Дисертації з теми "Integrin with metal ions"
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1
Reinhard, Björn M. "Chemistry of microsolvated metal ions." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969739273.
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2
Phillips, Rosemary Helen. "Metal ions and Helicobacter pylori." Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408125.
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3
Poteau, Xavier. "Fluorescent sensors for metal ions." Thesis, University of Central Lancashire, 2001. http://clok.uclan.ac.uk/21458/.
Повний текст джерелаАнотація:
The considerable current interest in the use of fluorescent molecules in molecular recognition is not new, but is one that has increased in importance in recent years due to their applications in many fields including trace analysis in chemistry and biochemistry. Using the "dual fluorescence" properties of TICT state compounds (Twisted Intramolecular Charge Transfer which gives an extra red-shifted emission band) and the key property of crown ether compounds which is their ability to complex ions, we designed and synthesised a range of new fluoroionophores and studied their photophysical behaviour towards a selection of alkaline and alkaline-earth metal ions. The new fluoroionophores (4-(i '-aza-4'-7'- 10 ,-i 3 '-tetraoxapentadecyl) benzonitrile, 4-( 1 '-aza-4'-7'- 10-i 3'-! 6'-pentaoxapentadecyl)benzonitrile, methyl-4- (1 '-aza-4'-7'-10'-13'-tetraoxapentadecyl)benzoate, 4'-N,N-(i "-aza-4",7",iO' ',l 3"- tetra oxapentadecyl)-3-hydroxyflavone and 4'-N,N-(l "-aza-4' ',7' ',lO", 13"- tetraoxapenta decyl)-3-methoxyflavone) have been shown to form TICT states upon excitation. The photophysics (absorption, emission, lifetimes) of these compounds are affected by the complexation of cations which reduce the donor character of the nitrogen belonging to the crown. The studied dications (Mg2 , Ca2 and Ba2') lead to larger spectral shifts and bigger values of the binding constant Ks than the studied monocations (Lie, Nat, K, CC) which can be interpreted in terms of a stronger electrostatic interaction between the nitrogen lone pair and the alkaline-earth metals than the alkali-metals. It appears that the selectivity demonstrated by these crown ethers towards the alkaline earth and alkali metals is not only explained by the "hole-size relationship" between the size of the crown ether cavity and the ionic mdii of the metal ions. The type of substituent on the phenyl of the azacrown ether has been shown to further influence the spectroscopic properties (shift of the absorption ansi emission bands). Nevertheless the photophysical properties of the azacrown ether derivatives studied does not show enhancement of the selectivity towards the studied metals on expansion of the delocalisation system. More complex mechanisms are in operation in flexible systems such as the azacrown derivatives used in this study geometry, conformation and rigidity all play roles in determining the binding strength and selectivity of these molecules.
4
OGGIANU, MARIANGELA. "Luminescent platforms for metal ions sensing." Doctoral thesis, Università degli Studi di Cagliari, 2021. http://hdl.handle.net/11584/314054.
Повний текст джерелаАнотація:
This PhD thesis reports on the strategies for the design of novel luminescent chemosensors as valid alternative to conventional optical sensors, to recognize environmental pollutants, mainly heavy metal ions and nitroaromatics. Luminescent lab-on-chip platforms, molecular and Hybrid-based chemosensors, and luminescent Nanosheets are the three platforms developed for sensing applications. Fluorescent dyes of the family of Xhantenes, Rhodamine (RhO) and Fluorescein (Fluo), Diketopyrrolopyrroles (DPPs) and 2,5 -dihydroxy-1,4-benzoquinone derivatives are the old-fashioned and new building blocks selected, respectively, to fabricate these optical sensors, because of their unique luminescent properties.
Particularly, 2,3-dicyano-5,6-dichloro-1,4-benzoquinone, was selected for its capability i) to produce two dimensional (2D) Coordination Polymers/Metal-Organic Frameworks (CPs/MOFs) and ii) to act as a good antenna ligand towards NIR and Vis. emitting Lanthanide ions. 2D CPs/MOFs, based on this linker, were obtained and miniaturized to 2D Nanosheets (NS), as challenging sensing platforms.
5
Ebreo, Darren. "The role of metal ions in metal-on-metal total hip replacement." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/59343/.
Повний текст джерелаАнотація:
Metal-on-metal (MoM) total hip replacement (THR) offered theoretical advantages of decreased wear and increased functional outcomes. MoM bearings have been associated with sterile inflammatory masses and significant soft tissue destruction with poorer outcomes following revision surgery. The natural history of adverse reactions to metal debris (ARMD) is unknown, but may represent contributions from bearing surface wear, taper junction wear, and corrosion. Immunological and genetic factors may influence susceptibility to development of ARMD. Between 1997 and 2004, 652 Ultima TPS THRs (DePuy) were implanted in 545 patients who went on to experience a high rate of early implant failure (13.8%). Management of these patients has evolved beyond regular clinical follow up with plain radiographs to include surveillance monitoring of trends in levels of blood metal ions and staging of disease using metal artefact reduction (MAR) MRI. This study investigated: • The natural history of ARMD in 28mm MoM THR using MAR MRI. • The possibility of diurnal variation of cobalt (Co) and chromium (Cr). • Differences in gene expression profiles of patients undergoing revision of a metal-on-polyethylene (MoP) THR for aseptic loosening and those with ARMD arising from MoM THR. In patients whose MARS MRI staging on initial scan is normal or where mild evidence of disease is demonstrated, further deterioration is unlikely. Where it does occur, the rate of deterioration is slow and there may be a latent period of many years. There is no diurnal variation in levels of cobalt (Co) in plasma or urine. There is diurnal variation in levels of plasma chromium, but this is not clinically significant. Patterns of gene expression in patients with aseptic loosening of a metal-onpolyethylene (MoP) THR, and patients with ARMD from a MoM THR investigated by a microarray experiment were found to be similar on a genome-wide level suggesting that they may share common factors in their aetiologies. These studies have helped to describe the natural history of ARMD on a cellular and radiological level, and have provided a contribution to the evidence base that will inform as to the optimum strategy for monitoring these patients before they develop catastrophic complications.
6
Bale, Simon J. "Retention-modification in HPLC using metal ions." Thesis, Loughborough University, 1988. https://dspace.lboro.ac.uk/2134/27578.
Повний текст джерелаАнотація:
The effects of transition metal ions as components of the mobile phase on the retentions in HPLC of 2-aminophenol and selected α-diketones were studied on both ODS-silica and porous polymer columns. The compounds were used as model compounds in an investigation which set out to derive a detailed understanding of the mechanisms Involved when metal ions are used to selectively modify the retention of compounds capable of interaction. This technique, which has parallels with ion-pair chromatography, provides another method by which the conditions of a separation may be altered and the selectivity adjusted to give better resolution.
7
Ndifor-Angwafor, Nche George. "Analysis of metal ions in nanoparticle growth." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443661.
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8
Skipper, N. "The alkali metal ions in aqueous solutions." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379533.
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9
Irikura, Karl K. Beauchamp Jesse L. "Gas-phase chemistry of organotransition metal ions /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06202007-111048.
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10
Cheng, Jing. "Characterisation of wool treated with metal ions." Thesis, Queensland University of Technology, 1993. https://eprints.qut.edu.au/227117/1/T%28S%29%2025_Cheng_1993.pdf.
