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Littérature scientifique sur le sujet « Stabilità colloide »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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Articles de revues sur le sujet "Stabilità colloide"

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Priyadarshini, N., M. Sampath, Shekhar Kumar, U. Kamachi Mudali et R. Natarajan. « Probing Uranium(IV) Hydrolyzed Colloids and Polymers by Light Scattering ». Journal of Nuclear Chemistry 2014 (26 mars 2014) : 1–10. http://dx.doi.org/10.1155/2014/232967.

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Tetravalent uranium readily undergoes hydrolysis even in highly acidic aqueous solutions. In the present work, solutions ranging from 0.4 to 19 mM (total U) concentration (1<pH<4) are carefully investigated by light scattering technique with special emphasis on polymerization leading to colloid formation. The results clearly indicate that the concentration has significant effect on particle size as well as stability of colloids. With increasing concentration the size of colloids formed is smaller due to more crystalline nature of the colloids. Stability of colloids formed at lower concentration is greater than that of colloids formed at higher concentration. Weight average molecular weight of the freshly prepared and colloidal polymers aged for 3 days is determined from the Debye plot. It increases from 1,800 to 13,000 Da. 40–50 atoms of U are considered to be present in the polymer. Positive value of second virial coefficient shows that solute-solvent interaction is high leading to stable suspension. The results of this work are a clear indication that U(IV) hydrolysis does not differ from hydrolysis of Pu(IV).
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Kurosawa, S., et S. Ueta. « Effect of colloids on radionuclide migration for performance assessment of HLW disposal in Japan ». Pure and Applied Chemistry 73, no 12 (1 janvier 2001) : 2027–37. http://dx.doi.org/10.1351/pac200173122027.

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Colloidal effect is one of the major factors to enhance the migration of radionuclides in groundwater. The experimental and theoretical studies of colloid mobility and colloid-facilitated radionuclide transport for the performance assessment of high-level radioactive waste (HLW) geological disposal is presented in this paper. The major aims of the study are (1) to study the filtration effect on colloids by the engineered barrier system, (2) to study bentonite colloid generation by erosion of the engineered barrier system, and (3) to calculate radionuclide migration with groundwater colloids through fractured rock systems. Alternative coagulants based on prehydrolyzed forms of aluminium or iron can be more effective than the traditional materials in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralization and hydroxide precipitation. Basic principles of colloid stability and metal ion hydrolysis are briefly reviewed, and the action of hydrolyzing metal coagulants is then discussed, with some examples from recent experimental studies. Although it is possible to interpret results reasonably well in terms of established ideas, there are still some uncertainties that need to be resolved
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Sasamoto, Hiroshi, et Shingo Onda. « Preliminary results for natural groundwater colloids in sedimentary rocks of the Horonobe Underground Research Laboratory, Hokkaido, Japan ». Geological Society, London, Special Publications 482, no 1 (7 septembre 2018) : 191–203. http://dx.doi.org/10.1144/sp482.1.

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AbstractColloid concentration is an important parameter in models of colloid-facilitated transport. The purpose of the present study is to characterize colloid concentrations and colloid stability in natural groundwater from the Horonobe Underground Research Laboratory (URL) in Hokkaido, Japan. The particle sizes of colloids in groundwaters from the Horonobe URL range from several nanometres to c. 500 nm, with a mode particle size of c. 120 nm. Evaluation of colloid stability by DLVO theory suggests that larger colloids (i.e. >100 nm in diameter) would be more stable than smaller colloids in some groundwaters. The estimated colloid particle concentrations when considering the results of DLVO calculations ranged from 2.33 × 106 to 1.12 × 108 particles/ml, and mass concentrations were estimated to range from 45 to 1540 µg l−1 for diameters greater than 100 nm. Colloids in Horonobe groundwaters appear to be less stable, with a moderate potential for transport, than colloids investigated in similar international studies. This reduced stability may be due to relatively higher ionic strengths and moderate dissolved organic concentrations in Horonobe groundwaters compared to their international counterparts.
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Kashyap, Swarnima, Shashank Mishra et Shantanu K. Behera. « Aqueous Colloidal Stability of Graphene Oxide and Chemically Converted Graphene ». Journal of Nanoparticles 2014 (13 novembre 2014) : 1–6. http://dx.doi.org/10.1155/2014/640281.

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Graphene oxide (GO) was prepared by modified Hummer’s method, and chemically converted graphene (CCG) was prepared by further reduction of the aqueous GO colloid. The effect of pH on particle size, particle charge, and light absorption of the aqueous colloids of GO and CCG was studied with titration against HCl or NaOH, to find the ideal characteristics for a stable dispersion. The GO colloid was stable in the pH range of 4–11, whereas the CCG colloid gained stability at a relatively narrower pH range of 7–10. Poor stability of the colloids was observed for both GO and CCG colloids at both extremes of the pH scale. Both of the colloids exhibited average size of ~1 micron in the low pH range, whereas for higher pH the size ranged between 300 and 500 nm. The UV-Vis spectra showed absorption peak at 230 nm for GO colloids that shifted to 260 nm for the CCG colloid. Such shift can be ascribed to restoring of electronic conjugation of the C=C bonds in CCG.
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Kalnina, Daina, Kārlis Agris Gross, Artur Medvids et Pavels Onufrijevs. « Formation of Negatively Charged AgI Colloid Nanoparticles by Condensation ». Advanced Materials Research 1117 (juillet 2015) : 159–63. http://dx.doi.org/10.4028/www.scientific.net/amr.1117.159.

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The stability of silver halide colloids is reported to be important for the toxicological outcome. This study shows a well-suited and cheap condensation reaction to obtain negatively charged silver iodide (AgI) nanoparticles without additional stabilization agents. Charged AgI colloids were synthesized from silver nitrate and potassium iodide solutions. An excess of potassium iodide not only imparted a negative charge, but provided a narrow particle size distribution (50 ± 10 nm). The change of optical properties in the colloid was investigated by UV-VIS spectroscopy. A silver iodide exciton absorption band at peak ~421nm (2.93eV), red-shifted over time. The peak at half maximum intensity increased from 13.3nm to 14.8 nm, characterizing the dispersity of AgI colloidal particles. Colloidal particles stabilized after 33 hours. In-situ real-time UV-VIS measurements provide a tool to adjust the particle characteristics and may serve to further optimize the performance in biological applications.
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Liu, Yongliang, Yud-Ren Chen, Xiangwu Nou et Kuanglin Chao. « Potential of Surface-Enhanced Raman Spectroscopy for the Rapid Identification of Escherichia Coli and Listeria Monocytogenes Cultures on Silver Colloidal Nanoparticles ». Applied Spectroscopy 61, no 8 (août 2007) : 824–31. http://dx.doi.org/10.1366/000370207781540060.

