Antibiotic Resistance and Substrate Utilization by Bacteria Affi liated with Cave Streams at Diff erent Levels of Mammoth Cave

Located in south-central Kentucky, Mammoth Cave is one of the most unique National Parks in the United States. The surface landscape includes complex relationships between the flora and fauna along with human influences. However, the primary ecological focus is concealed below ground. Over four-hundred miles of cave passages, created by fl owing groundwater over millions of years, host a variety of macro and micro organisms. The Green River has cut into the limestone formation over geologic time, creating a complex network of passages that are stacked, one below the other, with the newer levels of cave lying near the bottom. Palmer (2007, 1987) describes 4 main levels of cave passages in the Mammoth Cave system. A detailed discussion of the geology and conditions that formed the cave levels can be found in several reports (Palmer, 1987; Palmer 1989; White and White, 1989; Granger, et al, 2001). Precipitation continues to provide water that traverses from the surface, through the unsaturated vadose levels of the cave, and down to the water table in the lower level. Water enters the cave system through direct recharge at sinkholes and through diff use percolation. The rapid infiltration of stormwater often exceeds the carrying capacity of the upper cave passages and excess water is pushed into void pore-spaces near the top of bedrock. This stored water is slowly released and provides base-fl ow to cave streams that replenish the pools and streams in the lowest level of the cave (Ryan and Meimen, 1996). These perennial cave streams carry many of the organic compounds that provide energy to the cave ecosystem (Barr, 1976)

Modeling the Movement of Septic Water Chloride through a Soil Profile

The purpose of this study was to investigate the movement of chloride through a vadose zone located under failed and non-regulated septic tanks of Duhok city, Kurdistan of Iraq, potentially contaminating its groundwater. A physical vadose model (PVM) of a vertical flow direction was built in the laboratory to represent the city soil profile. The size of the PVM was 210 × 122 × 9.7 cm (height, width, and depth). Preliminary soil tests were conducted to better represent the lithology of study area. The PVM was then packed with regional silt clay soil, after modifying its texture, using an innovative packing procedure to preserve natural soil density and porosity. The model was run for a period of three months with newly collected septic water (black water from a septic tank) as an exclusive source of contaminants. Water samples from eight vertically arranged portals representing 12.5, 37.5, 62.5, 87.5, 112.5, 137.5, 162.5, and 187.5 cm levels in the subsurface soil profile were collected on a daily basis and analyzed weekly. Logistic regression and logarithmic models were developed to spatially predict the movement of chloride ions at different sampling depths in the soil profile until the system had reached the equivalent chloride concentration of the septic water or had stabilized. There was a good agreement between the physical model and the statistical models, however each model had its strengths and weaknesses. This study demonstrated that there is a potential for septic water to reach the water table within a 2–3 weeks period. Dilution and dispersion appear to play important roles in the fate and transport of septic water. This study has the potential to help the local authorities predict percolation rates and establish strategies for groundwater management in order to protect the public health

ADAPTATIONS OF INDIGENOUS BACTERIA TO FUEL CONTAMINATION IN KARST AQUIFERS IN SOUTH-CENTRAL KENTUCKY

Abstract: The karst aquifer systems in southern Kentucky can be dynamic and quick to change. Microorganisms that live in these unpredictable aquifers are constantly faced with environmental changes. Their survival depends upon adaptations to changes in water chemistry, taking advantage of positive stimuli and avoiding negative environmental conditions. The U.S. Geological Survey conducted a study in 2001 to determine the capability of bacteria to adapt in two distinct regions of water quality in a karst aquifer, an area of clean, oxygenated groundwater and an area where the groundwater was oxygen depleted and contaminated by jet fuel. Water samples containing bacteria were collected from one clean well and two jet fuel contaminated wells in a conduit-dominated karst aquifer. Bacterial concentrations, enumerated through direct count, ranged from 500,000 to 2.7 million bacteria per mL in the clean portion of the aquifer, and 200,000 to 3.2 million bacteria per mL in the contaminated portion of the aquifer over a twelve month period. Bacteria from the clean well ranged in size from 0.2 to 2.5 mm, whereas bacteria from one fuel-contaminated well were generally larger, ranging in size from 0.2 to 3.9 mm. Also, bacteria collected from the clean well had a higher density and, consequently, were more inclined to sink than bacteria collected from contaminated wells. Bacteria collected from the clean portion of the karst aquifer were predominantly (,95%) Gram-negative and more likely to have flagella present than bacteria collected from the contaminated wells, which included a substantial fraction (,30%) of Gram-positive varieties. The ability of the bacteria from the clean portion of the karst aquifer to biodegrade benzene and toluene was studied under aerobic and anaerobic conditions in laboratory microcosms. The rate of fuel biodegradation in laboratory studies was approximately 50 times faster under aerobic conditions as compared to anaerobic, sulfur-reducing conditions. The optimum pH for fuel biodegradation ranged from 6 to 7. These findings suggest that bacteria have adapted to water-saturated karst systems with a variety of active and passive transport mechanisms

Using validation sets to avoid overfitting in AdaBoost. to be seen

AdaBoost is a well known, effective technique for increasing the accuracy of learning algorithms. However, it has the potential to overfit the training set because its objective is to minimize error on the training set. We demonstrate that overfitting in AdaBoost can be alleviated in a time-efficient manner using a combination of dagging and validation sets. Half of the training set is removed to form the validation set. The sequence of base classifiers, produced by AdaBoost from the training set, is applied to the validation set, creating a modified set of weights. The training and validation sets are switched, and a second pass is performed. The final classifier votes using both sets of weights. We show our algorithm has similar performance on standard datasets and improved performance when classification noise is added

