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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.
601

Investigation of selected organic compounds on water quality along the Olifants river catchment

Mulanga, Tshimanga Christelle 06 1900 (has links)
Water is a crucial natural resource, indispensable to food production, life, the environment, power generation, industry, sanitation and hygiene. The presence of Organochlorine Pesticides (OCPs) in the environment is not wanted due to their negative effects on human beings and animals. As a result, there is a need to continuously monitor their presence in the environment. In this study, surface water samples were collected once a month during the dry season and during wet season from the selected five points along the Olifants River and stored at a temperature of < 50C before analysis. The OCPs were extracted with dichloromethane (DCM) using the Liquid-Liquid Extraction (LLE) method. After undertaking the sample through the clean- up process, the crude extracts obtained were put into the column chromatography and eluted with hexane, about 1.5 μL of the purified extracts were analysed by the Gas Chromatographic- Mass Spectrophotometer (GC/MS). The percentage recoveries, varied from 32- 116 % for p, p’-DDT and 4,4'-DDD respectively in triply spiked water samples. The standard deviation for most of the compounds is less than±0.04, with the exclusion of Heptachlor (±0.14). The seasonal variability of OCPs in water samples along Olifants River results show that in dry season, the Olifants River is mostly polluted at the Oxford site with (BHC-beta, Aldrin, Heptachlor-epoxide, Endosulfan-alpha and Endrin), at the Ga- Selati site with (Heptachlor-epoxide and Endrin) and at the Wolvekrans site with (Endosulfan-alpha), with Aldrin up to 834.20 ng/ L indicating the highest hazard toward the aquatic environment while in summer the Olifants River is mostly polluted at the Ga- selati site with BHC-beta and at the Waterval site with (Heptachlor and BHC-gamma) with BHC- gamma up to 560 ng/ L indicating the highest hazard toward the aquatic environment. The levels reached from the Olifants River catchment were meaningfully above the drinking water quality guidelines for organic chemical recommended by WHO, 2006 i.e. (BHC-gamma,DDT-44, Aldrin, dieldrin and Endrin are (2.0,1.0,0.03,0.03 and 0.6) respectively for the protection of the domestic use, aquatic ecology and agricultural use (irrigation and livestock watering) for compounds with local guideline values; while, the international water quality guidelines to protect the aquatic ecosystems are 0.00083 ng/mℓ (4,4’DDD), 0.00059 ng/mL (4,4’DDE), (4,4’DDT), 0.00021 ng/mL (heptachlor), 0.0092 ng/mℓ (α-HCH), 0.0186 ng/mL (γ- HCH), and chronic values are 0.056 ng/mL (ENDO I and II) and 0.0023 ng/mL endrin) (USEPA, 2002). Levels detected were significantly higher than some research studies conducted up to now in South African aquatic environments. These results confirm the contamination of the Olifants River catchment by the OCPs. / Water and Sanitation / M. Sc. (Environmental Science)
602

Improving the performances of the combustion engines by improving the ignition system / Amélioration des performances des moteurs à combustion par amélioration du système d'allumage

