Papers by Michael Jenkins
Science of The Total Environment, 2008
Poultry litter provides nutrients for crop and pasture production; however, it also contains feca... more Poultry litter provides nutrients for crop and pasture production; however, it also contains fecal bacteria, sex hormones (17β-estradiol and testosterone) and antibiotic residues that may contaminate surface waters. Our objective was to quantify transport of fecal bacteria, estradiol, testosterone and antibiotic residues from a Cecil sandy loam managed since 1991 under no-till (NT) and conventional tillage (CT) to which either poultry litter (PL) or conventional fertilizer (CF) was applied based on the nitrogen needs of corn (Zea mays L) in the Southern Piedmont of NE Georgia. Simulated rainfall was applied for 60 min to 2 by 3-m field plots at a constant rate in 2004 and variable rate in 2005. Runoff was continuously measured and subsamples taken for determining flow-weighted concentrations of fecal bacteria, hormones, and antibiotic residues. Neither Salmonella, nor Campylobacter, nor antimicrobial residues were detected in litter, soil, or runoff. Differences in soil concentrations of fecal bacteria before and after rainfall simulations were observed only for Escherichia coli in the constant rainfall intensity experiment. Differences in flow-weighted concentrations were observed only for testosterone in both constant and variable intensity rainfall experiments, and were greatest for treatments that received poultry litter. Total loads of E. coli and fecal enterococci, were largest for both tillage treatments receiving poultry litter for the variable rainfall intensity. Load of testosterone was greatest for no-till plots receiving poultry litter under variable rainfall intensity. Poultry litter application rates commensurate for corn appeared to enhance only soil concentrations of E. coli, and runoff concentrations of testosterone above background levels.
IEEE journal of selected topics in quantum electronics : a publication of the IEEE Lasers and Electro-optics Society
Optical coherence tomography (OCT) has great potential for deciphering the role of mechanics in n... more Optical coherence tomography (OCT) has great potential for deciphering the role of mechanics in normal and abnormal heart development. OCT images tissue microstructure and blood flow deep into the tissue (1-2mm) at high spatiotemporal resolutions allowing unprecedented images of the developing heart. Here, we review the advancement of OCT technology to image heart development and report some of our recent findings utilizing OCT imaging under environmental control for longitudinal imaging. Precise control of the environment is absolutely required in longitudinal studies that follow the growth of the embryo or studies comparing normal versus perturbed heart development to obtain meaningful in vivo results. These types of studies are essential to tease out the influence of cardiac dynamics on molecular expression and their role in the progression of congenital heart defects.
of the ribosome and its genes (Grimont and Grimont, 1986), and has been considered an effective g... more of the ribosome and its genes (Grimont and Grimont, 1986), and has been considered an effective genotypic Escherichia coli is a ubiquitous component of the intestinal mi- types (8.3%), comprising 33% of the total isolates, were shared among human and nonhuman sources in environmental water sampling times and were considered resident ribotypes. Two of the twenty resident ribotypes appeared at
Background/Question/Methods Over the past decade, prescribed burning has been increasingly used t... more Background/Question/Methods Over the past decade, prescribed burning has been increasingly used to reintroduce native fire regimes and restore fire-dependent communities. However, in contemporary landscapes the reintroduction of fire often brings unintended consequences, such as the invasion of exotic species. In the southern Appalachians, Paulownia tomentosa, an early successional species introduced from Asia, invades aggressively following both wild and prescribed fire. In Great Smoky Mountains National Park, considerable time and funding have been expended controlling this and other species following fire. Assessing the threat posed by species such as Paulownia tomentosa requires answers to two questions: (1) Where across the landscape is post-fire invasion most likely to occur? (2) Is the species able to persist and compete with native vegetation during post-fire succession? To address these questions, we sampled vegetation in 5 burns distributed across the southern Appalachians...
Applied and Environmental Microbiology
The ability to determine inactivation rates of Cryptosporidium parvum oocysts in environmental sa... more The ability to determine inactivation rates of Cryptosporidium parvum oocysts in environmental samples is critical for assessing the public health hazard of this gastrointestinal parasite in watersheds. We compared a dye permeability assay, which tests the differential uptake of the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) by the oocysts (A. T. Campbell, L. J. Robertson, and H. V. Smith, Appl. Environ. Microbiol. 58:3488-3493, 1992), with an in vitro excystation assay, which tests their ability to excyst and, thus, their metabolic potential and potential for infectivity (J.B. Rose, H. Darbin, and C.P. Gerba, Water Sci. Technol. 20:271-276, 1988). Formaldehyde-fixed (killed) oocysts and untreated oocysts were permeabilized with sodium hypochlorite and subjected to both assays. The results of the dye permeability assays were the same, while the excystation assay showed that no excystation occurred in formaldehyde-fixed oocysts. This confirmed th...
