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Jan, Mohamed Hamid Jan. "Iron absorption : control and oxidative stress." Thesis, King's College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444192.
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Kim, Yunji. "Meat Effects on Nonheme Iron Absorption." DigitalCommons@USU, 1991. https://digitalcommons.usu.edu/etd/5366.
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Studies were undertaken to investigate if gastric acidity and iron chelation to a meat component enhance nonheme iron absorption. Cereal meals, with and without added proteins, were gavaged into iron-deficient rats. The role of iron chelation was investigated by adding sodium phytate, an iron chelator implicated with decreased iron absorption, to the meals. The role of gastric acidity was investigated by treating the rats with cimetidine, which inhibits gastric acid production. In rats with normal acid production, beef, pork and chicken enhanced iron absorption when phytate had been added to the meals, suggesting a role for chelation in meat enhancement of iron absorption. However, the enhancement by beef and pork was insignificant in cimetidine-treated rats given the cereal + phytate meals, indicating that gastric acid production also plays a role in meat enhancement of iron absorption. Fish and egg white were sometimes inhibitory to iron absorption and, therefore, did not fit the pattern of enhancement demonstrated by beef, pork, and chicken. In a separate experiment, gastric acidity was not directly altered by the protein source included with cereal meals. No significant effects of the various proteins on iron absorption from cereal + phytate meals were observed in a final experiment involving iron-replete rats. In vitro iron solubilizing capacity of beef, pork, chicken, and egg white was positively correlated with enhanced iron absorption by iron-deficient rats.
Studies were performed to 1) investigate if ferric iron bound in complex with iron-solubilizing meat components is absorbable, 2) compare the relative iron-solubilizing capacity of meats, and 3) investigate the physicochemical and compositional characteristics of the meat components responsible for the iron solubilizing capability of meat. Iron-solubilizing components of beef were isolated from pH 2 HCl homogenates into dialysis bags (MWCO, 6-8 K). Radiolabelled iron complexes were then generated using ferric iron and either the ILC (isolated low-molecular-weight components) from undigested beef or ascorbate. The bioavailabilities of radioiron in these complexes or as ferric iron were measured as radioiron absorption into the blood one hour after injection into ligated duodenal loops of rats. Iron absorption values were ascorbate-ferrous complexes > beef ILC-ferric complexes > ferric iron (p < .05). In separate experiments, ILC from 0.1 g of various dietary protein sources (beef, pork, chicken, fish, or egg white) were added to 400 μg ferric iron in pH 2 HCl, the pH raised to 7.2, and soluble iron determined in the supernatant after centrifugation at 2,500 g for 10 min. Iron solubilizing capabilities of ILC were pork > beef > chicken > fish > egg white (p < .05). In a final series of experiments, the compositional and physicochemical characteristics of the ILC from the various dietary proteins were investigated.
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Hutchinson, Carol. "Iron absorption and serum non-transferrin bound iron in humans." Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429314.
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Storcksdieck, Stefan. "Dietary factors influencing non-heme iron absorption /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16795.
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Wawer, Anna. "Strategies to improve non-haem iron absorption." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48744/.
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Iron deficiency anaemia is one of the most prevalent nutritional deficiency disorders in the world. Food iron fortification is a widely used strategy to reduce the risk of deficiency but presents a major challenge to the food industry. The more bioavailable forms of iron, such as ferrous gluconate, cause adverse organoleptic changes when added to foods. The primary aim of the work described in this thesis was to test whether alginate would bind soluble forms of iron and thereby maintain its bioavailability. Initial in vitro studies demonstrated that alginate solutions and beads loaded with ferrous gluconate delivered iron in an available form for uptake into Caco-2 cells (measured by ferritin formation). A human study was undertaken to assess the bioavailability of ferrous gluconate in alginate beads, and it was found to be significantly lower than ferrous gluconate on its own, so further in vitro studies were undertaken to examine possible reasons for the inhibitory effect of the beads. It was concluded that alginate beads, containing calcium as a gelling agent, are not an effective delivery vehicle for soluble iron compounds. However, these findings should not rule out the potential use of alginates as a delivery system for iron, especially in diets containing high levels of phytate. Other related work reported in this thesis includes studies of iron availability from two wheat cultivars with varying phytate and iron concentrations, potential use of nicotianamine and 2'- deoxymugineic acid as iron enhancers, and investigations into calcium-iron interactions in a Caco-2 cell model, with the use of live cell imaging techniques and confocal microscopy.
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Shiono, Yuhta, Hisao Hayashi, Shinnya Wakusawa, et al. "Body iron stores and Iron restoration rate in Japanese patients with chronic Hepatitis C as measured during therapeutic Iron removal revealed neither Increased body iron stores nor effects of C282y and H63d mutations on iron indices." Nagoya University School of Medicine, 2001. http://hdl.handle.net/2237/5367.
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Shears, G. E. "Haem and non-haem iron absorption and their regulation." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383814.
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Cook, W. B. "Iron absorption in health and inflammatory bowel disease." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597923.
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Chapter 1 provides a general introduction while Chapter 2 investigates the relationships between dietary iron intake, disease activity and quality of life (QOL) in patients with IBD. Results indicated that non-haem iron intake was significantly associated with iron requirements for IBD patients but not healthy controls. Interestingly, for iron replete IBD patients, a significant positive correlation between iron intake and disease activity was noted. Correlation between QOL and iron intake was also observed. Chapter 3 investigated the acute effects of a single oral dose of ferrous sulphate on (i) iron absorption into serum and (ii) systemic nontransferrin bound iron (NTBI) generation. It also investigated whether baseline haematinics are an appropriate indicator of iron requirements in IBD subjects. Overall, iron absorption did not differ between IBD patients and healthy controls and both groups showed a similarly significant rise in NTBI following supplementation. However, in healthy controls baseline haematinics predicted iron absorption (i.e. iron requirements) but not in patients with IBD. Chapter 4 reports a laboratory-based investigation on the ability of different organic acids (OA) to alter the precipitation and redissolution properties of insoluble ferric hydroxide. The aim being to identify potential OA’s for use in a novel ferric iron supplement. Results showed that malic acid had significant effects on the precipitation and redissolution of ferric iron and may be efficacious as an iron supplement. Finally, in Chapter 5, <i>in vivo</i> testing of selected iron-organic acid mixtures was undertaken in human volunteers comparing the absorption to ferrous sulphate. Results showed that these were reasonably absorbed, albeit to a lesser extent than ferrous sulphate. Further work could trial these in IBD as side effects should be minimised while at least some iron would be absorbed.
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Sattarzadeh, Masoud. "Determination of iron & iodine absorption from iron and iodine double-fortified salt." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq28793.pdf.
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Leong, Weng-In. "Regulation of iron absorption during infancy and iron transfer to milk during lactation /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Tidehag, Per. "Iron absorption and iron status related to diet an experimental and epidemiological study /." Doctoral thesis, Umeå, Sweden : Dept. of Nutritional Research and Prosthetic Dentistry and the Biophysics Laboratory, Umeå University, 1995. http://books.google.com/books?id=f9BpAAAAMAAJ.
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Ummadi, Madhavi. "Uptake, Absorption, and Adsorption Kinetics of Ferrous and Ferric Iron in Iron-replete and Iron-deficient Rats." DigitalCommons@USU, 1994. https://digitalcommons.usu.edu/etd/5409.