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Surface-enhanced Raman (SERS) spectra of various batches of bacteria adsorbed on silver colloidal nanoparticles were collected to explore the potential of the SERS technique for rapid and routine identification of E. coli and L. monocytogenes cultures. Relative standard deviation (RSD) of SERS spectra from silver colloidal suspensions and ratios of SERS peaks from small molecules (K3PO4) were used to evaluate the reproducibility, stability, and binding effectiveness of citrate-reduced silver colloids over batch and storage processes. The results suggested consistent reproducibility of silver colloids over batch process and also stability and consistent binding effectiveness over an eight-week storage period. A variety of mixtures of E. coli/L. monocytogenes cultures with different colloidal batches revealed that, despite large variations in relative intensities and positions of SERS active bands, characteristic and unique bands at 712 and 390 cm−1 were consistently observed and were the strongest in E. coli and L. monocytogenes cultures, respectively. Two specific bands were used to develop simple algorithms in the evaluation of binding effectiveness of silver colloids over storage and further to identify E. coli and L. monocytogenes cultures with a 100% success. A single spectrum acquisition took 5∼6 min, and a minimum of 25 μL silver colloid was directly mixed with 25 μL volume of incubated bacterial culture. The short acquisition time and small volume of incubated bacterial culture make silver colloidal nanoparticle based SERS spectroscopy ideal for potential use in the routine and rapid screening of E. coli and L. monocytogenes cultures on large scales. This is the first report of the development of simple and universal algorithms for bacterial identification from the respective exclusive SERS peaks.
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Bolotov, Alexander N., Vladislav V. Novikov et Olga O. Novikova. « ON DEPENDENCE OF COLLOIDAL STABILITY OF MAGNETIC LIQUID ON STABILIZER DIELECTRIC CAPACITIVITY AND DISPERSION MEDIUM ». IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, no 4 (12 mai 2017) : 75. http://dx.doi.org/10.6060/tcct.2017604.5506.

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The purpose of this article is to research the possibility of using values of stabilizer dielectric capacitivity and dispersion medium to form a colloidal stability criterion of magnetic liquid. The authors researched colloidal stability of magnetic liquids with a low-polarity base, nonionogenous SAM-stabilizer (oligoester) and hydroximag nanoparticles. The received magnetic colloids were tested for stability in a gravity field to evaluate SAM stabilizing capacity. The authors propose Е-criterion that shows a relative difference between dielectric capacitivities of a dispersion medium and SAM-stabilizer. It was determined that such combination of dielectric capacitivity of solution component parts correlates with the values of SAM adsorption and colloid stability in the best way. The test results show that relative reduction of magnetization correlates well with a value of dispersion medium dielectric capacitivity due to irreversible sedimentative processes. In the next set of experiments, the authors did not change the magnetic colloid liquid content, but SAM-stabilizer. They research the dependence of colloidal stability of magnetic liquids based on a dioctyl sebacate of a stabilized SAM with various dielectric capacitivities. The test results prove regularity of increasing colloidal stability with decreasing E- criterion. The paper considers in details the physical and chemical mechanisms that help to develop the influence of dielectric capacitivity on magnetic liquid colloidal stability. The analysis of testing results showed that dielectric capacitivity of magnetic liquid components affects many physical-chemical phenomenons in the process of its synthesis. It is important that the behaviour of sorption processes on the surface of dispersed particles depends on dielectric capacitivity. The result of the empirical data research by magnetic liquid colloidal stability shows that with increasing dielectric capacitivity of dispersion medium in relation to stabilizer’s dielectric capacitivity the desorption processes of stabilizer’s molecules from a magnetic particles’ surface increses. As a result, the adsorption layer around particles becomes more incoherent and less competent. It reduces the value of a steric stabilization factor of a magnetic liquid colloidal structure. In practice it leads to deterioration or even loss of colloidal stability of magnetic liquid. The influence of dielectric capacitivity on colloidal stability using the effects of interparticle interaction is less important. To summarize, the article proves a dielectric E-criterion that can be used to provide rationale for the choice of SAM-stabilizer for magnetic liquids. According to this criterion, dielectric capacitivity of a dispersion medium should be slightly different from the similar property of SAM-stabilizer. Otherwise, molecule desorption processes of SAM from magnetic particles encourage quality degradation of covering adsorption layers, so colloidal stability worsens.Forcitation:Bolotov A.N., Novikov V.V., Novikova O.O. On dependence of colloidal stability of magnetic liquid on stabilizer dielectric capacitivity and dispersion medium. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 4. P. 75-81.
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Roto, Roto, Hani Prima Rasydta, Adhitasari Suratman et Nurul Hidayat Aprilita. « Effect of Reducing Agents on Physical and Chemical Properties of Silver Nanoparticles ». Indonesian Journal of Chemistry 18, no 4 (12 novembre 2018) : 614. http://dx.doi.org/10.22146/ijc.26907.

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Silver nanoparticles having uniform size and shape, a diameter range of 10–50 nm, excellent stability, and high zeta potential are always desirable for many applications. The silver nanoparticles were synthesized by chemical reduction method using some reducing agents in a polyvinyl alcohol solution. This study aims at determining the effect of reducing agents on the chemical and physical properties of silver nanoparticles. Ascorbic acid, sodium borohydride, hydrazine, sodium citrate, and glucose were used as reducing agents. Surface Plasmon Resonance (SPR) absorbance, morphology, zeta potential, crystal system, and stability of the products were studied. The results showed that the chemical and physical properties of the colloidal Ag nanoparticles were dependent on the reducing agents. In general, the produced silver nanoparticles have an fcc crystal system with a unit cell of 4.0906–4.0992 Å. The SPR absorbance of the colloids has the peak in the range of 401–433 nm. We found that the colloid of silver nanoparticles prepared by using ascorbic acid has uniform spherical shape, the diameter of about 20 nm, and zeta potential of -10.4 mV. After being stored for one month, the SPR absorbance of the colloid decreased by only 5%. This type of colloidal Ag nanoparticles prepared by using ascorbic acid is expected to be used for chemical sensors, an antibacterial agent, and so on.
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Макаров, А. С., Н. А. Шмигельская et В. А. Максимовская. « The effect of using gum arabic on the quality of different types of wines ». Magarach Vinogradstvo i Vinodelie, no 1(119) (24 mars 2022) : 84–89. http://dx.doi.org/10.35547/im.2022.54.77.013.

