Search results for " fluoride"
showing 10 items of 90 documents
Convective electrodiffusion processes through graft-modified charged porous membranes
1999
Convective diffusion and electrophoresis across a charged porous membrane showing variable permeability properties were studied. The membrane used was prepared by grafting poly(acrylic acid) (PAA) onto a porous polyvinylidene fluoride (PVDF) membrane. The degree of grafting was selected to be relatively low, 18 wt%, to compromise between the ion selectivity and hydraulic permeability of the membrane. The possible electric field induced effects on the membrane permselectivity were examined after the membrane had been characterized by convective diffusion and concentration cell potential measurements. The measured electrophoresis data, however, could be modelled using the extended Teorell–Mey…
Morphological, electrical and optical properties of organic light-emitting diodes with a LiF/Al cathode and an Al-hydroxyquinoline/diamine junction
2004
Abstract We report the results of the morphological, electrical and optical characterisation of double-layer Alq3-based organic emitting diodes with a lithium fluoride (LiF)/Al cathode. A detailed electron microscopy investigation of their cross-section shows the presence of LiF isolated grains underneath the Al film. Due to the introduction of the LiF layer, luminance was larger than 30,000 cd/m2 at a bias voltage VB=25 V with a maximum external luminous efficiency as large as 46 lm/W at VB=20 V. Performing on/off VB cycles at a very low frequency, each time a recovery of the initial electric and luminous performance was observed. The non-exponential decay of both electric current and lumi…
Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics
2012
A kinetic model is developed for the heterogeneous free-radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO 2. The model accounts for polymerization in both the dispersed (polymer-rich) phase and in the continuous (polymer-free) supercritical phase, for radical interphase transport, diffusion limitations, and chain-length-dependent termination in the polymer-rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer fe…
Tunable field effect properties in solid state and flexible graphene electronics on composite high – low k dielectric
2016
We demonstrate tunable field effect properties in solid state and flexible graphene field effect devices (FEDs) fabricated using a poly(methylmethacrylate) (PMMA) and lithium fluoride (LiF) composite dielectric. Increasing the concentration of LiF in the composite dielectric increases the capacitance, which thereby reduces the operating gate voltages of FEDs significantly from 10 V to 1 V to achieve similar conductivity. Electron and hole mobility of 350 and 310 cm2/V at VD = −5 V are obtained for graphene FEDs with 10% LiF concentration in the composite. Composite dielectric also enabled excellent FEDs on flexible substrates without any significant change in mobility and resistance. Flexib…
Cadmium binding proteins induced in exposed freshwater crayfish Procambarus clarkii.
1989
This work describes results on the characterization of cadmium binding proteins (Cd-BPs) obtained from cadmium exposed freshwater crayfish Procambarus clarkii. After acclimation to laboratory conditions, induction of Cd-BPs was achieved by water exposure at a concentration of 100 micrograms Cd/L during 2, 15, and 30 d. In accordance with the method followed by Engel and Brouwer, in each case two midgut glands were minced and homogenized in Tris-HC1 buffer with PMSF to prevent protease activity and DTT to maintain reducing conditions. The homogenate was centrifuged, heat treated, applied to a column of Sephadex G-75, and eluted with the same buffer (pH 8.6). Absorbances of the fractions coll…
PVDF based vibration measurements and their correlation with torque estimation in a FOC induction motor drive
2008
This paper presents a study concerning the vibrations generated by an induction motor drive controlled by field oriented control algorithm (FOC). The aim of the study is to identify suitable measurement points and analysis techniques in order to achieve information about vibration generated by an electric drive. Vibrations take origin both by the torque generated by the motor and the motor supply through an inverter, then they are transmitted to neighbouring structures. Torque is estimated on the basis of the estimated flux linkage; vibrations have been both measured and analysed numerically by FEM at two points of the cradle. The numerical and experimental analysis have been carried out fo…
Ethylene and phenylene bridged polysilsesquioxanes functionalized by amine and thiol groups as adsorbents of volatile organic compounds
2007
Abstract Ethylene and phenylene bridged polysilsesquioxane xerogels having amine and thiol groups attached to the surface have been obtained by the sol–gel method from 1,2-bis(triethoxysilyl)ethane or 1,4-bis(triethoxysilyl)benzene and functionalized silanes in the presence of an ammonium fluoride catalyst in an ethanol solution. The synthesized samples have a porous structure (700–850 m2/g) and a high content of functional groups (1.4–1.9 mmol/g). The obtained porous bridged polysilsesquioxanes exhibit a considerable affinity for adsorbing several organic compounds (n-hexane, n-heptane, benzene, cyclohexane, acetonitrile and triethylamine) from the gas phase. The sample with an ethylene br…
In Vitro Biocompatibility of Several Children's Toothpastes on Human Gingival Fibroblasts
2022
The European Academy of Paediatric Dentistry has recommended fluoride toothpastes from the eruption of the first teeth in children. Toothpastes stay in the mouth in contact with human gingival fibroblasts (hGFs) for a long time. Thus, the objective of this study was to compare the cytotoxicity of five different commonly used children’s toothpastes: Oral B Kids +3 (Procter & Gamble, Alicante, Spain), Fluor Kin Calcium (Kin, Madrid, Spain), PHB Junior (PHB, Barcelona, Spain), Colgate +3 (Colgate Palmolive, Madrid, Spain) and Vitis Kids (Dentaid, Valencia, Spain) on hGFs. The children’s toothpastes were exposed to hGFs at different concentrations (1:1, 1:2, 1:4). Afterwards, several tests …
First principles studies of the self trapped hole and the fluorine adsorption on the SrF2(111) surface
2013
Abstract By using density functional theory (DFT) with hybrid exchange potentials, namely DFT-B3PW, the ground states of self trapped hole and adsorbed fluorine atom on the strontium fluoride (1 1 1) surface are investigated. The self trapped hole at an interstitial anion site is denoted by H-center. In both the H-center and fluorine adsorption cases, the strong relaxations due to the surface effects are observed. In the H-center case, the unpaired electron distributes almost equally over two H-center atoms. This equivalent distribution of the unpaired electron is totally different from that of the bulk H-center [J. Phys. Chem. A 114 (2010) 8444]. The other case with an adsorbed fluorine at…
Up-conversion process in erbium doped lithium fluoride bulk crystal, lithium borate glass and glass ceramics
2007
In our research the up-conversion processes in Er doped bulk LiF crystal, lithium borate oxyfluoride glass and lithium borate oxyfluoride glass ceramics were studied: up- conversion and traditional photoluminescence spectra, the up-converted signal as a function of the laser power are presented. It was found that sharp luminescence bands in the visible part of the spectrum appear when the bulk crystal is subjected to IR irradiation at 980 nm by a laser diode. After the heat treatment of the glass submicron crystallites were detected by SEM technique. The presence of LiF crystalline phase in the oxyfluoride glass ceramics was proved by XRD method. The questions about the synthesis of the oxy…