Titanium species in titanium silicalite TS-1 prepared by hydrothermal method

The titanium species existing in titanium silicalite TS-1, which is prepared by hydrothermal method, were investigated using chemical analysis, XRD, FT-IR, Si-29 MAS NMR, UV-VIS, ESR. It has been observed that several kinds of titanium species may exist in titanium silicalite. The form that titanium atoms incorporate into the framework of titanium silicalite synthesized using tetrapropylammonium bromide (TPABr) as template differs from that using the classical method. But, the symmetry of titanium silicalite, changes from monoclinic to orthorhombic with the increase of titanium content in both methods. The Ti-O-2(-) originated from framework titanium and H2O2 has the moderate stability and may be active site in oxidation reaction. TS-1 synthesized using TPABr as template does not contain anatase, but contains a kind of partly condensed titanium species with six-fold coordination. The titanium species may correspond to 270-280 mn band in UV-VIS spectra and also can form Ti-O-2(-). But, this kind of Ti-O-2(-) is very stable and cannot be catalytic active site. So, the six-fold coordination titanium species may be inactive in both the oxidation reaction and the decomposition of H2O2. The hypothesis has been further proved by the phenomena that the titanium species is easily washed off using acid, and acid treating will not influence the catalytic performance of TS-1. (C) 2001 Elsevier Science B.V. All rights reserved.

Identifying framework titanium in TS-1 zeolite by UV resonance Raman spectroscopy

Framework titanium in Ti-silicalite-1 (TS-1) zeolite was selectively identified by its resonance Raman bands using ultraviolet (W) Raman spectroscopy. Raman spectra of the TS-1 and silicalite-1 zeolites were obtained and compared using continuous wave laser lines at 244, 325, and 488 nm as the excitation sources. It was only with the excitation at 244 nm that resonance enhanced Raman bands at 490, 530, and 1125 cm(-1) appeared exclusively for the TS-1 zeolite. Furthermore, these bands increased in intensity with the crystallization time of the TS-1 zeolite. The Raman bands at 490, 530, and 1125 cm(-1) are identified as the framework titanium species because they only appeared when the laser excites the charge-transfer transition of the framework titanium species in the TS-1. No resonance Raman enhancement was detected for the bands of silicalite-1 zeolite and for the band at 960 cm(-1) of TS-1 with any of the excitation sources ranging from the visible tb UV regions. This approach can be applicable for the identification of other transition metal ions substituted in the framework of a zeolite or any other molecular sieve.

Post-grafting preparation of large-pore mesoporous materials with localized high content titanium doping

A new post-grafting process, consisting of two steps of substrate preparation and sol - gel post-grafting, has been developed to prepare titanium-doped mesoporous SBA-15 material with a double-layered structure and locally concentrated titanium content at the inner pore surface. With this novel technique, the single phased and originally ordered mesostructures can be well conserved; in the conventional direct synthesis they can be partially damaged when the frameworks are doped with high content heteroatoms. Titanium species exist in an isolated, tetrahedral structure and are localized at the pore surface; this is beneficial to both reactant access and product release. Characterization with XRD, N-2 adsorption/desorption isotherms, HREM/ EDS, ICP, UV - Vis, and the newly developed UV - Raman spectroscopy confirm these results. Preliminary catalytic tests with the selective epoxidation of cyclohexene show good catalytic activity. Among them, sample TiSBA-15-10 with a Si : Ti molar ratio of 10 shows a TON value of 75 and a highest product ( epoxide) yield of 55%.

The use of transvaginal synthetic mesh for anterior vaginal wall prolapse repair: a randomized controlled trial

The aim of the study was to compare the efficacy and safety of transvaginal trocar-guided polypropylene mesh insertion with traditional colporrhaphy for treatment of anterior vaginal wall prolapse.This is a randomized controlled trial in which women with advanced anterior vaginal wall prolapse, at least stage II with Ba a parts per thousand yenaEuro parts per thousand+1 cm according to the Pelvic Organ Prolapse Quantification (POP-Q) classification, were randomly assigned to have either anterior colporrhaphy (n = 39) or repair using trocar-guided transvaginal mesh (n = 40). the primary outcome was objective cure rate of the anterior compartment (point Ba) assessed at the 12-month follow-up visit, with stages 0 and I defined as anatomical success. Secondary outcomes included quantification of other vaginal compartments (POP-Q points), comparison of quality of life by the prolapse quality of life (P-QOL) questionnaire, and complication rate between the groups after 1 year. Study power was fixed as 80 % with 5 % cutoff point (p < 0.05) for statistical significance.The groups were similar regarding demographic and clinical preoperative parameters. Anatomical success rates for colporrhaphy and repair with mesh placement groups were 56.4 vs 82.5 % (95 % confidence interval 0.068-0.54), respectively, and the difference between the groups was statistically significant (p = 0.018). Similar total complication rates were observed in both groups, with tape exposure observed in 5 % of the patients. There was a significant improvement in all P-QOL domains as a result of both procedures (p < 0.001), but they were not distinct between groups (p > 0.05).Trocar-guided transvaginal synthetic mesh for advanced anterior POP repair is associated with a higher anatomical success rate for the anterior compartment compared with traditional colporrhaphy. Quality of life equally improved after both techniques. However, the trial failed to detect differences in P-QOL scores and complication rates between the groups.

Sistema de instrumentação mecanizada reciprocante

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina Dentária

Stochastic Mesh-Based Multiview Reconstruction

A method for reconstruction of 3D polygonal models from multiple views is presented. The method uses sampling techniques to construct a texture-mapped semi-regular polygonal mesh of the object in question. Given a set of views and segmentation of the object in each view, constructive solid geometry is used to build a visual hull from silhouette prisms. The resulting polygonal mesh is simplified and subdivided to produce a semi-regular mesh. Regions of model fit inaccuracy are found by projecting the reference images onto the mesh from different views. The resulting error images for each view are used to compute a probability density function, and several points are sampled from it. Along the epipolar lines corresponding to these sampled points, photometric consistency is evaluated. The mesh surface is then pulled towards the regions of higher photometric consistency using free-form deformations. This sampling-based approach produces a photometrically consistent solution in much less time than possible with previous multi-view algorithms given arbitrary camera placement.

Titanium: An allergen of growing significance

info:eu-repo/semantics/published