Applicant: Ethell Vereen, Jr Background/Question/Methods: Transmission of Salmonella and Campylob... more Applicant: Ethell Vereen, Jr Background/Question/Methods: Transmission of Salmonella and Campylobacter to humans can occur by many routes, including consumption of food animal products or raw produce contaminated with animal waste, contact with animals and their environment, and contaminated water; including surface waters that are potential reservoirs and transmission routes for these pathogens. The presence of the pathogens Salmonella and Campylobacter in the stream network of the Satilla River Basin (SRB) were monitored monthly from August 2007 to August 2009 to ascertain potential relationships between these pathogens and varying levels of agriculture and poultry processing facilities within the SRB. Watersheds were sampled that: 1) represent agricultural areas receiving poultry litter application, 2) agricultural areas with poultry houses and receiving poultry litter application, 3) reference areas with little or no agricultural activity, 4) a small watershed receiving direct d...
Background/Question/Methods Amur honeysuckle (Lonicera maackii (Rupr.) Herder) is a non-native sh... more Background/Question/Methods Amur honeysuckle (Lonicera maackii (Rupr.) Herder) is a non-native shrub that was introduced to the United States from Asia in the 1890s. Since its introduction, it has aggressively colonized many forests throughout the central U.S., leading to decreased diversity and richness in native plant communities. We examined ground-layer vegetation in five Indiana mixed-hardwood forests that contained a gradient of Amur honeysuckle densities to determine which ecological gradients related to honeysuckle dominance influence native species composition. During the summer of 2010, we sampled ground-layer vegetation and environmental variables using a series of fixed-area plots placed along transects. We used percent cover estimates of native herbaceous vegetation and seedlings (woody stems <1.37 m tall) to calculate Shannon-Weiner diversity (H'), taxonomic richness (S), and taxonomic evenness (E) for each study site. Nonmetric multidimensional scaling (NMS) an...
Background/Question/Methods The Central Hardwood Region (CHR) was historically dominated by Querc... more Background/Question/Methods The Central Hardwood Region (CHR) was historically dominated by Quercus forests, woodlands, and savannas. Over the past century, changes in structure and species composition in CHR forests have been attributed to changes in the natural disturbance regime, with a pointed focus on reduced fire frequency. The primary objective of this research was to determine how mortality rates, species composition, and stand structure have varied in old-growth forests of the CHR over two decades. A network of permanent plots was established in 1992-93 and resampled in 2011-12 to quantify changes in the structure and composition of nine old-growth forests (five in Indiana and four in Missouri) within the CHR. These forests are on a general gradient of decreasing site productivity, starting in eastern Indiana and continuing to southwest Missouri. We hypothesize: (1) structure in these forests has remained relatively stable, however (2) forest composition is shifting from a ...
Background/Question/Methods Concurrent disturbances can interact to affect the diversity and spat... more Background/Question/Methods Concurrent disturbances can interact to affect the diversity and spatial structure of forest understory plant communities. Forest management and deer herbivory are two common disturbances that often occur concurrently. Plant communities in canopy gaps tend to be dominated by ruderals due to increased resource availability, whereas communities browsed by deer generally lack palatable species intolerant to herbivory. Such responses are usually measured at the gap scale, although spatial heterogeneity in resources and herbivory pressure can vary at finer spatial scales. We used the Bray-Curtis dissimilarity index (BC) and spatial modeling techniques to examine patterns in fine-scale (0.5-m – 6.0-m) community similarity within, on the edge of, and in closed-canopy forest near canopy gaps (1.25-ha – 4.43-ha), within and outside of deer exclosures. We expected stronger spatial patterns in gap centers compared to the adjacent forest, and expected deer herbivory ...
Background/Question/Methods The ecosystem management paradigm embraces the restoration and mainte... more Background/Question/Methods The ecosystem management paradigm embraces the restoration and maintenance of ecological processes across many scales, and coarse woody debris (CWD) is an essential element of forest ecosystems. Standing (SDW) and down dead wood (DDW) are important components whose many ecological roles are well documented, but our knowledge of management impacts on this resource is not well understood. Because CWD in hardwood forests has slow decay rates, it can influence ecological processes at local, stand, and landscape levels for several decades. Forest stands subject to management will experience long-term changes to CWD dynamics, thus, influencing future spatiotemporal inputs of CWD. We examined the quantity, quality, and spatial arrangement of CWD in a relict forest and two managed forests. We used variable radius plots on a 10 m x 10 m grid to sample stands. For DDW we measured large and small end diameters and length, and for SDW we measured diameter and height;...
