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2017
Tuesday, April 11th
3:45 PM

Variable Stars in M92 and M15

Riley Jordan, Whitman College

Science 159

3:45 PM - 4:00 PM

My presentation details the search for variable stars in the Galactic globular clusters M92 and M15, using images collected over a 12-year baseline from April 2003 to September 2015. Globular clusters are dense groups of stars that are old and metal-poor. Variable stars are stars that vary in magnitude or brightness. My research looked for RR Lyrae type variables in M92 and M15 using images collected with a 2.4m telescope. The images were reduced and coded to select the variable stars. New variable stars were found in both clusters, and periods for previously known variable stars were confirmed.

4:00 PM

Isochrone Fitting of Hubble Data in UV-Vis-IR Bands

Hallie Barker, Whitman College

Science 159

4:00 PM - 4:15 PM

Stellar evolution models are an important tool used by astronomers to study star clusters. By plotting stars within a cluster in terms of their color and magnitude, we can fit these highly complex theoretical models to the data and determine important information about the cluster. In our research, we used the Dartmouth Stellar Evolution Program, and the PAdova and TRieste Stellar Evolution Code to determine the age, distance and reddening of two globular clusters, M13 and M80, using photometry from the Hubble Space Telescope’s Wide Field Camera 3 and Advanced Camera for Surveys. In addition to finding these parameters, we also looked at how the two models compare to one another, and where they seem to have problems. We found that both models have systematic inaccuracies in the ultraviolet (UV) bands, and in particular that PARSEC predicts stellar metallicities that are too high in the UV.

4:15 PM

Synthesis of Photoactive NaYF4: Yb, Cr Nanoparticles

Teddy Pierce, Whitman College

Science 159

4:15 PM - 4:30 PM

Solar cells are a growing source of renewable energy. However, standard solar cells absorb only visible light, which makes up less than 10 percent of solar radiation reaching earth. By utilizing nanoparticles, it is possible to efficiently convert some of the ultraviolet and infrared radiation to visible light. This is done by inserting pairs of atoms, called dopants, into a nanoparticle lattice. One of these atoms will then absorb a specific wavelength of radiation and transfer the energy to the other atom, which will emit the energy at a different wavelength. Specific dopant pairs allow for the conversion of specific wavelengths of radiation. The NaYF4 lattice has been found to be an effective host for dopant pairs. By modifying synthesis from the literature for NaYF4: Yb, Er we hope to create an efficient synthesis for NaYF4: Yb, Cr, thereby allowing for the conversion of an additional set of wavelengths.

4:30 PM

Predicting Bond Strength in Transition Metal Species

Susan Nichols, Whitman College

Science 159

4:30 PM - 4:45 PM

The bonding between transition metals and other species is a large part of inorganic chemistry. Central to this is the need to predict these bonds, primarily through comparing bond strength. Unlike the field of organic chemistry, however, there is minimal experimental data for these bonds by which to compare predictions. One approach is based on an empirical model called Pearson’s Hard Soft Acid Base Theory. Since the model is experimentally based, this approach attempts to quantify the available data. Comparatively, another approach uses computational methods to create models of the bonds and then compares these models to experimental data for accuracy. My research analyzes both approaches by compiling previous research and determining connections between them.

4:45 PM

Spatial Determination of Organic Matter on Sediment Particles by Scanning Electron Microscope Analysis

Marra Clay, Whitman College

Science 159

4:45 PM - 5:00 PM

Natural organic matter is the dominant factor for determining equilibrium and kinetic processes during pollutant sorption and desorption phenomena in sediment and soil experiments. While several models are suggested for predicting these processes, few offer mechanistic interpretations since the spatial location of organic matter on sediment particles is unknown. I examined sediments from multiple locations using SEM-EDX to determine and analyze particles for their elemental composition, specifically the location of carbon. Through a carbon map of the sediment, my investigation shows that organic matter tends to gather in clumps on the aggregates and occasionally on rough edges, and is not spread evenly across a sediment matrix.