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This Weeks Colloquium: Andy Smith, Sept. 27, 2012

Andy Smith
University of Utah

Thursday, Sept. 27, 2012
102 JFB

Refreshments: 3:30 pm in 219 JFB
Lecture 4:00pm (102 JFB)

Title: TeV Gamma-ray Astrophysics: A Window To The Violent Universe

Abstract:

We are currently in the golden age of high energy gamma-ray astrophysics. While only 8 years ago the number of confirmed sources of TeV radiation in the cosmos numbered less than 5, due to the success of the current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs) such as VERITAS, HESS, and MAGIC, the number of catalogued TeV sources now exceeds 150. Due to the energy budget necessary for TeV gamma-ray production, the study of the universe in this regime reveals key information about some of the most exotic and violent objects in the universe such as the cores of AGN, pulsar winds, and supernova remnants. Additionally, gamma-ray astrophysics also stands to make key measurement on the particle physics properties and cosmic distribution of particle dark matter. In this talk I will review the detection technique used by ground based gamma-ray observatories and survey the most important results from the recent generation of IACTs. I will highlight the contributions of UU Physics and Astronomy in the recent progress of this field as well as illustrating our departments outlook for contributing to VERITAS, HAWC, and the next generation Cherenkov Telescope Array (CTA). CTA is expected to come on-line by the end of the decade and to significantly extend and expand the field of TeV astronomy by utilizing an array of over 50 telescopes.

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Zayd Ma Thesis Defense 09/25/12

Thesis Defense

Zayd Ma

Tuesday, September 25, 2012
10:00am (110 INSCC)

Title: The fundamental physics of spin-exchange optical pumping (SEOP) and a few applications of the resultant hyperpolarized 129Xe

Abstract:

This thesis is focused on the fundamental physics of spin-exchange optical pumping (SEOP) and a few applications of the resultant hyperpolarized 129Xe.

During SEOP, noble-gas and Rb atoms repeatedly collide. During these collisions the Rb valence-electron wavefunction overlaps with the noble-gas nucleus and if either the noble-gas nucleus or Rb electron are highly spin-polarized then the other will experience, on average, a small additional magnetic field that will manifest itself as a shift in the Larmor frequency. The size of the frequency shift is proportional to the magnetization of the polarized atoms and consequently can be used to perform polarimetry. Pulsed NMR was used to measure 3He and 129Xe Larmor frequency shifts, and optically detected continuous-wave electron paramagnetic resonance (EPR) was used to monitor the 87Rb hyperfine transition frequencies.

A successful calibration of the size of the frequency shift due to 129Xe-Rb collisions was done and, using this calibration, initial 129Xe polarimetry data was acquired by monitoring the 87Rb EPR frequency as a function of Xe concentration. The 129Xe polarimetry results were inconclusive due to an unexplained result regarding the sign of the frequency shift, however extensive progress was made in understanding the systematics associated with this type of measurement.

Hyperpolarized 129Xe from the Utah flow-through polarizer was also used in a biological application. The Larmor frequency of dissolved hyperpolarized 129Xe was used to detect and characterize the binding of Xe to wild-type and several mutations of bovine pancreatic trypsin inhibitor (BPTI) protein. In addition to hyperpolarized 129Xe NMR, 1H and 15N heteronuclear single quantum coherence (HSQC) NMR was done on Y23A BPTI in the presence of dissolved Xe. The results confirmed the existence of Xe binding to the cavity in Y23A and were consistent with the hypothesis that smaller cavities lead to bigger 129Xe chemical shifts.

Full program available here (PDF).

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This Week's Colloquium: Saveez Saffarian, Sept. 20, 2012

Saveez Saffarian
University of Utah

Thursday, Sept 20, 2012
102 JFB

Refreshments: 3:30 pm in 219 JFB
Lecture 4:00pm (102 JFB)

Title: Biophysics of Enveloped Virus Assembly

Abstract:

In this talk I will show how an enveloped virus is practically a well packaged nano-machine that is optimized for delivery of a genome and maximum replication in the host. Viruses are varied in size and shape but are generally below 200nm in size. They also spend a good portion of their life cycle outside of the living cells. To prepare for the long exile and re entry to the new host, viruses package their proteins very meticulously. It is this packaging process that is the main focus of the research in my lab and I will highlight a few exotic mechanisms we have found recently that shed light on the complexity of this process.

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This Week's Colloquium: Michael Vershinin, Sept. 13, 2012

Michael Vershinin
University of Utah

Thursday, Sept 13, 2012
102 JFB

Refreshments: 3:30 pm in 219 JFB
Lecture 4:00pm (102 JFB)

Title: Biophysics of Microtubule-Based Molecular Motors

Abstract:

Much of the motion observed in biology originates at a molecular level and can be traced to the functioning of just a few protein types often collectively referred to as molecular motors. The talk will specifically focus on processive microtubule-based motors responsible for most long distance transport inside eukaryotic cells. Such motors can be thought of as standalone mechanochemical machines but must also be understood in their native biological context. At present, neither function has a comprehensive quantitative description. The talk will discuss the challenges in the field, highlight our recent single molecule results contrasting single molecule function of kinesin and dynein motors and discuss their implications for microtubule-based transport in cells. I will also present our early efforts to study motor transport on complex filament networks. In addition, future directions and questions of interest will be briefly discussed.

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