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Систематизированы литературные данные о влиянии защитного коллоида гуммиарабика на сроки стабильности различных типов вин (игристых, ликерных). Показано, что применение защитных коллоидов способствует увеличению сроков стабильности игристых и ликерных вин против кристаллических и коллоидных (обратимых и необратимых) помутнений. Уточнено, что в состав гуммиарабика входят полисахариды, построенные из арабинозы, галактозы, рамнозы, галактуроновой и глюкуроновой кислот. Сделан вывод о том, что роль защитных коллоидов выполняют кислые полисахариды, содержащиеся в гуммиарабике. Показано, что при обработке виноматериалов для игристых вин защитным коллоидом коэффициент сопротивления виноматериала выделению диоксида углерода повышается на 20 %, скорость разрушения пены снижается на 14%, максимальный объем пены увеличивается на 7 %, что способствует улучшению пенистых и игристых свойств готовой продукции. Установлено, что при добавлении 500 мг/дм гуммиарабика в игристое вино его пенистые и игристые свойства повышаются в среднем на 40%. Применение гуммиарабика способствует повышению сроков стабильности игристых и крепленых вин против кристаллических и коллоидных помутнений. Literature data about the effect of protective colloid of gum arabic on the terms of stability of various types of wines (sparkling, liqueur) were systematized. It was shown that using of protective colloids contributed to an increase in the stability of sparkling and liqueur wines against crystalline and colloidal (reversible and irreversible) haze. It was also clarified that gum arabic contained polysaccharides developed from arabinose, galactose, rhamnose, galacturonic and glucuronic acids. It was concluded that the role of protective colloids was played by acidic polysaccharides contained in gum arabic. It is shown that when base wines for sparklings are treated with a protective colloid, the coefficient of base wine resistance to the release of carbon dioxide increases by 20%, the rate of foam break decreases by 14%, the maximum volume of foam increases by 7%, which contributes to the improvement of foamy and sparkling properties of the finished product. It is established that adding 500 mg/dm of gum arabic to sparkling wine increases its foamy and sparkling properties by an average of 40%. The use of gum arabic contributes to an increase in stability of sparkling and fortified wines against crystalline and colloidal haze.
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Drzewiński, Andrzej, Maciej Marć, Wiktor W. Wolak et Mirosław R. Dudek. « Effect of Magnetic Heating on Stability of Magnetic Colloids ». Nanomaterials 12, no 17 (3 septembre 2022) : 3064. http://dx.doi.org/10.3390/nano12173064.

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Stable aqueous suspension of magnetic nanoparticles is essential for effective magnetic hyperthermia and other applications of magnetic heating in an alternating magnetic field. However, the alternating magnetic field causes strong agglomeration of magnetic nanoparticles, and this can lead to undesirable phenomena that deteriorate the bulk magnetic properties of the material. It has been shown how this magnetic field influences the distribution of magnetic agglomerates in the suspension. When investigating the influence of the sonication treatment on magnetic colloids, it turned out that the hydrodynamic diameter as a function of sonication time appeared to have a power-law character. The effect of magnetic colloid ageing on magnetic heating was discussed as well. It was shown how properly applied ultrasonic treatment could significantly improve the stability of the colloid of magnetic nanoparticles, ultimately leading to an increase in heating efficiency. The optimal sonication time for the preparation of the magnetic suspension turned out to be time-limited, and increasing it did not improve the stability of the colloid. The obtained results are important for the development of new materials where magnetic colloids are used and in biomedical applications.
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Thèses sur le sujet "Stabilità colloide"

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GIUSTRA, MARCO DAVIDE. « Synthesis of multi-branched polymers for the stabilization of metallic nanoparticles ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366171.

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È fondamentale progettare e monitorare tutte le fasi preparative di un sistema di drug delivery in modo tale da raggiungere un determinato sito bersaglio. Ogni parte di un nanocarrier influenza sé stesso e l'ambiente circostante. Inoltre, per ottenere campioni monodispersi, il rivestimento e le eventuali funzionalizzazioni sono fondamentali per determinare la stabilità colloidale, prevedere il comportamento in un sistema biologico e raggiungere il target di interesse. In particolar modo, la razionalizzazione dei meccanismi di internalizzazione e la quantificazione dei carrier nei siti intracellulari è ancora oggi un tema di grande interesse in ambito nanomedico. In questo lavoro, è stata presentata una classe di polimeri multidentati di facile sintesi mostrando un'ampia applicabilità in combinazione con nanoparticelle (NPs) metalliche. I polimeri multidentati sono stati coinvolti in tre diversi progetti. Il primo progetto mirava a presentare un polimero multidentato come modello generale da applicare nel rivestimento di superfici metalliche. Per dimostrarlo sono stati effettuati diversi test prendendo in considerazione la composizione e la dimensione delle NPs. Questo polimero è stato confrontato con altri due tipi di rivestimenti comuni in letteratura. I dati ottenuti mostrano come il nuovo rivestimento fornisca una maggiore stabilità colloidale. In secondo luogo, sono stati ottenuti miglioramenti dal punto di vista della tossicità e della bio-funzionalizzazione. Nel secondo progetto, la catena polimerica è stata modificata con un altro ligando per ampliare il campo di applicazione di questi polimeri. La scelta della molecola è basata sull'affinità per alcune superfici metalliche. In questo caso la molecola scelta è il 4-amminotiofenolo, spesso utilizzata per applicazioni SERS. Inizialmente, il polimero è stato studiato rivestendo diversi tipi di NPs metalliche (oro e argento) e sono state eseguite analisi SERS. Le dimensioni e la forma hanno giocato un ruolo chiave, in particolare con le nanoparticelle cubiche concave risultando promettenti agenti diagnostici. Nella seconda parte del progetto, le nanoparticelle cubiche d'argento sono state utilizzate come modello per la valutazione del traffico cellulare e della maturazione endosomiale. Dei test preliminari sono stati effettuati a diversi pH (per emulare le variazioni di pH nelle fasi evolutive dell'endosoma) e studi in vitro sono stati eseguiti per verificare l'uptake delle NPs nelle cellule HeLa. Il terzo progetto mirava a utilizzare il polimero sintetizzato come precursore nella sintesi di nanoparticelle anisotropiche. La forma ottenuta inizialmente è stata quella di un petalo, ma aumentando la temperatura, i petali si sono assemblati a nanofiori con un diametro al di sopra di 100 nm. La presenza del polimero SERS-attivo rende queste nanoparticelle ottimi candidati per questa tipologia di applicazione.
Designing and monitoring all the preparation steps of a drug delivery system is essential to achieve a specific target. Each part of a nanocarrier affects the batch itself and the surrounding environment. In addition, to obtain monodispersed samples, the coating and any functionalization are crucial to determine the colloidal stability, to predict the behavior with a biological system, and the reaching of the target site. In particular, the achievement of intracellular sites by rationalizing the internalization mechanisms and quantifying the carriers in the target is still today a hot topic in the nanomedical field. Here, a class of multidentate polymers was presented: a simple way to synthesize them and show their broad applicability in combination with metal NPs. Multi-branched polymers were involved in three projects. The first project aimed to present a multidentate polymer as a general model to be applied in the coating of metal surfaces. To prove this, several tests were carried out by modulating the composition and size of the NPs. This easily synthesized polymer has been compared with two types of coatings common in literature. The obtained data show how the new surfactant provides high colloidal stable nanoparticles. Secondly, this leads to improvements from the point of view of toxicity and bio-functionalization. In the second project, the ligands polymer chain was modified to increase the range of application. Moreover, the choice of the ligand was based on the affinity for certain metal surfaces. In this case, the molecule is 4-aminotiophenol which is often used for SERS applications. Initially, the versatility of the polymer was investigated by coating different types of metallic NPs (gold and silver) and then SERS analyses were performed. Size and shape played a key role, especially with cubic concave nanoparticles that are promising for diagnostics application. In the second part of the project, cubic silver nanoparticles were used as a model for the evaluation of cell trafficking and endosomal maturation. Preliminary tests of NPs have been carried out at different pH (to emulate the pH variations in the endosomal evolution stages) and in vitro studies to check the nanoparticles uptake in HeLa cells were performed. The third project aimed to use the designed polymer as precursor in the synthesis of anisotropic nanoparticles. The shape obtained is a petal form. Subsequently, with the increase of the temperature, the petals assembled to nanoflowers above 100 nm. The presence of the active SERS polymer makes these nanoparticles, excellent candidates for this application.
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Jones, David Andrew Ross. « Depletion flocculation of sterically-stabilized particles ». Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364692.