Повний текст джерелаАнотація:
The importance and complexity of the interactions of metal ions with wool
keratin have been well recognised. This work aims to add to the knowledge of
these interactions and to demonstrate the application of chemometrics.
A systematic study of wool fibres treated with lead metal ion was carried out
using various instrumental analyses in an attempt to investigate the binding
mechanism of the lead / wool interaction. The instrumental techniques applied
included Fourier Transform Infrared (FT-IR) spectroscopy, transmission
electron microscopy, energy dispersive X-ray microanalysis, scanning
electron microscopy and X-ray photoelectron spectroscopy. It was shown that
the carboxylate group acted as a binding site for the lead ion. The formation
of lead sulfide as a result of lead / keratin interaction in the aqueous acidic
solutions at elevated temperature was substantiated. Chemometrics was
employed to reveal the trend for the IR spectra of lead treated wool samples
with different treatment conditions.
A comparative study was conducted for the wool keratin treated with Cr(III),
Cu(II), Fe(II), Ni(II) and Zn(II) ions. The order of structure modification at
the carboxyl group as a result of metal ion / wool interactions was obtained
using FT-IR spectroscopy combined with chemometric methods (PCA,
SIM CA and Fuzzy clustering). This order was found to contrast with the
similar ranking on the basis of uptakes alone. The treatment solution pH
changes were monitored to investigate the reaction schemes for metal /
carboxyl group interactions. The reaction schemes were found to be related to
the wool structure modification. FT-IR microscopic measurements of the
untreated and metal ion treated single wool fibres qualitatively agreed with the
results from normal FT-IR spectroscopy.
The Forosyn dyed wool / polyester fabric blends which are concerned with
metal - complex dyeing were analysed using diffuse reflectance FT-IR
spectroscopy with the aid of chemometric interpretation. The object of this
study was to attempt the matching and property prediction of these wool /
polyester blends.
11
Granzotto, Alberto. "Role of metal ions dyshomeostasis in neurodegeneration." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423606.
Повний текст джерелаАнотація:
In the present study metal ions role in neurodegenerative processes has been investigated. Two major pathways have been developed: 1) metal ions role in β-amyloid (Aβ folding and deposition from in vitro to in vivo; 2) calcium dyshomeostasis in an in vitro model of neurodegeneration.
Firstly, metal ions role (aluminum, copper, iron, zinc) in Aβ folding and deposition was assessed. Aβ misfolding is, in fact, believed to play a critical role in Alzheimer’s disease pathogenesis. Our data confirm that Aβ folding is closely related to the conjugated metal ion, thereby following peculiar metal ion-dependent conformational changes. Strikingly, we report that aluminum, a non physiological metal ion, is the most efficient in “freezing” Aβ in its oligomeric and most toxic state.
Within this framework we investigated the mechanisms underlying Aβ and Aβ-metal conjugates toxicity. To that aim we employed two natural compounds (resveratrol and cholesterol) acting on two different Aβ mechanisms of toxicity: oxidative stress and membrane damage, respectively.
In both cases, in vitro analysis revealed that resveratrol and cholesterol do not influence Aβ and Aβ-metal conjugates folding processes, but are still effective in protecting a neuronal-like cell line against Aβ toxicity. We reported that resveratrol was able to significantly reduce the Aβ-triggered generation of reactive oxygen species, meanwhile physiological concentrations of cholesterol were effective in protecting cellular membrane structure against Aβ (especially Aβ-Al) lipid disrupting activity.
To further assess that differently shaped Aβ-metal conjugates result in different biological responses, we investigated Aβ-Cu and Aβ-Zn role in influencing/altering gene expression profile in a neuronal-like cell line. We found that these two conjugates are effective in modulating expression of transcripts involved in inflammatory processes, oxidative stress, and in apoptotic cell death.
Following these in vitro studies we decided to investigate whether expression of transcripts involved in metal ions homeostasis resulted affected in an in vivo model of the disease, represented by the 3xTg-AD mice. Our data highlight a significant overlapping between the expression profiles of young 3xTg-AD mice compared with aged wild type mice; this finding support the notion that Alzheimer’s disease can be interpreted as a boosted variant of otherwise naturally occurring age-driven changes. In our dataset we found several differentially expressed transcripts involved in calcium homeostasis, a key metal ion for the physiology of the cell.
Secondly, calcium dyshomeostasis in striatal neurons following excitotoxic challenge was assessed. Striatal neurons degeneration is involved in several pathologies showing motor and behavioral sequelae, such as Huntington’s disease (HD). We tried to determine why a subpopulation of striatal neurons results spared in HD striata, showing a peculiar resistance towards excitotoxic challenges. Our data demonstrate that the striking resistance of these cells may be due to boosted scavenging capabilities embedded in such neuronal subpopulation, resulting in lack of ROS generation upon excitotoxic insults.
Collectively, these findings highlight the pivotal role played by metal ions in the development of neurodegenerative disorders. Noteworthy, not only endogenous and biologically relevant metal ions (iron, copper, zinc and calcium) seem involved in the pathogenesis of neurodegenerative disorders, but also exogenous metals (i.e.: aluminum) could have a key and subtle, although less investigated, role in neuronal degenerationIl presente lavoro di tesi si è suddiviso in due filoni principali che hanno come filo conduttore la disomeostasi di ioni metallici nei processi neurodegenerativi. La prima parte riporta lo studio sul ruolo di alcuni ioni metallici (alluminio, ferro, rame e zinco) nel processo di folding della proteina β-amiloide (Aβ), ritenuta uno dei fattori eziopatogenici del morbo di Alzheimer. I dati ottenuti dimostrano come i complessi Aβ-metallo-ione acquistino una peculiare conformazione dipendente dal metallo legato, conferendo così all’Aβ particolari proprietà citotossiche. Tale citotossicità risulta particolarmente evidente per il complesso Aβ-Al che è in grado di aumentare, in maniera significativa, la tossicità data dalla sola Aβ o dalla stessa Aβ coniugata con metalli diversi dall’Al. All’interno di questo quadro sperimentale si è poi cercato di indagare più nel dettaglio i meccanismi con i quali Aβ, e i suoi complessi metallici, esercitassero la loro citotossicità. A questo scopo sono stati impiegati due composti quali il resveratrolo e il colesterolo, che vanno ad agire su due meccanismi che stanno alla base della tossicità dell’Aβ, come lo stress ossidativo e l’alterata fluidità delle membrane cellulari. Nel primo caso, i dati in vitro hanno permesso di dimostrare come, agendo in maniera selettiva sulla produzione di specie reattive dell’ossigeno (ROS) Aβ-mediata, sia possibile ridurre la