The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Josette Camilleri - One of the best experts on this subject based on the ideXlab platform.
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Characterization and analyses of acid-extractable and leached trace elements in dental cements
International Endodontic Journal, 2012Co-Authors: Josette Camilleri, P. Kralj, Matija Veber, Emanuele SinagraAbstract:AIMS: Determination of the elemental constitution and investigation of the total and leachable arsenic, chromium and lead in Portland cement, pure tricalcium silicate, Biodentine, Bioaggregate and mineral trioxide aggregate (MTA) Angelus.\n\nMETHODOLOGY: The chemical composition of Portland cement, MTA Angelus, tricalcium silicate cement, Biodentine and Bioaggregate was determined using X-ray fluorescence (XRF). Measurements of arsenic, lead and chromium were taken with inductively coupled plasma-mass spectrometry (ICP-MS), following acid digestion on the Hydrated Material and on leachates of cements soaked in Hank's balanced salt solution (HBSS).\n\nRESULTS: All the cements investigated had a similar oxide composition with the main oxide being calcium and silicon oxide. Both the Portland cement and MTA Angelus had an additional aluminium oxide. The dental cements included a radiopacifying Material. All the Materials tested had higher acid-extractable arsenic content than the level set by ISO 9917-1 (2007) and an acceptable level of lead. Regardless these high levels of trace elements present in the Materials, the leaching in HBSS was minimal for all the dental Material tested in contrast to the high levels displayed by Portland cement.\n\nCONCLUSIONS: Dental Materials based on tricalcium silicate cement and MTA Angelus release minimal quantities of trace elements when in contact with simulated body fluids. The results of acid extraction could be affected by nonspecific matrix effects by the cement.
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Hydration Characteristics of Calcium Silicate Cements with Alternative Radiopacifiers Used as Root-end Filling Materials
Journal of Endodontics, 2010Co-Authors: Josette CamilleriAbstract:Introduction: Mineral trioxide aggregate (MTA) is composed of calcium silicate cement and bismuth oxide added for radiopacity. The bismuth oxide in MTA has been reported to have a deleterious effect on the physical and chemical properties of the Hydrated Material. This study aimed to investigate the hydration mechanism of calcium silicate cement loaded with different radiopacifiers for use as a root-end filling Material. Methods: Calcium silicate cement loaded with barium sulfate, gold, or silver/tin alloy was Hydrated, and paste microstructure was assessed after 30 days. In addition, atomic ratio plots of Al/Ca versus Si/Ca and S/Ca and Al/Ca were drawn, and X-ray energy dispersive analysis of the hydration products was performed to assess for inclusion of heavy metals. The leachate produced from the cements after storage of the cements in water for 28 days and the leaching of the radiopacifiers in an alkaline solution was assessed by using inductively coupled plasma. Results: The Hydrated calcium silicate cement was composed of calcium silicate hydrate, calcium hydroxide, ettringite, and monosulfate. UnHydrated cement particles were few. No heavy metals were detected in the calcium silicate hydrate except for the bismuth in MTA. Calcium was leached out early in large quantities that reduced with time. The barium and bismuth were leached in increasing amounts. Copper was the most soluble in alkaline solution followed by bismuth and barium in smaller amounts. Conclusions: The bismuth oxide can be replaced by other radiopacifiers that do not affect the hydration mechanism of the resultant Material. ?? 2010 American Association of Endodontists.
