ObjectivesSugar consumption has been decreasing in Japan, suggesting higher rates of sucrose-independent supragingival plaque formation. For developing an in vitro biofilm model of sucrose-independent supragingival plaque, this study aimed to investigate the compositions and functions on contributing to cariogenicity in comparison with sucrose-dependent biofilm. Materials and MethodsAn in vitro multispecies biofilm containing Actinomyces naeslundii, Streptococcus gordonii, S.mutans, Veillonella parvula and Fusobacterium nucleatum was formed on 24-well plates in the absence or presence of 1% sucrose. Compositions were assessed by plate culture, scanning electron microscopy and confocal laser scanning microscopy after fluorescent in situ hybridisation or labelling of extracellular polymeric substances (EPS). Functions were assessed by acidogenicity, adherence strength and sensitivities to anticaries agents. ResultsAlthough both biofilms exhibited a Streptococcus predominant bacterial composition, there were differences in bacterial and EPS compositions; in particular, little glucan EPS was observed in sucrose-independent biofilm. Compared with sucrose-dependent biofilm, acidogenicity, adherence strength and antimicrobial resistance of sucrose-independent biofilm were only slightly lower. However, dextranase degradation was substantially lower in sucrose-independent biofilm. ConclusionOur findings suggest that sucrose-independent biofilm may have cariogenicity as with sucrose-dependent biofilm. These in vitro models can help further elucidate plaque-induced caries aetiology and develop new anticaries agents.
Life cycle assessment (LCA) provides a standardized protocol for estimating a wide range of life cycle technology impacts. LCA is used to make comparisons between alternative technology systems and to identify opportunities for reducing environmental impacts at the local, regional, and global scales. This work demonstrates the importance of uncertainty and variability characterization in Life Cycle Assessment, using the study of freshwater consumption for a crop production unit process as an example. A sensitivity analysis and uncertainty analysis is performed on the estimation of two classes of freshwater consumption impacts at the farm level spatial scale: green and blue water (abbreviated as GW and BW respectively). Green water refers to the amount of water consumed that originated as local rainfall, blue water refers to the amount of water consumed that was abstracted from surface or groundwater sources. Thus, in the context of crop production green water is a function of land use and blue water is a function of the amount of irrigation water applied. It is found that green water is most sensitive to precipitation and rate of crop water uptake, with estimates range from +/- 20% and +/-18% of the estimate respectively. Neglecting sparse environmental data such as wind speed and relative humidity can introduce uncertainties of up to 30% of the estimate. Uncertainty in blue water consumption is driven by the amount of irrigation water applied. For cases of under irrigation, uncertainty in blue water consumption is equal to uncertainty in the water application data and averages 18% of the estimate. For cases of over irrigation, the uncertainty in blue water consumption is equal to the uncertainty in green water consumption. For cases of irrigation application matching the crop water demand, the uncertainty compounds, and is equal to 40% of the estimate on average. Through a process known as atmospheric recycling, evaporated water can return to the terrestrial ecosystem as precipitation within days or weeks of having entered the atmosphere, reducing the impact of freshwater consumption. Variability associated with temporal and spatial scales and with boundary selection has a substantial impact on the magnitude of the freshwater consumption impacts, but the consideration of these control volume issues has not been considered in the literature in the context of freshwater consumption impacts in LCA. A bounding analysis is performed to determine the effect of atmospheric recycling uncertainty has on freshwater consumption impacts. Atmospheric recycling can reduce the impact of freshwater consumption from 0 to 80% of the farm level estimate, depending on the region, spatial scale, and temporal scale considered within the control volume. In addition there exists unquantified uncertainty associated with how changes in land cover will effect precipitation, irrigation response, and associated freshwater consumption impacts in the context of LCA. Energy required for irrigation is estimated, specifically for water withdrawal from surface and groundwater sources, and water application by pressure and gravity irrigation systems. It is shown that the energetic cost of water withdrawal and application is higher in regions experiencing freshwater scarcity. It is suggested that further research into the interdependence of water and energy production, known as the water-energy nexus, be considered as an alternative approach to currently proposed freshwater impact characterization methods. It is argued that, although uncertainty associated with energy use for irrigation can as high as 40% of the estimate, particularly for groundwater extraction in areas under water stress, it can be bounded as opposed to the unbounded uncertainty associated with atmospheric recycling. (Abstract shortened by UMI.)
