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Séparation des isomères de l’hexane par des solides hybrides poreux (MOFs) / Separation of Hexane Isomers in Metal-Organic Frameworks (MOFs)Pinto Mendes, Patricia Alexandra 09 September 2014 (has links)
Le principal objectif de cette recherche est l’évaluation de nouveaux adsorbants nommés Metal-Organic Frameworks (MOFs) pour la séparation des isomères de l'hexane afin d'améliorer l'indice d'octane de l’essence. La séparation des isomères de l'hexane est actuellement réalisée par Total Isomerization Processes (TIP) basé sur l’utilisation de la zéolithe 5A qui permet d’isoler les paraffines «non normales». Afin d'améliorer et de tester d’autres adsorbants, des structures MOFs flexibles et rigides ont été synthétisées et évaluées pour cette séparation au travers de séries de courbes de perçage avec des mélanges d’isomères de l’hexane nHEX, 3MP, 22DMB et 23DMB. Cela a permis d'obtenir des isothermes d'adsorption à l'équilibre et une analyse de leurs performances a permis de trouver les structures plus performantes. L’UiO-66(Zr) fonctionnalisé par des groupes –Br, –NO2, et –NH2, les solides mésoporeux MIL-100(Cr) et son analogue fonctionnalisé MIL-100(Cr) greffé avec des alkylamines, le solide microporeux MIL-125(Ti) fonctionnalisé avec un groupe –NH2 et le tétracarboxylate de fer(III) microporeux MIL-127(Fe) sont les solides rigides étudiés. Les structures flexibles sont les dicarboxylates de fer(III) MIL-53(Fe) fonctionnalisés –(CF3)2, –2CH3, le ZIF-8 à base d’imidazolate et un polymorphe MIL-88B(Fe) fonctionnalisé –2CF3. La caractérisation de ces adsorbants cristallins a été réalisée par combinaison de diffraction des rayons X (XRPD), spectroscopie infrarouge (IR), analyse thermogravimétrique (TGA) et la porosimétrie d’adsorption d’azote. Les solides MIL-53(Fe)–(CF3)2 et ZIF-8 démontrent un effect de tamis moléculaires avec un comportement remarquable. / The main goals of this research are the synthesis of new specific adsorbents named Metal-Organic Frameworks (MOFs) for the separation of hexane isomers in order to improve the octane number of the gasoline. The separation of hexane isomers is actually performed using the conventional Total Isomerization Processes (TIP) with zeolite 5A which isolates only «non-normal paraffins». In order to improve and to test other alternatives, flexible and rigid frameworks were synthesized, performing a set of breakthrough curves with hexane isomers nHEX, 3MP, 22DMB and 23DMB with the purpose of obtaining adsorption equilibrium isotherms and further analysis of their performances in order to find new frameworks that offer better results. This concerned first the rigid frameworks UiO-66(Zr) functionalized with the functional groups –Br, –NO2, and –NH2; the mesoporous MIL-100(Cr) and its functionalized analogue MIL-100(Cr) grafted with alkylamines, the microporous Ti MOF MIL-125 functionalized with the functional group –NH2 and the iron tetracarboxylate MIL-127(Fe). The flexible frameworks were the Zn imidazolate ZIF-8, the iron(III) dicarboxylates MIL-53(Fe) functionalized with the functional groups –(CF3)2 and –2CH3 and the MIL-88 functionalized with the functional group –2CF3. The characterization of these crystalline adsorbents was achieved by X-Ray Powder Diffraction (XRPD), Infra-Red spectroscopy (IR), Thermogravimetric Analysis (TGA) and nitrogen surface area measurement. MIL-53(Fe)–(CF3)2 and ZIF-8 demonstrated molecular sieve effects with interesting and promossing behaviour for hexane isomers separation.
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Effects of Nitrogen, Phosphorus, and a Vitamin Mixture on Degradation rates of cresol isomersWolfe, V., Scheuerman, Phillip R., Gallagher, M., Lanza, G. R. 01 January 1995 (has links)
No description available.