Astanei, Dragoş-George 05 November 2014 (has links)
Face aux normes actuelles et futures, de plus en plus drastiques, concernant les émissions de polluants, les constructeurs automobiles cherchent en permanence à améliorer l'efficacité des moteurs à allumage commandé. Une des solutions les plus efficaces et applicables pour diminuer la quantité de polluants émis dans les gaz d’échappement (HC, CO, NOx) et réduire la consommation de carburant, est d’utiliser un mélange très pauvre (richesse du mélange inférieure à 0,6). Toutefois, ce concept de fonctionnement est limité par les systèmes d'allumage classiques qui ne peuvent pas garantir un allumage du mélange air / combustible dans de bonnes conditions, de manière à assurer une combustion complète, rapide et reproductible.Le sujet de cette thèse consiste en l'élaboration d'un nouveau système d'allumage basé sur une bougie d’allumage double, qui peut produire deux d'étincelles quasi-simultanées, dont la longueur cumulée est plusieurs fois plus élevée que celle d’étincelles produites par une bougie d'allumage classique. Pour valider ce système d'allumage, trois différents types d'analyses ont été réalisés: une analyse des paramètres électriques des décharges, un diagnostic du plasma par spectroscopie optique d'émission, et des essais in situ du système d'allumage sur deux moteurs à combustion interne avec analyse des gaz d'échappement et détermination des performances des moteurs.Ces tests ont révélé que l'utilisation du système d’allumage à double étincelle peut assurer une meilleure stabilité dans le fonctionnement du moteur (en particulier dans les conditions d'allumage difficiles, en utilisant des mélanges très pauvres) ; des performances accrues du moteur pour une même quantité de carburant consommé ; et une diminution de la quantité d’hydrocarbures imbrûlés et de monoxyde de carbone dans les gaz d'échappement, mais avec une plus grande émission d'oxydes d'azote par rapport à un système d'allumage classique. / Faced with the current and future more and more drastic standards for pollutant emissions, the car manufacturers are permanently trying to improve the efficiency of spark ignition engines. One of the most effective applicable solutions for reducing the quantity of pollutant emissions (HC, CO, NOx) from the exhaust gases and also to reduce the fuel consumption is to operate with very lean mixture (equivalent ratio lower than 0.6). However, this operation concept is limited by the actual ignition systems that cannot assure an air/fuel mixture ignition in good conditions, in order to assure a complete, fast and repeatable combustion. The subject of this thesis consists into developing of a new ignition system based on a double spark plug, which can produce two quasi-simultaneous spark discharges with cumulated length few times higher than the sparks produced by a conventional spark plug. For ignition system validation, three different types of analysis have been considered: the analysis of the discharges electrical parameters, the plasma diagnosis using optical emission spectroscopy methods and the tests of the ignition system on two internal combustion engines with the exhaust gases analysis and engine performances determination. The tests revealed that the utilization of the double spark ignition system can assure a better stability in engine operation (especially in difficult ignition conditions such using very lean mixtures), increased engine performances for the same amount of consumed fuel and it can provide a diminution of the unburned hydrocarbons and carbon monoxide quantities from the exhaust gases, but with an increased quantity of nitrogen oxides, compared with a conventional ignition system.
603

Desenvolvimento e aplicação de uma nova fase para extração por sorção em barra de agitação (SBSE) / Development and application of a new phase for stir bar sorptive extraction (SBSE)

