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Mammalian genomes are characterised by global and pervasive DNA methylation and this modification is generally thought to be inhibitory to transcription. An exception to this widespread DNA modification are genomic elements called CpG islands (CGI), contiguous regions of non-methylated DNA which encompass the transcription start site of two thirds of mammalian genes. Although CGIs represent the most prominent feature of mammalian promoters, the contribution of these elements to promoter function remains unclear. Work in this study shows that the histone lysine demethylase KDM2B (FBXL10/ JHDM1B) is a nuclear protein which binds specifically to non-methylated CpG dinucleotides and associates with CGI elements genome-wide through its zinc-finger CxxC (ZF-CxxC) DNA binding domain. Furthermore, in mouse embryonic stem cells, biochemical investigation revealed that KDM2B associates with Polycomb group E3 ubiquitin ligase RING1B to form a variant Polycomb repressive complex 1 (PRC1) characterized by the PCGF1 subunit. Considering that KDM2B has clear DNA-binding activity and that CGIs were reported to function as nucleation sites for polycomb repressive complexes, a potential role for KDM2B in mediating PRC1 recruitment to target genes was investigated. Stable depletion studies indicated that KDM2B is required for the normal targeting of RING1B to CGIs and the regulation of expression of a subset of Polycomb-occupied genes. By taking advantage of a genetic ablation system in which the DNA binding domain of KDM2B can be conditionally deleted, results in this thesis reveal that the ability of KDM2B to recognize non-methylated DNA is essential for polycomb domain formation and normal embryonic development. Finally, through the use of a de novo targeting assay, an unexpected PRC2 recruitment pathway was discovered which is dependent on PRC1-mediated H2AK119ub1 deposition. Together this work uncovers a novel mechanism linking KDM2B-dependent recognition of non-methylated DNA with recruitment of Polycomb proteins and provides the framework on which to further investigate the contribution of CGIs to formation of polycomb domains.

The purpose of this research is to determine the image of a Chilean university, as perceived by those inside and outside of the institution, in contrast with the general image of the e-learning system in Chile. The internal perceptions are those of current students and graduates of this Chilean university, while the external perceptions are those of businessmen and the target audience of e-learning, considered as adults between 26-55 years of age. The research is based on a mixed methodology, which addresses the stated problem through quantitative and qualitative methods. Closed and open-ended surveys were given to a sample of students and graduates of this Chilean university, as well as businessmen and the target audience. Interviews with specialists from the educational field were also conducted for complementing and deepening the understanding of the phenomenon of e-learning in Chile. Regarding the perceptions that students and graduates of this university have of it, the results of the research indicated that those who have experimented online education agreed in the positive features of the system, and valued it over the traditional one. On the other hand, the perceptions that businessmen and the target audiences of e-learning have about this system in Chile is not so categorical: it is a form of teaching-learning known by businessmen, and the extended but not all target audience. The majority of both samples expressed perceiving no difference between online versus on campus education. Even though only a minority continued appreciating face to face education over e-learning, in the case of having to select the educational modality, everyone in the target audience would not choose a program provided online. Finally, the image of this Chilean university when compared with perceptions of the e-learning system in general in Chile seems equivalent by the experts. It is a well known university as the e-learning system is, but not yet recognized by this format of content delivery, as it happens with the public validation of the academic quality of the online. E-learning is still in an incipient stage in the general education field in Chile, and it is necessary to look forward to the accreditation of e-learning as an effective educative system in the 21st century. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]

