On the transferability of ion parameters to the TIP4P/2005 water model using molecular dynamics simulations

Countless molecular dynamics studies have relied on available ion and water force field parameters to model aqueous electrolyte solutions. The TIP4P/2005 model has proven itself to be among the best rigid water force fields, whereas many of the most successful ion parameters were optimized in combination with SPC/E, TIP3P, or TIP4P/Ew water. Many researchers have combined these ions with TIP4P/2005, hoping to leverage the strengths of both parameter sets. To assess if this widely used approach is justified and to provide a guide in selecting ion parameters, we investigated the transferability of various commonly used monovalent and multivalent ion parameters to the TIP4P/2005 water model. The transferability is evaluated in terms of ion hydration free energy, hydration radius, coordination number, and self-diffusion coefficient at infinite dilution. For selected ion parameters, we also investigated density, ion pairing, chemical potential, and mean ionic activity coefficients at finite concentrations. We found that not all ions are equally transferable to TIP4P/2005 without compromising their performance. In particular, ions optimized for TIP3P water were found to be poorly transferable to TIP4P/2005, whereas ions optimized for TIP4P/Ew water provided nearly perfect transferability. The latter ions also showed good overall agreement with experimental values. The one exception is that no combination of ion parameters and water model considered here was found to accurately reproduce experimental self-diffusion coefficients. Additionally, we found that cations optimized for SPC/E and TIP3P water displayed consistent underpredictions in the hydration free energy, whereas anions consistently overpredicted the hydration free energy.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Complex Fluid ProcessingEngineering Thermodynamic

Erlernen der chirurgischen Knoten- und Nahttechnik - Effekte verschiedener Trainingsformen in einer kontrolliert-randomisierten Studie mit Studierenden der Zahnmedizin

Objective: The acquisition of surgical skills requires motor learning. A special form of this is intermanual transfer by transferring motor skills from the nondominant hand (NDH) to the dominant hand (DH). The purpose of this study was to determine the learning gains that can be achieved for the DH by training with the DH, the NDH, and by non-surgical alternative training (AT).Methods: 124 preclinical (n=62) and clinical (n=62) dental students completed surgical knot tying and suturing technique training with the DH, with the NDH, and an AT in a controlled randomized trial. Results: A statistically significant learning gain in knot tying and suture technique with the DH was evident only after training with the DH when compared to training with the NDH (p=4 OSATS points, 46.4% (n=32) benefited in their knot tying technique with the DH from training with the DH, 29.0% (n=20) from training with the NDH, and 24.6% (n=17) from an AT while 45.7% (n=32) benefited in their suturing technique with the DH from training with the DH, 31.4% (n=22) from training with the NDH, and 22, 9% (n=16) from an AT.Conclusions: Training with the DH enabled significantly better learning gains in the surgical knot tying and suturing techniques with the DH.Zielsetzung: Der Erwerb chirurgischer Fertigkeiten erfordert motorisches Lernen. Eine Sonderform davon ist der intermanuelle Transfer durch Übertragung motorischer Fertigkeiten von der nicht-dominanten Hand (NDH) auf die dominante Hand (DH). Mit Hilfe dieser Studie sollte ermittelt werden, welcher Lernzuwachs durch ein Training mit der DH, der NDH und durch ein nicht-chirurgisches, alternatives Training (AT) für die DH erzielt werden kann.Methodik: 124 Studierende des vorklinischen (n=62) und des klinischen Studienabschnitts (n=62) der Zahnmedizin absolvierten ein Training der Naht- und Knotentechnik mit der DH, mit der NDH und ein AT in einer kontrolliert randomisierten Studie. Ergebnisse: Ein statistisch signifikanter Lernzuwachs in der Knoten- und Nahttechnik mit der DH zeigte sich nur nach dem Training mit der DH im Vergleich zum Training mit der NDH (p=4 Punkte) profitierten 46,4% (n=32) von einem Training mit der DH, 29,0% (n=20) von einem Training mit der NDH und 24,6% (n=17) von einem AT. Bei der Nahttechnik mit der DH profitierten 45,7% (n=32) von einem Training mit der DH, 31,4% (n=22) von einem Training mit der NDH und 22, 9% (n=16) von einem AT.Schlussfolgerungen: Ein Training mit der DH zeigte einen statistisch signifikanten Lernzuwachs bei der chirurgischen Knoten- und Nahttechnik mit der DH

Preferential Adsorption in Mixed Electrolytes Confined by Charged Amorphous Silica

Preferential ion adsorption in mixed electrolytes plays a crucial role in many practical applications, such as ion sensing and separation and in colloid science. Using all-atom molecular dynamics simulations of aqueous NaCl, CaCl2, and NaCl-CaCl2 solutions confined by charged amorphous silica, we show that Na+ ions can adsorb preferentially over Ca2+ ions, depending on the surface structure. We propose that this occurs when the local surface structure sterically hinders the first hydration shell of the Ca2+ ion. Introducing a protrusion metric as a function of protrusion of deprotonated silanols, ion-specificity is successfully predicted on isolated, vicinal, and geminal silanols alike, provided that no other deprotonated silanols are found nearby. Furthermore, we introduce a new strategy to analyze the results as a function of distance from the surface. This approach effectively removes surface roughness effects allowing for direct comparison with classical electric double layer theory and distinction of specifically adsorbed ions and electrostatically adsorbed ions.Complex Fluid ProcessingEngineering Thermodynamic