Your textbook is still wrong about the Milky Way galaxy

Fifteen years ago, we modeled the distribution of stars in the Milky Way

using three components: an exponential disk, a power law spheroid, and a

bulge.  Then, we discovered the distribution of stars in the spheroid

was lumpy due to the accretion and tidal disruption of dwarf galaxies

that ventured too close the the Galactic center.  We now wonder whether

the Milky Way has a classical bulge at all; likely the bulge-like

feature we see is instead due to the Galactic bar.  And most recently,

we are discovering large scale departures from the standard exponential

disk.  New discoveries point to variations in the expected bulk

velocities of stars in the Galactic disk, and oscillations in the

spatial densities of disk stars.  Some believe these observations point

to a wave response to the passing of dwarf galaxies (or dark matter

lumps) through the Milky Way's disk.  These waves may also explain the

observed rings of stars, 15-25 kpc from the Galactic center, which is

farther out than we originally believed the disk to extend.

Refreshments will be served in CP 179 at 3:15 PM

Date:
-
Location:
CP155
Event Series:
Physics and Astronomy Colloquium

In situ X-ray Studies of Functional Oxides for Energy Systems

Functional oxides and their interfaces offer new opportunities to overcome the 
current limits of energy storage and conversion systems, e.g., water dissociation 
and formation. However, the understanding of complex oxide interfaces and 
their electrochemical properties is far from complete, particularly with regard to 
electronic and ionic dynamics occurring in aqueous solutions or ionic liquids under 
applied electric fields. To elucidate the physical and electrocatalytic properties 
of oxide surfaces and interfaces, it is necessary to build a model system and to 
employ in situ experimental tools to detect and analyze the complex time-dependent 
phenomena. In this talk, I will introduce recent in situ synchrotron studies [1,2] 
conducted at Argonne National Laboratory that combine structural, spectroscopic, 
and electrochemical characterization on model systems, e.g., epitaxial perovskite 
or layered oxide thin films. With this methodology, we can determine both the 
reactivity and stability of active sites on complex oxide surfaces during water 
dissociation and formation. This approach offers much needed insight into the 
electrocatalytic properties of oxide interfaces and provides new strategies for the 
creation of new stable and active energy materials designed at the atomic level. 
 
[1] S. H. Chang et al., ACS Nano 8, 1584 (2014). 
[2] S. H. Chang et al., Nature Commun. 5, 4191 (2014).
Date:
-
Location:
CP179
Event Series:
Condensed Matter Seminar
Subscribe to