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Various concentrations of ferrous and ferric iron solutions were held at room temperature for 60 min before they were assayed for ferrous iron, which may be unstable due to oxidation. The ferrous and ferric solutions (in pH 2 HCl) were maintained as such for 60 min without the use of chelators. There was no significant oxidation of ferrous iron. Also, four different levels of each ferrous and ferric iron were injected into proximal duodenal loops of rat intestine and uptake was determined at four different time intervals. Two iron-replete rats were assigned to each of the treatments. The in situ experiments showed that iron was taken up rapidly from pH 2.0 solutions of ferrous and ferric iron. Maximum amount of iron was taken up in the first 10 min. Uptake of ferrous iron was significantly greater (p < 0.05) than uptake of ferric iron, and there were significant differences in total uptake among the four iron levels used.
Uptake, absorption, and adsorption kinetics of both ferrous and ferric iron were determined in situ for both iron-replete and iron-deficient rats. Deficiency caused greater uptake and absorption, confirming a biological adaptation of these processes. Both uptake and absorption were greater for ferrous than for ferric iron and were possibly taken up by different pathways or by a ferrous-ferric pathway with preference for ferrous. Uptake and absorption kinetics were biphasic for both ferrous and ferric iron. The first phase demonstrated saturation kinetics and was followed by a nonsaturable phase at higher concentrations of luminal iron. Iron deficiency altered the uptake and absorption kinetics of ferrous and ferric iron, but not always in a similar manner, suggesting that ferrous and ferric iron were each taken up by a separate pathway. Indications were that enhanced absorption during deficiency was largely due to adaptation of ferric uptake. Iron adsorption was directly proportional to luminal iron concentration, but it was greater for ferric than for ferrous, possibly due to charge interactions. Iron deficiency caused increased adsorption of both ferrous and ferric iron, supporting the notion that adsorption acts to maintain iron in a form available for uptake.
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Oti-Boateng, Peggy. "Effects of dietary calcium on intestinal non-haem iron absorption during weaning." Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09pho881.pdf.
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Corrigenda tipped to title page. Bibliography: leaves 313-353. This study investigated the iron status and dietary intakes in 6-24 month old children in Australia and Ghana and assessed the effects of dietary calcium on intestinal iron absorption. The true prevalence of non-anaemic iron deficiency (NAID) and iron deficiency anaemia (IDA) and dietary intakes in infants and toddlers from a broad socio-economic background were assessed by haematological and biochemical parameters, semi-quantitative diet recall and anthropometric measurements. The high prevalence of iron deficiency and anaemia found in Australian and Ghanaian children can be attributed to the low intake of bioavailable iron in weaning diets which are often ingested with large amounts of calcium. While calcium has been shown to inhibit the absorption of iron, its mechanism of interaction with iron absorption at the intestinal level is not known. The rat was used as an experimental model to investigate the effects of dietary calcium on duodenal iron uptake. The results indicate there is a critical period during weaning when the consumption of high dietary calcium with low iron can retard growth potential. Dietary calcium significantly inhibits non-haem iron absorption at the intracellular level by up-regulating villus enterocyte ferritin concentrations under iron deficiency conditions.
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Thomas, Carla. "The validation and use of the rat intestinal epithelial cell line 6 (IEC-6) to study the role of ferroportin1 and divalent metal transporter 1 in the uptake of iron from Fe(II) and Fe(III)." University of Western Australia. Physiology Discipline Group, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0019.
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[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Iron is vital for almost all living organisms by participating in a wide variety of metabolic processes, including oxygen transport, DNA synthesis, and electron transport. However, iron concentrations in body tissues must be tightly regulated because excessive iron leads to tissue damage, as a result of formation of free radicals. In mammals since no controlled means of eliminating unwanted iron has evolved, body iron balance is maintained by alterations in dietary iron intake. This occurs in the duodenum where most dietary iron is absorbed. Absorption involves at least two steps, uptake of iron from the intestinal lumen and then its transport into the body, processes that occur at the apical and basal membranes of enterocytes, respectively. In chapter one of this thesis the background information relevant to iron absorption is described. Despite numerous studies, the role of these proteins in iron absorption remains unclear, partly because many studies have reported them in non-enterocyte cell lines where the expression of the proteins involved in iron absorption is unlikely and therefore the physiological significance of the findings uncertain. Therefore, the study of iron absorption would value from additional cell lines of intestinal origin being used, preferably derived from a species used to comprehensively study this process in vivo, namely the rat. Validation of such a model would enable comparisons to be made from a molecular level to its relevance in the whole organism. In chapter 3 of this thesis, the rat intestinal cell line 6 (IEC-6) was examined as a model of intestinal iron transport. IEC-6 cells expressed many of the proteins involved in iron absorption, but not the ferrireductase Dcytb, sucrase or αvβ3 integrin. In addition, in IEC-6 cells the expression of the apical transporter divalent metal transporter 1 (DMT1), the iron storage protein ferritin, the uptake of Fe(II) and Fe(III) were regulated by cellular iron stores as is seen in vivo. This suggests that IEC-6 cells are of a lower villus enterocyte phenotype. Presented in chapter 4 is the study of the uptake of iron from Fe(II):ascorbate and Fe(III):citrate by IEC-6 cells in the presence of a blocking antibody to the putative basolateral transporter ferroportin1 and of colchicine and vinblastine, different pHs, and over-expression of DMT1. It was shown that optimal Fe(II) uptake required a low extracellular pH and was dependent on DMT1. Uptake of Fe(III) functioned optimally at a neutral pH, did not require surface ferrireduction, and was increased during over-expression of DMT1. These observations suggest that intravesicular ferrireduction takes place before transport of Fe(II) to the cytoplasm by DMT1. This pathway was not blocked by a functional antibody against αvβ3 integrin but was inhibited by competition with unlabeled iron citrate or citrate alone. Surprisingly, a functional antibody against ferroportin1 had no effect on efflux but significantly reduced (p<0.05) uptake of Fe(II) by 40-50% and Fe(III) by 90%, indicating two separate pathways for the uptake of iron from Fe(II)-ascorbate and from Fe(III)-citrate in IEC-6 cells. Presented in chapter 5 is the development and validation of a technique for the removal of freshly isolated enterocytes from the rat duodenum and their use to study iron transport processes that enabled comparisons to be made between these cells, IEC-6 cells and the human enterocyte cell line Caco-2 cells. In chapter 6 a blocking antibody to ferroportin1 was shown to inhibit uptake of Fe(II) but not release of iron in freshly isolated duodenal enterocytes from rats and Caco-2 cells supporting the findings obtained with IEC-6 cells described in chapter 4. Fe(II) uptake was reduced only when the antibody was in contact with the apical membrane indicating its expression at the microvillus membrane. Confirming this, ferroportin1 was shown along the microvillus membrane of Caco-2 cells, in enriched microvillus membrane preparations and in enterocytes of duodenum tissue of rats where it co-localised with lactase. The significant findings to emerge from this thesis are that the IEC-6 cell is a valid model to study iron absorption producing results consistent with those found in freshly isolated enterocytes and in human enterocyte-like cells. In particular, ferroportin1 functions in the uptake of iron at the apical membrane possibly by modulating surface binding of Fe(II) to DMT1 or the activity of DMT1. In addition to this in Fe(II) uptake from Fe(III) ferroportin1 may also affect the number of Fe(III): citrate binding sites. Preliminary studies further characterizing the function of ferroportin1 at the apical membrane and at intracellular sites of IEC-6 cells along with integration of these data are discussed in chapter 7.
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Zhang, Fan. "Iron absorption and regulatory mechanisms: effects of fructooligosaccharide and other prebiotics." HKBU Institutional Repository, 2017. https://repository.hkbu.edu.hk/etd_oa/413.
