Using Minimum Spanning Trees to Observe Market Behavior -- Edward Mandere (BGSU)
A minimum spanning tree offers a way of visualizing relationships between companies that may give insights into future trends on the market. I investigated the stability of MST over time to see how stable these relationships were.
Searching for Single Stock and Multi-Stock Return Correlations -- Eli Sacks (BGSU)
I had previously been working on trying to find a correlation between past and future returns of a single stock, but found none. Here, I present the results of looking instead at a single stock's positive or negative returns alone, and comparing them to future returns, and also looking at the effect of a second stock's past returns on a stock's future returns, to see if one stock can be used to predict the other.
Investigation of Optoelectronic Properties of Thin Film n-type ZnS on p-type Si Substrate -- Nilanka Gurusinghe (BGSU)
Future applications in high-density data storage devices, data transfer and optically interfaced electronic devices require thin film semiconductors, which are working in the UV part of the electromagnetic spectrum. ZnS has a band gap energy of 3.68 eV at room temperature corresponding to ultraviolet radiation for optical inter-band transition, with a wavelength of 340 nm, which is ideal for the above purpose. Electro-absorption process, photoluminescence, and microwave photoconductivity of ZnS single crystals were investigated in many studies while comparatively fewer investigations are carried out on the photocurrent of thin film ZnS. I will present an overview of a project carried out to investigate the optoelectronic properties of thin film ZnS on Si substrate.
Carbon: an Old but New Material -- Sandy Zhang (BGSU)
As we all know, carbon is a fundamental substance of earthly biology, which doesn't conduct electricity well. However, in recent years, scientists have found that random networks of carbon nanotubes -- called nanonets -- can perform a variety of basic electronic functions. That is, carbon can serve as the foundation for electronic devices because carbon nanonets are able to mimic the conductive properties of metals such as copper or the conductive characteristics of semiconductors such as silicon. It is really a scientific breakthrough. Based on its particular chemical and physical property, carbon nanonets can be used to create some inexpensive and flexible products such as electronic paper and printable solar cells.
The HST/ACS Survey of Galactic Globular Clusters -- Dr. Ata Sarajedini (Univ. of Florida)
The HST/ACS Survey of Galactic globular clusters (GC) is a Treasury project designed to obtain photometry with S/N >=10 for main sequence stars with masses >= 0.2M_sun in a large sample of globulars using the Advanced Camera for Surveys (ACS) Wide Field Channel. The survey will produce an image atlas and source catalog with astrometry and photometry for stars in the target clusters using both newly obtained ACS observations as well as archival ACS and Wide Field Planetary Camera 2 imaging, where available. In the spirit of the HST Treasury concept, the overall goal of this "legacy" survey is to investigate fundamental aspects of Galactic GCs (e.g., luminosity functions, reddenings, distances, ages, proper motions, binary fractions, to name a few) and provide a lasting contribution to cluster studies by creating a uniquely deep and uniform database of a large sample of Galactic GCs. I will present an overview of the project as well as some of the most recent results.
The Measurement of the Reflectance of Thin Film ZnS -- Yang Wang (BGSU)
Reflectance is an important property of thin films. I will introduce the principle of reflectance and report on my measurements of ZnS.
What is a Planet? -- Chen Liu (BGSU)
For 76 years, our schools taught that Pluto was a planet. Last year, a new definition for "planet" banished Pluto. We should revise our definitions when necessary to reflect our better understanding of nature.
Macroscopic Quantum Tunneling and its Manifestations in Thin Superconducting Wires -- Dr. Alexey Bezryadin (Univ. of Illinois at Urbana-Champaign)
It is of fundamental importance to establish whether there is a limit to how thin a superconducting wire can be, while retaining its superconducting character - and if there is a limit, to determine what sets it. This issue may also be of practical importance in defining the limit to miniaturization of superconducting electronic circuits. One possible reason why superconductivity might break down is the phenomenon of macroscopic quantum tunneling, proposed by Leggett [1] and observed experimentally by Martinis, Devoret, and Clarke [2]. The problem of MQT in thin superconducting wires remains not completely resolved, although many groups have attacked this problem over the last two or three decades.
