When small particles (e.g., flour, pollen, etc.) come in contact with a liquid surface, they immediately disperse. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. This explosive dispersion is the consequence of capillary force pulling particles into the interface causing them to accelerate to a relatively large velocity. The maximum velocity increases with decreasing particle size; for nanometer-sized particles (e.g., viruses and proteins), the velocity on an air-water interface can be as large as Ϸ47 m/s. We also show that particles oscillate at a relatively high frequency about their floating equilibrium before coming to stop under viscous drag. The observed dispersion is a result of strong repulsive hydrodynamic forces that arise because of these oscillations.adsorption ͉ capillarity ͉ fluid-fluid interfaces ͉ monolayers T he following experiment can be easily performed in any reasonably well-equipped kitchen. Fill a dish partially with water, wait for a few minutes for the water to become quiescent, and then sprinkle a small amount of wheat or corn flour onto the water surface. The moment the flour comes in contact with the surface it quickly disperses into an approximately circular shaped region, forming a monolayer of dispersed flour particles on the surface (Fig. 1A). The interfacial forces that cause this sudden dispersion of flour particles are, in fact, so strong that a few milligrams of flour sprinkled onto the surface almost instantaneously covers the entire surface of the water contained in the dish.The above experiment can be performed using other finely granulated powders (e.g., corn flour, salt, sugar, sand, etc.) or even small seeds, such as mustard and sesame seeds and pollen (Fig. 1B). The tendency of powders to disperse, however, varies. The fact that salt and sugar dissolve in water is not important in this experiment, because the dispersion occurs at a time scale that is much smaller than the time taken by particles to dissolve. Also, the speeds with which particles disperse increases with decreasing size.In 2003, we did experiments on the migration of small particles sprinkled onto a liquid surface. When sand was sprinkled on water in a Petri dish, it first dispersed violently at large speeds, which was followed by a phase that was dominated by attractive lateral capillary forces during which particles slowly came back to form monolayer clusters. The same dynamics were observed for more viscous liquids except that the dispersion speeds were smaller. The fluid dynamics of the attractive phase are well understood (1-7), but to our knowledge, there is no mention in the past studies of the initial violent dispersion despite the fact that this dispersion is ubiquitous, and occurs for many common liquids and particles. ResultsVertical Acceleration of a Particle. In this article, our focus is on the first (dispersive) phase. We show that when a particle comes in contact with a liquid surface, it experiences...
Background The illness script method employs a theoretical outline (e.g., epidemiology, pathophysiology, signs and symptoms, diagnostic tests, interventions) to clarify how clinicians organized medical knowledge for clinical reasoning in the diagnosis domain. We hypothesized that an educational intervention based on the illness script method would improve medical students’ clinical reasoning skills in the diagnosis domain. Methods This study is a randomized controlled trial involving 100 fourth-year medical students in Shiraz Medical School, Iran. Fifty students were randomized to the intervention group, who were taught clinical reasoning skills based on the illness script method for three diseases during one clinical scenario. Another 50 students were randomized to the control group, who were taught the clinical presentation based on signs and symptoms of the same three diseases as the intervention group. The outcomes of interest were learner satisfaction with the intervention and posttest scores on both an internally developed knowledge test and a Script Concordance Test (SCT). Results Of the hundred participating fourth-year medical students, 47 (47%) were male, and 53 (53%) were female. On the knowledge test, there was no difference in pretest scores between the intervention and control group, which suggested a similar baseline knowledge in both groups; however, posttest scores in the intervention group were (15.74 ± 2.47 out of 20) statistically significantly higher than the control group (14.38 ± 2.59 out of 20, P = 0.009). On the SCT, the mean score for the intervention group (6.12 ± 1.95 out of 10) was significantly higher than the control group (4.54 ± 1.56 out of 10; P = 0.0001). Learner satisfaction data indicated that the intervention was well-received by students. Conclusion Teaching with the illness script method was an effective way to improve students’ clinical reasoning skills in the diagnosis domain suggested by posttest and SCT scores for specific clinical scenarios. Whether this approach translates to improved generalized clinical reasoning skills in real clinical settings merits further study.
Chylothorax is an unusual cause of pleural effusion, typically caused by trauma or malignancy. Waldenstrom’s macroglobulinaemia (WM) is a clinicopathological entity demonstrating lymphoplasmacytic lymphoma in the bone marrow with an IgM monoclonal gammopathy in the blood. Recurrent chylous effusions are often resistant to conservative treatment and may require surgical intervention. We present a unique case of a 50-year-old woman with recurrent chylothorax secondary to WM that completely resolved with ibrutinib therapy. To our knowledge, this is the eighth such case reported in literature and the first case of successful resolution of chylothorax with monoclonal antibody therapy.
Some internal medicine residency program directors have expressed concerns that their third-year residents may have been subjected to inappropriate communication during the 2016 fellowship recruitment season. The authors sought to study applicants’ interpersonal communication experiences with fellowship programs. Many respondents indicated that they had been asked questions that would constitute violations of the National Residency Matching Program (NRMP) Communications Code of Conduct agreement, including how they plan to rank specific programs. Moreover, female respondents were more likely to have been asked questions during interview experiences about other programs to which they applied, and about their family plans. Post-interview communication policies were not made clear to most applicants. These results suggest ongoing challenges for the internal medicine community to improve communication with applicants and uniform compliance with the NRMP communications code of conduct during the fellowship recruitment process.
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