Incorporating water use and water quality pollution impacts in life cycle assessment (LCA) methods is of great value for better management of water resources. Considerable research and impact assessment methods for water LCA have been developed. However, no consensus has been reached and water impacts are not treated consistently in LCA at present. In this dissertation, I have developed a water LCA approach, which assesses the impacts of water use and water quality pollution in an integrated way. In this approach, consumptive water use and nonconsumptive water use are separately assessed. Consumptive water use refers to freshwater that is extracted from a resource and used in such a way that it is not released back to the original watershed. Non-consumptive water use is water returned to the original watershed that may be used again. Consumptive water use might cause direct impacts on water quantity, while non-consumptive water use might result in direct impacts on water quality pollution. In the present work, environmental impacts on water resources and aquatic environments are estimated by applying relevant impact characterization factors to water consumption and pollutant emissions. In addition, cost of the wastewater treatment method selected is proposed as an impact indicator for water quality pollution. Three examples were used to demonstrate the application of this approach: 1) coal-fired electricity power generation; 2) Marcellus shale gas wells; 3) concrete manufacturing with cement and several cement substitutes. The example of coalfired electricity power generation showed that, on average, 1.2 cubic meters of freshwater are consumed per MWh of electricity generated, which could be primarily attributed to the cooling process. As for the water quality pollution, impacts from coal mining and electricity generation are comparable and influenced greatly by wastewater treatment. The case study of Marcellus shale gas wells showed that 0.005 to 0.02 liters of freshwater is consumed per MJ of gas produced, excluding utilization of gas at end use. Most of the potential water quality pollution impacts are associated with produced water from gas development. The case study of concrete with cement and cement substitutes showed that 8 to 14 cubic meters of freshwater withdrawal are required per cubic meter of conventional concrete with compressive strength of 20 to 35 MPa. Replacing cement with cement substitutes, glass powder and alkaline activated slag, in concrete could reduce its life cycle water withdrawal and impacts of water quality pollution. These three case studies demonstrate that a life cycle perspective can improve the understanding of water sustainability issues. For coal fired electricity generation and Marcellus shale gas development, direct water use for onsite operations have higher impacts than water use for supply chain production across their life cycle. In contrast, for concrete with cement and cement substitutes, indirect water use has much higher impacts than direct water use at production facilities. In addition, the application of this water LCA approach to industrial products enables the consideration of water impacts as a specific category and the comparison of water impacts with other environmental impacts. In this dissertation, life cycle greenhouse gas (GHG) emissions of the three products were estimated.
A combination of experimental investigation and process simulation was used to analyze the effect of various operational parameters on impurity back diffusion into ultrahigh pressure (UHP) gas distribution systems. Advanced and highly sensitive analytical equipment, such as the Tiger Optics MTO 1000 H2O cavity ring-down spectrometer (CRDS), was used in experiments to measure real time back diffusing moisture concentrations exiting an electro-polished stainless-steel (EPSS) UHP distribution pipe. Design and operating parameters; main and lateral flow rates, system pressure, restrictive flow orifice (RFO) aperture size, and lateral length were changed to impact the extent of back diffusing impurities from a venting lateral. The process model developed in this work was validated by comparing its predictions with data from the experiment test bed. The process model includes convection, molecular diffusion in the bulk, surface diffusion, boundary layer transport, and all modes of dispersion; applicable in both laminar and turbulent flow regimes. Fluid dynamic properties were directly measured or were obtained by solving Navier-Stokes and continuity equations. Surface diffusion as well as convection and dispersion in the bulk fluid played a strong role in the transport of moisture from vents and lateral branches into the main line. In this analysis, a dimensionless number (Peclet Number) was derived and applied as the key indicator of the relative significance of various transport mechanisms in moisture back-diffusion. Guidelines and critical values of Peclet number were identified for assuring the operating conditions meet the purity requirements at the point of use while minimizing UHP gas usage. These guidelines allowed the determination of lateral lengths, lateral diameters, flow rates, and restrictive flow device configurations to minimize contamination and UHP gas consumption. Once a distribution system is contaminated, a significant amount of purge time is required to recover the system background due to the strong interactions between moisture molecules and the inner surfaces of the components in a gas distribution system. Because of the very high cost of UHP gases and factory downtime, it is critical for high-volume semiconductor manufacturers to reduce purge gas usage as well as purge time during the dry-down process. The removal of moisture contamination in UHP gas distribution systems was approached by using a novel