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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Persistent Organic Pollutants in Australian Sewage Sludge: Environmental Monitoring and Land Application Risk Assessment

Clarke, Bradley, Bradley.clarke@student.rmit.edu.au January 2008 (has links)
Presented is a study of persistent organic pollutants in Australian sewage sludge, focusing on environmental monitoring and a sewage sludge land application human health risk contaminated with these compounds. The chemicals of concern were: • Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and
252

Producing, Preventing, and Explaining Persistent Complex Subliminal Stimulation Effects

Birgegård, Andreas January 2003 (has links)
<p>Strong recent focus on unconscious processes has increased interest in subliminal stimulation and similar experimental technologies. Assumptions about the persistence of effects of unconscious stimulation are generally conservative, referring to seconds or minutes (Silverman, 1977; Velmans, 1991). In Study I, five experiments (<i>N </i>= 365) showed complex effects of unconscious stimulation ten days after subliminal exposure, implying that persistence estimates need reevaluation. Experimental stimuli were "mommy and I are one" (MIO) and "mommy and I are dissimilar" (MIDIS), and neutral control stimuli. Effects consisted of higher correlations between measures pertaining to the self-mother relationship and measures of psychological adjustment. </p><p>These ethically problematic findings prompted investigation in Study II of whether debriefing information to participants could prevent persistent effects of subliminal stimuli, an issue not previously investigated. Two experiments (<i>N</i>=188) tested two kinds of information to participants following subliminal MIDIS or control stimulation. Results showed different persistent effects depending on participant sex. Simple information about the stimulus was effective in preventing these, but elaborate information describing the effects and mechanisms for them was not. The findings have implications for ethical recommendations for subliminal research, and suggest that this unexplored area requires more attention. </p><p>In Study III, a theoretical account for the persistent effects is presented, based on unconscious activation of a relational schema containing goal motivation. Unless the goal is fulfilled or activation dissipates due to attributability or irrelevance of the goal, the activation will be maintained (motivated maintenance). Being unconscious, the influence results in automatic schematic processing of environmental cues, including perceptual, judgment, and behavioral biases. These in turn interactively maintain the activation of the schema (interactive maintenance). </p><p>The discussion includes the conclusion that previous estimates of the persistence of unconscious stimulation effects need revision. Theoretical and empirical questions concerning the studies are discussed and ethical research implications are considered.</p>
253

Models of the Distribution of Persistent Organic Pollutants in the Marine Environment

Persson, N. Johan January 2003 (has links)
Persistent organic pollutants (POPs) is a group of chemicals that are toxic, undergo long-range transport and accumulate in biota. Due to their persistency the distribution and recirculation in the environment often continues for a long period of time. Thereby they appear virtually everywhere within the biosphere, and poses a toxic stress to living organisms. In this thesis, attempts are made to contribute to the understanding of factors that influence the distribution of POPs with focus on processes in the marine environment. The bioavailability and the spatial distribution are central topics for the environmental risk management of POPs. In order to study these topics, various field studies were undertaken. To determine the bioavailable fraction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated naphthalenes (PCNs), and polychlorinated biphenyls (PCBs) the aqueous dissolved phase were sampled and analysed. In the same samples, we also measured how much of these POPs were associated with suspended particles. Different models, which predicted the phase distribution of these POPs, were then evaluated. It was found that important water characteristics, which influenced the solid-water phase distribution of POPs, were particulate organic matter (POM), particulate soot (PSC), and dissolved organic matter (DOM). The bioavailable dissolved POP-phase in the water was lower when these sorbing phases were present. Furthermore, sediments were sampled and the spatial distribution of the POPs was examined. The results showed that the concentration of PCDD/Fs, and PCNs were better described using PSC- than using POM-content of the sediment. In parallel with these field studies, we synthesized knowledge of the processes affecting the distribution of POPs in a multimedia mass balance model. This model predicted concentrations of PCDD/Fs throughout our study area, the Grenlandsfjords in Norway, within factors of ten. This makes the model capable to validate the effect of suitable remedial actions in order to decrease the exposure of these POPs to biota in the Grenlandsfjords which was the aim of the project. Also, to evaluate the influence of eutrophication on the marine occurrence PCB data from the US Musselwatch and Benthic Surveillance Programs are examined in this thesis. The dry weight based concentrations of PCB in bivalves were found to correlate positively to the organic matter content of nearby sediments, and organic matter based concentrations of PCB in sediments were negatively correlated to the organic matter content of the sediment.
254

