Studies on the gaseous oxidation of sulphur dioxide

Imperial Users onl

Machine Learning Techniques for Characterizing IEEE 802.11b Encrypted Data Streams

As wireless networks become an increasingly common part of the infrastructure in industrialized nations, the vulnerabilities of this technology need to be evaluated. Even though there have been major advancements in encryption technology, security protocols and packet header obfuscation techniques, other distinguishing characteristics do exist in wireless network traffic. These characteristics include packet size, signal strength, channel utilization and others. Using these characteristics, windows of size 11, 31, and 51 packets are collected and machine learning (ML) techniques are trained to classify applications accessing the 802.11b wireless channel. The four applications used for this study included E-Mail, FTP, HTTP, and Print. Using neural networks and decision trees, the overall success (correct identification of applications) of the ML systems ranged from a low average of 65.8% for neural networks to a high of 85.9% for decision trees. These averages are a result of all classification attempts including the case where only one application is accessing the medium and also the unique combinations of two and three different applications

High-Throughput Cultivation of Bacterioplankton from the Gulf of Mexico and Genomics of the First Cultured LD12 Representative

Cultivation of microorganisms facilitates characterization of metabolism, interspecies dependencies, virus-host interactions, and other information necessary to resolve the functions and distribution of individual taxa. However, the metabolic and physiological capacities for the majority of microbes remains unresolved because of the lack of cultivated representatives for many groups limits our ability to test cultivation-independent observations. The Northern Gulf of Mexico offers a diversity of ecosystems under the continuous threat from natural and anthropogenic disturbances, yet little is known about its native bacterioplankton community. This dissertation sought to use high-throughput cultivation over three-years at six sites to isolate important coastal bacteria to uncover their role in biogeochemical cycling and ecosystem health. During the seventeen experiments, 7820 wells were inoculated, resulting in 328 repeatedly transferable cultivars. Isolates were placed into 49 monophyletic groups based on 16SR rRNA gene sequences, and represent multiple novel Species and Genera, including the first reported cultures of the SAR11 LD12 Alphaproteobacteria, OM241 Gammaproteobacteria, and acIV Actinobacteria clades. Cultivars also contribute to the expansion of cultured diversity of numerous cosmopolitan bacterioplankton such as SAR11 subclade IIIa and SAR116 Alphaproteobacteria, and BAL58, MWH-UniP1, and OM43 Betaproteobacteria. Physiological and genomic characterization of the first cultivated LD12 representative, Candidatus Fonsibacter ubiquis strain LSUCC0530, yielded novel insights into the potential metabolic capacity related to sulfur, ecotype differentiation based on temperature, as well as key gene losses associated with osmoregulation that provide a concise hypothesis for the evolution of salinity tolerance in SAR11. Comparison between the success of isolation and the relative abundance of the cultivar in the source water revealed that relative abundance was a good predictor of cultivation success for some frequently cultured clades, while it was unreliable for rarely cultivated clades such as SAR11 subclades IIIa, LD12 Alphaproteobacteria, acIV Actinobacteria, and HIMB59-type Alphaproteobacteria. We hypothesize that taxon-specific variations in dormancy and/or phenotypic variation rates among populations may affect the cultivation reliability of that clade rather than the isolation medium alone. The insights from this dissertation provide a new look at the complexity of cultivation even when providing an organism with its nutritional requirements while showcasing the importance of cultivation for answering ecological questions like the evolution of salinity tolerance

Effects of dietary selenium on growth and selected reproductive parameters in young boars

Thirty-three crossbred boars (47-58 days of age) maintained similarly on concrete were randomly allotted to receive a corn-soybean meal ration containing selenium at the basal level of 50(t1) ppb or supplemented with 100(t2) or 250(t23) ppb (from sodium selenite). All boars were fed their respective diets ad libitum until six months of age and were then hand-fed 2.2 kg/boar/day for the remainder of the study. Body weights and testicular widths were taken on each boar at biweekly intervals until six months of age and at monthly intervals thereafter. Blood samples were also taken at these times by vena cava puncture. Libido was routinely scored upon exposure to ovariectomized-estrogenized gilts, beginning at approximately five months of age. When possible, ejaculates were collected and various sperm cell characteris-tics evaluated by both bright-field and phase-contrast microscopy. Seven animals from each group, from which ejaculates were collected, were slaughtered at nine months of age. Anatomical and histological appraisal of testicular and epididymal tissue was made soon after slaughter. Regression of body weight and libido, measured in all 33 boars, and plasma testosterone levels for the 21 boars slaughtered were differ-ent (P \u3c 0.01), over time, among the three treatment groups. Values for each parameter were found to be greater for boars in t1 than for those in t2. which were greater than those in t3. A similar but less pro-nounced relationship to treatment (P \u3c 0.05) was found for testicular width as regressed over time. No treatment differences were observed in either weights or spermatozoan concentrations in the testes, capita-corporea, or caudae epididymides. Analysis of testicular lengths, weights, and circumferences also revealed no differences. Caudal epidi-dymal spermatozoa, examined using both bright-field and phase-contrast microscopy, revealed no evidence of structural changes due to treatment. Measurements were made of epididymal epithelial heights, with those in capita tending (P \u3c 0.10) to be greater in t1 than in t3. Testicular width as measured on the live animal was unrelated to total testicular spermatozoan concentration. These results suggest that dietary selenium, fed at the levels of 150 and 300 ppb, may act to significantly retard the development of certain reproductive processes in young boars as analyzed over time

