Effects of glass-ceramic produced by the sol-gel route in macrophages recruitment and polarization into bone tissue regeneration.

Effective bone substitute biomaterials remain an important challenge in patients with large bone defects. Glass ceramics produced by different synthesis routes may result in changes in the material physicochemical properties and consequently affect the success or failure of the bone healing response. To investigate the differences in the orchestration of the inflammatory and healing process in bone grafting and repair using different glass-ceramic routes production. Thirty male Wistar rats underwent surgical unilateral parietal defects filled with silicate glass-ceramic produced by distinct routes: BS - particulate glass-ceramic produced via the fusion/solidification route, and BG - particulate glass-ceramic produced via the sol-gel route. After 7, 14, and 21 days from biomaterial grafting, parietal bones were removed to be analyzed under H&E and Massons' Trichome staining, and immunohistochemistry for CD206, iNOS, and TGF-ß. Our findings demonstrated that the density of lymphocytes and plasma cells was significantly higher in the BS group at 45, and 7 days compared to the BG group, respectively. Furthermore, a significant increase of foreign body giant cells (FBGCs) in the BG group at day 7, compared to BS was found, demonstrating early efficient recruitment of FBGCs against sol-gel-derived glass-ceramic particulate (BS group). According to macrophage profiles, CD206+ macrophages enhanced at the final periods of both groups, being significantly higher at 45 days of BS compared to the BG group. On the other hand, the density of transformation growth factor beta (TGF-ß) positive cells on 21 days were the highest in BG, and the lowest in the BS group, demonstrating a differential synergy among groups. Noteworthy, TGF-ß+ cells were significantly higher at 21 days of BG compared to the BS group. Glass-ceramic biomaterials can act differently in the biological process of bone remodeling due to their route production, being the sol-gel route more efficient to activate M2 macrophages and specific FBGCs compared to the traditional route. Altogether, these features lead to a better understanding of the effectiveness of inflammatory response for biomaterial degradation and provide new insights for further preclinical and clinical studies involved in bone healing.

Silk fibroin-derived electrospun materials for biomedical applications: A review.

Electrospinning is a versatile technique for fabricating polymeric fibers with diameters ranging from micro- to nanoscale, exhibiting multiple morphologies and arrangements. By combining silk fibroin (SF) with synthetic and/or natural polymers, electrospun materials with outstanding biological, chemical, electrical, physical, mechanical, and optical properties can be achieved, fulfilling the evolving biomedical demands. This review highlights the remarkable versatility of SF-derived electrospun materials, specifically focusing on their application in tissue regeneration (including cartilage, cornea, nerves, blood vessels, bones, and skin), disease treatment (such as cancer and diabetes), and the development of controlled drug delivery systems. Additionally, we explore the potential future trends in utilizing these nanofibrous materials for creating intelligent biomaterials, incorporating biosensors and wearable sensors for monitoring human health, and also discuss the bottlenecks for its widespread use. This comprehensive overview illuminates the significant impact and exciting prospects of SF-derived electrospun materials in advancing biomedical research and applications.

Influência da inatividade física na capacidade funcional de idosos saudáveis durante a pandemia da Covid-19 / Influence of physical inactivity on the functional capacity of healthy older people during the Covid-19 pandemic