Juliana Yamashita Barletta 17 December 2010 (has links)
Uma fase polimérica inédita de polidimetilsiloxano/carvão ativado (PDMS-ACB) é proposta como fase extratora para extração por sorção em barras de agitação (SBSE). A barra de PDMS-ACB foi desenvolvida no laboratório usando um molde de teflon simples, demonstrando estabilidade e resistência aos solventes orgânicos. Utilizando uma única barra de PDMS-ACB mais de 150 extrações foram realizadas sem qualquer dano. A barra de SBSE contém aproximadamente 100 &micro;L de revestimento polimérico, 2,36 mm de diâmetro e 2,2 cm de comprimento. A barra PDMS-ACB foi aplicada na extração de seis pesticidas (ametrina, atrazina, bifentrina, carbofurano, metribuzim e tebutiurom), com propriedades predominantemente polares, comumente aplicados em plantações de cana-de-açúcar. A barra PDMS-ACB foi utilizada na determinação de pesticidas em garapa através de cromatografia gasosa hifenada à espectrometria de massa (GC-MS). O planejamento experimental foi empregado na etapa de otimização da extração SBSE, um planejamento fatorial fracionado avaliou a influência dos principais parâmetros envolvidos. Posteriormente, o planejamento composto central (CCD) com conformação estrela foi explorado para otimizar os fatores significativos na extração. Apenas 200 &micro;L de acetato de etila foram utilizados como solvente na dessorção líquida (LD). Para os compostos avaliados, o método apresentou limite de quantificação (LOQ) no intervalo de 0,5 - 40 &micro;g L-1, as recuperações variaram entre 0,18 - 49,50 % e a precisão intra-dia variou de 0,072 - 8,40 %. Concluída a etapa de validação, o método foi aplicado em amostras reais de garapa disponíveis comercialmente em São Carlos-SP. / A novel polydimethylsiloxane/activated carbon (PDMS-ACB) is proposed as new polymeric phases for stir bar sorptive extraction (SBSE). The PDMS-ACB was developed in lab using simple teflon\'s mold, demonstrating remarkable stability and resistance to organic solvents, over 150 extractions without any damage. SBSE bar contained 100 &micro;L of polymeric coating, a diameter of 2.36 mm and a length of 2.2 cm. It was applied to the determination of pesticides (ametryn, atrazine, bifenthrin, carbofuran, metribuzine and tebuthiuron) having predominantly polar properties, applied in sugarcane crops. PDMS-ACB was employed in the determination of pesticides in sugarcane juice using gas chromatography coupled to mass spectrometry (GC-MS). Experimental design was employed in the optimization step, a fractional factorial evaluated the main parameters involved in the extraction procedure. Afterwards, central composite design (CCD) was exploited to optimize the significant factors on the extraction. About 200 &micro;L of ethyl acetate were employed as solvent in the liquid desorption (LD). The method presented limit of quantification (LOQ) from 0.5 to 40 &micro;g L-1, recoveries varied 0.18 - 49.50% and precision intra-day 0.072 - 8.40%. Hence, the method was applied to the analysis of real sugarcane juice samples commercially available in São Carlos-SP.
604

Desenvolvimento e validação de método para determinação de hidrocarbonetos policíclicos aromáticos em camarão (Litopenaeus vannamei) / Method development and validation for polycyclic aromatic hydrocarbons determination in shrimp (Litopenaeus vannamei)