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Analyses of heavy metals in mineral trioxide aggregate and Portland cement
Journal of Endodontics, 2010Co-Authors: M. Schembri, G. Peplow, Josette CamilleriAbstract:Introduction: Portland cement is used in the construction industry as a binder in concrete. It is manufactured from chalk, limestone, and clay, which are clinkered at very high temperatures and ground with gypsum to form Portland cement. The raw Materials and the manufacturing process can result in the inclusion of heavy metals in Portland cement. Portland cement with a four to one addition of bismuth oxide is marketed as mineral trioxide aggregate (MTA), which is used mainly as a dental Material. Heavy metal inclusion can be of concern because MTA is in contact with hard and soft tissues. Methods: Measurements of arsenic, lead, and chromium in Hydrated gray and white Portland cement, ProRoot MTA, and MTA Angelus were conducted with graphite furnace atomic absorption spectrophotometry after acid digestion on the Hydrated Material. The leaching of the metal ions from the solid Material in water and simulated body fluid (SBF) was also determined. Results: All cement types showed high relative values of leached chromium compared with arsenic and lead in both the total metal content and leached species. The gray Portland cement showed the highest total amount of metal. The white Portland and both MTAs had lower values for all the leached metal ions. Conclusions: Both MTAs released more arsenic than the amount specified in ISO 9917-1 (2007). Portland cements and MTAs showed evidence of heavy metals in the acid-soluble form as well as leaching in deionized water and SBF. MTA contained levels of arsenic higher than the safe limit specified by the ISO 9917-1 (2007). © 2010 American Association of Endodontists.
C T Russell - One of the best experts on this subject based on the ideXlab platform.
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reflectance properties and Hydrated Material distribution on vesta global investigation of variations and their relationship using improved calibration of dawn vir mapping spectrometer
Icarus, 2015Co-Authors: Jeanphilippe Combe, E Ammannito, F Tosi, C A Raymond, Maria Cristina De Sanctis, Thomas B Mccord, C T RussellAbstract:Abstract Vesta’s surface albedo variations and Hydrated Material content share similar spatial distribution. This observation is consistent with carbonaceous chondrite meteorites as a likely source Material for dark surface units observed by the Dawn spacecraft, as presented by numerous publications. While these deposits have been studied extensively by analysis of data from the Framing Camera (FC) and the Visible and Infrared Spectrometer (VIR), we performed a new analysis based on an improved calibration of VIR. First we identified instrument and calibration artifacts, and we therefore developed corrections of the VIR flat field and response function. Then we developed a photometric correction for Vesta based on the lunar model by Shkuratov et al. (Shkuratov, Yu.G. et al. [1999]. Icarus 141, 132–155. http://dx.doi.org/10.1006/icar.1999.6154 ), and a semi-analytical inversion of the photometric parameters. This photometric model combines minimization of the scattering effects due to the topography (a disk function) and variations of multiple-scattering with phase angle (the phase function) caused by microscopic physical properties of the regolith. The improved calibration and photometric correction enable more accurate analysis of the spectral properties of Vesta’s surface Material, especially the reflectance at 1.4 μm and the 2.8 μm hydroxyl absorption band depth. We produced global and quadrangle maps that are used as a common dataset for this Icarus special issue on Vesta’s surface composition. The joint interpretation of both the 1.4 μm reflectance and the 2.8 μm absorption band depth reveals unusual spectral properties for a number of impact craters and ejecta compared to the rest of Vesta. An area including the Bellicia, Arruntia and Pomponia craters, where olivine might be present, has relatively high reflectance and a strong hydroxyl absorption band. Another area in the vicinity of Capparonia crater has a high content of Hydrated Materials, although with moderate reflectance and typical pyroxene-rich composition. Ejecta blankets west of Oppia crater have a spectral behavior similar to Capparonia, except for the wider and more complex shape of the hydroxyl absorption band. On the other hand, some low-Hydrated areas associated to crater floors and ejecta have higher reflectance and steeper spectral slope than most low-Hydrated terrains Vesta. A broad lane that extends from Rheasilvia rim at Matronalia Rupes to the northern regions hosts little to no Hydrated Materials and exhibits a moderate spectral slope, similar to Rheasilvia’s basin floor. These properties reinforce the hypothesis that the lane is composed of ejecta from Rheasilvia, as indicated by the distribution of pyroxene compositions by previous results from Dawn. A few small and fresh craters exhibit an association between low-reflectance, little to no Hydrated Materials and a strong positive spectral slope, suggesting optical effects by opaque coatings, as opposed to carbonaceous chondrite deposits, and possible coarser grains.
