INVESTIGATIONS OF HOW CHEMICAL REACTIONS WITH INJECTED CO2 ALTER THE GEOPHYSICAL PROPERTIES OF SEQUESTRATION SITES
Ryan Matos, Chemical Engineering
Mentor: Young-Shin Jun

A set of incubation experiments with deep saline aquifer field site rock samples and acidified saline solutions was conducted at atmospheric pressure and a temperature of 80 °C. The field site rock samples, a shale cap rock and a coarse sandstone, are intrinsic to the makeup of deep
saline aquifers and require study for carbon sequestration to be a viable option. These saline solutions, intended to mimic aquifer fluids after CO2 injection, varied in ionic strength of NaCl and in pH. After incubations of the rock samples with the simulated solutions for durations that ranged from fifteen minutes to two weeks, the solutions were measured using inductively-coupled plasma mass spectrometry. Results showed that concentrations of potassium and calcium ions increased over time for incubated cap rock samples, representing an ion exchange between K+, Ca2+, and Na+ ions and an alteration of the cap rock chemistry. The cap rock and sandstone samples were also analyzed postincubation using the BET gas adsorption method and x-ray diffraction. These analyses indicated changes in the reactive surface area of the cap rock sample and elucidated potential formation of secondary minerals. Further research is required to improve understanding of the dissolution and precipitation reactions innate to CO2 injection into deep saline aquifers and these reactions’ effects on the cap rock chemistry and mineralogy. This work provided fundamental information regarding the reactions at mineral-carbonated saline water interfaces at high temperatures and helped lay the groundwork for continued investigation.

NANOSCALE CHARACTERIZATION OF BONE MINERALIZATION
Ben. E. Alexander, Mechanical Engineering
Mentor: Guy Genin, Department of Mechanical, Aerospace & Structural Engineering

The nanostructure of bone determines its toughness and stiffness. Despite its importance, this nanostructure continues to be a topic of debate. At the macroscopic level, bone’s structure is well understood: bone contains ~40% by volume type I collagen and ~50% by volume of a stiff, carbonated apatite mineral (“apatite”), with the collagen structured in a hierarchical fashion. Views differ on the nanoscale distribution of apatite within the hierarchical level of fibrils, which are 50-500 nm diameter aggregations of aligned and ordered triple helix collagen molecules. Previous electron microscopy studies report that apatite exists within fibrils but not on their exterior; the view of this camp is that mineral lies predominantly in and near the end-to-end “gaps” between neighboring collagen molecules as will be discussed in this study. Atomic force microscopy studies, on the other hand, report extrafibrillar in addition to intrafibrillar apatite.To clarify the nanophysiologic distribution of apatite within bone, we perform steric modeling that supports the hypothesis that apatite exists in a banded pattern within collagen fibrils, and must also exist on the outside of fibrils. Additionally, we performed electron microscopy analyses that further support this hypothesis.

COMPUTATIONAL MODEL OF PROTEOGLYCAN-RICH EXTRACELLULAR MATRIX
Cameron Ball, Biomedical Engineering
Mentor: Robert P. Mecham, Department of Cell Biology & Physiology

Extracellular matrix (ECM) is largely composed of hyaluronic acid (HA), proteoglycan (PG), collagen fibers, and elastin globules. The ECM has an intimate relationship with the plasma membrane (PM), and interactions between the two occur at regular intervals approximately 20 nm apart. We postulated that the mechanics of PM-ECM microdomains might assist in the assembly of elastic fibers and limitation of stress propagation through the ECM. PGECM, short for ProteoGlycan ExtraCellular Matrix, simulates the response of the ECM to deformation of the PM. Modeled mechanical stress and electrostatic interactions determine the behavior of the in silico matrix. While HA and collagen give tension-resistant properties to the ECM, charged glycosaminoglycans (GAGs) on PG molecules allow the ECM to resist compression. Simulations predict that electrostatic interactions contribute negligibly to uniaxial stress development when the matrix is in tension but resist lateral matrix compression. The model also predicts that collagen molecules form effective barriers for stress propagation through the ECM, and that elastin (Eln) globules approach one another following deformation of the plasma membrane. Future models of ECM microdomains will incorporate frequency dependence and accurate geometries.