Vilela Júnior, Antônio Rodrigues 24 February 2017 (has links)
Brazil is among the ten largest cultivated shrimp producers in the world, with the northeast being the largest producer of shrimp cultivated in the country. These regions of cultivation may undergo strong anthropic stress due contamination by all sort of compounds, including the polycyclic aromatic hydrocarbons (PAH). These compounds have been the source of several studies because they are considered mutagenic and carcinogenic. The objective of this work is to develop an analytical method based on the matrix solid phase dispersion (MSPD) and gas chromatography coupled to mass spectrometry for determination of 16 PAH in shrimp. The optimal working conditions were 0.5 g of the sample; 0.5 g of C18; 1.5 g of alumina; 150 seconds of homogenization and 8 mL of acetonitrile as the elution solvent. These last three variables were established through a factorial design of 23 with triplicate at the central point plus six axial points, evaluating them by the methodology of response surface analysis. The validation of the analytical method presented linearity in the range of 0.9915 to 0.999 and sensitivity in the concentration range of 5 to 100 ng g -1; selectivity based on matrix effect, accuracy and precision, with recovery values between 70 - 104% coefficients of variation lower than 13%, in the three levels of fortification (10, 25 and 50 ng g -1); (dry weight) limits of 0.7 to 5.0 ng g -1 and 1 to 5 ng g -1 respectively, the robustness was evaluated through the contour charts, which indicated that the method can be considered robust. This method was applied in four samples (A, B, C and D), with HPA predominating from 2 to 4 rings, sample A being the one with the highest concentration (280 ng g-1 for total PAH). In the three samples (A, B and C) benzo [a] anthracene have reached concentrations of 21, 18 and 14 ng g-1 respectively, which is considered probable carcinogenic to humans. The method was considered efficient in the extraction of PAH, when compared to the methods reported in the literature. It integrates the process of extraction and cleaning in a single and economical method and the consumption of materials used during the process is minimized. / O Brasil está entre os dez maiores produtores de camarão do mundo, sendo a região nordeste a maior produtora de camarão cultivado no país. As regiões de cultivo estão sob forte estresse ambiental, acarretando contaminação por vários compostos, incluindo os hidrocarbonetos policíclicos aromáticos (HPA). Estes compostos têm sido fonte de diversos estudos, por apresentarem propriedades mutagênicas e carcinogênicas. Diante do exposto, este trabalho objetiva desenvolver um método analítico baseado na técnica de dispersão da matriz em fase sólida (MSPD) e cromatografia gasosa acoplada à espectrometria de massas, para determinação de 16 hidrocarbonetos policíclicos aromáticos (HPA) em camarão. As condições ótimas de trabalho foram 0,5 g da amostra; 0,5 g de C18; 1,5 g de alumina; 150 segundos de homogeneização e 8 mL de acetonitrila como solvente de eluição. Estas três últimas variáveis estabelecidas através de um planejamento fatorial 23 com triplicata no ponto central mais seis pontos axiais, avaliando-as pela metodologia de análise de superfície de resposta. A validação do método analítico apresentou linearidade na faixa de 0,9915 a 0,999 e sensibilidade no intervalo de concentração de 5 a 100 ng g-1; seletividade com base no efeito de matriz, exatidão e precisão, com valores de recuperação entre 70 - 104% coeficientes de variação inferiores a 13%, nos três níveis de fortificação (10, 25 e 50 ng g-1); limites de detecção e quantificação (peso seco) de 0,7 a 5,0 ng g-1 e 1 a 5 ng g-1 respectivamente; robustez foi avaliada através dos gráficos de contorno, o qual indicou que o método pode ser considerado robusto. Este método foi aplicado em quatro amostras (A, B, C e D), com predominância dos HPA de 2 a 4 anéis, sendo a amostra A com a maior concentração total de HPA, 280 ng g-1. Nas amostras A, B, C foram encontrados benzo[a]antraceno 21; 18 e 14 ng g-1, respectivamente, este que é considerado provável cancerígeno ao homem. O método pode ser considerado eficiente na extração de HAP, quando comparado aos métodos relatados na literatura. Integra o processo de extração e limpeza em uma única etapa e econômico, pois o consumo de materiais e minimizado. / São Cristóvão, SE
605

Composição química e capacidade sequestrante de espécies reativas de oxigênio e nitrogênio de mel orgânico brasileiro / Chemical composition and Nitrogen and Oxygen Reactive Species scavenging activity of Brazilian organic honey