technique dubbed pressure cyclic purge (PCP). EPSS piping was contaminated with moisture, from a controlled source, and then purged using a conventional purge technique or a PCP technique. Moisture removal rates and overall moisture removal was determined by measuring gas phase moisture concentration in real time via a CRDS moisture analyzer. When compared to conventional purge, PCP reduced the time required and purge gas needed to clean the UHP gas distribution systems. However, results indicate that indiscriminately initiating PCP can have less than ideal or even detrimental results. An investigation of purge techniques on the removal of gas phase, chemisorbed, and physisorbed moisture, coupled with the model predictions, led to the testing of hybrid PCP. The hybrid PCP approach proved to be the most adaptable purge technique and was used in next phase of testing and modeling. Experiments and modeling progressed to include testing the effectiveness of hybrid PCP in systems with laterals; more specifically, laterals that are "dead volumes" and results show that hybrid PCP becomes more purge time and purge gas efficient in systems with increasing number and size of dead volumes. The process model was used as a dry-down optimization tool requiring inputs of; geometry and size, temperature, starting contamination level, pressure swing limits of inline equipment, target cleanliness, and optimization goals; such as, minimizing pure time, minimizing purge gas usage, or minimizing total dry-down cost. (Abstract shortened by UMI.)
Life cycle assessment (LCA) is the assessment of environmental impacts of a product, process or service across its entire life cycle. This assessment is done based on a particular function of the product or process (for example: the function of drying hands for a hand dryer or providing cleaning service for a cleaning company). A product’s life cycle can include the extraction of raw materials, energy acquisition, its production and manufacturing, use, reuse, recycling and ultimate disposal. All these stages in a product’s life cycle result in the generation of wastes, emissions, and the consumption of resources. These environmental exchanges contribute to impacts such as, climate change, stratospheric ozone depletion, photooxidant formation (smog), eutrophication, acidification, toxicological stress on human health and ecosystems, depletion of resources, and noise pollution among others. LCA allows us to see where a product or service can be improved or manufacturing of new better products. Life cycle impact asssesment is the third phase of LCA in which the flow of materials associated with the product (or process) is translated into consumptions of resources and potential impacts to the environment. The purpose of the impact assessment phase is thus to interpret the life cycle emissions and resource consumption inventory in terms of indicators and to evaluate the impact on the entities that we want to protect.
The United Nations estimate that around 780 million people do not have access to clean and safe water and around 2.5 billion people do not have proper water sanitation. As a result, around 6–8 million people die each year due to water related diseases, such as cholera and dysentery, and disasters. As population increases the water problem will become more difficult to solve. Furthermore, climate change threatens to intensify water scarcity. The design of functional materials at the nanoscale offer unique solutions in molecular sorbents and catalytic systems that can develop into cost-effective solutions in water treatment by reducing the cost of the materials used and/or the energy consumption of the process. In this dissertation, the design, synthesis, characterization, and evaluation of function of nanocomposites is presented for (1) the efficient electrochemical generation of reactive oxygen species (ROS) for water treatment and sanitation using a novel composite of benzoyl-functionalized cotton cellulose and multi-walled carbon nanotubes (FC-MWCNT), and (2) a water permeable hydrogel with hyperactive metallic copper nanoparticles (NPs). The new FC-MWCNT nanocomposite, which utilizes functionalized cotton cellulose as a high-surface area support for pristine multi-walled carbon nanotubes, was characterized via scanning electron microscopy, infrared spectroscopy, thermographic analysis, Brunauer-Emmett-Teller surface area analysis, and cyclic voltammetry, exhibits high surface area (40 m2/g) and efficient electrocatalytic properties toward hydrogen peroxide. Furthermore, they were successfully applied toward the electrochemical degradation of methyl orange using only a -1.0 V potential, with optimal conditions at pH 3, 2.7 mM KCl, 0.219 M NaCl, in a treatment time of 4 minutes. The Cu-NPs nanocomposite, characterized by transmission electron microscopy, electron paramagnetic spectroscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and inductively-coupled plasma-optical emission spectroscopy, were capable of chemoadsorbing arsenate, with a capacity of 5.3 g of As per gram of nanocomposite, and mineralizing it in large quantities out of water with little to no Cu leakage. By first coordinating Cu (II) ions to polymers capable of photopolymerizing into hydrogels, then reducing the ions to Cu (0), we were able to produce well dispersed, highly active Cu NPs that are capable of chemoabsorbing up to 90% of Arsenic from water in a wide range of pH levels. The development of functional nanocomposite materials offer new, more efficient methods for the purification of water. FC-MWCNT were synthesized and were capable of electrochemically degrading methyl orange. Furthermore, highly active Cu NPs dispersed and sequestered throughout water-permeable hydrogels were also synthesized and successfully removed 90% of As at a wide pH range.