tossicità di Aβ e dei suoi complessi con metalli redox (rame e ferro) mediante un meccanismo di scavenging dei ROS ad opera del resveratrolo, dalle spiccate proprietà anti-ossidanti e neuro-protettive. A questo punto si è indagata la capacità dei vari complessi Aβ-metalloioni di alterare la struttura di membrane lipidiche attraverso l’uso di modelli di membrane cellulari. In precedenza si era dimostrato come il complesso Aβ-Al fosse l’unico complesso in grado di alterare significativamente la fluidità di layer lipidici. I dati ottenuti ci permettono di affermare che tale capacità è dovuta principalmente alla elevata idrofobicità superficiale del complesso Aβ-Al. Inoltre, agendo sulle membrane cellulari con concentrazioni fisiologiche di colesterolo è stato possibile ridurre l’”irrigidimento” delle membrane (lipidico) conseguente alla presenza di Aβ-Al, e ridurne la citotossicità. Si é quindi approfondito il ruolo geno-tossico dei succitati complessi Aβ-metalloioni andando ad indagare come questi siano in grado di modulare in maniera significativa (e metallo-dipendente) l’espressione genica di numerosi trascritti coinvolti nella patologia di Alzheimer. In particolare, il nostro interesse si è focalizzato sui complessi Aβ-Cu e Aβ-Zn, che si sono rivelati in grado di modulare selettivamente l’espressione di geni coinvolti in processi infiammatori, nello stress ossidativo e nella morte cellulare (apoptosi). Dopo questa serie di studi in vitro si è passati ad indagare l’espressione genica dell’intero genoma umano in un modello in vivo di patologia di Alzheimer. Lo scopo era quello di identificare il network o il pathway d’espressione coinvolti della disomeostasi cationica. I profili d’espressione del modello murino 3xTg-AD sono stati pertanto confrontati con quelli del controllo wild type. In questo contesto, si è scoperta una significativa sovrapposizione dei geni sovra- e sotto-espressi tra topi wild type anziani e topi 3xTg-AD giovani. Questo dato supporta l’idea che il substrato patologico dell’AD possa favorire un processo di invecchiamento precoce. All’interno del gruppo di geni trovati differenzialmente espressi, molti erano coinvolti nell’omeostasi del calcio, ione chiave per la fisiopatologia cellulare. Il secondo filone di ricerca ha riguardato lo studio del ruolo dello ione calcio nell’eccitotossicità dei neuroni dello striato. Tale fenomeno è particolarmente importante in alcune patologie neurodegenerative che hanno come segno caratteristico una progressiva e irreversibile perdita del controllo motorio, come ad esempio il morbo di Huntington. L’interesse si è focalizzato nel determinare il perchè una subpopolazione di neuroni striatali, caratterizzata dalla sovraespressione di nitrico-ossidosintasi, non vada incontro ad apoptosi in seguito a stress eccitotossico. I dati raccolti ci hanno permesso di stabilire che la resistenza di tale sottopopolazione al sovraccarico di calcio è dovuta principalmente ad una potenziata capacità di questi neuroni di detossificarsi rapidamente dalle specie ROS, di origine mitocondriale, specie che si generano durante fenomeni eccitotossici. Conclusione. Nel complesso i dati ottenuti sottolineano una volta di più un ruolo centrale degli ioni metallici nello sviluppo e/o nella progressione di alcune patologie a carattere neurodegenerativo. In particolare è importante notare come, a fianco di alcuni ioni metallici endogeni - che hanno un rilevante ruolo fisiologico (ferro, rame, zinco, calcio) -, anche altri ioni privi (apparentemente) di un ruolo biologico, ma coi quali ci interfacciamo quotidianamente, come ad esempio l’alluminio, sembrino svolgere un ruolo chiave in processi eziopatogenetici legati a fenomeni neurodegenerativi
12
Chen, Wan-Ru. "Interactions of tetracycline antibiotics with dissolved metal ions and metal oxides." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24698.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: Huang, Ching-Hua; Committee Member: Kim, Jaehong; Committee Member: Pavlostathis, Spyros; Committee Member: Stack, Andrew; Committee Member: Yiacoumi, Sotira
13
Lentz, Nicholas B. "Electrospray ionization mass spectrometry from cluster ions to toxic metal ions in biology /." [Ames, Iowa : Iowa State University], 2007.
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14
Balteanu, Iulia. "FT-ICR studies of transition metal cluster ions." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974430919.
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Smith, Alexis. "Coordination complexes of trivalent non-transition metal ions." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28400.
Повний текст джерелаАнотація:
Lathaxride(III) complexes of three potentially heptadentate Schiff base ligands were prepared by addition of lanthanide(III) salts to a solution containing a slight excess of ligand in the presence of poorly coordinating chloride ions or strongly coordinating nitrate ions. The complexes La(hatren), La(datren)(CH₃0H) and La(trac) were isolated in the presence of chloride ions, and were found to have the ligand bound in a hexadentate or heptadentate fashion. We were unable to isolate analogous complexes with the heavier lanthanides (Ln = Pr, Nd, Gd, Dy, Yb, Lu). The complexes Ln(H₃L)(NO₃)₃ (Ln = La, Pr, Nd, Gd, Dy, Yb; H₃L =
H₃hatren, H₃datren) and Ln(H₃trac)(NO₃)₃ (Ln = Pr, Nd, Gd, Dy, Yb) were isolated in the presence of nitrate ions, and were found to have the Schiff base ligand bound in a tridentate fashion ( where H₃datren = tris(2'-hydroxy-4',5'-dimethylacetopheniminoethyl)amine; H₃trac = tris(3-aza-4-methylhept-4-ene-6-one)amine; and H₃hatren = tris(2'-hydroxyacetophenirninoethyl)amine)
All products were characterized by infrared and mass spectroscopy, and by elemental analysis. ¹H-NMR spectroscopy indicated that the complexes were solution labile and dissociated in DMSO to yield free ligand and solvated lanthanide(III) ions.
The crystal structure of Gd(H₃trac)(NO₃)₃ was determined. The gadolinium(III) ion is nine coordinate. H₃trac is bound only through its three oxygen donor atoms, and the nitrate ions are bound in a bidentate fashion to the gadolinium center.
Aluminum (III) and gallium(III) complexes of 2-chloromethyl-5-hydroxy-4H-pyran-4-one (Hck) were isolated from a basic aqueous solution. The complexes Al(ck)₃ and Ga(ck)₃ were characterized by ¹H-NMR (CDCI₃), infrared and mass spectroscopy, as well as by elemental analysis. Al(ck)₃ was also characterized by ²⁷Al-NMR in CDCI₃.Science, Faculty of
Chemistry, Department of
Graduate
16
Abbasi, Alireza. "Structural and Spectroscopic Studies of Solvated Metal Ions." Doctoral thesis, Stockholm : Structural Chemistry, Arrhenius Laboratory, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-446.
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Cao, Yu. "Mass spectrometric study of alkali metal containing ions." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27890.
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Gernert, Ina [Verfasser]. "Redox Chemistry of Hydrated Metal Ions / Ina Gernert." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1173163182/34.
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Low, Wan Li. "Lipsome encapsulated antimicrobial metal ions and essential oils." Thesis, University of Wolverhampton, 2012. http://hdl.handle.net/2436/219012.