Camila Furtunato da Silva 21 July 2017 (has links)
O Brasil apresenta grande potencial para a exploração da apicultura, dado ao seu vasto território e flora diversificada, o que permite diferentes variedades de méis com propriedades únicas. O estado do Paraná é um dos maiores produtores de méis do país e o investimento em produção que atenda aos mercados mais exigentes estimulou a produção do mel orgânico. O conhecimento desde a antiguidade sobre os efeitos benéficos à saúde pelo mel vem estimulando a pesquisa deste alimento nobre. Assim, este trabalho teve por objetivo estudar méis orgânicos brasileiros certificados (MO) para a caracterização do perfil fenólico, volátil, além da avaliação da capacidade de sequestro das espécies reativas de oxigênio e nitrogênio. Os méis foram coletados nos apiários de apicultores com certificação orgânica de dois municípios do sul do Paraná, General Carneiro e Turvo-PR. Nos ensaios foram utilizados extratos fenólicos dos méis, obtidos por meio da utilização da resina Amberlite® XAD®2, bem como méis brutos in natura. Os extratos apresentaram conteúdo de compostos fenólicos significativo, sendo o melato (MO5), de General Carneiro, o de maior teor (117,68± 4,40 mg EAG/g). Para as análises de sequestro das espécies reativas de oxigênio e nitrogênio, os extratos fenólicos foram sempre superiores aos méis brutos in natura. Os extratos fenólicos, de maneira geral, apresentaram alta capacidade de sequestro para o radical peroxila (ROOo), ácido hipocloroso (HOCl) e óxido nítrico (NOo). Em relação aos melatos, o extrato MO7 apresentou alta capacidade para o sequestro do HOCl (EC50= 4,83 ± 0,13 ?g/mL), enquanto que o MO5 foi melhor para o sequestro do NOo (EC50=2,16 ± 0,18 ?g/mL). Pelo método HPLC-ABTS on-line foi possível identificar e quantificar a contribuição para a atividade antioxidante do ácido ferúlico no extrato (MO1) e do flavonoide kanferol na amostra (MO4). O ácido ascórbico foi identificado e quantificado por HPLC somente nos melatos (MO3, MO5 e MO7). Pela técnica de LC-MS/MS foram identificados a presença dos seguintes compostos fenólicos: ácido caféico, rutina e hesperidina em todos os extratos. A análise de compostos voláteis por SPME-CG/EM mostrou a presença de dois compostos, encontrados apenas nos melatos, que foram o terpineno-4-ol, que possui ação antifúngica, antiparasitológica e anti-inflamatória; e o 3,4-dimetil-1-deceno, podendo assim serem utilizados como marcadores químicos destes méis. O conhecimento da composição química destes méis, bem como a composição fenólica bioativa, contribui para o fornecimento de antioxidantes naturais para a dieta, atenuando assim os efeitos negativos dos radicais livres / Brazil has a great potential to explore beekeeping due to its vast territory and diversified flora, what allows different varieties of honeys with unique characteristics. Parana state is one of the largest honey producers and the investment in production that meets the most demanding markets stimulated the organic honey production. The knowledge since early in history regarding the beneficial health effects promoted by honey is stimulating the scientific research of this noble food. Thus, this paper aimed to study certified Brazilian organic honeys (MO) in order to determine the phenolic and volatile profiles, and also the evaluation of radical scavenging capacity against Nitrogen and Oxygen Reactive Species (RNS and ROS, respectively). The honeys were collected from apiaries from beekeepers with the organic certification from two municipalities of southern Parana, General Carneiro and Turvo, PR. In the essays, phenolic extracts were obtained from honeys by using Amberlite® XAD®2 resin, as well as crude in natura honeys. The extracts showed a significant content in phenolic compounds, with honeydew (MO5), from General Carneiro, showing the highest content (117,68 ± 4,40 mg AGE/g). For the analyzes to determine the radical scavenging capacity against RNS and ROS, the phenolic extracts always showed up superior results in comparison to crude in natura honeys. Phenolic extracts showed, in general, great capacity to scavenge peroxyl radical (ROOo), hypochlorous acid (HOCl) and nitric oxide (NOo). In relation to honeydews MO7 extract showed the highest capacity to scavenge HOCl (IC50= 4,83 ± 0,13 ?g/mL) while MO5 was the sample with better capacity to scavenge NOo (IC50=2,16 ± 0,18 ?g/mL). By using HPLC-ABTS on-line method it was possible to identify and to quantify the ferulic acid in MO1 extract, a compound with an important contribution to the antioxidant activity of this sample, as well as the flavonoid kaempferol in MO4 sample. Ascorbic acid was identified and quantified by HPLC only in the honeydew samples (MO3, MO5 and MO7). The analyzes developed by LC-MS/MS techniques indicated the presence of the phenolic compounds caffeic acid, rutin and hesperidin in all the extracts. The analysis of volatile substances developed by SPME-GC/MS promoted the identification of two compounds found only in the honeydew samples. The compounds were the terpinen-4-ol, which has antifungal, antiparasitological and anti-inflammatory activities; and 3,4-dimethyl-1-decene. Both compounds can be used as chemical markers of these honeys. The knowledge of the chemical composition of the studied honeys, as well as their bioactive phenolic composition, contributes to supply natural antioxidants to human diet, thus attenuating the negative effects of free radicals
606

Etude du procédé de co-pyrolyse de déchets plastiques et d’huiles de lubrification usagées dans le but de produire un combustible liquide alternatif

