Tesis sobre el tema "Ionic strength"
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1
Beriet, Carine. "Microelectrode studies in low ionic strength media". Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241602.
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Blair, Laura May. "Optimizing growth in low ionic strength solutions and the ameliorative effects of increased ionic strength on copper toxicity in Triticum aestivum (wheat) /". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22574.pdf.
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Weidgans, Bernhard M. "New fluorescent optical pH sensors with minimal effects of ionic strength". [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97274679X.
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Marcera, Donna M. "Conformational studies of carboxymethylcellulose in aqueous saline solutions as a function of ionic strength /". Online version of thesis, 1990. http://hdl.handle.net/1850/10684.
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Deeyaa, Blessing D. "DNA Photocleavage by 9-Aminomethylanthracene Dyes at pH 7.0: Ionic Strength Effects". Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/chemistry_theses/39.
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DNA photosensitizers are compounds that are capable of binding in to DNA strands through groove binding, intercalation, or electrostatic interactions. Excitation of these agents by light generates reactive oxygen species which causes extensive photo-oxidative damage to genomic DNA. Physiological concentrations of NaCl and KCl are ~ 150 mM and 260 mM within the cell nucleus where DNA is contained. Unfortunately, the ability of most photosensitizers to bind to double-helical DNA is reduced and photocleavage yields are diminished as concentrations of salt increase. The aim of this project is to observe the photocleavage of pUC19 plasmid DNA induced by N1,N1-bis(9-anthrymethyl)triethylenetetraamine tetrahydrochloride (AL-VIII 23) 1 or N,N-dimethyl-N’-(9-methylanthracenyl)ethylenediamine (NMEA) 2 in presence of salt. Spectroscopic titrations and DNA melting assays were used to study binding modes and affinities of both dyes to the helix upon the addition of salt.
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He, Yongtian. "Chromate reduction and immobilization under high pH and high ionic strength conditions". Columbus, OH : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1047476794.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xix, 219 p.: ill. (some col.). Includes abstract and vita. Advisor: Samuel J. Traina, Environmental Science Graduate Program. Includes bibliographical references (p. 201-219).
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Carvajal-Figueroa, Maria Teresa 1959. "Solubility of quinoline in aqueous systems: Effect of pH and ionic strength". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/291584.
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Nitrogen-heterocyclic compounds are commonly found in gas waste and coal cleaning residue. Within this general compound class, quinoline is especially important because it has the potential to induce liver carcinoma and it also has a high solubility in water. The pH-solubility profile of quinoline was determined in citrate-phosphate buffer at different ionic strengths. The pKa was observed to change with ionic strength. The intrinsic solubility is always reported as a constant. However, in this study the intrinsic solubility was observed to vary with ionic strength. The solubility of quinoline is dependent on pH as well as the ionic strength. At pH values lower than the pKa (4.96), quinoline is in the protonated form (QH⁺), and enhanced solubility was observed. At pH values higher than the pKa, quinoline is in the neutral form (Q) which is the form that determines intrinsic solubility (So). So decreased with increasing ionic strength. This observation can be explained as a salting out effect. From the solubility data the apparent ionization constant, pKa, of quinoline was obtained for the different systems.
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Patterson, Adele. "Retention properties of porous graphite". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342124.
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Hossain, Mohammad Moshin. "Effects of HCO3- and ionic strength on the oxidation and dissolution of UO2". Licentiate thesis, KTH, Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4172.
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The kinetics for radiation induced dissolution of spent nuclear fuel is a key issue in the safety assessment of a future deep repository. Spent nuclear fuel mainly consists of UO2 and therefore the release of radionuclides (fission products and actinides) is assumed to be governed by the oxidation and subsequent dissolution of the UO2 matrix. The process is influenced by the dose rate in the surrounding groundwater (a function of fuel age and burn up) and on the groundwater composition. In this licentiate thesis the effects of HCO3- (a strong complexing agent for UO22+) and ionic strength on the kinetics of UO2 oxidation and dissolution of oxidized UO2 have been studied experimentally.
The experiments were performed using aqueous UO2 particle suspensions where the oxidant concentration was monitored as a function of reaction time. These reaction systems frequently display first order kinetics. Second order rate constants were obtained by varying the solid UO2 surface area to solution volume ratio and plotting the resulting pseudo first order rate constants against the surface area to solution volume ratio. The oxidants used were H2O2 (the most important oxidant under deep repository conditions), MnO4- and IrCl62-. The kinetics was studied as a function of HCO3- concentration and ionic strength (using NaCl and Na2SO4 as electrolytes).
The rate constant for the reaction between H2O2 and UO2 was found to increase linearly with the HCO3- concentration in the range 0-1 mM. Above 1 mM the rate constant is independent of the HCO3- concentration. The HCO3- concentration independent rate constant is interpreted as being the true rate constant for oxidation of UO2 by H2O2 [(4.4 ± 0.3) x 10-6 m min-1] while the HCO3- concentration dependent rate constant is used to estimate the rate constant for HCO3- facilitated dissolution of UO22+ (oxidized UO2) [(8.8 ± 0.5) x 10-3 m min-1]. From experiments performed in suspensions free from HCO3- the rate constant for dissolution of UO22+ was also determined [(7 ± 1) x 10-8 mol m-2 s-1]. These rate constants are of significant importance for simulation of spent nuclear fuel dissolution.
The rate constant for the oxidation of UO2 by H2O2 (the HCO3- concentration independent rate constant) was found to be independent of ionic strength. However, the rate constant for dissolution of oxidized UO2 displayed ionic strength dependence, namely it increases with increasing ionic strength.
The HCO3- concentration and ionic strength dependence for the anionic oxidants is more complex since also the electron transfer process is expected to be ionic strength dependent. Furthermore, the kinetics for the anionic oxidants is more pH sensitive. For both MnO4- and IrCl62- the rate constant for the reaction with UO2 was found to be diffusion controlled at higher HCO3- concentrations (~0.2 M). Both oxidants also displayed ionic strength dependence even though the HCO3- independent reaction could not be studied exclusively.
Based on changes in reaction order from first to zeroth order kinetics (which occurs when the UO2 surface is completely oxidized) in HCO3- deficient systems the oxidation site density of the UO2 powder was determined. H2O2 and IrCl62- were used in these experiments giving similar results [(2.1 ± 0.1) x 10-4 and (2.7 ± 0.5) x 10-4 mol m-2, respectively].
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Hossain, Mohammad Moshin. "Effects of HCO₃- and ionic strength on the oxidation and dissolution of UO₂ /". Stockholm : Chemical Science and Engineering, KTH, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4172.
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Shaikh, Muhammad Javed 1955. "A regression model for mineral solubility as a function of ionic strength and temperature". Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/278069.
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An algorithm is developed to predict the solubility of gypsum and anhydrite as a function of ionic strength and temperature. Critically evaluated experimental data were used for fitting of an eight parameter equation using multiple regression analysis. The model was also used to fit the simulated solubility data for anhydrite and gypsum, generated by program PHRQPITZ. The correlation between the observed and fitted values was very high. The errors between experimental model and PHRQPITZ simulation were computed with the variation of temperature and ionic strength. A significant improvement in the errors was noticed by replacing the values of equilibrium constants in PHRQPITZ. Modifications have been made in the FORTRAN code of PHRQPITZ to convert the program for VAX and PC computers. Additional modifications were made in PHRQPITZ to convert the index numbering of elements/species compatible to another geochemical model PHREEQE. (Abstract shortened with permission of author.)
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Au, C. O. "The study of retention and function of C-14 labelled cationic and non-ionic starch in paper". Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330099.
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Ding, Hao. "Influence of solution ionic strength on aggregation of novel water soluble phosphines and two phase catalysis". Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-10042006-143900/.
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Barros, Davison Storai de. "Estudo espectroscopico e morfologico de filmes automontados de azocompostos". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249464.