Resumo Introdução: A pandemia da COVID-19 contribuiu para a diminuição das atividades habituais dos idosos, o que pode interferir na capacidade funcional (CF) dos mesmos. Objetivo: Verificar o impacto da inatividade física durante a pandemia da COVID-19 na CF de idosos e associar o nível de atividade física com a CF dos mesmos. Métodos: Participaram do estudo 20 idosos que frequentavam um programa de atividade física antes da pandemia da COVID-19. Foi avaliada a capacidade funcional pelo teste AVD-Glittre, teste de caminhada de 6 minutos (TC6) e Time Up and Go (TUG); os resultados foram comparados com os resultados dos testes obtidos em 2019 (antes da pandemia da COVID-19). Para verificar o nível de atividade física, foi aplicado o Questionário Internacional de Nível de Atividade Física (IPAQ). Os dados foram analisados pelo teste t pareado de Wilcoxon e teste de correlação de Pearson. Resultados: Houve um aumento do tempo da execução do teste de AVD-Glittre de 171.90 ± 35.56 para 272.00 ± 344.77 segundos, no TUG teste de 6.27 ± 119 para 6.92 ± 1.53 segundos, e no TC6 houve uma diminuição de 564.97 ± 85.22 para 464.65 ± 105.95 metros, com p<0.001 em todas as análises. A correlação entre IPAQ e o teste de AVD-Glittre foi fraca (r=0.11, p<0.63), fraca com TC6 (r= -0.10, p>0.001) e moderada com TUG (r=0.59, p>0.001). Conclusão: Houve diminuição da CF dos idosos durante a pandemia da COVID-19, o nível de atividade física influenciou no TUG.

Introduction: The COVID-19 pandemic contributed to a decrease in the usual activities of older adults, which may interfere with their functional capacity (FC). Objective: To verify the impact of physical inactivity during the COVID-19 pandemic on the older adults' FC and associate the level of older adults' physical activity with the FC. Methods: The study included 20 older people who attended a physical activity program before the COVID-19 pandemic. Functional capacity was evaluated by the ADL-Glittre test, 6-minute walk test (6MWT) and Time Up and Go (TUG) test. The tests' results were compared to the tests obtained in 2019 (before the COVID-19 pandemic). The International Physical Activity Level Questionnaire (IPAQ) was applied to verify the physical activity level. Data were analyzed using Wilcoxon's paired t-test and Pearson's correlation test. Results: There was an increase in the execution time of the ADL-Glittre test from 171.90 ± 35.56 to 272.00 ± 344.77 seconds, in the TUG test from 6.27 ± 119 to 6.92 ± 1.53 seconds, and in the 6MWT there was a decrease from 564.97 ± 85.22 to 464.65 ± 105.95 meters, with p<0.001 in all analyses. The correlation between IPAQ and the ADL-Glittre test was weak (r=0.11, p<0.63), weak with 6MWT (r= -0.10, p>0.001) and moderate with TUG (r=0.59, p>0.001). Conclusion: There was a decrease in the FC of older adults during the COVID-19 pandemic; the level of physical activity influenced the TUG.

Validation and reliability of the Glittre-ADL test to evaluate functional capacity in older adults

INTRODUCTION: The decline in functional capacity (FC) interferes with the functional independence of older adults, so it is important to assess the FC and use appropriate instruments for this. OBJECTIVE: To investigate the Glittre Activities of Daily Living (ADL) test's validity and reliability for assessing functional capacity in older adults. METHODS: Cross-sectional study with a sample of 100 elderly (68 ± 5.16 years). To assess the convergent validity, the Six-Minute Walk Test (6MWT) and the Timed Up and Go Test (TUG) were performed. The intra-examiner test-retest of the Glittre-ADL test was performed on the same day with a 30-minute interval between repetitions and inter-examiner reliability with an interval of seven days. RESULTS: There was a strong correlation between the Glittre-ADL test and the 6MWT (r=-0,75; p<0.001) and the TUG (r=0.77; p<0.001). The intra-examiner and inter-examiner reliability was excellent (ICC)=0.91 and 95% CI=0.14-0.97; p<0.001 and ICC=0.91; 95% CI: 0.86-0.94; p<0.001, respectively). CONCLUSION: The Glittre-ADL test demonstrated that it is valid and that its reliability is adequate to assess functional capacity in older adults.

Effect of bioactive glasses containing strontium and potassium on dentin permeability.

