Trigeminal nitric oxide synthase expression correlates with new bone formation during distraction osteogenesis

Nitric oxide synthase (NOS) has been reported to be involved with both bone healing and bone metabolism. The aim of this study was to test the null hypothesis that there is no correlation between new bone formation during mandibular distraction osteogenesis and NOS expression in the trigeminal ganglion of rats. Newly formed tissue during distraction osteogenesis and trigeminal NOS expression measured by the NADPH-diaphorase (NADPH-d) reaction were evaluated in 72 male Wistar rats by histomorphometric and histochemical methods. In animals submitted to 0.5 mm/day distraction osteogenesis, the percentage of bone tissue was higher in the basal area of the mandibles compared with the center and significantly increased through the experimental periods (P < 0.05). At the sixth postoperative week, the difference in bone formation between the continuous and acute distraction osteogenesis groups was the highest. Significant correlation between new bone formation by distraction osteogenesis and NADPH-d-reactive neurons was found, varying according to neuronal cell size (r = -0.6, P = 0.005, small cells strongly stained; r = 0.5, P = 0.018, large cells moderately stained). The results suggest that NOS may play a role in the bone healing process via neurogenic pathways, and the phenomenon seems to be neuronal cell morphotype-dependent. Further studies are now warranted to investigate the mechanistic link between the expression of trigeminal NOS and mandibular new bone formation by distraction osteogenesis.

Nanostructured europium oxide thin films deposited by pulsed laser ablation of a metallic target in a He buffer atmosphere

Nanostrucured europium oxide and hydroxide films were obtained by pulsed Nd:YAG (532 nm) laser ablation of a europium metallic target, in the presence of a 1 mbar helium buffer atmosphere. Both the produced film and the ambient plasma were characterized. The plasma was monitored by an electrostatic probe, for plume expansion in vacuum or in the presence of the buffer atmosphere. The time evolution of the ion saturation current was obtained for several probe to substrate distances. The results show the splitting of the plume into two velocity groups, being the lower velocity profile associated with metal cluster formation within the plume. The films were obtained in the presence of helium atmosphere, for several target-to-substrate distances. They were analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and atomic force microscopy, for as-deposited and 600 degrees C treated-in-air samples. The results show that the as-deposited samples are amorphous and have chemical composition compatible with europium hydroxide. The thermally treated samples show x-ray diffraction peaks of Eu(2)O(3), with chemical composition showing excess oxygen. Film nanostructuring was shown to be strongly correlated with cluster formation, as shown by velocity splitting in probe current versus time plots. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3457784]

Effect of precursor solution on the formation of perovskite phase of Pb(Mg-1/Nb-3(2/3))O-3 thin films

Precursor solutions for Pb(Mg1/3Nb2/3)O-3 (PMN) synthesis were obtained by Pechini's method. The influence of the concentration of organic materials on the phase formation has been studied. For this purpose, PMN solutions were prepared with different precursors and were characterized by thermogravimetric and differential thermal analysis. The obtained solutions were deposited onto a Si (100) substrate by dip coating and pre-treated in a hot plate at 300 degreesC for 1 h. The films were annealed at 600, 700, 800 and 900 degreesC for 1 h and characterized by X-ray diffraction. The perovskite phase was formed after annealing at 600 and 700 degreesC when the solution of PMN was prepared with a lower amount of organic material and starting with mobium oxide. By increasing the temperature to 800 or 900 degreesC, only the formation of pyrochlore phase was observed. With the solution prepared from mobium ethoxide, only the presence of pyrochlore phase was observed independently of the annealing temperature. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

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

Phase formation and characterization of BaBi2Ta2O9 obtained by mixed oxide procedure

Ferroelectric layefed-perovskite BaBi2Ta2O9 (BBT) has been prepared successfully by solid-state reaction. The influence of pressure and temperature/time annealing regime on the BBT phase formation was analyzed. The powders were characterized by thermal analysis and Xray diffraction and the sintered pellets by scanning electron microscopy. The crystalline BBT phase, free of secondary phases was obtained at 950 degreesC for 2 h. For an applied field strength of 380 kV/cm, a remnant polarization of 7.6 muC/cm(2) and an electric coercive field of 45.7 kV/cm were obtained. (C) 2004 Elsevier B.V. All rights reserved.