RENEWABLE ENERGY RESOURCES
Naitik Bhatt, Computer Engineering
Mentor: Arye Nehorai, Department of Electrical & Systems Engineering

Interest in energy solutions from renewable sources has grown significantly in the last decade. With the current movements in public opinion as well as renewable mandates from the state and federal government, finding ideal sources of renewable energy has become a topic of great importance. The utilization of technology can be very site specific, whether it be wind, solar, tidal, etc. These sites, combined with current land use, legislation, and load demand, all factor into the efficient use of a renewable resource. This work researches the leading technologies in renewable generation with the goal of compiling a comprehensive set of locations with the varying capacity factors available for each technology. Attention to cost effectiveness, as well as environmental impacts, and underlying legislation will be paid to ensure the quality and feasibility of the data. Attention to PV Solar and Wind will be emphasized.

AKOYA/BANDIT: PROXIMITY OPERATIONS AND REPEATABLE DOCKING WITH NANOSATELLITES
Kaitlin Burlingame, Mechanical Engineering
Mentor: Michael Swartwout, Department of Mechanical, Aerospace & Structural Engineering

Akoya/Bandit is an ongoing student-built docking mission. Bandit’s mission is to flight-test proximity operations technologies, including docking, safe navigation within 5 m of a target vehicle, on-orbit charging, and image-based navigation. The project was started in 2003 by students and faculty at Washington University, and proto-flight hardware and documentation were presented on 20 January 2009 as part of the Flight Competition Review of the University Nanosat-5 Program, culminating in a 2nd place finish in the national competition. The mission elements are a 35-kg host spacecraft (Akoya) and two 3-kg proximity-operations vehicles (Bandit-1 and Bandit-2). The minimum-success mission is to release Bandit-1 to a distance of one meter and recapture it, and can be accomplished open-loop using only Bandit-1’s clock and cold-gas thrusters. This mission is made possible by an error-tolerant “soft dock” consisting of a hook-and-loop fastener on an extended capture boom. Proximity operations are of significant interest in the aerospace community, and Bandit is unique in its docking method and its small size and cost. Over the past year, proximity operations using image based navigation on a free flying vehicle have been shown to be feasible and work on the mission is continuing to move forward.

INFLUENCE OF TEMPERATURE AND MAGNESIUM CARBONATE SATURATION ON THE
SEQUESTRATION OF CARBON DIOXIDE
David H. Case, Chemical Engineering
Mentor: Daniel Giammar, Department of Energy, Environmental & Chemical Engineering

Concerns about global climate change have led to research efforts aimed at sequestering anthropogenic carbon dioxide (CO2). These include precipitation of carbonate minerals with magnesium silicates in engineered reactors or following CO2 injection into deep saline aquifers. In this study experiments were performed to test the influence of temperature and magnesium carbonate (MgCO3) saturation on the nucleation and precipitation of carbonate minerals. The conditions studied are relevant to full-scale sequestration systems. Aqueous phase analysis by inductively coupled plasma mass spectroscopy (ICP-MS) quantified the rate and extent of precipitation of solid phase from solution. Temperature significantly affected the species of solid obtained, which is supported by thermodynamic calculations. Initial MgCO3 saturation level was a strong control on the rate and extent of solid precipitation. X-Ray diffraction (XRD) analysis was conducted to identify solids, which at 21°C and 56°C were magnesium carbonate minerals. At 98°C the solid phase was identified as magnesium hydroxide, Mg(OH)2. This suggests that at low- and mid-range temperatures carbon sequestration may be feasible, but other variables such as ionic strength, presence of nucleation sites, and pressure remain untested.

