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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.
11

The alkaline hydrolysis of esters in aqueous-organic solvent mixtures : the effects of solvents and of the activity coefficients of reactants on the kinetics of the alkaline hydrolysis of methyl acetate in aqueous dioxan, aqueous dimethyl sulphoxide and aqueous diglyme (bis (2-methoxyethyl ) ether) mixtures as solvents

Kazempour, Abdol Rassoul January 1978 (has links)
Values of the rate constant for the alkaline hydrolysis of methyl acetate in various aqueous-organic solvent mixtures (dimethyl sulfoxide 0<x40.2, dioxane 0 <, x., < 0.2, methyl ethyl ketone 0<x<0.06 and diglyme, i. e. ether-bis (2-methyloxethyl) 0x<0.10) have been determined for the temperatures 15 0 C, 25 0C and 35 0C conductometrically. To interpret these results the approach adapted is to experimentally determine the activity coefficient of the ester (YE ) and the activity of the water (aH20', mechanistically, at least one molecule of water is involved in the rate-determining step) and then to use the Bronsted-Bjerrum equation to determine the residual activity coefficient ratio of the participating ions, y (Yf - for Oil the transition state). Values of YE and aH 20 have been determined by a transpiration method, using gas-chromatographic analysis of the vapours of solutions of methyl acetate in aqueous-organic solvent mixtures of dir. ethyl sulfoxide, dioxane, methyl ethyl ketone and diglyme in the same composition ranges as above, tetrahydrofuran 04x org z<, 0.15, methanol, ethanol and tert-butanol in t1h6e range 04x0.20'at 25oC. These results indicate that on changing org the solvent composition YE varies by a larger factor than is predicted for the ratio YOH-/yýO_ by the Debye-Iluckel approach, and hence is the dominant factor in determining the effects of solvent composition on the rates of the hydrolysis. This is in contradiction to the assumptions of the electrostatic theories of Laidler and Eyring, and of Amis and Jaffe. The gas-chromatographic results also indicate that whilst the concentration of the water varies in each mixture studied, the activity coefficient varies in the opposite way to produce almost constant values of aý, 0* Using the transpiratioii/gas-chromatogralýlic method, the thermodynamic properties of the ternary systems, methyl acetate-water-organic Solvcat, using the organic solvents mentioned above (excepting, diglyme) have been investigated, and the results indicate that the variation of *ýE with solvent composition, for the dilute solutions of ester used, can be estimated from the thermodynamic properties of the binary water-organic solvent mixtures, using the Gibbs-Dahem equation. Single ion activity coefficients in the literature for small negative ions, to represent the OH_ ion, and for large ions, to rep-resent the transition state ion, have been used to explain the experimentally fomd variation of the residual activity coefficient -ratio with solvent composition. Hence, it is concluded that the importance of the parameters involved in the hydrolysis of esters - an ion-molecule reaction - in aqueousorganic solvent mixtures are in the order of Ymolecule > aH 20> YOH_/YM+ -> (dielectric constant), and that the nonelectrostatic effects -- thermodynamic effects - are more important in these studies than the electrostatic effects. From a preliminary investigation of the data in the literature the thermodynamic approach also yields a valid interpretation of the effect of solvent composition on the rates of the acid hydrolysis of esters.
12

Biotransformação bacteriana de ácido ferúlico obtido de resíduo lignocelulósico a 4-vinilguaiacol / Bacterial biotransformation of ferulic acid obtained from lignocellulosic residue to 4-vinylguaiacol