Dentin hypersensitivity (DH) is characterized by pain caused by an external stimulus on exposed dentin. Different therapeutic approaches have been proposed to mitigate this problem; however, none of them provide permanent pain relief. In this study, we synthesized and characterized experimental bioactive glasses containing 3.07 mol% SrO or 3.36 mol% K2 O (both equivalent to 5 wt% in the glass), and evaluated their effect on dentin permeability to verify their potential to treat DH. The experimental materials were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction to confirm the respective structures and chemical compositions. The reduction in the hydraulic conductance of dentin was evaluated at the three stages: minimum permeability; maximum permeability (24% ethylenediaminetetraacetic acid [EDTA] treatment); and final dentin permeability after treatment with the bioactive glasses. They all promoted a reduction in dentin permeability, with a significant difference for each sample and posttreatment group. Also, a significant reduction in dentin permeability was observed even after a simulated toothbrushing test, demonstrating effective action of these materials against DH. Besides, incorporating 3.07 mol% SrO was a positive factor. Therefore, strontium's desensitizing and re-mineralizing properties can be further exploited in bioactive glasses to promote a synergistic effect to treat DH.

Analysis of permeability and biological properties of dentin treated with experimental bioactive glasses.

OBJECTIVES: To evaluate obliterating capability and biological performance of desensitizing agents. METHODS: 50 dentin blocks were distributed according to the desensitizing agent used (n = 10): Control (Artificial saliva); Ultra EZ (Ultradent); Desensibilize Nano P (FGM); T5-OH Bioactive Glass (Experimental solution); F18 Bioactive Glass (Experimental solution). Desensitizing treatments were performed for 15 days. In addition, specimens were subjected to acid challenge to simulate oral environment demineralizing conditions. Samples were subjected to permeability analysis before and after desensitizing procedures and acid challenge. Cytotoxicity analysis was performed by using Alamar Blue assay and complemented by total protein quantification by Pierce Bicinchoninic Acid assay at 15 min, 24-h and 48-h time points. Scanning electron microscopy and energy dispersion X-ray spectroscopy were performed for qualitative analysis. Data of dentin permeability was analyzed by two-way repeated measures ANOVA and Tukey's test. For cytotoxicity, Kruskal-Wallis and Newman-Keuls tests. RESULTS: for dentin permeability there was no significant difference among desensitizing agents after treatment, but control group presented highest values (0.131 ± 0.076 Lp). After acid challenge, control group maintained highest values (0.044 ± 0.014 Lp) with significant difference to other groups, except for Desensibilize Nano P (0.037 ± 0.019 Lp). For cytotoxicity, there were no significant differences among groups. CONCLUSION: Bioglass-based desensitizers caused similar effects to commercially available products, regarding permeability and dentin biological properties. CLINICAL SIGNIFICANCE: There is no gold standard protocol for dentin sensitivity. The study of novel desensitizing agents that can obliterate dentinal tubules in a faster-acting and long-lasting way may help meet this clinical need.

Experimental gel containing bioactive glass-ceramic to minimize the pulp damage caused by dental bleaching in rats.

OBJECTIVES: This study evaluated if the use of a bioactive glass-ceramic-based gel, named Biosilicate (BS), before, after or mixed with bleaching gel, could influence the inflammation of the dental pulp tissue of rats' molars undergoing dental bleaching with hydrogen peroxide (H2O2). METHODOLOGY: The upper molars of Wistar rats (Rattus norvegicus, albinus) were divided into Ble: bleached (35% H2O2, 30-min); Ble-BS: bleached and followed by BS-based gel application (20 min); BS-Ble: BS-based gel application and then bleaching; BS/7d-Ble: BS-based gel applications for 7 days and then bleaching; Ble+BS: blend of H2O2 with BS-based gel (1:1, 30-min); and control: placebo gel. After 2 and 30 days (n=10), the rats were euthanized for histological evaluation. The Kruskal-Wallis and Dunn statistical tests were performed (P<0.05). RESULTS: At 2 days, the Ble and Ble-BS groups had significant alterations in the pulp tissue, with an area of necrosis. The groups with the application of BS-based gel before H2O2 had moderate inflammation and partial disorganization in the occlusal third of the coronary pulp and were significantly different from the Ble in the middle and cervical thirds (P<0.05). The most favorable results were observed in the Ble+BS, which was similar to the control in all thirds of the coronary pulp (P>0.05). At 30 days, the pulp tissue was organized and the bleached groups presented tertiary dentin deposition. The Ble group had the highest deposition of tertiary dentin, followed by the Ble-BS, and both were different from control (P<0.05). CONCLUSION: A single BS-based gel application beforehand or BS-based gel blended with a bleaching gel minimize the pulp damage induced by dental bleaching.