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Iron deficiency is the most prevalent nutrient deficiency in the world, leading to long-term developmental and health consequences in populations at risk. Also known as prebiotics, non-digestible oligosaccharides such as fructooligosaccharide (FOS), inulin, galactooligosaccharide (GOS) and lactulose resist digestion by gastric acid and pancreatic enzymes in vivo, but are preferentially fermented by beneficial intestinal bacteria once they reach the colon. Prebiotics have been shown to increase the absorption of minerals such as iron from diets, but results from studies reported in the literature at times are contradictory, and mechanisms involved are still unclear. A better understanding of the role of FOS and other prebiotics in iron absorption may lead to new dietary modification strategies to increase intake of iron absorption enhancers in plant-based diets. The objectives of this study were therefore to determine the effects of prolonged FOS, as well as Synergy 1 (a combination of long- and short-chain FOS), inulin, GOS and lactulose supplementation on iron status of anemic rats; and to assess the enhancing effects of FOS on iron absorption and elucidate the regulatory mechanism involved using the Caco-2 cell culture model. In our animal studies, male Sprague-Dawley rats were first fed a low-iron diet for 14 days prior to prebiotics supplementation to achieve an iron-deficient status. Rats receiving the low-iron diet (12 ppm Fe) showed significantly lower non-heme iron concentrations in liver, spleen and kidney, as well as lower hemoglobin level than rats receiving a normal diet (45 ppm Fe), confirming iron-deficiency anemia. At the onset of the feeding trials, anemic rats were further divided into groups with or without supplementation of prebiotics. Prebiotics were provided to the rats by dissolving in water at 5% (w/v). Rats were kept on their respective test diets for 28 or 35 days, and all had free access to food and water during the feeding trials. The results showed significantly higher hemoglobin and non-heme iron levels in anemic rats with FOS or GOS supplementation, suggesting that both FOS and GOS could have positive effects on the iron status of anemic subjects with a low-iron intake. Rat colon contents also showed significant changes in short-chain fatty acid (SCFA) concentrations, presumably due to fermentation of prebiotics by intestinal microflora. Changes in the expression of Duodenal cytochrome b (Dcytb) and Divalent metal transporter 1 (DMT-1) in Caco-2 cells were measured by Western Blot and Real Time PCR. Our results confirmed that Caco-2 cells 14 days post confluence provided a stable research model for gene expression studies related to iron absorption. At low iron level, especially with FOS or SCFA supplementation, Dcytb and DMT-1 expression levels were increased in Caco-2 cells. While at high iron level, expression of Dcytb or DMT-1 was mostly down-regulated. Effects of SCFA were much more pronounced than FOS at different iron concentrations, suggesting that any effects of dietary FOS on improving iron status would require fermentation by the intestinal microflora. Further studies on other prebiotics (e.g., GOS and lactulose) and different combinations of SCFA are warranted.
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Frazer, David Michael. "The molecular basis of intestinal iron absorption and its regulation /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17396.pdf.
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Raja, K. "Studies on the mechanism and regulation of intestinal iron absorption." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383490.
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Swindell, T. E. "Dietary and physiological factors influencing iron absorption in the rat." Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381746.
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Shirali, Sima. "Regulation of duodenal iron absorption and role of haem biosynthesis." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397799.
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Ahmad, Fuzi Salma F. "The effect of dietary components on non-haem iron absorption in healthy and iron-deficient women." Thesis, University of Chester, 2017. http://hdl.handle.net/10034/620397.
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Two clinical trials investigating the effect of modulating two dietary components, tea containing polyphenols and vitamin D aimed at improving non-haem iron absorption and iron status recovery, were carried out in a cohort of healthy and iron deficient UK women, respectively. Tea has been shown to be a potent inhibitor of non-haem iron absorption but it remains unclear whether the timing of tea consumption relative to a meal influences iron bioavailability, with limited published evidence, especially in human trials. The aim of the first study was to investigate the effect of tea consumption on non-haem iron absorption and to assess the effect of time interval of tea consumption on non-haem iron absorption relative to an iron-containing meal, in a cohort of healthy female participants using a stable iron isotope (57Fe).
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Laftah, Abas Humood. "Role of haem biosynthesis in the regulation of intestinal iron absorption." Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249734.
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Solanky, Nita Shantilal. "The molecular mechanisms of duodenal and placental iron absorption during pregnancy." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1446479/.
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During pregnancy duodenal iron absorption, placental transfer, and the release of iron from stores in the mothers liver, are increased to meet the requirements of the developing foetus. The regulatory mechanisms co-ordinating these events are for the first time illustrated here. Various proteins, notably hepcidin and hfe, have been implicated as having a role in iron homeostasis. By quantitating the expression of hepcidin and the duodenal iron transporters: DMT1, Tfr1, Dcytb and Ireg1, in mice raised on iron-deficient and iron-loaded diets, this study confirms that hepcidin expression is positively regulated by body iron status and negatively regulates duodenal DMTI. A parallel study in hfe knockout mice, demonstrates inappropriately low hepcidin expression and elevated duodenal DMT1 levels. This provides a possible explanation for the liver iron loading characteristic of hereditary haemochromatosis. The expression of hepcidin is studied in pregnant rats and is shown to decrease during the final trimester when duodenal and placental iron transfer is maximal. This decrease is preceded by a reduction in liver iron stores and subsequent reduction in hepcidin expression. Iron supplementation to pregnant dams, increases liver iron status and hepcidin expression, this corresponds with a decrease in duodenal and placental DMT1 expression, whilst iron deficiency during this period, increases both duodenal and placental uptake. This implies that the increase in duodenal iron absorption observed during pregnancy is, at least in part, a consequence of reduced liver iron stores. Using an in vitro model of the placental syncytiotrophoblast, DMT1 is localised to endosomal compartments, but not co-localised with either Tfr1 or Ireg1. Hepcidin is demonstrated to bind to the plasma membrane of these cells and reduce the uptake of diferric-transferrin. These results provide new insight into the molecular processes of iron homeostasis and implicate a regulatory role for hepcidin, not only in duodenal, but also in placental iron uptake.
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Pointon, Jennifer Jane. "The genetics of haemochromatosis." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249468.
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Moberg, Wing Anncatherine. "Absorption and accumulation of cadmium from cereal grains." Doctoral thesis, Umeå universitet, Patologi, 1993. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100549.