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Orientador: Teresa Dib Zambon AtvarsDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-08T05:02:01Z (GMT). No. of bitstreams: 1 Barros_DavisonStoraide_M.pdf: 2037047 bytes, checksum: bfc81c7ccb14370261c20ba48859e0ec (MD5) Previous issue date: 2006
Resumo: Neste trabalho são estudadas as propriedades fotoquímicas e morfológicas de filmes automontados compostos de um polieletrólito fraco e azocorantes em função das condições impostas nas soluções de origem, como o pH, a força iônica e tamponamento. Na automontagem, os filmes são fabricados pela deposição de camadas alternadas de dois materiais, de cargas elétricas opostas, a partir de suas soluções aquosas em um substrato de vidro. Os materiais usados foram o polieletrólito catiônico hidrocloreto de poli(alilamina) (PAH) e três azocorantes aniônicos: Vermelho do Congo (CR), Ponceau SS (PSS) e Alaranjado de Metila (MO). Foram fabricados filmes de PAH/CR, PAH/PSS e PAH/MO. Para avaliar somente o efeito do pH, foram usados três valores de pH (3, 7 e 10). Para verificar o efeito da força iônica, foram usadas soluções aquosas de cloreto de potássio em diferentes concentrações e, para verificar a influência de tampão, foram usados três sistemas tampão, um para cada valor de pH. Foram usadas as técnicas de espectroscopia UV-vis e turbidimetria para investigar as propriedades espectroscópicas das soluções, dos filmes e a solubilidade do PAH. Foi utilizada a técnica de microscopia de força atômica para verificar a morfologia do filme. Observa-se que a deposição dos corantes e do PAH no filme depende de suas densidades de carga, bem como da presença de outras espécies iônicas em solução. Tanto um aumento do pH como a presença de contra-íons, leva a uma redução da carga do PAH e causa um aumento de sua adsorção no filme, acompanhado de um aumento de rugosidade superficial. Porém, a primeira condição pode ou não diminuir as cargas dos corantes e a segunda enfraquece a atração eletrostática, reduzindo as suas deposições. As interações do par corante-PAH induzem a agregação dos corantes em solução e nos filmes. As diferenças estruturais dos corantes são igualmente importantes, pois o CR e o PSS são os que mais se depositam e apresentam diferentes comportamentos de deposição em função do pH. Verifica-se também que o PAH interage distintamente com diferentes contra-íons, o que pode ser explicado considerando-se a especificidade iônica e não o simples conceito de força iônica
Abstract: In this work, the photochemical and morphological properties of layer-by-layer self¿assembly films made of a weak polyelectrolyte and azodyes are studied in dependence of the solution¿s pH, ionic strength and buffering. In self-assembly technique, films are made from deposition of alternate layers of two compounds, which have opposite electrical charges, from their solutions onto a glass substrate. We employed the polyelectrolyte poly(allylamine) hydrochloride (PAH) which is positively ionized when in aqueous solution and the three different anionic azodyes: Congo Red (CR), Ponceau SS (PSS) and Methyl Orange (MO). Films of PAH/CR, PAH/PSS and PAH/MO were prepared. To investigate only the pH effect, three pH values were used (3, 7 and 10). To investigate the ionic strength, potassium chloride aqueous solution at different concentrations were used and to verify the buffer effect, three buffer systems were used, one for each pH. The UV-Vis Spectroscopy and Turbidimetry were employed to study the spectroscopic properties of the solutions, films and PAH solubility. The Atomic Force Microscopy was used to verify the film morphology. One observes that the dyes and PAH deposition depend on their charge densities as well the presence of other ionic species. An increase in solution¿s pH and/or the presence of counter-ions reduces PAH¿s charge increasing its adsorption on film, accompanied by a higher surface roughness. Differently, the first condition can or cannot reduce the dye¿s charge and the second weakens the electrostatic interaction, reducing dye adsorption. The pair dye-PAH interactions induces the dye aggregation both in solution and film. The structural differences between dyes are equally important, as CR and PSS are the ones that adsorb most and show different deposition behavior in function of solution¿s pH. Also, one verifies that PAH interacts distinctly with different counter-ions, a fact that can be explained considering ionic specificity and not by the simple concept of ionic strength
Mestrado
Físico-Química
Mestre em Química
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Knowles-Van, Cappellen Victoria Leilani. "The effects of ionic strength and aggregation on crystal growth kinetics : an application of photon correlation spectroscopy". Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/20786.
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Madenci, Dilek. "Study of the aggregation behaviour of egg yolk lecithin/bile salt mixtures by increasing the ionic strength". Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4918.
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This thesis describes a study of the aggregational behaviour of egg yolk lecithin (EYL), a natural lecithin, and bile salt mixtures especially with respect to an increase of the ionic strength of the solvent. Mixtures of two amphiphiles with very different spontaneous curvature as EYL lecithin and bile salt form mixed micelles and vesicles in aqueous solution. Their properties have been well-studied under physiological conditions, i.e. 150 mM electrolyte concentration and pH 7- 8, while other conditions are still hardly explored. Upon increasing ionic strength the formed structures and the transitional pathways (micelles, coexistence of micelles and vesicles, and vesicles) change the generated structures completely from those observed under physiological conditions. We quantitatively determined these structures formed in a broad range of electrolyte concentrations with various scattering techniques, x-ray, light and neutron scattering and calorimetry. With calorimetry, phase diagrams in the EYL and bile salt concentration phase plane were determined at various ionic strength ranging from physiological salt concentration to up to 1000 mM. Additionally a new electrochemical approach using functionalised electrodes, i.e. sensitive and selective to bile salt, and thus to control the bile salt concentration in solution (concentrations below the critical micellar concentration (cmc)) was attempted, since bile salt removal or injection drives the micelle-to-vesicle or the vesicle-to-micelle transition, respectively, of the mixed aggregational system of EYL/bile salt. Although this control was not achieved within the framework of this thesis, promising results show directions for future experiments.
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Fike, Wonae Bong. "Sorption of Cadmium, Copper, Lead, and Zinc as influenced by pH, ionic strength and selected soil components". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29430.
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Metals sorption in soils is influenced by several factors, including pH, ionic strength, the presence of ionic composition or organic ligands, total amount of metals, and adsorbent loading. These conditions should be considered when evaluating metal sorption capacity of soil material or when applying laboratory results to field conditions. Metal sorption experiments were conducted on Bertie sandy and Starr-Dyke clay loam soils from long-term field studies in which soils received annual applications of copper-rich pig manure for 16 years.
Adsorption of Cd, Cu, Pb, and Zn as affected by different background electrolytes at various concentrations was investigated. Electrolytes were Na+, Ca2+, or Al3+ in perchlorate solution, and their concentrations ranged from 0.001 to 0.5 molc L-1. Increasing ionic strength decreased metal adsorption capacity. Electrolyte cation composition had a greater effect on adsorption than did electrolyte concentration. The order of sensitivity to cation composition of the electrolyte was Zn > Cd > Cu > Pb, and this effect was greater in Bertie sandy loam than Starr-Dyke clay loam soils. Little difference in Cu and Pb adsorption was observed between Na+ and Ca2+ in background solution.
Most added Cu was adsorbed at low concentrations regardless of pH, but at high concentrations Cu sorption was strongly related to solution pH. Increases in pH resulted in greater Cu sorption due to pH-dependent negative charges and precipitation. The USEPA recommends that soil systems receiving high metal loading rates be maintained at pH 6.5 or above because of the increased metal adsorption. However, pig manure applications to the Bertie soil resulted in greater Cu in soil solution than in control (no manure) soil at pH > 6.5 due to soluble organic matter.
Using the Langmuir equation to determine adsorption maxima for soil systems does not always give adequate estimates of adsorption and values from the equations are highly dependent upon soil environmental parameters. Given the limitations in prediction of adsorption maxima, and given that the amount of nonsorbed metal is as important as the adsorbed amount, the isolines of metal remaining in soil solution were provided with a given set of soil environmental factors.Ph. D.
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Becht, Nils O. "A study of charge and hydrodynamic effects in protein ultrafiltration". Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/12639.
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This thesis is concerned with the study of different effects in protein ultrafiltration including device configuration, solution chemistry and membrane charge In the recent and more established literature membrane fouling remains a challenging problem that limits the wider application of ultrafiltration. Thus, investigations which can aid understanding and potentially reduce membrane fouling are of particular interest and in this study the problem has been addressed from several different angles Polyethersulfone membranes were studied at varying pH and two ionic strengths using bovine serum albumm and lysozyme as the model proteins. The study was conducted both in a stirred cell and a crossflow configuration in order to evaluate the influence of different system hydrodynamics on filtration This work was further substantiated through the application of filtration models An attempt was also made to modify the membrane surface by low temperature plasma modification with the intention to preferentially alter the characteristics of the membrane surface Both unmodified and plasma-modified polyethersulfone membranes were characterised using a range of analytical methods including flux data, streaming potential, contact angle and MWCO measurements to aid results interpretation. The research showed that MWCO data quoted by manufacturers is mostly greater than that obtained during laboratory studies The MWCO technique was also used to highlight differences between the unmodified and plasma-modified membranes demonstrating that the modification resulted in a membrane with tighter pores in the lower molecular weight region. Concentration polarisation effects were found to be reduced as a result of the plasmamodification The study of protein filtration at different pH and ionic strengths demonstrated that ionic strength effects were more pronounced than pH effects It was also shown that changes m the ionic strength can be used to alter the degree of protein rejection for the given system concentration polarisation was found to be higher during crossflow filtration compared to stirred cell filtration The thesis adds to existing knowledge in the area of ultrafiltration emphasizing the importance of device configuration, solution chemistry as well as the potential of charged membranes
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Islamoglu, Sezin. "Effect Of Ionic Strength On The Performance Of Polymer Enhanced Ultrafiltration In Heavy Metal Removal From Aqueous Solutions". Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607832/index.pdf.
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Effect of ionic strength on the efficiency of heavy metal removal and recovery from aqueous solutions via continuous mode polymer enhanced ultrafiltration (PEUF) method was examined. Application of PEUF to divalent ions of cadmium, nickel and zinc after their prior linking with polyethylenimine (PEI) results in complete removal of metal ions from single component aqueous solutions at high pHs.
Binding ability and hence the extent of metal retention in high ionic strength medium exhibits differences between solutions containing single and multicomponent metal mixtures. In single component metal solutions, extent of retention decreases but
binding order of metals remains unaffected both in low and high ionic strength medium. But, in binary component metal mixtures, with increase in ionic strength the binding order of metals changes. Fractional separation of Cd, Ni and Zn ions from equimolar binary and ternary mixtures of these metals and effect of ionic strength on fractional separation efficiency
were investigated. Depending on pH and salt concentration and metal pairs present in the solution fractional separation can be achieved.Dynamic and static light scattering experiments were performed in order to gain insight about the conformational changes in PEI structure due to the pH and ionic strength alternations in solution. It was found that, the increase in ionic strength reduces the size of the macromolecules.
