Mass Transport in the Stefan-Knudsen Transition Region during Vacuum Drying at Different Pressures in a Porous Structure Resembling Battery Electrodes.

A precise understanding of the mass transport kinetics of water inside the porous structure of battery electrodes is crucial to understanding and optimizing their post-drying process. This process and the moisture management during the production of Li-ion battery electrodes adjust and remove residual water from electrodes and are cost intensive. Furthermore, the amount of residual moisture in the electrode affects device performance. Mass transport phenomena in the Stefan and Knudsen transition affect these processes. In this manuscript, we investigate the mass transport in the interparticle gas phase of a porous structure gravimetrically by a magnetic suspension balance with a conditioned (humidity, temperature, and pressure) measurement cell. Emphasis lies on the pressure, porosity, and mass transport distance dependency of the desorption process. Comparing experimental data with a simulation of the interparticle gas phase shows that the mass transport close to ambient pressure can be described by Stefan diffusion through the porous structure. The experiments show the significance of Knudsen diffusion during the mass transport toward lower pressure. A proposed diffusion-coefficient model describes the Stefan and Knudsen region with a transition function, taking the mass transport phenomena overlap into account by lower and upper limits as transition values.

Safety parameters for indocyanine green in vitreoretinal surgery.

Since the early nineties removal of the internal limiting membrane (ILM) has been shown to be an effective and safe treatment option for conditions that involve the vitreoretinal interface. Peeling of the barely visible ILM, however, represents a challenge and complete removal is difficult and not always obvious. Damage at the vitreoretinal interface or unsatisfactory peeling may therefore be the result of the genuine procedure. Introduction of indocyanine green (ICG) for ILM staining led to better visibility of the ILM and greatly facilitated this surgical maneuver making ILM peeling more controllable, easier and faster. Consequently, enthusiastic acceptance resulted in an uncritical use not supported by preclinical safety data. Soon thereafter some clinical reports raised concerns about potential cytotoxic effects related to the intravitreal use of ICG. The following chapter summarizes the results of in vitro, ex vivo, in vivo and clinical studies related to the use of ICG in vitreoretinal surgery. Critical appraisal of the methodical procedures and results leads to the nonnegligible fact that ICG has a cytotoxic effect enhanced by photoactivation. The results of several studies as well as our experimental workup, however, showed that ICG toxicity to the retinal pigment epithelium is dependent on the dye concentration, the osmolarity of the solvent solutions, as well as on the lengths of dye exposure time and of the vitrectomy endolight illumination time. With respect to the safety margins and profile, ICG is therefore a useful surgical tool that is still widely applied, but that may be replaced by more inert and as efficient vital dyes.

Systematic evaluation of ICG and trypan blue related effects on ARPE-19 cells in vitro.

The aim of our study was a systematic analysis of the impact of variable parameters on indocyanine green (ICG) and trypan blue (TB) related cytotoxicity on human RPE cells. ARPE-19 cells were incubated with ICG (5.0-0.025mg/ml), with ICG-free solutions of corresponding osmolarities or with TB (1.5-0.0375mg/ml). Incubation lasted 1-20min with or without endolight illumination for 1min or 5min. Cell viability and morphology were examined after 6h, 24h and 72h to detect acute and delayed effects. In the absence of endolight, ICG cytotoxicity depends on osmolarity and exposure time. In the presence of endolight, cytotoxic effects are influenced by dye concentration. TB cytotoxicity depends on dye concentration and exposure time, but not on illumination. All observed cytotoxic effects were mainly acute. Both ICG and TB can be cytotoxic depending on concentration and exposure time. ICG related cytotoxic effects are additionally determined by osmolarity and phototoxicity. However, concentrations (<1mg/ml) and incubation times (<5min) as used in clinical practice would appear to be well tolerated.