Single linear molecules (e.g. nanotubes, DNA) have been used as templates for formation of metallic wires with extremely small diameters, as small as ~4 nm in some cases. A large group of such nanowires exhibit a dichotomy in transport properties, which can be understood as a quantum superconductor-insulator transition. The critical point appears close to the quantum resistance, suggesting that the transition is similar to the Schmid-Bulgadaev transition. This transition is a manifestation of macroscopic quantum tunneling. A phase diagram obtained on many wires is established and will be discussed. The apparent quasi-insulating behavior of some of the nominally superconducting wires can be understood in terms of a weak Coulomb blockade.
1. Leggett A J, 1980 Prog. Theor. Phys. Suppl. v.69 p.80; Leggett A J, 1978 J. Phys. (Paris), Colloq. 39 C6-1264.
2. Martinis J M, Devoret M H, and Clarke J, 1987 Phys. Rev. B v.35, p.4682.
Calcium Regulation in the Sarcomere, Muscle Contractions, and Jitter in Human Speech -- Neil Goldsmith (BGSU)
Jitter is defined as the cycle-to-cycle variability of the period duration of the acoustic signal coming from voice production. We believe this variability can be explained by physiological factors. One factor in particular is the variability in the signal to the muscles that control tension in the vocal folds. In order to test the importance of this action potential, we treat the vocal folds as a damped, driven, harmonic oscillator that is dependent on the muscle tension. A biochemically accurate model of a sarcomere is then developed in order to use the model to connect chemical concentrations with force production by the muscle. Since the sarcomere is the base contractile unit of muscle, it should therefore be the appropriate starting point for such a model. The model includes calcium release, diffusion, binding, and uptake. Magnesium concentrations are also modeled as they compete for calcium binding sites on parvalbumin, ATP, and troponin. The binding of calcium to troponin is of especial importance because it results in unblocking of actin sites. The actin will then interact with myosin in a multi-step process that is well understood but poorly quantified. This interaction leads to contraction of the sarcomere and thus force production. Attempts to make connections with Titze's data on multiple force twitches of the thyroaretynoid muscle and with Cooper's measurements of the tetanic contractions of the posterior cricoarytenoid muscle will be discussed.
Quantum Dots in the Biological Sciences -- Nicholas Schmall (BGSU)
Nanoscience continues to change the world around us. This presentation will focus on a burgeoning field in nanoscience called quantum dots. Quantum dots are nano-sized semiconductors which have a tremendous number of applications. I will focus mainly on their applications in the biological sciences, particularly medicine. I will also present information about developing quantum dots and the current effort to improve their production and applications.
Mathematica 6 in Education and Research -- Cliff Hastings (Wolfram Research)
(Note: this talk will take place in 123 Overman Hall)
This talk illustrates capabilities in Mathematica 6 that are directly applicable for use in teaching and research on campus. Topics of this
technical talk include:
Current users will benefit from seeing the many improvements and new features of Mathematica 6, but prior knowledge of Mathematica is not required.
Thermoelectric Effects of Skutterudite: Theoretical Background and Literature Review -- Harsha Attanayake (BGSU)
Thermoelectric Properties of 40% La Filled Skutterudite Thin Films: Analysis -- Dilupama Divaratne (BGSU)
Effective thermoelectric energy conversion devices require a high thermoelectric figure of merit. Low dimensional systems such as nanowires, however, may have enhanced thermoelectric figures of merit and thus exceed the bulk value due to quantum confinement effects and increased phonon boundary scattering. The efficiency of thermoelectric energy conversion devices is a function of the thermoelectric figure of merit ZT, where T is the absolute temperature and Z is defined a Z = S2 {sigma} / {kappa}. In the expression, S is the Seebeck coefficient, {sigma} is the electrical conductivity, and {kappa} is the thermal conductivity. Large values of ZT require high S, high {sigma}, and low {kappa}. It is very difficult to increase Z in bulk thermoelectric materials because these three properties are coupled with each other.
