Sol-gel preparation of near-infrared broadband emitting Er(3+)-doped SiO(2)-Ta(2)O(5) nanocomposite films

This article reports a study on the preparation, densification process, and structural and optical properties of SiO(2)-Ta(2)O(5) nanocomposite films obtained by the sol-gel process. The films were doped with Er(3+) and the Si:Ta molar ratio was 90:10. Values of refractive index, thickness and vibrational modes in terms of the number of layers and thermal annealing time are described for the films. The densification process is accompanied by OH group elimination, increase in the refractive index, and changes in film thickness. Full densification of the film is acquired after 90 min of annealing at 900 degrees C. The onset of crystallization and devitrification, with the growth of Ta(2)O(5) nanocrystals occurs with film densification, evidenced by high-resolution transmission electron microscopy. The Er(3+)-doped nanocomposite annealed at 900 degrees C consists of Ta(2)O(5) nanoparticles, with sizes around 2 nm, dispersed in the SiO(2) amorphous phase. The main emission peak of the film is detected at around 1532 nm, which can be assigned to the (4)I(13/2)->(4)I(15/2) transition of the Er(3+) ions present in the nanocomposites. This band has a full width at half medium of 64 nm, and the lifetime measured for the (4)I(13/2) levels is 5.4 ms, which is broader compared to those of other silicate systems. In conclusion, the films obtained in this work are excellent candidates for use as active planar waveguide. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis, characterization, and catalytic properties of a mesostructured lamellar xerogel tungsten oxide phase

Cetyltrimethylammonium bromide (CTAB) and n-hexadecylamine (HDA) have been used as template in the synthesis of a mesolamellar xerogel tungsten oxide phase (WO(3)/CTAB/HDA). The catalytic properties of the resulting material were investigated in the oxidation of cis-cyclooctene, styrene, and cyclohexane, using hydrogen peroxide (H(2)O(2)), terc-butyl hydroperoxide (t-BOOH), or m-chlorperbenzoic acid (m-CPBA) as oxygen transfer agent. In general, the catalytic results were comparable to those obtained with related systems, thus suggesting the potential application of this material as catalyst for epoxidation reactions. (C) 2011 Elsevier B.V. All rights reserved.

Effect of mesoporosity of vanadium oxide prepared by sol-gel process as cathodic material evaluated by cyclability during Li(+) insertion/deinsertion

The effect of pore structure on the behavior of lithium intercalation into an electrode containing porous V(2)O(5) film has been investigated and compared with the electrode containing a non-porous V(2)O(5) film. X-ray diffraction patterns indicate a lamellar structure for both materials. Nitrogen adsorption isotherms, t-plot method, and Scanning Electronic Microscopy show that the route employed for the preparation of mesoporous V(2)O(5) was successful. The electrochemical performance of these matrices as lithium intercalation cathode materials was evaluated. The porous material reaches stability after several cycles more easily compared with the V(2)O(5) xerogel. Lithium intercalation into the porous V(2)O(5) film electrode is crucially influenced by pore surface and film surface irregularity, in contrast with the non-porous surface of the V(2)O(5) xerogel.

Synthesis and electrochemical properties of vanadyl phosphate di-hydrate/polyaniline derivatives hybrid films

Vanadyl phosphate and its hybrid compounds have proven to undergo electrochemical intercalation and de-intercalation of lithium ions, which enables its use as cathode material for Li ion rechargeable batteries. In this context, vanadyl phosphate di-hydrate/polyaniline derivatives hybrid films were synthesized via the exfoliation and reconstruction approach in order to evaluate their potential use as cathode in ion lithium batteries. X-ray diffraction patterns indicate that the lamellar structure of the inorganic matrix is maintained, consistent with the topotactic process. In the scanning electron micrographs, hybrid films exhibit rough surface consisting of warped and cracked crystallites, quite different from vanadyl phosphate di-hydrate square platelets crystallites. Electrochemical evaluation using cyclic voltammetry and charge-discharge galvanostatic techniques shows small differences between the charge and the discharge curves, indicating an irreversibility of the hybrid systems. (C) 2009 Elsevier B.V. All rights reserved.

