Nonlinear dynamics and chaos simulation system analysis for improved design

Small errors proved catastrophic. Our purpose to remark that a very small cause which escapes our notice determined a considerable effect that we cannot fail to see, and then we say that the effect is due to chance. Small differences in the initial conditions produce very great ones in the final phenomena. A small error in the former will produce an enormous error in the latter. When dealing with any kind of electrical device specification, it is important to note that there exists a pair of test conditions that define a test: the forcing function and the limit. Forcing functions define the external operating constraints placed upon the device tested. The actual test defines how well the device responds to these constraints. Forcing inputs to threshold for example, represents the most difficult testing because this put those inputs as close as possible to the actual switching critical points and guarantees that the device will meet the Input-Output specifications. ^ Prediction becomes impossible by classical analytical analysis bounded by Newton and Euclides. We have found that non linear dynamics characteristics is the natural state of being in all circuits and devices. Opportunities exist for effective error detection in a nonlinear dynamics and chaos environment. ^ Nowadays there are a set of linear limits established around every aspect of a digital or analog circuits out of which devices are consider bad after failing the test. Deterministic chaos circuit is a fact not a possibility as it has been revived by our Ph.D. research. In practice for linear standard informational methodologies, this chaotic data product is usually undesirable and we are educated to be interested in obtaining a more regular stream of output data. ^ This Ph.D. research explored the possibilities of taking the foundation of a very well known simulation and modeling methodology, introducing nonlinear dynamics and chaos precepts, to produce a new error detector instrument able to put together streams of data scattered in space and time. Therefore, mastering deterministic chaos and changing the bad reputation of chaotic data as a potential risk for practical system status determination. ^

Changes in Caribbean paleoproductivity, diversity and benthic foraminiferal test size caused by the Neogene closing of the tropical Atlantic-Pacific ocean gateway

The purpose of this study was to test 3 hypotheses: (a) that late Miocene to early Pliocene constriction and complete closure of the Central American Seaway (CAS), connecting tropical Atlantic and East Equatorial Pacific (EEP) oceans, caused decreased productivity in the Caribbean, due to reduced coastal upwelling and an end to the connection with high-productivity Pacific waters, (b) reduced paleoproductivity resulted in decreased diversity in the Caribbean and, (c) this decreased availability of food (reduced paleoproductivity) was responsible for larger mean test size in the three most common benthic foraminiferal species Epistominella exigua, Oridorsalis umbonatus and Globocassidulina subglobosa. ^ These are tested by applying correlation analysis to 7 groups of paleoceanographic proxies, 3 indices of diversity measures and mean test size data from the Caribbean Ocean Drilling Project Site 999, to 47 core samples for the interval between 8.3-2.5 Ma. Results are compared with published Caribbean and Pacific deep-sea records. ^ The Caribbean, between 8.3-7.9 Ma, experienced reduced current velocity and lower ventilation of bottom waters. Thereafter, until 4.2 Ma, the seasonality of phytodetritus input increased and ventilation further reduced. From 4.2-2.5 Ma, paleoproductivity decreased, current velocity reduced, ventilation improved, and the seasonality of phytodetrital input decreased dramatically. The benthic foraminiferal diversity followed the same trend as paleoproductivity. Individual correlation analysis between mean test size of benthic foraminiferal species Epistominella exigua, Oridorsalis umbonatus and Globocassidulina subglobosa and paleoceanographic proxies yielded a positive and significant relationship with paleoproductivity. However, a combined datasets of all 3 species yielded a negative and significant relationship with species abundance. ^ Thus, the study concludes that (a) the gradual closure of the CAS led Caribbean diversity and paleoproductivity to decrease abruptly at 7.9 Ma, when the nutrient-rich Pacific deep waters were cut off, and then, again with the complete closure of the seaway at 4.2 Ma, (b) diversity and paleoproductivity are positively correlated in the Caribbean and (c) that the availability of food is an overriding factor that influences mean test size; lower availability of food and decreased abundance leads to larger test size. ^

Integrated surface-ground water modeling in wetlands with improved methods to simulate vegetative resistance to flow

In topographically flat wetlands, where shallow water table and conductive soil may develop as a result of wet and dry seasons, the connection between surface water and groundwater is not only present, but perhaps the key factor dominating the magnitude and direction of water flux. Due to their complex characteristics, modeling waterflow through wetlands using more realistic process formulations (integrated surface-ground water and vegetative resistance) is an actual necessity. This dissertation focused on developing an integrated surface – subsurface hydrologic simulation numerical model by programming and testing the coupling of the USGS MODFLOW-2005 Groundwater Flow Process (GWF) package (USGS, 2005) with the 2D surface water routing model: FLO-2D (O’Brien et al., 1993). The coupling included the necessary procedures to numerically integrate and verify both models as a single computational software system that will heretofore be referred to as WHIMFLO-2D (Wetlands Hydrology Integrated Model). An improved physical formulation of flow resistance through vegetation in shallow waters based on the concept of drag force was also implemented for the simulations of floodplains, while the use of the classical methods (e.g., Manning, Chezy, Darcy-Weisbach) to calculate flow resistance has been maintained for the canals and deeper waters. A preliminary demonstration exercise WHIMFLO-2D in an existing field site was developed for the Loxahatchee Impoundment Landscape Assessment (LILA), an 80 acre area, located at the Arthur R. Marshall Loxahatchee National Wild Life Refuge in Boynton Beach, Florida. After applying a number of simplifying assumptions, results have illustrated the ability of the model to simulate the hydrology of a wetland. In this illustrative case, a comparison between measured and simulated stages level showed an average error of 0.31% with a maximum error of 2.8%. Comparison of measured and simulated groundwater head levels showed an average error of 0.18% with a maximum of 2.9%. The coupling of FLO-2D model with MODFLOW-2005 model and the incorporation of the dynamic effect of flow resistance due to vegetation performed in the new modeling tool WHIMFLO-2D is an important contribution to the field of numerical modeling of hydrologic flow in wetlands.

