Tesi: "Membranes"

1

PAGLIERO, MARCELLO. "New membranes for membrane distillation process". Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1046350.

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The PhD research program was focused of the development of new hydrophobic membranes suitable for membrane distillation (MD) operation. In particular, the preparation of polymeric flat sheet membranes via nonsolvent induced phase separation (NIPS) technique was investigated. This method allows to fine-tune a large number of variables in order to obtain membranes with an ample variety of different morphologies and properties. Therefore, a systematic study on the important factors affecting the membrane structure, which in turn determines the distillation performance, was carried out. The selected polymer was polyvinylidene fluoride (PVDF), the solvent was dimethylformamide (DMF). First, the effect of the dope solution composition was evaluated. The polymer amount was found to be a key element in defining the porosity and the pore size of the final membrane. Moreover, a minimum critical concentration required to obtain a proper structure was identified on the basis of the dope solution viscosity. In fact, at lower concentrations brittle or defective films were produced. Another important preparation parameter thoroughly investigated was the coagulation bath strength. Harsh nonsolvents induce fast precipitation creating a dense skin above a macrovoid-dominated layer, while weak coagulation media promote a delayed demixing and generate uniform and symmetric structures. Using a semi crystalline polymer such as PVDF, the precipitation rate becomes even more important because it also influences the crystallization of the polymer. The strength of the coagulation bath was regulated by adding different amounts of ethanol to the water bath, from 0% up to 96% v/v. Optimization of this parameter allowed to prepare almost superhydrophobic membranes that were able to withstand the pressure and temperature conditions during vacuum membrane distillation (VMD) tests and to deliver high distillate fluxes and total salt rejection when treating a concentrated NaCl solution. A different approach to improve the membrane performance was exploited in further phase of activity. Different kinds of pore forming agents – such as polyethylene glycols and lithium chloride – were added to the dope solution in order to enhance the porosity and control the pore size. Since the support material can act as an added mass transfer resistance, it was decided to cast these membranes without any reinforcement. However, the absence of any rigid support caused severe shrinkage phenomena during the drying of the membranes leading to an almost complete collapse of the porous structure. It was found that the structure could be preserved by simply clamping the wet membrane on a stiff planar surface and leaving it to dry at room temperature. The amount and type of the additive had impacts on both kinetic and thermodynamic factors governing the phase separation process. By adjusting the dope solution composition, it was possible to favour one or the other to obtain membranes with the desired structure and performance. These unsupported membranes were not able to bear the pressure difference normally applied during VMD, therefore they were tested using a direct contact membrane distillation (DCMD) setup. Since the presence of the support material is mandatory for VMD application, the effect of different kinds of supports was investigated. In particular, several commercial nonwovens were used to prepare PVDF membranes based on the knowledge acquired during the first phase of the PhD activity. Moreover, along with the nonwovens, three polymeric nets, characterized by different structure and made with different polymers, were tested as possible supports. While the commercial nonwovens did not alter too much the performance and morphology of the PVDF membranes, using the nets some remarkable effects were registered. The alternation between holes and crests of the nets caused the formation of membranes with zones having different porosities. The VMD tests highlighted the better performance of the nonwoven casted membranes. However, the patterned surface of the net supported membranes resulted in lower flux decline when a concentrated NaCl solution was used as feed. Polymeric membranes are the most studied type for MD application both for the easy processability and the low production costs. Moreover, the commonly used polymers can withstand the normal operation conditions for desalination or wastewater treatment applications. However, the possibility of producing membranes able to resist higher temperatures and pressures would open the way to new MD applications. One of the possible paths to reach this goal is the exploitation of ceramic membranes. Ceramic material are nevertheless naturally hydrophilic and surface modification procedures must be carried out in order to turn such membranes hydrophobic. Therefore, the reaction between the surface hydroxyl groups of alumina commercial membranes and a silanizing agent was exploited. By changing the reaction conditions, it was possible to obtain highly hydrophobic membranes without affecting the initial pore size and porosity. This functionalizing surface layer proved to be stable up to 400°C which would allow to cover any possible MD operation condition.

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2

Roselló, Busquets Cristina. "Paper de la Sintaxina-1 i els lipid rafts en guia axonal i regeneració neural". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668211.

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Durant el desenvolupament del sistema nerviós cal que les cèl·lules formades a una zona concreta migrin fins a la seva posició final o bé que projectin els seus axons per tal de contactar amb les seves cèl·lules diana. En aquest procés participen multitud de molècules de guia axonal i els seus receptors, que produiran l’atracció o la repulsió de l’axó, guiant-lo fins a la seva posició final. En aquest procés el conus de creixement té un paper clau ja que és on es localitzen la majoria d’aquests receptors i on es dona el recanvi de membrana a través de l’exocitosi i endocitosi, necessàries pel creixement de l’axó. En aquests processos de fusió de membrana participen les proteïnes SNARE, entre elles la Sintaxina-1. Una de les molècules guia més importants durant el desenvolupament del sistema nerviós és la Netrina-1. Aquesta molècula té diferents receptors i segons al receptor que s’uneixi provocarà atracció o repulsió. Estudis previs demostren que la la Sintaxina-1 interacciona amb un dels receptors de la Netrina-1, el DCC, i que aquesta interacció és necessària, durant el desenvolupament de la medul·la espinal, per a l’atracció de les neurones comissurals in vitro. Hi ha pocs estudis on s’investigui el paper de les proteïnes SNARE en guia axonal in vivo. Per aquesta raó, en aquesta tesi estudiem el paper de les proteïnes SNARE, específicament de la Sintaxina-1, en la guia axonal de les neurones comissurals, durant el desenvolupament de la línia mitja i la medul·la espinal, en tres models animals diferents (mosca, pollastre i ratolí). Per mitjà de la supressió dels gens de diferents proteïnes SNARE, demostrem que la Sintaxina-1 és necessària per la correcta guia axonal de les neurones comissurals i el correcte desenvolupament de la medul·la a les tres espècies. A més, confirmem que la pèrdua de funció de la Sintaxina-1 comporta una pèrdua de la sensibilitat de les neurones comissurals a les molècules de guia axonal Netrina-1 i Slit-2 i que la funció de la Sintaxina-1 està conservada en diferents processos de guia axonal com la repulsió depenent de Slit/ROBO a les neurones comissurals, i la repulsió depenent de Netrina-1/UNC5 a les neurones de la EGL. La majoria dels mecanismes involucrats en la guia axonal durant el desenvolupament són molt similars als processos que es donen durant la regeneració. Gran part dels receptors que participen en guia axonal i creixement estan localitzats en microdominis de membrana rics en esfingolípids i colesterol, anomenats lipid rafts, i la seva funcionalitat depèn de la correcta localització en aquests microdominis. A més el colesterol proporciona ordre i rigidesa a les membranes. Aquí demostrem com al disminuir el colesterol de les membranes incrementem el creixement neurític, l’àrea dels conus de creixement, la densitat dels fil·lopodis i la ramificació de neurones immadures del sistema nerviós central i perifèric cultivats in vitro. A més, demostrem que la pèrdua de colesterol afavoreix la regeneració de neurones hipocampals axotomitzades in vitro, de la via perforant en cultius organotípics i del nervi ciàtic in vivo. Finalment, també demostrem que la Nistatina, una droga àmpliament utilitzada per eliminar els lipid rafts de les membranes, incrementa la regeneració in vitro de neurones d’hipocamp activant l’enzim òxid nítric sintasa i, en conseqüència, incrementant els nivells d’òxid nítric.
During the nervous system development neurons have to migrate and extend their axons to connect with their targets. In this process a huge amount of axon guidance molecules and their receptors participate to produce axon attraction or repulsion, guiding them to their final position. The growth cone has a key role in this process because the majority of receptors are localized in its surface and is where membrane turnover takes place. SNARE proteins are important components for membrane fusion in both, exocytosis and endocytosis, and their participation in axon guidance has been recently described. One important molecule during the nervous system development is Netrin-1. This guidance cue has different receptors and has the ability to produce attraction or repulsion depending on the receptor it binds. Recent studies have demonstrated that one of the SNARE proteins, Syntaxin-1, interacts with the Netrin-1 receptor DCC and that this interaction is necessary for the attraction of the commissural neurons. In this thesis we study the role of Syntaxin-1 during the commissural neuron guidance in three different animal models (fly, chicken and mouse). Deleting SNARE genes, we demonstrate that Syntaxin-1 is necessary for the correct commissural axon guidance and the correct spinal cord development in the three species. The mechanisms that regulate axon growth during development are very similar to processes that take place during axon regeneration. A variety of axon guidance receptors are localized in membrane microdomains enriched in cholesterol, termed lipid rafts, whose functionality depends on the proper localization within these microdomains. Here, we demonstrate that cholesterol depletion increases neurite growth, growth cone area, filopodia density and branching in immature neurons of the central and peripheral nervous system in vitro. Moreover, cholesterol depletion enhances axon regeneration after axotomy in vitro in dissociated hippocampal neurons, in slice organotypic cultures and in sciatic nerve in vivo. Finally, we also demonstrate that hippocampal regeneration in vitro is increased when nitric oxide synthase is activated by Nystatin treatments, a well-known drug used to disrupt lipid rafts from the cell membrane.

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3

Shi, Jinjun. "Composite Membranes for Proton Exchange Membrane Fuel Cells". Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1214964058.

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4

Mokrani, Touhami. "Transport of gases across membranes". Thesis, Peninsula Technikon, 2000. http://hdl.handle.net/20.500.11838/878.