Santos, Maitê Bernardo Correia dos 06 April 2018 (has links)
Submitted by Maitê Bernardo Correia dos Santos (maite.bernardo2@hotmail.com) on 2018-05-04T17:55:37Z No. of bitstreams: 1 DissertaçãoMaitê.pdf: 1281035 bytes, checksum: ae5f2a503b5f4d55e78f35720d549551 (MD5) / Rejected by Elza Mitiko Sato null (elzasato@ibilce.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: Seus resumos e lista de figuras e tabelas estão fora de ordem, seguir a norma ABNT NBR14724 de TRABALHO ACADÊMICO (TESES, DISSERTAÇÕES, TCCs), Elementos Pré-Textuais: Capa (obrigatório) Folha de rosto (obrigatório) –-[a contagem das folhas começa aqui] Errata (opcional) Folha de aprovação (obrigatório) Dedicatória(opcional) Agradecimento (opcional) Epígrafe (opcional) Resumo na língua vernácula (obrigatório) Resumo em língua estrangeira (obrigatório) Lista de ilustrações (opcional) Lista de tabelas (opcional)Lista de abreviaturas e siglas (opcional) Lista de símbolos (opcional) Sumário (obrigatório). Agradecemos a compreensão. on 2018-05-04T21:01:13Z (GMT) / Submitted by Maitê Bernardo Correia dos Santos (maite.bernardo2@hotmail.com) on 2018-05-10T19:50:31Z No. of bitstreams: 3 DissertaçãoMaitê.pdf: 1281035 bytes, checksum: ae5f2a503b5f4d55e78f35720d549551 (MD5) Dissertação Maitê.pdf: 1411585 bytes, checksum: cecbb98727975b6bfb0e62e9b1f46093 (MD5) Dissertação Maitê.pdf: 1411585 bytes, checksum: cecbb98727975b6bfb0e62e9b1f46093 (MD5) / Approved for entry into archive by Paula Torres Monteiro da Torres (paulatms@sjrp.unesp.br) on 2018-05-10T20:15:41Z (GMT) No. of bitstreams: 1 santos_mb_me_sjrp_int.pdf: 1411585 bytes, checksum: cecbb98727975b6bfb0e62e9b1f46093 (MD5) / Made available in DSpace on 2018-05-10T20:15:41Z (GMT). No. of bitstreams: 1 santos_mb_me_sjrp_int.pdf: 1411585 bytes, checksum: cecbb98727975b6bfb0e62e9b1f46093 (MD5) Previous issue date: 2018-04-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O Brasil, por sua condição de grande produtor agrícola, também é grande produtor de resíduos lignocelulósicos. Esses resíduos, muitas vezes considerados sub-produtos ou co-produtos, são fontes de açúcares, derivados da celulose e hemicelulose, e de compostos aromáticos, oriundos da lignina, que servem de substratos para diversos processos químicos e biológicos para obtenção de produtos de alto valor agregado. Um dos compostos liberados em abundância durante a desconstrução do material lignocelulósico é o ácido ferúlico cuja biotransformação pode resultar em derivados químicos com aplicações nas indústrias farmacêutica, de alimentos e de cosméticos. Neste trabalho estudou-se a bioconversão bacteriana do ácido ferúlico comercial e daquele obtido a partir da hidrólise alcalina da lignina, em 4-vinilguaiacol. A biotransformação de ácido ferúlico comercial em 4-vinilguaiacol foi estudada em meio líquido sintético contendo o ácido ferúlico em concentração inicial de 300 mg L-1, por 48 horas. Após 24 horas de cultivo, obteve-se um rendimento de 0,5 mmol L-1 de 4-vinilguaiacol que correspondeu a uma conversão de 32,4% do ácido ferúlico. Na continuidade do trabalho, a cepa foi utilizada para bioconverter o ácido ferúlico oriundo da hidrólise da lignina contido no lícor obtido por hidrólise alcalina do bagaço de cana-de-açúcar, cuja concentração de ácido ferúlico era de 310,14 mg L-1. Após 32 horas de cultivo obteve-se um rendimento de 1,3 mmol L-1 de 4-vinilguaiacol que correspondeu a uma conversão de 81,7% do ácido ferúlico presente no licor. Esses resultados obtidos demonstraram que a bactéria estudada atuou na descarboxilação do ácido ferúlico a 4-vinilguaiacol. / Brazil, is an important agricultural producer and also a big producer of lignocellulosic wastes. These material can generate sugars from cellulose and hemicellulose saccharification and aromatic compounds, derived from lignin, which serve as substrates for various chemical and biological processes to obtain the high added values products. One of the compounds released during the deconstruction of lignocellulosic material is ferulic acid whose biotransformation can lead to the generation of important products. This work aims at the bacterial bioconversion of commercial ferulic acid and those obtained from the alkaline hydrolysis of lignin to 4-vinylguaiacol. The biotransformation of commercial ferulic acid in 4-vinylguaiacol was studied in synthetic liquid medium containing the ferulic acid in an initial concentration of 300 mg L-1 , for 48 hours. After 24 hours of cultivation a yield of 0.5 mmol L-1 of 4- vinylguaiacol was obtained which corresponded to a conversion of 32.4% of the ferulic acid. In the continuity of the work, the strain was used to bioconvert the ferulic acid from the hydrolysis of the lignin contained in the lycor obtained by alkaline hydrolysis of the sugarcane bagasse that presented the ferulic acid concentration of 310.14 mg L- 1 . After 32 hours of cultivation, a yield of 4-vinylguaiacol was 1.3 mmol L-1 corresponding to a conversion of 81.7% of the ferulic acid. The results showed that the strain decarboxylated the ferulic acid to 4-vinylguaiacol.
13