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mineralogy of marcia the youngest large crater of vesta character and distribution of pyroxenes and Hydrated Material
Icarus, 2015Co-Authors: M C De Sanctis, A Frigeri, E Ammannito, F Tosi, S Marchi, F Zambon, C A Raymond, C T RussellAbstract:Abstract The young Marcia crater on Vesta displays several interesting features, including pitted and smooth terrains, exposure of relatively bright and dark Material, and enrichments of Hydrated Material in the ejecta. Several questions arise about the origin of Marcia and of the dark Material (exogenic Material vs volcanic or impact melts) and the smooth and pitted terrains. Here we describe the results of the spectral and thermal analysis of the Marcia crater, with a particular effort to assess the composition of the different units, identifying the presence of OH and its correlation with dark Material. Detailed studies of the Marcia crater wall, smooth and floor units reveal a compositional rich terrain with small areas enriched in diogenites with respect to the general eucritic regolith dominating the equatorial region of Vesta. The signature of OH is particularly clear in the pitted floor, dark Material, smooth unit, and ejecta. The pitted terrains, beside their appearance, also show thermal anomalies, being colder with respect to the surrounding terrains. The presence of OH, concentrated in darker layers, and the pitted crater floor indicate that the area where the Marcia impact event occurred was rich in volatiles. The results show how the relatively young impact events have modified the surface of Vesta, disrupting a layer of dark Material once present on Vesta’s equatorial terrain and exposing fresh, bright Material rich in pyroxene.
Emanuele Sinagra - One of the best experts on this subject based on the ideXlab platform.
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Characterization and analyses of acid-extractable and leached trace elements in dental cements
International Endodontic Journal, 2012Co-Authors: Josette Camilleri, P. Kralj, Matija Veber, Emanuele SinagraAbstract:AIMS: Determination of the elemental constitution and investigation of the total and leachable arsenic, chromium and lead in Portland cement, pure tricalcium silicate, Biodentine, Bioaggregate and mineral trioxide aggregate (MTA) Angelus.\n\nMETHODOLOGY: The chemical composition of Portland cement, MTA Angelus, tricalcium silicate cement, Biodentine and Bioaggregate was determined using X-ray fluorescence (XRF). Measurements of arsenic, lead and chromium were taken with inductively coupled plasma-mass spectrometry (ICP-MS), following acid digestion on the Hydrated Material and on leachates of cements soaked in Hank's balanced salt solution (HBSS).\n\nRESULTS: All the cements investigated had a similar oxide composition with the main oxide being calcium and silicon oxide. Both the Portland cement and MTA Angelus had an additional aluminium oxide. The dental cements included a radiopacifying Material. All the Materials tested had higher acid-extractable arsenic content than the level set by ISO 9917-1 (2007) and an acceptable level of lead. Regardless these high levels of trace elements present in the Materials, the leaching in HBSS was minimal for all the dental Material tested in contrast to the high levels displayed by Portland cement.\n\nCONCLUSIONS: Dental Materials based on tricalcium silicate cement and MTA Angelus release minimal quantities of trace elements when in contact with simulated body fluids. The results of acid extraction could be affected by nonspecific matrix effects by the cement.
M. Schembri - One of the best experts on this subject based on the ideXlab platform.
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Analyses of heavy metals in mineral trioxide aggregate and Portland cement
Journal of Endodontics, 2010Co-Authors: M. Schembri, G. Peplow, Josette CamilleriAbstract:Introduction: Portland cement is used in the construction industry as a binder in concrete. It is manufactured from chalk, limestone, and clay, which are clinkered at very high temperatures and ground with gypsum to form Portland cement. The raw Materials and the manufacturing process can result in the inclusion of heavy metals in Portland cement. Portland cement with a four to one addition of bismuth oxide is marketed as mineral trioxide aggregate (MTA), which is used mainly as a dental Material. Heavy metal inclusion can be of concern because MTA is in contact with hard and soft tissues. Methods: Measurements of arsenic, lead, and chromium in Hydrated gray and white Portland cement, ProRoot MTA, and MTA Angelus were conducted with graphite furnace atomic absorption spectrophotometry after acid digestion on the Hydrated Material. The leaching of the metal ions from the solid Material in water and simulated body fluid (SBF) was also determined. Results: All cement types showed high relative values of leached chromium compared with arsenic and lead in both the total metal content and leached species. The gray Portland cement showed the highest total amount of metal. The white Portland and both MTAs had lower values for all the leached metal ions. Conclusions: Both MTAs released more arsenic than the amount specified in ISO 9917-1 (2007). Portland cements and MTAs showed evidence of heavy metals in the acid-soluble form as well as leaching in deionized water and SBF. MTA contained levels of arsenic higher than the safe limit specified by the ISO 9917-1 (2007). © 2010 American Association of Endodontists.