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Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000.
Oxygen transport across biofilms and membranes may be a limiting factor in the operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in which fungi are immobilized within the wall of a porous polysulphone capillary membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide) were investigated in a bare membrane (without a biofilm being present). The work provides a basis for further transport study in membranes where biomass is present. The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet membranes. The diaphragm-cell method employs two well-stirred compartments separated by the desired membrane to be tested. The membrane is maintained horizontally. -The gas (solute) concentration in the lower compartment is measured versus time, while the concentration in the upper liquid-containing compartment is maintained at a value near zero by a chemical reaction. The resistances-in-series model can be used to explain the transfer rate in the system. The two compartments are well stirred; this agitation reduces the resistances in the liquid boundary layers. Therefore it can be assumed that in this work the resistance in the membrane will be dominating. The method was evaluated using oxygen as a test. The following factors were found to influence mass transfer coefficient: i) the agitation in the two compartments; ii) the concentration of the reactive solution and iii) the thickness of the membrane.

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5

Deyhim, Sina. "Deriving Gas Transport Properties of Microporous Silica Membranes from First Principles and Simulating Separation of Multi-Component Systems in Different Flow Configurations". Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31340.

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Amorphous silica membranes have molecular sieving properties for the separation of hydrogen from gas mixtures at high temperature. Consequently, they are considered to be applied in separation of a shifted syngas coming out of a water-gas-shift-reactor into the syngas and hydrogen. This separation is a key to an Integrated Gasification Combined Cycle (IGCC) plant, which would allow reducing the carbon footprint in power generation industry. The main objective of this thesis was to carry out a preliminary assessment of suitability of currently available amorphous silica membranes for this separation. However, the separation properties of amorphous silica membranes reported in the open literature vary by orders of magnitude. Therefore, in the first part of this thesis the separation properties of hypothetical silica membrane with different pore size distributions were predicted from first principles. Considering different possible gas transport mechanisms, it was concluded that gas transport in amorphous silica membranes is dominated by the activated and non-activated Knudsen diffusion. The activation energy for transport of different species was predicted using the concept of suction energy. Then, with arbitrary pore size distributions gas permeance of hypothetical silica membrane was predicted for different gas species. Since the pore size distribution of amorphous silica membrane cannot be known a priori, the developed model was used to determine the pore size distribution based on experimentally measured single gas permeances of three different species (kindly provided by Natural Resources Canada, CANMET Energy Technology Center (CETC) laboratory in Ottawa) by minimizing the error of the calculated permeance ratios with respect to the experimental values. The results indicate that, depending on how the objective function is defined, more than one pore size distribution can be found to satisfy the experimental permeance ratios. It is speculated that by increasing the number of experimentally determined permeances, a more unique pore size distribution for the tested silica membrane can be obtained. However, even at this early stage, the developed model provides a rational explanation for the effect of membrane densification on the properties of silica membranes. More specifically, a simultaneous decrease in membrane permeance and selectivity due to membrane densification, reported in the literature, is explained by shrinking the size of pores beyond a certain critical value, which depends on the kinetic diameter of gas molecules that are being separated. Comparing theoretically determined permeances, which match experimentally observed permeance ratios, revealed that the experimental permeances are considerably smaller than the theoretical values. The ratio of the two provided the basis for a scaling factor, a new concept that was introduced in this thesis. To simulate membrane module performance, a novel approach was introduced. More specifically, co- and counter-current flow configurations as well as cross-flow configuration were modeled by assuming no change in feed composition over an infinitesimally small element of membrane area. This led to a system of linear, rather than differential equations, which was readily solved numerically.

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6

Whitehead, L. "Computer simulation of biological membranes and membrane bound proteins". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297412.

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7

Dickson, Callum. "In silico modelling of membranes and drug membrane interactions". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25070.

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A new all-atom force field for the simulation of phospholipid bilayers using the AMBER molecular dynamics package has been developed, which is compatible with other AMBER protein, nucleic acid, carbohydrate and small molecule force fields. The force field has been validated by simulating bilayers of six different lipid types, finding favourable comparison to experiment for properties such as area per lipid, volume per lipid, bilayer thickness, NMR order parameters, scattering data, and lipid lateral diffusion. The modular nature of this force field allows numerous combinations of head and tail groups to create different lipid types, enabling the easy insertion of new lipid species. The lipid bilayer model has then been applied to the study of the interaction between radioimaging agents and membranes in an effort to understand the phenomena of non-specific binding, which remains poorly understood yet of serious detrimental consequence to the development of new imaging tracers. The effect of different concentrations of imaging agent on a homogeneous membrane has been examined using unbiased simulations, whilst the permeability coefficient of each imaging agent through a membrane has been calculated using biased simulations. It is found that radiotracers with low non-specific binding must adopt a certain orientation to cross the head group region of a membrane - this requirement may act as a barrier to membrane entry. Furthermore, once partitioned into the membrane, simulations predict that those radiotracers displaying a high degree of non-specific binding act to order lipid tail groups to a greater extent than those with low non-specific binding, reducing the permeability of the membrane and possibly acting to 'trap' radiotracer in the membrane. These simulations also predict that non-specific binding is not related to radiotracer membrane permeability through a homogeneous bilayer.

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Ma, Yaning. "Characterization of Membrane Permeability and Polymer-Stabilized Model Membranes". Thesis, The University of Arizona, 2007. http://hdl.handle.net/10150/193347.

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The permeability of lipid bilayer membranes to glucose and carboxyfluorescein has been studied in model membranes. Using an enzyme assay, the permeability of glucose was monitored spectrometrically with both large and giant unilamellar vesicles (LUVs and GUVs). The permeability of carboxyfluorescein was studied by entrapping the dye and monitoring its leakage over time from a single GUV. Permeability study using GUVs may provide new information that cannot be obtained from LUVs.The stability of lipid membranes was enhanced by incorporating polymer scaffold. LUVs were prepared with hydrophobic monomers partitioned and then polymerized inside the hydrophobic interior of the lipid bilayers. The sizes of the formed polymers were characterized using gel permeation chromatography and mass spectrometry. This study suggests that large molecular weight polymers were formed inside the lipid bilayers and that the stability of the membranes is related to the size of the polymers.

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Serrano, Albarrás Antonio. "Heteromeric composition of the Kv 1.3 channelosome = Composició heteromèrica del canalosoma Kv1.3". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/665245.

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Ion channels are transmembrane proteins containing aqueous pores which, once open, permit the pass of ions through the plasma membrane. This ion flux takes places following the electrochemical gradient for the specific ion. Kv1.3 is a voltage-gated potassium channel which is member of the Shaker superfamily. Its basic structure consists in a protein with six transmembrane domains, while the functional channel is formed by 4 copies of this protein. Kv1.3 participates in a great amount of physiological functions: nervous system, immune system, insulin signaling or cell proliferation. In the immune system, Kv1.3 is highly expressed both in lymphocytes as well as in mononuclear phagocytes. In both cell types, Kv1.3 regulates the immune activation and cell proliferation. Moreover, Kv1.3 is coexpressed with other ion channel proteins like Kv1.5 or KCNE4 in the immune cells. Kv1.5 is able to heteromerize with Kv1.3, generating heterotetramers with variable stoichiometries. Those heterotetramers produce intermediate phenotypes depending on the ratio of the subunits that generate them. On the other side, KCNE4 may interact with Kv1.3, but not with Kv1.5. Kv1.3 is greatly inhibited by the association with either of the two proteins. In the present thesis we focus in characterizing these interactions and the importance of stoichiometry in their effects. We demonstrate that the associations between Kv1.3 and Kv1.5; and between Kv1.3 and KCNE4 take place in immune cells. Moreover, by using a fusion protein we get to fix the stoichiometry of the Kv1.3-Kv1.5 complex to 1:1. With this stoichiometry, Kv1.5 acts as a dominant negative toward Kv1.3 in the complex. Further interactions are characterized by using several chimeric proteins. By using those chimaeras, it is revealed that the carboxyterminal domain is necessary for the correct function of the channel. On the other hand, we demonstrate that KCNE4 is able to interact with Kv1.3 regardless of Kv1.5 presence. Furthermore, the presence of Kv1.5 in the Kv1.3-KCNE4 interaction results in this association potentiating the function of the channel, instead of inhibiting it. These results are replicated both in heterologous systems as well as in native cells. This discovery presents a new paradigm by which the association with several modulatory proteins may result in the modification of the effect of each one of them. Taking into account the sheer number of different ion channel subunits, the number of different potential phenotypes is increased by a huge margin. KCNE1 is a regulatory subunit, as well as KCNE4. Unlike KCNE4, though, KCNE1 can interact with Kv1.5. In the present thesis we demonstrate for the first time that KCNE1 is not only able to associate with Kv1.5, but to potentiate its activity by a huge amount. This interaction also seems to affect the membrane microdomain targeting of Kv1.5 Finally, the 4 studied proteins are expressed in T lymphocytes, which are the main actors in the pathogenicity of autoimmune diseases. Therefore, we genotyped those genes in multiple sclerosis patients to identify different polymorphisms which could be linked to immune overactivity. After analyzing the different polymorphisms, we located some which could be of special relevance for the physiopathology of autoimmune diseases.
Los canales iónicos son proteínas transmembrana que contienen poros acuosos que permiten el paso de iones a través de la membrana plasmática a favor de gradiente electroquímico. Kv1.3 es un canal de potasio dependiente de voltaje de la superfamilia Shaker. La estructura básica consiste en una proteína con seis dominios transmembrana y el canal funcional está formado por cuatro copias de esta proteína. Kv1.3 participa en multitud de funciones del organismo: sistema nervioso, sistema inmunitario, señalización de la insulina o proliferación celular. En el sistema inmunitario está altamente expresado tanto en linfocitos como en fagocitos mononucleares. En ambos tipos celulares regula la activación inmunitaria y la proliferación celular. Además, se ve coexpresado con otras proteínas de relevancia como Kv1.5 o KCNE4. Kv1.5 puede heteromerizar con Kv1.3, dando lugar a heterotrámeros de estequiometrias variables. Por otro lado, KCNE4 puede interaccionar con Kv1.3, pero no con Kv1.5. Kv1.3 se ve potentemente inhibido por ambas asociaciones. En la presente tesis nos centramos en caracterizar estas interacciones y el peso de la estequiometría en sus efectos. Demostramos que ambas asociaciones tienen lugar en células del sistema inmunitario. Además, mediante una proteína de fusión logramos fijar la estequiometría del complejo Kv1.3-Kv1-5 en 1:1. Así, Kv1.5 demuestra ejercer como dominante negativo respecto a Kv1.3 en el complejo. Estas interacciones intramoleculares son estudiadas mediante el uso de diversas proteínas quiméricas para dilucidar el peso de los extremos carboxiterminales en la formación del canal y su función. Por otro lado, demostramos que KCNE4 afecta el canal de estequiometría 1:1 aumentado su actividad, en lugar de reducirla. Este descubrimiento presenta un nuevo paradigma en que la asociación con varias proteínas reguladoras puede resultar en la modificación del efecto de cada una de ellas. KCNE1 es una proteína reguladora al igual que KCNE4, pero que interactúa con Kv1.5. En la presente tesis demostramos como KCNE1 no solo interacciona con Kv1.5, sino que aumenta en gran medida su actividad. Finalmente, también genotipamos estos genes en pacientes de una enfermedad autoinmune como es la esclerosis múltiple, llegando a localizar diversos polimorfismos de posible interés fisiopatológico.

