The UAM ARK-LSAMP students and Dr. Marvin Fawley and Dr. Karen Fawley presented 3 posters at the ARK-LSAMP Spring Research Conference.
Heterogeneity of the Ribosomal External Transcribed Spacer Region in some Carex species. Elia Garcia, Karen Fawley and Marvin Fawley. School of Mathematical and Natural Sciences, University of Arkansas at Monticello, Monticello, AR 71656.The genus Carex L. is the largest genus in the monocot family Cyperaceae (the sedges), with over 2000 recognized species. The preeminent approach to identifying Carex species is to use the fruiting structures. However, to identify Carex specimens that are not yet fruiting, DNA sequence analysis could be the solution. There has been previous research using the DNA sequence of the nuclear ribosomal internal transcribed spacer region (ITS) to identify the Carex species, C. floridana and C. nigromarginata, in the vegetative condition. However, research using herbarium specimens of C. nigromarginata showed that some specimens possessed a combination of ITS sequences from C. floridana and C. nigromarginata. Additional research then showed that all examined specimens were actually heterogeneous in the ITS region. In this study, we extended the research to the ribosomal RNA external transcribed spacer region (ETS) to determine if heterogeneity also is present in this region. Our results clearly show that the ETS region is also heterogeneous. Interestingly, the ETS sequences of all specimens examined were more similar to the published sequence for C. floridana than that of C. nigromarginata. All of our research indicates that the ribosomal RNA regions cannot be used to identify these Carex species as presently define. Further research can be directed towards different gene regions to determine if DNA sequence analysis can be used to identify these species. Link to Poster
Further studies of heterogeneity in the nuclear ribosomal internal transcribed spacer region of the sedges, Carex nigromarginata and Carex floridana . Kylen Criner, Anabel De La Cruz, LaTarnesha Jacobs, Esgar Jimenez, Darren White, Karen Fawley and Marvin Fawley. School of Mathematical and Natural Sciences, University of Arkansas at Monticello, Monticello, AR 71656. The genus Carex L. is the largest genus in the monocot family Cyperaceae (the sedges), with over 2000 recognized species. The identification of Carex species can be very difficult and usually requires specimens with fruiting structures. In previous work, we examined the utility of sequence analysis of the nuclear ribosomal internal transcribed spacer region (ITS) to identify Carex specimens in the non-fruiting condition. However, specimens identified as Carex nigromarginata and Carex floridana were shown to be heterogeneous in the ITS region, with individual genomes possessing copies of the ITS similar to both C. nigromarginata and C. floridana. These results suggest that the ITS region is not useful for differentiating between these two species. One complication of the previous study was that pollen could possibly contaminate leaf tissue and result in the observed heterogeneity. In this study, we tested this possibility by using DNA extracted from root tissue and fruits for heterogeneity in the ITS region. Our results from both tissues show that heterogeneity is present in all specimens examined and indicate that the ITS region cannot be used to identify these species. Link to Poster
Dynamics of a Nonlinear Oscillator Driven by Pulse-Width
Modulated Square Waves.
Jaime Garcia and Juan Serna.
of Mathematical and Natural Sciences, University of Arkansas at Monticello,
Monticello, AR 71656.
We investigated a nonlinear mechanical oscillator, consisting of a mass
suspended by three springs and kicked by a train of pulse-width modulated square
waves. When these pulses "kicked" the system, the oscillator changed its
amplitude, frequency, and region of oscillation randomly, getting constrained
into periodic orbits in the phase plane. We studied the behavior of the
oscillator numerically as a function of the frequency of the system, the initial
elongation of the springs, and the frequency and strength of the square pulses.
The system showed sensitivity to the initial elongation of the springs and the
strength of the pulses, displaying chaotic behavior. This particular mechanical
system could be used to investigate quantum-classical analogies with
delta-kicked, nonlinear quantum oscillators.
Link to Poster
Link to Poster