WATER ORDERING ON ALUMINUM OXIDE SURFACES
Kalee Cassady, Chemical Engineering
Mentor: Cynthia Lo, Department of Energy, Environmental & Chemical Engineering

Aluminum oxide is a useful material in engineering applications such as environmental remediation for the removal of heavy metals from water, and advanced materials such as ceramics and coatings. The structure of the clean and hydroxylated aluminum oxide (11-20) surface has been studied using density functional theory. The lowest-energy surface structure has been found to be the stoichiometric surface, which is in stark contrast to the results on otheraluminum oxide surfaces (e.g., (0001), (1-102)). The hydroxylated surfaces have also been studied with density functional theory, where four water molecules have been dissociated per unit cell. The results show that the stoichiometric surface termination is favored in aqueous environments as well.

CHARACTERIZING ODORS USING ELECTRONIC NOSE SENSORS
Joy Weilin Chiang, Electrical Engineering
Mentor: Arye Nehorai, Department of Electrical & Systems Engineering

Electronic sensing technology is a developing field of study that has greatly advanced over the last decade. Currently, most research focuses on classifying odors within a limited odor set. Also of interest is detecting and distinguishing specific odors and the particular compounds within each odor, which may be relevant for developing novel medical diagnostic tools, for example. The goal of this project is to understand the responses of electronic nose sensors when exposed to specific food odors. In order to achieve this, we built an experimental setup consisting of an array of three chemical sensors, their corresponding signal conditioning circuitry, and a data acquisition device. For acquiring and processing the data measurements, a graphical user interface (GUI) was implemented in LabVIEW. A protocol was developed for calibrating the sensor responses to odorless air such that useful signals are obtained when the sensor array is exposed to food odors. We tested the experimental setup on a small set of foods and built their characterization profiles based on the sensor measurements. The designed GUI and experimental setup can be used as a starting point for future research exploring chemical array signal processing applications, such as food classification and chemical source localization.

DETERMINATION OF THE THERMODYNAMICS AND KINETICS OF IRON NANOPARTICLE
SELF-ASSEMBLY ON AN ALGINATE SUBSTRATE
Peter Colletti, Chemical Engineering & Systems Engineering 
Mentor: Young-Shin Jun, Energy, Department of Environmental & Chemical Engineering

The early stage aggregation kinetics and thermodynamics of the self-assembly process undertaken by iron nanoparticles in the presence of an alginate substrate are measured with atomic force microscopy (AFM). Samples of clean quartz substrate are exposed to solutions of iron nanoparticles and alginate in order to characterize the aggregation of iron nanoparticles on the surface, the coating of the surface with alginate, and the self-assembly process itself. This is determined by observing changes in the surface morphologies of the quartz substrate. No definitive information concerning the kinetics could be obtained, but aggregation and assembly patterns similar to those previously found by other researchers were observed.

THE HAITI PROJECT
Jamie Cummings, Mechanical Engineering
Mentor: Robin Shepard, Department of Energy, Environmental & Chemical Engineering

Haiti, the western hemisphere’s poorest country, is finding relief from its malnutrition woes through an innovative peanut butter. Meds and Food for Kids, an organization based out of St. Louis, runs a factory in Haiti that produces enough peanut butter to cure 3,000 malnourished children every year. The factory buys its peanuts from Haitian farmers, but due to mold growth caused by inadequate drying, approximately 40% of those peanuts are thrown out. Washington University’s Engineers Without Borders is working to solve this mold problem by developing a simple,  affordable peanut dryer that can be built by farmers in Haiti. This summer, students built and tested a passive solar
peanut dryer in St. Louis, which will ultimately help farmers reduce peanut mold and allow Meds and Food for Kids to produce more of their life-saving peanut butter.

