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Porosity and surfaces of coalsJackson, Paul January 1985 (has links)
No description available.
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Mecanismos de reação quimiluminescente entre peroxinitrito e metabólitos carbonílicos / Mechanisms of chemiluminescent reaction between peroxynitrite and carbonyl metabolitesRoyer, Leandro de Oliveira 05 August 2003 (has links)
O peroxinitrito é um oxidante versátil, sendo responsável por oxidações uni e bieletrônicas, adições nucleofílicas, nitrações, nitrosações, hidroxilações e geração de oxigênio singlete, possuindo papéis fisiológicos e deletérios. Estudos de EPR captação de spin mostraram que compostos carbonílicos podem sofrer abstração de um elétron por peroxinitrito, seguida de consumo de oxigênio e quimiluminescência; p.ex., isobutiraldeído (IBAL), acetoacetona (AA), 3-metilacetoacetpna (MAA), etil acetoacetato (EAA), etil 2-metilacetoacetato (EMAA) e succinilacetona (SA). A emissão de luz é provavelmente devida à espécies excitadas tripletes, formadas a partir da termólise de intermediários dioxetânicos. Os perfis de pH obtidos por consumo total de oxigênio e quimiluminescência em tampão fosfato, apontam o ânion peroxinitrito como oxidante e a forma enólica dos compostos carbonílicos como substratos. A análise de produtos sugere a ocorrência de uma reação em cadeia na presença de oxigênio. Estas reações podem ter importante papel biológico, considerando-se que (i) compostos carbonílicos são ubíquos em sistemas biológicos em condições fisiológicas e patológicas, (ii) peroxinitrito está relacionado a respostas fisiológicas e patológicas, (iii) carbonilas tripletes podem ser vistas como radicais alcoxil e, dessa forma, possuir papel deletério a biomoléculas. / Peroxynitrite displays an ample repertoire of chemical reactions -one- and two-electron oxidations, nucleophilic addition, nitration, nitrosation, hydroxylation, and singlet oxygen generation conferring it cell toxicity and signalling properties. Carbonyl compounds were shown by EPR spin-trapping to suffer one-electron abstraction by peroxynitrite, which is followed by oxygen consumption and chemiluminescence; e.g., isobutyraldehyde (IBAL), acetoacetone (AA), 3-methylacetoacetone (MAA), ethyl acetoacetate (EAA), ethyl 2-methylacetoacetate (EMAA) and succinylacetone (SA). Light emission probably arises from triplet species formed by the thermolysis of dioxetane intermediates. The pH profiles traced for oxygen uptake ·and chemiluminescence in phosphate buffer point to peroxynitrite anion as the oxidant and enolized carbonyls as the actual substrates. Product analysis suggests that a chain reaction occurs in the presence of oxygen. These reactions may play important biological roles considering that (i) carbonyl compounds are ubiquitous in biological systems under physiological and pathological conditions; (ii) peroxynitrite has been implicated in cell toxicity and signalling; (iii) triplet carbonyls may be viewed as alkoxyl radicals and, therefore, play a deleterious role in biomolecules.
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Mecanismos de reação quimiluminescente entre peroxinitrito e metabólitos carbonílicos / Mechanisms of chemiluminescent reaction between peroxynitrite and carbonyl metabolitesLeandro de Oliveira Royer 05 August 2003 (has links)
O peroxinitrito é um oxidante versátil, sendo responsável por oxidações uni e bieletrônicas, adições nucleofílicas, nitrações, nitrosações, hidroxilações e geração de oxigênio singlete, possuindo papéis fisiológicos e deletérios. Estudos de EPR captação de spin mostraram que compostos carbonílicos podem sofrer abstração de um elétron por peroxinitrito, seguida de consumo de oxigênio e quimiluminescência; p.ex., isobutiraldeído (IBAL), acetoacetona (AA), 3-metilacetoacetpna (MAA), etil acetoacetato (EAA), etil 2-metilacetoacetato (EMAA) e succinilacetona (SA). A emissão de luz é provavelmente devida à espécies excitadas tripletes, formadas a partir da termólise de intermediários dioxetânicos. Os perfis de pH obtidos por consumo total de oxigênio e quimiluminescência em tampão fosfato, apontam o ânion peroxinitrito como oxidante e a forma enólica dos compostos carbonílicos como substratos. A análise de produtos sugere a ocorrência de uma reação em cadeia na presença de oxigênio. Estas reações podem ter importante papel biológico, considerando-se que (i) compostos carbonílicos são ubíquos em sistemas biológicos em condições fisiológicas e patológicas, (ii) peroxinitrito está relacionado a respostas fisiológicas e patológicas, (iii) carbonilas tripletes podem ser vistas como radicais alcoxil e, dessa forma, possuir papel deletério a biomoléculas. / Peroxynitrite displays an ample repertoire of chemical reactions -one- and two-electron oxidations, nucleophilic addition, nitration, nitrosation, hydroxylation, and singlet oxygen generation conferring it cell toxicity and signalling properties. Carbonyl compounds were shown by EPR spin-trapping to suffer one-electron abstraction by peroxynitrite, which is followed by oxygen consumption and chemiluminescence; e.g., isobutyraldehyde (IBAL), acetoacetone (AA), 3-methylacetoacetone (MAA), ethyl acetoacetate (EAA), ethyl 2-methylacetoacetate (EMAA) and succinylacetone (SA). Light emission probably arises from triplet species formed by the thermolysis of dioxetane intermediates. The pH profiles traced for oxygen uptake ·and chemiluminescence in phosphate buffer point to peroxynitrite anion as the oxidant and enolized carbonyls as the actual substrates. Product analysis suggests that a chain reaction occurs in the presence of oxygen. These reactions may play important biological roles considering that (i) carbonyl compounds are ubiquitous in biological systems under physiological and pathological conditions; (ii) peroxynitrite has been implicated in cell toxicity and signalling; (iii) triplet carbonyls may be viewed as alkoxyl radicals and, therefore, play a deleterious role in biomolecules.
