Cavitation Induction by Projectile Impacting on a Water Jet

The present paper focuses on the simulation of the high-velocity impact of a projectile impacting on a water-jet, causing the onset, development and collapse of cavitation. The simulation of the fluid motion is carried out using an explicit, compressible, density-based solver developed by the authors using the OpenFOAM library. It employs a barotropic two-phase flow model that simulates the phase-change due to cavitation and considers the co-existence of non-condensable and immiscible air. The projectile is considered to be rigid while its motion through the computational domain is modelled through a direct-forcing Immersed Boundary Method. Model validation is performed against the experiments of Field et al. [Field, J., Camus, J. J., Tinguely, M., Obreschkow, D., Farhat, M., 2012. Cavitation in impacted drops and jets and the effect on erosion damage thresholds. Wear 290–291, 154–160. doi:10.1016/j.wear.2012.03.006. URL http://www.sciencedirect.com/science/article/pii/S0043164812000968 ], who visualised cavity formation and shock propagation in liquid impacts at high velocities. Simulations unveil the shock structures and capture the high-speed jetting forming at the impact location, in addition to the subsequent cavitation induction and vapour formation due to refraction waves. Moreover, model predictions provide quantitative information and a better insight on the flow physics that has not been identified from the reported experimental data, such as shock-wave propagation, vapour formation quantity and induced pressures. Furthermore, evidence of the Richtmyer-Meshkov instability developing on the liquid-air interface are predicted when sufficient dense grid resolution is utilised

Nanoscale Impurity Structures on the Surface of dx2−y2d_{x^2-y^2}-wave Superconductors

We study the effects of nanoscale impurity structures on the local electronic structure of $d_{x^2-y^2}$-wave superconductors. We show that the interplay between the momentum dependence of the superconducting gap, the geometry of the nanostructure and its orientation gives rise to a series of interesting quantum effects. Among these are the emergence of a zero bias conductance peak in the superconductor's density of states and the suppression of impurity states for certain nanostructures. The latter effect can be used to screen impurity resonances in the superconducting state.Comment: 4 pages, 5 figure

Impact of Social Mixing on Feedlot Steer Behavior

Angus crossbred steers from two genetically similar sources (n = 48 BCS and n = 48 McG), were transported separately (833.64 ± 85.29 km) 39-d prior to commingling and housed at a feedlot without visual or tactile contact. Steers, blocked by source and d -34 body weight, were randomly assigned to 12 pens (n = 8 steers/pen). Pens housed either: NOMIX—100% from BCS (n=3 pens) or McG (n=3 pens) or MIX—50% from BCS and 50% from McG (n = 6 pens). Video recordings were decoded on d 0, 1, and 2 for the number of agonistic behaviors, allogrooming bouts, and drinking bouts initiated by each steer during the first four hours post-mixing. Rumination behavior was recorded on d 1, 2, and 3 post mixing. Mixed models evaluated the impact of treatment, day, and their interaction on cattle behavior. Orthogonal contrasts compared the impact of source on performance of each behavior and Pearson correlations were used to compare total performance of each behavior throughout the study. NOMIX steers performed more (P = 0.08) drinking bouts (10.54 ± 1.27 bouts/steer/pen) than MIX steers (7.68 ± 1.05 bouts/steer/pen). Steers ruminated less on d 3 (NOMIX: 7.97 ± 0.29 hours/steer/day MIX: 8.06 ± 0.29 h/steer/d) than on d 1 (NOMIX: 8.55 ± 0.29 h/steer/d MIX: 8.22 ± 0.29 h/steer/d) or d 2 (NOMIX: 8.77 ± 0.29 h/steer/d MIX: 8.46 ± 0.29 h/steer/d) across all treatments. Steers in MIX pens (7.81±0.30 h/steer/d) spent more time ruminating than steers in NOMIX pens from McG (7.46±0.47 h/steer/d) than steers in NOMIX pens from BCS (8.39±0.52 h/steer/d). NOMIX pens initiated more (P < 0.01) headbutts overall (1.98 0.13 count/steer/pen) and mounts on d 2 (1.07 0.11 count/steer/pen) than those in MIX pens (1.30 0.18 and 0.39 0.15, respectively). Social mixing reduced agonistic behavior and may cause cattle to take longer to establish social hierarchies. Social mixing also decreases drinking behavior and delays social hierarchy establishment