Producing, Preventing, and Explaining Persistent Complex Subliminal Stimulation Effects

Birgegård, Andreas January 2003 (has links)
Strong recent focus on unconscious processes has increased interest in subliminal stimulation and similar experimental technologies. Assumptions about the persistence of effects of unconscious stimulation are generally conservative, referring to seconds or minutes (Silverman, 1977; Velmans, 1991). In Study I, five experiments (N = 365) showed complex effects of unconscious stimulation ten days after subliminal exposure, implying that persistence estimates need reevaluation. Experimental stimuli were "mommy and I are one" (MIO) and "mommy and I are dissimilar" (MIDIS), and neutral control stimuli. Effects consisted of higher correlations between measures pertaining to the self-mother relationship and measures of psychological adjustment. These ethically problematic findings prompted investigation in Study II of whether debriefing information to participants could prevent persistent effects of subliminal stimuli, an issue not previously investigated. Two experiments (N=188) tested two kinds of information to participants following subliminal MIDIS or control stimulation. Results showed different persistent effects depending on participant sex. Simple information about the stimulus was effective in preventing these, but elaborate information describing the effects and mechanisms for them was not. The findings have implications for ethical recommendations for subliminal research, and suggest that this unexplored area requires more attention. In Study III, a theoretical account for the persistent effects is presented, based on unconscious activation of a relational schema containing goal motivation. Unless the goal is fulfilled or activation dissipates due to attributability or irrelevance of the goal, the activation will be maintained (motivated maintenance). Being unconscious, the influence results in automatic schematic processing of environmental cues, including perceptual, judgment, and behavioral biases. These in turn interactively maintain the activation of the schema (interactive maintenance). The discussion includes the conclusion that previous estimates of the persistence of unconscious stimulation effects need revision. Theoretical and empirical questions concerning the studies are discussed and ethical research implications are considered.
255

Malaria and relapsing fever Borrelia : interactions and potential therapy

Lundqvist, Jenny January 2009 (has links)
Infectious diseases such as malaria and relapsing fever borreliosis (RF), cause severe human mortality and morbidity in developing countries. Malaria, caused by Plasmodium spp. parasites, is estimated by the World Health Organization to cause 1.5-2.7 million deaths annually. RF, caused by Borrelia spirochetes, has the highest prevalence described for any bacterial disease in Africa, with infection outcomes ranging from asymptomatic to fatal. RF borreliosis manifests in humans as a recurring fever and with other symptoms very similar to those of malaria. RF borreliosis has been regarded as a transient infection of the blood. However, B. duttonii exploits the brain as an immunoprivileged site escaping the host immune response while spirochetes in the blood are cleared. To investigate whether residual bacteria are dormant or actively dividing, mice with residual brain infection were administered ceftriaxone, a β-lactam antibiotic interfering with cell wall synthesis. Hence, it only affects actively dividing bacteria. Ceftriaxone eradicated brain RF infection in all treated mice, demonstrating that the bacteria are actively multiplying rather than in a dormant state. The findings support the therapeutic use of ceftriaxone for RF neuroborreliosis since penetration into cerebrospinal fluid is greater for ceftriaxone than for the often recommended doxycycline. The clinical features of malaria and RF are similar and diagnosis is further complicated by the frequently occurring concomitant malaria-RF infections. Therefore, we established a mouse model to study the pathogenesis and immunological response to Plasmodium/Borrelia mixed infection. Interestingly, malaria was suppressed in the co-infected animals whereas spirochete numbers were elevated 21-fold. The immune response in the concomitantly infected mice was polarized towards malaria leaving the spirochetes unharmed. Mice with co-infections also exhibited severe anemia and internal damages, probably attributed to escalating spirochete numbers. A secondary malaria infection reactivated the residual brain RF infection in 60% of the mice. This highlights the importance of co-infections as diagnostic pitfalls as well as the need for novel treatment strategies. Currently there is no commercial malaria vaccine and increasing drug resistance presents an urgent need for new malaria chemotherapeutics. Blood-stage malaria parasites are rapidly growing with high metabolic and biosynthetic activity, making them highly sensitive to limitations in polyamine supply. Disrupting polyamine synthesis in vivo with trans-4-methylcyclohexylamine (4MCHA) eradicated the malaria infection gradually, resulting in protective immunity. This leads the way for further biochemical and pharmacological development of the polyamine inhibitor 4MCHA and similar compounds as antimalarial drugs
256