Повний текст джерелаАнотація:
This study investigates the feasibility of using TTO and Ag+ alone and in combination either as free or liposome encapsulated agents. Based on the minimum lethal concentration (MLC), the fractional lethal concentration index (FLCI) showed that treatment with unencapsulated combinations of TTO and Ag+ exerted a synergistic effect against P. aeruginosa (FLCI = 0.263) and indifferent effects against S. aureus and C. albicans (0.663 and 0.880, respectively). Using polyvinyl alcohol (PVA) emulsified agents in combination, showed synergistic effects against P. aeruginosa and S. aureus (FLCI = 0.325 and 0.375, respectively), but C. albicans remained indifferent (FLCI = 0.733). Time kill experiments revealed that the combined agent concentrations and elimination time (to the lowest limit of detection, LOD) are as follows: C. albicans: 0.12%v/vTTO:2.5x10-4Ag+:1.5hrs, P. aeruginosa: 1%v/vTTO:3.2x10-4Ag+:15mins and S. aureus: 1.2%v/vTTO:3.2x10-4Ag+:30mins. Repeating these experiments with emulsified TTO encapsulated in liposomes (lipo-TTO:PVA30-70kDa) against P. aeruginosa and S. aureus reduced the effective amount of TTO required (compared to free TTO). However, this was not observed in C. albicans. The required effective concentration of Ag+ from liposome encapsulated Ag+ (lipo-Ag+) was shown to remain the same as free Ag+. The effective concentration and elimination time of liposomal agents in combination are as follows: C. albicans: 0.05%v/vTTO:PVA:8.9x10-5Ag:PVA:2.0hrs, P. aeruginosa: 0.25%v/vTTO:PVA:3.2x10-4Ag:PVA:30mins and S. aureus: 0.05%v/vTTO:PVA:6.0x10-4Ag:PVA:1.5hrs. These results showed the potential of using TTO and Ag+ in combination, along with liposome delivery systems to effectively lower the MLC. Scanning electron micrographs of microorganisms exposed to Ag+ showed a reduction in cell size when compared to untreated cells. Transmission electron micrograph of C. albicans showed the cell surface damaging potential of Ag+. Furthermore, this investigation also demonstrated the feasibility of using chitosan hydrogels as an alternative delivery system for TTO and/or Ag+. The development of these controlled release systems to deliver alternative antimicrobial agents may allow sustained targeted delivery at microbiocidal concentrations.
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Sameera, W. M. C. "Electronic structure of transition metal ions and clusters." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/1389/.
Повний текст джерелаАнотація:
This thesis uses density functional theory (DFT) to explore the electronic structure and reaction mechanisms of open-shell transition metal ions and clusters. The early part of the thesis (Chapters 2 and 3) is devoted to high-valent metal-oxo species, both mono- and bimetallic, while Chapter 4 describes some aspects of copper-catalysed carbon-carbon bond formation. Finally, Chapter 5 highlights the role of DFT in computing magnetic and spectroscopic properties of exchange-coupled iron clusters. Whilst the chemistry contained in the thesis is rather diverse, the underlying theme of open-shell transition metal ions is common to all chapters. Moreover, we are primarily concerned with the ways in which interactions between two or more adjacent open-shells (either two metals or a metal and a ligand radical) control structure and reactivity. After a brief introduction to relevant theoretical aspects in Chapter 1, we use Chapter 2 to establish a link between the electronic structure of the high-valent Mn(V)=O porphyrin monomer species and their ability to perform oxidation reactions. The reaction profiles for oxidation of a range of substrates depend critically on the electronic structure of the isolated oxidant. Where the electronic ground state is genuinely best described as Mn(V)=O, the interaction between oxidant and substrate is repulsive at large separations, only becoming attractive when the incoming nucleophile approaches close enough to drive an electron out of oxide p manifold. In contrast, where the ground state is better described as an oxyl radical form, Mn(IV)-O.+, the oxidation occurs in sequential one-electron steps, the first of which is barrierless. In Chapter 3, we extend these ideas to bimetallic systems, where the presence of two high-valent manganese centres allows the system to oxidise water. Specifically, we focus on two model systems which have been shown to oxidise water, a Mn-porphyrin-based system synthesised by Naruta and a Mn-based system reported by McKenzie where the ligands contain a mixture of pyridine and carboxylate donors. In both cases, we again find that the emergence of oxyl radical character is the key to the reaction chemistry. However, the radical character is ‘masked’ in the electronic ground states, either by transfer of an electron from the porphyrin ring (Naruta) or by formation of a di-μ-oxo bridge (McKenzie system). In Chapter 4 we turn our attention to copper chemistry, and the role of copper complexes in catalysing atom transfer radical additions (Kharasch additions). In this reaction, the copper cycles between Cu(I) and Cu(II) oxidation states, and the result is the formation of a new C-C bonds. This Chapter makes extensive use of hybrid QM/MM techniques to model the environment of the copper centre in the target polypyrazolylborate-copper complexes (TpxCu). Finally, in Chapter 5 we consider the electronic structure, magnetic and spectroscopic properties of a pair of exchange-coupled Fe3 clusters, [Fe3(μ3-O)(μ-4-O2N-pz)6X3]2- (where pz = pyrazolato, X = Cl, Br). Our primary goal was to establish how well broken-symmetry DFT is able to reproduce the observed Mössbauer spectroscopic parameters, which are extensively used to identify the chemical environments of iron species and, in the case of mixed-valence clusters, to establish the degree of delocalisation of the additional electrons. In recent years DFT has proved able to compute these parameters with encouraging accuracy, but it is not clear to what extent the known deficiencies in broken-symmetry wavefunctions will compromise this ability. Our work suggests that neither the isomer shift nor the quadrupole splitting are strongly influenced by the nature of the coupling between the metal ions, suggesting that broken-symmetry solutions can be used as a basis for computing these parameters in more complex clusters.
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Crabtree, Elaine. "The role of metal ions in LDL peroxidation." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266211.
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Lloyd, Bryony Helen. "Bacterial resistance to tellurite and other metal ions." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333673.
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Dey, Benu Kumar. "A study on metal ion complexation with a macrocyclic ligand : a thermodynamic, kinetic, and mechanistic investigation." Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09SM/09smd528.pdf.
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Palla, Veladri. "Heterometallic Interactions of d8-d10 Metal Ions in the Presence of +2 Cations." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/PallaV2007.pdf.
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Xia, Baohui, and 夏寶輝. "Metal-metal interactions in homo- and hetero-metallic complexes containing d0, d8 and d10 metal ions: spectroscopic and theoretical studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B42577317.
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Xia, Baohui. "Metal-metal interactions in homo- and hetero-metallic complexes containing d0, d8 and d10 metal ions spectroscopic and theoretical studies /." Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B42577317.
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Liu, Haichuan. "Reactions in gaseous metal-organic complexes induced by the photoexcitation of the metal chromaphores /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202004%20LIU.
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Mayr, Torsten. "Optical sensors for the determination of heavy metal ions." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964444569.
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Hetzer, Adrian. "Sequestration of metal and metalloid ions by thermophilic bacteria." The University of Waikato, 2007. http://hdl.handle.net/10289/2642.
