LaCNS Seminars Fall 2019 

Download app "Viewme" (viewme.ezuce.com) to view live seminars held in 1008B Digital Media Center. Send email to lacns@phys.lsu.edu for log-in information. 

  

Grace StokesFriday, September 13, 2019
12:30 p.m.
206 Williams Hall 

Dr. Grace Stokes (Clare Boothe Luce Assistant Professor, Chemistry & Biochemistry, Santa Clara University), host Gerald Schneider
Title: TBA

Abstract: TBA


  

Margaret ScheinerFriday, September 20, 2019
12:30 p.m.
206 Williams Hall

Dr. Margaret Scheiner (ORISE Program Manager, Oak Ridge Associated Universities), host Gerald Schneider
Title: TBA

Abstract: TBA 


 

Christopher WirthMonday, September 23, 2019
3:00 p.m.
1008B Digital Media Center

Dr. Christopher Wirth (Assistant Professor, Chemical & Biomedical Engineering, Cleveland State University), host Bhuvnesh Bharti
"Measuring the dynamics of colloidal particles with evanescent wave scattering"

Abstract: Our lab is focused on developing experimental, computational, and theoretical techniques for the measurement and interpretation of the dynamics of complex or ‘anisotropic’ colloidal particles in confined geometries. This talk will summarize two vignettes from that work, namely (1) the development of Brownian dynamics simulations (BDS) to predict the probability density of states for anisotropic particles and (2) developing Scattering Morphology Resolved Total Internal Reflection Microscopy (SMR – TIRM) to directly measure such dynamics. First, we used BDS to predict the dynamics of a Janus particle very near a boundary. Data from these simulations were used to evaluate the influence of cap thickness and surface charge mismatch on the rotational dynamics of a single Janus particle very near a boundary. We found the presence of 5 nm - 20 nm thick gold caps had a profound effect on the rotational dynamics of particles with experimentally relevant sizes. Although Janus particles with a diameter less than 1 m behaved as if they were isotropic, Janus particles with diameters larger than 1 m experienced strong rotational quenching. This simulation tool was also utilized to develop methodology for computing the potential energy landscape from observations of position and orientation. In the second part of my talk, I will describe evanescent wave scattering mapping experiments conducted for the development of SMR - TIRM. Data from these mapping experiments on ellipsoidal particles show a strong dependence of the scattering morphology on both the particle orientation and shape. When combined with light scattering simulations from the T-matrix method, this morphology map will provide comprehensive information about the position and orientation of anisotropic particles near a boundary. Such information can be used to formulate the potential energy landscape of the particle, as shown by results from our BDS tool. 


 

Friday, October 4, 2019Margarita Fomina
12:30 p.m.
206 Williams Hall

Dr. Margarita Fomina (Scientist, Oak Ridge Laboratory), host Gerald Schneider
"Lipid droplets in yeast, animal, and human: biophysical insight"

Abstract: All organisms store lipids for metabolic energy. Those lipids accumulate in the form of droplets inside cells. A lipid droplet is made of a hydrophobic lipid core surrounded by a phospholipid shell with associated proteins.

Surprisingly, in comparison with globular proteins, lipid droplets are rarely studied on the microscopic level, despite their vital importance in metabolism and energy storage. We investigated lipid droplets in vivo, revealing their physical properties and composition. Using quasi-elastic neutron scattering, the phase behavior and internal dynamics of lipid droplets affected by temperature were explored for the first time. Using mass spectrometry, the lipid composition of the droplets was obtained. The droplets’ size and volume were estimated via 3D microscopy. We compared the obtained characteristics of lipid droplets located in different types of cells (yeast, animal and human adipose [fat] tissues). As a model lipid system, we referred to a synthetic lipid vesicle.

Our investigation provided unique biophysical insight into natural, intact lipid systems in different organisms. This insight may elucidate the physical mechanisms governing fat cell necrosis induced by low temperatures during cryolipolysis (i.e., clinical treatment to reduce excess fat, or “fat freezing”). The analysis of yeast lipid droplets provided a basis for discussion of their energetic value in relation to their usefulness as biofuels.


 

Mary RobertsFriday, October 11, 2019
12:30 p.m.
206 Williams Hall

Dr. Mary Roberts (Professor, Chemistry, Boston College), host Gerald Schneider
Title: TBA

Abstract: TBA 


 

Zhili Xiao

Monday, October 21, 2019
3:00 p.m.
1008B Digital Media Center

Dr. Zhili Xiao (Argonne National Laboratory/Northern Illinois University), host Rongying Jin
Title: TBA

Abstract: TBA

 


Joshua SangoroFriday, November 22, 2019
12:30 p.m.
206 Williams Hall

Dr. Joshua Sangoro (Assistant Professor, Chemical and Biomolecular Engineering, University of Tennessee, Knoxville), host Gerald Schneider
"Mesoscale Organization and Dynamics in Ionic Liquids"

Abstract: The impact of mesoscale organization on transport and dynamics in ionic liquids is investigated by broadband dielectric spectroscopy and dynamic mechanical spectroscopy as well as x-ray and neutron scattering techniques, complemented by computational approaches. Signatures of slow, sub-α dynamics are identified in the dynamic-mechanical and dielectric spectra and employed to probe lifetimes and dynamics of mesoscale aggregates in ionic liquids. It is found that the dynamics of mesoscale aggregates dominate many physicochemical properties such as the static dielectric permittivity and viscosity. By using mixtures of ionic liquids to tune composition-dependent evolution of the morphology, it becomes possible to realize ionic liquids with enhanced physicochemical properties that are otherwise inaccessible in neat systems. This talk will discuss the role of mesoscale organization and dynamics on macroscopic physical properties of ionic liquids.