DENSITY FUNCTIONAL THEORY ANALYSIS OF METHANE DEHYDROGENATION ON PLATINUM
NANOCLUSTERS FOR LIQUID FUEL PRODUCTION
Nathan Fine, Chemical Engineering
Mentor: Cynthia Lo, Department of Energy, Environmental & Chemical Engineering

Methane has proven itself to be a useful precursor for the production of liquid fuels and other value-added chemicals through the Fischer-Tropsch process, but currently its potential is limited since it appears to be too energetically stable to undergo direct conversion to higher hydrocarbons and other liquid fuels. It is believed that more technologically advanced nanoscale catalysts may facilitate more economical and direct methods of production. In this study, the physisorption of methane on a 20-atom tetrahedral platinum nanocluster, and the chemisorption of dehydrogenated methane derivatives have been modeled using density functional theory. These calculations provide astrong base for computing the reaction pathway, using the nudged elastic band and related methods, for catalytic methane dehydrogenation on Pt nanoclusters. Furthermore, the nanoparticle structure, composition and placement on a metal oxide support may be varied to design catalysts with improved yield, selectivity, and stability for the direct synthesis of liquid fuels from methane.

ROBOTIC MICROPHONE SENSING: DATA PROCESSING ARCHITECTURES FOR
REAL-TIME ACOUSTIC SOURCE POSITION ESTIMATION
Zachary Knudsen, Biomedical Engineering & Applied Science; Raphael Schwartz, Biomedical Engineering & Applied Science
Mentor: Arye Nehorai, Department of Electrical & Systems Engineering

In the previous work “Acoustic source location using cross-correlation algorithms,” we found that the performance of the 2D position estimation algorithms using two pairs of microphones depends on array variables such as the distances between the individual and pairs of microphones, and also the sampling frequency. Therefore, we propose to build a robotic microphone array with autonomous control of the array geometry and sampling rate for improving the localization performance of an acoustic source in 2D space. In particular, in this project we focus on developing data processing architectures for estimating in real-time the 2D locations of an acoustic source. We implemented our algorithms in LabVIEW combined with Matlab and developed a graphical user interface that allows for easy interaction with the experimental setup. The system allows for tracking a fixed and moving wideband acoustic source.

ROBOTIC MICROPHONE SENSING: DESIGN OF A ROBOTIC PLATFORM AND ALGORITHMS FOR
ADAPTIVE CONTROL OF SENSING PARAMETERS
Charles LaFont, Mechanical Engineering
Mentor: Ayre Nehorai, Department of Electrical & Systems Engineering

In our previous undergraduate research project on “Acoustic source location using cross-correlation algorithms: we found that the performance of the 2D position estimation algorithms using two pairs of microphones depends on array variables such as the distances between the individual and pairs of microphones, and also the sampling frequency. Therefore, we propose to build a robotic microphone array with autonomous control of the array geometry and sampling rate for improving the localization performance of a wideband acoustic source in 2D space. In particular, in this project we designed two mobile robotic-platforms carrying a pair of microphones each. Each platform is capable of real-time communication between the PC and the robot microcontroller independently. We designed a control algorithm for modifying adaptively each robot position along a single axis such that the resolution for estimating the source position is improved. We tested the performance of our system using numerical examples and real experiments.

SOOT INCEPTION IN GASEOUS COUNTERFLOW DIFFUSION FLAMES UNDER
OXYGEN ENHANCED CONDITIONS
Sydnie Lieb, Mechanical Engineering
Mentor: Richard Axelbaum, Department of Energy, Environmental & Chemical Engineering

Due to the negative effects that soot has on health and the environment there is significant interest in reducing or eliminating its production during the combustion of carbon-based fuels. Soot free flames, known as permanently blue flames, have been observed experimentally; however there is debate regarding the physical explanation of these flames. Previously conducted computational work suggests that these flames result from a change in the activation energy of a key soot formation reaction during oxygen enhanced combustion. This work uses a one-dimensional gaseous laminar diffusion flame to study the experimental phenomena correlated with the computational results. The data show that in oxygen rich environments the activation energy associated the formation reaction drops to zero. This is an important result because it implies that the formation of soot is independent of temperature under these conditions. For a flame burning in air conditions, soot formation increases as the temperature increases; however in the oxygen rich environment the temperature can be increased without the onset of soot inception.