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Ryan, Joseph Nolte. « Groundwater colloids in two Atlantic coastal plain aquifers : colloid formation and stability ». Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14560.

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Norrfors, Karin. « Stability and sorption capacity of montmorillonite colloids : Investigation of size fractional differences and effects of γ-irradiation ». Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159944.

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Bentonite clay is intended to form one of the barriers in most repositories of spent nuclear fuel located in granite. One important function of the bentonite barrier is to retard transport of radionuclides in the event of waste canister failure. Bentonite has a high sorption capacity of cations and its main constituent is montmorillonite. In contact with groundwater of low ionic strength, montmorillonite colloids can be released from bentonite and thereby control transport of radionuclides sorbed onto the colloids. In colloid transport in bedrock fractures, size separation of clay colloids may occur due to physical and chemical interactions with the bedrock fracture surface. This may enhance or retard the overall transport of radionuclides, depending on the sorption capacities and stability of the differently sized clay colloids. The bentonite barrier will be exposed to γ-radiation from the spent nuclear fuel. Irradiation affects surface-related properties of bentonite. If an average sorption capacity value cannot be used for all colloid sizes or if sorption is affected by exposure to γ-irradiation, corrected sorption capacity values would give higher resolution in current reactive transport models. In order to study the size separation process, a protocol was developed and successfully applied to fractionate montmorillonite into different-sized colloid suspensions by means of sequential or direct centrifugation. The stability and sorption capacity were studied using these fractions. Both stability and sorption capacity were found to be similar for all colloid sizes. Bentonite exposed to γ-radiation sorbed less divalent cations with increasing radiation dose. The effect was not large enough to have any impact on diffusion. The presence of bentonite enhanced irradiation-induced corrosion of copper under anaerobic atmosphere. An average sorption capacity value for montmorillonite can be used for all colloid sizes in reactive transport models. The effect of γ-irradiation on sorption capacity is sufficiently large to require consideration in transport modelling.
Bentonite är planerad som en av barriärerna i de flesta slutförvar av använt kärnbränsle. Bentonite har en hög sorptionskapacitet för katjoner. Den huvudsakliga beståndsdelen av bentonit är montmorillonit. Montmorillonitkolloider kommer att frigöras från bentonitbufferten i kontakt med grundvatten av låg jonstyrka och på så vis styra transporten av sorberade radionuklider. Under den kolloidala transporten i bergsprickorna kan en separation med avseende på storlek uppstå genom interaktioner mellan kolloiderna och bergytan. Detta kan få till följd att den genomsnittliga transporten av radionuklider bromsas eller tilltar beroende på sorptionskapaciteten och stabiliteten av de olika kolloidstorlekarna. Bentonitbarriären kommer även att utsättas för γ-bestrålning från det använda kärnbränslet, vilket påverkar dess ytrelaterade egenskaper. Om inte ett medeltal för sorptionskapaciteten är giltigt för alla kolloidstorlekar eller om sorptionen påverkas av γ-bestrålning, behövs nya sorptionskapaciteter bestämmas och impliceras för noggrannare transportmodeller. En metod för att separera montmorillonitkolloider med avseende på storlek via direkt och stegvis centrifugering har utvecklats. Stabiliteten och sorptionskapaciteten för dessa fraktioner har studerats. Både stabilitet och sorptionskapacitet visade sig vara lika för alla kolloidstorlekar. Bestrålad bentonit sorberar mindre andel divalenta katjoner med ökad dos bestrålning. Effekten är dock inte stor nog för att slå igenom i diffusionsexperimenten. Förekomst av bentonit ökar även den strålningsinducerade korrosionen av koppar under anaeroba förhållanden. Ett medelvärde för sorptionskapaciteten kan användas för alla kolloidstorlekar i transportmodeller. Effekten av γ-bestrålning är dock stor nog för att implementeras i modellerna.

QC 20150213

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COLANGELO, DONATO. « Nuovi approcci alla chiarifica dei mosti e al fining dei vini per la stabilità colloidale ». Doctoral thesis, Università Cattolica del Sacro Cuore, 2019. http://hdl.handle.net/10280/57884.

