Visualization of Convection Patterns Near an Evaporating Meniscus using micro-PIV

Experimental visualizations of the three dimensional (3D) convection patterns generated near an evaporating meniscus in horizontally oriented capillary tubes are presented. These patterns are caused due to the differential evaporation along the meniscus. In this study, transparent capillary tubes with refractive index close to that of the evaporating liquid were used to minimize refraction effects and obtain velocity vectors near the walls. Polystyrene fluorescent particles of 0.5 lm diameter suspended in methanol were used to make the measure- ments in tubes of 75, 200 and 400 lm diameter. For the 75 lm tube, gravity was observed to have no effect on the flow patterns and an axisymmetric counter-rotating vortex pair was present along the horizontal and vertical center planes, suggesting the presence of a toroidal vortex near the meniscus. With an increase in tube size, buoyancy effects became apparent as the axisymmetric pattern broke down. A counter-rotating symmetric vortex pair was observed in the horizontal center plane, whereas in the vertical center plane, a single vortex dominated the flow and pushed the secondary vortex to a corner. Particle streak and lPIV images were obtained in multiple horizontal planes and a vertical center plane to understand this 3D flow behavior

Isolated Central Sulcus Hemorrhage: A Rare Presentation Most Frequently Associated with Cerebral Amyloid Angiopathy

Central sulcus hemorrhage is a rare imaging finding that can be related to cerebral amyloidosis in a normotensive non-traumatic elderly patient and present as an isolated finding or in association with other areas of involvement. We report a case presenting with an isolated central sulcus hemorrhage on computed tomography. Further imaging work-up excluded other potential causes of peripheral hemorrhages and established a putative diagnosis of cerebral amyloidosis

Celiac Artery Stenting to Facilitate Hepatic Yttrium-90 Radioembolization Therapy

Radioembolization offers a novel way to treat the nonresectable, liver predominant hepatic malignancies with better tumor response and overall progression-free survival rates. Transarterial catheter-based radioembolization procedure involves the hepatic arterial administration of glass- or resin-based beta emitting Yttirum-90 microspheres. Safe delivery of the tumoricidal radiation dose requires careful angiogram planning and coil embolization to quantify lung shunting and prevent systemic toxicity, respectively. Diagnostic pretreatment angiogram also serves to identify the hepatic arterial variant anatomy and other coexisting pathologies that might require a different or alternative approach. We describe a complex case of celiac artery stenosis with tortuous pancreaticoduodenal arterial arcade precluding access to the right hepatic artery for performing radioembolization. Celiac artery stenting of the stenosis was performed to facilitate subsequent safe and successful Yttrium-90 microsphere radioembolization

Experimental investigation of steady buoyant-thermocapillaryconvection near an evaporating meniscus

Micro-particle image velocimetry measurements of the 3D (three-dimensional) convection patterns generated near an evaporating meniscus in horizontally oriented capillary tubes are presented. Analysis of the vapor diffusion away from the meniscus reveals a zone of intense heat flux near the solid-liquid-vapor junction which creates a temperature gradient along the meniscus. This results in a surface tension gradient which, coupled with buoyancy effects, causes buoyant-thermocapillary convection in the liquid film. The relative influence of buoyancy and thermocapillarity on the flow was investigated for tube diameters ranging from 75 to 1575 µm. A transition from a pure 2D thermocapillary flow to a 3D buoyant-thermocapillary flow is observed with an increase in tube diameter. For the 75 µm tube, a symmetrical toroidal vortex is observed near the meniscus. For larger tubes, buoyancy effects become apparent as they dominate the flow field. The high mass fluxes in smaller-diameter tubes drive stronger vortices. Particle streaks and µPIV images obtained in multiple horizontal and vertical planes provide an understanding of this three-dimensional flow behavior. A scaling analysis shows the importance of thermocapillary convection in evaporating menisci