Fate of polybrominated diphenyl ethers during wastewater treatment process producing reclaimed water

Siegel, Kristy 01 January 2013 (has links)
Polybrominated diphenyl ethers (PBDEs), flame retardants, have been applied to consumer goods, such as furniture, electrical devices, textiles, and appliances for decades. Due to their physico-chemical properties, PBDEs are semi-volatile and easily leach off the consumer good during aging, stress, or normal wear and tear of the good. Once airborne, they pose an environmental health threat because they can adsorb onto dust particles, soil, or other particulates that can be inhaled, ingested, or come into contact with the dermal layer. Additionally, PBDEs have a molecular structure similar to other persistent organic pollutants, such as polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins and furans. They are a health threat due to their endocrine-disrupting nature by affecting thyroid functioning, fertility, and child development. The purpose of the study is to measure selected PBDEs in a wastewater treatment plant (WWTP) that produces reclaimed water, such that a mass balance can be completed, and to compare this mass balance with theoretically expected concentrations. The mass balance includes the collection of samples from wastewater, sewage sludge, and air at points within the WWTP. The PBDEs examined are BDE-28, 47, 99, 100, 153, 154, and 183. The second part of the study will compare effluent concentrations to reclaimed water concentrations in order to examine the potential exposure (if any) of using reclaimed water. Influent concentration of mean (sum7)PBDE was found to be 49,117 pg/L and effluent concentration was 4,603 pg/L, illustrating a 91% removal rate of PBDEs during the wastewater treatment plant. Sludge samples contained the highest total concentrations of PBDEs with mean (sum7)PBDE ranging from 14.0 to 41.3 ug/kg dry weight. Air samples were highest at the post-aeration (248 pg/m3 mean (sum7)PBDE) step due to the use of highly oxygenated air assisting in the release and volatilization of the PBDEs. Sludge was found to carry the largest mass loading at 14.2 lb/day (sum7)PBDE. Of the total mass loading of PBDEs from the WWTP, sludge is responsible for 86.7%, followed by reclaimed water and effluent (11.7% and 1.6%, respectively). The mass loading from air was negligible with less than 0.01% contribution to the total mass loading. Whereas reclaimed water overall had higher PBDE congener mean concentrations than the effluent, the independent samples t-test found no statistically significant differences between the two groups. The results of this study can be used to improve the wastewater treatment process to reduce the impact of PBDEs being released into the environment by WWTPs, and to educate the public on utilizing reclaimed water in a safe and healthy manner.
257

Oxygen Tension Modulates Growth Of Ovine Newborn Pulmonary Vascular Smooth Muscle Cells

