Volume 11 Issues 1 and 2 June and September 2012

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https://doi.org/10.33697/ajur.2012.006

After 10 Years: Back to Undergraduate Research Advisors

https://doi.org/10.33697/ajur.2012.007

Author(s):

C. C. Chancey

Affiliation:

University of Northern Iowa, Cedar Falls, Iowa 50614-0150 USA


The Effects of Hypergravity on Xenopus Embryo Growth and Cardiac Hypertrophy

https://doi.org/10.33697/ajur.2012.008

Author(s):

Bryce Joseph Duchman and Darrell Wiens

Affiliation:

Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614-0421 USA

ABSTRACT:

All life on earth has developed and evolved in a unity gravity (1G) environment. Any deviation below or above 1G could affect animal development, a period when much change occurs and sensitivity is high. We imposed simulated hypergravity through centrifugation and analyzed the effects on the overall body length and cardiac growth of Xenopus laevis embryos. We predicted that increased contractile force would be required from the heart to adequately circulate blood, dispersing nutrients, and that this would inhibit organism growth and possibly induce a state of hypertrophy. Embryos reaching gastrulation stage were exposed to a 7G or 1G (control) field via centrifugation for 96 hours. We then recorded behavior, mortality and took body length measurements. We found no significant differences in behavior or mortality, however, body length was significantly reduced by an average of 6.8% in the 7G group. We then fixed, embedded, sectioned and stained embryos in order to investigate the dimensions of cardiac tissue and of the cardiac region of the body using image analysis software. We found the 7G group had a significantly reduced average body cross-sectional area (-18%) and yet a significantly larger ventricular cross-sectional area (+36%) when compared to the 1G group. The average ratio of ventricle cross-sectional area to average body cross-sectional area was significantly higher in the 7G group when compared to the 1G. From these data, we conclude that hypergravity has a significant inhibitory impact on the Xenopus laevis embryo growth and causes a significant increase in ventricle size.


Observing Program Calculator for Eclipsing Binary Star Systems

Appendix: ephemeris calculator

https://doi.org/10.33697/ajur.2012.009

Author(s):

Colby Neal and Michael Braunstein

Affiliation:

Central Washington University, Department of Physics, Ellensburg, Washington 98926 USA

ABSTRACT:

A Microsoft Excel application has been developed to utilize eclipsing binary elements to calculate binary ephemerides that are useful in a program of observing binary systems. Binary star systems consist of two stars orbiting a common center of mass. Consistent monitoring of eclipsing binary stars is important for establishing fundamental astronomical parameters, such as mass and composition of the stellar system. The application that was developed supports effective use of resources in such monitoring applications. The main quantities computed by the application at the time of the eclipse include: local time, Julian date, starting Epoch, altitude of the system, phase of the moon, Local Mean Sidereal Time, and Local Hour Angle. Other quantities computed by the application include current Universal Time (UT), UT/Local Time correction, Julian Date, and current moon phase/percent illuminated. The observing application has been demonstrated to be effective in practical application to obtain differential photometry data for SV Camelopardalis, a system of interest because of variability in its period caused by a third body. The application can be easily modified for use with other highly periodic astronomical systems, for instance transits of extrasolar planets.


Isospectral Domains in Euclidean 3-Space

https://doi.org/10.33697/ajur.2012.010

Author(s):

Christopher Cox

Affiliation:

Department of Mathematics, Iowa State University, Ames, Iowa 50011 USA

ABSTRACT:

The question as to whether the shape of a drum can be heard has existed for around fifty years. The simple answer is ‘no’ as shown through the construction of isospectral domains. Isospectral domains are non-isometric domains that display the same spectra of frequencies of sound. These frequencies, deduced from the eigenvalues of the Laplacian, are determined by solving the wave equation in a domain omega , where alpha-omega is subject to Dirichlet boundary conditions. This paper presents methods to expand the already existing two dimensional transplantation proof into Euclidean 3-space and, through these means, provides a number of three dimensional isospectral domains.


Memory Accuracy for Emotional and Neutral Narratives: Investigating the Influence of Suggestive Misinformation on the Frequency of False Memories

https://doi.org/10.33697/ajur.2012.011

Author(s):

Laura E. Paige and Elizabeth A. Kensinger

Affiliation:

Psychology Department, Boston College, Chestnut Hill, Massachusetts 02467 USA

ABSTRACT:

Memory is a reconstructive process, impressionable and not always vigilant in detecting devices working against its accuracy. False memory occurs when memory for an event is infiltrated by new information or alterations are made to the information that was previously stored. The present study investigated the effect of emotional valence on false memory occurrence through the misinformation effect – memory errors that arise as a consequence of exposure to misleading information – by presenting participants with narratives in one of three valence conditions (negative, positive, neutral) and subjecting them to suggestive questions providing credulous misinformation following a one-hour delay. Results revealed that when collapsing across negative and positive conditions, overall false memory occurrences were significantly reduced for these narratives compared to the neutral condition. Some of the effects of emotion on memory accuracy were more pronounced for negative information than for positive or neutral information; response rates in the negative condition, as compared to the two other valence conditions, revealed an increase in hits and a decrease in false alarms suggesting negative valence enhances discriminability.


Diffusion of Water and Diatomic Oxygen in Poly(3-hexylthiophene) Melt: A Molecular Dynamics Simulation Study

https://doi.org/10.33697/ajur.2012.012

Author(s):

Julia Deitz, Yeneneh Yimer, and Mesfin Tsige

Affiliation:

Department of Polymer Science, University of Akron, 302 Buchtel Common, Akron, Ohio 44325 USA

ABSTRACT:

Diffusion behavior of water, diatomic oxygen, and a mixture of both into a poly(3-hexylthiophene)[P3HT] melt were investigated using Molecular Dynamics Simulation. Once simulations were complete, the data was analyzed to determine the diffusion coefficient of those molecules in P3HT using Fick’s law. The diffusion coefficient values were then plotted as a function of concentration and temperature to determine if trends existed. For both water and oxygen, no dependence was observed of the diffusion coefficient on concentration and temperature for the ranges studied. However, a variation in the diffusion coefficient on concentration was observed due to the expected inhomogeneity of the P3HT melt. In the presence of O2, the diffusion of H2O decreased significantly by a factor between four and five, while in the presence of H2O, the diffusion of O2 slightly decreased.