A chemical equilibrium model was developed in order to estimate the apparent binding constants of metal-PEI complexes. Based on the data obtained from continuous and batch mode PEUF experiments apparent binding constants were estimated and compared to reveal the performance differences between these operational modes.
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Mengestab, Tsegay. "Fate and Transport of Nano-TiO2 in Saturated Porous Media: Effect of pH, Ionic Strength and Flow Rate". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-252835.
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Titanium dioxide nanoparticles are widely used in a variety of products, such as pigments, paints, paper, plastics, cosmetics, nano-fibers, food coloring and photovoltaic cells, and the industry is growing at anexponential rate. It is believed that by 2025, 2.5 million tons of nano-TiO2 will be manufactured annually. Thus far, there has been very little research in the environmental impact of nano-TiO2. There is a need to understand the fate and transport of nanoTiO2 to mitigate their effect on human health, the ecosystems and the environment in general. The aim of this study was to investigate the impact of pH, flow rate and ionic strength on the deposition of nano-TiO2 in a saturated porous media (sand). Nano-TiO2 formed aggregates in solutions that had a pH near the point of zero charge for TiO2, which is at approximately pH 6.2 for TiO2. The formed aggregates showed very little mobility due to site blocking in the pores of the sandy medium, whereas at pH 7.5, the solutions’ concentration was more stable than at pH 6.3 and more mobile up to 10 mM. Above 10 mM, a decrease in mobility, due to reduction in repulsive energy interaction between the medium and the nanoparticles could be observed. Flow rate had also a marked effect on the deposition, i.e., the slower the flow rate, the higher on deposition, because of an increase in attachment efficiency. To verify the experimental results, a finite element solution of the reactive transport equation in one dimension was used to compare the fit between observed and simulated results. The model was run in inverse mode, to determine unknown parameter values such as dispersivity and detachment rate. In general, it was possible to obtain a good fit to theexperimental BTCs.Nanopartiklar av titaniumdioxid används allmänt i en mängd olika produkter, såsom pigment, färger,papper, plast, kosmetika, nanofibrer, matfärgläggning, och solceller. Branschen växer explosionsartat.Man tror att år 2025 kommer 2,5 miljoner ton nano-TiO2 tillverkas årligen. Hittills har väldigt lite forskning gjorts på området nano-TiO2. Det finns ett behov av att förstå transportprocesser och vad som händer med nanoTiO2 i miljön för att bla kunna mildra effekter av dessa partiklar på människors hälsa, ekologi och miljö. Syftet med denna studie var att undersöka effekten av pH, flöde och jonstyrka (IS) på transporten av nano - TiO2 i vattenmättade porösa medier (sand). Nano - TiO2 bildade aggregat i lösningar som hade ett pH nära pH(PZC), pH(PZC) är pH-värdet vid vilket laddningen är noll, ungefär pH 6,2 för TiO2. Vid pH 6,3 visade nano partiklarna mycket liten rörlighet på grund av fysisk igentäppning i porerna av sandmediet, medan vid pH 7,5 var lösningens koncentration mer stabil och partiklarna mer mobila upp till en jonstyrka på 10 mM. Över 10 mM, observerades en minskning i rörlighet, på grund av minskad repellerande energi mellan mediet och nano partiklarna.Flödeshastighet hade också en markant inverkan på retentionen av partiklar i kolonnen, ju långsammare flöde, desto större retention, på grund av mer gynnsamma förhållande för fastläggning av partiklar till mediet. För att verifiera de experimentella resultaten och jämföra observerade och simulerade resultat användes en lösning med finita-elementmetoden av den reaktiva transportekvationen i en dimension. Inversmodellering gjordes för att ta reda på okända parametervärden såsom dispersivitet och fastläggning. Det var i allmänhet möjligt att uppnå god överensstämmelse mellan observerade ochexperimentella genombrottskurvor.
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Lehmann, Christian [Verfasser]. "Optimization of cellulase CelA2 with improved performance in high ionic strength for the production of biofuels / Christian Lehmann". Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1043523448/34.
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Anop, Hanna. "Directing through low ionic strength, free polymers and metallic nanoparticles the self-organization of viral rod-shaped colloids". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0119.
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Les bactériophages en forme de filament, en raison de leurs propriétés physiques uniques, telles que leur monodispersité en taille et leur haute stabilité colloïdale, sont largement utilisés en matière molle en tant que système modèle de bâtonnets colloïdaux. En dispersions aqueuses, l'auto-organisation de ces virus s’est révélée être essentiellement conduite par l’entropie, ce qui implique des interactions purement répulsives entre les particules virales. Dans cette thèse, en modifiant la nature des interactions entre les bâtonnets viraux, nous avons étudié leur auto-organisation en phase cristal-liquides. Dans ce but, nous avons d'abord étudié un système de bâtonnets purement répulsifs à très basse force ionique, et longue répulsion électrostatique. Le comportement de phase de ces suspensions a été déterminé par l’utilisation de la diffusion des rayons X aux petits angles et de la microscopie optique. Nous avons montré que la phase Smectique-A n’est pas stable dans les cas de forte répulsion électrostatique entre particules virales et que le système présente une transition directe de la phase de Cholestérique à la phase Smectique-B en augmentant la fraction volumique. De plus, nos résultats mettent en évidence que les virus dans ces conditions ne forment pas de verres colloïdaux à forte concentration, ce qui contredit de récents travaux réalisés sur le même système.Dans une deuxième partie, nous avons modifié les interactions entre particules virales passant de purement répulsives à attractives en ajoutant des polymères libres aux suspensions, ce qui conduit à un effet de déplétion. En utilisant des polymères dont la taille est similaire au diamètre des bâtonnets, l'auto-organisation des virus, initiée dans la phase cristal-liquide cholestérique, conduit à une croissance de superstructures hélicoïdales. Dans ces structures, les bâtonnets sont principalement orientés le long de l'axe principal et présentent un ordre positionnel à longue portée, démontré par la diffusion des rayons X aux petits angles et le suivi de particules individuelles en microscopie optique. Les diagrammes de phase dse mélanges virus/polymères ainsi que la stabilité dans le temps des superstructures hélicoïdales ont été déterminés et comparés pour deux tailles différentes de polymères.Dans la dernière partie, nous avons favorisé les interactions attractives de Van der Waals dans notre système en introduisant des nanoparticules d'or dans des colloïdes hybrides auto-assemblés à base de virus. Ainsi, différents colloïdes hybrides consistant en un (en forme de sceptre) ou deux (dibloc) virus attachés à la même nanoparticule d'or ont été produits. Cette approche utilisant les nanoparticules d'or a été étendue afin de lier ensemble deux virus de différentes longueurs pour obtenir des diblocs colloïdaux asymétriques. L'auto-organisation des particules en forme de sceptre et des diblocs symétriques induite par déplétion a été explorée et les diagrammes de phases correspondants ont été établis. Nous avons ainsi montré que les interactions de Van der Waals entre nanoparticules d'or favorise la formation de fibrilles de type Smectique-B dans lesquelles les particules de virus sont organisées en une succession de couches séparées par des couches de nanoparticules d’or. Finalement, nous avons étudié l'effet de l'introduction d'une faible asymétrie dans de ces colloïdes hybrides et l’effet sur la ségrégation potentielle de leurs blocs respectifs au travers de la formation de phase lamellaire de type Smectique-A.Dans cette thèse, nous avons ainsi démontré une manière efficace de contrôler l'auto-organisation de colloïdes en forme de filament en modifiant leurs interactions, ce qui conduit à la formation de diverses morphologies auto-assemblées originalesFilamentous bacteriophages, due to their unique physical properties, such as size monodispersity and high colloidal stability, are widely used in soft condensed matter as a system of rod-shaped colloids. In aqueous dispersions, self-organization of these viruses has been shown to be essentially driven by entropy, which means purely repulsive (hard core) interactions between viral particles. In this thesis, by varying the nature of the interactions between viral rods, we have studied their resulting self-organization into liquid crystalline phases. For this purpose, we have first investigated the system of purely repulsive rods at very low ionic strength, where thick electric double layers are present. The phase behavior of virus suspensions at very low ionic strength has been determined using small angle X-ray scattering (SAXS) and optical microscopy techniques. We have found that the Smectic-A phase is not stable in case of high electrostatic repulsion between viral particles and that the system undergoes a direct Cholesteric to Smectic-B phase transition by increasing rod concentration. Moreover, our results evidence that viruses with thick double layers do not form colloidal glasses at high concentrations, which contradicts recently reported findings for the same system.In a second part, we have tuned viral particle interactions from purely repulsive to attractive ones by adding non-adsorbing polymers in their suspensions, which act as depletant agent. By using polymers with coil size comparable to the rod diameter, virus self-organization initiated from the Cholesteric liquid crystalline phase results in a growth of original chiral superstructures, called helical bundles. Viruses are mostly oriented along the main bundle axis and exhibit long-range positional order, as proved by SAXS and by single particle tracking using optical microscopy. Phase diagrams of virus/polymer two-component mixtures as well as the stability with time of the resultant helical superstructures have been determined and compared for two different polymer sizes.In the last part, we have increased Van der Waals attractive interactions in our viral system by introducing gold nanoparticles into self-assembled hybrid virus-based colloids. Thus, different hybrid virus-based colloids consisting of one (scepter-like) or two (diblocks) viral filaments attached to the same gold nanoparticle have been produced. This approach using gold nanobead has been extended to link together two bacteriophages of different lengths to achieve asymmetric colloidal diblocks. Self-organization of scepter-like particles and symmetrical diblocks driven by soft effective attraction has been explored and the corresponding phase diagrams have been established. We have found that Van der Waals attractive interactions between gold nanobeads incorporated into hybrid colloids favor formation of Smectic-B like fibrils in which virus particles are organized in periodic layers separated by layers of gold nanobeads. Finally, we have studied the effect of introducing a weak asymmetry into hybrid virus-based colloids and investigated the possible segregation of their respective blocks through the formation of the lamellar Smectic-A phase.Overall, we have demonstrated an efficient way to control self-organization of virus-based colloids by varying interactions between them, which results in formation of various original self-assembled morphologies
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Anjolaiya, Olanrewaju. "Sorption behaviour of metal contaminants in clay minerals, soils and matrices : understanding the influence of organic matter, pH, ionic strength and mineralogy". Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17523.
