Extraction of cesium ions from aqueous solutions using calix[4]arene-bis(tert-octylbenzo-crown-6) in ionic liquids

Solvent extraction of cesium ions from aqueous solution to hydrophobic ionic liquids without the introduction of an organophilic anion in the aqueous phase was demonstrated using calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) as an extractant. The selectivity of this extraction process toward cesium ions and the use of a sacrificial cation exchanger (NaBPh4) to control loss of imidazolium cation to the aqueous solutions by ion exchange have been investigated.

Quantification of all-ceramic crown margin surface profile from try-in to 1-week post-cementation

To use profilometry to assess the margin surface profile of all-ceramic crowns (ACC’s) at try-in and 1-week after cementation with dual-cured resin (DC, RelyX ARC, 3 M ESPE, St. Paul, MN, USA), self-adhesive dual-cured resin (SADC, RelyX Unicem, 3 M ESPE), light-cured resin (LC, RelyX Veneer, 3 M ESPE) or chemically cured resin-modified glass ionomer (RMGI, RelyX Luting Plus, 3 M ESPE) luting cement. Methods: Forty, sound, extracted, human, premolar teeth underwent a standardised preparation for ACC’s. IPS Empress (Ivoclar-Vivadent, Liechtenstein) crowns of standard dimensions were fabricated and 10 luted with each cement and stored in water for 7 days. Three groups of serial profiles were taken, the first of the tooth preparation, the second of the crown margins at try-in and lastly of the crown margins after cementation and 7 days water storage. Results: There were no significant differences in the crown margin surface profile between the four cement groups at try-in. The change in crown margin position between try-in and post-cementation was significantly greater for DC than for LC and RMGI. SADC was not significantly different to the other cements. There were no significant differences in the crown margin extensions between the four cement groups, however most of the IPS Empress ACC’s in this study were underextended but this was not statistically significant. Conclusions: IPS Empress ACC’s seated more fully with LC and RMGI than with DC cement

Optimising the locations of thermally sensitive equipment in an aircraft crown compartment

A Design of Experiments (DoE) analysis was undertaken to generate a list of configurations for CFD numerical simulation of an aircraft crown compartment. Fitted regression models were built to predict the convective heat transfer coefficients of thermally sensitive dissipating elements located inside this compartment. These are namely the SEPDC and the Route G. Currently they are positioned close to the fuselage and it is of interest to optimise the heat transfer for reliability and performance purposes. Their locations and the external fuselage surface temperature were selected as input variables for the DoE. The models fit the CFD data with values ranging from 0.878 to 0.978, and predict that the optimum locations in terms of heat transfer are when the elements are positioned as close to the crown floor as possible ( and ?min. limits), where they come in direct contact with the air flow from the cabin ventilation system, and when they are positioned close to the centreline ( and ?CL). The methodology employed allows aircraft thermal designers to optimise equipment placement in confined areas of an aircraft during the design phase. The determined models should be incorporated into global aircraft numerical models to improve accuracy and reduce model size and computational time. © 2012 Elsevier Masson SAS. All rights reserved.

Effect of the crown design and interface lute parameters on the stress-state of a machined crown-tooth system: A finite element analysis

The effect of preparation design and the physical properties of the interface lute on the restored machined ceramic crown-tooth complex are poorly understood. The aim of this work was to determine, by means of three-dimensional finite element analysis (3D FEA) the effect of the tooth preparation design and the elastic modulus of the cement on the stress state of the cemented machined ceramic crown-tooth complex. The three-dimensional structure of human premolar teeth, restored with adhesively cemented machined ceramic crowns, was digitized with a micro-CT scanner. An accurate, high resolution, digital replica model of a restored tooth was created. Two preparation designs, with different occlusal morphologies, were modeled with cements of 3 different elastic moduli. Interactive medical image processing software (mimics and professional CAD modeling software) was used to create sophisticated digital models that included the supporting structures; periodontal ligament and alveolar bone. The generated models were imported into an FEA software program (hypermesh version 10.0, Altair Engineering Inc.) with all degrees of freedom constrained at the outer surface of the supporting cortical bone of the crown-tooth complex. Five different elastic moduli values were given to the adhesive cement interface 1.8 GPa, 4 GPa, 8 GPa, 18.3 GPa and 40 GPa; the four lower values are representative of currently used cementing lutes and 40 GPa is set as an extreme high value. The stress distribution under simulated applied loads was determined. The preparation design demonstrated an effect on the stress state of the restored tooth system. The cement elastic modulus affected the stress state in the cement and dentin structures but not in the crown, the pulp, the periodontal ligament or the cancellous and cortical bone. The results of this study suggest that both the choice of the preparation design and the cement elastic modulus can affect the stress state within the restored crown-tooth complex.

Speciation of uranyl complexes in ionic liquids by optical spectroscopy

Uranyl complexes dissolved in room-temperature ionic liquids have diagnostic absorption and emission spectra which reflect the molecular symmetry and geometry. In particular, the characteristic vibrational fine structure of the absorption spectra allows identification of the molecular symmetry of a uranyl complex. The concept of speciation of. uranyl complexes is illustrated for the hydrated uranyl ion, the tetrachloro complex [UO2Cl4](2-), the trinitrato complex [UO2(NO3)(3)](-), the triacetato complex [UO2(CH3COO)(3)](-) and the crown ether complex [UO2(18-crown-6)](2+) in imidazolium and pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids. The competition between 18- crown-6 and small inorganic ligands for coordination to the uranyl ion was investigated. The crystal structures of the hydrolysis product [(UO2)(2)(mu(2)-OH)(2)(H2O)(6)] [UO2Br4](18-crown-6)(4) and imidazolium salt [C(6)mim](2)[UO2Br4] are described.