ObtenÃÃo de Ãlcoois de cadeia longa a partir da Cera de CarnaÃba. / Obtaining long-chain alcohols from the wax Carnauba

Milena Maria de Meneses Freitas 06 May 2011 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / As ceras naturais, como a carnaÃba, sÃo misturas complexas de Ãsteres compostos de Ãcidos graxos e alcoÃis de cadeia longa. ObtÃm-se a cera de carnaÃba pelo pà cerÃfero depositado na superfÃcie das folhas da palmeira Copernicia sp, popularmente conhecida como carnaubeira. O objetivo deste trabalho foi estudar a produÃÃo de Ãlcoois de cadeia longa a partir da cera de carnaÃba bruta utilizando diferentes mÃtodos de hidrÃlise alcalina. Amostras de cera de carnaÃba filtrada e refinada de cor amarela (tipo I) foram hidrolisadas por trÃs diferentes processos: (1) 5 g de cera de carnaÃba juntamente com 100 mL de soluÃÃo aquosa de hidrÃxido de potÃssio 2, 5, 10, 15 e 20 % (m/v) foram levadas em tempos de 15, 30, 60 e 120 minutos ao condensador de refluxo a 100ÂC; (2) 3 g de cera de carnaÃba juntamente com 50 mL de soluÃÃo aquosa de hidrÃxido de potÃssio 2, 5, 10, 15 e 20% (m/v) foram irradiadas em forno de microondas seguindo uma programaÃÃo de tempo e potÃncia; (3) 10 g de cera de carnaÃba juntamente com 200 mL de soluÃÃo de hidrÃxido de potÃssio a 2, 10 e 20 % (m/v) foram levadas ao reator quÃmico pressurizado. ApÃs o processo de hidrÃlise, as amostras foram filtradas, lavadas a quente, secas em estufa a 80ÂC/6h e transformadas em pÃ, calculando-se o rendimento e o Ãndice de acidez. As amostras hidrolisadas foram extraÃdas com heptano em Soxhlet por 4 horas e o material obtido foi analisado no espectrÃmetro de massas para a determinaÃÃo da composiÃÃo de alcoÃis de cadeia longa. As amostras hidrolisadas em microondas apresentaram os melhores resultados em rendimento e em Ãndice de acidez. Os alcoÃis triacontanol (A30), dotriacontanol (A32) e tetratriacontanol (A34) foram identificados nas amostras de cera de carnaÃba hidrolisadas pelos trÃs diferentes processos, sendo o dotriacontanol o mais abundante entre eles. / The natural waxes like carnauba, are complex mixtures of ester compounds of fatty acids and long chain alcohols. Carnauba wax is obtained from the waxy powder from the leafs of the Copernicia sp palm, known as carnaubeira. The objective of this work was to study the production of long chain alcohols from crude carnauba wax using different methods of alkaline hydrolysis. Samples of yellow carnauba wax (type I) were filtered refined and hydrolyzed by three different processes: (1) 5 g of carnauba wax along with 100 ml aqueous potassium hydroxide 2, 5, 10, 15 and 20% (w/v) were taken at times of 15, 30, 60 and 120 min the reflux condenser at 100 ÂC; (2) 3 g of carnauba wax, along with 50 mL of aqueous solution of potassium 2, 5, 10 , 15, and 20% (w/v) were irradiated in a microwave oven following a time schedule and power; (3) 10 g of carnauba wax along with 200 mL of potassium hydroxide 2, 10 and 20% (w/v) were brought to the pressurized chemical reactor. After the hydrolysis process, the samples were filtered, washed, dried at 80 C/6h and turned into powder. The process yeld and acidity were measured. The hydrolysed samples were extracted with Soxhlet heptane for 4 hours and the material was analyzed by gas-chromatography-mass spectrometry to determine the composition of long chain alcohols. The samples hydrolyzed in a microwave presented the best yield and acidity index. The alcohols triacontanol (A30), dotriacontanol (A32) and tetratriacontanol (A34) were identified in samples of carnauba wax hydrolyzed by the three different processes, and the dotriacontanol was the most abundant among them.
14

