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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.
491

Syntéza a charakterizace pokročilých molekul s implementovaným adamantanovým skeletem / Synthesis and characterisation of advanced molecules with implemented adamantane skeleton

Jančík, Ján January 2018 (has links)
This diploma thesis describes synthetic approach and characterization of advanced molecules with implemented adamantane skeleton and perspective use in attractive field of organic electronics. Three of four prepared molecules based on para-bis(2-thienyl)phenylene are original and totally new, and there were performed different synthetic approaches with comparison of yield, ecological and financial impact. Study of microwave synthetic approach was provided for cross-coupling reactions on para-bis(2-thienyl)phenylene skeleton. For all molecules were used ethyladamantyl and methyladamantyl substituents. Also, two completely new molecules based on 2,2':5',2''-terthiophene with ethyladamantyl and methyladamantyl substituents were prepared. In the next part were prepared new dimer structures of adamantane with possible application on field of polymers as bridge molecules. In the thesis were also made series of experiments for preparation of tetrasubstituted adamantane molecules, and for optimisation of preparation of spiroadamantane systems.
492

Stanovení obsahu organických sloučenin v pevném uhlíkatém zbytku / Determination of content of organic compounds in biochar

Novotná, Martina January 2020 (has links)
Biochar is created during the pyrolysis of organic biomass. Once added into the soil, it can improve its features. Biochars made from sewage sludge have various compositions. It is because of the vast difference between entrance materials. Organic pollutants can be absorbed into its surface during the cooling proces sof pyrolysis. If released into the enviroment, these compounds can cause inhibition of plant growth, get into food chains and adversely affect living organisms. Organic pollutans are determined most often by GC/MS after organic solvent extraction.
493

In-situ sanering av förorenad mark : Jämförelse och utvärdering av existerande och potentiella in-situ behandlingsmetoder för PAH, aromater, arsenik, bly, nickel och bensen

Lindberg, Fredrik January 2019 (has links)
This thesis deals with a contaminated area in the municipality of Östersund where a gas plant has previously been operating from 1914 to 1951. Operations at the property where the gas plant has been located currently consist of a workshop and commercial premises with associated car parking. In order to be able to build on the gas plant area, the municipality intends to implement post-treatment measures in the area. The substances found in the contaminated area (hotspot area E) are polycyclic aromatic hydrocarbons (PAH), aromatics, arsenic, nickel, lead and benzene. Measurement data indicate that these substances have been found at high levels, above the Swedish Environmental Protection Agency's guideline values for contaminated soil. Many areas today are polluted to the level that they pose great risks to the environment and people, and this thought requires the treatment of contaminated soil. A risk assessment for hotspot area E determined that PAH, aromatics, arsenic, nickel, lead and benzene pose an unacceptable risk, and the area is therefore deemed to need remediation. Based on nearby buildings, in-situ soil remediation is a suitable approach that fits. This study summarizes the progress made in remediation research and shows that soil remediation methods have different advantages and disadvantages, and different strains on human health and the environment. Based on this study, it may be more appropriate to wait for more efficient or cheaper remediation techniques to be developed, but with the idea that these substances are volatile, toxic, and dangerous to us humans and the environment. This means that they pose a potential risk to society and a tendency to spread easily. Conclusions that can be drawn are that all in-situ methods included in this work can be applied in Sweden based on the geological conditions. In order to achieve optimum in-situ soil remediation, site-specific conditions, such as large groundwater flow or heterogeneous soil, control the choice of remediation method.
494

Stanovení polyaromatických uhlovodíků v pevných matricích hydrosféry metodou QuEChERS - porovnání se stávajícími metodami / Determination of polycyclic aromatic hydrocarbons in hydrosphere solid matrices by QuWChERS - comparision with present methods

Sudová, Petra January 2012 (has links)
Thesis are aimed to the optimization and validation of the QuEChERS method for determination of polycyclic aromatic hydrocarbons in solid matrices of hydrosphere. The QuEChERS method was also used for determination of polycyclic aromatic hydrocarbons in real samples and for comparison of measured results, time and material costs of the method with currently employed methods: (1) accelerated solvent extraction connected with gel permeation chromatography (ASE/GPC), and (2) ultrasonic extraction connected with solid phase extraction (UZ/SPE). According to the validation criteria, the QuEChERS method is suitable for the determination of polycyclic aromatic hydrocarbons in solid matrices of hydrosphere. The QuEChERS technique provides comparable results to ASE/GPC and UZ/SPE. In terms of price and time for sample preparation, the QuEChERS method allows (unlike the methods ASE/GPC and UZ/SPE) fast and inexpensive determination of polycyclic aromatic hydrocarbons in solid samples of hydrosphere.
495