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Cadmium (Cd) is a potentially toxic trace element. Cereal grains contribute one-third to one-half of the Cd exposure via the diet. Among cereal grains, wheat generally contains the highest Cd concentration and the bran and germ fractions contain more Cd than the endosperm. An increase in the consumption of unrefined grains may cause an increase in the body burden of Cd if an increase in the exposure to Cd via the diet leads directly to increased Cd absorption and accumulation. However, there is evidence that certain factors may reduce the availability of Cd for absorption from the diet. The purposes of these studies were to refine an atomic absorption spectrometric method for measuring the accumulation of Cd from diets with low, naturally occuring concentrations of Cd, to evaluate the extent to which Cd is accumulated from different milling fractions of wheat and from different cereal grains, and to determine to what extent the presence of certain minerals and mineral-binding factors in the diet and the iron (Fe) status of the individual affect Cd accumulation from cereal grain diets. The results of the method studies showed that the amount of Cd in the liver and kidneys of rats after six weeks on different diets and the retention of 109Cd in these organs three weeks after the ingestion of 109Cd-labelled test meals of the diets were in agreement on the fractional and total accumulation of Cd from the diets. To a first approximation, the accumulation of Cd in the liver and kidneys in rats appears to be the product of the separate effects of the concentration of Cd in the diet which is available for absorption and the Fe status of the rats. The Cd concentration in grains varied by a factor of five between whole wheat and rye and the amounts of Cd accumulated in rats from diets with whole grains were nearly proportional to the Cd concentrations in the grains. The fractional accumulation of Cd was lower in rats given diets with whole grains or wheat fractions high in fiber and phytic acid than in rats fed endosperm wheat diets. This lower fractional Cd accumulation did not compensate for the high Cd concentrations in whole wheat and wheat bran. The fractional accumulation of Cd in the liver of rats is inversely related to their Fe status. The fractional Cd accumulation in the liver of rats with low Fe status was as much as ten times that in rats with high Fe status. The Cd accumulation in the kidneys appears to be even more sensitive to Fe status. The accumulation of Cd in human placenta supports these conclusions. Women who eat diets with less cereal grain fiber and who also maintain their Fe stores during pregnancy generally accumulate less Cd in the placenta than those who eat more grain fiber and/or have lower Fe status. On the basis of these results, it is recommended that as much as possible of the dietary fiber from cereal grains should derive from grains with low Cd concentrations. It is also imperative that the diet provide sufficient Fe and other nutrients to promote Fe status and thereby limit Cd accumulation.<br><p>Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 5 uppsatser.</p><br>digitalisering@umu
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Barrett, Jon Fenton Roy. "Stable isotopes and the absorption of non-haem iron during human pregnancy." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308775.
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Barrow, Dalna Michelle. "The characterization of two novel genes involved in mammalian intestinal iron absorption." Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409577.
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Chakraborty, Rupak. "Investigation of sub-bandgap absorption in iron pyrite : optical and electrical measurements." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87956.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 67-70).<br>We investigate sub-bandgap absorption in pyrite FeS₂ single-crystals, using both natural and synthetic crystals. Both types of crystals show non-negligible magnitudes of sub-bandgap absorption. To test whether the origin of the residual sub-bandgap absorption is partially due to a lower bulk bandgap than previously thought, we conduct temperature-dependent electrical measurements on natural and synthetic crystals. Unlike previous measurements on pyrite, our electrical measurements are done in a sulfur atmosphere to avoid FeS formation. Using conductivity data in the intrinsic regime along with extrapolated Hall mobility data, the extracted bandgap is more than 0.1 eV lower than the literature value of 0.95 eV. However, higher-temperature Hall data are needed to gain a more reliable bandgap estimate.<br>by Rupak Chakraborty.<br>S.M.
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Kolesov, Roman L. "Optical control of nuclear resonant absorption: theory and experiment." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/380.
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Modification of nuclear resonant absorption by means of laser radiation is analyzed both theoretically and experimentally. Theoretical analysis is done on the basis of four-level model of atom. This model includes both electronic and nuclear excitations. It is predicted that under coherent laser driving nuclear resonant Mossbauer absorption can be significantly modified, e.g. new Mossbauer resonances can appear, some of the existing resonances can vanish, both can be Rabi-split, broadened by laser action. In addition, it is predicted that Mossbauer absorption can be completely suppressed due to coherent population trapping. Experimental observation of laser-induced transformations of Mossbauer spectra of 57Fe2+ : MgO is accomplished. New Mossbauer lines appear with laser driving while the existing are broadened. Possible explanations of the observed changes in 57Fe2+ : MgO Mossbauer spectra are population of higher-lying electronic states of iron ion and significant modification of electronic relaxation processes due to modified Jahn-Teller interaction.
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Snape, Susan Dawn. "Studies on the mechanism of intestinal iron absorption with special reference to its intracellular transport." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254664.
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Wallace, Daniel Frederick. "The HFE gene in haemochromatosis and liver disease." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325304.
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Abd, Rashed Aswir. "The influence of dietary components on non-haem iron absorption by in vitro study." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551153.
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Dietary components have been known for many years to have a variable effect on non-haem iron uptake in humans. Since it is impractical and expensive to employ in vivo methods for iron uptake, in this study, a human intestinal Caco-2 cell line was utilised for investigation of the effect of dietary components on non-haem iron uptake. Using a radioactive iron isotope 55Fe, it is possible to observe iron uptake activity in Caco-2 cell whether or not the dietary components are present in the media. Several dietary components including ascorbate, J3-carotene, amino acids, organic acids and two types of polyphenols (rutin dihydrate and catechin dihydratejincreased iron uptake in Caco-2 TC7 cells. In contrast, phytate and zinc reduced iron uptake, and vitamin E showed no effect on iron uptake. Interestingly, effects of ascorbate, zinc and phytate on iron uptake were found to follow Michaelis-Menten equation. Fe(III) reduction was measured by analysing the formation of Fe(II) via the spectrophotometric measurement of Fe(II)-bathophenanthrolinedisulfonic acid. Ascorbate and J3-carotene had a significant effect on the reduction of Fe(III) to Fe(II), thereby increasing the aqueous solubility of iron. This study model also sheds some light on the potential capability of p-carotene to reduce Fe(III) before Fe(II) is taken up by the cells. Western blotting was used to study the effect of dietary components on the transporter proteins (DMTI and Iregl) levels. Western blotting demonstrated that most of the amino acids and organic acids tested were able to reduce the expression of membrane DMTI levels. On the contrary, zinc and phytate caused a significant increase effect in membrane DMTI levels (p<-O.05) but ascorbate had no effect in membrane DMTJ levels. Ireg1 was significantly increased in the presence of phytate in the medium but there was no effect of ascorbate, B-carotene and zinc on Ireg1. These findings provide evidence that although membrane DMT I levels responded to the addition of selected dietary components in the medium, most if not all had no effect on Ireg1 expression. The results suggest that the effect of dietary components on iron transporters is merely a mucosa) block phenomenon, where the first step of iron uptake is regulated by DMTJ. In addition, the effects of ascorbate are not simply on the reduction and chelation of iron, but also on the transporter protein DMTI itself.
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Mantalidi, A. "Understanding the formation of gold and iron based nanomaterials using X-ray absorption spectroscopy." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1530968/.
