Session B37: SPS Undergraduate Research I

Committee Work or How I Learned to Stop Complaining and Love the Process

Over the course of their career, most American scientists, be it at an independent university, government lab, or in the private sector, will at some point receive public funding to perform their research.~ Yet most of these individuals have only a vague sense of how their money was originally allocated. Most may be familiar with the intricacies of NSF, NIST, or any one of the agencies that compose the alphabet soup of the Federal Government, but what about before that, when the money and subsequent directives are being allocated to these agencies? In other words, what about congress? In an effort to better understand this process and to contribute to the reciprocal understanding by congress I embarked on a 10 week internship with the House Committee on Science, Space, and Technology, funded by the John and Jane Mather Foundation as part of the SPS Summer Internship Program. In my time with the committee I was able to attend multiple hearings and seminars on the Hill and see how policies with regard to science are created. In this talk I will discuss my experience and observations, for example that no one wished to be viewed as anti-science and that even those who are looked upon as very critical are often more critical of the opposing side of the aisle than of the actual science itself. In fact, I saw that the biggest hindrance to science in the political setting is the lack of understanding of just what it is. This the same problem faced by the general public and the steps toward fixing this issue may very well be the same.   

Wetting in Color: Designing a colorometric indicator for wettability

Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. While such indicators commonly rely on a specific photochemical response to an analyte, we exploit structural color, derived from coherent scattering from wavelength-scale porosity rather than molecular absorption or luminescence, to create a Wetting-in-Color-Kit (WICK). This inexpensive and highly selective colorimetric indicator for organic liquids employs chemically encoded inverse-opal photonic crystals to translate minute differences in liquids' wettability to macroscopically distinct, easy-to-visualize color patterns. The highly symmetric re-entrant inter-pore geometry imparts a highly specific wetting threshold for liquids. We developed surface modification techniques to generate built-in chemistry gradients within the porous network. These let us tailor the wettability threshold to specific liquids across a continuous range. As wetting is a generic fluidic phenomenon, we envision that WICK could be suitable for applications in authentication or identification of unknown liquids across a broad range of industries.   

EPR spectral study and modeling of lithium borovanadate RLi$_{2}$OB$_{2}$O$_{3}$KV$_{2}$O$_{5}$ glasses

Utilizing electron paramagnetic resonance EPR spectroscopy, lithium borovanadate RLi$_{2}$OB$_{2}$O$_{3}$KV$_{2}$O$_{5}$ glasses with R = 0.4 and K ranging from 0.1 to 0.5 were analyzed in order to elucidate the environment of unpaired 3d$^{1}$ electrons. Transitions associated with coupling of such electrons to vanadium nuclear spins were identified and modeled to reveal both g factor and A factor values. For a system with K = 0.3, representative data include: g$_{ll}$ = 1.9242, g$_{\bot }$ = 1.9693, A$_{ll}$ = 184.3768 cm$^{-1}$, A$_{\bot }$ = 64.6568 cm$^{-1}$, $\Delta $g$_{ll}$ = 0.0781, $\Delta $g$_{\bot }$ = 0.0330, and $\Delta $g$_{ll}$/$\Delta $ g$_{\bot }$ = 2.3670. A comparison revealing g$_{ll}<$ g$_{\bot } \quad <$g$_{e}$ is indicative of localized electrons residing in tetragonally-distorted octahedral sites. A slight increase observed in $\Delta $g$_{ll}$/$\Delta $ g$_{\bot }$ values when K = 0.1 to K = 0.3 is further evidence of a possible elongation of the octahedral site associated with increasing K values. This pattern, however, is not present in systems with K values greater than 0.3, suggesting that perhaps no further elongation of the site is possible due to bond constraints. A comprehensive model will be presented to summarize data for the entire family of lithium borovanadates studied here.   

Metal-Metal Oxide Nanoomposite for Solar Cell Applications

Currently, there is a large need for alternative energies and one good option is solar cells. A High efficiency solar cell generally consists of a number of thin layers: active layer consisting of a material having high absorption in the solar spectrum, transparent conducting layer, $p$- and $n$-type materials used to fabricate the junction, and electrodes for good Ohmic contacts. The presence of metal nanoparticles in metal oxide films improves significantly the solar absorbance of metal oxide films. The absorption depends on the bandgap of metal oxides which can be tuned by incorporation of metal nanoparticles. Tuning of the bandgap and absorption are the very important parameters to fabricate the solar cell devices. Thin films of M-MO (M = transition metals Co and Ni) nanocomposite have been grown on quartz substrate using pulse laser deposition technique. Structural properties have been characterized using X-ray diffraction and scanning electron microscopy. Electrical properties with and without light and absorption spectra have been measured using I-V characterization and UV-VIS spectroscopy techniques. Detailed results will be discussed in the presentation.   