Fused filament fabrication (FFF), a three-dimensional (3-D) printing process, is an emerging technology that has recently gained wide popularity among both consumers and manufacturers. As filament is heated to above its glass transition temperature in a 3-D printer, a portion may undergo thermal decompostion, which releases ultrafine particles (UFP) and volatile organic compounds (VOCs) with potential adverse respiratory health effects are released into the air. This study's central hypotheses is that emissions generated during 3-D printing are toxic and exposure to these emissions induces pulmonary and systemic adverse health effects. Considering that currently, limited understanding is available on the health impact of the FFF 3-D printer exposures, the overall goal of this research was to fill the knowledge gap by pursuing the following three studies. The aim of the first study was to assess acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) filaments 3-D printer emissions-induced cell toxicity. In this study, the particles and vapors released during printing were collected directly into the cell culture medium and delivered to the small airway epithelial cells at six concentrations. At 24 h, various endpoints, such as cellular uptake, cell viability, cell membrane damage, ROS production, total antioxidant capacity, glutathione peroxidase levels in cell lysates, cell death mechanisms (apoptosis and necrosis), and cytokines and chemokines released in cell supernatants were measured. To analyze the data, mixed model regression analyses were performed on these endpoints using particle numbers as the independent variable. The regression lines illustrated a significant doseresponse relationship between a decrease in cell viability and the number of emitted particles, which correlated with a significant dose-dependent increase in the LDH activity, and all other endpoints evaluated. The aim of the second study was to assess pulmonary and systemic toxicity in rats following whole-body inhalation exposure to ABS filament 3-D printer emissions. In this study, male Sprague Dawley rats were exposed to filtered air or ABS emissions for 1, 4, 8, 15, or 30 days (4 h/day, 4 days/week). The average mass concentration and number of particulate generated during 4-h real-time printing of three desktop 3-D printers operating simultaneously was 240 µg/m3 and 8.84 x 10⁴ particles/m³. At the start of the exposure (day 1), a predominant pro-inflammatory response was seen in BALF, represented by an increase in IFN-γ and TNF-α Th1-type cytokines followed by a switch to an anti-inflammatory response by day 15 of exposure represented by a rise in IL-10 Th2-type cytokine. The Th1/Th2 switch could be responsible for the initial “delayed” influx of the alveolar macrophages and its peak occurrence at 15 days of exposure, which corresponded with a significant increase in blood monocytes and platelet counts. Other systemic changes noted were that initially (day 1), a significant increase in both hepatic and renal biomarkers was found; however, at day 15 of exposure, only renal biomarkers were increased. At the longest exposure duration (day 30), all the endpoints evaluated returned to the control levels. Neither pulmonary oxidative stress responses nor histopathological changes of the lungs and nasal passages were found among the treatments. The aim of the third study was to evaluate the pulmonary effects of FFF 3-D printer emissions using a relevant human ALI organotypic airway tissue model to mimic the respiratory behavior upon exposure. Primary normal, human-derived bronchial epithelial cells (NHBEs) were directly exposed for 4 h to ABS filament emissions. NHBEs epithelium integrity and differentiation changes, cytotoxicity, tissue injury, and inflammatory and immune system regulation markers were evaluated following exposure and 24 h after the end of the exposure. Overall, at the conditions applied, exposure of NHBEs to ABS emissions did not affect epithelium integrity, ciliation, mucus production, or induce cytotoxicity. At 24 h after the exposure, significant increases in IL-12p70, IFN-γ, TNF-α, IL-17A, VEGF, and MIP-1α were noted in the basal cell culture medium of ABS-exposed cells compared to chamber control cells. Overall, toxicological evaluation of FFF 3-D printer emissions was conducted in three different conditions, 1) traditional submerged culture of human small airway epithelial cells, 2) repeated whole-body inhalation exposure of rats to freshly generated aerosols, and 3) advanced human ALI organotypic airway tissue model. At the experimental conditions applied, in both in vitro models and in vivo, 3-D printer emissions produced minimal to moderate pulmonary toxicity. Furthermore, these findings were consistent with results observed in the physiologically relevant in vivo-like in vitro model cultured at ALI. In conclusion, these studies indicate that the FFF 3-D printer emissions could induce moderate toxicological effects. These studies are significant as they are amongst the first and comprehensive studies published to evaluate the pulmonary and systemic toxicity of 3-D printer emissions. Further studies are needed to establish a more broad exposure-dose-response relationships and integration of in vivo and in vitro responses.

