Physics Colloquia

Spring 2018  (Fridays 2:00 PM in SE 319) For more information contact Shianne Noel

Date Speaker Title
Jan 26 J.B. Sokoloff A Proposed Mechanism for the Difference in the Radius Dependence of Water Flow through Carbon and Boron Nitride Nanotubes
Feb 23 Dr. Ted von Hippel  White Dwarfs, Gaia, and The Age of the Galaxy
     

Colloquium Abstracts

A Proposed Mechanism for the Difference in the Radius Dependence of Water Flow through Carbon and Boron Nitride Nanotubes

J.B. Sokoloff  (Northeastern University)

Falk, et. al., proposed a mechanism that qualitatively explains the large dependence on the tube radius of the slip length and permeability of water flowing through carbon nanotubes. Despite the fact that boron nitride nanotubes have a crystal structure that is similar that of carbon nanotubes, such large radius dependence of the slip length and permeability on tube radius is not observed in boron nitride nanotubes. The enhancement of the slip length and permeability when the radius reaches 15nm, which is much larger than the size of a water molecular and atomic spacing in the tube wall in carbon, but not boron nitride nanotubes, observed by Secchi, et. al., can be accounted for by a reduction in the contribution to the friction from electron excitations in the wall as the radius decreases, resulting from the dependence of the electron energy band gap on the tube radius.

White Dwarfs, Gaia, and The Age of the Galaxy

Dr. Ted von Hippel (Embry Riddle Aeronautical University)

What is the star-formation history of the Milky Way? How old are Galactic halo and thick disk stars? Traditional age-dating of stars relies on clusters, which only offer a limited view of these stellar populations. I will show that white dwarf stars offer a way forward. Specifically, I will show how optical and near-IR photometry, Gaia astrometry, and a Bayesian modeling approach allows us to determine precision ages (within 2%-5%) for individual white dwarfs and derive population ages.