Search results for "silica"
showing 10 items of 1092 documents
Spectroscopic and electrochromical properties of metallophthalocyanines in silicate bulks and thin films prepared by the sol–gel method
2000
Abstract Magnesium phthalocyanine (MgPc) and praseodymium bisphthalocyanine (Pr(Pc) 2 ) have been entrapped in bulks and thin films of porous silicate xerogels prepared via the sol–gel method. The electronic absorption data obtained for the complexes immobilized in bulk sol–gel matrices indicate the formation of complex equilibria between their monomeric forms and respective agglomerates. Thin xerogel films doped with metallophthalocyanines and connecting two slides of transparent ITO electrodes display changes in the absorption spectra caused by varying of the applied voltage. These changes appear to be reversible in certain ranges of the applied voltages.
In-situ observation of beta-ray induced UV optical absorption in a-SiO2: radiation darkening and room temperature recovery
2006
International audience; We studied the optical absorption in the 3.0-6.2 eV range induced in bulk amorphous SiO2 by beta-ray irradiation up to similar to 1 MGy at room temperature. The induced absorption was measured in situ both during irradiation and in the post irradiation time. Our data evidence E', center as the main defect induced by irradiation and the partial decay of their absorption band at about 5.8 eV after irradiation. A quantitative analysis of the time evolution of the induced absorption shows that the transmission recovery observed after irradiation is compatible with the reaction of radiation-induced defects with H-related (H-2, H2O) species diffusing in the amorphous matrix
Chromo-Fluorogenic Detection of Nerve-Agent Mimics Using Triggered Cyclization Reactions in Push-Pull Dyes
2010
A family of azo and stilbene derivatives (1-9) are synthesized, and their chromo-fluorogenic behavior in the presence of nerve-agent simulants, diethylchlorophosphate (DCP), diisopropylfluorophosphate (DFP), and diethylcyanophosphate (DCNP) in acetonitrile and mixed solution of water/acetonitrile (3:1 v/v) buffered at pH 5.6 with MES, is investigated. The prepared compounds contain 2-(2-N,N-dimethylaminophenyl)ethanol or 2-[(2-N,N-dimethylamino)phenoxy]ethanol reactive groups, which are part of the conjugated pi-system of the dyes and are able to give acylation reactions with phosphonate substrates followed by a rapid intramolecular N-alkylation. The nerve-agent mimic-triggered cyclization …
Follow‐up of patients subjected to direct and indirect pulp capping of young permanent teeth. A retrospective study
2021
Abstract Objective A retrospective study of the success rate of direct pulp capping (DPC) and indirect pulp capping (IPC) was carried out in children between 6–14 years‐old, considering separately primary caries or caries affecting teeth with molar incisor hypomineralization (MIH). Material and methods Data were collected in a dental public health service. Following the inclusion criteria, 232 treatments were analyzed. Success was defined by the presence of a functional tooth without clinical signs or symptoms of pulpal or periapical disease. The success rate was correlated to patient gender, the affected tooth and the indication of therapy using the chi‐squared and Fisher exact test. The s…
Self-assembled titania-silica-sepiolite based nanocomposites for water decontamination
2009
WOS: 000264524200020
Clinical evaluation of an Er:YAG laser combined with scaling and root planing for non-surgical periodontal treatment
2003
Objectifs: le but de cette etude clinique controlee etait de comparer les traitements de maladie parodontale avancee par une association de laser Er:YAG (KEY II®, KaVo, Germany) et de detartrage et surfacage radiculaire manuels (SRP) avec le laser seul. Materiel & Methodes: 20 patients sains presentant des destructions parodontales moderees a avancees furent traites au hasard en bouche divisee par une association de laser Er:YAG et de detartrage et surfacage radiculaire manuels (SRP) (test) et le laser seul (controle). L'energie utilisee en reglage pour le laser etait de 160 mJ/pulsation a un taux de repetition de 10 Hz. Prealablement au traitement, et 3, 6 etl2 mois apres, les parametres s…
Bimodal porous silica nanomaterials as sorbents for an efficient and inexpensive determination of aflatoxin M1 in milk and dairy products
2020
Abstract An extraction procedure was developed for the determination of aflatoxin M1 in milk and dairy products. A sorbent based on UVM-7 mesoporous silica was used as solid phase for the sample clean-up, and the analyte determination was carried out by HPLC coupled to a fluorescence detector. The material architecture was characterized by transmission electronic microscopy, X-ray diffraction, 29Si NMR and nitrogen adsorption-desorption. After the optimization of extraction parameters, the influence of the matrix has been evaluated, obtaining recoveries in the range 78–105% for whole and skimmed milk and yogurt matrix. The reusability of the material was also proved. The sensitivity of the …
Scheda IV.17, argentiere palermitano del quinto decennio del XVIII secolo, console Antonino Pensallorto, ostensorio, argento dorato sbalzato, cesella…
2011
Scheda storico-artistica dell'ostensorio di maestranza palermitana del quinto decennio del XVIII secolo e vidimato dal console Antonino Pensallorto. L'opera è custodita nel Museo d'Arte Sacra della Basilica Santa Maria Assunta di Alcamo.
Aqueous solubility diagrams for cementitious waste stabilization systems. 3. Mechanism of zinc immobilizaton by calcium silicate hydrate.
2002
Zinc oxide was added during hydration of alite (C3S) as an analogue for solidification/stabilization by cement of metal-bearing hazardous waste. Curing of samples was stopped at various intervals between 8 h and 100 d, and the reaction products were analyzed by both X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS at Zn, Ca, and Si K-edges). Calcium zincate hydrate (CaZn2(OH)6 x 2H2O) initially formed together with calcium silicate hydrate (CSH) vanishes from X-ray diffractograms after 14 d, and no other crystalline Zn-bearing phase could be detected thereafter. EXAFS Zn K-edge data analysis reveals that Zn(O,OH)4 tetrahedra continue to determine the first shell coordination…
Luminescence of silica glass containing aluminum oxide
2004
Abstract Optical properties of silica glass with different doping of Al 2 O 3 up to 1.5 mol% were studied. Alumina stimulates creation of a luminescence centers with specific band at 3.3 eV. A new band at 8.2 eV appears in luminescence excitation spectra. There is transport of energy to other luminescence centers associated with an impurity (Ag, Ce) at this energy. Alumina stimulates creation of E′ centers under γ-irradiation beside trapped hole on AlO 4 tetrahedron as well as creation of a silicon related oxygen deficient center (SiODC) under cathodoexcitation. Visually, the samples look inhomogeneous even after γ-irradiation. The explanation could be heterogeneity of the samples. Alumina …