UNC PHYSICS AND ASTRONOMY WEEKLY CALENDAR

 

 

MONDAY, NOVEMBER 16

12:15 p.m., Room 6, Phillips Hall (UNC-CH)

Nuclear Seminar

Samantha Hammond (Physics and Astronomy, UNC-CH)

“Laser Wakefield Accelerators”

 

4:00 p.m., Room 265, Phillips Hall (UNC-CH)

(Refreshments at 3:30 p.m., Room 277, Phillips Hall)

Physics and Astronomy Colloquium

Charles P. Slichter (Department of Physics, University of Illinois)

“60 years of surprises--NMR, a scientific evergreen”

Abstract:  Nuclear Magnetic Resonance, discovered in 1946, began as an alternative to molecular beam apparatus to study the spins and magnetic moments of nuclei. It rapidly moved to studies of condensed matter physics, then chemistry, then biology, and most recently medicine. The talk will describe the history, with examples from each area.

 

4:00 p.m., Room 301, Riddick Hall (NCSU)

(Refreshments are served from 3:30 to 4:00 in Riddick Hall's Hearth.)

Sayers Lecture

Stephen Hudgens (Santa Clara University)
“Phase-change Memory: Progress in Development of a New Computer Data Storage Technology[PDF]”

 

TUESDAY, NOVEMBER 17

No Event Scheduled

 

WEDNESDAY, NOVEMBER 18

3:30 p.m., Room 328, Phillips Hall (UONC-CH)

(Refreshments served at 4:30 p.m. in 310 Chapman (3^rd Floor Lobby Area))

(For more information, contact Dr. Brent McKee (bamckee@email.unc.edu))

Marine Sciences Seminar

Ashley Smyth (Graduate Student; UNC-CH Dept. of Marine Sciences)

"Alterations in Nitrogen Cycling Resulting from Oyster Mediated Benthic-Pelagic Coupling." 

Abstract:  Oyster reefs are important estuarine ecosystem engineers and provide a variety of ecosystem services including habitat, shoreline stabilization and nutrient processing.  Over the last century, oyster populations have declined due to over-harvesting, disease and reduction in water quality. Despite considerable research on many facets of oyster reefs, their interaction with estuarine nitrogen cycling is not completely understood. In coastal ecosystems, where nitrogen often limits primary productivity, assessing the impacts oyster reefs have on the transformation and transfer of nitrogen is critical for both understanding estuarine nitrogen cycling and establishing effective nutrient management strategies. To determine how oyster reefs affect water quality through modification of nitrogen cycling, nitrogen fluxes (N₂ by membrane inlet mass spectrometry) were measured from intact sediment cores from around and within oyster reefs and reference intertidal and subtidal flats in the Newport River Estuary system, NC.  Rates of N₂ production were significantly higher in sediments adjacent to oyster reefs (848.12 +/- 221.36 mmol N m^-2 yr^-1) relative to subtidal (131.62 +/- 34.30 mmol N m^-2 yr^-1) and intertidal flats (413.66 +/-  88.50 mmol N m^-2 yr^-1) without oysters. Potential dissimilatory nitrate reduction to ammonium (DNRA) was significantly higher in oyster reefs compared to reference sites. Net nitrogen removal was highest in the summer for all habitats. Additional manipulative experiments were conducted in which water column nutrient concentrations (and thus phytoplankton biomass) were varied to determine how eutrophication alters the ability of oyster reefs to enhance N removal. This information is complementary to existing knowledge regarding oyster reef impacts on nitrogen cycles; however, it more explicitly defines net removal of nitrogen and focuses on changes in nitrogen processing in oyster reef sediments. My work will help determine the potential contribution of oyster reefs to controlling eutrophication through modifications of estuarine nitrogen cycling.

 

THURSDAY, NOVEMBER 19

No Event Scheduled

 

FRIDAY, NOVEMBER 20

9:00 a.m., Room 258, Phillips Hall (UNC-CH)

Kristen Alexander (Physics and Astronomy, UNC-CH)

 

Abstract:  Surface enhanced Raman spectroscopy (SERS) is a phenomenon that arises

when light incident on nanoscopic metallic features excites localized

surface plasmons (i.e. collective oscillations of electrons) on the

surface of the metal. This effect can create intense local electric field

enhancements if the wavelength of the incident radiation is in resonance

with the plasmon frequency. When the surfaces of two noble metal

nanoparticles are brought within a few nanometers of each other, the

resulting enhanced electric fields are concentrated in the few square

nanometers of volume directly between the two nanoparticles. If a molecule

of interest is placed in this “hot spot”, its Raman signal can be enhanced

by several orders of magnitude, making the detection of trace amounts of

analyte possible. Thus, the ability to create high quality, reproducible

SERS substrates is of great interest to many fields, including chemistry,

physics and medicine. Unfortunately, predictions made regarding SERS using

computer simulations are difficult to verify experimentally, largely due

to the fact that the small length scales required to create the substrates

to be tested are beyond the capability of current lithography equipment.

This proposed research focuses on the development of methods that

circumvent this limitation with the ultimate goal of probing the

dependence of the SERS response on the interparticle gap size. My talk

will include (a) a formal statement of the difficulties that inhibit the

design of SERS experiments, (b) an overview of previous work done on this

subject and, (c) a full description of the methods proposed to complete

this research.