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Per via degli svantaggi inerenti l’uso di bentonite nella produzione di vini bianchi, la ricerca di alternative ha assunto di recente una grande importanza. Il lavoro presentato in questa tesi ha l’obiettivo di valutare l’applicabilità di tre approcci innovativi alla stabilizzazione colloidale dei vini: l’uso di chitosano, l’applicazione dei PEF e il riutilizzo di colonne di scambio cationico. L’aggiunta di chitosano è risultata nella rimozione delle chitinasi dal vino, permettendo di raggiungere un soddisfacente livello di stabilità. Gli effetti sul colore e sugli aromi, quando non significativi, non sono risultati essere peggiori rispetto ai risultati ottenuti da trattamenti con bentonite. L’applicazione dei PEF aveva lo scopo di innescare la denaturazione e l’aggregazione delle proteine tramite un sistema di trattamento-raffreddamento e filtrazione finale. I risultati suggeriscono che un buon grado di stabilità viene raggiunto solo con trattamenti particolarmente energetici ma questo a danno del colore del prodotto. Infine, lo scopo dello studio sulle resine di scambio cationico era quello di valutare la rigenerazione di questo supporto per un molteplice utilizzo operativo. La rimozione delle proteine adsorbite sul supporto è risultata essere possibile in specifiche condizioni di pH e forza ionica, con un consumo di acqua relativamente basso.
The search for fining alternatives to bentonite has assumed great importance in white winemaking due to the drawbacks of bentonite application. The research here presented aimed at observing the viability of three innovative approaches to wine stabilization, namely chitosan addition, PEF treatments and cation exchange applicability. Chitosan successfully removed chitinases from wine, allowing at the same time a sufficient degree of colloidal stability. Collateral effects on color and aroma compounds were non-significant or acceptable when compared with the effects observed for bentonite applications reported in literature. The use of PEF was aimed at accelerating protein unfolding and aggregation and was coupled to an in-line cooling and filtration system for efficient removal of colloidal aggregates. The results collected suggested that the treatment was capable of inducing a satisfactory colloidal stability only in high- energetic double-treated wine samples, with some deleterious consequences on the color. Finally, the aim of the research for cation-exchange resins application was to find environmentally friendly cleaning procedures to regenerate the resin capacity and allow reuse of the same resin for further cycles of fining. The removal of proteins bound to the resin was possible under specific pH and ionic strength conditions with relatively low consumption of water.
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Zhang, Li. « The study of phase separation in the miscibility gap and ion specific effects on the aggregation of soft matter system ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS106/document.

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Le procédé de séparation de phase est importante car elle détermine la structure des matériaux finaux. Il existe de nombreux systèmes qui ont plus d'une phase tels que des mousses et des gels. Les mousses sont des dispersions aqueuses de bulles de gaz dans une phase aqueuse et gels apparaissent lorsque certains microscopique unité de base commence à se rassembler formant un grand réseau solide qui enjambe l'espace macroscopique. Ils ont de nombreuses applications dans l'industrie et la vie quotidienne. Dans cette thèse, tout d'abord, je me concentre sur l'étude de différents types de séparation de phase. Deuxièmement, je étudié les effets spécifiques d'ions sur l'agrégation des particules colloïdales et tensioactif, le but est de faire des mousses stables. Dans la lacune de miscibilité il existe deux types de séparation de phase: la croissance nucléation et la décomposition spinodale, ils ont différents mécanismes et de la cinétique de croissance. Par conséquent, mon premier projet est d'étudier le processus d'évolution d'eux et de leurs effets sur la structure finale du matériau. Les gels peuvent être préparés par l'ajout de sel à la dispersion de particules colloïdales, ils ont un grand nombre d'applications telles que dans les aliments et la science des matériaux. Dans cette thèse, nous utilisons différents types de sels de comparer les propriétés de gel à partir de deux aspects macroscopiques et microscopiques. Obtenir des mousses stables est significatif dans la vue de leur beaucoup d'applications, mais les moyens de les faire sont pour la plupart compliqué. Dans cette thèse, nous pouvons obtenir des mousses stables par l'intermédiaire de deux façons. On est tout simplement en ajoutant des sels de solutions de tensioactifs, à travers lequel nous pouvons faire la mousse ultra-stable. Une autre façon est d'utiliser la phase de gel, nous avons étudié en tant que phase continue dans les mousses à arrêter le vieillissement de la mousse
Phase separation process is important as it determines the structure of the final materials. There are many systems that have more than one phase such as foams and gels. Aqueous foams are dispersions of gas bubbles in a water phase and gels appear when some basic microscopic unit starts to aggregate forming a large solid network that spans macroscopic space. They have many applications in industry and daily life. In the present thesis, firstly, I focus on studying different types of phase separation. Secondly, I studied the ion specific effects on the aggregation of colloidal particles and surfactant, the purpose is to make stable foams. In the miscibility gap there are two types of phase separation: Nucleation growth and spinodal decomposition, they have different growth mechanisms and kinetics. Therefore, my first p project is to investigate the evolution process of them and their effects to the final structure of material. Gels can be made by adding salt to the dispersion of colloidal particles, they have a large number of applications such as in food and material science. In this dissertation, we use different types of salts to compare gel properties from both macroscopic and microscopic aspects. Obtaining stable foams is significant in the view of their plenty of applications, but the ways to make them are mostly complicated. In this thesis, we can obtain stable foams via two ways. One is simply by adding salts to surfactant solutions, through which we can make ultrastable foam. Another way is using the gel phase we have studied as the continuous phase in foams to arrest the foam aging
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Dale, Phillip. « The colloidal stability of suspo-emulsions ». Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398542.

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Whyman, R. H. « Electrophoretic and stability studies of casein coated colloidal particles ». Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379647.

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Czigány, Szabolcs. « Subsurface colloids stability, sampling, and transport under gravitational and centrifugal accelerations / ». Online access for everyone, 2004. http://www.dissertations.wsu.edu/Dissertations/Summer2004/s%5Fczigany%5F080404.pdf.

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Herman, David J. « Controlling Colloidal Stability using Highly Charged Nanoparticles ». Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51566.