Modeling the Movement of Septic Water Chloride through a Soil Profile

The purpose of this study was to investigate the movement of chloride through a vadose zone located under failed and non-regulated septic tanks of Duhok city, Kurdistan of Iraq, potentially contaminating its groundwater. A physical vadose model (PVM) of a vertical flow direction was built in the laboratory to represent the city soil profile. The size of the PVM was 210 × 122 × 9.7 cm (height, width, and depth). Preliminary soil tests were conducted to better represent the lithology of study area. The PVM was then packed with regional silt clay soil, after modifying its texture, using an innovative packing procedure to preserve natural soil density and porosity. The model was run for a period of three months with newly collected septic water (black water from a septic tank) as an exclusive source of contaminants. Water samples from eight vertically arranged portals representing 12.5, 37.5, 62.5, 87.5, 112.5, 137.5, 162.5, and 187.5 cm levels in the subsurface soil profile were collected on a daily basis and analyzed weekly. Logistic regression and logarithmic models were developed to spatially predict the movement of chloride ions at different sampling depths in the soil profile until the system had reached the equivalent chloride concentration of the septic water or had stabilized. There was a good agreement between the physical model and the statistical models, however each model had its strengths and weaknesses. This study demonstrated that there is a potential for septic water to reach the water table within a 2–3 weeks period. Dilution and dispersion appear to play important roles in the fate and transport of septic water. This study has the potential to help the local authorities predict percolation rates and establish strategies for groundwater management in order to protect the public health

The Role of Attached and Free-Living Bacteria in Biodegradation in Karst Aquifers

Natural attenuation of groundwater contamination occurs at some level for all aquifers impacted with organic contaminants. The issues regarding natural attenuation are whether it takes place at a sufficient rate to be protective of human health and the environment. Implementation of a Monitored Natural Attenuation (MNA) remedial alternative for groundwater requires parties responsible for the contamination to demonstrate to regulators and the public that MNA is protective at a given site. Analysis of MNA for remediation of karst aquifers is hampered by a lack of understanding of biodegradation in karst environments. The lack of studies examining biodegradation in karst aquifers may in large part be due to the widespread perception that contaminants are rapidly flushed out of karst aquifers resulting in insufficient residence times for contaminants to biodegrade. In highly developed and well-connected conduit systems, the rate of contaminant migration is perceived to be much faster than the rate of biodegradation. This perception of contaminant transport is largely incorrect. Tracer studies for karst aquifers often indicate that these aquifers are characterized by diverse flow regimes and storage capabilities. Additionally, it is also believed that if bioremediation in bedrock aquifers is dependent upon contact between surface-attached bacteria and contaminants, then bioremediation would be limited by the low surface-area-to-volume ratio (SA/V) of karst aquifers. A quantitative basis, however, for accepting or rejecting the assumption that attached bacteria dominate the biodegradation process in karst conduits has not been shown. The objective of this research was to determine if free-living karst bacteria from contributed as much to toluene biodegradation as attached bacteria. This is an important area of research. Research indicates bacteria are both attached and free-living in karst aquifers and it is unrealistic to think that only the attached bacteria facilitate biodegradation. The groundwater use in all tests was taken from a karst aquifer know to be impacted by BTEX. The resulting first-order rate constants were computed to be 0.014 per hour for the open system and 0.0155 per hour for the packed reactor system. Biodegradation of toluene in flow-through laboratory karst systems of varying SA/V indicated that the observed biodegradation of toluene was attributable to free-living karst bacteria and not limited by low SA/V in karst. This was evidenced by the fact that the systems with five-fold variation in SA/V were shown to have observed pseudo first order reaction rate constants that differed by only 7.0%. If attached bacteria were primarily responsible for biodegradation and limiting, a proportional difference in the observed rates relative to the difference in surface area would be expected

Report on Transformative Agreements

This report was prepared for the University of Waterloo Library's Collection Strategy Committee to describe the current landscape of non-traditional publishing agreements between academic libraries and publishers. In addition to identifying and defining these types of agreements, this report provides criteria to use when deciding to sign a non-traditional agreement and suggests recommendations for moving forward with open access initiatives at Waterloo

A Holistic Understanding of Integrational Support from University Students’ Perspective Through Appreciative Inquiry

AbstractStudent integration into the academic community is a primary condition for student success and achievement. This research explores the potential enhancements of supportive activities and key peer facilitator traits to maximize social and academic integration of first year university students. Focus group interviews (n=16) were conducted with first-year students (n=93) coming directly from secondary school. Using Appreciative Inquiry, participants indicate that current informally organized support activities in a university environment during the first semester of the academic year are highly desirable (e.g. welcome activities, extra-curricular activities, co-curricular activities). The need for support in social integration in the beginning of the year and the need for support in academic integration at the end of the first semester clearly arise out of this study. When addressing some specific criteria related to the objectives, form and design, this paper suggests that peer-assisted support activities are particularly useful in increasing sustainable informal peer support and integration among students. This article aims to prompt further discussion on the potential, value and purpose of department-specific structural peer assisted support and peer learning approaches for integration of first year university students