Breyer, Sacha 14 October 2016 (has links)
Cette étude s’inscrit dans le cadre du projet MINERVE de la région wallonne quivise notamment à valoriser les anciens centres d’enfouissement technique et leur contenuau travers de la production de matières premières et de sources d’énergie. Plus particulièrement,l’objectif de ce travail est d’étudier un procédé de co-pyrolyse de déchetsplastiques et d’huiles de lubrification usagées, ayant pour finalité la production d’uncombustible alternatif liquide pour l’industrie, en vue d’une future montée en échelledu procédé.Pour ce faire, différentes approches ont été poursuivies. Premièrement, nous avonsmis en place un réacteur de 5 litres, agité et scellé hermétiquement, permettant demener des essais de co-pyrolyse. Des essais de co-pyrolyse d’un mélange de déchetsplastiques excavés et d’huiles de lubrification usagées ont été menés dans le réacteur.L’influence des paramètres clés du procédé, tels que la température maximale, la fractionmassique de plastiques dans le mélange ainsi que la vitesse de refroidissement, surle procédé et la qualité du produit fini a été étudiée. Nous avons été en mesure deproduire un combustible alternatif liquide, possédant un pouvoir calorifique d’environ30 MJ/kg, par la co-pyrolyse d’un mélange contenant 60% de plastiques, en chauffantle mélange durant 13 h, en atteignant une température maximale de 387°C et enlaissant la pression au sein du réacteur monter jusqu’environ 30 bars. Les besoins énergétiquesdu procédé ont été évalués à environ 8 MJ/kg de déchets à pyrolyser, grâce àun modèle de transferts thermiques développé pour le système constitué du réacteur deco-pyrolyse. Ensuite, une méthode a été développée pour déterminer le temps de fonted’une particule de plastique en fonction de sa plus petite dimension. L’application decette méthode nous a permis de déterminer que la plus petite dimension maximale quepeuvent avoir les particules de plastiques dans le mélange plastique/huile, pour queleur fusion ne limite pas le procédé de co-pyrolyse, est d’environ 3 cm. Deux analysesthermiques, la thermogravimétrie isotherme et la calorimétrie différentielle à balayage,ont été combinées pour caractériser le craquage thermique et son influence sur plusieurspolymères. L’influence du craquage thermique sur les polymères a été évaluée sur basede l’analyse de la fusion ou de la transition vitreuse du polymère. Les protocole et dispositifexpérimentaux de co-pyrolyse de déchets plastiques et d’huiles de lubrificationusagées à l’échelle du laboratoire ont été adaptés pour pouvoir co-pyrolyser un mélangecontenant du PVC. Différents essais de co-pyrolyse par étapes ont été menés pour évaluerl’influence des paramètres comme l’évolution de la température pendant l’essai, lecontenu en PVC du mélange et le plastique en mélange avec le PVC (LDPE ou PS).Enfin, les interactions qui prennent place entre le LDPE ou le PS et une huile, lorsde leur co-pyrolyse, ont été mises en évidence à l’aide d’essais de thermogravimétriehaute résolution. Nous avons tenté d’expliquer les interactions mises en évidence, grâceà une combinaison d’analyses thermiques permettant de caractériser, voire d’identifier,les produits de décomposition de l’échantillon, en continu ou en fin de chauffe.This study takes part in the MINERVE (Walloon region) which aims at enhancingthe old landfills and valorize their content through the production of raw materials andenergy sources. Specifically, the objective of this work is to study a co-pyrolysis processof waste plastics and used lubrication oils, whose purpose is the production of a liquidalternative fuel for industry, in order to future scaling up the process.To do so, different approaches have been pursued. First, we set up a 5 liter reactor,stirred and hermetically sealed for performing co-pyrolysis tests. Co-pyrolysis tests ofa mixture of excavated plastic wastes and used lubrication oils were performed in thereactor. The influence of key parameters, such as maximum temperature, the massfraction of plastics in the mixture and the cooling rate, on the process and the qualityof the fuel was investigated. We were able to produce a liquid alternative fuel, witha calorific value of about 30 MJ/kg by co-pyrolyzing a mixture containing 60 % ofplastic, heating the mixture for 13 h, reaching a maximum temperature of 387°C anda maximum pressure of about 30 bar. The energy requirements of the process wereevaluated at about 8 MJ per kg of waste through a heat transfer model developed forthe system consisting of the co-pyrolysis reactor. In addition, a method was developedto determine the time of melting of a plastic particle according to its smallest size.The application of this method allowed us to determine that the maximum smallestsize that can have plastic particles in plastic/oil mixture, so that their melting willnot limit the co-pyrolysis process, is about 3 cm. Two thermal analysis techniques,isothermal thermogravimetry and differential scanning calorimetry, were combined tocharacterize the thermal cracking and its influence on several polymers. The influence ofthermal cracking of the polymers was evaluated based on the analysis of the melting orglass transition of the polymer. The experimental protocol and device of waste plasticsand used lubricating oils co-pyrolysis have been adapted to co-pyrolyze a mixturecontaining PVC. Two-step co-pyrolysis tests were performed to evaluate the influenceof parameters such as the evolution of the temperature during the test, the PVCcontent of the mixture and the plastic that is mixed with PVC (LDPE or PS). Finally,interactions that take place between the LDPE or the PS and an oil, when co-pyrolyzed,have been identified with high resolution thermogravimetry experiments. We tried toexplain the identified interactions through a combination of thermal analyzes thatcharacterized or identified the sample decomposition products, continuously duringthe thermal decomposition or at its end. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
607