Cruz, Belen A 01 January 2014 (has links)
Background: Platelet activating factor (PAF) is a phospholipid synthesized by the action of phospholipase A2 and acetyl transferase. PAF possesses a wide range of biological activities. In the lung of the fetus and newborn, PAF binds to its G protein couple receptor to evoke its biological activities via a well-defined signaling pathway. High levels of PAF receptor (PAFr) activity in fetal ovine lung vascular smooth muscle cells (PVSMC) at baseline has previously been demonstrated, a finding that is further perpetuated by conditions of hypoxia similar to fetal lung environment. Additionally in fetal ovine PVSMC, a cross-talk between PAFr-mediated cell signaling and activity of the vasodilator cyclic nucleotides cGMP and cAMP acting via their respective receptors protein kinase (PK) G and PKA has been shown. The interaction of PAF with its receptor has been implicated in the pathogenesis of persistent pulmonary hypertension in the newborn (PPHN) which has a high incidence of hospitalization and death of newborn infants. Successful transition of fetus to newborn life entails a mechanism whereby vasoconstrictors necessary for fetal existence are abrogated in the immediate newborn. Hypothesis: We hypothesize that PPHN results from the failure to down regulate PAFr- mediated activity and /or failure to up-regulate activity of the vasodilators cGMP and cAMP. PPHN is triggered by chronic intrauterine or postnatal hypoxia. Then newborn PVSMC undergo hyperplasia and hypertrophy, which over time, results in irreversible vascular remodeling. Methods: My study aims to employ in vitro models to delineate the consequences of PAF-PAFr mediated pathway in the pharmacological effects of the cAMP-PKA and cGMP-PKG signaling and the involvement of this cross-talk in the pathogenesis of PPHN. I modeled my cell culture studies to mimic the low oxygen environment of fetal lungs (hypoxia), the normal oxygen environment of newborn lungs (normoxia) and high oxygen environment (hyperoxia) to which the newborn lung may be exposed in incidental clinical condition of PPHN. I studied the effect of PAF, a vasoconstrictor, cAMP/cGMP, vasodilators, and other inhibitors of the PAFr pathway on growth of newborn PVSMC, by DNA synthesis, and measured their effects on expression of mitogenic and non-mitogenic proteins. Results: We found that both hypoxia and hyperoxia decreased cell growth even in the presence of PAF which up-regulates cell growth in fetal PVSMC. Also PAF treatment of cells resulted in down regulation of the vasodilator proteins, PKA and PKG. Conclusion: Our data suggests that in the lung of the newborn a high activity of PAF-PAFr mediated activities will worsen the condition of PPHN imposed on the newborn lung by environmental or therapeutic conditions. We can speculate that, in the long run, these findings may translate into the establishment of less toxic protein-based management of PPHN.
258

EFFECTS ON SEMEN QUALITY AND ON ESTABLISHMENT OF PERSISTENT EQUINE ARTERITIS VIRUS (EAV) INFECTION IN STALLIONS FOLLOWING EXPERIMENTAL CHALLENGE WITH THE KENTUCKY 84 (KY84) STRAIN

Campos, Juliana Roberta 01 January 2012 (has links)
Equine arteritis virus (EAV) is the causal agent of equine viral arteritis (EVA), a disease of equids. Following EAV infection, up to 70% of stallions may become carriers and continuously shed the virus in their semen for varying time periods. The long-term carrier stallion has an important role in the transmission and maintenance of EAV in horse populations. Recently, it has been demonstrated a correlation between in vitro susceptibility of CD3+ T lymphocytes to EAV infection and establishment of long-term persistent infection among stallions following natural infections. In this study, we investigated whether stallions with in vitro EAV susceptible CD3+ T lymphocytes are at higher risk of becoming long-term carriers compared to those with the resistant phenotype following experimental infection with the KY84 strain of EAV. Furthermore, we investigated whether there is a significant effect of EAV infection on semen quality during acute phase of the infection. The data suggested that the establishment of the long-term carrier state seems to be associated with the in vitro CD3+ T lymphocyte susceptible phenotypes and that reduced semen quality resulted from the combined effect of fever and scrotal edema observed following EAV infection rather than the direct effect of the virus.
259