Chapter 1. Introduction to erionite. Erionite is an emerging naturally-occurring carcinogen that through continued and frequent exposure can lead to mesothelioma. Erionite exposure is mostly environmental and it affects individuals that live in areas where a natural deposit of the mineral exists.;Chapter 2. What is mesothelioma? Why should I should be afraid? How do you calculate the risk of mesothelioma? What are the results? Mesothelioma, a rare cancer and the most dreaded asbestos-related disease affects the lining of the chest cavity and extremely debilitating and terminal. Rates of Malignant Mesothelioma (MM) are dependent on exposure times, concentrations, smoking, age of first exposure, etc. Although there is currently no proof of emerging erionite-related illnesses in the U.S., mesothelioma normally takes 30 to 50 years to develop. In this chapter, a preliminary risk assessment calculation was conducted considering time weighting factors for different activities and exposure years based on the expected age of first exposure according to EPA's excess lifetime cancer risks (ELCRs). The results show an increased probability of mesothelioma occurrence as exposure is prolonged, ranging from 2 to 26 cases in 10,000 individual exposure. This is higher than EPA's acceptability risk standard of 1:10,000.;Chapter 3. How do you find these fibers in the environment? How do you separate them? How do you identify them? What was found? Asbestos or asbestos-like fibers (erionite) may be present in trace quantities in the environment which are non-detectible with the current analytical techniques. A recent advance in technology, the Fluidized Bed Asbestos Segregator (FBAS), is enabling us to identify and measure very small concentrations of erionite and asbestos in soil. This technique effectively and efficiently separates out erionite fibers from sampled soils while maintaining the integrity of the erionite fibers. Thus, the true structural characteristics and quantity of erionite fibers in the soils can be determined. The results show that traces of erionite in the analyzed soil samples, although well below the detection limit of 1% by traditional PCM/PLM methods, were reliably detected by the FBAS method and identified by Transmission Electron Microscopy (TEM) / Scanning Electron Microscopy (SEM) analysis.;Chapter 4. Where is erionite found? How did you map its location using soil sample data? The soil samples were collected by Center for Disease Control (CDC) / National Institute for Occupational Safety and Health (NIOSH), North Dakota University, and the U.S. Forest Service (USFS) in Slim Buttes region of the Sioux Ranger District on the Custer National Forest (CNF) in Harding County, South Dakota. The spatial variation of erionite concentrations in the soil across this research area was mapped using ArcGIS 10.2 software. The results show that the typical soil concentration of erionite on the surface of erionite-hosting geological layers is significantly higher, reaching almost 23%, compared to surrounding soils where the concentration was less than 0.01%. Figure 45 presents a map the predicted priority areas for additional research and investigation into erionite concentrations.;Chapter 5. What is the purpose of risk communication? How can it be accomplished within Harding County? The purpose of this chapter is to describe potential risk communication methods that can be used to convey a general sense of the increased risk of developing mesothelioma from breathing in erionite in Harding County. All the risk calculations presented in Chapter 2 have significant uncertainties associated with them. However, these calculations show similar results, i.e. there exists an amplified risk of mesothelioma from erionite exposure in the CNF. This last chapter provides an outline for developing recommendations for a risk communication plan that could be used by the local officials to formulate and convey risk messages to the three main audiences potentially impacted by exposure to erionite on the CNF: Harding County residents, USFS workers and CNF visitors. Based on extended risk literature research, demographic and epidemiological data and risk assessment calculations from previous chapters provide a framework for dialogue between community and authorities. Demonstrations of risk assessment results are communicated through visual displays in the form of numerical data, log scale presentation, and persuasive graphic images.;General conclusions. Naturally occurring erionite is generally consider safe if it is left undisturbed and encapsulated by soil and/or vegetation. There is currently very little evidence that living above or near geology that includes mineral fibers is a hazard, although risk calculations indicate a level of concern about erionite that justifies further investigations. (Abstract shortened by UMI.).

The growth of two strains of green microalgae, Chlorella vulgaris (UTEX 2714) and Chlamydomonas reinhardtii (UTEX 90) was tested in three types of media; Tris Acetate Phosphate (TAP), Bushnell Haas Broth (BHB), and Wright's Cryptophytes (WC buffered with either glycylglycine or Tris-base). Also, initial medium pH is ranging from 4 to 10, light intensity ranging from 100 to 600 micromol photons/m 2s, and CO2 concentrations ranging from 0.038% (ambient) to 12%, were tested. WC medium at pH 8 buffered with glycylglycine sustained the highest yield and best buffering capacity for growth of both C. vulgaris and C. reinhardtii. A light intensity of 200 micromol photons m-2s-1 provided for both good growth and electron transport rate (ETR). Both C. vulgaris and C. reinhardtii produced highest final yields when grown with 6% CO2. Also, lipid content increased with increasing CO2 concentration. Myristoleic acid (C14:1), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n9), linoleic acid (C18:2), and docosahexaenoic acid (DHA) were found in higher content when C. vulgaris was grown on 12% CO2, while the content of palmitoleic acid (C16:1), elaidic acid (C18:1t9), vaccenic acid (C18:1n7) were similar among all CO 2 concentration tested. CO2 capture was explored using two approaches: consumption of known quantities of CO2 in sealed serum bottles, and consumption of CO2 flowing through immobilized algal beads. In both cases, fixation rate decreased with increasing CO2 concentration. CO2 consumption generally decreased over the five day experiment. The rate observed using immobilized algae was 20% of the maximum obtained in liquid culture, indicating the need to future optimize this novel method for CO2 capture.

