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1
Mantri, Padmaja. "Arachidonic acid aci-Reductone strategies : asymmetric synthesis of 2-hydroxytetronic acid antimetabolities /". The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487848078452092.
Testo completo
2
Llewelyn, Peter William. "Supported heteropoly acids for acid catalysed reactions". Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54120/.
Testo completo
3
Hinton, Michael Raymond. "Xylaric Acid, D-Arabinaric Acid (D-Lyxaric Acid), L-Arabinaric Acid (L-Lyxaric Acid), and Ribaric Acid-1,4-Lactone ; synthesis and isolation - synthesis of Polyhydroxypolyamides therefrom". [Missoula, Mont.] : University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-03212009-142612/unrestricted/Hinton_umt_0136D_10002.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Montana, 2009.ETD number: etd-03212009-142612. Author supplied keywords: aldaric acids ; carbohydrates ; MM3 ; oxidation ; polyhydroxypolyamide ; polymers. Description based on contents viewed on June 11, 2009; title from author supplied metadata. Includes bibliographical references.
4
Kishino, Shigenobu. "Production of conjugated fatty acids by lactic acid bacteria". Kyoto University, 2005. http://hdl.handle.net/2433/86244.
Testo completoAbstract (sommario):
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第11617号
農博第1473号
新制||農||905(附属図書館)
学位論文||H17||N4010(農学部図書室)
UT51-2005-D366
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 清水 昌, 教授 加藤 暢夫, 教授 植田 充美
学位規則第4条第1項該当
5
Fang, Bin. "Remobilisation of Heavy Metals from Sediments Using Aminopolycarboxylic Acids". Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/630.
Testo completoAbstract (sommario):
This thesis describes a study of the remobilisation of heavy metals from sediments by three aminopolycarboxylic acids (APCAs). They are nitrilotriacetic acid, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. The investigation is introduced by examining the sources, uses and chemistry of these acids. The introduction also includes a discussion of what is known about the inclusion of heavy metals into sediments and their remobilisation from sediments. Typical concentrations of APCAs in natural waters and sediments have been catalogued from the literature. The advantages and disadvantages of various laboratory techniques employed for the remobilisation of heavy metals by APCAs from sediments are assessed, as is the use of such experiments in quantifying the role of APCAs in the remobilisation of heavy metals from sediments. Sediments from three areas were sampled for this study; they were the Alexandra Canal, Captains Flat and Jenolan Caves in New South Wales, Australia. In each area several sites were sampled. For each site there is a brief description of the catchment geology and hydrology. Selected sediment-associated waters in the areas were analysed for their metal concentrations as well as for ultratrace levels of APCAs employing a method developed in the present study. The waters were analysed for the major ions Ca2+, Mg2+, K+, Na+, Cl-, NO3- and SO42-. The sediments from selected sites in each of the areas were dried and fractionated. The dry total and fine sediments were analysed for their metal content and the latter was found to adequately represent the former in this respect. Water samples from the three areas showed different chemistries and exhibited more subtle differences between sites. In general, the Alexandra Canal waters are saline and alkaline and are a mixture of urban runoff and seawater; the Captains Flat waters are acidic and contain high sulfate from acid mine and tailings drainage; the Jenolan Caves waters are neutral and have the features characteristic of waters draining through limestone. The APCA contamination in all water samples when ranked against other global sites is very low. Although the current APCA levels in the waters appear low, it was concluded that they should be closely monitored so that efforts can be made to minimise the risk of APCAs being hazardous environmental contaminants and also that any remobilisation of heavy metals from sediments by APCAs can be controlled. Agitation and column laboratory-scale experiments were carried out in order to obtain an understanding of the remobilisation of metals by contamination levels of APCAs in water, both as the individual APCAs and as a mixture of APCAs. Complimentary experiments were carried out using a molar excess of APCAs calculated from the metal concentrations obtained by acid digestion (assuming 1:1 metal complex formation). Both types of remobilisation experiments were designed to investigate the role that redox potential (Eh) and concentration of APCAs in natural waters have on the remobilisation of heavy metals from the sediments. The agitation experiments were employed to assess metal remobilisation for the situation where the sediments are disturbed while the column experiments explored metal remobilisation for the case where the sediments are left undisturbed in situ. The major conclusions from the agitation experiments that used fine sediment from the Alexandra Canal were that 100 ppm APCA solutions will remobilise metals from the sediments under oxic conditions but only remobilise infinitesimally small amounts of metal under anoxic conditions. The use of fine sediments for the duplicate agitation experiments was found to give adequate duplication of results. A mixture of APCAs in solution acts similarly to the average of the three individual APCA solutions, showing that there are no antagonistic or synergistic effects likely to occur when they are found together in the environment. It was found that the mmoles of the metals remobilised exceeded the mmoles of the APCAs added when 500.0 mL of 100 ppm APCA solution was used on 50.00 g of sediment. This might be due to APCAs remobilising metals from the sediments in ways other than by complexation. Even though an excess of APCAs was available, metal remobilisation was not complete when the experiments were forced to terminate. During the 14 days of the experiment, only one quarter of the metals liberated from the sediment by HNO3 and 30 % H2O2 digestion were remobilised by the APCAs. Therefore an excess of free APCAs remains in solution. Fine sediments from Alexandra Canal, Captains Flat and Jenolan Caves were employed in the oxic agitation experiments using excess APCAs in solution. These experiments resulted in the following major conclusion: when producing an APCA remobilisation signature for trace and ultratrace metals, the geochemistry of the site is of secondary importance to the source of the contaminating metals. This is a feature of the trace and ultratrace metal speciation in the source rather than their concentration in it. From the different levels of calcium present in the three areas it was found that calcium is unlikely to form stable 1:1 APCA complexes at the pH values employed and is unlikely to compete with the heavy metal remobilisation by APCAs. Total sediments from Alexandra Canal and 100 ppm APCA solutions were employed for the column leaching experiments. From mass, pore water volumes and flow measurements it was shown that the ten mini cores taken from the same site were not true replicates. Despite this, when the sediments have settled and the pore waters removed from the cores, the levels of metal being leached stabilise and may represent a clearer picture of the in situ metal leaching from sediment with time. The levels of metal leached from the cores in 14 days suggest that during this period the cores are essentially anoxic, with the oxygen supplied from the oxic leaching solutions used for inorganic and microbial processes in the sediments. Agitation experiments appeared to yield an adequate picture of what would happen if free APCA solution came in contact with fine sediments suspended in the water column. Column leaching experiments employing total sediment were found to be only of limited value in assessing heavy metal remobilisation from undisturbed sediment. These experiments do not give a reliable assessment of the bioavailability of heavy metals and further testing of the acute and chronic toxicity of the sediments is recommended. APCA solutions that have been used in sediment and soil washing under conditions related to those used in the present study may contain an excess of the free APCAs as well as APCA heavy metal complexes and hence may be toxic to biota.
6
Fang, Bin. "Remobilisation of Heavy Metals from Sediments Using Aminopolycarboxylic Acids". University of Sydney. Chemistry, 2005. http://hdl.handle.net/2123/630.
