On-chip microelectrode impedance analysis of mammalian cell viability during biomanufacturing

The characterization of cell viability is a challenging task in applied biotechnology, as no clear definition of cell death exists. Cell death is accompanied with a change in the electrical properties of the membrane as well as the cell interior. Therefore, changes in the physiology of cells can be characterized by monitoring of their dielectric properties. We correlated the dielectric properties of industrially used mammalian cells, sedimented over interdigitated microelectrodes, to the AC signal response across the chip. The voltage waveforms across the electrodes were processed to obtain the circuit impedance, which was used to quantify the changes in cell viability. We observed an initial decrease in impedance, after which it remained nearly constant. The results were compared with data from the dye exclusion viability test, the cell specific oxygen uptake rate, and the online viable cell density data from capacitance probes. The microelectrode technique was found to be sensitive to physiological changes taking place inside the cells before their membrane integrity is compromised. Such accurate determination of the metabolic status during this initial period, which turned out to be less well captured in the dye exclusion tests, may be essential for several biotechnology operations.     

Does speed-reading training work,and if so,why? Effects of speed-reading training and metacognitive training on reading speed,comprehension and eye movements

Background

Commercial speed-reading training programs are typically marketed with the promise to dramatically increase reading speed without impairing comprehension. From the perspective of reading psychology, it seems quite unlikely that speed-reading training can indeed have such effects. However, research on the effectiveness of modern speed-reading training programs on reading performance in typical readers is sparse. The present study had two goals. First, we sought to extend prior research on speed-reading by assessing the effects of a speed-reading application on reading performance in a pre-training and post-training design with a control group. Second, we aimed to identify the mechanism underlying speed-reading training programs.

Methods

We assessed reading speed, comprehension and eye movements of 30 German-speaking undergraduates (M_age = 22.77 years, SD_age = 3.41 years) before and after they received a commercial, app-based speed-reading training, a metacognitive training or no training.

Results

Results revealed higher reading speed in the speed-reading condition and metacognitive condition compared with the control condition, although not to the extent claimed in the application. Eye-movement data indicated that the increase in reading speed was due to fewer and shorter fixations in measures reflecting late but not early lexical processing. No differences in comprehension performance were observed between the three conditions.

Conclusions

We discuss our findings in support of the idea that the increase in reading speed was not caused by a change in basic characteristics of participants' reading behaviour, but rather by an increase in their awareness of their own reading process. Further research is needed to investigate whether the observed effects are maintained over time.