Повний текст джерелаАнотація:
This Ph. D. thesis presents results and conclusions from studies 1) investigating the interaction between metal and metalloid ions and thermophilic bacteria, and 2) characterizing microbial populations in a geothermally active habitat with relatively high concentrations of metalloid ions and compounds. In initial cadmium ion toxicity assays, the minimal inhibition concentration for 46 thermophilic bacteria of the genera Aneurinibacillus, Anoxybacillus, Bacillus, Brevibacillus, Geobacillus, and Thermus were determined. The highest tolerances to cadmium ions (Cd2+) in the range of 400 to 3200 micro;M were observed for species belonging to the genus Geobacillus. The thermophilic Gram-positive bacteria Geobacillus stearothermophilus and G. thermocatenulatus were selected to describe further biosorption reactions between cadmium ions and chemically reactive functional groups (potential ligands) within and onto the bacterial cell walls. Data obtained from electrophoretic mobility, potentiometric titration and cadmium ion adsorption experiments were used to quantify the number and concentrations of ligands and to determine the thermodynamic stability constants for the ligand-cation complexes. The first reported surface complexation models (SCMs) quantifying metal ion adsorption by thermophilic microorganisms predicted cadmium adsorption and desorption by both studied Geobacillus strains over a range of pH values and for different biomasses. The results indicated the functional group, with a deprotonation constant pK value of approximately 3.8, to be more dominant in cation biosorption accounting for 66 and 80% of all titrable groups for G. thermocatenulatus and G. stearothermophilus, respectively. The generated SCMs are different from model parameters obtained from mesophilic species that have been studied to date and might indicate a different biosorption behavior for both studied Geobacillus strains. Another objective of this thesis was to characterize microbial populations in the hot spring Champagne Pool, located in Waiotapu, New Zealand. The thermal spring is approximately 65 m in diameter and discharges water at 75eg; C and pH 5.5, which is oversaturated with arsenic and antimony compounds that precipitate and form orange deposits. Recovered nucleic acids and adenosine 5'-triphosphate (ATP) concentrations obtained for Champagne Pool water samples indicated low microbial density and were in good agreement with relatively low cell numbers of 5.6 plusmn; 0.5 x10^6 cells per ml. Denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library analyses revealed the abundance of Sulfurihydrogenibium, Sulfolobus and Thermofilum-like populations in Champagne Pool. Two novel bacteria and one novel archaeon were successfully isolated with a distant phylogenetic relationship to Sulfurihydrogenibium, Thermoanaerobacter, and Thermococcus, respectively. Genotypic and metabolic characteristics differentiated isolate CP.B2 from described species of the genus Sulfurihydrogenibium. CP.B2 represents a novel genus within the Aquificales order, for which the name Venenivibrio stagnispumantis gen. nov., sp. nov. is proposed. V. stagnispumantis is a thermophilic, chemolithothrophic bacterium, that utilizes molecular hydrogen as electron donor and oxygen as electron acceptor and displayed growth in the presence of up to 8 mM NaAsO2 (As3+) and more than 20 mM Na2HAsO4.7H2O (As5+). However, growth was not observed when Na2HAsO4.7H2O and NaAsO2 were provided as the sole electron acceptor and donor pair. Arsenic resistance was conferred by the genes arsA and arsB
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Seo, Jin Seog. "Hydrolyzing phosphates with metal ions : di and trinuclear approach." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq30381.pdf.
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Ouyang, Hui. "Calmodulin interactions with peptides, hormones, drugs and metal ions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0025/NQ49528.pdf.
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Ager, Patrick. "Mobilizationpurging of aqueous metal ions into supercritical carbon dioxide." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20553.
Повний текст джерелаАнотація:
The technology of supercritical fluid extraction (SFE) offers the opportunity to efficiently extract both relatively non-polar analytes as well as ionic materials (such as metal ions) that can be mobilized with the addition of complexing reagents. The nebulizer of a conventional flame atomic absorption spectrometer (FAAS) was modified to extend the range of metals amenable to on-line detection. The flow injection thermospray-FAAS (FI-TE-FAAS) interface provided efficient detection for a variety of less volatile elements (Co, Cr(III), Cr(VI), Fe, Ni, Mn and Al) present as ions in aqueous media or as complexes in the supercritical fluid (SC-CO2) carrier phase. The range of possible metal analytes that can be monitored has been increased over the nine elements (Ag, As, Cd, Cu, Hg, Mn, Pb, Se and Zn) that could be detected with an all-silica interface. The acetylacetonate complexes offered considerable potential for metal detection in an SC-CO2 carrier phase. Limits of detection (LODs) were used to compare the instrument responses to different metals. (Abstract shortened by UMI.)
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Tobin, John M. (John Michael). "The uptake of metal ions by rhizopus arrhizus biomass /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73999.
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Taylor, T. M. C. "Modified phospholipids : Oxidation promoted by vesicle-bound metal ions." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382664.
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Shackleford, Stephen. "Development of an EQCM-based sensor for metal ions." Thesis, University of Central Lancashire, 2002. http://clok.uclan.ac.uk/8090/.
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A series of fundamental studies are presented of the components of a prototypical electrochemical quartz crystal microbalance (EQCM)-based sensor for metal ions. Designed for use in the nuclear industry, the sensor consists of a gold (Au) piezoelectrode modified by a Nafion® polymer layer impregnated with a cationic hydroxainic acid (HA), a ligand showing oxidation state specific selectivity towards actinide 4+ ions and a non-radioactive demonstrator ion, Fe3+ In its final configuration, the polymer layer will also contain a redox mediator, methylene blue (MB), to facilitate electrochemical conditioning of the analyte. The following results have been obtained from EQCM and microelectrode voltammetry studies of each of the component parts. The Gold Piezoelectrode - The dissolution and redeposition processes of Au in HNO3 solution at pH I & 0 were investigated as a function of sweep rate (v). At pH I and v < 10 mV s-1 , Au dissolves through a 3e’ oxidation at E > +1.00 V (vs. SCE), a process that, at v ≤ 10 mV s-1, is kinetically hindered with respect to under potential deposition (UPD) of OH surface sublattices and subsequent 2-D-phase oxide formation. The inhibition arises from a closed packed layer of nitrate ions at the gold surface, although the layer is disrupted and the inhibition removed by the gold dissolution and reprecipitation processes that occur during potential cycling at low v. The Hydroxamic Acid Ligand - Study of the oxidation of acetohydroxamic acid (AHA) in nitric acid revealed that three processes occur at Au electrodes at potentials in the vicinity of AHA oxidation at pH 0 & I: (a) oxidation of the Au surface; (b) oxidation of the AHA; (c) complexation of the AHA with electrogenerated Au3+ . The last process inhibits oxide formation and associated electrode passivation, so promoting the occurrence of the first two. The two current peaks associated with AHA oxidation show no associated mass change, indicating that AHA oxidation is controlled by semi-infinite diffusion. The waves correspond to I and 2 electron processes with current onsets of +0.55 V and ̴̴̴+0.80 V (vs. SCE) respectively. Oxidation of AHA appears to be irreversible and blocked at electrodes with minimal microscopic roughness by close packing of nitrate ions at the surface. The Polymer Layer and the Demonstrator Ion, Fe 3+ - Microelectrogravimetric studies of the Fe2+/3+ couple were conducted at bare Au, Nafion® modified Au and Nafion® modified Au impregnated with the hydrophobic cationic HA ligand, desferrioximine (DFA+) electrode. In background nitric acid (pH 1 & 0), the electrochemistry of Nafion ® layer partitioned Fe 2+/3+ ions exhibits thin layer cell behaviour with the polymer layer increasing in mass during reduction of Fe(III) due to an influx of highly hydrated H+ ions necessary to maintain electroneutrality. Studies on Nafion® layers impregnated with DFA+ and Fe3+ show that while Fe3+ complexes with DFA+, Fe2+ does not and that, upon reduction of the complexed ferric ion, the resultant Fe(II)-DFA+ complex dissociates suggesting that electrochemical expulsion of the analyte is possible. The Redox Mediator - At pH 7.9, the reduction of methylene blue (MB) to leucomethylene blue (LMB), occurs in two steps: (i) a reversible net 1.5 e transfer to form a solid charge transfer complex (LMB/LMB+) (ii) an irreversible reduction of LMB/LMB+ to LMB, the onset of which can be directly observed as an inflection in the voltamassogram, the first time that this has been reported. The reversibility of the MB to LMB reduction within the context of charge transfer complex electrogeneration suggests that MB may be a suitable mediator for actinide cation reduction within the polymer layer of the proposed sensor. It is known that the pendular amino-groups of LMB are protonated below pH 1, so rendering the resultant LMBH22+ soluble in aqueous solution. This means (a) difficulties associated with the irreversibile reoxidation of the solid LMB generated at pH 7.9 will be obviated at pH I; and (b) being a large cation, we could expect LMBH22+ to be retained within the Nafion® layer.
