No description available.

No description available.

No description available.

Objectives: One potential impact of oral probiotic products involves use of known bacterial antagonisms to alter the ecologic environment in periodontal pockets from one inhabited by pathogenic dental plaque microorganisms to one more favorable to colonization by non-pathogenic species (bacterial replacement). Until recently, the ability to introduce such beneficial effector bacteria into the oral cavity of periodontitis patients has been limited by the lack of specifically-formulated available commercial probiotic products. PerioBalance (Sunstar GUM), with two strains of the gram-positive, aerobic species Lactobacillus reuteri, and EvoraPlus (Oragenics), with freeze-dried strains of the gram-positive, aerobic species Streptococcus oralis, Streptococcus uberis, and Streptococcus rattus, are two recently-introduced commercial oral probiotic products proposed to have beneficial effects against periodontal disease. However, it is not known if the microbial species contained in these two oral probiotics are viable after the manufacturing process, and have the capability to exert inhibitory effects against putative periodontal bacterial pathogens when reconstituted in the oral cavity. Thus, the objective of the present study was to determine whether PerioBalance lactobacilli and EvoraPlus streptococci are viable upon product use, and possess in vitro inhibitory effects against fresh clinical strains of the putative periodontal bacterial pathogens, Tannerella forsythia and Prevotella intermedia/nigrescens, in the presence of anaerobic growth conditions. Methods: Commercial lots of PerioBalanceÒ and EvoraPlusÒ tablets were aseptically removed from the product packaging with sterile forceps, dissolved into Möller’s VMG I anaerobic dispersion solution, plated onto pre-reduced, enriched Brucella blood agar, and subjected to overnight anaerobic incubation at 35ºC in a culture cabinet containing 85% N2-10% H2-5% CO2, and to overnight aerobic incubation in a 5% CO2-95% air atmosphere. All culture plates were then visually examined under magnification for microbial colony growth. In vitro solid media competition assays were used to assess the in vitro inhibition capability of the two oral probiotics against T. forsythia and P. intermedia/nigrescens. Pioneer PerioBalance lactobacilli and EvoraPlus streptococci colonies were first grown on enriched Brucella blood agar media, followed by secondary spotting of T. forsythia and P. intermedia/nigrescens isolates immediately next to the established pioneer EvoraPlus and PerioBalanceÒ bacterial colonies such that they almost touched each other. After an additional overnight anaerobic incubation period, growth inhibition of the putative periodontal bacterial pathogens by the pioneer PerioBalance and EvoraPlus colonies was noted as the visual presence without magnification of a proximal zone of inhibition at the intersection of the pioneer colonies and the T. forsythia and P. intermedia/nigrescens colonies. Results: PerioBalance lactobacilli grew readily and in abundance in vitro on anerobically and anaerobically-incubated EBBA, with no other colony types or contaminating organisms. In contrast, EvoraPlus product samples purchased over-the-counter from drug stores in Maryland and Pennsylvania failed to exhibit any in vitro microbial growth under anaerobic and aerobic incubation conditions, with only EvoraPlus tablets obtained directly from the manufacturer yielding in vitro streptococcal growth. No in vitro inhibition was noted under anaerobic conditions of established PerioBalance lactobacilli and EvoraPlus streptococci pioneer colonies against subsequent growth of clinical isolates of T. forsythia and P. intermedia/nigrescens, with no zone of inhibition developing between their colonies and the immediately-adjacent established oral probiotic pioneer colonies. Conclusions: The two commercial oral probiotics evaluated varied considerably in the viability of their microbial constituents, with abundant growth of PerioBalance lactobacilli found in over-the-counter product material, and the lack of any EvoraPlus streptococci growth in product tablets obtained from sources other than directly from the manufacturer. Both oral probiotic products failed in vitro, in solid media competition assays, to inhibit growth of fresh clinical isolates the putative periodontal bacterial pathogens T. forsythia and P. intermedia/nigrescens under anaerobic growth conditions. These findings question the potential effectiveness of the two oral probiotic products to alter the subgingival ecology in periodontal pockets when anaerobic environmental conditions are present. Additional research is needed to assess the inhibitory potential of PerioBalance lactobacilli and EvoraPlus streptococci against additional isolates of subgingival bacterial species, and in circumstances where microaerophilic or aerobic environmental conditions are found. / Oral Biology