Electrical Characterization of Flexible Titanium Dioxide Memristors

The memristor is a new fundamental circuit element with a resistance that depends on the magnitude and polarity of the voltage applied to it and the length of time that voltage is applied. Memristors are also nonvolatile, which means that when the bias is removed, a memristor retains its last resistive state. While memristors have potential applications ranging from alternative computer architectures to memory in inexpensive lightweight wearable sensors, the mechanism behind its switching is not well understood. One of the major questions to be resolved is whether memristive switching is electric field dependent or charge dependent. In the former case, a minimum bias is needed for switching to occur. In the latter case, a minimum amount of charge needs to pass through the device to cause switching. I will present the results of electrically characterizing flexible memristors that consist of a nm-thick layer of titanium dioxide sandwiched between two metal contacts in an effort to help establish whether their switching is charge or field-driven.   

Two-Dimensional Ordering of DNA Origami Using Stacking Bonds

Utilizing the DNA Origami method we have designed nano-scale self-assembled structures. These structures are made using a 7000 base pair long single stranded DNA as a scaffold that is held in place by shorter single stranded DNA molecules using Watson-Crick DNA base pairings. The staples were chosen to attach at certain specific sites of the scaffold DNA so that a well-defined planar structure of double stranded DNA can be created at room temperature. In designing these origami structures we made use of the computer application caDNAno. Two geometrical structures with differing symmetries were created using the same scaffold. Edges of these structures were modified in such a way that the double stranded DNA of one structure's edge can stack onto the edge of the second structure. Similar modifications were recently shown by Woo and Rothemund (Nat Chem., 1755-4330, 2011) to enable the formation of extended DNA origami structures. We intend to extend this method to create two-dimensional square and triangular lattice structures. We discuss our experimental results and implications of this method for nano-scale self-assembly.   

Synthesis of Magnetic Nanoparticles for Biosensing Studies Using Magneto-Impedance Technology

Polymer nanocomposites (PNCs) have been shown to be a compact and durable solution for applications such as electromagnetic interference shielding and magnetically tunable microwave devices. We report studies aimed at exploring applications of PNCs to aid in bio-sensing, using the Giant Magneto-Impedance (GMI) effect. GMI is a change in the ac impedance of a ferromagnetic conductor in a varying dc magnetic field, and has been shown to be about 500 times more sensitive than its counterpart, Giant Magneto-Resistance (GMR). In our study, magnetite (Fe$_{3}$O$_{4})$ nanoparticles (mean size, 6$\pm $2 nm) were synthesized by thermal decomposition and dispersed in a polymer provided by the Rogers Corporation to create PNCs with 20, 50, and 80 wt{\%} compositions. The GMI of an amorphous magnetic ribbon was measured with and without the PNCs layered on the ribbon. The effects of nanoparticle concentration on the GMI sensitivity were studied, with a view toward applications in highly sensitive bio-molecular detection.   

Development of a Protocol to Study the Conformational Stability of Protein Using the Model Protein Cytochrome $c$

The function of a protein is inherently dependent upon the proper folding and the resulting tertiary structure of the molecule. The development of an unfolding procedure is desirable so that the structural stability of a protein molecule can be determined through the change in thermodynamic properties of the unfolding reaction. The protein cytochrome$ c$ has long been used in protein structural studies and monitored by circular dichroism (CD), absorption, and fluorescence spectroscopic techniques. Single amino acid mutations of wild type cytochrome $c$ were unfolded both chemically and thermally using the developed protocol and the unfolding was monitored by CD spectroscopy. Thermodynamic properties such as Gibbs free energy, enthalpy and melting temperature were used to interpret the results. The mutant proteins were calculated to have different thermodynamic properties than that of the native cytochrome $c$ during the unfolding process. When denatured at a lower pH, the proteins thermally unfolded more readily. The objective of this session is to present recent work addressing the denaturation of wild type and mutant proteins.   

Genotyping and phenotyping of an epigenetic modifier \textit{Unstable factor for orange1 (Ufo1)} in maize

Pericarp color 1 is a model system for the study of epigenetic gene regulation. It has more than 100 alleles that contribute to the color of the pericarp and cob glume of maize. Unstable factor for orange 1 (Ufo1) is a spontaneous dominant mutation that leads to a gain in pigmentation due to a decrease in methylation in p1 genes. This decrease in methylation of cytosine in the DNA leads to changes in chromatin structure. Finding the mechanism for this spontaneous mutation can lead to way of preventing the mutation increasing production colorless maize for food production. Through genotyping and phenotyping fine gene mapping, gene expression and whole genome profiling can be accomplished for plants with the Ufo1 mutation present.   

