Investigation of the Flow in a new Three-Dimensional Physical Model of the Human Larynx -- Saeed Torkaman & Bogdan Kucinschi (MIME Department, University of Toledo)
The vast majority of the experimental studies concerning the intraglottal pressure distributions in static glottal models consider only over-simplified, two-dimensional geometrical configurations, based on a single anterior cross-section of the larynx. In order to take into account the three-dimensionality of the glottal flow, a new phonation model (referred to as M6) was built at the University of Toledo. It is an incremental improvement of the well-established M5 physical larynx model from BGSU.
The new experimental device permits the measurement of the glottal pressure profiles in three intermediate anterior-posterior planes, as well as the glottal flow rate. A total of 42 pressure taps (3 rows with 14 taps in each plane) are available on the surface of the vocal folds. The new device will also allow the investigation of the flow behavior in the presence of the Arytenoid cartilage. It is a highly customizable device, and permits one to analyze 63 different glottal configurations. Currently, three representative symmetrical model vocal folds (i.e., uniform, convergent and divergent shapes, with an included angle of 10 deg and an indentation of 0.16 cm real-life) are investigated. The experimental measurement and data acquisition techniques will be presented, as well as the challenging aspects related to the design and manufacturing of M6.
The experimental program is supplemented by a program of computational investigations of the laryngeal flow. The sensitive issues related to both experimental and computational work will be discussed. A good agreement between empirical and computational results was obtained for the available configurations. In near future, the effects of other values of indentation will be investigated, as well as the impact of the Arytenoid cartilage on the glottal flow.
Long Period Variable Stars in Galactic Globular Clusters -- Andy Layden (BGSU)
Long period variable stars (LPVs) are red giants or supergiants that vary in brightness as they pulsate radially. Their periods range from months to several years, and amplitudes can be many magnitudes. Studying these pulsation properties as a function of position on the giant branch helps to constrain models of stellar structure, evolution, and pulsation. Studying LPVs in environments with known metallicity, age, and distance allows us to control these variables; globular clusters are an excellent environment. However, existing data on LPVs in globulars is poor. I will present preliminary results from two pilot studies to show that small telescopes such as BGSU's 0.5-m can make significant contributions to LPV research. I will then describe a long-term project we have begun to improve the census of LPVS in globular clusters.
The Study of LPVs in the Metal-Rich Globular Cluster NGC 6553 -- Elisabeth Kager (BGSU)
NGC 6553 is a metal-rich ([Fe/H] = -0.2) globular cluster near the bulge of the galaxy. Its metallicity and the fact that it is a bulge cluster makes it a type of cluster for which variable stars have not been studied very thoroughly. These two criteria make NGC 6553 a very interesting cluster to study but also a very tough one since it comes with challenges, such as foreground star contamination and foreground reddening. In this talk, previous studies of this cluster will be reviewed and experimental methods and goals for the project will be presented.
Dark Energy: Reexamination of the Copernican Principle and the Expansion of the Universe -- Derek Bas (BGSU)
Measurements of the redshift of type Ia Supernovae (SNe) have shown the SNe to be farther away than previously expected. The traditional explanation for this is the existence of a negative pressure fluid known as “dark energy” permeating all empty space ubiquitously. Recent speculation has uncovered altenative explanations, one of which brings into question the validity of the Cosmological Principle, or the idea that Earth is not in a central, specially favored position in the universe.
Synthesis of Antimony Based III-V Semiconductor Quantum Dots -- Ian R. Nemitz (BGSU)
Current research in quantum dots is becoming increasingly specific, so newer and more creative avenues of study are constantly being explored. Nearly all relative element combinations have been accomplished or at least attempted. One particular, and possibly useful, combinations has yet to be perfected, GaSb, which is the basis of the current research that will be introduced. Methods of successful and failed synthesis will be explained, and future methods will be discussed. Future tests and possible applications will also be discussed.
Intraglottal Pressure Distributions for Divergent Angles -- Jun Li (BGSU)
This research studies asymmetric vocal fold oscillations. This kind of oscillation is well known in normal and pathological voices, such as unilateral paralysis, arytenoid fixation and webbing. The research is quite relevant to aerodynamics, however, the driving aerodynamics is relatively poorly known, and has been oversimplified in previous studies. Thus, there is a need for empirical work for this research. The current work is based on the intraglottal pressures for divergentl conditions. It also contains static models for intricate pressure measurements.
Recent Research in Merging dS and ZnSe Quantum Dots -- Nick Schmall (BGSU)
The goal of my thesis is the methodology required to merge two different types of quantum dots, CdS and ZnSe. Preliminary results will be presented and the search for a possible signature of the merging will be discussed. Prospects for future tests of the merging process will also be discussed.
Random Matrix Theory Analysis of Financial Time Series -- Haowen Xi (BGSU)
This talk looks at the empirical feature of financial time series. We will introduce and show that the theory of random matrices is potentially of great interest to understand the statistical structure of the empirical correlation matrices in multivariate financial time series, and the collective dynamics of the market behavior. We find that there is remarkable agreement between the theoretical predication (based on the assumption that correlation matrix is random) and empirical data of probability density distribution of eigenvalues associated to the time series. We give specific example using major market index stock time series from DOWJONES and S&P 500.