Pseudomembranous Trigonitis: A Common but Underrecognized Urological Entity

Pseudomembranous trigonitis is the term used to describe squamous metaplastic changes of the bladder trigone, which affect nearly 40% of adult females. We present the characteristics of this underrecognized clinical entity and encourage further relevant research

Cavitation Induction by Projectile Impacting on a Water Jet

Following the work of Field et al. [4], who experimentally visualised cavity formation and shock propagation in impacted liquids at high velocities, the present study focuses on the simulation of the high velocity impact of a solid projectile on a water jet. The undeformable solid projectile is modelled through a direct forcing Immersed Boundary Method. The simulation is carried out using an explicit density based compressible solver, developed by Kyriazis et al. [6], which employs a two-phase flow model and includes phase change. This study gives a better insight on the phenomena following the impact of solids on liquids, including shock propagation and vapour formation, and demonstrates the capabilities of the presented Immersed Boundary Method to handle compressible cavitating flows

A longitudinal study of adolescent Internet addiction: the role of conscientiousness and classroom hostility

Over the last decade, research on Internet Addiction (IA) has increased. However, almost all studies in this area are cross-sectional and do not examine the context in which internet use takes place. Therefore, a longitudinal study examined the role of conscientiousness (as a personality trait) and classroom hostility (as a contextual factor) in the development of IA. The participants comprised 648 adolescents and were assessed over a two-year period (while aged 16–18 years). A three-level hierarchical linear model was carried out on the data collected. Findings revealed that: (i) lower conscientiousness was associated with IA and this did not change over time; and (ii) although being in a more hostile classroom did not initially have a significant effect, it increased girls’ IA vulnerability over time and functioned protectively for boys. Results indicated that the contribution of individual and contextual IA factors may differ across genders and over time. More specifically, although the protective effect of conscientiousness appeared to hold, the over-time effect of classroom hostility increased the risk of IA for girls. These findings are discussed in relation to the psychological literature. The study’s limitations and implications are also discussed

Successful Treatment of Postoperative External Biliary Fistula by Selective Nasobiliary Drainage

A 25-year old man presented with a high output external biliary fistula after an operation for a giant hydatid cyst of the liver. Endoscopic sphincterotomy was inadequate to close the fistula. A nasobiliary tube was selectively inserted into the leaking hepatic duct and bile was continuously aspirated. The fistula and the residual cavity healed completely. Details of the patients' management using this alternative technique, are discussed

Impact of Orthodontic Forces on Plasma Levels of Markers of Bone Turnover and Inflammation in a Rat Model of Buccal Expansion.

Plasma levels of protein analytes might be markers to predict and monitor the kinetics of bone and tissue remodeling, including maximization of orthodontic treatment stability. They could help predict/prevent and/or diagnose possible adverse effects such as bone dehiscences, gingival recession, or root resorption. The objective of this study was to measure plasma levels of markers of bone turnover and inflammation during orthodontic force application in a rat model of orthodontic expansion. Two different orthodontic forces for bilateral buccal expansion of the maxillary arches around second and third molars were applied in 10 rats equally distributed in low-force (LF) or conventional force (CF) groups. Four rats served as the control group. Blood samples were collected at days 0, 1, 2, 3, 6, 13, 21, and 58. Longitudinal concentrations of osteoprotegerin (OPG), soluble receptor activator of nuclear factor kappaB ligand (sRANKL), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor α (TNF), and parathyroid hormone (PTH) were determined in blood samples by a multiplex immunoassay. CF and LF resulted in a significantly maxillary skeletal expansion while the CF group demonstrated significantly higher expansion than the LF group in the long term. Bone turnover demonstrated a two-phase response. During the "early phase" (up to 6 days of force application), LF resulted in more sRANKL expression and increased sRANKL/OPG ratio than the CF and control animals. There was a parallel increase in PTH levels in the early phase in response to LF. During the "late phase" (6-58 days), the markers of bone turnover were stable in both groups. IL-4, IL-6, and IL-10 levels did not significantly change the test groups throughout the study. These results suggest that maxillary expansion in response to different orthodontic forces follows different phases of bone turnover that may be force specific