SAXS study of formation and growth of tin oxide nanoparticles in the presence of complexing ligands

The effect of acetylacetone (acac) complexing ligand on the formation and growth of tin oxide-based nanoparticles during thermohydrolysis at 70 degreesC of a tin precursor SnCl4-n(acac)(n) (0 less than or equal to n less than or equal to 2) solution was analyzed by in situ small-angle X-ray scattering. A. transparent and stable sol was obtained after 2 h of thermohydrolysis at 70 degreesC, allowing the quantitative determination of the particle volume distribution function and its variation with the reaction time. The number of colloidal particles for equivalent thermohydrolysis temperature and time decreases as the [acac]/[Sn] ratio in initial solution increases from 0.5 to 6. Instead, the amount of soluble species remaining in solution increases for increasing [acac]/[Sn] ratio within the same range. This indicates that increasing amounts of Sn-acetylacetone complexes partially prevent the hydrolysis and consequent formation of colloidal particles. The N-2 adsorption isotherm characterization of freeze-dried powders demonstrates that the average pore size is approximately equal to the average size (approximate to9 Angstrom) of the colloidal primary particles in the sol, and that the porosity and surface area (approximate to200 m(2) g(-1)) are independent of the acac content in the initial solution.

Formation of colloidal particles of hydrous iron oxide by forced hydrolysis

The mechanism of formation and growth of hydrous iron oxide (FeOOH) during the initial stages of forced hydrolyses of ferric chloride aqueous solution was studied by small angle X-ray scattering (SAXS). The effect of the hydrolysis temperature (60°C, 70°C and 80°C) and of the addition of urea on the formation of colloidal particles under isothermal conditions were investigated. Based on the experimental scattering functions in the Guinier range, we suggest the presence of elongated colloidal particles. The particle diameter and length, and their variation with time, were determined by fitting the form factor of prolate ellipsoids to the experimental scattering functions. We have assumed that our solutions are in a dilute state and that all colloidal particles are approximately of the same size. The colloidal particles have geometrical shapes similar to those of the subcrystals that build up the superstructure of β-FeOOH crystals, indicating that the formation of this hydrous iron oxide is governed by an aggregation process. Otherwise, the addition of urea hinders the growth and yields smaller particles, with a reduction in size greater than 50%. © 2000 Elsevier Science B.V. All rights reserved.

One-dimensional analytical model for oxide thin film growth on Ti metal layers during laser heating in air

This paper presents the theoretical and experimental results for oxide thin film growth on titanium films previously deposited over glass substrate. Ti films of thickness 0.1 μm were heated by Nd:YAG laser pulses in air. The oxide tracks were created by moving the samples with a constant speed of 2 mm/s, under the laser action. The micro-topographic analysis of the tracks was performed by a microprofiler. The results taken along a straight line perpendicular to the track axis revealed a Gaussian profile that closely matches the laser's spatial mode profile, indicating the effectiveness of the surface temperature gradient on the film's growth process. The sample's micro-Raman spectra showed two strong bands at 447 and 612 cm -1 associated with the TiO 2 structure. This is a strong indication that thermo-oxidation reactions took place at the Ti film surface that reached an estimated temperature of 1160 K just due to the action of the first pulse. The results obtained from the numerical integration of the analytical equation which describes the oxidation rate (Wagner equation) are in agreement with the experimental data for film thickness in the high laser intensity region. This shows the partial accuracy of the one-dimensional model adopted for describing the film growth rate. © 2001 Elsevier Science B.V.

Polymer treatment by plasma immersion ion implantation of nitrogen for formation of diamond-like carbon film

Nitrogen ions were implanted by plasma immersion in Kapton, Mylar and polypropylene, with the objective of forming a diamond-like carbon layer on these polymers. The Raman spectrum of the implanted polypropylene showed typical Diamond-Like Carbon (DLC) graphite (G) and disorder (D) peaks, with an sp 3/sp2 hybridization ratio of approximately 0.4 to 0.6. The XPS analysis of the three implanted polymers also showed peaks of C-C and N-C bonds in the sp3 configuration, with hybridization ratios in the same range as the Raman result. The implanted polymers were exposed to oxygen plasma to test the resistance of the polymers to oxygen degradation. Mass loss rate results, however, showed that the DLC layer formed is not sufficiently robust for this application. Nevertheless, the layer formed can be suitable for other applications such as in gas barriers in beverage containers. Further study of implantation conditions may improve the quality of the DLC layer.

