Ligand Exchange Inducing Efficient Incorporation of CisPt Derivatives into Ureasil-PPO Hybrid and Their Interactions with the Multifunctional Hybrid Network

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Distribution of refractory and volatile elements in CoRoT exoplanet host stars

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Pore size evolution during sintering of ceramic oxides

This paper reviews the influence of particle size distribution, agglomerates, rearrangement, sintering atmospheres and impurities on the pore evolution of some commonly studied oxides. These factors largely affect sintering mechanisms due to modifications of diffusion coefficients or evaporation-condensation. Very broad particle size distribution leads to grain growth and agglomerates densify first. Rearrangement of particles due to neck asymmetry mainly in the early stage of sintering is responsible for a high rate of densification in the first minutes of sintering by collapse of large pores. Sintering atmospheres play an important role in both densification and pore evolution. The chemical interaction of water molecules with several oxides like MgO, ZnO and SnO2 largely affects surface diffusion. As a consequence, there is an increase in the rates of pore growth and densification for MgO and ZnO and in the rate of pore growth for SnO2. Carbon dioxide does not affect the rate of sintering of MgO but greatly affects both rates of pore growth and densification of ZnO. Oxygen concentration in the atmosphere can especially affect semiconductor oxides but significantly affects the rate of pore growth of SnO2. Impurities like chlorine ions increase the rate of pore growth in MgO due to evaporation of HCl and Mg(OH)Cl, increasing the rate of densification and particle cuboidization. CuO promotes densification in SnO2, and is more effective in dry air. The rate of densification decrease and pore widening are promoted in argon. An inert atmosphere favors SnO2 evaporation due to reduction of CuO. © 1990.

Comportamento dos tecidos periapicais de dentes de cães após a obturação de canal com Sealapex acrescido ou não de iodoformio.

Some endodontists use iodoform in Sealapex in order to rend it more radiopac. This procedure is empiric and for this reason we decided to observe, histologically, if the iodoform introduces some modification in the biological properties of Sealapex. Thirty root canals of dogs' teeth were overinstrumented and filled, by lateral condensation technique, with gutta percha points and Sealapex, with or without iodoform. The iodoform was added in two different proportions: 30 mg or 112 mg for one centimeter of the base and one centimeter of the catalyst of Sealapex. The pieces were removed for histological studies, 6 months after the treatment. The histological results showed that Sealapex encourages apical closure by cementum deposition and that the addition of iodoform does not change that biological property.

Presença de detritos na região apical de dentes de cães apos o preparo biomecánico com ou sem o emprego de substância auxiliar cremosa.

The subject of this work is to observe if the employment of a cream (ENDO-PTC) during the root canal preparation contributes or not to the condensation of debris in the apical region. Twenty root canals of dogs teeth were divided into two experimental groups: in the first one, the biomechanical preparation was carried out up to the n. 50 Kerr file by using irrigation and aspiration with sodium hypochlorite. In the second experimental group the canal negotiation was done in the same way but using a cream (ENDO-PTC) with sodium hypochlorite as a lubrication substance. A final irrigation and aspiration with sodium hypochlorite was also done in this group. The animal was killed and the pieces prepared for histological analysis. The histological results show us that the employment of a cream during the negotiation of the root canal contributes to a higher condensation of debris in the apical area.

Effect of electrolyte on the gelation and aggregation of SnO2 colloidal suspensions

Electrolytes may modify the physical-chemical characteristics of colloidal particle interfaces in suspension, which can favour gel or aggregate formation. The influence of NH4Cl loading on the aggregation and gelation of SnO2 colloidal suspensions was investigated using measurements of rheology, turbidity and infrared spectra. A rapid aggregate growth for samples with Cl- > 20 mM was observed. With increasing age, gelation was observed due to formation of interaggregate bonds. For concentration of Cl- between 20 and 9 mM, the aggregation process was slower allowing the formation of gel with a network which was not destroyed as the gel was submitted to a small rate of shear. As aging continues, the condensation reaction between OH groups gave rise to the formation of Sn-O bonds, irrespective of the electrolyte loading. © 1992 Elsevier Science Publishers B.V. All rights reserved.

Drying of SnO2 hydrogels: effect of the electrolyte

The effect of the electrolyte (NH+ 4, Cl-) on the drying of SnO2 hydrogels was investigated by linear shrinkage, mass loss, gravimetric thermal analysis and infrared spectroscopy. Results show that the drying mechanism for monolithic SnO2 gels is highly dependent on the concentration of the electrolyte solution inside the pores. For higher concentrations, the drying process is governed by capillary forces while for the smaller ones (≤20 mM) syneresis shrinkage becomes predominant just before the end of the first drying period. This phenomenon is related to condensation reaction among the superficial OH groups and may hamper formation of monolithic SnO2. © 1992 Elsevier Science Publishers B.V. All rights reserved.

Spectroscopic characterization of SnO2 gels - Code: CP11

Excitation and dynamic emission spectra of Eu3+ ions were simultaneously used with FTIR and Raman spectroscopy to study the structural evolution during SnO2 sol → gel → xerogel conversion. Results make evident an increase of the surroundings symmetry for the Eu3+ ions dissolved in SnO2 matrix and a decrease of the amount of hydroxo groups (Sn-OH) during drying. These phenomena were associated to the pursuit of the condensation reaction after gelation. © 1994 Kluwer Academic Publishers.