We evaluated the volume of down deadwood (DDW) and the basal area of standing deadwood (SDW) from... more We evaluated the volume of down deadwood (DDW) and the basal area of standing deadwood (SDW) from a chronosequence of 110 silvicultural openings and 34 mature stands (72-105 years old) across three Ecological Landtype Phases (ELTP; wet-mesic bottomlands, mesic slopes, and dry-mesic slopes) in southern Indiana, USA. The volume of DDW decreased with increasing opening age and was lower in
Biomedical optics express, 2015
Cardiac conduction maturation is an important and integral component of heart development. Optica... more Cardiac conduction maturation is an important and integral component of heart development. Optical mapping with voltage-sensitive dyes allows sensitive measurements of electrophysiological signals over the entire heart. However, accurate measurements of conduction velocity during early cardiac development is typically hindered by low signal-to-noise ratio (SNR) measurements of action potentials. Here, we present a novel image processing approach based on least squares optimizations, which enables high-resolution, low-noise conduction velocity mapping of smaller tubular hearts. First, the action potential trace measured at each pixel is fit to a curve consisting of two cumulative normal distribution functions. Then, the activation time at each pixel is determined based on the fit, and the spatial gradient of activation time is determined with a two-dimensional (2D) linear fit over a square-shaped window. The size of the window is adaptively enlarged until the gradients can be determi...
Forest Ecology and Management
Because of the devastation caused by the combined impacts of the balsam woolly adelgid (Adelges p... more Because of the devastation caused by the combined impacts of the balsam woolly adelgid (Adelges piceae; BWA, a non-native insect) and chronic acid deposition, Picea-Abies (spruce-fir) forests are one of the most threatened vegetation communities in North America. Endemic Abies fraseri (Fraser fir), the dominant overstory species in these forests, has experienced near complete overstory mortality as result of the adelgid. Observed forest regeneration patterns suggest high spatial variability, with dense patches of Rubus spp. (blackberry), A. fraseri, and deciduous regeneration repeating across the landscape. To quantify the spatial variability and density of A. fraseri, Picea rubens (red spruce), and deciduous regeneration in these forests, we sampled 60 randomly selected plots within Picea-Abies forests of Great Smoky Mountains National Park (GSMNP). As a measure of local variability in regeneration, we used regeneration density within 30 1 × 1 m subplots per plot to calculate a coe...
Journal of endovascular therapy : an official journal of the International Society of Endovascular Specialists, 2015
The average number of charged pions produced in ..pi../sup +/d reactions at 15-GeV/c ..pi../sup +... more The average number of charged pions produced in ..pi../sup +/d reactions at 15-GeV/c ..pi../sup +/ momentum is 3.6 +- 0.1 and the average number of ..pi..°'s is 1.9 +- 0.2. The average number of ..pi..°'s produced is essentially independent of the number of charged pions. About 45% of the events have four or more charged pions in the final state.
Proceedings of the Water Environment Federation, 2005
ABSTRACT The ultraviolet (UV) irradiation dose required to prevent full development (embryonation... more ABSTRACT The ultraviolet (UV) irradiation dose required to prevent full development (embryonation) of unembryonated Ascaris suum eggs in buffered water was studied. UV irradiation has been used in the past on larvated (embryonated) Ascaris suum eggs in an attempt to produce an attenuated vaccine for use in pigs. Such studies used doses of irradiation aimed at decreasing the infectivity of the eggs given as inocula. However, to our knowledge, there have been no studies that have examined the dose of UV irradiation required for full inactivation of unembryonated and embryonated eggs, nor have there been any studies which have described the effects of UV light on different types of eggs (e.g. eggs from feces versus eggs from the uteri of female worms versus eggs with the cortical layer removed).In our studies, non-infectious (unembryonated) eggs were exposed to UV doses ranging from 0 mJ/cm2 to as much as 1053.63 mJ/cm2 using a collimated beam apparatus containing two low-pressure mercury vapor lamps. A comparison between “tanned” eggs (collected from the feces of naturally infected pigs), and “untanned” or “ex utero” eggs (obtained from the uteri of female worms), was conducted. A subset of each of these two groups of eggs was treated with Clorox® solutions at different concentrations (0.56% to 2.5% sodium hypochlorite), for varying times, in order to erode the cortical (albuminous), vitelline, and lipid layers of the eggshells.Decorticated (tanned and untanned) eggs treated with a 9-10% Clorox® solution for 25 or 10 min respectively, were found to be the most vulnerable to inactivation by UV irradiation. Corticated, tanned eggs, not treated with Clorox®, were the most resistant; this is the type of egg most likely to be encountered in the environment, and thus the type whose response to UV light perhaps has the most relevance to real-world situations. It should be noted that although an attempt was also made to use untanned, corticated eggs in the study, these proved to be extremely “sticky”, and we were unable to recover them from the surfaces of the Petri dishes and the culture flasks used.All Clorox®-decorticated groups (whether tanned or untanned) reached 100% inactivation, (which we defined as 0% embryonation after a period of 2 weeks at 28 °C in the presence of oxygen), after exposure to doses ≥25.1 mJ/cm2. Tanned, corticated eggs required much higher doses, ≥333.62 mJ/cm2, to reach complete inactivation. Thus, it appears that treatment of eggs with Clorox®, and perhaps the length of such treatment, leads to a reduction in the dose of UV required for full inactivation of unembryonated egg populations.Future studies are planned to determine the ability of infectious (embryonated eggs) to retain their infectivity in a mouse-model after exposure to this range (0-1096.63 mJ/cm2) of irradiation.