Chemical Recycling of Poly (Ethylene Terephthalate) and its Co-polyesters with 2, 5-Furandicarboxylic Acid using Alkaline Hydrolysis

Vinnakota, Keerthi January 2018 (has links)
No description available.
15

The alkaline hydrolysis of esters in aqueous-organic solvent mixtures. The effects of solvents and of the activity coefficients of reactants on the kinetics of the alkaline hydrolysis of methyl acetate in aqueous dioxan, aqueous dimethyl sulphoxide and aqueous diglyme (bis (2-methoxyethyl ) ether) mixtures as solvents.

Kazempour, Abdol Rassoul January 1978 (has links)
Values of the rate constant for the alkaline hydrolysis of methyl acetate in various aqueous-organic solvent mixtures (dimethyl sulfoxide 0<x40.2, dioxane 0 <, x., < 0.2, methyl ethyl ketone 0<x<0.06 and diglyme, i. e. ether-bis (2-methyloxethyl) 0x<0.10) have been determined for the temperatures 15 0 C, 25 0C and 35 0C conductometrically. To interpret these results the approach adapted is to experimentally determine the activity coefficient of the ester (YE ) and the activity of the water (aH20', mechanistically, at least one molecule of water is involved in the rate-determining step) and then to use the Bronsted-Bjerrum equation to determine the residual activity coefficient ratio of the participating ions, y (Yf - for Oil the transition state). Values of YE and aH 20 have been determined by a transpiration method, using gas-chromatographic analysis of the vapours of solutions of methyl acetate in aqueous-organic solvent mixtures of dir. ethyl sulfoxide, dioxane, methyl ethyl ketone and diglyme in the same composition ranges as above, tetrahydrofuran 04x org z<, 0.15, methanol, ethanol and tert-butanol in t1h6e range 04x0.20'at 25oC. These results indicate that on changing org the solvent composition YE varies by a larger factor than is predicted for the ratio YOH-/yýO_ by the Debye-Iluckel approach, and hence is the dominant factor in determining the effects of solvent composition on the rates of the hydrolysis. This is in contradiction to the assumptions of the electrostatic theories of Laidler and Eyring, and of Amis and Jaffe. The gas-chromatographic results also indicate that whilst the concentration of the water varies in each mixture studied, the activity coefficient varies in the opposite way to produce almost constant values of aý, 0* Using the transpiratioii/gas-chromatogralýlic method, the thermodynamic properties of the ternary systems, methyl acetate-water-organic Solvcat, using the organic solvents mentioned above (excepting, diglyme) have been investigated, and the results indicate that the variation of *ýE with solvent composition, for the dilute solutions of ester used, can be estimated from the thermodynamic properties of the binary water-organic solvent mixtures, using the Gibbs-Dahem equation. Single ion activity coefficients in the literature for small negative ions, to represent the OH_ ion, and for large ions, to rep-resent the transition state ion, have been used to explain the experimentally fomd variation of the residual activity coefficient -ratio with solvent composition. Hence, it is concluded that the importance of the parameters involved in the hydrolysis of esters - an ion-molecule reaction - in aqueousorganic solvent mixtures are in the order of Ymolecule > aH 20> YOH_/YM+ -> (dielectric constant), and that the nonelectrostatic effects -- thermodynamic effects - are more important in these studies than the electrostatic effects. From a preliminary investigation of the data in the literature the thermodynamic approach also yields a valid interpretation of the effect of solvent composition on the rates of the acid hydrolysis of esters. / Ministry of Science and Higher Education of Iran
16

