Physics

News & Events

Friday, June 22, 2018

Sewage, Sewage, Everywhere: Land, Air, and Water Exchange of Sewage Bacteria in the Saw Kill Watershed

M. Elias Dueker, Assistant Professor of Environmental Science

The extra-enteric ecology of sewage-indicating bacteria presents complexities for their use in management of water resources. Once released into the environment, these indicators may persist in sediments, and participate in multidirectional microbial exchange among water, sediment, and air. This complicates sewage pollution detection in public waterways, particularly in shallow freshwater tributaries prone to sediment resuspension. To address these challenges, we compared bacterial communities in sediment, water, and air in a small tributary of the Hudson River, above and below a sewage outflow. Using both culture-based and culture-independent methods, we found that sewage-associated bacteria, including sewage indicators, were present in sediment, water, and air on this waterway. Microbial communities from these ecological compartments were distinct, with sediment samples harboring greater microbial diversity than overlying water. Microbial communities responded to precipitation events, with water and sediment samples increasing in similarity with increases in waterway turbidity. While sediment samples clearly harbored sewage-indicating bacteria, they maintained a lower diversity of sewage-associated bacteria when compared to overlying water, suggesting that sediments may selectively promote environmental persistence of sewage-indicating bacteria.
Time: 3:30 pm – 4:00 pm
Location: Reem-Kayden Center Laszlo Z. Bito '60 Auditorium
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Friday, June 29, 2018

Beyond the Diffraction Limit: Imaging and Writing 3D Polymer Nanostructures with Visible Light

Chaitanya K. Ullal, Rensselaer Polytechnic Institute

Recent developments in far-field microscopy have enabled imaging at nanoscale resolutions using visible light. The circumvention of the diffraction limit opens the benefits of optical microscopy to polymer systems at the relevant nanometer length scales. These benefits include the ability to non-destructively provide local, dynamic and three-dimensional structural information. Specific examples related to colloidal crystals and block copolymers that would be challenging to image with contemporary techniques are used to highlight the potential of subdiffraction far-field fluorescence microscopy for the polymer and nanosciences. Ongoing work on imaging of nanoscale variations in cross-link density of colloidal gels and the application of super-resolution optics to lithography will also be presented.

Chaitanya Ullal is an assistant professor in the Department of Materials Science and Engineering at the Rensselaer Polytechnic Institute. He got his PhD in materials science and engineering at MIT and did a postdoc in the lab of Stefan Hell, at the MPI-BPC in Germany. He is a recipient of the NSF CAREER Award and the ACS PRF New Investigator Award. His research interests are related to unconventional nanofabrication, optics and polymers. A current emphasis of the group is the use of optical microscopy with nanoscale resolution to image and pattern nanostructured polymers.
Time: 3:00 pm – 4:00 pm
Location: Reem-Kayden Center Laszlo Z. Bito '60 Auditorium
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