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Many chemical and physical factors govern the mobility of metal contaminants in soils and clay systems; some of these chemical factors include mineralogical composition, cation exchange capacity, organic matter content, pH and the ionic strength of soil water. This makes understanding and therefore predicting the fate of metal contaminants in soils a complex undertaking. There were two broad objectives in this study. The first was to investigate binary and ternary sorption systems, with the aim to understand the effects that factors such as pH, ionic strength, organic matter and metal concentrations, have on sorption of simple clay minerals (bentonite and kaolinite) with metals (cadmium, caesium, nickel and strontium). The second was to investigate the retention of heavy metals and radionuclides by well characterised organic-rich and organic-poor clay soils, breaking them down to their individual components to help understand the effects of each component separately, the study also tested to see if the additivity principle holds for these heavy metals and radionuclides, the additivity principle presumes that the overall sorption behaviour of a complex mixture is a summation of the weighted individual sorption behaviours of its constituents. The study also determined the relationship between the natural organic matter (NOM) content and cation exchange capacity (CEC) of the soils and how these affect the mobility of the metals, while also considering the relative importance of the speciation of the metals. Two British clay soils (Mercia Mudstone and London Clay) and two Nigerian soils (an organic-rich Ikeja Loam and the other organic-poor Magodo Laterite) were characterised by X-ray diffraction (XRD) analysis. Batch techniques were employed for the sorption studies, and radiometric techniques, ICP-OES and ICP-MS were used to quantify metal distribution between phases. The sorption of dissolved organic matter to clay minerals is very dependent on pH; this dependence is greater with increasing concentration of organic matter. The formation of metal-humate complexes is dependent on the nature of the metal and pH. Caesium exhibits no discernible sorption to humic acid, cadmium sorption is enhanced by increasing alkalinity but this enhancement is slightly reduced in higher concentrations of humic acid, nickel sorption is mostly unaffected by pH except in higher concentrations of humic acid and enhanced only under very low concentrations of humic acid, while strontium sorption to humic acid is reduced with increasing alkalinity. The nature and preference of humic acid sorption for these metals are vital to understanding the role played by humic acid in the ternary sorption studies of metals, humic acid and clay minerals. Strongly acidic conditions dominate other factors affecting sorption such as ionic strength in sorption of metals to clay minerals. Caesium sorption to bentonite at pH 4 is poor and almost unaffected by ionic strength of the electrolyte solution; saturation of sorption sites is reached with low amounts of adsorbed caesium. Strontium also binds poorly to bentonite at pH 4, more so than caesium, but an ionic strength effect on sorption still exists and is discernible even under these conditions. Increasing alkalinity has the expected effect of increasing sorption capacity of bentonite for both metals. Bentonite has poor sorption properties, having low affinity for caesium and strontium, but has greater affinity for caesium than strontium. The presence of humic acid can enhance or suppresses sorption, this varies from metal to metal and from solid to solid, the degree of enhancement or suppression also depends on humic acid concentration. Kaolinite has better sorption properties than bentonie. Cadmium has greater sorption affinity for kaolinite in the absence of humic acid, but nickel sorption is more enhanced in the presence of humic acid. Although the presence of humic acid enhances cadmium and nickel sorption to kaolinite, low humic acid concentration provides the best conditions for maximum sorption of both metals. High concentrations of humic acid lead to colloid formation which block access of metals with larger hydration radii to sorption sites while also encouraging the formation of humic acid-metal complexes. As with bentonite, caesium and strontium are both poorly sorbed by kaolinite. Unlike with cadmium and nickel however, the enhancement of strontium sorption is supported by higher concentrations of humic acid, these confirm a greater preference for the formation of S-HA-Sr ternary and lower preference for the formation HA-Sr binary complexes. The presence of humic acid inhibits caesium binding, and retention but this reduces with increasing alkalinity, while the reverse is the case with strontium whose retention is very poor and improved in the presence of humic acid and increasing alkalinity. Both caesium and strontium are poorly sorbed and retained by kaolinite but their retention improves with increasing humic acid concentration and pH. Cadmium and nickel also exhibit poor retention to kaolinite but their retentions are more improved under alkaline conditions and higher humic acid concentrations, nickel more so than cadmium. Similar sorption affinities were exhibited by the British (London Clay and Mercia Mudstone) and Nigerian soils (Magodo Laterite and Ikeja Loam) for the metals studied, showing the significance of soil constituent contribution to sorption behaviour. Both British clay matrices have affinity for the metals in the order Cs >> Cd ≈ Ni >> Sr, London Clay has the greater sorption capacity for all the metals, the clay mineral content of Mercia Mudstone is almost entirely made up of Illite while London Clay contains a mixture of smectite, illite and kaolinite with smectite being the most prevalent clay mineral phase. These confirm that smectite-rich clay systems will exhibit better sorption and retention capacities for metal contaminants. Both Nigerian soils showed the same order of affinity for all the metals Cd >> Ni >> Cs >> Sr, cadmium s preferential sorption to kaolinite was observed in its greater sorption and retention by the Nigerian soils which are kaolinite-rich. This preferential sorption of cadmium by kaolinite is confirmed by the Standard Addition experiment where its contribution to cadmium sorption is clearly evident, a trend not replicated with nickel as the sorbing metal. The presence of organic matter in soils or clay systems improves their metal sorption capacity significantly, especially true for insoluble organic matter, however its significance is reduced as pH increases. The contribution of organic matter also depends on the sorption affinity of the metal for organic matter; metals such like strontium are more affected by organic matter presence. The overall sorption behaviour of complex systems such as soils is difficult to attribute to their individual constituents. The laterite soils can be considered a relatively simple soil system containing only four constituents in significant quantities, yet it is difficult to replicate its sorption behaviour using a replicate proportioned mixture of its constituent phases. The additively calculated sorption profiles for the synthetic laterite were different from those obtained experimentally, the reason for this is that the existence of significant particle size differences between the natural and synthetic soils give rise to differences in the availability of sorption sites which is evident from the different CEC values measured for both systems.
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Chien, Yung-Ching 1974. "The influence of ionic strength, magnesium ions and reactive surface area on calcite crystal growth morphology and surface microtopography /". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78339.
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The influence of ionic strength (I), magnesium ions and reactive surface area, on calcite crystal growth morphology and surface microtopography were investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Calcite overgrowths were precipitated from aqueous NaCl-NaHCO 3-CaCl2-MgCl2 solutions on reagent grade calcite seed powders and millimeter-size cleavage fragments in a chemo-stat system at 25ºC for up to 6 days. Aliquots of the reacting solutions were sampled regularly for analysis and the suspended seeds were separated for the preparation of Pt-C replicas and TEM imaging. Most cleavage fragments were recovered at the end of the experiments for AFM imaging.In all experiments, the euhedral {101¯4} rhombohedron of calcite seeds is modified at the same corners and edges within 24 hours of growth.
In the parent solutions seeded with a smaller amount of calcite seed powders and at I = 0.13 m, the crystal morphology of calcite seed overgrowths consists of {101¯4} and a new, prismatic form. The use of a smaller amount of seeds translates into considerably higher precipitation rates per unit surface area and leads to the development of fewer, new morphological growth features.
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Gao, Yan 1970. "Surface electrical properties of goethite and adsorption of phosphate and arsenate on iron oxyhydroxides in high ionic strength solutions". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36934.