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Dobson, Matthew Peter. "Studies of singly and doubly charged solvated metal ions." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321352.
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Kwon, Yeong Kun. "Chemistry of some complexes containing biologically significant metal ions." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46401.
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Botelho, Hugo M. "Metal ions and protein folding: conformational and functional interplay." Doctoral thesis, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2010. http://hdl.handle.net/10362/5151.
Повний текст джерелаАнотація:
Dissertation presented to obtain a PhD degree in Biochemistry at Instituto de Tecnologia Química e Biológica, Universidade Nova de LisboaMetal ions are cofactors in about 30% of all proteins, where they fulfill catalytical and structural roles. Due to their unique chemistry and coordination properties they effectively expand the intrinsic polypeptide properties (by participating in catalysis or electron transfer reactions), stabilize protein conformations (like in zinc fingers) and mediate signal transduction (by promoting functionally relevant protein conformational changes). However, metal ions can also exert have deleterious effects in living systems by incorporating in non-native binding sites, promoting aberrant protein aggregation or mediating redox cycling with generation of reactive oxygen and nitrogen species. For this reason, the characterization of the roles of metal ions as modulators of protein conformation and stability provides fundamental knowledge on protein folding properties and is instrumental in establishing the molecular basis of disease. In this thesis we have analyzed protein folding processes using model protein systems incorporating covalently bound metal cofactors – iron-sulfur (FeS) proteins – or where metal ion binding is reversible and associated conformational readjustments – the S100 proteins.(...)
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Lawrence, Helen. "Cellular recognition of metal ions and mechanisms of reactivity." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3323.
Повний текст джерелаАнотація:
Hip replacement is the main therapeutic intervention for end-stage osteoarthritis (OA). Metal-on-metal (MoM) hip implants were introduced to provide a durable alternative to ceramic and polyethylene devices, particularly in a younger patient population. However they are associated with the development of adverse reactions to metal debris (ARMD) which includes osteolysis, soft tissues necrosis, and inflammatory pseudotumours. MoM implants are usually fabricated from a cobalt-chrome alloy. Cobalt activates human Toll-like receptor 4 (TLR4), an innate immune receptor also activated by bacterial lipopolysaccharide (LPS). This study set out to investigate the inflammatory consequences of cobalt-mediated TLR4 activation through a series of in vitro assays developed throughout this work. In human MonoMac 6 macrophages cobalt was found to increase secretion and expression of pro-inflammatory cytokines including IL-8, IL-6 and CCL20. Using IL-8 as a marker of TLR4 activation a small molecule TLR4 antagonist, CLI-095, was shown to inhibit these effects, indicating that they are TLR4-dependent. Similar responses were observed in endothelial cells and osteoblasts. A monoclonal anti-TLR4 neutralising antibody inhibited cobalt-mediated IL-8 expression and secretion, while a polyclonal anti-TLR4 neutralising antibody did not. Further investigation showed that cobalt-mediated TLR4 activation increases expression of intercellular adhesion molecule 1 (ICAM1) and its soluble form sICAM-1. It also promotes primary monocyte and neutrophil migration. A TLR4 mutation did not prevent inflammatory responses to cobalt, although further assay optimisation is required. Co-stimulation of MonoMac 6 cells with cobalt and LPS or nickel caused downregulation of IL6, CCL2 and IL8 expression. Finally, unlike cobalt, chromium and strontium ions did not activate TLR4 and did not induce IL-6 or IL-8 secretion in macrophages. In summary, this study has shown that TLR4 activation by cobalt ions from MoM hip implants results in increased cellular inflammatory responses. The use of TLR4 inhibitors in this study suggests that TLR4 is a potential therapeutic target in ARMD. Overall, the TLR4 signalling pathway is an interesting avenue for further investigation into factors underlying MoM implant failure.
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Ca, Diep Vu. "NANOSTRUCTURED ASSEMBLIES FOR SOLID PHASE EXTRACTION OF METAL IONS." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1107552000.
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Xiao, Kexing. "Deprotonation Property of Polyoxometalates with Different Lacunary Metal Ions." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron155534024745702.
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Naqvi, Kazim Raza. "Role of transition metal ions in oxidative hair colouring." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/6955/.
Повний текст джерелаАнотація:
The objective of this Ph.D. project was to study the role of transition metal ions in oxidative hair colouring. Model systems corresponding to real-life hair colouring conditions were designed to examine copper(II) and iron(III) catalysed decomposition of alkaline hydrogen peroxide and hydroxyl radical formation. In a chelant-free system, copper(II) ions were more active in decomposing alkaline hydrogen peroxide compared to iron(III) ions. For copper(II) ions, the initial rate of decomposition of hydrogen peroxide and hydroxyl radical formation increased with an increase in initial concentration of copper(II) ions. Adding chelants to the reaction solution altered the catalytic activity of metal ions. EDTA and EDDS chelants with iron(III) generated more hydroxyl radical and decomposed higher amounts of hydrogen peroxide than the corresponding complexes of these chelants with copper(II) ions. Most studied chelants supressed catalytic activity of copper(II) ions except HEDP chelant which rapidly decomposed hydrogen peroxide. The results highlight that different metal-chelant systems have different level of catalytic activity in the decomposition of hydrogen peroxide. Adding large excess of calcium ions to the reaction solution influenced the binding of copper(II) ions. Unlike other chelants, only EDDS showed selective binding of copper(II) ions in the presence of calcium and suppressed the decomposition of hydrogen peroxide. Similar results were obtained for copper treated hair fibres, where EDDS again showed strong preference and selectivity for copper(II). This suggests that EDDS is the best chelant to control free radical mediated protein hair damage during oxidative hair colouring. The selectivity of EDDS chelant was explained using speciation plots. Catalytic activity of copper(II) ions was also examined in the presence of aromatic dye precursors. PPD/MAP combination suppressed decomposition of alkaline hydrogen peroxide which suggests that oxidative hair dyeing is likely to induce less protein damage to hair as compared to the bleaching systems. It is believed that some unknown intermediates are formed which chelate copper catalysts changing their chemical activity. Among the chelants examined in the current study, HEDP is an exception as its mixture with copper(II) ions led to rapid decomposition of alkaline hydrogen peroxide and showed a very unusual kinetic profile. A mechanistic study showed that the decomposition reaction proceeds via formation of an active catalyst that degrades the chelant and eventually seeds formation of catalytically-inactive basic copper phosphate/carbonate nanoparticles. The nanoparticles prevent any further catalytic reaction as freshly added Cu2+ ions quickly adsorb on their surface and do not form active catalyst. In a separate study, human hair samples were analysed to quantify the amount of calcium carbonate present in the bubble shaped structures lying over the hair shaft. SEM Images were analysed to estimate the amount of material present while quantitative gas IR analysis showed that the amount of calcium carbonate increased with increasing bubble count level. Calcium carbonate found by IR analysis was less than the values estimated by image analysis which suggested that calcium carbonate may not be the only material present in the bubble and some other unknown material may also be present.
