Application of impedance spectroscopy to evaluate the effect of different setting accelerators on the developed microstructures of calcium phosphate cements

The main goal of the present study was to evaluate the effect of different setting accelerator agents on the developed microstructures of calcium phosphate cements (CPCs) by employing the impedance spectroscopy (IS) technique. Six compositions of CPCs were prepared from mixtures of commercial dicalcium phosphate anhydrous (DCPA) and synthesized tetracalcium phosphate (TTCP) as the solid phases. Two TTCP/DCPA molar ratios (1/1 and 1/2) and three liquid phases (aqueous solutions of Na(2)HPO(4), tartaric acid (TA) and oxalic acid (OA), 5% volume fraction) were employed. Initial (I) and final (F) setting times of the cement pastes were determined with Gillmore needles (ASTM standard C266-99). The hardened samples were characterized by X-ray powder diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and apparent density measurements. The IS technique was employed as a non-destructive tool to obtain information related to porosity, tortuosity and homogeneity of the cement microstructures. The formulation prepared from a TTCP/DCPA equimolar mixture and OA as the liquid phase presented the shortest I and F (12 and 20 min, respectively) in comparison to the other studied systems. XRD analyses revealed the formation of low-crystallinity hydroxyapatite (HA) (as the main phase) as well as the presence of little amounts of unreacted DCPA and TTCP after 24 h hardening in 100% relative humidity. This was related to the proposed mechanisms of dissolution of the reactants. The bands observed by FTIR allowed identifying the presence of calcium tartrate and calcium oxalate in the samples prepared from TA and OA, in addition to the characteristic bands of HA. High degree of entanglement of the formed crystals was observed by SEM in samples containing OA. SEM images were also correlated to the apparent densities of the hardened cements. Changes in porosity, tortuosity and microstructural homogeneity were determined in all samples, from IS results, when the TTCP/DCPA ratio was changed from 1/1 to 1/2. The cement formulated from an equimolar mixture of TTCP/DCPA and OA as the liquid phase presented setting times, degree of conversion to low-crystallinity HA and microstructural features suitable to be used as potential bone cement in clinical applications. The IS technique was shown to be a very sensitive and non-destructive tool to relate the paste composition to the developed microstructures. This approach could be very useful to develop calcium phosphate bone cements for specific clinical demands.

Characterization of dense lead lanthanum titanate ceramics prepared from powders synthesized by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Groundwater geochemical evolution in the northern portion of the Guarani Aquifer System (Brazil) and its relationship to diagenetic features

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone reinforced with sisal fibers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The Effect of Water Immersion and UV Radiation Aging on the Shear Behavior of Woven Continuous Fiber/PEI Laminates

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Time Domain Analyses for Three-phase Lines with Corrected Modal Transformation Matrix

The results presented in this paper are based on a research about the application of approximated transformation matrices for electromagnetic transient analyses and simulations in transmission lines. Initially, it has developed the application of a single real transformation matrix for a double three-phase transmission lines, because the symmetry of the distribution of the phase conductors and the ground wires. After this, the same type of transformation matrix has applied for symmetrical single three-phase transmission lines. Analyzing asymmetrical single three-phase lines, it has used three different line configurations. For these transmission line types, the errors between the eigenvalues and the approximated results, called quasi modes, have been considered negligible. on the other hand, the quasi mode eigenvalue matrix for each case was not a diagonal one. and the relative values of the off-diagonal elements of the approximated quasi mode matrix are not negligible, mainly for the low frequencies. Based on this problem, a correction procedure has been applied for minimizing the mentioned relative values. For the correction procedure application, symmetrical and asymmetrical single three-phase transmission line samples have been used. Checking the correction procedure results, analyses and simulations have been carried out in mode and time domain. In this paper, the last results of mentioned research are presented and they related to the time domain simulations.

Investigation of the corrosion behaviour of AA 2024-T3 in low concentrated chloride media

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Two-matrix string model as constrained (2+1)-dimensional integrable system

We show that the 2-matrix string model corresponds to a coupled system of 2 + 1-dimensional KP and modified KP ((m)KP2+1) integrable equations subject to a specific symmetry constraint. The latter together with the Miura-Konopelchenko map for (m)KP2+1 are the continuum incarnation of the matrix string equation. The (m)KP2+1 Miura and Backhand transformations are natural consequences of the underlying lattice structure. The constrained (m)KP2+1 system is equivalent to a 1 + 1-dimensional generalized KP-KdV hierarchy related to graded SL(3,1). We provide an explicit representation of this hierarchy, including the associated W(2,1)-algebra of the second Hamiltonian structure, in terms of free currents.