Evaluation of Non-Contact Sampling and Detection of Explosives using Receiver Operating Characteristic Curves

Young, Mimy 07 November 2013 (has links)
The growing need for fast sampling of explosives in high throughput areas has increased the demand for improved technology for the trace detection of illicit compounds. Detection of the volatiles associated with the presence of the illicit compounds offer a different approach for sensitive trace detection of these compounds without increasing the false positive alarm rate. This study evaluated the performance of non-contact sampling and detection systems using statistical analysis through the construction of Receiver Operating Characteristic (ROC) curves in real-world scenarios for the detection of volatiles in the headspace of smokeless powder, used as the model system for generalizing explosives detection. A novel sorbent coated disk coined planar solid phase microextraction (PSPME) was previously used for rapid, non-contact sampling of the headspace containers. The limits of detection for the PSPME coupled to IMS detection was determined to be 0.5-24 ng for vapor sampling of volatile chemical compounds associated with illicit compounds and demonstrated an extraction efficiency of three times greater than other commercially available substrates, retaining >50% of the analyte after 30 minutes sampling of an analyte spike in comparison to a non-detect for the unmodified filters. Both static and dynamic PSPME sampling was used coupled with two ion mobility spectrometer (IMS) detection systems in which 10-500 mg quantities of smokeless powders were detected within 5-10 minutes of static sampling and 1 minute of dynamic sampling time in 1-45 L closed systems, resulting in faster sampling and analysis times in comparison to conventional solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis. Similar real-world scenarios were sampled in low and high clutter environments with zero false positive rates. Excellent PSPME-IMS detection of the volatile analytes were visualized from the ROC curves, resulting with areas under the curves (AUC) of 0.85-1.0 and 0.81-1.0 for portable and bench-top IMS systems, respectively. Construction of ROC curves were also developed for SPME-GC-MS resulting with AUC of 0.95-1.0, comparable with PSPME-IMS detection. The PSPME-IMS technique provides less false positive results for non-contact vapor sampling, cutting the cost and providing an effective sampling and detection needed in high-throughput scenarios, resulting in similar performance in comparison to well-established techniques with the added advantage of fast detection in the field.
608

The Skeletal Amino Acid Composition of the Marine Demosponge Aplysina cavernicola

