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In a previous paper, a new dielectric technique was used to estimate hematocrit (HTC) in extracorporeal blood circulation systems, independently of plasma conductivity or osmolarity. Although many impedance techniques have been formerly proposed in the literature, none has been evaluated against plasma conductivity and osmolarity. Herein, we estimate HTC based on permittivity changes and also with other four techniques found in the literature. Besides, the error incurred in each is also studied when plasma conductivity and osmolarity changed as much as 1 mS/cm and 50 mOsm/kg, respectively. The dielectric (permittivity) technique has an error close to 5.4%, while the others showed both tendencies, i.e., lower error (2.5%, two of them) and higher error (8.6% and 16.3%, the other two). The dielectric technique, even though did not produce the lowest error, provides a well-described physical model along with simple instrumentation. Index Terms--Beta relaxation, blood, cell membrane, erythrocytes.

Based on permittivity changes, a new method to measure hematocrit (HCT) in extracorporeal blood systems is presented. Human blood samples were tested at different HCT levels pairing the values of permittivity change, obtained by means of a commercial impedance analyzer, with traditional centrifugation measurements. Data were correlated using both linear and nonlinear regression. When using the lineal model, the comparison yielded a high correlation coefficient (r = 0.99). Theoretical simplifications suggest that the method is independent of changes in the conductivities of the intracellular and extracellular compartments. The influence of osmolarity and conductivity of the extracellular compartment was analyzed. It is shown that HCT can be predicted within an error lower than 5% when those parameters changed as much as 1 mS/cm and 50 mOsm/kg, respectively. Thus, the method appears as valid and viable showing good possibilities in applications such as renal dialysis. Index Terms--Blood, dielectrics, membrane, relaxation.

We measured impedance in a cell containing culture broth inoculated with E. coli, before and during bacterial growth. The electrode interface impedance components (R(sub i), X(sub i)) and the culture medium component R(sub m) were separated by making use of the Warburg's model frequency dependent properties. Measurements were carried out at different frequencies (from 18 Hz to 18 kHz) with a constant current impedance bridge as growth proceeded. It was found that: Growth curves for R(sub i) and X(sub i) showed a similar temporal pattern within the frequency range of 18-100 Hz. Dispersion was not observed in R(sub m), meaning that the same growth response was obtained within the 18-18 000

A group of bioengineering students developed an effective physiological recording system from inexpensive and mostly home-made materials. The project took over 26 weeks and was developed in three stages. Results were a single-channel mechanical recorder for myograms using a 40 centimeter long light wooden dowel manipulated by pulleys and levers; an electromechanical proximity transducer and recorder using an inductive proximity transducer; and digital data acquisition and display using A/D conversion, a Commodore 128 and GRAPHICS 1 software with a joystick.

The emphasis of protecting patients embodied in the Hippocratic Oath is proposed to be expanded to all sectors of health care. Partnerships between the industry and government are also encouraged to preserve the traditional values of medicine. Ironically, the modern system is more absorbed in medical innovations while the health of many children continue to deteriorate. Government policy is also more oriented towards the military whereas politicians continually give false promises of improved health care.