Analysis of Environmental-Ethical Concerns Within the United States Funeral Industry

Wisnewski, Olivia Ann 18 September 2023 (has links)
This thesis examines the failings in environmental-ethics present in the United States funeral industry, focusing on the lack of environmental ethical guidelines at an industrial and policy level. Utilizing an interdisciplinary approach through the lenses of environmental science, philosophical ethical considerations surrounding policy-based advocacy and ecocritical approaches to the concepts of reciprocity and harm reduction, this thesis makes recommendations to close the gaps in environmental ethical oversight. Focus is placed on mitigation of environmental harms resulting from changes in policy and legislation, and in-industry oversight, with an emphasis on the support of ecologically beneficial methods of the disposition of human remains. / Master of Arts / The funeral industry in the United States has developed in a way that eschews environmental consciousness in the services available to consumers. This thesis examines the historical development of the relationship between the funeral industry and the environment, and the way the rise of the corporate funeral model ignores environmental concerns, as well as presents contemporary environmental issues that impact the industry. Additionally, the thesis explores the gaps regarding environmental impact present in the ethical guidelines the funeral industry adheres to, and the lack of environmental accountability coming from both within the industry and from regulatory bodies and the United States government. Finally, this thesis provides recommendations for the industry, and associated advocacy groups surrounding corrections and policy and practice changes that will support more a more environmentally friendly version of the funeral industry. In this case, environmental friendliness is defined by practices which take pollution impacts into account, as well as consider the sustainability of resource use incurred by both traditional and emergent technologies.
17

Targeting RNA by the Antisense Approach and a Close Look at RNA Cleavage Reaction

Barman, Jharna January 2007 (has links)
This thesis summarizes the results of studies on two aspects of nucleic acids. Chemically modified antisense oligonucleotides (AONs) have been evaluated with regards to their suitability for mRNA targeting in an antisense approach (Paper I – III). The chemically modified nucleotidic units 2'-O-Me-T, 2'-O-MOE-T, oxetane-T, LNA-T, azetidine-T, aza-ENA-T, carbocyclic-ENA-T and carbocyclic-LNA-T were incorporated into 15-mer AONs and targeted against a 15-mer RNA chosen from the coding region of SV-40 large T antigen. The comparative study showed that a single modified nucleotide in the AON with North-East locked sugar (oxetane-T and azetidine-T) lowered the affinity for the complementary RNA whereas North locked sugars (LNA-T, aza-ENA-T, carbocyclic-ENA-T, and carbocyclic-LNA-T) significantly improved the affinity. A comparative RNase H digestion study showed that modifications of the same type (North-East type or North type) in different sequences gave rise to similar cleavage patterns. Determination of the Michaelis-Menten parameters by kinetic experiments showed that the modified AONs recruit RNase H resulting in enhanced turnover numbers (kcat) although with weaker enzyme-substrate binding (1/Km) compared to the unmodified AON. The modified AONs were also evaluated with regards to resistance towards snake venom phosphodiesterase and human serum to estimate their stability toward exonucleases. The aza-ENA-T and carbocyclic-ENA-T modified AONs showed improved stability compared to all other modified AONs. In general, the modified AONs with North type nucleotides (except LNA-T) were found to be superior to the North-East type as they showed improved target affinity, comparable RNase H recruitment capability and improved exonuclease stability. The second aspect studied in this thesis is based on physicochemical studies of short RNA molecules utilizing NMR based pH titration and alkaline hydrolysis reactions (Paper IV – V). The NMR based (1H and 31P) pH titration studies revealed the effect of guaninyl ion formation, propagated electrostatically through a single stranded chain in a sequence dependent manner. The non-identical electronic character of the internucleotidic phosphodiesters was further verified by alkaline hydrolysis experiments. The internucleotidic phosphodiesters, which were influenced by guaninyl ion formation, were hydrolyzed at a faster rate than those sequences where such guaninyl ion formation was prevented by replacing G with N1-Me-G.
18