Effect of diamond-like carbon thin film coated acrylic resin on candida albicans biofilm formation

Purpose: The purpose of this study was to evaluate the effect of diamond-like carbon thin films doped and undoped with silver nanoparticles coating poly(methyl methacrylate) (PMMA) on Candida albicans biofilm formation. The control of biofilm formation is important to prevent oral diseases in denture users. Materials and Methods: Forty-five PMMA disks were obtained, finished, cleaned in an ultrasonic bath, and divided into three groups: Gc, no surface coating (control group); Gdlc, coated with diamond-like carbon film; and Gag, coated with diamond-like carbon film doped with silver nanoparticles. The films were deposited using a reactive magnetron sputtering system (physical vapor deposition process). The specimens were characterized by optical profilometry, atomic force microscopy, and Rutherford backscattering spectroscopy analyses that determined differences in chemical composition and morphological structure. Following sterilization of the specimens by γ-ray irradiation, C. albicans (ATCC 18804) biofilms were formed by immersion in 2 ml of Sabouraud dextrose broth inoculated with a standardized fungal suspension. After 24 hours, the number of colony forming units (cfu) per specimen was counted. Data concerning biofilm formation were analyzed using ANOVA and the Tukey test (p < 0.05). Results: C. albicans biofilm formation was significantly influenced by the films (p < 0.00001), reducing the number of cfu, while not affecting the roughness parameters (p > 0.05). The Tukey test showed no significant difference between Gdlc and Gag. Films deposited were extremely thin (∼50 nm). The silver particles presented a diameter between 60 and 120 nm and regular distribution throughout the film surface (to Gag). Conclusion: Diamond-like carbon films, doped or undoped with silver nanoparticles, coating the base of PMMA-based dentures could be an alternative procedure for preventing candidosis in denture users. © 2013 by the American College of Prosthodontists.

Gas sensor applications of zinc oxide thin film grown by the polymeric precursor method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Protective film growth on tin in perchlorate and citric acid electrolytes

Voltammetry has been employed to study the influence of systematic additions of citric acid on the E-I curves of Tin in 0.5 M NaClO4, in order to verify the film growth in the presence of the organic acid and the inhibition of the pitting corrosion of the metal. The minimum concentration of the organic acid needed to change the GI curves is 10(-2) M, in the pH range 1.0-4.0. At pH 3.0 and 4.0, the scan rate dependence on current density, in the potential region of formation and reduction of the film, showed that in a first stage adsorption occurs. In a second stage, the v(1/2) dependence found can he explained by ohmic resistance control. The formation of tin/citric acid complexes, 10(-2) M, is suggested. The pitting inhibition may be due to the formation of a mixed layer of tin in citric acid concentrations higher than 10(-2) oxide and tin citrate complexes on the electrode surface. (C) 2001 Elsevier Science B.V. All rights reserved.

Endogenous nitric oxide formation correlates negatively with circulating matrix metalloproteinase (MMP)-2 and MMP-9 levels in black subjects

Deficient formation of endogenous nitric oxide (NO) contributes to cardiovascular diseases, and this may be associated with increased circulating levels of matrix metalloproteinase-9 (MMP-9), as previously shown in white subjects. Because interethnic differences exist with respect to risk factors, prevalence, and severity of cardiovascular diseases, we designed this study to examine whether the circulating levels of nitrites (a marker of endogenous NO formation) are associated with the plasma levels of MMP-9 and MMP-2 in healthy black subjects. We studied 198 healthy subjects self-reported as blacks not taking any medications. Venous blood samples were collected and plasma and whole blood nitrite levels were measured using an ozone-based chemiluminescence assay. Plasma MMP-2 and MMP-9 levels were determined by gelatin zymography. We found a positive correlation between plasma MMP-9 and MMP-2 levels (P < 0.0001, rs = 0.556). Interestingly, we found a negative relationship between the plasma MMP-9 levels and the plasma or whole blood nitrites levels (P = 0.04, rs = -0.149; and P < 0.0001, rs = -0.349, respectively). In parallel, we found similar negative relationships between plasma MMP-2 levels and plasma or whole blood nitrites levels (P = 0.02, rs = -0.172; and P < 0.0001, rs = -0.454, respectively). This is the first study to show that endogenous nitric oxide formation correlates negatively with the circulating levels of both MMP-2 and MMP-9 in black subjects. Our findings suggest a mechanistic link between deficient NO formation and increased MMPs levels, which may promote cardiovascular diseases.