Testo completoAbstract (sommario):
This thesis describes a study of the remobilisation of heavy metals from sediments by three aminopolycarboxylic acids (APCAs). They are nitrilotriacetic acid, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid. The investigation is introduced by examining the sources, uses and chemistry of these acids. The introduction also includes a discussion of what is known about the inclusion of heavy metals into sediments and their remobilisation from sediments. Typical concentrations of APCAs in natural waters and sediments have been catalogued from the literature. The advantages and disadvantages of various laboratory techniques employed for the remobilisation of heavy metals by APCAs from sediments are assessed, as is the use of such experiments in quantifying the role of APCAs in the remobilisation of heavy metals from sediments. Sediments from three areas were sampled for this study; they were the Alexandra Canal, Captains Flat and Jenolan Caves in New South Wales, Australia. In each area several sites were sampled. For each site there is a brief description of the catchment geology and hydrology. Selected sediment-associated waters in the areas were analysed for their metal concentrations as well as for ultratrace levels of APCAs employing a method developed in the present study. The waters were analysed for the major ions Ca2+, Mg2+, K+, Na+, Cl-, NO3- and SO42-. The sediments from selected sites in each of the areas were dried and fractionated. The dry total and fine sediments were analysed for their metal content and the latter was found to adequately represent the former in this respect. Water samples from the three areas showed different chemistries and exhibited more subtle differences between sites. In general, the Alexandra Canal waters are saline and alkaline and are a mixture of urban runoff and seawater; the Captains Flat waters are acidic and contain high sulfate from acid mine and tailings drainage; the Jenolan Caves waters are neutral and have the features characteristic of waters draining through limestone. The APCA contamination in all water samples when ranked against other global sites is very low. Although the current APCA levels in the waters appear low, it was concluded that they should be closely monitored so that efforts can be made to minimise the risk of APCAs being hazardous environmental contaminants and also that any remobilisation of heavy metals from sediments by APCAs can be controlled. Agitation and column laboratory-scale experiments were carried out in order to obtain an understanding of the remobilisation of metals by contamination levels of APCAs in water, both as the individual APCAs and as a mixture of APCAs. Complimentary experiments were carried out using a molar excess of APCAs calculated from the metal concentrations obtained by acid digestion (assuming 1:1 metal complex formation). Both types of remobilisation experiments were designed to investigate the role that redox potential (Eh) and concentration of APCAs in natural waters have on the remobilisation of heavy metals from the sediments. The agitation experiments were employed to assess metal remobilisation for the situation where the sediments are disturbed while the column experiments explored metal remobilisation for the case where the sediments are left undisturbed in situ. The major conclusions from the agitation experiments that used fine sediment from the Alexandra Canal were that 100 ppm APCA solutions will remobilise metals from the sediments under oxic conditions but only remobilise infinitesimally small amounts of metal under anoxic conditions. The use of fine sediments for the duplicate agitation experiments was found to give adequate duplication of results. A mixture of APCAs in solution acts similarly to the average of the three individual APCA solutions, showing that there are no antagonistic or synergistic effects likely to occur when they are found together in the environment. It was found that the mmoles of the metals remobilised exceeded the mmoles of the APCAs added when 500.0 mL of 100 ppm APCA solution was used on 50.00 g of sediment. This might be due to APCAs remobilising metals from the sediments in ways other than by complexation. Even though an excess of APCAs was available, metal remobilisation was not complete when the experiments were forced to terminate. During the 14 days of the experiment, only one quarter of the metals liberated from the sediment by HNO3 and 30 % H2O2 digestion were remobilised by the APCAs. Therefore an excess of free APCAs remains in solution. Fine sediments from Alexandra Canal, Captains Flat and Jenolan Caves were employed in the oxic agitation experiments using excess APCAs in solution. These experiments resulted in the following major conclusion: when producing an APCA remobilisation signature for trace and ultratrace metals, the geochemistry of the site is of secondary importance to the source of the contaminating metals. This is a feature of the trace and ultratrace metal speciation in the source rather than their concentration in it. From the different levels of calcium present in the three areas it was found that calcium is unlikely to form stable 1:1 APCA complexes at the pH values employed and is unlikely to compete with the heavy metal remobilisation by APCAs. Total sediments from Alexandra Canal and 100 ppm APCA solutions were employed for the column leaching experiments. From mass, pore water volumes and flow measurements it was shown that the ten mini cores taken from the same site were not true replicates. Despite this, when the sediments have settled and the pore waters removed from the cores, the levels of metal being leached stabilise and may represent a clearer picture of the in situ metal leaching from sediment with time. The levels of metal leached from the cores in 14 days suggest that during this period the cores are essentially anoxic, with the oxygen supplied from the oxic leaching solutions used for inorganic and microbial processes in the sediments. Agitation experiments appeared to yield an adequate picture of what would happen if free APCA solution came in contact with fine sediments suspended in the water column. Column leaching experiments employing total sediment were found to be only of limited value in assessing heavy metal remobilisation from undisturbed sediment. These experiments do not give a reliable assessment of the bioavailability of heavy metals and further testing of the acute and chronic toxicity of the sediments is recommended. APCA solutions that have been used in sediment and soil washing under conditions related to those used in the present study may contain an excess of the free APCAs as well as APCA heavy metal complexes and hence may be toxic to biota.
7
Blanco, Élodie. "Catalyseurs phosphates pour la déshydratation de l’acide lactique en acide acrylique". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10222/document.
Testo completoAbstract (sommario):
Différents phosphates ont été préparés et testés pour la déshydratation de l'acide lactique en phase gaz. La sélectivité en acide acrylique dépend fortement de la température de réaction mais peu du temps de contact. A 380°C, des valeurs de sélectivité allant de 19 à 50% ont été mesurées pour des phosphates alcalino-terreux qui sont stables sur au moins 24 h. Des mesures d'acido-basicité ont montré que ces phosphates contiennent une forte proportion de sites de même force faible. De plus, une corrélation entre la sélectivité en acide acrylique et le ratio molaire acide/base a été établie : elle atteint 50% pour un rapport proche de 1 et diminue lorsque ce ratio augmente. L'acide lactique étant thermiquement peu stable (fonction acide très réactive), nous nous sommes tournés vers la conversion du lactate d'éthyle pur. Les sélectivités en produits de déshydratation sont largement favorisées avec une sélectivité maximale de 87% à 15% de conversion. Cependant, les catalyseurs sont moins actifs et se désactivent fortement sur 24 h. La désactivation peut être inhibée par ajout d'eau dans la phase gaz. La caractérisation de surface a montré que les vitesses de réaction augmentent avec le rapport P/M et a révélé la présence d'une phase amorphe hydroxylée correspondant à des mono, dihydrogénophosphates ou des polyphosphates. Les groupements P-OH présents dans cette phase sont consommés ou modifiés en condition de réaction pour les deux réactifs suggérant qu'ils constituent des sites actifs. Enfin, le suivi DRIFT des TPD-NH3 a permis de proposer que des paires acide-base (M2+ et P-O-) sont dosées dans ce cas. Elles constitueraient le site d'adsorption de l'acide lactique conduisant ensuite à un mécanisme de déshydratation de type E2Various alkaline-earth phosphates were prepared and evaluated for gas phase dehydration of lactic acid. Selectivity to acrylic acid strongly depends on the reaction temperature but not on the contact time. At 380 °C, values ranging from 19 to 49% were measured for alkaline–earth phosphates catalysts that are stable for at least 24 h. Acid–base properties measurements revealed that such phosphates contain high proportion of acidic and basic sites with same weak strength. Furthermore, correlation between selectivity to acrylic acid and the acid–base balance was clearly established: it was 50% for balance close to 1 and decreased increasing this parameter. Because of poor thermal stability of lactic acid, we then focused on the ethyl lactate conversion. Selectivities in dehydration products were much higher with a maxima of 87% at 15% conversion. However, the catalysts were less active and stable. The deactivation can be inhibited adding water in the gas phase. Surface characterization of catalysts showed that catalytic activities are correlated with the P/M ratio and revealed the presence of an hydroxylated amorphous phase corresponding to mono / dihydrogenophosphates or polyphosphates. The P-OH species present in these phases are consumed or modified for both reactants suggesting that they are active sites. Finally, NH3-TPD measurements followed by DRIFT suggested that acid base pairs (M2+ and P-O-) are then probed. Such pairs would constitute the adsorption site of lactic acid which then dehydrate in acrylic acid by an E2 mechanism
8
Levy, Milne Ryna. "Differential metabolism of eicosapentaenoic acid and docosahexaenoic acid". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ56664.pdf.