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Molekulární patologie vybraných dědičných hyperbilirubinémií / Molecular pathology of selected inherited hyperbilirubinemiasŠlachtová, Lenka January 2015 (has links)
Inherited hyperbilirubinemias are a group of metabolic disorders, characterized by increased levels of total serum bilirubin or its conjugated fraction. Most of these hyperbilirubinemias are inherited autosomal recessively and are manifested in young age. Increased bilirubin reflects the genetic disturbances in one of the enzymes of heme degradation pathway, the defect of bilirubin conjugation (UGT1A1 gene) or its transport (ABCC2, OATP1B1, OATP1B3). All of these proteins are involved not only in elimination of bilirubin, but various substrates; therefore the performed studies have a great pharmacogenomics impact. We have studied the molecular pathology of hereditary hyperbilirubinemias in Caucasian and Roma population and to compare the clinical and biochemical results with the molecular genetic data. We described the impact of compound defect of c.-3279T>G and g.175492_175493insTA on total serum bilirubin and calculated the linkage disequlibrium of these two variants in promoter region of UGT1A1 gene. We also verified, that the population distribution of both variants is in concordance with the literature. In our second study, we have described the rare conjugated hyperbilirubinemia Dubin-Johnson type among 7 Roma families. We have found a novel variant NG_011798.1:c.[1013_1014delTG] together with...
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Analysis of benzofury compounds in blood using different sample preparation methods and ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS)Dye, Katherine 03 November 2015 (has links)
"Benzo Fury" compounds and derivatives are enactogens similar to 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in various aspects. These compounds are similar in structure to MDMA and MDA, as well as, elicit similar effects such as elevated mood, euphoria and hallucinations. This similarity in effect increases the potential for abuse as MDMA has become less prevalent in some regions as the use of these new psychoactive substances (NPSs) has increased. The benzofury compounds are used as legal alternatives to MDMA because of their marketing as “not for human consumption”. With the relative ease in obtaining NPSs via the Internet, it is possible that these drugs may soon be prevalent in the United States.
The project’s goal was to separate, detect, and quantitate the benzofury compounds and derivatives as well as MDA and MDMA in one method of analysis using ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS). The project also examined which method of sample preparation is more effective for these compounds.
Six benzofury compounds were researched: 5-(2-aminopropyl)benzofuran) (5-APB), 6-(2-aminopropyl)benzofuran) (6-APB), 5-(2-aminopropyl)-2,3-dihydrobenzofuran (5-APDB), 6-(2-aminopropyl)-2,3-dihydrobenzofuran (6-APDB), 1-(benzofuran-5-yl)-N-methylpropan-2-amine (5-MAPB) and 1-(benzofuran-6-yl)-N-methylpropan-2-amine (6-MAPB) as well as MDMA and MDA. These drugs were analyzed in blood. A liquid-liquid extraction (LLE) method and solid phase extraction (SPE) method were examined to determine which would be better for the separation, detection and quantitation of the benzofury compounds. For the development of the overall method, accuracy, precision, calibration curve, carryover, limit of detection, limit of quantitation, analyte stability, and recovery were examined.
The accuracy of the methods examined was greater than +/- 20%. For most analytes, the precision within-run and between-run did not exceed 20%, regardless of the sample preparation method used. A weighting of 1/x was applied to the calibration curve regardless of sample preparation method utilized. The carryover was less than 2% with the SPE method having less carryover (0.02% to 0.50%) than the LLE method (0.05% to 1.56%).
The limit of quantitation was determined to be greater than 10 ng/mL. While this was unexpected, the limit of detection calculations determined that this was correct. Using the LLE method in combination with the UFLC-MS/MS method developed, the limit of detection was determined to be at least 9.98 ng/mL. Compared to the LLE method, the SPE limit of detection was lower and calculated to be 3.75 ng/mL.
The percent recovery was examined for each of the analytes. It was determined that the SPE was capable of recovering 80% or more of the benzofury compounds and derivatives regardless of the concentration level. The LLE was not as successful in the recovering the benzofury compounds, the best recovery occurred at the 200 ng/mL level with only 65% or less recovered. Analyte stability exhibited a general decrease with variation prior to day 7 and then remains relatively stable until day 14.
It was anticipated that the quantitation of the drugs might be complicated due to the similarity in structure between the isomers as well as the similarity of structure between all of the compounds. While this may still be the case, the difficult separation resulted in a re-evaluation and alterations to the UFLC-MS/MS method to correct for these issues. With the change in the UFLC-MS/MS method, further method optimization is required to achieve the appropriate accuracy and limit of quantitation. It was found that the best combination of sample preparation and detection of the benzofury compounds and derivatives is to use SPE followed by an UFLC-MS/MS method.