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This dissertation focused on the potential use of highly charged nanoparticles to stabilize dispersions of weakly charged microparticles. The experimental components of the project centered on a model colloidal system containing silica microparticles at the isoelectric point where the suspensions are unstable and prone to flocculation. The stability of the silica suspensions was studied in the presence of highly charged nanoparticles. Initial experiments used polystyrene latex with either sulfate or amidine surface groups. Effective zeta potentials were measured with nanoparticle concentrations ranging from 0.001% to 0.5% vol. Adsorption levels were determined through direct SEM imaging of the silica microparticles, showing that the nanoparticles directly adsorbed to the microparticles (amidine more than sulfate), producing relatively large effective zeta potentials. However, stability experiments showed that the latex nanoparticles did not stabilize the silica but merely provided a reduction in overall flocculation rate. It was concluded that the zeta potential was an insufficient predictor of stability as there was still sufficient patchiness on the surface to allow for the silica surfaces to aggregate. Experiments using zirconia and alumina nanoparticles did achieve effective stabilization; both types stabilized the silica suspensions for longer than the observation period of approximately 15 hours. Stability was observed at concentrations of 10^-4% to 1.0% (zirconia) and 10^-2% vol. (alumina). These particles adsorbed directly to the microparticles (confirmed via SEM) and produced increasing effective zeta potentials with increasing nanoparticle concentrations. The adsorption resulted in significant electrostatic repulsion that was determined to be effectively irreversible using colloidal probe AFM. The improved stabilizing ability was attributed to the increased van der Waals attraction between the oxide nanoparticles (compared to polystyrene). Finally, an unexpected result of the CP-AFM force measurements showed that the repulsive forces between a nanoparticle-coated particle and plate lacked the normal dependence on the radius of the probe as predicted by the Derjaguin approximation. The forces observed in nanoparticle suspensions were virtually identical for 5 µm and 30 µm probes. Based on calculations of the shear rate in the gap, it was theorized that this phenomenon may have resulted from the shearing of adsorbed particles from the surfaces, which leads to similar interaction geometries for the two probe sizes.
Ph. D.
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Livres sur le sujet "Stabilità colloide"

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Tadros, Tharwat F., dir. Colloid Stability. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/9783527631070.

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Tadros, Tharwat F., dir. Colloid Stability. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/9783527631094.

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Tadros, Tharwat F., dir. Colloid Stability. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527631193.

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F, Tadros Tharwat, dir. Colloid stability and application in pharmacy. Weinheim, Germany : Wiley-VCH Verlag, 2007.

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Verwey, E. J. W. Theory of the stability of lyophobic colloids. Mineola, N.Y : Dover Publications, 1999.

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Clay swelling and colloid stability. Boca Raton : Taylor & Francis, 2006.

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Eric, Dickinson, Walstra Pieter, Royal Society of Chemistry (Great Britain). Food Chemistry Group., Nederlandse Vereniging voor Voedingsleer en Levensmiddelentechnologie. et International Symposium on "Food Colloids and Polymers" (1992 : Lunteren, Netherlands), dir. Food colloids and polymers : Stability and mechanical properties. Cambridge : Royal Society of Chemistry, 1993.

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Teorii͡a ustoĭchivosti kolloidov i tonkikh plenok. Moskva : "Nauka", 1986.

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Deri͡agin, Boris Vladimirovich. Theory of stability of colloids and thin films. New York : Consultants Bureau, 1989.

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González García, Álvaro. Polymer-Mediated Phase Stability of Colloids. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-33683-7.

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Chapitres de livres sur le sujet "Stabilità colloide"

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González García, Álvaro. « On the Colloidal Stability of Association Colloids ». Dans Polymer-Mediated Phase Stability of Colloids, 113–29. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-33683-7_7.

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Tadros, Tharwat. « General Principles of Colloid Stability and the Role of Surface Forces ». Dans Colloid Stability, 1–22. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch1.

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Tadros, Tharwat. « Colloid Stability Using Polymeric Surfactants ». Dans Colloid Stability, 235–62. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch10.

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Stubenrauch, Cosima, et Brita Rippner Blomqvist. « Foam Films, Foams and Surface Rheology of Non-Ionic Surfactants : Amphiphilic Block Copolymers Compared with Low Molecular Weight Surfactants ». Dans Colloid Stability, 263–306. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch11.

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Fainerman, V. B., V. I. Kovalchuk, M. E. Leser et R. Miller. « Effect of the Intrinsic Compressibility on the Dilational Rheology of Adsorption Layers of Surfactants, Proteins and Their Mixtures ». Dans Colloid Stability, 307–33. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch12.

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Toshev, Borislav V. « Metastability and Lability in Surface Phase Transitions : Surface Forces and Line Tension Effects ». Dans Colloid Stability, 335–52. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch13.

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Nedyalkov, Mickael. « Structure and Stability of Black Foam Films from Phospholipids ». Dans Colloid Stability, 353–82. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch14.

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Lalchev, Zdravko I. « Phospholipid Foam Films : Types, Properties and Applications ». Dans Colloid Stability, 383–408. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch15.

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Shchukin, Eugene D., et Alexander V. Pertsov. « Thermodynamic Criterion of Spontaneous Dispersion ». Dans Colloid Stability, 23–47. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch2.

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Ohshima, Hiroyuki. « Electrostatic Interactions between Colloidal Particles - Analytic Approximation ». Dans Colloid Stability, 49–72. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527631070.ch3.

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Actes de conférences sur le sujet "Stabilità colloide"

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Villeneuve, Pierre, Claire Bourlieu-Lacanal, David McClements, Eric Decker et Erwann Durand. « Lipid oxidation in emulsions and bulk oils : A review of the importance of micelles ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/lzak8107.

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Lipid oxidation is a major cause of quality deterioration in food or cosmetic products. In these matrices, lipids are often present in a bulk or in emulsified forms. In both systems, the rate, extent and pathway of oxidation are highly dependent on the presence of colloidal structures and interfaces because these are the locations where oxidation normally occurs. In bulk oils, reverse micelles (association colloids) are present and are believed to play a crucial role on lipid oxidation. Conversely, in emulsions, surfactant micelles are present that also play a major role in lipid oxidation pathways. This review discusses the current understanding of the influence of micellar structures on lipid oxidation. In particular, is discussed the major impact of the presence of micelles in emulsions, or reverse micelles (association colloids) in bulk oil on the oxidative stability of both systems. Indeed, both micelles in emulsions and associate colloids in bulk oil are discussed as nanoscale structures that can serve as reservoirs of antioxidants and pro-oxidants and are involved in their transport within the concerned system. Their role as nanoreactors where lipid oxidation reactions occur is also commented. Significance of your research to the AOCS membership? The results underline the importance of a better understanding of the role of micelles in the control of lipid oxidation in food or cosmetic products.
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Lin, Wei-Kuan, et Somin Eunice Lee. « Universal and quantitative measure of colloidal stability of plasmonic nanoparticles via comprehensive stability parameter method ». Dans Colloidal Nanoparticles for Biomedical Applications XV, sous la direction de Marek Osiński et Antonios G. Kanaras. SPIE, 2020. http://dx.doi.org/10.1117/12.2546244.

