Search results for "fluoride"
showing 10 items of 314 documents
Orthogonal functionalisation of upconverting NaYF4 nanocrystals.
2013
A simple and straightforward method for the orthogonal functionalisation of upconverting NaYF4 nanocrystals (UCNCs)-doped withYb(3+) and Er(3+)-based on N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide/N-hydroxysuccinimide (EDC/NHS) selective reactions between two dyes and two different reactive groups present at the periphery of the upconverting nanocrystals is reported. Organic-soluble UCNCs of 10 and 50 nm in size are encapsulated efficiently in a 1:1 mixture of two commercial 3000 Da poly(ethylene glycol) derivatives with two different reactive groups (amino and carboxylic groups). The water-dispersible UCNCs are non-cytotoxic, stable in the physiological environment, and present free ami…
Modeling of Growth and Dissolution of Nanotubular Titania in Fluoride-Containing Electrolytes
2009
In this paper, model calculations of diffusion processes and pH profiles inside TiO 2 nanotubes are performed in order to explore key factors in the growth mechanism of this system in aqueous electrolytes. An electrochemical steady state featured by an equivalent rate between oxide growth and dissolution is reached for a given current efficiency. Electrochemical oxide growth is found to be exclusively located at the pore bottom, whereas chemical oxide dissolution is uniformly distributed over the whole nanotube. It can be deduced from the results that electrolyte resistance or diffusion processes in the electrolyte inside the tubes are not limiting.
Agua de bebida en el lactante
2004
Se revisan tipos de aguas de consumo público y aguas de bebida envasadas. Se realizan recomendaciones sobre las características que debe reunir el agua destinada al lactante. Para la reconstitución correcta de todas las fórmulas de inicio comercializadas en España, el contenido en sodio debe ser menor de 25 mg/l. El agua de consumo público debe hervirse un máximo de 1 min (a nivel del mar) para evitar la excesiva concentración de sales. No precisa de ebullición el agua de bebida envasada. El nivel de flúor debe ser menor de 0,3 mg/l en el primer año de vida para evitar fluorosis. La concentración de nitratos en agua debe ser menor de 25 mg/l para evitar metahemoglobinemia. Aguas con una con…
Comparative quantum chemistry study of the F-center in lanthanum trifluoride
2020
Abstract In this study we report the results of first principle quantum chemical modeling of electronic structure and spatial configuration of LaF3 crystal containing the F-center. Theoretical predictions of atomic and electronic properties of LaF3 are given by means of density functional theory. From our modeling we predict that the F-center placed at fluorine ion position between the lanthanum planes at tysonite LaF3 is the most energetically stable. In order to interpret the structure of the optical absorption spectrum of X-irradiated LaF3 we performed calculations of excited and transition states of the F-center within the embedded cluster formalism using time dependent density function…
Hardening and long-range stress formation in lithium fluoride induced by energetic ions
2003
Abstract LiF crystals were irradiated with Au, Pb, Bi and S ions in the energy range 400–2300 MeV and studied by means of Vickers microindentation. Remarkable hardening effects are observed which depend on the applied fluence and ion species, and correlate with the ion energy loss along the ion path. Structural investigations reveal irradiation-induced stress extending deep into the adjacent non-irradiated crystal and leading to the formation of dislocations. X-ray diffraction measurements of the irradiated crystals show a decrease of the lattice constant indicating the presence of internal stress.
Production and release of ISOL beams from molten fluoride salt targets
2014
In the framework of the Beta Beams project, a molten fluoride target has been proposed for the production of the required 1013 18Ne/s. The production and extraction of such rates are predicted to be possible on a circulating molten salt with 160 MeV proton beams at close to 1 MW power. As a most important step to validate the concept, a prototype has been designed and investigated at CERN-ISOLDE using a static target unit. The target material consisted of a binary fluoride system, NaF:LiF (39:61 mol.%), with melting point at 649 °C. The production of Ne beams has been monitored as a function of the target temperature and proton beam intensity. The prototype development and the results of th…
Crossluminescence in some fluoride and chloride crystals with intrinsic and extrinsic defects
1991
Abstract The term “crossluminescence” (CRL) was originaly proposed for emission due to electronic transitions from valence band states to cation core band states. Analogous transitions involving cation core states are observed at defect centers.
Binding of fluoride and carbonate by open chain polyammonium cations
2004
The formation of open chain polyammonium cation-fluoride and -carbonate complexes was studied by potentiometric and calorimetric techniques at t=25 degrees C. Several species of H(i)AL (A=amine; L=F(-), CO(3)(2-)) are formed in both systems with a mean stability log K=1.0zeta (zeta=|z(anion)xz(cation)|) and log K=2.0zeta for fluoride and carbonate, respectively. The comparison with analogous systems (chloride and acetate for fluoride and hydrogenphosphate, sulfate and malonate for carbonate) showed that fluoride and carbonate form the most stable species with open chain polyammonium cations, among low molecular weight anions. The N-alkyl substitution does not play negligible role in the sta…
Combined chlorhexidine-sodiumfluoride mouthrinse for orthodontic patients: Clinical and microbiological study
2015
Background: Orthodontic appliances impede good dental plaque control by brushing. Antimicrobial mouth rinses were suggested to improve this performance. We therefore aimed to investigate the effects of combined mouthrinse containing chlorhexidine (CHX) and sodium fluoride (NaF) on clinical oral hygiene parameters,and plaque bacterial level. Material and Methods: In this double-blind clinical study, 60 fixed orthodontic patients aged 14-25 years were randomly assigned to one of four mouthrinses groups: 1- combined CHX /NaF 2- CHX 0.06% 3- NaF0.05% 4-placebo. Following baseline examination patients were instructed to use the assigned mouthrinse twice daily for 21 days. Bleeding index (BI), mo…
Erosive effect of industrialized fruit juices exposure in enamel and dentine substrates: An in vitro study
2021
Background Erosive tooth wear has been a highly prevalent and emerging phenomenon related to eating habits of the population. Aim: This study sought to investigate industrialized fruit juices exposure in enamel and dentine substrates in terms of erosive effect. Material and methods Human enamel and dentine specimens were randomized into 8 groups (n=8): Grape juice - Ades®, Grape juice - Del Valle Kapo®, Grape juice - Aurora®, Orange juice - Del Valle Kapo®, Orange juice - Ades®, Strawberry juice - Mais Vita®, Strawberry juice - Ades®, Citrus fruit juice - Tampico®. Specimens were submitted to an in vitro erosive challenge and to a microhardness test to evaluate the percentage of surface mic…