In this study we are dealing with thin films of Skutterudite. It is very difficult to measure the three quantities simultaneously as they are coupled with each other. So in order to measure the figure of merit we used the Harman method by measuring outputs of adiabatic and isothermal voltages when current is applied. When experimenting with thin films we had to face some new issues, as the substrate of the film conducts heat as well. The heat conductivity through the substrate is directly proportional to its thickness. The key idea of this study is to develop the relationship between the figure of merit and the substrate thickness at constant temperature.
The evolution of the LASER -- Chinthaka Liyanage (BGSU)
Since the demonstration of the first operating laser in 1960, lasers have evolved into an essential tool in human life from research laboratories at the cutting edge of quantum physics to medical clinics, supermarket checkouts and household electronics. A brief introduction will be given to laser principles and progress into Petawatt laser technology.
A Funny Thing Happened on the Way to Our Solar System: Graphene Cores in Graphitic Stardust -- Dr. Eric Mandell (BGSU)
Presolar grains, discovered in primitive chondritic meteorites like Murchison, are providing us with perspective on the primary sources of heavy atoms in the Milky Way, and specifically on condensed matter outflows from s-process (red-giant star) and r-process (supernovae) nucleosynthesis sources (Amari et. al. 1990, 1993; Bernatowicz, et. al. 1987, 1991, 1996; Hoppe et. al. 1995; Lugaro 2005). These stardust grains are identified as presolar by anomalous isotopic ratios (i.e. different than the galactic and solar average value). Among the many identified species of presolar grains are silicon carbide, corundum, spinel, diamond, graphite, and silicates (Lugaro 2005).
Graphitic stardust can be divided into several subsets based on grain morphologies observed in SEM and TEM imaging (Bernatowicz, et. al. 1996). Onion-type spherules can be categorized further in the TEM, after the grains have been cut with an ultramicrotome into ~70[nm] thick sections. While some of the onion grains have concentric (002) graphitic layers extending throughout the grain, in some cases surrounding a carbide seed crystal at the center of the grain, approximately two-thirds of the surveyed onion-type grains have condensed around a nanocrystalline core (Bernatowicz, et. al. 1996; Croat, et. al. 2005; Fraundorf et al. 2000; Mandell, et. al. 2006).
The results of a variety of materials characterization methods applied to the nanocrystalline cores are discussed here (HRTEM, Electron Diffraction, EELS, EFTEM imaging), revealing an unfolding story of their mysterious structure. The results of these analyses can be used to constrain proposed grain formation models.
Multifractal Investigation of Stock Data -- Eli Sacks
Investigation of multi fractal stock data using computer algorithms can determine whether there is a correlation between past and future returns from a single stock, or between the returns of multiple stocks. I will be presenting the program I wrote to try and determine the existence of such correlation for a single stock, and the plots generated from the output of this program.
Using Genetic Algorithms to Optimize Stock Portfolios -- Edward Mandere
In this experiment we used genetic algorithms to search for an investment strategy by dividing capital among different stocks with varying returns. The algorithm involves having a "manager" who divides his capital among various "experts" each of whom has a simple investment strategy. The expert strategies act like genes, experiencing mutation and crossover, in a selection process using previous returns as the fitness function. When the algorithm was run with test data where the optimal strategy favored non-uniform investment in one stock, it consistently beat a simple buy hold. However when the algorithm was run on actual stock data the system overwhelmingly stabilized at a population that closely resembled a simple buy hold portfolio, that is, evenly distribute the capital among all stocks.
Andy Layden -- Spring 2008