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Iron oxyhydroxides are ubiquitous in natural systems and have been recognized as strong adsorbents for Group V elements, such as arsenic and phosphorus. Consequently, the mobility and bioavailability of phosphate and arsenate in the marine environment are mostly regulated by the fate of iron oxyhydroxides. However, to this day, the majority of adsorption studies of phosphate and arsenate were performed in low ionic strength solutions. In this study, phosphate and arsenate complexation on goethite in a 0.7 M NaCl solution and seawater was characterized over a pH range of 3.0 to 10.0 in batch adsorption experiments. Phosphate complexation is described using electric double layer models which consider the presence of three monodentate surface complexes, each characterized by an intrinsic formation constant. Arsenate shows a similar adsorption pattern on goethite but a higher affinity than phosphate. A model including three surface complexes describes the arsenate adsorption at relatively high initial concentrations (i.e., 23 and 34 mumol/l) but overestimates the adsorption at a lower concentration (i.e., 8.8 mumol/l). The equilibrium model derived by combining the formation constants obtained in the single oxyanion subsystems predicts the shape of the competitive adsorption data but fails to reproduce it quantitatively. In competitive experiments, phosphate adsorption is underpredicted whereas arsenate adsorption is overpredicted.Magnesium, calcium and sulphate complexation on goethite was studied in a 0.7 M NaCl solution at 25°C and a pH range of 3.0 to 10.0 and their surface complexation constants were derived. Phosphate adsorption in a 0.7 M NaCl solution increases slightly in the presence of Mg and Ca and decreases at low pH upon the addition of SO4. In contrast, arsenate adsorption is not affected by the presence of Mg or Ca. Phosphate adsorption in seawater is reduced at low pH and enhanced at neutral pH relative to 0.7 M NaCl whereas arsenate adsorption is identical in both solutions except for a decrease at low pH in seawater. The equilibrium model derived by combining the single adsorbate subsystems predicts phosphate and arsenate adsorption in the PO 4-SO4-goethite and AsO4-Ca-goethite systems well, but fails to accurately reproduce the adsorption data in the PO4-Ca-goethite, PO4-Mg-goethite, PO4-seawater-goethite, AsO4-Mg-goethite and AsO4-seawater-goethite systems. The inclusion of ternary surface complexes >FeOMgHPO4-, >FeOMgH2PO 40, >FeOCaHPO4-, >FeOCaH 2PO40, >FeOMgHAsO4- and >FeOMgH2AsO40 in the latter systems improves model fits significantly. Phosphate adsorption in the competitive experiments in seawater is identical to that in the 0.7 M NaCl solution whereas arsenate adsorption in seawater is greater at pH > 7. In competitive experiments in seawater, phosphate adsorption is underpredicted at pH < 6.5 whereas arsenate adsorption is reproduced well using the Constant Capacitance Model (CCM) with the inclusion of the ternary surface complexes.
Phosphate and arsenate adsorption by ferrihydrite, in both 0.7 M NaCl and artificial seawater solutions, was studied at particle concentrations of 0.24 g/l and 0.025 g/l between pH 3.0 and 10.0. Both phosphate and arsenate surface complexation can be described using a model comprising three surface intrinsic constants which decrease with decreasing particle concentration. Ferrihydrite is a stronger adsorbent of PO4 and AsO4 on a per mass basis whereas goethite is a stronger sorbent in terms of chemical affinity. The CCM is able to predict PO4 and AsO4 adsorption on a mixture of goethite and ferrihydrite by combining the complexation constants derived from the single adsorbent subsystems. There is no evidence that adsorbed PO4 and AsO4 is released to solution when ferrihydrite is converted to hematite, an iron oxide with a much lower affinity for these oxyanions. The coprecipitation of both PO4 and AsO4 with hematite during the conversion may be responsible for these observations.
Finally, the surface complexation constants reported in this thesis may be incorporated into other models and contribute to the development of an experimental and thermodynamic database for marine geochemical systems.
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Garand, Alain. "The influence of ionic strength and fluoride ion concentration on the adsorption properties of gibbsite : phosphate and arsenate adsorption". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78363.
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Anomalously high concentrations of arsenic and phosphate are found in the sediments of the Saguenay Fjord relative to those of the Gulf and St. Lawrence Estuary. Whereas the source of phosphate is likely anthropogenic, arsenic appears to be scavenged from the bottom marine waters by settling detrital and authigenic particles. The surface waters of the Saguenay Fjord show a particulate aluminum anomaly ([Al]tot/[Al]diss > 1) that decreases downstream or with increasing salinity. The mineralogy of the aluminum particulate matter may be akin to gibbsite given the refining activities in the region. The adsorption of phosphate and arsenic to various mineral oxides is well established but the scavenging capacity of gibbsite in this estuarine environment is not known.In order to simulate the behavior of the adsorbent/adsorbate relationship during estuarine mixing, the adsorption capacity of gibbsite for arsenate and phosphate was measured in pure water; 0.67 M NaCl; 10 mM CaCl2; 10 mM CaCl2 + 0.64 M NaCl and in seawater in the absence and presence of the fluoride ion.
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Hachfi, Soussi Rima. "Ionic strength sensitivity of complex coacervation between ß-lactoglobulin & lactoferrin : From protein-protein interactions to the characterization of the coacervates". Electronic Thesis or Diss., Rennes, Agrocampus Ouest, 2023. http://www.theses.fr/2023NSARB369.
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La coacervation complexe est une séparation de phase liquide-liquide qui conduit à la formation d'une phase concentrée (coacervats). Ces coacervats permettent entre autres applications l’encapsulation efficace de molécules bioactives. Des travaux précédents focalisés sur le cas spécifique de la coacervation hétéroprotéique entre la lactoferrine (LF) et la ß-lactoglobuline (ßLG), ont établi les conditions optimales de coacervation. L’objectif de ce projet de thèse était de déterminer l’influence de la force ionique sur le processus d’interactions et d’assemblage des protéines ainsi que sur l’état final des coacervats. Ce travail a montré que la coacervation complexe entre LF et ßLG est hautement sensible à la force ionique. Au-delà de 20 mM, le processus de coacervation était aboli mais pas l’interaction au niveau moléculaire entre les protéines.La simulation par méthode de Monte Carlo a permis de montrer que l'énergie libre d'interaction a diminué avec l’augmentation de la force ionique du milieu. La caractérisation rhéologique a mis en évidence des propriétés exceptionnelle des coacervats avec notamment une viscosité 2500 fois supérieure à celle des protéines individuelles utilisées à une concentration protéique équivalente. Une diminution de la température ou une légère augmentation de la force ionique entraine une augmentation de la rigidité et la viscosité des coacervats. Ces résultats contribuent à mieux comprendre les interactions impliquées dans les solutions fortement concentrées en protéines en vue de leurs applications dans des matrices alimentaires comme substituts au additifs texturantsComplex coacervation is a liquid-liquid phase separation that leads to the formation of a highly concentrated phase or coacervates. The formed coacervates are proposed as carriers for bioactives thanks to their high encapsulation efficiency under defined optimal processing conditions. In this thesis, we investigated the specific case of heteroprotein complex coacervation of two globular milk proteins; lactoferrin (LF) and ß-lactoglobulin (ßLG) under specific physicochemical conditions. We aimed to determine how the ionic strength affects i- the LF/ßLG complex coacervation process and ii- the rheological properties of formed coacervates. We showed that a low ionic strength, below 5 mM of added NaCl, promoted the coacervation process. Above 20 mM of added salt, the complex coacervation was abolished even if the interaction between the two proteins was still detected.Monte Carlo simulations demonstrated that the interaction free energy between the two proteins remarkably decreases with increasing ionic strength. In addition to that, a complete rheological characterization illustrated that coacervates exhibited a viscoelastic liquid-like behavior and showed exceptional viscosity, which was 2500 times higher than that found for individual proteins at equivalent total protein concentration. A decrease of the temperature or a small increase of the ionic strength enhanced the rigidity and the viscosity of the coacervates. These results allow better understanding of the involved interactions in concentrated protein solutions and open new avenues for the use of coacervatesas texturizing agents in food matrices
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Gao, Yuan. "Ultrasonic Control of Ultrafiltration Membrane Fouling by Surface Water: Effects of Calcium, pH, Ionic Strength and Natural Organic Matter (NOM) Fractions". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285123886.
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Quinn, Kelly Ann. "Influence of solution and surface chemistry on yttrium and rare earth element sorption". [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001672.
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Nunes, Patrique Nelson Ramos. "Dynamic and interaction of cytochrome c with Pf1 virus". Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/5662.
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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em BioOrgânicaCytochrome c is a positive protein and the Pf1 virus surface is negative forging strong electrostatic complex. When a critical ratio concentration of Cytochrome c and Pf1 virus is achieved a spontaneous complex is formed. The maximum association upon addition of cytochrome c to Pf1 solutions is about 1700 cytochrome c molecules to one Pf1 virion particle. The effect of univalent salt concentration on protein polyelectrolyte complex formation was measured by Dynamic Light Scattering. Complex disaggregation occurred when monovalent salt concentration increased. The assembly process was also observed by NMR at low salt concentration in the system. The aggregate can be gradually dissociated in order to enable NMR spectra acquisition. Depending on virus/cytochorme c ratio or ionic strength concentration we could shift from free protein and virus in solution to transient binding or fully immobilized complex. It was possible to map the most affected regions of the oxidized heme cytochrome c, with chemical shift variation due to the binding to Pf1 virus, during salt titration. Dry and liquid samples of Cytochrome c and Pf1 at different ratios and pH were studied and evaluated by Atomic Force Microscopy. The system was also studied above the critical salt concentration of complex dissociation by PGSEDOSY NMR. A gradual decrease in the translational diffusion coefficient of cytochrome was caused by higher content of Pf1 virus in solution. We conclude that a strong electrostatic correlation between pf1 virus and cytochrome c occurs even after complex dissociation.