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In this thesis, X-ray Absorption Spectroscopy (XAS) is used to understand the speciation of molecular precursors in various reaction mixtures, elucidate potential effects on their structure from the presence of solvents and other reagents present, and monitor in situ their thermal decomposition leading to nanoparticle formation. XAS is a prominent technique for determining the local structure and oxidation state of an element of choice. Since long range order is not a requirement for XAS to be applied, it constitutes an ideal technique to study materials in solution phase. Chapter 1 provides a brief background of the key points in history that marked the commencement of the science of nanotechnology, as well as some of their important properties. An introduction on the general synthetic strategies of nanoparticles follows, focusing on the two main chemical methods that were employed in this thesis; the chemical reduction and the thermal decomposition. A background of the evolution of the Au nanoparticle syntheses is provided, followed by the latest developments in the field that involves the synthesis of anisotropic Au nanoparticles. Similarly to Au nanoparticles, a detailed literature survey on the synthesis methods of iron oxide nanoparticles is presented, focusing on the thermal decomposition route which is the synthesis of choice for the work undertaken in Chapter 6, accompanied by a small section devoted to the stabilisation methods of these nanomaterials. Chapter 2 discusses the basic theory of the laboratory and synchrotron based characterisation techniques that were utilised in this thesis. Special emphasis is given to XAS, as that is the key technique of this work. As a result, XANES and EXAFS are discussed in detail, and the data analysis procedure is also presented, due to its importance and extensive use in this thesis. The studies of Chapter 3 are focused on the speciation of [AuCl4]- in aqueous growth solutions, that upon addition of Au nanoparticle seeds, leads to the formation of Au nanoparticles with different morphologies. Since these growth solutions contain several reagents, this study addresses the effect of each reagent on the ligand environment and oxidation state of Au under realistic reaction conditions. For that purpose, ex situ studies were performed at the Au L3-edge upon stepwise addition of the reagents, and at the Ag k-edge whenever Ag+ was added to the growth solution. The studies at the Ag K-edge probed the effect of the growth solutions on the silver environment too. Ex situ XAS characterisation of the Au nanoparticles at the Au L3-edge and Ag K-edge was also performed, providing valuable information of the coordination and oxidation state of Ag at the final nanoparticles, which is a highly researched topic nowadays. Chapter 4 presents the results from the in situ XAS studies on Au nanoparticle formation in ethylene glycol, in the presence and absence of the particle stabilizer polyvinylpyrrolidone. The results revealed that the particle stabiliser has a retarding effect on the nucleation of the Au nanoparticles but also affects the final particle size. It was also illustrated that beam effects alter the specific decomposition process through interaction of the X-ray beam with the solvent. The studies illustrated in Chapter 5 investigate the structure and synthesis of Au-Pd bimetallic nanoparticles, and the speciation of the starting precursors. Initially, the ex situ characterisation of Au-Pd nanoparticles synthesised by two different syntheses is illustrated. The syntheses are performed in oleylamine/xylene, through the concomitant thermal decomposition of Au and Pd containing molecular precursors. The nanoparticles in the first case were prepared using Au(ethynyl-1-cyclohexanol) and [Pd(acac)2], while in the latter case, phase transferred [AuCl4]- and [Pd(acac)2] were used. Notably, the Au(ethynyl-1-cyclohexanol) precursor was used for the first time in the synthesis of Au-Pd bimetallic nanoparticles. The Au-Pd nanoparticle syntheses were investigated by in situ XAS to address the impact of the change of the Au precursor on the synthesis. Regarding the speciation of the starting materials, the results revealed that the structure of [Pd(acac)2] is dependent on the molar ratio of Pd to oleylamine, while the [AuCl4]- undergoes two structural changes prior to being reduced to the metallic state. The thermal decomposition of [Fe(acac)3] to iron oxide nanoparticles was investigated by in situ XAS for the first time, and the results are presented in Chapter 6. The decomposition of [Fe(acac)3] was studied in oleylamine, and in triethylene glycol in the presence and absence of polyvinylpyrrolidone. The role of the solvent was probed through XANES and LCF analysis, and was proven to be crucial since the decomposition profile of the precursor in these reactions varied considerably. In addition, the speciation was probed by EXAFS, and revealed that oleylamine induces changes to the precursor’s structure.
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Aslam, Mohamad Farshard. "The efficacy of nanoparticulate iron in correcting anaemia and its mechanisms of intestinal absorption." Thesis, University of Cambridge, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709354.
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Stacey, Rebecca Jane. "Lipid residues from late Iron Age pottery : patterns and processes in their absorption and preservation." Thesis, University of Bradford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516719.
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Kakpovbia, A. E. "Kinetics of the oxidative absorption of H2̲S from gas streams by Iron chelate solutions." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380598.
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Heuvel, Elisabeth Gertruda Hendrika Maria van den. "Application of dual stable isotope techniques to measure absorption of calcium, magnesium and iron in man." [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1998. http://arno.unimaas.nl/show.cgi?fid=8251.
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Shawki, Ali. "The Functional Properties and Intestinal Role of the H+-Coupled Divalent Metal-Ion Transporter 1, DMT1." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037106.
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Krauth, Oliver. "Investigation of the surface enhanced infrared absorption in the case of carbon monoxide on iron thin films." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=961929510.
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Jin, Ji-yun. "Boron chemistry in selected Virginia soils and hydroxy aluminum and iron systems." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54304.
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Greenhouse and laboratory experiments were conducted to investigate the distribution of native B, the availability of native and applied B in 14 Virginia soils and the specific reactions of B in soil and hydroxy Al and Fe systems.
Total B in the 14 soils ranged from 21.5 to 96.3 mg kg⁻¹. Only a small portion of the total B was in soil solution, non-specifically and specifically adsorbed forms and Mn minerals. These fractions of B are readily available to plants. A large part of the total B was associated with non-crystalline and crystalline Al and Fe minerals and soil silicates. These forms of B contribute little to B absorption by plants. Hot water soluble B, NH₄-acetate extractable B, mannitol exchangeable B and Mehlich III extractable B from the soils closely correlated with the concentrations in corn plants from native B in the greenhouse experiment. A yield response of corn plants to B application did not occur on the soils.
Both tissue B concentration from applied B and maximum B adsorption by the soils closely correlated with soil clay, hydroxylamine hydrochloride extractable Mn and NH₄—oxalate (pH 3.25) extractable Al and Fe (under UV light). These data indicated that soil clay and Al-, Fe- and Mn-oxides and hydroxides have high affinities to adsorb B in plant unavailable forms.
Boron adsorption on both gibbsite and goethite was pH and temperature dependent. At pH 6.5, boric acid was major species in the system and B was absorbed by the negatively charged surface of gibbsite and the positively charged surface of goethite. At pH 10, borate was primarily species in the system and B was adsorbed on negatively charged surfaces of both minerals. Boron adsorption was greater at pH 10 than at pH 6.5. An increase in temperature increased B adsorption on both minerals at both pH levels. This indicated that the B adsorption was an exothermic process. Boron adsorption on gibbsite and goethite shifted the ZPC of the minerals downward. This verified that specific B adsorption occurred on the surfaces. Aluminum substitution in goethite increased the affinity of the surface for B adsorption.<br>Ph. D.
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Dahl, Evelina, and Ida Berge. "Dietary factors and food preparation techniques related to iron absorption : Knowledge and practice in the Kandal Province, Cambodia." Thesis, Umeå universitet, Institutionen för kostvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-49283.
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Introduction Malnutrition and coexisting micronutrient deficiencies are common in the developing world. A high prevalence of anemia is found in Cambodia with children and women being the most affected. Anemia is defined as lack of red blood cells, resulting in impaired blood function and poor oxygen transport. Iron deficiency (ID) is often an underlying factor of anemia. Diet modifications to increase intake and absorption of iron can to some extent prevent iron deficiency anemia (IDA), which is often caused by lack of iron in the diet. Objective The aim was to study knowledge and practice regarding food preparation techniques and dietary factors related to iron absorption in Kandal Province, Cambodia. Method Structured interviews based on a written questionnaire consisting of 17 closed questions were conducted in eight villages in Kandal Province, Cambodia. A total of 143 questionnaires were collected for analysis. Chi-square tests were performed using SPSS 18.0 and the significance level was set to p<0.05. Results The food habits showed lack of diversity. The diet was mainly rice based and red meat consumption was low. The majority used an iron pot for cooking, although not many knew that it could enhance the iron content in the food. The knowledge on bioavailability of iron appears to be limited. A significant correlation was found between those who had received information on iron and those who stated that red meat is a good source of iron(p=0.046). Conclusion Knowledge on food preparation techniques, dietary sources of iron, stimulating- and inhibiting factors for iron absorption appears to be limited. Interventions including education on bioavailability and how to enhance the iron content in the diet are important and they should be adapted to the local community.<br>Bakgrund I utvecklingsländer är malnutrition och brister på mikronutrienter vanligt förekommande. En hög prevalens av anemi kan ses i Kambodja, framförallt hos kvinnor och barn. Anemi definieras som otillräckligt med röda blodkroppar, vilket orsakar dålig syretransporterande förmåga och blodfunktion. En vanlig orsak till anemi är järnbrist, vilket ofta är en följd av lågt intag av järn i kosten. Förändringar i kosten som leder till ett ökat intag och en ökad absorption av järn kan till viss del förhindra järnbrist. Syfte Att undersöka matlagningstekniker och kostfaktorer relaterade till järnabsorptionen samt kunskaper och vanor angående detta i Kandalprovinsen, Kambodja. Metod Strukturerade intervjuer utfördes i åtta byar i Kandalprovinsen, Kambodja. Dessa baserades på en kvantitativ enkät bestående av 17 slutna frågor. Totalt samlades 143 enkäter in för analys i SPSS 18,0. Chi-tvåtest användes för att testa skillnader mellan grupper och signifikansnivån bestämdes till p < 0,05. Resultat Måltidsmönstren visade på en ensidig konsumtion av livsmedel. Kosten var risbaserad och konsumtionen av rött kött var låg. Majoriteten av respondenterna tillagade sin mat i järngryta, däribland visste en liten andel att detta kunde höja järninnehållet i maten. Kunskaper om järnets biotillgänglighet tycks vara låga. Ett signifikant samband sågs mellan de som fått järninformation och de som valde rött kött som en god källa till järn (p=0,046). Slutsats Kunskaperna om matlagningstekniker, goda källor till järn, stimulerande och hämmande faktorer för järnabsorptionen förefaller vara begränsade. Interventioner baserade på utbildning i hur man kan förbättra järninnehållet i kosten är av stor vikt och bör anpassas till respektive samhälle.