Testo completo
9
Chesters, Nicola C. J. E. "Biosynthetic studies on tropic acid and piliformic acid". Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5211/.
Testo completoAbstract (sommario):
This thesis is divided into two parts and covers biosynthetic studies on two secondary metabolites, tropic acid in Part I and piliformic acid, in Part II.(S)-Tropic acid is the acid moiety of the alkaloids hyoscyamine and scopolamine, which are produced by a number of plants of the Solanacae family. An intriguing rearrangement of the L-phenylalanine side chain gives rise to the isopropanoid (S)-tropic acid skeleton. The detailed nature of the rearrangement has however remained elusive despite continued interest over the years. In chapter two the identification of intermediates between L-phenylalanine and (S)-tropic acid is discussed, which has placed (R)-D-phenyllactic acid as an immediate precursor. The stereochemical features of the rearrangement are described in chapter 3 and finally in chapter 4 a mechanism for the rearrangement is proposed. This is based on information obtained from the incorporation of various isotopically labelled precursors to tropic acid into two of the minor alkaloids, 3a-2'-hydroxyacetoxytropane and 3a- phenylacetoxytropane. This work was carried out in collaboration with Dr Richard Robins at the AFRC Institute of Food Research in Norwich. Piliformic acid is elaborated by the slow growing fungus Poronia piliformis. The incorporation of a number of isotopically labelled substrates into piliformic acid has revealed a mixed biosynthetic origin, comprising C(_8) and C(_3) fragments. These have been shown to be of acetogenic and citric acid cycle origins respectively. The C(_8) fragment has been further demonstrated to be a degradation product of a longer chain fatty acid. The mode of coupling of the two fragments has been investigated and suggests the intermediacy of a novel a-carboxyoctanoate. A pathway for the assembly of piliformic acid, involving a 1,3-hydrogen shift, is proposed, consistent with the above findings. These results are the subject of chapter 6.
10
Wuenschel, Jeffrey Carl Jr. "Effects of Feeding Supplemental Eicosapentanoic Acid and Docosahexanoic Acid to Beef Females on Reproductive Responses and Free Fatty Acids". Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/34958.
Testo completoAbstract (sommario):
The objective of this study was to determine the effects of dietary supplementation of eicosapentanoic (EPA) and docosahexanoic acids (DHA) on reproduction in beef females. In experiment 1, cows (n = 31) were individually fed rumen protected fish meal (FM) or no fish meal (C) supplements. Estrus was synchronized and ovulation induced on d 37. Ovarian follicular growth and diameter were determined by ultrasound on d 35 and d 37. Serum progesterone (P4) profiles were analyzed on d 37 through d 52. On d 52 cows were cannulated, primed with estradiol-17β at -240 min, and stimulated to release PGF2α by oxytocin injection at 0 min with blood sampled every 15 min from -30 min to 240 min. Supplement type did not affect (P > 0.05) follicular diameter, follicular growth or P4 concentrations. In cows fed FM, prostaglandin metabolite (PGFM) concentrations tended (P ≤ 0.10) to be reduced at 0, 30, and 60 min. In experiment 2, crossbred heifers (n = 214) received FM or C concentrates with corn silage from 30 d before estrous synchronization until 14 d after artificial insemination (AI). Serum fatty acid profiles were determined in five heifers from each group . Estrus detection and AI were conducted from d 37 through d 39. Dietary treatment increased (P < 0.05) EPA and DHA concentrations. Dietary treatment did not affect estrus response or AI conception rates and pregnancy rate. Supplementation of FM increased EPA and DHA concentrations but did not affect reproductive factors.Master of Science
11
Kontos, Christopher D. "The Irreversible Inhibition of D-amino Acid Oxidase with Trans-3-bromoacrylic Acid and Four Others Halo-vinylic Acids". W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539625302.
Testo completo
12
Kvasnina, O. V., e A. O. Shapovalenko. "Acid rains". Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/34855.
Testo completoAbstract (sommario):
Acid rains are harmful precipitations which make us get wet. Acid rains can be in the form of rain, hail or snow. They are very harmful from the ecological, economic and aesthetic point of view.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34855
13
Surucu, Birgul [Verfasser]. "Synthesis of Chlorogenic Acids and Chlorogenic Acid Lactones / Birgul Surucu". Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2012. http://d-nb.info/1035217090/34.
Testo completo
14
Baughman, Curtis Andrew. "Influence of in vitro elaidic acid or trans-vaccenic acid uptake and lactogenic hormone stimulation on fatty acid content of mouse mammary cells". Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/45087.
Testo completoAbstract (sommario):
The objective of the study was to examine the effects of trans-9-octadecenoic acid
(elaidic) and trans-II-octadecenoic acid (trans-vaccenic) on uptake and alteration of
exogenous fatty acids by mouse mammary epithelial cells. Cells from a subclone of the COMMA-D cell line were plated on uncoated plastic petri dishes and grown to confluence. Supplemental fatty acids bound to bovine serum albumin were added to the medium applied to the confluent cell cultures. Treatments included 200 JlM octadecanoic acid (CI8:0) as a control and 100 JlM CI8:0 with one of the following JlM ratios of cis-octadecenoic acid (cis-CI8:I) to elaidic or trans-vaccenic: 100:0, 75:25, 50:50, 0:100. In addition, all treatments were conducted with or without lactogenic hormone supplementation. The cellular protein to DNA ratio and total amount of fatty acids per mg protein were decreased (P < .05) by addition of lactogenic hormones. In treatments without hormone supplementation, however, the total amount of cellular fatty acids per mg protein was decreased (P < .05) by addition of either trans-CI8:I isomer. Results indicated a significant (P < .05) relationship between the concentration oftrans-C18:1 in the media and uptake of trans-C 18: 1 isomers, and retroconversion of trans-C 18: 1 to trans-C 16: 1. The
slopes of the lines for cellular C16:0, cis-C16:1, and cis-CI8:1 were less (P < .05) than
zero as concentration oftrans-CI8:1 in the media increased. However, trans-CI8:1
isomers did not influence the proportion of polar and nonpolar lipids synthesized by the cells. It appears that trans fatty acids may depress milk fat output by decreasing de novo fatty acid synthesis and cis-C 18: I content.Master of Science
15
Wächter, Simon Fabian [Verfasser]. "Effects of omega-3 fatty acids docosahexaenoic acid and eicosapentaenoic acid and their metabolites in acute inflammation / Simon Fabian Wächter". Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2012. http://d-nb.info/103038133X/34.
Testo completo
16
Mikhailov, Miroslav I. "Acid placement and coverage in the acid jetting process". Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1592.
Testo completo
17
Al-Obaidi, U. "Nitrous acid catalysed nitration of phenols in sulphuric acid". Thesis, University of Exeter, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373818.
Testo completo
18
Cree, Alistair Murray. "Fatigue in boric acid-sulphuric acid anodised aluminium alloys". Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247058.
Testo completo
19
Shim, Min Suk. "Molecularly Engineered Acid-Responsive Polymers for Nucleic Acid Delivery". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1291412851.
Testo completo
20
Carpenter, Chrissie Ann. "Mannaric acid and mannaric acid polyamides synthesis and characterization /". CONNECT TO THIS TITLE ONLINE, 2008. http://etd.lib.umt.edu/theses/available/etd-12112008-141014/.