Mapeamento do contorno estrutural do embasamento da bacia sedimentar de Curitiba - PR

The sedimentary Curitiba basin is located in the Central-Southern part of the first Parananense plateau, and comprises Curitiba (PR), and part of the neighbour Municipalities (fig.1). It is supposed to be of Plio-Pleistocene age. It has a shallow sedimentary fulfillment, represented by the Guabirotuba formation (BIGARELLA and SALAMUNI, 1962) which is dristributed over a large area of about 3.000km2. The internal geometry, not entirely known yet, is actually object of detailed research, that shows its geological evolution to Cenozoic tectonic movements. For the purpose of this study the definition of the structural contour of the basement and their depo-centers is fundamental. This paper presents the results of the integration of surface and subsurface data, processed by statistical methods, which allowed a more precise definition of the morphostructural framework of the basement. For the analysis of the geological spacial data, specific softwares were used for statistical processing for trend surfaces analysis. The data used in this study are of following types: a) drilling logs for ground water; b) description of surface points of geological maps (CRPM, 1977); c) description of points of geotechnical drillings and down geological survey. The data of 223 drilling logs for ground water were selected out of 770 wells. The description files of 700 outcrops, as well as planialtimetric field data, were used for the localization of the basement outcrop. Thus, a matrix with five columns was set up: utm E-W (x) and utm N-S (y); surface altitude (z); altimetric cote of the contact between sedimentary rocks and the basement (k); isopachs (l). For the study of the basement limits, the analysis of surface trends of 2(nd) and 3(rd) degree polinomial for the altimetric data (figs. 2 and 3) were used. For the residuals the method of the inverse of the square of the distance (fig.4) was used. The adjustments and the explanations of the surfaces were made with the aid of multiple linear regressions. The analysis of 3rd degree polinomial trend surface (fig.3) confirmed that the basement tends to be more exposed towards NNW-SSE explaining better the data trend through an ellipse, which striking NE-SW and dipping SW axis coincides with the trough of the basin observed in the trending surface of the basement. The performed analysis and the respective images offer a good degree of certainty of the geometric model of the Curitiba Basin and of the morphostructure of its basement. The surface trend allows to sketch with a greater degree of confidence the structural contour of the topgraphic surface (figs. 5 and 6) and of the basement (figs. 7 and 8), as well as the delimitation of intermediate structural heights, which were responsible for isolated and assymmetric depocenters. These details are shown in the map of figures 9 and 10. Thus, the Curitiba Basin is made up by a structural trough stretching NE-SW, with maximum preserved depths of about 80m, which are separated by heights and depocenters striking NW-SE (fig. 11). These structural features seems to have been controlled by tectonic reactivation during the Tertiary (HASUI, 1990) and which younger dissection was conditioned by neotectonic processes (SALAMUNI and EBERT, 1994).

Biocompatibility of an adhesive system applied to exposed human dental pulp

Human pulp tissue was directly capped with All Bond 2, or calcium hydroxide and evaluated 7, 30, or 60 days after the procedures. Histological analysis was performed to assess the inflammatory cell response, tissue disorganization, dentin bridging, and the presence of bacteria. At 7 days, with All Bond 2 capping, there was a large area of neutrophilic infiltrate underlying the pulp capping material, and the death of adjacent odontoblasts, was observed. However, with time, the neutrophilic reaction was replaced by fibroblastic proliferation with macrophages and giant cells surrounding globules of resin scattered in the coronal pulp tissue. The persistent inflammatory reaction and hyaline alteration of extracellular matrix inhibited complete pulp repair or dentin bridging. In contrast, at 7 days, the pulp tissue capped with calcium hydroxide exhibited odontoblast-like cells organized underneath coagulation necrosis. Pulp repair evolved into apparent complete dentin bridge formation at 60 days. All Bond 2 did not appear to allow any pulp repair and does not appear to be indicated for direct pulp capping of human teeth. Copyright © 1999 by The American Association of Endodontists.

Solid-state NMR, ionic conductivity, and thermal studies of lithium-doped siloxane-poly(propylene glycol) organic-inorganic nanocomposites

Hybrid organic-inorganic ionic conductors, also called ormolytes (organically modified electrolytes), were obtained by dissolution of LiClO 4 in siloxane-poly(propylene glycol) matrixes. The dynamic features of these nanocomposites were studied and correlated to their electrical properties. Solid-state nuclear magnetic resonance (NMR) spectroscopy was used to probe the effects of the temperature and nanocomposite composition on the dynamic behaviors of both the ionic species ( 7Li) and the polymer chains ( 13C). NMR, dc ionic conductivity, and DSC results demonstrate that the Li + mobility is strongly assisted by the segmental motion of the polymer chain above its glass transition temperature. The ac ionic conductivity in such composites is explained by use of the random free energy barrier (RFEB) model, which is agreement with their disordered and heterogenous structures. These solid ormolytes are transparent and flexible, and they exhibit good ionic conductivity at room temperature (up to 10 -4 S/cm). Consequently, they are very promising candidates for use in several applications such as batteries, sensors, and electrochromic and photoelectro-chemical devices.