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Chirality in the ¹³⁶Nd and ¹³⁵Nd nuclei / Chiralité dans les noyaux ¹³⁶Nd et ¹³⁵NdLv, Bingfeng 11 October 2019 (has links)
Le mode d’excitation collective exotique appelé chiralité a été étudié et des isomères de longue durée de vie ont été recherchés dans les noyaux ¹³⁶Nd et ¹³⁵Nd. Cinq paires de bandes Δ I=1 presque dégénérées et de même parité ont été identifiées à des spins élevés dans ¹³⁶Nd Les bandes observées ont été étudiées en utilisant la théorie de la fonctionnelle de densité covariante contrainte et rotation autour d'une axe incliné, et par un nouveau modèle de rotor plus particules développé pour décrire le couplage de particules dans quatre couches j à un rotor triaxial. Les propriétés de ces bandes doublet sont en bon accord avec les résultats des calculs théoriques. Par conséquent, l'existence de bandes chirales multiples (MχD) dans le noyau ¹³⁶Nd a été établie. Il s'agit de la première preuve expérimentale de l'existence de bandes chirales dans des noyaux pairs. Les cinq paires de bandes chirales constituent le plus grand ensablé de bandes chirales observé jusqu'à présent dans un seul noyau. De plus, le schéma de niveaux de ¹³⁶Nd a été considérablement étendu aux spins bas, moyens et très élevés. Les configurations possibles de toutes les bandes rotationnelles ont été attribuées á l'aide du modèle Nilsson-Strutinsky en rotation. La structure de ¹³⁶Nd a été clarifiée et les divers types d'excitations uni-particule et collectives ont été bien compris. Une nouvelle paire de bandes chirales á parité positive a été identifiée dans. Les caractéristiques des bandes soutiennent leur interprétation en termes de bandes chirales. Des bandes chirales à parité négative ayant été identifiées précédemment, la présence de multiple bandes chirales dans ¹³⁵Nd est ainsi établie. Les bandes chirales observées ont été étudiées en utilisant la théorie avec fonctionnelle de densité covariante contrainte et avec le modèle rotor plus particules; elles reproduisent fidèlement les données expérimentales, confirmant ainsi le phénomène MχD dans ce noyau. Les bandes chirales nouvellement observées dans ¹³⁵Nd représentent une étape importante dans la confirmation de l'existence du phénomène MχD dans les noyaux. La recherche d'états isométriques à longue durée de vie dans ¹³⁵Nd et ¹³⁶Nd a été aussi effectuée, mais n'a pas permis d'identifier de nouveaux isomères. Cependant, nous avons pu confirmer la présence des isomères déjà identifiés dans les noyaux ¹³⁸Nd, ¹³⁴Ce, ¹³⁶Pr, et ¹³⁷Pr dans nos données. / The exotic collective excitation mode called chirality has been investigated and long-lived isomers have been searched for in the ¹³⁶Nd and ¹³⁵Nd nuclei. Five pairs of nearly degenerate Δ I=1 bands with the same parity have been identified at high spins in ¹³⁶Nd. The observed bands were investigated by the constrained and tilted axis cranking covariant density functional theory and a new developed four single-j shells particle-rotor model. It was found that the properties of these doublet bands are in good agreement with results of the model calculations. Therefore, the multiple chiral doublets (MχD) phenomenon in the nucleus ¹³⁶Nd was confirmed. This was the first experimental evidence for the MχD bands in even-even nuclei. The five pairs of chiral doublet bands is the largest observed in a single nucleus until now. In addition, the level scheme of the ¹³⁶Nd has been extended significantly at low, medium, and very high spins. Possible configurations of all rotational bands have been assigned by using the cranked Nilsson-Strutinsky model. The band structure of ¹³⁶Nd was clarified and the various types of single-particle and collective excitations were well understood. A new pair of positive-parity chiral doublet bands has been identified in ¹³⁵Nd. The characteristics of the doublet bands support the chiral interpretation. Together with the previously reported negative-parity chiral doublet bands show the presence of MχD bands in ¹³⁵Nd. The observed doublet bands were compared with constrained covariant density functional theory and particle-rotor model calculations which nicely reproduce the experimental data, confirming the MχD phenomenon in this nucleus. The newly observed MχD bands in ¹³⁵Nd represent an important milestone in supporting the existence of MχD in nuclei. The search for long-lived isomeric states in ¹³⁵Nd and ¹³⁶Nd has also been performed. This did not lead to the identification of new isomers, but we could confirm the existence of the previously reported isomers in the nuclei ¹³⁸Nd, ¹³⁴Ce, ¹³⁶Pr, and ¹³⁷Pr in our data.