Anthropocentric water resources management affects aquatic habitats by changing streamflow regime. Understanding the impacts of water withdrawal from different sources and consumption by various economic sectors at different spatial and temporal scales is key to characterizing ecologically harmful stream flow disturbances. To this end, we developed a generic, integrative framework to characterize catchment scale water stress at annual and monthly time scales. The framework accounts for spatially cumulative consumptive and non-consumptive use impacts and associated changes in flow due to depletion and return flow along the stream network. Application of the framework to the U.S. Great Lakes Region indicates that a significant number of catchments experience negative water stress due to stream flow depletion caused by surface water and shallow groundwater withdrawals. In many other catchments, however, return flow from deep groundwater withdrawals compensates for the streamflow depletion to the extent that positive water stress is likely. Results illustrate the importance of using appropriate spatial and temporal scales to evaluate water stress, demonstrating that coarse temporal (i.e., annual vs. monthly) and spatial scales reduce the ability to detect water stress due to water withdrawals in vulnerable catchments in low-flow months.
The information technology (IT) owners are experiencing a greater cooling challenge because of the increase in power density due to modern computational needs. The non-uniform power density in each server is forcing the industry to use hybrid cooling technology. Server components of different cooling requirement needs air water hybrid cooling which offers variable design alternatives. Such hybrid cooling technology cools the high heat generating components by using water or water based fluid, whereas, the rest of the components are cooled by air using internal fans. Conventional air cooling is more than sufficient for the components with less thermal demand. Air cooling is cheap, highly available and it has better serviceability than any other cooling methods. The objective is to optimize the cooling power of the air cooling loop of such hybrid cooled server. As the major components are cooled by the water based fluid, the other components generate less heat which can be cooled by much less volume of air then supplied in air cooled server. The volume of air supplied is controlled by varying the air flow rate through the internal fans. Also number of fan was reduced to 3 instead of 5 to minimize the power consumption. Parameters like CPU and memory utilization are varied with the flow rate. ASHRAE recommends that the most data centers can be maintained between 20 and 25°C, with an allowable range of 15 to 32°C. But for this type of hybrid cooling servers, the processor is cooled by water. So the servers can operate at much higher inlet air temperature. In this paper the hybrid cooled servers will be characterized also. The server used for experimental testing has processor with 135 watt thermal design power. Also, the server utilizes distributed pumping i.e. each cold plate has its own pump. The test matrixes consider supply and return water temperatures, flow rate of coolant for optimizing the cooling power consumption. The supply inlet water temperature was varied by LabView code. Further, processor and outlet temperature was monitored for better understanding the case scenario. The relation between supply water temperature and different power utilization gives the data for modeling different cooling infrastructure. This in turn, will give an idea of power savings by utilizing such energy efficient hybrid solution for cooling servers in a datacenter.
This dissertation project studies the ability of 5-HT 2C receptor modulators to alter voluntary ethanol intake and to investigate the changes in neurotransmission that accompany 5-HT2C agonists in a neuronal pathway associated with reward, the mesolimbic pathway. The 5-HT2C receptors are expressed throughout this pathway including in the nucleus accumbens, NAc. Due to high transmembrane sequence homology of the 5-HT2 subfamily of receptors it is difficult to find selective agonists for the 5-HT2C receptor that do not activate 5-HT 2A/B receptors as well. This is problematic because while 5-HT 2C agonists are predicted to be a pharmacotherapy for alcoholism, agonists for 5-HT2A cause psychotomimetic effects and agonists for 5-HT 2B cause cardio-valvulopathy. Recently, a promising series of phenylaminotetralin-based structures, PAT, have been discovered and certain PATs have been shown to have functional selectivity at the 5-HT2 subfamily of receptors. Of special interest are compounds that can act as agonists at 5-HT2C while acting as antagonists/inverse agonists at 5-HT2A/B receptors. The goal of this dissertation is to determine if these functionally selective PATs can alter voluntary ethanol consumption, both under basal conditions and in ethanol deprived animals, and examine changes in neurotransmission that might mediate this effect.