Computational and Electronic Analog Implementation of the Hodgkin-Huxley Model of Action Potentials in Neurons

Alan Loyd Hodgkin and Andrew Huxley's mathematical model of action potential initiation and propagation in neurons is one of the greatest hallmarks of biophysics. Two techniques for implementing the Hodgkin-Huxley model were explored: computational and electronic analog. Computational modeling was done using NEURON 7.1. NEURON is a free, robust, and relatively user friendly simulation environment that enables quantitatively accurate computational modeling of neurons and neural networks. An analog electronic circuit was built using field-effect transistors (FETs) to simulate the non-linear, voltage-dependent (sodium and potassium) conductances that are responsible for membrane excitability. While the electronic analog qualitatively reproduces many of the key features of the action potential including overall shape, inactivation period, and propagation, it was difficult to quantitatively reproduce the Hodgkin-Huxley model. In addition, while the relative cost to build circuits equivalent to small membrane patches is minimal ($\sim ${\$}50), implementation of larger cells or networks would prove uneconomical. Still, both techniques are viable avenues toward introducing interdisciplinary research into either a computational or electronics lab setting at the undergraduate level.   

First-principles calculation of structural and electronic properties of memantine (Alzheimer's disease) and adamantane (anti-flu) drugs

Memantine is currently used as a treatment for mild to severe Alzheimer's disease, although its functionality is complicated. Using various density functional theory calculations and basis sets, we first examine memantine alone and then add ions which are present in the human body. This provides clues as to how the compound may react in the calcium ion channel, where it is believed to treat the disease. In order to understand the difference between calcium and magnesium ions interacting with memantine, we compute the electron affinity of each complex. We find that memantine is more strongly attracted to magnesium ions than calcium ions within the channel. By observing the HOMO-LUMO gap within memantine in comparison to adamantane, we find that memantine is more excitable than the anti-flu drug. We believe these factors to affect the efficiency of memantine as a treatment of Alzheimer's disease.   

Construction and Operation of a Differential Hall Element Magnetometer

A Differential Hall Element Magnetometer (DHEM) was constructed to measure the magnetic saturation and coercive fields of small samples consisting of magnetic nanoparticles that may have biomedical applications. The device consists of two matched Hall elements that can be moved through the room temperature bore of a 9 Tesla superconducting magnet. The Hall elements are wired in opposition such that a null response, to within a small offset, is measured in the absence of a sample that may be located on top of one unit. A LabVIEW program controls the current through the Hall elements and measures the net Hall voltage while simultaneously moving the probe through the magnetic field by regulating a linear stepper motor. Ultimately, the system will be tested to obtain a figure of merit using successively smaller samples. Details of the apparatus will be provided along with preliminary data.   

Magnetostriction of engineered magnetorheological elastomers

We have completed a study of the magnetostriction and poison ratio of several types of magnetorheological elastomers (MREs), including both hard and soft magnetic materials in silicone rubber matrices. While both random and aligned soft magnetic particles gave large ($\sim$1\%) magnetostriction, hard magnetic powders provided minimal actuation, regardless of whether they were aligned or not. In addition, we have created engineered lattices of magnetic wires and find the actuation highly dependent on the sample shape, and the angle of the magnetic field with respect to the alginment axis. We also propose some new structures based on hard magnetic wires which should provide piezomagnetic response.   

Physical Patterns Associated with 27 April 2011 Tornado Outbreak

The National Weather Service office in Memphis, Tennessee has aimed their efforts to improve severe tornado forecasting. Everything is not known about tornadogenesis, but one thing is: tornadoes tend to form within supercell thunderstorms. Hence, 27 April 2011 and 25 May 2011 were days when a Tornado Outbreak was expected to arise. Although 22 tornadoes struck the region on 27 April 2011, only 1 impacted the area on 25 May 2011. In order to understand both events, comparisons of their physical features were made. These parameters were studied using the Weather Event Simulator system and the NOAA/NWS Storm Prediction database. This research concentrated on the Surface Frontal Analysis, NAM40 700mb Dew-Points, NAM80 250mb Wind Speed and NAM20 500mb Vorticity images as well as 0-6 km Shear, MUCAPE and VGP mesoscale patterns. As result of this research a Dry-Line ahead of a Cold Front, Dew-points \r{ }5C and higher, and high Vorticity values$^{ }$were synoptic patterns that influenced to the formation of supercell tornadoes. Finally, MUCAPE and VGP favored the possibility of tornadoes occurrence on 25 May 2011, but shear was the factor that made 27 April 2011 a day for a Tornado Outbreak weather event.