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Transport of Deuterium-Labeled Tocopherols During PregnancyAcuff, Robert V., Dunworth, Robert G., Webb, Lisa W., Lane, Jonathan R. 01 January 1998 (has links)
With use of deuterium-labeled isotopes of RRR-and all-rac-α-tocopheryl acetate, the transport of vitamin E in pregnancy was evaluated to determine whether the placenta discriminates between these compounds. Fifteen pregnant subjects were recruited 5 d before delivery to receive 15, 30, 75, 150, or 300 mg vitamin E/d in capsules containing d3-RRR-α-tocopheryl acetate and d6-all-rac-α-tocopheryl acetate (1:1, by wt). Maternal blood was obtained before dosing, at hospital admission, and at parturition. Cord blood samples were obtained at parturition. Deuterium-labeled and unlabeled tocopherol contents were determined by gas chromatography-mass spectrometry in plasma and lipoproteins (chylomicrons, VLDL, LDL, and HDL). Maternal plasma and lipoproteins obtained at delivery had higher concentrations of d3-RRR-α- tocopherol than d6-all-rac-α-tocopherol regardless of the vitamin E dose administered (P < 0.05). Cord plasma at delivery also had higher concentrations of d3-RRR-α-tocopherol than d6-all-rac-α-tocopherol in plasma irrespective of the dose administered (P < 0.05). In lipoproteins isolated from cord blood, tocopherol concentrations were greatest in the HDL fraction (P < 0.05), whereas in maternal blood they were greatest in the LDL fraction (P < 0.05). We conclude that the placental-fetal unit, the fetal liver, or both further discriminate between RRR- and all-rac-α-tocopherol.
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Towards the Total Synthesis of Thioviridamide: Thiyl Radical Approach to the Beta-Thioenamide Linkage FormationKang, Jung-hoon 22 December 2008 (has links) (PDF)
We developed an approach to the β-thioenamide linkage contained in the S-(2-aminovinyl)cysteine (avCys) residue of thioviridamide.1,2 Kinetic and thermodynamic control of radical additions of thiols to ynamides were studied for the formation of β-thioenamide linkage. Thiyl radicals are electrophilic and ynamides are electron-rich alkynes. This complementary polarity of the radical and acceptor increases the likelihood of a successful radical addition reaction. Because little is known about these types of compounds (β-thioenamides), we were unsure what kinds of yields and stereoselectivities (cis vs. trans) to expect. The adduct stability is another issue to consider. Fortunately, under typical radical addition conditions, the two separable isomers (cis and trans) are formed in good yield. Selective formation of kinetic (cis) and thermodynamic (trans) isomers are controlled by reaction time and equivalents of thiol. We converted the kinetic isomer to the thermodynamic isomer to confirm that isomerization can occur under the reaction conditions. Alkyl and aryl thiols including cysteine-derived thiols with different ynamides were used in this process.
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Characterization of isomeric states in neutron-rich nuclei approaching N = 28Ogunbeku, Timilehin Hezekiah 08 December 2023 (has links) (PDF)
The investigation of isomeric states in neutron-rich nuclei provides useful insights into the underlying nuclear configurations, and understanding their occurrence along an isotopic chain can inform about shell evolution. Recent studies on neutron-rich Si isotopes near the magic number N = 20 and approaching N = 28 have revealed the presence of low-lying states with intruder configurations, resulting from multiple-particle, multiple-hole excitations across closed shell gaps. The characterization of these states involves measuring their half-lives and transition probabilities.
In this study, a new low-energy (7/2−1) isomer at 68 keV in 37Si was accessed via beta decay and characterized. To achieve this, radioactive 37Al and 38Al ions were produced through the projectile fragmentation reaction of a 48Ca beam and implanted into a CeBr3 detector, leading to the population of states in 37Si. The 68-keV isomer was directly populated in the beta-delayed one neutron emission decay of implanted 38Al ions. Ancillary detector arrays comprising HPGe and LaBr3(Ce) detectors were employed for the detection of beta-delayed gamma rays. The choice of detectors was driven by their excellent energy and timing resolutions, respectively.
