Collisional Quenching of Vibrationally Excited CO in Non-LTE Environment

The atmosphere of Saturn’s largest moon, Titan, is of growing interest to the space science community. However, since its atmosphere is not in local thermodynamic equilibrium (non-LTE), modeling it requires a deep understanding of the natural excitation and relaxation processes that occur there. Our group has studied CO, the primary reservoir of oxygen on Titan, and its rate of collisional quenching, to contribute toward improving atmospheric models. Using transient diode laser spectroscopy, a quenching rate can be elucidated to significantly higher precision than previously documented in literature. Our experimental procedure begins by flowing small amounts of CO, O3 and Ar through a 1 meter vacuum cell, and firing a 266 nm laser through the cell. O3 absorbs this wavelength and causes the mixture to undergo a temperature jump, allowing some amount of the CO to be excited to higher vibrational states. A mid-IR range diode laser is used to constantly measure the population of CO in a certain state, allowing us to determine the rate of change of the population in a state of interest as it collides with other molecules and is quenched. In this project we are exploring the effects of bath gas identity on CO energy transfer measurements. Specifically, we are investigating the effectiveness of Ar vs. Xe in quenching excited photofragments from the ozone photolysis initiating the temperature-jump. The most recent results of our work will be presented.

Making Accelerated NMR More Robust for Pharmaceutical Sciences

Pharmaceutical companies often face roadblocks in structure elucidation of both natural products and identification of impurities. Nuclear magnetic resonance spectroscopy (NMR) can overcome these problems in the drug discovery pipeline in a way mass spectrometry cannot by identifying absolute configuration. New technologies to accelerate structure elucidation include emerging advanced data sampling techniques like nonuniform sampling (NUS), which is powerful, but prone to artefacts. Sampling noise and aliasing artefacts are a barrier to using sparser NUS in complex 2D-NMR experiments. We find that weak aliasing artefacts are a growing concern in sparser 1D-NUS and can sometimes be misattributed to incomplete deconvolution of the broader point-spread function. As sparsity increases in NUS, we find that detrimental repeat sequences can occur early in the sampling schedule, correlating with aliasing artefacts in resulting spectra. By developing a convolutional screening approach to evaluate sampling schedules, these repeat sequences can be detected and characterized. Selecting schedules to avoid repeat sequences and using short periods of initial uniform sampling are effective at reducing these initial repeat sequences and enabling routine 25-33% 1D-NUS of challenging 2D-NMR experiments.

Stress Analysis of a Sheared Athermal System with Pins

Numerous studies have investigated the jamming transition in granular media. Recent research has indicated that quenched disorder in the form of fixed pins provide additional stabilizing forces to the system, which causes the jamming threshold to decrease and therefore provides a fourth degree of freedom in the jamming transition. Using molecular dynamics simulations, we study a two-dimensional, granular system subjected to a wall-driven flow in the vicinity of jamming in order to understand how pins affect the dynamics of the system. We implement a shear by freezing the top and bottom of the binary mixture, and move the walls at a constant shear rate. The system is a 50:50 binary mixture with purely repulsive harmonic interactions of size ratio 0.004:1:1.4 of pins:small:large particles. Pins are located on a square lattice. We will present results concerning shear stress and pressure as a function of packing fraction and strain rate. We will also show preliminary results for the statistics of the shear stress as function of time.

An Analysis of the Transportation of Metals and Trace Metals in an Abandoned Mine Drainage Treatment Site
Abandoned mine drainage (AMD) is a contaminant problem that watersheds across the United States face. AMD is the result of water traveling through abandoned mines, dissolving harmful metals into the water, which is then brought out into streams and rivers. These toxic metals can cause harm to aquatic life, and can affect recreational activities. The treatment site known as scarlift site 15 works to remove iron from the contaminated water and lower the pH. The main goal of this research was to analyze the travel and transportation of these toxic metals in scarlift site 15, a passive mine drainage treatment site located in Ranshaw, PA.
Water samples from the treatment center were collected, filtered, and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC). These results were used to observe the patterns of where the metals precipitated in the system. These patterns were used in conjunction with the size of the particles in order to see if they were traveling attached or with another metal.
Cobalt, nickel, and zinc all follow the trend of precipitation out of the water that aluminum has. Iron primarily comes out without other trace metals, implying that the trace metals were finding another way out of the water. In the system, the iron was not coming out from the treatment within the system, but rather it was precipitating out of the water from sitting in the pools of the treatment site.