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Kaspar, Jennifer Deloris. "Evaluating the extent of delocalization in mixed-valence iron dimers using X-ray absorption near-edge structure spectroscopy /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Pountney, David James. "Studies of the mechanism and regulation of intestinal iron absorption with special reference to a mucosal surface reducing activity." Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339140.
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Zweigel, Catarina. "Validering av metoder för analys av Cu, Fe och Na i processvatten med AAS-grafitugn." Thesis, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-20631.
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<p>Södra Cell Mörrum is one of the five paper pulp plants that are included in Södra Cell, and the paper pulp that is produced here is not only sold to Swedish paper mills. Most of the paper pulp is exported to different countries in Europe. In the manufacturing process the plant needs different kind of process water and there are guideline values for how much copper, iron and sodium this water is allowed to contain. Analyzes of this water is in the current situation done with an atomic absorption spectrometric instrument (AAS-instrument) with a flame.</p><p> </p><p>Measurements done with flame-AAS of samples that have concentrations near the guideline values for copper, iron and sodium, are not reliable. The reason for not being reliable is that the quantitation limits of these metals are higher than the limit values. An alternative method that should give more reliable values is to analyze with an AAS- instrument with a graphite furnace. The purpose of this project was to perform a method validation of the graphite furnace of the AAS-instrument in the analysis of Cu, Fe and Na. The focus of the project was to find the detection limits for each metal, study the variation and to see if it is possible to analyze these water samples with this technique.</p><p> </p><p>The concentrations of the calibration solutions is between 1-10 µg/l for Na, 5-25 µg/l for Cu and 2-20 µg/l for Fe.The detection limits for all metals were slightly below 1 µg/l and during the present circumstances in the laboratory; it would be difficult to get even lower detection limits. There are improvements that can be done to get to the even lower detection limits. The results from this work show that the variation in each sampling cup is very small but if you look at different sampling cups the variation could be large if the cups are not treated in the right way. Further validation analyzes like variation in between days needs to be done.<strong> </strong></p><p>It is possible to analyze these low concentrations of copper, iron and sodium in the water samples with the AAS- graphite furnace, but it is difficult because there are many factors that affect the results. Examples of such factors are the environment where the instrument is placed in the laboratory and the human factor. Further analyzes needs to be done to get a better view of how these factors affect the result.</p>
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Niculaes, Dina. "Iron oxide nanocubes for magnetic hyperthermia." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/441740.
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Durant la meva tesi s’han desenvolupat tres projectes principals, centrats en l'estudi de nanosistemes basats en l'ús de nanocubs d'òxid de ferro (IONCs) per a la hipertèrmia magnètica (HM).
S’ha demostrat l'ús innovador de la configuració de HM per a l'oxidació suau de nanocubs tipus core-shell Fe1-xO/Fe3-δO4 a una única fase de Fe3O4. Atès que els valors de la taxa d'absorció específica (SAR) dels nanocubs tipus core-shell wüstita/magnetita han estat menors en comparació amb els IONCs de magnetita amb una longitud d’aresta de cub similar, el nucli de FeO s’ha oxidat mitjançant estimulació MH. Després de diversos tractaments amb HM, els valors de SAR s’han duplicat, mentre que l'estabilitat col·loïdal, la distribució de mida i la forma no s’han vist afectades. Els IONCs estimulats magnèticament han mostrat un valor de magnetització de saturació més elevat, reflectint canvis estructurals i de composició, confirmats a través d'estudis de microscòpia electrònica i de dispositius superconductors d'interferència quàntica. El tractament suau amb HM també ha fet possible l'ancoratge de molècules biològicament rellevants a la superfície dels nanocubs, preservant la seva activitat i millorant alhora el rendiment tèrmic dels IONCs.
Els valors de SAR de IONCs tipus core-shell també s'han millorat acoblant els nanocubs en estructures de tipus cadena. Inicialment, es va desenvolupar l'agregació controlada dels IONCs durant la seva transferència en aigua, permetent la formació d'agregats (clústers) amb formats hidrodinàmics mitjans entre 30 i 100 nm. Així mateix, s’ha avaluat la resposta d’hipertèrmia de nanocubs individuals envers de nanoclústers col·loïdals tous de diferents mides. Les estructures denominades "dímers" i "trímers"—2D formades amb dos i tres IONCs—han mostrat valors SAR més alts.
S’ha aconseguit la càrrega de fàrmac en dos nanosistemes dissenyats per alliberament de fàrmac quimioterapèutic desencadenat mitjançant calor. Tots dos sistemes s’han basat en IONCs de magnetita revestits amb polímers termo-responsius carregats amb doxorubicina. L'objectiu era obtenir nanotransportadors estables a la temperatura corporal que alliberessin la càrrega exclusivament sota l'aplicació d'un camp magnètic altern (AMF). D'aquesta manera, un cop obtinguts els IONCs individuals revestits amb polímer termo-responsiu amb alts<br>Tres proyectos principales se desarrollaron durante mi tesis centrada en el estudio de nanosistemas basados en el uso de nanocubos de óxido de hierro (IONCs) para la hipertermia magnética (HM).
Se demostró el uso novedoso de la configuración de HM para la oxidación suave de nanocubos tipo core-shell Fe1-xO/Fe3-δO4 a una única fase de Fe3O4. Dado que los valores de la tasa de absorción específica (SAR) de los nanocubos tipo core-shell wüstita/magnetita fueron menores en comparación con los IONCs de magnetita con una longitud de borde de cubo similar, el núcleo de FeO se oxidó mediante estimulación MH. Después de varios tratamientos con HM, los valores de SAR se duplicaron, mientras que la estabilidad coloidal, la distribución del tamaño y la forma no se vieron afectadas. Los IONCs estimulados magnéticamente mostraron un valor de magnetización de saturación más elevado, reflejando cambios estructurales y de composición, confirmados a través de estudios de microscopía electrónica y de dispositivos superconductores de interferencia cuántica. El tratamiento suave con HM también hizo posible el anclaje moléculas biológicamente relevantes a la superficie de los nanocubos preservando su actividad y mejorando al mismo tiempo el rendimiento térmico de los IONCs.