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Kyriazi, Maria-Eleni, et Antonios G. Kanaras. « Investigating the stability of DNA-coated gold nanoparticles ». Dans Colloidal Nanoparticles for Biomedical Applications XIII, sous la direction de Xing-Jie Liang, Wolfgang J. Parak et Marek Osiński. SPIE, 2018. http://dx.doi.org/10.1117/12.2285833.

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Ziemer, John, Colleen Marrese-Reading et Manuel Gamero-Castano. « Colloid Thruster Propellant Stability After Radiation Exposure ». Dans 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2003. http://dx.doi.org/10.2514/6.2003-4853.

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Webley, Ann-Dorie, Stephanie Dungan et Susan Ebeler. « Local distribution of limonene in phospholipid vesicles ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/qxcj6124.

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The efficacy and quality of food products is affected by the distribution of hydrophobic solutes such as flavours and bioactive compounds. In order to improve food design, it is important to determine the local distribution of these solutes and the factors that affect their stability, incorporation and release. Colloidal assemblies of phospholipids are of particular interest, as they comprise safe, widespread natural amphiphiles that can solubilize hydrophobic compounds. However, there is a lack of accurate and non-destructive methods to study the local distribution of solutes between the sample matrix elements, the aqueous phase, and the vapor phase, making it difficult to assess the effect of structure on stability and release. Short time headspace microextraction allows us to determine the local distribution of hydrophobic solutes and the effect of colloidal structure while keeping the system intact. Using thermodynamic relationships, the detected concentrations of compounds in the vapour phase are used to determine local properties within the sample matrix. The colloids of focus in this study were phosphatidylcholine vesicles which were used to extend our previous work on micellar solutions by developing a quantification method for the solubilization and retention of volatile nonpolar compounds in vesicles. The local partitioning of the aroma molecule, limonene, was investigated in vesicles of various structures, lipid compositions, and at different temperatures. Vesicles were found to be much more effective at solubilizing limonene than short-chain phosphatidylcholine micelles. They yielded vesicle-water partition coefficients of ~104M–1 while the micelles had micelle-water partition coefficients of ~103M-1. Lipid composition and vesicle size did not have a significant effect on the partitioning properties, however, reducing the limonene concentration in the vesicles lowered the partition coefficient, suggesting some interaction effect at higher limonene concentrations. In addition, with saturated lipids, limonene fluidizes the gel membrane and lowers the phase transition temperature.
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Harsojo, Respitaningrum, Toto Afrianto et Harini Sosiati. « Study of the stability coated and uncoated nanosilver colloid ». Dans PADJADJARAN INTERNATIONAL PHYSICS SYMPOSIUM 2013 (PIPS-2013) : Contribution of Physics on Environmental and Energy Conservations. AIP, 2013. http://dx.doi.org/10.1063/1.4820289.

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Maturana, Daniel, Philipp Baaske et Stefan Duhr. « Improve Biologics stability in solution understanding the colloidal and conformational stability ». Dans International Symposium on Immunobiological. Instituto de Tecnologia em Imunobiológicos, 2021. http://dx.doi.org/10.35259/isi.2021_46639.

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Shabanova, M. A. « Sol-gel processes and aggregative stability of lyophilic inorganic colloids ». Dans International Conference on Science and Technology of Synthetic Metals. IEEE, 1994. http://dx.doi.org/10.1109/stsm.1994.835343.

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Williams, Wesley C. « Fundamental Issues of Nanofluid Behavior ». Dans 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89844.

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This paper will elucidate some of the behaviors of nanofluids other than the abnormal conductivity enhancement, which are of importance to the experimental and engineering use of nanofluids. Nanofluid is the common name of any sol colloid involving nanoscale (less than 100nm) sized particles dispersed within a base fluid. It has been shown previously that the dispersion of nano-particulate metallic oxides into water can increase thermal conductivity up to 30–40% over that of the base fluid and anomalously more than the mere weighed average of the colloid. There is a great potential for the use of nanofluids as a way to enhance fluid/thermal energy transfer systems. Due to the recentness of nanofluid science, there are still many issues which have not been fully investigated. This paper should act as a primer for the basic understanding of nanofluid behavior. Particle size and colloid stability are of key importance to the functionality of nanofluids. The pH and concentration/loading of nanofluids can alter the size of the nanoparticles and also the stability of the fluids. It will be shown through experiment and colloid theory the importance of these parameters. Furthermore, most of the existing literature uses volume percentage as the measure of particle loading, which can often be misleading. There will be discussion of this and other misleading ideas in nanofluid science.
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Bruce, Natalie, Francesca Farrell et Nicolas Laurand. « Temperature Stability of Elastomeric Colloidal Quantum Dot Colour Converter ». Dans 2019 IEEE 2nd British and Irish Conference on Optics and Photonics (BICOP). IEEE, 2019. http://dx.doi.org/10.1109/bicop48819.2019.9059578.

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Rapports d'organisations sur le sujet "Stabilità colloide"

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McGraw, M. A., et D. I. Kaplan. Colloid suspension stability and transport through unsaturated porous media. Office of Scientific and Technical Information (OSTI), avril 1997. http://dx.doi.org/10.2172/493372.

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Zhao, Pihong, Mavrik Zavarin, Zurong Dai et Annie B. Kersting. Pu Sorption, Desorption and Intrinsic Colloid Stability under Granitic Chemical Conditions. Office of Scientific and Technical Information (OSTI), septembre 2014. http://dx.doi.org/10.2172/1169859.

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Hawkett, Brian S. The Colloidal Stability of Magnetic Nanoparticles in Ionic Liquids. Fort Belvoir, VA : Defense Technical Information Center, septembre 2014. http://dx.doi.org/10.21236/ada608882.

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Cho, Tae Joon, et Vincent A. Hackley. Assessing the chemical and colloidal stability of functionalized gold nanoparticles. Gaithersburg, MD : National Institute of Standards and Technology, juin 2018. http://dx.doi.org/10.6028/nist.sp.1200-26.

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Panfil, Yossef E., Meirav Oded, Nir Waiskopf et Uri Banin. Material Challenges for Colloidal Quantum Nanostructures in Next Generation Displays. AsiaChem Magazine, novembre 2020. http://dx.doi.org/10.51167/acm00008.

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The recent technological advancements have greatly improved the quality and resolution of displays. Yet, issues like full-color gamut representation and the long-lasting durability of the color emitters require further progression. Colloidal quantum dots manifest an inherent narrow spectral emission with optical stability, combined with various chemical processability options which will allow for their integration in display applications. Apart from their numerous advantages, they also present unique opportunities for the next technological leaps in the field.
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Zhao, P., A. Kersting, Z. Dai et M. Zavarin. Pu(IV) Intrinsic Colloid Stability in the Presence of Montmorillonite at 25 & ; 80 C. Office of Scientific and Technical Information (OSTI), juin 2012. http://dx.doi.org/10.2172/1077196.