Elektronische Eigenschaften dotierter polyzyklischer aromatischer Kohlenwasserstoffe

Mahns, Benjamin 20 January 2015 (has links)
In der vorliegenden Arbeit wurde die elektronische Struktur verschiedener undotierter und mit Alkalimetallen beziehungsweise 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethan (F 4 TCNQ) dotierter, polyzyklischer aromatischer Kohlenwasserstoffe (PAK) untersucht. Diese Untersuchungen waren motiviert durch verschiedene Veröffentlichungen in denen supraleitendes Verhalten an unterschiedlichen alkalimetalldotierten PAK beschrieben wurde. Erste Studien erfolgten an undotiertem 1,2:8,9-Dibenzopentacen (DBP) und Pentacen unter Nutzung von Photoelektronenspektroskopie (PES), Elektronenenergieverlustspektroskopie (EELS) und Dichtefunktionaltheorie (DFT). Die spektroskopischen Methoden zeigten für beide Materialien eine große Ähnlichkeit der elektronischen Zustände, vor allem im niederenergetischen Bereich, welche durch die theoretischen Ergebnisse bestätigt wurde. Die elektronische Ähnlichkeit beider Materialien ist im starken Gegensatz zu dem in der Literatur bei Dotierung beobachteten Verhalten, bei dem Pentacen zum Mott-Isolator wird, während DBP Supraleitung zeigt. Weitere Untersuchungen erfolgten an Picen und Coronen. Bandstrukturrechnungen zeigten, dass Picen vermutlich ein stark korreliertes Elektronensystem besitzt. Neben dem mit PES ermittelten Ionisationspotential und der Austrittsarbeit waren auch die mit EELS gemessenen optischen Bandlücken der beiden Materialien sehr ähnlich. Unterschiede zeigten sich hingegen vor allem in der Dichte der gemessenen Zustände von Picen und Coronen am Ferminiveau. Bei der Untersuchung der elektronischen Eigenschaften von mit Kalium-dotierten Picen und Coronen wurde trotz der erfolgreichen Dotierung in keinem der untersuchten Filme eine Zustandsdichte am Ferminiveau beobachtet somit wurde auch keiner der untersuchten Filme metallisch. Dasselbe Verhalten konnte auch für Natrium-dotierte Filme beobachtet werden. Eine Diskussion dieses Ergebnisses, welches im Gegensatz zu der von anderen Gruppen in dotierten Molekülen beobachteten Supraleitung steht, erfolgte im Hinblick auf die Bildung unterschiedlich dotierter Phasen, Elektron-Phonon-Kopplung, der Formierung von Bi-Polaronen und Korrelationseffekten. Für ein weitergehendes Verständnis der dotierungsinduzierten elektronischen Eigenschaften in den untersuchten Molekülen wurden diese nicht nur mit Alkalimetallen, sondern teilweise auch mit elektronenziehenden Molekülen wie F 4 TCNQ interkaliert. Dabei entstanden Kristalle verschiedener Ladungstransfersalze. Eine ausführliche Charakterisierung erfolgte für Picen/F 4 TCNQ-Kristalle, welche im Rahmen dieser Arbeit zum ersten Mal hergestellt und untersucht wurden. Dabei wurde zunächst deren Kristallstruktur mit Röntgendiffraktometrie (XRD) bestimmt. Eine Abschätzung der Größe des Ladungstransfers innerhalb der Molekülpaare aus Picen/ F 4 TCNQ erfolgte über Infrarot- und Bindungslängendaten, die auf diese Weise gefunden Werte wurden zusätzlich durch DFT-Rechnungen untermauert. Transportmessungen zeigten außerdem, dass die hergestellten Kristalle entlang ihrer Hauptwachstumsrichtung Isolatoren sind. Die Untersuchung der elektronischen Eigenschaften wurde mit EELS und PES an Picen/ F 4 TCNQ -Dünnfilmen durchgeführt, welche durch die Verdampfung der Einkristalle hergestellt wurden. Die Molekülpaare zeigen einen Ladungstransfer, der neue elektronische Anregungen im Niederenergiebereich der mit EELS gemessenen Verlustfunktion hervorruft. Im weiteren Verlauf der Arbeit erfolgte eine Diskussion bezüglich des Charakters und der Lokalisierung dieser neuen Anregungen. Bei den PES-Messungen zeigte sich der Ladungstransfer durch energetische Verschiebungen in den gemessen Rumpfniveauspektren sowie durch im Vergleich zu den reinen Materialien deutlich veränderte Ionisationspotentiale. Trotz des erfolgreichen Ladungstransfers und der damit verbundenen Füllung von unbesetzten Zuständen mit Elektronen in F 4 TCNQ wurde jedoch in den Valenzbandspektren keine Emission am Ferminiveau beobachtet. DFT-Rechnungen ermöglichten schließlich Aussagen über den Charakter des Ladunstransfers und die daraus resultierende, fehlende Zustandsdichte am Ferminiveau.
496