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Wu, Diana. "Effect of membrane thickness and unsaturation on dye efflux rates induced by [delta]-Lysin from phosphatidylcholine vesicles /". Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/wud/dianawu.pdf.

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11

Marczewski, Dawid. "Membranes via particle assisted wetting". Doctoral thesis, Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200901190.

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Spreading of mixtures of oil with suitable silica particles onto a water surface leads to the formation of composite layers in which particles protrude at the top and at the bottom from the oil. Solidification of the oil and removal of the particles give rise to porous membranes. Pore widths and membrane thicknesses depend on particle sizes and usually are in the range of 70 – 80% of their diameters. Often freely suspended porous membranes are too fragile to operate them in pressure filtration without supportive structure. To improve mechanical stability of porous membranes, a mixture of silica particles with an oil is spread onto a nonwoven fibrous support that was drenched with water. Solidification of the oil and removal of particles yields porous membrane attached to the fibers of the support. Due to inhomogeneous surface of the fabric, the membranes that are attached to it are corrugated. To obtain flat supportive structures, glass beads with 75 μm in diameter are spread onto the water surface with the oil. Solidification of the oil and then removal of particles gives rise to porous membranes with pore diameters in micrometer range. Another concept of improvement of mechanical stability is the preparation of asymmetric membranes via spreading of a mixture of two sorts of particles with opposite surface properties with the oil onto the water surface. After solidification of the oil and removal of particles, membranes with pores width in the range from 30 – 50 nm are obtained. Slow removal of silica particles from composite monolayer that floats on the water surface gives rise to silica rings in intermediate stages of removal. Mixed matrix membranes with embedded carbon molecular sieves are prepared in a similar process as detailed above by using carbon particles instead of silica. Carbon molecular sieves protrude at the top and bottom from the polymeric matrix. Theoretical prediction of permeability and selectivity through these membranes are much higher than in membranes where particles are smaller than the membrane thickness
Spreitet man Mischungen eines Öls mit geeigneten Kieselgelpartikeln auf eine Wasseroberfläche, führt dies zur Bildung gemischter Schichten, in denen die Partikel auf der Ober- und Unterseite aus dem Öl herausragen. Härtet man das Öl aus und entfernt die Partikel, erhält man poröse Membranen mit einheitlichen Poren. Dabei hängen die Porenweiten und Membrandicken von der Partikelgröße ab und betragen üblicherweise 70 – 80 % von deren Durchmesser. Oft sind freitragende poröse Membranen zu zerbrechlich um mit ihnen Druckfiltration ohne Stützstruktur durchzuführen. Um die mechanische Stabilität von porösen Membranen zu erhöhen spreitet man eine Mischung aus Kieselgelpartikeln und einem Öl auf einem Vliesstoff, der mit Wasser getränkt ist. Das Aushärten des Öls und die Entfernung der Partikel führt zu einer porösen Membran, die an die Fasern der Stützstruktur angeheftet ist. Durch die inhomogene Oberfläche des Vliesgewebes sind die daran angehefteten Membranen gewellt. Um eine ebene Stützstruktur zu erhalten, werden Mischungen aus dem Öl und Glaskugeln mit einem Durchmesser von 75 μm verwendet. Das Aushärten des Öls und die Entfernung der Partikel führt zu ebenen porösen Membranen mit Porendurchmessern im Mikrometerbereich. Ein weiteres Konzept, um die mechanische Stabilität zu erhöhen, ist die Herstellung asymmetrischer Membranen mit Hilfe des Spreitens einer Mischung zweier Partikelsorten mit unterschiedlichen Oberflächeneigenschaften mit dem Öl auf die Wasseroberfläche. Nach dem Aushärten des Öls und der Entfernung der Partikel erhält man eine asymmetrische Membran mit kleinen Porenweiten an der Oberseite und großen Porenweiten an der Unterseite. Durch langsames Entfernen der Kieselgelpartikel aus der gemischten Schicht, die auf der Wasseroberfläche schwimmt, kann man in einem Zwischenstadium Kieselgelringe erhalten. Kompositmembranen (mixed matrix membranes) mit eingebetteten Kohlenstoffmolekularsieben werden in einem gleichen Prozess wie oben beschrieben hergestellt, indem man Kohlenstoffpartikel anstatt der Kieselgelpartikel verwendet. Die Kohlenstoffmolekularsiebe ragen auf der Ober- und Unterseite aus der Polymermatrix heraus. Die theoretisch vorhersagten Durchlässigkeiten und Selektivitäten solcher Membranen sind wesentlich höher als bei Membranen, in denen die Partikel kleiner als der Membrandicke sind

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SILVA, Mirele Costa da. "Membranas anisotrópicas de alumina sintetizada pelo método pechini para aplicações em processos de separação". Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1040.

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As membranas cerâmicas anisotrópicas obtidas a partir de pós sintéticos estão ampliando suas aplicações industriais, devido principalmente as vantagens que apresentam em termos de permeabilidade e resistência (química, térmica e mecânica). Este trabalho tem como objetivo obter membranas anisotrópicas com a camada filtrante de alumina sintetizada pelo método Pechini para aplicações em processos de separação. Foram preparadas membranas com geometria na forma de discos e posteriormente membranas tubulares com os melhores parâmetros avaliados na geometria de discos. O suporte foi preparado com uma massa composta por alumina comercial e bentonita, a camada intermediária foi obtida com uma argila caulinítica e a camada filtrante com a alumina sintetizada. As massas utilizadas para obtenção das membranas foram caracterizadas por análise química e térmica, difração de raios X (DRX), distribuição granulométrica e microscopia eletrônica de varredura (MEV). A alumina foi sintetizada pelo método Pechini nas relações 2:1, 3:1 e 4:1 de ácido cítrico:cátion metálico, calcinadas em diferentes temperaturas e caracterizadas por análise térmica, DRX, distribuição granulométrica, MEV e análise textural por BET. Cada camada que compôs a membrana foi caracterizada por MEV, microscopia ótica, porosimetria por intrusão ao mercúrio e análises de fluxo com água dessalinizada. A camada intermediária e a filtrante foram obtidas através da deposição de dispersões por dip-coating. Os resultados apresentaram membranas confeccionadas com sucesso, atingindo permeabilidade de 317,53 L/h.m2 Bar. As membranas foram eficientes para aplicação no tratamento de água oleosa, reduzindo a concentração de 70 mg/L de óleo em água em 100%; para aplicação na separação de índigo blue a membrana atingiu 100% de rejeição das partículas sólidas de uma solução com concentração de 0,25 g/L de índigo blue em água; no tratamento de águas utilizando o efluente bruto de um rio a membrana reduziu entre outros a cor, turbidez, íons, amônia, sílica e ferro e para aplicação na separação da proteína caseína atingiu 97,4% de rejeição em uma solução com concentração de 3,08 mg/L da caseína em água.
The anisotropic ceramic membranes obtained from synthetic powders are expanding their industrial applications, mainly because the advantages that present in terms of permeability and resistance (chemical, thermal and mechanical). The aim of this work is to obtain anisotropic membranes with the filtering layer of alumina synthesized by Pechini method for applications in separation processes. Membranes were prepared in the form of discs and later with tubular geometry with the best parameters evaluated on disk geometry. The support has been prepared with a ceramic mass consisted by a commercial alumina and bentonite. The intermediate layer was obtained with kaolinite clay and the filtering layer with synthesized alumina. The ceramic masses used for obtaining the membranes were characterized by chemical and thermal analysis, X-ray diffraction, particle size distribution and scanning electron microscopy (SEM). Alumina was synthesized by Pechini method in ratios of 2:1, 3:1 and 4:1 of citric acid:metallic cation. It were calcined at different temperatures and characterized by thermal analysis, X-ray diffraction, particle size distribution, and textural analysis by BET. Each layer that composed the membrane was characterized by SEM and optical microscopy, by intrusion mercury porosimetry and flow analysis with desalinated water. The intermediate and filter layer were obtained through the deposition of dispersions by dip -coating. The results showed membranes made with success, free from defects, with permeability of 317.53 L/h m 2 Bar. The membranes were efficient for the application in the treatment of oily water, reducing the concentration of 70 mg/L of oil in water at 100%; for application in separation of indigo blue the membrane reached 100% of rejectio n of solid particles of a solution with concentration of 0.25 g/L of indigo blue; water treatment using the raw sewage of a river the membrane reduced color, turbidity, ions present, ammonia, silica and iron and for application in separation of casein has been reached 97.4% of rejection in a solution with concentration 3.08 mg/mL.