Testo completo
21
Bood, Cecilia. "Acid retardation : recovery and recycling of acid and metal". Thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-78875.
Testo completoAbstract (sommario):
During the production of steel, an oxide scale is formed on the surface and to achieve anadequate quality of the surface the scale needs to be removed. Acid pickling is a surfacetreatment where the oxide scale is removed by acid. Over time the amount of dissolved metals in the acid solution increases leading to a decrease in the pickling efficiency, hence the acid solution needs to be renewed. The renewing can be performed by an operation process called acid retardation. In this process, the spent pickling solution passes through a column packed with an ion exchange material, resin. The absorption of strong acids is preferred by the resin, hence the movement of the acids in the resin bed will be retarded relative to the movement of the metal ions. Regeneration of the resin occurs when water is passing through the resin bed counter current to the flow of the spent pickling solution. This generates a by-product with low acid and high metal content, and a product containing high acid and low metal. The aim of this thesis was to investigate the acid retardation with regards to separation efficiency and the behaviour of acid and metal in the column. The results can further be used as the groundwork for a deeper understanding of the acid retardation and how to optimize the process. Experiments were performed in lab-scale columns with synthetic spent pickling solutions containing sulfuric, nitric and hydrofluoric acid and iron in different mixtures. During the experimental work, variation of the acid and metal concentration, the type of resin and the height of the column were performed. The results from the experimental work show that a concentration dependence between the concentration of acid and metal exists and the performance of different resin types varies depending on the acid and metal solution tested. The height might also affect the separation, but it is recommended that this is further investigated. Other recommendations for further work with a focus on understanding the acid retardation for optimization include variations of the volume of solution added to the column, variation in flow rate and slurry packing of the resin.
22
Bishop, Michael Jason. "The Application of Weak-Anion Exchange Chromatography for the Analysis of Organic Zwitterions Using LC/MS/MS". Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/chemistry_theses/5.
Testo completoAbstract (sommario):
A rapid and accurate quantitative method was developed and validated for the analysis of four urinary organic acids with nitrogen containing functional groups, formiminoglutamic acid (FIGLU), pyroglutamic acid (PYRGLU), 5-hydroxyindoleacetic acid (5-HIAA), and 2-methylhippuric acid (2-METHIP) by liquid chromatography tandem mass spectrometry (LC/MS/MS). The chromatography was developed using a weak anion-exchange amino column that provided mixed-mode retention of the analytes. The elution gradient relied on changes in mobile phase pH over a concave gradient, without the use of counter-ions or concentrated salt buffers. A simple sample preparation was used, only requiring the dilution of urine prior to instrumental analysis. The method was validated based on linearity (r2 ¡Ý 0.995), accuracy (85¨C115%), precision (C.V. < 12%), sample preparation stability (¡Ü 5%, 72h), and established patient ranges. The method was found to be both efficient and accurate for the analysis of urinary zwitterionic organic acids.
23
Nardi, Francesca. "Modulation of skeletal muscle insulin sensitivity and SNAT2 amino acid transporter expression by fatty acid availability". Thesis, University of Dundee, 2015. https://discovery.dundee.ac.uk/en/studentTheses/1dc97813-95d2-4771-9342-a869b6027618.
Testo completo
24
Iggman, David. "Dietary Fatty Acids and Cardiometabolic Risk : Influence on Lipoproteins, Insulin Resistance and Liver Fat". Doctoral thesis, Uppsala universitet, Klinisk nutrition och metabolism, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-252066.
Testo completoAbstract (sommario):
The aim of this thesis was to investigate how dietary fatty acids affect the risk for cardiometabolic disease, i.e. cardiovascular disease (CVD), type 2 diabetes and obesity. The overall hypothesis was that unsaturated fatty acids and especially the predominant polyunsaturated fatty acid (PUFA) linoleic acid (LA), 18:2n-6, would decrease cardiometabolic risk compared with saturated fatty acids (SFAs), in line with current recommendations to partly replace dietary SFA with PUFA. Papers I and V were observational studies based on the community-based cohort Uppsala Longitudinal Study of Adult Men (ULSAM). Adipose tissue fatty acid composition was determined as biomarker for dietary fat intake. Studies II, III and IV were randomised short-term interventions on human volunteers, in which different dietary fats were provided to the participants. In 71-year-old men, adipose tissue LA and α-linolenic acid (18:3n-3) were associated with insulin sensitivity (euglycaemic clamp), although this association was diminished for LA after adjusting for lifestyle variables. Different SFA displayed divergent associations; only palmitic acid (16:0) was inversely associated with insulin sensitivity (Paper I). In Cox regression analyses, LA was modestly associated with decreased all-cause mortality, but not CVD mortality during 15 years follow-up (Paper V). In a 3+3-week cross-over study on 20 weight-stable volunteers with dyslipidaemia, all foods were provided. A rapeseed oil-based diet distinctly lowered low-density lipoprotein cholesterol and triglycerides compared with a dairy-fat based diet (butter, cream and fatty cheese). Insulin sensitivity or coagulation factors were not affected (Paper II). In a 10-week randomised trial on 67 abdominally obese participants, PUFA (mostly sunflower oil) decreased liver fat compared with SFA (mostly butter) under isocaloric conditions. In individuals considered highly compliant to study diets, lipoproteins were also decreased during the PUFA diet (Paper III). In a 7-week double-blind randomised trial on 41 healthy volunteers, PUFA (sunflower oil) decreased the total:HDL cholesterol ratio compared with SFA (palm oil) during moderate weight gain (1.5 kg) (Paper IV). In conclusion, LA (PUFA) intake is associated with decreased cardiometabolic risk compared with higher SFA intake, overall supporting a beneficial role of non-tropical vegetable oils in place of solid fats in preventing fatty liver and cardiometabolic disorders.
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Fleary-Roberts, Nadia. "Towards the total synthesis of domoic acid and the isodomoic acids". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/towards-the-total-synthesis-of-domoic-acid-and-the-isodomoic-acids(a32fd085-8e09-47b5-b533-ef259b1ae8a2).html.
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Sedehizadeh, Simon. "Towards the total synthesis of domoic acid and the isodomoic acids". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/towards-the-total-synthesis-of-domoic-acid-and-the-isodomoic-acids(6a1a5ea8-f5a5-4185-8222-5d3486165ac9).html.
Testo completo
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Maisonet, Mildred, Ruby Yadav e Edward Leinaar. "Role Of Perfluorooctanoic Acid On Serum Fatty Acids, Nhanes, 2003-2004". Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/2.
Testo completoAbstract (sommario):
Background: Fatty acids (FA) have a role on energy storage and membrane formation. FA consists of an aliphatic chain with varying number of carbon and a carboxylic functional group. Perfluorooctanoic acid (PFOA) exhibits a similar structure to that of the FA. Given their structural resemblance, we hypothesized that alterations in FA metabolism could arise from competition with PFOA for endogenous FA binding sites in transport and with FA binding proteins. Objectives: Explore associations of serum concentrations of perfluorooctanoic acid (PFOA) with serum concentrations of linoleic (LA), eicosapentanoic (EPA), and docosapentanoic (DHA) acid in adults. Methods: We analyzed data from 1,829, 20-80 years old participants in the 2003–2004 National Health and Nutrition Examination Survey (NHANES). Linear regression models were used to estimate adjusted predicted means of the FA (in µmol/L) for quartiles of PFOA (in ng/mL) and explore linear trends. Results: Increasing concentrations of PFOA were not associated with adjusted predicted means of serum LA (Q1 3534, Q2 3445, Q3 3778, Q4 3399) (p trends=0.6460). Increasing concentrations of PFOA, however, were associated with increasing trends in adjusted predicted means of serum EPA (Q1 49.8, Q2 51.5, Q3 60.9, Q4 55.7).