Applied and environmental microbiology, 1997
The ability to determine inactivation rates of Cryptosporidium parvum oocysts in environmental sa... more The ability to determine inactivation rates of Cryptosporidium parvum oocysts in environmental samples is critical for assessing the public health hazard of this gastrointestinal parasite in watersheds. We compared a dye permeability assay, which tests the differential uptake of the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) by the oocysts (A. T. Campbell, L. J. Robertson, and H. V. Smith, Appl. Environ. Microbiol. 58:3488-3493, 1992), with an in vitro excystation assay, which tests their ability to excyst and, thus, their metabolic potential and potential for infectivity (J.B. Rose, H. Darbin, and C.P. Gerba, Water Sci. Technol. 20:271-276, 1988). Formaldehyde-fixed (killed) oocysts and untreated oocysts were permeabilized with sodium hypochlorite and subjected to both assays. The results of the dye permeability assays were the same, while the excystation assay showed that no excystation occurred in formaldehyde-fixed oocysts. This confirmed th...
Invasive Plant Science and Management, 2015
ABSTRACT The expansion of populations of invasive species continues to compromise the ecological ... more ABSTRACT The expansion of populations of invasive species continues to compromise the ecological and economic integrity of our natural resources. The negative effects of invasive species on native biota are widely reported. However, less is known about how the duration (i.e., age of oldest invaders) and intensity (i.e., density and percent cover) of an invasion influences native plant diversity and abundance at the microsite scale. We examined the influence of density, percent cover, and age of Amur honeysuckle (a nonnative invasive shrub), and several environmental factors on native plant taxa at 12 mixed hardwood forests in Indiana, USA. Overall, study sites with the greatest taxonomic diversity (Shannon&#39;s Diversity; H′), richness (S), percent cover, and density of native vegetation also had the lowest percent cover of Amur honeysuckle in the upper vertical stratum (1.01 to 5 m). Based on linear mixed model analyses, percent cover of Amur honeysuckle in the upper vertical stratum was consistently and negatively correlated with H′, S, total percent cover, and woody seedling density of native taxa at the microsite scale (P &lt; 0.05). Duration of Amur honeysuckle at the microsite scale was not significant when percent cover of Amur honeysuckle in the upper vertical stratum was included in models. However, duration of Amur honeysuckle invasion was significantly correlated with dependent variables and with upper-stratum honeysuckle cover, suggesting that older Amur honeysuckle in a microsite resulted in greater light competition from above for native understory plant species. Beyond increased cover and shading, our results do not provide evidence of duration-related effects from long-term dominance of honeysuckle in our sampled mixed hardwood forest sites. Nomenclature: Amur honeysuckle; Lonicera maackii (Rupr.) Herder. Management Implications: Nonnative invasive plants continue to pose one of the most serious threats to ecosystems worldwide. While the negative effects of invasive plants have been well documented, it is still unclear how the combined effect of duration of invasion and intensity (amount of occupied growing space) of an invader can influence native diversity at the microsite scale. We addressed this knowledge gap by examining how the duration and intensity of Amur honeysuckle invasion influenced the diversity and abundance of native plants in hardwood ecosystems of Indiana. Our results indicated that while percent cover of Amur honeysuckle in the upper vertical stratum (1.01 to 5 m) exhibited a strong negative correlation with native plant diversity and abundance at the microsite scale, duration of Amur honeysuckle invasion was not important when honeysuckle percent cover was included in the statistical models. However, when only duration of invasion was considered, it did show a significant negative correlation with native plant diversity and abundance and upper-stratum honeysuckle cover. It therefore appears that microsites where Amur honeysuckle has persisted longer contain a greater percent cover of this invasive shrub, resulting in greater light competition from above and reduced diversity and abundance of native flora. Information about the combined effects of Amur honeysuckle invasion intensity and duration can help forest managers prioritize control efforts in areas where existing sources of native plant propagules are present in microsites where Amur honeysuckle invasion is less intense. Also, our results suggest that the rate of community recovery after honeysuckle removal may not be heavily influenced by cumulative effects related to the duration of invasion. Such information is important for management efforts to support the long-term recovery of native plant communities in invaded ecosystems. Such information may be critical to the long-term recovery of native plant communities in these invaded ecosystems.
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Papers by Michael Jenkins