Coalescence of contaminated water drops at an oil/water interface: Influence of micro-particles

The effect of micro-particles and interface aging on coalescence of millimetre-sized water drops with an oil/water interface is studied over long times. The system is not pure and interface contamination grows with time, resulting in a slow but continuous decrease of interfacial tension over time (from 35 to 10 mN/m), which is measured in situ using an original technique. Without added micro-particles, coalescence times are randomly distributed and uncorrelated to drop diameter or interfacial tension. In presence of 10 !m size hollow glass particles at the oil/water interface, coalescence times become more reproducible and show a clear dependence upon drop diameter and interface aging. Results are consistent with a classical drainage model assuming that the critical thickness at which interstitial film ruptures scales as the micro-particle diameter, a result that tends to validate the bridging scenario. Interestingly, the film retraction speed during the coalescence process does not follow theoretical predictions in a planar geometry. High-speed imaging of the retracting film reveals that the hole rim is bending upward while retracting, resulting in a strong slowdown of retraction speed. This is caused by the difference of interfacial tension between oil/drop freshly formed interfaces and the aged oil/water interface

Illumination matters part IV: blackout and whiteout in flexible ureteroscopy - first report on a phenomenon observed by PEARLS

PURPOSE: To date, no study has evaluated effects of varying brightness settings on image quality from flexible ureteroscopes submerged in saline. The aim was to evaluate blackout and whiteout occurrences in an in-vitro kidney calyx model. MATERIAL AND METHODS: We evaluated a series of contemporary flexible ureteroscopes including the Storz Flex-Xc and Flex-X2s, Olympus V3 and P7, Pusen 7.5F and 9.2F, as well as OTU WiScope using a 3D-printed enclosed pink in-vitro kidney calyx model submerged in saline. Endoscopic images were captured with ureteroscope tip placed at 5 mm,10 mm and 20 mm distances. The complete range of brightness settings and video capture modes were evaluated for each scope. Distribution of brightness on a grayscale histogram of images was analyzed (scale range 0 to 255). Blackout and whiteout were defined as median histogram ranges from 0 to 35 and 220 to 255, respectively (monitor image too dark or too bright for the human eye, respectively). RESULTS: Blackout occurred with the P7, Pusen 7.5F, 9.2F and WiScope at all distances, and V3 at 20 mm - with lowest brightness settings. Whiteout occurred with Flex-X2s, V3 and P7 at 5 mm and 10 mm, as well as with V3 and P7 at 20 mm - mostly with highest brightness settings. The Flex-Xc had neither blackout nor whiteout at all settings and distances. CONCLUSION: Blackout or whiteout of images is an undesirable property that was found for several scopes, possibly impacting diagnostic and therapeutic purposes during ureteroscopy. These observations form a guide to impact a urologist's choice of instruments and settings

Pulsed thulium:YAG laser-ready to dust all urinary stone composition types? Results from a PEARLS analysis.

PURPOSE To evaluate whether stone dust can be obtained from all prevailing stone composition types using the novel pulsed thulium:YAG (p-Tm:YAG), including analysis of stone particle size after lithotripsy. METHODS Human urinary stones of 7 different compositions were subjected to in vitro lithotripsy using a p-Tm:YAG laser with 270 µm silica core fibers (Thulio$^{®}$, Dornier MedTech GmbH$^{®}$, Wessling, Germany). A cumulative energy of 1000 J was applied to each stone using one of three laser settings: 0.1 J × 100 Hz, 0.4 J × 25 Hz and 2.0 J × 5 Hz (average power 10 W). After lithotripsy, larger remnant fragments were separated from stone dust using a previously described method depending on the floating ability of dust particles. Fragments and dust samples were then passed through laboratory sieves to evaluate stone particle count according to a semiquantitative analysis relying on a previous definition of stone dust (i.e., stone particles ≤ 250 µm). RESULTS The p-Tm:YAG laser was able to produce stone dust from lithotripsy up to measured smallest mesh size of 63 µm in all seven stone composition types. Notably, all dust samples from all seven stone types and with all three laser settings had high counts of particles in the size range agreeing with the definition stone dust, i.e., ≤ 250 µm. CONCLUSION This is the first study in the literature proving the p-Tm:YAG laser capable of dusting all prevailing human urinary stone compositions, with production of dust particles ≤ 250 µm. These findings are pivotal for the broader future implementation of the p-Tm:YAG in clinical routine

Global description of crack propagation in ceramics

International audienceThe subject of crack propagation in brittle materials is sometimes confusing, since many terms or concepts are not always clearly defined, as toughness, sub-critical crack propagation, threshold, R-curve, etc. However, crack propagation can be simply and rigorously analysed by considering the equilibrium point in terms of energy release rate, as defined by the Griffith criteria, based on fundamentals of physics. The departure from this equilibrium leads to crack velocities related to dissipative mechanisms. Reinforcement mechanisms of any type can shift the equilibrium towards higher driving force values, giving an increase of crack resistance. The degradation of this reinforcement, as the case of cyclic fatigue, simply reduces the resistance to propagation. The total description of the behaviour is therefore included in the crack velocity-energy release rate (v - G) graph. However, the major point is the equilibrium, because in addition to its theoretical importance, it is of practical interest for brittle materials, since it corresponds to an energy value below which no propagation occurs

Thermodynamic study of the ternary system LiCl-Li2CO3-H2O

National audienc

Thermodynamic study of the ternary system LiCl-Li2CO3-H2O

National audienc