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Medugno, Cláudia Conti. "Fases de membranas fluidas -L3 a partir de lipídio sintético e pentanol na região diluída - e o respectivo dialisado". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266692.

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Orientador: Elias Basile Tambourgi
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A fase L3 (esponja) foi observada no final dos anos 80 e representa uma nova classe de auto moldagem para sistemas surfactantes em água. Esse trabalho descreve a descoberta e a posterior caracterização de uma fase ternária composta do lipídio sintético catiônico brometo de dioctadecildimetil amônio (DODAB), pentanol e água, em uma região diluída. Esta é a primeira descrição de uma fase L3 preparada com um lipídio com uma cabeça polar relativamente pequena e duas cadeias de hidrocarboneto com 18 carbonos cada. A região no diagrama triangular pentanol/água/DODAB na qual a fase existe foi caracterizada utilizando as técnicas de isotropia óptica e anisotropia em relação a uma sonda de espectroscopia de ressonância paramagnética do elétron. A proposta de uma fase L3 foi feita por comparação com um sistema similar relatado pelo grupo de Monpellier. A descrição aceita é que, em uma relação estreita de concentração surfactante e cosurfactante, ocorre fusão de membrana com a formação de uma rede de bicamadas altamente interligadas e distribuídas aleatoriamente no espaço. A hipótese de formação da fase L3 é que o grupo hidroxila do pentanol se pareie com as cabeças de lipídios e esse fato é capaz de alterar a curvatura das bicamadas. As várias preparações de DODAB e pentanol mantiveram-se inalteradas durante pelo menos cinco anos apenas até 3 mM, a concentração máxima que pode ser chamada de L3, que é termodinamicamente estável. Para tornar o sistema mais atraente para muitos usos potenciais, é necessário aumentar a concentração do lipídio. Concentrações até 10 mM decompõem-se após algumas horas em pequenas gotas e cristais, a chamada multifase. O passo seguinte foi remover completamente o álcool por diálise contínua. O resultado foi o aparecimento de uma fase semelhante à água, que não pode ser obtida de outro modo. Uma sequência de medidas espectroscópicas e cromatográficas demonstrou que o álcool foi eliminado totalmente por diálise e o lipídio permanece retido. Há uma notável diferença com outros sistemas binários água/DODAB. Na mesma concentração, todos têm acentuada turbidez. A hipótese é que a presença de álcool na bicamada promove uma reorganização capaz de transformar um sistema particulado em bicontínuo. Está agora bem aceito que a força motriz dessas transformações são as mudanças de curvatura na bicamada. Os esforços para caracterizar esses sistemas são justificados, uma vez que são fáceis de preparar e têm utilizações potenciais como a síntese de compostos com poros mesoestruturados, transporte de drogas e cristalização de proteínas
Abstract: The amphiphilic L3 (sponge) phase was observed in the late 80's and represents a new class of self-assembly for surfactant-water systems. This work describes the discovery and subsequent characterization of a ternary phase composed of synthetic cationic lipid dioctadecildimetil ammonium bromide (DODAB), pentanol and water in a diluted region. This is the first description of a L3 phase prepared from a lipid with a relatively small polar head and two hydrocarbon chains with 18 carbons each one. The region of the triangle diagram in which there is L3 phase was characterized using optical isotropy and anisotropy to a probe with electron paramagnetic resonance spectroscopy technique. The proposal of an L3 phase was made by comparison with a similar system reported by the group of Montpellier. The description accepted is that in a narrow close ratio of surfactant/cosolvent concentrations, membrane fusion occurs with the formation of a highly interconnected and randomly distributed network of bilayers in space. The assumption of formation of the L3 phase is that the hydroxyl group of pentanol pairs with the lipid heads and this fact is able to change the bilayer curvature. The various DODAB/pentanol preparations remained unchanged and stable for five years only up to the concentration of 3 mM of lipid, the maximum concentration that can be called L3 phase, which is thermodynamically stable. To make the system more attractive for many potential uses it was necessary to increase the weight of the lipid. Concentrations up to 10 millimolar, after a few hours, break down into tiny droplets and small crystals, so-called multiphase. The next step was to completely remove the alcohol by continuous dialysis. The result was the appearance of a phase similar to water, which cannot be obtained otherwise. A sequence of spectroscopic and chromatography measurements showed that the alcohol was entirely eliminated by dialysis as the lipid was retained. There is a notable change when compared with other DODAB/water binary preparations. In the same concentration, all of them have pronounced turbidity. The hypothesis is that the presence of alcohol in the bilayer promotes reorganization, transforming a particulate into a bicontinuum system. Efforts to characterize these systems are justified because they are easy to prepare and have potential uses in the synthesis of inorganic solid new materials with nanostructured pores, and as drug carriers and vehicles for the crystallization of proteins
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutora em Engenharia Quimica

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Fawzy, Mohamed Khaled Adel <1990&gt. "Innovative Ceramic Membranes for Sweeping Gas Membrane Distillation: Membrane Characterization and Process Development". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9284/1/PhD_Thesis_Mohamed_Fawzy.pdf.

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The employment of tubular hydrophobic carbon-based titania membranes in sweeping gas membrane distillation (SGMD) was studied in this PhD thesis. The characterization of some of the membrane morphological properties was implemented by experimental and modeled results of gas permeation tests. The dusty gas model was adopted in gas permeation modeling. Two different approaches were followed during modeling. The first approach considered the morphological properties of each single membrane layer. As for the second approach, average membrane morphological properties were characterized without considering the unique contribution of each layer. The investigation of the module performance during SGMD operations was achieved by experimental and modeling studies for NaCl (aq.). The model considered the Knudsen and molecular diffusion mechanisms. The module was capable of undergoing experiments at temperatures up to 110°C. Experimental flux results went in agreement with the modeled values obtained on using the morphological properties of each membrane layer. On the contrary, the modeled values obtained on considering average membrane morphological properties deviated significantly from the experimental results. The model was also used to estimate the effect of the operating conditions and flow configuration on water flux. Other modeling studies of the modules were performed for ethanol (aq.) to predict the effect of the operating conditions on the membrane selectivity. The Maxwell-Stefan approach was followed in this case. Eventually, a hypothetical sweater desalination process was proposed incorporating SGMD (using the modules studied in this thesis) as the desalination unit. Process development and optimization were carried out. The optimized case corresponded to SGMD liquid inlet temperature of 107°C for an SGMD vessel having a length of 5.4 m. This corresponded to a water production cost of 20.9 $/m3 such that the feed heating was the determinant cost item. This cost could be mitigated in case of using a waste heat source.

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Wessolowski, Axel. "Amphipathische Hexapeptide - Interaktion mit Membranen Amphipathic hexapeptides - interaction with membranes /". [S.l.] : [s.n.], 2004. http://www.diss.fu-berlin.de/2004/150/index.html.

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Van, Volden Olivier. "Les membranes d'électrodialyse :propriétés physico-chimiques des membranes monofonctionnelles constituant les membranes bipolaires". Doctoral thesis, Universite Libre de Bruxelles, 2000. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211783.

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Barron, Olivia. "Catalyst Coated Membranes (CCMs) for polymerelectrolyte Membrane (PEM) fuel cells". Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_4757_1307336145.

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The main objective of this work it to produce membrane electrode assemblies (MEAs) that have improved performance over MEAs produced by the conventional manner, by producing highly efficient, electroactive, uniform catalyst layers with lower quantities of platinum electrocatalyst. The catalyst coated membrane (CCM) method was used to prepare the MEAs for the PEM fuel cell as it has been reported that this method of MEA fabrication can improve the performance of PEM fuel cells. The MEAs performances were evaluated using polarisation studies on a single cell. A comparison of polarisation curves between CCM MEAs and MEAs produced in the conventional manner illustrated that CCM MEAs have improved performance at high current densities (>
800 mA/cm2).

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Tremblay, André Y. "The role of structural forces in membrane transport: Cellulose membranes". Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5886.

