CPA Postdoc L(a)unch- May 5
Dr. Paresh Kumar Samantaray, CCE
Throw or Throw-not; I won't pollute: Compostable e-beam Cross-linked PGA/PBAT Composites in Flexible Food Packaging
Dr. Yide Zhang, EAS
Ultrafast Phase Imaging of Propagating Current Flows in Myelinated Axons and Electromagnetic Pulses in Dielectrics
Lunch will be provided starting 11:45 AM!
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Throw or Throw-not; I won't pollute: Compostable e-beam Cross-linked PGA/PBAT Composites in Flexible Food Packaging
The accumulation of plastic waste in the natural environment and the associated production of microplastics (<5 mm in size) that contaminate air, water, and soil have incentivized global action to tackle plastic pollution. This has stimulated the rapid development of biodegradable plastics worldwide. Biodegradable plastics are those that are susceptible to degradation by biological activity (e.g., broken down by microorganisms, such as bacteria or fungi) accompanied by decomposition into environmentally acceptable substances with desirable properties (e.g., water, carbon dioxide (CO2), methane (CH4), and biomass). In the first part of the talk, I will highlight how microplastics are formed, and I will provide compelling reasons to promote the use of biodegradable bioplastics. Next, I will highlight a commercial approach in designing thermoplastic food packaging films derived from polyglycolic acid and polybutylene adipate-co-terephthalate with electron-beam mediated cross-linking. Here, the electron beam plays a dual role. Firstly, it cross-links the surface of the films and improves the oxygen and moisture barrier performance, both improved due to blending with PBAT. Second, it does not compromise the toughness or extension at the break of the polymer blend, both desirable for flexible packaging applications.
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Ultrafast Phase Imaging of Propagating Current Flows in Myelinated Axons and Electromagnetic Pulses in Dielectrics
Visualizing the spatiotemporal dynamics of propagation is fundamental to understanding processes in different areas of science and technology ranging from biology to physics. Two examples are the propagation of action potentials (APs) along myelinated axons and electromagnetic pulses (EMPs) as ultrafast processes in biology and physics, respectively. While existing models can accurately predict their propagation speed and dynamics, a tool to experimentally visualize propagation may highlight characteristics unique to specific samples or materials. However, due to the extreme speed and sensitivity requirements, APs propagating along myelinated axons and EMPs propagating in dielectrics have not yet been visualized with existing imaging modalities. Here, we demonstrate differentially enhanced compressed ultrafast photography (Diff-CUP) to directly visualize propagations of passive current flows, which plays a central role in AP propagation, at approximately 100 m/s along internodes, i.e., continuous myelinated axons between nodes of Ranvier, from Xenopus laevis sciatic nerves and of EMPs at approximately 5×107 m/s through lithium niobate. Enabled by the ultrahigh speed and large sequence depth of compressed ultrafast photography and the high sensitivity of a differentially-enhanced Mach-Zehnder interferometer, Diff-CUP can capture ultrafast phase events at 200 billion frames per second with a sequence depth of up to 350 frames and a phase sensitivity of 20 µrad. The calculated conduction speeds agree with measurements by other techniques, and the spatiotemporal dynamics of these two propagation processes are consistent with the results from computational models, indicating that Diff-CUP can cross these two extreme timescales while maintaining high phase sensitivity.