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Smith, Kelly. "Characterization of the Barrier Properties of the Human Nail". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1289237023.
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Cincotta, Malayika. "Soil Aggregates: The mechanistic link to increased dissolved organic carbon in surface waters?" ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/961.
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Dissolved organic carbon (DOC) plays an important role in the global carbon (C) cycle because increases in aqueous C potentially contribute to rising atmospheric CO2 levels. Over the past few decades, headwater streams of the northern hemisphere have shown increased amounts of DOC coinciding with decreased acid deposition. Although the issue is widely discussed in the literature, a mechanistic link between precipitation composition and stream water DOC has not yet been proposed.
In this study, the breakup of soil aggregates is hypothesized as the mechanistic link between reduced acid deposition and DOC increases in surface waters. Specific hypotheses state that soil aggregate dispersion (and the ensuing release of DOC from these aggregates) is driven by a decrease in soil solution ionic strength (IS, decreasing the tendency of flocculation) as well as a shift from divalent to monovalent cations (reducing the propensity for cation bridging) in soil solution.
These hypotheses were tested on soil samples collected from several riparian zone and hillslope positions along three flagged transects in the acid-impacted Sleepers River Research Watershed in northeastern Vermont. To determine soil C content by landscape position, samples from transects spanning hilltop to hillslope and riparian area, as well as replicated hillslope and riparian samples (n=40) were analyzed. Aqueous soil extracts simulate the flushing of soils during hydrologic events (e.g. rain or snowmelt) and were used to test the effect of soil solution chemistry on DOC release. Extracts were prepared with solutions of varying IS (0-0.005M) and composition (CaCl2 and NaCl) on replicated soil samples (n=54) and changes in DOC release and aggregate size were monitored. As IS of the extraction solution increased, the amount of DOC in solution decreased, and aggregate size increased. This was presumably due to cations bridging and diffuse double layer effects. This effect was reversed in low ionic strength solutions where DOC release was significantly higher and average aggregate size was smaller. While extraction solution controlled the amount of C liberated, landscape position impacted the quality, but not quantity, of released DOC.
This study is the first to propose a mechanistic link observed changes in DOC in surface waters and recovery from acidification and provides initial experimental evidence that soil aggregates indeed play a role in the generation of DOC.
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Devine, Eric [Verfasser] y Detlef H. [Akademischer Betreuer] Krieter. "Increased removal of protein bound uremic toxins through reversible modification of the ionic strength during hemodiafiltration / Eric Devine. Betreuer: Detlef H. Krieter". Würzburg : Universitätsbibliothek der Universität Würzburg, 2013. http://d-nb.info/1043906606/34.
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Abu, Eme A. "Spectroelectrochemical sensing of tris (2,2 bipyridyl) ruthenium (II) dichloride hexahydrate in low ionic strength samples and the spectroelectrochemical characterization of aeruginosin A". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337351210.
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Olsen, Amanda Albright. "Forsterite Dissolution Kinetics: Applications and Implications for Chemical Weathering". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28213.
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Silicate minerals are the most common mineral group in the earth's crust so it is not surprising that their weathering reactions dominate the chemistry of many earth surface processes. This project used forsterite as a model system to identify the important factors that affect silicate mineral dissolution rates and grain lifetimes in the weathering environment.
I determined an empirical rate law for forsterite dissolution of forsterite in oxalic acid solutions: based on a series of 124 semi-batch reactor experiments over a pH range of 0 to 7 and total oxalate concentrations between 0 and 0.35 m at 25°C. These experiments show that oxalate-promoted dissolution rates depend upon both oxalate concentration and pH. I propose a reaction mechanism in which a hydrogen ion and an oxalate ion are simultaneously present in the activated complex for the reaction that releases H4SiO4 into solution. By analogy, I propose that water acts as a ligand in the absence of oxalate.
I also ran 82 batch reactor experiments in magnesium and sodium sulfate and magnesium and potassium nitrate solutions. These experiments show that ionic strength up to 12 m, log mMg up to 4 m, and log mSO4 up to 3 m have no effect on forsterite dissolution rates. However, decreasing aH2O slows forsterite dissolution rates. The effect of decreasing dissolution rates with decreasing aH2O is consistent with the idea that water acts as a ligand that participates in the dissolution process.Forsterite dissolution rate data from previously published studies were combined with results from my experiments and regressed to produce rate laws at low and high pH. For pH < 5.05 or and for pH > 5.05 or I then developed a diagram that shows the effect rate-determining variables on the lifetime of olivine grains in weathering environments using these rate laws.Ph. D.
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Qin, Yan. "The highly conserved LepA is a ribosomal elongation factor that back-translocates the ribosome and is essential for viability at high ionic strength". [S.l.] : [s.n.], 2006. http://www.diss.fu-berlin.de/2006/124/index.html.
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Manono, Malibongwe Shadrach. "An investigation into the effect of ionic strength of plant water on valuable mineral and gangue recovery of a platinum bearing ore from the Merensky reef". Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/11985.
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Includes synopsis.Includes bibliographical references.
Higher solids and water recoveries were obtained at higher ionic strength. The increase in the ionic strength in the absence of any depressant caused an increase in Cu and Ni recovery.
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Won, Jooyoung [Verfasser] y Gerald [Akademischer Betreuer] Brezesinski. "Dynamic and equilibrium adsorption behaviour of ß-lactoglobulin at the solution/tetradecane interface: Effect of solution concentration, pH and ionic strength / Jooyoung Won ; Betreuer: Gerald Brezesinski". Potsdam : Universität Potsdam, 2016. http://d-nb.info/1218792973/34.
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Kuhn, Kátia Regina 1984. "Gelificação a frio de proteinas do soro e fibras de linhaça através da adição de sais de calcio ou sodio". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255553.
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Orientadores: Rosiane Lopes da Cunha, Angelo Luiz Fazani CavallieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Biopolímeros, como as proteínas e os polissacarídeos, são utilizados pela indústria de alimentos por desempenharem um papel essencial na estrutura, textura e estabilidade dos produtos. O entendimento das interações biopoliméricas é importante para melhorar suas propriedades funcionais, como por exemplo, a capacidade de gelificação, e para o desenvolvimento de novos produtos. Sendo assim, este trabalho teve como objetivo estudar as interações macromoleculares de sistemas contendo proteínas do soro de leite (WPI) e/ou polissacarídeo da linhaça (FG) em sistemas gelificados a frio pela adição de sais de cálcio ou sódio, buscando correlacionar estas interações com as propriedades mecânicas e de estrutura dos géis formados. Inicialmente realizou-se a caracterização reológica do polissacarídeo da linhaça e foi observado um comportamento de fluido pseudoplástico e propriedades de gel fraco. Com a adição de sais, verificou-se uma redução na viscosidade intrínseca e nos módulos elástico e viscoso das soluções. Em uma segunda etapa, foram estudados géis puros de WPI (5, 6, 7, 8 e 9% m/m) formados pela difusão de sais de cálcio ou sódio através de membranas de diálise e observou-se a formação de estruturas opaca e translúcida, sendo que o aumento na concentração de WPI levou a uma diminuição na claridade e porosidade dos géis e a um aumento na rigidez, elasticidade e capacidade de retenção de água, em ambos os sistemas (CaCl2 e NaCl). Os géis de WPI formados pela difusão de sais de cálcio apresentaram-se mais rígidos e elásticos, menos deformáveis e com menor capacidade de retenção de água em relação aos géis de sódio. Por último, foram estudados sistemas mistos WPI (8% m/m) ¿ FG (0,1; 0,3 e 0,5% m/m) utilizando dois procedimentos para incorporação de sais, a difusão através de membranas de diálise e a adição direta, e observou-se que o método de preparo dos géis levou a sistemas com propriedades mecânicas bastante distintas. No método de difusão lenta de sais, visualizou-se a formação de géis heterogêneos (separação de fases macroscópica). Nestes sistemas, o aumento na concentração de FG levou a diminuição da rigidez, deformabilidade e da capacidade de retenção de água dos géis como conseqüência da incompatibilidade termodinâmica entre os biopolímeros e descontinuidade da estrutura da rede do gel. No entanto, foi no método de adição direta de sais de sódio que obteve-se os géis bipoliméricos mais fortes, sendo este método o mais indicado visando melhor estrutura e propriedades mecânicas dos géis formados com maior viabilidade de uso em escala industrial
Abstract: Biopolymers, such as proteins and polysaccharides, are used by the food industry for playing an essential role in the structure, texture and stability of the products. An understanding of the biopolymers interactions is important for improvement of their functional properties, such as gelation, and for the new products development. Thus, the aim of this work it was to study macromolecular interactions between whey protein isolate (WPI) and/or flaxseed gum (FG) at cold-set gels formed by calcium or sodium salts addition, by correlation of these interactions with the mechanical properties and structure of the formed gels. Initially, flaxseed gum rheological characterization was realized and it was observed a shear thinning behavior and ¿weak gel¿ properties. Salts addition led to a decrease in intrinsic viscosity and in the storage and loss modulus of solutions. In a second step of this work, pure WPI gels (5, 6, 7, 8 and 9% w/w) formed by calcium or sodium salts diffusion through dialysis membranes were studied and it was observed the formation of structures opaque and translucent, where the increase WPI concentration led to a decrease in the clarity and porosity of the gels and to an increase in hardness, elasticity and water-holding capacity, in both systems (CaCl2 and NaCl). WPI gels formed by calcium salts diffusion were harder and more elastic, less deformable and with lesser ability to hold water in relation to sodium gels. Finally, mixed WPI (8% w/w) ¿ FG (0.1, 0.3 and 0.5% w/w) systems using two procedures for incorporation of salts were studied, the diffusion through dialysis membranes and the direct addition, and it was observed that the gels preparation method led to systems with quite different mechanical properties. By slow salts diffusion, it was observed the heterogeneous gels formation (macroscopic phase separation). In these systems, the increase FG concentration led to a decrease of the hardness, deformability and water-holding capacity of the gels as a consequence of the thermodynamic incompatibility between biopolymers and gel network discontinuity. However, it was by sodium salts direct addition that it were obtained stronger bi-polymeric gels, being this the most appropriate method to better structure and mechanical properties of the formed gels with higher viability for use in industrial scale
Mestrado
Mestre em Engenharia de Alimentos
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Pedroli, Francesco. "Dielectric strength and leakage current : From synthesis to processing optimization". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI014.
