Nathaniel Narra, Tymour Forouzanfar, Jan Wolff
In this study 6 pre-operative designs for PMMA based reconstructions of cranial defects were evaluated for their mechanical robustness using finite element modeling. Clinical experience and engineering principles were employed to create multiple plan options, which were subsequently computationally analyzed for mechanically relevant parameters under 50N loads: stress, strain and deformation in various components of the assembly. The factors assessed were: defect size, location and shape. The major variable in the cranioplasty assembly design was the arrangement of the fixation plates...
2017: PloS One
https://www.readbyqxmd.com/read/28606606/potential-risks-of-using-cement-augmented-screws-for-spinal-fusion-in-patients-with-low-bone-quality
#14
M Martín-Fernández, A López-Herrradón, A R Piñera, F Tomé-Bermejo, J M Duart, M D Vlad, M G Rodríguez-Arguisjuela, L Álvarez-Galovich
BACKGROUND CONTEXT: Dramatic increases in the average life expectancy have led to increases in the variety of degenerative changes and deformities observed in the aging spine. The elderly population can present challenges for spine surgeons, not only because of increased comorbidities, but also because of the quality of their bones. Pedicle screws are the implants used most commonly in spinal surgery for fixation, but their efficacy depends directly on bone quality. While PMMA-augmented screws represent an alternative for patients with osteoporotic vertebrae, their use has raised some concerns due to the possible association between cement leakages (CLs) and other morbidities...
June 9, 2017: Spine Journal: Official Journal of the North American Spine Society
https://www.readbyqxmd.com/read/28606420/pressure-transmission-area-and-maximum-pressure-transmission-of-different-thermoplastic-resin-denture-base-materials-under-impact-load
#15
Hubban Nasution, Krid Kamonkhantikul, Mansuang Arksornnukit, Hidekazu Takahashi
PURPOSES: The purposes of the present study were to examine the pressure transmission area and maximum pressure transmission of thermoplastic resin denture base materials under an impact load, and to evaluate the modulus of elasticity and nanohardness of thermoplastic resin denture base. METHODS: Three injection-molded thermoplastic resin denture base materials [polycarbonate (Basis PC), ethylene propylene (Duraflex), and polyamide (Valplast)] and one conventional heat-polymerized acrylic resin (PMMA, SR Triplex Hot) denture base, all with a mandibular first molar acrylic resin denture tooth set in were evaluated (n=6)...
June 9, 2017: Journal of Prosthodontic Research
https://www.readbyqxmd.com/read/28605612/influence-of-different-curing-modes-on-polymerization-behavior-and-mechanical-properties-of-dual-cured-provisional-resins
#16
S Shibasaki, T Takamizawa, T Suzuki, K Nojiri, A Tsujimoto, W W Barkmeier, M A Latta, M Miyazaki
This study determined the influence of curing mode on polymerization behavior and mechanical properties of dual-cured provisional resins. Three dual-cured bisacryl-based provisional resins were used: Tempsmart (TS; GC Corp), Luxatemp Automix Solar (LX; DMG Chemisch Pharmazeutishe Fabrik GmbH), and Integrity Multi·Cure (IG; Dentsply Caulk). A self-cured bisacryl-based provisional resin, Protemp Plus (PP; 3M ESPE) and a conventional poly(methyl methacrylate) (PMMA) provisional resin, Unifast III (UF; GC Corp) were used as controls...
June 12, 2017: Operative Dentistry
https://www.readbyqxmd.com/read/28604148/porous-fibres-with-encapsulated-functional-materials-and-tunable-release
#17
Yijun Chen, James G Boyd, Mohammad Naraghi
A novel sequential processing approach to fabricate versatile fibres containing encapsulated materials is presented. It is based on developing highly porous fibres, to be filled with functional materials and coated with protective layers. Applicability of the approach to develop porous Poly(methyl methacrylate)(PMMA) fibres with encapsulated antibacterial salts within a coating is demonstrated. The salt was introduced to the fibre via a sacrificial solvent. Desired solvent properties to ensure successful filling was discussed...
June 10, 2017: Journal of Microencapsulation
https://www.readbyqxmd.com/read/28598156/ultrafast-self-assembly-of-sub-10-nm-block-copolymer-nanostructures-by-solvent-free-high-temperature-laser-annealing
#18
Jing Jiang, Alan G Jacobs, Brandon Wenning, Clemens Liedel, Michael O Thompson, Christopher K Ober
Laser spike annealing was applied to PS-b-PDMS diblock copolymers to induce short-time (millisecond time scale), high-temperature (300 to 700 °C) microphase segregation and directed self-assembly of sub-10 nm features. Conditions were identified that enabled uniform microphase separation in the time frame of tens of milliseconds. Microphase ordering improved with increased temperature and annealing time, whereas phase separation contrast was lost for very short annealing times at high temperature. PMMA brush underlayers aided ordering under otherwise identical laser annealing conditions...
June 9, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28597392/packaging-of-implantable-accelerometers-to-monitor-epicardial-and-endocardial-wall-motion
#19
Luigi Brancato, Tristan Weydts, Wouter Oosterlinck, Paul Herijgers, Robert Puers
Acceleration signals, collected from the inner and the outer heart wall, offer a mean of assessing cardiac function during surgery. Accelerometric measurements can also provide detailed insights into myocardial motion during exploratory investigations. Two different implantable accelerometers to respectively record endocardial and epicardial vibrations, have been developed by packaging a commercially available capacitive transducer. The same coating materials have been deposited on the two devices to ensure biocompatibility of the implants: Parylene-C, medical epoxy and Polydimethylsiloxane (PDMS)...
September 2017: Biomedical Microdevices
https://www.readbyqxmd.com/read/28594312/warning-about-the-use-of-critical-size-defects-for-the-translational-study-of-bone-repair-analysis-of-a-sheep-tibial-model
#20
Johan Lammens, Marina Maréchal, Liesbet Geris, Joshua Vanderaa, Hadewych Van Hauwermeiren, Frank P Luyten, Hendrik Delport
The repair of large long bone defects requires complex surgical procedures as the bone loss cannot simply be replaced by autologous grafts due to an insufficient bone stock of the human body. Tissue engineering strategies and the use of Advanced Therapy Medicinal Products (ATMPs) for these reconstructions remain a considerable challenge, in particular since robust outcomes in well-defined large animal models are lacking. To be suitable as a model for treatment of human sized bone defects we developed a large animal model in both skeletally immature and mature sheep and made close observations on the spontaneous healing of defects...
June 8, 2017: Tissue Engineering. Part C, Methods
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