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The phenomena governing Transition RO/UF (nanofiltration) membrane transport have been critically studied. The residuals and predicted pore sizes of 965 individual permeation runs performed on 70 cellulose membranes were used to discriminate between several restricted transport models and various solute-solvent-membrane material interactions. Solute-membrane interactions were found to be mediated by the presence of structured solvent at the surface of the membrane. Two new interaction parameters, $\Psi\sb{DP}$ and $\kappa\sp\prime$ describing structural solvent forces at the surface of a membrane have been quantified. For solvent mediated interactions, the potential energy of a solute molecule $\phi\sbsp{DP}{\prime}(\underline d$) at a distance $\underline d$ from the membrane surface can be obtained by combining $\Psi\sb{DP}$ and $\kappa\sp\prime$ and the Stokes-Einstein radius a$\sb{s}$ of the solute as follows:$$\phi\sbsp{DP}{\prime}(\underline d) = -\Psi\sb{DP}\ a\sb{s}\ e\sp{-\kappa\sp\prime(\underline{d}-a\sb{s})}$$ A method to evaluate $\Psi\sb{DP}$ from simple permeation experiments and $\kappa\sp\prime$ from direct force measurements is given. This approach permits the decoupling of solute size and solute-membrane material interactions in predicting separation. The inverse of $\kappa\sp\prime$ was found to be approximately equal to the diameter of a solvent molecule. A linear correlation was obtained between the square root of $\Psi\sb{DP}$ and the solubility parameter $\delta\sb{SP}$ for all solutes tested in this work. The slope of this correlation reflects the ability of the membrane material to structure water dipoles at a solid-liquid interface. The ordinate's intercept of this correlation was equal to the solubility parameter of the solvent which implies that steric solute interactions $(\Psi\sb{DP}\to 0)$ occur when $\delta\sb{SP}$ of the solute approaches that of the solvent. The results of this study indicate that a solute molecule can penetrate hydrated layers of solvent at the surface of a material to different extents depending on its size and solvent compatibility. These findings are assumed to be applicable to reverse osmosis transport and indicate that if a membrane material is to be used in RO it must be capable of structuring solvent molecules at its surface. Several parametric studies were performed using the surface force pore flow (SFPF) model to determine the exact shape of the velocity profile in the membrane pore under conditions of solute adsorption and rejection. These studies were performed at various feed concentrations and values of $\lambda$ for polyethylene glycol, of molecular weight 1000, and casein. The shape of the solute separation vs. solute radius curve was studied parametrically as a function of pressure for four restricted transport models. The shape of this curve was also determined, using a radially dependent pore model (RDPM), for adsorptive and repulsive van der Waals interactions, electrical double layer (DLVO) interactions, increased viscosity in the membrane pore and effects of chain permeability and the shape of the interacting surface. Morphological reasons are given for the general inability to reduce the pore radius of cellulose membranes below 1.5 nm. Viscometric measurements performed on cellulose casting solutions indicate that the dissolved elements of the solution exist as rigid, rod-like structures. It is proposed, that the pore size of cellulose membranes be limited by the regular occurrence of indentations on the protofibril surface and by stacking limitations, enhanced by the geometry of the protofibrils. This interpretation is conform with the folded ribbon model of a cellulose protofibril described in the literature.

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Choi, Jonghyun. "Nanofiber Network Composite Membranes for Proton Exchange Membrane Fuel Cells". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1260461818.

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Lycon, David Steven. "Flux enhancement and fouling reduction in a centrifugal membrane process". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/NQ44796.pdf.

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Guillot, Isabelle. "Les membranes d'hémodialyse : biocompatibilité et rétrofiltration". Bordeaux 2, 1996. http://www.theses.fr/1996BOR2P069.

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Aziz, Mujahid. "The recovery of copper by tubular supported liquid membranes". Thesis, Cape Peninsula University of Technology, 2006. http://hdl.handle.net/20.500.11838/894.

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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, Cape Town, 2006
During recent years, the use of liquid membranes has gained general interest in the treatment of effiuents where solute concentrations are low and large volumes of solutions should be processed, and, if possible, without generating any secondary waste. Liquid membrane processes have been proposed as a clean technology, owing to their characteristics, i.e. high specificity, low energy and utilization. Two liquid membrane processes have been used in metal recovery, which are the liquid surfactant membrane (LSM), which corresponds to double water-in-oil emulsion and solid . supported liquid membranes (SLM), which are made by dispersing or impregnating the extractant within the pores of in.ert solid support. Previously, the recovery of eu (IT) in a SLM system was conducted by other membrane models such as hollow fibre, spiral and flat sheet. Only a small measure of success on scale-up and industrialization of these models has been attained. One of the disadvantages of the hollow fibre system was the small lumen size through which the feed needed to pass. Pores became clogged by suspended particles because the pressure drop over the small diameter augments lower flow rates and therefore, pre-filtering is necessary (Rathore, et al., 2001). In this study the behaviour of a tubular SLM reactor with an inner diameter of the lumen approximately fifty times bigger than that of the hollow fibre are used in order to solve the problem of clogging. This tubular reactor was incorporated in to a bench scale plant and proved successful in copper extraction. By observing transient data, mass transport coefficients were determined and compared to published values.

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Borgsmiller, Karen McNeal. "Synthetic membranes for chiral separations". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11824.

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Björnsson, Jonas. "Stretched Membranes". Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1581.

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This thesis deals with relativistic membranes and, in particular, a limit called stretched membranes. The thesis also considers the relation of membranes to the conjectured M-theory and string theory. The thesis is divided into two parts. One introductory part where I introduce areas which are of relevance for the second part.

The second part consists of the scientific papers.

In the first part I make a general introduction to string theory. Furthermore, I discuss different limits of membrane theory. Then, I make a short review of the different conjectures of M-theory and briefly mention different consistency checks of these conjectures. The last subject in the first part concerns an area, which is not

in direct connection to the other chapters in the thesis. This is a short introduction to the general treatment of theories with constraints.

The second part of the thesis consists of the included articles. The common topic of these is that they give a new approach to the treatment of membranes. We here make a partial gauge-fixing of the constraints which, by choosing an appropriate limit, will yield a perturbation theory around a free string-like theory. The stringlike

theory is the usual string theory with an extra parameter dependence. This perturbation theory we solve by infinitesimal canonical transformations.

The corresponding quantum theory is also discussed. We show that a particular ordering gives critical dimensions 27 and 11 for the bosonic and fermionic case respectively.

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Oldham, Alexis Jean. "Modulation of lipid domain formation in mixed model systems by proteins and peptides". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-1/r1/oldhama/alexisoldham.pdf.

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Wagh, Priyesh Ashokrao. "SYNTHESIS OF BIOLOGICALLY-INSPIRED NANOFILTRATION MEMBRANES USING PROTECTED, MUTATED, AND SIMULATED AQUAPORINS". UKnowledge, 2018. https://uknowledge.uky.edu/cme_etds/92.

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Gram-negative bacterial cells are surrounded by a cell membrane which protects the cell and controls the transport of nutrients and waste products in and out of the cells at a fast rate. This rapid transport of nutrients and wastes through the cell membrane is made possible by channel proteins called porins. Various types of porins present in the cell membrane have specific functions depending on their selectivity towards different nutrients, and channel proteins selective towards water are called aquaporins. These proteins restrict the passage of all entities except water molecules and they provide a fast transport rate of water molecules at 109 molecules/second per channel. The high selectivity of porins has led to their incorporation into synthetic systems, and one example is the addition of porins to separations membranes in order to enhance their performance in terms of selectivity and permeability, in a field called biomimetics. The concept of incorporating aquaporins into synthetic membranes has been studied for the last 10 years in order to enhance the water permeability and selectivity of membranes for water purification; however, there are still limitations such as high costs, difficulties in fabrication of aquaporins, their alignment into synthetic membrane assembly, low stability, and limitations on number of aquaporin molecules that can be introduced into synthetic membranes limit their applicability. In recent years, concurrent with the work on aquaporin-based biomimetic membranes, there has been an increase in the study of synthesizing molecules with similar structure-function relationships of aquaporins. These artificial channels attempt to mimic the high-water permeability and selectivity of aquaporins, while being synthesized using simple chemistry, being solvent compatible, and requiring less space on the membrane surface which helps to incorporate more channels into the membrane assembly. The objectives of this study were to first incorporate aquaporins into synthetic nanofiltration membranes without chemical alteration them to prevent flattening or denaturing of aquaporins; then, the second objective was to install functional groups on aquaporins and align them in the direction of water flow; lastly, the third objective was to synthesize artificial channels in order to overcome the issues with aquaporin stability, alignment, and efficient packing of water channels onto the membrane surface. For the first objective, aquaporins were treated with a polysaccharide, gum Arabic, and incorporated into an amphiphilic polymer, polyvinyl alcohol with alkyl side chains (PVA-alkyl), in order to simulate the natural housing of lipid bilayer for aquaporins and to protect them from denaturing. Long alkyl chains provided the hydrophobic component, while PVA provided the hydrophilic component of the amphiphilic polymer. Membranes modified with aquaporins displayed lower flux declines and higher flux recoveries after reverse flow filtration, along with improved rejection values for both protein and salt solutions as compared to PBI and PBI-PVA-alkyl membranes. However, there was leakage of ions between channels. Therefore, in order to improve the rejection of protons, ions and other impurities, the channels were aligned with the direction of water flow. Functional groups were installed on Aquaporins using site-directed mutagenesis for covalent attachment to the polymer matrix so that the proteins could be immobilized to the membranes and aligned in the direction of the flow. Aquaporin constructs were modified to bear affinity tags or unique amino acids at the N-terminus of the aquaporin molecule, which was used to facilitate directional immobilization. Each aquaporin monomer was modified with a unique amino acid Cys group at the N-terminus right after the first Met, and due to the aquaporin tetrameric nature, these Cys groups became four anchors for attachment. The presence of these four Cys anchors per aquaporin tetramer was used to attach on the membrane surface in alignment with the feed water flow direction. Membranes modified with mutated aquaporins showed consistently higher salt rejection values of ~70% irrespective of feed concentration, along with higher flux recoveries and lower flux declines. Commercial NF-270 membranes provide a monovalent salt (NaCl) rejection of ~50% and divalent salt (MgCl2) rejection of 97%. Also, approximate coverage of membrane surface with attached aquaporins was calculated using simulation studies. Simulation studies showed that immobilized aquaporins with PVA-alkyl provided a diffusion rate equivalent to 64% coverage on the membrane surface. This showed that aquaporins didn’t cover the entire surface area of the membrane. However, immobilized aquaporins were responsible for the rejection of a portion of ions passing through the membrane. In order to overcome the limitations of aquaporin incorporation into polymer membranes, artificial organic frameworks were added as surface modification on PBI membranes. Organic frameworks were synthesized as derivatives of hybrid bisamides. The series of bisamides 1-4 consist of 6-amino-pyridine-2-dicarboxylic acid, 6-hydroxymethyl-pyridine-2-carboxylic acid and ethylenediamine, trimethylenediamine, putrescine, and cadaverine depending on the length of carbon chain. These frameworks are amphiphilic in nature and have strong chemical attachment due to the presence of amines and carboxylic acids into each building block. These molecules were introduced into the membrane matrix using carbodiimide chemistry. FTIR results showed the attachment of these bisamide molecules onto the surface of a modified PBI membrane. Also, modified membranes showed a reduced molecular weight cut off (MWCO) for neutral organic molecules. Overall, membranes modified with aquaporins have shown a potential to provide consistently high salt rejections with increasing feed solutions. Also, preliminary results have shown that bisamide molecules can be attached onto the membrane surface as organic frameworks and have a potential to be an alternative for aquaporins based biomimetic membranes.