Multi-energy well kinetic modeling of novel PAH formation pathways in flames

Giramondi, Nicola January 2016 (has links)
Polycyclic Aromatic Hydrocarbons (PAHs) are harmful by-products formed during combustion of hydrocarbons under locally fuel-rich conditions followed by incomplete combustion. PAHs act as precursors during the formation of soot. PAHs and soot are harmful for human health and legislation limits the emission of unburned hydrocarbons and soot. Consequently, other measures are necessary in order to limit the production of PAHs and soot in internal combustion engines applications, entailing a possible decrease of fuel efficiency and higher technical requirements for automotive manufactures. The combustion chemistry of PAHs is not fully understood, which prompts the need of further investigations. The chemical dynamics shown by novel pathways of PAH formation involving vinylacetylene addition to the phenyl radical opens up new horizons for the potential contribution to PAH formation through this class of reactions. In the present work novel pathways of the formation of naphthalene and phenanthrene are investigated for a laminar premixed benzene flame and a laminar ethylene diffusion flame. The purpose is to improve the prediction of the aromatic species concentration in the flames. A pathway chosen due the high potential aromatic yield is assessed through preliminary flame calculations relying on simplifying assumptions concerning reaction rates. Certain isomerisation steps of the pathway occur within a time-scale characteristic of thermal relaxation processes. Therefore, the solution of the energy grained master equation is necessary in order to calculate the phenomenological reaction rates resulting from a non-equilibrium kinetic modeling. Quantum chemical calculations are performed in order to calculate molecular properties of the species involved. These properties are subsequently processed to determine the rate constants of the sequence of multi-energy well reactions. Moreover, the chemical dynamics of the pathway is analyzed and the effect of temperature and pressure on the kinetic parameters is investigated. Despite of the potential yield demonstrated through the preliminary flame calculations, the computed rate constants show that the studied reactions are insignificant for the formation of naphthalene and phenanthrene in the studied flames. An effort is put on evaluating if the non-equilibrium kinetic modeling adopted for the calculation of the kinetic parameters is consistent with the kinetic modeling used in the flame calculations. The current work provides an efficient method to compute rate constants of multi-energy well reactions at different thermodynamic conditions, characteristic of flames and of combustion in commercial devices or in internal combustion engines. Pathways with a slightly different chemical dynamics should be tested applying the current methodology. Moreover, further studies should be aimed at overcoming possible limits of the kinetic modeling of multi-energy well reactions occurring in combustion environments.
497

Injection Treatment for Lower Back Pain in Older Adults with Lumbar Spinal Stenosis: A Dissertation