Avaliação da hidrólise alcalina da gordura sobre a biodegradação anaeróbia de soro de queijo

Alessi, Maria Clara Machado 26 August 2005 (has links)
The cheese whey represents the most important reject of the industry of dairy products, mainly due to its expressive generated volume. The cheese whey is a problematic substrate under the environmental point of view, presenting high amounts of carbohydrates, proteins and fats, giving it a chemical demand of oxygen of approximately a hundred times larger than the one of the domestic waste. An alternative for its treatment would be the anaerobic fermentation, which reduces its pollutant impact, making possible even the recovery of the energy from the formed biogas. However, the low biodegradation rate of the fats in the cheese whey difficulties the anaerobic treatment, reducing the mass transfer, leading to biomass loss and to the collapse of the reactor. In this context, this work had as objective to evaluate the effect of the preliminary stage from the alkaline hydrolyses of the fats in the anaerobic biodegradation of the cheese whey. A complet experimental design, being considered as the independent variables factors as time and the concentration of NaOH indicated the best hydrolyses conditions as 0,1% of NaOH, reaction time at 15h in 35°C and 200 rpm. In the study of the biodegradability of the cheese whey was used as inoculum a sludge colleted in a anaerobic reactor from the effluents treatment of a food industry. The COD removal and the biogas production were monitored by time, in different concentrations of the cheese whey solution in the basal medium. The removal of COD and the biogas production were higher in the experiments with the previously hydrolyzed solutions, especially for larger concentrations of cheese whey. These results shows that the alkaline hydrolyzes may be an alternative in the biological treatment of effluents with high fat concentration. / O soro de queijo representa o mais importante rejeito da indústria de laticínios, devido principalmente ao expressivo volume gerado. O soro é um substrato problemático sob o ponto de vista ambiental, pois apresenta elevados teores de carboidratos, proteínas e gorduras, que lhe conferem uma Demanda Química de Oxigênio cerca de cem vezes maior que a do esgoto doméstico. Uma alternativa de tratamento do mesmo seria a fermentação anaeróbia, através da qual se reduziria seu impacto poluidor, além de possibilitar a recuperação de energia do biogás formado. No entanto, a baixa taxa de biodegradação das gorduras presentes no soro dificulta o tratamento anaeróbio, reduzindo a transferência de massa, levando à perda de biomassa e até o colapso do reator. Neste contexto, o trabalho teve como objetivo avaliar o efeito de uma etapa preliminar de hidrólise alcalina das gorduras sobre a biodegradação anaeróbia do soro. Um planejamento experimental fatorial 32, considerando-se como variáveis independentes os fatores tempo e a concentração de NaOH indicou as melhores condições de hidrólise como sendo 0,1% de NaOH, tempo de reação de 15 h a 35°C e 200 rpm. No estudo da biodegradabilidade do soro foi empregado como inóculo um lodo coletado em um reator anaeróbio de tratamento de efluentes de uma indústria alimentícia. A remoção de DQO e a produção de biogás foram monitoradas ao longo do tempo, mediante diferentes concentrações da solução de soro no meio basal. A remoção de DQO e a produção de biogás foram mais elevadas nos experimentos com a solução previamente hidrolisada, especialmente para maiores teores de solução de soro. Estes resultados mostram que a hidrólise alcalina pode ser uma alternativa no tratamento biológico de efluentes com altos teores de gordura. / Mestre em Engenharia Química
19

Mätfel vid fuktmätning i emissionsskadad betong / Error when performing moisture measurement in emission-damaged concrete