Flow distribution and jet behavior analysis of fabric filter's pulse-jet cleaning.

Particulate Matter (PM) pollution is an alarming environmental problem and one of the most used PM control devices in industry is fabric filter, with a pulse-jet cleaning system. A better understanding of the flow behavior of such pulse-jets is essential to improve cleaning efficiency and diminish dust emissions. Therefore, the present study aims to analyze the flow patterns of the cleaning pulse of an industrial-scale bag filter, with high-pressure and low-pressure systems, using transient three-dimensional CFD simulations. The results show that the center bags in a row take slightly higher shares of air volume and the larger part of it is due to secondary flow. The simulations also give insights into the degree of centralization of the jets: misalignment is progressively reduced along the purge tube, being less pronounced in the high-pressure than in the low-pressure system. Although the mass flow is higher in the high-pressure system, the distribution of the flow among the bags is relatively uniform and similar for both systems.Implications: This work shows, through simulations, that the behaviour of the air pulse during the cleaning is not uniform. There is a variation of the pulse along the duct, due to the movement of the wave that is formed. Besides wave intensity and pressure, the position and shape of the cleaning nozzle also affects the air pulse.

Experimental gel containing bioactive glass-ceramic to minimize the pulp damage caused by dental bleaching in rats

Abstract Objectives This study evaluated if the use of a bioactive glass-ceramic-based gel, named Biosilicate (BS), before, after or mixed with bleaching gel, could influence the inflammation of the dental pulp tissue of rats' molars undergoing dental bleaching with hydrogen peroxide (H2O2). Methodology The upper molars of Wistar rats (Rattus norvegicus, albinus) were divided into Ble: bleached (35% H2O2, 30-min); Ble-BS: bleached and followed by BS-based gel application (20 min); BS-Ble: BS-based gel application and then bleaching; BS/7d-Ble: BS-based gel applications for 7 days and then bleaching; Ble+BS: blend of H2O2 with BS-based gel (1:1, 30-min); and control: placebo gel. After 2 and 30 days (n=10), the rats were euthanized for histological evaluation. The Kruskal-Wallis and Dunn statistical tests were performed (P<0.05). Results At 2 days, the Ble and Ble-BS groups had significant alterations in the pulp tissue, with an area of necrosis. The groups with the application of BS-based gel before H2O2 had moderate inflammation and partial disorganization in the occlusal third of the coronary pulp and were significantly different from the Ble in the middle and cervical thirds (P<0.05). The most favorable results were observed in the Ble+BS, which was similar to the control in all thirds of the coronary pulp (P>0.05). At 30 days, the pulp tissue was organized and the bleached groups presented tertiary dentin deposition. The Ble group had the highest deposition of tertiary dentin, followed by the Ble-BS, and both were different from control (P<0.05). Conclusion A single BS-based gel application beforehand or BS-based gel blended with a bleaching gel minimize the pulp damage induced by dental bleaching.

Bioactive gel-glasses with distinctly different compositions: Bioactivity, viability of stem cells and antibiofilm effect against Streptococcus mutans.

In this study, an evaluation was performed to determine the in vitro bioactivity, viability of stem cells, and antibiofilm effect against Streptococcus mutans of two bioactive gel-glass 60SiO2-36CaO-4P2O5 (BG-A) and 80SiO2-15CaO-5P2O5 (BG-B) compositions. Both materials were bioactive and undergo the formation of hydroxycarbonate apatite (HCA) on their surfaces when immersed in simulated body fluid (SBF) after 12h, but the BG-A composition showed a more significant formation rate. The pH variation of the samples during the test in SBF indicated that an abrupt change had occurred for the BG-A composition within the first few hours, and the pH was subsequently maintained over time, supporting its stronger antibacterial effects against S. mutans. For the in vitro viability test using mesenchymal stem cells (MSCs), the BG-B showed significantly higher cell viability compared to the BG-A composition at concentrations of 0.125, 1.25 and 12.50mg/mL for 2days. These results indicated that the higher solubility of the BG-A glass favors bioactivity and antibacterial effects. However, as a result of rapid degradation, the increase in the concentration of ions in the cell culture medium was not favorable for cell proliferation. Thus, by varying the composition of glasses, and consequently their dissolution rate, it is possible to favor bioactivity, antimicrobial activity or stem cell proliferation for a particular application of interest.