While the idea of critical break rate of water distribution pipeline (defined as the break rate after which it is no longer economical to continuously repair) has been accepted in the literature and among the practicing engineers, the formula to obtain the critical break rate has remained elusive. In this dissertation, an equation for identifying the threshold break rate of a pipe is developed. The threshold break rate equation gives a rule of thumb for pipe replacement decision. Input parameters to obtain the threshold break rate of a pipe are repair and replacement costs, interest rate, and the length of the pipe. In addition, a methodology that enables the use of threshold break rate with the failure intensity and hazard functions is developed. The methodology is drawn by considering the relationships of the definitions of the threshold break rate with intensity and hazard functions in the context of a repairable system's failure process modeling. As a result, the newly developed threshold break rate equation can be coupled with any appropriate intensity and hazard function to obtain economically optimal replacement time of a pipe. Also, practical usage of the threshold break rate is demonstrated with a number of numerical examples. Design aids in the form of charts and tables are provided. The threshold break rate can be easily obtained either graphically or with the aid of the tables. The methodology that links the threshold break rate and failure rate (intensity and hazard) functions is extended to accommodate stress multiplying environmental factors in the form of the proportional intensity and hazards model. The two models consist of an age dependent failure rate function and a covariate structure. They are applied to a case study area pipe system to obtain optimal replacement times for individual pipes in the system. As a result, important hazard characteristics of water distribution pipes are drawn, and implications on the optimal replacement analysis are discussed. A pipe break prediction model is also developed in this research. The model spans the space between the linear and exponential break trends. The model is applied to the case study area pipe system with various cost options. The results from this analysis are discussed in terms of practical implementation of the replacement strategies. / Ph. D.

Water distribution system pipes span thousands of miles and form a significant part of the total infrastructure of the country. Rehabilitation of this underground infrastructure is one of the biggest challenges currently facing the water industry. Water main deterioration is twofold: the main itself loses strength over time and breaks; also, there is degradation of water quality and hydraulic capacity due to build of material within a main. The increasing repair and damage costs and degrading services demand that a deteriorating water main be replaced at an optimal time instead of continuing to repair it. In addition, expanding business districts, indirect costs, and interruptions including protected areas, waterways and roadways require examination of trenchless technologies for pipe installation. In this thesis a new threshold break rate criterion for the optimal replacement of pipes is provided. As opposed to the traditional present worth cost (PWC) criterion, the derived method uses the equivalent uniform annualized cost (EUAC). It is shown the EUAC based threshold break rate subsumes the PWC based threshold break rate. In addition, practicing engineers need a user-friendly decision support system to aid in the optimal pipeline replacement process. They also need a task-by-task cost evaluation in a project. As a part of this thesis a comprehensive decision support system that includes both technology selection knowledge base and cost evaluation spreadsheet program within a graphical user interface framework is developed. Numerical examples illustrating the theoretical derivations are also included. / Master of Science

Existing literature on the relationship between ridehailing (RH) and transit services is limited to empirical studies that rely on self-reported answers and lack spatial and temporal contexts. To fill this gap, the research takes a novel approach that uses real-time geospatial analyzes. Using this approach, we estimate the extent to which ride-hailing services have contributed to the recent decline in public transit ridership. With source data on ridehailing trips in Chicago, Illinois, we computed the real-time transit-equivalent trip for the 7,949,902 ridehailing trips in June 2019; the sheer size of this sample is incomparable to the samples studied in existing literature. An existing Multinomial Nested Logit Model was used to determine the probability of a ridehailer selecting a transit alternative to serve the specific origin-destination pair, P(Transit|CTA) . The study found that 31% of RH trips are replaceable, 61% are not replaceable, and 8% lie within the buffer zone. We measured the robustness of this probability using a parametric sensitivity analysis, and performed a two-tailed t-test, with a 95% confidence interval. In combination with a Summation of Probabilities, the results indicate that the total travel time for a transit trip has the greatest influence on the probability of using transit, whereas the airport pass price has the least influence. Further, the walk time, number of stops in the origin and destination census tracts, and household income also have significant impacts on the probability of using transit. Lastly, we performed a Time Value Analysis to explore the cost and trip duration difference between RH trips and their transit-equivalent trips on the probability of switching to transit. The findings demonstrated that approximately 90% of RH trips taken had a transit-equivalent trip that was less expensive, but slower. The main contribution of this study is its thorough approach and fine-tuned series of real-time spatial analyzes that investigate the replaceability of RH trips for public transit. The results and discussion intend to provide perspective derived from real trips and encourage public transit agencies to look into possible opportunities to collaborate with ridehailing companies. Moreover, the methodologies introduced can be used by transit agencies to internally evaluate opportunities and redundancies in services. Lastly, we hope that this effort provides proof of the research benefits associated with the recording and release of ridehailing data. / Master of Science / Existing literature on the relationship between ridehailing (RH) and transit services is limited to empirical studies that rely on self-reported answers and lack spatial and temporal contexts. To fill this gap, the research takes a novel approach that uses real-time geospatial analyzes. Using this approach, we estimated the extent to which ride-hailing services have contributed to the recent decline in public transit ridership. With source data on ridehailing trips in Chicago, Illinois, we computed the real-time transit-equivalent trip for the 7,949,902 ridehailing trips in June 2019; the sheer size of this sample is incomparable to the samples studied in existing literature. An existing Multinomial Nested Logit Model was used to determine the probability of a ridehailer selecting a transit alternative to serve the specific origin-destination pair, P(Transit|CTA) . The study found that 31% of RH trips are replaceable, 61% are not replaceable, and 8% lie within the buffer zone. We measured the robustness of this probability using a parametric sensitivity analysis, and performed a two-tailed t-test, with a 95% confidence interval. In combination with a Summation of Probabilities, the results indicate that the total travel time for a transit trip has the greatest influence on the probability of using transit, whereas the airport pass price has the least influence. Further, the walk time, number of stops in the origin and destination census tracts, and household income also have significant impacts on the probability of using transit. Lastly, we performed a Time Value Analysis to explore the cost and trip duration difference between RH trips and their transit-equivalent trips on the probability of switching to transit. The findings demonstrated that approximately 90% of RH trips taken had a transit-equivalent trip that was less expensive, but slower. The main contribution of this study is its thorough approach and fine-tuned series of real-time spatial analyzes that investigate the replaceability of RH trips for public transit. The results and discussion intend to provide perspective derived from real trips and encourage public transit agencies to look into possible opportunities to collaborate with ridehailing companies. Moreover, the methodologies introduced can be used by transit agencies to internally evaluate opportunities and redundancies in services. Lastly, we hope that this effort provides proof of the research benefits associated with the recording and release of ridehailing data.