Formation and Characterization of Oriented Micro-and Nanofibers Containing Poly (ethylene oxide) and Pectin

Formation of oriented or aligned micro- and nanofibers using biocompatible materials opens the possibility to obtain engineered tissues that can be used in medicine, environmental engineering, security and defense, among other applications. Pectin, a heteropolysaccharide, is a promising material to be incorporated into the fibers because, besides being biocompatible, this material is also biodegradable and bioactive. In this work, the formation of oriented fibers using solutions containing pectin and polyethylene oxide (biocompatible polymers), and chloroform (as the solvent) is investigated. The injection of solution into an intense electric field defined between two parallel electrodes was used to obtain oriented fibers. This novel approach is a modification of the conventional electrospinning process. The presence of pectin in the fibers was confirmed by FTIR analysis. Fibers with diameters of hundreds of nanometers and several centimeters long can be collected. The incorporation of pectin leads to a higher variation of the diameter of the fibers, and a trend to larger fiber diameters. This behavior can be related to the presence of pectin clusters in the fibers. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.057203jes] All rights reserved.

Structure formation of amphiphilic molecules at the air,water interface and after film transfer

One of the basic concepts of molecular self-assembly is that the morphology of the aggregate is directly related to the structure and interaction of the aggregating molecules. This is not only true for the aggregation in bulk solution, but also for the formation of Langmuir films at the air/water interface. Thus, molecules at the interface do not necessarily form flat monomolecular films but can also aggregate into multilayers or surface micelles. In this context, various novel synthetic molecules were investigated in terms of their morphology at the air/water interface and in transferred films. rnFirst, the self-assembly of semifluorinated alkanes and their molecular orientation at the air/water interface and in transferred films was studied employing scanning force microscopy (SFM) and Kelvin potential force microscopy. Here it was found, that the investigated semifluorinated alkanes aggregate to form circular surface micelles with a diameter of 30 nm, which are constituted of smaller muffin-shaped subunits with a diameter of 10 nm. A further result is that the introduction of an aromatic core into the molecular structure leads to the formation of elongated surface micelles and thus implements a directionality to the self-assembly. rnSecond, the self-assembly of two different amphiphilic hybrid materials containing a short single stranded desoxyribonucleic acid (DNA) sequence was investigated at the air/water interface. The first molecule was a single stranded DNA (11mer) molecule with two hydrophobically modified 5-(dodec-1-ynyl)uracil nucleobases at the terminal 5'-end of the oligonucleotide sequence. Isotherm measurements revealed the formation of semi-stable films at the air/water interface. SFM imaging of films transferred via Langmuir-Blodgett technique supported this finding and indicated mono-, bi- and multilayer formation, according to the surface pressure applied upon transfer. Within these films, the hydrophilic DNA sequence was oriented towards air covering 95% of the substrate.rnSimilar results were obtained with a second type of amphiphile, a DNA block copolymer. Furthermore, the potential to perform molecular recognition experiments at the air/water interface with these DNA hybrid materials was evaluated.rnThird, polyglycerol ester molecules (PGE), which are known to form very stable foams, were studies. Aim was to elucidate the molecular structure of PGE molecules at the air/water interface in order to comprehend the foam stabilization mechanism. Several model systems mimicking the air/water interface of a PGE foam and methods for a noninvasive transfer were tested and characterized by SFM. It could be shown, that PGE stabilizes the air/water interface of a foam bubble by formation of multiple surfactant layers. Additionally, a new transfer technique, the bubble film transfer was established and characterized by high speed camera imaging.The results demonstrate the diversity of structures, which can be formed by amphiphilic molecules at the air/water interface and after film transfer, as well as the impact of the chemical structure on the aggregate morphology.