Comparação entre a PSE planejada pelo treinador com a percebida por jovens atletas de atletismo / Comparison between the RPE planned by coach with perceived by youth athletes of track and field

O sucesso do treinamento esportivo para jovens depende, também, de uma relação ótima entre a intensidade da sessão de treinamento prescrita pelo treinador e percebida pelo atleta, desta maneira, o objetivo do trabalho foi comparar a percepção subjetiva de esforço (PSE) indicada por jovens atletas de atletismo com a planejada pelo treinador para sessão de treinamento. Participaram do estudo 28 voluntários, de ambos os sexos, atletas de atletismo com pelo menos seis meses de treinamento, com média de idade 14,0 ± 1,32 anos, massa corporal 52,4 ± 11,5 e estatura 162,7 ± 9,3 cm, e o treinador da equipe, que tinha seis anos de experiência. O treinador apresentou previamente a execução do treinamento a PSE planejada para cada atleta, e a PSE dos jovens foi coletada 30 minutos após o término de cada sessão. A PSE planejada pelo treinador foi diferente da indicada pelo atleta (3,6 ± 1,2 e 3,1 ± 1,54, respectivamente) e também nas três intensidades; leve 1,80 ± 0,41 e 2,92 ± 1,13, moderada 3,54 ± 0,72 e 4,19 ± 1,45 e forte 7,35 ± 1,33 e 4,46 ± 0,63, respectivamente. Os jovens participantes deste trabalho percebem valores distintos de PSE quando comparada com a planejada pelo treinador, sendo que, para as intensidades leve e moderada sua PSE é menor e para a intensidade pesada é maior do que a planejada. Preconiza-se que haja acompanhamento diário das intensidades percebidas pelos atletas de atletismo durante o treinamento e também comparação constante com o que é planejado pelo treinador...(AU)

The success of sport training for young athletes, also depends, a great relationship between the intensity of the training session prescribed by coach and perceived by athlete, in this way, the aim of this study was to compare the rate of perceived exertion (RPE) indicated by the athlete and coach was planned to training session. The study included 28 healthy volunteers of both sexes , track and field athletes with at least 6 months of training, mean age 14.0 ± 1.32 years, body mass 52.4 ± 11.5 and 162.7 ± height 9.3 cm, and the coach of the team, he had 6 years of experience. The coach had previously done the training PSE planned for each athlete, and PSE youth was collected 30 minutes after the end of each session. The PSE planned by the coach was different from the athlete indicates (3.6 ± 1.2 e 3.1 ± 1.54, respectively), and also in the three intensities; Lightweight 1.80 ± 0.41 and 2.92 ± 1.13 , moderate 3.54 ± 0.72 and 4.19 ± 1.45 strong and 7.35 ± 1.33 and 4.46 ± 0.63, respectively. The young participants of this study perceive different values of RPE compared with planned by the coach and for low and moderate intensities, his RPE is smaller and the strong intensity is higher than planned. We recommend that there is daily monitoring of intensities perceived by track and field athletes during the training and also regular comparison between coaches planned and athletes perceived...(AU)

Evaluation of antibiofilm and mechanical properties of new nanocomposites based on acrylic resins and silver vanadate nanoparticles.