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Kupiainen, L. (Laura). "Dilute acid catalysed hydrolysis of cellulose – extension to formic acid". Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789526200033.
Testo completoAbstract (sommario):
Abstract New methods are being sought for the production of chemicals, fuels and energy from renewable biomass. Lignocellulosic biomass consists mainly of cellulose, hemicellulose and lignin. Cellulose and hemicellulose can be converted to their building blocks, i.e. sugars, via hydrolysis. This thesis is focused on glucose production from cellulose by dilute acid hydrolysis. Acid hydrolysis has the drawback of limited glucose yields, but it has the potential to become a short-term solution for biochemical production. During acid hydrolysis, the cellulose chain is split into glucose, which undergoes further decomposition reactions to hydroxymethylfurfural, levulinic acid, formic acid and by-products like insoluble humins. The present thesis aims to increase our knowledge on complicated acid-catalysed hydrolysis of cellulose. Glucose decomposition and cellulose hydrolysis were studied independently in laboratory experiments. Kinetic modelling was used as a tool to evaluate the results. The effect of the hydrogen ion on the reactions was evaluated using formic or sulphuric acid as a catalyst. This thesis provides new knowledge of cellulose hydrolysis and glucose decomposition in formic acid, a novel catalyst for high-temperature dilute acid hydrolysis. Glucose yields from cellulose hydrolysed in formic or in sulphuric acid were comparable, indicating that a weak organic acid could function as a cellulose hydrolysis catalyst. Biomass fibres in the form of wheat straw pulp were hydrolysed more selectively to glucose than a model component, microcrystalline cellulose, using formic acid. Glucose decomposition took place similarly in formic and sulphuric acid when the temperature dependence of the hydrogen ion concentration was taken into account, but a significant difference was found between the reaction rates of cellulose hydrolysis in formic acid and in sulphuric acid. The observations can be explained by changes in the cellulose hydrolysis mechanism. Thus, it is proposed in this thesis that side-reactions from cellulose to non-glucose compounds have a more significant role in the system than has earlier been understoodTiivistelmä Uusia menetelmiä etsitään kemikaalien, polttoaineiden ja energian valmistamiseen uusiutuvasta biomassasta. Eräs biomassa, ns. lignoselluloosa, koostuu pääasiassa selluloosasta, hemiselluloosasta ja ligniinistä. Selluloosa ja hemiselluloosa voidaan muuttaa hydrolyysin avulla niiden rakennuspalikoikseen eli sokereiksi. Tämä väitöskirja keskittyy glukoosin tuottamiseen selluloosasta laimean happohydrolyysin menetelmällä. Happohydrolyysi kärsii rajoittuneesta glukoosin saannosta, mutta sillä on potentiaalia tulla lyhyen aikavälin ratkaisuksi biokemikaalien tuotannossa. Happohydrolyysin aikana selluloosaketju pilkkoutuu glukoosiksi, joka reagoi edelleen hajoamisreaktioiden kautta hydroksimetyylifurfuraaliksi, levuliini- ja muurahaishapoiksi ja kiinteäksi sivutuotteeksi. Tämän tutkimuksen tavoitteena on kasvattaa ymmärrystämme monimutkaisesta happokatalysoidusta selluloosan hydrolyysistä. Glukoosin hajoamista ja selluloosan hydrolyysiä tutkittiin erikseen laboratoriokokein. Kineettistä mallinnusta käytettiin työkaluna arvioimaan tuloksia. Vety-ionien vaikutus reaktioihin arvioitiin käyttämällä muurahais- ja rikkihappoja katalyytteinä. Tämä väitöskirja antaa uutta tietoa selluloosan hydrolyysistä ja glukoosin hajoamisreaktioista muurahaishapossa, joka on uusi katalyytti korkean lämpötilan laimean hapon hydrolyysissä. Glukoosisaannot muurahaishappo-hydrolysoidusta selluloosasta olivat vertailukelpoisia vastaaviin rikkihappo-hydrolyysi saantoihin. Tämä viittaa siihen, että heikko orgaaninen happo voisi toimia selluloosahydrolyysin katalyyttinä. Kun katalyyttinä käytettiin muurahaishappoa, vehnän oljesta tehdyt kuidut hydrolysoituivat selektiivisemmin glukoosiksi kuin mallikomponenttina toimineen mikrokiteisen selluloosan. Kun vetyionikonsentraation lämpötilariippuvuus otettiin huomioon, glukoosi hajosi samalla tavalla sekä muurahais- että rikkihappokatalyytissä, mutta merkittävä ero havaittiin selluloosahydrolyysin reaktionopeudessa. Havainnot voidaan selittää selluloosahydrolyysin mekanismissa tapahtuvilla muutoksilla. Väitöskirjassa esitetään, että sivureaktioilla selluloosasta ei-glukoosi-tuotteiksi on merkittävä vaikutus systeemiin
29
Jiang, Shende. "Enantiospecific synthesis of (-)-5-epi-shikimic acid and (-)-shikimic acid". Thesis, Teesside University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411008.
Testo completo
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Orozco, Angela Maria. "Dilute acid hydrolysis of municipal solid waste using phosphoric acid". Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501392.
Testo completo
31
Nguyen, Van Chuc. "Catalytic production and esterification of aqueous solution of lactic acid". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1136.
Testo completoAbstract (sommario):
Cette thèse porte sur la production d'acide lactique par conversion de la biomasse lignocellulosique catalysée par des acides de Lewis solides dans l'eau puis l'estérification d'acide lactique aqueux avec de l'éthanol. La conversion de la cellulose est étudiée en autoclave, en utilisant comme catalyseurs, de la zircone et de l'alumine contenant du W ou Sn (ZrW, AlSn) et différents hydroxydes métalliques. L'étude de la conversion de la cellulose en acide lactique en présence de ZrW non calcinée, ZrW calcinée, Zr(OH)4 et ZrO2, montre que la phase active du catalyseur est constituée de Zr4+, les centres acides de Lewis et de groupes hydroxyles. Les performances catalytiques des catalyseurs AlSn, préparés à partir de chlorure d'étain comme précurseur, dépendent fortement de la présence résiduelle de chlorure, ce qui favorise la formation d'acide lévulinique. Les hydroxydes de certains métaux de transition se sont révélés être des catalyseurs solides efficaces pour la conversion de la cellulose en acide lactique. Il a été observé que le rendement en acide lactique dépend de la concentration et de la basicité des groupes OH superficiels des hydroxydes de métaux de transition et de la présence de sites acides de Lewis. L'estérification de l'acide lactique, à différentes concentrations en l'eau, a été étudiée en présence d'Amberlyst 15, de charbon sulfoné et d'oxyde de graphène pour étudier l'activité et la tolérance à l'eau de catalyseurs solides acides à base de carbone. Il est montré, par calorimétrie d'adsorption d'ammoniac, que l'oxyde de graphène présente des sites superacides et qu'il conduit à la plus grande activité et tolérance à l'eau. L'augmentation de la teneur en eau montre un fort effet inhibiteur sur l'activité du charbon sulfoné alors que d'Amberlyst 15 et l'oxyde de graphène sont plus tolérants. Les catalyseurs ne sont pas stables dans des conditions d'estérification, en présence d'eauThis thesis reports the synthesis of lactic acid from lignocellulosic biomass catalyzed by solid Lewis acid catalysts in water and then esterification of aqueous lactic acid solutions with ethanol. The cellulose conversion was tested in autoclave, in hot water, using zirconia and alumina containing W or Sn (ZrW, AlSn) and different solid metal hydroxides. The conversion of cellulose to lactic acid using uncalcined ZrW, calcined ZrW, Zr(OH)4 and ZrO2 shows that the active surface of the catalyst consists of Zr4+ Lewis centers and OH groups. The catalytic performances of AlSn catalysts, prepared from Sn chloride as precursors, strongly depend on the residual amount of chloride which favors the formation of levulinic acid. Some hydroxides of transition metals were disclosed as efficient solid catalysts for the conversion of cellulose to lactic acid. The yield of lactic acid was observed to depend on the concentration and the basicity of the superficial OH groups and on the presence of Lewis acid sites. The esterification of lactic acid, at different concentrations in water, was studied using Amberlyst 15, sulfonated carbon and graphene oxide to evaluate the activities and water tolerance of carbon based solid catalysts. Graphene oxide, shown by calorimetry of NH3 adsorption to exhibit super-acid sites, leads the highest activity and water tolerance. Increasing amounts of water has a strong inhibiting effect on the activity of sulfonated carbon and less influence on activity of Amberlyst 15 and graphene oxide. However, all catalysts were not stable in esterification conditions, in presence of water
32
Agarwal, Shailesh Ramjilal. "Pharmacological modeling and regulation of excitatory amino acid transporters (EAATS)". CONNECT TO THIS TITLE ONLINE, 2007. http://etd.lib.umt.edu/theses/available/etd-09262007-111510/.