Briggs, Virginia G. 28 August 2009 (has links)
Background:Lower back pain is one of the most common health-related complaints in the adult population. Thirty percent of Americans 65 years and older reported symptoms of lower back pain in 2004. With an aging population, the proportion of people over the age of 65 is expected to reach 20% by the year 2030. Because of this increase in older adults, lumbar spinal stenosis (LSS) associated with arthritic changes will also likely increase. In older adults, lower back pain is most often caused by degenerative lumbar spinal stenosis. Stenosis is the narrowing ofthe spinal canal, causing pressure on the nerve roots and is frequently treated surgically. Lumbar spinal stenosis is one of the most common reasons for back surgery in patients 65 years and older 2. However, risks associated with surgery increase with age 3-5 and older patients may choose non-surgical treatment for their lower back pain, including injection treatment. Injection treatment, usually consisting of anti-inflammatory medications and analgesics, has improved since the mid-1990's when fluoroscopic guidance was developed. Information about injection treatment for lower back pain is limited, especially in the older population. An extensive review of published literature regarding injection treatment revealed a paucity of information about older adults diagnosed with lumbar spinal stenosis. In this study, three aims were designed to gain more information about the effectiveness of injection treatment in older patients with lumbar spinal stenosis. In the first (retrospective) study, information about receipt of second injections and time between injections was collected to examine injection usage. In the second and third (prospective) studies, information about pain relief and functional return following injection treatment was collected to examine the effectiveness of injection treatment in patients age 60 and older diagnosed with lumbar spinal stenosis. To our knowledge, such results have not been repolted for this population in the literature. Objective:Injection treatment is a commonly used non-surgical procedure to alleviate lower back pain in older adults. However, older patients do not have enough information about how long pain relief will last after treatment or the amount of pain relief and functional return they will experience. These studies focused on three topics: 1) usage of injection treatment; 2) effectiveness of injection treatment on pain relief; 3) effectiveness of injection treatment on functional return. In addition, the variations of the effectiveness were examined by selected patient attributes. Methods:In a retrospective study, medical records of patients aged 60 years or older from a high volume dedicated spine center at the University of Massachusetts Memorial Hospital were retrospectively reviewed. This study included those diagnosed with degenerative LSS, who had not received an injection for lower back pain within six months, and whom were treated between June I, 2006 and May 31, 2007. In two prospective studies, patients scheduled for lumbar injection treatment between January 1 and June 30, 2008 were selected from the University of Massachusetts Memorial Hospital Spine Center. Selection criteria included patients age 60 and over, diagnosed with degenerative lumbar spinal stenosis and no previous lumbar injection within 6 months or lumbar surgery within 2 years. The Pain sub-score of the SF-36 questionnaire was used to measure pain at baseline and at one and three months post injection. The Physical Component Score (PCS) of the SF-36 questionnaire and the Oswestry Disability Index (ODI) were used to measure function at baseline and at one and three months post injection. Variations in longitudinal changes in scores by patient characteristics were analyzed in both unadjusted (univariate) analyses using one-way analysis of variance (ANOVA), and adjusted (multiple regression) analyses using linear mixed effects models. Results: In the retrospective cohort, the mean age of the cohort was 68, 64% were female, 59% were married, with a mean Body Mass index of 32 kg/m2. Of 92 eligible patients, 57% returned for a second injection within six months of the first. The mean number of months between injections was 4.8 for all patients, ranging from 1 to 22 months. When patient characteristics were examined, the only variable that showed a statistically significant difference was age. Patients aged 70 years and older were found to be 67% less likely to return for a second injection when compared to patients age 60-69 (OR=0.33 (0.12 - 0.94)p In the prospective cohort, information was collected on 62 patients. Mean Pain scores improved significantly from baseline to one month (14.1 points), and from baseline to three months (8.3 points). Post injection changes in Pain scores varied by Body Mass Index (BMI) and baseline emotional health. Based on a linear mixed effects model analysis, higher baseline emotional health, as measured by the SF-36 Mental Component Score (MCS>50), was associated with greater reduction in pain over three months when compared to lower emotional health (MCS Conclusion: Patients over age 70 do not return for repeat injection as frequently as patients age 60-69. In addition, each year a patient ages over age 60, they are 10% less likely to return for a repeat injection. Lower back pain in older adults with LSS is clinically significantly alleviated after injection treatment. In addition, injection treatment for LSS is associated with return of lost function needed for daily living activities in older adults. Pain relief and functional return varies by patient personal and clinical characteristics. Higher emotional health was associated with more pain relief and more functional return experienced over three months following injection treatment. Additional information is needed about why older patients do not return for second injections at the same rate as younger patients and how emotional health affects response to injection treatment in older adults.
498

Exposition in vitro de lymphocytes T humains aux hydrocarbures aromatiques polycycliques : étude des effets immunotoxiques / In vitro exposure of human T lymphocytes to polycyclic aromatic hydrcarbons : study of immunotoxic effects