OBJECTIVE: The purpose of this study was evaluate, for the first time, the impact of incorporation of nanostructured silver vanadate (ß-AgVO3) in antibiofilm and mechanical properties of dental acrylic resins (poly(methyl methacrylate), PMMA). DESIGN: The ß-AgVO3 was synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, and microanalysis (SEM/EDS). Resins specimens were prepared with 0-10% wt.% ß-AgVO3 and characterized by SEM, XRD and optical microscopy. The antibiofim activity of the samples against Candida albicans and Streptococcus mutans was investigated by XTT reduction test, colony-forming units (CFUs), and confocal laser scanning microscopy (CLSM). The flexural strength, hardness, and surface roughness of the samples containing ß-AgVO3 were compared with the pure PMMA matrix. RESULTS: The incorporation of 10% ß-AgVO3 significantly reduced the metabolic activity of C. albicans and S. mutans (p<0.05). There was a reduction in microbial load (CFU/mL) of microorganisms for the different concentrations used (p<0.05), which was confirmed by confocal microscopy. The addition of ß-AgVO3 did not change the mechanical properties of hardness and surface roughness of the resins (p>0.05). However, flexural strength decreased with the addition of amounts greater than 1% (p<0.05). CONCLUSIONS: ß-AgVO3 additions in dental acrylic resin may have an impact on inhibition of biofilm of main microorganisms associated with dental prostheses. However, the viability of clinical use should be evaluated in function of changed promoted in some mechanical properties.

In vitro study of the antibacterial properties and impact strength of dental acrylic resins modified with a nanomaterial.

STATEMENT OF PROBLEM: The accumulation of bacteria on the surface of dental prostheses can lead to systemic disease. PURPOSE: The purpose of this in vitro study was to evaluate the growth of Staphylococcus aureus and Pseudomonas aeruginosa on the surface of autopolymerizing (AP) and heat-polymerizing (HP) acrylic resins incorporated with nanostructured silver vanadate (ß-AgVO3) and its impact strength. MATERIAL AND METHODS: For each resin, 216 circular specimens (9 × 2 mm) were prepared for microbiologic analysis and 60 rectangular specimens (65 × 10 × 3.3 mm) for mechanical analysis, according to the percentage of ß-AgVO3: 0%, control group; 0.5%; 1%; 2.5%; 5%; and 10%. After a biofilm had formed, the metabolic activity of the bacteria was measured using the XTT reduction assay (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) (n=8), and the number of viable cells was determined by counting colony forming units per milliliter (CFU/mL) (n=8). Confocal laser scanning microscopy (CLSM) was used to complement the analyses (n=2). The mechanical behavior was evaluated by impact strength assays (n=10). Data were analyzed by 2-way ANOVA, followed by the Tukey honestly significant difference (HSD) post hoc test (α=.05). RESULTS: The addition of 5% and 10% ß-AgVO3 significantly decreased the metabolic activity of P. aeruginosa for both resins (P<.05). The HP resin promoted a greater reduction in metabolic activity than the AP resin (P<.05). No difference was found in the metabolic activity of S. aureus according to the XTT (P>.05). The number of CFU/mL for S. aureus and P. aeruginosa decreased significantly when 5% and 10% ß-AgVO3 were added (P<.001). These concentrations significantly reduced the impact strength of the resins (P<.001) because the system was weakened by the presence of clusters of ß-AgVO3. CONCLUSION: The addition of ß-AgVO3 can provide acrylic resins with antibacterial activity but reduces their impact strength. More efficient addition methods should be investigated.

Bioactivity and cell proliferation in radiopaque gel-derived CaO-P2O5-SiO2-ZrO2 glass and glass-ceramic powders.