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Daoudi, Meriem. "Performances et durabilité des membranes alternatives aux membranes PFSA". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0011.

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Le principal objectif de cette thèse est la recherche d'un compromis entre la durabilité, le coût et, à terme, la résistance à haute température des membranes ionomères utilisées dans les piles à combustible de type PEMFC (Proton Exchange Membrane Fuel Cell). À cet égard, le ionomère poly (éther éther cétone) sulfoné (sPEEK) a été choisi du fait de ses bonnes propriétés mécaniques et de sa tenue à haute température. Cependant, les membranes sPEEK offrent une faible stabilité chimique par rapport aux membranes PFSA (PerFluoroSulfonic Acid) de référence. Afin de lever ce verrou, deux approches ont été mises en place : prétraitements et/ou hybridation des membranes sPEEK. L'impact des prétraitements des membranes poly (éther éther cétone) sulfoné sur leurs propriétés fonctionnelles, leurs structures chimiques et leurs performances en pile a été étudié. Plusieurs techniques de caractérisation physico-chimiques ainsi que des outils de diagnostic électrochimiques ont permis de corréler les performances en pile aux propriétés de sorption et de transport des différentes membranes. Par la suite, la durabilité des meilleurs de ces échantillons a été étudiée via deux approches ex-situ et in-situ. L'approche ex-situ a permis d'avoir un premier aperçu de la stabilité chimique des membranes. En complément, les tests de dégradation in-situ ont permis d'évaluer la stabilité des membranes sous l'effet des sollicitations chimiques et mécaniques rencontrées dans les cellules de piles à combustible en fonctionnement. Pour cela, un test de vieillissement accéléré a été développé, associant cyclages en potentiel, cyclages en humidité, et maintiens prolongés en circuit ouvert. Enfin, la deuxième approche consiste, en plus de l'application d'un prétraitement, en l'hybridation des membranes par voie sol-gel. Plusieurs précurseurs à fonctions sacrificielles ou rédox ont été imprégnés au sein des membranes poly (éther éther cétone) sulfoné. L'analyse des performances en pile ainsi que de la durabilité des membranes en appliquant le test de dégradation accéléré ont mis en évidence l'efficacité de cette approche : les performances et la durabilité de certaines membranes hybrides ont même dépassées celles des membranes PFSA de référence
The main objective of this thesis is to find a compromise between durability, cost, and eventually the ability to sustain high temperatures ionomer membranes used in PEMFC (Proton Exchange Membrane Fuel Cell). This work focused on sulfonated poly (ether ether ketone) membranes (sPEEK), which were chosen because of their good mechanical properties and high temperature resistance. However, sPEEK membranes suffer from a poor chemical stability, compared to the reference PFSA (PerFluoroSulfonic Acid) membranes. In order to overcome this problem, two approaches have been developed: pretreatment and/or hybridization of sPEEK membranes.The impact of sulfonated poly (ether ether ketone) membranes pretreatments on their functional properties, chemical structure and fuel cell performances was studied. Several physico-chemical characterization techniques as well as electrochemical diagnostic tools were used to correlate the cell performance with the sorption and transport properties of tested membranes.Subsequently, the durability of the best of these samples was studied via ex-situ and in-situ approaches. The ex-situ approach provided a first insight into the chemical stability of the membranes. In addition, the in-situ degradation tests allowed to evaluate the durability of the membranes under chemical and mechanical stresses very close from those encountered during fuel cell cells operation. For this purpose, an accelerated aging test was developed, combining potential cycling, humidity cycling and open-circuit prolonged hold.Finally, the second approach consists, in addition to the application of a pretreatment, in the hybridization of the membranes by sol-gel processes. Several precursors with sacrificial or redox functions were impregnated into the sulfonated poly (ether ether ketone) membranes. The analysis of fuel cell performances and membrane durability after applying the accelerated stress test have highlighted the efficiency of this approach: the performance and durability of some hybrid membranes even exceeded those of the reference PFSA membranes

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28

Barbe, Aron Mervyn. "The fouling of hydrophobic, microporous membranes used in osmotic distillation". Thesis, Queensland University of Technology, 2001.

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29

Pridmore, Catherine Jane. "Analytical methods for the study of membranes and peptide-membrane interactions". Thesis, Durham University, 2010. http://etheses.dur.ac.uk/807/.

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Abstract (sommario):

This thesis describes analytical work carried out to determine the stability and properties of lipid and peptide-lipid systems. Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and tandem mass spectrometry (MSMS) analyses were carried out to establish a validated protocol for the complete identification of phospholipids, including the nature of the headgroup and acyl chains and the positions of the acyl chains on the glycerol backbone. Statistical differences were observed in the relative intensities of peaks corresponding to the neutral loss of the acyl chain from the sn-1 and sn-2 positions of POPE, POPC and OPPC, with a preferential cleavage of the chain from the sn-2 position of all three in the absence of added salt and a preferential cleavage at the sn-1 position in the presence of sodium or lithium ions. This knowledge was applied to the identification of unknown lipid mixtures both on the standard MALDI target plate and directly onto thin layer chromatography plates after separation. The above techniques, together with other analytical methods including thin layer chromatography and dynamic light scattering, were applied to the study and identification of lipids modified by actions such as hydrolysis and oxidation under conditions used for binding analyses of peptides and small molecules. Long-term analyses of samples containing synthetic melittin and liposomes showed that over time melittin both promotes the hydrolysis of liposomal lipids and is itself acylated. Analyses of the binding of a prototypical peptide (human neutrophil defensin HNP-2) to membranes, using methods that included dichroism and fluorescence spectroscopy, demonstrated that HNP-2 dimers act on lipid membranes via a carpet-type mechanism and allowed the rate of the formation of bound HNP-2 states to be determined. HNP-2 was modeled as a consecutive two-step process following pseudo-first order kinetics. The first step (membrane association) was rapid, with a half-life of around 0.5 minutes, while the second step (reorientation and partial insertion into the membrane) was slower by an order of magnitude.

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30

Daisley, Gavin Rhys. "Membrane Aromatic Recovery System (MARS) : improved membranes and a further application". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508324.

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31

Xu, Lili. "Electrically tuneable membranes : revolutionising separation and fouling control for membrane reactors". Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715263.

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The overall aim of this research is to develop unique conducting polyaniline (PANI) membranes that can be electrically tuned to achieve different fluxes and selectivity. The target application is in a tuneable membrane reactor, where these membranes allow the fouling layer to be pushed off/through membranes by application of external potential. To achieve this, several different types of PANI membranes were examined. The permeation properties of HCl-doped PANI membranes can be modified electrically to produce in-situ tuneable separations. However, acid dopant leaching and membrane brittleness limit the further application of these membranes. Polymer acid doped PANI membranes using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) or PAMPSA were investigated as a solution. These PAMPSA doped PANI membranes displayed improved mechanical strength and filtration stability. However, the membranes showed decreased electrical conductivity, leading to a limited tuneable permeance and selectivity under applied potential. To overcome this new challenge, expanded graphite and a large acid (dodecylbenzene sulfonic acid or DBSA) were incorporated into the PAMPSA doped PANI membranes to increase the conductivity. Despite increasing both conductivity and electrical tuneability, the resulting membranes were more porous with looser molecular weight cut-off (outside of the desired NF/low UF MWCO range) than without modification. Efforts to tighten PAMPSA doped membranes to the same MWCO as HCl doped membranes using volatile co-solvents (THF and acetone) were unsuccessful: porosity was due to the large acid dopants. Membranes were examined for their potential for in-situ fouling removal of model foulant bovine serum albumin under applied voltage. This was successful and defouling extent was found to be closely related to membranes with higher conductivity and greater acid stability. Overall, it has been demonstrated that the conducting polyaniline composite membranes can be made to be stable to acid leaching and be more mechanically robust, whilst also being externally electrically tuned to different molecular selectivities with the potential for in-situ fouling control.

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32

LADHA, PARAG. "POLYMERIC MEMBRANE SUPPORTED BILAYER LIPID MEMBRANES RECONSTITUTED WITH BIOLOGICAL TRANSPORT PROTEINS". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145901880.

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33

Sorensen, E. Todd. "Cross-linkable polyimide blends for stable membranes". Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/10086.

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34

Ren, Bin. "Catalyst loaded porous membranes for environmental applications : Smart Membranes". Thesis, KTH, Materials Science and Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4619.

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This project involves the fabrication and testing of microporous, polymer membranes designed to remove minute amounts of toxic air pollutants such as formaldehyde from air streams. The hypothesis to be tested is that active, the silver contained within the porous polymer membranes results in high formaldehyde retention.

