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 (3rd 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.