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The most important parameter in bioprocesses is biomass, where not only the quantity produced in a culture but also the behavior that is presented are important concerns. It is clear that conditions of operation in a bioreactor affect biomass production, but how operation conditions affect the measurement of biomass on-line is of special interest. We studied the effect of bioreactor operating condition variations on model parameters using impedance spectroscopy for biomass monitoring. The model parameters analyzed were capacitance, resistance, alpha (α), conductivity delta (∆σ) and critical frequency (fc). These model parameters were obtained by fitting data from impedance measurements to an equivalent circuit model and Cole-Cole conductivity model. The effect of operating conditions on the medium with no cells was estimated by the percentage of change in each model parameter. The operating conditions with the most significant percentage of change were determined, by comparing to the percentage of change of the same model parameters obtained, during a fermentation of Bacillus thuringiensis as a cellular model. Equivalent circuit parameters were mainly affected by variation in pH, temperature and aeration, whereas Cole-Cole parameters were affected by variation in agitation, aeration, temperature and pH. Therefore, any variation in these operating conditions (within the test interval) during a fermentation may generate changes in monitoring parameters, which will not be a direct consequence of any change in the properties of the biomass.

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RESUMO

This article focuses on studying the rheological behavior of isotropic and anisotropic magnetorheological elastomers (MREs), made of carbonyl iron microparticles dispersed into a silicone⁻rubber matrix by considering 20 and 30 wt % of microparticles. Sample sets were prepared for each composition, with and without the application of an external magnetic field. Experimental measurements of the material rheology behavior were carried out by a shear oscillatory rheometer at constant temperature, to determine both the shear storage modulus (G') and shear loss modulus (G'') for all characterized samples. Then, experimental data collected from the isotropic and the anisotropic material samples were used to plot the Cole-Cole diagrams to quantify the interfacial adhesion between carbonyl iron microparticles and the silicone-rubber matrix. Furthermore, the Fractional Zener Model (FZM) with two spring-pots in series is used for quantitative analysis of collected experimental data.

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Se presentan los resultados de un estudio piloto de detección temprana de cáncer de cuello uterino basado en la medición de las propiedades eléctricas del tejido epitelial de cérvix. El objetivo de esta investigación fue estudiar parámetros del espectro de impedancia eléctrica correlacionados con neoplasia intraepitelial. Fueron realizadas setenta mediciones en nueve pacientes en las instalaciones del Hospital Universitario de Santander y el Hospital de Floridablanca, bajo supervisión médica y con previa autorización de las mismas. Las medidas se tomaron con el impedanciometro mono canal MARK III, desarrollado en la Universidad de Sheffield (UK), y una sonda tetrapolar previamente calibrada. Este dispositivo inyecta una corriente de 20uA al tejido y mide la respuesta en voltaje del mismo, además de cumplir con las normas internacionales de seguridad eléctrica para el paciente, BS5724 e IEC601, incluidas en la norma Colombiana NTC-IEC 60601. Los resultados obtenidos mostraron una alta correlación entre los parámetros Ro, Ri y T del modelo Cole-Cole, que ajustan los datos del espectro de impedancia eléctrica, y el estado histopatológico del tejido. Estos resultados sugieren una sensibilidad y especificidad superiores al 80%.

We present the results of a study using the electrical properties of the tissues for early cervical cancer detection. Our objective was to study electrical impedance parameters and their intraepitelial neoplasia correlations. Electrical Bioimpedance in "In-Vivo" and "Ex-Vivo", was measured in patients from the "Hospital Universitario de Santander" and "Hospital de Floridablanca," this was made under medical supervision and patient authorization. The biompedamciometer MARK III, developed in Sheffield (UK), and a calibrated tetrapolar probe were used. This device inject a current of 20mA to the tissue and it measures the voltage response. It is important to note that the MARK III is under internacional Standard of electrical security, BS5724 e IEC601; these standards are contemplated in the ICONTEC NTC-IEC 60601. The results show a high correlation between the electrical impedance spectrum parameters Ro, Ri y T, and the histopathology condition of the tissue condition. The sensibility and specificity suggested are major of 80%.

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