Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Acute kidney injury biomarkers: renal angina and the need for a renal troponin I

Acute kidney injury (AKI) in hospitalized patients is independently associated with increased morbidity and mortality in pediatric and adult populations. Continued reliance on serum creatinine and urine output to diagnose AKI has resulted in our inability to provide successful therapeutic and supportive interventions to prevent and mitigate AKI and its effects. Research efforts over the last decade have focused on the discovery and validation of novel urinary biomarkers to detect AKI prior to a change in kidney function and to aid in the differential diagnosis of AKI. The aim of this article is to review the AKI biomarker literature with a focus on the context in which they should serve to add to the clinical context facing physicians caring for patients with, or at-risk for, AKI. The optimal and appropriate utilization of AKI biomarkers will only be realized by understanding their characteristics and placing reasonable expectations on their performance in the clinical arena

Low-velocity impact behavior of Al 6061/SiC particulate metal matrix composites

This study addresses the effects of impact velocity (impact energy) and particle volume fraction and particle size on the impact behavior of particle-reinforced metal matrix composites (Al 6061/SiC). Their effects on the contact force and plastic dissipation histories, the residual stress, and plastic strain distributions were also analyzed. The impact velocity and particle volume fraction and particle size were found to have a significant effect. The contact forces and durations increased significantly with increasing impact velocity. The predicted peak contact forces were in minimal errors for lower impact velocities, whereas the predicted impact durations were slightly longer. The composite structures become stiffer when the particle volume fraction is increased. Consequently, the contact force was increased, whereas the impact durations were shortened. However, a larger particle size resulted in lower contact forces, but longer impact durations. Particle reinforced composites can dissipate more kinetic energy in case the particle volume fraction decreases and the particle size increases. Increasing impact velocity and particle volume fraction increased residual stress levels and the plastic strain. Increasing the particle size resulted in the residual stress distributions to become non-uniform but increases in the plastic deformations.This study addresses the effects of impact velocity (impact energy) and particle volume fraction and particle size on the impact behavior of particle-reinforced metal matrix composites (Al 6061/SiC). Their effects on the contact force and plastic dissipation histories, the residual stress, and plastic strain distributions were also analyzed. The impact velocity and particle volume fraction and particle size were found to have a significant effect. The contact forces and durations increased significantly with increasing impact velocity. The predicted peak contact forces were in minimal errors for lower impact velocities, whereas the predicted impact durations were slightly longer. The composite structures become stiffer when the particle volume fraction is increased. Consequently, the contact force was increased, whereas the impact durations were shortened. However, a larger particle size resulted in lower contact forces, but longer impact durations. Particle reinforced composites can dissipate more kinetic energy in case the particle volume fraction decreases and the particle size increases. Increasing impact velocity and particle volume fraction increased residual stress levels and the plastic strain. Increasing the particle size resulted in the residual stress distributions to become non-uniform but increases in the plastic deformations.</p

Measurement of Internal Residual Strain Gradients in Metal Matrix Composites Using Synchrotron Radiation

Low density titanium based metal matrices combined with high strength and stiffness ceramic fibers are under widespread investigation for possible use in high temperature aerospace applications [1]. Inherent in the processing of these composite materials are the residual stresses resulting from the thermal expansion coefficient mismatch between the fiber and matrix. A tensile hoop and a compressive radial stress result upon cooling from the consolidation temperature because the fiber has a smaller expansion coefficient [2]. The thermal stresses can be very large and may exceed the matrix yield or even fracture stress [3]