Cerâmicas apresentam excelente durabilidade química, resistência ao desgaste, biocompatibilidade, respeito ao meio ambiente e estética. Uma das propriedades mais importantes a ser considerada em implantes dentários totalmente cerâmicos é a fadiga cíclica, devido às solicitações mecânicas cíclicas as quais os implantes estão subjugados durante processos de mastigação, que pode induzir milhares de ciclos de tensão por dia em uma restauração, com isso exibir significativo crescimento subcrítico de trinca e assim poder diminuir a resistência de componentes cerâmicos, ao longo do tempo. Nesse trabalho, a previsão de vida em fadiga cíclica do compósito ZrO2-Al2O3 foi investigada. Mistura de pós contendo 80% de ZrO2 e 20% de Al2O3 foi compactada e sinterizada a 1600 °C. As amostras sinterizadas foram caracterizadas por difração de raios X e microscopia eletrônica de varredura. Dureza, tenacidade e resistência à fratura por flexão foram determinadas, e os resultados utilizados na determinação dos parâmetros de fadiga. Os testes de fadiga foram realizados em dispositivo de flexão em 4 pontos, sob freqüência de 25 Hz e razão de tensão de 0,1. Um aumento do nível de tensão levou à redução do tempo de vida sob fadiga. Baseado nos parâmetros determinados pelos ensaios mecânicos e de fadiga, e utilizando-se a estatística de Weibull, associada a modelos de determinação de crescimento subcrítico de falha, a velocidade de propagação de trincas nesse compósito é determinada e relacionada com os mecanismos de transformação martensítica e tensão residual entre as fases. Os componentes submetidos ao carregamento cíclico exibiram propagação subcrítica de trinca, em níveis de tensão significativamente menores do que o KIC. Apesar desta susceptibilidade ao crescimento subcrítico de trinca, cálculos com base nos parâmetros de fadiga e nas tensões aplicadas indicam que os componentes com estruturas do compósito ZrO2-Al2O3 podem exibir vidas maiores que 20 anos, se o diâmetro do componente estrutural é adequadamente projetado.

Ceramics provide excellent chemical durability, wear resistance, biocompatibility and respect for the environment. One of the most important properties to be considered in fully ceramic dental implants is the cyclic fatigue due to cyclic mechanical stress to which the implants are overwhelmed during mastication processes which can induce thousands of stress cycles per day in a restoration, thereby significant display subcritical crack growth and so can reduce the resistance of ceramic components, over time. In this work, the prediction of fatigue life cycle of ZrO2-Al2O3 composite was investigated. A powder mixture containing 80% ZrO2 and 20% Al2O3 was compacted and sintered at 1600 °C. The sintered samples were characterized by X-ray diffraction and scanning electron microscopy. Hardness, toughness and bending strength were determined and the results used in determining the parameters of fatigue. The fatigue tests were performed on device 4 point bending under 25 Hz frequency and stress ratio of 0.1. An increased level of stress has led to reduction of lifetime under fatigue. Based on parameters determined by the mechanical tests and fatigue, and using Weibull statistic associated with models for determining growth subcritical fault, the rate of crack propagation in composite is determined and related to phase transformation mechanism and residual stress between the phases. The components subject to cyclic loading exhibited subcritical crack propagation at stress levels significantly lower than KIC. Despite this susceptibility to subcritical crack growth, calculations based on the parameters of fatigue and the applied voltages indicate that the composite structures with components ZrO2-Al2O3 can exhibit lifetime greater than 20 years, if the diameter of the structural member is suitably designed.

This work describes the use of clavulanic acid (CA) precipitation as the final step in the process of purification of CA from fermentation broth as an alternative to conventional methods employed traditionally. The purpose of this study was to use a stable intermediate (t-octylamine) between the conversion of CA to its salt form (potassium clavulanate), thereby enabling the resulting intermediate (amine salt of clavulanic acid) to improve the purification process and maintain the stability of the resulting potassium clavulanate. To this end, response surface methodology was employed to optimize the precipitation step. For the first reaction, five temperatures (6.6 to 23.4 ºC), concentrations of clavulanic acid in organic solvent (6.6 to 23.4 mg/mL) and t-octylamine inflow rates (0.33 to 1.17 drop/min) were selected based on a central composite rotatable design (CCRD). For the second reaction, five temperatures (11.6 to 28.4 ºC), concentrations of clavulanic acid amine salt in organic solvent (8.2 to 41.8 mg/mL) and concentrations of potassium 2-ethylhexanoate (0.2 to 1.2 molar) were also selected using CCRD. From these results, precipitation conditions were selected and applied to the purification of CA from the fermentation broth, obtaining a yield of 72.37%.