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Zhao, P., A. Kersting, Z. Dai et M. Zavarin. Stability of Intrinsic Pu colloids in the Presence of Montmorillonite at 25 and 80C : High-fired and freshly prepared PuO2 oxides. Office of Scientific and Technical Information (OSTI), août 2013. http://dx.doi.org/10.2172/1093423.

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Wicker, Louise, Ilan Shomer et Uzi Merin. Membrane Processing of Citrus Extracts : Effects on Pectinesterase Activity and Cloud Stability. United States Department of Agriculture, octobre 1993. http://dx.doi.org/10.32747/1993.7568754.bard.

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The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.
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Chefetz, Benny, Baoshan Xing et Yona Chen. Interactions of engineered nanoparticles with dissolved organic matter (DOM) and organic contaminants in water. United States Department of Agriculture, janvier 2013. http://dx.doi.org/10.32747/2013.7699863.bard.

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Background: Engineered carbon nanotubes (CNTs) are expected to be increasingly released into the environment with the rapid increase in their production and use. The discharged CNTs may interact with coexisting contaminants and subsequently change environmental behaviors and ecological effects of both the CNTs themselves and the contaminants. Dissolved organic matter (DOM) plays a critical role in the transport of CNTs in the aquatic environment, affecting both CNT's surface properties through adsorption, and its colloidal stability in solution. Therefore, CNT-bound DOM complexes may interact with coexisting contaminants, thus affecting their environmental fate. With increasing production and use of CNTs, there is an increasing risk that humans could be exposed to CNTs mainly through ingestion and inhalation. Since CNTs can be carriers of contaminants due to their high adsorption affinity and capacity, the distribution of these nanoparticles in the environment holds a potential environmental and health risk. Project objectives: The overall goal of this project was to gain a better understanding of the environmental behavior of engineered nanoparticles with DOM and organic pollutant in aqueous systems. The scope of this study includes: characterizing various types of engineered nanoparticles and their interaction with DOM; binding studies of organic contaminants by nanoparticles and DOM-nanoparticle complexes; and examining interactions in DOM-nanoparticles-contaminant systems. Major conclusions, solutions and achievements: DOM has a pronounced effect on colloidal stability of CNTs in solution and on their surface chemistry and reactivity toward associated contaminants. The structure and chemical makeup of both CNTs and DOM determine their interactions and nature of formed complexes. CNTs, contaminants and DOM can co-occur in the aquatic environment. The occurrence of co-contaminants, as well as of co-introduction of DOM, was found to suppress the adsorption of organic contaminants to CNTs through both competition over adsorption sites and direct interactions in solution. Furthermore, the release of residual contaminants from CNTs could be enhanced by biomolecules found in the digestive as well as the respiratory tracts, thus increasing the bioaccessibility of adsorbed contaminants and possibly the overall toxicity of contaminant-associated CNTs. Contaminant desorption could be promoted by both solubilization and sorptive competition by biological surfactants. Scientific and agricultural implications: The information gained in the current project may assist in predicting the transport and fate of both CNTs and associated contaminants in the natural environment. Furthermore, the results imply a serious health risk from contaminant-associated CNTs.
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Shomer, Ilan, Louise Wicker, Uzi Merin et William L. Kerr. Interactions of Cloud Proteins, Pectins and Pectinesterases in Flocculation of Citrus Cloud. United States Department of Agriculture, février 2002. http://dx.doi.org/10.32747/2002.7580669.bard.

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The overall objective was to understand the cloud flocculation of citrus juice by characterization of the interactions between proteins and pectins, and to determine the role of PE isozymes in catalyzing this phenomenon. Specific objectives were to: 1. identify/characterize cloud-proteins in relation to their coagulable properties and affinity to pectins; 2. to determine structural changes of PME and other proteins induced by cation/pectin interactions; 3. localize cloud proteins, PME and bound protein/pectates in unheated and pasteurized juices; 4. to create "sensitized" pectins and determine their effect on clarification. The original objectives were not changed but the methods and approach were modified due to specific research requirements. Two i postulates were: 1. there is a specific interaction of cloud proteins with de-esterified regions of ! pectin and this contributes to cloud loss; 2. isozymes of pectin-methyl-esterase (PME) vary in efficiency to create sensitized pectins. The appearance of citrus fruit juice is an important quality factor and is determined by the color and turbidity that .are conferred by the suspended particles, i.e., by the cloud and its homogeneity. Under some circumstances the cloud tend to flocculate and the juice clarifies. The accepted approach to explain the clarification is based on pectin demethoxylation by PME that promotes formation of Ca-pectate. Therefore, the juice includes immediate heat-inactivation upon ~ squeezing. Protein coagulation also promotes cloud instability of citrus fruit extracts. However, the clarification mechanism is not fully understood. Information accumulated from several laboratories indicates that clarification is a more complex process than can be explained by a single mechanism. The increasing trend to consume natural-fresh juice emphasizing the importance of the knowledge to assure homogeneity of fresh juice. The research included complementary directions: Conditions that induce cloud-instability of natural- juice [IL]. Evaluate purification schemes of protein [USA]. Identifications of proteins, pectin and neutral sugars ([IL]; Structure of the cloud components using light and electron microscopy and immuno-labeling of PME, high-methoxyl-pectin (HMP) and low-methoxyl-pectin (LMP); Molecular weight of calcium sensitized pectins [US]; Evaluation of the products of PME activity [US]. Fractions and size distribution and cloud components [IL-US]. The optimal pH activity of PME is 7 and the flocculation pH of the cloud is 3-4. Thus, the c roles of PME, proteins and pectins in the cloud instability, were studied in pH ranges of 2- 7. The experiments led to establish firstly repeatable simulate conditions for cloud instability [IL]. Thermostable PME (TS-PE) known to induce cloud instability, but also thermolabile forms of PME (TL-PE) caused clarification, most likely due to the formation and dissolution of inactive :. PE-pectin complexes and displacement of a protective colloid from the cloud surface [US]. Furthermore, elimination of non-PME protein increases TS-PE activity, indicating that non-PME proteins moderate PME activity [US]. Other experiments Concomitantly with the study of the PME activity but promotes the association of cloud-proteins to pectin. Adjusting of the juice pH to f 7 retains the cloud stability and re-adjusting of the pH to 40% DE reacts to immuno-labeling in the cloud fragments, whereas
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