Development of new methodologies for the detection, measurement and on going monitoring of ground deformation using spaceborne SAR data

Duro, Javier 18 June 2010 (has links) (PDF)
Persistent Scatterer Interferometric techniques are very powerful geodetic tools for land deformation monitoring that offer the typical advantages of the satellite remote sensing SAR (Synthetic Aperture Radar) systems : a wide coverage at a relatively high resolution. Those techniques are based on the analysis of a set of SAR images acquired over a given area. They overcome the decorrelation problem by identifying elements (in resolution cells) with a high quality returned SAR signal which remains stable in a series of interferograms. These techniques have been useful for the analysis of urban areas, where man-made objects produce good reflections that dominate over the background scattering, as well as in field areas where the density of infrastructures is more limited. Typically, PSI technique requires an approximate a priori temporal model for the detection of the deformation, even though characterizing the temporal evolution of a deformation is commonly one of the objectives of any study.This work is focused on a particular PSI technique, which is named Stable Point Network (SPN) and that it has been completely developed by Altamira Information in 2003. The work concisely outlines the main characteristics of this technique, and describes its main products: average deformation maps, deformation time series of the measured points, and the so-called maps of the residual topographic error, which are used to precisely geocode the PSI products. The main objectives of this PhD are the identification and analysis of the drawbacks of this processing chain, and the development of new tools and methodologies in order to overcome them. First, the performances of the SPN technique are examined and illustrated by means of practical cases (based on real test sites made with data coming from different sensors) and simulated scenarios.Thus, the main drawbacks of the technique are identified and discussed, such as the lack of automatic quality control parameters, the evaluation of the input data quality, the selection of good points for the measurements and the use of a functional model to unwrap the phases based on a linear deformation trend in time. Then, different enhancements are proposed. In particular, the automatic quality control of the coregistration procedure has been introduced through the analysis of the inter-pixel position of some natural point targets-like pixels identified within the images. The enhancements in the selection of the final points of measurements (the final PSI map) come by means of the analysis of the SAR signal signature of the strong targets presented within the image, in order to select only the center of the main lobe as point of measurement. The introduction of robustness within some critical steps of the technique is done by means of the analysis of the rotational of the estimates in close loops within a network of relative measurements, and by means of the implementation of a different integration methodology, which can be ran in parallel in order to compare it with the classical one. Finally, the main drawback of the technique, the use of a linear model for the detection of ground deformations, is addressed with the development of a new fitting methodology which allows possible change of trends within the analyzed time span. All those enhancements are evaluated with the use of real examples of applications and with simulated data. In particular, the new methodology for detecting non-linear ground deformations has been tested in the city of Paris, where a large stacking of ERS1/2 and ENVISAT SAR images are available. Those images are covering a very large time period of analysis at where some known non-linear ground deformations where occurring
260

Exploring the Independent and Combined Effects of Persistent Organic Pollutants and Hypoxia on Human Adipocyte Functions

Myre, Maxine 14 January 2014 (has links)
Persistent organic pollutants (POPs) and adipose tissue hypoxia have been shown to independently affect adipocyte functions. The goals of this study were to (1) determine the effect of PCB-77, PCB-153, and DDE on the differentiation of human preadipocytes, and (2) investigate the cross-talk between PCB-77 and hypoxia in differentiated human adipocytes. First, human preadipocytes were exposed to PCB-77, PCB-153, or DDE during the entire 14-day differentiation period. We found no effect of low POP levels on lipid accumulation. Second, differentiated human adipocytes were exposed to a combination of PCB-77 and hypoxia. We demonstrated gene-specific cross-talk between PCB-77 and hypoxia, showing an additive effect of PCB-77 on VEGF, MCP-1, and adiponectin, as well as an inhibition of PCB-77-induced expression of CYP1A1 by hypoxia. This work has expanded our understanding of the role of POPs and hypoxia in differentiated human adipocytes.

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