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Savage, Chandra Shannon. "Ions, isotopes, and metal cyanides: Observational and laboratory studies." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290082.
Повний текст джерелаАнотація:
Chemistry in the interstellar medium is very different from the processes which take place in terrestrial settings. Environments such as circumstellar envelopes, molecular clouds, and comets contain diverse and complex chemical networks. The low temperatures (10-50 K) and densities (1-10⁶ cm⁻³) allow normally unstable molecules to exist in significant quantities. At these temperatures, the rotational energy levels of molecules are populated, and thus these species can be detected by millimeter-wave radio astronomy. The detection and quantification of interstellar molecules, including metal cyanides and molecular ions, is the basis of this dissertation work. While conducting observations of CN and ¹³CN to determine the ¹²C/¹³C ratio throughout the Galaxy, it was found that the ratios in photon-dominated regions (PDRs) were much higher than those in nearby molecular clouds. This can be explained by isotope-selective photodissociation, in which the ¹²CN molecules are self-shielded. However, the chemistry in these regions is poorly understood, and other processes may be occurring. In order to understand one of the chemical networks present in PDRs, observations of HCO⁺, HOC⁺, and CO⁺ were made toward several of these sources. Previous studies indicated that the HCO⁺/HOC⁺ ratio was much lower in PDRs, due to the presence of CO⁺. The new observations indicate that there is a strong correlation between CO⁺ and HOC⁺ abundances, which suggests that other molecular ions which have not been detected in molecular clouds may be present in PDRs. There is a significant obstacle to the detection of new interstellar molecular ions, however. The laboratory spectra are virtually unknown for many of these species, due to their inherent instability. Thus, techniques which can selectively detect ionic spectra must be utilized. One such method is velocity modulation, which incorporates an AC electrical discharge to produce and detect ions. Previously, velocity modulation spectroscopy was employed only at infrared wavelengths. The final phase of this dissertation work was to design, build and test a velocity modulation spectrometer which functions at millimeter/sub-mm wavelengths. This system was then used to measure the previously unknown pure rotational spectrum of SH⁺ (X3Σ⁻).
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Baker, Douglas Hugh. "Formation and desorption of negative ions from metal surfaces." W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539623825.
Повний текст джерелаАнотація:
Investigations of negative ion and electron emission from gas-covered metal surfaces due to the impact of low energy (30-300 eV) positive ions and, separately, photons (2-5 eV) are presented. In both cases, the negative ion formation process is thought to occur via electron tunneling from the surface or its substrate to a sputtered or photodesorbed neutral atom or molecule.;In particular, absolute total negative ion and electron yields for collisions of positive alkali ions with a gas-covered Mo substrate have been measured. Mass analysis of the sputtered negative ions show that O{dollar}\sb2\sp-{dollar} is the dominant ion at low impact energies. This coupled with the fact that threshold energies for observing secondary negative ions and electrons are the same suggests that electron production is correlated to the O{dollar}\sb2\sp-{dollar} production, and specifically that electrons are the result of autodetachment of excited O{dollar}\sb2\sp-{dollar}. This hypothesis provides an explanation of the mechanism responsible for the emission of electrons at low impact energies.;Relative yields for photodesorbed H{dollar}\sp-{dollar} from a barium substrate have been measured as a function of photon wavelength for the range of 245 to 585 nm. A description of the formation of H{dollar}\sp-{dollar} due to photodesorption of BaH on a surface is consistent with the known energetics of the system. An estimate of the absolute yield of photodesorbed H{dollar}\sp-{dollar} per incident photon has been made.
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Schilling, J. Bruce Goddard William A. Beauchamp Jesse L. "Experimental and theoretical aspects of hydrocarbon activation by transition metal ions in the gas phase." Diss., Pasadena, Calif. : California Institute of Technology, 1987. http://resolver.caltech.edu/CaltechTHESIS:11062009-094101367.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--California Institute of Technology, 1987. UM #87-19,702.Advisor names found in the Acknowledgements pages of the thesis. Title from home page. Viewed 01/15/2010. Includes bibliographical references.
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Chen, Yongsheng. "Synthesis and properties of benzannulenes and their metal complexes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0013/NQ32706.pdf.
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Tkaczyk, Cathy. "Ions released from metal-on-metal hip implants: «in vitro» and «in vivo» investigations." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86703.
Повний текст джерелаАнотація:
Studies have shown that Co and Cr particles and ions can enter the bloodstream and accumulate in tissues and organs of patients after metal-on-metal (MM) total hip arthroplasty (THA). These ions can generate reactive oxygen species (ROS) that can be deleterious for cells. We first assessed the biological effects of Cr(VI), Co(II), and Cr(III) by testing their effect on antioxidant enzymes (SODs, CAT, GPx, HO-1) that represent a primary defense system against ROS. We demonstrated that Cr(VI) induced the protein expression (translation) of antioxidant enzymes, whereas it had no effect on the mRNA expression (transcription). Co(II) induced the expression of both protein and mRNA of HO-1 only. Cr(III) had no effect on the activity of these enzymes. We then suggested that a difference in molecular structure may be at the origin of their differential effects and showed that Cr(III) can form precipitable complexes, whereas Co(II) and Cr(VI) cannot form complexes in the same experimental conditions. These Cr(III) complexes, formed in simulated-physiological fluids, were constituted by an organic phase (amino acids, phosphate) tangled with an inorganic phase (Cr, Ca, Na). Interestingly, these Cr(III) complexes interacted only with albumin in presence of fetal bovine serum, whereas they interacted with 8 different human serum proteins in presence of human serum. The interaction of Cr(III) complexes with serum proteins affect their internalization by macrophages, complexes formed with human serum being more easily internalized than those bound to bovine proteins. Lastly, results suggested that the levels of Co and Cr ions in patients with MM THA are not sufficient to induce significant oxidative stress in the blood of these patients, bringing optimism over concern for the long term biological effects of Co and Cr ions released from metal-metal bearings. In conclusion, this thesis gives very valuable information on the biological effects of Cr and Co ions and gives insight iDe nombreuses études ont montré que les particules et ions métalliques (Cr(III), Co(II) et Cr(VI)) générés par l'usure de prothèses de hanche métalliques (PHM) se retrouvent dans le flux sanguin des patients et s'accumulent également dans leurs tissus et leurs organes. Ces ions peuvent génèrer des radicaux libres qui peuvent à leur tour être nocifs pour la cellule. Nous avons déterminé les effets de ces ions sur les enzymes antioxidantes (SODs, CAT, GPx, HO-1) qui représentent la première ligne de défense cellulaire contre les radicaux libres. Nos travaux ont révélé que le Cr(VI) induit l'expression de ces protéines (traduction) mais non l'expression de leur ARNm (transcription). Le Co(II) induit l'expression de la proteine et de l'ARNm de HO-1 seulement alors que le Cr(III) n'a aucun effet sur l'expression de ces enzymes. Nous avons par la suite suggéré, que la structure moléculaire de ces ions pouvait avoir une influence sur leurs différents effets. Les résultats ont montré que le Cr(III) formait des complexes constitués d'une partie organique (acides aminés et phosphates) et d'une partie inorganique (Cr, calcium et sodium), alors que ni le Co(II), ni le Cr(VI) ne formaient de complexes dans les mêmes conditions expérimentales. En présence de sérum bovin fétal, les complexes de Cr(III) pouvent se lier seulement à l'albumine, alors qu'en présence de sérum humain, ces mêmes complexes intéragissent avec 8 protéines de nature differente. Cette intéraction avec les protéines humaines semble augmenter l'internalisation des complexes par les macrophages. Finalement, les résultats démontrent que la concentration d'ions Co et Cr présents dans le sang de patients portant une PHM est insuffisante pour induire un stress oxydant et apportent un souffle optimiste sur les effets à long terme des ions métalliques chez les patients. Dans son ensemble ce projet apporte de nouveaux éléments de connaissances sur les effets biologiq
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Martinez, Ortega Maria Eugenia. "Lipid metal organic networks." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Повний текст джерела
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Cruz, González Sara. "Availability of metal ions and ZnO nanoparticles in aqueous media." Doctoral thesis, Universitat de Lleida, 2015. http://hdl.handle.net/10803/314762.