Special Issue on Feature Papers for Celebrating the Fifth Anniversary of the Founding of Processes

Note: In lieu of an abstract, this is an excerpt from the first page. Chemical Processes A major focus of Processes is chemical process engineering with applications to both traditional industries and emerging industries for renewable chemicals and energy production. The Special Issue contains four papers in this area. The first paper describes the development and simulation of a model prediction controller for achieving the desired viscosity curve in the continuous production of a non-Newtonian fluid [1]. The second paper addresses the problem of minimizing fuel consumption in fuel gas networks through a superstructure-based method and mixed-integer nonlinear programming [2]. The interesting possibility of extending the favorable characteristics of cuboid packed-bed devices originally designed for chromatographic separations to packed-bed chemical reactors is explored in the third paper [3]. The fourth paper addresses the optimal design of ammonia production plants based on adsorption for unreacted nitrogen and hydrogen recovery and wind energy for electricity generation [4]

Byproduct Cross Feeding and Community Stability in an In Silico Biofilm Model of the Gut Microbiome

The gut microbiome is a highly complex microbial community that strongly impacts human health and disease. The two dominant phyla in healthy humans are Bacteroidetes and Firmicutes, with minor phyla such as Proteobacteria having elevated abundances in various disease states. While the gut microbiome has been widely studied, relatively little is known about the role of interspecies interactions in promoting microbiome stability and function. We developed a biofilm metabolic model of a very simple gut microbiome community consisting of a representative bacteroidete (Bacteroides thetaiotaomicron), firmicute (Faecalibacterium prausnitzii) and proteobacterium (Escherichia coli) to investigate the putative role of metabolic byproduct cross feeding between species on community stability, robustness and flexibility. The model predicted coexistence of the three species only if four essential cross-feeding relationships were present. We found that cross feeding allowed coexistence to be robustly maintained for large variations in biofilm thickness and nutrient levels. However, the model predicted that community composition and short chain fatty acid levels could be strongly affected only over small ranges of byproduct uptake rates, indicating a possible lack of flexibility in our cross-feeding mechanism. Our model predictions provide new insights into the impact of byproduct cross feeding and yield experimentally testable hypotheses about gut microbiome community stability

A Multiscale Model to Investigate Circadian Rhythmicity of Pacemaker Neurons in the Suprachiasmatic Nucleus

The suprachiasmatic nucleus (SCN) of the hypothalamus is a multicellular system that drives daily rhythms in mammalian behavior and physiology. Although the gene regulatory network that produces daily oscillations within individual neurons is well characterized, less is known about the electrophysiology of the SCN cells and how firing rate correlates with circadian gene expression. We developed a firing rate code model to incorporate known electrophysiological properties of SCN pacemaker cells, including circadian dependent changes in membrane voltage and ion conductances. Calcium dynamics were included in the model as the putative link between electrical firing and gene expression. Individual ion currents exhibited oscillatory patterns matching experimental data both in current levels and phase relationships. VIP and GABA neurotransmitters, which encode synaptic signals across the SCN, were found to play critical roles in daily oscillations of membrane excitability and gene expression. Blocking various mechanisms of intracellular calcium accumulation by simulated pharmacological agents (nimodipine, IP3- and ryanodine-blockers) reproduced experimentally observed trends in firing rate dynamics and core-clock gene transcription. The intracellular calcium concentration was shown to regulate diverse circadian processes such as firing frequency, gene expression and system periodicity. The model predicted a direct relationship between firing frequency and gene expression amplitudes, demonstrated the importance of intracellular pathways for single cell behavior and provided a novel multiscale framework which captured characteristics of the SCN at both the electrophysiological and gene regulatory levels

Cyanobacterial Blooms in Highland Lake, ME

Cyanobacterial blooms, like algal blooms, are a much studied phenomena; and many triggers that cause these blooms are well understood. Usually, excess nutrients (such as soluble nitrogen or phosphate) are prerequisite for a bloom to occur. Since 2013, annual summer cyanobacterial blooms have been observed at Highland Lake (HL), located in Cumberland County, Maine. Data going back more than 15 years, collected by the Highland Lake Association, shows this is a new phenomenon in this body of water. Other investigators have shown HL water chemistry to have high aluminum to phosphorous and aluminum to iron ratios. These metals bind phosphate making it unavailable to most microbes, decreasing the probability a bloom will occur. This raises the questions of what particular cyanobacteria are present, and the source of phosphate

All in or A` la carte: Preferences of Medical Tourists Towards Value of Co-Creation

Patients Beyond Borders (2014) defines a medical tourist as anyone who travels across international borders for the purpose of receiving nonemergency medical care. It has been estimated that the market size in USD ranges from 38.5 to 55 billion based upon eleven million cross-border patients worldwide spending an average of 3,500 – to 5,000 USD per visit. Further, Patients Beyond Borders suggests that the top Medical tourism destinations are Costa Rica, India, Israel, Malaysia, Mexico, South Korea, Taiwan, Thailand, Turkey and the United States