High speed versus conventional grinding in high removal rate machining of alumina and alumina-titania

High removal rate (up to 16.6 mm(3)/s per mm) grinding of alumina and alumina-titania was investigated with respect to material removal and basic grinding parameters using a resin-bond 160 mu m grit diamond wheel at the speeds of 40 and 160 m/s, respectively. The results show that the material removal for the single-phase polycrystalline alumina and the two-phase alumina-titania composite revealed identical mechanisms of microfracture and grain dislodgement under the grinding conditioned selected. There were no distinct differences in surface roughness and morphology for both materials ground at either conventional or high speed. An increase in material removal rate did not necessarily worsen the surface toughness for the two materials at both speeds. Also the grinding forces for the two ceramics demonstrated similar characteristics at any grinding speeds and specific removal rates. Both normal and tangential grinding forces and their force ratios at the high speed were lower than those at the conventional speed, regardless of removal rates. An increase in specific removal rate caused more rapid increases in normal and tangential forces obtained at the conventional grinding speed than those at the high speed. Furthermore, it is found that the high speed grinding at all the removal rates exerted a great amount of coolant-induced normal forces in grinding zone, which were 4-6 times higher than the pure normal grinding forces. (c) 2004 Elsevier Ltd. All rights reserved.

Er(3+)-doped silica-hafnia films for optical waveguides and spherical resonators

In this paper we present some result on sol-gel derived silica-hafnia systems. In particular we focus on fabrication, morphological and spectroscopic assessment of Er(3+)-activated thin films. Two examples of silica-hafnia-derived waveguiding glass ceramics, prepared by top-down and bottom-up techniques are reported, and the main optical properties are discussed. Finally, some properties of activated microspherical resonators, having a silica core, obtained by melting the end of a telecom fiber, coated with an Er(3+)-doped 70SiO(2)-30HfO(2) film, are presented. (C) 2009 Elsevier B.V. All rights reserved.

Preparation of protein-loaded-PLGA microspheres by an emulsion/solvent evaporation process employing LTCC micromixers

This study presents the possibilities offered by microfluidic structures for the production of polymeric microspheres, using a process based upon the production of an emulsion. LTCC (Low Temperature Co-fired Ceramics) micromixers have been used for the preparation of polymeric microspheres. The effect of the geometry of the micromixers has been studied, with a specific focus on the size of the microspheres. as well as the control release properties of a model protein loaded within these microspheres. (C) 2008 Published by Elsevier B.V.

The microstructure of mechanically alloyed MoSi2 with Ni and Al additions

The effect of Ni and Al additions on grain boundary silica in mechanically alloyed and hot isostatically pressed (HTPed) MoSi2 was investigated. Mechanical alloying Mo and Si in the absence of Al produced finely dispersed silica within a fine grained structure. Mechanically alloyed and HIPed Mo and Si with Ni and Al partially transformed the silica to crystalline oxide phases, including Al2O3. An improvement in high temperature properties is not expected due to the retention of a grain boundary silica film. Rapid grain growth resulted during HIPing, possibly due to the formation of a Ni/Fe/Al liquid phase.

A numerical study of effect of grain boundaries on elastic and plastic properties in nanocomposite materials

Nanocomposite materials have received considerable attention in recent years due to their novel properties. Grain boundaries are considered to play an important role in nanostructured materials. This work focuses on the finite element analysis of the effect of grain boundaries on the overall mechanical properties of aluminium/alumina composites. A grain boundary is incorporated into the commonly used unit cell model to investigate its effect on material properties. By combining the unit cell model with an indentation model, coupled with experimental indentation measurements, the ''effective'' plastic property of the grain boundary is estimated. In addition, the strengthening mechanism is also discussed based on the Estrin-Mecking model.