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Les polymères électro-actifs (EAP) tels que le P (VDF-TrFE-CTFE) se sont révélés très prometteurs dans le domaine des capteurs et actionneurs flexibles. Les avantages de l'utilisation des PAE pour les appareils électriques intelligents sont dus à leur faible coût, leurs propriétés élastiques, leur faible densité et leur capacité à être fabriqués en différentes formes et épaisseurs. Au cours des années précédentes, le terpolymère P (VDF-TrFE-CTFE) a attiré de nombreux chercheurs en raison de sa propriété ferroélectrique relaxante qui présente des phénomènes d'électrostriction élevés. Malgré leur attractivité, cette classe de matériaux possède encore deux limitations technologiques principales: une faible tension de claquage et le niveau élevé de courant de fuite lorsque des tensions élevées sont appliquées. La dépendance quadratique de la réponse de déformation et de la densité d'énergie mécanique sur le champ électrique appliqué met en évidence la pertinence du champ électrique de claquage EAP, tout en réduisant les pertes diélectriques. La faible rigidité diélectrique du terpolymère P (VDF-TrFE-CTFE) s'avère être une préoccupation majeure pour obtenir des performances d'actionnement élevées. De plus, le grand champ électrique nécessaire pour atteindre des niveaux de déformation satisfaisants (≥ 40 V / µm, environ) conduit inévitablement à un niveau élevé de courant de fuite et donc à une durée de vie courte. Ce travail démontre qu'il est possible d'augmenter considérablement le claquage électrique et de diminuer les pertes diélectriques en contrôlant les paramètres de traitement des procédés de synthèse et de fabrication des polymères. L'amélioration de la rigidité diélectrique intrinsèque est obtenue en ajustant le poids moléculaire du terpolymère et en améliorant la pureté de la dissolution polymère utilisée pour la fabrication de films de terpolymère. La réduction des pertes diélectriques, et avec une attention particulière aux pertes de conduction à haute tension (ou courant de fuite), est obtenue par l'introduction d'un nouveau traitement thermique dans le processus de fabrication du film, appelé recuit électro-thermiqueElectro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators. The advantages of using EAPs for smart electrical devices are due to their low cost, elastic properties, low density and ability to be manufactured into various shapes and thicknesses. In earlier years, P(VDF-TrFE-CTFE) terpolymer attracted many researchers due to its relaxor-ferroelectric property that exhibits high electrostriction phenomena. Although their attractiveness, this class of materials still owns two main technological limitations: low breakdown voltage and the high level of leakage current when high voltages are applied. The quadratic dependence of the strain response and mechanical energy density on the applied electric field highlights the relevance of EAP breakdown electric field, while reducing the dielectric losses. The low dielectric strength of P(VDF-TrFE-CTFE) terpolymer turns out to be a main concern for achieving high actuation performances. Moreover, the large of electric field required to attain satisfactory levels of deformation (≥ 40 V/µm, about) inevitably lead to high level of leakage current and thus short life-time. This work demonstrates that it is possible to dramatically increase the electrical breakdown and decrease the dielectric losses by controlling processing parameters of the polymer synthesis and fabrication procedures. Enhancement of intrinsic dielectric strength is obtained by tuning the terpolymer molecular weight and by improving the purity of polymeric dissolution used for fabrication of terpolymer films. The reduction of dielectric losses, and with particular attention at the high-voltage conduction losses (or leakage current) are achieved by the introduction of a novel thermal treatment in the film fabrication process, called electro-thermal annealing
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Wafa, Al-Dajani Waleed. "On the bleachability of alkaline pulps : the influence of residual lignin structure /". Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3231.
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Venkataraman, Manoj. "THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS". Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3656.
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Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Gao, Xin. "Localized Corrosion Initiation of Steel in CO2 Environments". Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1596657895973621.
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Prédélus, Dieuseul. "Rôle des hétérogénéités texturale et structurale du sol sur le transfert et la rétention des nanoparticules dans la zone non saturée : Expérimentation et modélisation". Thesis, Vaulx-en-Velin, Ecole nationale des travaux publics, 2014. http://www.theses.fr/2014ENTP0006/document.
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La production croissante des nanoparticules issues du développement des nanotechnologies et leur incorporation dans des produits de consommation vont inévitablement conduire à leur introduction dans l’environnement. Ces particules peuvent constituer un vecteur de substances polluantes en raison du transport facilité des contaminants organiques ou inorganiques potentiellement adsorbés sur leurs surfaces ou représentent elles-mêmes un risque pour l’environnement et la santé humaine. La zone non saturée joue une fonction importante de filtration naturelle des eaux de recharge des nappes. Les mécanismes de transport et de rétention des nanoparticules à travers cette zone sont complexes du fait des hétérogénéités de type structural et textural de celle-ci. Ces hétérogénéités sont à l'origine des écoulements préférentiels et d’un grand nombre de facteurs d'interaction physico-chimiques liés aux propriétés des nanoparticules et de la zone non saturée elle-même. L'objectif de la thèse est de mieux comprendre les effets de ces hétérogénéités sur le transport des nanoparticules dans un milieu non saturé hétérogène afin de mieux prévenir le devenir des nanoparticules dans le sol. Dans ce contexte, trois matériaux granulaires (un sable et des mélanges sable-gravier) ont été mis en place en colonne (10 cm de diamètre x 30 cm de hauteur) et dans le lysimètre LUGH du LEHNA (100 x 160 x 100 cm3) pour simuler le transport des nanoparticules dans le sol. Le but est de déterminer le rôle des hétérogénéités texturale (différentes granulométries) et structurale (barrière capillaire) du sol, en prenant en compte les effets de la force ionique de la solution et de la vitesse d’écoulement sur le transfert des nanoparticules en conditions non saturées. Des nanoparticules de silice marquées par des molécules organiques fluorescentes ont été développées en tant que nanotraceur particulaire dans le cadre de cette étude, l’ion bromure a été utilisé pour caractériser l’écoulement de l’eau. Le modèle de transfert de non équilibre hydrodynamique à fractionnement de l'eau en deux phases mobile et immobile, MIM, incluant un terme de rétention et de relargage des nanoparticules, décrit correctement les courbes d'élution de nanoparticules, pour les expériences en colonne. Cette étude a permis de caractériser les effets liés aux différentes tailles des grains du sol et à la barrière capillaire sur la rétention des nanoparticules. Les expériences réalisées avec différentes forces ioniques montrent que pour les forces ioniques comprises entre 1 et 50 mM, la rétention est croissante comme prédit la théorie DLVO ; cependant à partir d’une force ionique supérieure à 100 mM il se produit une inversion de la rétention. Lorsque la vitesse d’écoulement diminue, la rétention augmente, probablement en partie à l’interface air-eau. Le lysimètre LUGH a permis d’identifier le rôle de la barrière capillaire sur la rétention des nanoparticules. Un modèlenumérique 3D basé sur l’équation de Richards pour l’écoulement et les équations convection dispersion couplées avec un module de rétention pour les nanoparticules a été dévelopé. Les résultats montrent que la rétention a augmenté à l’interface sable-milieu bimodal. Le profil de rétention de nanoparticules indique qu’elles sont majoritairement retenues en surface du sol, puis la rétention diminue avec la profondeur, pour les expériences réalisées en colonne. Le nanotraceur constitue un outil puissant pour l’étude du rôle des hétérogénéités dans le transfert des particules dans un sol non saturéIncreasing production of nanoparticles from nanotechnology development and incorporation into consumer products will inevitably lead to their introduction into the environment. These particles can be a vector of pollutants due to the facilitated transport of organic and inorganic contaminants potentially adsorbed on their surfaces or represent a risk to the environment and human health themselves. The unsaturated zone plays an important function of natural water filtration recharge. The transport and retention mechanisms of nanoparticles through this zone are complex due to the structural and textural soil heterogeneities. These heterogeneities are causing preferential flows and are responsible a large number of physical and chemical interaction related to the nanoparticles properties. The aim of the thesis is to better understand effects of soil heterogeneities on the transport of nanoparticles in a heterogeneous unsaturated media to better prevent the fate of nanoparticles in the vadose zone. In this context, three granular materials (sand and sand - gravel mixtures) were introduced in column (10 cm diameter x 30 cm high) and the lysimeter LUGH of Lehna (100 x 160 x 100 cm3) to simulate the transport of nanoparticles in the soil. The goal is to determine the role of heterogeneous textural (different sizes) and structural (barrier capillary) heterogeneities of the soil, taking into account the effects of the ionic strength of the solution and the flow rate on the transfer of the nanoparticles in unsaturated conditions. Silica nanoparticles labeled with fluorescent organic molecules have been developed as particulate v in this study, the bromide ion has been used to characterize the flow of water. The transfer model of non-equilibrium hydrodynamic fractionation of water and two mobile and immobile phases, MIM, including a retention and release term of the nanoparticles, properly described breakthrough curves of nanoparticles on column experiments. This study allowed to characterize the effects related of different grain sizes of soil and capillary barrier on the nanoparticle retention. Experiments with different ionic strengths show for the ionic strength between 1 and 50 mM, the retention increased as predicted by the DLVO theory. However, from an ionic strengh greater than 100 mM an inversion retention occurs. When the flow rate decreases, retention increases, air - water interface increases and trapps probably the nanoparticles. Lysimeter LUGH allowed to identify the role of the capillary barrier on the retention of nanoparticles. A 3D numerical model based on Richards equation for flow and the convection dispersion equations coupled with a mechanical module for nanoparticle trapping was developed. Results show retention increased in the sand-bimodal interface. The retention profile indicates that nanoparticles are predominantly retained at the soil surface, then the retention decreases with depth, for the column experiments. The nanotracer is a powerful tool for studying the role of heterogeneous in the transfer of particles in an unsaturated soil
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Londinová, Monika. "Fluorescence ve výzkumu hydrofilních oblastí asociativních koloidů". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216403.