The present work describes the study of the growth and the cytotoxic and antitumor activities of the extracts of the marine microorganisms Streptomyces acrymicini and Streptomyces cebimarensis, the latter a new strain. Both microorganisms were collected from coastal marine sediments of the north coast of São Paulo state. Growth was performed in a shaker and in a bioreactor using Gym medium and the broths of both microorganisms were extracted with ethyl acetate and n-butanol. Three extracts, two organic and one aqueous, from each microorganism were obtained and tested for cytotoxic and antitumor activity using the SF-295 (Central Nervous System), HCT-8 (Colon) cell lines, and the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The growth methods were compared and show that, although the shaker presented reasonable results, the bioreactor represents the best choice for growth of these microorganisms. The biological activity of the different extracts was evaluated and it was demonstrated that the growth methodology may influence the secondary metabolite production and the biological activity.

A study was made of the extraction of clavulanic acid (CA) from a fermented medium and its concentration and purification. The fermented broth was obtained by cultivation of Streptomyces clavuligerus in complex medium containing glycerol as the Carbon and energy source, and soybean protein isolate as the Nitrogen source. The extraction steps proposed here were evaluated from the standpoint of Yield, purification factor and concentration factor. The extractions were carried out with ethyl acetate, butyl acetate, 2-butanol, n-butanol and methyl isobutyl ketone. The distribution coefficient was related to the solvent properties and it was found that distribution coefficient is directly proportional to the product of the dielectric constant, with solubility. It was observed that extraction with butanol leads to a higher distribution coefficient than ethyl acetate; however, the higher solubility of water in butanol impairs the final precipitation of clavulanic acid. The optimal condition with ethyl acetate occurs at pH 1.63, yielding an extraction factor of 35.6% with a distribution coefficient of 0.73.

Oxidative stress and reticulocyte maturity index (RMI) were studied in 27 patients who underwent bone marrow transplantation (BMT). Plasmatic lipoperoxide levels of those patients with unfavorable evolution were significantly increased on days 12-14 post-transplant (median 1.83 µM, range 0.78-5.82) compared with preconditioning levels (median 1.05 µM, range 0.36-1.84) (p <0.05). Patients with favorable evolution revealed significantly higher lipoperoxide levels during conditioning regime (median 1.42 µM, range 0.31-4.50) (p<0.05). Starting from the 3rd post-transplant week a significant and continuous decrease was observed, with a median of 0.77 µM (range 0.21-1.48 p<0.05) for the 3rd, and a median of 0.60 µM (range 0.11-1.48 for the 4th week (p<0.01). A significant increase in total antioxidant activity was observed in the three patients who died up to the 35 days post-transplant. Recovery of bone marrow function was detected by RMI after a median time of 17 days (range 11-24) post-allogeneic transplantation. The threshold established for absolute neutrophil count was achieved after a median of 21 days (range 14-28) (p< 0.001). An increase of plasma lipoperoxides on days 12-14 post-transplant may be a predictive value of unfavourable evolution. RMI was the earlier indicator of engraftment in allogeneic BMT.

El estrés oxidativo y el índice de madurez reticulocitaria (IMR) fueron estudiados en 27 pacientes sometidos a trasplante de médula ósea (TMO). En los pacientes con evolución no favorable, los lipoperóxidos mostraron un incremento entre el día 12-14 postransplante (mediana 1.83 µM rango 0.78-5.82) con respecto al precondicionamiento (mediana 1.05 µM rango 0.36-1.84 p<0.05).Los pacientes con evolución favorable revelaron un incremento de lipoperóxidos durante el condicionamiento (p<0.05) (mediana: 1.42 µM rango: 0.31-4.50) y un descenso significativo durante la tercera semana (mediana 0.77 µM rango 0.21-1.48) y cuarta semana postrasplante (mediana 0.60 µM rango 0.11-1.48) con respecto a los valores precondicionamiento (p<0.05 y p<0.01 respectivamente). La actividad antioxidante total aumentó significativamente en los pacientes que evolucionaron al óbito dentro de los 35 días postrasplante (n:3). El IMR reveló engraftment en los TMO alogénicos en el día 17 (rango 11-24) vs neutrófilos: día 21 (rango14-28 p<0.001). El incremento de lipoperóxidos durante los días 12-14 postrasplante fue predictor de evolución no favorable. El IMR resultó el más temprano detector de engraftment en TMO alogénicos.