Random Matrix Theory in the Financial Market -- Sandy Zhang (BGSU)
In the stock market, what most attracts investors are two things: net return and risk, or volatility. The problem of finding the least risky investment which earns a given return is the most crucial problem that investors care about. Such an investment is called an optimal portfoilo. Random Matrix Theory (RMT) has been applied to many scientific fields. In the financial market, this techology can also be used to analyze the cross-correlation matrix, C, of price changes. It has been found that random matrix theory can make an estimate for C which outperforms the standard estimate in terms of setting up an investment which carries a minimum level of risk.
Theoretical modeling of polycrystalline thin-film photovoltaics -- Lilani Attygalle (BGSU)
While various methods are used today to understand and improve thin-film photovoltaic devices, many questions remain unanswered. We believe that the classical p-n junction model developed and successfully applied to describe the 1st generation crystalline devices, becomes unrealistic as applied to thin-film non-crystalline PV. We have investigated more realistic models of photovoltaic junctions using analytical and numerical methods. We tried to account for the following features overlooked in the exciting classical models of CdS-based thin-film photovoltaics.
1) Strong pyro- and piezo- electricity of CdS grains known in many applications.
2) Random electric potential in the presence of metal electrodes.
3) Hopping transport through thin-film structures.
4) The effects of hopping transport leakiness and gigantic capacitive energy on ultra-thin-film PV.
Our understanding points at new venues in thin-film photovoltaic technology.
Magnetic Resonance in Nano-Scale Transistors -- Patrick M. Lenahan (Penn State)
The Surface Wave Model of Phonation Threshold and a Physical Model of the Vocal Fold Mucosa: Theory and Experiment -- Lewis Fulcher and Chen Liu (BGSU)
The classic two-mass model of Ishizaka and Flanagan (1972) pointed out the importance of the vertical phase difference between the top and bottom parts of the vocal folds in the transfer of energy from the flow of air through the glottis to the kinetic energy of the vocal folds. In an analysis of the physics of small oscillations of the vocal folds, Titze proposed that the essence of the energy transfer mechanism could be captured in a surface wave model of the motion of the vocal fold mucosa. His work resulted in a simple analytic formula for the rectangular glottis that predicted the phonation threshold pressure to be a linear function of the glottal half-width, to be directly proportional to the energy dissipation properties of the vocal fold, and to be reduced by the presence of a vocal tract. In order to test these hypotheses, Titze and colleagues have done a series of experiments with a physical model of the larynx that uses a silicone membrane to enclose fluids with different viscosities or viscoelastic biomaterials of interest for phonosurgical procedures, such as hyaluronic acid or fibronectin. Several of the qualitative features predicted by Titze's analytic formula are supported by the experiments. We are exploring the assumptions one needs to make in order to add precision to the comparison of theory and experiment, that is, to make the comparisons quantitative instead of qualitative. The first set of improvements will be based on entrance loss coefficients and exit coefficients determined from the intraglottal pressure distributions measured with model M5, a static physical model of the larynx. Lucero's calculation of the effects of air viscosity at small glottal widths will also be examined.
Radiative Recombination of Spatially Extended Excitons in (ZnSe/CdS)/CdS Heterostructured Nanorods -- Nishshanka Hewa-Kasakarage (BGSU)
We report on organometallic synthesis of luminescent (ZnSe/CdS)/CdS semiconductor heterostructured nanorods (hetero-NRs) that produce an efficient spatial separation of carriers along the main axis of the structure (type II carrier localization). Nanorods were fabricated using a seeded-type approach by nucleating the growth of 20-100 nm CdS extensions at [000 ( 1] facets of wurtzite ZnSe/CdS core/shell nanocrystals. The difference in growth rates of CdS in each of the two directions ensures that the position of ZnSe/CdS seeds in the final structure is offset from the center of hetero-NRs, resulting in a spatially asymmetric distribution of carrier wave functions along the heterostructure. Present work demonstrates a number of unique properties of (ZnSe/CdS)/CdS hetero-NRs, including enhanced magnitude of the quantum confined Stark effect and subnanosecond switching of absorption energies that can find practical applications in electroabsorption switches and ultrasensitive charge detectors.
Evolutionary Paths in Starbursting Transition Dwarf Galaxies -- Kate Dellenbusch (BGSU)
(Note: this seminar starts early, as Kate must teach at 4:30)
Dwarf galaxies are the structurally simplest and most numerous type of galaxy in the universe, but many questions about their formation and evolution remain. Is there an evolutionary link between dwarf elliptical and dwarf Irregular galaxies? If there is a link, how does this process take place? I will discuss an interesting sample of dwarf galaxies that may be a "missing link" in dwarf galaxy evolution, providing us with a window into the galaxy evolution process. These objects exhibit a puzzling combination of characteristics, sharing properties typical of both irregular and elliptical galaxies. Based on these characteristics and results from moderately deep optical imaging, I will explore possible evolutionary histories for such starbursting "transition" dwarf galaxies.
Andy Layden -- Spring 2009