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The properties of the hyaluronan were investigated by using different fluorescence probes, because hyaluronan is a hopeful carrier of an active matter in medicine and cosmetics. Selected fluorescence probes were: cationic acridine orange, Nile Blue A, methylene blue, amphiphilic 4-Di-2-ASP and anionic fluorescein. Except from fluorescence and absorption spectra of the probes were observed electrostatic and hydrophobic interactions as well. The probes in solvents with different polarity (MeOH, EtOH, DMSO) showed the bathochromic shift in the emission maximum and quenching of the fluorescence with the increasing polarity of the solvents. The influence of the ionic strength on fluorescence properties of the probe acridine orange and 4-Di-2-ASP was investigated in aqueous solutions of chlorides. The formation of acridine orange dimer is inhibited with increasing ionic strength. CaCl2 increased the ionic strength the most, then prevented repulsion of carboxylate groups, so it means the expansion of hyaluronan cluster into the solution. However, the emission of the probe 4-Di-2-ASP was quenched with the addition of CaCl2 the most. The first additions of COO– groups cause the formation of dimers of AO shown as decreasing in extinction coefficient and fluorescence intensity. Next addition of the hyaluronan caused a depolymerization of formed dimers and the increase of the emission intensity. The repolymerization caused the decrease and then again the increase. In case of 4-Di-2-ASP was the pattern of the fluorescence (the intensity and the position of the emission) firstly the same, but at the concentration of 1 g dm-3 the emission intensity increased. The probes MB and F were used for spectroscopic studies of the interaction between methylene blue-fluorescein complex and anionic and cationic surfactants. The absorbance of separate MB and F changed only with the addition of surfactants with the opposite electric charge. Absorbance of the mixture MB-F changed with the addition of the CTAC surfactant, while the addition of SDS into the mixture caused only the change of MB absorption spectra.
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Möller, Johannes [Verfasser], Metin [Akademischer Betreuer] Tolan y Roland [Akademischer Betreuer] Winter. "Liquid-liquid phase separation and intermolecular interactions in dense protein solutions : High pressure SAXS studies on lysozyme solutions of high ionic strength / Johannes Möller. Betreuer: Metin Tolan. Gutachter: Roland Winter". Dortmund : Universitätsbibliothek Dortmund, 2014. http://d-nb.info/1096224976/34.
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Möller, Johannes Verfasser], Metin [Akademischer Betreuer] [Tolan y Roland [Akademischer Betreuer] Winter. "Liquid-liquid phase separation and intermolecular interactions in dense protein solutions : High pressure SAXS studies on lysozyme solutions of high ionic strength / Johannes Möller. Betreuer: Metin Tolan. Gutachter: Roland Winter". Dortmund : Universitätsbibliothek Dortmund, 2014. http://nbn-resolving.de/urn:nbn:de:101:1-201604121768.
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Junior, Izan Mascarenhas Silva. "A mobilidade eletroforética e o perfil de potencial da membrana celular". Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2995.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorO objetivo do presente trabalho foi estudar o comportamento dos potenciais superficiais e do perfil de potencial atraves da membrana de eritr ocito em func ao da forca i onica e das cargas superficiais, usando um modelo que leva em conta as cargas el etricas do glicoc alix e das proteınas citoplasm aticas, al em das cargas superficiais da bicamada lipıdica e os efeitos dos eletr olitos divalentes. Programas especıficos em linguagem C foram elaborados para o c alculo desses potenciais, tomando como dados num ericos resultados experimentais de medidas de mobilidade eletrofor etica de eritr ocitos para diferentes valores de forca i onica. Neste c alculo, o metodo para tratamento dos dados eletrofor eticos indicado por Hsu et al.[57] foi incluıdo em nosso modelo. A equac ao de Poisson-Boltzmann nao linear foi resolvida por computac ao num erica, usando o metodo de Runge-Kutta de quarta ordem, obtendo-se os perfis de potencial. Os resultados mostraram que a estimativa da densidade de carga el etrica na superfıcie de c elulas usando a equac ao cl assica de Helmholtz-Smoluchowski conduz a valores que nao conseguem refletir as forcas que regem o comportamento eletrofor etico das mesmas. O presente modelo gerou valores de potenciais superficiais e perfis de potencial para a membrana do eritr ocito bem distintos daqueles obtidos anteriormente para um modelo descrito por uma equac ao de Poisson-Boltzmann linear. Nossos resultados confirmam que a avaliac ao de parametros el etricos superficiais da membrana de eritr ocito, envolvendo dados oriundos de eletroforese, deve incluir c alculos hidrodin amicos al em de eletroest aticos, como sugerido por Hsu et al. [57].
The aim of present work was to study the behavior of the surface potentials and the potential profile across erythrocyte membrane in function of ionic strength and surface charge, using a model which takes into account electrical charges on glycocalyx and citoplasmatic proteins, in addition surface charges on lipid bylayer and effects due to mono and divalent electrolytes. Programs in C language were build to estimate the surface potentials, and experimental values of electrophoretic mobilities of erythrocytes for different ionic strength were applied. For this calculation, the method indicated by Hsu et al. [57] for treating electrophoretic data was included in our model. The non linear Poisson-Boltzmann equation was solved by numerical computation, using the forth order Range-Kutta method, to give the potential profiles. Results showed that values of electric charge on cellular surface obtained by applying the classical Helmholtz-Smoluchowski equation were not able to represent the forces involved in the electrophoretic behavior of cells. The present model generate values for surface potentials and potential profiles different from those obtained in previous work for a model described by linear Poisson- Boltzmann equation. According to our results, the estimation of surface electric parameters for the erythrocyte membrane from electrophoretic data must ese hydrodynamics and electrostatics calculations, as suggested by Hsu et al. [57]
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Tripský, Andrej. "Návrh, výroba a testování grafenových biosenzorů". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417170.
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Pokrok ve vývoji nanotechnologií nám poskytuje dobrou příležitost k vývoji nových špičkových zařízení. Tato práce si klade za cíl vyrobit, popsat a změřit grafenové pH senzory na dvou různých substrátech - polymeru parylenu C a SiO2. Tento pH senzor je prvním krokem ve vývoji nositelné náplasti monitorující stav kůže a možné infekce. Grafen je 2D materiál na bázi uhlíku se zajímavými vlastnosti a nadějnými aplikacemi. Úspěšně jsme provedli dva různé experimenty sloužící k charakterizaci grafenových senzorů a jejich odezvu na různé hodnoty pH. V prvním experimentu jsme použili horní elektrolytické hradlo k určení bodu neutrality (Diracův bod). Druhý experiment popsal změnu rezistence grafenu jako funkce pH. Dále jsme také funkcionalizovali grafen polyanilinem, abychom zlepšili jeho vlastnosti. Prokázali jsme citlivost grafenových senzorů na pH pro oba substráty a objevili jsme několik výzev jako potřebu kontroly iontové síly, experimentů samotných a destrukce grafenu.
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Echeverri, Mauricio. "Phase Diagram Approach to Fabricating Electro-Active Flexible Films: Highly Conductive, Stretchable Polymeric Solid Electrolytes and Cholesteric Liquid Crystal Flexible Displays". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1352949368.
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