Los valores de SAR de IONCs tipo core-shell también se han mejorado ensamblando los nanocubos en estructuras de tipo cadena. Inicialmente, se desarrolló la agregación controlada de los IONCs durante su transferencia en agua, permitiendo la formación de agregados (clusters) con tamaños hidrodinámicos medios entre 30 y 100 nm. Asimismo, se evaluó la respuesta de hipertermia de nanocubos individuales frente a nanoclusters coloidales blandos de diferentes tamaños. Las estructuras denominadas "dímeros" y "trímeros"—2D formadas con dos y tres IONCs—mostraron valores SAR más altos.
Se logró la carga de fármaco en dos nanosistemas diseñados para liberación de fármaco quimioterapéutico desencadenada mediante calor. Ambos sistemas se basaron en IONCs de magnetita revestidas con polímeros termo-responsivos cargados con doxorrubicina. El objetivo era obtener nanotransportadores estables a la temperatura corporal que liberaran la carga exclusivamente bajo la aplicación de un campo magnético alterno (AMF). De este modo, una vez obtenidos los IONCs individuales revestidos con<br>Three main projects were conducted during my thesis that was focused on the study of nanosystems based on iron oxide nanocubes (IONCs) for magnetic hyperthermia (MH).
The novel use of MH set-up for the mild oxidization of Fe1-xO/Fe3-δO4 core-shell nanocubes to single Fe3O4 phase was demonstrated. As specific absorption rate (SAR) values of wüstite/magnetite core-shell nanocubes were lower compared to magnetite IONCs of similar cube edge length, the FeO core was oxidized by MH stimulation. After several MH treatments, the SAR values increased twice, while colloidal stability, size distribution and shape remained unaffected. The magnetically stimulated IONCs showed higher saturation magnetization, reflecting structural and compositional changes, as confirmed by electron microscopy and superconductive quantum interference device studies. The mild MH treatment also opened up the possibility of attaching biologically relevant molecules to the surface of nanocubes and preserving their activity while improving the IONCs heat performance.
The SAR values of core-shell IONCs were also enhanced by clustering the nanocubes in chain like structures. Initially, the controlled clustering of the IONCs during their water transfer was developed, enabling the formation of clusters with mean hydrodynamic sizes between 30 and 100 nm. The hyperthermia response of individual nanocubes vs. soft colloidal nanoclusters of different sizes was evaluated. The so called “dimers” and “trimers”—2D structures formed with two and three IONCs—showed higher SAR values.
Drug loading on two nanosystems designed for heat-triggered chemotherapeutic drug release was achieved. Both systems were based on magnetite IONCs coated with thermo-responsive polymers loaded with doxorubicin. The goal was to have stable nanocarriers at body temperature that would release the cargo exclusively upon the application of an alternating magnetic field (AMF). Once individually thermo-responsive polymer coated IONCs with high SAR values were obtained, the heat-triggered doxorubicin release under AMF—at biologically relevant field conditions—was qualitatively, but not quantitatively proven.
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Mabusela, Bongolwethu Professor. "The effect of initial pH on surface properties of ferric ion precipitates formed during microbial oxidation of ferrous ion by Leptospirillum ferriphilum in a CSTR." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2553.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.<br>While bioleaching is a proven technology for the efficient recovery of base metals from sulphide minerals, its sustenance is dependent on the continuous availability of ferric ion, Fe3+, in soluble form, in the bioleach liquor. However, the solubility of ferric ion is low at higher pH that it tends to precipitate, resulting in the formation of ferric ion precipitates. The formation of ferric ion precipitates in bio-hydrometallurgy decreases the leaching efficiency by trapping the leached metals in solution through an adsorption mechanism which is not well understood. Although the surface properties of the precipitate could be linked to its metal adsorption properties, there has not been a detailed study that gives any indication or explanation of the adsorption mechanism. Therefore, the aim of this study was to investigate the effect of initial pH on the surface properties of ferric ion precipitate and relate this to the adsorption characteristics of the precipitate for desired metals.
Biooxidation experiments catalysed by Leptospirillum ferriphilum were conducted in a CSTR with a working volume of 1L. The biooxidation experiments were conducted at pH values of 1.3, 1.5, 1.7, 1.9 and 2.2 at a constant temperature of 35 0C for 14 days. The recovered precipitates were characterized by X-ray diffraction, elemental analyses, SEM, particle size distribution (PSD) and zeta potential. Zeta potential measurements were conducted to investigate what role initial pH plays in modifying the precipitate surface charge and what role the surface charge of each precipitate plays in the nature of adsorption of copper ions onto the precipitate surface. The amount of copper adsorbed onto the precipitate was quantified by the magnitude of the change in surface charge after adsorption experiments.
Quantification results showed that the amount of ferric ions precipitates formed increased from 4.31g to 13.26g with an increase in initial pH (from 1.3 to 2.2). The results also showed that significant precipitation of ferric ion occurred during the exponential phase while insignificant precipitation was observed during the stationary phase.
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Nakajima, Sho. "Mechanistic and Synthetic Studies on Iron-Bisphosphine-Catalyzed Cross-Coupling Reactions of Alkyl Halides." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225616.
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Camacho, Julianna G. "The influence of calcium on the inhibition of arsenic desorption from treatment residuals in extreme environments." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3198.
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One of the most toxic environmentally mobile compounds found in water is arsenic. It has been used as a pesticide to control insects, fungi, weeds and rodents since the early part of this century because of its high toxicity. Sorption of toxic metals onto a metal oxy-hydroxide is the most popular and practical arsenic removal method from contaminated water. Water treatment with oxy-hydroxides creates arsenic containing residuals, which are usually disposed of in landfills. To prevent leaching, stabilization of the solid residuals is required. It has been reported that calcium may inhibit arsenic desorption and/or benefit arsenic sorption. The objective of this investigation is to assess arsenic leaching in the presence of calcium and phosphate ions at extreme pH. Two hypotheses have been identified to explain the decrease in soluble arsenic in the presence of calcium. One explanation is that arsenic reacts with calcium to form calcium arsenic solids. The second hypothesis is that calcium affects the surface properties of the oxy-hydroxide solid in solution.
Results show that calcium enhances the removal by iron oxides and prevents the leaching of arsenic from the residuals. Isotherm experiments show that arsenic adsorption can be described as occurring on nonporous powders or powders with pore diameters larger than micro-pores. Physically, with increase in adsorbate concentration, second and more layers are completed until saturation when the numbers of adsorbed layers becomes infinite. Further, experimental data were fitted to a Brunauer, Emmett and Teller isotherm (BET) model which assumes the initial layer can act as substrate for further adsorption. Finally, calcium-arsenic and calcium-phosphate solids were predicted to be formed by Visual MINTEQ modeling program. Nevertheless, from the x-ray diffraction output calcium-arsenic or calcium-phosphate solids were not identified.
Because no calcium arsenate solids were found it was concluded that calcium affects the surface properties of the oxy-hydroxide solids in solution. Increasing the pH produces negative surface charge, which in turn increases repulsion between the negatively charged hydrated arsenate ions and the Fe(OH)3 surface. CalciumÂs positive charge might neutralize this effect enhancing the sorption of arsenic onto the oxy-hydroxide. Also, it was concluded that the competition between arsenic and phosphate was reduced by the same mechanisms.
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Boubnov, Alexey [Verfasser], and J. D. [Akademischer Betreuer] Grunwaldt. "Structural studies on iron-based exhaust gas catalysts by means of X-ray absorption spectroscopy / Alexey Boubnov. Betreuer: J.-D. Grunwaldt." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1073204839/34.