Long-term follow up of abdominal rectosigmoidectomy with posterior end-to-side stapled anastomosis for Chagas megacolon

Aim Chagas` disease is an endemic parasitosis found in Latin America. The disease affects different organs, such as heart, oesophagus, colon and rectum. Megacolon is the most frequent long-term complication, caused by damage to the myoenteric and submucous plexus, ultimately leading to a functional barrier to the faeces. Patients with severe constipation are managed surgically. The study aimed to analyse the 10-year minimum functional outcome after rectosigmoidectomy with posterior end-to-side anastomosis (RPESA). Method A total of 21 of 46 patients were available for follow up. Patients underwent clinical, radiological and manometric evaluation, and the results were compared with preoperative parameters. Results Of the 21 patients evaluated, 81% (17) were female, with a mean age of 60.6 years. Good function was achieved in all patients, with significant improvement in defaecatory frequency (P < 0.0001), usage of enemas (P < 0.0001) and patient satisfaction. Barium enema also showed resolution of the colonic and rectal dilatation in 19 cases evaluated postoperatively. Conclusion Minimal 10-year follow up of RPESA showed excellent functional results, with no recurrence of constipation.

Evaluation of swallowing in children with vomiting after feeding

Vomiting after feeding is a symptom of gastroesophageal reflux (GER) and of eosinophilic esophagitis (EE), which are considered to be a cause of infant feeding disorder. The objective of the present study was to evaluate swallowing in children with feeding disorder manifested by vomiting after feeding. Using clinical and videofluoroscopic methods we studied the swallowing of 37 children with vomiting after feeding (mean age = 15.4 months), and of 15 healthy children (mean age = 20.5 months). In the videofluoroscopic examination the children swallowed a free volume of milk and 5 ml of mashed banana, both mixed with barium sulfate. We evaluated five swallows of liquid and five swallows of paste. The videofluoroscopic examination was recorded at 60 frames/s. Patients had difficulty during feeding, pneumonia, respiratory distress, otitis, and irritability more frequently than controls. During feeding, children with vomiting, choke were irritable, and refused food more frequently than controls, and during the videofluoroscopic examination the patients had more backward movement of the head than controls for both the liquid and paste boluses. There was no difference in the timing of oral swallowing transit, pharyngeal swallowing transit, or pharyngeal clearance between patients and controls. We conclude that children with vomiting after feeding may have difficulties in accepting feeding, although they have no alteration of oral and pharyngeal phases of swallowing.

Effect of Gender on Swallow Event Duration Assessed by Videofluoroscopy

There are data suggesting that women swallow liquids at a lower flow rate and ingest smaller volumes in each swallow than men. Our objective in this work was to compare swallowing in asymptomatic men and women by videofluoroscopy. We studied 18 men [age = 33-77 years, mean = 61 (10) years] and 12 women [age = 29-72 years, mean = 53 (15) years] who swallowed in duplicate 5 and 10 ml of liquid and paste barium boluses. None of the volunteers had dysphagia, neurologic diseases, or oral, pharyngeal, or esophageal diseases. The videofluoroscopic examination showed that for the 5-ml bolus, women had a longer oropharyngeal transit [liquid: men, 0.63 (0.21) s, women, 0.88 (0.39) s; paste: men, 0.64 (0.35) s, women, 0.94 (0.58) s], longer oral transit [liquid: men, 0.41 (0.21) s, women, 0.59 (0.35) s; paste: men, 0.39 (0.28) s, women, 0.59 (0.42) s], and longer pharyngeal clearance [liquid: men, 0.36 (0.11) s, women, 0.45 (0.16) s; paste: men, 0.42 (0.25) s, women, 0.56 (0.27) s] compared with men (p < 0.05). We conclude that there are differences in swallowing between men and women, with women having a longer oropharyngeal transit than men for a 5-ml bolus.