Orenäs Nissas, Sebastian, Rahimi, Nangyalay January 2018 (has links)
När människors hälsobesvär misstänks vara byggnadsrelaterat är det viktigt att klarlägga källan till problemet. Fukt kan vid högre nivåer ge upphov till mikrobiella eller kemiska reaktioner som orsakar emissioner från byggnadsmaterial som kan ha negativa hälsoeffekter. För att utreda om byggnaden är problemkällan görs skadeutredningar. I utredningarna är det viktigt att identifiera vilka emissioner som förekommer i inomhusmiljön för att kunna åtgärda den eventuella skadan. Med hjälp av fuktprofiler som skapas genom fuktmätningar kan det utredas om varifrån fukten kommer. En vanlig orsak i Norden till förhöjda koncentrationer av emissioner i inomhusmiljön är fuktskadade betongkonstruktioner med en pålimmad plastmatta. I en sådan konstruktion utgör plastmattan ett tätt skikt som inte låter fukten i betongen avdunsta. Betong, som är alkalisk, kan i kombination med höga fuktnivåer utlösa en kemisk process, så kallad alkalisk hydrolys, som bryter ned mjukgörare i golvlim och PVC-mattor. Detta leder till att nedbrytningsprodukterna 2-etyl-1-hexanol och n-butanol dels emitteras till inomhusluften och dels migrerar ned i betongen där de fixeras. Det är i det skedet betongen blir emissionsskadad på grund av att de kemiska ämnena som fixerats i betongen kan lagras där under en lång tid och kan om förhållandena förändras, exempelvis vid renovering, avge dessa ämnen till inomhusluften. Eftersom 2-etyl-1-hexanol och n-butanol utgör majoriteten av nedbrytningsprodukterna, används de därför som indikatorämnen vid skadeutredningar. Om indikatorämnena upptäcks i inomhusluften är det troligt att en skada i golvkonstruktionen har inträffat och detta kontrolleras då med fuktmätningar. Problemet med fuktmätningar i emissionsskadad betong är dock att det befaras av fuktskadeutredare att dessa indikatorämnen påverkar fuktmätningarna genom att man mäter till en lägre relativ fuktighet (RF) än vad det faktiskt är. Examensarbetet är utformat som ett experimentellt arbete med fuktmätningar som utförts i Polygon AK:s laboratorium. I laborationerna testades huruvida indikatorämnena, 2-etyl-1-hexanol samt n-butanol, påverkar fuktmätningar. Detta gjordes genom att prover med ren betong först RF-bestämdes för att sedan droppa i ovanstående ämnen i proverna och därefter följdes utvecklingen i RF. Vidare kontrollerades eventuell drift i mätinstrumenten genom egenkontroller både före och efter varje uppföljning. Mätresultaten från gjorda försök visade att den effekt som befarats av skadeutredare ej märkts av, det vill säga att indikatorämnena skulle ha en påverkan genom att fuktnivån mäts till något lägre jämfört med den verkliga fuktnivån. Effekten påvisades varken genom lägre uppmätta fuktnivåer eller genom mätinstrumentens drift. / When people's illness are suspected to be building-related, it is important to clarify the source of the problem. Moisture at higher levels can trigger microbial or chemical reactions which causes emissions from building materials that may have adverse health effects. In order to investigate whether the building is the source of the problem or not, indoor environment investigations are conducted to investigate the matter. In the investigations it is important to identify what kind of emissions that occurs in the indoor environment in order to fix the possible damage or damages. Using moisture profiles created with moisture measurements, it is possible to determine where the moisture comes from. A common cause in the Nordic countries for increased concentrations of emissions in the indoor environment is moisture-damaged concrete structures with a glued plastic mat. In such constructions, the plastic mat is a compact layer that does not allow the moisture in concrete to evaporate. Concrete, which is alkaline, can in combination with high moisture levels trigger a chemical process, called alkaline hydrolysis, which degrades plasticizers in floor adhesives and plastic mats. This results in the degradation products 2-ethyl-1-hexanol and n-butanol, which are being emitted to the indoor air and partly migrating down into the concrete where they are fixed. At that moment the concrete gets emission-damaged because of the degradation products that has been fixed into the concrete where they can be stored for a long time and can with changed conditions, for instance during renovation, emit these degradation products to the indoor air. Since 2-ethyl-1-hexanol and n-butanol constitutes the majority of degradation products, they are therefore used as indicators during damage investigations. If the indicators are detected in the indoor air, it is likely that a damage has occured in the floor construction and this is later checked with moisture measurements. However, the problem with moisture measurements in emission-damaged concrete is that some investigators fears that these indicators affects the moisture measurements by measuring a lower relative humidity (RH) than it actually is. The thesis is structured as an experimental work with moisture measurements performed in Polygon AK's laboratory. In the laboratory it was tested whether the indicators, 2-ethyl-1-hexanol and n-butanol, affects moisture measurements. This was done with specimens of pure concrete by first determining the RH followed by dropping the indicators into the samples and then the development in RH was followed. Furthermore, eventual drifting in the measuring instruments was checked before and after each follow-up. The measurement results from the experiments showed no effect of what the damage investigators feared of, that the indicators would have an impact by measuring the moisture level lower than the actual moisture level. The effect was not detected either by lower measured humidity levels or by drifting of the measuring instruments.
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Développement d’une méthode d’extraction et d’analyse de nanoparticules d’argent dans le boeuf haché par spectrométrie de masse à plasma à couplage inductif en mode particule unique