OPTIMUM FLOATING AUTGYRO WIND TURBINE
Jessica Loyet, Mechanical Engineering
Mentor: David A. Peters, Department of Mechanical, Aerospace & Structural Engineering

Atmospheric scientist Ken Caldeira calculated that if we were able to tap into just 1% of the energy stored in high altitude winds, we could provide enough energy to power the entire Earth. One technology that may be used to harvest this energy is autogyros. An autogyro, first successfully flown in 1923, is a rotorcraft similar to a helicopter that uses the upwards flow of air created during flight to turn its freespinning rotors to provide lift for the vehicle. I worked on a system of four autogyros attached to a frame that can be flown like a kite, 10,000 feet in the air. Not only is this system designed to operate at higher efficiency levels than other windmills, but it will also cause significantly less environmental damage. Design graphs to determine the optimum efficiency of different systems were produced in this work.

NRF TECHNICAL CORE: CONTROLLED SYNTHESIS OF METALLIC NANOSTRUCTURES
Kyle Oetjen, Biomedical Engineering
Mentor: Yujie Xiong, Department of Biomedical Engineering

Over the past decade, metallic nanostructures have been widely used not only for fundamental research but also for practical uses in our lives. The research community has yet to unlock the huge potential in these nanostructures with reliable and precise controlling means in their production process. At the Washington University Nano Research Facility (NRF), we are able to control the shape, size, structure, composition, surface group, and surface charge of metallic nanostructures, leading to the feasibility of finely controlling their properties and functions and fully exploiting their applications or investigating their implications.

CARBON DIOXIDE AND METHANE CONVERSION TO LIQUID FUEL
Brent Sherman, Chemical Engineering
Mentor: Cynthia Lo, Department of Energy, Environmental & Chemical Engineering

Rising atmospheric levels of carbon dioxide and methane contribute to global warming. While sequestration would reduce these levels, turning the unwanted gases into a valuable product would be better. The direct conversion of carbon dioxide and methane to liquid fuels using an integrated nanocatalyst of platinum on cerium oxide is the focus of this research. Using computer modeling, the nanocatalyst will be designed. Preliminary results indicate strong chemisorption of methane onto platinum and weak physisorption of carbon dioxide onto stoichiometric ceria. Previous work indicates that carbon dioxide will be strongly chemisorbed onto a reduced ceria surface, thus activating it for the desired reaction.

HIGH DIMENSIONALITY SCHEDULING TECHNIQUES FOR OPEN SOFT REAL-TIME SYSTEMS
Braden Sidoti, Computer Science
Mentor: Christopher Gill, Department of Computer Science & Engineering

Open soft real-time systems, such as mobile robots, must cope with unpredictable variables both effectively and efficiently. These systems drastically differ from traditional real-time scheduling systems and need new underlying assumptions in its framework— a new model must be created to address these systems more effectively. In previous work, a Markov Decision Process (MDP) was used to design scheduling policies for open soft real-time systems subject to a utilization share goal. This technique produced optimal scheduling policies but became too computationally intensive for scheduling more than four or five tasks. In reality, a system can easily have upwards of dozens of tasks making this technique impractical. In this research we used a partitioned model to approximate an exact schedule and investigated parameter optimization techniques. When compared to the greedy model, the partitioned model produces higher quality policies. Although we are not able to compare policies generated by this new approach to truly optimal policies determined with a MDP, this new process is a step towards an improved and practical scheduler for open soft real-time systems.

PESTICIDE ALDICARB ADSORPTION ONTO SOIL DURING WATER REUSE:
FOURIER TRANSFORM INFRARED SPECTROSCOPY STUDY
Anca Timofte, Chemical Engineering
Mentor: Young-Shin Jun, Department of Energy, Environmental & Chemical Engineering