Monolayers consist of different sizes of sPS particles are assembled first on the silicon wafers by spin coating method and convective assembly method, respectively. Then each kind of monolayer with one dimension of sPS particles is deposited with a nanometer scaled silver thin film with a bench top metal evaporator. The porous membranes are produced by assembly of close-packed colloidal crystals of silver capped polystyrene template particles and subsequent infiltration with polyurethane prepolymer. The prepolymer is cured by UV exposure. The sPS particles are removed from the particle polymer membrane by treatment with organic solvents resulting in the formation of inverse opal structures. Silver does not dissolve in the organic solvents and cannot leave the pores due to the small size of connecting holes in an inverse opal. All the monolayers, cylindrical colloidal crystals and microcapillaries after infiltration of polyurethane had been characterized by optical microscope, and the porous membranes had been characterized by SEM.

The application of porous membranes with silver caps is to absorb formaldehyde in the air, while in fact the silver caps are oxidized and become Ag2O, which will initiate a gas-phase/solid reaction with formaldehyde. In the future, TiO2 will be applied together with Ag2O, since TiO2 is another good absorbent for formaldehyde

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35

Poletto, Patrícia. "Caracterização de membranas de poliamida 66 preparadas pelo método de inversão de fases". reponame:Repositório Institucional da UCS, 2010. https://repositorio.ucs.br/handle/11338/573.

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Neste trabalho foram preparadas membranas de poliamida 66 (PA 66) pelo método de inversão de fases (IF) e caracterizadas com o objetivo de verificar sua possível aplicação em processos de separação. As membranas de PA 66 foram preparadas utilizando dois solventes diferentes, ácido fórmico (AF) e ácido clorídrico (HCl) e água como não-solvente. As membranas preparadas na forma de filmes (não suportadas) foram caracterizadas por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) e calorimetria exploratória diferencial (DSC), onde os resultados mostraram que a estrutura química e o comportamento térmico da PA 66 não foram alterados como o uso de ácidos como solventes. Os filmes apresentaram estrutura assimétrica, com formação de camada densa na parte superior seguida de subestrutura de poros esféricos observada por microscopia eletrônica de varredura (MEV). A espessura de camada densa variou de 10 à 25 μm, para o filme preparado em AF e HCl, respectivamente. O aumento da espessura da camada densa, ou seja, a redução de espaços vazios influenciou diretamente os resultados de percentual de água absorvida e porosidade total. A porosidade foi de 15 contra 50% para os filmes preparados em AF e HCl, respectivamente. O fluxo de vapor de água foi menor para os filmes com maior espessura de camada densa, devido ao aumento da resistência ao transporte de massa. Com o objetivo de aumentar a resistência mecânica dos filmes de poliamida, foram preparadas membranas suportadas em tecido de poliéster para posterior aplicação em processos de separação que utilizam altas pressões. As membranas suportadas foram caracterizadas pelas técnicas de BET para determinação de tamanho médio de poros, ensaios de osmose inversa (OI) e ultrafiltração (UF). Ambas as membranas preparadas em AF e HCl apresentaram valores de tamanho de poro muito próximos quando analisado por BET. O ensaio de compactação com água pura realizado a 40 bar de pressão revelou que as membranas preparadas em AF sofrem maior compactação na sua estrutura apresentando fluxo de permeado em torno de 22 Lm-2h-1 enquanto a membrana preparada em HCl apresentou fluxo de 312 Lm-2h-1. No ensaio de OI, a rejeição máxima ao cloreto de sódio foi de 7% e 4% para a membrana AF-3 e HCl-3, respectivamente. Nos ensaios de ultrafiltração (UF), realizados a 15 bar, ambas as membranas apresentaram valores de rejeição próximos a 70% para albumina de ovo e 80% para albumina bovina. Com esse resultado, podemos concluir que ambas as membranas apresentaram características de tamanho de poro e rejeição para aplicações em processos de UF.
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In the present study, polyamide 66 (PA 66) membranes were prepared by phase inversion (PI) and characterized in order to verify their potential application in separation processes. PA 66 membranes were prepared using two different solvents, formic acid (FA) and chloridric acid (HCl), and water as a non-solvent. Membranes prepared in film form (not supported) were characterized by Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) and the results showed that the chemical structure and thermal behavior of the PA 66 were not altered by the use of acids as solvents. The films revealed an asymmetric structure with a dense top layer and a porous sublayer featuring spherical pores observed by scanning electron microscopy (SEM). The thickness of the dense layer varied from 10 to 25 μm in films prepared with FA and HCl, respectively. The increase in thickness of the dense layer, i.e., the reduction of empty spaces, directly influenced the results regarding water absorption percentage and total porosity. The porosity found was 15% and 50% for films prepared with FA and HCl, respectively. Water vapor flux was lower in films with a thicker dense layer as a result of a greater resistance to mass transfer. In order to increase mechanical resistance in polyamide films, supported membranes with polyester fabric were prepared for latter application in separation processes through high pressure. Supported membranes were characterized by BET techniques for the determination of pore size, reverse osmosis and ultrafiltration assays. Both membranes prepared with FA and HCl showed very similar pore sizes when analyzed by/with BET. A compression assay with pure water performed at a pressure of 40 bar revealed that membranes prepared with FA undergo greater compaction of its structure and had a permeate flux value of approximately 22 Lm-2h-1 whereas the membrane prepared with HCl had a permeate flux value of 312 Lm-2h-1. On reverse osmosis assays, the maximum rejection to sodium chloride was 7% and 4% for FA-3 and HCl-3 membranes, respectively. On ultrafiltration assays, performed at 15 bar, both membranes had rejection values close to 70% for egg albumin and 80% for bovine albumin. Based on this result, it is possible to conclude that both membranes revealed pore size and rejection characteristics for application in ultrafiltration processes.

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36

Keuler, Johan Nico. "Optimising catalyst and membrane performance and performing a fundamental analysis on the dehydrogenation of ethanol and 2-butanol in a catalytic membrane reactor". Thesis, Link to the online version, 2000. http://hdl.handle.net/10019.1/1277.

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37

Bighane, Neha. "Novel silica membranes for high temeprature gas separations". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43732.

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Abstract (sommario):

Membrane materials for gas separations span a wide range including polymers, metals, ceramics and composites. Our aim is to create economical hydrothermally stable membranes that can provide high H₂-CO₂ separation at a temperature of 300 degree Celsius, for application in the water-gas shift reactor process. The present work describes the development of novel silica and silica-titania membranes from the controlled oxidative thermolysis of polydimethylsiloxane. The scope of this thesis is fabrication of membranes, material characterization and preliminary gas permeation tests (35-80 degree Celsius) on PDMS derived silica membrane films. The developed membranes can withstand up to 350 degree C in air. High permeabilties of small gas penetrants like He, H₂ and CO₂ have been observed and fairly high separation factors of O₂/N₂=3, H₂/N₂= 14 and H₂/CH₄=11 have been obtained. As the temperature of operation increases, the permeability of hydrogen increases and the separation factor of H₂ from CO₂ increases. The silica membranes exhibit gas separation factors higher than the respective Knudsen values. Additionally, design and construction of a new high temperature gas permeation testing system is described, which will cater to gas permeation tests at temperatures up to 300 degree Celsius for future work. The thesis also includes a detailed plan for future studies on this topic of research.

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38

Boulter, Jonathan Michael. "Structural and functional studies of the erythrocyte anion exchanger, band 3". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297079.

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39

Guseva, Ksenia. "Formation and cooperative behaviour of protein complexes on the cell membrane". Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=203444.

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In this work we analyse aspects of dynamics and organization of biological membranes from a physical prospective [i.e. perspective]. We provide an analysis of the process of self-assembly and spatial organization of membrane proteins. We illustrate the analysis by considering a channel activated by membrane tension called mechanosensitive channels (MS), in E. coli and the twin arginine translocation system (Tat). We analyse the mechanism of formation of oligomeric protein complexes formed by identical subunits. By derivation of a mathematical approach based on Smoluchowski coagulation equation, we study the deficiency of the process of complex formation, taking into account both irreversible aggregation, as well as fragmentation. We find that a small fragmentation rate increases the efficiency of the formation process, however if the fragmentation rate vanishes the irreversible process is very inefficient. Our second aim is to determine how the spatial organization can affect the function of channels, which are regulated by elastic forces. We map these short-range interactions into a discretized system, from which we obtain the spatial distribution of the channels and its effect on the gating dynamics. We find that organized channels activate at lower membrane tensions, but possess a delay in the reaction time. In the last part we determine how the formation of transient pores on the membrane depends on the dynamics of its assembly process. We analyse the pores formed by the Tat complex, which is responsible for protein transport through the membrane. This system functions by polimerization in response to a signal of transport demand from a protein in the cell cytoplasm. The direct correlation of the size of the assembled pore and the size of the protein determines the speed of the translocation process. Using a differential equation approach we obtain that the flux of a given protein depends quadratically on its size.

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40

Aubert-Mammou, Corinne. "Etude comparative des lipides de graines de quelques crucifères (colza, moutarde, sisymbre)". Toulouse, INPT, 1994. http://www.theses.fr/1994INPT010A.

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Ce travail est consacre a l'etude de onze echantillons d'huiles de graines de cruciferes: colza, moutarde noire, moutarde blanche, et sisymbre. Les proportions relatives des sterols, 4-methylsterols et alcools triterpeniques contenus dans l'insaponifiable ont ete determinees par clhp. Les principaux sterols ont ete isoles et identifies par rmn du proton et du carbone 13. Un schema biosynthetique a ete propose. Les tocopherols ont ete analyses de facon qualitative et quantitative. Les acides gras ont ete analyses par cpg. Apres fractionnement par ccm argentique et clhp, certains acides gras minoritaires (acides gras monoinsatures de la serie n-7) ont ete purifies et identifies par rmn du proton et du carbone 13. Dans les huiles riches en acide erucique, des correlations entre les teneurs en acides erucique et linolenique et en brassicasterol ont ete mises en evidence. Des correlations entre les acides gras ont permis de proposer une filiation biosynthetique. Les triacylglycerols ont ete fractionnes par clhp et par ccm argentique. La nature des acides gras en position sn-2 du glycerol a ete determinee par hydrolyse des triacylglycerols par la lipase pancreatique de porc. Les proportions des diverses especes moleculaires de triacylglycerols ont ete determinees et ont permis de differencier les divers types d'huiles

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41

Stephens, Brian Dominic. "BIOCOMPOSITE PROTON EXCHANGE MEMBRANES*". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1147968573.