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Everett, James. "The aggregation and reduction of iron minerals by the Alzheimer's disease peptide ß-amyloid (1-42) : an X-ray absorption study." Thesis, Keele University, 2015. http://eprints.keele.ac.uk/2502/.
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Iron is vital for healthy brain function. However when present in a redox-active form or in excess concentrations it can be toxic. Interestingly, increased levels of redox-active iron biominerals have been shown to exist in Alzheimer’s disease (AD) tissues, including lesions comprised of the AD peptide β-amyloid (Aβ). These iron phases are capable of producing reactive oxygen species, resulting in the generation of oxidative stress manifesting as neuronal injury. As oxidative stress and the accumulation of iron are recognised as early stage events in AD, the presence of redox-active iron may prove fundamental in the development of AD pathology. The origin of these redox-active iron biominerals is unclear but recent studies suggest their formation may involve the interaction of Aβ with unbound brain iron and/or the malfunction of the iron storage protein ferritin. Despite these observations, the relationship between Aβ and iron is poorly understood, and the products of Aβ/iron interaction remain unknown. In this thesis, synchrotron-based x-ray techniques are combined with traditional biological approaches to examine the interactions between Aβ and various synthetic and naturally occurring iron forms. Through this methodology Aβ is shown to incorporate ferric iron phases into its fibrillar structure in vitro, with this interaction resulting in the chemical reduction of iron into a redox-active state. Further to this, Aβ is demonstrated to disrupt ferritin structure resulting in the chemical reduction of its redox-inactive iron core in vitro. Additionally the interaction of Aβ with crystalline iron phases is shown destroy iron crystal structure. Finally, redox-active iron is shown to be associated with regions of AD pathology, including fibrillar Aβ-like structures, within a transgenic mouse model of AD in situ. These findings suggest an origin for the redox-active iron forms and oxidative stress previously witnessed in AD tissue, thereby shedding light on the process of AD pathogenesis.
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Rebellato, Ana Paula 1977. "Biscoitos elaborados com farinhas de trigo fortificadas com ferro : teor do mineral e qualidade físico-química durante a estocagem." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254642.
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Previous issue date: 2012<br>Resumo: No Brasil a ANVISA através da Resolução nº 344 de 2002, instituiu a obrigatoriedade do enriquecimento de farinhas de trigo e milho com ácido fólico e ferro. A deficiência de ferro é apontada como a principal causa da anemia ferropriva. A fortificação de alimentos com ferro é a estratégia indicada pelas instituições que atuam na área de saúde como a mais eficiente para o combate à anemia. Entretanto, a ingestão excessiva deste mineral está associada a danos oxidativos e tem sido relacionada com a manifestação de várias doenças. Dessa forma, o alcance dos objetivos dos programas de fortificação de alimentos está relacionado à garantia da ingestão recomendada para os nutrientes adicionados e aos atributos físico-químicos, que devem ser monitorados no veículo utilizado e no produto final. Este trabalho teve como objetivos adequar e validar uma metodologia para a determinação de ferro em amostras de biscoitos elaborados com farinha de trigo fortificada, utilizando a técnica de Espectrometria de Absorção Atômica com chama e acompanhar os parâmetros físico-químicos (umidade, acidez, índice de peróxido e teor de lipídeos) durante o período de estocagem (150 dias). O método para determinação do teor de ferro em biscoitos foi validado para os parâmetros precisão, seletividade, recuperação, sensibilidade, linearidade, limite de detecção (LD) e limite de quantificação (LQ) e se mostrou adequado. O teor médio de ferro presente nos biscoitos tipo cream cracker, água e sal, maisena e amanteigado foram: 5,0 a 8,6; 5,3 a 7,8; 2,5 a 6,8; 3,7 a 5,7 mg 100 g-1, respectivamente. Foi verificada diferença significativa entre lotes de mesma marca e entre marcas do mesmo tipo, através da ANOVA e do Teste de Tukey (p<0,05). Para os parâmetros físico-químicos, os valores obtidos ao longo do período de estocagem variaram; umidade de 1,8 a 6,3%; acidez de 1,5 a 7,4 mg NaOH 0,1 mol L-1 100g-1; índice de peróxido de valor não detectado (nd) a 95,1 meq Kg-1 de gordura. Para o teor de lipídeos e ferro, o menor e o maior valor encontrado foram 9,8 e 18,0% e 2,1 e 9,2 mg 100 g-1, respectivamente. Foi possível verificar que existe diferença significativa entre os valores obtidos para cada lote de mesma marca ao longo do período de estocagem. Nenhum tipo de correlação entre a umidade e os valores de acidez presentes nas matrizes, foi observado, da mesma forma que não foi verificada nenhuma correlação entre o índice de peróxido e o teor de ferro. Notou-se que há necessidade de melhorar a qualidade dos ingredientes utilizados no preparo dos biscoitos a fim de manter um padrão de qualidade uniforme durante todo o período de validade. As variações observadas no teor de ferro indica a necessidade de uma legislação mais específica, estabelecendo concentrações (mínima e máxima) para o mineral utilizado na fortificação de farinha de trigo que estará presente em alimentos prontos para o consumo, a fim de garantir o sucesso da campanha de fortificação<br>Abstract: Through the resolution no. 344 of 2002, ANVISA (Brazilian Regulatory Institute) assigned the obligation of enriching wheat and corn flours with folic acid and iron. Iron deficiency is pointed out as the main cause of anemia, so food fortification with this mineral is the most efficient strategy indicated by the health institutions that work towards the combat of anemia. However, excessive ingestion of this mineral is associated with oxidative damages and has also been related to the occurrence of several diseases. So the fortification programs must guarantee the recommended intake, and not more than that, as well as to maintain the physicochemical attributes, by monitoring both the vehicle of fortification and the final product. This work redesigned and validated one methodology for iron determination in samples of biscuits produced with fortified wheat flour, by using Flame Atomic Absorption Spectrometry (FAAS). It also measured physicochemical parameters (moisture, acidity, peroxide index and fat content) during the storage period (150 days). The method for iron determination in biscuits is shown to be adequate and was validated for the parameters precision, sensibility, selectivity, recovery, accuracy, linearity, limit of detection (LOD) and quantification (LOQ). The iron content in biscuits of the types cream cracker, salt and water, cornstarch cookies (maizena) and butter cookies were, respectively: 5.0 to 8.6, 5.3 to 7.8, 2.5 to 6.8, and 3.7 to 5.7 mg 100 g-1. ANOVA and Tukey tests (p<0,05) were applied to verify if there was significant difference between batches of the same brand and among the brands of the same type of biscuits. For the physicochemical parameters, all the values obtained throughout the storage period varied. Moisture was from 1.8 to 6.3%; acidity was from 1.5 to 7.4 mg NaOH (0,1 mol.L-1) 100 g-1; peroxide index was form non-detectable (nd) to 95.1 meq Kg-1 of fat. The lowest and the highest values for fat content were 9.8 and 18% the range for iron was from 2.1 to 9.2 mg 100 g-1 for iron. There was significant difference between the values obtained for each batch of the same brand throughout the storage period. But there was no correlation between the moisture present in the matrix and the acidity values, neither there was between the peroxide index and iron content. It is necessary for the industries of biscuits to improve the stability of the ingredients to maintain uniformity during all the storage period. The observed variation of iron content indicates the need for a more specific legislation, which establishes minimum and maximum concentrations for the mineral added to fortify wheat flour, aiming to guarantee the success of the fortification campaign<br>Mestrado<br>Ciência de Alimentos<br>Mestra em Ciência de Alimentos