The Lake Washington, and Sammamish basin contains a complex mix of life history strategies of Oncorhynchus nerka. These life history strategies include 1) Anadromous sockeye that remain in the lake for one or two years before migrating to the ocean and returning to fresh water as mature adults; 2) “Residual” sockeye salmon that breed with and are genetically a part of the anadromous population but do not migrate to the ocean, and 3) “kokanee” salmon that are genetically distinct from anadromous and residual sockeye. Kokanee salmon are native to the basin and are thought to have evolved when glaciers or other barriers restricted access to the ocean. Although once extremely abundant throughout the basin, native kokanee are now thought to be found only in Lake Sammamish. Large numbers of kokanee-like fish continue to occasionally migrate from Lake Washington into the Sammamish river and its tributaries. Intriguingly, these “mystery nerka” migrate and spawn later than the sockeye/residual population and may represent a fourth distinct O. nerka population (e.g. a remnant of native Lake Washington kokanee, or a newly evolved kokanee population derived from sockeye ancestors). Sockeye, residuals, and kokanee use gill rakers, bony extensions in the throat, to capture prey. In other cases where kokanee have evolved from sockeye ancestors, the number and size of gill rakers differs – a reflection of the of the different types environments they mature in and the different types of prey available in freshwater vs. saltwater. In this research we document the variation in gill raker number and length in the Lake Washington/Sammamish populations of O. nerka in an attempt to 1) investigate trophic adaptations within the basin associated with life history strategy and location of maturation, and 2) to assess the relationship of “mystery nerka” to the other populations known to occur in the basin.

Gravity remains one of the biggest mysteries in physics. Since Einstein’s Theory of Relativity not many new discoveries have happened. There are several big questions remaining about it such as: Why is it so much weaker than the other forces of nature? Is it mediated by a particle like the other forces? Is there a unifying theory between gravity and quantum mechanics? Does gravity have a place in the standard model? There are many theories proposed today which attempt to answer these questions, such as the presence of extra dimensions in string theory. If the effects of these theories exist, they would be present at small length scales (less than 1 mm). In order to test these theories, our lab uses a torsion balance experiment at sub-millimeter lengths. Our torsion balance experiment consists of an attractor mass on a turn table, and a detector mass hanging from a thin wire. Each has wedges cut out of it in the same pattern. The test is run by operating the turntable and measures the gravitational torque experienced by the detector mass. My project is to use a code that simulates the gravitational torque in order to investigate its dependence on different orientations and geometrical aspects of the experiment, as well as to improve on future runs of the experiment. This experiment will shed light on previously unknown aspects of Gravity and hopefully provide new discoveries to the field of gravitational physics.

Our research group performs one of the highest-precision tests of Einstein’s equivalence principle, perhaps the most fundamental property of gravitation, using a sensitive rotating torsion balance. Among the leading experimental challenges are temporal and spatial temperature variation. Notably, horizontal temperature gradients across the apparatus, if not properly characterized, can emulate an equivalence-principle violating signal. We have implemented thermal shielding and run tests to measure the thermal effects on our measurement. Past tests have shown a need for both absolute and differential temperature sensors with higher sensitivity. Hence, my research project focuses on investigating the effect of temperature gradient on our experiments by constructing a thermal monitoring system. I have designed, laid out, constructed, and tested sensitive bridge thermistor circuits that can function as both absolute and differential temperature sensors. Current tests of our prototypes have shown that temperature sensitivities reaching 10 micro-Kelvin in one second (10^-5K/Hz^0.5). We are scaling-up these sensors and plan to deploy them in this academic year. Successful completion of this project will yield improved understanding of the temperature gradients within our experimental apparatus, allowing us to test the equivalence principle with yet higher precision.