Eastern Hemlock Tsuga canadensis is a coniferous tree native to eastern North America. It ranges from northeastern Minnesota eastward through southern Quebec, and from the southern Appalachian Mountains to northern Georgia and Alabama.;This majestic tree is threatened with elimination by an invasive species Hemlock Woolly Adelgid (HWA) Adelges tsugae introduced in the USA in 1924, which is believed to be a native of Asia. HWA reduces shoot growth, provokes branch dieback, and eventually tree death.;One strategy to help mitigate the fast spread of HWA is to determine what may cause host potential resistance to HWA and how to use this information to develop HWA-resistant management program. This project was initiated to....;To do that, randomly selected trees have been studied in Allegheny National Forest in 2006 with monthly data collection by hand-held soil probe instruments measuring temperature and water content noting the time of sampling and also some of them have been instrumented with station recording equipment called Hobo with recorders inserted at 15 cm soil depth and collecting temperature and water content data continuously. Net N mineralization and net nitrification were calculated using the in situ incubation technique, in this method the values of extractable nitrate-N and ammonium-N in incubated soil are compared to the initial. Exchangeable ammonia was extracted from air-dried soil samples that were sieved through a 2 mm sieve, using 2 M KCl in a 10:1 solution:soil ratio.;Statistical analysis was conducted using SAS with data collected, the main effects were thinning treatment (reference, thinning), soil pH, soil organic matter percentage, tree DBH, soil temperature, sampling months.;The thinning (treatment) is statistically significant (p=0.053). The thinned plots mineralize more total nitrogen, almost 10 mg/kg of soil, approximately 50% than the reference plots. Thus, the observed N mineralization rate for the growing season was 21.7 mg/kg to 30 cm soil depth in control plots, or 65.8 kg N/ha. The estimated rate of N mineralization in HWA-infested stands was 30 times the observed rate, reaching 1973 kg/ha.;A series of spatial prediction maps of the landscape Nitrogen levels were created by using ArcGIS 9.2 software that helped acquire a spatial perspective of the soil N mineralization rates in forest ecosystems at a large scale. These spatial prediction maps will become increasingly important once the HWA infests the study site and will be visible impacts of N mineralization rates change in forest soil.;By creating a data base before HWA infestation of the stand and continuing gathering data after HWA infestation, with the help of the nitrogen mineralization model we will be able to elucidate the stand nutrient vs. HWA cause and effect relationship.;Nitrogen forms are an important water quality parameter, but in excess, it can be detrimental to waterways and their ecosystems. Enriched nutrient loads to streams may alter surface water quality and disrupt management of watersheds used by municipal treatment water. Nitrate and cations diffusion into the surface water can reduce its drinking quality. Blue-baby syndrome (Methemoglobinemia) can be caused by high nitrate found in drinking waters.

This work continues a long history of efforts to study the flow of fluids through packed beds-- more specifically, through beds made of uniform packing particles, and generated under high pressure, -- and to probe the sources of band broadening in liquid chromatography, referred to more commonly as axial dispersion. Any investigation of the radial distribution of local chromatographic characteristics should consider on-column, local, multichannel detection. The results presented in this work were obtained with an experimental set-up which can accommodate at least 10 optical fiber assemblies functioning as on-column, local microdetection probes when implanted into the exit frit of an HPLC column. High performance liquid chromatographic columns are not radially homogeneous. A rather homogeneous core is surrounded by a thick layer of heterogeneous packing situated along the column wall. The thickness of this layer is variable. The flow distribution in these columns is cylindrical, nearly flat in the column center, within approximately half the column radius from the center and falls behind rather rapidly towards the wall. Because the concentration profile of an analyte along the wall passes later and is wider than in the column center, the signal of a bulk detector is bound to exhibit an increased width, and some degree of tailing. The extent to which the peak tails is proportional to the degree of deformation of the mobile phase flow profile. The local column efficiency is at most locations higher than the overall efficiency determined with an on-line conventional detector. It varies across the column cross-section as follows: it is higher in the central core region, while in the external region it decreases with decreasing distance to the column wall. As a consequence, analytical columns are operated under experimental conditions where a significant fraction of their potential performance is wasted. A small concentration sensor placed at the column axis would see narrower, better resolved and more concentrated bands. The consequence of this heterogeneous behavior of the column is that the conventional elution profile is a complex convolution of the convection and dispersion phenomena taking place in a chromatographic column. Obviously, two space coordinates, the column length and its radius and not only the former, are needed in a realistic model of chromatography [Guiochon, 1995].