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Wilson, Peter Stanley. "Rediscovering Arsenoacetic Acid". The University of Waikato, 2009. http://hdl.handle.net/10289/2778.
Testo completoAbstract (sommario):
Arsonoacetic acid, H₂O₃As¹CH₂COOH, and arsenoacetic acid, punitively [AsVCH₂COOH]₂ have been synthesised according to historical literature methods, and have been characterised using modern techniques. Arsonoacetic acid was shown by an X-ray crystal structure analysis to be a molecular species with an extensive hydrogen bonding network in the crystal. Arsenoacetic acid proved to be more enigmatic. Electrospray mass spectra suggested it consisted of a mixtures of rings (RAs)n, n = 3-11, with n = 6 dominating. This was partly confirmed by a crystal structure of (AsCH₂COOH)₆ (as the pyridine solvate). On the other hand, ¹H and ¹³C NMR gave spectra that indicated only a single component for arsenoacetic acid. The formation of crystals of the high temperature phase of elemental sulfur, β-S8, at ambient temperature is also discussed.
34
Henderson, Laura. "Acid-catalysed hydroaminations". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54172/.
Testo completoAbstract (sommario):
FR901483 was to be synthesised to highlight the applicability of the acid-catalysed hydroamination reaction to natural product synthesis. FR901483 contains a
35
Boyd, E. Andrew. "Phosphinic acid synthesis". Thesis, University of Kent, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278113.
Testo completo
36
Beckett, Philip Ronald. "Amino acid oxidation". Thesis, University of Aberdeen, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253828.
Testo completoAbstract (sommario):
The aim of the study was to determine the efficiency with which the carbon skeletons of essential amino acids are utilised by the pig when they are limiting in its diet. This requires the oxidation rate of an amino acid to be measured accurately using a tracer labelled with an isotope of carbon or hydrogen. The use of carbon labelled tracers requires the animal to be enclosed in a sealed chamber for the collection of CO2; to avoid this the use of [3H]-labelled tracers was investigated. The oxidation rates of [14C]-labelled tracers when the tracee was limiting and the animal's nitrogen intake was 2 g/kg0.75.d, showed that leucine was used with an efficiency of 0.88; for phenylalanine and histidine the efficiency was over 0.99. When the animal's nitrogen intake was reduced to 0.23 gN/kg0.75.d, and the limiting amino acid was removed entirely from the diet, the oxidation rates did not change significantly. The oxidation rates of [3H]amino acids were very variable compared to the [14C]amino acids and the techniques used were critically analysed. Three reasons were identified for the differences between the [14C]- and [3H]tracers. These were the measurement of tritiated water, the purity of the infused tracers and the position of the isotope in the labelled amino acid. The first two were solved by the adaption of techniques to the high accuracy required. The third reason was a problem of isotope becoming incorporated into synthetic pathways via exchange reactions. No amino acids were available labelled with a [3H] atom which would not be incorporated; therefore it was necessary to synthesise one. L-[33H]valine was chosen because a suitable precursor for its synthesis, L-[2,3-3H]valine was available and because L-[1-14C]valine was also available for comparison The L-[2,3-3H]valine was acetylated to produce N-acetyl-D, L-[3-3H]valine which was then hydrolysed by the stereospecific enzyme acylase I to yield N-acetyl-D-[3-3H]valine and L-[3-3H]valine. The products were separated using a cation exchange column and the L-[3-3H]valine was purified by paper chromatography. Contamination with D-[3-3H]valine was measured using D-amino acid oxidase and L-[2,3-3H]valine using L-amino acid oxidase. The oxidation rates of L-[1-14D]valine and L-[3-3H]valine were compared in the rat and the oxidation rate of L-[3-3H]valine was significantly higher. The experiment was repeated using L-[3-3H]valine synthesised by Amersham International plc. using the same method; the structure was established by NMR. In this case both tracers were oxidised at the same rate. The difference in the first experiment was therefore probably due to slight contamination of L-[3-3H]valine with L-[2,3-3H]valine, the tritium in position 2 being removed by reversible transamination of valine, i.e., not only during its oxidation. Finally, the two tracers were compared in the pig. It was found that the valine flux rates calculated from the two tracers were in closer agreement when a correction was made for infused D-labelled valine. Using the techniques developed throughout this work, L-[1-14C]valine and L-[3-3H]valine measured the same rate of valine oxidation. L-3-3H]valine was a more precise tracer of valine oxidation.
37
Homola, Ondřej. "Acid Drop Age". Master's thesis, Vysoké učení technické v Brně. Fakulta výtvarných umění, 2015. http://www.nusl.cz/ntk/nusl-232447.
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Rutkowski, Piotr. "Acid-catalysed hydroaminations". Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/77061/.
Testo completoAbstract (sommario):
This thesis describes the use of Brønsted acid catalysis to promote 6-exo-trig cyclisations in the synthesis of N-heterocyclic compounds. In Chapter one, a general overview of alkaloid structures is given, together with a number of general ways for their synthesis, with a particular focus on the Bischler-Napieralski and Pictet-Spengler methods. Hydroamination as a synthetic method is then briefly reviewed to set into context the present project to develop and optimize an acid-catalysed hydroamination method as an alternative protocol to the Picted-Spengler reaction. Chapter two describes different synthetic routes towards the construction of 2-vinylphenylethylamines and their subsequent cyclisations into tetrahydroisoquinoline alkaloids via the acid-catalysed hydroamination methodology. Key aspects of the diastereochemical outcome of the reaction are discussed, as well as the spectral features and limitations of the researched chemistry. Chapter three describes application of the acid-catalysed hydroamination in the making of more complex, polycyclic structures. Synthesis of polymethoxylated tetrahydroisoquinolines, benzhydryl derivatives and a relay synthesis of racemic salsolidine is described. An attempt to synthesise racemic alkaloid, crispine, is briefly discussed, as well as synthesis of an aporphine and a berberine skeleton. Chapter four covers the attempt to extend the acid-catalysed hydroamination chemistry to unprotected indoles and trans-annular cyclisations. Future work and areas of chemistry in which the acid-catalysed hydroamination underperformed or failed to deliver the desired results altogether are briefly discussed. Chapter five contains the experimental remarks and characterisation data.
