Physics Colloquium

Fall 2015

Thursdays 4:00 p.m., Room 104 Physics
Refreshments served at 3:40 p.m.
Colloquium organizer: Daniel Fischer
(Link to main colloquium page)

Green - open date
Yellow - tentative (reserved)
Red - firm commitment

Date Speaker/Title
Sept. 3 tba
Sept. 10 John Rogers (University of Illinois, Urbana-Champaign)
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Title: Semiconductor Nanomaterials for Transient Electronics and 3D Circuits
Abstract: A remarkable feature of modern integrated circuit technology is its ability to operate in a stable fashion, with almost perfect reliability. Recently developed classes of electronic materials create an opportunity to engineer the opposite outcome, in the form of devices that can dissolve completely in water to yield completely benign end products. The enabled applications include zero-impact environmental monitors, 'green' consumer electronics and bio-resorbable biomedical implants - none of which can be achieved with technologies that exist today. In this talk, we will describe foundational concepts in materials science and assembly processes for these types of systems, in 1D, 2D and 3D architectures. Bioresorbable, wireless sensors of intracranial temperature and pressure for treatment of traumatic brain injury provide application examples in biomedicine.
Host: Dan Waddill
Sept. 17 Artem Rudenko (Kansas State University, Manhattan)
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Abstract: tbd
Host: Daniel Fischer
Sept. 24 tba
Oct. 1 Peter Mueller (Argonne National Laboratory)
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Title: Searching for "New Physics" at the micro-Kelvin Scale
Abstract: Where is the "New Physics" hiding? The cosmos appears full of it; in the lab we must be looking high and low. Precision tests of fundamental symmetries and interactions at low energies (eV) complement searches for physics beyond the Standard Model at high-energy (TeV) facilities such as the LHC. In the low-energy regime, certain radioactive isotopes have unique properties that can isolate or enhance telltale signs of new physics. Preparing and manipulating these rare isotopes with laser light in neutral atom traps at micro-Kelvin temperatures offers extraordinary control of the atoms external and internal degrees of freedom - ideal conditions for precision measurements. I will present experimental efforts using these techniques at the Physics Division at Argonne. They concern a search for a permanent electric dipole moment of the isotope radium-225 that would indicate sources of time-reversal violation beyond the Standard Model, and a study of the beta-decay of helium-6 to search for exotic couplings in the weak interaction.
Host: Daniel Fischer
Oct. 8 tba
Oct. 15 tba
Oct. 29 Fateme Rezaei (MS&T)
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Title: CO2 Capture on Amine-Functionalized Polymer Hollow Fiber Sorbents in Rapid Temperature Swing Adsorption
Abstract: The use of novel polymeric hollow fibers loaded with silica supported amine sorbents in rapid temperature swing adsorption (RTSA) has been recently demonstrated as a practical approach for scaling up post-combustion CO2 capture. Hollow fiber sorbent contactors function as a "nanoscopic heat exchangers", where flue gas is fed through the shell-side of fiber module and heating/cooling media is fed through the bore. The unique structure of the porous hollow fiber sorbent allows coupling of efficient heat transfer with effective gas contacting, achieving essentially isothermal sorption while providing a lower parasitic load compared to a traditional fixed bed process. In this work, we report the synthesis and application of cellulose acetate/silica supported amine hollow fiber sorbents that demonstrate high dynamic CO2 capacities under dry and wet operation conditions. For amine-based hollow fiber sorbents to be useful in practical CO2 capture applications, it is crucial to exhibit a stable performance and a long lifetime in the presence of flue gas impurities. The stability of amine-functionalized fibers in the presence of SOx and NOx impurities were also evaluated by performing cyclic runs. Deactivated fibers were regenerated via post-spinning amine infusion, allowing recovery of the full sorption capacity of fiber sorbents after deactivation due to oxidation or poisoning by SO2 or NO2. Furthermore, the numerical simulation of cyclic RTSA operation is presented here. The potential for significant savings in terms of energy, capital and operational costs exists with this scalable CO2 capture technique based on polymer/silica supported amine fiber sorbents.
Host: Cihan Kurter
Nov. 5 Giovanni Vignale (University of Missouri, Columbia)
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Title: Many-body effects in graphene
Abstract: The peculiar band structure of graphene, coupled with electron-electron interactions, is responsible for the breakdown of the Fermi liquid concept in the undoped material. Interesting many-body effects are also predicted to occur in doped graphene layers, where the Fermi liquid picture still applies with an enhanced Fermi velocity. In this talk I review some of these effects, which should be observable in optical and infrared spectroscopies, magnetic susceptibility measurement, and thermal transport measurements. Due to the lack of Galilean invariance, both the plasmon frequency and the Drude weight in the optical conductivity are enhanced relative to the conventional RPA values. The orbital magnetic susceptibility, which vanishes in the free-electron approximation, is found to be positive, i.e. paramagnetic, with a value that is completely controlled by the electron-electron interaction. The quasiparticle lifetime is long and leads to a large electronic component of the thermal conductivity, which strongly violates the Wiedemann-Franz law. I review these theoretical predictions vis-a-vis the current state of the experiment.
Host: Cihan Kurter
Nov. 12 Thomas Vojta (MS&T)
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Nobel Prize Colloquium
Abstract: tbd
Nov. 19 Bernold Feuerstein (European Severe Storms Laboratory (ESSL) / MPIK, Heidelberg)
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Title: Tornado and Severe Weather Research in Europe
Abstract: Ingredient based theory of convective storms relies on the fact that the atmosphere follows the same laws of physics anywhere and anytime on this planet - i. e. it does not care about the geography nor the calendar. Once the ingredients are present, (severe) local weather events will be the consequence. In Europe, the total damage due to severe convective storms amounts 6 to 10 billion U.S. dollars per year. The talk will give an overview on tornado and severe weather research in Europe with special emphasis on the European Severe Weather Database (ESWD) operated by the ESSL. Starting with some historical remarks, exemplary case studies will be presented and recent results for the tornado climatology of Europe based on ESWD data will be discussed.
Host: Daniel Fischer
Dec. 3 Paul Rulis (University of Missouri, Kansas City)
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Title: Amorphous molecular solids: Modeling and Fabrication Challenges
Abstract: The problem of designing materials with advanced functional properties is a grand technological challenge with exceptional implications. Amorphous molecular solids form an application-rich material class that are increasingly becoming targets for design because their large number of degrees of freedom provides flexibility in achieving multi-functionality as well as a widely tunable range of properties. One of the challenges to modeling amorphous solids is that they exist in any number of metastable configurations which depend strongly on fabrication process and experimental environment. Modeling methods must somehow attempt to capture this complexity, including the connection between sample history and the particular structural variant associated with a given potential energy minimum. A successful modeling method must account for the existence of complex substructures that must somehow be retained in the final model as well as the huge number of variants possible as a result of variable starting components and non-equilibrium growth conditions. This talk will explore the challenges associated with modeling amorphous molecular solids and some of the potential methods that may be used to overcome them.
Host: Julia Medvedeva
Dec. 10 Schearer Prize Competition