Increasing surface hydrophilicity with biopolymers: a combined single bubble collision, QCM-D and AFM study.

HYPOTHESIS: Naturally extracted polysaccharides, such as guar gum, are promising candidates for environmentally friendly flotation reagents. It is hypothesized that the kinetics of collision of sub- to millimeter gas bubbles with a hydrophobic graphite surface, and the stability of thin liquid film formed between the bubble and surface is affected by an adsorbed layer of guar gum. EXPERIMENTS: A combination of gravimetric (quartz crystal microbalance with dissipation) and imaging (atomic force microscopy) techniques was used to investigate the adsorption of guar gum on graphite surface, while high-speed camera imaging allowed for direct observation of the bubble collision process with guar gum-modified graphite surfaces with millisecond resolution. FINDINGS: Atomic force microscope topography images revealed a guar gum concentration-dependent interconnected network of guar gum molecules adsorbed at graphite surface. These adsorbed molecules at low surface coverage, changed the wettability of the graphite surface, resulting in a film drainage time longer by an order of magnitude, while at higher surface coverage successfully prevented bubble attachment to the graphite surface. Most importantly, the adsorbed layer changed the strength of the bubble's bouncing off the graphite surface. This enhanced bubble bouncing can be correlated with the film drainage time and used to predict a successful bubble-particle attachment.

The relationship between Empathy and listening styles is complex: implications for doctors in training.

BACKGROUND: Effective communication is the key to a successful relationship between doctors and their patients. Empathy facilitates effective communication, but physicians vary in their ability to empathize with patients. Listening styles are a potential source of this difference. We aimed to assess empathy and listening styles among medical students and whether students with certain listening styles are more empathetic. METHODS: In this cross-sectional study, 97 medical students completed the Jefferson scale of Empathy (JSE) and the revised version of the Listening Styles Profile (LSP-R). The relationship between empathy and listening styles was assessed by comparing JSE scores across different listening styles using ANOVA in SPSS software. A p-value less than 0.05 was considered significant. RESULTS: Overall, the students showed a mean empathy score of 103 ± 14 on JSE. Empathy scores were lower among clinical students compared to preclinical students. Most of the medical students preferred the analytical listening style. The proportion of students who preferred the relational listening style was lower among clinical students compared to preclinical students. There was no significant relationship between any of the listening styles with empathy. CONCLUSION: Our results do not support an association between any particular listening style with medical students' empathic ability. We propose that students who have better empathetic skills might shift between listening styles flexibly rather than sticking to a specific listening style.

Macroscale superlubricity induced by film-forming polymer brush-grafted colloidal additives.

HYPOTHESIS: Modifying surfaces with concentrated polymer brushes (CPBs) is an effective way to reduce friction of tribo-pairs lubricated with liquids. We investigate the hypothesis that colloids grafted with CPBs (hybrid colloids) can deposit onto tribo-substrates by varying the solvent quality with respect to the polymer, in order to obtain ultra-low coefficients of friction (CoFs), so-called superlubricity. EXPERIMENTS: Hybrid colloids are synthesized and characterized, and a dynamic light scattering compares their swellings in aqueous solutions of glycerol or polyethylene glycol. A mini-traction machine with viscoelastic tribo-pairs is used for lubrication experiments. Adsorption of colloids and film structures are tested using a quartz crystal microbalance and an atomic force microscope. FINDINGS: The solvent controls whether hybrid colloids spontaneously adsorb to the substrate under quiescent conditions or require contact forces to enable (tribo-)deposition. In both cases, the friction in the boundary-mixed lubrication regimes is lower upon increasing the degree of swelling of CPBs and upon increasing coverage of deposited colloids. The greatest lubrication enhancement and surface coverage occur for the spontaneously adsorbed colloids, with ultra-low CoFs of order 10-3 over a large range of speeds. The results demonstrate the potential for hybrid colloids to be used as solvent dispersible "friction modifier additives".