39
Jung, Yun-Kyoung 1979. "Production of conjugated linoleic acid and conjugated linolenic acid by Bifidobacterium breve JKL03 and its application". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82258.
Testo completoAbstract (sommario):
Conjugated linoleic acid (CLA) is predominantly found in foods of ruminant origin such as milk and processed cheese, and has gained much interest recently due to its beneficial health and biological effects on animals and humans.The bioconversion of linoleic acid (LA) and linolenic acid (LNA) by a selected Bifidobacterium from healthy infant feces was studied. Bifidobacterium breve JKL03 had the ability to convert linolenic acid (0.2 mg/ml) to CLNA in fermentation of skim milk medium for 24 h up to a yield of 72.0% (up to 74.7% under aerobic conditions) and linoleic acid (0.2 mg/ml) into CLA by fermentation in skim milk medium for 24 h up to a yield of 23.9% (up to 28.0% under aerobic conditions).
B. breve JKL03 was also co-fermented with Lactobacillus acidophilus (NCFMRTM strain), a commonly added starter culture, to observe the resulting effects on growth during fermentation for yogurt production. Fermentation of LNA in skim milk with B. breve JKL03 and L. acidophilus (NCFM) maintained high CLNA production level. On the other hand, CLA production in the same media with both strains did not exhibit as high level as with the single B. breve.
These results are important for the advancement of knowledge on the production of CLA and CLNA in dairy products and for knowledge on the basic metabolic mechanisms for such conversion.
40
Brian, King Himm Mo. "Biochemical analysis and genetic engineering of oleaginous fungi for the production of eicosapentaenoic acid and free fatty acid derivatives". Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263714.
Testo completo
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Chang, Bong-Kyu. "The solubility and purity of amino acid crystals : II. Preferential incorporation of L-valine over L-leucine into L-isoleucine crystal during the crystallization from HCl solution". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/10951.
Testo completo
42
Spray, Caroline Ann. "4-ketoproline derivatives as chiral templates in synthesis". Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239542.
Testo completoAbstract (sommario):
(2S)-trans-4-Hydroxyproline has been studied as a chiral template for the preparation of kainoids. Conversion to protected 4-ketoproline derivatives has allowed functionalisation at C-3 to be investigated. Although the tendency to epimerisation has caused problems, we have successfully introduced a variety of alkyl side chains with cis stereochemistry at this position. Functionalisation of the 3-alkyl-4-ketoprolines at C-4 has been investigated and a method has been found to prepare compounds which are functionalised stereospecifically at both C-3 and C-4. These have potential for study as kainate analogues. During our studies on the synthesis of kainoids, an unusually stereospecific deuteriation has been discovered. We have exploited this in a synthesis of (2S,3S)-[3- 2Ht]-proline, (2S,3R)-[3-2Ht]-proline and (2S)-[3,3-2H21-proline.
43
Alghamdi, Abdulwahab. "Evaluation of acid fracturing based on the "acid fracture number" concept". Texas A&M University, 2006. http://hdl.handle.net/1969.1/3835.
Testo completoAbstract (sommario):
Acid fracturing is one of the preferred methods to stimulate wells in carbonate
reservoirs. It consists of injecting an acid solution at high enough pressure to break
down the formation and to propagate a two-wing crack away from the wellbore. The
acid reacts with the carbonate formation and this causes the etching of the fracture
surfaces. After the treatment, the created etched surfaces do not close perfectly and that
leaves behind a highly conductive path for the hydrocarbons to be produced. We
distinguish the issue of treatment sizing (that is the determination of the volume of acid
to be injected) and the issue of creating optimum fracture dimensions given the size of
the treatment. This is reasonable because the final cost of a treatment is determined
mainly by the volume of acid injected and our goal should be to achieve the best
performance of the treated well. The well performance depends on the created fracture
dimensions and fracture conductivity and might change with time due to various reasons.
This research evaluates two field cases from Saudi Aramco where acid fracturing
treatment has been used to stimulate a carbonate formation. I investigated the following issues: a) how effective was the treatment to restoring the initial productivity, b) how did
the productivity of the well change with time; c) what are the possible reasons for the
change in performance, d) what are our options to improve acid fracture design in the
future?
Based on our research work both near-well liquid drop-out and fractureconductivity
deterioration can impact the production in different proportion. Moreover,
the fracturing model tends to overestimate the fracture conductivity in some cases as
shown in SA-2. Also, the ÂAcid fracture Number concept proves to be an effective way
to evaluate the acid fracturing treatment. Several recommendations were made based on
this research work as described in the last part of my thesis.
44
Ebikeme, Charles E. "Amino acid transporters and amino acid metabolism in trypanosoma brucei brucei". Connect to e-thesis, 2007. http://theses.gla.ac.uk/55/.
Testo completoAbstract (sommario):
Thesis (Ph.D.) - University of Glasgow, 2007.Ph.D. thesis submitted to the Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, 2007. Includes bibliographical references.
45
Ebikeme, Charles E. "Amino acid transporters & amino acid metabolism in Trypanosoma brucei brucei". Thesis, University of Glasgow, 2007. http://theses.gla.ac.uk/55/.
Testo completoAbstract (sommario):
The development of new drugs against Human African Trypanosomiasis is much needed due to toxicity, efficacy and availability problems with current drug treatments for this resurgent parasitic disease. Delivery of drugs into cells is an important determinant of therapeutic efficacy of drugs. An effective means of selective drug delivery is to use plasma membrane transport systems to mediate the entry of drugs into the cell. Some amino acid transporters fulfil the criteria needed for successful exploitation of nutrient transport systems for drug delivery. The Trypanosoma brucei genomic database was screened to identify the full gene repertoire of amino acid transporters. From this, candidate genes were selected and functional genetic approaches were employed to characterise candidate amino acid transporter genes. Further characterisation of TbAATP1, a RNAi cell line shown to be a transporter of small neutral amino acids (serine, glycine, cysteine, asparagine and alanine), showed a role in threonine uptake. Amino acid analogues were tested for trypanocidal activity. Of the 96 tested, two (Azaserine and Levodopa) were investigated in more detail, paying special attention to the nature of their trypanocidal action and possible route of entry through an amino acid transporter. Azaserine showed a trypanostatic action as well multiple routes of entry into the protozoan interior (as shown by inhibition of glutamine, phenylalanine and tyrosine uptake). The trypanocidal Levodopa showed entry through a tyrosine specific transporter. However, it is possible that Levodopa’s trypanocidal activity may not be as a result of the analogue itself, but secondary products of the analogue. Amino acids are important for protozoa as energy sources as well as forming pools of soluble osmolites. Amino acid usage in trypanosomes was investigated. Upregulation of proline transport and catabolism in response to reduced glucose availability was exhibited by the genome strain of T. brucei. Moreover, this metabolic shift could be mimicked by addition of GlcNAc to the medium, which blocks the hexose transporter limiting glucose entry to the cell. Systems biology approaches were initiated to investigate the undergoing metabolic changes. More specifically, mass spectrometry methodologies were employed to investigate underlying metabolite changes in procyclic form trypanosomes grown in differing medium.
46
McMullan, E. A. "The electrochemical reduction of carbon dioxide, glyoxylic acid and oxalic acid". Thesis, University of Ulster, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356452.
Testo completo
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Panta, Raghava Reddy. "Studies towards the total synthesis of (-)-kainic acid and allokainic acid". Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/47474/.