Decadal Change in Vegetation and Soil Phosphorus Pattern across the Everglades Landscape

Wetlands respond to nutrient enrichment with characteristic increases in soil nutrients and shifts in plant community composition. These responses to eutrophication tend to be more rapid and longer lasting in oligotrophic systems. In this study, we documented changes associated with water quality from 1989 to 1999 in oligotrophic Everglades wetlands. We accomplished this by resampling soils and macrophytes along four transects in 1999 that were originally sampled in 1989. In addition to documenting soil phosphorus (P) levels and decadal changes in plant species composition at the same sites, we report macrophyte tissue nutrient and biomass data from 1999 for future temporal comparisons. Water quality improved throughout much of the Everglades in the 1990s. In spite of this improvement, though, we found that water quality impacts worsened during this time in areas of the northern Everglades (western Loxahatchee National Wildlife Refuge [NWR] and Water Conservation Area [WCA] 2A). Zones of high soil P (exceeding 700 mg P kg−1 dry wt. soil) increased to more than 1 km from the western margin canal into the Loxahatchee NWR and more than 4 km from northern boundary canal into WCA-2A. This doubling of the high soil P zones since 1989 was paralleled with an expansion of cattail (Typha spp.)-dominated marsh in both regions. Macrophyte species richness declined in both areas from 1989 to 1999 (27% in the Loxahatchee NWR and 33% in WCA-2A). In contrast, areas well south of the Everglades Agricultural Area, including WCA-3A and Everglades National Park (ENP), did not decline during this time. We found no significant decadal change in plant community patterns from 1989 and 1999 along transects in southern WCA-3A or Shark River Slough (ENP). Our 1999 sampling also included a new transect in Taylor Slough (ENP), which will allow change analysis here in the future. Regular sampling of these transects, to verify decadal-scale environmental impacts or improvements, will continue to be an important tool for long-term management and restoration of the Everglades.

Multiplex PCR for Assessment of Tetracycline Resistance (tet) Genes in Antibiotic-Resistant Soil Bacteria and the Ecological Implications

Antibiotics are becoming increasingly prevalent in bacterial communities due to clinical and agricultural misuse and overuse in their environment. As exposure increases, so does the incidence of microbial resistance. Such is the case with bacterial resistance to tetracyclines, a phenotype often acquired through the horizontal gene transfer of tet genes between bacteria. The objective of this project was to analyze the bacterial diversity of tet resistance genes in soil from Miami-Dade County. Bacterial isolates were Gram-stained and the Kirby-Bauer antibiotic disk diffusion test was performed to determine each bacterium’s degree of resistance. The 16S rRNA gene from antibiotic-resistant isolates was amplified by PCR and sequenced to identify the isolates. All isolates’ tet genes were amplified by multiplex PCR, sequenced, and compared. Among eight isolates, three distinct species were positively identified based on their 16S rRNA sequences and four distinct tet genes were identified, though all tested susceptible to tetracycline via the Kirby-Bauer test. This project clarifies some aspects of the ecology of antibiotic resistance genes, their natural ecological function and the potential for the expansion of intrinsic multi-antibiotic resistance into new ecosystems and/or hosts.

Initial placement methods for Haitian adult ESOL students : the NYS place test plus profile data compared to subjective assessment

Few valid and reliable placement procedures are available to assess the English language proficiency of adults who enroll in English for Speakers of Other Languages (ESOL) programs. Whereas placement material exists for children and university ESOL students, the needs of students in adult community education programs have not been adequately addressed. Furthermore, the research suggests that a number of variables, such as, native language, age, prior schooling, length of residence, and employment are related to second language acquisition. Numerous studies contribute to our understanding of the relationship of these factors to second language acquisition of Spanish-speaking students. Again, there is a void in the research investigating the factors affecting second language acquisition and consequently, appropriate placement of Haitian Creole-speaking students. This study compared a standardized instrument, the NYS Place Test, used alone and in combination with a writing sample in English, to subjective judgement of a department coordinator for initial placement of Haitian adult ESOL students in a community education program. The study also investigated whether or not consideration of student profile data improved the accuracy of the test. Finally, the study sought to determine if a relationship existed between student profile data and those who withdrew from the program or did not enter a class after registering. Analysis of the data by crosstabulation and chi-square revealed that the standardized NYS Place Test was at least as accurate as subjective department coordinator placement and that one procedure could be substituted for li other. Although the writing sample in English improved accuracy of placement by the NYS test, the results were not significant. Of the profile variables, only length of residence was found to be significantly related to accuracy of placement using the NYS Place Test. The number of incorrect placements was higher for those students who lived in the host country from twenty-five to one hundred ten months. A post hoc analysis of NYS test scores according to level showed that those learners who placed in level three also had a significantly higher incidence of incorrect placements. No significant relationship was observed between the profile variables and those who withdrew from the program or registered but did not enter a class.