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42

Malewitz, Timothy. "Modeling Equilibrium Salt Partitioning in Neosepta AMX and Selemion AMV Antion Exchange Membranes". Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1249342152.

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43

Hartshorn, Christopher M. "Studies of the molecular effects of a solid support upon lipid membranes and membrane bound proteins". Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Fall2009/c_Hartshorn_101209.pdf.

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44

Yurdakul, Ahmet Ozgur. "Acid Doped Polybenzimidazole Membranes For High Temperature Proton Exchange Membrane Fuel Cells". Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608506/index.pdf.

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Acid Doped Polybenzimidazole Membranes for High Temperature Proton Exchange Membrane Fuel Cells Author: Ahmet Ö
zgü
r Yurdakul One of the most popular candidates for high temperature PEMFC&rsquo
s is phosphoric acid doped polybenzimidazole (PBI) membrane due to its thermal and mechanical stability. In this study, high molecular weight PBI was synthesized by using PPA polymerization. The stirring rate of reaction solution was optimized to obtain high molecular weight. The inherent viscosity of polymer was measured at four points in 96 percent sulphuric acid solution at 30 degree centigrade by using an Ubbelohde viscometer. The highest average molecular weight was found as approximately 120,000 using the Mark-Houwink equation. The polymer was dissolved in N,N-dimethylacetamide at 70 degree centigrade with an ultrasonic stirrer. The membranes cast from this solution were doped with phosphoric acid solutions at different concentrations. The doping levels of the membranes were 6, 8, 10 and 11 moles phosphoric acid/PBI repeat unit. The mechanical strength of the acid doped membranes measured by tensile tests were found as 23, 16, 12 and 11 MPa, respectively. Conductivity measurements were made using the four probe technique. The membranes were placed in a conductivity cell and measurements were taken in humidity chamber with temperature and pressure control. The conductivity of membranes was measured at 110, 130 and 150 degree centigrade in both dry air and water vapor. The highest conductivity was 0.12 S/cm at 150 degree centigrade and 33 percent relative humidity for the membrane doped with 11 moles of H3PO4. The measurements showed that conductivity increased with increasing doping and humidity. Moreover, membranes had acceptable conductivity levels in dry air.

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45

Baghbanzadeh, Mohammadali. "Nano-composite Membranes and Zero Thermal Input Membrane Distillation for Seawater Desalination". Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35742.

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In this PhD thesis, seawater desalination by Membrane Distillation (MD) has been explored from the perspective of process and membrane. Regarding the process, an innovative, energy efficient, and environmentally friendly Zero Thermal Input Membrane Distillation (ZTIMD) process was proposed. ZTIMD uses thermal energy stored in seawater, which makes the process sustainable by being independent of the external sources of thermal energy, which is one of the major contributors to the cost and energy consumption of conventional MD desalination processes. Economic feasibility study was carried out for the ZTIMD process, and it was demonstrated that drinking water could be produced with a cost of $0.28/m3, which is approximately half of the cost of conventional desalination processes. Regarding the membrane, novel MD membranes were developed through incorporation of nanomaterials in polyvinylidene fluoride (PVDF). Different nanomaterials including superhydrophobic SiO2, amine modified hydrophilic SiO2, CuO, and CaCO3 were used for this purpose. It was shown that membrane structure and consequently its performance could be affected by the nanoparticle properties, concentration, presence of backing material, PVDF blend ratio, and penetration time. In a best membrane developed in this work, almost 2500% increase was observed in the Vacuum Membrane Distillation (VMD) flux over that of the neat PVDF membrane at a feed temperature of 27.5 °C and vacuum pressure of 1.2 kPa, when 7.0 wt.% hydrophilic SiO2 nanoparticles were added into a PVDF membrane supported with Non-Woven Fabric (NWF) polyester. The membrane possessed near perfect selectivity.

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46

Suk, Daniel Eumine. "Development of surface modifying macromolecule blended polyethersulfone membranes for vacuum membrane distillation". Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29319.

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Surface modifying macromolecule (SMM) has been developed aiming at the preparation of membranes with greater surface hydrophobicity and greater chemical resistivity at a lower cost than conventional hydrophobic membranes. Throughout the whole work in this study, the membranes, which contains SMM as an additive and PES as a base polymer, are called 'SMM blended PES membranes' or 'SMM modified PES membranes'. The objective of this study is the preparation of SMM blended membranes to be used for the removal of VOCs from their aqueous solutions by the membrane distillation process. In the first part of this work, a SMM, "tSMM", was synthesized by a traditional method and the tSMM blended PES membranes were prepared to study the effects of tSMM on PES membranes by different methods; e.g. bubble-point method and gas permeation, pure water permeation (PWP), contact angle measurement, and X-ray photoelectron spectroscopy (XPS). In particular, based on the XPS results, the kinetics of surface migration of tSMM was studied. According to the results of experimental and theoretical studies, it was observed that the tSMM blended membranes prepared had a potential to be used in membrane distillation (MD), however to meet the requirement of MD membrane, relatively long evaporation time (over 10 minutes) and high evaporation temperature (110°C) should be needed during membrane preparations. In the second part of this work, a novel SMM, "nSMM" was designed and synthesized. Synthesized nSMMs from two different batches (nSMM1 and nSMM2) were characterized by GPC and the weight average molecular weight (Mw) of nSMM2 was about twofold of nSMM1. Furthermore, "nSMM" blended PES membranes were prepared and characterized. According to the results, the nSMM seems to be a better alternative to tSMM for membrane distillation, since a shorter period at room temperature was required for "nSMM" to migrate to the membrane surface. The ultrafiltration (UF) tests also gave the information on the effects of nSMM on PES membranes. nSMM was fully segregated to the surface of membrane forming a distinctive surface layer and this was observed from optical microscope and scanning electron microscopy (SEM) results. In the end of the second part, the nSMM blended PES membranes were successfully applied in vacuum membrane distillation (VMD) for the removal of ethanol from water.

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47

Lu, Jun-xia. "Solid-state NMR studies of phospholipid model membranes and membrane-associated macromolecules". Oxford, Ohio : Miami University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1184090235.

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48

Bannwarth, Sebastian [Verfasser]. "Characterization of Membranes and Membrane Processes by Electrical Impedance Spectroscopy / Sebastian Bannwarth". Aachen : Shaker, 2017. http://d-nb.info/113817842X/34.

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49

Winkler, Gudrun. "Effects of configuration on the operation of membranes in membrane biological reactors". Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7960.

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The aim of this work included the investigation of the impact of membrane material properties on fouling propensity and permeate flux decline in MBR biomass systems. Furthermore, the impact of membrane configuration on the respective fouling behaviour was of interest. A direct comparative study of different membrane module configurations including a multi-tubular membrane (MT), a single flat sheet module (FS) and a hollow fibre (HF) pilot scale module was undertaken. Membrane module filtration performances, especially with respect to their fouling propensity under varying hydraulic conditions, were investigated to ultimately evaluate the impact of varying parameters such as aeration and biomass make up on fouling and to determine optimised operational parameters. Subsequently, a range of different membrane materials, such as flat sheet membrane samples made of polyethylene (PE), polyethersulfone (PES), polysulfone (PS) and polyvynilidene fluoride (PVDF) and a single-tube made of PVDF and PES were characterised and their fouling propensity to MBR biomass was studied at bench-scale. Cont/d.

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50

Hill, Melinda Lou. "Polymeric and Polymer/Inorganic Composite Membranes for Proton Exchange Membrane Fuel Cells". Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/37597.

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Abstract (sommario):

Several types of novel proton exchange membranes which could be used for both direct methanol fuel cells (DMFCs) and hydrogen/air fuel cells were investigated in this work. One of the main challenges for DMFC membranes is high methanol crossover. Nafion, the current perfluorosulfonic acid copolymer benchmark membrane for both DMFCs and hydrogen/air fuel cells, shows very high methanol crossover. Directly copolymerized disulfonated poly(arylene ether sulfone)s copolymers doped with zirconium phosphates and phenyl phosphonates were synthesized and showed a significant reduction in methanol permeability. These copolymer/inorganic nanocomposite hybrid membranes show lower water uptake and conductivity than Nafion and neat poly(arylene ether sulfone)s copolymers, but in some cases have similar or even slightly improved DMFC performance due to the lower methanol permeability. These membranes also show advantages for high temperature applications because of the reinforcing effect of the filler, which helps to maintain the modulus of the membrane, allowing the membrane to maintain proton conductivity even above the hydrated glass transition temperature (Tg) of the copolymer. Sulfonated zirconium phenyl phosphonate additives were also synthesized, and membranes incorporating these materials and disulfonated poly(arylene ether sulfone)s showed promising proton conductivity over a wide range of relative humidities. Single-Tg polymer blend membranes were studied, which incorporated disulfonated poly(arylene ether sulfone) with varied amounts of polybenzimidazole. The polybenzimidazole served to decrease the water uptake and methanol permeability of the membranes, resulting in promising DMFC and hydrogen/air fuel cell performance.
Ph. D.

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Tesi sul tema "Membranes"

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