Structural, cytochemical, immunocytochemical and ultrastructural characterization of blood granulocytes of the roadside hawk Buteo magnirostris (Gmelin, 1788) (Avian, Falconiform)

In the peripheral blood of the roadside hawk, Buteo magnirostris, the following types of granulocytic leucocytes were identified: heterophil, eosinophil and basophil. The heterophils presented acidophilic and spindle shaped granules, the eosinophils possess spherical eosinophilic granules and the basophils showed spherical and basophilic granules. The heterophils and eosinophils presented positive cytochemical reaction to glycogen and basic polyaminoacid, while the eosinophils presented sudanophilic granules, which were also positive for myeloperoxidase. The heterophils, alone, presented positivity for acid phosphatase in some granules and immunoreactivity to TGF-β1 was observed only in the cytoplasm of the eosinophils. Electron microscopy demonstrated the heterophil granules as predominantly spindle shaped, being strongly electron-dense, while the eosinophils had numerous uniformly electron-dense spherical granules and the basophils presented three different types of granules identified according to their electron-density and the aspect of their matrix.

The effects of low laser irradiation on angiogenesis in injured rat tibiae

The influence of He-Ne laser radiation on the formation of new blood vessels in the bone marrow compartment of a regenerating area of the mid-cortical diaphysis of the tibiae of young adult rats was studied. A small hole was surgically made with a dentistry burr in the tibia and the injured area received a daily laser therapy over 7 or 14 days transcutaneously starting 24 h from surgery. Incident energy density dosages of 31.5 and 94.5 Jcm-2 were applied during the period of the tibia wound healing investigated. Light microscopic examination of histological sections of the injured area and quantification of the newly-formed blood vessels were undertaken. Low-level energy treatment accelerated the deposition of bone matrix and histological characteristics compatible with an active recovery of the injured tissue. He-Ne laser therapy significantly increased the number of blood vessels after 7 days irradiation at an energy density of 94.5 Jcm-2, but significantly decreased the number of vessels in the 14-day irradiated tibiae, independent of the dosage. These effects were attributed to laser treatment, since no significant increase in blood vessel number was detected between 8 and 15 non-irradiated control tibiae. Molecular mechanisms involved in low-level laser therapy of angiogenesis in post-traumatic bone regeneration needs further investigation.

Effects of long-term cyclosporin therapy on gingiva of rats--analysis by stereological and biochemical estimation.

Cyclosporin A (CsA) is used as an immunosuppressive agent and its prominent side effect is the induction of gingival overgrowth, which remains a significant problem. The risk factors appraised include the duration of treatment. However, there are no stereological and biochemical studies exploring the effects of long-term CsA therapy on gingival tissue. The purpose of the present study was to investigate the level of TGF-beta1 in saliva and describe the densities of fibroblasts and collagen fibers in the gingival tissue of rats treated with CsA for long periods. Rats were treated for 60, 120, 180 and 240 days with a daily subcutaneous injection of 10 mg/kg of body weight of CsA. At the end of the experimental periods, saliva was collected for the determination of TGF-beta1 levels. After histological processing, the oral epithelium and the connective tissue area were measured as well as the volume densities of fibroblasts (Vf) and collagen fibers (Vcf). After 60 and 120 days of CsA treatment, there was a significant increase in Vf and Vcf as well as a significant increase in TGF-beta1 levels. After 180 and 240 days, reduction in the gingival overgrowth associated with significant decreases in the level of TGF-beta1, and also decreased Vf and Vcf, were observed. The data presented here suggest that after long-term therapy, a decrease in TGF-beta1 levels occurs, which might contribute to an increase in the proteolytic activity of fibroblasts in the gingiva, favoring the normality of extracellular matrix synthesis.

Non-transposed three-phase line analyses with a single real transformation matrix

In transmission line transient analyses, a single real transformation matrix can obtain exact modes when the analyzed line is transposed. For non-transposed lines, the results are not exact. In this paper, non-symmetrical and non transposed three-phase line samples are analyzed with a single real transformation matrix application (Clarke's matrix). Some interesting characteristics of this matrix application are: single, real, frequency independent, line parameter independent, identical for voltage and current determination. With Clarke's matrix use, mathematical simplifications are obtained and the developed model can be applied directly in programs based on time domain. This model works without convolution procedures to deal with phase-mode transformation. In EMTP programs, Clarke's matrix can be represented by ideal transformers and the frequency dependent line parameters can be represented by modified-circuits. With these representations, the electrical values at any line point can be accessed for phase domain or mode domain using the Clarke matrix or its inverse matrix. For symmetrical and non-transposed lines, the model originates quite small errors. In addition, the application of the proposed model to the non-symmetrical and non-transposed three phase transmission lines is investigated. ©2005 IEEE.