Chalifoux, Alexandre 05 1900 (has links)
La caractérisation de nanomatériaux dans des matrices alimentaires et animales suscite un intérêt scientifique important afin d’évaluer les risques potentiels de l’exposition liés à l’utilisation grandissante des nanomatériaux par plusieurs industries, y compris un certain nombre d’applications agroalimentaires. Un facteur limitant à l’étude et la réglementation des nanomatériaux dans des matrices complexes telle que la nourriture est l’absence de méthodes standardisées pour l’extraction et l’analyse de nanoparticules, tout en évitant l’altération de certaines caractéristiques physicochimiques des nanoparticules. Les travaux présentés dans ce mémoire abordent l’optimisation de plusieurs approches de préparation d’échantillon (hydrolyse enzymatique et alcaline) pour l’extraction de nanoparticules d’Ag préalablement équilibrées dans une matrice de boeuf haché mi-maigre. Les nanoparticules extraites ont été analysées par spectrométrie de masse à plasma à couplage inductif en mode particule unique (SP-ICP-MS) permettant la mesure de leur taille et concentration, mais aussi de la concentration en métal dissous, le tout à de très faibles concentrations (de l’ordre du ng/L). La validation de l’analyse par SP-ICP-MS a été réalisée par évaluation de la répétabilité, de la détermination des limites de détection et par une investigation de l’influence du traitement de données sur l’interprétation des résultats. Les pertes de nanoparticules lors de la préparation des échantillons ont été minimisées par l’identification et l’optimisation de paramètres clés tels que la composition du médium d’extraction, l’utilisation d’ultrasons et de la manipulation de l’échantillon après dégradation de la matrice. Les meilleurs recouvrements ont été obtenus par hydrolyse alcaline de la matrice en utilisant de l’hydroxyde de tetramethylammonium (TMAH), mais les échantillons obtenus étaient moins stables et plus susceptibles aux altérations des propriétés physicochimiques des nanoparticules que pour la dégradation par hydrolyse enzymatique utilisant lipase et pancréatine de porc. / The regulation and characterization of nanomaterials in foods and animal matrices are of great interest due to the potential risks associated with their exposure and the increasing number of instances where they are used within the food industry. One factor limiting the scientifically rigorous regulation of nanoparticles in foods is the lack of standardized procedures for the extraction of nanoparticles (NP) from complex matrices, without alteration of their physico-chemical properties. To this end, two sample preparation approaches (enzymatic- and alkaline-based hydrolyses) were tested and optimized in order to extract 40 nm Ag NP, following their equilibration with a fatty ground beef matrix. Extracted NP were characterized using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), allowing the determination of NP size and concentrations and also dissolved metal concentrations at trace levels. Validation of the SP-ICP-MS analysis was achieved by an evaluation of the repeatability and accuracy and by a determination of the various detection limits. Finally, we also looked into the influence of data treatment on interpretation of the results. NP losses during the sample preparation were minimized by identifying and optimizing key parameters such as the composition of the extraction media, usage of ultrasonication or the handling of the sample after separation from the undigested matter, among other points. The alkaline approach using TMAH (tetramethylammonium hydroxide) was found to have the highest recoveries, however processed samples were found to be less stable and more prone to alteration of the Ag NP physicochemical characteristics than samples processed using an enzymatic digestion based upon pork pancreatin and lipase.

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