To address future water supply shortage due to climate changes, development of effective conservation strategies of sustainable water supplies are required. A potential promising solution to prevent water shortage is the aquifer recharge with wastewater effluents. However, to perform a more effective and safe operation of this process, a better understanding of the fate and transport of remaining pollutants, such as pharmaceuticals or pesticides in the effluent is necessary. Aldicarb, a carbamate insecticide used on a wide range of crops, needs to be removed from wastewater, if this is to be used to recharge fresh water aquifers. Our research project investigates the adsorption of aldicarb onto soil as it flows through it, as it would in the recharging process. We aimed to identify which soil mineral components are most responsible for aldicarb adsorption. We studied the interaction between aldicarb and different model minerals (which could be present in soil) individually—aluminum oxide, iron oxide, manganese dioxide, calcite, and quartz— and field-collected soils. Using Diffuse Reflectance Fourier Transform Spectroscopy to study the forming or breaking of bonds between aldicarb and model and field soils, we concluded that calcite and quartz are responsible for aldicarb binding to soils. We also investigated the effect of humic and fulvic acids, naturally occurring organic matter found in soil, on aldicarb adsorption. For this, we coated calcite and quartz with fulvic acid and humic acid and let the coated samples react with aldicarb in a batch equilibrium experiment. Using the results of these experiments, we determined a quantitative contribution from quartz and calcite to overall aldicarb adsorption and identified the functional groups of aldicarb responsible for binding to soil.

PETERS PRACTICAL TIP CORRECTION PROCEDURE FOR APPLICATION TO COMPUTED LIFT
Jennifer Varriano, Mechanical Engineering
Mentor: David Peters, Department of Mechanical, Aerospace & Chemical Engineering

The use of the Prandtl tip-loss correction is quite common in the analysis of rotating wings. It is a correction factor between blade loading (i.e., circulation) and the induced flow near the blade tip that accounts for the effects of a finite number of blades. This factor is placed on the loading-to-inflow theory before it is coupled with blade-element theory in order to find the final inflow and loading distributions. With proper correction, the inflow should be such that the loading goes to zero at the blade tip. However, sometimes it is useful to correct a loading distribution after the fact (that is, after an inflow theory and lifting theory have been already coupled). Often the Prandtl correction factor is used as the means to correct the blade loading and to insure that it goes to zero at the blade tip; but direct application of the factor is not appropriate for such an application. In this project, we show how to make lift corrections to account for blade number after the coupled lift-inflow distribution has been computed without the effect the blade number.

EXPRESSION OF DIFFERENT IONIC CHANNEL PROTEINS THROUGH
THE VENTRICULAR WALL OF NORMAL AND FAILING HUMAN HEARTS
Vinod K. Ravikumar, Biomedical Engineering; Alexey V. Glukhov, Vadim V. Fedorov, Igor R. Efimov, Department of Biomedical Engineering, Washington University, St. Louis, MO

Heart failure (HF) is a condition of the heart impairing its structure and/or function of providing appropriate blood flow to the entire body. HF is a common cause of death, claiming 200,000 deaths in the United States alone, half of which stem from ventricular tachyarrhythmias. HF results in electrophysiological (EP) remodeling which includes the changes in expression of ion channel proteins and forms the functional substrate for arrhythmogenesis. Currently, HF, and HF-associated arrhythmias in particular, are largely untreated due to difficulty in interpreting symptoms to lead to an appropriate diagnosis, and a large number of treatments are diet-based since our limited knowledge of arrhythmia at the molecular level prevents us from creating ion channel specific drugs to cure such HF related diseases.

DUAL FREQUENCY TRANSMIT AND RECEIVE SURFACE COILS FOR MRI SCANNERS
Benton Reynolds2, Biomedical Engineering; Greg Lanza2, Frank Hockett2, Biomedical Engineering Department, Washington University, St. Louis, MO2; Cardiology Department, Washington University School of Medicine, St. Louis, MO2.

An MRI machine produces a magnetic field to orient the spin of atoms in the body, and then another magnetic field pushes the orientation of the spin in another direction. The frequency of this magnetic field determines which atoms change direction. Typically, MRI machines focus only on lone proton atoms, or hydrogen atoms. However, in an attempt to gain resolution and clarity of images, it is desirable to scan for fluorine atoms as well. Doing this requires a dual-frequency coil that can transmit and receive magnetic field information from both proton and fluorine atoms. This was done by designing a circuit board with components that create a magnetic field for both proton and fluorine frequencies. After designing, calculating, and prototyping were done for this coil, testing was performed on phantom rats and mice. Phantoms are chemically and dimensionally similar to the real thing, but are easier to use. The images produced using the new MRI surface coil were of high quality. This will be useful for scanning for tumors in the future, especially considering the increased flexibility of a fluorine scan.