The beta-gamma timing method was utilized to measure the half-life of the new isomeric state in 37Si. This dissertation also discusses other timing techniques employed to search for and characterize isomeric states following beta decay of implanted ions. Notably, the half-life of the newly observed (7/2−1) isomeric state in 37Si was measured to be 9.1(7) ns. The half-life of the previously observed closely-lying (3/2−1) state at 156 keV was determined to be 3.20(4) ns, consistent with previously reported values. Reduced ground-state transition probabilities associated with the gamma-ray decay from these excited states were in agreement with results obtained from shell model calculations.
In addition to the investigation of isomeric states in 37Si, isomeric 0+ states in 34Si and 32Mg nuclei belonging to the N = 20 “island of inversion” were characterized and searched for, respectively. The isomeric 0+ state in 34Si was populated following the beta decay of implanted 34Mg ions and its 34Al daughter nucleus. Similarly, the 0+ state in 32Mg was searched for via the beta-delayed one neutron emission decay of implanted 33Na ions.
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Effect of Plant Genotype and Processing Techniques on Stability and Content of Tomato Carotenoids by Infrared SpectroscopyRubio Diaz, Daniel E. 24 August 2010 (has links)
No description available.
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Sources, transport and fate of perfluoroalkyl acids in the atmosphereJohansson, Jana January 2017 (has links)
Perfluoroalkyl acids (PFAAs) are man-made chemicals which have been observed in the global environment, even in locations far away from where they are emitted. These persistent substances are taken up in humans and biota and may have toxic effects. Knowledge about how PFAAs are dispersed in the environment is needed to discern strategies to manage their sources and to evaluate the efficacy of adopted legislation. This thesis aimed to increase our understanding of the sources of PFAAs to the atmosphere and how PFAAs are transported in air. The results of Paper I demonstrated that gaseous perfluorooctanoic acid (PFOA) sorbs to typical glass fibre filters (GFFs) used in high-volume air sampling of PFAAs. As a consequence, the fraction of gaseous PFOA present in sampled air is underestimated, while the fraction of PFOA associated with aerosols is overestimated. Replacing GFFs with filters deactivated through silanisation and siliconisation did not eliminate this sampling artefact and is therefore not recommended as a means to determine the gas-particle partitioning of PFAAs. In Paper II, monitoring of the mass of PFOA transferred from water solutions of pH 0.2-5.5 demonstrated that the acid dissociation constant of linear PFOA and the four most ubiquitous branched PFOA isomers is around or below 1. Furthermore, the results demonstrated that the presence of counter ions and organic matter in water retarded, rather than enhanced, the volatilisation of PFOA. Therefore, volatilisation of all isomers of PFOA from environmental waters is expected to be negligible. To further study the transfer of PFAAs from environmental waters to air, Paper III simulated the process of sea spray generation in the laboratory. Strong enrichment of PFAAs was observed from bulk water to the surface microlayer and to aerosols. The enrichment increased with PFAA chain length, indicating that this process is of greater importance for more surface active substances. The highest enrichment was observed in aerosols < 1.6 µm, which can travel over long distances if not rained out. Based on the measured aerosol enrichment factors we estimated that approximately 70 metric tonnes of PFAAs are aerosolised from the global oceans yearly and that 3% of this mass is deposited in terrestrial environments. Paper IV reported the occurrence of branched PFOA isomers in deposition sampled in five geographical locations. The presence of these isomers demonstrated that atmospheric transformation of fluorotelomer alcohols is not the only ongoing source of PFAAs to air. We hypothesised that, additionally, both sea spray aerosols and direct emissions from manufacturing sources contributed to the contamination of the precipitation on different spatial scales. Although further research is required to determine the relative importance of different sources to the atmosphere locally and globally, this thesis has substantially advanced the state-of-the-science by i) demonstrating the significance of an air sampling artefact discussed as an uncertainty in the scientific literature over the past decade, ii) definitively ruling out volatilisation from environmental waters as a source of PFOA to air, iii) demonstrating transfer of PFAAs from seawater to air via sea spray aerosols and thus quantifying the environmental importance of this process, and iv) ultimately demonstrating that several types of sources of PFAAs impact the global atmosphere and thus PFAA contamination patterns in precipitation. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
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