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Making wood durable. A sustainable approachwith linseed oil / Att göra trä beständigt. Ett hållbart tillvägagångssätt med linoljaOlsson, Helena January 2019 (has links)
Linseed oil has been and is used for vast number of applications, such as in food and paint industry, and wood preservation. It is a good environmental choice, as it originates from renewable sources. Linseed oil is mainly a mixture of triglyceride of fatty acids, both saturated and mono- or polyunsaturated, which allows the oil to oxidize. The oxidation occurs via an auto-oxidation mechanism with the carbon-carbon double bonds and oxygen from the air, reacts to form a polymer. Herein, four different linseed oils (three commercial ones and one industrially available) were analyzed to obtain a better understanding of why different oils provide different protection of wooden materials. This was done by a study of the unoxidized oil, followed by an oxidation time-resolved study of oxidized oil films. The analysis was done by nuclear magnetic resonance, gas chromatography - mass spectrometry and/or inductively coupled plasma atomic emission spectroscopy. This study provided the fatty acid profile of the oils, which were similar for all oils. The unoxidized oils contained some metals ions which probably originate from additives. Aluminum, cobalt, iron, manganese, and zinc was detected in some of the oils at concentrations up to 135 mg/L, but only manganese was detected in all oils and its concentration was much higher than all other metals together. The time-resolved oxidation study had some problems with the solubility of the formed polymers. Several solvents were examined, such as dimethylsulfoxide, alkaline alcohol solutions and toluene, before chloroform-d was chosen as solvent. Though, chloroform-d was not a perfect solvent; it was capable to solve a fraction of the sample, but the fraction decreased with oxidation time. After fifteen days of oxidation, only a few percent of the sample could be dissolved, but for short oxidation times (<48 h) the majority of the samples were dissolved. The oils were analyzed after thirteen different oxidation times. Some structural changes appeared, for example loss of unsaturated protons and some oxidation products arose, such as peroxides and aldyhydes. The diffusion coefficient decreased over the first 3-4 days of oxidation, as expected when the polymerization progressed. After a week of oxidation, the diffusion coefficient increased again, this could possibly be explained by the solubility problem for the large polymer formed. Contrary, at shorter oxidation times this method probably could still be used, as the majority of the sample was dissolved. However, the solubility problem made it impossible to conclude anything about the oxidation rate at longer oxidation times and thus prevented any ranking of the oils. / Linolja har använts och används för många olika tillämpningar, till exempel i mat- och färgindustrin, samt för att bevara trä. Det är klimatmässigt ett bra val, då det kommer från en förnyelsebar källa. Linolja innehåller huvudsakligen en blandning av triglycerider av fettsyror, som både kan vara mättade, enkelomättade eller fleromättade, detta gör att linolja kan oxidera och torka. Oxidationen sker via en auto-oxidation mekanism, med kol-kol dubbelbindningarna och syre från luften som producerar till en polymer. I detta projekt undersöktes fyra olika linoljor (tre kommersiella och en industriell), för att ge en bättre förståelse till varför olika oljor ger olika bra skydd för trämaterial. Detta gjordes genom att undersöka de icke-oxiderade oljorna och sedan göra en tidsstudie på oxiderade oljefilmer. Alla dessa prover analyserades med nuclear magnetic resonance, gas chromatography - mass spectrometry and/or inductively coupled plasma atomic emission spectroscopy. Studien gav resultat på sammansättningen av fettsyror i oljorna, vilken var liknande för alla oljorna. De icke-oxiderade oljorna innehöll ett par metaller, som förmodligen kommer från additiv. Aluminium, kobolt, järn, mangan och zink hittades i några av oljorna i koncentrationer upp till 135 mg/L, men bara mangan var detekterad i alla oljorna och dess koncentration var högre än alla andra metaller tillsammans. Tidsstudien hade problem med lösligheten av proverna. Flertalet lösningsmedel undersöktes, exempelvis dimetylsulfoxid, alkaliska alkohollösningar och toluen, innan kloroform-d valdes som lösningsmedel. Däremot var kloroform-d inte ett perfekt lösningsmedel, den hade förmågan att lösa en del av proverna, men den delen minskade med oxidationstid. Efter femton dagar kunde den bara lösa ett par procent, men efter kortare oxideringstider (<48 h) gick majoriteten av proven att lösa. Oljorna analyserades vid tretton olika oxideringstider. Några strukturella förändringar uppmättes, till exempel minskade mängden dubbelbindningar, och ett par biprodukter från oxideringen detekterades, så som peroxider och aldehyder. Diffusionskonstanterna för oljorna minskade under de första 3-4 dagarna av oxidering, precis som förväntat under polymeriseringen. Efter en vecka av oxidering ökade diffusionskonstanterna igen, det kan förmodligen förklaras av löslighetsproblemen, då diffusionskonstanten är beroende av koncentrationen. Å andra sidan, vid kortare oxideringstider kan denna metod fortfarande användas, eftersom vid denna tidpunkt löste sig fortfarande majoriteten av provet. Dock, löslighetsproblemet gjorde det omöjligt att dra slutsatser kring längre oxideringstider och därmed förhindrades rangordning av oljorna.
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