IMPROVED PHOTOSYNTHETIC PRODUCTIVITY FOR RHODOBACTER SPHAEROIDES VIA SYNTHETIC
REGULATION OF THE LIGHT HARVESTING ANTENNA LH2.
Jacob Rubens1, Jaffre Athman1, Jacob Cecil1, Stephanie Chang1, Brendan Cummings2, Biomedical Engineering; Colin Foley1, Jeff Knudsen3, Biomedical Engineering & Applied Science; Alice Meng2, Biomedical Engineering; Thomas Stevens2,  Biomedical Engineering; Christine Kirmaier4, Yinjie Tang3, Department of Energy, Environmental & Chemical Engineering; Robert Blankenship1,4, Biology Department, Washington University, St. Louis, MO1; Department of Biomedical Engineering, Washington University St. Louis, MO2; Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, MO3; Department of Chemistry, Washington University, St. Louis, MO4.

Photosynthetic light harvesting antennas function to collect light and transfer energy to a reaction center for photochemistry. Phototrophs evolved large antennas to compete for photons in natural environments where light is scarce. Consequently, cells at the surface of photobioreactors over-absorb light, leading to attenuated photobioreactor light penetration and starving cells on the interior of photons. This reduction of photosynthetic productivity has been identified as the primary impediment to improving photobioreactor efficiency. While reduction of antenna size improves photosynthetic productivity, current approaches to this end uniformly truncate antennas and are difficult to manipulate from the perspective of bioengineering. We aim to create a modifiable system to optimize antenna size throughout the bioreactor by utilizing a synthetic regulatory mechanism that correlates expression of the pucB/A LH2 antenna genes with incident light intensity. This new application of synthetic biology serves to transform the science of antenna reduction into the engineering of antenna optimization.

CYTOSKELETAL DYNAMICS IN 3D
Pascal M. Schaefer1, Guy M. Genin2, Biology Department, Washington University, St. Louis, MO1; Mechanical Engineering Department, Washington University, St. Louis, MO2.

Dynamic mechanical properties of fibroblast cells in two-dimensional culture are driven by coupling between focal adhesion assemblies and actin stress fibers. However, cells in two-dimensional culture appear to have mechanical properties that differ drastically from those of cells in natural three-dimensional environments. The lack of existing measurements in three dimensions led us to design the following experiments.

ANALYSIS OF SYSTEMATIC BIASING OF AUDITORY FIELD RECEPTIVE FIELD CHARACTERIZATION
WITH BAND-PASSED NOISE
Edgar Y. Walker, Biomedical Engineering; and Dennis L. Barbour, Biomedical Engineering Department, Washington University, St. Louis, MO.

Accurate identification of receptive fields of auditory neurons serves the critical role in characterizing and formulating models of the sound processing schemes in auditory system for mammals. Traditionally, auditory neuronal receptive fields have been measured using pure tones. However, neurons in lateral belts are known to respond poorly to pure tones at any frequency or level. Given this, band-passed noise has been used in estimating the center frequency of receptive field. In this study, we evaluate the effect of utilizing band-passed noise in estimating central frequency of the auditory receptive field. We do so by constructing computational models of auditory neurons, and subjecting the neurons to sounds that have the same characteristics as real sounds used in the corresponding real physiology experiments. The model indicates that using band-passed noise in estimation of central frequency results in systematic bias when applied to auditory nerves with asymmetric receptive field. Furthermore, the model indicates that the phenomenon of bandwidth tuning may be explained as an artifact of biased measurement of the central frequency. The use of band-passed noise in estimating central frequency therefore should be done with more care and may even be discouraged.