In this study, 10 mol% ZrO2 was added to a 27CaO-5P2O5-68SiO2 (mol%) base composition synthesized via a simple sol-gel method. This composition is similar to that of a frequently investigated bioactive gel-glass. The effects of ZrO2 on the in vitro bioactivity and MG-63 cell proliferation of the glass and its derivative polycrystalline (glass-ceramic) powder were investigated. The samples were characterized using thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectroscopy (EDS). Release of Si, Ca, P and Zr into simulated body fluid (SBF) was determined by inductively coupled plasma (ICP). Upon heat treatment at 1000 °C, the glass powder crystallized into an apatite-wollastonite-zirconia glass-ceramic powder. Hydroxycarbonate apatite (HCA) formation on the surface of the glass and glass-ceramic particles containing ZrO2 was confirmed by FTIR and SEM. Addition of ZrO2 to the base glass composition decreased the rate of HCA formation in vitro from one day to three days, and hence, ZrO2 could be employed to control the rate of apatite formation. However, the rate of HCA formation on the glass-ceramic powder containing ZrO2 crystal was equal to that in the base glassy powder. Tests with a cultured human osteoblast-like MG-63 cells revealed that the glass and glass-ceramic materials stimulated cell proliferation, indicating that they are biocompatible and are not cytotoxic in vitro. Moreover, zirconia clearly increased osteoblast proliferation over that of the Zr-free samples. This increase is likely associated with the lower solubility of these samples and, consequently, a smaller variation in the media pH. Despite the low solubility of these materials, bioactivity was maintained, indicating that these glassy and polycrystalline powders are potential candidates for bone graft substitutes and bone cements with the special feature of radiopacity.

The influence of phosphorus precursors on the synthesis and bioactivity of SiO2-CaO-P 2O 5 sol-gel glasses and glass-ceramics.

Bioactive glasses and glass-ceramics of the SiO(2)-CaO-P(2)O(5) system were synthesised by means of a sol-gel method using different phosphorus precursors according to their respective rates of hydrolysis-triethylphosphate (OP(OC(2)H(5))(3)), phosphoric acid (H(3)PO(4)) and a solution prepared by dissolving phosphorus oxide (P(2)O(5)) in ethanol. The resulting materials were characterised by differential scanning calorimetry and thermogravimetry, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and by in vitro bioactivity tests in acellular simulated body fluid. The different precursors significantly affected the main steps of the synthesis, beginning with the time required for gel formation. The most striking influence of these precursors was observed during the thermal treatments at 700-1,200 °C that were used to convert the gels into glasses and glass-ceramics. The samples exhibited very different mineralisation behaviours; especially those prepared using the phosphoric acid, which had a reduced onset temperature of crystallisation and an increased resistance to devitrification. However, all resulting materials were bioactive. The in vitro bioactivity of these materials was strongly affected by the heat treatment temperature. In general, their bioactivity decreased with increasing treatment temperature. For crystallised samples obtained above 900 °C, the bioactivity was favoured by the presence of two crystalline phases: wollastonite (CaSiO(3)) and tricalcium phosphate (α-Ca(3)(PO(4))(2)).

Proposta de calibração de modelos hidrodinâmicos aplicados a unidades de contato utilizando uma função de distribuição de tempos de residência / A proposal of calibration of hydrodynamic models of contact units using a residence time distribution function

O desempenho de unidades de contato que operam em regime de fluxo contínuo depende, entre outros, do padrão de escoamento que se desenvolve no seu interior. Já o levantamento de dados experimentais, como a elevação da superfície d'água e do campo de velocidades, não é uma tarefa fácil. Por tais razões, o uso de modelos numéricos na obtenção de padrões de escoamento em unidades de contato tem se tornado uma boa alternativa. A falta de dados hidrodinâmicos para a calibração e verificação de modelos numéricos tem sido um dos principais fatores que vem limitando o uso mais extensivo dessa ferramenta. O presente trabalho propõe uma nova técnica de calibração de modelo numérico, baseada no ajuste de curvas de passagem obtidas pelo modelo numérico e as obtidas experimentalmente ao longo das unidades de contato. A metodologia proposta é parcialmente avaliada e os resultados indicam ser essa uma técnica bastante promissora.

The performance of continuous flow contact units relies, among other factors, on the flow pattern inside them, and that the measurement of flow patterns in this type of unit is not an easy task. For this reason, the use of numerical models to obtain flow patterns in contact units has become a good alternative. However, the lack of hydrodynamic data to calibrate the models has been one of the main factors limiting a more extensive use of numerical models for this purpose. This work proposes a new calibration technique for numerical models which is based on the best fitting of measured and simulated flow through curves throughout the unit. The proposed methodology is partially evaluated and the results indicate it to be very promising.