[Electrode forms for reducing tumor mass using high frequency current].

The effect of surfactant on the rheological properties of some cream formulations was studied. Two surfactants from two different series were combined to determine the combination which yielded the most viscoelastic structure for creams. The surfactants were the soybean derivatives soya sterol, polyethylene glycol 10 soya sterol and polyethylene glycol 25 soya sterol and the sorbitol derivatives sorbitan monooleate and sorbitan trioleate. The rheological properties of the creams were studied using oscillation stress sweep, oscillation frequency sweep and viscosity tests. Droplet size distribution and conductivity of the creams were also determined. The combination polyethylene glycol 10 soya sterol and sorbitan trioleate yielded the most viscoelastic structure with linearly viscoelastic behaviour.

Electric Conductivity↗

PubMed2000

Current oscillations under voltage-clamp conditions: an interplay of series resistance and negative slope conductance.

Using the patch-clamp technique, we observed profound oscillations of the whole-vacuole outward current across the tonoplast of Mesembryanthemum crystallinum L. (common ice plant). These current oscillations showed a clear voltage dependence and appeared at membrane potentials more positive than 90-100 mV. This paper describes the oscillations in terms of two separate mechanisms. First, the Mesembryanthemum vacuolar membrane shows a negative slope conductance at membrane potentials more positive than 100-120 mV. The fact that the oscillations and the negative slope conductance show a similar threshold potential suggests that (part of) the same mechanism is involved in both phenomena. The second mechanism involved is the voltage drop across the series resistance. As a result, the potential actually experienced by the vacuolar membrane deviates from the command potential defined by the patch-clamp amplifier. This deviation depends in an Ohmic manner on the current magnitude. We suggest that the interplay of the negative slope conductance and the voltage drop across the series resistance can cause a positive feedback which is responsible for the current oscillations.

Electric Conductivity↗

PubMed2000

High-frequency dielectric study of side-chain dynamics in poly(lysine) aqueous solutions.

The high-frequency dielectric properties of poly(lysine) of different chirality in aqueous solutions have been measured in the frequency range from 1 MHz to 1.8 GHz. The dielectric spectra show the existence of relatively small dielectric dispersions at around 100 MHz that have been attributed to internal motion in the polymer chain, due to side-chain polar groups. Our results indicate that the local structure of the chain and its possibility to undergo a conformational transition induced by pH does not modify the main feature of the side-chain dynamics, the dielectric strength being largely proportional to the concentration of charged groups. A similar behavior has been found in poly(alpha-glutamate) and in poly(gamma-glutamate) aqueous solutions, where the dielectric parameters appear to be related to the change in the charge density on the main chain, rather than to the accompanying conformational helix-coil transition.

Electric Conductivity↗