Liamin, Marie 21 December 2017 (has links)
Les hydrocarbures aromatiques polycycliques (HAPs), tels que le benzo(a)pyrène (B[a]P), sont des contaminants environnementaux ubiquistes générés lors de la combustion de matière organique. Ces composés ont été associés au développement d'effets toxiques sur la santé humaine, notamment des effets cancérigènes et immunotoxiques, principalement liés à l'activation du récepteur aux hydrocarbures aromatiques (RAh). Parmi les cellules du système immunitaire, les lymphocytes T apparaissent comme des cibles majeures des HAPs. Des résultats antérieurs, obtenus au laboratoire, ont montré que l'activation des lymphocytes T humains en culture primaire conduit à l’augmentation de l'expression et de la fonction du RAh, suggérant la capacité accrue de ces cellules à répondre à une exposition aux HAPs. Nos objectifs sont : (1) de déterminer les effets du B[a]P sur les profils d'expression génique dans les lymphocytes humains normaux en utilisant des approches à haut débit telle que l'analyse transcriptomique sur puce à ADN, (2) d’évaluer les effets génotoxiques et immunotoxiques du B[a]P en mesurant respectivement les dommages à l'ADN induits et leurs actions immunosuppressives et (3) d’analyser la modulation de ces effets en présence d'autres HAPs. Notre travail identifie les lymphocytes T humains normaux comme un bon modèle pour étudier les effets génotoxiques et immunotoxiques des HAPs, et pour prédire les problèmes de santé humaine liés à l’exposition à ces contaminants. Il permet également de mieux comprendre la régulation par les HAPs de la réponse immune et propose de nouveaux biomarqueurs potentiels de l'exposition à ces contaminants environnementaux. / Polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (B[a]P), are ubiquitous environmental contaminants generated during organic matter combustion. These compounds have been associated with the development of toxic effects on human health, including carcinogenic and immunotoxic effects, mainly related to Aryl hydrocarbon Receptor (AhR) activation. Among the immune system cells, T lymphocytes appear as major targets of PAHs. Previous results, obtained in the laboratory, have shown that activation of primary human T lymphocytes leads to a functional AhR expression increase, suggesting their ability to respond to PAH exposure. Our specific aims are: (1) to determine the effects of B[a]P on gene expression profiles in human normal lymphocytes by using large-scale approaches such as microarray-based transcriptome analysis, (2) to monitor the genotoxic and immunotoxic effects of B[a]P by measuring DNA damage and immunosuppressive actions, respectively and, (3) to analyze the modulation of these effects by the presence of other PAHs. Our work propose primary cultures of activated human T lymphocytes as a good model for studying both genotoxic and immunotoxic effects of environmental contaminants such as PAHs and predicting human health issues. It also gains a comprehensive insight into the immune response regulation after PAH exposure and provides potential new biomarkers of exposure to these environmental contaminants.
499

Study of Genes Relating To Degradation of Aromatic Compounds and Carbon Metabolism in Mycobacterium Sp. Strain KMS

Zhang, Chun 01 May 2013 (has links)
Polycyclic aromatic hydrocarbons, produced by anthropological and natural activities, are hazardous through formation of oxidative radicals and DNA adducts. Growth of Mycobacterium sp. strain KMS, isolated from a contaminated soil, on the model hydrocarbon pyrene induced specific proteins. My work extends the study of isolate KMS to the gene level to understand the pathways and regulation of pyrene utilization. Genes encoding pyrene-induced proteins were clustered on a 72 kb section on the KMS chromosome but some also were duplicated on plasmids. Skewed GC content and presence of integrase and transposase genes suggested horizontal transfer of pyrene-degrading gene islands that also were found with high conservation in five other pyrene-degrading Mycobacterium isolates. Transcript analysis found both plasmid and chromosomal genes were induced by pyrene. These processes may enhance the survival of KMS in hydrocarbon-contaminated soils when other carbon sources are limited. KMS also grew on benzoate, confirming the functionality of an operon containing genes distinct from those in other benzoate-degrading bacteria. Growth on benzoate but not on pyrene induced a gene, benA, encoding a benzoate dioxygenase α-subunit, but not the pyrene-induced nidA encoding a pyrene dioxygenase α-subunit; the differential induction correlated with differences in promoter sequences. Diauxic growth occurred when pyrene cultures were amended with benzoate or acetate, succinate, or fructose, and paralleled delayed expression of nidA. Single phase growth and normal expression of benA was observed for benzoate single and mixed cultures. The nidA promoters had potential cAMP-CRP binding sites, suggesting that cAMP could be involved in carbon repression of pyrene metabolism. Growth on benzoate and pyrene requires gluconeogenesis. Intermediary metabolism in isolate KMS involves expression from genes encoding a novel malate:quinone oxidoreductase and glyoxylate shunt enzymes. Generation of C3 structures involves transcription of genes encoding malic enzyme, phosphoenolpyruvate carboxykinase, and phosphoenolpyruvate synthase. Carbon source modified the transcription patterns for these genes. My findings are the first to show duplication of pyrene-degrading genes on the chromosome and plasmids in Mycobacterium isolates and expression from a unique benzoate-degrading operon. I clarified the routes for intermediary metabolism leading to gluconeogenesis and established a potential role for cAMP-mediated catabolite repression of pyrene utilization.
500

Association between Maternal Occupational Exposure to Polycyclic Aromatic Hydrocarbons and Risk of Selected Birth Defects in the National Birth Defects Prevention Study

Santiago-Colón, Albeliz January 2018 (has links)
No description available.

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