Esthetic restorative materials and opposing enamel wear

This in vitro study compared the effects of a gold alloy (Degulor M), four dental ceramics (IPS Empress, IPS Empress 2, Duceram Plus, Duceram. LFC) and a laboratory-processed composite (Targis) on the wear of human enamel. The amount of wear of the enamel (dental cusps) and restorative materials (disks) were tested in water at 37 degrees C under standard load (20 N), with a chewing rate of 1.3 Hz and was determined after 150,000 and 300,000 cycles. Before the test, the average surface roughness of the restorative materials was analyzed using the Ra parameter. The results of this study indicate that Targis caused enamel wear similar to Degulor M and resulted in significantly less wear than all the ceramics tested. IPS Empress provoked the greatest amount of enamel wear and Degulor M caused less vertical dimension loss. Targis could be an appropriate alternative material to ceramic, because it is esthetic and produces opposing enamel wear comparable to gold alloy.

EFFECT OF METAL PRIMERS ON MICROTENSILE BOND STRENGTH BETWEEN ZIRCONIA AND RESIN CEMENTS

Statement of problem. There are no established clinical procedures for bonding zirconia to tooth structure using resin cements. Purpose. The purpose of this study was to evaluate the influence of metal primers, resin cements, and aging on bonding to zirconia. Material and methods. Zirconia was treated with commercial primers developed for bonding to metal alloys (Metaltite, Metal Primer II, Alloy Primer or Totalbond). Non-primed specimens were considered as controls. One-hundred disk-shaped specimens (19 x 4 mm) were cemented to composite resin substrates using Panavia or RelyX Unicem (n=5). Microtensile bond strength specimens were tested after 48 hours and 5 months (150 days), and failure modes were classified as type 1 (between ceramic/cement), 2 (between composite resin/cement) or 3 (mixed). Data were analyzed by 3-way ANOVA and Multiple Comparison Tukey test (alpha=.05). Results. The interactions primer/luting system (P=.016) and luting system/storage time (P=.004) were statistically significant. The use of Alloy Primer significantly improved the bond strength of RelyX Unicem (P<.001), while for Panavia, none of the primers increased the bond strength compared to the control group. At 48 hours, Panavia had statistically higher bond strength (P=.004) than Unicem (13.9 +/- 4.4MPa and 10.2 +/- 6.6MPa, respectively). However, both luting systems presented decreasing, statistically similar; values after aging (Panavia: 3.6 +/- 2.2MPa; Unicem: 6.1 +/- 5.3MPa). At 48 hours, Alloy Primer/Unicem had the lowest incidence of type 1 failure (8%). After aging, all the groups showed a predominance of type 1 failures. Conclusions. The use of Alloy Primer improved bond strength between RelyX Unicem and zirconia. Though the initial values obtained with Panavia were significantly higher than RelyX Unicem, after aging, both luting agents presented statistically similar performances. (J Prosthet Dent 2011;105:296-303)

Effect of temperature and heating rate on the sintering of leucite-based dental porcelains

The aim of this work was to determine the effect of temperature and heating rate on the densification of four leucite-based dental porcelains: two low-fusion (Dentsply Ceramco and Ivoclar) and two high-fusion commercial porcelains (Dentsply Ceramco). Porcelain powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), particle size distribution, helium picnometry, and by scanning electron microscopy. Test specimens were sintered from 600 to 1050 degrees C, with heating rates of 55 degrees C/min and 10 degrees C/min. The bulk density of the specimens was measured by the Archimedes method in water, and microstructures of fracture surfaces were analyzed by scanning electron microscopy (SEM). The results showed that densification of specimens increased with the increase in temperature. The increase in the heating rate had no effect on the densification of the porcelains studied. Both high-fusion materials and one of the low-fusing porcelains reached the maximum densification at a temperature that was 50 degrees C lower than that recommended by the manufactures. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.