This Week at Physics

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Events on Friday, February 24th, 2012

Special NOON Astronomy Talk
The early Evolution of the Milky Way Satellite Galaxies
Time: 12:00 pm
Place: 4421 Sterling Hall
Speaker: Professor Gerhard Hensler, Institute of Astronomy, University of Vienna
Abstract: The dwarf spheroidal galaxies (dSphs) around the Milky Way (MWG)
belong to the most poorly understood class of astronomical objects
and serve as the most challenging targets of astrophysical researchfor various reasons:
At first, in LCDM cosmology a huge number of subhalos are expected
to surround massive galaxies what is contrasted by the observed number of satellite galaxies around the MWG. In addition, it is debated whether the recently detected ultra-faint dSphs can account for this mismatch.
Secondly, the still at present observable accretion of satellite galaxies by the MWG should have led to the built-up of the Galactic halo and left behind kinematic and chemical witnesses by their stars. Besides that these expected signatures and similarities between halo stars and existing dSphs are not observed, also their spatial distribution and number pose serious questions to our understanding of satellite-galaxy
evolution. To solve these problems numerical simulations from cosmological to galactic scales and semi-analytical galaxy models have been undertaken by numerous authors which will be highlighted, but also critically reviewed here.
New comprehensive approaches will be presented and their results compared with observations.
Host: Professor Emeritus Ed Churchwell
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Theory Seminar (High Energy/Cosmology)
Title to be announced
Time: 2:00 pm
Place: 5280 Chamberlin Hall
Speaker: JiJi Fan, Princeton University
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Physics Department Colloquium
FT-IR spectrochemical imaging: Design and applications with Focal Plane Array and multiple beam synchrotron radiation source
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: Carol Hirschmugl, UW-Milwaukee
Abstract: * This work has been done with support from NSF (MRI-DMR-0619759 and CHE-1112433) and the Synchrotron Radiation Center, which is also supported by NSF (DMR-0537588) and UW-Milwaukee and UW-Madison.

FT-IR spectrochemical imaging, which combines the chemical specificity of mid-infrared spectroscopy with spatial specificity, is an important demonstration of label-free molecular imaging. Mid-infrared optical frequencies are resonant with the vibrational frequencies of functional groups, thus an absorption spectrum is a "molecular fingerprint" of the material at every pixel. Each spectrum can be correlated with known material properties to extract chemical information. Synchrotron based FT-IR spectrochemical imaging, as recently implemented at the Synchrotron Radiation Center in Stoughton, WI, demonstrates the new capability to achieve diffraction limited chemical imaging across the entire mid-infrared region, simultaneously, with high signal to noise ratio.

IRENI (Infrared Environmental Imaging) extracts a large swath of radiation (320 hor. x 25 vert. mrads2) to homogeneously illuminate a commercial IR microscope equipped with an infrared Focal Plane Array (FPA) detector. Wide field images are collected. IRENI rapidly generates high quality, high spatial resolution data. The relevant advantages (spatial oversampling, speed, sensitivity and signal to noise ratio) will be presented and demonstrated using examples from a variety of disciplines, including formalin fixed and flash frozen tissue samples, live cells, fixed cells, paint cross sections, polymer fibers and novel nano-materials will be presented.

M.J. Nasse, et al. "High resolution Fourier-transform infrared chemical imaging with multiple synchrotron beams", Nature Methods, 8, (2011) 413-416

E.C. Mattson, et al. "Evidence of Nanocrystalline Semiconducting Graphene Monoxide During Thermal Reduction of Graphene Oxide in Vacuum," ACS Nano 5, pp 9710-9717

M.Z. Kastyak-Ibrahim, et al. "Biochemical label-free tissue imaging with subcellular -resolution synchrotron FTIR with Focal Plane Array Detector," NeuroImage 60, (2012) 376-383.

Host: Himpsel
Poster: http://www.physics.wisc.edu/twap/posters/2012/2519.pdf
Video: http://www.physics.wisc.edu/vod/2012/02/24.html
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