Hidehiko Higaki - One of the best experts on this subject based on the ideXlab platform.
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Influence of axial direction on performance of biomimetic sealing system
2015 International Conference on Renewable Energy Research and Applications, ICRERA 2015, 2016Co-Authors: Yoshitaka Nakanishi, Jason Sanderson, Takuro Honda, Keiji Kasamura, Yuta Nakashima, Hidehiko HigakiAbstract:© 2015 IEEE.A biomimetic bearing seal system has been developed to reduce frictional loss and improve the separation of air and water. The seal mimics the Material properties and mechanical characteristics of articular cartilage found in natural synovial joints. It is made of the Hydrated Material polyvinyl formal (PVF), which has a porous structure, high wear resistance, and exhibits low frictional resistance when lubricated with polyethylene glycol. The analysis presented assesses the effectiveness of this shaft seal system and standard oil seals in two different shaft configurations (horizontal and vertical) to evaluate the effects on the torsional resistance and sealing ability. It is shown that PVF seals have a lower initial torque and a higher wear resistance in comparison with oil seals in both configurations. The average torque measurements were lowest in the horizontal configuration PVF seal. In the vertical configuration, the upper (toward air) PVF seal suffered from a reduction in lubricant, which was thought to be caused by settling in the lubrication reservoir, thereby slightly increasing the average frictional resistance. To maximize the system performance, the sensitivity of the frictional property to the axial direction should be considered.
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Biomimetic sealing system for streamflow generation
Proceedings of 2013 International Conference on Renewable Energy Research and Applications, ICRERA 2013, 2013Co-Authors: Yoshitaka Nakanishi, Yuichi Oka, Kenryo Shimazu, Syoji Mine, Yasuaki Matsumoto, Hidehiko HigakiAbstract:Renewable energy research has been promoted to slow down climate change and maintain economic growth. Streamflow is valued as a source of energy, and environmentally friendly and low-friction sealing system that employs biomimetic technologies is proposed for its utilization. A dynamo-electric generator and ancillary systems with waterproof construction are installed under water. Lip seals with a rotating shaft function to prevent the ingress of water from the outside and excellent frictional properties with various rotation speeds are required to improve the power generation efficiency with constantly changing water flow. The sealing system was successfully developed using a Hydrated Material (polyvinyl formal; PVF) that mimics articular cartilage in a natural synovial joint. Polyethylene glycol (PEG) dissolved in distilled water, which is a non-Newtonian fluid, was used as a lubricant. These Materials have low toxicity and low environmental impact. The biomimetic sealing system exhibits excellent frictional properties with extremely low ingress of water. © 2013 IEEE.
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Eco-friendly bearing for tidal power generation
2012 International Conference on Renewable Energy Research and Applications (ICRERA), 2012Co-Authors: Yoshitaka Nakanishi, Kenryo Shimazu, Yasuaki Matsumoto, Hidehiko HigakiAbstract:An environmentally friendly and low-friction bearing for applications such as tidal power generation is proposed using biomimetic technologies. A biomimetic bearing was successfully developed using a Hydrated Material, polyvinyl formal (PVF), which mimics articular cartilage in a natural synovial joint. A non-Newtonian fluid, polyethylene glycol (PEG) dissolved in distilled water, was used as a lubricant, and the biomimetic bearing exhibited excellent frictional properties at start-up, at steady state, and at near zero velocity.