Ueberlein, Susanne, Machill, Susanne, Niemann, Hendrik, Proksch, Peter, Brunner, Eike 07 May 2015 (has links)
It has been discovered during the past few years that demosponges of the order Verongida such as Aplysina cavernicola exhibit chitin-based skeletons. Verongida sponges are well known to produce bioactive brominated tyrosine derivatives. We could recently demonstrate that brominated compounds do not exclusively occur in the cellular matrix but also in the skeletons of the marine sponges Aplysina cavernicola and Ianthella basta. Our measurements imply that these yet unknown compounds are strongly, possibly covalently bound to the sponge skeletons. In the present work, we determined the skeletal amino acid composition of the demosponge A. cavernicola especially with respect to the presence of halogenated amino acids. The investigations of the skeletons before and after MeOH extraction confirmed that only a small amount of the brominated skeleton-bound compounds dissolves in MeOH. The main part of the brominated compounds is strongly attached to the skeletons but can be extracted for example by using Ba(OH)2. Various halogenated tyrosine derivatives were identified by GC-MS and LC-MS in these Ba(OH)2 extracts of the skeletons.
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Bioflavouring piv pomocí studeného chmelení za použití českých chmelů / Beer bioflavouring by dry hopping using czech cultivars of hops

Gajdušek, Martin January 2021 (has links)
This diploma thesis deals with the influence of dry hopping on selected analytical and sensory properties of beer. The effect of dry hopping was observed using Czech hop varieties Kazbek and Uran, which were added to the wort during the main fermentation phase in doses of 3 and 6 gdm-3. The contact time of hops with wort was 3, 6 and 9 days. The experimental part describes the technology of preparation of the reference beer, in which dry hopping were subsequently performed. A parallel measurement was performed on each sample. In terms of the basic parameters of beer, the effect of dry hopping, especially its length, on the ethanol content was observed. With a longer period of dry hopping, the concentration of ethanol in beer increased. The higher alcohol concentration was also associated with a decrease in the apparent extract. In terms of color and pH of beer, the effect of dry hopping has not been proven. Elemental analysis performed by optical emission spectrometry with inductively coupled plasma revealed an increase in the concentration of calcium, magnesium, and iron due to dry hopping. No statistically significant difference was observed for manganese and barium compared to the reference. In terms of bitterness, a significant increase was identified in dry hopped beers compared to the reference, the value being dependent on the dose of hops used. The effect of the hop variety has not been proved. Concentrations of organic acids determined by ion-exchange chromatography with a conductivity detector were affected by dry hopping only in the case of lactic acid and acetic acid. An increase in lactic acid was observed compared to the reference, also related to the degree of fermentation. While in the acetic acid content the hop samples showed a lower concentration than the reference sample. The concentrations of myrcene, humulene and geraniol were determined by gas chromatography with a mass detector. These are volatile components of hop essential oils. Dry hopped samples recorded significantly higher concentrations of all aromatic substances compared to the reference. In terms of hop time, the highest concentrations were shown by samples hopped for three days. The results of the sensory analysis show that the overall best rated sample is a sample hopped with the Kazbek variety with a dose of 3 gdm-3 for three days. Beer which was dry hopped for the shortest time also showed the lowest intensity of bitterness, which was perceived positively.
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Aromaticky aktivní látky vybraných druhů bylin / Aroma active compounds of selected types of herbs

Škutová, Pavla January 2018 (has links)
This diploma thesis deals with the identification of aroma active compounds in medicinal herbs. The group consists of 5 types of herbs: lemon balm (Melissa officinalis), pot marigold (Calendula officinalis), clary sage (Salvia sclarea), milk thistle (Silybum marianum), goat’s rue (Galega officinalis). These plants are known for their positive effects in folk medicine. The SPME-GC-MS method was chosen to characterize the fragrances. During the identification of volatile compounds, emphasis was put on suspected fragrance allergens listed in EC Regulation 1223/2009 in Annex III. Overall 106 compounds were identified together with 8 allergens in lemon balm, pot marigold contained 104 compounds with 7 allergens included, 82 compounds including 5 allergens in clary sage, 73 compounds were identified in milk thistle including 6 allergens and 110 compounds with 9 allergens included in goat’s rue.

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