Effect of dentine surface treatment on leakage of root fillings with a glass ionomer sealer.

The purpose of this study was to observe the quality of seal of the glass ionomer cement, Ketac-Endo, after treatment of the root canal wall. The root canals of 140 extracted human teeth were prepared biomechanically. The root canals were treated with either EDTA or received an intracanal dressing of calcium hydroxide or camphorated paramonochlorphenol. The root canals were filled by the lateral condensation technique with gutta-percha points and the sealer Ketac-Endo, or zinc oxide-eugenol cement or Sealapex. The teeth were placed into a 2% methylene blue dye solution inside a flask, which was attached to a vacuum pump. Leakage was measured linearly. Sealapex exhibited significantly less leakage than Ketac-Endo or zinc oxide-eugenol cement (P<0.01). The use of EDTA and intermediary dressings reduced significantly (P<0.01) the leakage observed with the zinc oxide-eugenol sealer and Ketac-Endo.

Apical leakage following root canal dressing with calcium hydroxide.

The purpose of this study was to analyse the apical leakage in teeth filled by the lateral condensation technique following medication with calcium hydroxide. One hundred and twenty extracted human teeth were biomechanically prepared by using exclusively reaming motion with files up to #40. Half of the teeth received a calcium hydroxide dressing for 3 days. The medication was removed by irrigation and reaming motion with files #40 up to #70. The teeth were divided in 6 experimental groups, according to the dimension of the utilized instrument. The root canals were filled and posteriorly the teeth were placed into a 2% methylene blue dye solution inside a flask, which was attached to a vacuum pump. Leakage was measured linearly, and the results showed significantly (p<0.01) less leakage in the experimental groups that received calcium hydroxide dressings than in the control groups. The results persisted even after the removal of 300 micrometers of dentin from the root canal dentinal walls.

Apical leakage after root canal filling with an experimental calcium hydroxide gutta-percha point

This study was an in vitro analysis of the apical seal of root canals filled with an experimental calcium hydroxide gutta-percha point. One hundred and ten recently extracted human permanent teeth with a single root were used. The root canals were biomechanically prepared, and some received a dressing of calcium hydroxide for 7 days. Root canals not dressed were filled by the lateral condensation technique with either regular gutta-percha or calcium hydroxide gutta-percha points. The dressed root canals were filled with the same sealers and regular gutta-percha points. The specimens were placed into a 2% methylene blue dye solution under vacuum, and the apical leakage was linearly evaluated. The experimental groups with calcium hydroxide dressing and the one with calcium hydroxide gutta-percha points exhibited significantly (p < 0.05) less leakage than the groups filled with regular gutta-percha points. The results obtained indicated that calcium hydroxide guttapercha points produced an improvement in the apical sealing quality of the root canal filling. Copyright © 1996 by The American Association of Endodontists.

Scaling in the BCS to Bose crossover problem in different partial waves

The BCS superconductivity to Bose condensation crossover problem is studied in two dimensions in S, P, and D waves, for a simple anisotropic pairing, with a finite-range separable potential at zero temperature. The gap parameter and the chemical potential as a function of Cooper-pair binding B c exhibit universal scaling. In the BCS limit the results for coherence length ξ and the critical temperature T c are appropriate for highT c cuprate superconductors and also exhibit universal scaling as a function of B c.

Effect of different root canal sealers on periapical repair of teeth with chronic periradicular periodontitis

Teeth with induced chronic periradicular periodontitis in dogs were root canal treated. After the biomechanical preparation, using K files and 5.25% sodium hypochlorite as the irrigant solution, all root canals were dressed with an antibacterial dressing based on calcium hydroxide, which was left in place for 7 days. After this time, the root canals were obturated with lateral condensation of cold gutta-percha with either a calcium hydroxide root canal filling material (Sealapex) or a zinc oxide-eugenol sealer (Fill Canal). After 270 days, histopathological analysis showed better apical and periapical repair in the teeth obturated with Sealapex (P < 0.05).

Universal scaling in BCS superconductivity in three dimensions in non-s waves

The solutions of a renormalized BCS equation are studied in three space dimensions in s, p and d waves for finite-range separable potentials in the weak to medium coupling region. In the weak-coupling limit, the present BCS model yields a small coherence length ξ and a large critical temperature, T c, appropriate for some high-T c materials. The BCS gap, T c, ξ and specific heat C s(T c) as a function of zero-temperature condensation energy are found to exhibit potential-independent universal scalings. The entropy, specific heat, spin susceptibility and penetration depth as a function of temperature exhibit universal scaling below T c in p and d waves.

Reaction of dogs' teeth to root canal filling with mineral trioxide aggregate or a glass ionomer sealer

This study was conducted to observe the reaction of apical tissues of dogs' teeth after root canal filling with gutta-percha and mineral trioxide aggregate (MTA) or a glass ionomer (Ketac-Endo) as a sealer. The root canals were instrumented and filled by the lateral condensation technique with the sealers studied. Animals were killed 6 months later, and the specimens were removed and prepared for histological analysis. Results showed no inflammatory reaction of apical tissue and total closure of the apical foramen of all the teeth sealed with MTA. The teeth sealed with Ketac-Endo showed two cases of partial closure and different degrees of chronic inflammatory reaction. In conclusion, MTA exhibited better biological properties than Ketac-Endo. Copyright © 1999 by The American Association of Endodontists.