One of the grand challenges for the 21st century is the replacement of petroleum derived energy with sustainable alternatives. While there are numerous potential sources for renewable energy (geothermal, wind, etc.), only solar energy provides enough energy per year to allow humanity to maintain its current levels of consumption. Unfortunately, the Earth receives solar energy intermittently, and the energy that is received is quite diffuse. In order to ensure a steady supply of energy, therefore, we must develop methods for concentrating and storing solar energy for later use. We may look to nature for inspiration in our attempts to store solar energy; photosynthetic organisms have been converting solar energy into fuels for several billion years. Nature's strategy of storing solar energy in fuels is also attractive from a practical standpoint, in that technologies for distributing and consuming fuel have been developed for use with current petroleum based energy sources. In order to convert incoming solar energy into fuel, plants rely on photosystem II, which receives solar energy trapped by chloroplasts and releases chemically reduced quinone species and oxygen gas. The heart of photosystem II is the oxygen-evolving complex, a tetramanganese core where the solar energy from incident photons is used to extract electrons from water and transfer them to the quinone, producing oxygen in the process. Development of synthetic water-oxidation catalysts (WOCs) to serve the role of the oxygen-evolving complex is crucial to the production of artificial photosynthetic devices, i.e. devices capable of converting incident solar energy into a fuel. Current generation WOCs have a number of flaws preventing the widespread deployment of artificial photosynthetic devices, however. In order for a WOC to serve on a commercial scale it must be robust, efficient, and scalable. Commonly WOCs are analyzed by driving the water-oxidation reaction chemically via the addition of cerium(IV) ammonium nitrate (CAN). CAN is, however, stable only at very low pH values, which prevents proper characterization of WOCs that are not acid resistant and does not allow for insight into the water-oxidation mechanism near neutral pH where an artificial photochemical device would be operated. In Chapter 1 of this thesis, we discuss chemical oxidants that may be used to characterize WOCs, including several alternatives to CAN. One of the alternative oxidants to CAN which we discuss is sodium periodate (NalO4), which is a mild two electron oxidizing agent which is stable over a fair range of pH values. Using sodium periodate, we characterize Wilkinson's iridium acetate trimer, [1r30(0Ac)6(H2O) 3][OAc), as a water-oxidation catalyst in Chapter 2. It is found that Wilkinson's iridium acetate trimer serves as a WOC, but rapidly degrades to form iridium dioxide nanoparticles. This degradation can be prevented by the addition of sodium acetate to the solution mixture, which also increases the observed rate of water-oxidation. Based on kinetic data, we are able to show that the oxygen observed in the reaction by Wilkinson's iridium acetate trimer results from catalytic oxidation of water rather than coupling of the periodate, supporting its usefulness as a chemical oxidant. In Chapter 3, we test the ability of sodium periodate to drive a number of WOCs which were previously characterized using CAN. We find that by using sodium periodate rather than CAN we are able to better characterize our pentamethylcyclopentadienyl (Cp*) iridium catalysts, including observing different rates of reaction upon ligand substitution which was not evident when CAN was used. We also find that sodium periodate is unable to drive a number of literature catalysts, which we attribute to the relatively low driving force provided by the oxidant. By comparing the behavior of the various catalysts in the presence of periodate, we are able to demonstrate the advantages of using periodate as a chemical oxidant to drive WOCs, as well as some of its potential drawbacks. In Chapter 4, we use sodium periodate to characterize the mechanistic pathway of Cp*Ir WOCs. We find that the catalysts remain homogeneous over long time periods, but the Cp* ligand is oxidized off of the complexes, leading to the formation of an Ir(IV) dimer species. We demonstrate that this species is a competent WOC, and characterize it via EPR, NMR, mass spectrometry and UV-vis spectrometry.