Testo completoAbstract (sommario):
This study commenced with an investigation into a total synthesis of the antibiotic platensimycin 1.1 in chapter one. The key reaction for accessing the synthetically challenging fused ring system involved a meta-photocycloaddition reaction and the chapter one describes our attempts at the syntheses of the key substrates. Much of the chemistry was unsuccessful however we were able to attempt a key photochemical reaction however the desired compound was not obtained. On the basis of these outcomes we refocused our efforts towards the syntheses of kainic acid 2.1 and allokaininc acid 2.2 in chapter two. We aimed to devise a stereoselective synthesis of both kainic acid 2.1 and the allokainic acid 2.2, utilising the diastereofacial selectivity inherent in the previously synthesised oxazolidinone 2.240. Oxazolidinone 2.240 was subjected to a stereo and regiocontrolled 1,3-dipolar cycloaddition to give isoxazole 2.279. Reduction, followed by dehydration of isoxazole 2.279 gave the enone 2.287 which forms the Michael acceptor in the key Michael addition reaction. The 1,4 addition on enone 2.287, gave the two diastereomers 2.328 and 2.329 which underwent sequential Wittig reaction, and Krapcho decarboxylation to give the formal synthesis of allokainic acid 2.2 and epikainate 2.346 respectively. An investigation was also conducted with the aim of altering the stereochemistry of the dicarboxylic group in compound 2.329, in order to produce a novel route to the stereoselective synthesis of kainic acid 2.1.
48
Slabbert, R. S. "Acid tolerance and organic acid susceptibility of selected food-borne pathogens". Interim : Interdisciplinary Journal, Vol 13, Issue 2: Central University of Technology Free State Bloemfontein, 2013. http://hdl.handle.net/11462/296.
Testo completoAbstract (sommario):
Published ArticleThe development of tolerance to low pH levels and the existence of cross-resistance may promote survival of bacteria in acidic foodstuff and in acidic environments such as the human stomach, in so doing escalating the probability of food poisoning. Similar to antimicrobial resistance developing, there is growing concern that effectiveness of organic acids may decrease as a result of the emergence of acid-tolerant food-borne pathogens. The objectives of this study were to determine the development of acid tolerance in selected food-borne pathogenic bacteria and to explore the activity of organic acids against acid tolerant pathogens. Bacterial strains were screened for acid-tolerance and susceptible strains were induced through exposure to increasing concentrations of an inorganic acid, as well as acidic foodstuffs. Susceptibility to six organic acids at various pH levels was assessed in order to evaluate the possible relationship between altered antimicrobial activity and acid tolerance. Salmonella enterica sv. Enteritidis ATCC 13076 and Escherichia coli ATCC 25922 were found to rapidly develop acid tolerance, while intrinsic acid tolerance was noted in Salmonella enterica sv. Typhimurium ATCC 14028. Pseudomonas aeruginosa ATCC 27853 demonstrated intermediate intrinsic acid tolerance. As expected, pH played a significant role in inhibitory activity of the organic acids as these compounds exhibit optimum antimicrobial activity at a lower pH (pH ≤5). It is, however, necessary to further elucidate the two-way role of pH in foodstuff concomitant to the addition of an organic acid.
49
Hsieh, Yi-ching, e 謝宜妌. "Three-Dimensional Metal-organic Hybrid Materials of Metals with Dicarboxylic Acids: 2-Amino terephthalic Acid, Terephthalic Acid,Oxalic Acid and Thiophene-2,5-dicarboxylic Acid". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/67840538538135951390.
Testo completoAbstract (sommario):
碩士國立中正大學
化學暨生物化學研究所
99
Using various dicarboxylates, namely 2-aminoterephthalate (N-BDC), terephthalate (BDC), Oxalate (Ox), thiophene-2,5-dicarboxylate (TDC), as bridging ligands to connect metal cations, led to the formation of a series of novel coordination polymers, which are {(Me2NH2)[In(TDC)2]•2(DMA)}n (1), {Ca2(TDC)2(DMA)2}n (2), {Nd2(BDC)3(DMA)2}n (3), {Na2Mn(TDC)2(DMF)2}n (4), {Yb3(NH2-BDC)4(NH3-BDC)(H2O)2．4DMA}n (5), {Mn(TDC)(DMA) }n (6), {(Me2NH2)[Sm(C2O4)(AcO)2] }n (7). Complex 1 is three-dimensional framework with two-fold interpenetration. Complexes 2, 3, 4, 5 , and 6 are three-dimensional frameworks, and complex 7 is two-dimensional framework. Besides, the fluorescent emissions for complexes 1, 2, 4 and 6 show an emission band due to intraligand emission, and complexes 3, 5, 7 exhibit a broad band, which can be attributed to ligand to metal charge transfer transition (LMCT). Finally, Powder X-ray diffraction patterns of complexes 1, 2, 3 and 4 have stable and robust porous frameworks, which show permanent porosity without any guest molecules in the pores.
50
WU, JUN-YI, e 吳俊毅. "Solid-Liquid Equilibrium for Binary Mixtures of Maleic Acid, Malonic Acid, Heptanedioic Acid, Nonanedioic Acid, Decanedioic Acid, 2,2-Dimethylsuccinic Acid, 2,3-Dimethylsuccinic Acid and 3-Methylglutaric Acid". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/s852sv.
Testo completoAbstract (sommario):
碩士中國文化大學
化學工程與材料工程學系奈米材料碩士班
105
We use the Differential Scanning Calorimetry ( DSC ) of the solid-liquid equilibria to measure the seven organic binary mixtures in the study ― maleic acid ( 1 ) + malonic acid ( 2 ) ,maleic acid ( 1 ) + heptanedioic acid ( 2 ) ,maleic acid ( 1 ) + nonanedioic acid ( 2 ) ,maleic acid ( 1 ) + decanedioic acid ( 2 ) ,maleic acid ( 1 ) + 2,2-dimethylsuccinic acid ( 2 ) ,maleic acid ( 1 ) + 2,3-dimethylsuccinic acid ( 2 ),3-Methylglutaric acid ( 1 ) + 2,3-dimethylsuccinic acid ( 2 ).The measured results from the seven set of organic binary mixtures are fitted using the Wlison. To demonstrate the measured result graphically, we employ Nonrandom Two-liquid Theory ( NRTL ) activity coefficient models that allow for further estimating the eutectic point (x1) and the eutectic temperatures (TE). The result shows us that the solids liquid equilibria for seven organic bianary mixtures were calculated by the Wilson and NRTL models ― maleic acid ( 1 ) + malonic acid ( 2 ) (x1=0.460 and 0.504, TE=347.53 K and 349.66 K, AADT less than 0.38 % ) ; maleic acid ( 1 ) + heptanedioic acid ( 2 ) (x1=0.331 and 0.327, TE=360.19 K and 360.82 K, AADT less than 0.27 % ) ; maleic acid ( 1 ) + nonanedioic acid ( 2 ) (x1=0.374 and 0.377, TE=366.91 K and 366.81 K, AADT less than 0.11 % ) ; maleic acid ( 1 ) + decanedioic acid ( 2 ) (x1=0.582 and 0.583, TE=38.27 K and 384.09 K, AADT less than 0.14 % ) ; maleic acid ( 1 ) + 2,2-dimethylsuccinic acid ( 2 ) (x1=0.504 and 0.506, TE=381.44 K and 380.89 K, AADT less than 0.15 % ) ; maleic acid ( 1 ) + 2,3-dimethylsuccinic acid ( 2 ) (x1=0.336 and 0.368, TE=361.55 K and 366.21K, AADT less than 0.20 % ) ; 3-Methylglutaric acid ( 1 ) + 2,3-dimethylsuccinic acid ( 2 ) (x1=0.549 and 0.529, TE=341.59 K and 341.47 K, AADT less than 0.11 % ) This studt provided reference for research of the data of solid liquid equilibrium and the basis reference data for industry segregation process.