This dissertation develops an economic equipment replacement model suitable for Flexible Manufacturing Systems (FMSs). An FMS represents an integrated machining system which produces multiple products and utilizes multiple inputs including avital materials handling system. The system's interactive nature defies traditional replacement works which are confined to one-for-one as well as like-for-like situations. The model developed in this work addresses the issue of multiple machine replacement. Considerations incorporated include layout, transportation, materials handling capacity, flexibility, capacity expansion/contraction, obsolescence and deterioration, inputs substitution, and equipment depreciation. This model is demand driven. The optimality criterion is the maximization of the after-tax future worth of the system at the end of a specified planning horizon. The 1983 ACRS rules are used. Illustrative examples are provided throughout. / Ph. D.

Yes / We develop an analytical real-option solution to the after-tax optimal timing boundary for a replaceable asset whose operating cost and salvage value deteriorate stochastically. We construct a general replacement model, from which seven other particular models can be derived, along with deterministic versions. We show that the presence of salvage value and tax depreciation significantly lowers the operating cost threshold that justifies (and thus hastens) replacement. Although operating cost volatility increases defer replacement, increases in the salvage value volatility hasten replacement, albeit modestly, while increases in the correlation between costs and salvage value defer replacement. Reducing the tax rate or depreciation lifetime, or allowing an investment tax credit, yield mixed results. These results are also compared with those of less complete models, and deterministic versions, showing that failure to consider several stochastic variables and taxation in the replacement process may lead to sub-optimal decisions.

Yes / Currently available replacement heart valves all have limitations. This study aimed to produce and characterize an acellular, biocompatible porcine pulmonary root conduit for reconstruction of the right ventricular outflow tract e.g., during Ross procedure. A process for the decellularization of porcine pulmonary roots was developed incorporating trypsin treatment of the adventitial surface of the scraped pulmonary artery and sequential treatment with hypotonic Tris buffer (HTB; 10 mM Tris pH 8.0, 0.1% (w/v) EDTA, and 10 KIU aprotinin), 0.1% (w/v) sodium dodecyl sulfate in HTB, two cycles of DNase and RNase, and sterilization with 0.1% (v/v) peracetic acid. Histology confirmed an absence of cells and retention of the gross histoarchitecture. Im-munohistochemistry further confirmed cell removal and partial retention of the extracellular matrix, but a loss of collagen type IV. DNA levels were reduced by more than 96% throughout all regions of the acellular tissue and no functional genes were detected using polymerase chain reaction. Total collagen levels were retained but there was a significant loss of glycosaminoglycans following decellularization. The biomechanical, hydrody-namic, and leaflet kinematics properties were minimally affected by the process. Both immunohistochemical labeling and antibody absorption assay confirmed a lack of a-gal epitopes in the acellular porcine pulmonary roots and in vitro biocompatibility studies indicated that acellular leaflets and pulmonary arteries were not cytotoxic. Overall the acellular porcine pulmonary roots have excellent potential for development of a tissue substitute for right ventricular outflow tract reconstruction e.g., during the Ross procedure.