Повний текст джерелаАнотація:
La presència de determinats metalls, ja sigui en forma del metall lliure, formant complexos amb lligands o en forma de nanopartícules metàl•liques té efectes negatius en el medi ambient. Per aquest motiu, l’estudi de la disponibilitat de metalls és important per determinar el seu impacte mediambiental.
En aquest treball s'ha estudiat un sistema i una tècnica per a la mesura de la disponibilitat. El sistema té la particularitat de contenir, en dispersió, nanopartícules d’òxids metàl•lics. Una primera part de l’estudi s’enfoca a la caracterització físic-química de dispersions sintètiques de nanopartícules. Aquesta part estudia l’efecte que tenen les condicions del medi (pH, salinitat, contingut de matèria orgànica, etc.) en el comportament de les nanopartícules. S'han determinat processos com són l’agregació, solubilització i sedimentació, en funció de les condicions del medi. Tots aquests processos juguen un paper molt important en el destí de les nanopartícules en el medi ambient i en la seva toxicitat.
La segona part d’aquesta tesi es centra en l’aplicació de la tècnica analítica DGT (Diffusive Gradient in Thin films) per la mesura de fluxos de metall disponibles en solucions aquoses. En el present treball, s’ha determinat la solubilitat de nanopartícules en dispersions aquoses. Per altra banda s'ha estudiat la tècnica DGT des d’un punt de vista físic-químic. Les contribucions dels fluxos de complexos s’avaluen amb un paràmetre que té en compte les constants de dissociació dels complexos així com la seva difusió. S'han estudiat les acumulacions de metalls que en solució tenen com especies dominants complexos carregats elèctricament. Si aquesta càrrega és negativa, l’acumulació disminueix en baixar la força iònica i a l’inrevés en el cas contrari. Aquest fenomen s’explica per la repulsió electrostàtica entre la càrrega negativa del disc de resina i el complex quan aquest és parcialment làbil. En conclusió, la resina sembla jugar un paper més actiu del que es pensava en l’acumulació de metalls en DGT.La presencia de determinados metales, ya sea en forma del metal libre, formando complejos con ligandos o en forma de nanopartículas metálicas tiene efectos negativos en el medio ambiente. Por este motivo, el estudio de la disponibilidad de metales es importante para determinar su impacto medioambiental. En este trabajo se ha estudiado un sistema y una técnica para la medida de la disponibilidad. El sistema tiene la particularidad de contener, en dispersión, nanopartículas de óxidos metálicos. Una primera parte del estudio se enfoca a la caracterización físico-química de dispersiones sintéticas de nanopartículas. Esta parte estudia el efecto que tienen las condiciones del medio (pH, salinidad, contenido de materia orgánica, etc) en el comportamiento de las nanopartículas. Se han determinado procesos como son la agregación, solubilidad y sedimentación, en función de las condiciones del medio. Todos estos procesos juegan un papel muy importante en el destino de las nanopartículas en el medio ambiente y en su toxicidad. La segunda parte de esta tesis se centra en la aplicación de la técnica analítica DGT (Diffusive Gradiente in Thin films) para la medida de flujos de metal disponibles en soluciones acuosas. En el presente trabajo, se ha determinado la solubilidad de nanopartículas en dispersiones acuosas. Por otra parte se ha estudiado la técnica DGT desde un punto de vista físico-químico. Las contribuciones de los flujos de complejos se evalúan con un parámetro que tiene en cuenta las constantes de disociación de los complejos así como su difusión. Se han estudiado las acumulaciones de metales que en solución tienen como especies dominantes complejos cargados eléctricamente. Si esta carga es negativa, la acumulación disminuye al bajar la fuerza iónica y viceversa en el caso contrario. Este fenómeno se explica por la repulsión electrostática entre la carga negativa del disco de resina y el complejo cuando éste es parcialmente lábil. En conclusión, la resina parece jugar un papel más activo de lo que se pensaba en la acumulación de metales en DGT.
The presence of certain metals, either in the form of free metal, forming complexes with ligands or as metal nanoparticles has negative effects on the environment. For this reason, the study of the availability of metals is important in determining its environmental impact. In this work a system and a technique for measuring availability have been studied. The system contains, in dispersion, metal oxide nanoparticles. A first part of the study focuses on the physical and chemical characterization of synthetic dispersions of nanoparticles. This part examines the effect of environmental conditions (pH, salinity, organic matter content, etc.) in the behavior of nanoparticles. Processes such as aggregation, solubilisation and sedimentation, are determined depending on environmental conditions. All these processes play an important role in the fate of nanoparticles in the environment and their toxicity. The second part of this thesis focuses on the application of the analytical technique DGT (Diffusive Gradient in Thin films) for measuring the flow of available metals in aqueous solutions. In the present study, the solubility of nanoparticles in aqueous dispersions has been determined. Moreover the DGT technique has been studied from a physical-chemical point of view. The contribution of the flux of complexes has been evaluated with a parameter, the lability degree, which takes into account the dissociation constants of the complexes and their diffusion. The accumulations of metals which in solution are present as dominant metal complexes electrically charged have been studied. If the charge is negative, the accumulation decreases with the decrease of the ionic strength and vice versa in the opposite case. This phenomenon is explained by the electrostatic repulsion between the negatively charged resin disk and the complex when it is partially labile. In conclusion, the resin seems to play a more active role than previously thought in the accumulation of metals in DGT.
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Luo, Ming. "Transition-metal ions in II-VI semiconductors ZnSe and ZnTe /." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4630.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xiv, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 135-141).