Elisabeth Saalman

Effect of 2.45 GHz microwave radiation on permeability of unilamellar liposomes to 5(6)-carboxyfluorescein. Evidence of non-thermal leakage

The influence of 2.45 GHz microwave radiation on the membrane permeability of unilamellar liposomes was studied using the marker 5(6)-carboxyfluorescein trapped in phosphatidylcholine liposomes. The release of the fluorescent marker was followed by spectrofluorimetry after an exposure of 10 minutes to either microwave radiation or to heat alone of the liposome solutions. A significant increase of the permeability of carboxyfluorescein through the membrane was observed for the microwave-exposed samples compared to those exposed to normal heating only. Exposure to 2.45 GHz microwave radiation of liposomes has been previously found to produce increased membrane permeability as compared with heating. However, in contrast to previous studies, the observations reported here were made above the phase transition temperature of the lipid membrane. The experimental setup included monitoring of the temperature during microwave exposure simultaneously at several points in the solution volume using a fiberoptic thermometer. Possible mechanisms to explain the observations are discussed.

Active Learning in Engineering Education: a (re)introduction.

ABSTRACT The informal network ‘Active Learning in Engineering Education’ (ALE) has been promoting Active Learning since 2001. ALE creates opportunity for practitioners and researchers of engineering education to collaboratively learn how to foster learning of engineering students. The activities in ALE are centred on the vision that learners construct their knowledge based on meaningful activities and knowledge. In 2014, the steering committee of the ALE network reinforced the need to discuss the meaning of Active Learning and that was the base for this proposal for a special issue. More than 40 submissions were reviewed by the European Journal of Engineering Education community and this theme issue ended up with eight contributions, which are different both in their research and Active Learning approaches. These different Active Learning approaches are aligned with the different approaches that can be increasingly found in indexed journals.

Effect of microwave radiation on permeability of liposomes. Evidence against non-thermal leakage

The effect of 2.45 GHz microwave radiation on the permeability of unilamellar phosphatidylcholine liposomes has been studied. Leakage of 5(6)-carboxyfluorescein from the liposomes was measured using spectrofluorimetry after exposure to either microwaves or thermal heating for 5-20 min intervals. The exposure temperature, 37.6 +/- 0.5 degrees C, was well above the phase transition temperature of the lipid membrane. The microwave exposure did not result in any non-thermal increase in permeability above that produced by thermal heating. This study refutes the results reported by Saalman et al. [1] in which an increased liposome permeability due to microwave exposure was reported. The refined analysis in the present study shows that this increased liposome permeability was not a non-thermal microwave effect.

Infrared spectroscopic study of polymers exposed to ethylene oxide

Fourier transform infrared spectroscopy has been used to study thin polymer films exposed to ethylene oxide (EO). The i.r. technique represents a new way of studying this subject. The polymers studied were poly(vinyl chloride), polyethylene and polystyrene. They were exposed to EO, either in a small commercial EO-sterilizer which uses pure EO and operates at subatmospheric pressure, at a temperature of 37 or 55 degrees C, or under experimental laboratory conditions. The absorption and diffusion of EO in the polymers was studied. Potential reaction products, such as ethylene glycol and ethylene chlorohydrin, were looked for but could not be traced. The detection limit of the method was 1 ppm (microgram/g) EO. Typical spectra of the polymer films, before and after exposure to EO, are shown. Diffusion coefficients for poly(vinyl chloride) and polyethylene have been calculated.

SimChemistry as an active learning tool in chemical education

The publicly available free computer program, SimChemistry, was used as an active learning tool in the chemical engineering curriculum at the University College of Boras, Sweden. The activity involved students writing their own simulation programs on topics in the area of molecular structure and interactions. Evaluation of the learning experience was done using interviews and by comparing learning outcomes with previous teachings of the topics. Overall, the outcome was interactively engaging group work, high quality construction of simulations, and a much better ability to explain molecular-level chemical concepts and their relations. An interesting perception that emerged during the interviews was that many of the students were unable to explicitly describe the improvement in learning that they had experienced. However, they did recognize that learning had occurred, and all firmly and positively recommended that the initiative be continued for subsequent courses.